Goose populations that winter in Oregon's Lower Willamette Valley have increased from 25 000 to more than 250 000 birds in the last 25 years, resulting in heavy grazing of wheat and other crops. To map and document the extent and intensity of goose impacts on wheat fields, we combined rectified aerial photography with both globally positioned ground observations and vertical platform photographs. Aerial photos revealed areas of fields with sparse wheat cover while platform photos documented the cause. We estimated wheat cover in ground level photographs by ratioing red, green and blue digital numbers. From platform photographs we recorded occurrence of grazing (from grazed leaf tips), intensity of grazing (from residual plant cover and leaf length), and other indicators of goose use (footprints and droppings). Because the ground photographs were spatially positioned, we could use this information to verify the cause of "thin" wheat. Crop damage from grazing/trampling, water submergence, and other factors was evident. Our results illustrate practical ways to combine aerial and groundlevel image analysis, spectral observations, and global positioning systems to quantify field conditions in wheat.

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Authors arerangescienrist USDA-ARS, Fort Keogh Livestockand Range Research Loboratory, Miles City, Mont. 59301; research animal scientist USDA-ARS, Forage and Livestock Research Laboratory, El Reno, Okla. 73036; range ecologist USDI-BLM, Oregon State University, Corvallis, Ore. 97331; range scientist and research leader, and range scientist (retired) USDA-ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City, Mont. 59301. Abstract Impacts of 7 range treatments and climate on late spring herbage standing crops (SC) were measured in rangelands near Miles City, Mont., from 1983 to 1990. Treatments, established in 8 pastures at 2 sites, were: (1) untreated control + season long grazing (SL); (2) soil tillage (ST) + SL; (3) ST + drill seeding legumes (DS) + SL; (4) brush control (BC) + ST + DS + switchback grazing (utilizing 2 pastures); (5) BC + ST + DS + SL; (6) ST + nitrogen fertilization + SL; and (7) contour furrowing (CF) + aerial seeding legumes + SL. Data were analyzed using years as a repeated measure. Treatments increased (prO.05) total SC 320 kg/ha over controls, but did not affect species/species group composition. Treated pastures produced similar (p10.10) SC of 881 kg/ha. Total SC averaged 490 kg/ha more (p10.05) in 1983,1986,1987,1989, and 1990 than in 1984,1985, and 1988. Perennial cool-season grass SC was greatest in 1986 (651 kg/ha). Peak annual grass SC (337-506 kg/ha) occurred in 1983 and 1984, the 2 years following ST or CF, and 1989 and 1990, the 2 years following severe drought. Although regression analyses showed fall, winter, and spring precipitation and temperature were closely related to spring SC, less than 50% of the variation in SC was accounted for when precipitation and temperature were summed on a l-month, 2-month, or 3-month basis. Above-average fall and spring precipitation (September and April) resulted in the greatest total SC. Species composition varied temporally with changing weather conditions and management strategies.

Effhxcy of a continuous release marker device (CRD) containing chromium oxide to estimate fecal output was evaluated in two It-day grazing trials with beef steers (n q 10, trial 1; n q 7, trial 2). Trial 1 was conducted on mature green irrigated tall wheatgrass (Elytrigiaponticu[Podp.] Holub) pasture during September. Trial 2 was conducted on dormant native range during December. Fecal output was determined by total fecal collection (TFC) and the CRD for each steer. Fecal output estimates from the CRD were based on a chromium release rate (980 mg/day) provided by the manufacturer. Estimates of daily fecal dry matter output (kg) in trial 1 were 2.70 and 2.69, and in trial 2 were 3.19 and 2.89 from the TFC and CRD, respectively. Differences between TFC and CRD were not significant in trial 1 (P q 0.59) but were significant in trial 2 (P

Livestock grazing has been implicated as a cause of the unhealthy condition of ponderosa pine forest stands in the western United States. An evaluation of livestock grazing impacts on natural resources requires an understanding of the context in which grazing occurred. Context should include timing of grazing, duration of grazing, intensity of grazing, and species of grazing animal. Historical context, when and under what circumstances grazing occurred, is also an important consideration. Many of the dense ponderosa pine forests and less-than-desirable forest health conditions of today originated in the early 1900s. Contributing to that condition was a convergence of fire, climate, and grazing factors that were unique to that time. During that time period, substantially fewer low-intensity ground fires (those that thinned dense stands of younger trees) were the result of reduced fine fuels (grazing), a substantial reduction in fires initiated by Native Americans, and effective fire-suppression programs. Especially favorable climate years for tree reproduction occurred during the early 1900s. Exceptionally heavy, unregulated, unmanaged grazing by very large numbers of horses, cattle, and sheep during the late nineteenth and early twentieth centuries occurred in most of the U.S. West and beginning earlier in portions of the Southwest. Today, livestock numbers on public lands are substantially lower than they were during this time and grazing is generally managed. Grazing then and grazing now are not the same. Dinámica de Bosques y Pastoreo de Ganado en un Contexto HistóricoResumen: El pastoreo de ganado ha sido implicado como una causa de la mala salud de los bosques de pino ponderosa en el occidente de Estados Unidos. La evaluación de los impactos del pastoreo sobre los recursos naturales requiere de conocimiento del contexto en que ocurrió el pastoreo. El contexto debe incluir al período de ocurrencia, la duración y la intensidad del pastoreo, así como la especie de animal que pastoreó. El contexto histórico, cuando y bajo que circunstancias ocurrió el pastoreo, también es una consideración importante. Muchos de los bosques densos de pino ponderosa y de las condiciones, menos que deseables, de salud de los bosques actuales se originaron al principio del siglo pasado. Contribuyó a esa condición una convergencia de factores, fuego, clima y pastoreo, que fueronúnicos en ese tiempo. Durante ese período, hubo sustancialmente menos incendios superficiales de baja intensidad (que afectaron a grupos densos deárboles más jóvenes) como resultado de la reducción de combustibles finos (pastoreo), una reducción sustancial en los incendios iniciados por Americanos Nativos y programas efectivos de supresión de incendios. Al inicio del siglo pasado hubo años con clima especialmente favorable para la reproducción deárboles. Al final del siglo diecinueve y comienzo del veinte hubo pastoreo no regulado ni manejado, excepcionalmente intensivo, por una gran cantidad de caballos, reses y ovejas en la mayor parte del oeste de E.U.A. y ...