Effects of Different Land Use Patterns on Soil Properties in the Lower Reaches of Niyang River of Tibet

[Objectives]This study was conducted to provide scientific basis for rational utilization and sustainable management of agricultural and forestry land resources in southeast Tibet.[Methods]Soil samples were stratified by standard sampling method(0-10,10-20,20-40,40-60 and 60-100 cm)in the lower reaches of Niyang River Basin under three different types of land cover of forest,grassland and farmland.The effects of different land use on soil properties were studied.[Results]Soil temperature and humidity affected soil properties together.The pH value and bulk density increased with the increase of soil depth for farmland,grassland and forest soil.Natural forest had the highest soil nutrient contents,followed by farmland,and grassland had the lowest soil nutrient contents.Soil organic carbon and organic nitrogen contents decreased with the increase of soil depth in the three land use patterns,and the surface aggregation of soil organic carbon and organic nitrogen was more obvious.Compared with natural vegetation,the organic carbon content of farmland was significantly reduced by 8.5%-15.3%and the organic nitrogen content by 11.1%-11.7%.[Conclusions]The change of land use is a proper way to benefit the development of soil properties and improve soil properties and quality in Niyang River Basin.

Effects of Different Land Cover Types on Soil Microbial Biomass Carbon and Nitrogen in the Lower Reaches of Niyang River

[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the rational use and sustainable management of land resources in this area.[Methods]Taking the 3 types of land cover(cultivated land,grass land and forest land)in the lower reaches of Niyang River in Tibet as the research object,the contents,distribution characteristics and relationships of soil organic carbon,organic nitrogen,microbial biomass carbon,microbial biomass nitrogen and readily oxidizable organic carbon,and their relationships were studied in 0-10,10-20,20-40,40-60,and 60-100 cm soil depth.[Results]The soil organic carbon content of forest land was higher than that of grass land and cultivated land;the vertical change trend of soil organic carbon content decreased with the increase of depth(P<0.05),and it was mainly concentrated in the soil with a depth of 0-20 cm.The soil organic carbon content was significantly different among forest land,grass land and cultivated land(P<0.05),but there was no significant difference between cultivated land and grass land(P>0.05).The soil organic nitrogen content was significantly different among cultivated land,grass land,and forest land(P<0.05),but there was no significant difference between grass land and forest land(P>0.05).The readily oxidizable organic carbon,microbial biomass carbon and nitrogen in forest land were higher than that in cultivated land and grass land.The change trend of soil readily oxidizable organic carbon,microbial biomass carbon and microbial biomass nitrogen was similar to the change of soil organic carbon content,showing a significant positive correlation.In addition to being subject to land cover,soil microbial biomass carbon and nitrogen content were also subject to the interaction of factors such as soil temperature,humidity,pH and vegetation types.[Conclusions]Changes in land cover significantly affect soil organic carbon and nitrogen,readily oxidizable organic carbon,microbial biomass carbon and nitrogen content.

Diversity Characteristics of Bryophytes on the Eastern and Western Slopes of Sejila Mountain

[Objectives]To study the characteristics of bryophytes in subalpine cold zone and related transition zone.[Methods]The study was divided into scale A and scale B.On the scale of A,specimens were collected from Tongmai-Pailong-Dongjiu-Lulang-Sejila Pass-Nyingchi Town-Bagi Village along the national Highway 318.A sample plot was set for each 100 m altitude increase,and samples were collected between each two sample plots as well.On the scale of B,bryophyte specimens were collected and studied in the fixed sample plot of the Tibetan Nyingchi Alpine forest Ecosystem Research Observatory.[Results]Through the sampling and collection of bryophytes in Sejila Mountain,more than 3000 specimens were identified with the classical classification method.There were 216 species of bryophytes belonging to 82 genera and 24 families.The bryophytes in the study area differed obviously in different vegetation types and slopes.The species richness of Sabina saltuaria-Abiesgeorgei var.smithii forest was the highest.Theαdiversity of Abiesgeorgei var.smithii forest was the highest,followed by Sabina saltuaria-Rhododendron forest,and that of alpine shrub was the lowest.Diversity studies showed that theβdiversity of Sabina saltuaria-Rhododendron forest and Rhododendron forest on the eastern slope was the largest,and those of alpine shrub and Sabina saltuaria-Abiesgeorgei var.smithii forest were the lowest.However,theβdiversity of Abiesgeorgei var.smithii forest on the western slope was the highest,and those of alpine shrub and Abiesgeorgei var.smithii forest were the lowest.[Conclusions]There are obvious differences in the distribution of bryophytes on the eastern and western slopes of Sejila Mountain of Tibet.