Response of Nitrogen Mineralization in Soil Aggregates to Changes in Soil Moisture and Temperature in the Three Gorges Reservoir Area's Typical Plantation
[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.
Three Gorges Reservoir AreaaggregatesN mineralizationtemperaturemoisture
NETL
NSTL
万方数据
