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Ecological Relationships between Poisonous Plants and Rangeland Condition: A Review

Michael H. Ralphs
Journal of Range Management
Vol. 55, No. 3 (May, 2002), pp. 285-290
DOI: 10.2307/4003136
Stable URL: http://www.jstor.org/stable/4003136
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Ecological Relationships between Poisonous Plants and Rangeland Condition: A Review
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Abstract

In the past, excessive numbers of livestock on western U.S. rangelands, reoccurring droughts, and lack of management resulted in retrogression of plant communities. Poisonous plants and other less palatable species increased with declining range condition and livestock were forced to eat these poisonous species because of a shortage of desirable forage, resulting in large, catastrophic losses. The level of management on most western rangelands has improved during the last 60 years, resulting in marked improvement in range condition; yet losses to poisonous plants still occur, though not as large and catastrophic as in the past. Some poisonous species are major components of the pristine, pre-European plant communities [tall larkspur (Delphinium barbeyi Huth), Veratrum californicum Durand, water hemlock (Cicuta douglasii (DC.)Coult. & Rose), bracken fern (Pteridium aquilinum (L.) Kuhn), chokecherry (Prunus virginiana L.), Ponderosa pine (Pinus ponderosa Lawson), and various oak species (Quercus spp.)]. Although populations of many poisonous seral increaser species have declined with better management, they are still components of plant communities and fluctuate with changing precipitation patterns [locoweed (Astragalus and Oxytropis spp.), lupine (Lupinus spp.), death camas (Zigadenus spp.), snakeweed (Gutierrezia spp.), threadleaf groundsel (Senecio longolobis Benth.), low larkspur (Delphinium nuttallianum Pritz.), timber milkvetch (Astragalus miser Dougl. ex Hook.), redstem peavine (A. emoryanus (Rydb.) Cory), western bitterweed (Hymenoxys odorata D.C.), orange sneezeweed (Helenium hoopesii Gray), twin leaf senna (Cassia roemeriana Schelle), and white snakeroot (Eupatorium rugosum Houtt)]. Many of the alien invader species are poisonous: [Halogeton glomeratus (Bieb.) C.A. Mey, St. Johnswort (Hypericum perforatum L.), poison hemlock (Conium maculatum L.), tansy ragwort (Senecio jacobaea L.), hounds tongue (Cynoglossum officinale L.), leafy spurge (Euphorbia esula L.), yellow star thistle (Centaurea solstitialis L.) and other knapweeds (Centaurea spp.)]. Poisoning occurs when livestock consume these plants because they are either relatively more palatable than the associated forage, or from management mistakes of running short of desirable forage. /// En el pasado, el número excesivo de ganado en los pastizales del oeste de los Estados Unidos, las sequías recurrentes y la falta de manejo resultaron en la retrogresión de las comunidades vegetales. Las plantas tóxicas y otras especies menos gustadas se incrementaron declinando la condición del pastizal y el ganado fue forzado a comer estas especies tóxicas debido a la escases de forraje deseable, resultando en perdidas grandes y catastróficas. Durante los últimos 60 años, el nivel de manejo de la mayoría de los pastizales del oeste ha mejorado resultando en una marcada mejoría de la condición del pastizal; pero las perdidas por plantas tóxicas todavía ocurren, aunque no son tan grandes ni catastróficas como en el pasado. Algunas especies tóxicas son componentes principales de las comunidades vegetales prístinas pre-europeas ["Tall larkspur" (Delphinium barbeyi Huth), Veratrum californicum Durand, "Water hemlock" (Cicuta douglasii (DC.)Coult.. & Rose), "Bracken fern" (Pteridium aquilinum (L.) Kuhn), "Chokecherry" (Prunus virginiana L.), "Ponderosa pine" (Pinus ponderosa Lawson) y varias especies de encino (Quercus spp.)]. Aunque las poblaciones de muchas de estas especies tóxicas incresoras han disminuido con un mejor manejo, ellas todavía son componentes de las comunidades vegetales y fluctúan con los patrones cambiantes de precipitación ["Locoweed" (Astragalus and Oxytropis spp.), "Lupine" (Lupinus spp.), "Death camas" (Zigadenus spp.), "Snakeweed" (Gutierrezia spp.), "Threadleaf groundsel" (Senecio longolobis Benth.), "Low larkspur" (Delphinium nuttallianum Pritz.), "Timber milkvetch" (Astragalus miser Dougl. ex Hook.), "Redstem peavine" (A. emoryanus (Rydb.) Cory), "Western bitterweed" (Hymenoxys odorata D.C.), "Orange sneezeweed" (Helenium hoopesii Gray), "Twin leaf senna" (Cassia roemeriana Schelle) y "White snakeroot" (Eupatorium rugosum Houtt)]. Muchas de las especies invasoras extranjeras son tóxicas: [Halogeton glomeratus (Bieb.) C.A. Mey, "St. Johnswort" (Hypericum perforatum L.)," Poison hemlock" (Conium maculatum L.), "Tansy ragwort" (Senecio jacobaea L.), "Hounds tongue" (Cynoglossum officinale L.), "Leafy spurge" (Euphorbia esula L.), "Yellow star thistle" (Centaurea solstitialis L.) y otras "Knapweeds" (Centaurea spp.)]. El envenenamiento ocurre cuando el ganado consume estas plantas porque ellas son de una gustocidad relativamente mayor que el forraje asociado o por errores de manejo durante escases de forraje deseable.

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