Natural forest disturbance events can influence soil biogeochemical processes in two ways - by creating downed woody debris (DWD; fallen tree boles or branches) and by creating canopy gaps that alter forest microclimate. DWD represents a substrate for microbial growth and a persistent store of carbon and nutrients, but microbial activity is also sensitive to temperature and moisture. We studied the potential interaction of DWD and canopy gaps on soil microbial processes, and wondered if microclimatic conditions resulting from the manipulation of forest structure would be enough to inhibit production, thereby altering a critical ecosystem process. Gaps and DWD (>10 cm diameter) were added to a maturing, even-aged, second-growth northern hardwood forest (the Flambeau Experiment; N Wisconsin, USA) to enhance structural complexity and promote key ecosystem processes typically associated with late-successional forests. We investigated the influence of DWD and gaps on soil microbial community composition, extracellular enzyme activity and soil characteristics. Soils were sampled near intermediately and highly decayed DWD and 2 m away from DWD (control) in gaps and closed canopy a decade after manipulation.

DWD decomposition influenced the surrounding soil differentially depending on decay class and canopy condition. Mean C- and P-potential extracellular enzyme activities (BG, BX and AP) were enhanced near highly decayed DWD in gaps. The relative abundance of bacteria (actinomycete, anaerobic, gram-negative and -positive) remained constant in gaps but decreased from May to August in closed canopy. In gaps, soil total exchangeable cations increased by 34.6%, available phosphorus by 152% and fungal to bacterial ratios by 23.3% but temperatures decreased by 3.42% suggesting that canopy condition continues to affect soil properties and microbial processes a decade after gap creation. These results highlight the contribution of DWD to the forest floor and the influence of decaying wood characteristics on belowground ecosystems critical to future forest productivity. Retaining or adding heterogeneously distributed DWD of varying decay status may be essential to maintain ecosystem functions associated with nutrient cycling and microbial community dynamics in managed forests.

天然森林干扰事件可以通过两种方式影响土壤生物地球化学过程-通过产生被砍伐的木屑（DWD；倒下的树树干或树枝）和通过形成冠层间隙来改变森林的微气候。DWD代表了微生物生长的基质以及碳和养分的持久存储，但微生物活性也对温度和湿度敏感。我们研究了DWD和冠层间隙在土壤微生物过程中的潜在相互作用，并想知道由操纵森林结构产生的微气候条件是否足以抑制产量，从而改变了关键的生态系统过程。将间隙和DWD（直径大于10厘米）添加到成熟，均匀老化的第二生长的北部硬木森林中（弗兰博实验；威斯康星州北部，美国），以提高结构复杂性并促进通常与后期成功森林有关的关键生态系统过程。我们调查了DWD和差距对土壤微生物群落组成，细胞外酶活性和土壤特性的影响。在操作十年后，在间隙和封闭的冠层中，在接近中等衰减的DWD和距DWD（对照）2 m的附近取样土壤。

DWD分解根据衰减类别和冠层条件对周围土壤产生不同的影响。在间隙中高度衰减的DWD附近，平均C和P电位胞外酶活性（BG，BX和AP）增强。缝隙中细菌的相对丰度（放线菌，厌氧菌，革兰氏阴性菌和阳性菌）保持恒定，但从5月到8月在封闭的树冠中下降。在缝隙中，土壤总可交换阳离子增加了34.6％，有效磷增加了152％，真菌与细菌的比率增加了23.3％，但温度降低了3.42％，表明在缝隙形成后的十年，冠层状况继续影响土壤特性和微生物过程。这些结果突出了DWD对森林地面的贡献，以及腐朽的木材特性对地下森林生态系统的影响，这些对未来森林生产力至关重要。保持或添加具有不同衰减状态的非均质分布DWD，对于维持与人工林中养分循环和微生物群落动态有关的生态系统功能可能至关重要。