| As an important way of interference in forest ecosystem,the formation and changes of forest gap eonstitute a dynamic mosaie structure of forest ecosystem and plays an important role in the regeneration of vegetation and the cycle of vegetation.The endangered and rare plant Tsuga longibracteata has ecological functions,such as maintaining the ecological balance,water conservation,etc.,but it is always faced with poor site condition,difficult to update in forest of Tianbaoyan National Nature Reserve.So,the analysis of forest gaps on Tsuga longibracteata forest regeneration promoting effect has become the focus of this paper.This study adopted the method of sample plot survey,and five kinds of typical Tsuga longibracteata forest(Tsuga longibracteata pure forestsn Tsuga longibractoata+Cyclobalanopsis glauca mixed forests、Tsuga longibracteata+Rhododendron simiar in mixed forests、Tsuga longibracteata+Phyllostachys hererocycla mixed forests、Tsuga longibractea’a+hardvwood mixed forests)gaps in Tianbaoyan National Nature Reserve were surveyed,through the study of different stands on Tsuga longibracteata forest inside and outside of the forest gaps of the species diversity,the micro-environment characteristics and features of the fallen logs,analysised the effect of forest gaps of Tsuga longibracteata in different stands,different size,different developmental stages and different positions for the species richness and diversity,discussed the dynamic changes of different locations,different periods of light intensity,air and soil temperature and humidity and other micro environmental factors in different stands and area forest gaps,revealed distribution pattern and gradient change of fallen logs density,coverage area and volume of different diameter and different length,different decay classes structure in the different stands forest gaps.It also provide a scientific basis for the regeneration and succession of the endangered species Tsuga longibracteata and the protection and restoration of forest gaps disturbance response.The results showed that:(1)Analysis of the diversity species of forest gaps:Forest gaps can increase the Tsuga Tianbaoyan forest community species richness and species diversity,and species distribution of outside of forest gaps than inside of forest gaps is more uniform;the different levels of each stand for the use degree of different size forest gaps is significant difference,all levels of the large gap species diversity is greater than small gap,and the sensitivity of gap size changes:shrub layer>herb layer>tree layer;different developmental stages of forest gaps is influence significantly for all levels of species diversity,the species diversity of middle,late phase gap is relatively large in the tree layer and the species diversity of early,middle phase gap is relatively large in the shrub layer and herb layer,the sensitivity of gap developmental stages changes:herb layer>shrub layer>tree layer;the species richness and diversity of the edge area is close to the central area and numerical is the highest in different stands,followed by the expansion area,the species richness and diversity of the non-gap area is the lowest;forest gap edge area due to edge effect and to increase the effect of species diversity,with forest gap from the early period to the late development,weaken the intensity of edge effect,the gap began to constantly to the original forest community recovery,which the edge effect of Tsuga tongibracteata+hardwood mixed forests gap is stronger.(2)Analysis of the micro-environment characteristics of forest gap:The micro-environment characteristics of Tsuga longibracteata forest gap with the increase of gap area,the greater the light intensity and air temperature,the more intense the air and soil temperature and humidity change;light intensity and air temperature of forest Gap from the central area to the non-gap area showed deereasing trend,and soil temperature and humidity with different stands,the ehanges in the different position also showed heterogeneity;the diurnal variation of average illuminance of gaps was normal distribution curve,and the morning and evening was relatively low,and the noon was highest;the diurnal variation of average air and soil temperature of gaps was single peak convex curve,and the morning and evening was relatively low,and the afternoon was highest,but the air and soil humidity had the opposite trend;the dynamic changes of air and soil temperature are negatively correlated with air and soil humidity.The differences were significant in the size and the variation range of the light intensity,air and soil temperature and humidity of the forest stands,the micro-climatic conditions of small gap is close to the forest,the change of temperature and humidity is s Tab.the temperature and humidity of large gap is more intense.Overall,the change of micro-environment of Tsuga longibracteata+hardwood mixed forests is relatively sTab.,special layer structure and composition of the vegetation,the complex spatial environmental heterogeneity of Tsuga longibracteata+Phyllostachys heterocycla mixed forests promotes the Tsuga longibracteata seedling regeneration and growth in the two stands.(3)Analysis of fallen logs characteristics of forest gap:The fallen logs density,coverage area and volume of all forest stands inside and outside of forest gaps were showing the law:Tsuga longibracteata+Phyllostachys heterocycla mixed forests>Tsuga longibracteata+Rhododendron simiarum mixed forests>Tsuga longibracteata+hardwood mixed forests>Tsuga longibracteata+Cyclobalanopsis glauca mixed forests>Tsuga longibracteata pure forests,roughly reflect with the increase of altitude gradient decreases,the fallen logs coverage area and volume inside of forest gaps was significantly greater than outside of forest gaps;the fallen logs density of all forest stands inside and outside of forest gaps in 0～10cm diameter class was greater,the volume was the smallest,and the fallen logs density was decreased with the increasing of the diameter class,and the fallen logs coverage area of the 10～20cm diameter class was the largest,the advantage of fallen logs inside of forest gaps in diameter larger than 20cm was more obvious than outside of forest gaps,the advantage of fallen logs outside of forest gaps in 0～10cm diameter class was greater;all forest stands inside and outside of forest gaps,the proportion of fallen logs density in 1～3m length class was the largest,the number of fallen logs in ≥ 9m length class was the smallest,the advantage of fallen logs inside of forest gaps in 6～9m and≥9m length class was more obvious than outside of forest gaps,the advantage of fallen logs outside of forest gaps in 1～3m and 3～6m length class was greater;the fallen logs density inside of forest gaps in Ⅲ and Ⅱdecay classes was the greatest,the fallen logs density outside of forest gaps in II and I decay classes was the greatest,the fallen logs density inside and outside of forest gaps in Ⅳ and V decay classes was the smallest;the fallen logs coverage area and volume size inside and outside of forest gaps were showing the law:Ⅲ>Ⅱ>Ⅰ>Ⅳ>V;the distribution of the number of the fallen logs inside of forest gaps has a great advantage in Ⅲ and IV decay classes,and the number of the fallen logs outside of forest gaps is dominant in Ⅰ and Ⅱ decay class;the different Tsuga longibraclfoarest stands inside and outside of forest gaps has significant influenee on the quantitative characteristics of fallen logs. |
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