Effects of changing scale on landscape pattern analysis: scaling relations

Landscape pattern is spatially correlated and scale-dependent. Thus, understanding landscape structure and functioning requires multiscale information, and scaling functions are the most precise and concise way of quantifying multiscale characteristics explicitly. The major objective of this study was to explore if there are any scaling relations for landscape pattern when it is measured over a range of scales (grain size and extent). The results showed that the responses of landscape metrics to changing scale fell into two categories when computed at the class level (i.e., for individual land cover types): simple scaling functions and unpredictable behavior. Similarly, three categories were found at the landscape level, with the third being staircase pattern, in a previous study when all land cover types were combined together. In general, scaling relations were more variable at the class level than at the landscape level, and more consistent and predictable with changing grain size than with changing extent at both levels. Considering that the landscapes under study were quite diverse in terms of both composition and configuration, these results seem robust. This study highlights the need for multiscale analysis in order to adequately characterize and monitor landscape heterogeneity, and provides insights into the scaling of landscape patterns. This revised version was published online in May 2005 with corrections to the Cover Date. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photosynthetic light use efficiency of three biomes across an east–west continental-scale transect in Canada

Light use efficiency (LUE) is used widely in scaling and modeling contexts. However, the variation and biophysical controls on LUE remain poorly documented. Networks of eddy covariance (EC) towers offer an opportunity to quantify _g, the ratio of P, gross primary productivity, to Q_a, absorbed photosynthetically active radiation (PAR), across climate zones and vegetation types. Using data from the Fluxnet Canada Research Network (n = 24 sites) in 2004, we examined the relationship between daily and yearly _g, driving variables, and site characteristics on a site-specific and plant functional type (PFT) basis using tree regression and linear regression. Data were available for three biomes: grassland, forest, and wetland. Yearly _g values ranged from 0.1 to 3.6 g C MJ⁻¹ Q_a overall. Daily _g was highest in the grassland (daily median ± interquartile range: 3.68 ± 1.98 g C MJ⁻¹ Q_a), intermediate in the forested biome (0.84 ± 0.82 g C MJ⁻¹ Q_a), and lowest for the wetlands (0.65 ± 0.54 g C MJ⁻¹ Q_a). The most important biophysical controls were light and temperature, to the exclusion of water-related variables: a homogeneity of slopes model explained c. 75% of the variation in daily _g. For a subset of sites with diffuse PAR data, the ratio of diffuse to total PAR, a proxy for cloudiness, was a key predictor. On the yearly time scale, _g was related to leaf area index and mean annual temperature. Aggregating to PFTs did not show functional convergence within any PFT except for the three wetland sites and the Picea mariana toposequence at the daily time step, and when using the Köppen climate classification on a yearly time step. The general lack of conservative daily _g behavior within PFTs suggests that PFT-based parameterizations are inappropriate, especially when applied on shorter temporal scales.     

Soil biology,soil ecology,and global change

Summary This overview paper addresses aspects of scaling in space and time, and scaling in relation to micro-and macrohabitats. Ecological processes in soils are examined for possible generalizations about processes and organisms, across a wide range of different habitats. Problems of scaling in space and time that have an important impact on processes associated with global change are outlined.     

A Nonlinear Model for Estimating Hoof Surface Area in Unshod Meat-type Horses

The aim of this study was to develop a simple, inexpensive, and noninvasive technique for estimating the hoof surface area (HSA) of unshod horses under field conditions. It was hypothesized that HSA in horses can be extrapolated from simple linear hoof measurements. Two linear measurements—lateromedial width and dorsoplantar width—were obtained from all four feet of 57 unshod meat-type horses. Different algorithms for determining HSA were developed. The most simple equation was HSA = (1.229 × LM)^1.071 × (DP)^0.772 (where LM = lateromedial width and DP = dorsoplantar width), representing a good nonlinear model with a standard deviation of error for the estimate of 5.150 and a coefficient of multiple determination of 0.9384. This formula may be helpful as a repeatable, nonintrusive, and easily performed in vivo estimation of the hoof surface of unshod horses, at least in the studied breed.     

区域尺度土壤入渗参数空间变异性规律研究

以在杨凌区进行的土壤入渗试验为基础,利用标定理论、统计学与地统计学相结合的方法研究了Philip入渗公式的标定过程,以及标定因子的空间变异规律.研究结果表明:在研究区域内不同标定因子中αA标定的效果最优,可用αA对入渗曲线进行标定;利用统计学原理计算了不同置信水平和精度要求下入渗测点的合理取样数;采用ArcGIS软件对标定因子αA的空间变异规律进行了分析;建立了可根据易测定的土壤物理参数直接估算αA的土壤转换函数,并通过验证,其结果可较好地解决区域尺度内土壤入渗参数的点面转换问题.     

土壤水力特性的空间尺度效应研究进展

研究土壤水力特性的空间尺度效应,在生态水文模拟和农业水肥精准管理方面具有重大意义。水力特性空间变异研究方法主要有统计法、随机模拟法、土壤转换函数法和分形理论法;由于土壤中物理、化学和生物等过程作用的尺度不同,导致其空间变异方式亦不相同,当前主要采用地统计学、谱分析、多重分形和小波分析等方法研究水力特性的尺度效应。研究过程中仍有一些问题需解决,其中尺度转换始终是非常重要的问题,并且要与GIS等技术相结合。     

Contrasting methods for estimating evapotranspiration in soybean

Crop scientists are often interested in canopy rather than leaf water estimates. Comparing canopy fluxes for multiple treatments using micrometeorological approaches presents limitations because of the large fetch required. The goal of this study was to compare leaf-scale to field-scale data by summing soil water evaporation (E) and leaf transpiration (T) versus ET using tower eddy covariance (EC) and scaling leaf transpiration to the canopy level using a two-step scaling approach in soybean [Glycine max (L.) Merr.]. Soybean transpiration represented 89-96% of E + T when combining the soil water evaporation with leaf transpiration on the five measurement days during reproductive growth. Comparing E + T versus ET from the EC system, the E + T method overestimated ET from 0.68 to 1.58 mm. In terms of percent difference, the best agreement between the two methods was 15% on DOY 235 and the worst agreement occurred on DOY 234 (41%). A two-step scaling method predicted average ET within 0.01 mm of the EC ET between 10:00 and 14:15 on an hourly time-step on DOY 227 under uniform sky conditions and average ET within 0.03 mm of the EC ET on DOY 235 under intermittent sky conditions between 10:00 and 15:15. Pooling the scaled-leaf data and comparing them with the measured EC ET data exhibited a strong linear relationship (r = 0.835) after accounting for bias (6%). Findings from this study indicate satisfactory results comparing absolute differences are likely not obtainable by summing leaf transpiration with soil water evaporation to calculate canopy water fluxes. However, scaling leaf transpiration provided a robust measure of canopy transpiration during reproductive growth in soybean under these conditions and merits additional study under different climatic and crop conditions.     

新疆农田不同施肥区土壤昆虫群落丰富性与多样性

 【目的】在新疆国家灰漠土土壤肥力与肥料效益长期监测基地，对10种施肥处理，即（1）撂荒（不施肥、不耕作、不种植，Aband.）、（2）对照（种植、不施肥，CK）、（3）施氮肥（N）、（4）施氮磷肥（NP）、（5）施氮钾肥（NK）、（6）施磷钾肥（PK）、（7）施氮磷钾化肥（NPK）、（8）施氮磷钾化肥+有机肥（有机氮和化肥氮的比例为7﹕3）（MNPK）、（9）化肥用量增加50%配施有机肥（1.5 MNPK）、（10）化肥配施秸秆(SNPK)与新疆灰漠土区农田土壤昆虫群落之间的关系进行研究。【方法】采用改良干漏斗（Modified Tullgren）分离土壤（0～20 cm）中的土壤昆虫，同时利用陷阱法收集活动在地表的各类土壤昆虫。【结果】两种方法共获得土壤昆虫4 915只（未知标本128只），隶属9目33科。大型土壤昆虫个体数和类群数在Aband.处理中分布最多，中小型土壤昆虫则分别在N和PK处理中分布最多；MNPK处理土壤动物组成最丰富，N处理土壤动物分布最均匀。农田土壤昆虫类群分布受施肥影响极其显著（X0.05（9）=23.38，P＜0.005），Aband.区土壤昆虫群落与其它施肥处理土壤昆虫群落差异极显著（P＜0.01）。利用非度量多维标度分析法对土壤昆虫群落分类排序，则灰漠土土壤昆虫群落划分为5组，即NPK、MNPK、1.5MNPK和CK为一组，NP和PK为一组，NK和N为一组，SNPK和Aband.各为一组，表明土壤昆虫分布与肥料性质有关。主成分中前两个主成分解释总变量的98.51%，其中第一主成分反映了单施N肥和SNPK还田对土壤昆虫群落具有促进作用；第二主成分反映了1.5MNPK对土壤昆虫群落促进作用，表明施肥处理对土壤昆虫类群影响不平衡。【结论】新疆灰漠土区，肥料的种类与性质影响着土壤昆虫类群多样性与丰富性，且其影响具有不均衡性。     

土壤水文过程与溶质迁移转化研究进展

总结和概括了土壤水与溶质、能量研究的发展历程,介绍了土壤水与溶质、土壤热耦合运移研究的基本理论和模型发展,分析了当前水土系统理论和应用方面存在的难点和尚未解决的问题,展望了在大气-植被-土壤系统研究基础上进一步在土水系统中研究水文质耦合理论,提出构建分布式耦合模型系统亟待解决的关键技术问题。