This viewpoint paper examines criteria for preparing and evaluating manuscripts that involve stochastic approaches. Increasing use of stochastic mathematics to address inherent uncertainty in natural systems has meant increasing challenges to write and evaluate the manuscripts reporting such research. The paper provides a set of criteria directed at aiding authors, referees and associate editors in writing and evaluating this research. The paper asserts that for research papers to be acceptable to a management science journal such as the Journal of Range Management, they should at least be mathematically appropriate, functionally valid, pragmatically justified, technically comprehensible, and generally readable. It then examines the relationship of the concept of synthesis to the management implications sections of journal articles. The paper advocates increased attention to the concept of synthesis in making papers that report stochastic research in particular, and technical research in general, more understandable to readers, and more useful in range management science.

The animal unit has been a multiple-use concept in the natural resource sciences. This paper examines the animal unit as an example of a general process of concept design, a process involving multiple options for defining the concept, and multiple objectives and multiple applications for the concept in range management science. Based on this analysis, the animal unit is abstracted as a unit of energy demand independent of interactive considerations of forage or environment. The proposed definition optimizes the utility and universality of the concept by minimizing confounding in the concept's most important applications. The result is a simplified concept that can be used to explicitly express animal equivalences, and can be used in a web of more complex, interactive concepts and models involving human objectives, natural resources, and livestock. The animal unit and animal-unit equivalent are relatively simple examples of synthetic concepts involving communication that are central to the identity of range management science.

The goal of this study was to determine the potential to revegetate weed-infested rangeland by maximizing niche occupation and resource capture by desirable species. We hypothesized that as desirable species richness increases, weed establishment and growth decrease, provided that the desirable species differ in niche. Three desirable species with differing spatial and temporal growth patterns, [Agropyron cristatum (L.) Gaertn., var. Hycrest (crested wheatgrass), Elytrigia intermedia (Host) Nevski, var. Rush (intermediate wheatgrass), and Medicago sativa L., var. Arrow (alfalfa)], and 1 weed [Centaurea maculosa Lam. (spotted knapweed)], were grown in a multiple replacement series. All species were sown simultaneously in spring 1996, simulating revegetation of a site containing spotted knapweed seeds in the seed bank because of prior infestation. Desirable species richness varied among plots, while the total number of desirable seeds sown per plot was held constant. Although the desirable species were shown to differ in niche, desirable species richness or mixture did not affect soil water depletion or spotted knapweed recruitment in 1996 or 1997. These results suggest that revegetation of weed-infested rangeland must also include active control of weeds emerging from the soil seed bank. Only then can other strategies, such as maximizing niche occupation by desirable species, be expected to provide long-term success.

Stipa clarazii, Ball. has been shown to be more tolerant to defoliation and a superior competitor to S. tenuis Philo and S. ambigua Speg. 3 perennial grasses native to semiarid rangelands in central Argentina. Mechanisms contributing to its great defoliation tolerance and competitive ability, however, are largely unexplored. We examined tolerance to defoliation and ammonium uptake rates on defoliated and undefoliated plants of those species at 10, 25, and 50 ppm NH4+ using (NH4)2SO4 solutions containing 60 atom %15N excess. By mid-spring, greater regrowth following defoliation in S. clarazii than in S. tenuis or S. ambigua indicated greater defoliation tolerance in the first than in the other 2 species. Stipa clarazii had similar of higher ammonium uptake rates than S. tenuis and S. ambigua. Higher ammonium uptake rates in S. clarazii thus appear to be one of the mechanisms most likely contributing to its greater competitive ability and defoliation tolerance when compared to the other 2 species. Defoliated plants of all 3 species had similar or greater ammonium uptake rates than undefoliated plants. These results suggest that photosynthetic canopy reestablishment may be achieved without sacrificing root function in these perennial grasses, at least as long as carbon reserves do not become a limiting factor. Ammonium uptake rates increased when NH4+ concentrations increased in the labeled solutions in S. clarazii, S. tenuis and S. ambigua. This result demonstrates the capacity of the root system for increasing nutrient acquisition during periods of high resource availability.

Grasslands in the interior British Columbia of Canada are adjacent to forests and are susceptible to tree encroachment. Grazing, fire suppression, and climate variability are among factors affecting vegetation dynamics in the ecotone between grassland and forest, but topographic factors such as slope aspect, slope degree and elevation may interact with these factors and result in uneven changes in vegetation among landscape elements. Nine sites with a total of approximately 50,000 ha of grasslands and forests in the Cariboo/Chilcotin forest region of British Columbia were selected to study the effect of slope aspect, slope degree and elevation on vegetation distribution, dynamics and forest expansion from the 1960's to 1990's. Vegetation maps of the 1960's and 1990's were generated using aerial photos and overlaid with GIS layers including aspect, slope and elevation. The classification of open grassland, treed grassland, open forest and closed forest was based on the percent coverage of coniferous species, ranging from 0-5%, 5-15%, 15-35%, and ≥ 35%, respectively. A probability index (P-value) was developed to test the effect of aspect, slope, and elevation on vegetation distribution, dynamics, and forest expansion based on the distribution and changed areas. Results show that open grasslands occurred on southerly aspects and the shift to treed grassland occurred mostly on these aspects. The probability of vegetation shift from open to treed grasslands decreased with increasing slope degree, probably due to the less favorable moisture regime on steep slopes. Treed grassland also shifted to open forest on south facing slopes and more level sites. In contrast, closed forest most often occurred on northerly facing slopes and the shift from open to closed forests was most likely to occur there. The greatest changes in vegetation cover types occurred at mid-elevations between 700 and 1,000 m. Management plans aimed at the control of tree encroachment and forest ingrowth should take these topographic factors into consideration.

Long-term herbaceous response data following herbicidal treatment of honey mesquite (Prosopis glandulosa Torr.) are needed to develop more accurate projections regarding economic feasibility of these treatments and to model ecological interactions between woody and herbaceous plants in rangeland systems. Our objective was to measure herbaceous yield and mesquite regrowth 10 or 20 years after mesquite was aerially sprayed with either mesquite top-killing or root-killing herbicides. Treatments evaluated included mesquite top-killing herbicides at 10-12 years (T10) and 19-21 years (T20) post-treatment, mesquite root-killing herbicides at 10-12 years (R10) and 19-21 years (R20) post-treatment, and an untreated control where mesquite were 30 years old (C30). Treatments were applied in the late 1970's or late 1980's. Grass yields, measured annually from 1998 through 2000, were quantified within patches of 3 perennial grass functional groups: cool-season mid-grasses, warm-season mid-grasses, or warm-season short-grasses. Cool-season annual grass yields were also quantified within these perennial grass patches. By 1998, mesquite canopy cover was 55, 47, 36, 24, and 12% in C30, T20, T10, R20, and R10 treatments, respectively. Warm-season mid-grass yields were most sensitive to differences in mesquite cover in all 3 years and declined sharply when mesquite cover exceeded 30%. Cool-season mid-grass yields declined slightly with increasing mesquite cover. Warm-season short-grass and cool-season annual grass yields were not related to mesquite cover, except in 2000 when warm-season short-grass yield beneath mesquite canopies increased with increasing mesquite cover. Results suggest that herbicide treatment life (defined by increased perennial grass yield in response to mesquite treatments) was at least 20 years for the root-killing herbicide, but no longer than 10 years for the top-killing herbicide.

Responses of plant communities to mechanical treatments such as aeration on semiarid rangelands are not clearly understood. Our objective was to compare woody and herbaceous plant cover, density, and diversity on aerated and nontreated rangelands. Five rangeland sites that were aerated with a double/tandem drum aerator during summer 1998 and 5 sites of nontreated rangeland were selected for study on the Chaparral Wildlife Management Area, La Salle County, Tex. Woody plant cover was estimated using the line-intercept method, and stem density was estimated in 30 × 1.5 m plots in 1999 and 2000. Forb and grass cover and density were estimated in 20 × 50 cm quadrats during spring and fall 1999. Woody and herbaceous plant diversity did not differ between treatments. On aerated sites percent woody plant cover was 4-fold less 1-year after aeration and increased 89% from the first to the second growing-season post treatment. Canopy cover of honey mesquite (Prosopis glandulosa Torr.), twisted acacia (Acacia schaffneri S. Wats.), and Texas pricklypear (Opuntia lindheimeri Engelm.) was greater on non-treated sites. By the second growing season after aeration, density of honey mesquite was greater on aerated sites, whereas Texas pricklypear had declined on aerated sites. Density of spiny hackberry (Celtis pallida Torr.) and Texas persimmon (Diospyros texana Scheele) was greater on aerated sites during the first growing-season post treatment. Cover and stem density of hog-plum (Colubrina texana T. G.), coma (Bumelia celastrina Kunth), and whitebrush [Aloysia gratissima (Gill. Hook.) Tron.] did not differ among aerated and nontreated sites by the first growing season after aeration. Forb cover was greater on aerated sites in spring 1999. Fringed signalgrass [Brachiaria ciliatissima (Buckl.) Chase], fall witchgrass [Digitaria cognata (Schult.) Pilger], and bristlegrass (Setaria spp. Beauv.) cover was greater on aerated sites in spring and fall 1999, whereas purple threeawn (Aristida purpurea Nutt.) was greater on nontreated sites. It is unclear to what degree environmental factors such as pre- and post-treatment climatic conditions and herbivory may have influenced vegetation response to aeration. The rapid regrowth of many woody plants following aeration may require the application of maintenance treatments within a relatively short time period to maintain treatment benefits. Aeration reduced total woody plant cover, increased the density of desirable woody plants, maintained woody plant diversity, increased grass cover, and may be a useful tool in managing South Texas rangelands for white-tailed deer (Odocoileus virginianus Boddaert) and cattle.

Individual animal selection has been proposed as a tool for increasing uniformity of grazing on rugged rangeland. Daily grazing patterns of cows previously identified as preferring steeper slopes and higher elevations (hill climbers) were compared to cows preferring gentler slopes and lower elevations (bottom dwellers). Cows were ranked for slope use and vertical distance traveled to water during late summer in 1997 using horseback observers. In 1998, 9 extreme cows based on 1997 rankings (4 hill climbers and 5 bottom dwellers) were tracked using Global Positioning System (GPS) collars for 3 weeks during late summer on foothill rangeland. Hill climbers (1027 hours) arrived at water about 1 hour later (P = 0.04) than bottom dwellers (0928 hours). Hill climbers and bottom dwellers left water at the same time (1801 hours, P = 0.3). During this interval, 90% and 98% of the observations were within 100 and 200 m of water, respectively. While cattle were away from water (1901 to 0846 hours), 56%, 77%, and 87% of the observations were within 200, 300, and 400 m, respectively, from the cow's location at 0700 hours. Hill climbers spent 14% of their time on steeper slopes (20 to 30 degrees) while bottom dwellers spent 7% (P = 0.01), and hill climbers (41%) tended (P = 0.07) to spend less time on gentler slopes (0 to 10 degrees) than bottom dwellers (47%). Hill climbers (1323 m) were observed at higher elevations (P = 0.01) than bottom dwellers (1277 m). Horizontal distance traveled to water (633 m) was similar (P > 0.1) for hill climbers and bottom dwellers. Cow location during the early morning (0700 hours) was a good predictor of terrain used during the morning and previous evening grazing bouts. Cows tracked in this study did not appear to regularly associate with each other. They usually grazed in different areas of the pasture and regularly used different water sources. Individual cows within a herd can use different terrain even though many aspects of the grazing patterns are similar. Location of cows during the early morning and perhaps the time that cows travel to water can be used to identify differences in terrain use among individual animals.