• Persistence of a Severe Drought Increases Desertification but not Woody Dieback in Semiarid Savanna

      Carissa, L.W.; Twidwell, D.; Franz, T.E.; Taylor, C.A., Jr.; Rogers, W.E. (Society for Range Management, 2016)
      Increases in precipitation variability, coupledwith higher temperatures, will lead to greater frequencies of severe, prolonged droughts for many regions with the expectation of attendant increases in woody plant die-off events. We took advantage of a 2-yr extension of a severe drought following an initial study of woody plant dieback in a woody-encroached semiarid savanna in west-central Texas, United States. This study tests for the emergence of alternative vegetation trajectories as a result of continued drought persistence: 1) whether additional woody plant dieback occurred following the initial study, leading to a grass-dominated community, or 2) whether desertification became amajor feature (defined as a loss of herbaceous cover and increase in bare ground). Neither the emergence of a grass-dominated community nor the prevalence of desertification was observed during the initial study. After 2 additional yr of drought, we found that dieback of woody plants did not increase above previously observed levels, suggesting that the prolongation of drought did not cause the emergence of a grassdominated community in this heavily encroached rangeland. However, drought severity did lead to increases in desertification, with increases in bare ground owed to declines in grass cover. While previous research at this long-term research site suggests that desertification is transient with grasses rebounding once precipitation returns to predrought levels, rangelandmanagers should be aware of lags in vegetation response to drought and the increased potential for a shift toward a bare-ground dominated community following extended extreme drought. In this Texas semiarid savanna, major losses in herbaceous cover lagged behind woody plant dieback, so dieback of the woody component might hold promise as an indicator for near-termpotential of desertification. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Prescribed Fire Effects on Population Dynamics of an Annual Grassland

      Berleman, S.A.; Suding, K.N.; Fry, D.L.; Bartolome, J.W.; Stephens, S.L. (Society for Range Management, 2016)
      Medusahead (Elymus caput-medusae [L.] Nevski) is a highly damaging invasive annual grass in California rangelands. While it has been shown that prescribed fire can be a successful tool in controllingmedusahead populations, fire treatments are not always successful. Given the sociological and economic constraints of prescribed fire use, it is critically important that we maximize likelihood of treatment success. We conducted experimental investigation of population dynamics of competing species from different functional groups: invasive annual medusahead, naturalized but forageable nonnative wild oat (Avena spp. Pott ex Link), and native perennial purple needlegrass (Stipa pulchra [Hitchc.] Barkworth). We observed population dynamics at the 1-m2 scale before and after treatments of prescribed fire and seed-limitation (weed whipping in a 1-m buffer area). We asked 1) what is the role of seed dispersal from burn edges on subsequent medusahead population size? and 2) how do density and fecundity of the dominant species respond to fire? Results showed that 1) seed dispersal is an important factor in recovery dynamics and 2) wild oat fecundity significantly increases in the year after fire while medusahead and needlegrass fecundity seem minimally affected. Ultimately, managers should consider fire as a preferable first-entry tool and should thoroughly consider shape and size of planned burns, aswell aswhat vegetation is present to play a role in post-treatment seed-dispersal dynamics. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Response of Delphinium occidentale and Associated Vegetation to Aminocyclopyrachlor

      Greet, B.J.; Mealor, B.A.; Kniss, A.R. (Society for Range Management, 2016)
      Duncecap larkspur (Delphinium occidentale [Wats.] Wats.) is an important perennial weed on high-elevation rangelands because of significant cattle losses due to toxic alkaloids in the plant. Aminocyclopyrachlor was evaluated at six rates between 17.5 and 315 g ai · ha-1 for larkspur control alone, and in combination with chlorsulfuron or metsulfuron, at a high-elevation location in Wyoming. Aminocyclopyrachlor-containing treatments were compared with 1120 g ai · ha-1 picloram and 63 g ai · ha-1 metsulfuron-methyl. Herbicides were applied to two sites in a randomized complete block design with four replicates each on June 18, 2010 at the first site and June 28, 2011 at the second site. Larkspur mortality, plant species richness, vegetation cover, and grass biomass datawere collected 1 yr after treatment. Cover datawere used to calculate vegetation diversity and to assess changes in species composition associated with herbicide application. A four-parameter log-logistic model was used to evaluate larkspur mortality, species richness, and vegetation cover in response to aminocyclopyrachlor rate. Ninety-percent larkspur reduction was obtained with aminocyclopyrachlor applied alone at rates of 168-303 g ha-1, depending on site. Mixture of aminocyclopyrachlor plus chlorsulfuron at a 2.5:1 ratio required 102-127 g ha-1 of aminocyclopyrachlor to reduce larkspur 90%. Aminocyclopyrachlor plus metsulfuron was the most effective herbicide combination for larkspur control of those we evaluated, requiring 47+15 g ha-1, respectively, to reduce larkspur 90%. Species richness and diversitywere reduced by herbicide rates required to effectively control larkspur. Graminoid biomass was not significantly impacted by herbicide or rate. Aminocyclopyrachlor may be a useful tool for duncecap larkspur control. Addition of chlorsulfuron ormetsulfuron to aminocyclopyrachlor increased larkspur control but had a greater impact on associated nontarget vegetation. © 2016 The Society for Range Management. Published by Elsevier Inc.
    • Smoke and Ash Effects on Seedling Emergence from Germinable Soil Seed Bank in Fescue Prairie

      Ren, L.; Bai, Y. (Society for Range Management, 2016)
      Seedling recruitment plays a crucial role in recovering plant communities after disturbance. As a natural disturbance, fire canmediate species composition in fescue prairie. However, little was known about the effects of important fire cues on seedling recruitment in fescue prairie. Soil seed bank samples were taken fromthe top 5 cm of the soil profile and separated into litter, 0- to 1-cm, and 1- to 5-cm layers. Seedlings emerging from soil seed banks incubated in the greenhouse were examined after applying smoke, ash, and smoke plus ash in 2013 and 2014, to assess their effects on the density, richness, and composition of seedlings emerging from the soil seed bank in fescue prairie. Smoke plus ash significantly increased the number of Artemisia ludoviciana Nutt. seedlings emerging from 0- to 1-cm soil layer and Conyza canadensis (L.) Cronquist seedlings emerging fromthe litter layer (P < 0.05), while ash significantly increased the number of Artemisia frigida Willd. seedlings emerging from 0- to 1-cm soil layer (P < 0.05). Densities of total seedlings emerging from the 0- to 1-cm soil layer were increased by smoke plus ash in 2013 and by ash in 2014 (P < 0.05). Smoke plus ash and ash alone had more prominent effects on seedling density and richness of native forbs. Species composition was altered by ash in the 0- to 1-cm, 0- to 5- cm, and all layers combined in 2013 (P < 0.05). Direct fire cues appear to stimulate recruitment of some species, especially native forbs, contributing to potential changes in species composition of fescue prairie. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Synthesis Paper: Assessment of Research on Rangeland Fire as a Management Practice

      Limb, R.F.; Fuhlendorf, S.D.; Engle, D.M.; Miller, R.F. (Society for Range Management, 2016)
      Rangelands are fire-dependent ecosystems severely altered through direct fire suppression and fuels management. The removal of fire is a dominant cause of ecological sites moving across thresholds with the majority of North American rangelands currently showingmoderate or high departure from reference conditions. Recognizing the need to restore fire on rangelands and incorporate prescribed fire into management plans, the Natural Resource Conservation Service initiated the Conservation Effects Assessment Project (CEAP) to evaluate the validity current practices through peer-reviewed scientific literature. We updated the CEAP review and broadened the discussion of prescribed fire as a global management practice. We reviewed and summarized prescribed fire literature available through Web of Science using search terms in the title. The majority of literature (40%) evaluated plant responses to fire with fire behavior and management (29%), wildlife and arthropods (12%), soils (11%), and air quality (4%) evaluated less frequently. Generally, fire effects on plants are neutral to positive and the majority of negative responses lasted less than 2 years. Similarly, soil responses were recovered within 2 yr after burning. However, most studies did not report how long treatments were in place (62%) or the size of experimental units (52%). The experimental literature supporting prescribed burning is in need of greater managerial relevance that can be obtained by directly addressing spatial scale, temporal scale, and interaction with other disturbances, including drought and grazing. Reliance on information from single fires applied on small plots tracked for a relatively short time interval greatly constrains inferences and application to ecosystem management and information should be applied with caution. Therefore, conservation purposes need to incorporate temporal dynamics to the extent that this information is available. The complex interaction of scientific knowledge, social concerns, and variable policies across regions are major limitations to the successful and critical restoration of fire regimes. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Transition of Vegetation States Positively Affects Harvester Ants in the Great Basin, United States

      Holbrook, J.D.; Pilliod, D.S.; Arkle, R.S.; Rachlow, J.L.; Vierling, K.T.; Wiest, M.M. (Society for Range Management, 2016)
      Invasions by non-native plants can alter ecosystems such that new ecological states are reached, but less is known about how these transitions influence animal populations. Sagebrush (Artemisia tridentata) ecosystems are experiencing state changes because of fire and invasion by exotic annual grasses. Our goal was to study the effects of these state changes on the Owyhee and western harvester ants (Pogonomyrmex salinus Olsen and P. occidentalis Cresson, respectively). We sampled 358 1-ha plots across the northern Great Basin,which captured unburned and burned conditions across 1-31 years postfire. Our results indicated an immediate and consistent change in vegetation states fromshrubland to grassland between 1 and 31 years postfire. Harvester ant occupancy was unrelated to time since fire, whereas we observed a positive effect of fire on nest density. Similarly, we discovered that fire and invasion by exotic annuals were weak predictors of harvester ant occupancy but strong predictors of nest density. Occupancy of harvester ants wasmore likely in areas with finer-textured soils, low precipitation, abundant native forbs, and low shrub cover. Nest densitywas higher in arid locations that recently burned and exhibited abundant exotic annual and perennial (exotic and native) grasses. Finally,we discovered that burned areas that received postfire restoration had minimal influence on harvester ant occupancy or nest density compared with burned and untreated areas. These results suggest that fire-induced state changes from native shrublands to grasslands dominated by non-native grasses have a positive effect on density of harvester ants (but not occupancy), and that postfire restoration does not appear to positively or negatively affect harvester ants. Although wildfire and invasion by exotic annual grasses may negatively affect other species, harvester ants may indeed be one of the few winners among a myriad of losers linked to vegetation state changes within sagebrush ecosystems. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.