Study On The Physiological Characteristics And Humic Indicators Of Sphagnum Palustre

Sphagnum are main species in northern peat bog development,with large impacts on the global carbon budget and freshwater storage.In this dissertation,Sphagnum palustre L.and peat cores were examined to study the changes of cell structure,physiological characteristics,chemical composition,and spectroscopic characteristics of soluble organic matter(DOM),fulvic acid(FA),humic acid(HA)and chlorophyll during the peat formation.The goals were to understand the change of Sphagnum during humification,and to find suitable humification indicators for peatland,so as to provide new ideas for the study of carbon cycle and conservation of peatland,and enrich the scientific theory of global peatland protection.The main results are as follows:1.The structure of S.palustre buds,mature S.palustre and peat in different layers were observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).It was found that with the development of S.palustre buds,the hole membranes on the water holes of leaves and stems had a tendency to disappear.The hyaline cells of S.palustre in different layers were damaged progressively with the increase of depth,and began to deform greatly at collapsed and defoliated layer of S.palustre layer(CDL),and some hyaline cells residues could still be observed from peat at 5–10 cm(P5-10)in peat layer.The thylakoid lamellar structure of chloroplasts in chlorophyllous cells of leaves and stems was destroyed at yellow layer of S.palustre(YL),and a large number of osmiophilic granules were produced.The thylakoid lamellar structure of chloroplasts disappeared at brown layer of S.palustre(BL),accompanied by cell abscission in stems.Based on the results of structural changes,it could be concluded that the damage of chlorophyllous cells of S.palustre were earlier than that of hyaline cells,and stem cells earlier than leaf cells.2.Using ultraviolet-visible spectrophotometer,infrared spectrophotometer,fluorescence spectrophotometer and other instruments,I studied the S.palustre and peat in different layers.It was found that the transformation of organic matter(OM)and the change of physiological characteristics were very complex.The content of organic carbon(OC)and polyphenols(PP)in S palustre decreased with the increase of depth from capitulum to peat during the transformation.Most of the other indicators showed a unimodal pattern with the increase of depth.The maximum absorption of Fe ions by S.palustre per unit dry weight was at YL,the maximum of soluble sugar(SS)was at BL,the maximum of reduction and acidic ability was at CDL,and the maximum contents of lignin-like substances(LL),soluble protein(SP),and carboxylic organic acid functional groups were at grass root layer of S.palustre(GRL).The content of these organic substances in S.palustre was higher than that in peat.From the results of infrared spectroscopy combined with two-dimensional correlation analysis(2D COS),phenol changed fastest.S.palustre exchange capacity and small molecule organic acid played important roles in the formation of acidic environment in the wetland of Qi Zimei Mountains.Through the cultivation of S.palustre in different layers,it was found that S.palustre at YL and BL still had strong potential reproductive capacity.However,the propagation and growth of buds need certain conditions such as appropriate light,water,temperature,nutrition and relatively acidic environment.After the formation of humus at CDL,GRL and P-10,the reproductive capacity was basically lost.Although it was not suitable as explants,it was suitable as matrix for reproduction and growth.3.Through the study of DOM,FA and HA extracted from S.palustre and peat at different depths by various methods,it was found that the method of parallel factor analysis combined with Emission-excitation matrix spectroscopy(PARAFAC-EEMs)was a powerful tool to understand the humification process from S.palustre to peat.The humus components in the extracted FA and HA increased with the increase of depth.The humus content in DOM increased with the increase depth from YL to peat at 0–5 cm(P0-5),but then decreased,which might be related to the change of solubility or aggregation of humus components.From the results of infrared spectroscopy combined with 2D COS,the changes of protein and aroma were faster,while the changes of polysaccharide and phenol were slower,during the formation of FA and HA.4.By using PARAFAC-EEMs,chlorophyll fluorescence peaks were found at the majority of S.palustre and peat layers,and statistical analysis with DOM humification indicators showed that chlorophyll components were highly correlated with most indicators commonly used to examine humification.Moreover,chlorophyll is more effective because it is not easily disturbed by acid,alkali and background.Therefore,this method can be used to study the humification of peatland effectively.