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【PNAS 等】利用植物蒸腾作用改善干旱预测 等
发布时间:2016-09-05  来源:土壤与农业可持续发展国家重点实验室  浏览:392

谢树成 等。微生物与地质温压的一些特效地质作用。中国科学-地球科学,2016,46(8):1087-1094

Abstract

微 生物不仅能够灵敏地响应地质环境的变化, 而且还可以通过多种途径参与各类地质地球化学作用过程. 微生物通过元素的生物地球化学循环对各类地质环境起作用, 这早已为人们所熟悉. 微生物还可以在地表环境诱导形成一些深部高温高压环境才能形成的矿物. 一些微生物功能群能够在地表常温常压环境实现蒙皂石的伊利石化, 形成长石类自生矿物, 沉淀白云石, 产生地质脂类等地质过程, 这些过程在没有生物参与时需要一定的温压条件才能发生. 微生物之所以具有这些特殊的地质作用, 是因为它们拥有活性酶、具有比较大的比表面积及表面丰富的官能团. 微生物可以通过这些具有催化能力的活性酶的作用, 并通过代谢作用和生理过程等, 降低一些热力学反应的吉布斯自由能, 克服一些化学反应的动力学障碍. 微生物还因具有较大的比表面积及表面丰富的官能团而能够通过物理吸附降低矿物晶核表面的自由能. 微生物通过这些生物化学过程和生物物理过程达到与一定温压条件类似的化学过程和物理过程, 从而使一些深部地质过程在地表常温常压环境得以实现. 由此提出了微生物与一些地质温压具有等效地质作用的新思想.


【利用植物蒸腾作用改善干旱预测】Abigail L.S. Swann et al. Plant responses to increasing CO2 reduce estimates of climate impacts on drought severity. PNAS, 2016, doi: 10.1073/pnas.1604581113

Abstract

Rising atmospheric CO2 will make Earth warmer, and many studies have inferred that this warming will cause droughts to become more widespread and severe. However, rising atmospheric CO2 also modifies stomatal conductance and plant water use, processes that are often are overlooked in impact analysis. We find that plant physiological responses to CO2 reduce predictions of future drought stress, and that this reduction is captured by using plant-centric rather than atmosphere-centric metrics from Earth system models (ESMs). The atmosphere-centric Palmer Drought Severity Index predicts future increases in drought stress for more than 70% of global land area. This area drops to 37% with the use of precipitation minus evapotranspiration (P-E), a measure that represents the water flux available to downstream ecosystems and humans. The two metrics yield consistent estimates of increasing stress in regions where precipitation decreases are more robust (southern North America, northeastern South America, and southern Europe). The metrics produce diverging estimates elsewhere, with P-E predicting decreasing stress across temperate Asia and central Africa. The differing sensitivity of drought metrics to radiative and physiological aspects of increasing CO2 partly explains the divergent estimates of future drought reported in recent studies. Further, use of ESM output in offline models may double-count plant feedbacks on relative humidity and other surface variables, leading to overestimates of future stress. The use of drought metrics that account for the response of plant transpiration to changing CO2, including direct use of P-E and soil moisture from ESMs, is needed to reduce uncertainties in future assessment.

    一项研究提出,在大气二氧化碳(CO2)不断升高的情况下植物水流失的减少,这样的结果可能会带来比目前指标预测值更小的未来干旱压力。植物开放叶片气 孔,吸收二氧化碳,但是这个过程导致水同时流失到了大气中。科研人员假定大气二氧化碳水平的增加可能减少与碳摄取有关的植物水流失,这可能使土壤湿度增 加,而且减少干旱。为了预测未来蒸腾作用的变化如何可能改变干旱压力,Abigail Swann及其同事比较了来自没有纳入二氧化碳对蒸腾作用影响的帕尔默干旱指数的干旱压力预测与考虑了二氧化碳强迫的蒸腾作用变化的干旱指数。帕尔默干旱 指数预测了未来干旱压力将很可能在全球超过70%的陆地面积上增加,但是对于考虑到二氧化碳强迫的蒸腾作用变化的干旱指数来说,这个值下降到了37%。这 些指标都表明了干旱压力很可能在北美南部、南美东北部和南欧增加,这些地区的降水量不断减少。然而,考虑到二氧化碳强迫的蒸腾作用变化的指数提示,干旱压 力很可能在温带的亚洲和中非地区减少。这组作者说,考虑到植物对大气二氧化碳生理响应的干旱指数可能减少干旱估计的不确定性,并且改善对农业、水资源和野 火风险的预测。(来源:EurekAlert!)


【陆地生态系统生物质周转】Karl-Heinz Erb et al. Biomass turnover time in terrestrial ecosystems halved by land use. Nature Geoscience 9, 674–678 (2016)

Abstract

The terrestrial carbon cycle is not well quantified1. Biomass turnover time is a crucial parameter in the global carbon cycle2, 3, 4, and contributes to the feedback between the terrestrial carbon cycle and climate2, 3, 4, 5, 6, 7. Biomass turnover time varies substantially in time and space, but its determinants are not well known8, 9, making predictions of future global carbon cycle dynamics uncertain5, 10, 11, 12, 13. Land use—the sum of activities that aim at enhancing terrestrial ecosystem services14—alters plant growth15 and reduces biomass stocks16, and is hence expected to affect biomass turnover. Here we explore land-use-induced alterations of biomass turnover at the global scale by comparing the biomass turnover of the actual vegetation with that of a hypothetical vegetation state with no land use under current climate conditions. We find that, in the global average, biomass turnover is 1.9 times faster with land use. This acceleration affects all biomes roughly equally, but with large differences between land-use types. Land conversion, for example from forests to agricultural fields, is responsible for 59% of the acceleration; the use of forests and natural grazing land accounts for 26% and 15% respectively. Reductions in biomass stocks are partly compensated by reductions in net primary productivity. We conclude that land use significantly and systematically affects the fundamental trade-off between carbon turnover and carbon stocks.


【河流网络的环境DNA传输】Kristy Deiner et al. Environmental DNA reveals that rivers are conveyer belts of biodiversity information. Nature Communications, 7, 12544.

Abstract

DNA sampled from the environment (eDNA) is a useful way to uncover biodiversity patterns. By combining a conceptual model and empirical data, we test whether eDNA transported in river networks can be used as an integrative way to assess eukaryotic biodiversity for broad spatial scales and across the land–water interface. Using an eDNA metabarcode approach, we detect 296 families of eukaryotes, spanning 19 phyla across the catchment of a river. We show for a subset of these families that eDNA samples overcome spatial autocorrelation biases associated with the classical community assessments by integrating biodiversity information over space. In addition, we demonstrate that many terrestrial species are detected; thus suggesting eDNA in river water also incorporates biodiversity information across terrestrial and aquatic biomes. Environmental DNA transported in river networks offers a novel and spatially integrated way to assess the total biodiversity for whole landscapes and will transform biodiversity data acquisition in ecology.

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