亚热带地区竞争型和忍耐型树种叶片可溶性有机质数量及光谱学特征

气候变化下,不同生态策略的树种对环境变化有着不同的响应能力,影响其叶片淋溶产生的DOM(Dissolved organic matter)的数量和质量,进而影响土壤的养分循环。通过探究亚热带地区不同生态策略树种叶片DOM数量及光谱学特征的差异,评估不同数量和结构特征DOM输入到土壤对养分循环的影响。本研究选取6种树种鲜叶进行浸提,其中竞争型(Competitive,C)和忍耐型(Stress-tolerant,S)各3种(树参(Dendropanax dentiger),黄绒润楠(Machilus grijsii),黄牛奶树(Symplocos cochinchinensis(Lour.)),细柄阿丁枫(Altingia gracilipes),丝栗栲(Castanopsis fargesii)和罗浮栲(Castanopsis faberi))。通过溶解性有机碳(Dissolved organic carbon,DOC)、溶解性有机氮(Dissolved organic nitrogen,DON)表征DOM的数量特征,通过紫外吸收值(Special Ultraviolet-Visible Absorption,SUVA),腐殖化指标(Humification index,HIX)和傅里叶红外光谱(Fouriertransform infrared,FTIR)等光谱指标表征DOM质量特征。结果表明:不同生态策略树种的叶浸提液中可溶性有机碳浓度无显著差异,但是C策略树种浸提液中可溶性有机氮浓度大于S策略的DON浓度。此外,S策略的芳香化指数(Aromatic index,AI)和腐殖化指数(HIX)均高于C策略。C策略树种的发射荧光强度也高于S策略,说明C策略树种DOM腐殖化程度较低,易分解物质含量高;S策略难分解物质多,腐殖化程度较高。傅里叶红外光谱结果表明,各树种叶浸提的DOM存在相似的吸收峰,其中以H键键合的—OH伸缩振动最强且C策略树种结果相对简单,验证了荧光光谱的结果。总体而言,与C策略相比,S策略树种叶片浸提的DOM结构更复杂,养分含量更高。这可能是因为,S策略树种对环境变化具有更高的适应性。由于其DOM结构相对复杂,输入土壤后减缓土壤碳周转速率,在未来气候变化情景下,S策略树种可能有利于土壤碳汇的形成。

Spectral characteristics and quantities of dissolved organic matter released from leaves with competitive and stress-tolerant ecological strategies in a subtropical region

Plants have different ecological strategies in response to environmental stress under global climate change, and the spectral characteristics and quantities of dissolved organic matter (DOM) leaching from leaves depend on the plant''s ecological strategy. DOM leaching due to different strategies will influence soil nutrient cycling. The objective of this study was to investigate the differences in the spectral characteristics and quantities of DOM derived from leaves of plants (Dendropanax dentiger, Machilus grijsii, Symplocos cochinchinensis (Lour.), Altingia gracilipes, Castanopsis fargesii, and Castanopsis faberi) with different ecological strategies in a subtropical region. In this study, we sampled fresh leaves from 6 kinds of plants, including 3 competitive-type plants (C-strategy) and 3 stress-tolerant-type plants (S-strategy). We examined dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) to determine the quantities of DOM, and employed Special Ultraviolet-Visible Absorption (SUVA), Humification Index(HIX) and Fourier-Transform Infrared (FTIR) to analyze the spectral characteristics of DOM. The results showed that there were no significant differences in the DOC concentrations between C-type and S-type plants. However, DON was higher in C-type plants compared to S-type plants. In addition, we examined the structural characteristics of DOM between the C-and S-strategies using SUVA, fluorescence, and FTIR absorption spectrometry. The aromatic index and HIX were in the order:S > C. In addition, the synchronous fluorescence spectra were stronger in C-type compared to S-type plants, which suggests that DOM leaching from the leaves of a C-type plant was greater. The degree of humification was lower in the labile materials, while it was higher in the S-type plants. FTIR spectroscopy indicated that DOM from different types of leaves exhibited similar absorption peaks, with the strongest absorption arising from the prolonged vibration of H-bonding hydroxyl groups in all cases. This result shows that DOM from C-type plants has a simple structure that is in accord with fluorescence spectra. Overall, DOM from S-type plants was richer in nutrient composition and had a more complex structure compared to that from C-type plants. Our results suggested that S-type plants have better adaption under environment stress. Owing to the complex structure of DOM from S-type plants, it would reduce soil carbon turnover after leaching into the soil. Therefore, S-type plants are more effective in the formation of soil carbon sink under climate change.