The Study Of Adaptation Ability And Strategy Of Three Types Of Plants In Grassland In Low-phosphorus Environment

Natural grassland degradation in northern of China is serious because of climate change and irrational use, which lead to soil fertility declining and lower soil phosphorus content. Combined with the increased nitrogen deposition in recent years, phosphorus becomes one of the most important factors of restricting natural grassland productivity. Soil phosphorus deficiency not only affects the plant growh, but also reduces the primary productivity of grassland. The different responses of different vegetations to soil phosphorus availability can becomes one of the factors of natural grassland vegetation succession. In our study, we select three plants( Leymus chinensis, Potentilla acaulis, Medicago ruthenicus) in natural grassland to research the low phosphorus adaptability and the adaptive strategyof different vegetations and in order to reveal the driving role of soil effective phosphorus in natural grassland vegetation succession.We carried out our experiment at greenhouse of Grassland Research Institute of Chinese Academy of Agricultural Sciences in 2015. In order to form four kinds of soil with different phosphorus supplying capacity, we chose the severe low phosphorus soil(available phosphorus content only 3.00 mg P2O5 ? kg-1) and set four phosphorus add gradient(0, 30, 90, 180 mg P2O5 ? kg-1). Leymus chinensis, Potentilla acaulis and Medicago ruthenicus were three selected plants. We gorw three plants in different pots with different phosphorus supplying capacity and set six repeat each processing. We measured morphological indicators, plant biomass, phosphorus content index, and measure pH, acid phosphatase activity and the phosphorus content of collected rhizosphere and non-rhizosphere soil at the end of plants growth. Results as follows:(1) Leymus chinensis and Potentilla acaulis showed responses to the soil phosphorus supplying capacity but Medicago ruthenicus is not sensitive to the soil phosphorus supplying capacity. The phosphorus efficiency of ground dry weight, root dry weight and total dry weight of Leymus chinensis were 69.5%, 38.3%, 56.5%, Potentilla acaulis was 59.1%, 54.1%, 59.1% and Medicago ruthenicus was 82.4%, 81.4%, 85.5%. Total dry weight of Leymus chinensis on 0 mg P2O5 ? kg-1 was significantly different with total dry weight on amount of 30 mg P2O5 ? kg-1, 90 mg P2O5 ? kg-1,180 mg P2O5 ? kg-1. While total dry weight was not significantly different on the amount of 30 mg P2O5 ? kg-1 and 90 mg P2O5 ? kg-1 with it on the amount of 180 mg P2O5 ? kg-1. For Potentilla acaulis, only total dry weight on the amount of 0 mg P2O5 ? kg-1 was significantly different with others. Total dry weight of Medicago ruthenicus had no significant difference at four different environment. The results showed that the sensitivity to soil phosphorus supplying capacity were Leymus chinensis > Potentilla acaulis > Medicagoruthenicus at a perspective of the total dry weight. The different responses to soil phosphorus between Leymus chinensis and Potentilla acaulis may be one of the driving mechanisms of natural grassland vegetation succession.(2) The different morphological index of Leymus chinensis to soil phosphorus supplying capacity showed significant differences. Different soil phosphorus supplying capacity changes the morphological traits of Potentilla acaulis and Medicago ruthenicus in a substantially equal magnitude. Soil phosphorus supplying capacity significantly changed the leave shape and plant morphology of Leymus chinensis, but had a small effect on Potentilla acaulis and Medicago ruthenicus. The results of leave and plant morphology show that the sensitivity on soil phosphorus supplying capacity: Leymus chinensis > Potentilla acaulis and Medicago ruthenicus.(3) The root shoot ratio of three species firstly increased and then decreased with soil phosphorus supplying capacity. And phosphorus utilization efficiency of three species firstly increased and then decreased too. Acid phosphatase activity of three species did not show significant changes with the change of soil phosphorus supplying capacity. The results showed that three species also adapt to low phosphorus environment by changing the distribution of photosynthetic production of ground and underground and changing the phosphorus utilization efficiency.(4) There are significant differences in distribution of photosynthetic production of ground and underground, phosphorus utilization efficiency, phosphorus accumulation rate of rhizosphere soil between three species. The root shoot ratio showed that Leymus chinensis > Potentilla acaulis and Medicago ruthenicus, and the root shoot ratio of Leymus chinensisshows was most sensitive for soil phosphorus supplying capacity. The phosphorus utilization efficiency showed that Leymus chinensis > Medicago ruthenicus > Potentilla acaulis. Combined analysis of soil available phosphorus of rhizosphere, pH, acid phosphatase activity, the results showed that the different distribution of photosynthetic productson of ground and underground, phosphorus utilization efficiency, rhizosphere soil phosphorus accumulation rate between Leymus chinensis and Potentilla acaulismay was one of the driving mechanism of natural grassland vegetation succession.