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Biological soil crusts (BSC) play a major role in water and nutrient fluxes in semi-arid and arid areas, affecting the establishment of vascular plants and contributing to the spatial arrangement of vegetated and open areas. However, little is known regarding their effects on the performance of extant vegetation. By using experimental manipulations (surface soil cutting and herbiciding), we evaluated the effect of the physical structure and the biotic component of smooth biological soil crusts on soil moisture dynamics, and on the nutrient and water status, growth rate, and reproductive effort of Stipa tenacissima tussocks in a semi-arid steppe. Soil moisture content was weakly reduced after cutting the soil surface...
Spatial heterogeneity may have differential effects on the distribution of native and nonnative plant species richness. We examined the effects of spatial heterogeneity on native and nonnative plant species richness distributions in the central part of Rocky Mountain National Park, Colorado, USA. Spatial heterogeneity around vegetation plots was characterized using landscape metrics, environmental/topographic variables (slope, aspect, elevation, and distance from stream or river), and soil variables (nitrogen, clay, and sand). The landscape metrics represented five components of landscape heterogeneity and were measured at four spatial extents (within varying radii of 120, 240, 480, and 960 m) using the FRAGSTATS...
The rhizosphere differs from the bulk soil in a range of biochemical, chemical and physical processes that occur as a consequence of root growth, water and nutrient uptake, respiration and rhizodeposition. These processes also affect microbial ecology and plant physiology to a considerable extent. This review concentrates on two features of this unique environment: rhizosphere geometry and heterogeneity in both space and time. Although it is often depicted as a soil cylinder of a given radius around the root, drawing a boundary between the rhizosphere and bulk soil is an impossible task because rhizosphere processes result in gradients of different sizes. For instance, because of diffusional constraints, root uptake...
* 1 Patch structural complexity affects local species richness and population densities. Anthropogenic disturbance may alter complexity and heterogeneity, resulting in changes in community structure. Most studies in this area have dealt with human-induced habitat degradation. We investigated a converse situation, in which anthropogenic activity increases productivity and complexity of an arid habitat. * 2 Recently, large areas in the northern Negev Desert have been altered: a series of contour catchments was constructed to accumulate run-off to support planted trees. We examined the effect of patch alteration by focusing on the lizard assemblage in the planted plots. Seven pairs of plots were established, one plot...
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We investigated butterfly responses to plot-level characteristics (plant species richness, vegetation height, and range in NDVI [normalized difference vegetation index]) and spatial heterogeneity in topography and landscape patterns (composition and configuration) at multiple spatial scales. Stratified random sampling was used to collect data on butterfly species richness from seventy-six 20 � 50 m plots. The plant species richness and average vegetation height data were collected from 76 modified-Whittaker plots overlaid on 76 butterfly plots. Spatial heterogeneity around sample plots was quantified by measuring topographic variables and landscape metrics at eight spatial extents (radii of 300, 600 to 2,400 m)....
Conclusions: Structurally complex landscapes support more species than simple landscapes, implying that habitat patches in complex landscapes receive a higher diversity of potential colonists from the overall species pool than do patches of the same size and quality in less complex landscapes. Thresholds/Learnings: Synopsis: Structurally complex landscapes support more species than simple landscapes, implying that habitat patches in complex landscapes receive a higher diversity of potential colonists from the overall species pool than do patches of the same size and quality in less complex landscapes. Movement across habitats is a common phenomenon in many species and the spillover of organisms from natural habitats...
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Synopsis: This paper describes the spatial distribution of pH measurements from 60 sites distributed throughout the Kychlan River catchment, a 67km⊃2; boreal watershed in northern Sweden. Water samples were collected during a period of winter baseflow and during a spring flood episode. Chemical analyses included pH, Dissolved Organic Carbon (DOC), major cations (K, Mg, Na, Ca) and total filterable aluminum. Spring flood pH was shown to be highest in larger, lower altitude catchments underlain by fine sorted sediments, and lowest in small, higher altitude catchments underlain by a mixture of peat wetlands and forested till. There was also a trend with distance downstream of higher pH, acid neutralizing capacity and...
    map background search result map search result map Effects of spatial heterogeneity on butterfly species richness in Rocky Mountain National Park, CO, USA Spatial heterogeneity of the spring flood acid pulse in a boreal stream network. Effects of spatial heterogeneity on butterfly species richness in Rocky Mountain National Park, CO, USA Spatial heterogeneity of the spring flood acid pulse in a boreal stream network.