阔叶红松混交林林隙大小和林隙内位置对小气候的影响

Effects of forest gap size and within-gap position on the microclimate in Pinus koraiensis-dominated broadleaved mixed forest

在阔叶红松混交林的大、中、小林隙的中心和通过林隙中心的南、北、东、西冠空隙边缘共5个观测点安装HOBO自动气象站,测定2010年6—9月的气温、相对湿度、光量子通量密度(PPFD)以及林隙中心的总辐射和降水量,并在郁闭林分和空旷地设对照,分析了不同大小林隙之间以及林隙中心与林隙边缘之间小气候的差异及其随时间的动态变化,比较了晴天和阴天对林隙小气候因子日变化的影响.结果表明:PPFD依照大林隙、中林隙和小林隙的次序依次降低;对于同一林隙,林隙中心的PPFD大于边缘处;林隙中心的月均气温和月均总辐射均为7月>6月>8月>9月,并按照空旷地、大林隙、中林隙、小林隙和郁闭林分的次序依次递减;月均相对湿度为8月>7月>9月>6月,并按照郁闭林分、小林隙、中林隙、大林隙和空旷地的次序依次递减;不同大小林隙和空旷地观测期间降水总量和各月降水量基本上按照空旷地、大林隙、中林隙和小林隙的次序依次减少.晴天,大林隙PPFD、气温和相对湿度的变化幅度大于小林隙,阴天则相反.

HOBO automatic weather stations were installed in the central parts and at the south,north,east,and west edges of large,medium,and small gaps in a Pinus koraiensis-dominated broadleaved mixed forest in Xiaoxing＇anling Mountains to measure the air temperature,relative humidity,and photosynthetic photon flux density（PPFD） in these locations and the total radiation and precipitation in the gap centres from June to September 2010,taking the closed forest stand and open field as the controls.The differences in the microclimate between various size forest gaps and between the gap centers and their edges as well as the variations of the microclimatic factors over time were analyzed,and the effects of sunny and overcast days on the diurnal variations of the microclimatic factors within forest gaps were compared,aimed to offer basic data and practice reference for gap regeneration and sustainable management of Pinus koraiensis-dominated broadleaved mixed forest.The PPFD was decreased in the order of large gap,medium gap,and small gap.For the same gaps,the PPFD in gap centre was greater than that in gap edge.The mean monthly air temperature and total radiation in gap centres were declined in the sequence of July,June,August,and September,and the amplitudes of the two climatic factors were decreased in the order of open field,large gap,medium gap,small gap,and closed forest stand.The mean monthly relative humidity in gap centres dropped in the order of August,July,September,and June,and the amplitude of this climatic factor was decreased in the sequence of closed forest stand,small gap,medium gap,large gap,and open field.The total and monthly precipitations for the three different size gaps and open field during measurement period generally decreased in the order of open field,large gap,medium gap,small gap,and closed forest stand.In sunny days,the variations of PPFD,air temperature,and relative humidity were greater in large gap than in small gap,but in overcast days,it was in opposite.