Study On The Effect Of Moso Bamboo Invasion On Carbon Stock And Soil Properties Of Forest Stands

Forests are the most important carbon source and sink in terrestrial ecosystem and play vital roles in mitigating global climate change.The current situation of forest invasion by plants is very serious,which brings a great test to the structure and function of forest ecosystem.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,which may have an impact on forest health and ecological functions.In this experiment,Chinese fir pure forest（CS）,bamboo pure forest（CZ）,bamboo invasions Chinese fir forest（ZS）,bamboo invasions Sweetgum forest（ZK）in Qianshan national forest park,Hubei province were selected as the research objects.The soil physical and chemical properties,microbial community,the contrast bamboo invasion of stand growth and the carbon sequestration benefits were investigated of different stands.To investigate the difference in carbon storage between Chinese fir（Cunninghamia lanceolata）and Sweetgum（Liquidambar formosana）stands during Moso bamboo（Phyllostachys edulis）invasion and the changes in soil properties.The experimental results are as follows:（1）The diameter at breast height and stand density of moso bamboo increased during the invasion of two species of stands,Chinese fir and Sweetgum,while Chinese fir and Sweetgum declined continuously with the intensification of the invasion.In the invasive stands of moso bamboo,the individual biomass of Chinese fir gradually decreased while its own biomass began to increase.2 surveys in 2019 and 2020 found that the biomass of the invasive stands was significantly higher than that of pure stands,influenced by the dominance of moso bamboo in the stands.In terms of organ biomass distribution,both were stem>branch>root,with the root biomass of moso bamboo significantly higher than that of fir and maple in both invasive stands,about 2-4 times that of the tree layer（Chinese fir and Sweetgum）.（2）The invasion of moso bamboo affected the soil physicochemical properties:compared with the pure moso bamboo forest,the soil bulk weight increased in two invasive stands,while the soil water content and porosity showed a decreasing trend.soil p H in four stands was acidic between 4 and 5.Soil organic matter content was lower in April and July than in November and January in all four stands,with seasonal characteristics,and was significantly lower in the two pure stands than in the two invaded stands（P<0.05）.Compared with the pure stands,the invasion of moso bamboo significantly increased the nutrient contents of total nitrogen and phosphorus in the 0-15 cm soil layer,with the highest relative to the invaded maple stands;however,the invasion caused a decrease in total nitrogen content in the 15-30 cm soil,and had less effect on total phosphorus.（3）Among the four forest types,the soil bacterial community structure was best in the pure stands of moso bamboo,while the soil fungal community structure was best in the invaded fir stands of moso bamboo.During the invasion process,the soil fungal community structure was improved to a certain extent,but the soil bacterial community structure showed the opposite trend.In addition,the moso bamboo invasion caused changes in the composition and abundance of soil microbial community species.Redundancy analysis（RDA）showed that environmental factors explained a high percentage of soil bacterial and fungal community species as well as distribution in the four stands,and there was a significant correlation between soil physicochemical properties,especially soil p H,organic matter,temperature and microbial communities.（4）The emission fluxes of greenhouse gases from the soils of the four forest stands have obvious seasonal dynamics,and soil temperature and moisture are the key environmental factors limiting the emission fluxes of the two greenhouse gases.The emission patterns of N₂O and CO₂ were similar,with an increasing trend and maximum emission in April and July,and a decreasing trend and minimum emission in October and January,while CH₄,as a sink,showed opposite changes to N₂O and CO₂.The invasion of moso bamboo led to an increase in soil N₂O and CO₂ emission fluxes and annual cumulative emission fluxes,and the trend was higher in maple forests than in fir forests.CH₄,on the other hand,gradually decreased with the invasion of moso bamboo,with the largest fluxes absorbed by pure fir forests.（5）The ecosystem carbon stocks of the four forest stands in 2019 were moso bamboo-invaded maple forest（151.28 t C/hm²）>pure fir forest（137.83 t C/hm²）>moso bamboo-invaded fir forest（130.85 t C/hm²）>pure moso bamboo forest（119.72t C/hm²）;in 2020,the survey again showed moso bamboo-invaded fir forest（180.06t C/hm²）>moso bamboo-invaded maple forest（180.06 t C/hm²）.In both surveys,the invasive stands were the largest,and during the invasion process,the carbon stocks of the pure moso bamboo and the two invasive stands increased rapidly.In terms of the distribution of ecosystem carbon stocks,the soil layer occupied the largest proportion,between 49.57%and 60.60%,followed by the vegetation layer,between 34.44%and43.71%,and the root system was the smallest,less than 10%.Soil carbon stocks showed a decreasing trend during the invasion,while the vegetation layer showed the opposite.