Responses Of Plant Diversity To Pb-polluted Soil And Its Ecological Benefits

The conservation of plant diversity in agro-ecosystems is presently of great concern worldwide. Researches have been showing that plant diversity performs a variety of ecological services beyond the production of food, including recycling of nutrients, regulation of microclimate, soil erosion control, and restoration of degraded environment. The purpose of this study is to investigate the absorption and accumulation of lead through plant biodiversity and the compound action of plant biodiversity and mycorrhizae. At the same time, the weeds that can accumulate higher lead were selected through intercropping with crops to decrease the harm caused by lead to these crops. The new idea of using plant biodiversity to remove or decrease heavy metal in soil was put up. This offered new thoughtfulness for the bioremediation of heavy metal polluted soil. To investigate the ecological functions of plant diversity in heavy metal lead (Pb) polluted soil, plot and pot experiments of various soil Pb levels, and various plant species and plant species combinations were conducted during 2001-2004. The results obtained in these experiment are as follows:1 The responses of various plant species to elevated Pb in soilUnder monoculture, the growth of 17 weeds (Kummerowia striata, Lxeris chinensis, Digitaria ciliaris, Echinochloa crusgalli var. mitis, Poaannua, Lolium perenne, Avenafatua, Vicia cracca, Veroncia didyma, Plantago virginica, Gnaphalium qfflne, Trifolium repens, Oxalis corncidata) and 2 crops (Glycine max and Oryza sativa) was not significantly affected when Pb concentration was 334.53mg/kg. Height and biomass of plants did not significantly differ from those grown in Pb elevated soil and their controls (P > 0.05). Compared to control, PbABSTRACTconcentration in roots of all species significantly increased in Pb treatment except Amaranthus spinosus and Amaranthus paniculatu, and Pb concentration in shoots of all species except Kummerowia striata, Digitaria ciliaris, Poa annua, Veroncia didyma, Ggnaphalium affine, Trifolium repens and Amaranthus paniculatus showed the similar trend as roots. In Pb elevated soil, the concentration of lead (Pb) in all species except Amaranthus paniculatus, was much higher than shoot Pb concentration, indicating that Pb was mainly accumulated in roots. Mycorrhizae were positively, negatively or neutrally influenced by Pb treatments. Compared to control, mycorrhizal infection rate of Echinochloa crusgalli var. mitis, Plantago virginica, Gnaphalium affine, Oxalis cornculata and Eragrostis pilosa was enhanced (P < 0.01), Lxeris chinensis, Poa annua, Lolium perenne, Avenafatua, Vicia cracca and Trifolium repens was reduced (P < 0.01), and Kummerowia striata, Digitaria ciliaris, Veroncia didyma, Amaranthus paniculatus, Amarathus spinosus, Eleusine indica, Glycine max and Oryza saliva was not affected. The vesicular numbers in mycorrhizal roots were also impacted by Pb treatments. In Pb elevated soil, vesicular numbers of Poa annua, Lolium perenne, Avena fatua, Vicia cracca, Amaranthus paniculatus, Amarathus spinosus, Eleusine indica, Eragrostis and Oryza sativa did not change, but vesicular numbers of Veroncia didyma, Plantago virginica, Gnaphalium affine, Trifolium repens, Oxalis cornculata, Echinochloa crusgalli var. mitis increased significantly, and vesicular numbers of Glycine max decreased. Mycorrhizal fungal spores were significantly influenced by Pb treatments. Except Vicia cracca, Trifolium repens, Oxalis cornculata, Amaranthus paniculatus, Eleusine indica, Echinochloa crusgalli var. mitis and Oryza sativa, mycorrhizal fungal spores of other species decreased significantly in Pb treatments (P<0.01).Uptake of nitrogen and phosphorus was not impacted by Pb treatments except Lxeris chinensis, Digitaria ciliaris and Echinochloa crusgalli var. mitis.The phosphorus (P) concentration of Lxeris chinensis and Digitaria ciliaris increased significantly and nitrogen (N) concentration of Echinochloa crusgalli var. mitis decreased in elevated Pb soil.2 The Responses of two co-occurred specie...