Evaluating the accuracy and generality of a hybrid patch model

Abstract

Forest patch models have been used extensively to simulate vegetation development under current and changing environmental conditions. However, their physiological foundation is subject to criticism and recent validation experiments against long-term growth and yield data have shown major deficiencies in reproducing observed growth patterns of mixed-species forests. Here we describe the modified forest patch model PICUS Version 1.3, a model variant that couples the structurally detailed three-dimensional patch model PICUS Version 1.2 and the physiologically based stand-level production module of the 3-PG (Physiological Principles in Predicting Growth) model. The approach attempts to combine the ability of PICUS v1.2 to simulate forest dynamics on time scales relevant to forest succession with a simplified but successful production model based on the concept of radiation-use efficiency. We evaluated the hybrid model in a series of simulation experiments. Results indicated a realistic response to a climate sensitivity experiment: the response to environmental gradients was well captured both in terms of productivity on time scales of a rotation length and of forest succession over several hundreds of years. Testing against independent long- term growth and yield data revealed good correspondence between observed and predicted values of volume production and stand structure. Further model development should include a dynamic soil component to consider effects of nutrient cycling.

Modelling bark beetle disturbances in a large scale forest scenario model to assess climate change impacts and evaluate adaptive management strategies

“…PICUS v1.41 is a modular forest modelling framework centred around a hybrid patch model which incorporates a number of flexible sub-models for scenario analysis (e.g., forest management, bark beetle damage, rockfall protection; Seidl et al 2005;Seidl et al 2007a;Woltjer et al 2008). Here, besides a brief overview of the general model logic the bark beetle disturbance sub-model will be described in more detail.…”

“…Inter-and intra-species competition, seed dispersal and mortality are modelled based on the approach presented by Lexer and Hönninger (2001) whereas stand level net primary production is modelled according to the simplified physiological principles of radiation use efficiency of the 3-PG model (Landsberg and Waring 1997). The hybridisation of both concepts is described in Seidl et al (2005). The model has been successfully evaluated with regard to the simulation of equilibrium species composition over broad environmental gradients in the Eastern Alps as well as against long-term growth and yield data of uneven-aged, multi-species stands (Seidl et al 2005).…”

“…The hybridisation of both concepts is described in Seidl et al (2005). The model has been successfully evaluated with regard to the simulation of equilibrium species composition over broad environmental gradients in the Eastern Alps as well as against long-term growth and yield data of uneven-aged, multi-species stands (Seidl et al 2005). The latest version of PICUS v1.41 includes a process-based soil model of dynamic C and N cycling (Currie et al 1999) addressing interactions between aboveground production processes and belowground C and N dynamics (cf.…”

“…The development of a bark beetle disturbance module for the EFISCEN framework built on the hybrid stand level model PICUS v1.41 (Lexer and Hönninger 2001;Seidl et al 2005) which includes a detailed sub-model of bark beetle induced mortality of Norway spruce (Seidl et al 2007a). A two-stage meta-modelling approach was used to extract process behaviour from PICUS and integrate it into EFISCEN.…”

Un modèle générique des effets de l’éclaircie et de la densité des peuplements sur la croissance des forêts, la mortalité et l’accroissement net

“…If Monarch birch is excluded, our range of q is between 0.06 and 0.321. For additional assessment of q variability, a simulation experiment was conducted with the hybrid patch model PICUS v1.4 (Seidl et al, 2005) that models mortality at the individual tree level. Starting from generic homogeneous initial stand conditions 100 y simulations over an array of species and environmental conditions (cf.…”