EN中文

Journal of Geographical Sciences >

2017 , Vol. 27 >Issue 2: 183 - 204

DOI: https://doi.org/10.1007/s11442-017-1371-y

Research Articles

Effects of an ecological conservation and restoration project in the Three-River Source Region, China

  • SHAO Quanqin ,
  • CAO Wei ,
  • FAN Jiangwen ,
  • Lin Huang , * ,
  • XU Xinliang
Expand
  • Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China

Author: Shao Quanqin (1962-), Professor, E-mail:

*Corresponding author: Huang Lin (1981-), PhD and Associate Professor, E-mail:

Received date: 2016-03-03

  Accepted date: 2016-06-03

  Online published: 2017-04-10

Supported by

National Nature Sciences Foundation of China, No.41571504

National Key Technology Research and Development Program, No.2013BAC03B00

Copyright

Journal of Geographical Sciences, All Rights Reserved
Fold

Abstract

The first-stage of an ecological conservation and restoration project in the Three-River Source Region (TRSR), China, has been in progress for eight years. However, because the ecological effects of this project remain unknown, decision making for future project implementation is hindered. Thus, in this study, we developed an index system to evaluate the effects of the ecological restoration project, by integrating field observations, remote sensing, and process-based models. Effects were assessed using trend analyses of ecosystem structures and services. Results showed positive trends in the TRSR since the beginning of the project, but not yet a return to the optima of the 1970s. Specifically, while continued degradation in grassland has been initially contained, results are still far from the desired objective, ‘grassland coverage increasing by an average of 20%-40%’. In contrast, wetlands and water bodies have generally been restored, while the water conservation and water supply capacity of watersheds have increased. Indeed, the volume of water conservation achieved in the project meets the objective of a 1.32 billion m3 increase. The effects of ecological restoration inside project regions was more significant than outside, and, in addition to climate change projects, we concluded that the implementation of ecological conservation and restoration projects has substantially contributed to vegetation restoration. Nevertheless, the degradation of grasslands has not been fundamentally reversed, and to date the project has not prevented increasing soil erosion. In sum, the effects and challenges of this first-stage project highlight the necessity of continuous and long-term ecosystem conservation efforts in this region.

Key words： Three-River Source Region; ecological conservation and restoration; ecosystem monitoring and assessment; ecological effects

Cite this article

SHAO Quanqin , CAO Wei , FAN Jiangwen , Lin Huang , XU Xinliang . Effects of an ecological conservation and restoration project in the Three-River Source Region, China[J]. Journal of Geographical Sciences, 2017 , 27(2) : 183 -204 . DOI: 10.1007/s11442-017-1371-y

1 Introduction

The continued degradation of ecosystems in the Three-River Source Region (TRSR) as a result of the combined effects of climate change and human activities has been of major concern to the community. Indeed, with this in mind, the State Council approved ‘The general planning on ecological conservation and restoration in the TRSR nature reserve in Qinghai Province’ (abbreviated here to ‘The Plan’) in 2005, and decided to invest RMB 7.5 billion yuan in undertaking the first stage of the project (PGQP, 2003), aimed at curbing ecological deterioration in conservation areas, improving and consolidating the results of ecological conservation and restoration, and laying the foundations for later, large-scale implementation of ecological conservation and restoration. Thus, a comprehensive scientific understanding of the ecological effects of the project to date is critical for further effective implementation and scientific management of ‘The Plan’.
A large number of similar domestic and foreign ecological monitoring and assessment projects have been carried out, including the United Nations Millennium Ecosystem Assessment (MA) program which proposed new concepts in ecological assessment, and established a conceptual framework for assessing ecosystem services, based on qualitative judgments of literature (MEA, 2003). In the US, ecosystem condition assessments have been carried out at the national scale using indicators including distributions and patterns of ecosystems, chemical and physical characteristics, products and services, landscape pattern, and the species present in ecosystems (Heinz Center, 2008). Since 2011, on the basis of these data, the US has been developing a ‘National Ecological Observatory Network’ (NEON) to monitor the biosphere (Abbot et al., 2015). Also in North America, Canada has developed an ecological monitoring and assessment network to assess the state of the environment based on long-term observational data (Vaughan et al., 2001). In China, ecological quality has been typically quantified using weight and normalization methods, as well as indicators including biological abundance, vegetation coverage, water network density, land degradation, and pollution load. These approaches are simple, but they lack key indicators of ecosystem services (CNEMC, 2004; EPIS of PRC, 2006; Li et al., 2006). Also, a series of systematic ecological assessments have been carried out at different scales from site to regional, such as the ‘Western Ecosystem Comprehensive Assessment’; however, a systematic and comprehensive evaluation system has not been developed yet (Liu et al., 2006; Guo et al., 2016).
Internationally, key ecological projects stemmed from the ‘Roosevelt Project’ initiated in the US in 1934, including a range of initiatives carried out later around the world, such as the ‘Stalin Plan for Reforming Nature’ in the Former Soviet Union, the ‘Green Dam Project’ in North Africa, the ‘Green Plan’ in Canada, the ‘Watershed Management Plan’ in Japan, the ‘Forestry Ecological Engineering’ project in France, the ‘National Afforestation Program’ in the Philippines, the ‘Social Forestry Program’ in India, the ‘Green Watershed Management Plan’ in South Korea, and the ‘Southern Himalayas Ecological Restoration Project’ in Nepal (Li, 2007). Evaluation of these ecological restoration projects began in the 1950s as the Soviet Union, the United States, France, and Japan carried out evaluations of forest ecological services on the basis of in situ observations and other approaches (Xu, 1992; Wang et al., 2000), to analyze the ecological, economic, and social benefits from a sustainable development perspective (Liu, 2006). Subsequently, evaluation of the effects of ecological projects has evolved from the use of qualitative to more quantitative approaches.
China first carried out a pilot evaluation on the comprehensive effects of forestry ecological engineering in 1989. Since then, a series of systems of evaluation have been developed afor the ‘Three-North Shelter Forest Program’, the ‘Grain for Green Project’, the ‘Natural Forest Protection Project’, and other major ecological initiatives. Specifically, the normalized difference vegetation index (NDVI) and vegetation coverage (Cai, 2009), the amount and value of ecosystem services (SFA, 2014), as well as other ecological service indexes, including water regulation, soil and water conservation, sand-fixing, microclimate improvement, and agricultural non-point source pollution control (Yu et al., 2010; Xiao et al., 2012) have all been used to evaluate the effects of ecological projects in China. Subsequently, methods including empirical investigation, analytic hierarchy processing, and ecosystem value estimation have been widely adopted in China as part of ecological evaluation process (Hu et al., 2010). National standards for the evaluation of ecological projects have also been enacted (i.e. National Standards of the P.R.C., 2009; SFA, 2015), and national evaluation reports on project effectiveness have been released (SFA, 2014). However, existing assessments of ecological projects lack systematic index systems; thus, it is not currently possible to assess how well projects meet the targets set at initiation. A further widespread issue is that many existing efforts tend to use just the single year before project implementation as the ‘baseline’, rather than considering a longer-term, or more stable background. In many cases, this leads to an inaccurate assessment of project effects.
Thus, in order to effectively evaluate the ecological effects of the first-stage project in the TRSR, we improved the study in three aspects. First, an integrated approach was taken by combining in situ observations with remote sensing, and process-based models. Second, a comprehensive index system for the evaluation of ecological effect was proposed that takes ecosystem structure, quality, and services into account. Third, ‘dynamic process of ecological background’ were used for evaluation. Overall, our evaluation is expected to quantify the effects of the ecological restoration project, and to provide scientific support for the future of this conservation and restoration project as it moves into a second phase.

2 Materials and methods

2.1 Study area

The TRSR is located in the hinterland of the Qinghai-Tibet Plateau. As the source region for the Yangtze, Yellow, and Lancang rivers, which together supply about 40 billion m3 of water downstream each year, the TRSR is often referred to as the ‘Chinese water tower’. The region covers an area of 363,000 km2, with grassland, wetland, forest, and cropland accounting for 65%, 8.5%, 4.7%, and 0.3% of the regional total area, respectively (Xu et al., 2008). Grassland in this region is mainly comprised of alpine meadow and alpine grassland, which accounts for 76% and 23% of the total grassland area, respectively. The first stage of the TRSR ecological conservation and restoration project, implemented between 2005 and 2012, comprised 22 sub-projects classified into three categories: ecological protection, construction of infrastructure to support the livelihood and productivity of farmers and herdsmen, and supporting projects. Overall, the project implementation area included 18 nature reserves (Figure 1), covering an area of 152,300 km2, accounting for 21% of the total area of Qinghai Province, and 42% of the TRSR, respectively.
Figure 1 Distribution map of nature reserves in the TRSR, Qinghai Province, China

2.2 Assessment index system

In terms of scientific applicability and operability, the index series used for assessing the effects of this project was built based around the integrated assessment indicator system for grassland ecosystems in the TRSR (Liu et al., 2009), as well as a local standard, ‘technical specification of ecological effects assessment of ecosystem protection and recovery projects in the TRSR’ (LSQP, 2014), developed when planning the targets of this ecological project. As outlined in Table 1, the index series included four major criteria groups broken down into 15 first class, and 75 second class indexes (Table 1).
Table 1 Index series used for assessment of the ecological effect of the TRSR ecological projection and restoration project
Category of index Evaluation index
First class indexes Second class indexes
Ecosystem
macrostructure		 Ecosystem macrostructure Ecosystem classification area, rate of change, dynamic degree
Ecosystem macroscopic structural change index
Ecosystem quality Grassland degradation and recovery Grassland degradation and recovery classification area, proportion of degraded grassland and recovered grassland, grassland degradation change index
Vegetation status Vegetation biomass, vegetation coverage, net primary productivity (NPP), vegetation change condition index
Macro-ecological situation Land cover status index, land cover conversion index
Plant species diversity Species richness, species importance value, diversity index, evenness index
Environmental quality Surface water quality index, soil environmental quality index, air quality index
Upper limit of permafrost depth
Ecosystem quality change index
Ecosystem
services		 Water regulation River runoff in dry season, water regulation volumes, water regulation service retention, river runoff in summer flood season, runoff adjustment coefficient
Soil conservation Sediment concentration, soil erosion, soil retention, soil conservation service
Forage supply Grassland yield, grassland theoretical stock-carrying capacity
Water supply River runoff, lake area, lake volume, glacier area, ground water resources
Ecosystem services change index
Ecosystem change factors Climate change Temperature, precipitation, wet coefficient
Human activities Ecological project, grazing pressure index
Contributions influenced by ecological project and climate change Ecosystem project changes influence index
Contributions to NPP change, water regulation service, soil conservation service, sand fixing service influenced by ecological project
Contributions to NPP change, water regulation service, soil conservation service, sand fixing service influenced by climate change

2.3 Data acquisition and processing

2.3.1 Ground monitoring and field observation
The terrestrial ecosystem monitoring system for the TRSR encompasses 492 sites (Figure 2) that are mainly used to monitor changes in different ecosystems (e.g. grassland, forest, wetland, and desert), hydrology and water resources, soil conservation, meteorological elements. In total, millions of observational data points regarding vegetation productivity, plant compositional structure, soil properties, grassland degradation, hydrology, and meteorology were acquired between 2005 and 2012 by this monitoring system. In addition, during the course of project implementation, a great deal of fieldwork was also conducted, including surveys for remote sensing interpretation and verification of land use and cover change (LUCC) and grassland degradation (Liu et al., 2008; Xu et al., 2008), sampling surveys to measure the water holding capacity of soil, soil erosion 137Cs (Shao et al., 2011; Sun et al., 2011), investigations of soil physical and chemical properties, grassland plots to investigate and verify grassland productivity and grass yield simulation results (Fan et al., 2010; Wang et al., 2010), as well as cyclic sampling data collected from five, large 5 km2 plots that were interrogated using remote sensing and ground-scale transformation (Bing et al., 2012).
2.3.2 Remote sensing interpretation and parameter inversion
Landsat MSS and TM images taken in the 1970s, the 1990s, in 2004, and by the HJ satellite in 2012 were interrogated to interpret LUCC on the basis of earth science, climatology, and ecological data (Xu et al., 2008). Thus, on this basis, we generated spatial datasets for forests, grasslands, croplands, wetlands and water, settlements, and other ecosystems, and analyzed the temporal and spatial dynamics of each ecosystem. Spatial data at the 1:100,000 scale for grassland degradation, and trends in degraded grassland ecosystems, in the TRSR between the 1970s and 1990s, and between the 1990s and 2004, were produced using the remote sensing grassland degradation/restoration classification system and by taking both forms and causes into account (Liu et al., 2008). Thus, the existing land use dynamic index model was improved and developed into an ecological situation change index (i.e. a land cover conversion index) (Zhao et al., 2010) that was then used to quantify the changing status as the ecosystems.
Figure 2 Distribution map of ecosystem field monitoring networks in the TRSR
2.3.3 Model simulation
The Global Production Efficiency Model (GLOPEM) was augmented and used in this study, with model parameters localized using large plot data obtained by cyclic sampling (Wang et al., 2010). Specifically, the NDVI at three different scales (TM 30 m, MODIS 250 m, and 1 km) was used to verify the results of model parameters and simulations by establishing conversion relationships between the three scales (Chen et al., 2012). NPP data at 16-day intervals and at 1 km spatial resolution within the TRSR between 1988 and 2012 were simulated, and grassland types, seasonal pasture zones, livestock statistics, earliest survey of grassland resources, and monitoring data on grassland resources in the TRSR were input to simulate grassland yield and the grazing pressure index using GLOPEM, the Underground Productivity Model (Fan et al., 2010), and the algorithm of the Grazing Pressure Index (Fan et al., 2011).
The precipitation storage method was used to simulate the water regulation capacity of forests, grasslands, and wetland ecosystems in the TRSR. Specifically, an improved K-value correction method was developed to avoid spatial disparities by using ground surveys, remote sensing, meteorological data, and average river runoff on a year-by-year basis. Indeed, using runoff data, the efficiency coefficient R was determined, which denotes the runoff reduction capacity of an alpine meadow ecosystem compared to bare land (Wu, 2014).
Water erosion in the TRSR was calculated using the Revised Universal Soil Loss Equation (RUSLE) (Renard et al., 1997). For this analysis, parameters in RUSLE including the rainfall erodibility factor (R), the soil erodibility factor (K), slope length and steepness factor (LS), the cover-management factor (C), and the support practice factor (P) were all localized. Intervals for rainfall erodibility and grassland coverage factors were set to 16 days to avoid time asynchronism. An observational dataset containing annual sediment concentrations from four major hydrological stations in the Yangtze and Yellow rivers was used for validating the results of RUSLE, and the R2 was set to 0.72.

2.4 Project ecological effects

As part of this assessment, we proposed the concept of a ‘dynamic process of ecological background’, in which we consider both the average ecosystem status 5-10 years before the start of the project, and trends in ecosystem change over the past 20-30 years, as an ecological background. As a result, this ‘dynamic process of ecological background’ solves the uncertainty in ecological effect assessment that is caused by periodicity of rainfall, helps to master changing processes in the ecosystem accurately, and enables scientific assessment of ecological restoration.
Based on the ‘dynamic process of ecological background’, both the objectives of the project, and a comprehensive assessment of the project ecological effects were carried out. Comparisons between average status and trends in many indicators, including ecosystem structure, quality and services, before, and after, the project, as well as inside, and outside, nature reserves were made. Simulated results in both average climate, and real climate, modes were generated and compared, and ecological effects were assessed in the context of climate change.
On the basis of the specific project assessment objectives, the evaluation period was divided into four categories: 30 years before the implementation of the project (mid-1970s to 2004), 14 years before the implementation of the project (1990-2004), eight years before the implementation of the project (1997-2004), and the project period (2004-2012).

2.5 Factors contributing to ecosystem change

Climate change and implementation of the TRSR ecological project are the main factors contributing to ecosystem change in this region. Thus, in order to determine the relative contributions of these two factors to ecosystem change, a number of datasets including NPP, soil erosion, and water regulation capability, simulated under both average and real climatic conditions, were compared. Results simulated on the basis of average climatic variables reflect the effects of the ecological project with climate factors excluded, while results simulated using real climatic variable are a synthesis both of climate change and the ecological project. Therefore, contribution rates of climate change and the ecological project to ecosystem change can be determined by contrasting the results under average climate conditions and real climate conditions before and after the implementation of the project (hereafter before and after the project). Specifically, separate contributions can be calculated as follows:
\[C_{project}=\frac{G_{Al}-G_{Ap}}{G_{Rl}-G_{Rp}}\ \ (1)\]
Cnature=1-Cproject (2)
where Cproject denotes the contribution rate of the ecological project; Cnature is the contribution rate of natural factors (dominated by climate change); GAl and GAp are indicator values after and before the project under average climate conditions; and GRl and GRp denote the indicator values after and before the project under real climatic conditions.

3 Results

3.1 Macro-ecological change

Since the implementation of the ecological project, water-bodies in the TRSR have been partially expanded, and former desert ecosystem has been partially transformed into grassland ecosystem. Indeed, the overall ecosystem structure has gradually developed in a benign direction; 30 years before the initiation of this project, the net decreases in grasslands and wetlands (including water-bodies) were 1389.9 km2 and 375.14 km2, respectively, while the net increase in desert was 674.38 km2. In contrast, over the 8-year project period, grassland area has increased by 123.70 km2, wetland and water areas have increased by 279.85 km2, and the desert ecosystem has decreased by 492.61 km2. Use of the ‘ecological situation change index’ shows that, while the macro-ecological situation was getting worse over the whole area 30 years before the project, it improved over the course of the 8-year project period (Figure 3).
Annual average vegetation cover in 2005-2012 also improved markedly compared with the situation between 1998 and 2004. Indeed, vegetation cover increased in 79.18% of the TRSR, while just slightly, and obviously, improved areas accounted for 43.67% and 35.51%, respectively (Figure 4).
Figure 3 Distribution of ecosystem types in the TRSR in 2012, and the ecological change index from the 1970s to 2012
Figure 4 Changes in average vegetation cover before, and after, implementation of the TRSR project

3.2 Trends in grassland degradation and recovery

According to ecological background survey findings, the degradation pattern in the TRSR had been basically formed since the 1970s; around 40.1% of grassland in this region was degraded to different degrees between the 1970s and 2004. However, after this project, 68.52% of degraded grassland was unchanged, 24.85% was slightly improved, and 6.17% was greatly improved. Latest degradation represented 0.12%, while areas of aggregated degradation represented only 0.34% (Figure 5).
Figure 5 Distribution of degraded grassland in the TRSR over the period 1990-2004 (a), and grassland restoration over the period 2004-2012 (b)
From 1988 to 2004, the average amount of grass production in the TRSR was 533 kg/hm2; these grasslands were also 1.42 times totally overgrazed, even reaching as much as 2.5 times overgrazed between the winter and spring. During the eight years of this project, grass production reached 694 kg/hm2, about a 30.31% increase, while ‘ecological migration’ and a reduction in livestock were implemented on some severely degraded grassland at an average reduction rate of 20%. As a result of these two factors, the grazing pressure index decreased 36.1% (Figure 6).
From 2005 to 2012, vegetation coverage of natural grassland was 69%-83% and showed an increasing trend, especially in temperate steppe; this means that the degrading grassland trend in the TRSR was initially contained, and project implementation had both a direct and positive effect on grassland coverage. However, because it is very hard to improve alpine grassland areas as they are limited by temperature, precipitation, altitude, and other factors, the project goal to improve vegetation cover 20%-40% over the TRSR was not achieved.
Figure 6 Comparative changes in grassland yield before, and after, implementation of this project, as well as annual variation in the livestock pressure index in the TRSR

3.3 Water regulation and water supply services

The water regulation services in forested and grassland ecosystems improved from 1997 to 2012 (Figure 7). Over this period, the average annual water regulation volume was 15.36 billion m3/yr, while the per unit amount was 430.67 m3/hm2/yr. From 1997 to 2004, the average annual water regulation volume in forested and grassland ecosystems was 14.249 billion m3, and the trend was 0.166 billion m3/10yr. From 2005 to 2012, the average annual water regulation volume increased 15.6%, reaching 16.471 billion m3/yr, while the variation trend was 1.93 billion m3/10yr. In the Yangtze, Yellow, and Lancang river basins, water regulation volumes also improved as a result of the ecological project, showing increases of 923 million m3/yr, 1.048 billion m3/yr, and 130 million m3/yr, respectively.
Overall, the net increase in water and wetlands in the TRSR from 2004 to 2012 was 279.85 km2, 9.11% of that in 2004. Water regulation volume also improved from 24.239 billion m3/yr to 24.424 billion m3/yr over this period.
The total increase in water regulation and water supply was around 2.41 billion m3, more than the project objective, an increase of 1.32 billion m3.
Figure 7 Changes and annual variation in water regulation volume of forested and grassland ecosystems in the period 1997-2012
Of particular note, the annual runoff in the Yellow River Basin recovered remarkably compared with levels before the project, while the annual runoff at Tangnaihai and Jimai hydrological stations increased 3.69 billion m3 and 1.71 billion m3, respectively (Figure 8). Although this total increase in annual runoff was more than the project objective, an increase of 1.2 billion m3, the declining trend seen since the 1970s had not yet been reversed. Indeed, runoff from the Tuotuohe hydrological station in the Yangtze River Basin has continued to increase as a result of climate warming and accelerated melting of snow and ice, while the annual runoff at Zhimenda hydrological station recovered fast, increasing 3.92 billion m3/yr (Figure 8) compared with before the project. Of particular note, the declining trend in annual runoff in the Yangtze River Basin has been initially curbed after a long time.
Figure 8 Annual total runoff at major hydrological stations in the source regions of the Yangtze and Yellow rivers

3.4 Soil conservation services

From 1997 to 2012, soil retention in the TRSR conformed to an upward trend, with an average annual value of 635 million t/yr (Figure 9). Indeed, due to vegetation recovery, soil conservation capacity has improved remarkably; average annual soil retention changed from 546 million t/yr to 723 million t/yr, a 32.5% increase. However, in spite of this, soil erosion still showed a slight upward trend from 1997 to 2012 (Figure 10); from 2005 to 2012, average annual soil erosion was 320 million tons, an increase of 20 million tons (16 million m3) compared with 1997-2004. These data show that, in this regard, one objective of ‘The Plan’ was not achieved. Indeed, precipitation increased markedly from 2005 to 2012 in the TRSR, which not only helped vegetation recovery, but also led to an increase in rainfall erosivity, the main reason for the increase in soil erosion.
Figure 9 Changes, and annual variation, in soil erosion (a) and soil retention volume (b) in the period 1997-2012

3.5 Dynamic ecological status analysis of key project areas

High quality ecosystems in the TRSR, including forests, grassland, wetland and water, decreased by 386 km2 from 1990 to 2014, while deserts and some other ecosystems increased by 389.2 km2. Indeed, outside the project area, high quality ecosystems saw a net decrease of 98.8 km2, while deserts and other ecosystems increased by 97.4 km2. From 2005 to 2012, high quality ecosystems in the project area increased by 252.2 km2, more than the 173 km2 increase seen outside the project area. Deserts and other ecosystems decreased by 252.2 km2 inside the project area but by only 180.8 km2 outside the project area (Table 2).
Table 2 Changes in ecosystem area (km2) inside, and outside the nature reserves before and after project implementation
Period Regions Cropland Forest Grassland Wetland Desert Others
1990-2004 (before the project) Nature
reserves		 -3.22 -12.8 -362.4 -10.8 +387.6 +1.6
Outside nature reserves +1.32 -0.7 -83.4 -14.7 +43.8 +53.6
2004-2012 (after the project) Nature reserves Unchanged +12.1 +135.2 +104.9 -192.1 -60.1
Outside nature reserves +7.84 +3.3 -11.4 +181.1 -300.5 +119.7
Comparison after and before the project Nature
reserves		 Reduced at first then unchanged Reduced at first then increased Reduced at first then increased Reduced at first then increased Increased at first then
reduced		 Increased at first then reduced
Outside
nature reserves		 Continuously increased Reduced first
then increased		 Continuously reduced Reduced at first
then increased		 Increased at first
then reduced		 Continuously
increased
Comparison of inside and
outside		 Inside is better than outside Inside is better than outside Inside is better than outside Inside is better than
outside		 Inside is better than outside Inside is better than outside

Note: ‘-’ indicates decrease, ‘+’ indicates increase; ‘inside’ indicates the reserve, ‘outside’ indicates outside the reserve.

From 1990 to 2004, the ecological change indexes of 18 nature reserves were all negative, showing that the ecological status of each nature reserve had decreased. Of these, the ecological change index of Animaqing was the worst, followed by Xingxinghai and Zaling-Eling Lake. However, in contrast, from 2004 to 2012, the ecological change indexes of all nature reserves were positive with the exception of Nianbaoyuze; these data show that ecological status has improved as a result of this project, especially in Xingxinghai, Zaling-Eling Lake, and Tongtian River (Figure 10).
From 1990 to 2004, the area of degraded grassland in nature reserves was 43490.67 km2, accounting for 49.4% of degraded grassland in the TRSR. However, from 2005 to 2012, this was improved markedly; areas of degraded grassland inside nature reserves, outside nature reserves, and in the entire TRSR were 7.30%, 5.05%, and 6.16%, respectively (Table 3).
Average annual vegetation coverage from 1990 to 2004 inside nature reserves was 5.57% more than that was outside, but increasing to 6.19% from 2005 to 2012. In contrast, from 1997 to 2004, average annual NPP inside nature reserves was 46.02 g C/m2 higher than that measured outside, increasing to 58.86 g C/m2 higher from 2005 to 2012 (Table 4).
Data show that vegetation coverage in nine nature reserves, including Zhongtiejungong, Guozongmucha, Yueguzonglie, Zhalin-Erlin Lake, Xingxinghai, Nianbaoyuzhe, Geladandong, Animaqin, and Tongtianhe, decreased from 1997 to 2004 but increased from 2005 to 2012. Indeed, in the other nine nature reserves vegetation coverage increased both from 1997 to 2004 and from 2005 to 2012. Rates of increase in vegetation coverage in 13 nature reserves were higher than those recorded outside, and average annual NPP from 1990 to 2004 in all nature reserves increased compared with 2004-2012. Because increases inside nature reserves were higher than those recorded outside, comparisons show that this project has played a very important role in vegetation recovery across the TRSR, and that vegetation recovery inside nature reserves has been more remarkable than that seen in other regions (Figure 11).
Figure 10 Ecological change indexes for nature reserves from 1990 to 2004 (a) and from 2004 to 2012 (b)
Table 3 Restoration areas of grassland, 2004-2012
Region Degraded grassland, 1990-2004 Obviously improved grassland, 2005-2012
Area (km2) Proportion of degraded grassland in entire area (%) Area (km2) Proportion of degraded grassland in each area (%)
Nature reserves 43490.67 49.4 3173.00 7.30
Outside nature reserves 44591.40 50.6 2252.81 5.05
The TRSR 88082.07 100 5425.81 6.16
Table 4 Comparisons of vegetation coverage and NPP inside, and outside, nature reserves before, and after, project implementation
Period Region Vegetation coverage (%) NPP (g C/m2)
1997-2004 Nature reserves 47.15 246.86
Outside nature reserves 41.58 200.84
Difference between inside and
outside		 5.57 46.02
2005-2012 Nature reserves 50.34 306.23
Outside nature reserves 44.15 247.37
Difference between inside and
outside		 6.19 58.86
Difference between former and latter periods Nature reserves 3.19 59.37
Outside nature reserves 2.57 46.53
Difference between inside and
outside		 0.62 12.84
Figure 11 Changes in vegetation coverage and NPP in nature reserves before, and after, project implementation

3.6 Attribution analysis of ecosystem changes

3.6.1 Effects of the ecological project on ecosystems
On the basis of simulation results, climate change is a dominating influence on vegetation recovery in the TRSR. However, in the project area, and especially in the Yellow River Basin, engineering techniques have actually made more of a contribution to ecosystem restoration.
Indeed, in key project areas, a number of different ecological restoration measures were implemented. Of these, the ‘Restoring Grazing Land to Grassland Project’ reduced the number of livestock in the project area, which decreased the grazing pressure index. In addition, the ‘Black Beach Grassland Treatment Project’ and the ‘Rodent Control Project’ helped to restore degraded grassland as well as to prevent the occurrence of new degradation. Artificial precipitation increased soil moisture and the area of lakes and wetlands, while the recovery of degraded grasslands and an increase in grassland productivity promoted water regulation and played an important role in ecology and production of downstream.
3.6.2 Effects of climate change on ecosystems
Temperature and precipitation in the TRSR both show a decreasing trend from southeast to northwest. Indeed, while temperatures in this region have continued to get warmer, precipi-tation has changed periodically; from 1975 to 2004, the climate in this region was getting warmer and drier. Average annual temperature and precipitation were -0.58℃ and 470.6 mm, respectively, while their trends were 0.42℃/10yr and -9.3 mm/10yr, respectively. In contrast, from 2004 to 2012, the climate was getting warmer and wetter; average annual temperature and precipitation were 0.48℃ and 518.7 mm, respectively, and their trends were 0.19℃/10yr and 68.4 mm/10yr, respectively (Figure 12). Temperatures rose most in the mid-east of the region, and least in the northwest, while precipitation showed a remark-able increase in the mid-west (Figure 13). Warming climate led to an advancing rate of vege-tation re-greening and melting of permafrost and glaciers increased runoff. Coupled with this increase in precipitation and runoff, water area increased, and vegetation began to experience a more favorable growing environment. These effects led to faster vegetation recovery and a decreasing rate of desertification.
Figure 12 Variations in annual average temperature and annual precipitation in the TRSR, 1975-2012
3.6.3 Contribution rates of the ecological project and climate change to ecosystem changes
Under real, and average, climate conditions, changes in NPP were 21.79 and 13.49 g C/m2/yr before, and after, the project; thus, the contribution rate of increasing NPP from the ecological project was 61.9%, while it was 38.1% due to the influence of climate change. In contrast, water regulation changes under the two climate conditions were 2.222 billion and 534 million m3/yr, respectively; thus, the contribution rate due to the ecological project was 24%, while 76% was due to climate change. Water erosion changes under the two climate conditions were 2000 and -1600 t/yr; thus, the contribution rate of the ecological project to the increase in water erosion was -80%, while the influence of climate change was 180% (Table 5).
Figure 13 Variations in annual average temperature and annual precipitation in the TRSR, 2004-2012
Table 5 Evaluation indexes for 1997-2004 and 2005-2012 under real, and average, climate conditions
Evaluation index Difference between 1997-2004
and 2005-2012		 Contribution rate of ecological project Contribution rate of climate change
Real climate conditions Average climate conditions
NPP (g C/m2/yr) 21.79 13.49 61.9% 38.1%
Water conservation (108 m3/yr) 22.22 5.34 24% 76%
Soil water erosion (t/yr) 2000 -1600 -80% 180%
On the basis of these results, it is clear that vegetation recovery in the TRSR was actually affected by two factors: the ecological project, and climate change (i.e., precipitation increase and temperature rise). Although climatic factors before, and after, the project did not change under average conditions, vegetation parameters in the GLOPEM, RUSLE, and water regulation models could partly be influenced by climate change. Thus, the contribution rate of the ecological project might be overestimated; the method used to determine this contribution rate should be improved in future studies.

4 Discussion and conclusions

It is worth noting that coverage of the TRSR ecological conservation and restoration project actually only accounts for 40% of this region. Throughout the project, while the trend in grassland degradation was partially curbed, only 6.17% of degraded grassland obviously recovered, and grassland coverage improved rather than community structure. All-in-all, 68.52% of degraded grassland in this region remained unchanged, while some in the Yellow and Yangtze river basins remained degraded at the end of the project, especially in Maduo, Qumalai, the north of Chenduo, and the southeast of Zhiduo. Grassland degradation has thus not been radically curbed across the region as a result of this project.
Over the implementation period of this project, although grassland increased by 123.70 km2, this accounts for only 8.9% of the net loss in the 1970s. In contrast, desert area decreased by 492.61 km2, accounting for 73% of the area that increased in the 1970s. Finally, because wetlands and water area increased by 287.87 km2, accounting for 76.7% of the area that was lost in the 1970s, it can be argued that ecosystem recovery was not as good as it could have been.
While the runoff in the Yellow River Basin increased as a result of this project, observational data from Tangnaihai hydrological station shows that this is still at a lower level than it was in the 1970s and 1980s (Table 6). Indeed, because the continued increase in runoff recorded at the Tuotuohe hydrological station in the Yangtze River Basin is mostly the result of melting of permafrost and glaciers due to climate warming, this will be unsustainable over the long-term.
Indeed, implementation of this project has also not yet contained the increasing trend in soil erosion; compared with 1997-2004, annual average soil loss has increased by 15.7 million m3/yr at the end of this project. According to inter-annual variability in sediment concentrations recorded at each hydrological station (Figure 14), soil erosion generally showed an increasing trend from 2004 to 2012, most likely the result of grassland degradation. Thus, although vegetation coverage has increased markedly throughout the TRSR, soil erosion has still increased; this is likely because vegetation coverage is just one factor that prevents soil erosion. Increasing vegetation cover can promote soil retention capabilities to some extent, but the recovery of the root layer is more important and occurs over much longer timescales.
Table 6 Variations in annual runoff at the major control hydrological stations in the Yangtze and Yellow river basins (108 m3)
Period Yellow River Basin Yangtze River Basin
Tangnahai station Jimai station Zhimenda station Tuotuohe station
(data from May to October)
1975-1980 221.21 46.26 115.85 4.85
1975-1990 236.10 47.90 131.37 6.14
1975-2004 200.65 39.87 124.29 7.52
1975-2011 201.40 41.90 132.40 9.10
1991-2004 165.20 31.26 116.20 9.11
1997-2004 161.00 30.20 122.10 11.70
2004-2011 197.90 47.30 161.30 13.10
Figure 14 Differences in grassland vegetation coverage in the TRSR from 2005 to 2012 compared with the 1980s
In sum, this first-stage project in the TRSR has been promising and effective in general; however, our studies also indicate that existing challenges to the ecological restoration of the TRSR still remain, and that a continued and long-term effort will still be needed.
To conclude, this study has comprehensively assessed the effects of the first phase of an ecological conservation and restoration project in the TRSR. Results lead to three main conclusions.
(1) Overall trends in ecosystem degradation have initially been contained; indeed, as a result of this project, ecosystem structure has gradually improved. For example, local water-body areas in the TRSR have been expanded, and some deserts have been converted into grasslands. Annual average vegetation coverage has remarkably increased, and the macro-ecological situation has improved, but still not to the levels of the 1970s. Indeed, the grassland degradation trend has been initially contained; this project has had a positive effect on improving grass coverage, but the natural characteristics of alpine meadows limit the rate of increase. In contrast, wetlands and water bodies have generally been restored in the region, while the capacity for water regulation and water supply have been improved, and the target of increasing water regulation volume has been achieved. River runoff into the Yellow River Basin shows that the target, a 1.2 billion m3 increase, has been achieved. In addition, soil retention capacity has been improved; indeed, the amount of soil retention continues to increase. However, the soil erosion targets in ‘The Plan’ have not been achieved, as erosion during the project period has increased by 20 million tons.
(2) Key project areas have experienced more improvements in their ecological situation than non-project areas and there is significant spatial heterogeneity. In addition to impacts due to climate, implementations of ecological protection and construction have had obvious, and positive, effects on promoting vegetation recovery inside nature reserves. Indeed, vegetation recovery and ecosystem improvements have enhanced ecosystem services as well as the quality of wildlife habitats. In terms of ‘decreasing livestock and migrating people’, the number of wild animals in this region has increased markedly, especially in the Yellow River Basin, and compared with non-protected areas, the NPP of grasslands inside nature reserves has also clearly increased. Therefore, the ecological conservation and restoration project has led to positive effects in addition to climate impact.
(3) Project effects can be summarized in terms of ‘preliminary containment in degradation, partial improvement in recovery’ within the TRSR. We found that climatic factors (including an artificial rain project) played a dominant role in vegetation restoration, while ecological projects also had a positive effect. Indeed, in the project region, especially key areas around the Yellow River Basin, the contributions of ecological projects to ecosystem restoration are more remarkable.
Overall, the ecological effects of this project are remarkable, and the objectives of ‘The Plan’ have been basically achieved.

The authors have declared that no competing interests exist.

References

Publishing order | Descend order by publishing year | Descend order by cited within
[1]
Abbot M, Dawson T, Clark J et al., 2015. NEON science capability assessment. Clark J et al., 2015. NEON science capability assessment. .

[2]
Bing L F, Shao Q Q, Liu J Y,et al.., 2011. Runoff characteristics in flood and dry seasons in source regions of Yangtze River and Yellow River based on wavelet analysis.Scientia Geographica Sinica, 31(2): 232-238. (in Chinese)

[3]
Bing L F, Shao Q Q, Wang J B, 2012. Heterogeneity and error estimation of grassland biomass based on cyclic sampling approach.Acta Agrestia Sinica, 20(2): 257-267. (in Chinese)From cyclic sampling results of 2008 and 2010 in Qinghai,variogram parameters were used to describe the heterogeneity of above-ground biomass and below-ground biomass.The spatial correlation threshold was 2258.75 and 3720.52 m,respectively.The variation of above ground biomass was greater in Maduo than in Haibei for two years.The variation of above-ground biomass for all the sampling points was smaller in 2010.The below-ground biomass was larger in Zhenqin and Batang than in Haibei for 2008 and 2010.The smallest below-ground biomass was in Maduo.The interannual variation of mean below-ground biomass was smaller in Haibei and Maduo than in Zhenqin and Batang.Estimation errors of both above-ground biomass and below-ground biomass were quite different.The estimation errors increased for both above-ground biomass and below-ground biomass as the sampling distance increased.The lowest value of above-ground biomass,below-ground biomass and their ratios were all at the sampling distance of 2500 meters.

DOI

[4]
Cai B F, 2009. Study on the Monitoring and Evaluation of the Three North Shelterbelt Project. Beijing: Chemical Industry Press. (in Chinese)

[5]
Chen Z Q, Shao Q Q, Liu J Y,et al.., 2012. Analysis of net primary productivity of terrestrial vegetation on the Qinghai-Tibetan Plateau, based on MODIS remote sensing data.Science in China (Earth Sciences). doi: 10.1007/s11430-012-4389-0. (in Chinese)

[6]
China National Environmental Monitoring Centre (CNEMC), 2004. Study on Ecological Environmental Quality Assessment China. Beijing: China Environmental Science Press. (in Chinese)

[7]
Fan J W, Shao Q Q, Liu J Y,et al.., 2010. Dynamic changes of grassland yield in the Three River Headwater Region from 1988 to 2005.Acta Agrestia Sinica, 18(1): 5-10. (in Chinese)The Three River Headwater Region is the source of the Yangtze,Yellow,and Lantsang rivers.The objectives of this study were to analyze the dynamic changes of grassland productivity and explore the natural and human driven mechanisms causing the grassland ecosystem changes.Findings in this study would be applied to the development of scientific strategies and programs for grassland restoration,management,and utilization and assess the effectiveness of the ecological engineering project.Dynamic changes of grassland yield of the region from 1988 to 2005 were analyzed using the GLOPEM model.The results indicate that grassland productivity in the region fluctuated periodically with a 3 to 5 year cycle.The variation coefficient of annual productivity increased from the east to the west of the region and from marsh,alpine meadow,alpine steppe,to temperate steppe grasslands.In general,grassland yield in the region showed an increasing trend during the studied 18-year period,especially a remarkable increase in alpine steppe and grasslands in the west of the region.The analysis indicates that the increased grassland productivity during the 18 years was influenced by climatic change.These findings indicate that we should keep clear-headed understanding to the contingent increase of ecosystem supply function which probably covers up the long-term negative impact of climatic change on the holistic functions of ecosystem.

DOI

[8]
Fan J W, Shao Q Q, Wang J B,et al.., 2011. An analysis of temporal-spatial dynamics of grazing pressure on grassland in the Three Rivers Headwater Region.Chinese Journal of Grassland, 33(3): 64-72. (in Chinese)Temporal-spatial dynamics of grazing pressure on grassland in Three Rivers headwater region in 1988-2005 were analyzed.The results showed that grassland was overgrazed averagely by 1.5 times,and even 2 times in winter-spring pasture in last 18 years.Meanwhile grazing pressure was steadily relieved,especially in winter-autumn pasture,which showed that grassland in Three Rivers headwater region has been utilized reasonably year by year.It is considered that overgrazing is one of the main factors resulting in grassland ecosystem degradation.Thus livestock number should be reduced further to a suitable level in order to restore degraded grassland and protect important functions of ecosystem based on the state ecologic strategy in the region.

[9]
Fryrear D W, Saleh A, Bilbro J D,et al.., 1998. Revised Wind Erosion Equation (RWEQ). Wind Erosion and Water Conservation Research Unit, Technical Bulletin 1, Southern Plains Area Cropping Systems Research Laboratory, USDA-ARS.

[10]
Gong G L, 2014. Research on the spatial-temporal changes of wind erosion in northern China and the influence factors [D]. Beijing: Chinese Academy of Sciences. (in Chinese)

[11]
Guo B, Zhou Y, Zhu J F,et al.., 2016. Spatial patterns of ecosystem vulnerability changes during 2001-2011 in the Three-River Source Region of the Qinghai-Tibetan Plateau, China.Journal of Arid Land, 8(1): 23-35.

[12]
Hu Y F, Liu J Y, Qi Y Q,et al.., 2010. Positivist analysis on the effects of ecological projects in the farming-pastoral transition belt of Inner Mongolia Autonomous Region.Geographical Research, 29(8): 1452-1460. (in Chinese)As the participants and affected persons of ecological projects in the Inner Mongolia Autonomous Region during the past decade, local farmers should be involved when we assess the effects and efficiency of those ecological projects, and their comments and favorites should also be paid more attention when the government makes decisions on the future ecological project planning. Using questionnaire-based investigation and positivist analysis methods, this paper aimed to explore the ecological project effects in the typical farming-pastoral transitional zone of northern China. The survey covered 144 families in 3 counties of Inner Mongolia (Taipusi Qi, Wuchuan County, and Siziwang Qi). Results showed: (1) Returning cropland to forest/grassland, enclosing grassland to prevent grazing, and seasonal delaying grazing were the 3 main types of ecological project. A high participation rate was closely related to the family's core business. (2) Based on an integrated assessment taking into account water, soil, atmospheric and biological factors, local farmers' responses referred that they did not think the past ecological projects brought obvious and favorable post-effects for the local environments, although our detailed study indicated that ecological projects had prevented local environmental degradation, reduced sandstorm frequency, and increased the number of wild animal species. (3) Family income and the productivities of tillage and husbandry were promoted after the implementation of ecological projects, though the gross yields of grain and livestock were decreased. The critical factors affecting family income included farming/herding production technology and geographical location. (4) Limiting livestock's amounts, returning farmland, and protecting degraded grassland were the 3 most favorite measures to protect/restore local ecosystems for local framers. Further measures for returning farmland and eco-migration would be supported if compensation was enough. The rate of support was related to family income, available labor transfer approaches, and subsequent guarantees.

DOI

[13]
Li S D, 2006.China Ecological Status Report 2005: Ecological Comprehensive Index & Ecological Status Assessment. Beijing: Science Press. (in Chinese)

[14]
Li S D, 2007. World’s Important Ecological Engineering. Beijing: Science Press. (in Chinese)

[15]
Liu J Y, Shao Q Q, Fan J W, 2009. The integrated assessment indicator system of grassland ecosystem in the Three-River Headwater’s Region.Geographical Research, 28(2): 273-283. (in Chinese)Based on the MA conceptual framework and characteristics of grassland ecosystem in the Three-River Headwaters region,we proposed an integrated assessment index system of grassland ecosystem of the region.In this system,there are 4 indicator groups,of which,15 indicators at the first level,and 75 indicators at the second level,which are used for assessing grassland ecosystem structure,supporting,regulating and provisioning services.The integrated assessment index system of grassland ecosystem is aimed at characteristics of grassland ecosystem in the Three-River Headwaters region in the eastern Tibetan Plateau and the human demands for this region.This system includes a set of indicators of land cover and grassland degradation for assessing the grassland ecosystem structure,and a set of indicators,for example,primary production and soil formation,etc.,for assessing the ecosystem supporting service,and a set of indicators,for example,carbon,evaporation and transpiration,run-off,etc.,for assessing the ecosystem regulating service,and a set of indicators,such as,water and grassland carrying capacity,etc.,for assessing the ecosystem provisioning service.In this system,we designed remote sensing classification system on grassland degradation in order to make a dynamic analysis on the process of grassland ecosystem degradation in the decade time scale,and remote sensing classification system on grassland degradation trend for assessing ecological effect of the recent ecological restoration project in the year time scale.

DOI

[16]
Liu J Y, Shao Q Q, Xu X L, 2008. The spatial and temporal characteristics of grassland degradation in the Three-River Headwater’s Region in Qinghai Province.Acta Geographica Sinica, 63(4): 364-376. (in Chinese)Using MSS images in the middle and late 1970s, TM images in the early 1990s and TM/ETM images in 2004, grassland degradation in the Three-River Headwaters Region is interpreted through analysis on RS images in two time series, then the spatial and temporal characteristics of grassland degradation since the 1970s in the Three-River Headwaters Region are analyzed. The results show that grassland degradation in the Three-River Headwaters Region is a continuous changing process which has large area of influence and long time scale, and the drastic intensification phenomenon does not exist in the 1990s as a whole. Grassland degradation pattern in the Three-River Headwaters Region took shape initially in the middle and late 1970s, since the 1970s, this degradation process has taken place continuously, characterizing obviously different rules in different regions. Such as, in humid and sub-humid meadow grassland, grassland firstly fragmentizes, then the degree of vegetation coverage decreases continuously, and finally "black-soil-patch" degraded grassland formed. But in semiarid and arid steppe regions, the degree of grassland vegetation coverage decreases continuously, and finally desertification formed. Because grassland degradation has obvious regional diversity, grassland degradation in the Three-River Headwaters Region could be classified into seven regions, and each region has different characteristics in type, grade, scale and time process of grassland degradation.

DOI

[17]
Liu J Y, Yue T X, Ju H B et al., 2006. Integrated Ecosystem Assessment in Western China. Beijing: China Meteorological Press. (in Chinese)

[18]
Liu Y, 2006. Study on post-evaluation of theory and application of the forest ecological engineering in China [D]. Beijing: Beijing Forestry University. (in Chinese)

[19]
Local Standard of Qinghai Province (LSQP), 2014. Technical Specification of Ecological Effects Assessment of Ecosystem Protection and Recovery Projects in Sanjiangyuan Region (DB63/T1342-2015).

[20]
Millennium Ecosystem Assessment (MEA), 2003. Ecosystems and Human Well-being. Washington: Island Press.

[21]
National Standards of the People’s Republic of China, 2009. Evaluation in Project for the Construction of Conversion of Cropland to Forest (GB/T23233-2009). Beijing: Standards Press of China. (in Chinese)

[22]
Renard K G, Foser G R, Weesies G A,et al.., 1997. Predicting soil erosion by water: A guide to conservation planning with the Revised Universal Soil Loss Equation (RUSLE). Washington: US Department of Agriculture, Agricultural Research Service.

[23]
Shao Q Q, Liu J Y, Huang L,et al.., 2013. Integrated assessment on the effectiveness of ecological conservation in The TRSR National Nature Reserve.Geographical Research, 32(9): 1645-1656. (in Chinese)

[24]
Shao Q Q, Xiao T, Liu J Y,et al.., 2011. Soil erosion rates and characteristics of a typical alpine meadow using the 137Cs technique in Qinghai-Tibet Plateau.Chinese Science Bulletin, 56. doi: 10.1007/s11434-011-4477-0. (in Chinese)

[25]
State Forestry Administration (SFA), 2014. National Report on the Ecological Benefits of Grain for Green Program in 2013. Beijing: China Forestry Publishing House. (in Chinese)

[26]
State Forestry Administration (SFA), 2015. Technical Specification on Evaluation of the Three North Shelterbelt Project (LY/T 2411-2015). Beijing: Standards Press of China. (in Chinese)

[27]
Sun W Y, Shao Q Q, Liu J Y,et al.., 2011. The variation characteristics of soil organic carbon of typical alpine slope grasslands and its influencing factors in the ‘Three-River Headwaters’ Region.Journal of Natural Resources, 26(12): 2072-2087. (in Chinese)Exploring the distribution characteristics of soil organic carbon and its influencing factors under different degraded types of alpine slope grasslands was crucial to better understand the changes of soil organic carbon content and responses to global climate change.Two types of alpine grassland(alpine meadow and alpine steppe),and the impact mechanism of soil organic carbon were studied under the influences of external environment,such as water erosion,wind erosion,freezing-thawing erosion and rodent damage in the "Three-River Headwaters" region.The results showed that: the contents of soil organic carbon of alpine meadow dominated by Kobresia pygmaea and Kobresia humilis were higher than alpine steppe dominated by Stipa purpurea Griseb.Under the conditions of the lightly degraded and water erosion,the average content of alpine meadow QMH1 was 2.2 times(P0.01) of alpine steppe QMH2 which was 3.5 km away from QMH1.And it was similar to the conditions of the lightly degraded and wind erosion,the average content of alpine meadow WDL was 3.8 times(P0.01) of alpine steppe BDQ.Under the influence of water erosion,the soil organic carbon of alpine grassland was transferred downward along the slope grassland.The soil organic carbon content of lower slope(downward 580 m distance from the top slope) of alpine meadow ML1 was 22% higher(P0.05)than the upper slope(upward 580 m distance from the top slope).The overlying distribution characteristics of soil organic carbon for ML2 alpine meadow was performed,not only decreased with the increase of degradation,but also migrated downward along the slope grassland due to water erosion.The soil organic carbon content of extremely degraded grassland,located on the lower slope compared with severely degraded grassland,was 49.3%(P0.05) higher than severely degraded grassland for ML2 alpine meadow.Wind erosion made rough the soil surface of grassland and accelerated mineralization of soil organic carbon.The average content of soil organic carbon of ELH lightly impacted by lake breeze was 27.9% higher than ZLH(P0.05) strongly impacted by lake breeze.The soil organic carbon content was reduced by freeze-thaw erosion,but the difference was not significant.Rodent damage not only reduced the content of soil organic carbon,but also accelerated deterioration of grassland,the average content of soil organic carbon of moderate degradation SDⅠ-Ⅲ around the rat holes were 2.1 time of the extremely degraded grassland SDⅣ-Ⅵ;and the average content of soil organic carbon of the moderately degraded grassland ML2Ⅰ-Ⅱ away from rat holes was 1.6 times of the extremely degraded grassland ML2Ⅳ-Ⅵ.The soil organic carbon of alpine slope grassland was aggravated due to influence by wind erosion,water erosion,freeze-thaw and rodent damage.

[28]
The Environmental Protection Industry Standard of People’s Republic of China (EPIS PRC), 2006. Technical Criterion for Eco-environmental Status Evaluation (HJ/T 192-2006). Beijing: China Environmental Science Press. (in Chinese)

[29]
The People’s Government of Qinghai Province (PGQP), 2005. The General Planning on Ecological Protection and Construction in the TRSR Nature Reserve, Qinghai Province. (in Chinese)

[30]
The H. John Heinz III Center for Science, Economics and the Environment, 2008. The State of Nation’s Ecosystems 2008: Measuring the Lands, Waters, and Living Resources of the United States.Review: The State of the Nation's Ecosystems: Measuring the Lands, Waters, and Living Resources...

DOI

[31]
Vaughan H, Brydges T, Fenech A,et al.., 2001. Monitoring long-term ecological changes through the Ecological Monitoring and Assessment Network: Science-based and policy relevant.Environmental Monitoring and Assessment, 67(1/2): 3-28.

[32]
Wang J B, Liu J Y, Shao Q Q,et al.., 2009. Spatial-temporal patterns of net primary productivity for 1988-2004 based on GLOPEM-CEVSA model in the ‘Three-River Headwaters’ region of Qinghai Province, China.Chinese Journal of Plant Ecology, 33(2): 254-269. (in Chinese)Aims The "Three-River Headwaters" Region, as the headwaters of important rivers and an area sensitive to global climate change, has become a recent research focus. Our objective is to model and assess the spatial-temporal pattern of net primary production (NPP) and its control mechanisms. Methods We applied the GLOPEM-CEVSA model, which has been validated with carbon flux observation in forest, grassland and cropland. The main inputs are spatially interpolated meteorological data and fraction of photosynthetically active radiation absorbed by vegetation canopy, using 1 km resolution of the Advanced Very High Resolution Radiometer of the National Oceanic and Atmospheric Administration in 1988–2004. Important findings Modeled NPP ranged from 36.13 gC·m–2·a–1 for desert to 267.90 gC·m–2·a–1 for forest, and the mean was 143.17 gC·m–2·a–1. Spatially, NPP decreased from southeast to northwest, as influenced by geography and climate. Variability of NPP was the largest in desert (41.75%), was similar for cropland (25.93%), grassland (22.31%) and wetland (24.72%) and was the smallest in forest (20.79%). During 1988–2004, NPP increased at the rate of 7.8–28.8 gC·m–2 per 10 years in the western area, but decreased 13.1–42.8 gC·m–2 per 10 years in the central and eastern areas. At 99 and 95% significance levels, the area with NPP increasing (regression slope b0) was 13.43% and 20.34%, respectively, of the whole area, and mainly distributed in the western region, while the area with NPP decreasing (b0) was 0.75% and 3.77%, respectively, of the whole area and distributed in the central and western areas and was more concentrated near the main rivers at higher significance levels. Increases of NPP in the western area may have been affected by increasing temperature and precipitation, while central and eastern areas may have been impacted by human activities, especially along the Yangtze, Yellow and other rivers with intensive human habitation and where the warmer and drier climate has led to more serious grassland degradation. The effects of human activities on NPP were not analyzed because data on human activity were unavailable and spatial interpolation of the impact is difficult.

[33]
Wang L X, Wang B R, 2000. Forestry Ecological Engineering. Beijing: China Forestry Publishing House. (in Chinese)

[34]
Wu D, 2014. Research on water regulation service of the main terrestrial ecosystems in China [D]. Beijing: Chinese Academy of Sciences. (in Chinese)

[35]
Xiao W F, Huang Z L, Tang W P et al., 2012. Monitoring and Evaluation of Ecological Benefits of National Land Conversion Program in Three Gorges Reservoir Area. Beijing: Science Press. (in Chinese)

[36]
Xu X L, Liu J Y, Shao Q Q,et al.., 2008. The dynamic changes of ecosystem spatial pattern and structure in the Three-River Headwater Region in Qinghai Province during recent 30 years.Geographical Research, 27(4): 829-838. (in Chinese)Supported by MSS images in the mid and late 1970s,TM images in the early 1990s and TM/ETM images in 2004,the spatial distribution data set of ecosystem types was acquired through analysis and distinguishment,then the dynamic changes of spatial pattern and structure of ecosystems in the Three-River Headwaters region were analyzed since the 1970s.The results showed that alpine grassland occupied the largest area in the Three-River Headwaters region,and the area of alpine grassland occupied 64.68% of the total land area and 99.58% of the total grassland area.Wetland,glacier and mountain permanent snow-cover were characteristic ecosystems in the Three-River Headwaters region,with marsh area occupying 26.09% of the total area of water and wetland ecosystem,and glacier and mountain permanent snow-cover area 9.02% of the total area of water and wetland ecosystem.As the characteristic ecosystems in the Three-River Headwaters region,wetland,glacier and mountain permanent snow-cover played important roles in providing stable water resource.During recent 30 years,the changes of ecosystem spatial pattern in the Three-River Headwaters region have been stable and rather slow,with an annual changing rate of farmland,forest,grassland,water and wetland,and hungriness ecosystem being less than 0.5% respectively,the least but stable in the Yangtze and Yellow river basins,even the whole country.The changes of grassland,water and wetland ecosystem have occupied a dominant position in the Three-River Headwaters region since the mid and late 1970s.The changes of grassland mainly occurred in the central and eastern parts of the region,dominated by reclamation of grassland and conversion of grassland into unused land such as bare land,sandy and salt land.And the changes of water and wetland ecosystem mainly occurred in the vast western and northern parts of the region,represented by conversion of water body into beach land and conversion of wetland into grassland.

DOI

[37]
Xu X Q, 1992. Integrated Evaluation on Synthetically Efficiency of Forests. Beijing: China Forestry Publishing House. (in Chinese)

[38]
Yu X X, Gu J C, Yue Y J et al., 2010. Benefit Evaluation on Forestry Ecological Projects. Beijing: Science Press. (in Chinese)

[39]
Zhao Z P, Liu J Y, Shao Q Q, 2010. Characteristic analysis of land cover change in the Nature Reserve of the Three River’s Source Region.Scientia Geographica Sinica, 30(3): 415-420. (in Chinese)Based on remote sensing classification system of China land use/cover change,we used four phases Landsat remote sensing images of middle and late 1970s,late 1980s,2004 and 2008 for the process analysis of nature reserve land cover change in Three River's Source Regions during the recent 30 years.The results showed that in total,grassland area experienced a process of increase-decrease-increase during the recent 30 year.From middle and late 1970s to 2004,decline of grassland coverage was the main appearance of land cover change,and land cover status had a deterioration trend.During the recent 4 years,grassland deteriorated trend alleviated.All zones had ameliorated trend of land cover change and core and buffer zones were more significant than experimental zone,which may related with the implementation of Planning.

DOI

Options
Outlines

/

〈 〉