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

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

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。

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 NHn-N, NO3--N, TMN had significant seasonal variations under three land uses types （P〈0.05）, nematodes and soil fauna exclusions decreased the contents of NHa-N, NO3--N and TMN in four seasons, but did not alter their seasonal variation trends. The seasonal variation of NH：-N under three land uses types all showed summer〉antumn〉spring〉winter; seasonal variation of NO3--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 rag/（ kg＂ d） , 0.29 mg/（kg-d） , respectively） , but in crop-poplar integrated system, the maximum soil net N minerali- zation rate appeared in summer （0.45 rag/（ 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 varianee 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.