Effect Of Ant Nesting On Soil Respiration In Different Secondary Restoration Stages Of Xishuangbanna Tropical Forest

At present,global warming caused by elevated atmospheric CO₂ concentration is one of serious human environment problem.Soil respiration is the main output pathway of soil carbon,and its small changes may lead to significant changes in atmospheric CO₂ concentration.Therefore,it is of great scientific significance to explore the mechanism of soil respiration and its influence on global warming.Ant nesting induces a significant change of soil microbial and physicochemical properties,which can lead to significant changes in soil respiration rate.Xishuangbanna is an important area where tropical rainforest areas ranks the large in China and ant abundance is very rich.Due to the changes in agricultural production mode and the increase in population,tropical forests have been severely damaged,forming secondary recovery types with large areas at different successional stages.The Li-6400 photosynthetic apparatus?equipped with soil respiration chamber?was used to measure respiration from ant nests and the reference soils in different succession stages of tropical forests of Xishuangbanna tropical forest botanical garden of the Chinese Academy of Sciences?Mallotus paniculatus communities,Musa acuminata communities,Mellettia leptobotrya communities,Syzygium oblatum communities?.Analysing the effect of ants nesting on soil microbial biomass carbon and soil physicochemical properties and their effects on soil respiration dynamics,thus elucidating the process and mechanism of ants nesting on the soil respiration dynamics of tropical forests in different recovery stages of Xishuangbanna,it aims to provide theoretical and data support for understanding the impact of large soil animals on global change.The main results are as follows:?1?The soil respiration rates of the ant nests in the tropical forest communities in different recovery stages of Xishuangbanna were higher than those in the reference soils.The order of the increase in soil respiration rate of ant nests to four communities was:Musa acuminata communities?53.08%?> Syzygium oblatum communities?44.76%?>Mallotus paniculatus communities?44.39%?> Mellettia leptobotrya communities?31.29%?.The order of the soil respiration rate of the ant nest was: Musa acuminata communities > Syzygium oblatum communities > Mellettia leptobotrya communities >Mallotus paniculatus communities;the reference soils is Musa acuminata communities > Mellettia leptobotrya communities > Syzygium oblatum communities >Mallotus paniculatus communities.?2?The soil respiration rates of tropical forest communities in different recovery stages of Xishuangbanna have obvious seasonal dynamics,which shows that the wet season?6,9 month?is larger than the dry season?3,12 month?,and the soil respiration rate of ant nests is greater than that of reference soils.The change range of soil respiration rate of the 4 communities was: Mallotus paniculatus communities(ant nests:3.11 9.10 ?mol CO₂ m^-2s^-1;reference soils: 2.56 6.90 ?mol CO₂ m^-2s^-1),Musa acuminata communities(ant nests: 5.38¹1.0 ?mol CO₂ m^-2s^-1;reference soils: 2.88 ⁷.58 ?mol CO₂ m^-2s^-1),Mellettia leptobotrya communities(ant nests: 3.51 ?mol 9.32?mol CO₂ m^-2s^-1;reference soils: 2.51 7.4 ?mol CO₂ m^-2s^-1),Syzygium oblatum communities(ant nests: 4.51 10.2 ?mol CO₂ m^-2s^-1;reference soils: 3.25 5.89 ?mol CO₂ m^-2s^-1).?3?The change of soil soil temperature,water and microorganism under the effect of ant nesting had a significant effect on soil respiration.The seasonal dynamics of soil temperature,water and microbial biomass carbon in the 4 communities were closely related to soil respiration,and they were significantly positively correlated with soil respiration rate?P<0.01?.The contribution rate of soil temperature and soil microbial biomass carbon to ant nests soil respiration rate was greater than that to reference soils in the 4 communities.Except the contribution rate of soil moisture in ant nest to soil respiration rate of Syzygium oblatum communities is lower than reference soils,which in Mallotus paniculatus communities,Musa acuminata communities and Mellettia leptobotrya communities is higher than reference soils.The contribution of soil temperature on soil respiration rate was lower than that of soil moisture on soil respiration contribution rate in Mallotus paniculatus communities and Musa acuminata communities,in contrast,the Mellettia leptobotrya communities and Syzygium oblatum communities are opposite.It shows that with the recovery of tropical forests,soil temperature and moisture act together on the soil respiration rate,and the effect of soil temperature gradually increases.?4?The change of soil physicochemical properties under the effect of ant nesting had a significant effect on soil respiration.The soil bulk density of ant nests was smaller than that of the reference soils in the 4 communities,and the other soil physicochemical properties were more than the reference soils.The correlation of soil physicochemical properties to soil respiration rate was different: Soil readily oxidized organic carbon was significantly positively correlated with the soil respiration rate of Mellettia leptobotrya communities?P<0.01?,which was positively correlated with the soil respiration rate of Musa acuminata communities?P<0.05?.Soil organic matter was significantly positively correlated with the soil respiration rate of Mallotus paniculatus communities,Mellettia leptobotrya communities and Syzygium oblatum communities?P<0.01?,which was positively correlated with the soil respiration rate of Musa acuminata communities?P<0.05?.Soil total nitrogen was significantly positively correlated with the soil respiration rate of Musa acuminata communities and Mellettia leptobotrya communities?P<0.01?,which was positively correlated with the soil respiration rate of Mallotus paniculatus communities and Syzygium oblatum communities?P<0.05?.Soil ammonium nitrogen was positively correlated with the soil respiration rate of Mallotus paniculatus communities?P<0.05?;which was not significantly positively correlated with the other 3 communities.Soil nitrate nitrogen was significantly positively correlated with the soil respiration rate of Mallotus paniculatus communities and Syzygium oblatum communities?P<0.01?,which was positively correlated with the soil respiration rate of Musa acuminata communities?P<0.05?.Soil hydrolyzable nitrogen was significantly positively correlated with the soil respiration rate of Mallotus paniculatus communities,Mellettia leptobotrya communities,and Syzygium oblatum communities?P<0.01?.The results of principal component analysis?PCA?showed that in the 4 communities,except the soil respiration rate was negatively correlated with the soil p H,and positively correlated with other soil physicochemical properties in Musa acuminata communities.The soil respiration rates of the other 3 communities were negatively correlated with soil bulk density and positively correlated with other physicochemical properties.And soil hydrolyzable nitrogen had the strongest correlation on soil respiration in the 4 communities.