Data from: Plant traits of propagule banks and standing vegetation reveal flooding alleviates impacts of agriculture on wetland restoration

1. Restoration of degraded plant communities requires understanding of community assembly processes. Human land use can influence plant community assembly by altering environmental conditions and species’ dispersal patterns. Flooding, including from environmental flows, may counteract land use effects on wetland vegetation. We examined the influence of land use history and flood frequency on the functional composition of wetland plant communities along a regulated river. 2. We applied fourth corner modelling to determine species’ trait-based responses to flooding and land use by combining data on i) the occupancy and abundance of species in propagule banks and standing vegetation, ii) species traits, and iii) environmental conditions of 22 standing vegetation and 108 soil propagule bank study sites. We used analysis of deviance to test how well each dataset characterised trait–environment interactions, and generalised linear models to identify traits related to species’ responses. 3. The occupancy and abundance of native species in the propagule bank and standing vegetation increased with flood frequency and decreased with duration of agricultural land use. Species in standing vegetation with water-borne propagule dispersal (hydrochory) showed similar trends. In contrast, species with higher specific leaf area were associated with longer land use duration. 4. Identifying trait–based differences in the propagule bank and standing vegetation can help disentangle effects of dispersal and environmental filters. The occupancy and abundance of hydrochorous species in standing vegetation were negatively related to land use duration, but hydrochorous species were positively related to land use duration based on their abundance in the propagule bank. This suggests that land use does not limit plant dispersal, but acts as an in situ abiotic filter limiting species presence in standing vegetation. 5. Synthesis and applications. Land use duration and flood frequency have opposite effects on plant community traits in floodplain wetlands of the Macquarie Marshes, Australia. Legacies of agriculture can impede restoration of plant communities. Environmental flows that increase flooding may alleviate these impacts, especially in areas that have been used for agriculture for over 20 years, by providing dispersal and environmental filters that favour native wetland species. More flooding will likely be required to restore floodplains with longer histories of agricultural land use compared to floodplains less impacted by agriculture.04-Apr-2017

1. 退化植物群落的修复需以深入理解群落组装（community assembly）过程为前提。人类土地利用可通过改变环境条件与物种扩散格局，对植物群落组装过程产生干扰。而洪水（包括环境流量引发的洪水）可抵消土地利用活动对湿地植被的负面影响。本研究以一条受调控河流沿岸的湿地植物群落为研究对象，考察土地利用历史与洪水频率对其功能组成的影响。
2. 本研究采用第四角模型（fourth corner modelling），结合三类数据集开展分析，以明确物种基于功能性状对洪水与土地利用的响应：① 繁殖体库与现存植被中物种的占有率与多度数据，② 物种功能性状数据，③ 22个现存植被样点与108个土壤繁殖体库样点的环境条件数据。研究采用偏差分析（analysis of deviance）检验各数据集对性状-环境互作的表征能力，并通过广义线性模型（generalised linear models）识别与物种响应相关的功能性状。
3. 繁殖体库与现存植被中的本土物种，其占有率与多度随洪水频率升高而增加，随农业土地利用时长增加而降低。现存植被中具有水媒传播（hydrochory）策略的物种，也呈现出相似的变化趋势。与之相对，比叶面积（specific leaf area）更高的物种，则与更长的土地利用时长呈显著正相关。
4. 区分繁殖体库与现存植被间基于功能性状的差异，有助于厘清扩散过滤与环境过滤的效应。现存植被中水媒传播物种的占有率与多度随土地利用时长增加而降低，但基于繁殖体库中的多度数据来看，水媒传播物种的多度与土地利用时长呈显著正相关。这表明土地利用并未限制植物的扩散，而是作为原位非生物过滤因子，限制本土湿地物种在现存植被中的定植与存续。
5. 综合与应用。澳大利亚麦考里沼泽（Macquarie Marshes）漫滩湿地中，土地利用时长与洪水频率对植物群落功能性状具有截然相反的调控效应。农业活动遗留的生态影响会阻碍植物群落的修复进程。通过提升洪水规模的环境流量，可有效缓解这些负面影响，尤其是在农业利用时长超过20年的区域，这类环境流量可为本土湿地物种提供适宜的扩散与环境过滤条件。相较于受农业活动影响较轻的漫滩，拥有更长农业土地利用历史的漫滩，需要更为频繁的洪水事件才能实现生态修复。2017年4月4日