• Livestock Browsing, Not Water Limitations, Contributes to Recruitment Failure of Dobera glabra in Semiarid Ethiopia

      Tsegaye, Diress; Moe, Stein R.; Haile, Mitiku (Society for Range Management, 2009-11-01)
      The study used nursery and field experiments to investigate why recruitment of Dobera glabra (Forssk) Poir., a native food source for both humans and livestock, often fails in the semiarid rangelands of Afar, Ethiopia. We hypothesized that soil water limitations and browsing by livestock would be the primary mechanisms accounting for the failure of natural regeneration. We used three sets of experiments—1) seedling performance in response to shade and watering in a nursery, 2) field regeneration with and without browsing, and 3) regeneration beneath trees with and without browsing—to examine regeneration success. Seedlings were established in plots from seeds sown directly into the soil for nursery and field experiments, but natural germination occurred beneath trees. Survival and relative growth rates (RGR) were used to monitor seedling performance. Seedlings that received neither shade nor watering treatments had lower seedling survival (53 +/- 15%) as compared with other treatment combinations. Highest seedling survival was recorded under shade and 1 d watering wk-1 treatment combinations (92 +/- 1%). However, shade treatments had a minimal increase on seedling RGR. Water limitation is not a crucial limiting factor for D. glabra recruitment, as 53% of the seedlings survived without both shade and supplemental water for 1 yr. Field experiments, however, demonstrated that browsing greatly reduced seedling survival (below 15%) and suppressed growth of surviving seedlings, suggesting that browsing is the major factor preventing natural recruitment. Natural recruitment of D. glabra is unlikely with the existing continuous and intensive grazing/browsing in Afar rangelands, where the mobility of pastoralists is restricted. We suggest that planting nursery-raised seedlings in home gardens of settled pastoralists and establishment of grazing reserves in some key range sites that contain D. glabra could help offset the recruitment failure of native food species D. glabra in Afar rangelands. 
    • Managing Complex Problems in Rangeland Ecosystems

      Boyd, Chad S.; Svejcar, Tony J. (Society for Range Management, 2009-11-01)
      Management of rangelands, and natural resources in general, has become increasingly complex. There is an atmosphere of increasing expectations for conservation efforts associated with a variety of issues from water quality to endangered species. We argue that many current issues are complex by their nature, which influences how we approach them. We define a complex problem as one that varies in time and space. In other words, one answer may not be correct for all sites or during all years. For simple problems a generalized answer may be sufficient, and even for complex problems, general rules provide a good starting point. However, we suggest that it is important to distinguish between simple and complex problems. Several key obstacles emerge when considering complex natural resource problems, namely, 1) no single entity can handle all aspects of the problem and 2) significant knowledge gaps exist and will continue to exist into the future. We suggest that overcoming these obstacles will benefit from 1) a framework for effective partnerships and 2) a mechanism for continuous learning. Managing complex problems will require some combination of the following: 1) a process-based understanding of the problem (i.e., what causes variation in time and space), 2) adaptive management, and 3) effective coordination of research and management. There are many examples of organizations applying portions of these approaches to complex problems; however, it seems that in many cases the process has simply evolved in that direction rather than being a planned strategy. We suggest that as a profession we need to have a discussion about the nature of the problems we are addressing and how researchers and managers can jointly address these problems. 
    • Smoke Solutions and Temperature Influence the Germination and Seedling Growth of South African Mesic Grassland Species

      Ghebrehiwot, Habteab M.; Kulkarni, Manoj G.; Kirkman, Kevin P.; Van Staden, Johannes (Society for Range Management, 2009-11-01)
      Fire, natural or of anthropologic origin, is a recurrent phenomenon in South African mesic grassland. The species composition of these grasslands is sensitive to fire, particularly fire frequency. However, the mechanisms involved in influencing species composition are not fully understood. Currently there is a general suggestion that plant-derived smoke and smoke-isolated biologically active butenolide compound provide an important germination cue for a range of Poaceae species. Studies also show that these smoke solutions play a role in vegetative growth of many plants. We examined if this fire-response syndrome is related to the effect of plant-derived smoke-water (1:500 v/v) and smoke-derived butenolide compound (1028 M) on seed germination and seedling growth of six major constituent species of the grassland. In addition, the interaction of the smoke solutions with temperature was examined by incubating seeds at a range of temperatures. Treating seeds with smoke-water and butenolide, the germination rate and final germination percentage were greater in three of the six species. Themeda triandra Forssk. and Tristachya leucothrix Trin. ex Nees showed the greatest response, with final germination increased from 43% to 67% and 35% to 63%, respectively. With increasing temperature (> 30 degreesC), Aristida junciformis Trin. Rupr., Hyparrhenia hirta (L.) Staph, and Panicum maximum Jacq. responded positively to the test solutions. In nearly all the species tested, smoke- water-treated seeds produced significantly longer shoots or roots. However, the degree of response varied from species to species and across different temperatures. Findings from this study suggest that plant-derived smoke and its interaction with temperature may significantly influence the germination and seedling growth of the South African mesic grassland species, which can further alter the grassland composition. 
    • Understanding Change: Integrating Rancher Knowledge Into State-and-Transition Models

      Knapp, Corrine Noel; Fernandez-Gimenez, Maria E. (Society for Range Management, 2009-11-01)
      Arid and semiarid rangelands often behave unpredictably in response to management actions and environmental stressors, making it difficult for ranchers to manage for long-term sustainability. State-and-transition models (STMs) depict current understanding of vegetation responses to management and environmental change in box-and-arrow diagrams. They are based on existing knowledge of the system and can be improved with long-term ecological monitoring data, histories, and experimentation. Rancher knowledge has been integrated in STMs; however, there has been little systematic analysis of how ranchers describe vegetation change, how their knowledge informs model components, and what opportunities and challenges exist for integrating local knowledge into STMs. Semistructured and field interviews demonstrated that rancher knowledge is valuable for providing detailed management histories and identifying management-defined states for STMs. Interviews with ranchers also provided an assessment of how ranchers perceive vegetation change, information about the causes of transitions, and indicators of change. Interviews placed vegetation change within a broader context of social and economic history, including regional changes in land use and management. Despite its potential utility, rancher knowledge is often heterogeneous and partial and can be difficult to elicit. Ranchers’ feedback pointed to limitations in existing ecological site-based approaches to STM development, especially issues of spatial scale, resolution, and interactions among adjacent vegetation types. Incorporating local knowledge into STM development may also increase communication between researchers and ranchers, potentially yielding more management-relevant research and more structured ways to document and learn from the evolving experiential knowledge of ranchers. 
    • Very-High-Resolution Panoramic Photography to Improve Conventional Rangeland Monitoring

      Nichols, Mary H.; Ruyle, George B.; Nourbakhsh, Illah R. (Society for Range Management, 2009-11-01)
      Rangeland monitoring often includes repeat photographs as a basis for documentation. Whereas photographic equipment and electronics have been evolving rapidly, photographic monitoring methods for rangelands have changed little over time because each picture is a compromise between resolution and area covered. Advances in image sensors, storage media, and image-processing software allow enormous amounts of information to be collected efficiently and inexpensively, so multiple pictures taken at full zoom can be combined into a single high-resolution panoramic image. This project was initiated to integrate very-high-resolution panoramic images with conventional rangeland monitoring methods addressing three resource management categories: riparian areas, wildlife, and invasive species.