Maik Veste

Sustainable Land Use in Deserts

Deserts, Land Use and Desertification.- River Diversion, Irrigation, Salinization, Desertification - an Inevitable Succession.- I: The Aral Sea Crisis.- The Aral Sea Crisis Region.- Flora of the Dry Seafloor of the Aral Sea.- Vegetation Dynamics on the Dry Seafloor of the Aral Sea.- Methods of Conservation and Restoration of Vegetation Cover on the Aral Sea Coast.- Vegetation Dynamics on the Syrdarya Delta and Modern Land Use.- Ecological Basis for Botanical Diversity Conservation within the Amudarya and Syrdarya River Deltas.- The Tugai Forests of Floodplain of the Amudarya River: Ecology, Dynamics and Their Conservation.- Soil Crusts in the Amudarya River Delta: Properties and Formation.- Irrigation and Land Degradation in the Aral Sea Basin.- Ecology of the Aqueous Medium in the Area Surrounding the Aral Sea.- Potable Water: Research into Seasonal Changes and Conditions in the Aral Sea Region.- II: Salt Stress.- Halophytes on the Dry Sea Floor of the Aral Sea.- Halophytes: Structure and Adaptation.- Environmental State and an Analysis of Phytogenetic Resources of Halophytic Plants for Rehabilitation and Livestock Feeding in Arid and Sandy Deserts of Uzbekistan.- Salinity: A Major Enemy of Sustainable Agriculture.- III: Impact of Grazing.- Remarkable Differences in Desertification Processes in the Northern and Southern Richtersveld (Northern Namaqualand, Republic of South Africa).- Colour Plates.- How Grazing Turns Rare Seedling Recruitment Events to Non-Events in Arid Environments.- Vegetation Degradation in Northeastern Jordan.- Impact of Grazing on the Vegetation of South Sinai, Egypt.- Arid Rangeland Management Supported by Dynamic Spatially Explicit Simulation Models.- IV: Desertification Processes and Monitoring.- Remote Sensing of Surface Properties. The Key to Land Degradation and Desertification Assessments.- Evaluation of Potential Land Use Sites in Dry Areas of Burkina Faso with the Help of Remote Sensing.- Degradation of the Vegetation in the Central Kyzylkum Desert (Uzbekistan).- Modern Geomorphological Processes on the Kazakhstanian Coast of the Caspian Sea and Problems of Desertification.- Anthropogenic Transformation of Desert Ecosystems in Mongolia.- Assessment of the Modern State of Sand-Desert Vegetation in Kazakhstan.- V: Reclamation.- Water-Harvesting Efficiency in Arid and Semiarid Areas.- The Effects of Landscape Structure on Primary Productivity in Source-Sink Systems.- Sedimentary Environments in the Desiccated Aral Sea Floor: Vegetation Recovery and Prospects for Reclamation.- Seeding Experiments on the Dry Aral Sea Floor for Phytomelioration.- Rehabilitation of Areas of Irrigation Now Derelicted Because of Strong Salinization in Ecologically Critical Zones of Priaralia.- Desert Soil Recultivation and Monitoring of (Phyto-) Toxicity: Pilot Project in Three Phases Lasting for 4 Years.- Contributions to a Sustainable Management of the Indigenous Vegetation in the Foreland of Cele Oasis - A Project Report from the Taklamakan Desert.- The Control of Drift Sand on the Southern Fringe of the Taklamakan Desert - an Example from the Cele-Oasis.- The Role of Biological Soil Crusts on Desert Sand Dunes in the Northwestern Negev, Israel.- Restoration of Disturbed Areas in the Mediterranean - a Case Study in a Limestone Quarry.- Indigenous Agroforestry for Sustainable Development of the Area around Lake Nasser, Egypt.- Ziziphus - a Multipurpose Fruit Tree for Arid Regions.- Root Morphology of Wheat Genotypes Grown in Residual Moisture.- Field Studies in Solar Photocatalysis for Detoxification of Organic Chemicals in Waters and Effluents.- VI: National Programs.- Activity of the Consulting Centre to Combat Desertification in Turkmenistan.- Desertification in China and Its Control.- Environmental Problems of the Southern Region of Kazakhstan.- National Strategy and Action Plan to Combat Desertification in Kazakstan.- VII: Social and Economic Aspects.- Economic-Demographic Strategies and Desertification: Interactions in Low-Income Countries.- Final Remarks.

Succession of N cycling processes in biological soil crusts on a Central European inland dune

Biological soil crusts (BSCs) are microbial assemblages that occur worldwide and facilitate ecosystem development by nitrogen (N) and carbon accumulation. N turnover within BSC ecosystems has been intensively studied in the past; however, shifts in the N cycle during BSC development have not been previously investigated. Our aim was to characterise N cycle development first by the abundance of the corresponding functional genes (in brackets) and second by potential enzyme activities; we focussed on the four processes: N fixation (nifH), mineralisation as proteolysis and chitinolysis (chiA), nitrification (amoA) and denitrification (nosZ). We sampled from four phases of BSC development and from a reference located in the rooting zone of Corynephorus canescens, on an inland dune in Germany. BSC development was associated with increasing amounts of chlorophyll, organic carbon and N. Potential activities increased and were highest in developed BSCs. Similarly, the abundance of functional genes increased. We propose and discuss three stages of N process succession. First, the heterotrophic stage (mobile sand without BSCs) is dominated by mineralisation activity. Second, during the transition stage (initial BSCs), N accumulates, and potential nitrification and denitrification activity increases. Third, the developed stage (established BSCs and reference) is characterised by the dominance of nitrification.

Using the natural 15N abundance to assess the main nitrogen inputs into the sand dune area of the North-Western Negev desert (ISRAEL)

The variation of the natural 15N abundance is often used to evaluate the origin of nitrogen or the pathways of N input into ecosystems. We tried to use this approach to assess the main input pathways of nitrogen into the sand dune area of the north-western Negev Desert (Israel). The following two pathways are the main sources for nitrogen input into the system: i. Biological fixation of atmospheric nitrogen by cyanobacteria present in biological crusts and by N2-fixing vascular plants (e.g. the shrub Retama raetam); ii. Atmospheric input of nitrogen by wet deposition with rainfall, dry deposition of dust containing N compounds, and gaseous deposition. Samples were taken from selected environmental compartments such as biological crusts, sand underneath these crusts (down to a depth of 90 cm), N2-fixing and non-N2-fixing plants, atmospheric bulk deposition as well as soil from arable land north of the sandy area in three field campaigns in March 1998, 1999 and 2000. The δ15N values measured were in the following ranges: grass −2.5‰ to +1.5‰; R. reatam: +0.5‰ to +4.5‰; non-N2-fixing shrubs +1‰ to +7‰; sand beneath the biological crusts +4‰ to +20‰ (soil depth 2–90 cm); and arable land to the north up to 10‰. Thus, the natural 15N abundance of the different N pools varies significantly. Accordingly, it should be feasible to assess different input pathways from the various 15N abundances of nitrogen. For example, the biological N fixation rates of the Fabaceae shrub R. reatam from the 15N abundances measured were calculated to be 46–86% of biomass N derived from the atmosphere. The biological crusts themselves generally show slight negative 15N values (−3‰ to −0.5‰), which can be explained by biological N fixation. However, areas with a high share of lichens, which are unable to fix atmospheric nitrogen, show very negative values down to −10‰. The atmospheric N bulk deposition, which amounts to 1.9–3.8 kg N/ha yr, has a 15N abundance between 4.4‰ and 11.6‰ and is likely to be caused by dust from the arable land to the north. Thus, it cannot be responsible for the very negative values of lichens measured either. There must be an additional N input from the atmosphere with negative δ15N values, e.g. gaseous N forms (NO x , NH3). To explain these conflicting findings, detailed information is still needed on the wet, particulate and gaseous atmospheric deposition of nitrogen.

The Role of Biological Soil Crusts on Desert Sand Dunes in the Northwestern Negev, Israel

Biological soil crusts are important microphytic communities and significantly influence both structure and processes within the ecosystem. They are built up from cyanobacteria, green algae, fungi, mosses and lichens. Various crust types could be found, depending on dune slope aspect and dewfall availability. In the sand dunes of the northern Negev they cover large areas and stabilize the sand surface against wind and water erosion. Free-living and symbiontic cyanobacteria are capable of nitrogen fixation and are important nitrogen sources in the desert sand dunes. As biological crusts enhance the surface stability and soil fertilization, they are to be considered a key factor in the protection of arid and semiarid ecosystems and, thus, in combating desertification in terms of sand dune remobilization.

Dew Formation and Activity of Biological Soil Crusts

Biological soil crusts are prominent in many drylands and can be found in diverse parts of the globe including the Atacama desert, Chile, the Namib desert, Namibia, the Succulent-Karoo desert, South Africa, and the Negev desert, Israel. Because precipitation can be negligible in deserts ? the Atacama desert being almost rain-free ? or restricted to infrequent rains during short rainfall seasons, atmospheric moisture in the form of dew and/or fog can be a major, regular supplier of water for cryptogams. To study in situ microclimatic boundary conditions of dew formation and/or influence on biological crust activity in a hot desert, a variety of intensive field experiments were conducted by the authors in the Haluza sand dune region, North- Western Negev desert. Microclimatic parameters such as the radiative energy budget, specific humidity, or difference between air temperature and dewpoint are needed to determine the onset and termination of lichen photosynthetic activity. In the present paper, the physiological activation of soil lichens was measured by chlorophyll fluorescence (as used by Schroeter et al. 1992; Leisner et al. 1997). For the biological sand crusts, general meteorological stations were established on a dune slope or along a transect, in addition to intensive field campaigns where a variety of meteorological sensors were operated in parallel with manual and automatic microlysimeter dew measurements of both physical and biological crusts. The purpose focused on acquiring detailed information on the dew formation and drying process and dew quantities that could condense overnight. Full details regarding the experiments and instrumentation may be found in Jacobs et al. (1999, 2000a), Veste et al. (2001), Heusinkveld et al. (2006) and Littmann and Veste (2006).

Variability of CAM in leaf-deciduous succulentsfrom the Succulent Karoo (South Africa)

Summary Seasonal or drought-induced deciduousness is a common adaptational strategy in aboveground persistent succulent species native to the Succulent Karoo (South Africa). This feature may appear together with crassulacean acid metabolism (CAM) in stems and/or leaves. Due to differences in morphology or life cycle, different species may exhibit different degrees of flexibility in the expression of CAM. The potential for CAM plasticity has not been investigated in leaf-deciduous succulents of the Succulent Karoo. Diurnal gas exchange and nocturnal organic acid accumulation were measured to investigate whether the expression of CAM may vary in Tylecodon paniculatus (L.F.) Toelken (Crassulaceae), Monilaria moniliformis (Mesembryanthemaceae) and Ceraria fruticulosa H. Pearson & Stephens (Portulacaceae), a selection of leaf-deciduous succulents. These species differ both in leaf and stem morphology. In the seasonal deciduous Tylecodon paniculatus only obligate CAM was found, regardless of the plant water status. When droughted Monilaria moniliformis switches directly from CAM-cycling (C 3 -like diurnal gas exchange patterns combined with nocturnal acid accumulation) to CAM-idling (gas exchange completely ceased while acid accumulation still continued). This seasonal deciduous species has also both succulent leaves and stem. A highly flexible CAM expression (CAM-cycling, full-CAM and CAM-idling) was observed in the drought deciduous Ceraria fruticulosa (non-succulent stem showing no CAM) in response to changes in water availability. The ecological significance of the observed diversity in the flexibility of CAM expression was discussed in terms of morphological traits, and the relative ecological significance of both metabolic adaptation and leaf-deciduousness. Saisonaler oder durch Trockenstress induzierter Blattwurf ist eine relativ haufige Uberlebensstrategie in oberirdisch uberdauernden Sukkulenten der Sukkulenten Karoo in Sud Afrika. Diese Eigenschaft kann in Kombination mit einem Crassulaceen Saurestoffwechsel (CAM) im Spros und/oder in den Blattern auftreten. Der CAM gilt allgemein als ein physiologischer Anpassungsmechanismus an Trockenheit. In Arten mit unterschiedlicher Morphologie oder Lebenszyklen kann er unterschiedlich flexibel auftreten. Diurnaler Gaswechsel und nachtliche Akkumulation von Apfel- und Zitronensaure wurden in den saisonal bzw. durch Trockenstress induziert laubwerfenden Arten Tylecodon paniculatus (L.F.) Toelken (Crassulaceae), Monilaria moniliformis (Mesembryanthemaceae) and Ceraria fruticulosa H. Pearson & Stephens (Portulacaceae) gemessen, um deren CAM-Auspragung zu charakterisieren. Tylecodon paniculatus zeigte unabhangig vom Blattwasserzustand ausschlieslich obligaten CAM. Im Gegensatz dazu wechselte Monilaria moniliformis bei Trockenstress von typischem CAM-cycling (C 3 -typisches Gaswechselmuster, aber nachtliche Akkumulation organischer Sauren) direkt zu CAM-idling. Der diurnale Gasaustausch ist dann bei dieser saisonal laubwerfenden Art nahezu vollstandig unterbunden, die nachtliche Saureakkumulation bleibt aber bestehen. Hohe CAM-Flexibilitat konnte auch bei Ceraria fruticulosa gezeigt werden. In Abhangigkeit von der Wasserversorgung traten bei dieser trockenstress-induziert laubwerfenden, blattsukkulenten Art (nicht-sukkulenter Stamm ohne CAM) hier alle bisher beschriebenen Formen des CAM (CAM-cycling, obligater CAM und CAM-idling) auf. Diese Variabilitat in der CAM-Flexibilitat der unterschiedlichen laubwerfenden Blattsukkulenten wird im Hinblick auf mogliche morphologische Einflusse, sowie die relative okologische Relevanz beider Anpassungsstrategien (CAM, Sukkulenz) diskutiert.

Black locust (Robinia pseudoacacia L.) ecophysiological and morphological adaptations to drought and their consequence on biomass production and water-use efficiency

BackgroundSuccessful plantation efforts growing Robinia pseudoacacia L. (black locust) in the drier regions of Hungary and East Germany (Brandenburg), have demonstrated the potential of black locust as an alternative tree species for short-rotation biomass energy plantations.MethodsThe response of black locust to water limitation was investigated in a lysimeter experiment. Plants were grown under three different soil moisture regimes, with values set at 35%, 70%, and 100% of the soil water availability, namely WA35, WA70, and WA100. Their morphological adaptation and productivity response to water constraint were assessed together with their water-use efficiency. Furthermore, the ecophysiological adaptation at the leaf level was assessed in terms of net photosynthesis and leaf transpiration.ResultsDuring the growing season, plants in the WA35, WA70, and WA100 treatments transpired 239, 386, and 589 litres of water respectively. The plants subjected to the WA35 and WA70 treatments developed smaller leaves compared with the plants subjected to the WA100 treatment (66% and 36% respectively), which contributed to the total leaf area reduction from 8.03 m2 (WA100) to 3.25 m2 (WA35). The total above-ground biomass produced in the WA35 (646 g) and WA70 (675 g) treatments reached only 46% and 48% of the biomass yield obtained in the WA100 (1415 g). The water-use efficiency across all treatments was 2.31 g L−1. At vapour pressure deficit (VPD) values <1.4 kPa trees growing under the WA35 soil moisture regime showed a stomatal down-regulation of transpiration to 5.3 mmol m−2 s−1, whereas the trees growing under the WA100 regime did not regulate their stomatal conductance and transpiration was 11.7 mmol m−2 s−1, even at VPD values >2 kPa.ConclusionsBlack locust plants can adapt to prolonged drought conditions by reducing water loss through both reduced transpiration and leaf size. However, under well-watered conditions it does not regulate its transpiration, and therefore it cannot be considered a water-saving tree species.

Sensitivity of a Sandy Area to Climate Change Along a Rainfall Gradient at a Desert Fringe

Global climate change has become a strongly and frequently addressed issue in the last decades. The aspect is crucial in dry-land areas, which cover approximately one third of the globe’s total land area. The relationship between average annual rainfall and environmental variables has attracted the attention of many scientists. Climatologists use aridity indices to express relationships between climatic and environmental variables (Köppen 1931; Budyko 1974; Wallen 1967; Bailey 1979). These indices, based on purely climatic variables such as annual precipitation, temperature, evaporation and radiation, tend to imply that the acuteness of aridity is inversely related to annual precipitation. Although aware that soil water content depends on local soil type and precipitation regime, Walter (1939, 1960) asserted that at a larger, global scale, standing biomass is positively correlated to average annual rainfall. This approach is still followed by many researchers who assume a positive relationship between average annual rainfall and environmental variables such as water availability for plants, vegetation cover, productivity, species diversity, soil properties, human activity, and erosion rates for sub-humid to arid areas (Issar and Bruins 1983; Shmida 1985; Seely 1991; Lavee et al. 1991; Kutiel et al. 2000; Meron et al. 2004). This approach is certainly correct at the global scale, as well as for non-irrigated annual crops in dry-land areas. It is, however, questionable for arid and semi-arid areas, usually regarded as highly sensitive to climate change, especially for perennial plants. With decreasing annual rainfall, the number of rainstorms and storm rain amounts decrease. Under such conditions, water availability for plants may be highly dependant on the relationships between rainfall and surface properties which greatly influence the degree to which water will percolate or will be transformed into runoff, thereby significantly affecting the spatial redistribution of water resources. For example, it is well known that rocky hill slopes devoid of extensive soil and vegetation cover are characterized by extremely low infiltration rates, and quickly develop surface runoff. Due to the short duration of most individual rain showers, flow distances are short, resulting in water concentration and deep water percolation at nearby down-slope positions (Yair and Danin 1980; Yair 1983, 1994,

Synergic hydraulic and nutritional feedback mechanisms control surface patchiness of biological soil crusts on tertiary sands at a post-mining site

Abstract In a recultivation area located in Brandenburg, Germany, five types of biocrusts (initial BSC1, developed BSC2 and BSC3, mosses, lichens) and non-crusted mineral substrate were sampled on tertiary sand deposited in 1985- 1986 to investigate hydrologic interactions between crust patches. Crust biomass was lowest in the non-crusted substrate, increased to the initial BSC1 and peaked in the developed BSC2, BSC3, the lichens and the mosses. Water infiltration was highest on the substrate, and decreased to BSC2, BSC1 and BSC3. Non-metric multidimensional scaling revealed that the lichens and BSC3 were associated with water soluble nutrients and with pyrite weathering products, thus representing a high nutrient low hydraulic feedback mode. The mosses and BSC2 represented a low nutrient high hydraulic feedback mode. These feedback mechanisms were considered as synergic, consisting of run-off generating (low hydraulic) and run-on receiving (high hydraulic) BSC patches. Three scenarios for BSC succession were proposed. (1) Initial BSCs sealed the surface until they reached a successional stage (represented by BSC1) from which the development into either of the feedback modes was triggered, (2) initial heterogeneities of the mineral substrate controlled the development of the feedback mode, and (3) complex interactions between lichens and mosses occurred at later stages of system development.

Effects of Drought Frequency on Growth Performance and Transpiration of Young Black Locust (Robinia pseudoacacia L.)

Black locust (Robinia pseudoacacia L.) is a drought-tolerant fast growing tree, which could be an alternative to the more common tree species used in short-rotation coppice on marginal land. The plasticity of black locust in the form of ecophysiological and morphological adaptations to drought is an important precondition for its successful growth in such areas. However, adaptation to drought stress is detrimental to primary production. Furthermore, the soil water availability condition of the initial stage of development may have an impact on the tree resilience. We aimed to investigate the effect of drought stress applied during the resprouting on the drought tolerance of the plant, by examining the black locust growth patterns. We exposed young trees in lysimeters to different cycles of drought. The drought memory affected the plant growth performance and its drought tolerance: the plants resprouting under drought conditions were more drought tolerant than the well-watered ones. Black locust tolerates drastic soil water availability variations without altering its water use efficiency (2.57 g L−1), evaluated under drought stress. Due to its constant water use efficiency and the high phenotypic plasticity, black locust could become an important species to be cultivated on marginal land.