A continent under stress: interactions, feedbacks and risks associated with impact of modified land cover on Australia's climate

Global climate change is the major and most urgent global environmental issue. Australia is already experiencing climate change as evidenced by higher temperatures and more frequent and severe droughts. These impacts are compounded by increasing land use pressures on natural resources and native ecosystems. This paper provides a synthesis of the interactions, feedbacks and risks of natural climate variability, climate change and land use/land cover change (LUCC) impacting on the Australian continent and how they vary regionally. We review evidence of climate change and underlying processes resulting from interactions between global warming caused by increased concentration of atmospheric greenhouse gases and modification of the land surface. The consequences of ignoring the effect of LUCC on current and future droughts in Australia could have catastrophic consequences for the nation's environment, economy and communities. We highlight the need for more integrated, long-term and adaptive policies and regional natural resource management strategies that restore the beneficial feedbacks between native vegetation cover and local-regional climate, to help ameliorate the impact of global warming.     

气候变化背景下全球陆地干湿变化研究综述

气候变化背景下,全球水循环加剧,出现了大气变干与植被变绿等陆地干湿变化趋势的解耦现象,旱区面积变化也存在争议。为回答上述问题,在梳理常见干湿指标变化趋势与驱动因素的基础上,根据指标变化方向对其进行归类,然后从机理角度解析影响不同指标趋势耦合或解耦的关键要素,并提出未来干湿变化研究展望。结果表明,气候变化背景下,饱和水汽压差、干燥度指数和土壤水分指标显著变干,植被绿度和生产力显著变湿(增加),降水、径流、陆地水储量和其他复合指标区域分异明显、但整体趋势不显著。二氧化碳浓度增加、气温升高和土地利用变化是导致不同指标趋势分异的重要因素,不同指标的趋势分异也解释了旱区面积评估在不同维度上的差异。未来研究中应开展干湿变化的综合评估,其综合性主要体现在以下四个方面：1)关注大气-生态-水文多维度评估;2)解析自然与人类双重压力下,不同维度要素间的关联、互馈过程,及其对系统干湿演变的促进、限制与调节作用;3)重视干湿演变程中的极端灾害事件和空间上以旱区为代表的气候变化敏感性区域;4)构建以脆弱性评估与适应性治理为核心的气候变化应对路径。     

The living heart: Climate gradients predict desert mountain endemism

Mountain regions are centers of biodiversity endemism at a global scale but the role of arid‐zone mountain ranges in shaping biodiversity patterns is poorly understood. Focusing on three guilds of taxa from a desert upland refugium in Australia, we sought to determine: (a) the relative extent to which climate, terrain or geological substrate predict endemism, and (b) whether patterns of endemism are complimentary across broad taxonomic guilds. We mapped regional endemism for plants, land snails, and vertebrates using combined Species Distribution Models (SDMs) for all endemic taxa (n = 82). We then modelled predictors of endemism using Generalised Additive Models (GAMs) and geology, terrain, and climate variables. We tested for the presence of inter‐ and intraguild hotspots of endemism. Many individual plant and land snail taxa were tightly linked with geology, corresponding to small distributions. Conversely, most vertebrate taxa were not constrained to specific geological substrates and occurred over larger areas. However, across all three guilds climate was the strongest predictor of regional endemism, particularly for plants wherein discrete hotspots of endemism were buffered from extreme summer temperatures. Land snail and vertebrate endemism peaked in areas with highest precipitation in the driest times of the year. Hotspots of endemism within each guild poorly predicted endemism in other guilds. We found an overarching signal that climatic gradients play a dominant role in the persistence of endemic taxa in an arid‐zone mountain range system. An association with higher rainfall and cooler temperatures indicates that continuing trends toward hotter and drier climates may lead to range contractions in this, and potentially other, arid‐zone mountain biotas. Contrasting patterns of endemism across guilds highlight the need to couple comprehensive regional planning for the protection of climate refugia, with targeted management of more localized and habitat specialist taxa.     

新疆焉耆盆地人类活动与气候变化的效应机制

通过对新疆焉耆盆地及其周边近40a(1973—2014)的气候变化趋势检测、LUCC和生物量估算,探讨气候变化和人类活动的生态效应机制,研究区域陆地生态系统演变及其归因。分析结果表明:(1)焉耆盆地山区和平原区降水变化都有明显的突变点,并呈现增加趋势,蒸发量在山区减少,在平原区波动性减少趋势;(2)LUCC分析表明,山区裸地面积减少5.40%,冰川面积减少3.36%,高地植被面积增加8.76%;同时平原区天然绿洲面积增加1.96%,沙漠面积减少1.62%,水域面积减少1.30%,人工绿洲面积增加15.41%,湿地面积增加1.27%;(3)山区陆地生态系统对区域气候变化非常敏感,其中降水变化是决定山区地表植被生存状态和分布的重要因素;(4)人类活动的推动作用和有益气候变化的支撑是绿洲平原区生态系统好转的原因,其中人口急剧增加和社会经济快速发展,导致绿洲平原区生态系统结构及其时空分布的主要因素。焉耆盆地及其周围区域陆地生态系统的演变对气候变化和人类活动有明显的时空尺度效应,其反应程度各不相同。     

土地利用变化对土壤有机碳的影响研究进展

土壤有机碳是陆地碳库的重要组成部分,也是当前全球碳循环和全球变化研究的热点。土地利用/覆被变化及土地管理变化通过影响土壤有机碳的储量和分布,进而影响温室气体排放和陆地生态系统的碳通量。研究土地利用变化影响下的土壤有机碳储量及其动态变化规律,有助于加深理解全球气候变化与土地利用变化之间的关系。在阅读国内外有关文献的基础上,分别从土地利用及其管理方式变化的角度,概括了土地利用变化对土壤有机碳的影响过程与机理;针对当前研究的两大类方法,即实验方法和模型方法,分类详细介绍了它们各自的特点以及存在的一些问题。在此基础上,提出今后土地利用变化对土壤有机碳影响研究的发展趋势。     

Impacts of land cover changes on climate trends in Jiangxi province China

Land-use/land-cover (LULC) change is an important climatic force, and is also affected by climate change. In the present study, we aimed to assess the regional scale impact of LULC on climate change using Jiangxi Province, China, as a case study. To obtain reliable climate trends, we applied the standard normal homogeneity test (SNHT) to surface air temperature and precipitation data for the period 1951–1999. We also compared the temperature trends computed from Global Historical Climatology Network (GHCN) datasets and from our analysis. To examine the regional impacts of land surface types on surface air temperature and precipitation change integrating regional topography, we used the observation minus reanalysis (OMR) method. Precipitation series were found to be homogeneous. Comparison of GHCN and our analysis on adjusted temperatures indicated that the resulting climate trends varied slightly from dataset to dataset. OMR trends associated with surface vegetation types revealed a strong surface warming response to land barrenness and weak warming response to land greenness. A total of 81.1 % of the surface warming over vegetation index areas (0–0.2) was attributed to surface vegetation type change and regional topography. The contribution of surface vegetation type change decreases as land cover greenness increases. The OMR precipitation trend has a weak dependence on surface vegetation type change. We suggest that LULC integrating regional topography should be considered as a force in regional climate modeling.     

Is the future female for turtles? Climate change and wetland configuration predict sex ratios of a freshwater species

Climate change and land-use change are leading drivers of biodiversity decline, affecting demographic parameters that are important for population persistence. For example, scientists have speculated for decades that climate change may skew adult sex ratios in taxa that express temperature-dependent sex determination (TSD), but limited evidence exists that this phenomenon is occurring in natural settings. For species that are vulnerable to anthropogenic land-use practices, differential mortality among sexes may also skew sex ratios. We sampled the spotted turtle (Clemmys guttata), a freshwater species with TSD, across a large portion of its geographic range (Florida to Maine), to assess the environmental factors influencing adult sex ratios. We present evidence that suggests recent climate change has potentially skewed the adult sex ratio of spotted turtles, with samples following a pattern of increased proportions of females concomitant with warming trends, but only within the warmer areas sampled. At intermediate temperatures, there was no relationship with climate, while in the cooler areas we found the opposite pattern, with samples becoming more male biased with increasing temperatures. These patterns might be explained in part by variation in relative adaptive capacity via phenotypic plasticity in nest site selection. Our findings also suggest that spotted turtles have a context-dependent and multi-scale relationship with land use. We observed a negative relationship between male proportion and the amount of crop cover (within 300 m) when wetlands were less spatially aggregated. However, when wetlands were aggregated, sex ratios remained consistent. This pattern may reflect sex-specific patterns in movement that render males more vulnerable to mortality from agricultural machinery and other threats. Our findings highlight the complexity of species' responses to both climate change and land use, and emphasize the role that landscape structure can play in shaping wildlife population demographics.     

中国遥感干旱指数时空特征及其对气候和地表覆盖变化的响应

干旱严重影响植被生长,威胁粮食安全,基于遥感计算的植被状态指数（Vegetation Condition Index,VCI）、温度状态指数（Temperature Condition Index,TCI）和植被健康指数（Vegetation Health Index,VHI）是常用的干旱指数,被广泛应用于干旱监测。为了探究近年来我国干旱特征及其对气候和地表覆盖变化的响应,分析了2003-2016年期间VCI、TCI和VHI的时空变化特征;采用最小二乘（OLS）和偏相关分析方法分析了这些指数对气候和地表覆盖变化的响应。基于上述干旱指数计算的干旱频率表明,中温带中部和南温带等地区干旱发生频率高,干旱指数变化趋势表明在2003-2016年期间中国大部分地区干旱缓解,但在中温带、南温带和高原气候区等局部地区干旱加剧;总体而言,干旱指数随着年平均温度的上升和年降水量的降低而减小,VHI与温度和降水量的相关性在不同气候区的一致性优于VCI和TCI;裸土的减少和植被的增加导致干旱指数增大,树木转变为低矮植被干旱指数降低。     

Varying responses in mean surface air temperature from land use/cover change in different seasons over northern China

Research on the impacts of land use change on climate change has become a foremost topic in the field of global climate change research. Although many researchers have studied the impacts of LUCC, data related to these impacts on the Chinese climate system remain sparse because of the diversity of China’s regional changes in land use, especially related to agricultural changes. Therefore, additional studies are needed that address regional LUCC in combination with climate modeling. Two simulations with current land use/cover patterns and potential natural vegetation cover were used to investigate the impact of LUCC on surface air temperature in northern China. Simulations of 11 years of climate in northern China (1 January 1990–31 December 2000) were carried out using Regional Environment Integrated Modeling System 2.0 (RIEMS2.0). The results showed that: (1) When potential natural vegetation cover types were changed to current vegetation cover types, mean summer surface air temperature decreased in the central northeastern area, eastern Gansu Province and Ningxia Hui Autonomous Region, but increased in Shanxi, Henan and Anhui provinces. Also, surface air temperature changed significantly on a local scale in the central northeastern area, central Henan Province and eastern Gansu Province (P < 0.05). In winter, major portions of the study area exhibited non-significant decreases in mean surface air temperature. (2) In summer, a temperate forests removal simulation in northern China behaved more like a tropical forests removal simulation. In winter, removal of the temperate forests in northern China behaved more like a boreal forests removal simulation. In model grids where forest were converted to cropland, the net radiation absorbed has less influence on surface air temperature at lower vs. higher latitudes. Further, latent heat flux has a stronger influence on surface air temperature at lower latitudes.     

Possible impacts of climate change on natural vegetation in Saxony (Germany)

Recent climate changes have had distinct impacts on plant development in many parts of the world. Higher air temperatures, mainly since the end of the 1980s, have led to advanced timing of phenological phases and consequently to an extension of the general growing season. For this reason it is interesting to know how plants will respond to future climate change. In this study simple phenological models have been developed to estimate the impact of climate change on the natural vegetation in Saxony. The estimations are based on a regional climate scenario for the state of Saxony. The results indicate that changes in the timing of phenophases could continue in the future. Due to distinct temperature changes in winter and in summer, mainly the spring and summer phases will be advanced. Spring phenophases, such as leafing or flowering, show the strongest trends. Depending on the species, the average timing of these phenophases could be advanced by 3–27 days by 2050. Phenophases in autumn show relatively small changes. Thus, the annual growth period of individual trees will be further extended, mainly because of the shift of spring phases. Frequent droughts in summer and in autumn can compensate for the earlier leafing of trees, because in this case leaf colouring and leaf fall would start some weeks earlier. In such cases, the growing period would not be really extended, but shifted to the beginning of the year.