近30年来陕北黄土高原土地利用动态变化分析

基于1975年的LandsatMSS影像,1986年、1997年和2006年的Landsat TM影像,利用遥感影像的计算机自动分类和目视解译,得到这4a的土地利用信息。利用ERDAS中的GIS分析模块和统计方法对这4a的土地利用图进行统计分析,得到1975-1986年、1986-1997年和1997-2006年这3个时间段的土地利用变化的数量、速度、幅度、空间格局特征。结果表明:耕地经历了一个先增加后减少的过程,草地、林地先减少后增加,居民地一直处于增加状态,未利用地从整体上来说处于减少状态,只不过在中期有一定数量的波动;在前期和中期土地利用类型间的相互转化基本一致,后期土地利用类型间的相互转化有所增强;耕地、草地、林地和未利用地是该地区土地利用变化的主导类型,主要是耕地、草地与其它土地利用类型间的相互转化。

相似性降水条件下北洛河水沙变化特征

降水是河流径流来源也是水土流失的主要动力,通过选择相似降水年组比较河流水沙变化,可以更好揭示土地利用变化对河流水沙变化的影响。采用1954年到1996年北洛河状头水文站实测资料,根据年份差大于5年,年雨量差小于20 mm和汛期雨量差小于10 mm等三个指标确定了8个相似降水年组。通过比较相似性降水年组径流量和输沙量变化,分析了不同时间河流水沙变化特点;并通过组间比较初步探讨了北洛河水沙变化趋势。分析表明,与1980年相比,1996年除汛期径流量增加外,年径流量,年与汛期的输沙量和含沙量均增加;在其他时段,输沙量在1970年代后期以前呈减少趋势,年径流量和汛期径流量有增加趋势,而年均和汛期含沙量均有减少趋势。

Application of Dempster-Shafer evidence theory to unsupervised classification in multisource remote sensing

The aim of this paper is to show that Dempster-Shafer evidence theory may be successfully applied to unsupervised classification in multisource remote sensing. Dempster-Shafer formulation allows for consideration of unions of classes, and to represent both imprecision and uncertainty, through the definition of belief and plausibility functions. These two functions, derived from mass function, are generally chosen in a supervised way. In this paper, the authors describe an unsupervised method, based on the comparison of monosource classification results, to select the classes necessary for Dempster-Shafer evidence combination and to define their mass functions. Data fusion is then performed, discarding invalid clusters (e.g. corresponding to conflicting information) thank to an iterative process. Unsupervised multisource classification algorithm is applied to MAC-Europe'91 multisensor airborne campaign data collected over the Orgeval French site. Classification results using different combinations of sensors (TMS and AirSAR) or wavelengths (L- and C-bands) are compared. Performance of data fusion is evaluated in terms of identification of land cover types. The best results are obtained when all three data sets are used. Furthermore, some other combinations of data are tried, and their ability to discriminate between the different land cover types is quantified

黄土区退果还耕对黑垆土硝态氮积累和迁移的影响

在黄土高原沟壑区王东沟小流域,针对塬面、梁地和坡地三种地形,分别选取了盛果期果园、老果园和退果还耕地等,研究了退果还耕条件下,三种地貌类型土壤剖面中水分含量变化及NO_3~--N、NH_4~+-N积累和迁移规律。结果表明,无论塬面、梁地或者坡地上,果园土壤水分含量显著降低(10%～14%);果园退耕后,土壤水分开始缓慢恢复。盛果期,塬面NO_3~--N峰值主要处于100—200 cm之间,退果还耕后,100 cm以上土层中NO_3~--N含量降低,100cm以下NO_3~--N积累量在增加,并且峰值不断向下移动。盛果期果园NO_3~--N积累量为631～3032 kg/hm~2;退果还耕地、老果园NO_3~--N积累量都显著高于盛果期果园。盛果期40%以上的NO_3~--N积累在100—200 cm土层,但退果还耕地上50%左右集中分布在200—300 cm土层。土地利用与管理方式的变化对NH_4~+-N分布特征的影响并不明显。

基于RS的黄河中游多沙粗沙区土地利用变化分析

据1975年的Landsat MSS、1986年和1997年的Landsat TM影像资料,运用遥感影像计算机自动分类方法获取土地利用信息,用GIS空间分析方法以及数理统计方法全面分析了黄河中游多沙粗沙区1975~1986年和1986~1997年两个时期内各土地利用类型的变化幅度、变化速度、数量变化的区域差异、变化方向以及变化方向的区域差异等。结果表明:后期土地利用类型间的相互转化有所增强;耕地、草地、林地和未利用地是本区土地利用变化的主导类型,耕地、草地与其它土地利用类型间的相互转化分布校广;后期耕地被居民地占用的面积和毁林开荒的面积比前期有所增加。

Spatio-temporal changes in annual accumulated temperature in China and the effects on cropping systems, 1980s to 2000

Change in thermal conditions can substantially affect crop growth, cropping systems, agricultural production and land use. In the present study, we used annual accumulated temperatures > 10 degrees C (AAT10) as an indicator to investigate the spatio-temporal changes in thermal conditions across China from the late 1980s to 2000, with a spatial resolution of 1 x 1 km. We also investigated the effects of the spatio-temporal changes on cultivated land use and cropping systems. We found that AAT10 has increased on a national scale since the late 1980s, Particularly, 3.16 x 10(5) km(2) of land moved from the spring wheat zone (AAT10: 1600 to 3400 degrees C) to the winter wheat zone (AAT10: 3400 to 4500 degrees C). Changes in thermal conditions had large influences on cultivated land area and cropping systems. The areas of cultivated land have increased in regions with increasing AAT10, and the cropping rotation index has increased since the late 1980s. Single cropping was replaced by 3 crops in 2 years in many regions, and areas of winter wheat cultivation were shifted northward in some areas, such as in the eastern Inner Mongolia Autonomous Region and in western Liaoning and Jilin Provinces.

Distribution characteristics of (CS)-C-137 in wind-eroded soil profile and its use in estimating wind erosion modulus

Due to its inert reaction in soil system and distinctive vertical distribution in soil profile, caesium-137 (Cs-137) has been used as a tracer to assess wind erosion. In this study, 62 soil samples were collected from 4 sampling sites in Taipusi County, Inner Mongolia; Caesium-137 activities for those soil samples were measured using a gamma-ray spectrometry in Sichuan University, Chengdu. Distribution pattern of Cs-137 in vertical soil profile was different for different land use and land cover types. Caesium-137 was distributed homogeneously in plow layer of cropland, and negatively exponential in low to medium cover grassland. Distribution pattern in high covered grassland was represented by a peak at 2-4 cm soil depth followed by a negative exponential curve. Based on those findings, simplified mass balance model was chosen to estimate the rate of wind erosion for cropland, while profile distribution model was used for grassland. Estimated wind erosion rates were 7990, 4270 and 1808 Mg(.)km(-2.)a(-1) for cropland, low cover grassland and medium cover grassland, respectively. Wind erosion intensity correlated negatively with plant cover.

新疆自然区划单元土地利用/覆盖分布图谱研究

Under the direction of Geo-informatic Tupu theory, based on comprehensive natural division in Xinjiang and 1:100000 land use and land cover vector data in 2000 from resource and environment database of CAS, the paper gave out some distribution Tupu of land resource types in different regions of Xinjiang. GIS tools such as ARCTOOLS and ARCV1EW were used to clip the unit of each natural division. Some useful conclusions were established. Then the lower reaches of Tarim River were selected as typical area to analyze the ecological environment evolvement from 2000 to 2004 since the beginning of ecological water delivering. The comprehensive space-time analysis provided a method to monitor the effect dynamically. The main contents of the thesis are listed as follows: (1) Similarities and differences between North Xinjiang and South Xinjiang, 6 second-classified regions and 37 third-classified regions. The conclusion of each region emphasized the percentage of area of main land types, characteristic description and distribution of cultivated land > woodlands grassland-, water area^ urban and rural land and unused land. (2) Thematic Tupu of each region. It concluded artificial oasis Tupu, the proportion between dense-grass% moderate-grass and sparse-grass, pattern of land resources and the land use degree. The artificial oasis mean cultivated land^ woodland^ urban & rural land and other construction land. The proportion of grassland disclosed the quality of all grassland and showed the development of them. Pattern of land resources and the land use degree gave out the detailed development direction and development degree of each region. (3) Ecological environment evolvement of the lower reaches of Tarim River. The effects of each ecological water delivering were compared.

Spatial distribution of upland beetles in relation to landform, vegetation and grazing management

Dennis, P., Aspinall, R. J., Gordon, I. J. (2002). Spatial distribution of upland beetles in relation to landform vegetation and grazing management. Basic and Applied Ecology, 3 (2), 183?193. Sponsorship: SEERAD RAE2008

Monitoring the vegetation start of season (SOS) across the island of Ireland using the MERIS global vegetation index

The aim of this study was to develop a methodology, based on satellite remote sensing, to estimate the vegetation Start of Season (SOS) across the whole island of Ireland on an annual basis. This growing body of research is known as Land Surface Phenology (LSP) monitoring. The SOS was estimated for each year from a 7-year time series of 10-day composited, 1.2 km reduced resolution MERIS Global Vegetation Index (MGVI) data from 2003 to 2009, using the time series analysis software, TIMESAT. The selection of a 10-day composite period was guided by in-situ observations of leaf unfolding and cloud cover at representative point locations on the island. The MGVI time series was smoothed and the SOS metric extracted at a point corresponding to 20% of the seasonal MGVI amplitude. The SOS metric was extracted on a per pixel basis and gridded for national scale coverage. There were consistent spatial patterns in the SOS grids which were replicated on an annual basis and were qualitatively linked to variation in landcover. Analysis revealed that three statistically separable groups of CORINE Land Cover (CLC) classes could be derived from differences in the SOS, namely agricultural and forest land cover types, peat bogs, and natural and semi-natural vegetation types. These groups demonstrated that managed vegetation, e.g. pastures has a significantly earlier SOS than in unmanaged vegetation e.g. natural grasslands. There was also interannual spatio-temporal variability in the SOS. Such variability was highlighted in a series of anomaly grids showing variation from the 7-year mean SOS. An initial climate analysis indicated that an anomalously cold winter and spring in 2005/2006, linked to a negative North Atlantic Oscillation index value, delayed the 2006 SOS countrywide, while in other years the SOS anomalies showed more complex variation. A correlation study using air temperature as a climate variable revealed the spatial complexity of the air temperature-SOS relationship across the Republic of Ireland as the timing of maximum correlation varied from November to April depending on location. The SOS was found to occur earlier due to warmer winters in the Southeast while it was later with warmer winters in the Northwest. The inverse pattern emerged in the spatial patterns of the spring correlates. This contrasting pattern would appear to be linked to vegetation management as arable cropping is typically practiced in the southeast while there is mixed agriculture and mostly pastures to the west. Therefore, land use as well as air temperature appears to be an important determinant of national scale patterns in the SOS. The TIMESAT tool formed a crucial component of the estimation of SOS across the country in all seven years as it minimised the negative impact of noise and data dropouts in the MGVI time series by applying a smoothing algorithm. The extracted SOS metric was sensitive to temporal and spatial variation in land surface vegetation seasonality while the spatial patterns in the gridded SOS estimates aligned with those in landcover type. The methodology can be extended for a longer time series of FAPAR as MERIS will be replaced by the ESA Sentinel mission in 2013, while the availability of full resolution (300m) MERIS FAPAR and equivalent sensor products holds the possibility of monitoring finer scale seasonality variation. This study has shown the utility of the SOS metric as an indicator of spatiotemporal variability in vegetation phenology, as well as a correlate of other environmental variables such as air temperature. However, the satellite-based method is not seen as a replacement of ground-based observations, but rather as a complementary approach to studying vegetation phenology at the national scale. In future, the method can be extended to extract other metrics of the seasonal cycle in order to gain a more comprehensive view of seasonal vegetation development.

Soil Carbon stocks and schanges in the Republic of Ireland

The soil carbon (C) stock of the Republic of Ireland is estimated to have been 2048 Mt in 1990 and 2021 Mt in 2000. Peat holds around 53% of the soil C stock, but on 17% of the land area. The C density of soils (t C ha-1) is mapped at 2 km*2 km resolution. The greatest soil C densities occur where deep raised bogs are the dominant soil; in these grid squares C density can reach 3000 t C ha-1. Most of the loss of soil C between 1990 and 2000-up to 23 Mt C (1% of 1990 soil C stock)-was through industrial peat extraction. The average annual change in soil C stocks from 1990 to 2000 due to land use change was estimated at around 0.02% of the 1990 stock. Considering uncertainties in the data used to calculate soil C stocks and changes, the small average annual 'loss' could be regarded as 'no change'.

Water quality impacts and palaeohydrogeology in the East Yorkshire Chalk Aquifer, UK

A large hydrochemical data-set for the East Yorkshire Chalk has been assessed. Controls on the distribution of water qualities within this aquifer reflect: water-rock interactions (affecting especially the carbonate system and associated geochemistry); effects of land-use change (especially where the aquifer is unconfined); saline intrusion and aquifer refreshening (including ion exchange effects); and aquifer overexploitation (in the semi-confined and confined zones of the aquifer). Both Sr and I prove useful indicators of groundwater ages, with I/Cl ratios characterising two sources of saline waters. The hydrochemical evidence clearly reveals the importance of both recent management decisions and palaeohydrogeology in determining the evolution and distribution of groundwater salinity within the artesian and confined zones of the aquifer. Waters currently encountered in the aquifer are identified as complex (and potentially dynamic) mixtures between modern recharge waters, modern seawater, and old seawaters which entered the aquifer many millennia ago.

The Movebank data model for animal tracking

Studies of animal movement are rapidly increasing as tracking technologies make it possible to collect more data of a larger variety of species. Comparisons of animal movement across sites, times, or species are key to asking questions about animal adaptation, responses to climate and land-use change. Thus, great gains can be made by sharing and exchanging animal tracking data. Here we present an animal movement data model that we use within the Movebank web application to describe tracked animals. The model facilitates data comparisons across a broad range of taxa, study designs, and technologies, and is based on the scientific questions that could be addressed with the data.