草地土壤有机质不同组分氮库对长期氮添加的响应  

Responses of soil nitrogen in different soil organic matter fractions to long-term nitrogen addition in a semi-arid grassland

作　　者：武运涛 杨森 王欣[1] 黄俊胜 王斌 刘卫星 刘玲莉 WU Yun-Tao;YANG Sen;WANG Xin;HUANG Jun-Sheng;WANG Bin;LIU Wei-Xing;LIU Ling-Li(State Key Laboratory of Vegetation and Environmental Change,Institute of Botany,Chinese Academy of Sciences,Beijing 100093,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院植物研究所植被与环境变化国家重点实验室,北京100093 [2]中国科学院大学,北京100049

出　　处：《植物生态学报》2021年第7期790-798,共9页Chinese Journal of Plant Ecology

基　　金：国家重点基础研究发展计划(2019YFA0607302);中国科学院战略性先导科技专项(A类)(XDA23080301);国家自然科学基金(31901138)。

摘　　要：土壤氮库对生态系统的养分循环至关重要。目前多数研究主要关注氮沉降对土壤总氮的影响,而对土壤不同有机质组分的氮库对氮沉降响应的研究较为缺乏。该研究基于内蒙古典型草地的长期多水平施氮(0、8、32、64 g·m^(–2)·a^(–1))实验平台,利用土壤密度分级方法,探究氮添加处理13年后典型草地中两种土壤有机质组分(颗粒态有机质(POM),矿质结合态有机质(MAOM))氮含量的变化及调控机制。结果显示:土壤总碳含量、POM和MAOM的碳含量在施氮处理间均没有显著差异。土壤总氮含量则随着施氮水平增加呈显著增加的趋势,同时施氮处理下POM的氮含量显著上升,而MAOM的氮含量没有变化。进一步分析发现,施氮促进植物地上生物量积累,增加了凋落物量及其氮含量,从而导致POM的氮含量增加。由于MAOM主要通过黏土矿物等吸附土壤中小分子有机质形成,其氮含量受土壤中黏粒与粉粒含量影响,而与氮添加水平无显著相关关系。该研究结果表明长期氮添加促进土壤氮库积累,但增加的氮主要分布在稳定性较低的POM中,受干扰后容易从生态系统中流失。为了更准确地评估和预测氮沉降对陆地生态系统的氮循环过程的影响,应考虑土壤中不同有机质组分的差异响应。Aims Soil nitrogen(N) plays a vital role in regulating the structure and function of ecosystems and is affected by N deposition. Most previous studies focus on the responses of the N content in bulk soil to N deposition, but the responses of the N content in different soil organic matter(SOM) fractions remain unclear. We aimed to investigate how long-term N addition influenced soil N of different SOM fractions in a semi-arid grassland.Methods A manipulated N addition experiment with 4 levels of N addition(0, 8, 32 and 64 g·m^(–2)·a^(–1)) has been conducted for 13 years in Duolun country, Nei Mongol. SOM was separated to particulate organic matter(POM)and mineral associated organic matter(MAOM) by density fractionation. The plant and soil properties were also measured.Important findings The results showed that N addition had no significant effect on the carbon(C) content in bulk soil, POM, or MAOM. With increasing levels of N addition, the N content in bulk soil and in POM increased significantly. Furthermore, we found that the increased N content of POM was mainly associated with greater aboveground biomass following N addition. The N content of MAOM is mainly correlated with soil texture, but was not affected by N addition. These results suggest that continuous N addition can increase the soil N in bulk soil, but the increased N is mostly distributed in labile POM pools, which can be vulnerable to land use and climate change.

关 键 词：氮添加 氮含量 颗粒态有机质 矿质结合态有机质 

分 类 号：S812.2[农业科学—草业科学]