Effects Of Doubled CO₂ Concentration On Utilization Of Main Nutrients In Soil Planted With Different Species

Soil nutrients is the material basis for plant growth and development, and play an important role in nutrient cycles and energy flow in terrestrial ecosystem. Global climate change caused by elevated atmospheric CO2 concentration ([CO2]) will affect plant nutrient uptake and soil nutrient concentrations supplied to the plant. However, soil nutrient responses to elevated [CO2] in different species planted in forest land is still poorly understood. This study use five economic and ecological woody species(Betula platyphylla, Acer mono, Larix gmelinii, Phellodendron amurense, Fraxinus mandschurica) and six common herbaceous plants(Perilla frutescens, Elymus dahuricus, Amaranthus tricolor, Onobrychis viciaefolia, Aquilegia viridiflora, Chenopodium album)to examine the changes of plant biomass, soil nutrients and microbes under the conditions of doubled [CO2] (350 to 700 μmol·mol-1) treatments. Our results show that:(1) Doubled [CO2] in this experiments increased in plant biomass growth, but the biomass growth was significant differences with plant life form. For herbaceous plants, doubled [CO2] promoted root biomass growth greater than aboveground.(2) Total soil nutrients, such as total C, total N, total P and total K, in pots of woody seedling planted were not affected by doubled [CO2] treatments compared with the pots of non-seedling planted. In pots of herb seedlings planted, excepting total P which significant decrease, all other total nutrients also not changed. In addition, the concentrations of total nutrients in pot soil were changed among the woody species and herbaceous plants in this experiments.(3) Doubled [CO2] significantly reduced soil nitrate N concentration, but the magnitude of reductions differed among species with the reduction ranges from 17%(Perilla frutescens) to 57%(Elymus dahuricus) in this experiments. The reasons may be the species with faster growth have a greater demand for soil nitrate nitrogen, and increase the utilization efficiency of soil nitrate N under doubled [CO2] treatment. By contrast, soil ammonium N in pots with woody and herbaceous seedling planted were not affected by doubled [CO2], but the concentrations of which have greater differences among the species. The concentrations of soil available P and K in pots were not changed for woody species under doubled [CO2] treatments, but significant reduction only occurred in some herbaceous plants.(4) Soil microbial biomass C in pot soil of woody species and herbaceous plants species differed significantly under doubled [CO2] treatments. Doubled [CO2] treatments increases soil microbial biomass N, but the degree of response were different among species. Legumes species, such as Onobrychis viciaefolia, showed stronger N-fixing ability under doubled [CO2] treatments as comparing with the pot soil of non-species planted, the microbial biomass N under 350μmol·mol-1 and 700μmol·morl-1 treatment increased by 193% and 223%, respectively.