Herbivory and drought generate short-term stochasticity and long-term stability in a savanna understory community.
Herbivory and drought generate short-term stochasticity and long-term stability in a savanna understory community.
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食草和干旱在稀树草原林下群落中产生短期随机性和长期稳定性。
DOI：
10.1002/eap.1649
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
T. Young
中科院分区：
文献类型：
--
作者：
C. Riginos;Lauren M. Porensky;K. Veblen;T. Young
降雨和食草性是草原植物动态的基本驱动因素，但很少有研究在实验环境中检验这些因素之间的长期相互作用。了解这种相互作用是很重要的，因为降雨正变得越来越不稳定，本土野生草食动物正被牲畜取代。牲畜放牧和间歇性低降雨量被认为是相互作用的，导致的群落变化比单独的任何一个因素都要大。我们研究了肯尼亚长期围栏实验(KLEE)15年来四个干旱时期草本植物群落组成的变化和稳定性模式，该实验包括六种不同的牛、本地野生食草动物(例如斑马、瞪羚)和巨型食草动物(长颈鹿、大象)的组合。我们使用主响应曲线来分析每个草食动物处理相对于一个共同的初始群落的变化轨迹，并询问干旱如何促进这些处理中的群落变化。我们检查了与不同时间尺度对应的三个稳定性指标(阻力、变异性和周转率)，发现每一个指标对放牧的反应都不同。同时包括牛和野生食草动物的处理具有更高的抗性(15年内净变化较小)，但在较短的时间尺度上更具变异性；相反，较轻放牧的处理(不包括草食动物或野生草食动物)由于一致的、线性的、短期变化的积累而显示出较低的抗性。在所有草食动物处理中，在干旱期间和干旱后立即发生的群落变化最大。但是，虽然干旱在较少放牧的处理中促成了方向的变化，但在较重放牧的处理中，干旱导致了更高的变异性和抗性。在轻度放牧处理中(特别是在干旱之后)，群落的大部分变化是由于可口的小花臂尾轮虫盖度的大幅增加。这些结果表明，在放牧强度连续体的中低端，草食和干旱如何共同作用，导致草原群落发生变化。在一个具有长期放牧进化历史的系统中，适度放牧有助于长期稳定。这与人们经常认为的牲畜放牧会导致草原系统发生定向、不稳定的变化的假设背道而驰。
Rainfall and herbivory are fundamental drivers of grassland plant dynamics, yet few studies have examined long-term interactions between these factors in an experimental setting. Understanding such interactions is important, as rainfall is becoming increasingly erratic and native wild herbivores are being replaced by livestock. Livestock grazing and episodic low rainfall are thought to interact, leading to greater community change than either factor alone. We examined patterns of change and stability in herbaceous community composition through four dry periods, or droughts, over 15 years of the Kenya Long-term Exclosure Experiment (KLEE), which consists of six different combinations of cattle, native wild herbivores (e.g., zebras, gazelles), and mega-herbivores (giraffes, elephants). We used principal response curves to analyze the trajectory of change in each herbivore treatment relative to a common initial community and asked how droughts contributed to community change in these treatments. We examined three measures of stability (resistance, variability, and turnover) that correspond to different temporal scales and found that each had a different response to grazing. Treatments that included both cattle and wild herbivores had higher resistance (less net change over 15 years) but were more variable on shorter time scales; in contrast, the more lightly grazed treatments (no herbivores or wild herbivores only) showed lower resistance due to the accumulation of consistent, linear, short-term change. Community change was greatest during and immediately after droughts in all herbivore treatments. But, while drought contributed to directional change in the less grazed treatments, it contributed to both higher variability and resistance in the more heavily grazed treatments. Much of the community change in lightly grazed treatments (especially after droughts) was due to substantial increases in cover of the palatable grass Brachiaria lachnantha. These results illustrate how herbivory and drought can act together to cause change in grassland communities at the moderate to low end of a grazing intensity continuum. Livestock grazing at a moderate intensity in a system with a long evolutionary history of grazing contributed to long-term stability. This runs counter to often-held assumptions that livestock grazing leads to directional, destabilizing shifts in grassland systems.
影响因子：
2
作者：
Gao, Y. Z.;Giese, M.;Taube, F.
通讯作者：
Taube, F.