Plant resources and diversity analysis of Sejila Mountain in southeast Tibet

Sejila Mountain is located in Linzhi City,southeast Tibet.The terrain is high,and the climate is cold and dry.The special ecological environment determines the richness and diversity of plant resources.In this study,the plant resources and diversity of Sejila Mountain were studied through field investigation,literature review and specimen identification.282 plant species belonging to 199 genera and 81 families were collected from July to August in 2021.The dominant families are Asteraceae,Ranunculaceae and Rosaceae.In terms of life form,perennial herbs are the main form,accounting for 58.16%of the total.178 species of medicinal plants were collected,including 33 species of Tibetan medicine.In terms of medicinal parts,the whole grass is mainly used as medicine,followed by roots and rhizomes.In conclusion,our study has updated the plant resources and diversity of Sejila Mountain.Based on the investigation and research,some suggestions were put forward to strengthen the protection and utilization of the plant resources in Sejila Mountain.

Population structure and spatial pattern analysis of Quercus aquifolioides on Sejila Mountain,Tibet,China

Understanding population structure provides basic ecological data related to species and ecosystems.Our objective was to understand the mechanisms involved in the maintenance of Quercus aquifolioides populations.Using a 1 ha permanent sample plot data for Q.aquifolioides on Sejila Mountain,Tibet Autonomous Region(Tibet),China,we analyzed the population structure of Q.aquifolioides by combining data for diameter class,static life table and survival curve.Simultaneously,the spatial distribution of Q.aquifolioides was studied using Ripley’s L Function in point pattern analysis.The results showed:(1) Individuals in Q.aquifolioides populations were mainly aggregated in the youngest age classes,that accounted for94.3% of the individuals; the older age classes had much smaller populations.Although the youngest age classes(ClassesⅠ and Ⅱ) had fewer individuals than Class Ⅲ,the total number of individuals in classes Ⅰ and Ⅱ was also greater than in classes Ⅳ to Ⅸ.In terms of tree height,fewsaplings,more medium-sized saplings and few large-sized trees were found.The diameter class structure of Q.aquifolioides populations formed an atypical ‘pyramid’type; the population was expanding,but growth was limited,tending toward a stable population.(2) Mortality of Q.aquifolioides increased continuously with age; life expectancy decreased over time,and the survivorship curve was close to a Deevey I curve.(3) The spatial distribution pattern of Q.aquifolioides varied widely across different developmental stages.Saplings and medium-sized tree showed aggregated distributions at the scales of 0–33 m and 0–29 m,respectively.The aggregation intensities of saplings and medium-sized trees at small scales were significantly stronger than that of large-sized trees.However,large-sized trees showed a random distribution at most scales.(4) No correlation was observed among saplings,medium-and large-sized trees at small scales,while a significant and negative association was observed as the scale increased.Strong competition was found among saplings,medium-and large-sized trees,while no significant association was observed between medium-and largesized trees at all scales.Biotic interactions and local ecological characteristics influenced the spatial distribution pattern of Q.aquifolioides populations most strongly.

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.

Influence of topography,soil properties and plant community on the biomass of Abies georgei var.smithii seedlings in Southeast Tibet

Biomass of seedlings at different developing stages of growth is important information for studying the response of species to site conditions.The objectives of this study was to explore the distribution characteristics of AGB(above-ground biomass)and BGB(below-ground biomass)of Abies georgei var.smithii seedlings of different ages,and investigate the effects of topography(slope aspect,altitude),plant community characteristics(crown density,species diversity,etc.),and soil properties(soil physical and chemical properties)on the biomass and its allocation.Seedlings in five age classes(1–2,3–4,5–6,7–8,and 9–10 years old)were collected by full excavation from 6 elevations(3800 m,3900 m,4000 m,4100 m,4200 m,4300 m)on the north and south slopes of Sejila Mountain in Tibet.15seedlings of each age class were investigated at one altitude.The individual effects of seedling age(SA)and the interaction effects of SA,slope aspect(SL),and elevation(EG),namely,SL×EG,SL×SA,EG×SA,and SL×EG×SA,had significant effects on the AGB of the seedlings(p<0.05),whereas BGB was only significantly affected by SA(p<0.001).The AGB and BGB of the seedlings showed a binomial growth trend with the increase in seedling age,and had an allometric relationship at different elevations,α(allometric exponential)varied from 0.913 to 1.046 in the northern slope,and from 1.004 to 1.268 in the southern slope.The biomass of seedlings on the northern slope was remarkably affected by stand factors,with a contribution rate of 47.8%,whereas that on the southern slope was considerably affected by soil factors with a contribution rate of 53.2%.The results showed that age was the most important factor affecting seedling biomass.The allometric pattern of seedling biomass was relatively stable,but in a highaltitude habitat,A.georgei var.smithii seedlings increased the input of BGB.Understanding seedling biomass allocation and its influencing factors is useful for evaluating plants’ability to acquire resources and survival strategies for adaptation to the environment in Tibet Plateau.