| Thirty-four representative forest gaps of the three typical forest types of linden-Korean pine,birch-Korean pine and spruce-fir Korean pine forests were selected as the study object in Liangshui National Nature Reserve,Dailing District,Yichun City,Little Xing’an Mountains.We studied the effect of gap size on microenvironment characteristics(climatic factors,soil physicochemical properties,soil microbial diversity,structure characteristics of border trees and fallen trees,plant diversity)in gaps.Analysis of variance was adopted to compare the differences in the micro-environmental factors in gaps of different sizes of different forest types in the growing season,and three gaps of large,middle and small sizes were selected in linden-Korean pine forest,and the withered leaf litter bags of Pinus koraiensis,Tilia amurensis and Betula costata were placed in gaps and in the corresponding closed stands,and principal component analysis was used to discuss the variation of the soil biochemical properties during the process of litter decomposition in gaps.Redundancy analysis and multiple linear regression model were applied to ordination of the correlation factors and influential factors of biodiversity,and the environmental factors that were significantly correlated with biodiversity were selected.Through the above research and thus it revealed the effect of gap size on microenvironment characteristics in gaps.It was aimed to explore the internal relationships among "Gap-Environment-Vegetation’ of broad-leaved Korean pine forest,and to provide the basic data and the theory basis for the reasonable interpretation of the maintaining mechanism of biodiversity and the scientific management and transformation of the existing Korean pine plantations.The results are as follows:(1)Effects of gap size on the dynamic variation of the micro-environmental factors in gaps of three forest types in the growing seasonThe effects of gap size on Photosynthetic Photon Flux Density in linden-Korean pine forest,air temperature and precipitation in spruce-fir Korean pine forest and air relative humidity in birch-Korean pine forest were more significant than other forest types;the effects of gap size on soil temperature,water content,pH value,organic matter,the ratio of carbon to nitrogen,ammonium nitrogen and nitrate nitrogen in birch-Korean pine forest and in spruce-fir Korean pine forest and soil total nitrogen and invertase activity in linden-Korean pine forest and in spruce-fir Korean pine forest were more significant than other forest types.(2)Effects of gap size and litter decomposition on soil biochemical propertiesWith the increase in gap size,the influential degree to principal component(ordination of score coefficient)of soil dissolved organic carbon and nitrogen rose significantly,whereas the influential degree of inorganic carbon and nitrogen declined significantly.The influential degree to principal component of soil dissolved organic carbon and nitrogen under the decomposition of Pinus koraiensis withered leaves was higher than that under the decomposition of Tilia amurensis and Betula costata withered leaves,whereas the influential degrees of soil inorganic carbon and nitrogen and microbial biomass carbon and nitrogen under the decomposition of Pinus koraiensis withered leaves were lower than that under the decomposition of broad withered leaves.With the increase in decomposition time of litters,the influential degree to principal component of soil inorganic carbon and nitrogen presented a trend that rose at first and then declined,and the influential degree of soil active organic carbon and nitrogen presented a trend that declined at first and then rose.Plate method and PLFA method were used to analyze the effect of litter decomposition on soil microbial community structure and it showed that:soil microbial community structure was significantly correlated with litter carbon,litter C/N,soil microbial biomass nitrogen and soil dissolved organic nitrogen.Besides,the PLFA concentrations of bacteria in the soil under the decomposition of Pinus koraiensis withered leaves was significantly lower than other treatments(P<0.05),whereas the differences in PLFA concentrations of fungi and actinomycetes in the soil under the decomposition of different litter types were not significant(P>0.05).(3)Effects of gap size and forest type on the characteristics of gap border trees and fallen trees in gapsMost of the ratios of diameter to height(D/H)of the selected gaps were 0.5～1.5,border trees were concentrated in the height of 15～25 m,the diameter at breast height of 20 cm below,and the diameter class structure was in line with index distribution(R2=0.896),the ratio of crow inclination was concentrated in 0.4～0.6(D/H of 0.5～1.0)and 0.6-0.8(D/H of 1.0～1.5).Fallen trees were concentrated in the length of 10 m below,the diameter of 20 cm below,and the length class and diameter class structures were in line with logarithmic distribution(R2=0.897)and index distribution(R2=0.989),respectively,the decay degree was concentrated in I grade and II grade,and its structure was in line with linear distribution(R2=0.945),The formation of fallen trees was mainly by trunk base snapping and uprooting.From broad-leaved Korean pine forest to coniferous Korean pine forest,the importance values of border trees and fallen trees of Korean pine and the hardwoods of maple,birch,linden,elm and oak and some unknown fallen trees of the hardwoods in gaps decreased significantly(P<0.05),whereas the importance values of border trees and fallen trees of spruce and fir and some unknown fallen trees of coniferous woods increased significantly(P<0.05).Correlation analysis showed that:with the increase in gap D/H,the number of border trees increased significantly,but due to the effect of the size of expanded forest gap,the relative density decreased significantly(P<0.05),whereas the number and the diameter of fallen trees were significantly and positively correlated with D/H of expanded gap(P<0.05).(4)Effects of gap size on plant diversity of the three forest types Apart from that under the gap D/H of 0.5～1.0 in linden-Korean pine forest,the important values of woody plants were all higher than those of herbaceous plants in gaps under different D/H of the three forest types.Through the comparison among the three forest types,the important values of seedlings of woody plants in spruce-fir Korean pine forest,those of juveniles in birch-Korean pine forest and those of herbaceous plants in linden-Korean pine forest were all significantly higher than that in the other forest types(P<0.05).Through the comparison of the nearly three years’ height increments of the main regenerated tree species of arbor among the three forest types under different D/H,it was found that in gaps under the D/H of 0.5～1.0,the increments of Abies nephrolepis and Picea asperala were higher than other tree species,and significantly higher in spruce-fir Korean pine forest than that in the other forest types(P<0.05);in gaps under the D/H of 1.0～1.5,the increments of Picea asperata and Betula costata in linden-Korean pine forest,Abies fabri and Pinus koraiensis in birch-Korean pine forest,and Abies nephrolepis and Pinus koraiensis in spruce-fir Korean pine forest were all significantly higher than that in the other forest types,respectively(P<0.05).There were significantly higher woody plant diversity in linden-Korean pine forest and herbaceous plant diversity in spruce-fir Korean pine forest than that in the other forest types(P<0.05).Through the ordination of factors correlated with plant diversity,among the environmental factors that correlated with the quantity characteristics of arbor and shrub,soil urease and the individual densities of the seedlings,soil invertase and proteinase and the total average height of the seedlings and juveniles,litter standing crop and regeneration densities were all significantly correlated with each other,meanwhile,the characteristics of fallen trees were significantly correlated with the average ground diameter of the juveniles of arbor and shrub,and the characteristics of border trees were significantly correlated with the regeneration density of shrub and herbage.The quantity characteristics of component tree species of arbor were more significantly correlated with gap characteristics;and the quantity characteristics of component species of shrub and herbage were more significantly correlated with soil characteristics.The quantity characteristics of the component tree species of arbor and shrub were significantly correlated with the diameter of fallen trees and the ratio of crow inclination of border trees,soil organic matter and total nitrogen,and herbage coverage,and the regeneration density of the component species of herbage was significantly correlated with the number of border trees,litter standing crop and forest type.The nearly three years’ increments of the regenerated tree species of arbor Abies nephrolepis,Tilia,Picea asperata,Betula costata in gaps and the characteristics of border trees and fallen trees,the nearly three years’increments of Acer ukurunduense and Acer trgmentosum and D/H and shrub density respectively,the nearly three years’ increments of Pinus koraicensis and Fraxinus mandshurica and soil urease and invertase respectively,the nearly three years’increments of Abies fabri and soil total nitrogen,the nearly three years’ increments of Quercus mongolica and litter standing crop were all significantly correlated with each other.There were significantly correlations between Shannon-Wiener diversity index H,richness index R,evenness-dominance-abundance index Z of woody plants and Z of herbaceous plants and shrub characteristics,ecological dominance λ of woody plants and H,R,λ of herbaceous plants and the characteristics of border trees and fallen trees,evenness index J of woody plants and herbaceous plants and soil organic matter,Simpson diversity index D of woody plants and D/H,D of herbaceous plants and soil total nitrogen.The multiple regression model showed that the effects of soil enzymes,D/H,the ratio of crow inclination of border trees,shrub height and forest type on plant diversity in gaps were more significant.In conclusion,gap size,to varying degrees,regulates the dynamic variations of microclimate characteristics and soil properties in broad-leaved Korean pine forest gaps of three forest types in the growing season,the structure characteristics of gap border trees and fallen trees in gaps,and the species regeneration,growth and diversity of arbor,shrub and herbage.Meanwhile,litter decomposition also has certain abilities to regulate the content of soil carbon and nitrogen fractions of different forms and the characteristics of soil microbial community structure in gaps.In addition,biodiversity in gaps and the environmental factors among gap characteristics,soil characteristics,the characteristics of shrub and herbage,and the characteristics of forest type were significantly associated with each other in different degrees,and it was also significantly affected by soil enzymes,D/H,the ratio of crow inclination of border trees,shrub height and forest type. |
PDF Full Text Request