| The Greater Khingan Mountains is one of the main permafrost regions in China.The latest concern is that due to global changes in temperature,the original permafrost environment has also been changed,with the gradual degradation of permafrost and continuous thickening of active permafrost soil layer.The living environment of the vegetation in the Greater Khingan Mountains has been changed by its influence.Larix gmelinii is the most dominant tree species in the forests of the Greater Khingan Mountains,which together with the frozen soil of the Greater Khingan Mountains constitute the cold and humid environment in this area.Therefore,we can better understand the interdependent relationship between Larix gmelinii and frozen soil by studying the characteristics of Larix gmelinii and its undergrowth plants on different permafrost active layers.It provides theoretical basis for good management and long-term development of larch forest in the Greater Khingan Mountains.Therefore,this study in order to utilize modern larch as the research object,In the field laboratory,permafrost temperate activity is monitored by drilling the soil and placing thermometers in the soil.Combined with quantitative ecological and statistical data processing methods,the change characteristics of active permafrost thickening by larch index and its plant ecological characteristics under the forest are studied.The main research results and conclusions are as follows:(1)With the deepening of the active permafrost layer,the DBH growth rate of Larix gmelinii showed an increasing trend.The DBH growth rate and volume growth rate of Larix gmelinii in each active layer sample plot in the permafrost area are both lower than that of Larix gmelinii in the non-permafrost area,while the tree height growth rate and the active layer of permafrost have no obvious changes.(2)Different active layers have different effects on the temperature and nutrients of permafrost soil.The soil temperature shows a trend of gradual increase with the increase of permafrost active layers.The contents of soil organic matter,total nitrogen and total phosphorus in the permafrost area increased with the increase of the active layer of permafrost.Except for the 1.9m active layer plot,the contents of soil organic matter,total nitrogen and total phosphorus in all the active layer plots in the permafrost area decreased compared with those in the non-permafrost area.The soil total potassium content showed a decreasing trend,and the soil total potassium content in all the active layer samples in the permafrost region was increased compared with that in the non-permafrost region.(3)With the change of the active layer of permafrost,the undergrowth plants of Larix gmelinii forest have different responses to the change of the active layer.The Shannon diversity index and richness index of the active layer samples in the permafrost region increased with the increase of the active layer,but decreased compared with the non-permafrost region.The species dominance index of each active layer in the permafrost region decreased with the increase of the active layer,which was higher than that of the non-permafrost region.Aboveground biomass of shrub layer and herb layer under larch forest increased with the increase of active layer,and aboveground biomass in permafrost area decreased compared with non-permafrost area.The total number of species in each community showed a trend of increasing gradually.(4)Redundancy analysis showed that there was a strong correlation between DBH growth rate of Larix gmelinii and Shannon diversity index and richness index,has the strong correlation between found six permafrost soil factors is analyzed and the thickness of permafrost active layer,active layer of the surface of the ground temperature to utilize modern larch diameter at breast height growth rate and the interpretation of the undergrowth species diversity variation rate is highest,is the main factor affecting its growth. |
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