模拟氮沉降对油松土壤热水浸提有机物的影响

Effects of Simulated Nitrogen Deposition on Hot-Water Extractable Organic Matter in Rhizosphere and Non-Rhizosphere of Pinus tabulaeformis

为了研究黄土高原林区氮沉降对油松土壤热水浸提有机物的影响及其根际效应,选择了6个施氮梯度[0,2.8,5.6,11.2,22.4,44.8g/(m^2·a)],采用油松盆栽模拟试验,连续培养了6年。对油松根际、非根际热水浸提有机物进行了研究,结果表明:不高于5.6g/(m^2·a)的模拟氮沉降量可以显著增加根际热水浸提有机碳含量,5.6g/(m^2·a)及以上的氮沉降对热水浸提有机碳的影响未达到显著水平。热水浸提总氮、热水浸提硝态氮、热水浸提有机氮、热水浸提有机氮占热水浸提总氮和土壤全氮比例均随氮沉降量的增加而升高,且根际与非根际差异明显。紫外特征值的结果表明,氮沉降会增加芳香族化合物及羧基含量,一定水平的氮沉降会增加热水浸提有机物的易降解组分的分解。较低的氮沉降增加了根际热水浸提有机物,非根际则有差别。热水浸提有机物官能团特征发生改变且变化并不一致。SUVA254,E280和ASI可作为指征代谢类型对氮沉降响应的潜在指标。

Nitrogen deposition has an important influence on hot-water extractable organic matter in rhizosphere and non-rhizosphere of Pinus tabulaeformis in the Loess Plateau.Pot experiments of Pinus tabulaeformis were continuously cultured for six years,with adding six nitrogen gradients[0,2.8,5.6,11.2,22.4 and44.8 g/（m^2·a）].With respect to hot-water extractable organic matter（hot-water extractable organic carbon,HWOC;hot-water extractable organic nitrogen,HWON）in rhizosphere and non-rhizosphere of Pinus tabulaeformis,nitrogen deposition content with less than 5.6 g/（m^2·a）markedly increased HWOC.Nitrogen deposition content with more than or equal to 5.6 g/（m^2·a）did not significantly affect HWOC.HWTN（hot-water extractable total nitrogen）, HWON, HWON/HWTN, HWTN/TN（total nitrogen）and HWON/TN increased with increase of nitrogen deposition content.There were remarkable differences between rhizosphere and non-rhizosphere situations.Nitrogen deposition increased aromatic compounds and carboxyl content by UV characteristic values.A certain level of nitrogen deposition would decompose easydecomposable components of hot-water extractable organic matter.Under a certain range of low nitrogen deposition,hot water extractable organic matter in rhizosphere increased,which is different from that in non-rhizosphere.Functional group contents of hot water extract organic matter could be changed,but the changes were not consistent.Two indicators may permit to indicate metabolic type response differences for nitrogen deposition.One is SUVA254 and E280（associated with ammonia nitrogen,another is ASI（associ-ated with nitrate nitrogen）.