BIOS:RISE Biodiversity and Disturbance: Raster based Investigations in Semi-arid Ecosystems

BE 2192/5-1(5-2,5-3)

Disturbances of several kind and intensity can lead to biodiversity loss and consequently to structural and functional changes in ecosystems. On the other hand disturbances are a key factor in maintaining biodiversity (WHITE and JENTSCH 2000). Especially in Europe human induced disturbances in terms of land use changes were primarily responsible for the present biodiversity. Biodiversity, in turn, plays a key role regarding the reaction of ecosystems to perturbations (TILMAN et al. 1998).

Land use change can be seen as alteration in a disturbance regime. In the context of sustainability the explanation and prediction of the consequences of land use change on spatial heterogeneity of vegetation cover and biodiversity is of great importance.

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Aims and Methods

We intend to develop methods which elucidate the impacts of human land use on spatial patterns of plant diversity. We investigate the characteristics of beta-diversity on several scales using proximity measures.

Perturbations cause intrinsic changes in diversity patterns. Therefore spatial diversity is a valuable tool in environmental assessment. If it were possible to quantify the impact of anthropogenic disturbances on spatial patterns of plant diversity, we could also predict potential changes in these patterns based on socio-economic scenarios.

Identifying patterns of biodiversity (e.g. by analysis of plant functional types) and how they are affected by disturbance and site conditions, is a chance to develop a method for the ecological assessment of perturbations which is not bound to taxonomic units. This would be of great importance, especially for developing countries, where floristic data is often lacking integrity.

The present changes in the biosphere affect, among other things, climate, depositions, the capacity and virtue of vectors, the distribution of land use models and their intensity. It is expected that these changes affect spatial patterns of diversity as well. Therefore we need methods to assess these changes quantitatively and effortlessly.

The investigations are meant to form a basis for future comparisons. They enable us to predict the impact of land use change on different scales. Our focus is not to completely monitor the phylogenetic diversity of a certain area but to develop a representative and functional method that is widely applicable.

Hypotheses:

1. Disturbances like human land use shape the spatial organization of beta-diversity in ecosystems.
2. Spatial patterns of qualitative diversity (beta-diversity) can be interpreted based on disturbance impacts, if site characteristics are considered.
3. The diversity of functional groups (i.e. PFT) is more closely related to spatial patterns of disturbance and site characteristics than plant species richness and therefore can be used as a measure of qualitative diversity.
   

Working program

We use a hierarchically nested sampling and anticipate that through the nested sampling approach we will find the scale on which disturbance induced changes in diversity emerge. To evaluate the impact of disturbances on biodiversity patterns we compare disturbed and undisturbed sites alongside a gradient. Additionally, we want to explore the possibilities of PFT's (plant functional types) to interpret patterns of diversity.

Found patterns will be related to disturbance events and site characteristics. The intersection of topographical space, biodiversity properties, disturbance regime and site characteristics will be processed inside a GIS. Multivariate data analysis will be used to analyse convergent tendencies of the data of several similarity spaces

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Field Sites

Plateau du Rekkam south west of Debdou/Morocco

The area of investigation is situated at the edge of the Plateau du Rekkam south west of Debdou/Morocco approximately 120 km from the Algerian Border at 34°N 3°W. Orographically favoured and therefore provided with a relative humid climate there is a forest enclave as an isolated outpost of mediterranean hard wood forest between the steppe ecosystems of the Plateau and those of the Moulouya valley. While down slope sparse Tetraclinis articulata-forests are found, the vegetation cover of the upper slope is dominated by Quercus ilex. In the whole region, which has been dominated by nomads throughout time, the population of privileged areas tends to settle to a form of semi-nomadism. The traditional farming is based on sheep and goats. Locally forest grazing is an important economic factor. From the settlements which are surrounded by irrigated and cultivated fields the cattle is driven to the wooded slopes, which leads to a high disturbance pressure on vegetation cover.

For this reason the region is especially suitable for the investigation described above: It can be seen as an example for human impact on biodiversity and therefore on his own resources for living. Through comparison with former investigations (BEIERKUHNLEIN 1985) we want to figure out changes in biodiversity. At the time of the former study the forecast was rather pessimistic ("If human impact leads to a further thinning of vegetation cover, under the current climatic and topographic conditions they are to anticipate intense erosion and irreversible damages."). Hence, temporal pattern are an additional point to the spatial patterns that will be examined.

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List of publications of this Project