Department of Plant Sciences, University of California, Davis, Davis, California, USA.
Center for Environmental Biology, University of California, Irvine, Irvine, California, USA.
Ecol Appl. 2023 Sep;33(6):e2899. doi: 10.1002/eap.2899. Epub 2023 Jul 10.
A trait-based community assembly framework has great potential to direct ecological restoration, but uncertainty over how traits and environmental factors interact to influence community composition over time limits the widespread application of this approach. In this study, we examined how the composition of seed mixes and environment (north- vs. south-facing slope aspect) influence functional composition and native plant cover over time in restored grassland and shrubland communities. Variation in native cover over 4 years was primarily driven by species mix, slope aspect, and a species mix by year interaction rather than an interaction between species mix and slope aspect as predicted. Although native cover was higher on wetter, north-facing slopes for most of the study, south-facing slopes achieved a similar cover (65%-70%) by year 4. While community-weighted mean (CWM) values generally became more resource conservative over time, we found shifts in particular traits across community types and habitats. For example, CWM for specific leaf area increased over time in grassland mixes. Belowground, CWM for root mass fraction increased while CWM for specific root length decreased across all seed mixes. Multivariate functional dispersion remained high in shrub-containing mixes throughout the study, which could enhance invasion resistance and recovery following disturbance. Functional diversity and species richness were initially higher in drier, south-facing slopes compared to north-facing slopes, but these metrics were similar across north- and south-facing slopes by the end of the 4-year study. Our finding that different combinations of traits were favored in south- and north-facing slopes and over time demonstrates that trait-based approaches can be used to identify good restoration candidate species and, ultimately, enhance native plant cover across community types and microhabitat. Changing the composition of planting mixes based on traits could be a useful strategy for restoration practitioners to match species to specific environmental conditions and may be more informative than using seed mixes based on growth form, as species within functional groups can vary tremendously in leaf and root traits.
基于特征的群落组装框架在指导生态恢复方面具有巨大潜力，但由于不确定特征和环境因素如何随时间相互作用影响群落组成，限制了该方法的广泛应用。在这项研究中，我们研究了种子混合物的组成和环境（南北向坡面朝向）如何随时间影响恢复草地和灌丛群落的功能组成和本地植物覆盖。4 年来，本地覆盖的变化主要受物种混合、坡面朝向以及物种混合与年份相互作用的驱动，而不是如预测的那样受物种混合和坡面朝向的相互作用的驱动。尽管在研究过程中的大部分时间里，较潮湿的北坡上的本地覆盖较高，但到第 4 年，南坡的覆盖达到了相似的水平（65%-70%）。虽然群落加权均值（CWM）值通常随着时间的推移变得更加资源保守，但我们发现了跨群落类型和生境的特定特征的变化。例如，在草地混合物中，CWM 的比叶面积随时间增加。在地下，所有种子混合物的根质量分数 CWM 增加，而比根长 CWM 减少。在整个研究过程中，含有灌木的混合物的功能离散度仍然很高，这可以增强入侵抗性和干扰后的恢复。与北坡相比，在较干燥、南坡上的功能多样性和物种丰富度最初较高，但到 4 年研究结束时，这些指标在北坡和南坡相似。我们发现，在南坡和北坡以及随时间推移，不同的特征组合受到青睐，这表明基于特征的方法可用于识别良好的恢复候选物种，并最终提高不同群落类型和小生境的本地植物覆盖。根据特征改变种植混合物的组成可能是恢复实践者的有用策略，与基于生长形式的种子混合物相比，这可能更具信息性，因为功能组内的物种在叶和根特征上可能有很大差异。
