| Due to the pit and mound microsites formed by treefall in the Pinus koraiensis-dominated broadleaved mixed forest, increased the complexity of the forest, promoted the regeneration ability of surrounding trees and grasses in the forest community, and improved the light, temperature, moisture and other environmental conditions of gaps at the same time. So the microsites formed by uprooting trees play an important role in maintaining forest species diversity and forest landscape pattern.This paper researched on characteristics of pit and mound microsites by uprooting tress and microenvironment effects on seedling.2.55hm2fixed sample plot was set up in Pinus koraiensis-dominated broad-leaved mixed forest, the characteristics of42treefalls and their pit and mound microsites and the status of vegetation regeneration were investigated. Soil water content, soil temperature, relative air humidity, photosynthetically active radiation (PAR) on five microsites (mound top, mound face, pit wall, pit bottom, and intact forest floor) were measured June2011; Three representative forest gaps with pit-mound microsites formed by uprooted trees were selected, the clearing and closed forest was set up as controls, PAR, air temperature, relative humidity and total radiation, precipitation in the gap center, PAR, air temperature, relative humidity in the mound top in different size gaps were measured using multichannel automatic meteorological stations. The difference of microclimate between gap center and mound top of forest gaps of different size in different months was compared, the monthly variations in the microclimatic factors in the center of forest gaps of different size and the diurnal variations in the microclimatic factors in the center of forest gaps and the mound top under typical weather conditions were analyzed, quantity characteristics of main tree species in the three different sizes uprooting gaps, and the pit and mound microsites effect on regeneration of tree species in the forest gaps were researched.The results show that:among five mirosites chosen in this study, PAR was highest at mound top (527.9μmol·m-2·s-1) and lowest in intact forest floor (58.7μmol·m-2·s-1); soil temperature was highest at mound top (16℃) and lowest in pit bottom (13.3℃); soil water content was highest at pit bottom (34.62%) and lowest in mound face (0.5%); relative air humidity was highest at the intact forest floor (75.95%) and lowest in mound top (68.03%). The frequence of five tree species which formed pit/mound complex decreased in the order of42.9%(Pinus koraiensis),31.0%(Picea asperata Mast),16.7%(Betula platyphylla Suk),7.1%(Abies fabri),2.4%(Prunus padus). The orientation of the two-thirds of42falltrees went down to northwest direction. Highly significant correlations existed between treefall volume and pit depth, pit length, mound height, mound width, respectively; there was negative correlation between treefall volume and mound thickness; significant and highly significant correlations existed between pit width (r=0.328, P=0.017), pit length (r=0.527, P=0), and mean diameter at breast height (DBH), respectively. Species richness among different microsites decreased in the order of intact forest floor, pit, and mound. The cover of all tree species degraded in the order of intact forest floor, pit, and mound.Mean monthly PAR, air temperature in the three gaps of different size were listed in the decreasing order of large gap, middle gap, and small gap, mean monthly relative humidity did in the decreasing order of small gap, middle gap, and large gap; for the same gap, mean monthly PAR, air temperature in the mound top was higher than in the gap center, mean monthly relative humidity in the gap center was higher than in the mound top; both mean monthly total radiation and mean monthly air temperature of forest gaps of different size and controls were ranked in the decreasing order of July, August, and September as well as the clearing, the large gap, middle gap, small gap, and closed stand, whereas mean monthly relative humidity did in the decreasing order of closed forest, small gap, middle gaps, large gap and the clearing. The difference in mean monthly relative humidity between closed stand and various gaps, and between closed stand and clearing reached significant level (P<0.05); monthly precipitation from July to September decreased successively in the order of the clearing, the large gap, middle gap, small gap, and closed stand, whether in sunny day or in overcast day, mean daily PAR and air temperature in the mound top were higher than in the gap center, mean daily relative humidity was opposite; whether in the mound top or in the gap center, mean daily PAR and air temperature in sunny day were higher than in overcast day, relative humidity mean daily in overcast day were higher than in sunny day.The order of density and important value of trees in the different size forest gaps was Pinns koraiensi>Picea asperata Mast>Prunus padus>Ulmus elm>Abies nephrolepis, The order of density and important value of shrub was Corylus mandshurica>Acanthopanax senticosu>Sorbaria sorbifolia>Loniceara caeurlea>Deutzia glabrata>Philadelphus schrenkii, the order of the important value of tree seedling species in the forest gap renew layer was pit>forest gap center>mound; the order of the important value of shrub seedling species was forest gap center>pit>mound.This study provide the basis data and practical reference for the renewal of the original broad-leaved Korean pine gap, degraded ecosystem restoration and sustainable management. |
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