Effects Of Phyllostachys Edulis Invading Evergreen Broad-leaved Forest On Soil Respiration And Active Organic Carbon And Nitrogen

Moso bamboo?Phyllostachys edulis?is a native species that has recently expanded its range by invading the broad-leaved forests of southern China.Invasion of moso bamboo should alter soil carbon and nutrient cycling because the physiological characteristics of moso bamboo often differ from those of native species.Here,we studied the effects of moso bamboo invasion on soil active organic carbon and nitrogen in evergreen broad-leaved forest,mixed bamboo-broad-leaved forest,and pure moso bamboo?broad-leaved forest,mixed forest,moso bamboo forest?forest used space-for-time substitution.Soil respiration were measured by LI-8100 A.Soil water-soluble organic carbon and nitrogen and microbial biomass carbon and nitrogen were measured to characterize the effects of moso bamboo invasion on soil active organic carbon and nitrogen in evergreen broad-leaved forest and how its effects might vary seasonally.We found that:?1?The total soil respiration and its components?heterotrophic respiration,autotrophic respiration?of the three forest types?broad-leaved forest,mixed forest,moso bamboo forest?at different stages of Moso bamboo invasion all have obvious seasonal patterns,which are expressed as soil respiration rate is greatest in summer and smallest in winter.?2?The annual cumulative soil CO₂ emissions and the annual average soil respiration rate gradually increased with the invasion stage?P<0.01?,which was specifically manifested as non-invasion?broadleaved forest?<invasion?mixed forest?<complete invasion?moso bamboo forest?.?3?The proportion of heterotrophic respiration and autotrophic respiration in total soil respiration was not significantly changed after moso bamboo invasion.In the three forest stands,the heterotrophic respiration rate was about twice the autotrophic respiration rate.?4?In this study area,soil temperature is the main driving factor for soil respiration,and soil moisture content is not the limiting factor in this area.The contribution rate of soil temperature to broad-leaved forest,mixed forest,and bamboo forest is higher than 80%.The two-factor model of temperature and humidity did not increase the contribution rate of soil temperature.?5?Soil active organic carbon indicators?WOSC,MBC?in broad-leaved forest,mixed forest,and moso bamboo forest have consistent seasonal characteristics,showing the highest in autumn and the least in summer.The seasonal characteristics of active organic nitrogen indicators?WSON,MBN?are not the same as those of active organic carbon indicators,and their lowest values appear in winter.?6?The content of active organic carbon and nitrogen in surface soil gradually decreased with the invasion stage?P<0.05?,and the content was specifically broad-leaved forest> mixed forest> Moso bamboo forest.?7?In this study,soil respiration rate was extremely significantly correlated with the content of activated carbon and nitrogen in the soil surface?P<0.01?,indicating that there is a certain coupling mechanism between soil carbon emissions and soil activated carbon and nitrogen.