Data from: The importance of forest structure to biodiversity-productivity relationships

While various relationships between productivity and biodiversity are found in forests, the processes underlying these relationships remain unclear and theory struggles to coherently explain them. In this work, we analyse diversity–productivity relationships through an examination of forest structure (described by basal area and tree height heterogeneity). We use a new modelling approach, called ‘forest factory’, which generates various forest stands and calculates their annual productivity (above-ground wood increment). Analysing approximately 300 000 forest stands, we find that mean forest productivity does not increase with species diversity. Instead forest structure emerges as the key variable. Similar patterns can be observed by analysing 5054 forest plots of the German National Forest Inventory. Furthermore, we group the forest stands into nine forest structure classes, in which we find increasing, decreasing, invariant and even bell-shaped relationships between productivity and diversity. In addition, we introduce a new index, called optimal species distribution, which describes the ratio of realized to the maximal possible productivity (by shuffling species identities). The optimal species distribution and forest structure indices explain the obtained productivity values quite well (R2 between 0.7 and 0.95), whereby the influence of these attributes varies within the nine forest structure classes.

尽管森林生态系统中已观测到生产力与生物多样性间存在多种关联，但此类关联的内在机制仍未明确，现有理论亦难以对其作出统一连贯的阐释。本研究通过解析以断面积（basal area）和树高异质性（tree height heterogeneity）表征的森林结构，对多样性-生产力关联展开分析。我们采用一种名为‘森林工厂（forest factory）’的新型建模方法，该方法可生成多样林分并计算其年生产力（annual productivity），即地上木材生长量（above-ground wood increment）。通过对约30万个林分的分析，我们发现森林平均生产力并不会随物种多样性的提升而升高；相反，森林结构才是关键影响变量。对德国国家森林清查（German National Forest Inventory）的5054块样地进行分析，可观测到类似规律。此外，我们将林分划分为9类森林结构类别，并在此框架下发现，生产力与多样性间存在递增、递减、恒定乃至钟形的多种关联模式。除此之外，我们还提出了一种名为最优物种分布（optimal species distribution）的新指数，该指数用于描述实际生产力与通过随机置换物种身份所能达到的最大生产力之间的比值。最优物种分布与森林结构指数可较好地解释所观测到的生产力数值（决定系数R²介于0.7至0.95之间），且上述两类属性的影响效应在9类森林结构类别中存在显著差异。