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

枯木是天然森林生态系统的关键结构属性。从树木衰老到进入森林地面，枯木是生物多样性、土壤生产力和全球生物地球化学循环的许多复杂过程的核心。中欧和北欧充分认识到枯木对森林生态系统多样性的贡献，以及森林做法、枯木数量和质量减少以及多样性丧失之间的关系。然而，我们对枯木对其他生态系统和土壤功能的贡献，如养分和碳循环，仍然是支离破碎的。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。枯木躺在或埋在森林地面上有助于森林土壤的生物化学和结构异质性以及群落结构和功能。这种贡献的性质和大小与树种和木材腐烂阶段有关。我建议通过在受监测林分的永久地块中进行的研究来证实这一一般假设：(1)使用死亡树干的时间序列，(2)实验室对已知树龄或给定腐烂等级的木材样本进行孵化，以及(3)控制森林地面上的死木量的操纵实验。我打算比较两个火灾后的先锋树种，杰克松(Pinus bank siana Lamb.)腐烂树干的进化。和杨树(Pillius tremuloides Michx.)关于它们的生化特征以及微生物功能多样性和氮素动态。

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.