[Phylogenetic structure of Abies georgei var. smithii community at different spatial scales in Sygera Mountains of Tibet, China]. / 不同空间尺度西藏色季拉山急尖长苞冷杉群落谱系结构特征.

We analyzed the phylogenetic structure of trees within six diameter classes (1-2, 2-4, 4-7, 7-11, 11-16, >16 cm) in quadrats with different size of 5 m×5 m,10 m×10 m, 20 m×20 m, 50 m×50 m, 100 m×100 m in a Abies georgei var. smithii community in a 4 hm2 stem-mapping plot located in subalpine dark coniferous forest of Sygera Mountains, southeast Tibet. In various spatial scales, both net relatedness index (NRI) and nearest taxon index (NTI) of the community were larger than zero, indicating a clustered phylogenetic structure with the largest clustering intensity at small spatial scale (5 m×5 m). Community of small-size classes were phylogenetically clustering. In large-size classes (DBH>7 cm) phylogenetic over dispersion became more common, with dispersion increased with increasing tree size under all spatial scales. The intensity of phylogenetic clustering in young trees increased with increasing spatial scales, while the intensity of over dispersion in large trees (DBH>7 cm) increased with spatial scale. Our results suggested that environmental filtering in small-size trees and competitive exclusion in large-size trees might be the main ecological processes driving community assembly in this region.

The complete chloroplast genome of Abies georgei Orr var. smithii, a species endemic to the Qinghai-Tibet Plateau, China.

Abies georgei Orr var. smithii is an evergreen coniferous species of Pinaceae, and is endemic to the Qinghai-Tibet Plateau of China. Considering its vital ecological functions in this unique area, the complete chloroplast (cp) genome was constructed in this study to provide genetic information for its further study of conservation and evolution. The complete cp genome is 121,213 bp in length with GC content of 38.3%, and contains a tetrad structure, including a large single copy region of 76,278 bp, a small single copy of 42,575 bp, and two very short repeats of 1,180 bp for each. Besides, it contains 113 genes in total, including 74 CDSs, 35 tRNAs, and four rRNAs. This genome has been deposited in Genbank under accession number of MT527722.

[New records of medicinal plants in Tibet].

By the fourth survey of Chinese medicinal resources, new medicinal plants records of 2 genera and 5 species were reported in Tibet. They are two genera Rhynchoglossum and Asteropyrum, and five species including Rh. obliquum, A. peltatum, Urena repanda, Schefflera khasiana and Mimulus tenellus. All the voucher specimens are preserved in Herbarium of Tibet Agriculture and Animal Husbandry University.

Types and species diversity of Cupressus communities in Southeast Tibet, China.

Cupressus communities are the important parts of natural forests in Southeast Tibet, with significance on plateau biodiversity conservation and ecological security. To clarify their types and plant species diversity, we analyzed species composition and diversity indices, diameter class pattern of constructive species in different communities in Milin County, Lang County and Bomi County, Southeast Tibet. The results showed that Cupressus communities could be classified into four types: C. torulosa-Lonicera lanceolate + Philadelphus tomentosus-Pteris cretica var. nervosa + Digitaria violascens community (Community1), C. gigantea-Desmodium elegans + Sophora moorcroftia-na-Tripogon filiformis + Cymbopogon distans + Orinus thoroldii community (Community2), C. gigantea-Leptodermis purdomii-Chenopodium hybridum + O. thoroldii community (Community 3), and C. gigantea-Ceratostigma minus-A. desertorum + O. thoroldii + Tribulus terrester community (Community 4). Across those four community types, Margalef index, Shannon index, Pielou index and interspecies encounter probability index all ranked with the decreasing order of Community1, Community2, Community 3 and Community 4. Diameter class pattern of the constructive species showed that many young and few middle/old individuals were within the four communities. High mortality rate occurred during the interim period from young to middle age classes. In general, populations of Cupressus plants showed a declining trend.

Integrated analysis of transcriptomic and metabolomic data reveals critical metabolic pathways involved in rotenoid biosynthesis in the medicinal plant Mirabilis himalaica.

Mirabilis himalaica (Edgew.) Heimerl is among the most important genuine medicinal plants in Tibet. However, the biosynthesis mechanisms of the active compounds in this species are unclear, severely limiting its application. To clarify the molecular biosynthesis mechanism of the key representative active compounds, specifically rotenoid, which is of special medicinal value for M. himalaica, RNA sequencing and TOF-MS technologies were used to construct transcriptomic and metabolomic libraries from the roots, stems, and leaves of M. himalaica plants collected from their natural habitat. As a result, each of the transcriptomic libraries from the different tissues was sequenced, generating more than 10 Gb of clean data ultimately assembled into 147,142 unigenes. In the three tissues, metabolomic analysis identified 522 candidate compounds, of which 170 metabolites involved in 114 metabolic pathways were mapped to the KEGG. Of these genes, 61 encoding enzymes were identified to function at key steps of the pathways related to rotenoid biosynthesis, where 14 intermediate metabolites were also located. An integrated analysis of metabolic and transcriptomic data revealed that most of the intermediate metabolites and enzymes related to rotenoid biosynthesis were synthesized in the roots, stems and leaves of M. himalaica, which suggested that the use of non-medicinal tissues to extract compounds was feasible. In addition, the CHS and CHI genes were found to play important roles in rotenoid biosynthesis, especially, since CHS might be an important rate-limiting enzyme. This study provides a hypothetical basis for the screening of new active metabolites and the metabolic engineering of rotenoid in M. himalaica.

[Spatial point pattern analysis of Abies georgei var. smithii in forest of Sygera Mountains in southeast Tibet, China].

In this study, based on a 4 hm2 stem-mapping plot, we analyzed spatial distributions of Abies georgei var. smithii, the dominant species in forest of Sygera Mountains in southeast Tibet, China. Pair-correlation function was used to characterize univariate spatial point patterns of three size classes of the population and bivariate spatial patterns between those and different sizes of dead wood. A. georgei var. smithii population was characterized by reverse J-shaped DBH distribution, indicating an increasing population. Saplings of the population were spatially obviously aggregated at the small scales (0-7 m), and mid-sized trees and large-sized trees of the population were randomly or uniformly distributed. The aggregation intensities of A. georgei var. smithii decreased with the increasing diameter classes and spatial scales. Saplings and mid-sized trees were significantly and negatively associated with large-sized trees at the small scales (0-35 and 0-30 m), but the associations reversed at the large scales (45-100 and 80-100 m). In addition, with the increasing age difference between diameter classes of the population, the intensities of positive or negative correlations increased. Spatial associations between saplings and dead large-sized trees, and between mid-sized trees and dead large-sized trees were negative at the small scales (0-34 and 5-27 m), but positive at the large scales (49-100 and 73-100 m). This suggested that released niche space due to dead large-sized trees is not enough to weaken their negative impacts on saplings. We concluded that self-thinning effect and Janzen-Connell hypothesis may be the main mechanisms for the spatial pattern formation of A. georgei var. smithii population.

[Study on medicinal plant resources and diversity in Rhinopithecus bieti national natural reserve of Markam in Tibet].

This research was a part of the investigation of traditional Chinese medicine resources survey in Markam. The medicinal plants in natural reserve were studied for the first in this paper. There were 300 species in 202 genera of 54 families, among them there were 7 species of ferns in 5 genera of 5 families, 6 species of gymnosperms in 4 genera of 3 families, and 287 species of angiosperms in 194 genera of 61 families. There were 166 species Tibetan medicinal plants in 102 genera of 47 families. Quantitative analysis was carried out in 6 aspects of family and genus composition, medicinal parts, drug properties, flavour of a drug, Tibetan medicine, toxicity and new plants. The concrete suggestions of protection and exploitation were put forward, which provided scientific basis for the sustainable utilization of medicinal plants in this area.