The influence of forest floor changes on the success and composition of tree regeneration

森林地表变化对树木更新成功率和组成的影响

• 批准号: 502047310
• 负责人: Professor Dr. Jürgen Bauhus
• 金额: --
• 依托单位: Professur für Waldbau
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/502047310?language=en
• 关键词: influence; forest; floor; changes; success

Climate change will greatly impact tree species composition and hence biodiversity and ecosystem functioning of forests. So far indirect effects such as changes in regeneration success as a result of altered substrate conditions for seed germination, modifications in nutrient availability or seed predation and subsequent shifts in the competition among tree species have received very little attention, although they may be crucial for future forest resilience and adaptive capacity. In central Europe, drivers such as increasing temperatures, increasing proportions of deciduous species and ongoing eutrophication may lead to a reduction in forest floor (FF) mass and other FF properties with unknown consequences for the regeneration of tree species. Most research on the influence of FF on tree regeneration dates back to the 1960-1970s, long before widespread P deficiency and climate change were important considerations. Our project aims to close this knowledge gap by studying the influence of changes in FF properties on the regeneration success of important tree species in temperate mixed European beech forests. Specifically, we will address the combined influence of climate change and FF changes on the regeneration success of three target species, Fagus sylvatica, Picea abies, Acer pseudoplatanus. In addition to the direct influence of these two factors, we will analyse indirect influences through changes in the availability of nutrients and water or mycorrhization, changes in biotic factors such as fungal pathogens and seed predation, and changes in the competition among tree species as well as between seedlings and other understorey vegetation. For that purpose, we will assess the germination rates as well as the mortality, growth (e. g., density, height, biomass of roots and shoots), the competitive status as well as mycorrhization and nutrition of seedlings in an experimental approach. In mesocosm experiment with soil columns from sites differing in soil P status and hence FF mass, we focus on the germination and initial establishment process. Here we will test whether decreasing FF thickness influences the susceptibility of seeds and germinants to 1) fungal infestation with changes in seasonal distribution of precipitation (wetter winters) and 2) to desiccation in dry periods. We further test whether 3) the establishment success depends on FF structure. In a field experiment, where seeds of the three species are sown at six sites contrasting in P availability mean annual temperature, we test whether decreasing FF thickness promotes 4) competition for tree seedlings from understorey and 5) increases competition for P and other nutrients between mature trees and seedlings. If successful, our project will provide an important contribution to understanding the regeneration dynamics in forest ecosystems under changing environmental conditions.

气候变化将极大地影响树种组成，从而影响森林的生物多样性和生态系统功能。到目前为止，间接影响，如种子萌发的基质条件改变导致的更新成功的变化，养分可获得性或种子捕食的改变，以及随后树种之间竞争的变化，得到的关注很少，尽管它们可能对未来的森林复原力和适应能力至关重要。在中欧，气温升高、落叶物种比例增加和持续的富营养化等驱动因素可能导致森林地面质量和森林地面其他属性的减少，对树种的再生产生未知的后果。大多数关于林木更新影响的研究可以追溯到1960-1970年代，那时普遍的磷缺乏和气候变化是重要的考虑因素。我们的项目旨在通过研究林木特性的变化对欧洲温带山毛榉混交林中重要树种更新成功的影响来弥合这一知识差距。具体地说，我们将讨论气候变化和FF变化对三个目标物种更新成功的影响，这三个目标物种是：青冈、云杉、枫树。除了这两个因素的直接影响外，我们还会分析养分和水分或菌根化的变化、真菌病原体和种子捕食等生物因素的变化，以及树种之间以及苗木与其他林下植被之间竞争的变化，从而分析间接影响。为此，我们将评估发芽率以及死亡率，生长(如密度，高度，根和地上部分的生物量)，竞争地位，以及苗木的菌化和营养。在中观土柱实验中，我们重点研究了不同土壤磷状况和FF值的场地土柱的萌发和初始建立过程。在这里，我们将测试减小FF厚度是否会影响种子和萌发植物对真菌侵染的敏感性：1)降水季节分布的变化(较潮湿的冬季)；2)干燥时期的干燥。我们进一步检验了3)建立的成功是否依赖于FF结构。在田间试验中，将三个树种的种子播种在六个地点，对比了P有效年平均温度的差异，我们测试了减少林木厚度是否促进了对林下树苗的竞争，以及5)增加了成熟树木和幼苗对P和其他养分的竞争。如果成功，我们的项目将为了解不断变化的环境条件下森林生态系统的更新动态做出重要贡献。