Zheng Shuxia, Li Wenhuai, Lan Zhichun, Ren Haiyan, Wang Kaibo
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling 712100 Shaanxi, China.
Sci Rep. 2015 Dec 11;5:18163. doi: 10.1038/srep18163.
Abundant evidence has shown that grazing alters plant functional traits, community structure and ecosystem functioning of grasslands. Few studies, however, have tested how plant responses to grazing are mediated by resource availability and plant functional group identity. We examined the effects of grazing on functional traits across a broad range of species along a soil moisture gradient in Inner Mongolia grassland. Our results showed that trait syndromes of plant size (individual biomass) and shoot growth (leaf N content and leaf density) distinguished plant species responses to grazing. The effects of grazing on functional traits were mediated by soil moisture and dependent on functional group identity. For most species, grazing decreased plant height but increased leaf N and specific leaf area (SLA) along the moisture gradient. Grazing enhanced the community-weighted attributes (leaf NCWM and SLACWM), which were triggered mainly by the positive trait responses of annuals and biennials and perennial grasses, and increased relative abundance of perennial forbs. Our results suggest that grazing-induced species turnover and increased intraspecific trait variability are two drivers for the observed changes in community weighted attributes. The dominant perennial bunchgrasses exhibited mixed tolerance-resistance strategies to grazing and mixed acquisitive-conservative strategies in resource utilization.
大量证据表明，放牧会改变草原的植物功能性状、群落结构和生态系统功能。然而，很少有研究测试植物对放牧的反应是如何由资源可用性和植物功能群身份介导的。我们沿着内蒙古草原的土壤湿度梯度，研究了放牧对广泛物种功能性状的影响。我们的结果表明，植物大小（个体生物量）和地上部分生长（叶片氮含量和叶密度）的性状综合征区分了植物物种对放牧的反应。放牧对功能性状的影响由土壤湿度介导，并取决于功能群身份。对于大多数物种来说，沿着湿度梯度，放牧降低了株高，但增加了叶片氮和比叶面积（SLA）。放牧增强了群落加权属性（叶片氮群落加权均值和比叶面积群落加权均值），这主要由一年生植物、二年生植物和多年生草本植物的正向性状反应引发，并增加了多年生杂类草的相对丰度。我们的结果表明，放牧导致的物种更替和种内性状变异性增加是观察到的群落加权属性变化的两个驱动因素。占主导地位的多年生丛生禾草对放牧表现出混合的耐受-抗性策略，在资源利用方面表现出混合的获取-保守策略。
