Determinants of grassland community structure: a comparison of the community-level consequences of species interactions and loss of biodiversity

本研究主要针对育空地区南部北方林区的生物多样性、植物群落结构和生态系统功能进行研究。这包括林下植被和草地，并提供了了解1.自然群落是如何结构的，2.生物多样性在这些群落中扮演什么角色，3.它们如何发挥作用，以及4.它们如何应对干扰的机会？为了使结果更具普遍性，从而对生态学理论的发展做出贡献，我在其他草原(不列颠哥伦比亚省内陆的半干旱草原、内盖夫沙漠的干旱一年生草原、塞伦盖蒂的稀树草原)和森林林下植被(中国南部的热带森林)进行了类似的比较项目。从四个主要问题出发，我调查了：(I)不同的植物群落功能群如何影响植物群落动态和生态系统功能；植物群落的选定成分被移除并监测相应的反应。(Ii)如果植物群落主要是通过营养限制(自下而上的调节)、草食(自上而下的调节)或它们的相互作用来组织的；我们的实验(持续21年)操纵土壤养分水平和草食动物水平，然后我们监测对单个植物物种、种群和群落的影响。(3)植被、土壤和微生物对长期试验性处理的反应；在21年小区中测量的反应。(4)竞争是否对社区结构有重大影响，这些影响的大小是否以可预测的方式沿生产力梯度变化？(V)尺度对I-IV中测量的反应的影响；其中一些实验将在不同的尺度上重复进行。(Vi)气候变暖、干湿对群落组成和生态系统功能的影响，以及这些影响如何随生产力的变化而变化。(Vii)食物网的复杂性和生产力如何影响热带相互作用的相对强度，以及营养结构的变化如何影响生态系统功能？

My research focuses on biodiversity, plant community structure and ecosystem function in the boreal forest region in southern Yukon. This includes both understorey vegetation and grasslands and provides opportunity to understand 1. how natural communities are structured, 2. what role biodiversity plays in these communities 3. how they function, and 4. how they respond to perturbations? To make the results more generalizable, and thereby contribute to the development of ecological theory, I have (or have had) parallel comparative projects in other grasslands (semi-arid grasslands of Interior British Columbia, arid annual grasslands in the Negev desert, savanna grasslands in Serengeti), and forest understorey (tropical forests in southern China). Stemming from the 4 primary questions I investigate: (i) how different plant functional groups influence plant community dynamics and ecosystem function; selected components of a plant community are removed and consequent responses monitored. (ii) if the plant communities are organized primarily by nutrient limitation (bottom-up regulation), by herbivory (top-down regulation), or by their interaction; our experiments (running for 21 years) manipulate soil nutrient levels and herbivore levels, and we then monitor the consequences on individual plant species, populations, and communities. (iii) vegetation, soil, and microbial responses to long-term experimental treatments; responses measured in the 21-yr plots. (iv) if competition has significant impacts on community structure and if the magnitude of these impacts change in predictable ways along productivity gradients? (v) the effects of scale on the responses measured in i-iv; some of these experiments will be repeated at different scales. (vi) the effects of warming, wetting/drying on community composition and ecosystem function, and how these change with productivity. (vii) how food web complexity and productivity influence the relative strength of tropic interactions, and how changes in trophic structure influence ecosystem function?