Data from: Comparing herbaceous plant communities in active and passive riparian restoration

Understanding the efficacy of passive (reduction or cessation of environmental stress) and active (typically involving planting or seeding) restoration strategies is important for the design of successful revegetation of degraded riparian habitat, but studies explicitly comparing restoration outcomes are uncommon. We sampled the understory herbaceous plant community of 103 riparian sites varying in age since restoration (0 to 39 years) and revegetation technique (active, passive, or none) to compare the utility of different approaches on restoration success across sites. We found that landform type, percent shade, and summer flow helped explain differences in the understory functional community across all sites. In passively restored sites, grass and forb cover and richness were inversely related to site age, but in actively restored sites forb cover and richness were inversely related to site age. Native cover and richness were lower with passive restoration compared to active restoration. Invasive species cover and richness were not significantly different across sites. Although some of our results suggest that active restoration would best enhance native species in degraded riparian areas, this work also highlights some of the context-dependency that has been found to mediate restoration outcomes. For example, since the effects of passive restoration can be quite rapid, this approach might be more useful than active restoration in situations where rapid dominance of pioneer species is required to arrest major soil loss through erosion. As a result, we caution against labeling one restoration technique as better than another. Managers should identify ideal restoration outcomes in the context of historic and current site characteristics (as well as a range of acceptable alternative states) and choose restoration approaches that best facilitate the achievement of revegetation goals.

明确被动修复（Passive Restoration，即减轻或消除环境胁迫）与主动修复（Active Restoration，通常指栽种或播种）策略的修复成效，对成功规划退化河岸生境（Riparian Habitat）的植被恢复工作至关重要，但直接对比不同修复策略效果的相关研究仍较为少见。本研究对103个河岸样地的林下草本植物群落（Understory Herbaceous Plant Community）开展了采样调查，这些样地的修复后年限跨度为0至39年，且采用的植被恢复技术涵盖主动修复、被动修复及未修复三种类型，旨在对比不同修复策略在各样地间的修复成效差异。研究发现，地貌类型、遮阴率及夏季径流量，可解释所有样地下林功能群落的组成差异。在被动修复样地中，草本与杂类草的盖度及物种丰富度与样地修复年限呈负相关；而在主动修复样地中，仅杂类草的盖度与物种丰富度随修复年限增加而降低。相较于主动修复，被动修复样地的本土植物盖度及物种丰富度更低，但入侵物种（Invasive Species）的盖度与物种丰富度在不同修复策略间无显著差异。尽管部分结果表明，主动修复更有助于提升退化河岸生境的本土物种丰富度，但本研究同时也凸显了调控修复成效的情境依赖性（Context-Dependency）。例如，被动修复的起效速度通常较快，若需快速形成先锋物种（Pioneer Species）优势以遏制严重的土壤侵蚀流失，被动修复或许比主动修复更具应用价值。据此，我们呼吁避免片面认定某一种修复技术更优。管理人员应结合历史与当前的样地特征（以及一系列可接受的替代恢复状态）明确理想修复目标，并选择最能助力实现植被恢复目标的修复策略。