Spectral Characteristics And Quantities Of Dissolved Organic Matter Released From Leaves With Different Ecological Strategies In A Subtropical Region

Plants have different ecological strategies in responses to environmental stress under global climate change,and the spectral characteristics and quantities of dissolved organic matter(DOM)leaching from leaves depend on plant’s ecological strategies,DOM leaching due to different strategies will influence nutrition cycling of soil.The objective of this study was to investigate the differences in the spectral characteristics and quantities of dissolved organic matter(DOM)derived from leaves of the plant with different ecological strategies in a subtropical region.In this study,we sampled fresh leaves from 36 kinds of plants,including competitive type(C-strategy),competitive-stress type(CS-strategy),stress-tolerant type(S-strategy)and competitive-stress-ruderal type(CSR-strategy).We examined dissolved organic carbon(DOC),dissolved organic nitrogen(DON)and dissolved organic phosphorus(DOP)to represent the quantities of DOM and examined Special Ultraviolet-Visible Absorption(SUVA),Humification index(HIX),Fourier-transform infrared(FTIR)and three-dimensional fluorescence spectra(EEMs)to represent the spectral characteristics of DOM.The results showed that the order of DOC and DON concentration is S>CS>S on the C-S axis.Furthermore,we examined the structural characteristic of DOM using UV,fluorescence,and Fourier-transform infrared(FTIR)spectroscopy.The aromatic index(AI),hydrophobic index(SUVA260)and humification index(HIX)were in the order:S>CS>C,we could know that the DOM leaching from S-type plants displayed stronger aromatic and hydrophobic properties.In addition,FTIR absorption spectrometry 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,and C-type’s peaks show on the short wavelength is more less than other types.The result of EMMs-PARAFAC showed that in addition to the aromatic protein-like components(Ex/Em = 230 nm/300 nm),there is also tiny amounts of humic-like substances(Ex/Em = 275/300)exists in DOM of leaves leaching solution.The main conclusions of the correlation analysis of DOM spectral characteristics,quantitative characteristics and plant functional traits are as follows:1.SUVA254 and SUVA260 have a significant positive correlation with LDMC.To a certain extent,it can be concluded that the complexity of DOM leaching from plants is positively correlated with the material content of leaves.2.The concentration of DOC extracted from leaves were positively correlated with humic DOM fractions.3.DOC and DOP extracted from leaves were not linearly correlated with leaf area and leaf weight,but they were linearly correlated with leaf area and leaf weight.Overall,DOM from S type plants was richer in nutrient composition and had a more complex structure compared to C type plants.Our results suggested that S type plants have better adaption under stress.Owing to the complex structure of S type plants,DOM from such plants 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.