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

枯木是天然森林生态系统的一个重要结构属性。从树木衰老到与森林地面结合，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。在中欧和北方，人们普遍认识到枯木对森林生态系统多样性的贡献，以及森林做法之间的关系，枯木数量和质量的减少以及多样性的丧失。然而，我们对枯枝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转化，增加了其成分的化学稳定性。森林土壤中的枯枝落叶层不仅影响着土壤的生物化学和结构异质性，而且也影响着森林土壤的群落结构和功能。这种贡献的性质和程度与树种和木材腐烂阶段有关。我建议证实这一一般假设的方法进行的研究，在永久地块的监测站（1）使用时间序列的死树干，（2）实验室培养的木材样品的已知年龄或给定的腐烂类和（3）操纵实验中的森林地面上的死木材的数量将被控制。我打算比较两个火灾后的先驱物种，杰克松（松banksiana羔羊）腐烂的树干的演变。和白杨（Populus tremuloides Michx.）从生物化学特性、微生物功能多样性和氮素动态等方面进行了研究。

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.