| The desert steppe,typical steppe and meadow steppe of Hulunbuir were selected as the research objects in our study.We measured the vegetation community and species distribution characteristics,plant and soil carbon(C),nitrogen(N),phosphorus(P)nutrient content and stoichiometric characteristics under 3 grassland utilization methods(grazing prohibition,mowing and grazing).The relationship between them and environmental factors also were analyzed.This study aimed to clarify the interactions and changes between plants and soil carbon,nitrogen,and phosphorus under different gland utilization methods in Hulunbuir grassland.It also provided a scientific basis for the reconstruction of Hulunbuir grassland ecosystem.and the rational allocation of vegetation models.The results were as follows:(1)Compared with grazing,grazing prohibition and mowing both increased the species number,coverage,height,and aboveground biomass of plant communities.Grazing prohibition and mowing improved species diversity and abundance.Artemisia frigida,Salsola ruthenica and other degradation indicator species had the highest important values in grazing plots.Under mowing and grazing prohibition,the important value of perennial high-quality forage grasses with good palatability increased compared to grazing,like Carex duriuscula,Stipa grandis,Agropyron cristatum,and Leymus chinensis.This indicated that grazing prohibition and mowing were beneficial to the positive development of grasslands.(2)At the population and community scales,different utilization methods had no significant effects on plant carbon content.The nitrogen and phosphorus content in mowing plot was higher than grazing plot.At population scales,there were significant differences response of nutrient content of different species to grassland utilization methods.At community scales,the nitrogen and phosphorus content of plants was shown to be significantly higher than mowing and grazing in typical steppe and meadow steppe.In addition,the nutrient element contents of the other plots were not significantly different.Compared with continuous grazing,both grazing prohibition and mowing were beneficial to the accumulation of soil carbon and nitrogen content in a certain extent,and the mowing effect was more significant.(3)Among the three utilization methods of grassland,the C/N and C/P of plants in the mowing plot were the lowest.The average value of plant N/P was less than 14,and it can be preliminarily considered that the growth of plants in Hulunbuir was restricted by nitrogen.The overall C/N difference between the plots of various utilization methods was not large.C/P showing the rule of mowing> grazing prohibition> grazing.(4)The nitrogen content of plants had a extremely significant positive correlation with annual precipitation and altitude,a positive correlation with soil bulk density,and a extremely significant negative correlation with p H and Shannon diversity index.Soil organic carbon content had a extremely significant positive correlation with annual precipitation and altitude,and a extremely significant negative correlation with p H.Soil total nitrogen and total phosphorus had a extremely significant negative correlation with p H.Soil C/P with Shannon diversity index and Margalef richness index showed a extremely significant positive correlation.(5)From west to east,also from desert steppe,typical steppe to meadow steppe,the number of species,vegetation coverage,height and aboveground biomass all showed an upward trend.Among them,only aboveground biomass had a significant difference under different grassland types.There was no significant difference in plant carbon,nitrogen,and phosphorus content among the three grassland types.Plant carbon content was the highest in meadow steppe,nitrogen content was the highest in desert steppe,and phosphorus content was minimal in the three types of grassland.The contents of soil carbon,nitrogen and phosphorus were as follows: desert steppe <typical steppe < meadow steppe. |
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