中国南方热带两种人工林土壤中溶解性有机质特征及其影响因素

CHARACTERISTICS AND INFLUENCING FACTORS OF DISSOLVED ORGANIC MATTER IN SOILS OF TWO TROPICAL PLANTATIONS IN SOUTH CHINA

张子婷

11849171

硕士

环境工程

王俊坚

2020-05-29

2020-05-29

哈尔滨工业大学

深圳

土壤中的溶解性有机质（DOM）作为碳库中最活跃的部分，在生物地球化学循环过程中起着重要作用。森林土壤是陆地系统中最大的土壤碳库，其中人工林的面积占据森林面积的近 7%，且中国的人工林种植面积最大，研究中国人工林中的DOM 性质对于全面认识土壤碳库具有重要意义。然而，人工林土壤环境并非均质和长期稳定，月份变化、人工林类型和土壤深度都与 DOM 的特征和组分有紧密联系，同时长期氮沉降也影响着全球碳循环和其他生态循环过程。但是，DOM 的特征以及月份、人工林类型、土壤深度和氮沉降共同作用下对 DOM 的影响还不清楚。本文以中国南方热带氮限制桉树人工林和氮富集大叶相思人工林为研究对象，分析雨季中 20 cm 和 40 cm 深度壤中流 DOM 的浓度和组成等特征，以及它们对中剂量与高剂量人为氮添加（分别为 50 和 100 kg N ha-1yr-1）的响应。主要运用紫外吸收和三维荧光光谱探究有机质的来源信息与组分的变化，同时利用分子水平木质素单体生物标志物的方法作为互补性手段，探究 DOM 中木质素的来源和降解情况。本研究得到的主要结论为：研究发现随着雨季的进入，溶解性有机碳（DOC）浓度和木质素含量、降解程度有显著下降的趋势。从雨季初期到末期，木质素的输入减少，并且输入了相对更多的新鲜木质素。DOM 的芳香性和腐殖化程度随月份变化升高，腐殖质类物质减少，说明被消耗的有机质主要是一些非芳香性易降解的物质。不同人工林类型和土壤深度之间的 DOM 特征也具有显著差异，桉树人工林和浅层土壤中 DOM 的腐殖程度分别高于大叶相思人工林和深层土壤。相比浅层 20 cm 深度土壤水中，40 cm 土壤水中的 DOC 的浓度和木质素的含量更低，芳香族物质和类腐殖质组分更少。大叶相思人工林容易达到氮饱和状态，DOM 对氮添加的响应更为明显。中剂量氮添加增加 DOC 的浓度，高剂量氮添加降低 DOC 的浓度。因此不能低估氮添加在短期内增加碳库的作用，也不能忽视高量的氮添加酸化土壤降低DOC 的浓度的影响。总体上，中氮添加促进了木质素的输入，并且中氮添加使 DOC的浓度的增加，进而促进了木质素的共代谢，从而增大了木质素的降解程度。中氮添加显著增加了 40 cm 土壤水中腐殖质和芳香族化合物，在 20 cm 不明显。高氮添加降低了 20 cm 土壤水中木质素的降解程度，却增大了 40 cm 的降解程度，且因此在研究氮添加的对 DOM 影响时，应该充分考虑土壤深度的交互影响。 本研究推进了对我国人工林土壤 DOM 的特征和其影响因素的认识，有利于全面认识人工林系统中的土壤功能，更好地理解日益增加的氮沉降与土壤碳循环的联系。

As the most active part of carbon pool, dissolved organic matter (DOM) in soil plays an important role in biogeochemical cycle. Forest soil is the largest soil carbon pool in the terrestrial system, among which the area of plantations accounts for nearly 7% of the forest area, and China has the largest plantation area. Therefore, it is of great significance to study the DOM properties of Chinese plantation for a comprehensive understanding of the soil carbon pool. However, the soil environment of plantations is not homogeneous and long-term stable. Seasonal changes, plantation types and soil depth are closely related to the properties and components of DOM. Meanwhile, long-term nitrogen deposition also affects the global carbon cycle and other ecological cycles. However, it is still not clear about the effects of season, plantation type, soil depth, and nitrogen deposition on the DOM characteristics. Here, this study analyzed the concentrations and characteristics of DOM in 20 cm and 40 cm soils during the rainy season. And analyzed their responses to the treatment of medium- (50 kg N ha-1 yr-1) and high-levels (100 kg N ha-1 yr-1) of nitrogen addition for the tropical plantations of nitrogen-restricted Eucalyptus urophyllaand non-nitrogen-restricted Acacia auriculiformis in South China as examples. The source information and component changes of organic matter were explored mainly by ultraviolet-visible and 3D fluorescence spectra. Meanwhile, the molecular markers of lignin phenols were used as complementary means to explore the source and degradation of molecules in DOM. The main results of this study are as follows: From the early to late rainy season, the dissolved organic carbon (DOC)concentration, lignin content and degradation degree had significant decreasing trends.Over time, lignin inputs decreased and relatively more fresh lignin was introduced. The degree of aromaticity and humus of DOM increased as the rain season proceeded. The humus substances decreased, indicating that the consumed organic matter was mainly non-aromatic and easily degraded substances. The DOM characteristics of different plantation types and soil depths were also significantly different, and the degree of DOM humus in Eucalyptus urophylla plantation and shallow soil was higher than that in Acacia auriculiformis plantation and deep soil, respectively. Acacia auriculiformis plantation is easy to reach the state of nitrogen saturation, and the DOM characteristics were more responsive to nitrogen addition. The DOC concentration and lignin content were lower and the aromatic substances and humic-like components were less in the 40 cm soil than those in the shallow 20 cm soil.he medium nitrogen addition increased DOC concentration, while high nitrogenaddition decreased DOC concentration. Therefore, the role of nitrogen addition in increasing the carbon pool in the short term cannot be underestimated, and the effect of high nitrogen addition on acidizing soil to reduce the DOC concentration cannot be ignored. In general, the addition of medium nitrogen promoted the input of lignin, and the increase of DOC concentration promoted the co-metabolism of lignin, thus increasing the content and degradation degree of lignin. The degradation degree of lignin in 20 cm soil was decreased by high nitrogen addition, but the degradation degree of lignin in 20 cm soil was increased by 40 cm. The humic-like and aromatic compounds in 40 cm soil were significantly increased by medium nitrogen addition, which was not significantly altered at 20 cm. Therefore, the heterogeneity of soil at different depths should be fully considered when studying the effect of nitrogen addition on DOM.The present study promotes the understanding of the characteristics of soil DOM in tropical plantation soils of South China, which will support a more comprehensive understanding of soil functions in plantation systems and the relationship between increasing nitrogen deposition and soil carbon cycling in plantation ecosystems.

人工林 土壤溶解性有机质 光谱特征 木质素标志物 月份变化

plantation soil dissolved organic matter spectroscopic characteristics lignin biomarkers monthly change

中文

联合培养

南方科技大学

张子婷. 中国南方热带两种人工林土壤中溶解性有机质特征及其影响因素[D]. 深圳. 哈尔滨工业大学,2020.