阔叶红松混交林林隙大小和掘根微立地对小气候的影响

在小兴安岭阔叶红松混交林2.55 hm²样地内,选取由掘根倒木形成且具有坑和丘微立地的3个代表性林隙,并以空旷地和郁闭林分为对照,利用多通道HOBO自动气象站于2011年7-9月测定了不同大小林隙中心和丘顶部的光合有效辐射(PAR)、气温、相对湿度以及林隙中心的总辐射和降水量,比较了不同月份不同大小林隙中心和丘顶部微气候因子的差异,分析了不同大小林隙中心微气候因子的月变化以及不同大小林隙在典型天气条件下林隙中心和丘顶部微气候因子的日变化.结果表明: 3个不同大小林隙的月均PAR和月均气温排序是大林隙>中林隙>小林隙,月均相对湿度排序是小林隙>中林隙>大林隙;同一林隙中,丘顶部月均PAR和月均气温大于林隙中心,月均相对湿度为林隙中心>丘顶部;不同大小林隙和对照月均总辐射与月均气温均为7月>8月>9月,空旷地>大林隙>中林隙>小林隙>郁闭林分,月均相对湿度为郁闭林分>小林隙>中林隙>大林隙>空旷地.郁闭林分与各林隙以及与空旷地之间的月均相对湿度差异均显著;7-9月总降水量按照空旷地、大林隙、中林隙、小林隙、郁闭林分的次序依次递减;无论晴天与阴天,丘顶部日均PAR和日均气温都大于林隙中心,日均相对湿度则相反;无论丘顶部还是林隙中心,晴天日均PAR和日均气温都大于阴天,日均相对湿度则为阴天>晴天.

Effects of suspended solid on the survival, growth, and antioxidant enzyme activities of Mactra veneriformis

Three representative forest gaps with pit-mound microsites formed by uprooted trees were selected within the 2.55 hm² plot in a Pinus koraiensis dominated broad leaved mixed forest in Xiao Xing’an Mountains of Northeast China. The cleared land and closed stand were set up as the controls, and the PAR, air temperature and relative humidity in the centers of different size gaps and in mound top as well as the total radiation and precipitation in the gap centers were measured between July and September, 2011 by using multichannel automatic meteorological stations. The differences of the microclimate between the gap centers and mound top in different months were compared, and the monthly and diurnal variations of the microclimatic factors in the gap centers and in the mound top under typical weather conditions were analyzed. The results showed that the mean monthly PAR and air temperature in the three gaps of different sizes were in the order of large gap > medium gap > small gap, and the mean monthly relative humidity was in the order of small gap > medium gap > large gap. For the same size gap, the mean monthly PAR and air temperature were higher in the mound top than in the gap center, whereas the mean monthly relative humidity was higher in the gap center than in the mound top. Both the mean monthly total radiation and the mean monthly air temperature in the forest gaps and in the controls were in the order of July > August > September and of cleared land > large gap > medium gap > small gap > closed stand, while the mean monthly relative humidity was in the order of closed stand > small gap > medium gap > large gap > cleared land. The differences in the mean monthly relative humidity between closed stand and various gaps and between closed stand and cleared land reached significant level. The monthly precipitation from July to September decreased in the order of cleared land > large gap > medium gap > small gap > closed stand. Whether in sunny days or in overcast days, the mean daily PAR and air temperature were higher in mound top than in gap center, and the mean daily relative humidity was in opposite. Whether in mound top or in gap center, the mean daily PAR and air temperature were higher in sunny days than in overcast days, while the mean daily relative humidity was higher in overcast days than in sunny days.