Gap Characteristics Of Larix Principis-rupprechtii Mayr. And Pinus Tabulaeformis Carr. Mixed Forest And Their Effects On Shrubbery And Grasses Species Diversity

Gaps created by cuttings in forests as a kind of small scale and transitoryinterference, playing a critical role in development of forest structure andimprovement of woodland environment. They can provide good living place forregenerative seedlings,as well as important environment which maintain the forestbiodiversity,and they are of great significance in the succession of forest ecosystem.This study takes Larix principis-rupprechtii Mayr. and Pinus tabulaeformis Carr.mixed forest of Xinfeng Forestry in Mulan Forestry Management Bureau of Hebeiwhich lies in Yanshan Mountain as research object, respectively surveyed gapcharacteristics as well as shrubbery and grasses species diversity through line transectand quadrat method, the data are analyzed by use of SPSS17.0and ForStat, it is aimedat studying gap characteristics and their influence on shrubbery and grasses speciesdiversity. The main results were as follows:(1) Among the38gaps, gaps ranged from40-60m2were in the majority(23.68%).Area proportion of gaps ranged from100-120m2was maximum, which was30.59%.True form of gaps were all irregular polygon, most gaps(35)were similar tothe oval,92.11%of the total number. Prophase and anaphase gaps were the mostwhose percentages were respectively31.58%and39.47%.（2）There were190gap makers,which were all Larix principis-rupprechtiiMayr.and Pinus tabulaeformis Carr., the proportion of Pinus tabulaeformis Carr. waslarger(54.21%);number of gaps of2gap makers was maximum(6), which was15.79%of the total; the diameter class of gap markers were mainly less than25cm and wereall stumps, which fully demonstrated that the gaps in the area were often influencedby people but the disturbance intensity was small. There were124Pinustabulaeformis Carr. and59Larix principis-rupprechtii Mayr. among the183gapborder trees, individuals with height of15-17m were most,which was23.50%of thetotal; diameter class of border trees were mainly concentrated on20-35cm, which was57.92%of the total, this reflected part of the gap border trees were younger.(3) Gap characteristics had influences on shrubbery and grasses speciesdiversity.There were143shrubbery and grasses species in Larix principis-rupprechtiiMayr. and Pinus tabulaeformis Carr. mixed forest, Spiraea pubescens was dominantspecies among shrubbery, grasses dominant species was Carex lanceolata Boott. Gaps ranged from40-60m2had maximum species number and individual number. Speciesrichness of shrubbery was maximum in gaps of120-140m2, while species richness ofgrasses was maximum in gaps of40-60m2and it reduced gradually along with thearea.(4)Species number of shrubbery and grasses in central zone of gaps was higher thanother zones(94), individual number in southern region was maximum. There were nosignificant differences on R and ecological dominance(λ)of shrubbery betweendifferent zones of gaps(P﹥0.05),for D,H and Js, eastern region(E) is significantlyhigher than north region(P﹤0.05), differences between other regions were notsignificant(P﹥0.05); there were no significant differences between diversity indexesin different zones of grasses(P﹥0.05). Among the shape indexes of gaps, opendegree(K)had significant correlation with D,H and R of shrubbery, had significantcorrelation with Js of grasses, effect of other shape indexes on species diversity wasnot obvious.