A Simulation Model of Mesophytic Perennial Grasslands

Abstract

Grasslands are complex ecosystems and their processes are affected by soil, meteorological, and management variables. In this context, dynamic simulation models are useful to understand these processes and to design grassland use strategies. The aim of this study was to develop and validate a simulation model of perennial pasture growth based on soil and climate variables. A first approach considered that soil fertility levels were adequate; therefore, soil water availability and phytomass level were the main variables affecting pasture growth. The subroutines considered were water balance, pasture growth, and root biomass dynamics. The hypotheses regarding the functioning of the system were formulated as a group of equations which were solved numerically with a program written in Visual Basic®. Model validation was performed by statistical comparison between simulated DM and DM obtained from experiments conducted in Valdivia (39º47' S., 73º15' W; 9 m a.s.l.). In these experiments we measured DM accumulation on naturalized grassland and ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pastures under frequent defoliation. Soil data, temperature, solar radiation, and rainfall were obtained from a meteorological station located in Valdivia. The coefficient of determination between simulated values and those measured in the experiments were higher in the DM accumulation (R 2 = 98%) simulations. When pasture was subjected to frequent defoliation, the degree of fit of the model was lower (R 2 = 60%); however, the model was able to predict the trend in the data.

Carrying capacity of a high Andean pasture for the conservation and sustainable management of vicuña

“…No existen problemas de salinidad. Castellaro et al (2012) argumentan los pastizales son ecosistemas complejos y sus procesos se ven afectados por el suelo, las variables meteorológicas y de gestión.…”

Integrating models across temporal and spatial scales to simulate landscape patterns and dynamics in mountain pasture-woodlands

“…To date, pasture modelling has focused on grass dynamics without considering interactions with woody vegetation and cattle (e.g., Jouven et al 2006;Trnka et al 2006;Castellaro et al 2012), while simulations of woody encroachment in semi-natural grasslands focused on tree dynamics and ignored herbaceous plants and grazing by livestock (e.g., Mairota et al 2014). Models that include grazing, pasture management and interactions between woody and non-woody plants are typically developed for very fine spatial grains and small spatial extents (e.g., cell size of 1-5 m 2 and total extent of 2 ha; Lohmann et al 2012;Komac et al 2013), which do not reflect the typical size of pasture management units (i.e., [50 ha).…”