Change and variation in a hyer-arid cultural landscape: A merhodological approach using remote sensing timeseries (Landsat MSS and TM, 1973-1996) from the Wadi vegetation of the eastern desert of Egypt

Nine wadi localities in a hyper-arid environment have been registered in the field and studied using earth observation data. Branch height, crown – and trunk – diameter, and indicators of land-use such as present traces of browsing, lopping and charcoal production were registered for arboreal vegetation, mostly Acacia tortilis and Balanites aegyptiaca. A point mapping (GPS) was selected to optimise subsequent integration with raster data and to facilitate a detailed interpretation of change images. Field data and change images are interpreted according to two gradients, one cultural and one hydrological. Derived tree maps are overlaid referenced TM data in order to detect differences between pixels with and without vegetation. The Red band is the most consistent spectral band in its content of vegetation information. Nevertheless it is apparent that several methodological and technical factors constrain the possibilities to register vegetation in this environment of very scarce vegetation cover. Similar problems are also recognised in the change analysis which is based on the difference between Red bands of the years compared. Four different datasets are part of the analysis: 1973, 1979, 1984 (all Landsat MSS images) and 1996 (TM). Field data indicate that changes are taking place in the cultural landscape of the Eastern Desert, and the change is primarily due to processes that both in causes and consequences is associated with ‘deforestation’. Although several sources of errors introduce variations in the change images, the images do reflect the field observations

Longevity and growth of Acacia tortilis; insights from 14C content and anatomy of wood

Background: Acacia tortilis is a keystone species across arid ecosystems in Africa and the Middle East. Yet, its life-history, longevity and growth are poorly known, and consequently ongoing changes in tree populations cannot be managed in an appropriate manner. In other arid areas parenchymatic bands marking growth zones in the wood have made dendrochronological studies possible. The possibilities for using pre- and post-bomb 14C content in wood samples along with the presence of narrow marginal parenchymatic bands in the wood is therefore tested to gain further insight into the age, growth and growth conditions of A. tortilis in the hyper-arid Eastern Desert of Egypt. Results: Based on age scenarios and the Gompertz growth equation, the age of trees studied seems to be from 200 up to 650 years. Annual radial growth estimated from calibrated dates based on the post-bomb 14C content of samples is up to 2.4 mm, but varies both spatially and temporally. Parenchymatic bands are not formed regularly. The correlation in band pattern among trees is poor, both among and within sites. Conclusion: The post-bomb 14C content of A. tortilis wood gives valuable information on tree growth and is required to assess the age scenario approach applied here. This approach indicates high longevities and slow growth of trees. Special management measures should therefore be taken at sites where the trend in tree population size is negative. The possibilities for dendrochronological studies based on A. tortilis from the Eastern Desert are poor. However, marginal parenchymatic bands can give insight into fine scale variation in growth conditions and the past management of trees

Mortality, Recruitment and Change of Desert Tree Populations in a Hyper-Arid Environment

BACKGROUND: Long-term vegetation changes in hyper-arid areas have long been neglected. Mortality, recruitment and change in populations of the ecologically and culturally important and drought persistent Acacia tortilis and Balanites aegyptiaca are therefore estimated in the Eastern Desert of Egypt, and are related to the primary agents of change, water conditions and human intervention. METHODOLOGY: A change analysis using high-resolution Corona images (1965) in combination with field data (2003) is the basis for recruitment, mortality and change estimates. For assessing the influence of water conditions on patterns in recruitment and survival, different types of generalized linear models are tested. CONCLUSIONS: The overall trend in population size in that part of the Eastern Desert studied here is negative. At some sites this negative trend is alarming, because the reduction in mature trees is substantial (>50%) at the same time as recruitment is nearly absent. At a few sites there is a positive trend and better recruitment. Frequent observations of sprouting in saplings indicate that this is an important mechanism to increase their persistence. It is the establishment itself that seems to be the main challenge in the recruitment process. There are indications that hydrological variables and surface water in particular can explain some of the observed pattern in mortality, but our results indicate that direct human intervention, i.e., charcoal production, is the main cause of tree mortality in the Eastern Desert

Acacia trees on the cultural landscapes of the Red Sea Hills

This paper examines interactions between five pastoral nomadic culture groups of the Egyptian and Sudanese Red Sea Hills and the acacia trees Acacia tortilis (Forssk.) Hayne subsp. tortilis and subsp. raddiana growing in their arid environments. A. tortilis is described as a keystone species both ecologically and culturally: the trees play such critical roles in ecosystems and social groups that their removal would greatly impact both systems. Interviews in the field with the Semitic, Arabic-speaking Ma‘aza and Ababda, and the Cushitic, Beja, Bidhaawyeet-speaking Bishaari, Amar Ar and Hadandawa nomads probed the cultural and ecological contexts of acacias in pastoral nomadism, revealing deep insight into traditional ecological knowledge and traditional perceptions and uses of the trees. The paper describes how this knowledge guides pastoral decision-making, with acacias as a particularly critical component of the pastoral livelihood in both normal and stressful circumstances. A. tortilis is the most important reliable vegetation resource for nomads while also providing fuel and other useful products, ecosystem services for people and animals, and increased biodiversity by providing diverse microhabitats and resources for other species. We describe aspects of kinship, territorial organization, spiritual beliefs and tribal law underlying the significance of trees on the cultural landscape. We discuss environmental and economic challenges to human/tree relationships and to pastoral livelihoods. We challenge views of nomads as agents of ecological destruction, and propose maintenance and restoration of traditional pastoralism as viable alternatives in dryland development

Long-term dynamics of wadi trees in a hyper-arid cultural landscape

This study focuses on the long-term dynamics of wadi (dry river valley) trees, in particular Acacia tortilis (Forssk.) Hayne, in the hyper-arid Eastern Desert of Egypt. The project was motivated by the importance of drought enduring trees for the local indigenous population, by the lack of studies on vegetation changes in hyper-arid areas, and in particular by the fact that understanding the long-term dynamics of trees is essential responding to ongoing changes effectively. Lack of data and methods offering appropriate spatial and temporal resolution has impeded research on long-term dynamics, so the use of high resolution, historical satellite data, 14C content and the anatomy of wood to obtain the necessary data is emphasised. Imagery from the first generation US reconnaissance satellite CORONA, taken already in 1965, offer a spatial (2.7 m) and temporal dimension for ecological information which other data sources cannot furnish at a comparable cost, coverage, resolution or accessibility. The vast majority of mature trees mapped in 2003 is identifiable in the imagery. A change analysis (1965-2003) reveals a negative trend in population size at most of the sites studied. Of mature trees 41 % have died. Recruitment was in general very poor at all sites, but the great capacity of saplings to resprout seems to be a major strategy to increase their persistence. A set of parameters related to water conditions, derived from the SRTM DEM, could not explain observed patterns in recruitment among sites, although it could explain some of the observed variation in mortality. Nevertheless, charcoal production seems to be the major cause of mortality. A method was developed to assure that image-based mortality estimates derived without contemporaneous reference data can be applied with great confidence. This is of particular importance when appropriate management strategies are to be adopted. The pre- and post-bomb 14C content in A. tortilis wood is used to estimate age and growth. Annual growth varies in space and time (0.2 – 2.4 mm), and the ages of the trees studied seem to lie between 200 and 650 years. In combination with the low recruitment observed, this suggests that the landscape will need very long time to recover from the ongoing and rapid deforestation. If this current trend is to be arrested, urgent action is required and must take into account the traditional management practices of the pastoral nomads who for millennia have lived in and developed sustainable strategies in accordance with local climatic conditions and available resources

Change and variation in a hyer-arid cultural landscape: A merhodological approach using remote sensing timeseries (Landsat MSS and TM, 1973-1996) from the Wadi vegetation of the eastern desert of Egypt

Nine wadi localities in a hyper-arid environment have been registered in the field and studied using earth observation data. Branch height, crown – and trunk – diameter, and indicators of land-use such as present traces of browsing, lopping and charcoal production were registered for arboreal vegetation, mostly Acacia tortilis and Balanites aegyptiaca. A point mapping (GPS) was selected to optimise subsequent integration with raster data and to facilitate a detailed interpretation of change images. Field data and change images are interpreted according to two gradients, one cultural and one hydrological. Derived tree maps are overlaid referenced TM data in order to detect differences between pixels with and without vegetation. The Red band is the most consistent spectral band in its content of vegetation information. Nevertheless it is apparent that several methodological and technical factors constrain the possibilities to register vegetation in this environment of very scarce vegetation cover. Similar problems are also recognised in the change analysis which is based on the difference between Red bands of the years compared. Four different datasets are part of the analysis: 1973, 1979, 1984 (all Landsat MSS images) and 1996 (TM). Field data indicate that changes are taking place in the cultural landscape of the Eastern Desert, and the change is primarily due to processes that both in causes and consequences is associated with ‘deforestation’. Although several sources of errors introduce variations in the change images, the images do reflect the field observations

Hydromorfologiske endringer i Vikja som følge av regulering

I forbindelse med pågående fiskebiologiske undersøkelser i Vikja, ble LFI Uni Miljø bedt om å gjøre en undersøkelse av hvordan elva hadde fått endret hydromorfologien som følge av reguleringen og hvorvidt en slik undersøkelse kunne dokumentere endringer i forholdene for fiskeproduksjonen før og etter reguleringen. Reguleringen av Vikja startet i 1954 og siste del av reguleringen var ferdigstilt i 1967. Videre var hovedhensikten å utvikle et nyttig metodeverktøy med overføringsverdi for tilsvarende vurderinger av ulike typer historiske inngrep i andre vassdrag.Statkraf

Variables used as indicators of water conditions in models of recruitment and survival.

<p>The variables are used either in the Regional (R; each site has one estimate) or Local (L; each tree has one estimate) models. Transformations are applied to achieve a normal distribution of variables. Aspect is sinus transformed to facilitate its interpretation. Outlying observations were removed from the dataset.</p