摘要
[目的]气温升高和降水增多已成为全球气候正在面临的挑战,为了探究全球气候变化对三峡库区森林土壤氮动态的影响,以期为预测该地区土壤养分循环变化和制定提升森林生产力的经营措施提供理论依据.[方法]以马尾松-栓皮栎混交人工林为研究对象,将土壤筛分为大团聚体、中团聚体、小团聚体和微团聚体(粒径为:2 000～8 000、1 000～2 000、250～1 000和＜250 μm),以室内培养方法观察团聚体净氮转化在土壤水分为 40%、60%和 80%田间最大持水量(命名为 0.4 FCW、0.6 FCW和 0.8 FCW),和温度为5、15、25和 35℃下的差异.[结果]比表面积较大的小粒径团聚体中有机质、总氮含量和微生物生物量碳、氮更高,而其速效磷含量显著低于大团聚体.随粒径减小,团聚体净硝化和净氮矿化速率逐渐增加,其中净硝化贡献了超过 85%的净氮矿化.团聚体净硝化和净氮矿化速率随土壤含水量和温度的增加先上升后下降,最大值出现在 0.6 FCW和 25℃.不同粒径团聚体的净氨化、净硝化和净氮矿化速率整体在 0.60 FCW和15℃/25℃时对温度上升最敏感;通过建立二元二次方程,估算出净氨化最大速率出现在土壤水分和温度为 0.70 FCW和 23.0℃,净硝化和净氮矿化最大速率出现在土壤水分和温度为 0.58 FCW～0.60 FCW和24.5～27.5℃.[结论]团聚体的物理结构保护了三峡库区人工林土壤有机氮免受微生物分解,而温度上升和降水增多促进了该地区马尾松-栓皮栎针阔混交人工林土壤净氮转化,这将有利于提高土壤的氮供应能力.但长期来看,这种变化催生土壤有机质和氮的流失,增加磷限制的风险,必要时应开展长期监测和施用磷肥措施.
Abstract
[Objective]Rising temperatures and precipitation have become challenges.In order to investig-ate the effects of climate change on soil nitrogen(N)dynamics in forests of the Three Gorges Reservoir area and to provide a basis for predicting changes in soil nutrient cycling in this area and enhancing forest productivity.[Method]The soil was sieved into large macroaggregates,coarse aggregate,small macroag-gregates,and microaggregates(particle sizes:8 000-2000,2000-1 000,1 000-250,and<250 μm)in a mixed plantation of Pinus massoniana-Quercus variabilis.Differences in net N conversion of aggregates were observed at soil moisture of 40%,60%,and 80%of the maximum water holding capacity in the field(named 0.4 FCW,0.6 FCW,and 0.8 FCW),and at temperatures of 5℃,15℃,25℃,and 35℃ using in-door incubation methods.[Results]The levels of soil organic matter(SOM),total N and microbial biomass carbon(C),and nitrogen were higher in small-size aggregates with larger specific surface areas,while available phosphorus(P)was significantly lower.The rates of net nitrification and net N mineralization of aggregates gradually increased with decreasing particle size,with net nitrification contributing more than 85%of net N mineralization.The rates of net nitrification and net N mineralization of aggregates first in-creased and then decreased with the increase of soil water moisture and temperature,and the maximum values appeared at 0.6 FCW and 25℃.The overall net ammonification,net nitrification,and net N mineral-ization rates of aggregates of different particle sizes were most sensitive to temperature increase at 0.60 FCW and 15℃/25℃.By developing a quadratic equation,the optimum soil moisture and temperature for the net ammonification rate were 0.70 FCW and 23.0℃,and the optimum soil moisture and temperature for the net nitrification and net nitrogen mineralization rates were 0.58 FCW-0.60 FCW and 24.5℃-27.5℃.[Conclusion]The physical structure of aggregates protects organic N from decomposition in the plantation in the Three Gorges Reservoir area.Rising temperatures and precipitation promote net N trans-formation in the soils,which is conducive to improving the N supply capacity of the soil;However,there is a risk of soil organic matter,N loss,and P limitation over the long term,so that monitoring and fertilizer measures can be carried out if necessary.
基金项目
中央级公益性科研院所基本科研业务费专项(CAFYBB2022XD002)
国家科技期刊平台
NSTL
万方数据