Distribution and persistence of temporary wetland habitats in arid Australia in relation to climate

The distribution and area of temporary wetlands across the arid zone of Australia are highly variable. Any change in their distribution or extent due to climate change and/or extraction of water has the potential to adversely impact dependent biota. Satellite imagery was used to determine the spatial and temporal distribution of wetlands across arid Australia over an 11‐year period. Synoptic climate data were examined to identify the weather systems that caused wetland filling events. Simple threshold models relating rainfall to wetland filling for seven large regions of Australia were developed to examine patterns of wetland filling over the last 100 years. These data were used to examine the climatic processes that drive wetland filling and the likely impacts of climate change on wetland distribution. The strongest climatic influence on wetland filling in the arid zone was tropical weather systems. Their influence extended into southern regions and their effects were often widespread. Variation in wetland area in all regions of the arid zone was high. The Lake Eyre Basin experienced more large flood events than other regions and had the most large, persistent wetlands that remain unregulated by humans. Hindcasting of past filling events indicated that there was a general pattern of frequent wetland filling across inland Australia in the 1910s, 1950s and 1970s, and less frequent wetland filling in the late 1920s, 1930s and 1960s. Furthermore, there appeared to be no period greater than 12 months over the previous 95 years when there was no predicted wetland filling in the arid zone. Wetland ecosystems dependent on a few infrequent heavy rainfalls are clearly vulnerable to any change in frequency or magnitude of these events. Climate change that results in a drying or reduced frequency of large flood events, exacerbated by extraction of water for agriculture, could be catastrophic for some biota, particularly waterbirds, which use a mosaic of wetland habitat at broad spatial scales.     

青藏高原植被生长季NDVI时空变化与影响因素

青藏高原是中国乃至亚洲的生态屏障,研究其植被对气候变化的响应对区域生态保护具有重要的现实意义.基于MOD09A1数据反演的生长季归一化植被指数(NDVI),分析2001-2018年青藏高原植被生长季NDVI时空特征和变化趋势,结合气象站点数据阐释NDVI与气候因子的关系.结果 表明:研究期间,青藏高原植被生长季NDVI...     

The implication of irrigation in climate change impact assessment: a European‐wide study

This study evaluates the impacts of projected climate change on irrigation requirements and yields of six crops (winter wheat, winter barley, rapeseed, grain maize, potato, and sugar beet) in Europe. Furthermore, the uncertainty deriving from consideration of irrigation, CO₂ effects on crop growth and transpiration, and different climate change scenarios in climate change impact assessments is quantified. Net irrigation requirement (NIR) and yields of the six crops were simulated for a baseline (1982–2006) and three SRES scenarios (B1, B2 and A1B, 2040–2064) under rainfed and irrigated conditions, using a process‐based crop model, SIMPLACE . We found that projected climate change decreased NIR of the three winter crops in northern Europe (up to 81 mm), but increased NIR of all the six crops in the Mediterranean regions (up to 182 mm yr^?1). Climate change increased yields of the three winter crops and sugar beet in middle and northern regions (up to 36%), but decreased their yields in Mediterranean countries (up to 81%). Consideration of CO₂ effects can alter the direction of change in NIR for irrigated crops in the south and of yields for C3 crops in central and northern Europe. Constraining the model to rainfed conditions for spring crops led to a negative bias in simulating climate change impacts on yields (up to 44%), which was proportional to the irrigation ratio of the simulation unit. Impacts on NIR and yields were generally consistent across the three SRES scenarios for the majority of regions in Europe. We conclude that due to the magnitude of irrigation and CO₂ effects, they should both be considered in the simulation of climate change impacts on crop production and water availability, particularly for crops and regions with a high proportion of irrigated crop area.     

干旱半干旱区生态系统凝结水的影响因素及其作用研究进展

凝结水是干旱半干旱生态系统重要的水分补给来源,对于维持生态系统功能具有重要意义。综述了干旱半干旱生态系统气象条件、地形环境和植被属性等因素对凝结水形成的影响,以及气候和环境变化对凝结水产量的影响机制。在此基础上,进一步从植被生长、生物土壤结皮、小型动物、微生物和地表水热平衡过程等方面,探讨了凝结水产量变化对干旱半干旱生态系统组成和过程的重要作用。最后对未来相关研究提出以下建议：（1）增加长时间序列的凝结水观测数据分析,（2）系统探讨凝结水对干旱半干旱区生态系统功能的综合影响,并（3）完善气候变化背景下凝结水与生态系统关系的相关研究。本文旨在对该领域的未来研究提出综述、建议和展望。     

气候变化背景下松嫩平原玉米灌溉需水量估算及预测

开展农作物需水规律研究对于干旱半干旱区域旱作物节水灌溉和水分管理实践具有重要意义。以松嫩平原玉米为研究对象,研究玉米生育期需水量规律及灌溉需水量。结果表明:(1)历史时期和未来气候变化情景下,松嫩平原玉米全生育期和L~(mid)时段灌溉需水量等值线沿西南—东北方向递减,其中全生育期和L~(mid)时段2000s灌溉需水量临界等势线(灌溉需水量为0的等势线)分别比1970s北移70.2km和53.4km,全生育期和L~(mid)时段2040s灌溉需水量临界等势线分别比2010s北移30.9km和55.2km。(2)历史时期和气候变化情景下玉米全生育期灌溉需水量随年代呈波动增加趋势,其中前者以29.1mm/(10a)速度增加,后者以17.5mm/(10a)速度增加。(3)未来温度和降雨量变化对玉米需水量的贡献率为波动上升趋势,与1970s相比,2000s温度和降雨量变化对玉米需水量的贡献率为22.1%,增加6.8亿m~3灌溉水量;2040s温度和降雨量变化对玉米需水量的贡献率为38.3%,增加12.6亿m~3灌溉水量。     

干旱地区斑块状植被格局形成的水分驱动机制及其研究进展

斑块状分布是植被在水分匮乏环境中长期适应的结果,其演替过程可以作为生态系统响应气候变化和人类活动产生突变的"指示器"。本文通过对斑块状植被的起源、生态水文过程及其对干旱区植被恢复的启示等方面进行综述,提出了我国干旱区植被恢复中目前尚存在的主要问题。认为斑块状植被的形成可能受气候变化、人类活动、植物自身的生物学特性及其对环境胁迫的适应等方面的影响,但不是主要因素,植被斑块和裸地斑块之间在不同空间尺度的水分再分配是其在干旱半干旱地区形成并且能够维持稳定的关键。斑块状植被是一个高效的雨水集流系统,裸地斑块是整个系统径流的"源",而植被斑块是整个系统径流的"汇",保护植被斑块的同时维持一定面积的裸地对于整个生态系统的稳定都具有极其重要的意义。斑块状植被也是一个非常脆弱的生态系统,气候的剧烈波动以及人类的过度活动都可能导致生态系统功能丧失,最终产生不可逆转的影响,因此需要加以严格保护。     

Using species distribution models to select species resistant to climate change for ecological restoration of bowé in West Africa

Bowalization is a particular form of land degradation and leads to lateral expansion of ferricrete horizons. The process occurs only in tropical regions. In this study, the most adapted and resistant species towards climate change were identified on bowé. The 15 most common bowé species of the subhumid and semi‐arid climate zones of Benin were submitted together with significant environmental variables (elevation, current bioclimatic variables, soil types) to three ecological niche modelling programmes (Maxent, Domain and GARP). For future prediction (2050), IPCC4/CIAT and IPCC5/CMIP5 climate data were applied. Asparagus africanus, Andropogon pseudapricus and Combretum nigricans were identified as the most resistant species for ecological restoration of bowé in the semi‐arid climate zone and Asparagus africanus, Detarium microcarpum and Lannea microcarpa in the subhumid climate zone. The ‘Pull’ strategies were identified as appropriate for ecological restoration of bowé in Benin.     

近10年来蒙古高原植被覆盖变化对气候的响应

基于东亚干旱半干旱地区内蒙古和蒙古国67个气象站的观测资料和SPOTVEGETATION归一化植被指数(NDVI)数据,借助线性趋势、MK趋势性检验、最大化合成法和相关分析等常用数理统计方法,研究了内蒙古和蒙古国地区的植被覆盖变化和气候变化及其响应关系。结果表明:①近49年内蒙古和蒙古国地区年均气温显著上升,降水变化不明显。年均气温在空间上呈现出南高北低的空间分布格局,降水量表现出由西向东递增趋势。②空间分布上,内蒙的植被覆盖状况好于蒙古国。时间变化上,该地区植被覆盖变化分为2个阶段,1998—2001年NDVI呈整体退化趋势,2002—2012年波动上升,其中2009—2012年连续3a上升。空间变化上,内蒙古境内植被退化的区域主要集中在锡林郭勒盟周边地区,蒙古国境内退化的区域分布在中西部地区。③蒙古国境内荒漠和草原植被NDVI与降水呈正相关关系,与气温呈负相关。而对于内蒙古而言荒漠和草原植被的NDVI也与降水呈正相关关系,森林植被与气温呈正相关。就政策层面:内蒙古区域近年来受国家重大生态政策退耕还林、退牧还草的影响,大部分东部和西部植被恢复较快。在今后如果增强两国的文化和政策交流学习,将会对未来的游牧民族文化的保留和发展提供契机。     

Two new fossil woods from the early Miocene of Kutch,Gujarat, India and their significance

The Kutch region of western India (Gujarat State) is today arid to semiarid and characterised by mostly ephemeral streams which carry water during the monsoon. The uneven distribution of rainfall and disturbed topography are the result of climate change during the Cenozoic period. Two fossil woods, namely Bauhinium palaeomalabaricum Prakash and Prasad (Fabaceae) and Ebenoxylon indicum Ghosh and Kazmi (Ebenaceae), are described from Kutch in order to provide insights into the palaeovegetation and palaeoclimate. Because the modern representatives of the present and previously described taxa from the same horizon are thermophilic in nature and grow in evergreen to deciduous forests, a warm and humid climate is interpreted. Furthermore, the finding of some mangrove taxa in the assemblage indicates the lagoonal to intertidal environment at the time of deposition.     

Combining field experiments and predictive models to assess potential for increased plant diversity to climate‐proof intensive agriculture

Agricultural production systems face increasing threats from more frequent and extreme weather fluctuations associated with global climate change. While there is mounting evidence that increased plant community diversity can reduce the variability of ecosystem functions (such as primary productivity) in the face of environmental fluctuation, there has been little work testing whether this is true for intensively managed agricultural systems. Using statistical modeling techniques to fit environment–productivity relationships offers an efficient means of leveraging hard‐won experimental data to compare the potential variability of different mixtures across a wide range of environmental contexts. We used data from two multiyear field experiments to fit climate–soil–productivity models for two pasture mixtures under intensive grazing—one composed of two drought‐sensitive species (standard), and an eight‐species mixture including several drought‐resistant species (complex). We then used these models to undertake a scoping study estimating the mean and coefficient of variation (CV) of annual productivity for long‐term climate data covering all New Zealand on soils with low, medium, or high water‐holding capacity. Our results suggest that the complex mixture is likely to have consistently lower CV in productivity, irrespective of soil type or climate regime. Predicted differences in mean annual productivity between mixtures were strongly influenced by soil type and were closely linked to mean annual soil water availability across all soil types. Differences in the CV of productivity were only strongly related to interannual variance in water availability for the lowest water‐holding capacity soil. Our results show that there is considerable scope for mixtures including drought‐tolerant species to enhance certainty in intensive pastoral systems. This provides justification for investing resources in a large‐scale distributed experiment involving many sites under different environmental contexts to confirm these findings.     

The influence of climate on patterns of termite eating in Australian mammals and lizards

Abstract The present paper examines patterns of termite eating in Australian mammals and lizards (total numbers of species, volume percentage of diet) relative to climate (arid, semi-arid, temperate-mesic). Most termite eaters in arid and semi-arid Australia are lizards. Termite consumptio as a proportion of total lizard diet decreases from arid to mesic climates. More mammal species are relatively termite specialized (>50%) in arid than in semi-arid and mesic regions. Termite consumption in echidnas resembles that of the lizards: relatively high in the arid and relatively low in the mesic zone. For the Dasyuridae, termites comprise only a minor fraction (< 10%) in their diet, irrespective of climate. It is argued that the climatic peculiarities of inland Australia (scant and variable rainfall) cause marked seasonality in termite availability, supporting specialized termite eaters in only the most energy-frugal forms (lizards, echidnas). Areas of future research are identified.     

植被变化对气候的反馈机制及调节效应

植被通过光合作用固定大气中的CO₂来减缓温室效应，同时植被也通过改变地表能量收支影响温室效应。在过去的气候-植被研究中，大多关注气候变化对植被的影响，而植被对气候反馈的研究相对较少。植被通过调节地表能量收支、水通量等重要地气过程影响局地、区域乃至全球气候，在气候变化中的作用十分重要。因此，需要厘清植被对气候的反馈效应机制及其结果，并识别其地域差异。从生物地球物理和生物地球化学过程两方面分析植被与气候之间的作用机制，对全球及关键区域内植被变化对局地、区域乃至全球的气候反馈效应进行了系统总结：（1）生物地球物理反馈的区域特征明显，生物地球化学反馈则表现在全球尺度上，二者相互作用但难以统一；（2）植被破坏带来的气候影响在气温效应方面与生态系统的类型及地理分布相关：热带森林破坏带来增温效应，北方森林破坏带来降温效应，温带森林破坏则会通过增加森林反照率抵消丢失的固碳降温效应，气温效应表现不明显；（3）当前研究对关键过程机制考虑不够完善，不同研究方法的结果差异较大，且缺乏高质量观测数据的验证；同时考虑生物地球物理和生物地球化学的净气候反馈研究尚无法支撑植树造林对气候变化单一减缓作用的常规理解。本文可为科学评估植树造林对气候变化作用的方向与强度提供理论依据。     

AVHRR NDVI与气候因子的相关分析

对中国１６０个气象站１０ａ的连续ＡＶＨＲＲ ＮＤＶＩ数据、气象观测数据进行相关分析,并结合植被覆盖类型资料深入探讨了ＡＶＨＲＲ ＮＤＶＩ／气温和ＡＶＨＲＲ ＮＤＶＩ／降水相关系数的地区差异及其随植被类型变化规律。研究结果表明,对中国的大部分地区,气温对植被的影响超过降水。就自然植被而言,其对降水的敏感性趋势为草本植被大于灌木植被,灌木植被大于乔木植被。就农作物而言,降水影响取决于耕作制度、作物种类     

植被气候关系与我国的植被分区

气候制约着植被的地理分布,植被是区域气候特征的反映和指示,两者之间存在密不可分的联系.揭示植被与气候之间的关系是正确认识植被分布的前提,是进行植被区划的理论基础.植被区划是植被研究的归纳和总结,是其他自然地理区划和农林业区划的基础.本文在简要回顾中国植被气候关系及植被分区的研究历史的基础上,对我国以往的主要植被分区原则、依据和方案进行了评述,对有争议的主要植被界线进行了讨论.我们认为,在当今我国大部分地区的原生植被已遭到破坏的现实情况下,根据原生植被及其衍生植被类型的分布,确定其分布与限制性气候因子的关系,以此来进行植被带(区)的划分,不仅反映植被气候间密不可分的关系,在实践上也便于操作.尽管在一些植被带的命名、具体界线的划定上有分歧,但最近的中国植被分区方案大都认为我国基本的植被区有8至9个,即针叶林、针阔叶混交林、落叶阔叶林、常绿落叶阔叶混交林、常绿阔叶林以及雨林季雨林、草原、荒漠以及高寒植被.通过分析主要植被带附近的植被、气候等特征,本文认为,1)秦岭淮河线是一条重要的水分气候带,而不是温度带,不是亚热带植被的北界;2)我国亚热带植被的北界基本上沿长江北岸,从杭州湾经太湖、安徽宣城、铜陵经大别山南坡到武汉往西,与WI值130-140 ℃·月一致;3)我国热带区域的面积极小,仅分布在海南岛的东南部和台湾南端及其以南地区; 4) 我国东部地区暖温带的水热条件南北差异甚大,建议以秦岭淮河为界,将暖温带划分为两个植被带,即落叶阔叶疏林带和落叶常绿阔叶混交林带;华北地区的地带性植被为落叶阔叶疏林.最后,本文还强调了对应于气候变化进行动态植被分区的重要性.     

Precipitation impacts on vegetation spring phenology on the Tibetan Plateau

The ongoing changes in vegetation spring phenology in temperate/cold regions are widely attributed to temperature. However, in arid/semiarid ecosystems, the correlation between spring temperature and phenology is much less clear. We test the hypothesis that precipitation plays an important role in the temperature dependency of phenology in arid/semiarid regions. We therefore investigated the influence of preseason precipitation on satellite‐derived estimates of starting date of vegetation growing season (SOS) across the Tibetan Plateau (TP). We observed two clear patterns linking precipitation to SOS. First, SOS is more sensitive to interannual variations in preseason precipitation in more arid than in wetter areas. Spatially, an increase in long‐term averaged preseason precipitation of 10 mm corresponds to a decrease in the precipitation sensitivity of SOS by about 0.01 day mm^?1. Second, SOS is more sensitive to variations in preseason temperature in wetter than in dryer areas of the plateau. A spatial increase in precipitation of 10 mm corresponds to an increase in temperature sensitivity of SOS of 0.25 day °C^?1 (0.25 day SOS advance per 1 °C temperature increase). Those two patterns indicate both direct and indirect impacts of precipitation on SOS on TP. This study suggests a balance between maximizing benefit from the limiting climatic resource and minimizing the risk imposed by other factors. In wetter areas, the lower risk of drought allows greater temperature sensitivity of SOS to maximize the thermal benefit, which is further supported by the weaker interannual partial correlation between growing degree days and preseason precipitation. In more arid areas, maximizing the benefit of water requires greater sensitivity of SOS to precipitation, with reduced sensitivity to temperature. This study highlights the impacts of precipitation on SOS in a large cold and arid/semiarid region and suggests that influences of water should be included in SOS module of terrestrial ecosystem models for drylands.     

干旱,半干旱地区作物育种的困惑与出路

粮食问题主要取决于一年生谷类作物产量。作物产量低而不稳的原因主要是病虫害及各种胁迫生境,其中干旱缺水为最大的产量限制因素,提高作物生产力的途径有二：其一是改善作物的生长环境,其二是通过育种手段选育在各肿胁迫环境中具有优良表现的基因型（品种）。矮秆化育种手段使水肥充裕区小麦产量有显著的提高,是通过提高收获指数获得的。干旱、半干旱地区育种却未能获得显著效果,要提高干旱、半干旱地区小麦育种的成效,对干旱     

Optimality principles explaining divergent responses of alpine vegetation to environmental change

Recent increases in vegetation greenness over much of the world reflect increasing CO₂ globally and warming in cold areas. However, the strength of the response to both CO₂ and warming in those areas appears to be declining for unclear reasons, contributing to large uncertainties in predicting how vegetation will respond to future global changes. Here, we investigated the changes of satellite-observed peak season absorbed photosynthetically active radiation (F_max) on the Tibetan Plateau between 1982 and 2016. Although climate trends are similar across the Plateau, we identified robust divergent responses (a greening of 0.31 ± 0.14% year⁻¹ in drier regions and a browning of 0.12 ± 0.08% year⁻¹ in wetter regions). Using an eco-evolutionary optimality (EEO) concept of plant acclimation/adaptation, we propose a parsimonious modelling framework that quantitatively explains these changes in terms of water and energy limitations. Our model captured the variations in F_max with a correlation coefficient (r) of .76 and a root mean squared error of .12 and predicted the divergent trends of greening (0.32 ± 0.19% year⁻¹) and browning (0.07 ± 0.06% year⁻¹). We also predicted the observed reduced sensitivities of F_max to precipitation and temperature. The model allows us to explain these changes: Enhanced growing season cumulative radiation has opposite effects on water use and energy uptake. Increased precipitation has an overwhelmingly positive effect in drier regions, whereas warming reduces F_max in wetter regions by increasing the cost of building and maintaining leaf area. Rising CO₂ stimulates vegetation growth by enhancing water-use efficiency, but its effect on photosynthesis saturates. The large decrease in the sensitivity of vegetation to climate reflects a shift from water to energy limitation. Our study demonstrates the potential of EEO approaches to reveal the mechanisms underlying recent trends in vegetation greenness and provides further insight into the response of alpine ecosystems to ongoing climate change.     

气候变化背景下中国农业气候资源变化Ⅶ.青藏高原干旱半干旱区农业气候资源变化特征

基于青藏高原干旱半干旱区1961-2007年55个气象站点地面观测资料,利用五日滑动平均法及GIS软件的IDW模块进行栅格处理,对比分析了研究区1961-1980年（时段Ⅰ）和1981-2007年（时段Ⅱ）各气候要素的时空变化特征及其气候倾向率.结果表明：1961-2007年,研究区喜凉作物生长季内日照时数的变化不明显,喜温作物生长季内日照时数呈增加趋势,但空间分布的变化较小;与时段Ⅰ相比,时段Ⅱ喜温作物生长季内积温值≥1500 ℃·d的地区面积扩大33.9%;降水量的空间分布总体表现为由东南低地向西北内陆逐渐递减,研究期间青藏高原东南部喜凉作物生长季内降水量均达到800 mm,其他地区喜凉作物生长季内降水量的气候倾向率有正有负,变幅相对较小,与时段Ⅰ相比,时段Ⅱ喜温作物生长季内降水量≥400 mm的分布面积扩大了40%;参考作物蒸散量（ET₀）总体略有增加,其空间分布格局与日照时数和积温的分布相似,时段Ⅱ较时段Ⅰ喜温作物生长季内ET₀≥400 mm的分布面积扩大了35.7%.研究期间,青藏高原作物生长季内的热量与降水资源有一定幅度增加,这对农牧业生产非常有利,但ET₀的增大表明潜在蒸发增大,需进一步加强研究气候变化对该区域农牧业生产带来的可能影响.     

气候变化背景下中国农业气候资源变化Ⅸ.中国农业气候资源时空变化特征

利用中国558个气象台站1961-2007年地面气象观测资料,分析了不同区域农业气候资源变化的差异,并分析和比较了1961-1980年(时段Ⅰ)和1981-2007年(时段Ⅱ)的农业气候资源变化特征.结果表明： 与时段Ⅰ相比,时段Ⅱ中国年均气温增加了0.6 ℃,喜凉作物生长期内≥0 ℃积温和喜温作物生长期内≥10 ℃积温分别平均增加123.3和125.9℃·d;1961-2007年,年均气温增幅最大的区域是东北地区,喜温作物生长期内≥10 ℃积温增幅最大的是华南地区.对全国而言,与时段Ⅰ相比,时段Ⅱ在全年、喜凉和喜温作物生长期内日照时数分别减少了125.7、32.2和53.6 h;1961-2007年,长江中下游地区年日照时数的减幅最多,喜凉和喜温作物生长期内日照时数减少量最大的地区分别是华北和华南地区;在全年、喜凉和喜温作物生长期内,中国的降水量和参考作物蒸散量总体均表现为减少趋势,其中,华北地区在全年、喜凉和喜温作物生长期内降水量的减幅均最大,长江中下游地区参考作物蒸散量在全年和喜温作物生长期内的减幅最大,西北地区参考作物蒸散量在喜凉作物生长期内的减幅最大.研究期间,中国气候在全年和喜温作物生长期内总体表现为暖干趋势,其中,喜温作物生长期内西南、华北和东北地区为暖干趋势,长江中下游、西北和华南地区为暖湿趋势,喜凉作物生长期内华北地区为暖干趋势,西北地区为暖湿趋势.     

农作物需水量随气候变化的响应研究

利用甘肃省近80个气象站1961~2000年的常规气象观测资料以及夏秋主要粮食作物平均生育期资料,采用FAO推荐的Penm an-M on te ith公式结合作物系数,计算了各站夏秋主要粮食作物的需水量,分析作物需水量随时间和空间的变化特点以及对气候变化的响应.结果表明:农作物需水量与种植区的气候类型关系十分密切,从干旱-半干旱-半湿润-湿润地区其需水量呈现减小的趋势,越是干旱的地区作物需水量越大,越是湿润的地区作物需水量越小.作物需水量随气候变化的响应比较明显,在干旱、半干旱地区表现尤为突出.不同作物品种需水量相差较大,对气候的响应机制也有差异,一般来说夏粮的需水量小于秋粮,夏粮需水量对气候变化的响应比秋粮敏感.