Chair of Silviculture, Institute of Forest Sciences, University of Freiburg, Freiburg, Germany.
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.
Glob Chang Biol. 2019 Dec;25(12):4257-4272. doi: 10.1111/gcb.14792. Epub 2019 Sep 5.
There is increasing evidence that mixed-species forests can provide multiple ecosystem services at a higher level than their monospecific counterparts. However, most studies concerning tree diversity and ecosystem functioning relationships use data from forest inventories (under noncontrolled conditions) or from very young plantation experiments. Here, we investigated temporal dynamics of diversity-productivity relationships and diversity-stability relationships in the oldest tropical tree diversity experiment. Sardinilla was established in Panama in 2001, with 22 plots that form a gradient in native tree species richness of one-, two-, three- and five-species communities. Using annual data describing tree diameters and heights, we calculated basal area increment as the proxy of tree productivity. We combined tree neighbourhood- and community-level analyses and tested the effects of both species diversity and structural diversity on productivity and its temporal stability. General patterns were consistent across both scales indicating that tree-tree interactions in neighbourhoods drive observed diversity effects. From 2006 to 2016, mean overyielding (higher productivity in mixtures than in monocultures) was 25%-30% in two- and three-species mixtures and 50% in five-species stands. Tree neighbourhood diversity enhanced community productivity but the effect of species diversity was stronger and increased over time, whereas the effect of structural diversity declined. Temporal stability of community productivity increased with species diversity via two principle mechanisms: asynchronous responses of species to environmental variability and overyielding. Overyielding in mixtures was highest during a strong El Niño-related drought. Overall, positive diversity-productivity and diversity-stability relationships predominated, with the highest productivity and stability at the highest levels of diversity. These results provide new insights into mixing effects in diverse, tropical plantations and highlight the importance of analyses of temporal dynamics for our understanding of the complex relationships between diversity, productivity and stability. Under climate change, mixed-species forests may provide both high levels and high stability of production.
越来越多的证据表明，混交林可以提供比单一树种更高水平的多种生态系统服务。然而，大多数关于树种多样性与生态系统功能关系的研究都使用森林清查数据（在非控制条件下）或非常年轻的人工林实验数据。在这里，我们调查了最古老的热带树种多样性实验中多样性-生产力关系和多样性-稳定性关系的时间动态。萨迪纳利亚于 2001 年在巴拿马建立，有 22 个地块，形成了从一个、两个、三个和五个本地树种丰富度的梯度。利用描述树木直径和高度的年度数据，我们计算了基面积增量作为树木生产力的代表。我们结合了树木邻域和社区层面的分析，并测试了物种多样性和结构多样性对生产力及其时间稳定性的影响。两种尺度的总体模式一致，表明邻域中的树木-树木相互作用驱动了观察到的多样性效应。从 2006 年到 2016 年，在两个和三个物种的混合物中，平均超生产力（混合物的生产力高于单一种群）为 25%-30%，在五个物种的林分中为 50%。树木邻域多样性增强了群落生产力，但物种多样性的影响更强，并随着时间的推移而增加，而结构多样性的影响则下降。群落生产力的时间稳定性通过两种主要机制随着物种多样性的增加而增加：物种对环境变异性的异步响应和超生产力。在强烈的厄尔尼诺相关干旱期间，混合物中的超生产力最高。总体而言，正的多样性-生产力和多样性-稳定性关系占主导地位，在最高的多样性水平下具有最高的生产力和稳定性。这些结果为不同的热带人工林的混合效应提供了新的见解，并强调了分析时间动态对我们理解多样性、生产力和稳定性之间复杂关系的重要性。在气候变化下，混交林可能提供高水平和高稳定性的生产。
