Fuel moisture exerts considerable influence on fire behavior and effects but varies substantially spatially and temporally. A portion of the spatial variation in dead surface fuel moisture of woodland and forest ecosystems is likely attributed to differences in stand conditions (i.e. stand density and composition). Existing evidence suggests that the role of stand conditions on dead surface fuel moisture is inconsistent across studies and more research examining the effects of stand conditions on seasonal microclimate and fuel moisture is needed. This study examined the effects of different stand conditions within Oregon white oak (Quercus garryana) woodlands and forests, including intact oak-dominated stands without Douglas-fir (Pseudotsuga menziesii), oak stands that have been invaded by Douglas-fir (encroached), and thinned stands with Douglas-fir removed within Oregon white oak ecosystems of northern California on seasonal variation of microclimate and dead surface fuel moisture. Stand condition had a strong effect on microclimate and fuel moisture over time with thinned stands consistently having warmer and drier conditions with lower fuel moisture than encroached stands in most surface fuel components. Differences in fuel moisture among stand conditions were most pronounced in the late spring and early fall. Observed fuel moisture values did not correlate well with estimates from remotely automated weather stations or process-based calculations, especially when observed fuel moisture values exceeded 20%. Collectively, these findings provide strong evidence that stand conditions can modify microclimate that contributes to variation in dead surface fuel moisture within Oregon white oak ecosystems of northern California. These differences are often not considered within commonly used fuel moisture estimates, emphasizing the need to develop better models and tools to allow managers to more accurately anticipate fuel moisture conditions in varying stands to model landscape variation in fire behavior and effects and to meet fuel reduction and restoration objectives.

燃料水分对火灾行为和效果产生相当大的影响，但在空间和时间上变化很大。林地和森林生态系统死表面燃料水分的部分空间变化可能归因于林分条件（即林分密度和组成）的差异。现有证据表明，林分条件对死表面燃料水分的作用在各项研究中不一致，需要更多研究来检查林分条件对季节性小气候和燃料水分的影响。本研究考察了俄勒冈州白橡木 ( Quercus garryana ) 林地和森林中不同林分条件的影响，包括没有花旗松 ( Pseudotsuga menziesii ) 的完整橡树为主的林分)、已被花旗松入侵（被侵占）的橡树林分，以及在加利福尼亚北部俄勒冈州白橡木生态系统中因小气候和死表面燃料水分的季节性变化而去除花旗松的变薄林分。随着时间的推移，林分条件对微气候和燃料水分有很大影响，在大多数表面燃料成分中，与被侵占的林分相比，变薄林分始终具有更温暖和更干燥的条件，燃料水分更低。不同林分条件下燃料水分的差异在春末和初秋最为明显。观察到的燃料水分值与远程自动气象站的估计或基于过程的计算没有很好的相关性，尤其是当观察到的燃料水分值超过 20% 时。总的来说，这些发现提供了强有力的证据，表明林分条件可以改变微气候，从而导致加利福尼亚北部俄勒冈州白橡木生态系统内死表面燃料水分的变化。在常用的燃料水分估计中通常不会考虑这些差异，强调需要开发更好的模型和工具，使管理人员能够更准确地预测不同林地的燃料水分条件，以模拟火灾行为和影响的景观变化，并满足燃料减少和恢复目标。