Study On Water Conserving Efficiency Of Four Representative Communities In Limestone Mountain Areas In Chongqing

The limestone areas of Chongqing characterized as thin soil layer,lack of soil capacity,low water storage capacity,great infiltration coefficient.The topographty based mainly on slope land, and the great stress of population,large proportion of cultivation on steep slope,high coefficient variation of rainfall,mostly happen reserve succession.In the study,four representative vegetations on limestone mountain areas were chosen for researching,the four vegetations were:Cupressus funebris community,Neosinocalamus affinis community,Trachycarpus foribunda community and Broussonetia papyrifera community.By comparing the water conserving efficiency of canopy layer,litter layer,soil layer,it is the aim of the study to offer theory for choosing the vegetation restoration patterns or species for vegetation restoration on limestone areas in chongqing.The study included:(1)The characters were described by surveying four typical vegetations on limestone mountain areas.(2)By surveying leaves and water holding experiments of them in canopy, the water holding capacities of capony were compared;and by air-dry and water holding experiments and surveying of litters,the water holding capacities of litter were compared.The water holding capacities of overground parts of four vegetations were compared while integrated the canopy layer and the letters layer.(3)By studying the soil bulk density and water holding capacity,the maximal water holding capacities of soil in the four communities were gained;By the lidded and not lidded experiments,the water osmosis speed and water evaporation speed of the four communities were gained.By measuring indexes about the root biomass and modality,the water holding capacities of the four communities were compared.The result showed that the community physiognomy was characterized by the Phanerophytes which had herbaceous quality,entire margin,compound and mesophyll leaves.Though its vertical structure and coverage structure indicated that the areas belonged to Subtropical Zone,the microenviroment of this areas was a little droughty,so it was also indicated that this area belonged to prephase of secondary succession.By comparing the four vegetations,it was gained that the condition of B.papyrifera community was the droughtest.The result also showed that the maximal water-holding capacity in per area of four different canopies presented as N.affinis community＞B.papyrifera community＞C.funebris community＞T.fortunei community;the thickness of litters under the four communities presented as C.funebris community＞N.affinis community＞B.papyrifera community＞T.fortunei community;the storage of litters presented as N.affinis community and C.funebris community larger than T.fortunei community and B.papyrifera community;natural water-holding percentage of litters presented as N.affinis community＞C.funebris community＞B.papyrifera community＞T.fortunei community; the maximal water-holding capacity of litters presented as N.affinis community and C.funebris community larger than T.fortunei community and larger than B.papyrifera community.The maximal water-holding capacity of overground part of four vegetations presented as N.affinis community＞C.funebris community＞T.fortunei community and B.papyrifera community.The results of camparing the water holding capacity of 0-4cm soil by measuring the soil bulk density and water holding capacity,showed that the maximal water holding capacity of soil in the four communities were C.funebris community,there were no significant differences between the others.The values of the total pore,non-capillary pore and capillary pore show that of C.funebris community's was the best and B.papyrifera commynity's was the worst.In the lidded and not lidded experiments,there were no significant differences of the maximal water osmosis speed between the four different communities;and water evaporation speed of C.funebris community was the largest,B.papyrifera commyuity's was the least.The root biomass and all modality indexes manifested the water holding capacity of B.papyrifera commynity was the worst.Through integrating the soil bulk density,water osmosis speed,water evaporation speed,root biomass and all modality indexes showed the water holding capacity of B.papyrifera commynity was the worst,C.funebris community's was the best,and there were no significant differences between the other two communities.In conclusion,the water conserving efficiencies of the four typical vegetations in Chongqing limestone areas were gained by integrating the canopy layer,litter layer and soil layer.The results showed:the water conserving efficiency of B.papyrifera community was the worst;the water conserving efficiency of over ground part of N.affinis community were best;root system and soil layer of C.funebris community were the best.In a word,N.affinis and C.all can be used as the species for vegetation restoration,and both have their own predominance.