@article {50247,
	title = {Spatial variability of soil and nutrient characteristics of semi-arid grasslands and shrublands, Jornada Basin, New Mexico},
	journal = {Ecohydrology},
	volume = {1},
	year = {2008},
	note = {//USDA//LTER-V//entered 06/02/2008; PDF on file},
	month = {2008},
	pages = {3-12},
	abstract = {<p>Heterogeneity of vegetation and soil properties is characteristic of semi-arid and arid environments. The potential underlying causes of the dynamics that create this spatial variability, with consequent impacts on landscape connectivity and thus ecological and ecohydrological processes, are not clearly understood. An investigation was carried out into the spatial variability of ponded infiltration rate, soil moisture, soil-aggregate stability, vegetation cover, random roughness and nutrient content in the soil (ammonium, nitrate and phosphorus) at grassland and shrubland sites for two spatial scales in the Jornada Basin, in the northern part of the Chihuahua desert. At the plant-interplant scale, statistically significant differences exist between vegetated and non-vegetated sites for soil moisture and infiltration rate within both shrublands and grasslands. The spatial distributions of all other parameters follow a more complex scheme at this scale. At the landscape scale, distinct differences exist for most parameters between the grasslands and the shrubland sites. Geostatistical analysis revealed that the autocorrelation lengths are not simply a function of average shrub sizes, but may be caused by a more complex pattern probably related to the spatial layout of rill and inter-rill areas and other localized transfers of soil resources through the redistribution of water and wind. These results demonstrate the importance of understanding spatial linkages of processes within the landscape in understanding dryland ecosystem dynamics. Copyright {\textcopyright} 2007 John Wiley \&amp; Sons, Ltd.</p>
},
	keywords = {article, connectivity, desert ecosystems, desertification, grassland, hydrology, Jornada, Jornada Basin, journal, landscape ecology, shrubland, soil characteristics, spatial variability, soil nutrients, spatial variability, spatial variability},
	doi = {10.1002/eco.1},
	url = {files/bibliography/JRN00515.pdf},
	author = {Eva N. M{\"u}ller and John Wainwright and A.J. Parsons}
}
@article {50363,
	title = {The stability of vegetation boundaries and the propagation of desertification in the American Southwest: a modelling approach},
	journal = {Ecological Modelling},
	volume = {208},
	year = {2007},
	note = {//NMSU, USDA//LTER-V//entered 08/15/2007; updated 11/20/2007},
	month = {2007},
	pages = {91-101},
	abstract = {<p>A process-based approach to spatially distributed, overland-flow modelling is employed to assess the impact of water and nutrient redistribution at the landscape scale caused by short, high-intensity rainstorm events across grassland{\textendash}shrubland vegetation boundaries of a semi-arid ecosystem in the south-western United States. The modelling scenarios showed that simulated fluxes from shrubland into grassland lead to a gain of water resources but to a loss of nutrient resources in the grassland areas close to the boundary. Simulated fluxes from grasslands into shrublands do not lead to a gain of water resources, but to an increase of nutrient resources for the shrubland areas close to the boundary. On the basis of the modelling results, a new hypothesis for the on-going desertification process in the southwestern United States is proposed. It is hypothesised that a vegetation boundary is stable when two conditions prevail to balance the lower resistance of grassland within the existing environmental setting with the higher resistance of shrubland: that the depletion of soil nutrients by the action of overland flow in the grassland zone close to the boundary is in balance with the replenishment rates of grassland by other nutrient cycling, and that the grassland gains enough water resources from the upslope shrublands. In contrast, a vegetation boundary potentially becomes unstable when the grassland acquires a competitive disadvantage towards shrubland regarding water benefit and nutrient depletion due to the combined effects of overland-flow dynamics and some external forces such as extensive overgrazing or climate change. The modelling results suggest that landscape linkages through the redistribution of water and soil resources across vegetation-transition zones at the landscape scale and feedback dynamics of overland-flow processes play a significant role in the persistence of land degradation in the US Southwest. {\textcopyright} 2007 Elsevier B.V. All rights reserved.</p>
},
	keywords = {article, desertification, hydrology, connectivity, hydrology, ecotones, hydrology, grassland, hydrology, model, hydrology, nutrient resources, hydrology, shrubland, journal, model, desertification, model, overland flow, model, vegetation boundaries, vegetation boundaries},
	doi = {10.1016/j.ecolmodel.2007.04.010},
	url = {files/bibliography/JRN00486.pdf},
	author = {Eva N. M{\"u}ller and John Wainwright and A.J. Parsons}
}
