Effects of vegetation heterogeneity and surface topography on spatial scaling of net primary productivity

Due to the heterogeneous nature of the land surface, spatial scaling is an inevitable issue in the development of land models coupled with low-resolution Earth system models (ESMs) for predicting land-atmosphere interactions and carbon-climate feedbacks. In this study, a simple spatial scaling algorithm is developed to correct errors in net primary productivity (NPP) estimates made at a coarse spatial resolution based on sub-pixel information of vegetation heterogeneity and surface topography. An eco-hydrological model BEPS-TerrainLab, which considers both vegetation and topographical effects on the vertical and lateral water flows and the carbon cycle, is used to simulate NPP at 30 m and 1 km resolutions for a 5700 km 2 watershed with an elevation range from 518 m to 3767 m in the Qinling Mountain, Shanxi Province, China. Assuming that the NPP simulated at 30 m resolution represents the reality and that at 1 km resolution is subject to errors due to sub-pixel heterogeneity, a spatial scaling index (SSI) is developed to correct the coarse resolution NPP values pixel by pixel. The agreement between the NPP values at these two resolutions is improved considerably from R 2 = 0.782 to R 2 = 0.884 after the correction. The mean bias error (MBE) in NPP modelled at the 1 km resolution is reduced from 14.8 g C m −2 yr −1 to 4.8 g C m −2 yr −1 in comparison with NPP modelled at 30 m resolution, where the mean NPP is 668 g C m −2 yr −1 . The range of spatial variations of NPP at 30 m resolution is larger than that at 1 km resolution. Land cover fraction is the most important vegetation factor to be considered in NPP spatial scaling, and slope is the most important topographical factor for NPP spatial scaling especially in mountainous areas, because of its influence on the lateral water redistribution, affecting water table, soil moisture and plant growth. Other factors including leaf area index (LAI) and elevation have small and additive effects on improving the spatial scaling between these two resolutions.

[1]  Jing M. Chen,et al.  Quantifying the effect of canopy architecture on optical measurements of leaf area index using two gap size analysis methods , 1995, IEEE Trans. Geosci. Remote. Sens..

[2]  S. Pacala,et al.  A METHOD FOR SCALING VEGETATION DYNAMICS: THE ECOSYSTEM DEMOGRAPHY MODEL (ED) , 2001 .

[3]  G. Bonan,et al.  Influence of Subgrid-Scale Heterogeneity in Leaf Area Index, Stomatal Resistance, and Soil Moisture on Grid-Scale Land–Atmosphere Interactions , 1993 .

[4]  J. Chen,et al.  Net primary productivity distribution in the BOREAS region from a process model using satellite and surface data , 1999 .

[5]  Claudia Notarnicola,et al.  Topographical and ecohydrological controls on land surface temperature in an alpine catchment , 2010 .

[6]  Josef Cihlar,et al.  Net primary productivity mapped for Canada at 1-km resolution , 2002 .

[7]  M. Tamura,et al.  Integrating remotely sensed data with an ecosystem model to estimate net primary productivity in East Asia , 2002 .

[8]  Weimin Ju,et al.  Spatially explicit simulation of peatland hydrology and carbon dioxide exchange: Influence of mesoscale topography , 2008 .

[9]  R. D. Black,et al.  An Experimental Investigation of Runoff Production in Permeable Soils , 1970 .

[10]  J. Kimball,et al.  The effects of spatial aggregation of complex topography on hydroecological process simulations within a rugged forest landscape: development and application of a satellite-based topoclimatic model , 2004 .

[11]  Jing Chen,et al.  Net primary productivity following forest fire for Canadian ecoregions , 2000 .

[12]  Jing Chen,et al.  Spatial scaling of evapotranspiration as affected by heterogeneities in vegetation, topography, and soil texture , 2006 .

[13]  S. Running,et al.  A general model of forest ecosystem processes for regional applications I. Hydrologic balance, canopy gas exchange and primary production processes , 1988 .

[14]  Jing M. Chen,et al.  Evaluation of leaf-to-canopy upscaling methodologies against carbon flux data in North America , 2012 .

[15]  Francis H. S. Chiew,et al.  Effect of sub‐grid‐scale variability of soil moisture and precipitation intensity on surface runoff and streamflow , 2001 .

[16]  A. R. Sibbald,et al.  Scaling up of a mechanistic dynamic model in a GIS environment to model temperate grassland production at the regional scale , 2006 .

[17]  Jing M. Chen,et al.  Daily canopy photosynthesis model through temporal and spatial scaling for remote sensing applications , 1999 .

[18]  Paul G. Jarvis,et al.  Scaling processes and problems , 1995 .

[19]  Günter Blöschl,et al.  Observed spatial organization of soil moisture and its relation to terrain indices , 1999 .

[20]  R. Grant.  Modeling topographic effects on net ecosystem productivity of boreal black spruce forests. , 2004, Tree physiology.

[21]  B. Ambroise.  Topography and the water cycle in a temperate middle mountain environment: the need for interdisciplinary experiments , 1995 .

[22]  H. Mooney,et al.  Modeling the Exchanges of Energy, Water, and Carbon Between Continents and the Atmosphere , 1997, Science.

[23]  Jan M. H. Hendrickx,et al.  Down-scaling of SEBAL derived evapotranspiration maps from MODIS (250 m) to Landsat (30 m) scales , 2011 .

[24]  M. Stokes,et al.  An Introduction to Tree-Ring Dating , 1996 .

[25]  W. Ju,et al.  Effects of topography on simulated net primary productivity at landscape scale. , 2007, Journal of environmental management.

[26]  Weimin Ju,et al.  Distributed hydrological model for mapping evapotranspiration using remote sensing inputs , 2005 .

[27]  Malcolm G. Anderson,et al.  The role of topography in controlling throughflow generation , 1978 .

[28]  M. Wigmosta,et al.  A distributed hydrology-vegetation model for complex terrain , 1994 .

[29]  Jan M. H. Hendrickx,et al.  DOWN-SCALING OF SEBAL DERIVED EVAPOTRANSPIRATION MAPS 1 FROM MODIS ( 250 m ) TO LANDSAT ( 30 m ) SCALE 2 3 , 2009 .

[30]  Jing M. Chen,et al.  Effects of lateral hydrological processes on photosynthesis and evapotranspiration in a boreal ecosystem , 2011 .

[31]  R. B. Jackson,et al.  A global analysis of root distributions for terrestrial biomes , 1996, Oecologia.

[32]  I. D. Moore,et al.  Topographic Effects on the Distribution of Surface Soil Water and the Location of Ephemeral Gullies , 1988 .

[33]  Günter Blöschl,et al.  Preferred states in spatial soil moisture patterns: Local and nonlocal controls , 1997 .

[34]  Eric F. Wood,et al.  Effects of Digital Elevation Model Accuracy on Hydrologic Predictions , 2000 .

[35]  J. Chen,et al.  A process-based boreal ecosystem productivity simulator using remote sensing inputs , 1997 .

[36]  Jianguo Wu,et al.  Dealing with Scale in Landscape Analysis: An Overview , 2000, Ann. GIS.

[37]  P. Jarvis.  The Interpretation of the Variations in Leaf Water Potential and Stomatal Conductance Found in Canopies in the Field , 1976 .

[38]  R. Dickinson,et al.  The Common Land Model , 2003 .

[39]  Qijiang Zhu,et al.  Spatial distribution of net primary productivity and evapotranspiration in Changbaishan Natural Reserve, China, using Landsat ETM+ data , 2004 .

[40]  G. Campbell,et al.  An Introduction to Environmental Biophysics , 1977 .

[41]  J. Chen.  Spatial Scaling of a Remotely Sensed Surface Parameter by Contexture , 1999 .

[42]  J. Pisek,et al.  Effects of foliage clumping on the estimation of global terrestrial gross primary productivity , 2012 .

[43]  Philippe Ciais,et al.  A framework for benchmarking land models , 2012 .

[44]  J. Berry,et al.  A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species , 1980, Planta.

[45]  S. Archer,et al.  Spatial scaling of ecosystem C and N in a subtropical savanna landscape , 2009 .

[46]  Jing M. Chen,et al.  Mapping evapotranspiration based on remote sensing: An application to Canada's landmass , 2003 .

[47]  Jing Chen,et al.  Spatial scaling of net primary productivity using subpixel information , 2004 .

[48]  B. Fu,et al.  Soil moisture variation in relation to topography and land use in a hillslope catchment of the Loess Plateau, China , 2001 .