| Forest gap widely exists in the forest as a special property of microstructure; forest gap formation enhances the heterogeneity of disturbed habit and influences the structure and dynamic process of community, finally affects landscape structure and function. The spatiotemporal distribution patterns in the photosynthetic photon flux density (PPFD), air temperature, air relative humidity, soil temperature and soil water content in primary Pinus koraiens-dominated broadleaved mixed forest gap in XiaoXing'an Mountains were analyzed by using classical statistics and geological statistics method. The results showed:The diurnal maximum PPFD in the forest gap appeared between 11:00 and 13:00 on sunny or overcast days. On sunny days, the maximum PPFD during various time periods did not located in fixed locations, the diurnal maximum PPFD occurred in the canopy edge of northern part of the gap; while on overcast days, it occurred in the center of the gap. The mean monthly PPFD in the gap was the highest in June, the lowest in September, with the largest range observed in July. The maximum air temperature happened between 9:00 and 15:00 on sunny days, between 15:00 and 19:00 on overcast days; the locations were 8 m in the southern part of the gap center both on sunny and overcast days. From 5:00 to 9:00, the air temperature at measured positions in the gap was higher on overcast days than on sunny days; but from 9:00 to 19:00, it was opposite. The mean monthly air temperature was the highest in June, and the lowest in September; The maximum relative humidity appeared between 5:00 and 9:00 on both sunny and on overcast days, and occurred in the canopy border of western part of the gap, with the relative air humidity on overcast days being always higher than that on sunny days. The mean monthly relative humidity was the highest in July, the lowest in June. Heterogeneity of PPFD was higher on sunny days than on overcast days, but the heterogeneity of air temperature and relative humidity were not obvious. The maximum PPFD, air temperature, relative humidity were not located in the same position among different months during the growing season. For mean monthly PPFD and air temperature, their variation in gradient was higher in and around the center of gap; while for mean monthly relative humidity, it was higher in the edge of forest gap.The difference in soil temperature existed among differently measuring locations. Monthly mean values of soil surface temperature, its extreme temperature and the temperature in shallow soil layers (5 cn and 20 cm) changed in the time sequence inconsistency. Stills and ranges of soil temperature was dynamic in different months, complex degree of patch shapes was different. As for monthly mean values, the soil surface temperature and its maximum temperature were highest in June, the minimum soil surface temperature was highest in August, and the minimum soil surface temperature in shallow layer was highest in July. Maximum soil temperature occurred in different positions in different months in the growing season. There was significantly spatiotemporal heterogeneity in soil temperature among forest gap, understory and bare ground.There was difference in soil water content among differently sampling locations in the forest gap. Monthly mean soil water content in 0-7.6 cm,0-12 cm and 0-20 cm decreased in the order of September, July, August and June, mean soil water content in the same month dropped in the order of 0-7.6 cm,0-12 cm and 0-20 cm. Stills and ranges of the mean soil water content were dynamic in different months, their intensity and scale of spatiotemporal heterogeneity was 0-7.6 cm>0-12 cm>0-20 cm, the complex degree of patch shapes was different. Monthly mean of soil water content was highest in 0-7.6 cm in September, the lowest in 0-20 cm in June. The maximum of soil water content appeared in the forest gap center and its nearby areas.The environmental factors in the studied forest gap presented significantly spatiotemporal heterogeneity, their heterogeneity intensity and scale were dynamic in different months; the variation of environment factors was also different among forest gap, understory and bare ground. This could have greater influence on the regeneration of Pinus koraiens-dominated broadleaved mixed forests gap. Therefore, the study on changing rules of various environmental factors during the process of gap regeneration, the analysis on the reason and the effect of the formation of regeneration patterns would provide references for sustainable management, biological diversity maintenance and secondary forest restoration for Pinus koraiens-dominated broadleaved mixed forests.
|
PDF Full Text Request