Soil Moisture and vegetation cover patterns after logging and burning an old-growth Douglas-fir forest in the Andrews Experimental Forest, 1960-1983

This soil moisture study was initiated in 1960 to investigate the effects of patch clearcut logging and slash burning (1962-63) in an old-growth Douglas-fir forest in the Oregon Cascade Range. Since soil moisture and vegetation sampling continued regularly until 1980, this is a unique data set that represents nearly two decades of post-treatment information. Plant cover exerts a profound influence on soil moisture levels through its effects on interception, infiltration, evaporation, and transpiration. In the Douglas-fir forests of the Pacific Northwest, clearcut logging and slash burning are common practices that can dramatically alter plant cover and soil moisture. Logging can increase soil moisture by temporarily reducing cover and associated water use, and burning may further augment soil moisture levels by suppressing the survival and regrowth of vegetation. Indeed, part of the rationale for slash burning in the region is to control shrubs and other vegetation that would otherwise compete with conifer seedlings for available moisture, light, and nutrients. Within a few years after burning, however, invading vegetation may deplete soil moisture to levels comparable to forested areas. Such observations point to the value of long-term information to better understand dynamic soil moisture and plant cover responses to forest practices.

本土壤湿度研究始于1960年，旨在探究美国俄勒冈州喀斯喀特山脉内原始花旗松（Douglas-fir）林的块状皆伐作业与1962-1963年的采伐剩余物焚烧所产生的生态效应。由于土壤湿度与植被采样工作持续开展至1980年，本数据集具备独特研究价值，其涵盖了近二十年的林分处理后长期监测数据。植物覆被通过影响降水截留、土壤入渗、蒸发与蒸腾过程，对土壤湿度水平产生深远调控作用。在太平洋西北地区的花旗松林中，皆伐与采伐剩余物焚烧是常见营林措施，可显著改变植物覆被结构与土壤湿度状态。皆伐可通过暂时性降低植被覆被与相应水分消耗，提升土壤湿度；而焚烧则可抑制植被存活与再生，进一步提高土壤湿度水平。事实上，该区域实施采伐剩余物焚烧的核心动因之一，便是控制灌木与其他植被，避免其与针叶树幼苗争夺可利用的水分、光照与养分。然而，焚烧数年后，入侵植被会逐渐消耗土壤湿度，使其恢复至接近原生林的水平。此类观测结果凸显了长期监测数据的重要价值，有助于更深入理解营林活动下土壤湿度与植物覆被的动态响应机制。