Time filter

Source Type

Boise, ID, United States

Serpe M.D.,Boise State University | Roberts E.,Boise State University | Eldridge D.J.,University of New South Wales | Rosentreter R.,USDI Bureau of Land Management
Soil Biology and Biochemistry | Year: 2013

Invasion by the exotic annual grass Bromus tectorum has increased the cover and connectivity of fine litter in the sagebrush steppes of western North America. This litter tends to cover biological soil crusts, which could affect their metabolism and growth. To investigate this possible phenomenon, biological soil crusts dominated by either the moss Bryum argenteum or the lichen Diploschistes muscorum were covered with B. tectorum litter (litter treatment) or left uncovered (control treatment) and exposed to natural field conditions. After periods of five and ten months, we removed the litter and compared the photosynthetic performance of biological soil crusts from the two treatments. Litter induced photosynthetic changes in our samples. In both B. argenteum and D. muscorum, biological soil crusts that had been covered with litter for ten months had lower rates of gross photosynthesis and lower chlorophyll content than control samples. Similarly in both biological soil crust types, litter reduced the rate of dark respiration. For D. muscorum, the reduction in dark respiration fully compensated for the decrease in gross photosynthesis, resulting in similar values of net photosynthesis in the two treatments. In contrast, for B. argenteum, net photosynthesis was four-times greater in the control than the litter treatment. Also under litter cover, D. muscorum showed three common adaptations to shade conditions: a decrease in the light compensation point, in the light intensity needed to achieve 95% of maximal net photosynthesis, and in the chlorophyll a/. b ratio. None of these changes was apparent in B. argenteum. Overall, our results indicate that photosynthetic responses to the presence of litter varied among species of the crust biota and that the litter can reduce the photosynthetic capacity of biological soil crusts. These results help to explain field observations of decreases in biological soil crust cover and changes in biological soil crust composition with increases in litter cover, and suggest that the landscape-wide invasion by B. tectorum may have substantial effects on biological soil crust performance and therefore their capacity to function in semiarid shrublands. © 2013 Elsevier Ltd. Source

Perkins D.L.,USDI Bureau of Land Management | Jorgensen C.L.,U.S. Department of Agriculture | Rinella M.J.,U.S. Department of Agriculture
Forest Science | Year: 2015

Mountain pine beetles (Dendroctonus ponderosae Hopkins) have been killing pines on millions of ha throughout the western United States since 2000. One species being affected is whitebark pine (Pinus albicaulis Engelm.), a five-needle pine already experiencing a number of other threats. Whitebark pine is a keystone species providing a variety of values including watershed protection and food and habitat for wildlife. An increasingly used method of protecting pines from mountain pine beetles involves the antiaggregation pheromone verbenone, but no studies have evaluated the ability of verbenone applied annually to protect whitebark pines throughout mountain pine beetle outbreaks. We applied verbenone pouches annually for 7 years until an outbreak ended. Probabilities that whitebark pines survived through the end of the outbreak were 0.34 ± 0.15 for control trees and 0.68 ± 0.17 for trees treated with verbenone once per year. Evidence from a second verbenone treatment that was discontinued before the end of the outbreak suggested that applying verbenone twice, as opposed to once, per year may more effectively protect trees. Increased survival did not appear to vary with tree size (i.e., dbh). We believe increased survival of the magnitude we observed could reduce risks to threatened whitebark pine populations. © 2015 Society of American Foresters. All rights reserved. Source

Allen S.,USDI Bureau of Land Management
Marine Policy | Year: 2014

The movement toward catch shares by NOAA Fisheries and fisheries managers worldwide responds to dysfunctional fisheries plagued by a host of interrelated problems including radically shortened seasons, a race to fish, supply gluts, lowered product quality, increased bycatch, safety issues, excess capacity, and lack of profitability. However, the NOAA Catch Shares Policy recognizes that catch shares are not appropriate for every fishery, and others have agreed that the success of catch shares programs depends on their fit with ecological, economic, and social characteristics. This article describes the characteristics of the Hawaii-based deep-set longline fleet, identified by NOAA Fisheries as a possible candidate for catch shares because it operates under a bigeye tuna quota instituted by the Western and Central Pacific Fisheries Commission. One of the main concerns in the fishery is the potential for closing during the holiday season, a culturally important time for fish consumption in Hawaii. An evaluation of the fishery suggests that many of the problems leading to development of catch shares programs in other fisheries are not present, but that some warning signs exist which could be addressed by catch share programs or other management alternatives. © 2013. Source

Cox S.E.,USDI Bureau of Land Management | Booth D.T.,U.S. Department of Agriculture | Likins J.C.,USDI Bureau of Land Management
Environmental Management | Year: 2016

Increasing human population and intensive land use combined with a warming climate and chronically diminished snowpacks are putting more strain on water resources in the western United States. Properly functioning riparian systems slow runoff and store water, thus regulating extreme flows; however, riparian areas across the west are in a degraded condition with a majority of riparian systems not in proper functioning condition, and with widespread catastrophic erosion of water-storing peat and organic soils. Headcuts are the leading edge of catastrophic channel erosion. We used aerial imagery (1.4–3.3-cm pixel) to locate 163 headcuts in riparian areas in the Sweetwater subbasin of central Wyoming. We found 1-m—the generally available standard resolution for land management—and 30-cm pixel imagery to be inadequate for headcut identification. We also used Structure-from-Motion models built from ground-acquired imagery to model 18 headcuts from which we measured soil loss of 425–720 m3. Normalized by channel length, this represents a loss of 1.1–1.8 m3 m−1 channel. Monitoring headcuts, either from ground or aerial imagery, provides an objective indicator of sustainable riparian land management and identifies priority disturbance-mitigation areas. Image-based headcut monitoring must use data on the order of 3.3 cm ground sample distance, or greater resolution, to effectively capture the information needed for accurate assessments of riparian conditions. © 2015, Springer Science+Business Media New York (outside the USA). Source

Louhaichi M.,Oregon State University | Louhaichi M.,International Center for Agricultural Research in the Dry Areas | Carpinelli M.F.,U.S. Department of Agriculture | Richman L.M.,USDI Bureau of Land Management | Johnson D.E.,Oregon State University
Rangeland Journal | Year: 2012

Medusahead [Taeniatherum caput-medusae (L.) Nevski], a non-native, winter-annual grass (Poaceae), has invaded rangelands throughout the western USA. Medusahead is an aggressive competitor that crowds out native plants and reduces forage for wildlife and livestock. Sulfometuron methyl is a sulfonylurea herbicide used to control medusahead, but its effect on non-target native forbs is largely unknown. We assessed the impact of an autumn application of sulfometuron methyl on native forbs on the sagebrush/bunchgrass steppe of eastern Oregon over 3 years. We applied 70ga.i./ha (1.0oz. a.i./acre) of sulfometuron methyl to randomly selected locations on three sites in a split-plot-in-time (repeated-measures) experimental design. Three years after treatment, 6 of the 11 forb species studied had a significant reduction in density (P<0.05), with densities ranging from 3 to 60% of the pre-treatment levels. The results of this study suggest that the benefit of medusahead control by sulfometuron methyl should be weighed against the damage to non-target species. © Australian Rangeland Society 2012. Source

Discover hidden collaborations