| Mowing and grazing are regarded as two effective measures of grassland management.Irrational grazing directly affects the health and sustainable development of grassland.How to establish a scientific and reasonable grassland management system,protect and restore the inherent structure and function of grassland is of great significance to the ecological service function and social value of grassland.This study takes the temperate desert grassland in Yanchi County,Ningxia Province,the southern edge of Mu Us Sandy Land as the research object,Three mowing treatments were designed of mowing removal(A),mowing in situ mulching(B)and mowing in situ mulching and adding mulching(C)and three mowing frequencies of once a year(Al,B1,C1),twice a year(A2,B2,C2)and three times a year(A3,B3,C3),the added mulching came from A.In vegetation and soil,on the basis of comprehensive survey,carried out under different mowing frequency and cover processing desert grassland plant community structure,herbage nutrient,soil physical and chemical properties,soil carbon flux and grassland productivity pattern,relative feeding value and crude protein yield research,in order to provide decision-making basis for the use of fenced grassland,provide theory basis for ecosystem services.The main results are as follows.(1)Mowing and mulching increased aboveground biomass in desert steppe and showed an increasing trend with the increase of mowing frequency.A1 treatment was beneficial to the increase of plant community density.At the same cutting frequency,Shannon-Wiener diversity index of B2 and C2 was higher than that of A,and C1 was beneficial to the increase of Margalef index.There was a positive correlation between aboveground biomass and community a diversity.The compensatory index of B3 and C3 was significantly different from that of A1(P<0.05).(2)Cutting increased the contents of crude protein,crude fat and dry matter,and the higher the cutting frequency,the higher the content of crude protein.Under the same cutting frequency,increasing vegetation coverage was not conducive to the increase of crude protein content.Both high frequency cutting and addition coverage were significant(P<0.05)decreased plant community acidity and neutral detergent fiber,A3 and B3 significantly(P<0.05)increased the relative feeding value of plant communities.There was a positive correlation between crude protein and ash,crude fat and relative feeding value(P<0.001),and dry matter(P<0.01),neutral and acid detergent fibers(P<0.001)were negatively correlated.(3)The soil compactness of A2 and A3 treatments increased with the increase of soil depth,while that of B2,B3 and C3 treatments increased first and then decreased.The proportion of aggregates larger than 5 mm under three times a year cutting frequency treatment was higher than that under one and two times a year cutting frequency treatment,and the treatments of once a year and three times a year cutting reduced the soil pH in the 10-30 cm layer.Total soil respiration rate reached its peak in early September,and soil autotrophic respiration rate was significantly different from temperature only under three mowing treatments a year(P<0.01).B3 treatment increased the soil organic matter content in 2030 cm soil.Cutting three times a year was beneficial to the accumulation of total nitrogen,total phosphorus and available potassium in soil.Different cutting frequency treatments and mulching increased the content of alkali-hydrolyzable nitrogen in soil,and the content of available phosphorus in soil decreased with the increase of soil depth.(4)Redundancy analysis showed that community productivity was closely related to community a diversity under twice-yearly mowing,and crude protein,ether extract,ash,soil phosphorus and available potassium were positively correlated with relative feeding value under thrice-yearly mowing.Soil organic matter and plant dry matter were positively correlated with productivity,crude protein yield and relative feeding value of one or three mowing treatments a year.Community a diversity had the highest contribution to annual mowing,soil nutrient had the lowest contribution to biannual mowing,and plant nutrient quality had the highest contribution to biannual and triannual mowing.In conclusion,mowing and mulching significantly improved the plant nutritional quality of desert steppe,decreased the neutral and acid detergent fiber,and increased the relative feeding value of forage.High-frequency mowing and mulching not only increased soil nutrients,but also promoted the overcompensatory growth of plants,thus improving the vegetation productivity of desert steppe.Three mowing treatments a year was more beneficial to increase the total amount of plant nutrients in desert steppe. |
