Coarse woody debris and its relationship with forest floor structure and functions

枯木是天然林生态系统的重要结构属性。从树木衰老到融入森林地面，枯木是生物多样性、土壤生产力和全球生物地球化学循环背后的许多复杂过程的核心。枯木对森林生态系统多样性的贡献，以及森林实践、枯木数量和质量下降以及多样性丧失之间的关系，在中欧和北欧得到了充分认识。然而，我们对枯木对其他生态系统和土壤功能（如养分和碳循环）的贡献的理解仍然是零碎的。我的工作假设是，在整个腐烂过程中，枯木经历了化学和物理变化，从而增加了其成分的化学稳定性。森林地表上或地下的枯木对森林土壤的生物化学和结构异质性以及群落结构和功能都有影响。这种贡献的性质和幅度与树种和木材腐烂阶段有关。我建议通过在监测林分的永久地块中进行的研究来证实这一普遍假设：(1)使用死洞的时间序列，(2)已知年龄或给定腐烂等级的木材样本的实验室孵化，以及(3)控制森林地面上死木数量的操纵性实验。本研究旨在比较两种火灾后的先驱树种——短叶松（Pinus banksiana Lamb.）和白杨（Populus tremuloides Michx.）腐烂孔的生化特征、微生物功能多样性和氮动力学。

Deadwood is a key structural attribute of natural forest ecosystems. From tree senescence to its incorporation into the forest floor, deadwood is central to many complex processes underlying biological diversity, soil productivity and global biogeochemical cycles. The contribution of deadwood to forest ecosystem diversity, as well as the relationships among forest practices, decreases in deadwood quantity and quality and the loss of diversity, are well recognized in central and northern Europe. Yet our understanding of deadwood contribution to other ecosystem and soil functions such as nutrient and carbon cycles is still fragmentary. My working hypothesis is that throughout decay, dead wood undergoes chemical and physical transformations that increase the chemical stability of its components. Deadwood lying on or buried within the forest floor contributes to the biochemical and structural heterogeneity as well as the community structure and functions of forest soils. The nature and magnitude of this contribution is linked to tree species and wood decay stage. I propose to substantiate this general hypothesis by means of studies conducted in permanent plots of monitored stands (1) using chronosequences of dead boles, (2) laboratory  incubations of wood samples of known age or given decay classes and (3) manipulative experiments where the amount of dead wood on the forest floor will be controlled. I intend to compare the evolution of decaying boles of two post-fire pioneer species, jack pine (Pinus banksiana Lamb.) and aspen (Populus tremuloides Michx.) with respect to their biochemical characteristics as well as microbial functional diversity and nitrogen dynamics.