Effects Of Moso Bamboo Expansion On Soil Carbon Fraction And Its Stability In A Subtropical Broadleaf Forest

Forests are the most important carbon source and sink in terrestrial ecosystem and play vital roles in mitigating global climate change.Moso bamboo(Phyllostachys edulis)has a wide distribution and occupies an important position among the bamboo resources in China.It is reliance on well-developed underground bamboo whips,strong invasive ability and rapid forest establishment have invaded the surrounding forests on a large scale.Moso bamboo a native species that has recently expanded its range by invading the broad-leaved forests of southern China.In order to reveal the effect of moso bamboo expansion of broadleaf evergreen forest on soil carbon fraction and its stability,this study took Dashanchong Forest Park in Changsha County,Hunan Province as the sample site,and selected broadleaf evergreen forest,bamboobroad mixed less moso bamboo forest,bamboo-broad mixed more moso bamboo forest,and moso bamboo pure forest(hereinafter referred to as(broadleaf forest,mixed less forest,mixed more forest,moso bamboo forest)in the order of increasing percentage of moso bamboo expansion sample zone,and measured the different soil carbon fraction of each forest stand type.The different soil carbon fractions of each forest type were determined.These include organic carbon,microbial biomass carbon,soluble organic carbon,easily oxidized organic carbon,particulate organic carbon,mineral-bound organic carbon,as well as fine root biomass carbon stock,apoplastic biomass carbon stock and soil mineralization culture.To explore the effect of moso bamboo expansion on soil carbon stock and its stability in broadleaf forests.The main results obtained are as follows:(1)Soil bulk weight content of different stand types ranged from 1.00-1.33 g/m3,soil pH ranged from 4.55-4.95,and soil SWC ranged from 27-37%.Overall,soil BD increased significantly with the expansion of moso bamboo.pH and SWC increased with non-significant differences(P>0.05).(2)With the expansion of moso bamboo,the content of soil organic carbon(SOC),microbial quantity carbon(MBC)and soluble carbon(DOC),easily oxidizable carbon(ROC)particulate organic carbon(POC),and mineral bound organic carbon(MOC)were significantly reduced.Along the expansion of moso bamboo,SOC and ROC contents decreased and then increased,and compared to before expansion or decreased,the difference was significant(P<0.05).both MBC and DOC contents gradually decreased with the expansion of moso bamboo deeper and reached the significance level(P<0.05).Both POC and MOC decreased by 24.08%and 39.71%with the expansion of moso bamboo,with significant differences(P<0.05).Soil carbon stocks showed a significant decrease(P<0.05),the proportion of each reactive carbon increased gradually,and the stability index decreased,with higher organic carbon conversion efficiency,higher soil loss,higher relative amount of unprotected organic carbon,and lower soil stability in moso bamboo forests compared to broadleaf forests.Each soil carbon fraction showed significant positive correlation with SWC(P<0.05),negative correlation with BD(P<0.05),and no correlation with pH(P>0.05).All carbon fractions showed significant positive correlation with each other(P<0.05).With the expansion of moso bamboo,the apoplastic biomass and carbon stock decreased,with the least and,moso bamboo forest decreasing by 25.74%,and the fine root biomass and carbon stock gradually increased,3 and 2.5 times more than those of broad-leaved forest respectively.Both apomictic and fine root organic carbon content gradually decreased,by 16.8%and 19.18%.The content of soil organic carbon is related to a variety of factors,with nutrients from apoplastic matter being one of the influencing factors and main sources of soil carbon content,leading to significantly higher soil carbon stocks in broad-leaved forests than in moso bamboo forests cause.The biomass of the moso bamboo root system is approximately three times higher than that of the broadleaf forest root system because during the expansion of the moso bamboo,the moso bamboo root system first replicates and then extends to the surrounding forest through asexual reproduction,resulting in a rapid increase in the biomass of the underground root system of the moso bamboo.(3)With the expansion of moso bamboo,apoplastic biomass and carbon stock decreased,and the least in mixed multiforest stands.It decreased by 25.74%compared with broadleaf forest.The expansion of moso bamboo reduced the accumulation of apoplastic material on the surface.Fine root biomass and carbon stock gradual1y increased,3 and 2.5 times more than in broad-leaved forests,respectively.The well-developed underground root system of moso bamboo increased the root biomass.Both apoplastic and fine root organic carbon contents showed decreases.The content of soil organic carbon is related to a variety of factors,and the carbon of apoplastic matter is one of the main influencing factors and main sources of soil carbon content.With the expansion of moso bamboo,the apoplastic biomass and carbon stock decreased,with the least and,moso bamboo forest decreasing by 25.74%,and the fine root biomass and carbon stock gradually increased,3 and 2.5 times more than those of broad-leaved forest respectively.Both apomictic and fine root organic carbon content gradually decreased,by 16.8%and 19.18%.The content of soil organic carbon is related to a variety of factors,with nutrients from apoplastic matter being one of the influencing factors and main sources of soil carbon content,leading to significantly higher soil carbon stocks in broad-leaved forests than in moso bamboo forests cause.The biomass of the moso bamboo root system is approximately three times higher than that of the broadleaf forest root system because during the expansion of the moso bamboo,the moso bamboo root system first replicates and then extends to the surrounding forest through asexual reproduction,resulting in a rapid increase in the biomass of the underground root system of the moso bamboo.(4)The total amount and rate of organic carbon mineralization changed significantly with the expansion of moso bamboo,and there were differences in the depth of soil layers,with the 0-15 cm soil layer being significantly higher than other soil layers.The mineralization rate decreased with the expansion of moso bamboo,and the slowest mineralization rate was found in mixed multi-storey stands.Both the rate and total amount of soil organic carbon mineralization were significantly higher in broadleaf forests than in moso bamboo forests.The cumulative mineralization rate gradually decreased with the expansion of moso bamboo.Soil carbon sequestration capacity was stronger in moso bamboo.There was a significant positive correlation between mineralization rate and cumulative mineralization and each carbon fraction(P<0.05).There was no significant relationship between cumulative mineralization rate and carbon fraction(P>0.05).There was a significant change in the total amount and rate of organic carbon mineralization after the expansion of moso bamboo,and this change existed in soil depth and expansion stage,and the high content of organic carbon produced by apoplastic matter and root secretion and the higher active carbon content of soil were the main reasons for the high total and rate of carbon mineralization.