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	Below-ground competition drives the self-thinning process of Stipa purpurea populations in northern Tibet
	Zhu J. T.; Jiang, L.; Zhang, Y. J.; Jiang, Y. B.; Tao, J.; Tian, L.; Zhang, T.; Xi, Y.
	2015
关键词	Above-ground biomass Below-ground biomass Competition Density dependence Harsh environments Population self-thinning Precipitation gradient positive interactions density relationship shoot ratios communities diversity gradient plants grasslands fertility substrate
英文摘要	QuestionsAbove-ground, below-ground and individual mass-density relationships for perennial herbs were examined along a natural precipitation gradient in northern Tibet. We asked: (1) how do the self-thinning exponents respond to variation in precipitation; and (2) what mechanisms drive the observed population self-thinning? LocationThe alpine grassland of northern Tibet. MethodsForty-seven fenced sites along a precipitation gradient were established and surveyed in 2011 and 2012. Data (geographic coordinates, elevation, and vegetation information) were collected for Stipa purpurea populations at each site. Population self-thinning exponents were estimated using reduced major axis regression. ResultsThe self-thinning exponents for below-ground (-1.27, -0.47) and individual biomass (-1.26, -0.46) increased with increasing mean annual precipitation, but those for above-ground biomass decreased with precipitation (0.18, -0.25). Soil resources (moisture and nutrients) are a more important constraining factor for below-ground components than light is for above-ground components. Root competition for below-ground resources dominated in S.purpurea population self-thinning. The driving force of density regulation changed from above-ground competition to below-ground competition with increased drought stress. Our results indicate that an increased root/shoot ratio was linked to enhanced below-ground competition and weakened above-ground competition. Our study further confirmed the hypothesis that plant populations in different environments exhibit different biomass allocation patterns, which, in turn, leads to different biomass-density relationships. ConclusionsOur study revealed the mechanisms of population self-thinning for perennial herbs in the extreme environment of northern Tibet, where below-ground processes play a critical role in regulating population self-thinning. Our study also advances understanding of the interactions between above- and below-ground processes, providing baseline knowledge useful for local grassland management.
出处	Journal of Vegetation Science
卷	26
期	1
页	166-174
语种	英语
ISSN号	1100-9233
DOI标识	10.1111/jvs.12207
内容类型	SCI/SSCI论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/43611]
专题	地理科学与资源研究所_历年回溯文献
推荐引用方式 GB/T 7714	Zhu J. T.,Jiang, L.,Zhang, Y. J.,et al. Below-ground competition drives the self-thinning process of Stipa purpurea populations in northern Tibet. 2015.

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