Nicholas School of the Environment, Duke University Marine Lab, Beaufort, North Carolina, USA.
Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina, USA.
Ecology. 2024 Jul;105(7):e4323. doi: 10.1002/ecy.4323. Epub 2024 May 20.
Understanding how climate and local stressors interact is paramount for predicting future ecosystem structure. The effects of multiple stressors are often examined in small-scale and short-term field experiments, limiting understanding of the spatial and temporal generality of the findings. Using a 22-year observational dataset of plant and grazer abundance in a southeastern US salt marsh, we analyzed how changes in drought and grazer density combined to affect plant biomass. We found: (1) increased drought severity and higher snail density both correlated with lower plant biomass; (2) drought and snail effects interacted additively; and, (3) snail effects had a threshold, with additive top-down effects only occurring when snails were present at high densities. These results suggest that the emergence of multiple stressor effects can be density dependent, and they validate short-term experimental evidence that consumers can augment environmental stress. These findings have important implications for predicting future ecosystem structure and managing natural ecosystems.
了解气候和当地胁迫因素如何相互作用对于预测未来的生态系统结构至关重要。通常在小规模和短期野外实验中研究多种胁迫因素的影响，这限制了对这些发现的空间和时间普遍性的理解。本研究利用美国东南部盐沼长达 22 年的植物和食草动物丰度观测数据集，分析了干旱和食草动物密度变化如何共同影响植物生物量。结果表明：（1）干旱严重程度增加和蜗牛密度升高均与植物生物量降低相关；（2）干旱和蜗牛的影响呈累加效应；（3）蜗牛的影响存在阈值，仅当蜗牛密度较高时才会出现叠加的自上而下的效应。这些结果表明，多种胁迫因素的影响可能与密度有关，并且验证了短期实验证据，即消费者可以增强环境胁迫。这些发现对于预测未来生态系统结构和管理自然生态系统具有重要意义。
