蚂蚁筑巢定居活动对热带森林土壤氮库及组分分配的影响

Effect of Ant Nesting Activity on Soil Nitrogen Component Allocation in the Xishuangbanna Tropical Forests

蚂蚁作为生态系统工程师,其筑巢定居活动能调控土壤微生物活动及理化环境,进而驱动热带森林土壤氮库动态及其组分分配过程。以西双版纳白背桐群落为研究对象,设置蚁巢和非蚁巢2种处理,分析蚂蚁筑巢活动引起土壤温度、水分、容重、pH及碳库(总有机碳、微生物生物量碳、易氧化有机碳)的改变对氮库(全氮、铵氮、硝氮及水解氮)及其分配(水解氮/全氮、铵氮/全氮、硝氮/全氮)的影响特征。结果表明:(1)蚂蚁筑巢显著提高了土壤氮库各组分含量(P=0.008),蚁巢全氮、水解氮、铵氮、硝氮含量分别是非蚁巢的1.26、1.2、1.13、1.37倍;(2)蚂蚁筑巢显著影响土壤氮库组分的时空变化(P=0.019),湿季与干季蚁巢全氮、水解氮、铵氮、硝氮含量,分别是非蚁巢的1.13-1.37倍,且沿土层减幅(53.9%-64.3%)显著低于非蚁巢(60.5%-76.4%);(3)蚂蚁筑巢显著改变了各氮组分分配的时空格局,蚁巢各月份氮组分占比(1.94%-11.0%)显著高于非蚁巢(1.60%-9.78%),蚁巢氮组分分配最大值在5-10 cm(4.83%),而非蚁巢却在0-5 cm土层(4.53%);(4)蚂蚁筑巢显著降低土壤pH和容重(3.18%-10.3%),增加土壤温度和含水率(3.08%-8.68%),提高土壤碳库组分含量(105%-116%);(5)主成分分析表明,土壤碳库各组分含量及温度变化是调节氮库动态的主要驱动因子,而土壤pH和容重变化是氮组分分配的主控因子。因此,蚂蚁筑巢通过改变热带森林土壤微气候、紧实度及碳库各组分含量,进而调控土壤氮库及分配的时空动态。研究结果有助于阐明热带森林土壤氮库各组分分配过程的生物学调控机制。

As major ecosystem engineers,ants can regulate soil microbial activity and physicochemical environment through their nesting activities,which in turn drive the dynamics of soil nitrogen pool and its component allocation in the tropical forests.We explored the effects of ant-mediated alterations in soil temperature,moisture,bulk density,pH,and carbon pool(i.e.,total organic carbon,microbial biomass carbon,and oxidizable organic carbon)on the nitrogen pool(i.e.,total,ammonium,nitrate,and hydrolysis nitrogen)and its allocation(i.e.,hydrolysis nitrogen/total nitrogen,ammonium nitrogen/total nitrogen,and nitrate nitrogen/total nitrogen).The results were as the following:(1)ant nesting significantly increased the concentrations of soil N pool components(P=0.008).The values of total,hydrolyzed,ammonium,and nitrate nitrogen were 1.26,1.2,1.13 and 1.37 times higher in the ant nests than in the reference soils,respectively.(2)Ant nesting significantly affected the spatiotemporal changes in soil N pool components(P=0.019).The concentrations of total,hydrolyzed,ammonium,and nitrate nitrogen in the wet and dry seasons were 1.13-1.37 times higher in ant nests than in reference soils,respectively.They reduced by 53.9%-64.3%along the soil layer,which was lower than that(60.5%-76.4%)in the reference soils.(3)Ant nesting significantly changed the spatiotemporal allocation patterns of each nitrogen fraction.The allocation proportion of nitrogen fractions in each month was significantly higher in ant nests(1.94%-11.0%)than in reference soils(1.60%-9.78%).The maximum allocation of nitrogen fraction in the ant nests was in the 5-10 cm soil layer(4.83%),but it was in the 0-5 cm soil layer(4.53%)in the reference soils.(4)Ant nesting significantly reduced soil pH and bulk weight(3.18%-10.3%),increased soil temperature and water content(3.08%-8.68%),and elevated soil carbon fractions(105%-116%).(5)Principal component analysis showed that soil carbon components and temperature were the main driving factors regulating N pool dynamics,while soil pH and bulk density were the main controlling factors for N component allocation.Therefore,ant nesting regulated the spatiotemporal dynamics of soil nitrogen pool and its allocation by changing soil microclimate,compactness,and carbon components in the tropical forests.The results would increase our understanding of the biological regulation mechanism of the soil nitrogen accumulation-allocation processes in the tropical forests.