外源磷输入对农区湿地土壤碳库有效性及周转特性的影响

通过添加土壤原总磷(TP)0~60%的过磷酸钙和室内培养的技术手段,研究了外源磷素输入对农区湿地土壤碳库有效性及其周转特性的动态影响。结果表明,随外源磷素输入水平的增加,土壤可溶性有机碳(DOC)含量和微生物量碳(MBC)含量增加;土壤总有机碳(TOC)含量下降,下降率最高达23%。活性有机碳成分中,外源磷输入对高活性有机碳(HLOC)影响最显著,60%磷素输入处理HLOC含量比未施加外源磷素高54%;易氧化有机碳(ROC)含量随外源磷输入水平的增加而下降,最大下降率为22%;中活性有机碳(MLOC)含量、活性有机碳(LOC)含量无明显改变。涉碳循环生物酶中,β-葡聚糖苷酶(βG)和纤维二糖水解酶(CBH)活性均随外源磷素输入水平的增加而显著提升,但脱氢酶(DH)活性并无显著变化。此外,土壤碳矿化强度和潜在矿化势也与外源磷素输入后的土壤TP呈正相关。总体来看,外源磷素输入显著增加了湿地土壤碳库的有效性及周转速率。

Effect of exogenous phosphorus input on the availability and turnover characteristics of soil carbon pool in agro-riparian wetlands

Exogenous nutrients significantly influence wetland ecosystems. In particular, the invasion of exogenous nitrogen (N) and phosphorus (P) significantly influences carbon cycle in wetland soils which further changes global carbon cycle in soil-atmosphere continuum. While there are currently several studies on exogenous N, the study of exogenous P is still lacking. To explore the effect of the input of exogenous P on the availability and turnover characteristics of soil carbon pool in wetlands, an experiment was de-signed for the simulation of the dynamics of exogenous P accumulation. The study simulated additive P gradient rates of 0 (P-0), 5% (P-5), 10% (P-10), 20% (P-20), 30% (P-30) and 60% (P-60) relative to initial total phosphorus (TP) content of sampled soils. Super-phosphate was the mode of addition of P to the soil coupled with the simulation of laboratory data. The changes in characteristics of soil carbon composition and biochemical indicators of P with the input of different levels of exogenous P were analyzed using con-ventional biochemical testing methods. The study also integrated several other factors for Pearson correlation analysis. The results showed that soil TP and Olsen-P contents strictly followed the loading rates of superphosphate, with a notable increase in microbial biomass phosphorus (MBP). The activity of acid phosphatase (AcP) was significantly suppressed by P addition. Dissolved organic carbon (DOC) and microbial biomass carbon (MBC) increased with increasing inputs of exogenous P, while total organic carbon (TOC) decreased at a maximum rate of 23%. For active organic carbon components of the soil, highly labile organic carbon (HLOC) was 54% higher under P-60 treatment than under the control group (P-0). Then recalcitrant organic carbon (ROC) content remarkably decreased with increasing input of exogenous P, with a maximum rate of decline of 22%. To certain extent, the results indicated that soil carbon pool was activated and the efficiency of availability increased. However, mid-labile organic carbon (MLOC) and labile organic carbon (LOC) almost had no change with increasing input of exogenous P. The MLOC and LOC ingredients were stable in the soil. The activities ofβ-1,4-glucosidase (βG) and cellobiohydrolase (CBH) significantly increased with increasing levels of ex-ogenous P, but the activity of dehydrogenase (DH) remained largely unchanged. For the analysis of mineralization characteristics of soil organic carbon (SOC), exogenous P addition significantly accelerated SOC mineralization rate. The cumulative mineralization increased with increasing addition of exogenous P. Potential mineralization potential of SOC was positively correlated with the addi-tion of exogenous P. From the above, exogenous P input increased the consumption of soil carbon pool and transformed soil carbon pool from steady state to unstable state. It also increased the activity and content of biological enzyme by stimulating microbial activ-ity. In summary, the availability and turnover rates of wetland soil carbon pool and the risk of wetland soil carbon output significantly increased under exogenous P input.