Maxim Shoshany

Influence of slope aspect on Mediterranean woody formations: Comparison of a semiarid and an arid site in Israel

This study investigates the effects of slope aspect on plant community characteristics such as plant cover, species composition and above-ground biomass production in Mediterranean trees and shrubs in two climatological regions. Two experimental sites were selected in a climatic gradient that runs from the foothills of the Judean Hills to the northern Negev desert in Israel. In each site, 16 quadrats of 10 m × 10 m (eight south-facing and eight north-facing slopes) were established and the vegetation was recorded. Dominant tree and shrub species were measured using allometric parameters of area and volume, and representative branches were cut and weighed. Species studied were Quercus calliprinos, Phillyrea latifolia, Pistacia lentiscus, Cistus creticus, Coridothymus capitatus, and Sarcopoterium spinosum. The results showed that slope aspect had significant effects on the composition, structure and density of the plant communities developing in both sites. Vegetation structure within a site changed significantly in the short distance separating the north and south-facing slopes, and that pattern remained generally constant when comparing the two sites along the rainfall gradient. The data collected here provides new insight into the slope aspect effects on biomass allocation of different woody life forms of eastern Mediterranean plant communities.

Vegetation establishment on the southern Israeli coastal sand dunes between the years 1965 and 1999

Abstract Since 1960, the Israeli coastal dunes have undergone a stabilization process that is manifested in the increase of vegetation cover and in a decrease in the abundance of sand-living flora and fauna species. The objective of the study was to quantify, using remote sensing and GIS, the rate and extent of vegetation expansion and their resultant temporal changes on Israel’s southern coastal dunes between the years 1965 and 1999. The results indicate that during the entire study period, the vegetation-covered area grew by 82% at an annual average growth rate of 1.75%. Concurrently, the bare shifting dune area decreased by 37% at an annual average growth rate of 1.34%. The conspicuous trend over the period studied, despite regressive processes, is a transition from bare shifting dunes to stabilized, vegetation-covered dunes. The extrapolation of the results, assuming continuation of processes and no destruction effects, indicates that with the decrease in the bare shifting dunes, the ratio of bare shifting dunes and sparse vegetation coverage landscape will equalize by between 2007 and 2010. According to this extrapolation, between 2012 and 2015, no bare shifting dune landscape will remain, and the study area will be covered with sparse- and dense-level vegetation cover. Beginning in 2035, the entire study area will be covered in vegetation whose density will be between 60 and 100%. Meso-climate and land use changes are among the factors that might explain this phenomenon.

Land-use and population density changes in Israel—1950 to 1990: analysis of regional and local trends

Abstract Population density in Israel during the early 1990s reached one of the highest levels (545 persons/km2) in the Western World. This study aims at assessing relationships between population and developed area (built-up and infrastructure areas) growth between 1950 and 1990, based on data collected for 6 national level districts, as well as 6 local sites in the Mount Carmel area representing a region of high ecological significance. The main findings are: (1) Population densities in developed areas were much higher than those recorded for the total district area and exhibited a continuously decreasing trend; (2) an excess of more than 50% in the growth of built-up and infrastructure areas was observed relative to population increases; (3) population densities in government-owned lands (representing the majority of the lands) were significantly lower than population densities found in lands owned by the private sector; and (4) trends of developed area growth in the Mount Carmel region were similar to those observed at the national level, despite the high ecological sensitivity of this region.

The relationship between ERS-2 SAR backscatter and soil moisture: generalization from a humid to semi-arid transect.

A linear relationship between ERS-2 SAR backscattering coe c cient (s0) and volumetric soil moisture was determined at both ends of a rainfall gradient in Israel. A Normalized radar Backscatter soil Moisture Index (NBMI) was derived and related strongly to soil moisture concentration. This index may allow the mapping of soil moisture conditions over large areas with C band SAR data.

Multidate adaptive unmixing and its application to analysis of ecosystem transitions along a climatic gradient

Environmental heterogeneity characterizes Mediterranean regions and zones of transition between humid and arid climates. Mapping of shrubs, dwarf shrubs, and herbaceous growth is of primary importance for understanding ecosystem function in these vulnerable environments. High spatial fragmentation in these three cover types implies that they are highly mixed at spatial resolutions greater than a few meters. A new methodology is presented which uses phenological differences between shrubs, dwarf shrubs, and herbs to map fractions of each at subpixel scales. To account for seasonal differences, Landsat images acquired at the end of winter and at the beginning and end of summer were analyzed. Differentiation between elementary vegetation and soil cover fractions was achieved using a well-known multispectral unmixing technique in an adaptive way. In this way, an image-based zonal partition facilitated spectral end-members selection according to seasonal variations and to climatic/biotic/lithologic transitions. The methodology was then applied to three Landsat images of an area representing a climatic gradient in the center of Israel. New maps of spatial changes in vegetation cover fractions along the climatic gradient were produced. An important element of the new data relates to the distribution of dwarf shrubs in general, and of Sacroproterium spinosium in particular. These dwarf shrubs are of major ecological significance in countries of the eastern part of the Mediterranean Basin due to their rapid invasion into abandoned fields and burnt areas.

Seasonal vegetation cover changes as indicators of soil types along a climatological gradient: a mutual study of environmental patterns and controls using remote sensing

Abstract A remote sensing analysis of the temporal changes of vegetation cover in the arid and semi-arid regions of the Judean Desert and Judean Mountains was carried out in order to reveal the controlling factor of the environmental system. Assessment of ditTerent combinations of temperal changes in the region using GIS techniques indicated that it is possible to differentiate between two major patterns of vegetation cover change. The classification of the region according to these patterns has produced a map that is highly correlated to the soil map of the region, thus suggesting that the soil is an important environmental controlling factor in the region. From the remote sensing point of view, the patterns of vegetation cover change may serve as indicators of soil types in similar arid and semi-arid environments.

Aboveground biomass allocation and water content relationships in Mediterranean trees and shrubs in two climatological regions in Israel

Thisstudy investigated the variation along basipetal gradients of the relationshipsbetween the foliage/wood allocation ratios of biomass and of water content, inMediterranean trees and shrubs, at two different locations along a climaticgradient. Understanding of the biomass allocation and water relations inMediterranean trees and shrubs provides useful information on growth patternsofthese species, and on resource dynamics of these plant communities. Twoexperimental sites were selected along a climatological transect that runs fromthe foothills of the Judean Hills to the northern Negev desert in Israel. Ateach site, 16 quadrats of 10 × 10 m (eight on south-facingslopes and eight on north-facing slopes) were marked. The aboveground biomassofdominant tree and shrub species were estimated. Main branches of trees andshrubs were cut, their foliage and wood biomass were separately weighed, andtheir respective water contents were determined. The species studied includedthe evergreen sclerophylls, Quercus calliprinos, Phillyrealatifolia and Pistacia lentiscus, and thesemi-deciduous species, Cistus creticus, Coridothymuscapitatus and Sarcopoterium spinosum. Theresults indicated that the foliage/wood ratio decreased from the periphery ofthe crown to the interior of the trees and shrubs: foliage biomass and waterwere mainly limited to the top 30 cm of the crown in all studiedspecies. Leaves had higher relative water contents than woody tissues in theupper part of the crown. However; when the whole tree or shrub was considered,the relative water content was found to be mostly allocated to the woodystructures. The results are discussed in terms of biomass allocation in variouslife forms of the eastern-Mediterranean plant communities and how they areaffected by slope aspect and climatic conditions.

Landscape fragmentation and soil cover changes on south- and north-facing slopes during ecosystems recovery: an analysis from multi-date air photographs

Abstract A quantitative analysis is presented, of soil and vegetation patch patterns from air photographs of three dates (1956, 1976 and 1990). Relationships between changes in soil cover and landscape fragmentation are assessed for north- and south-facing slope units in the semi-arid zone of Israel undergoing recovery following severe overgrazing and woodcutting phases. Soil loss accompanied by an increase in rock fragment exposure, and an increase in soil erodibility due to a decrease in aggregate size and organic matter content are the two main characteristics of soil changes in this area. Changes in both of these characteristics are highly correlated with soil brightness properties as recorded from aerial photographs. The methodology developed combines image processing techniques, enabling differentiation between soil and vegetation patches, with raster Geographical Information Systems (GIS) techniques, allowing patch distribution, fragmentation and form to be analyzed. Expansion of vegetation patches and contraction of soil patches were found to follow similar lines of spatial pattern evolution when parameterized according to their size, form and density. Assessment of temporal changes in soil and vegetation patch composition indicated that there is a phase difference of 12 years between the processes taking place on the two slope units. Hypothetical descriptions of soil patch fragmentation and vegetation patch expansion processes between 1920 and 2010 were formulated following the analysis of data between 1956 and 1990. Evidence of soil brightness changes provided indications for the continuation of soil loss, mainly in large patches (a few thousands of square meters in size) undergoing relatively slow fragmentation.

Herbaceous biomass retrieval in habitats of complex composition: a model merging SAR images with unmixed landsat TM data

A remote sensing methodology for herbaceous areal above-ground biomass (AAB) estimation in a heterogeneous Mediterranean environment is presented. The methodology is based on an adaptation of the semiempirical water-cloud backscatter model to complex vegetation canopies combined with shrubs, dwarf shrubs, and herbaceous plants. The model included usage of the green leaf biomass volumetric density as a canopy descriptor and of cover fractions derived from unmixing Landsat Thematic Mapper image data for the three vegetation formations. The inclusion of the unmixed cover fractions improves modeling synthetic aperture radar backscatter, as it allows separation between the different radiation interaction mechanisms. The method was first assessed with reference to the reproduction of the backscatter from the vegetation formations. In the next phase, the accuracy of AAB retrievals from the backscatter data was evaluated. Results of testing the methodology in a region of climatic gradient in central Israel have shown a good correspondence between observed and predicted AAB values (R/sup 2/=0.82). This indicates that the methodology developed may lay a basis for mapping important and more advanced ecological information such as primary production and contribute to better understanding of processes in Mediterranean and semiarid regions.

Influence of a climatic gradient upon vegetation dynamics along a Mediterranean-arid transect

Changes in plant cover, species richness and spe- cies diversity were recorded over a 2-year period along a climatic gradient running from a Mediterranean region (Judean Mountains) to the Dead Sea desert area. Changes along the climatic gradient were found not to be gradual. A narrow belt exists in which a drastic decline in all plant parameters occurs. This belt divides the research area into two main systems- the Mediterranean and the arid. The belt shifts eastwards and westwards depending on rainfall. The shifting range is limited to the area between the xeric Mediterranean and the arid regions.