Summary

Activity 2.2 Landscape Processes
Project Coordinator: Sandra Lavorel

Overview

Task 2.2.1 Responses of Vegetation to Land Use and Disturbance

Gaining a generic understanding of the effects of changes in natural and human disturbance regimes on landscape vegetation patterns requires the development of a conceptual framework based on the characterization of plant species response to disturbance. Previous GCTE research has contributed to the development of plant functional classifications to describe response to climate and atmospheric changes. Vegetation response to a given change in disturbance regime depends both on the long and short-term disturbance history of the local flora, and the resulting landscape patterns. Therefore the identification of plant functional groups for response to disturbance needs to operate in a comparative manner across regions with different disturbance and land use histories. Analysis of relationships between disturbance regime and species traits will be used to build functional groups based on species response to a given disturbance type. Landscape-scale models will then be developed to analyze the interactions between landscape pattern, vegetation functional group composition, and disturbance regimes. Simulations will be run for regions having different functional group spectra, landscape patterns and disturbance histories.

Task 2.2.2 Relationships between Global Change and Fire Effects at Landscape Scales

Fire is a major disturbance that will be influenced by climate, direct effects of CO2 on vegetation, and land use, and will in turn feed back to landscape pattern and processes. Because fire affects ecosystems across a broad range of temporal and spatial scales, its inclusion within a framework that predicts changes in vegetation dynamics and ecosystem processes as a consequence of climate, atmospheric and land use changes is problematic. This Task will identify the inputs and outputs of data and models (e.g., weather, succession, ecosystem processes, etc.) required to design fire simulation approaches that can predict fire effects over extensive spatial and temporal scales. Along with assessment of fire regimes produced by changing weather patterns, the effect of human intervention will be included in model structures. Systematic model comparisons across a variety of models that operate at different spatial and temporal scales will be designed to 1) identify important processes that influence fire dynamics, and 2) examine effects of the spatial and temporal scales of data and simulation methods. Results will be used for the development of a DGVM fire module.

Task 2.2.3 Plant dispersal and migration modelling 

Landscape, regional, and global models need to incorporate realistic dispersal and migration functions to capture species range shifts like those that happened after glaciations. Today the extent and connectivity of habitat is being changed by humans and is likely to impede migration. Sucessful modeling of dispersal and migration should identify how landscape structures will interact with climatic change and ecological processes to determine future distributions. First, data-based functions are needed to improve current landscape dispersal models. These data will be used for model comparisons on different landscapes in order to examine how much landscape fragmentation can impede species migration, and to identify dispersal- or recruitment-limited taxa or groups. Further comparisons will assess the sensitivity to dispersal of a variety of landscape models of vegetation dynamics. The scaling properties derived for dispersal functions on differing landscapes will form the basis to derive rules for use in DGVMs or regional scale vegetation models. The implementation of this Task will operate through a network where empiricists and modelers will collaborate. Exchanges with pest dispersal modelers and paleo-ecologists will also be encouraged.

Task 2.2.4 Linking Changing Landscape Pattern and Ecosystem 

Many ecological processes of interest in global change studies, such as productivity, biogeochemical cycling, and water and energy exchange, operate at a number of scales. This Task deals with the effects of the mechanisms of changes in landscape patterns on ecosystem functioning, and how these effects are expressed in the larger scale (landscape and higher) functioning. Critical questions to be addressed in this Task are:

1. When can indicators of ecosystem functioning be simply aggregated as an area-weighted sum of local values, and when, on the contrary, do distribution and patchiness of landscape elements affect these summations?
2. For a given landscape what are the dominant mechanisms causing such non-linearity, and how do they change over time?

The answers to these questions, obtained through analyses of data collected along GCTE transects and at other target sites, will be needed to predict the interactive effects of global change drivers on the relationship between landscape complexity and ecosystem functioning. Heuristic models that examine the interactions of cross-scale processes with patch scale dynamics will be developed.