基于邻域因子的土地利用空间格局分析——以北京市海淀区为例

土地利用空间格局及其变化分析是土地资源可持续利用的重要指标，本文建立了一种基于邻域因子的土地利用空间格局分析方法，用于定量分析土地利用类型在不同距离邻域内的空间聚集、排斥作用及其变化趋势。并以北京市海淀区为例进行了土地利用空间格局分析，结果表明该方法可以准确描述不同土地利用类型的空间分布规律及其变化趋势。该方法可以作为常规景观指数的有益补充，还可以为土地利用变化模拟模型提供重要信息。     

基于IPAT-S脚本语言的土地利用情景分析及其应用

建立一种土地利用情景分析方法，该方法以土地利用转换系统最小变动为原则，对不同土地利用的情景设置，利用线性目标优化的Markov链方法生成逐年土地利用面积转换矩阵和各土地利用类型面积。IPAT-S脚本语言实现了上述方法，并提供了上述方法与土地利用空间格局模拟进行耦合的接口。应用上述方法对海淀区2002～2015年土地利用变化进行了多情景分析，结果表明不同的土地利用情景设置对土地利用结构具有明显影响，城镇和工矿用地的集约度对耕地和园地面积的缩减速度具有决定性的作用。     

基于土地利用与其功能动态耦合性的县域国土空间分类体系构建

国土空间分类是建立国土空间规划体系并监督实施的基础。该研究综合应用地理探测器q统计和地理时空分析法，基于土地利用及其功能的时空异质性和动态耦合性，建立了一种国土空间分类体系构建方法，并以四川省邛崃市为例，开展了县域国土空间分类体系构建及其与土地利用分类体系的衔接关系研究。结果表明：1）2010-2020年，邛崃市土地利用优势国土空间功能存在时空异质性，土地利用与其优势国土空间功能在空间分布上存在耦合性，二者耦合度以及与地类耦合的国土空间功能结构均存在时间异质性，这证实在国土空间分类体系构建中考虑土地利用及其功能的时空异质性和动态耦合性的必要性；2）邛崃市国土空间分类体系由3个一级空间类型、7个二级空间类型和14个三级空间类型组成，不同于国土空间分类理论框架体系，进一步证实土地利用及其功能的时空异质性和动态耦合性会影响国土空间分类结果，基于土地利用及其功能的时空异质性和动态耦合性构建的国土空间分类体系更符合实际，可以避免定性分析理论构建产生的偏差；3）建立了国土空间类型与土地利用类型的对应关系，实现"虚"的国土空间功能通过"实"的土地利用得以表达，为利用历史数据和成果资料提供了有效途径。研究可以为当前国土空间规划与管理提供参考。     

土地利用变化研究方法的探讨 ——以西吉县80年代土地利用变化为例

土地利用是全球变化研究的核心领域与热点问题,本文以西吉县80年代土地利用变化为例,探讨了土地利用变化的研究方法.结果表明,应用不同比例尺、不同土地利用分类系统的土地利用现状图进行土地利用变化研究是可行的.其主要步骤包括土地利用分类系统的转化;空间叠加分析;确定土地利用类型转移概率矩阵;表格分析等.     

土地利用变化研究方法的探讨——以西吉县80年代土地利用变化为例

土地利用是全球变化研究的核心领域与热点问题 ,本文以西吉县 80年代土地利用变化为例 ,探讨了土地利用变化的研究方法。结果表明 ,应用不同比例尺、不同土地利用分类系统的土地利用现状图进行土地利用变化研究是可行的。其主要步骤包括 :土地利用分类系统的转化 ;空间叠加分析 ;确定土地利用类型转移概率矩阵 ;表格分析等。     

基于空间LDA模型的高分辨率遥感影像地物覆盖分类

高空间分辨率遥感影像可以更为精确地分析地物覆盖类型,但空间分辨率的提高也对现有分类方法带来了新的挑战,隐狄利克雷分配(latent dirichlet allocation,LDA)模型能够建立遥感影像底层特征和高层语义之间的联系,但是当前LDA模型在遥感影像分析领域的应用以场景分类和图像检索为主,已有的一些关于土地覆盖分类研究缺少对高分辨率遥感数据的空间关系进行挖掘。该文在标准LDA模型的基础上,利用词包模型构建方法生成的影像文档和单词对象来展开试验,利用多尺度分割挖掘影像中对象的空间关系,设计"主题流行度"和"主题内容"2种形式的影像文档区域属性,以协变量的形式作为LDA模型的先验知识,提出一种空间LDA模型(Space-LDA)。利用无锡宜兴市Quick Bird影像验证该模型在高分辨率遥感影像分类中的有效性,结果表明空间LDA模型分类结果不仅明显优于标准LDA,而且对区域尺度的变化具有一定的鲁棒性,空间区域信息同时从主题流行度和主题内容2个层面提供了推理信息,使模型具有更灵活的结构。     

利用ASTER遥感资料提取南京城郊土地利用信息的研究

土地资源是社会经济发展最基本的物质基础，利用遥感技术可对土地资源进行分类调查。在对地观测方面，高光谱遥感与一般遥感影像相比,能提供更高质量的信息源。先进的空间热辐射反射计(ASTER)覆盖可见光、近红外、短波红外和热红外的14个波段，分辨率从15 m到90 m，对长江流域环境监测、地表覆盖变化、短期气候预测、自然灾害监测等，对于了解该区资源、生态与环境具有重要的意义。该文利用2001年ASTER数据对南京城郊地区进行了土地利用分类，首先采用多元统计方法提取分类特征波段。然后以非监督分类获得初始训练样本，对训练区进行多次像元提纯后，运用监督分类方法对南京城郊土地利用信息进行分类。研究表明，多种分类方法相结合可从ASTER影像更好地提取土地利用信息，达到较好得分类精度。     

多元信息支持的岩溶区土地利用信息提取方法构建

土地利用信息是重要的基础数据,其准确程度将对其后续应用工作的结果产生重要影响。岩溶区地形复杂、地表覆盖类型多样,使用目视解译和传统监督分类的方法都存在一定的局限。通过结合遥感影像和植被指数、湿度指数、地形等多元信息,结合主成分分析方法,利用决策树实现上述多元信息建模,进而以实地调查样点为目标函数获取决策树的分类决策参数阈值,从而构建了多元信息支持的岩溶区土地利用信息提取方法。经试验区的模型应用和样点验证表明,该方法获取的土地利用信息基本符合典型岩溶区土地利用比例和分布特征,总体分类精度达到82%。该方法能够加深对多维遥感信息的认识,充分挖掘出其中隐含的信息,并根据这些信息提高岩溶区土地利用信息提取的精度,尤其能体现出岩溶区地貌特征对土地利用空间分布的影响。     

不同尺度下的土地利用变化驱动力研究——以常州市新北区为例

以常州市新北区为研究区域,探寻不同研究尺度下土地利用驱动力变化。分别从全局尺度和局部空间尺度,应用典型相关分析和空间网格化Logistic回归分析方法进行土地利用变化驱动力的定量化分析。结果表明:在全局尺度上,GDP变化量、社会固定资产投资额变化量、工业总产值变化量、农业总产值变化量、农村居民人均纯收入变化量、人均GDP变化量、总人口变化量和城镇化率变化量,是影响常州市新北区土地利用变化的主要因素。在局部空间尺度上,对常州市新北区土地利用变化造成显著影响的因子,主要包括距水系最近距离、距城镇最近距离、距省级以上公路最近距离和距城乡主干道最近距离。经济的快速发展和人口增长是常州市新北区土地利用变化的主要社会经济驱动力;交通可达性和中心城镇影响下的空间区位条件是影响土地利用变化的重要空间差异化因素。我国快速城镇化进程中区域土地利用变化受人口增长、经济发展、交通体系和政策等影响较大。     

基于决策树的龙口市土地利用/覆盖分类研究

LUCC是全球变化研究的重要内容,土地利用/覆盖信息的获取是其前提和基础。决策树分类法是每次利用一定的规则,对遥感影像进行逐级细化的分类模型,具有直观、高效等特点。在综合分析每一种土地利用/覆盖类型各种特征的基础上,探讨将不同土地利用/覆盖类型的光谱特征、空间特征、波段比值特征等信息融入决策树分类模型,对龙口市土地利用/覆盖信息进行自动分类的方法,取得了较高的分类精度。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

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     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.