UTILIZING INFORMATION ON SITE HYDROLOGY IN GROWTH AND YIELD MODELING: PEATLAND MODELS IN THE MOTTI STAND SIMULATOR

Abstract

In order to reliably and accurately forecast development of forest stands under different environmental circumstances, the prediction models included should flexible and adjustable to the features specific to each site. In addition to natural processes, the effects of various forestry operations has to be taken into account. In Finland, decision support system MOTTI has been designed to be applicable to both mineral soil and peatland sites. The system includes stand simulator with mortality and biomass dynamics predicted with empirical models. Because site hydrology significantly affects the growth pattern of trees in forested peatlands, trees on peatland sites have their specific growth models in which time since drainage operation has been used to describe the status of site water conditions. In MOTTI, the effect of first-time ditching and ditch network maintenance are modelled separately; the growth pattern of trees following the first-time ditching is predicted as a function of time, and the response of stand growth to ditch network maintenance is predicted as a function of geographical location, site quality, stand stocking, and time. Impairment of ditches is described with a probabilistic model that indicates the need to make ditch-network maintenance and is based on time since ditching, geographical location, and depth of the organic layer. By linking together the different models, MOTTI can be used as a tool to plan common management operations in peatland stands.