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In an attempt to describe some major relationships between soil and plant compartments in a shortgrass steppe, the process of water loss from the system and plant water relations throughout a drying cycle were studied. The water supply was manipulated and some soil and plant variables monitored throughout a drying cycle. Leaf conductance and leaf water potential of blue grama (Bouteloua gracilis) were measured periodically at predawn and noon. Soil water content and water potential of different layers were also monitored.Three different periods were distinguished in the water loss process throughout a drying cycle. These distinctions were made taking into account the relative contribution of different soil layers. Leaf conductance and water potential at noon slowly declined throughout the first 50 days of plant growth. After that, they rapidly decreased, reaching values of 0.29 mm s and-5.0 MPa, respectively. The predawn leaf water potential remained unchanged around-0.5 MPa during the first 45 days, then rapidly decreased. This occurred when soil water of the wettest soil layer was near depletion.Predawn leaf water potentials were highly correlated with water potentials of the wettest layer. Leaf conductance and water potential at noon were correlated with effective soil water potential (soil water potential weighted by the root distribution in the profile). We concluded that root surface area limited the water flow through an important part of the day in this semiarid ecosystem. Axial root resistance did not appear important in determining the equilibrium status between leaves and the wettest soil layer.

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Summary 1.Restoration of native plant communities on previously disturbed land requires the identification and modification of environmental factors that impede or restrict ecosystem succession or development. One of the key factors in successful reclamation is to ensure colonization and persistence of native species within an area. Therefore, the identification of microsite types that favour colonization by native species should improve our ability to successfully reclaim degraded areas. 2. The objectives of this study were to (i) identify and describe microsite types that were conducive to the establishment of five native plant species ( Euphrasia frigida , Galium normanii , Thymus praecox , Cerastium spp. and Rumex acetosa ) on degraded and reclaimed sites in Iceland; and (ii) to determine the effects of reclamation activities that included the application of manure and inorganic fertilizer on the distribution of microsite types and seedling establishment. Reclamation sites of different ages were examined on an eroded area where the target community was a grass or shrub heath. 3. The spatial distribution of plant establishment was not random but varied among microsite types and study sites. More seedlings than expected were found in microsite types characterized by small rocks and biological soil crusts. These may have entrapped seed and provided more soil stability and moisture than other microsite types. The cover of these microsite types varied among the study sites but the pattern of seedling establishment among the five native forbs was similar. 4. Synthesis and applications . Practical reclamation methods are improved by identifying those factors that promote successful seedling establishment by native species. Application of fertilizer without additional seeding proved to be a simple reclamation approach that increased the availability of one favourable microsite type, enhanced the establishment of native species and subsequently allowed vegetation cover to expand. Seed of native plants may be difficult to obtain commercially, but this approach can be used on degraded land where propagules are available but recovery is slowed by soil instability or nutrient limitations.