Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China.
Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China.
Sci Total Environ. 2015 Jun 1;517:76-85. doi: 10.1016/j.scitotenv.2015.02.068. Epub 2015 Feb 24.
Revegetations in riparian ecosystem are important in regulating soil nitrogen (N) dynamics. However, impacts of revegetation on soil N cycling and thereby on ecosystem functioning are not fully understood. We conducted an in situ incubation in the water level fluctuation zone (WLFZ) of the Three Gorges Reservoir region to evaluate soil N transformation including net N mineralization rate, net ammonification rate, net nitrification rate, net denitrification rate, N leaching and plant N uptake as well as the soil inorganic N (NH4(+)-N and NO3(-)-N) concentration in the top soils (0-20 cm) following revegetations (implementing tree, shrub and herb plantations) over two years. The soil inorganic N concentration and N leaching were lower in the tree soils than in herb and shrub soils. Tree plantations decreased net N mineralization rate and net ammonification rate compared to herb and shrub soils, possibly due to lower soil organic carbon (SOC) input and soil temperatures. Whereas tree plantations increased soil net denitrification rate compared to herb and shrub soils because of higher tree NO3(-)-N uptake together with higher net nitrification rate. The inorganic N in the tree and shrub soils were lower in fall and summer, respectively, which was dependent on the seasonal variations in plant N uptake, soil N transformation, and N leaching. Thus, our results suggest that tree plantations could decrease soil inorganic N concentration and N leaching by altering both the quantity and quality of SOC and thereby potentially improve water quality in the riparian zone.
河岸生态系统的植被恢复对于调节土壤氮（N）动态非常重要。然而，植被恢复对土壤氮循环的影响，以及对生态系统功能的影响，还不完全清楚。我们在三峡库区水位波动带（WLFZ）进行了原位培养实验，以评估土壤氮转化，包括净矿化速率、净氨化速率、净硝化速率、净反硝化速率、氮淋失和植物氮吸收，以及表层土壤（0-20cm）中的土壤无机氮（NH4（+）-N 和 NO3（-）-N）浓度。在两年的植被恢复（实施树木、灌木和草本植物种植）后，树木土壤中的土壤无机氮浓度和氮淋失低于草本和灌木土壤。与草本和灌木土壤相比，树木种植降低了净矿化速率和净氨化速率，这可能是由于土壤有机碳（SOC）输入和土壤温度较低所致。而树木种植增加了土壤净反硝化速率，高于草本和灌木土壤，这是由于树木吸收的硝酸盐（NO3（-）-N）较高，同时净硝化速率也较高。树木和灌木土壤中的无机氮在秋季和夏季分别较低，这取决于植物氮吸收、土壤氮转化和氮淋失的季节性变化。因此，我们的结果表明，树木种植可以通过改变 SOC 的数量和质量来降低土壤无机氮浓度和氮淋失，从而有可能改善河岸带的水质。
