【作者】 周利强；

【导师】 杨万勤；

【作者基本信息】 四川农业大学 ， 森林培育学， 2009， 硕士

【摘要】 镉(Cadmium,Cd)是环境中毒性最强的重金属元素之一,其引起的生态环境问题一直是环境科学研究的热点。本研究以杂交杨(Populus deltoides×Populus nigra)为材料,通过盆栽试验研究了紫色土和冲积土中不同浓度的Cd处理对杨树生长和C、N、P元素积累的影响以及Cd在土壤-杨树系统中的迁移与分配特征,以期为Cd污染土壤的无害化利用、城市森林建设和速生丰产林基地建设等提供一定科学依据。研究结果表明:1.土壤中低浓度的Cd污染对杨树叶片的净光合速率有一定的抑制作用,处理浓度相同时,冲积土杨树叶片的净光合速率高于紫色土杨树。紫色土中,低浓度Cd对叶片气孔导度有显著促进作用,胞间二氧化碳浓度和气孔导度一致增加,而在冲积土中变化不显著。低浓度Cd处理对叶片蒸腾速率的影响不显著。杨树叶片叶绿素a、叶绿素b的含量以及叶绿素a/b在冲积土Cd处理环境中没有显著变化,而在紫色土Cd处理环境中,叶绿素a的含量显著减少。冲积土中,不同的密度对杨树在光合作用和叶绿素含量的影响不显著。单株杨树的叶面积随Cd浓度的增大而减小,Cd处理对杨树的叶面积的生长有显著影响。冲积土中,处理相同的不同密度之间,密度的增加对杨树单株叶面积生长产生了抑制。2.低浓度Cd处理对杨树高和地径的生长无显著的影响,不同的土壤对杨树生长的影响更显著,相同的处理浓度下高生长和地径的生长均表现为冲积土显著高于紫色土。冲积土中,密度对杨树生长的影响较低浓度的Cd处理明显。低浓度的Cd处理对杨树根部、茎部、凋落叶的生物量生长与分配均无显著的影响,紫色土中,根部、茎部和凋落叶生物量占总的生物量的分配比例大致为0.53:0.27:0.20,而冲积土中这一比例约为0.38:0.42:0.20。不同的土壤之间生物量的生长与分配差异显著,栽植密度增大单株杨树生物量生长受到抑制。3.土壤-植物系统中,随着处理浓度的增大,杨树吸收积累Cd的量增大,土壤中Cd的含量减小,凋落叶归还到土壤中的Cd的量呈现无规律性的变化,但总体上紫色土归还的量较冲积土小。单株杨树Cd的积累量随处理浓度的增大而增加。Cd在杨树不同器官之间的分配,在紫色土中,根部、茎部和凋落叶Cd的积累量占总积累量的比例大至为0.545:0.453:0.002,冲积土中的比例为0.416:0.577:0.007。杨树在紫色土中将吸收的Cd主要储藏在根部,而冲积土中Cd则主要分布在茎部。栽植密度增大单株杨树所积累的Cd的量减少。4.低浓度Cd处理对杨树C、N和P积累量的影响并不显著,不同的土壤间差异明显,冲积土中处理相同时,杨树各器官中的积累量不同密度间的差异显著。杨树各器官C的积累量在紫色土中为根部＞茎部＞凋落叶,其比例为大致为0.49:0.33:0.18;冲积土中为茎部＞根部＞凋落叶,比例约为0.37:0.42:0.21。杨树各器官N的积累量在紫色土CK中根部、茎部、凋落叶的分配比例为0.56:0.22:0.22,其余处理的分配比大致为0.50:0.18:0.32;冲积土中T3处理根茎叶分配为0.39:0.26:0.35,其余处理的分配比例大致为0.35:0.28:0.37。紫色土中,CK处理时P在根、茎、凋落叶中的分配比例为0.47:0.30:0.23,其余处理中的比例为0.50:0.23:0.27;冲积土中根部、茎部、凋落叶中P的积累量的比例为0.35:0.39:0.26。更多还原

【Abstract】 Cadmium is one of heavy metal elements which are of high toxicity in environment. The ecological environmental problems induced by cadmium are hotspots were widely studied in environmental science.In this paper,potted hybridized popular tree was used to study the effect of different Cd concentrations in purple soil and alluvial soil on the growth and C,N,P accumulation of P.deltoids×P.nigra as well as Cd migration and distribution, which provided certain scientific basis for making innoxious use of Cd polluted soil, construction of urban forest and construction of fast-growing and high-yield plantation base.The results showed that:1.Low concentration of Cd pollution in the soil have inhibited effect on net photosynthetic rate of P.deltoids×P.nigra tree leaves to an extent,which were higher in alluvial soil than in purple soil at the same Cd concentration treatment.In purple soil,low Cd concentration can promote stomata conductance significantly,Carbon dioxide concentration among cells also increased with stomata conductance.While in alluvial soil, these changes were not significant and low Cd concentration had no significant effect on transpiration rate.Content of chlorophyll a,chlorophyll b and their proportion in P. deltoids×P.nigra leaves in alluvial soil were not significant affected by Cd treated.But content of chlorophyll a in P.deltoids×P.nigra leaves in purple soil were reduced significantly under Cd treated environment.In alluvial soil,planting density had no significant effect on photosynthesis and chlorophyll content of P.deltoids×P.nigra.Leaf area of individual tree decreased along with the increase of Cd concentration.Cd treatment had a significant effect on leaf area of P.deltoids×P.nigra.In alluvial soil,different densities with the same treatment were studied.Leaf area growth of individual tree was inhibited by density increase.2.Low Cd concentration treatment showed no significant effect on the tree height and ground diameter of P.deltoids×P.nigra,however,the difference of soil type showed obvious effect,effect on the tree height growth and ground diameter growth in alluvial soil were higher than that in purple soil at the same Cd concentration treatment.In alluvial soil, effect of density on growth of P.deltoids×P.nigra was more obvious than that of low Cd concentration treatment.Low Cd concentration had no significant effect on the biomass growth and distribution in root,stem and defoliation of P.deltoids×P.nigra.In purple soil, ration of biomass percentage in root,stem,defoliation to total plant biomass was 0.53:0.27: 0.20,which was 0.38:0.42:0.20 in alluvial soil.Biomass growth and distribution of trees in different soil type were of significant difference,increase of planting density showed inhibition on biomass growth of individual plant.3.In the soil-plant system,Cd volume taken up by tree was increased and Cd volume in soil was reduced with the increase of treated concentration.Cd volume that was returned to soil through defoliation varied irregularly.Generally,the total Cd volume returned by defoliation in purple soil was less than that in alluvial soil.Cd accumulation in individual plant increased with the increase of treated Cd concentration,which indicated that treated Cd concentration had a positive correlation with plant Cd accumulations to an extent.Cd volume distributions in different organs of P.deltoids×P.nigra were as follows:In purple soil,Cd volume in root,stem and defoliation was 0.545:0.453:0.002 in proportion,while in alluvial soil that was 0.416:0.577:0.007.Cd were mainly stored in root of P.deltoids×P.nigra planted absorbed from purple soil,but in alluvial soil,the absorbed Cd was mainly stored in stem.Increase planting density reduced the Cd accumulation in individual plant.4.Low Cd concentration had no significant effect on the C,N and P accumulation in P.deltoids×P.nigra.But C,N and P accumulations were different in different soil types. In alluvial soil with same treatment,C,N and P accumulations in tree organs were significantly different under different planting density.In purple soil,C accumulations were ranked in descending order as:root(0.49)＞stem(0.33)＞defoliation(0.18),while in alluvial soil was stem(0.37)＞root(0.42)＞defoliation(0.21).In purple soil,N accumulations in CK were root(0.56),stem(0.22),and defoliation(0.22);in other treatments were root(0.50),stem(0.18),and defoliation(0.32).In alluvial soil,under T3 treatment the N accumulation in root,stem,and defoliation was 0.39,0.26,and 0.35 separately;while under other treatments were root(0.35),stem(0.28),and defoliation (0.37) respectively.In purple soil,P accumulations in CK were root(0.47),stem(0.30), defoliation(0.23),under other treatments was root(0.50),stem(0.23),defoliation(0.27), and in alluvial soil all treatments were as root(0.35),stem(0.39),and defoliation(0.26).更多还原