Spatial Variation in Remnant Grasses After a Grassland-to-Shrubland State Change: Implications for Restoration

Abstract

Around the world rangelands that have been degraded, such as historical desert grasslands now dominated by woody shrubs, are resistant to restoration efforts. The goal of this descriptive research was to examine the potential for black grama (Bouteloua eriopoda [Torr.] Torr.) recovery by remnant plants in a degraded area as a function of plant location across a landscape. Our objectives were 1) to document the historical dominant vegetation as a perennial grassland and determine broad-scale changes in dominance through time and 2) to examine fine-scale patterns of black grama presence and basal area with respect to microenvironmental conditions that indicate the landscape positions favorable for restoration. Historical vegetation maps starting in 1858, a field survey in 2002-2003 of the location of all individual black grama plants in a 29-ha area, and spatial data layers in a geographic information system were used to address these objectives. Upland grasses, including black grama, dominated the study site in 1858, although tarbush (Flourensia cernua DC.) was the dominant species by 1915, and creosotebush (Larrea tridentata [DC.] Cov.) is the current dominant. A total of 3 334 black grama plants were found for an average density of 0.01 plants m À2. High spatial variation was found in the occurrence and basal area of black grama plants that was related to water availability rather than livestock grazing: most plants were found in or adjacent to an arroyo (67%), at a northern aspect (47%), and outside experimental exclosures established in 1930 (43%). Largest average basal areas were found in the livestock exclosure, and in general, average basal area was not related with aspect or canopy microsite. These remnant plants can be used as propagule sources in restoration efforts, and information on microsite conditions for black grama survival can be used to improve restoration potential for similar sites. Resumen Al rededor del mundo los pastizales que han sido degradados, tal como los histó ricos pastizales desérticos actualmente dominados por arbustos leñ osos, son resistentes a las acciones de restauració n. La meta de esta investigació n descriptiva fue examinar el potencial del ''Black grama'' (Bouteloua eriopoda [Torr.] Torr.) para recuperarse a partir de plantas remanentes en áreas degradadas en funció n de la localizació n de la plantas a través del paisaje. Nuestros objetivos fueron: 1) Documentar la vegetació n dominante histó rica como pastizal perenne y determinar los cambios a gran escala en la dominancia a través del tiempo; 2) Examinar los patrones, a escala fina, de la presencia del ''Black grama'' y el á rea basal con respecto a las condiciones microambientales que indiquen posiciones favorables del paisaje para la restauració n. Para lograr los objetivos se usaron mapas histó ricos de vegetació n desde 1858, un muestro de campo de 2002-2003 de la localizació n de todas las plantas individuales de ''Black grama'' en un á rea de 29 ha y capas de datos espaciales de sistemas de informació n geográfica...

Wildland Fuel Fundamentals and Applications

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Spatiotemporal Variability of Wildland Fuels in US Northern Rocky Mountain Forests

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