Journal of Geographical Sciences ›› 2019, Vol. 29 ›› Issue (7): 1081-1097.doi: 10.1007/s11442-019-1646-6

• Orginal Article • Previous Articles     Next Articles

How forest gaps shaped plant diversity along an elevational gradient in Wolong National Nature Reserve?

Li CHEN1,2(), Wangya HAN1,2, Dan LIU1,2, Guohua LIU1,2,*()   

  1. 1. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-environmental Sciences, CAS, Beijing 100085, China
    2. School of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-05-10 Accepted:2019-01-22 Online:2019-07-25 Published:2019-07-25
  • Contact: Guohua LIU E-mail:lichen_st@rcees.ac.cn;ghliu@rcees.ac.cn
  • About author:

    Author: Chen Li (1989-), PhD, specialized in landscape ecology. E-mail: lichen_st@rcees.ac.cn

  • Supported by:
    National Key Research and Development Program of China, No.2016YFC0502102

Abstract:

Understanding the underlying ecological processes that control plant diversity within (α-diversity) and among (β-diversity) forest gaps is important for managing natural forest ecosystems, and it is also a prerequisite for identifying the formation and maintenance mechanisms of forest plant communities. In this study, we focused on the interrelationships among habitat type (gap/non-gap plots), gap size, elevation and environmental factors, and we explored their effects on plant diversity (α-diversity and β-diversity). To do this, a total of 21 non-gap (i.e., closed canopy) plots (100 m2) and 63 gap plots, including 21 with large gaps (200-410 m2), 21 with medium gaps (100-200 m2) and 21 with small gaps (38.5- 100 m2),were selected along an elevational gradient in a subalpine coniferous forest of southwestern China. Using structural equation models (SEMs), we analyzed how forest gaps affected plant diversity (α-diversity and β-diversity) along an elevational gradient. The results showed that (1) as elevation increased, unimodal patterns of α-diversity were found in different-sized gaps, and β-diversity showed a consistent sinusoidal function pattern in different-sized gaps. The gap size was positively related to α-diversity, but this effect disappeared above 3500 masl. Moreover, the patterns of α-diversity and β-diversity in non-gap plots were irregular along the elevational gradient. (2) SEMs demonstrated that many environmental factors, such as the annual mean air temperature (AMAT), ultraviolet-A radiation (365 nm, UV-A365), ultraviolet-B1 radiation (297 nm, UV-B297), moss thickness (MT), soil carbon/nitrogen ratio (C/N ratio), NH4-N and NO3-N, were significantly affected by elevation, which then affected α-diversity and β-diversity. The photosynthetic photon flux density (PPFD), UV-A365 and UV-B297 were significantly higher in plots with forest gaps than in the non-gap plots. Moreover, the PPFD and UV-A365 were positively and directly affected by gap size. Surprisingly, except for the NH4-N and the C/N ratios, the below-ground environmental factors showed little or no relationships with forest gaps. All of these effects contributed to plant diversity. Overall, the above-ground environmental factors were more sensitive to gap-forming disturbances than the below-ground environmental factors, which affected α-diversity and β-diversity. The predicted pathway in the SEMs of the elevational effects on α-diversity and β-diversity was relatively complicated compared with the effects of forest gaps. These results can provide valuable insights into the underlying mechanisms driving the diversity-habitat relationship in the subalpine coniferous forests of southwestern China.

Key words: forest gap, elevation, environmental factors, plant diversity, subalpine coniferous forest