贝加尔针茅草原土壤原位矿化过程中碳氮转化耦合特征

Characteristics and coupling relationship of soil carbon and nitrogen transformation during in-situ mineralization cultivation in Stipa baicalensis steppe

依托在贝加尔针茅草原建立的长期模拟氮沉降试验平台(始于2010年),运用PVC顶盖埋管法进行原位培养试验,研究不同氮添加下贝加尔针茅草原土壤碳氮组分、净硝化速率、净氨化速率、有机碳转化速率的变化特征及碳氮耦合关系。试验处理包括:对照N0,低氮添加(15、30、50 kg·hm^-2·a^-1)记为N15、N30和N50,高氮添加(100、150、200、300 kg·hm^-2·a^-1)记为N100、N150、N200和N300。结果表明:培养期间,N15、N30、N50和N100处理的净硝化速率显著高于对照N0(P<0.05),分别增加了40.80%、110.31%、206.83%和202.04%;N30、N50和N100净氨化速率显著低于对照N0(P<0.05),分别降低了16.88%、169.60%和150.67%;N15和N30处理的净矿化速率高于对照N0,分别增加了150%和50%;N50、N100、N150和N200处理的净矿化速率低于对照N0,分别降低了254.52%、161.50%、33.90%和79.85%。土壤有机碳与土壤全氮呈极显著正相关,土壤可溶性有机碳与土壤可溶性有机氮呈极显著正相关,土壤微生物生物量碳与土壤微生物生物量氮呈极显著负相关。有机碳转化速率显著影响微生物生物量氮转化速率,且符合一元线性回归方程。连续高氮沉降会降低土壤净氮矿化速率和有机碳转化速率,对土壤碳氮循环产生负面影响。

This research was based on the long-term simulated nitrogen deposition test platform in Stipa baicalensis steppe(began in 2010). The changes of soil carbon and nitrogen composition, net nitrification rate, net ammoniation rate, organic carbon conversion rate and coupling of soil carbon and nitrogen in Stipa baicalensis steppe under different nitrogen additions were studied by the in-situ closed-top PVC tube incubation methods. Test treatments included N0(0 kg·hm^-2·a^-1), low-N(15, 30, 50 kg·hm^-2·a^-1 was denoted as N15, N30, N50), and high-N(100, 150, 200, 300 kg·hm^-2·a^-1 was denoted as N100, N150, N200, N300).The results showed that during incubation time the net nitrification rate of N15, N30, N50, and N100 were significantly increased by 40.80%, 110.31%, 206.83%, and 202.04% than that of control N0(P<0.05), respectively. The net ammonification rate of N30, N50, and N100 treatments were significantly decreased by 16.88%, 169.60%, and 150.67% than that of control N0(P<0.05), respectively. The net mineralization rate of N15 and N30 treatments were increased by 150% and 50% than that of control N0, respectively. The net mineralization rate of N50, N100, N150, and N200 treatments were decreased by 254.52%, 161.50%, 33.90%, and 79.85% than that of control N0, respectively. There were significantly positive correlation between soil organic carbon and total nitrogen, dissolved carbon and dissolved nitrogen. There was a significantly negative correlation between microbial biomass carbon and microbial biomass nitrogen. The transformation rates of soil organic carbon had significant effects on the soil ammonification and microbial immobilization rates, and it can be well simulated by model of linear regression equation.Continuous high nitrogen deposition can reduce the soil net nitrogen mineralization rate and the organic carbon conversion rate, and have a negative impact on the soil carbon and nitrogen cycle.