Digital photography and subsequent image analysis for ground-cover measurements can increase sampling rate and measurement speed and probably can increase measurement accuracy. Reduced monitoring time (labor cost) can increase monitoring precision by allowing for increased sample numbers. Multiple platforms have been developed for close-to-earth remote sensing. Here we outline a new, 5.8-kg aluminum camera stand for acquiring stereo imagery from 2 m above ground level. The stand is easily transported to, from, and within study sites owing to its low weight, excellent balance, and break-down multipiece construction.

Tree encroachment in the ecotone between grassland and forest of interior British Columbia has resulted in decreasing grazing potential of rangelands. The 2 dominant tree species in this region, Douglas fir (Pseudotsuga menziesii var. glauca) and ponderosa pine (Pinus ponderosa), require stratification for seed dormancy release. The objective of this study was to determine whether seeds of these species can be stratified and dormancy released under grassland conditions. Field stratification experiments were conducted over 4 years using 2 Douglas fir and 3 ponderosa pine seed collections. A laboratory experiment was conducted to determine the effect of seedcoat removal, light, and stratification duration on dormancy release. Dormancy in Douglas fir and ponderosa pine was released after 1 to 2 months of stratification under grassland seedbed conditions when seeds were placed in the field in late fall and early winter. Continuous stratification until the following May was correlated with higher germination rate. One week of stratification in the laboratory was sufficient to break dormancy in the 2 species and a similar effect can be achieved by exposure to light. Seed coat removal for ponderosa pine also released dormancy, indicating that this structure imposes dormancy. Therefore, the grassland seedbeds near the forest edge can provide suitable conditions to break dormancy of Douglas fir and ponderosa pine seeds, contributing to tree encroachment into adjacent grasslands. Managements aiming to control tree encroachment should take the interaction between tree seed and grassland seedbed conditions into consideration, and the control should be focused on the elimination of seeds and seedlings but not on the germination stage.

Livestock seed dispersal (fecal seeding) is gaining recognition as a method to reintroduce desirable species to degraded rangelands. A field study was conducted to determine the influence of cattle dungpat thickness on the recruitment of Sandberg bluegrass (Poa secunda Presl.), bluebunch wheatgrass (Psuedoroegneria spicata [Pursh] A. Love), and ‘Hycrest’ crested wheatgrass (Agropyron desertorum [Fisch. ex Link] Schult. × A. cristatum [L.] Gaert.) in naturally and artificially deposited dungpats. Four Holstein heifers each were fed 60 000 seeds of each species. Twenty-four hours after feeding seeds, dung was collected from 2 animals receiving each plant species and formed into uniform, artificial dungpats (2 kg in mass) with thicknesses of 1, 2, and 4 cm, and respective diameters of 40, 28, and 20 cm, and deposited on bare soil. The other 2 animals receiving each plant species were used to deposit natural dungpats, varying in mass, thickness, and diameter, on bare soil. Seedling recruitment in all dungpat types was greatest for crested wheatgrass, followed by Sandberg bluegrass and bluebunch wheatgrass. Recruitment for all species was generally greatest in 1-cm-thick artificial dungpats, followed in order by 2-cm-thick artificial dungpats, natural dungpats, and 4-cm-thick artificial dungpats. Most seedlings, regardless of species, emerged and survived in the interior region of 1- and 2-cm-thick artificial dungpats and at the periphery of 4-cm-thick artificial dungpats. Most seedlings of crested wheatgrass and Sandberg bluegrass emerged and survived in cracks and depressions in the interior region of natural dungpats, whereas more bluebunch wheatgrass seedlings emerged and survived at the periphery of natural dungpats. Results indicate that the efficacy of cattle seed dispersal is influenced by the seedling vigor of species (seeds) consumed and the thickness of dungpats in which the ingested seeds are deposited. Grass species with weak seedling vigor (Sandberg bluegrass and bluebunch wheatgrass) have lower recruitment than species with strong seedling vigor (crested wheatgrass), particularly in dung > 2 cm thick.

Traditional forage nutrient analysis from benchtop near infrared spectroscopy (NIRS) or common laboratory chemical procedures provides accurate, point -based information, but often does not provide it in a timely way to allow changes in forage or animal management. The objective of this study is to determine the feasibility of estimating concentrations of nitrogen, neutral  detergent fiber (NDF), and acid detergent fiber (ADF) of live, standing forages using a handheld hyperspectral spectroradiometer (radiometer), and to compare these estimates to values determined via NIRS and laboratory chemical methods. Calibration equations were developed from canopy reflectance measurements from monocultures of Bermuda grass and then applied to a test data set to predict N, NDF, and ADE Statistical analyses showed that forage composition estimates from the radiometer were equivalent to those from the NIRS. Such a remote-sensing approach would enable real-time assessment of forage quality, would allow mapping of the nutritional landscape, could be used as a tool to better manage pastures and supplements, and would assist in making harvesting decisions.

Information on nutritive values of each plant part in each phenological stage could help range managers choose suitable grazing times to achieve higher animal performance without detriment to vegetation. Thus, nutritive value of different plant parts of 5 grass species in 3 phenological stages (vegetative, flowering, and seed production) from 2 sites were investigated. Species included: Agropyron tauri Boiss and Bal., Agropyron trichophorum Richt, Bromus tomentellus Boiss, Festuca ovina Hack, and Hordeum bulbosum L. Samples of leaf, stem, and flower from 5 locations at each site for each species were analyzed for dry matter ratio of plant parts, crude protein, acid detergent fiber, neutral detergent fiber, dry matter digestibility, and metabolizable energy. A completely randomized design with a factorial arrangement of species and phenological stage was analyzed with 5 replicates for each location. Plant part was included as a subplot factor in a split plot arrangement. Nutritive values differed significantly (P < 0.05) both within and among plant parts and phenological stages for each species. Phenological stages indicated a significant difference on nutritive value of plant parts, with leaves having the highest nutritive value. Thus, forage with a higher leaf-to-stem ratio should improve animal performance because at the beginning of the 2nd phenological stage, the plant had desirable quantity and quality of forage with higher leaf-to-stem ratio.

This study reports on changes in plant functional group composition, litter quality, and soil C and N mineralization dynamics from a 9-year sheep grazing study in Inner Mongolia. Addressed are these questions: 1) How does increasing grazing intensity affect plant community composition? 2) How does increasing grazing intensity alter soil C and N mineralization dynamics? 3) Do changes in soil C and N mineralization dynamics relate to changes in plant community composition via inputs of the quality or quantity of litter? Grazing plots were set up near the Inner Mongolia Grassland Ecosystem Research Station (IMGERS) with 5 grazing intensities: 1.3, 2.7, 4.0, 5.3, and 6.7 sheep ha-1 yr-1. Plant cover was lower with increasing grazing intensity, which was primarily due to a dramatic decline in grasses, Carex duriuscula, and Artemisia frigida. Changes in litter mass and percentage organic C resulted in lower total C in the litter layer at 4.0 and 5.3 sheep ha-1 yr-1 compared with 2.7 sheep ha-1 yr-1. Total litter N was lower at 5.3 sheep ha-1 yr-1 compared with 2.7 sheep ha-1 yr-1. Litter C:N ratios, an index of litter quality, were significantly lower at 4.0 sheep ha-1 yr-1 relative to 1.3 and 5.3 sheep ha-1 yr-1. Cumulative C mineralized after 16 days decreased with increasing grazing intensity. In contrast, net N mineralization (NH+4 + NO-3) after a 12-day incubation increased with increasing grazing intensity. Changes in C and N mineralization resulted in a narrowing of CO2-C:net Nmin ratios with increasing grazing intensity. Grazing explained 31% of the variability in the ratio of CO2-C:net Nmin. The ratio of CO2-C:net Nmin was positively correlated with litter mass. Furthermore, there was a positive correlation between litter mass and A. frigida cover. Results suggest that as grazing intensity increases, microbes become more C limited resulting in decreased microbial growth and demand for N.

Arbuscular mycorrhizae (AM) can ameliorate the impact of disturbance on agroecosystem sustainability. The objective of this study was to describe mycorrhizal colonization patterns in contrasting grazing situations (exclosure and continuous grazing) and topographical positions (upland and lowland) in the flooding pampa (Argentina). We determined the mycorrhizal colonization of the community as a whole and of Dallis grass (Paspalum dilatatum Poir.), a highly palatable, dominant species. We characterized colonization by the proportion of root length occupied by fungi and their different structures. At the community level, there was higher total colonization in the grazed area than in the exclosure. In contrast, Dallis grass showed higher total colonization and higher proportion of vesicles and arbuscules in the exclosure than in the grazed area. For both levels, colonization was higher in the lowland than in the upland position. Differences were observed only in winter and spring, not in summer. Our results show that 1) continuous grazing is associated with an increase of mycorrhizal colonization at the community level and 2) community-level patterns of mycorrhizal colonization cannot be inferred from dominant species. To our knowledge, this is the first characterization of AM abundance at the plant community level under contrasting long-term grazing conditions in a subhumid grassland.

Thousands of forb species are distributed among the diverse rangelands of North America. However, little is known about livestock grazing effects on the demographics and potential demise of palatable forbs in grassland ecosystems. A study was designed to quantify the cumulative effects of summer grazing on the demographics of stiff sunflower (Helianthus rigidus [Cass.] Desf. spp. subrhomboides [Rydb.] Heiser), a highly palatable, late-seral, perennial forb. Pastures were grazed for 5-7 days in mid-June or mid-July during 1995-1997 at 16, 32, or 48 animal unit days (AUD) per hectare. All grazing treatments reduced the plant height of stiff sunflower. However, population densities were maintained throughout the study at light stocking rates (16 AUD ha-1). In contrast, a single year of heavy stocking (48 AUD ha-1) in June reduced spring stiff sunflower densities 55%. Densities declined about 30% after 1 year at moderate stocking rates (32 AUD ha-1) in either month or heavy stocking in July. After 3 years of short-duration grazing in June, moderate and heavy stocking rates eliminated some colonies and reduced mean pasture densities by about 90% compared with 40% and 70% reductions in moderately and heavily stocked July-grazed pastures, respectively. Reductions in spring densities corresponded to increases in premature senescence the previous year when more than 30% of the plants turned brown before mid-August. Critical levels of premature senescence were likely to occur when more than 60% of stiff sunflower plants within colonies were grazed. Light stocking rates are rare on privately owned Nebraska Sandhills rangeland (4.7 million ha); therefore, vigorous populations of stiff sunflower are most likely to occur in pastures used predominantly during the dormant season.

The Nevada Plots exclosure system was constructed in 1937 following passage of the Taylor Grazing Act to assess long-term effects of livestock grazing on Nevada rangelands. A comparison of vegetation characteristics inside and outside exclosures was conducted during 2001 and 2002 at 16 sites. Data analysis was performed with a paired t test. Out of 238 cover and density comparisons between inside and outside exclosures at each site, 34 (14% of total) were different (P 0.05). Generally, where differences occurred, basal and canopy cover were greater inside exclosures and density was greater outside. Shrubs were taller inside exclosures at 3 sites grazed by sheep (Ovis aries). Perennial grasses showed no vertical height difference. Aboveground plant biomass production was different at only 1 site. Plant community diversity inside and outside exclosures were equal at 11 of 16 sites. Species richness was similar at all sites and never varied 4 species at any site. Few changes in species composition, cover, density, and production inside and outside exclosures have occurred in 65 years, indicating that recovery rates since pre-Taylor Grazing Act conditions were similar under moderate grazing and grazing exclusion on these exclosure sites.