| As one of the main components of coastal wetland,mangrove wetland is characterized by high productivity and high biodiversity.Biodiversity is an ecological complex,which formed by organisms and their environment,as well as various ecological processes related to it.It is related to ecological balance,the harmonious development of human and nature,and has important direct or indirect values to human life and production.Functional diversity is one of the key and important contents of biodiversity.Plant functional traits are the biological characteristics of plants adapting to the external environment,which can respond to the changes of species' living environment and can be used to characterize functional diversity.The mangrove area of Guangdong province is 14224 ha,which is the largest mangrove distribution area in China.The research of mangrove biodiversity and functional traits of mangrove species in Guangdong province is coducive to the better protection of mangrove,sustainable utilization of mangrove,and promotion for harmonious development of humans and mangrove.In this study,mangrove plants in Guangdong province were taken as the research object,and the biodiversity of mangrove plants in different distribution areas,the environmental impact factors and the niche charcrtersisics of dominant mangrove species were studied.The differences of leaf functional traits among five major mangrove species in different regions and their responses to environmental factors were analyzed.In addition,the PCR amplification rate,species identification rate and the ability to construct phylogenetic tree of rbcL,mat K,trn H psbA and ITS were studied.These researc provided basic materials for the study of the functional character diversity,genealogy diversity,community structure and phylogeny of mangrove plants,as well as the theoretical reference for mangrove afforestation and understory regeneration.The main results were as follows:(1)The species richness index of mangrove plants in different regions was quite different.The species richness in western Guangdong was generally higher than that in the eastern Guangdong,but the number of mangrove species in majority area ranged from2 to 6,indicating that the species of mangrove in Guangdong province was not rich enough.The differences of mangrove species diversity index in different regions were affected by environmental factors.In eastern Guangdong,the species diversity index was closely related to latitude,while the evenness index was mainly affected by soil moisture content and tidal salinity.In the pearl river delta region,species diversity index was closely related to latitude and soil bulk density;species evenness was mainly affected by soil p H and tidal salinity.In Zhanjiang area,the species diversity index was mainly affected by soil p H and latitude;species evenness was closely related to flooding depth.The species diversity in wester Guangdong(except Zhanjiang)was mainly affected by the content of soil organic matter,soil total nitrogen and soil total phosphorus;species evenness was closely related to tidal salinity.(2)The importance value of nine mangrove plants in Guangdong province were Sonneratia apetala Buch.Hamplantation > Aegiceras corniculatum(L.)Blanco > Avicennia marina(Forssk.)Vierh.> Kandelia obovata Sheue,Liu & Yong> Sonneratia caseolaris(L.)Engl.)> Excoecaria agallocha Linn.> Acanthus ilicifolius L.> Bruguiera gymnorrhiza(L.)Savigny)> Laguncularia racemosa(L)C.F.Gaertn.The niche similarity of the nine mangrove species ranged from 0.01 to 0.58,but the niche similarity of most species pairs was low.The range of niche overlap of nine mangrove species was 0.02-1.44.The most closely related three specie pairs were K.obovate and S.caseolaris,S.apetala and K.obovate,A.corniculatum and A.marina.(3)There were significant differences in leaf area,leaf aspect ratio,leaf shape coefficient and leaf thickness of K.obovata,A.marina,E.agallocha,B.gymnorrhiza and A.corniculatum in different regions(P<0.001).With the decrease of latitude,the leaf shape coefficient of K.obovata,E.agallocha and B.gymnorrhiza also decreased,the leaf area decreased and the leaf became more flat.At the same time,with the decrease of latitude,the leaf thickness of A.corniculatum increased,which was the response of A.corniculatum to environmental factors in order to reduce transpiration and maintain leaf water balance.The accumulation of leaf dry matter was significantly related to its photosynthesis.The correlation coefficient between the leaf area and dry weight of E.agallocha and A.corniculatum reached 0.76 or more.The leaf total nitrogen contents of K.obovata,A.marina,B.gymnorrhiza and A.corniculatum were significantly(P<0.05)or extremely significantly(P<0.01)positively correlated,and the leaf toal nitrogen and leaf total phosphorus content were mostly related to the leaf aspect ratio and leaf shape,indicating that nutrients played important roles in the leaf construction of mangrove plant.The name and proportion of principal functional traits of the five mangrove plants were different,but the scores of leaf area,leaf total carbon content and leaf total nitrogen content of five mangrove plants all were relatively high.Leaf area reflected the plant's ability to obtain resources,carbon and nitrogen were indispensable elements for plant growth and affected or regulated plant growth and physiological processes.They can be used as common important leaf functional trait indexes of these five mangrove plants.(4)The RDA sequencing of plant leaf functional traits and environmental factors showed that different leaf functional traits had different responses to soil factors,and the degree was also different.Soil p H can promote the release of phosphorus,and the total phosphorus content in leaves of K.obovata and E.agallocha was positively correlated with soil p H.Soil provided a variety of nutrients for the growth of plants and affected the morphological characteristics of plants.The leaf perimeters of E.agallocha and A.corniculatum was positively correlated with soil organic matter content.Soil bulk density represented the weight of soil per unit volume.The heavier the soil was,the more compact the soil was and the lower the water content was.B.gymnorrhiza and A.corniculatum are generally distributed in the middle and high tide zones,which need to grow in the soil with appropriate water content.In addition,when the water was insufficient,they can reduce the transpiration and water loss by reducing their own leaf area.Therefore,the leaf area of B.gymnorrhiza and A.corniculatum are closely and positively correlated with soil bulk density.(5)The variable sites of rbcL fragments was the least,and the selected primer sequences had strong universality,good quality and the highest species recognition rate.In addition,the phylogenetic tree of mangrove plants in Guangdong province could be constructed accurately only by using rbcL fragment.The trn H-psbA fragment could recognize mangrove plants that rbcL fragment couldn't recognize.By comprehensive comparison,rbcL fragment and trn H-psbA fragment were recommended to study the DNA barcode of mangrove plants. |
PDF Full Text Request