Scaling up of a mechanistic dynamic model in a GIS environment to model temperate grassland production at the regional scale

Regional-scale ecological processes are mediated by processes occurring at local scales. Spatially explicit models are needed to understand the broad-scale consequences of a large number of local processes, driven by factors which are heterogeneous at a broad scale. A Geographic Information System (GIS)-based mechanistic model, which can be used as a flexible tool to investigate the regional-scale effects of changes in environmental factors on herbage production from a Lolium perenne sward, was developed and used to investigate the consequences of aggregating driving variables at different resolutions. The model allows rigorous scaling up of previously existing field-based modelling approaches within a GIS context. The model's mechanistic approach allows flexibility in the simulation of the separate effects of environmental driving variables and of cutting regimes. The driving variables (temperature, solar radiation, available soil moisture and soil nitrogen status) are scaled up using geostatistical techniques. The model is used to evaluate weekly changes in herbage production under environmental conditions, variable both in space and time, under different cutting regimes. It is shown that, in this model, aggregation at 1 km2 is a good compromise between accuracy and practical feasibility, and that, while ignoring heterogeneity over many square kilometres can induce large errors, their magnitude and direction also depend on the model response curve to an input variable. The results obtained were consistent with the known trends in influential environmental factors. The programming within a GIS makes the model flexible in its application and, therefore, makes it easy to apply at a variety of scales.

[1]  I. R. Johnson,et al.  A model of instantaneous and daily canopy photosynthesis , 1984 .

[2]  F. Woodward,et al.  A Nitrogen-led Model of Grass Growth , 1996 .

[3]  P. Reich,et al.  Functional traits, productivity and effects on nitrogen cycling of 33 grassland species , 2002 .

[4]  C. Hays,et al.  Comparison of Agricultural Impacts of Climate Change Calculated from High and Low Resolution Climate Change Scenarios: Part I. The Uncertainty Due to Spatial Scale , 2001 .

[5]  I. R. Johnson,et al.  Dynamic model of the response of a vegetative grass crop to light, temperature and nitrogen , 1985 .

[6]  C. Topp,et al.  Simulating the impact of global warming on milk and forage production in Scotland: 1. The effects on dry-matter yield of grass and grass-white clover swards , 1996 .

[7]  W. Parton,et al.  The role of cattle in the volatile loss of nitrogen from a shortgrass steppe , 1986 .

[8]  Nicholas J. Hutchings,et al.  A model of the grazing of hill vegetation by sheep in the UK. I. The prediction of vegetation biomass , 1997 .

[9]  Jørgen E. Olesen,et al.  Comparison of scales of climate and soil data for aggregating simulated yields of winter wheat in Denmark. , 2000 .

[10]  K. Matthews,et al.  A soil wetness class map for Scotland: New assessments of soil and climate data for land evaluation , 1994 .

[11]  Gianni Bellocchi,et al.  An indicator of solar radiation model performance based on a fuzzy expert system , 2002 .

[12]  M. Field,et al.  The meteorological office rainfall and evaporation calculation system -- MORECS , 1983 .

[13]  Mark A. Sutton,et al.  Coupling soil-plant-atmosphere exchange of ammonia with ecosystem functioning in grasslands , 2002 .

[14]  C. Hays,et al.  Comparison of Agricultural Impacts of Climate Change Calculated from High and Low Resolution Climate Change Scenarios: Part II. Accounting for Adaptation and CO2 Direct Effects , 2001 .

[15]  Edzer Pebesma,et al.  Spatial aggregation and soil process modelling , 1999 .

[16]  Anthony J. Parsons,et al.  A Spatially Explicit Population Model of Stoloniferous N-Fixing Legumes in Mixed Pasture with Grass , 1996 .

[17]  F. Bormann,et al.  Transport and Loss of Nitrous Oxide in Soil Water After Forest Clear-Cutting , 1986, Science.

[18]  Bingru Huang,et al.  Physiological Responses to Heat Stress Alone or in Combination with Drought: A Comparison between Tall Fescue and Perennial Ryegrass , 2001 .

[19]  J. Briggs,et al.  Controls of nitrogen limitation in tallgrass prairie , 1991, Oecologia.

[20]  R. G. Hurd,et al.  An Analysis of the Growth of Young Tomato Plants in Water Culture at Different Light Integrals and CO2 ConcentrationsII. A Mathematical Model , 1974 .

[21]  P.E.V. Williams,et al.  Animal production and European pollution problems , 1995 .

[22]  The effect of stocking rate and fertilizer usage on income variability for dairy farms in England and Wales , 1984 .

[23]  I. Johnson,et al.  Modelling Photosynthesis in Monocultures and Mixtures , 1989 .

[24]  M. Cannell,et al.  Temperate Grassland Responses to Climate Change: an Analysis using the Hurley Pasture Model , 1997 .

[25]  H. H. Laar,et al.  Products, requirements and efficiency of biosynthesis: a quantitative approach. , 1974, Journal of theoretical biology.

[26]  Wilfred M. Post,et al.  The use of models to integrate information and understanding of soil C at the regional scale , 1997 .

[27]  A M MacDonald,et al.  The impact of climate change on the soil/moisture regime of Scottish mineral soils. , 1994, Environmental pollution.

[28]  I. R. Johnson,et al.  A Model of Grass Growth , 1983 .

[29]  I. R. Johnson,et al.  Vegetative crop growth model incorporating leaf area expansion and senescence, and applied to grass , 1983 .

[30]  J. Goudriaan,et al.  ON APPROACHES AND APPLICATIONS OF THE WAGENINGEN CROP MODELS , 2003 .

[31]  Gilles Lemaire,et al.  Growth Rate and % N of Field Grown Crops: Theory and Experiments , 1991 .

[32]  K. Moore,et al.  The importance of local processes to landscape patterns of grassland vegetation diversity , 2004 .

[33]  Bryant,et al.  Acclimation of photosynthesis to elevated CO2 under low-nitrogen nutrition is affected by the capacity for assimilate utilization. Perennial ryegrass under free-Air CO2 enrichment , 1998, Plant physiology.

[34]  David L. Strayer,et al.  What kind of spatial and temporal details are required in models of heterogeneous systems , 2003 .

[35]  Spatio-temporal modelling of broad scale heterogeneity in soil moisture content: a basis for an ecologically meaningful classification of soil landscapes , 2004, Landscape Ecology.