Plants Water Use Strategy In The Peak For Est-lake Basin Of South Eastern Of Yunnan Province

Special hydrogeology environment and complex ecosystems have caused the geological arid,karst desertification intensification and high habitat heterogeneity in the karst region of southwest China.In the process of habitat restoration,the reconstruction of vegetation community is an important link to promote soil moisture-nutrient cycling and water conservation.Different community plant water can make response and adaptation mechanism according to different habitats and form water use strategy so that it have a huge impact on watershed hydrological cycle and the restoration of habitat.Therefore,the optimization of tree species and community is of great significance.In order to study plants water use strategy in different habitats and provide scientific governance suggestions for karst region,in the Puzhehei peak forest-lake basin of southeastern of Yunnan Province,several dominant plant species in Bauhinia hookeriana shrubbery,Pistacia weinmannifolia secondary forest and Pinus yunnanensis plantation were choosed as the study objects.Potential water sources plants utilized can be traced by hydrogen and oxygen stable isotope technique and the contribution can be calculated by Iso Source model.The differences of plants water use sources can be presented with the changes of seasons,communities and habitats.At the same time,the water use efficiency of plant was studied by measuring the ?13C value of plant leaf.And in combination with length of roots and the underground biamass,the water adaptability of different habitats is discussed,and according to the function and mechanism of water production of upstream,midstream and downstream in the basin,in line with principle of " trees suitablity to sites ",vegetation adapt to the habitat can be choosed to get on reconstruction work.The main conclusions of the study indicated that:(1)From the rainy season to the dry season,plants in in three communities water utilization average proportions of 0-40 cm superficial and shallow layers of soil water decreased from 31% to 25.6%,and the proportions of 40-80 cm medium and deep layers of soil water was 44.6% to 33%,the proportion of epikarst water or pore waterfrom 24.6% to 41.3%.In view of the changes of geologic drought and seasonal rainfall,three communities plants had good water adaptabilities in different habitats.(2)Quercus variabilis in different growth phases from the sample area of Pistacia weinmannifolia secondary forest have similar water utilization proportions all the year round,therefore there maybe the relationships of water competition.While there are different water use strategies between mature and young Pistacia weinmannifolia because of their distingushing growth of roots systems.(3)Bauhinia hookeriana shrubbery mean utilization proportions of epikarst water accounting to 33.7%,while plants in Pistacia weinmannifolia secondary forest and Pinus yunnanensis plantation can adjust the proportions of soil water from different depths and groundwater.In the synchronous restoration of vegetation and habitat,plants' dependence of epikarst water have gradually reduced,which make effects of protectation to maintain karst landscapes.(4)The plants ?13C mean value of Bauhinia hookeriana shrubbery,Pistacia weinmannifolia secondary forest and Pinus yunnanensis plantation were-28.599 ‰,-2 29.513 ‰ and-29.180 ‰,respectively in the order of size is: Bauhinia hookeriana shrubbery > Pinus yunnanensis plantation > Pistacia weinmannifolia secondary forest,stony habitat> soil habitat> stony-soil habitat.Habitat and community type have a great influence on plant ?13C composition,and then Bauhinia hookeriana shrubbery which grown on the rocky habitat plant water use efficiency is the highest.And the drought tolerance strategy was adopted to resist the perennial water stress.With developed root system,?13C of Pistacia weinmannifolia secondary forest and Pinus yunnanensis plantation plants were smaller,and drought-avoiding strategy were mainly adopted to deal with seasonal water deficit.Plants age of three communties is young,so that plants ?13C in rainy season relatively earlier is higher than the later dry season.(5)The order of seasonal variation of plant?13C is: Pistacia weinmannifolia secondary forest> Pinus yunnanensis plantation > Bauhinia hookeriana shrubbery.The change of ?13C with the adjustment of water use strategy with the change of season was significant,which indicated that the response and adaptation of Pistaciaweinmannifolia secondary forest plants and Pinus yunnanensis plantation plants to habitat water conditions were timely and sensitive.(6)In the process of ecological restoration,the selection of plants with higher habitat adaptability will adhere to the principle of "trees suitablity to sites",which is beneficial to soil growth and water conservation.From this point of view,to carry out the mountain closure,it is suggested that the upper part of the peak forest choose shrub community as soli and water conservation forests.And native Bauhinia hookeriana can be choosed as dominant species;In the middle of peak forest,to carry out vegetation restoration work,Pistacia weinmannifolia secondary forest is selected and choose Pistacia weinmannifolia as dominant species which have deep root system and higher water use efficiency;In the bottom of peak forest which possess deep soil layers and well water conditions,Pinus yunnanensis plantations can be choosed to achieve the role of water conservation.(7)In the process of exploring the surface water mechanism of the basin,it is found that the sinkhole lake,the sinkhole pore water,the Dajianshan reservoir,the Xingou wetland and the Zengchan reservoir are important for the hydrological process of the whole basin.According to the characteristics of habitat,around the sinhole,the Dajianshan reservoir,and the Zengchan reservoir which located in slow slopes and contituous soil habitats,mixed forest of Pinus yunnanensis with the dominant species in Pistacia weinmannifolia secondary forests contain Pistacia weinmannifolia and Quercus variabilis were selected for the preferred water conservation forest combination for the restoration of water conservation function.;In the Xingou wetland,Pistacia weinmannifolia secondary forest and Bauhinia hookeriana shrubbery dominant tree species(Bauhinia hookeriana and Pterolobium punctatum Kurz,etc.)which have deep systems and flexible water use strategiey can promote soil development,hydrological function and habitat succession.