封育对草地深层土壤碳储量及其固持速率的影响

Dynamics of Carbon Storage and Its Sequestration Rate in Deeper Soil Layers Following Long-term Fenced Grasslands

为了揭示长期封育草地深层土壤碳、氮固持及固持速率,采用空间序列代替时间序列的方法,研究了黄土高原宁夏固原云雾山自然保护区长期封育草地土壤有机碳(SOC)、土壤全氮(STN)储量及其固持速率的变化特征。结果表明封育30年草地0—500cm各土层SOC储量显著高于封育10年草地和放牧草地,封育10年草地不同深度SOC储量与放牧草地并无差异;封育30年、10年和放牧草地STN储量在各土层无统计学上的差异,而封育30年不同深度STN储量显著高于封育10年和放牧草地;封育30年SOC,STN固持主要发生在10~30年间,0—500cm固持量分别为(482.5±39.3)Mg/hm^2,(27.7±2.4)Mg/hm^2,封育前10年有机碳、全氮固持量小,分别为(42.8±6)Mg/hm^2,(3.4±2.1)Mg/hm^2;封育30年0—500cm土层SOC和STN固持分别为(525.3±62.0)Mg/hm^2,(25.0±3.0)Mg/hm^2,固持速率分别为(17.5±2.1)Mg/(hm^2·a),(0.83±0.3)Mg/(hm^2·a);碳氮比随着封育年限增加而增大,随土层深度增加而降低。封育草地深层土壤有巨大固碳潜力,评估碳氮固持不仅要时间尺度,也要考虑深层土壤碳氮固持,以达到对生态系统碳氮储量评估的无偏估计。

In order to measure soil carbon and nitrogen storages and their sequestration rates in long-term fenced grasslands,different period fenced grasslands in variety location stand for sequential vegetation restoration in Guyuan Yunwushan of the Loess Plateau were selected.The results showed that soil organic carbon(SOC)storage in each soil layers of 0—500cm soil depth,in 30 years of fenced grassland is significantly higher than in 10 years of fenced grassland and grazing grassland,but there was no significant difference of SOC storage in each soil layer between 10 years of fenced grassland and grazing grassland;there were also no significant difference of soil total nitrogen(STN)storage in different soil layers between 30 years of fenced grassland and 10 years of fenced grassland and grazing grassland,while STN storage in the 30 years of fenced grassland was significantly higher than 10 years of fenced grassland and grazing grassland;meanwhile,during the 30 years of enclosure,the SOC and STN sequestration accumulated dramatically between the 10 th year and the 30 th year,the values were(482.5±39.3)Mg/hm^2 and(27.7±2.4)Mg/hm^2,respectively,but during the first 10 years of fenced grassland,the amounts of SOC and STN sequestration were very small,which were(42.8±6)Mg/hm^2 and(3.4±2.1)Mg/hm^2,respectively;SOC and STN sequestration in 0—500cm soil depth after 30 years of enclosure of was(525.3±62.0)Mg/hm^2 and(25.0±3.0)Mg/hm^2,respectively,SOC and STN sequestration rates in 0—500cm soil depth were(17.5±2.1)Mg/(hm^2·a)and(0.83±0.3)Mg/(hm^2·a);C/N ratio had decreased with increase of soil depth,but it had increased with increase of fencing dura-tion.This study demonstrated that deeper soil layers in fenced grassland have great potential for carbon sequestration,the SOC and STN accumulated mainly happened between the 10 th and 30 th years of enclosure,so,the more attention should be paid to fencing period scales and carbon and nitrogen storage in deeper soil layer in order to achieve unbiased estimate of carbon and nitrogen storage in ecological assessment.