Effects Of Microhabitats And Associated Herbaceous Plants On Litter Decomposition Of Salix Cupularis In Alpine Desertified Meadow

Salix cupularis is a good wind-proof,sand-fixing plant,and a pioneer in the restoration and restoration of alpine sand areas in northwestern Sichuan.It has been found through many years of restoration and management that Salix cupularis have strong adaptability to the desertification environment and can effectively improve soil nutrients condition.Litter decomposition is a key link in the material cycle.In the restoration of alpine desertification,the decomposition of Salix cupularis litter is important for the improvement of soil nutrient conditions.In the process of restoration and restoration of desertified meadow,the restoration of grassland forage can be used to restore the grazing production of local herdsmen.Therefore,the restoration of herbaceous plants is very important.In the restoration measures of cutting wicker and sowing pasture,different herbaceous species have inconsistent carbon and nitrogen content,and the amount and quality of the additives provided for litter are different,which will inevitably affect Salix cupularis litter decomposition.In this experiment,the characteristics of different associated grass species and Salix cupularis(the size of the shrub and the different micro-positions under the crown)were used as the research factors to find the size and crown width of the Salix cupularis that is most suitable for the decomposition of alpine bush litter.Location and herbaceous plants more suitable for the restoration of desertified meadow.The main conclusions of this test are as follows:(1)Under different sizes of Salix cupularis,the micro-position had significant effects on mass loss rate,carbon and nitrogen changes,C/N and lignin/N,and these indexes changed significantly with the decomposition time.The increase in N content and the decrease in C/N are favorable for the subsequent decomposition of litter,but the increase in lignin content slows down the decomposition rate.The content of cellulose and lignin in the whole decomposition process was higher than the initial value,indicating that the degradation of cellulose and lignin was lower than that of nutrient particles until the 19 th month of decomposition.Under different sizes of Salix cupularis,the mass loss rate of litter in the outer and middle circle is close,and the mass loss rate from high to low is small,large and middle shrub,and higher than the mass loss rate of litter in the inner ring.The 50% and 95% decomposition time of the Salix cupularis litter showed that the litter decomposition of the shrub base of the shrub and shrub was slower.In summary,the most suitable location for the decomposition of alpine willow litter is the outer ring of small shrubs.(2)The total dissolved organic carbon in the soil increased first and then decreased,and it was the highest at the 10 th month of decomposition.The 13 th month showed a downward trend and was lower than the initial content,while the soil invertase activity also increased from 13 months,indicating that it was from the 13 th.At the beginning of the month,the soil carbon cycle has intensified.With the decomposition of litter,the contents of soil nitrate nitrogen,ammonium nitrogen and organic matter increased,and the contents of nitrate nitrogen and ammonium nitrogen were always higher than the middle circle and outer ring,and the soil nutrient content between different micropositions.The heterogeneity is obvious.Repeated measures analysis of variance showed that the decomposition time and the micro-position under the crown had significant effects on invertase and urease(P<0.05),and there were no significant effects on Salix cupularis in different sizes,but the decomposition time and different sizes of Salix cupularis and the micro position under the crown has no significant effect on cellulase and protease.Soil enzymes participate in the biochemical reaction of soil carbon and nitrogen cycle.In this experiment,the activities of invertase and urease were significantly different at different micro-positions,and increased with the decomposition of litter,indicating that invertase and urease were in soil carbon and nitrogen cycle.The contribution is higher than cellulase and protease.PCA analysis showed that urease and invertase were significantly correlated with soil soluble organic total nitrogen,nitrate nitrogen,ammonium nitrogen,water content and organic matter;cellulase was only related to soil soluble total carbon,and protease was only related to soil soluble total nitrogen.And the correlation is significant.(3)Under the Salix cupularis associated with Elymus nutans,the mass loss rate of litter in each microsites was the highest,and it was higher than the mass loss rate of no associated grass species under the same size of Salix cupularis,indicating Elymus nutans promotes the decomposition of litter.Under the concomitant of three herbaceous plants,at the 19 th month of decomposition,the total nitrogen content of the leaves of Salix cupularis increased compared with the initial value,and all of them are higher than the total nitrogen content in the litter under the influence of no associated plants.Among them,the most increased was Salix cupularis associated with Elymus nutans.Compared with the control without associated plants,there was no significant difference in litter C/N associated with Elymus nutans at the 19 th month of decomposition,but C/N of litter leaves under shrubs associated with Festuca ovina and Elymus sibiricus are increased significantly.The changes of carbon and nitrogen contents and C/N in the litter of different grasses associated,the litter quality change under the shurb associated with Elymus nutans was more favorable for the subsequent decomposition than Festuca ovina and Elymus sibiricus.This is a good explanation for the fact that the mass loss rate of litter associated with Elymus nutans increased sharply at the 19 th month of decomposition,and was significantly higher than that of the litter mass loss rates associated with Festuca ovina and Elymus sibiricus.This result indicates that in the alpine desertified grassland with Salix cupularis as the group,the sowing of Elymus nutans can more effectively promote the decomposition of Salix cupularis litter and enhance soil fertility.It is a herb that is more suitable for the restoration of such desertification in the region.