分类： 地球科学 >> 地球科学史 提交时间： 2018-09-17 合作期刊: 《干旱区科学》
摘要： Biological soil crusts (BSCs) are bio-sedimentary associations that play crucial ecological roles in arid and semi-arid regions. In the Gurbantunggut Desert of China, more than 27% of the land surface is characterized by a predominant cover of lichen-dominated BSCs that contribute to the stability of the desert. However, little is known about the major factors that limit the spatial distribution of BSCs at a macro scale. In this study, the cover of BSCs was investigated along a precipitation gradient from the margins to the center of the Gurbantunggut Desert. Environmental variables including precipitation, soil particle size, soil pH, electrical conductivity, soil organic carbon, total salt, total nitrogen, total phosphorus and total potassium were analyzed at a macro scale to determine their association with differing assemblages of BSCs (cyanobacteria crusts, lichen crusts and moss crusts) using constrained linear ordination redundancy analysis (RDA). A model of BSCs distribution correlated with environmental variables that dominated the first two axes of the RDA was constructed to clearly demonstrate the succession stages of BSCs. The study determined that soil particle size (represented by coarse sand content) and precipitation are the most significant drivers influencing the spatial distribution of BSCs at a macro scale in the Gurbantunggut Desert. The cover of lichen and moss crusts increased with increasing precipitation, while the cover of cyanobacteria crusts decreased with increasing precipitation. The cover of lichen and moss crusts was negatively associated with coarse sand content, whereas the cover of cyanobacteria crusts was positively correlated with coarse sand content. These findings highlight the need for both the availability of soil moisture and a relatively stable of soil matrix, not only for the growth of BSCs but more importantly, for the regeneration and rehabilitation of disturbed BSC communities in arid and semi-arid lands. Thereby, this study will provide a theory basis to effectively increase soil stability in desert regions.
分类： 地球科学 >> 地理学 提交时间： 2021-04-22 合作期刊: 《干旱区科学》
摘要： Winter snowpack is an important source of moisture that influences the development of biological soil crusts (BSCs) in desert ecosystems. Cyanobacteria are important photosynthetic organisms in BSCs. However, the responses of the cyanobacterial community in BSCs to snowpack, snow depth and melting snow are still unknown. In this study, we investigated the cyanobacterial community composition and diversity in BSCs under different snow treatments (doubled snow, ambient snow and removed snow) and three snow stages (stage 1, snowpack; stage 2, melting snow; and stage 3, melted snow) in the Gurbantunggut Desert in China. In stages 1 and 2, Cyanobacteria were the dominant phylum in the bacterial community in the removed snow treatment, whereas Proteobacteria and Bacteroidetes were abundant in the bacterial communities in the ambient snow and doubled snow treatments. The relative abundances of Proteobacteria and Bacteroidetes increased with increasing snow depth. The relative abundances of Cyanobacteria and other bacterial taxa were affected mainly by soil temperature and irradiance. In stages 2 and 3, the relative abundance of Cyanobacteria increased quickly due to the suitable soil moisture and irradiance conditions. Oscillatoriales, Chroococcales, Nostocales, Synechococcales and unclassified Cyanobacteria were detected in all the snow treatments, and the most dominant taxa were Oscillatoriales and Chroococcales. Various cyanobacterial taxa showed different responses to snowpack. Soil moisture and irradiance were the two critical factors shaping the cyanobacterial community structure. The snowpack depth and duration altered the soil surface irradiance, soil moisture and other soil properties, which consequently were selected for different cyanobacterial communities. Thus, local microenvironmental filtering (niche selection) caused by snow conditions may be a dominant process driving shifts in the cyanobacterial community in BSCs.
分类： 生物学 >> 生态学 提交时间： 2023-06-13 合作期刊: 《干旱区科学》
摘要：Drought is a critical limiting factor affecting the growth and development of plants in arid and semi-arid areas. Photosynthesis, one of the most important physiological processes of plants, can be significantly inhibited by drought. Photosystem II (PSII) is considered the main attack target when photosynthesis is affected by drought. To clarify how PSII components of the ephemeral plant Erodium oxyrhinchum (grown in the Gurbantunggut Desert, China) respond to drought treatment, we evaluated the functional activity of PSII by determining chlorophyll fluorescence and gas exchange parameters under different drought treatment levels (control (400 mL), moderate drought (200 mL), and severe drought (100 mL)). Under moderate drought treatment, significant decreases were found in net photosynthetic rate (Pn), effective quantum yield of PSII (Y(II)), relative electron transfer rate of PSII (rETR(II)), oxygen-releasing complex, probability of an absorbed exciton moving an electron into the electron transport chain beyond primary quinone receptor QA– (Φ(Eo)), probability of a trapped exciton moving an electron into the electron transport chain beyond primary quinone receptor QA– (ψ(Eo)), and performance index of PSII (PIabs). Compared to control treatment, marked increases were observed in water use efficiency (WUE), relative variable fluorescence at the J step (VJ), initial fluorescence (Fo), and dissipated energy per active reaction center (DIo/RC) under moderate drought treatment, but there were no substantial changes in semi-saturated light intensity (IK), active reaction centers per cross-section (RC/CS), and total performance index of PSII and PSI (PItotal, where PSI is the photosystem I). The changes of the above parameters under severe drought treatment were more significant than those under moderate drought treatment. In addition, severe drought treatment significantly increased the absorbed energy per active reaction center (ABS/RC) and trapping energy per active reaction center (TRo/RC) but decreased the energy transmission connectivity of PSII components, RC/CS, and PItotal, compared to moderate drought and control treatments. Principle component analysis (PCA) revealed similar information according to the grouping of parameters. Moderate drought treatment was obviously characterized by RC/CS parameter, and the values of Fo, VJ, ABS/RC, DIo/RC, and TRo/RC showed specific reactions to severe drought treatment. These results demonstrated that moderate drought treatment reduced the photochemical activity of PSII to a certain extent but E. oxyrhinchum still showed strong adaptation against drought treatment, while severe drought treatment seriously damaged the structure of PSII. The results of this study are useful for further understanding the adaptations of ephemeral plants to different water conditions and can provide a reference for the selection of relevant parameters for photosynthesis measurements of large samples in the field.
分类： 地球科学 >> 地球科学史 提交时间： 2020-10-20 合作期刊: 《干旱区科学》
摘要： In forest ecosystems, interactions between overstory trees and understory herbs play an important role in driving plant species diversity. However, reported links between overstory tree and understory herb species diversity have been inconsistent, due to variations in forest types and environmental conditions. Here, we measured species richness (SR) and diversity (Shannon-Wiener (H') and Simpson's (D) indices) of overstory trees and understory herbs in the protected Tianshan Wild Fruit Forest (TWFF), Northwest China, to explore their relationships along the latitudinal, longitudinal, elevational, and climatic (current climate and paleoclimate) gradients in 2018. We found that SR, and H' and D diversity indices of overstory trees and understory herbs exhibited a unimodal pattern with increasing latitude and elevation (P<0.05) and negative associations with longitude (P<0.01). Along the climatic gradients, there were U-shaped patterns in SR, and H' and D diversity indices between trees and herbs (P<0.05). SR, and H' and D diversity indices for overstory tree species were positively associated with those for understory herbs (P<0.01). These findings indicate that overstory trees and understory herbs should be protected concurrently in the TWFF to increase effectiveness of species diversity conservation programs.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2018-03-02 合作期刊: 《干旱区科学》
GAO, Bei
ZHANG, Daoyuan
LI, Xiaoshuang
YANG, Honglan
LIANG, Yuqing
CHEN, Moxian
ZHANG, Yuanming
ZHANG, Jianhua
WOOD, Andrew
摘要： Bryum argenteum Hedw. is a desiccation tolerant bryophyte and belongs to one of the most important components of the biological soil crusts (BSCs) found in the deserts of Central Asia. Limited information is available on rehydration-responsive proteins in desiccation tolerant plants. As a complement to our previous research analyzing the rehydration transcriptome, we present a parallel quantitative proteomic effort to study rehydration-responsive proteins. Bryophyte gametophores were desiccated (Dry) and rehydrated for 2 h (R2) and 24 h (R24). Proteins from Dry, R2 and R24 gametophores were labeled by isobaric tags for relative and absolute quantitation (iTRAQ) to determine the relative abundance of rehydration-responsive proteins. A total of 5503 non-redundant protein sequences were identified and 4772 (86.7%) protein sequences were annotated using Gene Ontology (GO) terms and Pfam classifications. Upon rehydration 239 proteins were elevated and 461 proteins were reduced as compared to the desiccated protein sample. Differentially up-regulated proteins were classified into a number of categories including reactive oxygen species scavenging enzymes, detoxifying enzymes, Late Embryogenesis Abundant (LEA) proteins, heat shock proteins, proteasome components and proteases, and photosynthesis and translation related proteins. Furthermore, the results of the correlation between transcriptome and proteome revealed the discordant changes in the expression between protein and mRNA.
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