Data from: Patch dynamics and temporal dispersal partly shape annual plant communities in ephemeral habitat patches

Most organisms in ephemeral habitat patches have resting stages which form a local species pool in response to temporal variations in the patch’s availability and suitability. Temporal dispersal from the local species pool may, therefore, be an important process shaping the community assembly, particularly soon after patch creation, and possibly interacting with environmental filtering. As the temporal variation of the environmental conditions has a major effect on the composition of the local species pool, we investigated how well contemporary conditions (both patch availability and patch suitability) and temporal dispersal (approximated by environmental temporal variation and temporal distance) explain the changes in community composition in a given locality through successive ephemeral habitat cycles. We used arable weeds in annual crops as models. We calculated temporal weed community dissimilarity indices between weed communities surveyed in cropping seasons at intervals of two to eight years within a given field. The weeds were surveyed twice each cropping season to account for any changes in the relative contributions of temporal dispersal and contemporary conditions during the season. Patch availability explained most of the temporal weed dissimilarity, suggesting that patch dynamics have the greatest effect on weed community assembly. Temporal distance and temporal variation of the environmental conditions had more effect at the start of the cropping season than later, while patch suitability had more effect in the middle of the season. These results suggest that temporal dispersal drives the weed community assembly when ephemeral habitat patches are created. These assemblies are further shaped by environmental filtering. This is consistent with a temporal source-sink dynamic mechanism where the seed bank acts as the main weed source. However, a large part of temporal weed dissimilarity remains unexplained, suggesting that other ecological processes such as spatial dispersal and founder effect may also shape the weed community.

绝大多数栖息于短暂生境斑块（ephemeral habitat patches）中的生物均拥有休眠阶段（resting stages），这些休眠阶段会响应斑块可利用性与适宜性的时间变化，形成本地物种库（local species pool）。因此，从本地物种库开展的时间扩散（temporal dispersal），可能是驱动群落构建（community assembly）的关键过程，尤其在斑块形成初期尤为显著，且可能与环境过滤（environmental filtering）存在交互作用。由于环境条件的时间变异对本地物种库的组成具有重要影响，本研究探讨了当代环境条件（包括斑块可利用性与斑块适宜性）以及时间扩散（以环境时间变异与时间距离近似表征）能够在多大程度上解释特定生境中连续经历短暂生境周期的群落组成变化。本研究以一年生作物田中的农田杂草（arable weeds）作为研究模型，计算了同一块农田内间隔2至8年的多个种植季所调查的杂草群落之间的时间相异性指数（dissimilarity indices）。为了量化种植季内时间扩散与当代条件对相对贡献的动态变化，我们在每个种植季开展了两次杂草调查。分析结果显示，斑块可利用性对时间尺度上的杂草群落相异性解释度最高，表明斑块动态对杂草群落构建的影响最为显著。时间距离与环境条件的时间变异在种植季初期的影响强于后期，而斑块适宜性则在种植季中期的影响更为突出。上述结果表明，当短暂生境斑块形成时，时间扩散主导了杂草群落的构建过程，而环境过滤进一步塑造了这些群落结构，这与以种子库（seed bank）作为主要杂草源的时间源汇动态机制（source-sink dynamic mechanism）相符。然而，仍有相当一部分时间尺度上的杂草群落相异性无法被解释，这暗示其他生态过程，例如空间扩散与奠基者效应（founder effect），同样可能参与塑造杂草群落。