Louw Cornelius J, Parrini Francesca, Marshal Jason P
Conservation Ecology Research Unit, Department of Zoology and Entomology University of Pretoria Hatfield South Africa.
School of Animal, Plant and Environmental Sciences, University of the Witwatersrand Johannesburg South Africa.
Ecol Evol. 2024 Dec 4;14(12):e70689. doi: 10.1002/ece3.70689. eCollection 2024 Dec.
While studies often focus on density-dependent responses of ungulate populations to resource limitations at large spatial scales, the dynamics at smaller scales remain relatively unexplored. To address this gap, we investigated the temporal dynamics of ungulate abundance in a small dystrophic grassland ecosystem over 20 years, with minimal management interventions. We used annual counts and herd composition data to explore density-dependent responses at the population level and attempt to link such responses to demographic mechanisms. Counts were corrected using a state-space modeling approach. Populations of most species increased from low densities to approximate equilibrium densities. Our findings reveal evidence of density-dependent responses in population growth that shaped the population abundance dynamics. Additionally, juvenile-to-adult ratios exhibited patterns of density-dependent reductions in recruitment. This study suggests grassland ecosystems with moderate annual rainfall are regulated primarily by bottom-up processes.
虽然研究通常关注有蹄类动物种群在大空间尺度上对资源限制的密度依赖性反应，但较小尺度上的动态仍相对未被探索。为了填补这一空白，我们在一个小型营养不良草原生态系统中，在最少管理干预的情况下，对有蹄类动物数量的时间动态进行了20年的调查。我们使用年度计数和畜群组成数据来探索种群水平上的密度依赖性反应，并试图将这些反应与人口统计学机制联系起来。计数使用状态空间建模方法进行校正。大多数物种的种群数量从低密度增加到近似平衡密度。我们的研究结果揭示了种群增长中密度依赖性反应的证据，这些反应塑造了种群数量动态。此外，幼体与成体的比例呈现出密度依赖性的招募减少模式。这项研究表明，年降雨量适中的草原生态系统主要受自下而上的过程调节。
