The role of herb layer characteristics and productivity for forest ecosystem functioning

草本层特征和生产力对森林生态系统功能的作用

• 批准号: 43905521
• 负责人: Professor Dr. Helge Bruelheide
• 金额: --
• 依托单位: State Key Laboratory of Vegetation and Environmental Change
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/43905521?language=en
• 关键词: role; herb; layer; characteristics; productivity

While ecosystem functioning can be affected by tree or herb layer diversity in isolation, the structural complexity of forests allows for additional niche complementarity, competition and facilitation across strata. In the first phases of BEF-China, we studied top-down and bottomup effects between herb and tree layer diversity in subtropical forests. We found ecosystem functions like herb layer productivity to be influenced by environmental variables, but also initial control of tree diversity on herb layer invasibility.In the third phase, we now address the mechanisms behind tree layer x herb layer interactions. We continue to quantify herb layer characteristics and their feedback effects on the trees in the Main Experiment. In addition, we will take into account effects of herb layer x tree diversity interactions on tree recruitment and address the role of the herb layer for the nutrient balance of all plots.As major objectives, we will test 1.a) for increasing effects of tree diversity with diminishing influence of the Ecoscape on the herb layer and 1.b) for effects of functional group presence in the herb layer on tree layer x productivity relationships, 2.) for Janzen-Connell effects by studying woody recruitment in the Main Experiment, and 3.) for important quantitative contributions of the herb layer to the whole CNP balance of the ecosystem.In a first work package removal of woody weeds will be done in the context of the BEFmod experiment to study bottom-up effects on the trees. In a second work package, we aim to predict future stand development in the Main Experiment after weeding stop by studying recruitment of woody species. We will quantify the amount of woody recruits in the herb layer for early reproducing tree species of the Main Experiment. By means of seed addition experiments, we will test for Janzen-Connell effects as alternative hypothesis why monocultures might underperform in productivity. We address the roles of negative distance and density dependence vs. environmental filtering for woody recruits and will test for positive diversity effects along a tree diversity gradient that show reduced Janzen-Connell effects. In a third work package, our subproject will quantify herb layer leaf nutrient concentrations (P and N, Ca, Mg, K) with NIRS and calculate herb layer contents on a plot basis as a measure of resource acquisition following P fertilization. In cooperation with SP5, these analyses will show how nutrient contents and stocks in the herb layer respond to tree diversity, the Ecoscape and nutrient limitation, and thus, will contribute an important term to the overall nutrient balance in the Main Experiment.Our subproject will help identifying interaction effects of stratum level diversity and thus help deciding about the extent as to which complementarity, competition and facilitation between herb and tree layer change in up growing subtropical forests.

虽然生态系统的功能可能单独受到乔木层或草本层多样性的影响，但森林的结构复杂性允许更多的生态位互补、竞争和跨层促进。在北京森林论坛-中国的第一阶段，我们研究了亚热带森林草本层和乔木层多样性之间的自上而下和自下而上的效应。我们发现像草本层生产力这样的生态系统功能不仅受环境变量的影响，而且对草本层入侵的树木多样性也有初步的控制作用。在第三阶段，我们现在讨论乔木层与草本层相互作用的机制。在主要的实验中，我们继续量化草本层的特征及其对树木的反馈效应。此外，我们将考虑草本层与树木多样性的相互作用对树木更新的影响，并解决草本层对所有样地养分平衡的作用。作为主要目标，我们将测试1)在减少生态景观对草本层的影响的情况下增加树木多样性的效果，以及1)草本层中存在的功能基团对乔木层x生产力关系的影响，2)通过在主要实验中研究伍迪的招募，来研究Janzen-Connell效应，以及3.)对于草本层对整个生态系统CNP平衡的重要数量贡献。在第一项工作中，将在BEFmod实验的背景下去除木本植物杂草，以研究自下而上对树木的影响。在第二个工作包中，我们的目标是通过研究木本植物的补充来预测除草停止后主要试验中未来的林分发展。我们将在草本层中量化木本新梢的数量，为早期繁殖树种的主要实验。通过种子添加实验，我们将检验詹森-康奈尔效应作为单一栽培可能表现不佳的另一种假说。我们讨论了木本新兵的负距离和密度依赖与环境过滤的作用，并将沿着显示减少Janzen-Connell效应的树木多样性梯度测试正向多样性效应。在第三个工作包中，我们的子项目将使用近红外光谱量化草本层叶片营养浓度(P和N、Ca、Mg、K)，并以小区为基础计算草本层含量，以此作为磷肥后资源获取的衡量标准。与SP5合作，这些分析将显示草本层的养分含量和储量如何对树木多样性、生态景观和养分限制做出反应，因此，将在主要实验中对整体养分平衡做出重要贡献。我们的子项目将有助于确定地层水平多样性的交互作用，从而帮助决定在生长中的亚热带森林中草本层和乔木层之间的互补、竞争和促进变化的程度。