中国西南地区地形起伏度的最佳分析尺度确定

[目的]确定中国西南地区地形起伏度的最佳分析尺度并进行地形分级,明确区域地形结构特点并进行地貌结构划分。[方法]以ASTER GDEMv2数据为基础,通过Python模块编程,利用窗口分析方法提取西南地区各典型地貌以及整个区域n×n(n=2,3,4,…,181,182,183)窗口下的平均地形起伏度,进而采用均值变点分析方法确定最佳统计窗口。[结果](1)西南地区地形起伏度的最佳分析尺度为2.43km^2;(2)区域地形起伏度以中小起伏为主,其中小起伏(200~500m)占38.68%,中起伏(500~1 000m)占23.58%;(3)从空间分布来看,西南地区的地形起伏度呈现中部高,东南部次之,西北部和东北部较低的特征。[结论]以2.43km^2为最佳统计窗口提取的西南地区地形起伏度符合区域地形起伏特征,同时较好地兼顾了各地貌类型的起伏特点。     

陕西省地形起伏度最佳计算单元研究

[目的]确定陕西省地形起伏度最佳计算单元,分析地形起伏度的空间分布规律,为地貌类型划分提供基础数据。[方法]以陕西省90 m×90 m的航天飞机雷达地形测绘使命(SRTM)数字高程模型(DEM)数据为基础,首先利用邻域统计分析法〔矩形邻域选取2×2,3×3,4×4,…,35×35共34个不同大小的邻域窗口,圆形邻域窗口选取20个(邻域半径R为2~21)〕对陕西省地形起伏度进行提取,然后统计不同矩形窗口和圆形窗口下的各种地形起伏度类型所占面积比例,接着运用均值变点分析法计算最佳计算单元,最后完成陕西省地形起伏度分级图的绘制,并对地形起伏度特征进行分析。[结果]不同地形起伏度类型所占面积比例的变化各有不同。按矩形邻域计算的地形起伏度最佳计算单元为12×12,对应面积为898 704m2,按圆形邻域计算的地形起伏度最佳计算单元为R=8,对应面积为1 254 191.4m2,这说明在使用邻域分析法提取地形起伏度时,采用圆形邻域有别于采用矩形邻域。陕西省地形总体较平缓,主要以小起伏、中起伏为主。[结论]简单实用的均值变点分析法,是确定最佳计算单元的一种较为理想的方法。     

基于DEM数据的地貌分类研究——以西秦岭为例

传统的地貌学分类不仅费时费力,而且很难做到全面、准确、系统、定量。而基于DEM数据的地貌分类省时省力,可以做到标准一致、系统统一、定量准确。但是如何利用DEM数据进行地貌类型的划分,还需要进行一些尝试和探索。西秦岭地区地势起伏较大,地貌类型多样,具有典型代表性,以该区进行地貌类型划分的尝试,可以为今后地貌类型的定量、快速、系统划分提供依据和方法。以90 m×90 m的SRTM3-DEM数据为基础,运用均值变点法求得西秦岭地区地势起伏度的最佳统计分析窗口面积为2.34 km2,并结合实际地貌形态,采用高程和地势起伏度2个指标对该地区地貌形态进行了划分,共划分出14种地貌形态,可以大致与传统的地貌类型相对应,但是其系统性、定量化以及效率却比传统方法大大提高,从而为基于DEM的地貌类型的快速定量系统划分提供了经验与方法。     

基于3S技术的地形起伏度与区域土壤侵蚀的相关性研究

地形起伏度直接影响着地面的径流变化,是导致土壤侵蚀的主要根源之一。分析两者相关性的前提是准确提取地形起伏度,而确定研究数据尺度下地形起伏度的最佳分析窗口是得出可靠结果的保障。在3S技术的支持下,运用均值变点法分析罗甸县基于DEM（空间分辨率为30 m×30 m）的最佳分析窗口,并依据2007年修正的土壤侵蚀分类分级标准估算研究区各样本单元的土壤侵蚀量,对两者进行相关性分析。结果表明:罗甸县在该尺度数据源下的最佳分析窗口为32×32,最佳统计面积为0.921 6 km²,实证了均值变点分析方法提取地形最佳分析窗口的可行性;地形起伏度与区域土壤侵蚀模数的相关系数为0.519 1,充分说明了作为宏观地形因子之一的地形起伏度是区域土壤侵蚀的主导因素之一。     

地形起伏度最佳统计单元算法的比较研究

基于90m分辨率SRTM DEM数据,利用邻域分析法在不同大小窗口下(2×2,3×3,4×4,…,30×30)对山西省地形起伏度进行了提取,运用人工作图法、最大高差法、模糊数学法、均值变点分析法和累积和(CUSUM)分析算法分别计算最佳统计单元,对统计单元计算方法的准确性及适用性进行分析,提出山西省地形起伏度提取的最佳统计单元。研究分析表明:均值变点分析法和累积和分析算法是相对比较有效的方法;运用均值变点分析法与累积和分析算法计算所得的最佳统计单元分别为11×11(0.980 1km~2)和14×14(1.587 6km~2);均值变点分析法是计算最佳统计单元的一种最为理想的方法;对于同一地区而言,不同DEM数据类型、不同分辨率DEM,所使用的最佳统计单元大小也不同。     

基于变点分析法提取废弃采石场地形起伏度的方法

地形起伏度是废弃采石场水土保持治理和生态重建的重要地形指标之一。以0.5m,0.7m,1m,1.5m等12种不同水平分辨率DEM为数据源,采用GIS的窗口递增分析法和均值变点分析法对12种不同分辨率DEM的地形起伏度的最佳分析窗口进行了分析。结果表明:12种不同分辨率的最佳分析窗口都是为9×9网格,相应地提取地形起伏度的最佳统计面积与其相应的水平分辨率关系比较密切,呈幂函数的关系。以0.5m水平分辨率的DEM数据提取地形起伏度的最佳分析窗口面积为20.25m~2,并计算出大于5m地形起伏度的区域占总面积的13.12%。均值变点分析法确定地形起伏度也同样适用于废弃采石场的地形分析。     

基于DEM的淮河源地貌形态类型划分

[目的]对淮河源地貌形态类型进行划分研究,为该区土地利用、旅游和城市规划以及生物多样性保护提供参考依据。[方法]以淮河源地区为研究对象,基于分辨率为30m的DEM数据,采用地貌形态划分方案中具有代表性的柴宗新方案、徐汉明方案和高玄彧方案,运用空间分析中的邻域分析、重分类、地图代数以及转换工具等,分别对各方案下的淮河源地貌形态类型进行划分并与实际勘察地形进行对比与分析,探寻适合淮河源地貌基本形态划分的最佳方案。[结果]柴宗新方案要素单一,不能确切反映地貌的基本特征;高玄彧方案中的2级分类对研究区并未发挥其作用,该方案比较适合高程高,地貌形态类型多的地区;徐汉明方案采用相对高度和海拔高度2个条件作为地貌基本形态划分的依据,此方案即兼顾了绝对高度的客观作用,又考虑了人们观察山地的真实感受,因此徐汉明方案比较适合淮河源地貌形态的划分。[结论]根据徐汉明方案将淮河源地区地貌形态划分为平原、丘陵、低山和中低山4种类型,主要以平原和丘陵为主,表现为东低西高,北低南高的地势特征。     

基于DEM的京津冀地区地形起伏度分析

京津冀地区地貌类型复杂,全局单值最佳分析窗口在该地区地形起伏度提取中具有局限性。采集了区内不同地貌、地貌组合样本,采用均值变点法分别提取了各样本地形起伏度的最佳分析窗口,分析了地形地貌对最佳分析窗口的影响,在此基础上提取了京津冀地区的地形起伏度。结果表明:京津冀地区地形起伏度随分析窗口面积的增大而增大,对两者对应关系的拟合效果幂函数优于对数函数;区内因地形地貌差异存在4.64和5.35 km2两个最佳分析窗口,前者可以表达400 m以内的高差,后者更适合于表达400 m以上的高差;利用4.64和5.35 km2双窗口方案提取的地形起伏度优于单窗口方案,前者改善了后者对平坦地区起伏度的夸大;京津冀地区的地形起伏度在0~1 145 m之间,以平坦、中起伏和小起伏为主。     

基于汇流累积计算的沟壑密度分析方法

沟壑密度是评价地表侵蚀影响,水土流失情况,进行地貌类型分析等的重要指标。文章基于研究区填洼后的DEM,利用地表汇流累积分析原理和栅格重分类方法,通过研究沟道覆盖区栅格数与汇流累积栅格二值化阈值间的关系,选择合适的阈值用于提取地表沟道。然后结合自然地表高程,分析合理的高程和相对高程栅格重分类阈值并进行高程栅格二值化,将二值化结果作为乘积模板并配合栅格细化算法优化沟道提取结果。最终利用1 km²单位面积规则格网对沟道提取结果进行目标栅格数统计计算,得到地表沟壑密度值。结果显示,该方法基于30 m分辨率DEM提取的西安市地表沟壑密度均值为1.29 km/km²。除雁塔区,其余各行政区统计均值与前人研究结果基本吻合。试验结果证明,基于本方法可以高效较精确地计算该市地表沟壑密度,分析结果可以量化研究区沟壑密度特征值以及通过栅格像元灰度变化体现沟壑密度变化趋势。     

基于DEM和均值变点法的措勤县地形起伏度分析

地形起伏度能够反映特定区域的地势起伏特征，采用均值变点法可以有效确定地形起伏度的最佳分析窗口。利用措勤县ASTER GDEM 30 m分辨率高程数据，在GIS平台支持下，通过Python编程，采用邻域分析法在不同窗口大小下提取地形起伏度，运用均值变点法确定措勤县最佳分析窗口。研究表明：(1)措勤县最佳分析窗口为27×27的矩形单元，分析窗口面积为0.656 1 km²。(2)措勤县地形起伏度范围为0～688 m,将其分为5类，起伏度值为70～200 m的丘陵地形和200～500 m的小起伏山地地形为措勤县主要地形，占比分别为37.62%和33.24%;起伏度值为30～70 m的台地地形和0～30 m的小起伏平地地形，占比分别为16.22%和12.57%;地形起伏度值为500 m以上的中起伏山地地形面积最小，占比为0.35%。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.