A Simulation Model for Decomposition in Grasslands

Abstract

A model has been developed to simulate the dynamics of decomposers and substrates in grasslands. Sub~trates r~presented are humic material, feces, and dead plant and animal remains. Exc~pt for humic ma~enal, sub_strates are fur!her divid_ed _into a rapidly and a slowly decomposing f~actwn. The proportiOn of rapidly decomposmg matenal m a substrate is predicted from its initial mtroge_n content. The bel_owground P?r~ion of ~he system is divided into layers because temperature and soil water.' the most Important dnvmg vanables for the model, vary with depth. Decomposition rates are pr~dicted from temperature, water tension, and inorganic nitrogen concentration.T~xon?mic groups o~ decomposers are not distinguished, but a distinction is made between active an~ m_active states, which differ in respiration rate, in death rate, and in that only active decomposers assimilate substrate.The model's pre~ictions comp~re favora~ly t? data on COz evolution and to litter bag experiments, but not to ATP esti~ates of active microbial biOmass. The model indicates a profound influence of depth o~ _decompositiOn rates and on decomposer biomass dynamics, growth yield, and secondary productivity.

Decomposition and nutrient dynamics of litter from four species of freshwater emergent macrophytes

“…Equation 1 is valid only for temperatures greater than 0 "C; we assumed that dW/dt =0 for T< 0 "C. Equation 1 was subsequently modified so as to distinguish between the decay of labile material and the persistence of refractory material. The need for a modification of decomposition models to include both labile and refractory parts was noted by Bunnell et al (1977), Hunt (1978), Heal et a/. Wieder &Lang (1982).…”

“…These processes are regulated by a complex array of variables; two of the most important factors are climate and substrate chemical quality. Climatic variables that influence decomposition include temperature, moisture, and evapotranspiration (Bunnell et al, 1977;Hunt, 1978;Meentemeyer, 1978;Howard & Howard, 1979;Boddy, 1983). Decomposition of litter has also been shown to be affected by such factors as the C:N ratio, initial nutrient levels, and ligninlignocellulose content (Witkamp, 1966;Fogel & Cromack, 1977;Godshalk & Wetzel, 1978;Aber & Melillo, 1980;Schlesinger & Hasey, 1981;Berg et al, 1982;Melillo et al, 1982;Hodson et al, 1984).…”

Organic matter flow in the food web at a temperate heath under multifactorial climate change

“…The integration of nutrient availability with carbon sequestration in decomposition and terrestrial carbon cycle models may include the biomass of active and inactive microbial and detritivore decomposers. [6,32,33] However, in a study where 13 C-labelled detritus and prey biomass were artificially increased, the density response of detritivore Collembola was related to increase of detritus, while the observed stable density of predator spiders still gained energy from Collembola. [34] Oelbermann et al [34] concluded that such a lack of response to resource supplementation is not necessarily due to the absence of a trophic linkage, but may be caused by compensatory changes in mortality factors, such as cannibalism, intraguild predation or prey quality.…”

Seasonal Variation of Carbon and Nitrogen Emissions from Turfgrass

“…A double, four-parameter exponential decay model (Equation (1)) [13] [20], simulating decomposers and substrates (labile and the recalcitrant constants) dynamics in grasslands, was used to describe the decay pattern. …”