Effect Of Exogenous Phosphorus On Vegetation Restoration In The Loess Hilly Region

Vegetation rehabilitation is an important part of eco-construction in the loess hilly region,and the soil is the basis of vegetation restoration. Focusing on the issues about slow process ofvegetation recovery and shortage of soil phosphorus nutrition in the loess hilly region,through field investigation, pot experiment, phosphorus fertilizer in-situ adding experiment infield and the seeds germination experiment in lab, This thesis studied the phosphorus nutritioncharacteristics and the correlation between soil and plant of main constructive plant species.Further, the impact of different exogenous phosphorus on the growth and development ofseeding and adult plants, as well as the photosynthetic characteristics were explored. Thereproduction ability of several typical plants was discussed also. The main progress was asfollows:(1) Soil available phosphorus content of the loess hilly region was at a very low level andleaf phosphorus content of several typical plants was lower than the global average; soil-plant phosphorus nutritional status of natural vegetation and artificial vegetation reflected thestronger adaptability in low soil phosphorus environment of natural vegetation than artificialvegetation. The average content of soil and leaf phosphorus were1.54mg·kg-1and1.43mg·g-1respectively in study area, the ratio of soil available phosphorus to total phosphorus content ofherbaceous vegetation was less than that of artificial forest. Artificial forest appeared to behigher demand of soil available phosphorus content than herbage vegetation of naturalrestoration, it also had a better improvement on soil available phosphorus. Therefore, leafphosphorus content of natural vegetation did not change as much as soil phosphorus changes,which reflected that natural vegetation has a stronger adaptability than artificial vegetation inlow soil phosphorus environment.(2) Influence of exogenous phosphorus on seeding growth and development was variedwith phosphorus fertilizer level and vegetation type, parabolic change was observed with theelevating of phosphorus fertilizer level, also adding phosphorus fertilizer could significantlyincrease leaf phosphorus content, reduce the ratio of nitrogen to phosphorus of leaf andimprove plant seedings phosphorus nutrition. Besides it also showed significant promotion onphotosynthesis of plant seedings, however, excessive phosphorus fertilizer limited thephotosynthesis. The optimal phosphorus fertilizer level of Caragana intermedia and Robinia pseudocacia were135kg·hm-2and210kg·hm-2(P2O5), and showed more sensitive toexogenous than Artemisia gmelinii. Leaf phosphorus content of three plant seedings linearincreased with the adding of phosphorus fertilizer.(3) Exogenous phosphorus adding can significantly promoted the adult plant stem andbranch growth, it had a greater impact on artificial vegetation than natural vegetation. Theresponse of plant to phosphorus still existed difference between years. Application ofexogenous phosphorus improved adult plant leaf phosphorus nutrition, reduce the ratio ofnitrogen to phosphorus of leaf. The ratio of nitrogen to phosphorus of leaf was more than16after adding exogenous phosphorus, reflecting the status of plant phosphorus nutritionshortage after addition of exogenous phosphorus in the experiment condition. Application ofexogenous phosphorus had no significant effect on plant seed germination rate, whithdemonstrated that exogenous phosphorus application was not a practical approach to improvethe capacity of plant propagation and update. Compared with natural vegetation restoration,artificial vegetation planting will probably greatly accelerate the process of vegetationrestoration.