Shrub density effects on the community structure and composition of a desert animal community

Positive interactions between shrubs and animals are frequent in desert ecosystems. Shrub canopies can provide refuge to some animal species from predators and shelter from stressful environmental conditions by ameliorating high temperatures through lowering the amplitude of variation. Consequently, there have been many contrasts of shrub versus open effects; however, we extend this approach further by testing these effects on a gradient of shrub densities in the Carrizo National Monument, California. We tested the hypothesis that shrub density is a landscape-level predictor of vertebrate community composition and structure. We used camera traps, transects, and focal observations to estimate animal density and composition, alongside the deployment of temperature sensors. Plots were established within shrub patches ranging from 0 to 12 shrubs per 10m radius. Plots with relatively higher shrub densities had increased the abundance and richness of vertebrate animal species. Temperature and residual dry matter were also important mediators of animal density and richness. Shrub cover was also an important driver of animal communities but we propose that shrub density is a more rapid proxy for vegetation effects in deserts relevant to wildlife conservationists, and managers.

荒漠生态系统中，灌木与动物之间的正向交互频发。灌木冠层可为部分动物物种提供躲避天敌的庇护所，并通过降低温度波动幅度缓解高温胁迫，为其提供适宜的栖息环境。因此，已有诸多研究对比了灌木生境与开阔生境的生态效应；但本研究于加利福尼亚州卡里佐国家纪念地（Carrizo National Monument）开展实验，通过设置灌木密度梯度进一步拓展了该研究思路。我们验证了“灌木密度可作为景观尺度上预测脊椎动物群落组成与结构的指示因子”这一假说。本研究利用红外相机陷阱（camera traps）、样线调查（transects）与定点观测法估算动物种群密度与群落组成，并同步布设温度传感器。我们在半径10米范围内灌木数量介于0至12株的灌木斑块中设置样地。结果显示，灌木密度相对较高的样地中，脊椎动物的种群丰度与物种丰富度均有所提升。温度与残留干物质同样是影响动物种群密度与物种丰富度的重要调控因子。灌木盖度同样是驱动动物群落变化的重要因素，但我们认为，相较于灌木盖度，灌木密度能够更快速地反映荒漠植被对野生动物保护与管理工作的影响。