Aim: Land use is the foremost cause of global biodiversity decline, but species do not respond equally to land-use practices. Instead, it is suggested that responses vary with species traits, but long-term data on the trait-mediated effects of land-use on communities is scarce. Here we study how forest understory communities have been affected by two land-use practices during 4-5 decades, and whether changes in plant diversity are related to changes in functional composition. Location: Finland. Time period: 1968-2019. Major taxa studied: Vascular plants. Methods: We resurveyed 245 vegetation plots in boreal herb-rich forest understories, and used hierarchical Bayesian linear models to relate changes in diversity, species composition, average plant size, and leaf economic traits to reindeer abundance, forest management intensity, and changes in climate, canopy cover and composition. Results: Intensively managed forests decreased in species richness and had increased turnover, but management did not affect functional composition. Increased reindeer densities corresponded with increased leaf dry matter content, evenness and diversity, and decreased height and specific leaf area. Successional development in the canopy was associated with increased specific leaf area and decreased leaf dry matter content and height in the understory over the study period. Effects of reindeer abundance and canopy density on diversity were partially mediated by vegetation height, which had a negative relationship with evenness. Observed changes in climate had no discernible effect on any variable. Main conclusions: Functional traits are useful in connecting vegetation changes to the mechanisms that drive them, and provide unique information compared to turnover and diversity metrics. These trait-dependent selection effects could inform whether species benefit or suffer from land use changes and explain observed biodiversity changes under global change.

中文翻译：

---

对土地利用和林冠动态的基于性状的响应改变了森林底层林的长期多样性变化

目的：土地利用是造成全球生物多样性下降的最主要原因，但物种对土地利用做法的反应不同。取而代之的是，建议的反应因物种特征而异，但缺乏关于土地利用的特征介导作用对社区的长期影响的长期数据。在这里，我们研究了在4-5年中两种林地使用方式对森林林下群落的影响，以及植物多样性的变化是否与功能成分的变化有关。地点：芬兰。时间段：1968-2019。研究的主要分类单元：维管植物。方法：我们对富含北方草本植物的林下植被进行了245个植被调查，并使用分级贝叶斯线性模型将多样性，物种组成，平均植物大小和叶片经济性状的变化与驯鹿的丰度，森林经营强度，以及气候，树冠覆盖和成分的变化。结果：集约经营的森林物种丰富度下降，营业额增加，但经营没有影响功能组成。驯鹿密度的增加与叶片干物质含量，均匀度和多样性的增加以及高度和特定叶面积的减少相对应。在研究期内，冠层的连续发育与比叶面积的增加以及林下层叶片干物质含量和高度的降低有关。驯鹿丰度和冠层密度对多样性的影响部分地由植被高度介导，与平坦度呈负相关。观测到的气候变化对任何变量均无明显影响。主要结论：功能性状在将植被变化与驱动其变化的机制联系起来时非常有用，并且与周转率和多样性指标相比，可提供独特的信息。这些依赖于性状的选择效应可以告知物种是从土地使用变化中受益还是受其影响，并可以解释在全球变化下观察到的生物多样性变化。