Work package 5
- Published: Monday, 16 January 2012 13:09
- Written by Joost Vlaming (SU)
Landscape assessments on thresholds dynamics
- To assess the changes in structure (biodiversity and pattern), functional status, and provision of services of the CASCADE dryland ecosystems that have experienced severe degradation and regime shifts.
- To evaluate the potential for restoring ecosystem structure and functioning from degraded stages resulting from regime shifts.
Description of work and role of partners
The main objective of WB5 is to investigate the regime shifts in the CASCADE dryland sites (rangelands, steppes, scrublands, arable land, and woodlands). Common indicators will be used for assessing major structural and functional changes in vegetation composition and (spatial) structure and related ecosystem services that results in regime shifts. Results of WB5 will be used to test models developed in WB6. Furthermore, for a selection of dryland ecosystems in which several restoration actions have been applied, we will follow the same approach in order to evaluate potential tipping points and thresholds for restoration success. Positively evaluated preventive and restorative land management will feed into a thorough assessment process in WB7.
Task 1: Site-specific characterisation of regime shifts
We use the SER definition for degraded ecosystems (Society for Ecological Restoration International, http://www.ser.org) : Ecosystems that have lost integrity and health as the direct or indirect result of human activities. In some cases, these impacts to ecosystems have been caused or aggravated by natural agencies such as wildfire, floods, storms, or volcanic eruption, to the point at which the ecosystem cannot recover its pre-disturbance state or its historic developmental trajectory. Degraded ecosystems have permanently reduced their capacity to provide services. Degradation is described in terms of loss of ecosystem structure and function. Table 7.1 lists the degradation indicators selected for the six study sites, most of them related to changes (often loss) of plant cover, and changes in plant cover pattern and plant species composition. CASCADE addresses a variety of driving factors, such as grazing/browsing, droughts, wildfires, aquifer overexploitation (see WB2) that may lead dryland ecosystems to regime shifts, and will consider a wide range of Mediterranean dryland ecosystems, including croplands, rangelands, steppes, shrublands and woodlands. Depending on the target ecosystem in the CASCADE study sites, the relevant ecosystem functions and services at risk may vary. Task 1 will assess and describe the main site-specific structural and functional changes resulting from the degradation process.
Task 2:Plant pattern dynamics and overall ecosystem functioning
In all sites we will use a common methodology to assess ecosystem degradation processes and shifts (WB5, task 2), both in terms of structure (spatial plant pattern) and function (soil functioning indices). The degree of ecosystem degradation is assessed comparing those indices in the disturbed ecosystem with respect to the reference ecosystem in the same region, the reference representing the pre-disturbance state. Permanent changes of disturbed ecosystems with respect to reference ecosystems will indicate regime shift. To assess the degradation in terms of loss of ecosystems services, a minimum set of ecosystem service indicators will be analysed in all sites, e.g. land productivity, water and soil conservation, carbon sequestration, and biodiversity. In order to harmonize the assessment of regime shifts in the various types of ecosystems and to frame it in a general conceptual model, a small number of common indicators of plant pattern and ecosystem functioning will be assessed in all sites. Changes in plant spatial pattern will be assessed through both aerial images (of varying resolution and extent depending on the patterns assessed) and ground-based assessment. From these images a simple indicator of bare-soil connectivity, flowlength will be estimated. Other indicators that will be considered are increased variability in vegetation patterns, decrease of organic carbon, soil water repellency and soil compaction. Changes in overall ecosystem functioning will be assessed through soil functioning indices.
Task 3: Restoration potential
For a selected set of degraded drylands where restoration actions have been applied, WB5 will assess the impact of restoration on the structure and function of the degraded ecosystems, By comparing with both degraded and functional areas, WB5 and will evaluate the potential of these restoration actions for reversing the degradation status of the target ecosystems assessed. Inputs from WB2 on selected driving forces will be related to WB5 field assessment on regime shifts and sudden changes in the provision of ecosystem services. WB3 and WB4 will provide insights into the mechanisms involved and the factors modulating the changes. Results from WB5 will feed into the modelling tasks (WB6) and will be complemented by the assessment of the management strategies implemented in the various field sites (WB7).