封育对羊草草地土壤碳矿化激发效应和温度敏感性的影响

土壤碳矿化(或土壤异养呼吸)的温度敏感性和激发效应是深入揭示土壤呼吸控制机理及其对未来气候变化响应与适应的重要研究方向。该文以自由放牧(FG0)、封育11年(FG11)、封育31年(FG31)的羊草(Leymus chinensis)草地为研究对象, 通过0、5、10、15、20、25 ℃培养, 探讨了封育对羊草草地土壤碳矿化激发效应和温度敏感性的影响。结果表明: 封育年限、添加葡萄糖、培养温度和培养时间对土壤碳矿化速率均具有显著的影响, 不同因素间存在显著的交互效应(p < 0.000 1)。FG0的羊草草地土壤碳矿化累积量显著高于FG11和FG31的, 在添加葡萄糖处理下也呈现相同的趋势。长期封育降低了羊草草地土壤碳矿化的激发效应。在添加葡萄糖后, 培养前7天的土壤碳矿化的激发效应随温度增加而增加, 增加2.28-9.01倍; 在整个56天培养期间, 激发效应介于2.21-5.10倍, 最高值出现在10或15 ℃。土壤碳矿化速率可用经典的指数方程来表示, FG0草地的土壤碳矿化的温度敏感性指数(Q₁₀)大于长期封育草地(FG11和FG31); 与未添加处理相比, 添加葡萄糖显著增加了土壤碳矿化速率的温度敏感性, 即在添加葡萄糖后土壤微生物呼吸受温度的影响更大。长期封育会降低羊草草地土壤的碳矿化速率、温度敏感性和激发效应, 从而降低土壤碳周转速率和释放速率, 使内蒙古地区长期封育草地仍然具有碳固持能力。     

Is biofuel policy harming biodiversity in Europe?

We assessed the potential impacts of land-use changes resulting from a change in the current biofuel policy on biodiversity in Europe. We evaluated the possible impact of both arable and woody biofuel crops on changes in distribution of 313 species pertaining to different taxonomic groups. Using species-specific information on habitat suitability as well as land use simulations for three different biofuel policy options, we downscaled available species distribution data from the original resolution of 50 to 1 km. The downscaled maps were then applied to analyse potential changes in habitat size and species composition at different spatial levels. Our results indicate that more species might suffer from habitat losses rather than benefit from a doubled biofuel target, while abolishing the biofuel target would mainly have positive effects. However, the possible impacts vary spatially and depend on the biofuel crop choice, with woody crops being less detrimental than arable crops. Our results give an indication for policy and decision makers of what might happen to biodiversity under a changed biofuel policy in the European Union. The presented approach is considered to be innovative as to date no comparable policy impact assessment has been applied to such a large set of key species at the European scale.     

Modeling urban landscape dynamics: A review

Reviewed here is the historical development of urban growth models, showing how different disciplines and diverse theories have come together over time to produce the models used today. This review is divided into two sections, the first section reviews the early models that are rooted in transportation and land-use planning and form the foundation on which nearly all modeling efforts are based. These models are already well documented in the literature and an overview here is sufficient. In the second section, an exploration is made into the theories and approaches that have been integrated into urban modeling efforts. The concepts are outlined and one or more contemporary examples are highlighted. These theories and approaches represent the major areas of development that exist in published work.     

黄土丘陵沟壑区集水区尺度土地利用格局变化的水土流失效应

以陕北杏河集水区1985和1995年两期土地利用数据为基础,结合水文、DEM数据,定性分析了土地利用格局变化条件下的水土流失效应,其中采用双累积曲线法来界定土地利用格局基本没有变化的时间段,用C值在坡度、距河流距离上的分布来表征土地利用格局,用不同时期降雨量／径流量、降雨侵蚀力／输沙率相对增加的比例来表征水土流失效应。研究结果表明：(1)1981～2000年,土地利用格局变化剧烈的年份为1990～1991年,可以用1985、1995年两期数据分别代表20世纪80年代和90年代的土地利用;(2)从20世纪80年代到90年代,杏河集水区的C值有明显的增加趋势,在较陡坡度和距河流距离较近处,C值增加的幅度相对较大;(3)土地利用格局变化明显改变了降雨量-径流量、降雨侵蚀力-输沙率的关系,出现了从20世纪80年代到90年代,虽然降雨量／降雨侵蚀力在整体上呈现明显下降的趋势,但是水土流失量,却表现出同比增加的现象,而且这种增加在不同月份也有差异。用本文中的方法来表征土地利用格局和水土流失效应,其结果具有较好的比配性,可以用来定性分析土地利用格局与水土流失的关系。但是,由于水土流失效应的表征方法没有考虑降雨的空间变异特征,该方法尚不适于雨量站点比较密集、降雨空间变异较大的区域。此外,在进一步的研究中,还需要注意遥感数据解译的准确性、C值精度、土地条件的变化等问题。     

Effects of Land-Use Change on Carbon Stocks in Switzerland

We assessed how consequences of future land-use change may affect size and spatial shifts of C stocks under three potential trends in policy—(a) business-as-usual: continuation of land-use trends observed during the past 15 years; (b) extensification: full extensification of open-land; and (c) liberalization: full reforestation potential. The build-up times for the three scenarios are estimated at 30, 80 and 100 years, respectively. Potential C-stock change rates are derived from the literature. Whereas the business-as-usual scenario would cause marginal changes of 0.5%, liberalization would provoke a 13% increase in C stocks (+62 MtC). Gains of 24% would be expected for forests (+95 MtC), whereas open-land C stock would decrease 27% (−33 MtC). Extensification would lead to a C stock decrease of 3% (−12 MtC). Whereas forest C is expected to increase 12% (+36.5 MtC) at high elevations, stocks of open-land C would decline 38.5% (−48.5 MtC). Most affected are unfavorable grasslands, which increase in area (+59%) but contribute only 14.5% to the C stocks. C sinks would amount to 0.6 MtC y⁻¹ assuming a build-up time of 100 years for the liberalization scenario. C stocks on the current forest area are increasing by 1 MtC y⁻¹. The maximal total C sink of 1.6 MtC might thus suffice to compensate for agricultural greenhouse gases (2004: 1.4 Mt CO₂–C equivalents), but corresponds only to 11–13% of the anthropogenic greenhouse gas emission in Switzerland. Thus, even the largest of the expected terrestrial C stocks under liberalization will be small in comparison with current emissions of anthropogenic greenhouse gases.     

Geographical range size of tropical plants influences their response to anthropogenic activities

Biodiversity patterns may be influenced by the species geographical range sizes, but this is rarely shown. We used a highly replicated and large-scale study in coastal Ecuador to determine for the first time the importance of latitudinal range size of plant species in their response to land-use activities. We examined herbaceous plant communities of five land-use types with decreasing anthropogenic disturbance (from the most intervened rice and pasture to the less intervened managed agroforest, abandoned agroforest, and forest) in a low and a high impact human-dominated landscape. All species were classified in four latitudinal range size quartiles, from the 25% species with the narrowest to the 25% with the widest range size. We found notable differences between patterns of total species richness and those of individual range size quartiles. Whereas total species richness was higher in more intervened land-use types, percentages of narrow-ranged species were significantly higher in less intervened land-use types. In contrast, percentages of wide-ranging species were higher in more intervened land-use types. Hence, responses of plant species to human activities were influenced by traits that determine their range sizes. An analysis of floristic similarity between land-use types revealed that narrow-ranged species were mainly preserved in forest fragments, but the other land-use types supported many unique narrow-ranged species and therefore made an important contribution to their preservation at the landscape level. Conservation efforts should combine protection of natural habitats with strategies to maintain a diversity of low-intensity land-use types, looking for win-win solutions or trade-offs between biodiversity conservation and human welfare in human-dominated landscapes.     

土地利用变化对三峡库区重庆段植被净初级生产力的影响

研究土地利用变化对区域植被净初级生产力(Net Primary Productivity,NPP)的影响对于明确区域植被固碳能力与土地利用变化的关系,以及维持生态系统结构稳定具有重要意义。以三峡库区重庆段为例,基于2000—2015年MOD17A3数据和土地利用数据,分析研究区NPP时空分布特征并从景观生态学的角度探讨土地利用变化对区域植被NPP的影响。研究表明:(1)NPP年均值16年间波动不大,空间分布上从东到西逐渐减少;(2)研究期内林地面积增加,耕地和草地面积减小,而NPP总量从25.6 TgC增加到了28.5 TgC,其中耕地NPP约占总量的44%,林地次之(40%),草地最少(14%),2000—2005年、2005—2010年、2010—2015年土地利用变化对NPP变化的贡献率分别为26.49%、59.76%、17.27%;(3)区域生态景观指数中的香农多样性指数SHDI、斑块密度PD与NPP呈正相关,而聚合度AI与NPP呈负相关,景观格局类型和景观格局变化均影响区域植被NPP的增长。要提高区域植被NPP,需优化土地利用格局,增加景观异质性和斑块密度,重视培育幼龄林,并控制成熟林的数量。     

Do we need land‐cover data to model species distributions in Europe?

Aim To assess the influence of land cover and climate on species distributions across Europe. To quantify the importance of land cover to describe and predict species distributions after using climate as the main driver. Location The study area is Europe. Methods (1) A multivariate analysis was applied to describe land‐cover distribution across Europe and assess if the land cover is determined by climate at large spatial scales. (2) To evaluate the importance of land cover to predict species distributions, we implemented a spatially explicit iterative procedure to predict species distributions of plants (2603 species), mammals (186 species), breeding birds (440 species), amphibian and reptiles (143 species). First, we ran bioclimatic models using stepwise generalized additive models using bioclimatic variables. Secondly, we carried out a regression of land cover (LC) variables against residuals from the bioclimatic models to select the most relevant LC variables. Finally, we produced mixed models including climatic variables and those LC variables selected as decreasing the residual of bioclimatic models. Then we compared the explanatory and predictive power of the pure bioclimatic against the mixed model. Results (1) At the European coarse resolution, land cover is mainly driven by climate. Two bioclimatic axes representing a gradient of temperature and a gradient of precipitation explained most variation of land‐cover distribution. (2) The inclusion of land cover improved significantly the explanatory power of bioclimatic models and the most relevant variables across groups were those not explained or poorly explained by climate. However, the predictive power of bioclimatic model was not improved by the inclusion of LC variables in the iterative model selection process. Main conclusion Climate is the major driver of both species and land‐cover distributions over Europe. Yet, LC variables that are not explained or weakly associated with climate (inland water, sea or arable land) are interesting to describe particular mammal, bird and tree distributions. However, the addition of LC variables to pure bioclimatic models does not improve their predictive accuracy.