不同土地利用类型土壤动物对土壤氮矿化季节变化的影响

以苏北沿海地区3种土地利用类型(杨树人工林、农田、杨农复合林)为研究对象,通过设置不同驱除土壤动物处理(撒萘驱除所有土壤动物、撒噻唑磷驱除土壤线虫、未驱除即对照),采用顶盖埋管法测定土壤矿质N含量及净N矿化速率,研究土壤动物对N矿化季节变化的影响。结果表明:①不同土地利用类型土壤NH⁺₄-N、NO^-₃-N、土壤总矿化N(TMN)含量均呈显著的季节变化(P＜0.05),驱除线虫和所有土壤动物显著降低了不同季节的土壤NH⁺₄-N、NO^-₃-N和TMN含量,但并没有改变它们的季节变化基本趋势。3种土地利用类型土壤NH⁺₄-N含量的季节变化均表现为夏＞秋＞春＞冬; 对于NO^-₃-N和TMN含量的季节变化,杨树林和杨农复合林均表现为夏＞秋＞春＞冬,而农田则表现为秋＞夏＞春＞冬; ②不同土地利用类型净N矿化速率季节差异显著(P＜0.05),杨树林和农田的净N矿化速率最大值出现在秋季(分别为0.25、0.29 mg/(kg·d)),杨农复合林净N矿化速率最大值出现在夏季(0.45 mg/(kg·d))。驱除线虫和驱除所有土壤动物显著降低了所有土壤利用类型春、夏、秋季的土壤净N矿化速率(P＜0.05),而未改变杨农复合林净N矿化速率的季节变化趋势。驱除所有土壤动物改变了杨树林和农田的净N矿化速率的季节变化趋势,杨树林和农田驱除所有土壤动物的季节变化表现为夏＞秋＞春＞冬,而对照表现为秋＞夏＞春＞冬。重复测量方差分析表明,季节和驱除土壤动物处理对净N矿化速率有显著的交互作用(P＜0.01),表明驱除土壤动物可能会影响净N矿化速率的季节变化。

Effects of soil fauna on seasonal variations of soil N mineralization under different land use type

A field experiment was conducted under three different land use types(i.e. poplar plantation, cropland and crop-poplar integrated system)with three treatments including control, nematodes exclusion and soil fauna exclusion in a coastal area of northern Jiangsu. By application closed-up incubation method, the seasonal variations of soil mineral N and net N mineralization rate were analyzed. The results showed that the contents of NH⁺₄-N,NO^-₃-N,TMN had significant seasonal variations under three land uses types(P＜0.05), nematodes and soil fauna exclusions decreased the contents of NH⁺₄-N,NO^-₃-N and TMN in four seasons, but did not alter their seasonal variation trends. The seasonal variation of NH⁺₄-N under three land uses types all showed summer＞autumn＞spring＞winter; seasonal variation of NO^-₃-N and TMN showed summer＞autumn＞spring＞winter under poplar plantation and crop-poplar integrated system while autumn＞summer ＞spring＞winter in cropland. In all sites, soil net N mineralization rates showed significant seasonal dynamic(P＜0.05). Maximum soil net N mineralization rate both under poplar plantation and cropland appeared in autumn(0.25 mg/(kg·d), 0.29 mg/(kg·d), respectively), but in crop-poplar integrated system, the maximum soil net N mineralization rate appeared in summer(0.45 mg/(kg·d)). Nematode and soil fauna exclusion all could lower the net N mineralization rates of three land use types in spring, summer and autumn, while did not alter the net N mineralization rates under crop-poplar integrated system, but soil fauna exclusion affected the seasonal dynamics of net N mineralization rates under the poplar plantation and cropland. The net N mineralization rates under poplar plantation and cropland showed summer＞autumn＞spring＞winter with soil fauna exclusion, while autumn＞summer＞spring＞winter with control. Analysis of variance for repeated measurement showed that there were significant interaction effects between sampling times and soil fauna treatments(P＜0.01), indicating that soil fauna may affect the seasonal variations of net N mineralization rates.