增温与降水变化对青藏高原高寒草甸土壤nirS反硝化菌群落丰度和群落结构的影响

全球变化已成为国际研究热点。青藏高原属典型生态脆弱带,该地区升温幅度更加明显,已导致大量冰川融化和明显降水变化,进而使该地区水循环和土壤水分发生巨大变化。温度和降水的变化可能会引起土壤微生物丰度和群落结构的改变,进而影响生物地球化学循环。但青藏高原地区土壤微生物群落结构和功能对全球变化响应的研究较少。研究了模拟增温和降水变化对青藏高原高寒草甸土壤nirS反硝化菌群落丰度和群落结构的影响。研究表明,增温1、2、4℃对nirS基因丰度影响不显著;增加降水100%时,增温4℃处理显著增加nirS基因丰度(P0.05)。在未升温与升温2℃背景下增加和减少降水对nirS基因丰度的影响不显著。增温和增减降水均显著影响nirS反硝化菌群落结构,且两个因子具有一定的交互作用。CCA结果显示,增温和降水的共同解释变量中,增温对nirS反硝化菌群落结构变化的影响达极显著(P0.01),解释了其中的54.2%,降水变化解释了45.5%(P0.05)。     

Temporal and spatial variation characteristics of China shrubland net primary production and its response to climate change from 2001 to 2013

Aims Net primary production (NPP) is the input to terrestrial ecosystem carbon pool. Climate and land use change affect NPP significantly. Shrublands occupy more than 20% of the terrestrial area of China, and their NPP is comparable to those of the forests. Our objective was to estimate China shrubland NPP from 2001 to 2013, and to analyze its variation and response to climate change.Methods We used a Carnegie-Ames-Stanford Approach (CASA) model to estimate the NPP of six shrubland types in China from 2001 to 2013. Furthermore, we used Theil-Sen slope combined with Mann-kendall test to analyze its spatial variation and a linear regression of one-variable model to analyze its inter- and intra-annual variation. Finally, a multi-factor linear regression model was used to analyze its response to climate change.Important findings We found the annual mean NPP of China shrubland was 281.82 g•m^-2•a^-1. The subtropical evergreen shrubland has the maximum NPP of 420.47 g•m^-2•a^-1, while the high cold desert shrubland has the minimum NPP of 52.65 g•m^-2•a^-1. The countrywide shrublands NPP increased at the rate of 1.23 g•m^-2•a^-1, the relative change rate was 5.99%. The temperate deciduous shrubland NPP increased the fastest with a speed of 3.05 g•m^-2•a^-1 and subalpine evergreen shrubland had a decreasing trend with a speed of -0.73 g•m^-2•a^-1. Moreover, the other four shrublands NPP had a growing trend, only subalpine deciduous shrubland NPP did not change significantly. The response of NPP to climate change of different seasons varies to different shrubland types. In general, the NPP variation was mainly affected by precipitation, and the spring warming also contributed to it. The increase of countrywide shrubland NPP may promote its contribution to the regional ecosystem function.     

New imidazoquinoxaline derivatives: Synthesis,biological evaluation on melanoma,effect on tubulin polymerization and structure–activity relationships

Microtubules are considered as important targets of anticancer therapy. EAPB0503 and its structural imidazo[1,2-a]quinoxaline derivatives are major microtubule-interfering agents with potent anticancer activity. In this study, the synthesis of several new derivatives of EAPB0503 is described, and the anticancer efficacy of 13 novel derivatives on A375 human melanoma cell line is reported. All new compounds show significant antiproliferative activity with IC₅₀ in the range of 0.077–122 μM against human melanoma cell line (A375). Direct inhibition of tubulin polymerization assay in vitro is also assessed. Results show that compounds 6b, 6e, 6g, and EAPB0503 highly inhibit tubulin polymerization with percentages of inhibition of 99%, 98%, 90%, and 84% respectively. Structure–activity relationship studies within the series are also discussed in line with molecular docking studies into the colchicine-binding site of tubulin.     

Effects of climate variability on the demography of wild geladas

Nonhuman primates are an essential part of tropical biodiversity and play key roles in many ecosystem functions, processes, and services. However, the impact of climate variability on nonhuman primates, whether anthropogenic or otherwise, remains poorly understood. In this study, we utilized age‐structured matrix population models to assess the population viability and demographic variability of a population of geladas (Theropithecus gelada) in the Simien Mountains, Ethiopia with the aim of revealing any underlying climatic influences. Using data from 2008 to 2019 we calculated annual, time‐averaged, and stochastic population growth rates (λ) and investigated relationships between vital rate variability and monthly cumulative rainfall and mean temperature. Our results showed that under the prevailing environmental conditions, the population will increase (λ _s = 1.021). Significant effects from rainfall and/or temperature variability were widely detected across vital rates; only the first year of infant survival and the individual years of juvenile survival were definitively unaffected. Generally, the higher temperature in the hot‐dry season led to lower survival and higher fecundity, while higher rainfall in the hot‐dry season led to increased survival and fecundity. Overall, these results provide evidence of greater effects of climate variability across a wider range of vital rates than those found in previous primate demography studies. This highlights that although primates have often shown substantial resilience to the direct effects of climate change, their vulnerability may vary with habitat type and across populations.     

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies.     

Projected climate impacts to South African maize and wheat production in 2055: a comparison of empirical and mechanistic modeling approaches

Crop model‐specific biases are a key uncertainty affecting our understanding of climate change impacts to agriculture. There is increasing research focus on intermodel variation, but comparisons between mechanistic (MMs) and empirical models (EMs) are rare despite both being used widely in this field. We combined MMs and EMs to project future (2055) changes in the potential distribution (suitability) and productivity of maize and spring wheat in South Africa under 18 downscaled climate scenarios (9 models run under 2 emissions scenarios). EMs projected larger yield losses or smaller gains than MMs. The EMs’ median‐projected maize and wheat yield changes were ?3.6% and 6.2%, respectively, compared to 6.5% and 15.2% for the MM. The EM projected a 10% reduction in the potential maize growing area, where the MM projected a 9% gain. Both models showed increases in the potential spring wheat production region (EM = 48%, MM = 20%), but these results were more equivocal because both models (particularly the EM) substantially overestimated the extent of current suitability. The substantial water‐use efficiency gains simulated by the MMs under elevated CO₂ accounted for much of the EM?MM difference, but EMs may have more accurately represented crop temperature sensitivities. Our results align with earlier studies showing that EMs may show larger climate change losses than MMs. Crop forecasting efforts should expand to include EM?MM comparisons to provide a fuller picture of crop–climate response uncertainties.     

Climate‐driven speedup of alpine treeline forest growth in the Tianshan Mountains,Northwestern China

Forest growth is sensitive to interannual climatic change in the alpine treeline ecotone (ATE). Whether the alpine treeline ecotone shares a similar pattern of forest growth with lower elevational closed forest belt (CFB) under changing climate remains unclear. Here, we reported an unprecedented acceleration of Picea schrenkiana forest growth since 1960s in the ATE of Tianshan Mountains, northwestern China by a stand‐total sampling along six altitudinal transects with three plots in each transect: one from the ATE between the treeline and the forest line, and the other two from the CFB. All the sampled P. schrenkiana forest patches show a higher growth speed after 1960 and, comparatively, forest growth in the CFB has sped up much slower than that in the ATE. The speedup of forest growth at the ATE is mainly accounted for by climate factors, with increasing temperature suggested to be the primary driver. Stronger water deficit as well as more competition within the CFB might have restricted forest growth there more than that within the ATE, implying biotic factors were also significant for the accelerated forest growth in the ATE, which should be excluded from simulations and predictions of warming‐induced treeline dynamics.     

Factors controlling the stable isotope composition and C:N ratio of seston and periphyton in shallow lake mesocosms with contrasting nutrient loadings and temperatures

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