Disturbance history is known to affect fire risk by altering fuel dynamics, but the effects of disturbance on micro-meteorological conditions that influence fire are poorly understood. Logging and wildfire can significantly alter the height and density of vegetation in forests. These structural attributes can influence aspects of the sub-canopy microclimate that may influence forest flammability. We used portable weather stations to measure the effects of time since logging and time since wildfire on air temperature, relative humidity, vapour pressure deficit and windspeed at 119 sites in coastal forest in south-eastern Australia. These data were used to calculate fuel moisture and within forest Forest Fire Danger Index (FFDI). Data were collected on 345 days (12 days per site on average), over three consecutive fire seasons. Temperature, vapour pressure deficit, windspeed and forest FFDI all decreased with time since logging, while relative humidity and fuel moisture content increased. Windspeeds also decreased with time since wildfire. These effects continued for at least 60 years after disturbance. Over the duration of our study, fuel was available to burn (below 16% fuel moisture content) 1.4 times more often in recently logged sites (zero years since logging) compared to sites that had not been logged for 71 years. Recently logged sites were also predicted to have a high Fire Danger Rating (FFDI = 12–24) on 24 days, compared to just two days at sites last logged 71 years ago. Our findings indicate that the changes in vegetation associated with logging and to a lesser extent wildfire, increase the risk of fire. This research provides new insights into the effects of antecedent logging and wildfire on forest flammability that can be used to inform the management of fire prone forests.

已知扰动历史通过改变燃料动力学来影响火灾风险，但扰动对影响火灾的微气象条件的影响却知之甚少。伐木和野火可以显着改变森林植被的高度和密度。这些结构属性会影响可能影响森林可燃性的亚冠层小气候方面。我们使用便携式气象站测量了澳大利亚东南部沿海森林 119 个地点的伐木后时间和野火后时间对气温、相对湿度、蒸汽压不足和风速的影响。这些数据用于计算燃料水分和森林火灾危险指数 (FFDI)。在连续三个火灾季节中收集了 345 天（平均每个站点 12 天）的数据。温度，自伐木以来，蒸汽压不足、风速和森林 FFDI 均随时间下降，而相对湿度和燃料水分含量则增加。自野火以来，风速也随着时间的推移而下降。这些影响在干扰后至少持续了 60 年。在我们的研究期间，与 71 年未记录的地点相比，最近伐木的地点（伐木后零年）的燃料可燃烧（低于 16% 的燃料水分含量）是 1.4 倍。预计最近记录的站点在 24 天内具有较高的火灾危险等级 (FFDI = 12–24)，而上次记录的站点在 71 年前只有两天。我们的研究结果表明，与伐木相关的植被变化以及较小程度的野火会增加火灾的风险。