Detecting grassland spatial variation by a wavelet approach

Insight into the spatial variation of an ecosystem can provide better understanding of ecological processes and patterns in different scales. Detecting these multiple scales of spatial variation in grassland landscapes is valuable for determining management options, designing proper sampling regimes, and selecting suitable resolutions of remote sensing products. The objective of this study is to examine how environmental factors affect spatial variation of biophysical properties in mixed grassland ecosystems. Field leaf area index (LAI), soil moisture, and topographical parameters (relative elevation, upslope length, and a wetness index) were obtained in three parallel transects of a grassland ecosystem in Saskatchewan, Canada in 2004. One 20‐m resolution SPOT 4 (HRVIR) image was acquired at the same period of the growing season but in the following year. Normalized difference vegetation index (NDVI) was calculated from the satellite image of the centre 381‐m transect and two extensive 2560‐m perpendicular transects. A wavelet approach was used to identify the scales of variations. Statistical results showed that LAI is significantly correlated to the wetness index (r2 = 0.37) and soil moisture (r2 = 0.43). The wetness index is better than relative elevation and upslope length in demonstrating the effect of topography on grassland vegetation. The variation of soil moisture is significant at two small scales of about 20 m and 40 m, and that of the wetness index is at the large scale of 120 m. The variation of grassland LAI is significant at three scales (20 m, 40 m, and 120 m), which indicates that the spatial variation of LAI might be controlled by both topography and soil moisture, though the 120 m is the dominant scale of variation in LAI. NDVI significantly correlated with grassland LAI along the centre transect. The effect of topography on grassland LAI is also proven by the significant relationships between NDVI and the wetness index. The wavelet analysis identifies the variation of two extensive transects at the scale of about 120 m, which is similar to the dominant variation scale of grassland LAI. These results confirmed that the effect of topography on spatial variation can be identified from the appropriate satellite image. This study suggests that the spatial scales of soil and topographic data aid in the selection of appropriate satellite image resolution for monitoring and managing ecosystems.

[1]  Lawrence B. Flanagan,et al.  Interacting effects of temperature, soil moisture and plant biomass production on ecosystem respiration in a northern temperate grassland , 2005 .

[2]  T. Green,et al.  Measurement, scaling, and topographic analyses of spatial crop yield and soil water content , 2004 .

[3]  Sari C. Saunders,et al.  Identifying scales of pattern in ecological data: a comparison of lacunarity, spectral and wavelet analyses , 2005 .

[4]  R. O'Neill,et al.  Lacunarity indices as measures of landscape texture , 1993, Landscape Ecology.

[5]  Jiquan Chen,et al.  The patch mosaic and ecological decomposition across spatial scales in a managed landscape of northern Wisconsin, USA , 2002 .

[6]  Ferenc Csillag,et al.  Wavelets, boundaries, and the spatial analysis of landscape pattern , 2002 .

[7]  J. C. McGrew,et al.  An Introduction to Statistical Problem Solving in Geography , 1993 .

[8]  Luca Ridolfi,et al.  On the spatial and temporal links between vegetation, climate, and soil moisture , 1999 .

[9]  Aslak Grinsted,et al.  Nonlinear Processes in Geophysics Application of the Cross Wavelet Transform and Wavelet Coherence to Geophysical Time Series , 2022 .

[10]  M. Fortin,et al.  Spatial patterns of soil temperature and moisture across subalpine forest-clearcut edges in the southern interior of British Columbia , 2003 .

[11]  A. Robock,et al.  Scales of temporal and spatial variability of midlatitude soil moisture , 1996 .

[12]  John M. Briggs,et al.  The effect of spatial scale on Konza landscape classification using textural analysis , 1989, Landscape Ecology.

[13]  Birgitta Svensson,et al.  Plants, insects and birds in semi-natural pastures in relation to local habitat and landscape factors , 2001, Biodiversity & Conservation.

[14]  L. Ji,et al.  Assessing vegetation response to drought in the northern Great Plains using vegetation and drought indices , 2003 .

[15]  Sylvie Galle,et al.  Relationships between soil moisture and growth of herbaceous plants in a natural vegetation mosaic in Niger , 1997 .

[16]  D. Kikodze,et al.  Facilitation by unpalatable weeds may conserve plant diversity in overgrazed meadows in the Caucasus Mountains , 2000 .

[17]  F. Chapin,et al.  SOIL HETEROGENEITY AND PLANT COMPETITION IN ANANNUAL GRASSLAND , 1997 .

[18]  Nathaniel A. Brunsell,et al.  Determination of scaling characteristics of AVHRR data with wavelets: Application to SGP97 , 2003 .

[19]  Mark R. T. Dale,et al.  The use of wavelets for spatial pattern analysis in ecology , 1998 .

[20]  Lori M. Bruce,et al.  Automated detection of subpixel hyperspectral targets with continuous and discrete wavelet transforms , 2001, IEEE Trans. Geosci. Remote. Sens..

[21]  Ferenc Csillag,et al.  On the measurement of diversity-productivity relationships in a northern mixed grass prairie (Grasslands National Park, Saskatchewan, Canada) , 2001 .

[22]  Yanhong Tang,et al.  Spatial pattern changes in aboveground plant biomass in a grazing pasture , 1998, Ecological Research.

[23]  R. M. Lark,et al.  Analysis and elucidation of soil variation using wavelets , 1999 .

[24]  C. Torrence,et al.  A Practical Guide to Wavelet Analysis. , 1998 .

[25]  The impact of using area-averaged land surface properties —topography, vegetation condition, soil wetness—in calculations of intermediate scale (approximately 10 km2) surface-atmosphere heat and moisture fluxes , 1997 .

[26]  Rudolf Richter.  Model SENSAT: a tool for evaluating the system performance of optical sensors , 1990, Defense, Security, and Sensing.

[27]  I. Gordon,et al.  Spatial distribution of upland beetles in relation to landform, vegetation and grazing management , 2002 .

[28]  Jiquan Chen,et al.  Vegetation responses to landscape structure at multiple scales across a Northern Wisconsin, USA, pine barrens landscape , 1999, Plant Ecology.

[29]  G. Griffiths,et al.  Landscape pattern and species richness; regional scale analysis from remote sensing , 2000 .

[30]  Wei Wei,et al.  The use of the Mexican Hat and the Morlet wavelets for detection of ecological patterns , 2005, Plant Ecology.

[31]  Ole Wendroth,et al.  State-space approach to spatial variability of crop yield , 1992 .

[32]  G. Bradshaw,et al.  Detecting climate-induced patterns using wavelet analysis. , 1994, Environmental pollution.

[33]  C. Osmond,et al.  Encyclopedia of plant physiology. New series. Volume 12B. Physiological plant ecology II. Water relations and carbon assimilation. , 2011 .

[34]  Agustín Lobo,et al.  Analysis of fine-scale spatial pattern of a grassland from remotely-sensed imagery and field collected data , 1998, Landscape Ecology.

[35]  David S. Stoffer,et al.  Time series analysis and its applications , 2000 .

[36]  S. Islam,et al.  EFFECTS OF SPATIAL VARIABILITY ON THE SCALING OF LAND SURFACE PARAMETERIZATIONS , 1997 .

[37]  M. Sebastià.  Role of topography and soils in grassland structuring at the landscape and community scales , 2004 .

[38]  Richard E. Farrell,et al.  Scale‐Dependent Relationship between Wheat Yield and Topographic Indices , 2004 .

[39]  Bing Cheng Si,et al.  Near‐saturated surface soil hydraulic properties under different land uses in the St Denis National Wildlife Area, Saskatchewan, Canada , 2004 .

[40]  D. Sims,et al.  Optimum pixel size for hyperspectral studies of ecosystem function in southern California chaparral and grassland , 2003 .

[41]  P. Teillet,et al.  Transformation of Atmospheric and Solar Illumination Conditions on the CCRS Image Analysis System , 1979 .

[42]  H. Olff,et al.  Interactions between above‐ and belowground biota: importance for small‐scale vegetation mosaics in a grassland ecosystem , 2000 .

[43]  R. Gardner,et al.  Quantitative Methods in Landscape Ecology , 1991 .

[44]  Frederick J. Swanson,et al.  Landform Effects on Ecosystem Patterns and Processes , 1988 .

[45]  Does extensification of rich grasslands alter the C and N cycles, directly or via species composition? , 2005 .

[46]  Christopher B. Field,et al.  Functional patterns in an annual grassland during an AVIRIS overflight , 1993 .

[47]  D. R. Nielsen,et al.  Spatial variability of wheat yield and soil properties on complex hills , 1988 .

[48]  S. Schmidtlein,et al.  Mapping of continuous floristic gradients in grasslands using hyperspectral imagery , 2004 .

[49]  S. Pickett,et al.  Spatial Heterogeneity During Succession: A Cyclic Model of Invasion and Exclusion , 1991 .

[50]  K. Beven,et al.  A physically based, variable contributing area model of basin hydrology , 1979 .

[51]  Robert K. Peet,et al.  Scale dependence of vegetation‐environment correlations: A case study of a North Carolina piedmont woodland , 1993 .

[52]  N. Nakagoshi,et al.  Responses of Cyperus brevifolius (Rottb.) Hassk. and Cyperus kyllingia Endl. to varying soil water availability , 2005 .

[53]  David J. Tongway,et al.  Spatial organisation of landscapes and its function in semi-arid woodlands, Australia , 1995, Landscape Ecology.

[54]  W. Cohen,et al.  An improved strategy for regression of biophysical variables and Landsat ETM+ data. , 2003 .

[55]  G. Hay,et al.  Remote Sensing Contributions to the Scale Issue , 1999 .

[56]  J. A. Schell,et al.  Monitoring vegetation systems in the great plains with ERTS , 1973 .

[57]  T. Spies,et al.  Characterizing canopy gap structure in forests using wavelet analysis , 1992 .

[58]  Robert H. Shumway,et al.  Time Series Analysis and Its Applications (Springer Texts in Statistics) , 2005 .

[59]  F. Csillag,et al.  The Influence of Vegetation Index and Spatial Resolution on a Two-Date Remote Sensing-Derived Relation to C4 Species Coverage , 2001 .

[60]  G. Hunt,et al.  Scale‐dependent correlations between the abundance of Brünnich's guillemots and their prey , 1999 .

[61]  D. Deering.  Measuring forage production of grazing units from Landsat MSS data , 1975 .

[62]  Robert V. O'Neill,et al.  Patternandscale: statistics for landscape ecology , 1991 .

[63]  Marie-Josée Fortin,et al.  Spacial patterns of soil temperature and moisture across subalpine forest-clearcut edges in the southern interior of British Columbia , 2003 .