挠力河流域水土资源平衡及耕地合理利用规模特征

水土资源平衡是耕地合理开发与利用的前提,为定量评估粮食主产区水土资源平衡关系,促进耕地可持续利用,该研究提出“以水定地”的耕地配置模式,并以三江平原腹地的挠力河流域为研究区,在多源水土信息数据支持下,依据农田土壤水分平衡原理构建水土资源平衡模型,以评估水土资源平衡态势,进而揭示该流域耕地合理利用规模特征。结果表明:1)2000年以来,挠力河流域水田持续扩张,旱地轻度萎缩,至2018年其水田化系数已达37.33%,垦殖率为62.61%。旱地和水田的水分胁迫蒸散能力处于同一水平,但水田的水分亏缺量显著高于旱地;2)当前,挠力河流域的灌溉供水量范围为21.23~211.91 mm,富锦市、友谊县和集贤县处于水资源超载状态,且水田均呈“土多水少”状态,饶河县、宝清县、七台河市和双鸭山市辖区则“土少水多”;3)依据“以水定地”耕地配置模式,该流域水田面积可增加11.02万hm2,对应的水田化系数控制在44.76%以下。富锦市、友谊县和集贤县应适度控制或减小水田利用规模,宝清县应成为未来“旱改水”的重点备选区。研究结果对挠力河流域乃至三江平原的耕地有序开发及保障农业可持续发展具有重要现实意义。     

基于MCR模型的城镇生态安全格局构建和建设用地开发模式

近年来,在中国城市土地开发的顶层设计中越发强调生态空间的重要性,充分识别城市生态安全格局并探讨建设用地空间扩展格局成为划定生态保护红线、确定城市开发边界和"三规合一"空间管制等政策实施的迫切需求。该文以唐山市为例,基于"生态过程—格局"理论和GIS的空间相关性分析、距离分析和叠加分析等方法,从综合水安全、地质灾害预警、生物生境保护、水土保持、游憩安全5个方面,整合构建了底线安全格局、缓冲安全格局和最优安全格局3种不同等级的综合生态安全格局。该文在MCR模型算法引入不同等级"源"的权重系数,以综合生态安全格局为阻力因子,并结合城镇中心的吸引力、主要道路的吸引力和政策调控(区域开发重点)等城镇用地扩展影响因素,得到在不同约束条件下的区域空间扩展阻力面,分别确定了唐山市在"生态安全约束型""经济增长主导型"和"生态与经济并重"3种模式下城镇空间可能的发展范围,经过多方案比较,"生态与经济并重"城镇建设用地空间发展模式是未来城镇健康有序发展的最优模式,这种发展模式既有利于减少大规模、高强度的城镇化和工业化过程所造成的城市发展和环境保护之间的用地冲突,也可为城市用地布局规划和生态红线划定提供科学依据。     

黄河三角洲不同土地利用方式对土壤的改良效应

通过对黄河三角洲地区棉田、果园、林地和荒地4种不同土地利用方式下土壤样品的采集与理化指标的分析,研究了该区域不同土地利用方式对轻度盐渍化土壤的改良功能。结果显示:果园土壤的容重、pH值和全盐含量等物理性状要优于其它3种用地方式;棉田土壤有机质与全N、全P和全K含量超过果园与林地土壤,而速效N和速效P含量以果园土壤最高,速效K含量以棉田最高,果园土壤最低;果园土壤C/N比值明显高于其它3种用地方式,以荒地土壤的C/N比值最低。综合分析认为:种植果树对土壤的物理性状改良效果较好,种植棉花对土壤的化学性状具有较好的改良效果。     

Land-use history has a stronger impact on soil microbial community composition than aboveground vegetation and soil properties

The response of soil microbial communities following changes in land-use is governed by multiple factors. The objectives of this study were to investigate (i) whether soil microbial communities track the changes in aboveground vegetation during succession; and (ii) whether microbial communities return to their native state over time. Two successional gradients with different vegetation were studied at the W. K. Kellogg Biological Station, Michigan. The first gradient comprised a conventionally tilled cropland (CT), mid-succession forest (SF) abandoned from cultivation prior to 1951, and native deciduous forest (DF). The second gradient comprised the CT cropland, early-succession grassland (ES) restored in 1989, and long-term mowed grassland (MG). With succession, the total microbial PLFAs and soil microbial biomass C consistently increased in both gradients. While bacterial rRNA gene diversity remained unchanged, the abundance and composition of many bacterial phyla changed significantly. Moreover, microbial communities in the relatively pristine DF and MG soils were very similar despite major differences in soil properties and vegetation. After >50 years of succession, and despite different vegetation, microbial communities in SF were more similar to those in mature DF than in CT. In contrast, even after 17 years of succession, microbial communities in ES were more similar to CT than endpoint MG despite very different vegetation between CT and ES. This result suggested a lasting impact of cultivation history on the soil microbial community. With conversion of deciduous to conifer forest (CF), there was a significant change in multiple soil properties that correlated with changes in microbial biomass, rRNA gene diversity and community composition. In conclusion, history of land-use was a stronger determinant of the composition of microbial communities than vegetation and soil properties. Further, microbial communities in disturbed soils apparently return to their native state with time.     

六盘山北侧华北落叶松林分的水分利用效率研究

为定量研究华北落叶松人工林水分利用特征,2010年5-10月在宁夏六盘山北侧叠叠沟林场的华北落叶松人工林固定样地内,通过测定树干径向生长、林分叶面积指数变化、草本生物量变化、树干液流速率变化、植物降雨截持等,估计了华北落叶松人工林及各层的生产力、水分消耗和水分利用效率。研究表明：林分总生产力11.76t/hm2,其中乔木层占75.2%,草本层占24.8%;在整个生长期内,林分生产力各月的分量呈现先升高后降低的季节变化格局。林分总蒸散量为433.9mm,其中乔木层与草本层（包括土壤蒸发）耗水各约占一半,分别为总蒸散的50.5%和49.5%;林分蒸散在生长季中呈现先升高后降低的季节变化格局。在整个生长季,华北落叶松人工林的水分利用效率为2.71g/kg,其中乔木层的水分利用效率为4.04g/kg,草本层水分利用效率为1.36g/kg;其季节变化与乔木层的水分利用效率变化相类似,说明乔木层对于华北落叶松林分水分利用效率的影响较大。     

基于信息熵与空间洛伦兹曲线的土地利用空间结构分析——以重庆市合川区为例

结合重庆市合川区2009年土地利用数据,运用信息熵、均匀度、优势度及空间洛伦茨兹曲线等方法,对其土地利用现状、存在问题及土地利用结构进行了分析,研究了合川区30个街镇土地利用空间布局,这对于引导合川区土地利用结构的合理化与土地利用的可持续发展具有重要的意义。结果表明:（1）合川区土地利用结构信息熵在空间上差异性明显,总体上可以分为信息熵高值区、信息熵中值区和信息熵低值区,三者的土地利用结构均衡程度逐步降低;（2）合川耕地与其他用地的分布较为均衡,园地、林地和牧草地的分布则相对集中;（3）合川区30个街镇具有各自的土地利用特色,充分利用区域资源优势,发展特色产业,进而优化土地利用结构。     

密度、氮肥互作对小麦产量及氮素利用效率的影响

为了探明小麦产量和氮素利用效率同步提高的最佳施氮量和种植密度,制定合理的栽培措施,实现高产高效提供理论依据,以大穗型品种泰农18（T18）和中穗型品种山农15（S15）为试材,在大田条件下设置4个播种密度（60、75、90和105 kg/hm2）和3个施氮水平（0、180和240 kg/hm2）,研究了氮密互作对小麦子粒产量和氮素利用效率的影响。结果表明,播种密度和施氮量均显著影响冬小麦产量及构成因素,且两者间存在明显的互作效应;两因素中密度是导致产量变化的主导因素。子粒产量提高引起氮肥农学利用效率和氮肥吸收利用率的协同提高。综合考虑产量和氮素利用效率等因素,在本试验条件下,泰农18的适宜播量为102 kg/hm2,适宜的施氮量为180 kg/hm2;而山农15的适宜播量为83 kg/hm2,适宜的施氮量为180 kg/hm2。说明在冬小麦高产栽培过程中,可以通过调节施氮量和播种密度,充分利用氮密互作效应,在提高氮素利用率的同时,获得较高的子粒产量。     

Seasonal variation in canopy reflectance and its application to determine the water status and water use by citrus trees in the Western Cape, South Africa

This study describes the diurnal and seasonal dynamics of the canopy reflectance, water use and water status of Midknight Valencia citrus trees under semi-arid conditions. Hyperspectral canopy reflectance data was collected on 30 trees at monthly intervals over a period of 16 months in a commercial orchard in South Africa. The mean canopy reflectance in the wavelength range 350-2500 nm followed a clear seasonal trend influenced by environmental conditions and tree phenology. Mean monthly reflectance peaked in summer (∼22%) while the lowest value (∼15%) was reached in winter with the seasonal changes in the sun's position accounting for a significant proportion of the variations. A sensitivity analysis of a Penman-Monteith transpiration model showed that water use by individual trees changed by up to 13% when the canopy reflectance was varied over the seasonal range of measured values. This suggested that the seasonal changes in tree water use influenced the seasonal trend of the canopy reflectance. Thus monitoring the canopy reflectance of citrus trees could offer information on the tree water status. To test this, sap flow data of water uptake and loss by the trees were compared with the canopy spectra. Sap flow data showed a heavy reliance by the citrus trees on the internally stored water with up to 25% of the daily total transpiration withdrawn from the trees’ internal water storage pools when soil water was limited. This depletion of internally stored water, and hence the change in tree water status, was detected using spectral indices based on the first order derivatives of the canopy reflectance centered at two and, at most, four spectral bands. We conclude that even if citrus trees are evergreen, their canopy reflectance changes significantly throughout the year with a considerable impact on tree energy balance and water use. In addition, the contribution of the internally stored water to daily transpiration is a possible indicator of drought stress for citrus trees detectable from changes in canopy reflectance and it has potential applications in irrigation scheduling using canopy level spectral information.     

土地利用变化对漓江流域生态服务价值影响

应用Costanza的生态服务价值计算方法,参照中国陆地生态系统单位服务价值系数,分析了土地利用变化对漓江流域生态系统服务功能的影响.漓江流域生态系统服务价值在1991-2006年间减少了14.906 2×10~8元,年平均减少0.993 8×10~8元.生态服务价值系数较高的林地、耕地和水域等转化为生态服务价值系数较低的建设用地和园地,是流域生态服务价值受损的主要原因.流域生态系统9类单项服务价值均呈现下降趋势.尤其是土壤形成与保护、水源涵养、气体调节、生物多样性保护和气候调节等服务价值的损失较大.马尔可夫链模型的预测结果表明:如果保持1991-2006年的土地利用变化趋势,漓江流域生态系统服务价值在未来将呈现不断下降的趋势.敏感性分析表明,生态系统服务价值对价值系数缺乏弹性,研究结果可信.     

哈尔滨市耕地利用效益特征分析

提高耕地利用效益是缓解粮食供应压力的有效手段。以黑龙江省粮食主产区哈尔滨市为例,从经济效益、社会效益及生态效益3个方面构建耕地利用效益评价指标体系,以哈尔滨市1997-2006年的数据为基础,运用熵值法确定各指标权重,并通过建立协调度模型,定量评价出1997-2006年哈尔滨市耕地利用效益系统协调度。结果表明:1997-2006年哈尔滨市耕地利用系统协调度处于波动状态,耕地综合利用效益并不稳定,但总体呈上升趋势。耕地利用经济效益和社会效益协调度变化不大,综合效益与生态效益的协调度曲线走势趋同,表明哈尔滨市耕地利用综合效益主要受生态效益的影响。最后从根本上提出有效措施实现哈尔滨市耕地利用效益的提高。