Vegetation redistribution is predicted to intensify soil organic carbon loss under future climate changes on the Tibetan Plateau.

Vegetation redistribution may bring unexpected climate-soil carbon cycling in terrestrial biomes. However, whether and how vegetation redistribution alters the soil carbon pool under climate change is still poorly understood on the Tibetan Plateau. Here, we applied the G-Range model to simulate the cover of herbs, shrubs and trees, net primary productivity (NPP) and soil organic carbon density (SOCD) at the depth of 60 cm on Tibetan Plateau for the individual years 2020 and 2060, using climate projection for Representative Concentration Pathways (RCP) 4.5 and RCP8.5 scenarios with the RegCM4.6 model system. Vegetation redistribution was defined as the transitions in bare ground, herbs, shrubs and trees between 2020 and 2060, with approximately 57.9 % (RCP4.5) and 59 % (RCP8.5) of the area will redistribute vegetation over the whole Tibetan Plateau. The vegetation cover will increase by about 2.4 % (RCP4.5) and 1.9 % (RCP8.5), while the NPP and SOCD will decrease by about -14.3 g C m-2 yr-1 and -907 g C m-2 (RCP4.5), and -1.8 g C m-2 yr-1and -920 g C m-2 (RCP8.5). Shrubs and trees will expand in the east, and herbs will expand in the northwest part of the Plateau. These areas are projected to be hotspots with greater SOCD reduction in response to future climate change, and will include lower net plant carbon input due to the negative NPP. Our study indicates that the SOC pool will become a carbon source under increased air temperature and rainfall on the Tibetan Plateau by 2060, especially for the area with vegetation redistribution. These results revealed the potential risk of vegetation redistribution under climate change in alpine ecosystems, indicating the policymakers need to pay attention on the vegetation redistribution to mitigate the soil carbon emission and achieve the goal of carbon neutrality on the Tibetan Plateau.

Dietary habits of pastoralists on the Tibetan plateau are influenced by remoteness and economic status.

In general, dietary habits of pastoralists are livestock-derived, but are also influenced by external food sources under globalization. We hypothesized that dietary habits of pastoralists would be influenced by their remoteness, and that changes from the traditional diet would result in deviations in the local ecological chain. To test this hypothesis, we determined the δ13C and δ15N values of soil, plants, and hair of animals and pastoralists (n = 885). The δ13C value in human hair reflects the proportions of protein originating from C3 and C4 plants; whereas, the δ15N value reflects the proportions of protein derived from plants and animals, with higher values indicating a greater consumption of meat. The isotopic signatures enabled us to estimate the variation in dietary habits of pastoralists across a socio-economic gradient of easily accessible to remote areas on the Tibetan plateau, and to determine the trophic transfer of the isotopes along an ecological chain. The trophic magnification factor (TMF) evaluated the trophic transfer of δ15N in the soil-plants-animals-pastoralists ecological chain. The high δ15N values in soil and plants were not recovered in animals and pastoralists in easily accessible and developed areas, indicating the use of external feed and food resources, and that they deviated from the ecological chain. The mean δ13C (-22.0 ‰) and δ15N values (6.9 ‰) of pastoralists indicated diets consisting mainly of local C3 plants and animal products. However, pastoralists in remote areas relied more on meat protein and on the local ecological chain than pastoralists in easily accessible areas, as their δ15N values and trophic magnification factor of δ15N in the ecological chain were greater. In addition to remoteness, per capita GDP influenced dietary changes in pastoralists, with richer pastoralists consuming more external food. We concluded that dietary changes of pastoralists in the easily accessible areas were due to external food resources and alterations in the local ecological chain of animals and plant-based foods available to the pastoralists.

Ant nests increase litter decomposition to mitigate the negative effect of warming in an alpine grassland ecosystem.

Warming can decrease feeding activity of soil organisms and affect biogeochemical cycles. The ant Formica manchu is active on the nest surface and prefers a hot, dry environment; therefore, warming may provide a favourable environment for its activities. We hypothesized that F. manchu benefit from warming and mitigate the negative effects of warming on litter decomposition. We examined the effects of ant nests (nest absence versus nest presence) and warming (+1.3 and +2.3°C) on litter decomposition, soil properties and the plant community in alpine grassland. Decomposition stations with two mesh sizes were used to differentiate effects of microorganisms (0.05 mm) and macroinvertebrates (1 cm) on decomposition. Ant nests increased litter decomposition with and without macroinvertebrates accessing the decomposition station when compared to plots without ant nests. Only litter decomposition in ant nests with macroinvertebrates having access to the decomposition station was not affected negatively by warming. Plots with ant nests had greater soil carbon, nutrient contents and plant growth than plots without ant nests, regardless of warming. Our results suggest that ant nests maintain ecosystem processes and functions under warming. Consequently, a management strategy in alpine grasslands should include the protection of these ants and ant nests.

Cultivable bacteria in the supraglacial lake formed after a glacial lake outburst flood in northern Pakistan / Bacterias cultivables en el lago supraglacial formadas después de una inundación repentina en un lago glacial en el norte de Pakistán

Recently, a supraglacial lake formed as a result of a glacial lake outburst flood (GLOF) in the Dook Pal Glacier. Lake debris and meltwater samples were collected from the supraglacial lake to determine bacterial diversity. Geochemical analyses of samples showed free amino acids (FAAs), anions, cations, and heavy metals. Comparable viable bacterial counts were observed in meltwater and debris samples. Using R2A media, a total of 52 bacterial isolates were identified: 40 from debris and 12 from meltwater. The relative abundance of Gram-positive (80.8%) bacteria was greater than Gram-negative (19.2%). Molecular identification of these isolates revealed that meltwater was dominated by Firmicutes (41.6%) and Proteobacteria (41.6%), while lake debris was dominated by Firmicutes (65.0%). The isolates belonged to 14 genera with the greatest relative abundance in Bacillus. Tolerance level of isolates to salts was high. Most of the Gram-positive bacteria were eurypsychrophiles, while most of the Gram-negative bacteria were stenopsychrophiles. Gram-negative bacteria displayed a higher minimum inhibitory concentration of selected heavy metals and antibiotics than Gram-positive. This first-ever study of culturable bacteria from a freshly formed supraglacial lake improves our understanding of the bacterial diversity and antibiotic resistance released from the glaciers as a result of GLOF.(AU)

Cultivable bacteria in the supraglacial lake formed after a glacial lake outburst flood in northern Pakistan.

Recently, a supraglacial lake formed as a result of a glacial lake outburst flood (GLOF) in the Dook Pal Glacier. Lake debris and meltwater samples were collected from the supraglacial lake to determine bacterial diversity. Geochemical analyses of samples showed free amino acids (FAAs), anions, cations, and heavy metals. Comparable viable bacterial counts were observed in meltwater and debris samples. Using R2A media, a total of 52 bacterial isolates were identified: 40 from debris and 12 from meltwater. The relative abundance of Gram-positive (80.8%) bacteria was greater than Gram-negative (19.2%). Molecular identification of these isolates revealed that meltwater was dominated by Firmicutes (41.6%) and Proteobacteria (41.6%), while lake debris was dominated by Firmicutes (65.0%). The isolates belonged to 14 genera with the greatest relative abundance in Bacillus. Tolerance level of isolates to salts was high. Most of the Gram-positive bacteria were eurypsychrophiles, while most of the Gram-negative bacteria were stenopsychrophiles. Gram-negative bacteria displayed a higher minimum inhibitory concentration of selected heavy metals and antibiotics than Gram-positive. This first-ever study of culturable bacteria from a freshly formed supraglacial lake improves our understanding of the bacterial diversity and antibiotic resistance released from the glaciers as a result of GLOF.

Root exudates enhanced rhizobacteria complexity and microbial carbon metabolism of toxic plants.

Root exudates and rhizosphere microorganisms play key roles in the colonization of toxic plants under climate change and land degradation. However, how root exudates affect the rhizosphere microorganisms and soil nutrients of toxic plants in degraded grasslands remains unknown. We compared the interaction of soil microbial communities, root exudates, microbial carbon metabolism, and environmental factors in the rhizosphere of toxic and non-toxic plants. Deterministic processes had a greater effect on toxic than non-toxic plants, as root exudates affected rhizosphere microorganisms directly. The 328 up-regulated compounds in root exudates of toxic plants affected the diversity of rhizosphere microorganisms. Rhizosphere bacteria-enriched enzymes were involved in the phenylpropanoid biosynthesis pathway. Root exudates of toxic plants form complex networks of rhizosphere microorganisms, provide high rhizosphere nutrients, and increase microbial carbon metabolism. The interaction between root exudates and rhizosphere microorganisms is the key mechanism that enables toxic plants to spread in degraded grassland habitats.

Instability of decoupling livestock greenhouse gas emissions from economic growth in livestock products in the Tibetan highland.

Livestock production is the major livelihood for a growing local population on the Tibetan plateau. However, government policy is to reduce the number of livestock due to the large quantities of greenhouse gasses (GHG), in particular methane, produced by ruminants and the degradation of the grasslands. For this policy to be effective, with little effect on livelihoods, there should be a decoupling of GHG emissions from economic growth of livestock products. This study examined the synergetic effects of policies, extreme climate events and GHG emissions from livestock at the headwater region of the Yellow River since 1980. Optimization models of GHG emissions efficiency and drivers were developed and parameterized. Trade-offs between GHG emissions from livestock and economic growth from livestock, determined by the decoupling model, showed that from 1980 to 2015: 1) the GHG emissions decreased by 39%; (2) CH4 emissions from livestock decreased by 33%, and yaks emitted the most (accounted for 99.6%) among livestock; (3) N2O emissions decreased by 34%; (4) trade-offs between livestock GHG emissions and grassland uptake indicated that the grazing livestock system functioned as a net carbon sink; (5) the efficiency factor, especially technical efficiency, was the main driver of GHG emissions; and (6) GHG emissions from livestock were in a decoupling state from economic growth from livestock. However, decoupling has not been stable as inter-annual fluctuations have been large mainly due to extreme climatic events, such as snowstorm disasters, which indicates that the grazing system was still relatively fragile. The GHG emissions can be reduced further by mitigating CH4 emissions, and enhancing CO2 sequestration on grazed pastureland. The ongoing transformation of livestock industry development on the Tibetan plateau is associated with uncertainty under the background of global GHG mitigation.

Long-term active restoration of extremely degraded alpine grassland accelerated turnover and increased stability of soil carbon.

Soil nutrient contents and organic carbon (C) stability are key indicators for restoration of degraded grassland. However, the effects of long-term active restoration of extremely degraded grassland on soil parameters have been equivocal. The aims of this study were to evaluate the impact of active restoration of degraded alpine grassland on: (a) soil organic matter (SOM) mineralization; and (b) the importance of biotic factors for temperature sensitivity (Q10 ) of SOM mineralization. Soils were sampled from intact, degraded and restored alpine grasslands at altitudes ranging between 3,900 and 4,200 m on the Tibetan Plateau. The samples were incubated at 5, 15 and 25°C, and Q10 values of SOM mineralization were determined. Structural equation modeling was used to evaluate the importance of vegetation, soil physico-chemical properties and microbial parameters for Q10 regulation. The Q10 of N mineralization was similar among intact, degraded and restored soils (0.84-1.24) and was higher in topsoil (1.09) than in subsoil (0.92). The best predictive factor of CO2 -Q10 for intact grassland was microbial biomass, for degraded grassland was basal microbial respiration, and for restored grassland was soil bulk density. Restoration by planting vegetation decreased the Q10 of SOM mineralization as soil bulk density, the most important negative predictor, increased in restored grassland. The Q10 of SOM mineralization in topsoil was 14% higher than in subsoil because of higher microbial abundance and exo-enzyme activities. The NH4 + content was greatest in intact soil, while NO3 - content was greatest in degraded soil. The SOM mineralization rate decreased with grassland degradation and increased after long-term (>10 years) restoration. In conclusion, extremely degraded grassland needs proper long-term management in active restoration projects, especially for improvement of soil nutrients in a harsh environment.

Climate warming benefits alpine vegetation growth in Three-River Headwater Region, China.

Environmental factors that drive vegetation change in the Three River Headwater Region (TRHR) on Qinghai-Tibetan Plateau are largely unknown. In particular, the response of alpine grasslands in the TRHR to changing climate and ecological compensations is still poorly understood. Here, we present data on vegetation trends of the TRHR from 1982 to 2015 by employing multiple high-resolution satellite data to determine the mean annual normalized difference vegetation index (NDVI). In addition, spatio-temporal changes in climate were monitored by long-term climate data collection and by using the distributed modeling system. It emerged that: 1) there was a weak increasing trend, albeit not significant, in overall TRHR NDVI, ranging between 0.23 and 0.27; whereas, grassland NDVI ranged between 0.43 and 0.50, and displayed a significant (r2adj = 0.46; P = 0.004) linear increase with year; 2) annual average temperature was below 0 °C and increased linearly (r2adj = 0.60; P = 0.01) at a rate of 0.06 °C/yr from 2000 to 2015, which was almost four times faster than the rate of global warming; and 3) average rainfall was 493 mm/yr, with no significant yearly trend. In conclusion, climate warming enhanced vegetation growth and recovery in the TRHR since 2000; whereas, rainfall did not show a trend. However, vegetation changes on the spatial scale demonstrated zoning and segmentation effects. Consequently, for restoration of degraded lands in the TRHR, effective one-to-one ecological conservation projects, which are particular to an eco-fragile area, should be implemented. In addition, these results are important for regional planning of livestock stocking rates and animal husbandry systems, which can have great impact on the livelihood of the people in the area.

A lower blood pressure threshold to define hypertension: the effect on prevalence, control rate, and constituent ratio of systolic and/or diastolic hypertension.

OBJECTIVE: To evaluate the impact of the new US hypertension criteria [systolic blood pressure/diastolic blood pressure (SBP/DBP ≥130/80 mmHg)] on hypertension prevalence and the constituent ratio of three hypertension phenotypes. PARTICIPANTS AND METHODS: This study included 1185 adult participants, who received blood pressure (BP) measurements for 3 days over a 7-day period. At each visit, the BP was measured three times and the average was used as the final value. The criteria of hypertension were if the participant had received treatment with antihypertensive drugs for at least 2 weeks, or SBP/DBP of at least 140/90 mmHg (old criteria) or at least 130/80 mmHg (new criteria) for the untreated participants. The diagnosis of hypertension was made on the basis of first-day BP values (epidemiological method) or the average of the 3-day BP values (clinical method), respectively. The constituent ratios of isolated systolic, isolated diastolic, and systolic-diastolic hypertension were evaluated. RESULTS: When using the old criteria, the overall epidemiological prevalence of hypertension was 41.1% and the overall clinical prevalence of hypertension was 34.8%. When using the new criteria, these values increased to 64.3 and 57.4%, respectively. Meanwhile, against the old criteria, the new criteria increased the constituent ratio of systolic-diastolic hypertension from 24.4 to 50.5% (P<0.001) for the epidemiological method and from 19.1 to 45.7% (P<0.001) for the clinical method in the newly diagnosed hypertensive patients. CONCLUSION: The hypertension criteria of at least 130/80 mmHg not only significantly increased the clinical prevalence of hypertension, but significantly altered the constituent ratio of three hypertension phenotypes among the newly diagnosed hypertensive patients.

Prediction of new superhard boron-rich compounds.

Boron solids exhibit a fascinating geometric and electronic structure. The properties of alpha-rhombohedral boron can be significantly changed by the addition of other atomic constituents. It is found that Pauling's bond valence principle plays an important role in designing boron-rich semiconductors. We have designed the novel boron-rich phases B12N2X (X = Zn, Cd, Be) with the boron carbide type structure by combining Pauling's bond valence principle with first-principles techniques. Their energy gaps, bulk moduli, microhardnesses, and total energies have been calculated. The results show that they are new superhard materials and potential semiconductors. It has been elucidated why B12N2 is metallic but B12N2Be is a semiconductor. This should open up new potential areas for predicting novel boron-rich compounds for industrial applications.