The influence of sampling scheme and interpolation method on the power to detect spatial effects of forest birds in Ontario (Canada)

Spatial ecology is becoming an increasingly important component of resource management, and the general monitoring of how human activities affect the distribution and abundance of wildlife. Yet most work on the reliability of sampling strategies is based on a non-spatial analysis of variance paradigm, and little work has been done assessing the power of alternative spatial methods for creating reliable maps of animal abundance. Such a map forms a critical response variable for multiple scale studies relating landscape structure to biotic function. The power to reconstruct patterns of distribution and abundance is influenced by sample placement strategy and density, the nature of spatial auto-correlation among points, and by the technique used to extrapolate points into an animal abundance map. Faced with uncertainty concerning the influence of these factors, we chose to first synthesize a model reference system of known properties and then evaluate the relative performance of alternative sampling and mapping procedures using it. We used published habitat associations of tree nesting boreal neo-tropical birds, a classified habitat map from the Manitou Lakes area of northwestern Ontario, and point count means and variances determined from field studies in boreal Canada to create 4 simulated models of avian abundance to function as reference maps. Four point sampling strategies were evaluated by 4 spatial mapping methods. We found mixed-cluster sampling to be an effective point sampling strategy, particularly when high habitat fragmentation was avoided by restricting samples to habitat patches >10 ha in size. We also found that of the 4 mapping methods, only stratified ordinary point kriging (OPK) was able to generate maps that reproduced an embedded landscape-scale spatial effect that reduced nesting bird abundance in areas of higher forest age-class fragmentation. Global OPK was effective only for detecting broader, regional-scale differences. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of area and isolation of woodland patches on herbaceous plant species richness across Great Britain

Richness of Ancient Woodland Indicator plant species was analysed in 308 woodland patches that were surveyed during the Countryside Survey of Great Britain carried out in 1998. The Countryside Survey recorded vegetation plots and landscape structure in 569 stratified 1 km sample squares and developed a remotely-sensed land cover map of the UK. Using these datasets, we tested the hypothesis that Ancient Woodland Indicator species richness in woodland fragments was limited by patch area, shape and spatial isolation and that woodland patches located in the lowland region of Great Britain would respond differently than those in the upland region. The variation in Ancient Woodland Indicator species richness in the British lowlands (n = 218) was mainly explained by patch area and two measures of connectivity, the length of hedgerows and lines of trees in the 1 km square and the area of woodland within 500 m of the vegetation plot. By contrast, variation in Ancient Woodland Indicator species richness in the British uplands (n = 90) was related to Ellenberg scores of the vegetation communities sampled – a surrogate for habitat quality – and no significant effect of spatial structure was detected. It therefore appears that the degree of fragmentation of woodland in the British lowlands limits the distribution of Ancient Woodland Indicator species, while in the uplands, failed colonisation is a matter of habitat quality rather than a result of landscape structure.This revised version was published online in May 2005 with corrections to the Cover Date.     

Assessing the sustainability of cropping systems in single- and multi-site studies. A review of methods

The multiple new challenges facing agriculture require the development of innovative cropping systems with high environmental, economic and social performances. Many research programmes are currently focusing on the design of such cropping systems. Some include the multicriteria assessment of cropping systems by diverse methods and approaches. Some of these research programmes are supported by experimental or farmers’ networks, generating new opportunities for data analysis and raising new research and methodological questions. In this article, we provide an overview based on a review of 56 articles, comparing the various methods for sustainability assessment in single- and multi-site studies. Articles were classified according to three characteristics: (i) their objectives, (ii) the study design (single- vs. multi-site), (iii) the type of system assessed (fictitious vs. real). Our analysis was structured around four items: (i) the variables used to describe cropping systems and production situations and the use of these variables in the assessment process, (ii) the criteria and associated indicators assessed, (iii) the methods used to explore multiple aspects of the performance of cropping systems, (iv) the use of reference values. We identified key points to be taken into account in multi-site studies. The application of the proposed guidelines to experimental networks should facilitate the identification of high-performance cropping systems and the identification of the drivers of cropping system performance.     

近32年来新疆地区植被覆盖的时空变化

基于拟合的长时间序列数据监测新疆植被时空动态变化。结果表明,近32年来,新疆植被总体呈现增加趋势,但存在明显的阶段变化和空间差异;植被生长季NDVI值西部和西北部高,东部和东南部低;1982-2013年间新疆植被改善面积大于退化面积,绿洲农田植被覆盖区改善明显、草原区退化严重;整个研究区域的植被重心从北向南移动,天山以北的植被重心呈现西南-东北方向移动,天山以南呈现近似东西方向的移动。     

基于信息熵的耕地土壤养分与环境影响因子空间相关性研究

[目的] 探究耕地土壤养分含量空间格局及与环境因子的空间相关性,为区域耕地土壤施肥管控及农业生态环境保护等相关工作提供理论依据。[方法] 以湖北省枣阳市耕地为研究对象,选取土壤有机质、全氮、速效钾、缓效钾和有效磷5种土壤养分指标,并收集整理成土母质、土壤类型、土壤pH值、高程（DEM）、地表起伏度、坡度、植被覆盖度指数（NDVI）、平均气温、平均降水量和土地利用方式10种环境影响因子,利用普通克里金插值和信息熵原理,分析每种土壤养分的空间分布特征以及每种土壤养分空间分异特征与环境因子的相关性。[结果] 枣阳市土壤缓效钾空间异质性不明显,全域含量水平较高;其他4种养分均表现出不同程度的空间异质性。信息熵结果表明,5种土壤养分含量空间格局与成土母质、土壤类型和气候因子相关性均较强但相关程度存在差异;地形因子与全氮和有机质含量空间相关性较强,土壤pH值与土壤速效钾、缓效钾和有效磷相关性较强。[结论] 枣阳市土壤养分格局受自然因素影响较强,但相关性指数K值都较低,说明受到人为施肥与农作物消耗以及灌溉排水导致的土壤水化学反应及养分流失的影响。     

基于GIS与分区Kriging的采煤沉陷区土壤有机碳含量空间预测

中国煤炭产量占世界煤炭总产量的46.9%,年塌陷的耕地面积约为200 km~2,对农田土壤有机碳库扰动十分剧烈。由于农田的土壤有机碳库是减少陆地生态系统碳排放的最大潜在因素,中国以及世界上的其他煤炭开采大国必须更好地对煤炭开采区的土壤有机碳库进行科学管理,这也是煤炭低碳开采的重要途径。而预测精度好的煤炭开采沉陷区土壤有机碳含量空间预测方法是科学管理煤炭开采沉陷区土壤有机碳库的前提。该文以徐州九里煤炭开采沉陷区作为研究区,通过普通Kriging插值法和以结合沉陷积水情况为辅助变量的分区Kriging插值法这2种方法来对研究区的土壤有机碳含量进行了空间预测,并通过比较验证样点的预测值与实测值来对比2种方法的预测精度,确定每种方法的可行性。研究发现,结合区域内部积水情况来进行的分区Kriging插值法求得到的预测值与实测值的相关系数为0.7564,远高于直接进行Kriging插值得到的预测值与实测值的相关系数0.5086,并且两者的均方根误差分别为0.35和0.55,说明前者的预测精度更高。因此结合沉陷积水情况的分区Kriging插值模式是更适宜煤炭开采沉陷区土壤有机碳含量的空间预测模型。     

精准农业中不同取样间距下Kriging插值精度对比研究

为了研究土壤不同养分的合理取样间距,研究选择了平顶山地区典型烟田为研究对象,在面积为4 hm2的地块上以20 m×20 m网格采样,共采集耕层(0~20 cm)土壤样品111个。在GIS软件平台上对采样点进行行列删除,人为改变取样间距大小,并运用地质统计学和普通克里格插值方法进行插值,生成了土壤各养分分布图。同时,随机选取7个样点,并将其在不同取样密度下的Kriging插值结果与实测值进行比较。由插值误差分析、独立检验、面积分析和养分分布图可以看出:在该研究区域内,碱解氮、速效磷、速效钾、速效铁和速效锌以20 m取样间距较为合适,有机质和速效铜的合理取样间距为60 m,速效锰则以40 m取样间距较适宜。研究目的是为该地区确定合理的土壤取样间距提供理论依据。     

南疆果园滴灌条件下土壤盐分的空间异质性分析——以农十四师224团典型地块为例

土壤盐渍化是制约干旱半干旱地区农业生产的主要障碍因子之一,在新疆,尤其是南疆,盐渍化更为严重。系统认识和掌握盐渍土的空间变异特征对于治理改良盐渍土和土壤盐渍动态变化研究具有重要意义。基于区域变量理论,在GIS和地统计学技术支持下,通过地统计学的半变异函数和Kriging空间插值,以南疆和田地区农十四师224团为研究区,定量分析了试验区内不同层次土壤盐分的空间变异特征。结果表明:140~180 cm土层土壤盐分含量半方差函数的理论分布模型属于指数模型,其它各层属于球状模型;各土层含盐量在一定的区域范围内具有空间结构特征,都呈中等强度空间自相关性;由kriging插值可知,各土层含盐量的空间分布主要表现为条带状伴有斑块状分布。总体来说,试验区土壤盐渍化与次生盐渍化的防治是近期农业管理中所必须考虑的重要因素。     

平原区土壤质地的反射光谱预测与地统计制图

基于地统计方法的土壤属性制图通常需要大量的采样与实验室测定。本研究提出利用可见光近红外(visible-nearinfrared spectroscopy,VNIR)光谱技术测定替代实验室测定,并与地统计方法相结合预测土壤质地的空间变异。通过建立砂粒(0.02 mm),粉粒(0.002~0.02 mm),黏粒(0.002 mm)含量的VNIR光谱预测模型,将模型预测得到的质地数据和建模点实测质地数据一同用于地统计分析和Kriging插值制图。以江苏北部黄淮平原地区为案例的研究结果表明,砂粒、粉粒、黏粒含量的预测值和实测值的均方根误差(RMSE)分别为8.67%、6.90%3、.51%,平均绝对误差(MAE)分别为6.46%、5.60%、3.05%,显示了较高的预测精度。研究为快速获取平原区土壤质地空间分布提供了新的可能的途径。     

不同采样尺度下土壤碱解氮空间变异性研究——以榆树市农田土壤为例

在精准农业的实施过程中,研究如何用较少的样本来反映田间信息的空间变异规律,再用科学的插值方法进行插值和预估是精准农业研究中的一个关键问题。以东北典型黑土区——吉林省榆树市为研究区域,在榆树市弓棚镇13号村内选择相对平整的地块进行土壤采样并测试其土壤养分。在对原始采样格网点按一定的样点间隔和布局进行抽取的基础上,利用克里格插值方法和BP神经网络方法分别进行空间插值,比较不同采样尺度（40m×40m,56m×56m,80m×80m,113m×113m,160m×160m五个尺度）对空间插值精度的影响。结果表明:（1）随着采样尺度的增大,碱解氮的空间结构系数C/（C₀+C）有减小的趋势,表明采样间距以内的不可估计误差逐渐增大,其空间结构的表现能力在逐渐减弱;（2）Kriging插值精度总体优于BP神经网络,随着采样尺度的增加,两种模型的模拟精度都有所下降,BP神经网路的插值精度和Kriging模型的插值精度的差距逐渐减小;（3）两种模型在113m×113m尺度上插值精度都发生了突变,如考虑碱解氮的空间变异规律和经济因素,碱解氮的最佳采样尺度应在80～113m。