灌溉供水可靠度的经济设计

灌溉供水可靠度是评价灌溉设计与管理的重要指标,但现行的灌溉保证率指标由于不能反映灌溉供水的时间效应和程度效应,评价结果与实际相差较大。对此本文引入作物水分生产函数,通过反演对时段赋权和对缺水分级,提出了一种改进的灌溉供水可靠度评价方法。该方法能将灌溉供水的可靠度与其产量水平挂钩,具有明确的经济意义,且简单实用,对灌溉管理有一定的借鉴作用。     

设施农业雨水集蓄利用与番茄灌溉方案优化

为充分利用雨水资源,提高设施农业灌溉用水效率,该研究对雨水蓄水池容积和大棚番茄灌溉方案进行了优化.以天津市武清区一设施农业小区为研究区,根据2020年6个场次降雨,对蓄水池集雨情况进行分析,基于AquaCrop模型优化大棚番茄灌溉方案,最终设置3种集雨灌溉情景,采用水量平衡法,分别绘制不同情景的丰、平、枯水年雨水集蓄系...     

Available organic nitrogen in temperate, subtropical, and tropical soils extracted with different solutions

Extraction of organic N by chemical solutions has been used to assess the amount of available N in soil. We tested the efficiency of several solutions in extracting organic N from tropical, subtropical and temperate soils. A conventional 0.067 M phosphate buffer successfully extracted organic N from all 23 soils examined. High-performance size exclusion chromatograms showed a single peak at about 7,800 Da for all phosphate buffer extracts irrespective of soil types. The peak area correlated with the organic N concentration of extracts. Tropical soils had lower retention of organic N than other soils according to the conventional and sequential extraction with phosphate buffer. Organic N extracted with sulfuric acid was significantly (P < 0.001) correlated with the amount of extracted Fe, suggesting that Fe might play a role in the retention of organic N in soil.     

中国1999－2009年土地覆盖动态变化的时空特点

基于SPOT NDVI时间序列研究中国近10 a来（1999－2009年）土地覆盖动态变化的时空特点。首先,对BISE模型进行改进并对数据进行预处理;其次,结合光谱角分类和最小距离分类算法各自的优势构建了一个新的分类算法（SAM-MDM）,并对多年NDVI数据分类和后处理,提高了分类精度,能满足土地覆盖变化趋势分析要求;再次,应用土地覆盖动态度模型和GIS叠加方法分析了全国土地覆盖的时空变化,建立了土地覆盖类型转移概率矩阵;最后,应用马尔科夫（Markov）过程建立了类型转移演化模型,对未来20 a土地覆盖动态变化过程进行了预测。通过该研究探讨了中国土地覆盖近10 a来在时间上的动态变化特点、空间上的变化差异、土地覆盖类型的转移概率分布和未来10～20 a的时空变化趋势。     

基于BCC_CPSv2模式的淮河流域月参考作物蒸散概率订正预报

参考作物蒸散（Reference Crop Evapotranspiration,ET0）预报在农业水资源配置、区域干湿演变评估方面有着重要作用。该研究基于国家气候中心第二代气候预测系统（Beijing Climate Center Second-Generation Climate Prediction System,BCC_CPSv2）模式预报数据和1991－2020年淮河流域地面气象观测数据,利用分位数映射法对模式预报的气象要素进行概率订正,采用Penman-Monteith公式计算ET0,并评估了订正前后BCC_CPSv2模式对淮河流域月ET0和气象要素的预报性能。结果表明：1）模式对平均气温、净辐射和相对湿度的预报值较观测值偏小,风速预报值在3－6月偏小,其他月份偏大,4个气象要素预报的均方根误差（Root Mean Square Error,RMSE）分别为1.84 ℃、1.70 MJ/m2d、15.79%和1.39 m/s;气象要素预报偏差导致2－6月ET0预报值较计算值偏小,1月和7－12月偏大,区域平均RMSE为0.59 mm/d,绝对百分比误差（Mean Absolute Percentage Error,MAPE）为21.9%。2）概率订正有效降低了气象要素和ET0的预报误差。气温、净辐射、相对湿度和风速预报订正值的RMSE均小于订正前;80%月份ET0预报订正值的RMSE小于订正前,区域平均RMSE减小了0.23 mm/d,MAPE减小了11.2%。3）夏半年和冬半年ET0预报误差的首要来源分别是净辐射和相对湿度,主要是由于模式对这2个要素的预报精度较低且ET0对其敏感,误差容易传递。可见,基于模式概率订正的月尺度ET0预报方法精度较高,可以为水资源优化管理、灌溉制度制定和农业中长期需水决策提供参考。     

Potential causes of population declines in forest fragments in an Amazonian frog

Forest fragmentation results in population declines and extinctions for many forest vertebrates, but little is known about the mechanisms causing declines in fragments. We investigated potential causes of declines in forest fragments for an Amazonian forest frog (Colostethus stepheni) at an experimental fragmentation study site in central Amazonian Brazil using field estimates of abundance and vital rates coupled with population simulations. Although adult male survival was not reduced by fragmentation, mean clutch size was reduced by 17%. Population simulations demonstrate that a reduction in clutch size of this magnitude is sufficient to cause the observed magnitude of population declines in fragments. Female snout-vent length was also reduced in fragments and may be related to the observed reduction in clutch size.     

Where to put things? Spatial land management to sustain biodiversity and economic returns

Expanding human population and economic growth have led to large-scale conversion of natural habitat to human-dominated landscapes with consequent large-scale declines in biodiversity. Conserving biodiversity, while at the same time meeting expanding human needs, is an issue of utmost importance. In this paper we develop a spatially explicit landscape-level model for analyzing the biological and economic consequences of alternative land-use patterns. The spatially explicit biological model incorporates habitat preferences, area requirements and dispersal ability between habitat patches for terrestrial vertebrate species to predict the likely number of species that will be sustained on the landscape. The spatially explicit economic model incorporates site characteristics and location to predict economic returns for a variety of potential land uses. We apply the model to search for efficient land-use patterns that maximize biodiversity conservation objectives for given levels of economic returns, and vice versa. We apply the model to the Willamette Basin, Oregon, USA. By thinking carefully about the arrangement of activities, we find land-use patterns that sustain high levels of biodiversity and economic returns. Compared to the 1990 land-use pattern, we show that both biodiversity conservation and the value of economic activity could be increased substantially.     

基于 Hazen 概率曲线的合肥大兴地区土壤 Pb 元素背景含量与污染叠加含量区分

基于 Hazen 概率曲线,选取合肥大兴地区,探讨了土壤污染重金属元素 Pb 背景含量与污染叠加含量的区分方法.结果表明:合肥大兴地区 Pb 元素的背景含量为 27.2 μg/g,与安徽省 Pb 元素含量的平均值(26 μg/g)比较接近;Pb 元素污染叠加含量与背景含量的界线点为 36.3 μg/g,与据此含量数值计算得出的地积累污染指数的含义相符合.基于 Hazen 概率曲线区分合肥大兴地区土壤 Pb 元素背景含量与污染叠加含量的方法是有效的,有必要将该方法推广到土壤中其他重金属污染元素以及其他地区作进一步研究.     

雨水花园对实际降雨径流的调控效果研究

基于海绵城市倡导的雨水自然积存、自然渗透、自然净化理念,根据西安地区降雨特征,设计建造了入渗型和防渗型两套雨水花园。2015~2017年对33场次降雨事件径流调控效果进行了监测分析。结果表明:(1)以原状土为填料的防渗型雨水花园设施水量削减率为11.2%~100%(中位数=69.14%);(2)污染物浓度超越概率分析结果显示,径流雨水经过雨水花园系统后,总氮、氨氮、总磷和化学需氧量出流浓度超过地表水环境质量标准Ⅳ类限制的概率,与入流浓度超过地表Ⅳ限制的概率相比,分别降低了58.57%,2.71%,20.57%和29.71%;(3)雨水花园设施场次径流水量削减率与污染物负荷削减率的相关关系在0.857以上;(4)通过监测的场次降雨量及系统进水和出水水质水量,估算的雨水花园系统年径流污染物浓度去除率为11.93%~60.97%,径流污染物年负荷削减率基本在70%以上。     

不同基因型冬小麦Na~+吸收动力学特征及其耐盐性

在水培条件下,以4种不同基因型冬小麦小偃6号、NR9405、陕229和RB6为试验材料,采用浓度梯度法等研究了小麦幼苗的Na+吸收动力学特征及其与耐盐性的关系。结果表明:冬小麦对Na+的吸收可分为两个阶段,盐浓度在NaCl 50～80 mmol L-1以下(低盐)时,4种冬小麦的Na+吸收动力学参数Vmax和Km分别为Na+0.50、0.30、0.58、0.55 mg g-1h-1和Na+18.50、3.89、70.90、30.68 mmol L-1;在NaCl 50～80mmol L-1以上(中、高盐)时,4种冬小麦的Vmax和Km分别为1.81、1.56、2.11、2.11 mg g-1h-1和Na+107.20、70.29、121.06、102.67 mmol L-1。在低盐环境中冬小麦对Na+的排斥率为90%左右,而在高盐环境中对Na+的排斥率只有50%～60%。低盐胁迫下小偃6号和NR9405对Na+的吸收速率较陕229和RB6高50%,Na+的排斥率品种间相差不大;在中、高盐胁迫下陕229和RB6对盐分吸收累积速率较小偃6号和NR9405高15%,而后者对Na+的排斥率较前者高10%。高盐胁迫下高的Na+吸收速率和低的Na+排斥效应可能是陕229和RB6不耐盐的重要原因。