Analysis On The Causes And Countermeasures Of Siberian Larch Degradation In Altai Mountain

Forest degradation refers to the phenomenon of ecosystem changes such as the reduction of forest land area,the change of stand structure,and the decline of ecological service function compared with the original forest.Natural forest is an important part of the forest ecosystem.The natural forests in Altai Mountains in Xinjiang are widely distributed,more than90% of which are Siberian larch.According to the management department,the degradation of the natural forests in Altai Mountains is relatively obvious.Therefore,this study aimed at the natural forest in Altai Mountain with Siberian larch as the main tree species as the research object,through questionnaire survey,sample plot survey,experimental analysis and other ways,to explore the main reasons for the degradation of Larix gmelini in Altai Mountain,Xinjiang,and put forward restoration countermeasures accordingly,providing a reference for the protection and restoration direction of Larix gmelini in Altai Mountain.With the help of origin and other software,the relevant data were screened to analyze the impact of different impact factors on Siberian larch and relevant repair strategies.With the help of questionnaire survey,the possible degradation direction of Siberian larch was determined,based on which different targeted tests were carried out,and the causes of degradation and feasible restoration directions were proposed according to the test results.The main research results are as follows:(1)According to the questionnaire survey,the possible factors causing the degeneration of larch include 10 factors,such as low seed vigor,pests and diseases,allelopathy of litter,low seed setting rate of over mature forest,light transmittance,physical barrier of litter or turf,water,extreme climate,overgrazing and human interference.Among them,physical barriers of litter or turf,overgrazing and water conditions are the main reasons for the possible degradation of Siberian larch,accounting for 75.96%,61.80% and 59.84% respectively.The conclusion is that the degradation of larch is the common result of many factors,and this paper focuses on the impact of grazing and cutting slope direction.The results show that they all have a certain impact on the degradation of larch,which can be used as a reference factor for remediation.(2)According to the questionnaire survey,many staff who have been engaged in forestry practice in Altai Mountain for a long time believe that overgrazing is an important reason for the degradation of larch.The survey shows that 61.8% believe that the degradation of larch in Altai Mountain is caused by cattle and sheep eating and trampling.According to the simulation test,goats chew larch seedlings seriously,sheep prefer larch seedlings,while cattle and horses have poor preference for larch seedlings.Therefore,in the future grazing prohibition process,we should focus on limiting goats and sheep in the larch seedling forest area,and we can moderately relax the grazing of cattle and horses.Considering that cattle and horses can trample on larch seedlings,we must also limit the number of cattle and horses when the seedling height is less than 60cm(the height of cattle and horses raising their legs).These conclusions can provide a useful direction for us to carry out grazing prohibition and grazing restriction measures.(3)According to the field investigation of larch under different grazing intensities in Altai Mountain,the average DBH and average tree height of larch species accounted for a large proportion in the moderate grazing sample plots,indicating that the age structure of the population was aging;In the light grazing sample plots,the age forest structure of larch is relatively more reasonable;Similarly,the number of natural forest trees in moderate grazing is the largest;Among them,M *(Lloyd’s average crowding degree),I(clumping index)and M */m(Lloyd’s clumping index)indexes of larch species under moderate grazing are the maximum values,indicating that their aggregation intensity is the largest;In moderate grazing,the regeneration diversity of seedlings under the forest is the best.To sum up,it is necessary to moderately prohibit and restrict grazing for the degradation of larch population.(4)According to the growth of larch in the slope direction of the sample plot after cutting,larch species in the half sunny slope and half shady slope sample plots occupy the upper space and are large diameter species,with average DBH of28.58 cm and 26.7cm respectively.The importance value of larch species in the half sunny slope sample plot is the largest,66.47,which is the dominant species in the half sunny slope sample plot;The semi sunny slope cutting sample plots are small diameter(0 < d ≤ 12 cm)and large diameter(d > 24 cm)natural forest tree species,and the height class(h > 21 m)natural forest tree species are more,the semi shady slope cutting sample plots are medium diameter class(12 cm < d ≤24 cm)natural forest tree species,and the medium height class natural forest tree species are more,and the shady slope cutting sample plots are low height class(3 m < h ≤ 11 m)and medium height class(11 m < h ≤ 21 m)natural forest tree species more;Larch seedlings are only found in the half sunny slope cutting sample plots,and they are highly concentrated in Grade V(H ≥ 100cm).From this,it can be seen that the semi sunny slope cutting sample plot is more suitable for the growth of larch species,which is consistent with that of larch as a sun loving positive species through discussion.Therefore,when conducting larch repair,such as replanting seedlings,it is very important to select the appropriate slope direction for replanting larch seedlings to improve the survival rate.