EOARC has many current and ongoing research projects. Click on any topic below to view projects relating to that topic for descriptions and contact information.
Current Rangeland Ecology and Management Research at EOARC
Carbon dioxide (CO2) is an important component of our atmosphere. It is used by plants during photosynthesis to capture and store energy from sunlight. The concentration of CO2 in the air never has been constant, however during the last century, levels of CO2 in the atmosphere have increased at an accelerated rate. This becomes important to mankind for two reasons.
First, since carbon dioxide is used by plants to capture and store energy, increasing concentrations of this compound probably have a fertilizing effect for plants. This has several important implications relating to plant productivity, water use efficiency and nutritional quality. In native ecosystems, differing abilities to use CO2 may lead to shifts in community composition and structure.
Second, carbon dioxide is one of those gasses which contributes to what is called the greenhouse effect, the warming of the earth's surface temperatures by the "insulating" effect of gasses such as carbon dioxide. There is considerable
debate over the consequences of any such warming effect.
To help address this issue, this research center, along with several other Agricultural Research Service locations has undertaken a long-term study to measure the amount of carbon dioxide taken up and released by plants and soil on rangelands throughout the United States. Here at EOARC, we have established a study looking at the dynamics of CO2 flux on burned and unburned sagebrush rangeland.
The study is still underway, however we are finding that these rangelands are acting as sinks for carbon dioxide for most of the year. What that means is that the plants take up more CO2 than is released by above and below ground respiration.
The picture to the right shows the equipment we use to estimate the direction and magnitude of CO2 movement between the atmosphere and surface. In a nutshell, the system measures carbon dioxide concentration at two heights, along with other needed information, and we then use these data to estimate the rate of movement toward or away from the surface.
One of the challenges of living and working in the Great Basin is the variable climate. However, there has been surpisingly little research on the effect of weather variation on rangeland vegetation. The difficulty in manipulating weather is part of the reason for the lack of prior research. One can attempt to document year-to-year changes in vegetation and relate the changes back to weather patterns. However, this approach requires very long time frames and there is still the problem of many variables to sort out (weather is more complex than just rainfall and temperature).
In this study we chose to focus on one question, "How does precipitation timing influence Great Basin vegetation?" This is a difficult subject to study because one cannot easily manipulate precipitation timing. Our approach was to exclude all precipitation with fixed location rain shelters and use an overhead sprinkler system to "rain on" three different zones under each rain shelter at the desired time.
We have five 30'x100' rain shelters each with three 30'x30' zones to which rain is applied at different times. Our three rainfall treatments (zones) are : 1) average current rainfall distribution, 2) a higher proportion of rainfall during winter, and 3) a higher proportion of rainfall during the spring. All three treatments recieve the same amount of precipitation.
Our measurements include variables such as plant development and productivity, species composition and cover, rooting activity, reproductive output, and soil moisture and nitrogen.
We hope the results of this study will help land managers better understand the impacts of weather on vegetation trends. Managers are faced with the challenge of separating the effects of weather from those induced by management. We also know that the Great Basin has undergone large changes in weather patterns in the past and will likely do so in the future. The results of this study might help us predict how climatic shifts will influence vegetation.
The 16,000 acre experimental range was established in 1937. The original directors of the experimental range had the foresight to establish thirteen 4-acre exclosures that have not been grazed by livestock since 1936. There was a detailed sampling of the vegetation when the exclosures were established, and several additional samplings over the past 60+ years. Most recently we have sampled for plant species compostion and cover inside and outside the exclosures in 1991, 1994, and 1997. The data is being analyzed for both changes over time, and grazing effects.
In three of the exclosures we added a burning treatment to the mix thus, we have grazed and ungrazed plots that were either burned, or left unburned. This arrangement will allow us to determine if there are interactions between burning and grazing. The burning treatments were applied during the fall of 1993 and sampling was conducted during 1992, 1993, 1994, and 1999. The first two samplings were prior to the burn, the second two after. An article detailing this study is currently in preparation. We will continue to take vegetation measurements in the exclosures in the foreseeable future.
For more information about this research contact Tony Svejcar or Rick Miller.
Western juniper (Juniperus occidentalis Hook var. occidentalis Vasek) currently occupies 5 million acres in Oregon, 3 million acres in northeastern California, a ½ million acres in Nevada and Idaho, and a few limited stands in southeastern Washington. In Oregon, western juniper is the most extensive conifer type. This species occupies a broad array of environments and soils varying from poorly drained heavy clays to excessively drained pumice sands. It is a relatively long lived species, exceeding ages of 1,000 years with the oldest living tree reported at 1600 years (Oregon's oldest tree recorded to date). On dry rocky sites, dead trees can remain standing for up to 600 years with the center growth ring dating as far back as 50 to 100 BC. However, an estimated 95% of western juniper is less than 100 years old.
Despite the large degree of variability of environments occupied by western juniper and the varying stages of woodland succession occupying today's landscapes, juniper woodlands are frequently treated generically in management, resource inventories, and wildlife habitat assessments. Our woodland expansion research program is; (1) documenting the chronology of expansion, (2) evaluating the impact of increasing tree dominance on understory plant composition across different soils and plant communities, and (3) evaluate the affects of woodland succession on abundance and diversity of avian populations.
Since the late 1800s western juniper has been actively encroaching or increasing in density in Intermountain plant communities ranging from shallow rocky heavy clay soils occupied by low sagebrush to deep clay loam or loam soils occupied by mountain big sagebrush or aspen groves. Accelerated juniper establishment began during the 1870s. The most rapid period of establishment occurred between 1885 and 1925, a period of wetter than average conditions, few fires, and intensive livestock grazing. The majority of western juniper woodlands are still in a state of change, succeeding from open juniper shrub steppe communities to closed woodlands.
As juniper dominance increases on a site the shrub understory declines. In the mountain big sagebrush alliance, sagebrush cover declined to approximately 80% of maximum potential as juniper increased to about 50% of maximum canopy cover. Mountain mahogany, bitterbrush, and aspen also declined as juniper dominance increased. Herbaceous cover and species diversity declined and bare ground increased with increasing juniper dominance in the mountain big sagebrush/Thurber needlegrass association. However, herbaceous cover on the deeper soils characterized by Idaho fescue did not decrease with increasing juniper dominance.
If you are interested in this study, check these recent publications , or contact Rick Miller , Tony Svejcar , or Jon Bates at this location.
In the Intermountain West, it is estimated that 3 to 5%, or nearly 1.25 million ha, of western juniper woodland is old-growth. Old growth juniper has largely been ignored throughout this region. Attention has primarily focused on the rapidly expanding postsettlement stands of juniper throughout the western United States. Resource inventories, management plans, range improvement practices, research, and wildlife habitat evaluations typically have not differentiated between old-growth juniper and postsettlement woodlands. In addition, work describing old growth stand characteristics has been derived from more mesic heavily forested communities. These stand characteristics may not directly apply to semi-arid woodlands in the Intermountain West. Future work and inventories of old growth woodlands requires criteria for defining old growth across different habitats.
Increasing recognition by land managers and land owners of the existence of these communities has prompted questions about how to recognize old-growth, old growth community structure and composition, ecological importance of old growth, and appropriate management. Our recent efforts have focused on determining the age of old growth woodlands, describing composition and structure, developing criteria for identifying old growth woodlands based on community structure and tree growth form, and measuring abundance and diversity of birds and small mammals in old growth stands.
This study is still ongoing, however, facts of interest are: (1) trees can exceed ages of 1,000 years with the oldest living western juniper aged at 1600 years, (2) trees on arid sites can remain standing dead for hundreds of years, (3) the most extensive stands of old growth typically grow on the wind blown pumice sands of central Oregon, (4) most of these old stands are relatively open, ranging between 10 and 20% tree cover, (5) old woodlands in central Oregon support a relatively high abundance of birds during the breeding season, and (6) these old woodlands provide important avian wintering habitat. We have identified one extensive old growth woodland in the High Desert Ecological Province, which is typically characterized by widely scattered presettlement trees growing on shallow rocky soils. Woodland structure is very different on these igneous soils. Canopy cover ranges from 30% on the south aspect to 50% on the north aspect and few shrubs exist in the understory.
If you are interested in this study, check these recent publications , or contact Rick Miller.
The recent expansion of western juniper throughout eastern Oregon and northeastern California began during the late 1800s. Postsettlement juniper woodland expansion in the West has been most frequently attributed to the introduction and overstocking of livestock, the reduced role of fire, and optimal climatic conditions during the late 1800s. However, few studies have been conducted that directly support this idea. Only a handful of studies have documented mean fire intervals in the sagebrush steppe biome, and few if any have evaluated the chronosequence of the introduction of livestock, the reduced role of fire, and climatic conditions with the initiation of postsettlement woodland expansion.
This study was designed to: (1) document the chronology of western juniper age distribution; (2) document pre- and postsettlement mean fire intervals in a mountain big sagebrush steppe community; and (3) determine the proportion of large to small fires, and evaluate their relationship to growing conditions in years preceding and concurrent with fire events. The work is being conducted throughout central and southeast Oregon, and northeast California.
We are still constructing fire histories for many mountain big sagebrush communities throughout the study area. However, we have completed our work in the Chewaucan River Basin. In this 5,000 ha watershed we found western juniper expansion began between 1875 and 1885, with peak expansion rates occurring between 1905 and 1925. The fire record spans 1601 to 1996. Before 1897, mean fire intervals within individual clusters ranged from 12 to 15 years with years between fires varying between 3 to 28. Nearly one third of the fires in the basin were large and usually proceeded by one year of above-average growing conditions. Two fire events were recorded in the sparsely vegetated low sagebrush site, 1717 and 1855. The last large fire occurred in the study area in 1870 and the last small fire in 1897. The time sequence of wet climatic conditions between 1870 and 1915, introduction of livestock, and the reduced role of fire support the hypothesis that these factors contributed to the postsettlement expansion of western juniper.
We are in the process of developing fire histories for 7 additional sites. The fire record ranges from the early 1500s to present. Mean fire return intervals vary from 12 to 20 years, however, not all samples have been analyzed.
If you are interested in this study, check these recent publications , or contact Rick Miller at this location.
Fire played an important role in shaping many of the shrub steppe communities in the Intermountain West prior to Eurasian settlement. However, the role of fire was very dependent on plant community type. Presettlement fires occurred every 15 to 25 years in the relatively wet mountain big sagebrush communities decreasing to 50 to 100 years in the more arid Wyoming big sagebrush communities, to less than 100 years in low sagebrush stands. However, the role of fire has significantly changed across sagebrush communities since the late 1800s.
Recent concerns about fire, prescribed and wild, have increased the need for information on whole system responses. The lack of this type of information makes it difficult to address some of the questions raised by burning. Our research effort has focused on the response of plant and animal communities in sagebrush steppe community types to wild and prescribed fire. This ongoing effort is currently looking at; (1) changes in plant composition and structure in mountain and Wyoming big sagebrush, and low sagebrush communities, and (2) evaluate the affects of fire on abundance and species composition of birds, small mammals, and butterflies in mountain big sagebrush communities. The work is being conducted in southeast Oregon, northwest Nevada, and northeast California.
Preliminary results for mountain big sagebrush prescribed and wild fires:
1. Response of perennial grass cover was inconsistent, however, perennial and annual forbs consistently increased in the burned areas.
2. Litter cover is reduced from 4.5% to less the 1% following a fire but approaches preburn levels after 3 growing seasons.
3. Bareground is increased from 1 to 3 years following fire.
4. Introduced annual grasses, which accounted for less than 1% cover prior to burning, did not increase following fire.
5. Bird abundance on burn communities varied from being similar to greater than unburned sites.
6. The abundance of butterflies appear to be unaffected by fire, however, species composition is altered.
If you are interested in this study, check these recent publications , or contact Rick Miller .
It is generally accepted that aspen stands in the Blue Mountains and Northern Great Basin are in an ongoing state of decline. In some cases only one or two trees remain in a stand, and it is reasonable to conclude that extensive stand loss has occurred during the last several decades. The purpose of this study is to investigate the status and trend of aspen stands in the Blue Mountains and evaluate the success of ongoing aspen rehabilitation methodologies. The primary objectives are:
From the stated objectives we hope to 1) develop a better understanding of the past and present status, and trend of aspen; 2) identify aspen rehabilitation methods now in use and evaluate their level of success; 3) identify factors leading to aspen decline; 4) develop a working partnership between EOARC, BLM and USFS to initiate an intensive study of aspen in the Blue Mountains and northern Great Basin that will provide managers with methodologies of rehabilitation that have a high expectation of success and increase the knowledge base of aspen ecology.
In the Northwest Great Basin, aspen communities uniquely contribute to the biodiversity of a semi-arid, sagebrush-dominated landscape. In this same region, western juniper is encroaching into aspen stands. Aspen stands below 2,133 m elevation were sampled in northwest Nevada, northeast California, and southeast Oregon for density, canopy cover, age, stand structure, and recruitment of western juniper and aspen. Soils and tree litter from both species were collected to analyze the effects of western juniper in areas previously influenced by aspen. Additionally, two large aspen complexes in southeast Oregon were intensively aged to determine disturbance (fire) frequencies.
Western juniper encroachment into aspen stands peaked from 1920 to 1939 with 77% of all juniper trees sampled establishing during this period. Five percent were greater than 100 years and none exceeded 145 years. Three-fourths of aspen stands sampled have established populations of western juniper. Twenty-three percent have a dominant canopy of western juniper. Twelve percent of aspen stands sampled were completely replaced by western juniper. Average density of western juniper was 1,573 trees per hectare of aspen. Seventy percent of aspen stands sampled had zero recruitment of new aspen. Within the study area aspen stands averaged 98 years old. Forty-eight percent of stands were greater than 100 years old. There was an inverse correlation between aspen canopy cover and western juniper canopy cover (r2 = .80, p = .0001).
Soils influenced by western juniper had a higher C:N ratio and pH; higher amounts of salts, lime, and sulfate; and lower amounts of magnesium, iron, copper, and manganese (p < .05). Aspen litter had a lower C:N ratio than western juniper litter (p < .05). Prior to 1870, the two major aspen complexes sampled had mean fire return intervals of 10 and 11 years. However, the most recent disturbance in either complex was 80 to 90 years ago. This lack of disturbance (fire) coupled with aspen stand decadence and low recruitment levels leaves aspen communities in the Northwest Great Basin vulnerable to western juniper encroachment and replacement.
If you are interested in this study, contact Rick Miller , or Marty Vavra.
Attempts to classify the “health” or “functionality” of riparian systems typically focus on morphology of the stream channel and associated banks, and attempt to relate this information to the potential hydrologic activity of the stream. In this paradigm, riparian vegetation composition is often viewed as a consequence of stream morphology, or, alternatively, a direct result of management actions (i.e. livestock grazing). This view of riparian plant community ecology is incomplete, in that it does not take into consideration other site factors (e.g. soil texture, limiting layers…) which may influence the presence or absence of a given plant community type. At present, there is little empirical information on the site factors required for establishment and persistence of specific plant community types in riparian zones in southeast Oregon. In upland areas, the type of “ecological site” denotes the particular suite of environmental conditions present at a given site and serves as a useful reference for deducing the range of plant community types capable of existing at that site. It is our view that a similar approach applied to riparian areas may increase our understanding of plant community dynamics in these systems. Our overall aim in this project is to delineate environmental factors that influence plant community composition of riparian areas in southeast Oregon. We will simultaneously examine the specific and interactive effects of management actions.
Fieldwork will take place on Rattlesnake Creek, Sawtooth Creek, and Nicoll Creek, in northern Harney County, OR during the 2000 and 2001 growing seasons. We will attempt to sample a set of sites that represents our interpretation of the range of plant community types extant on a given drainage. At each site we will estimate vegetation composition and record soil properties, stream characteristics. Management information will be obtained from the appropriate management agency or landowner. We will attempt to sample a total of 25 sites per creek during the 2000 and 2001 growing seasons, for a total of 150 sites.
In the data analysis phase of this project we will use statistical procedures to group similar plant communities and define important environmental variables which influence plant community type (e.g. soil texture, soil moisture, elevation). Similar procedures will be used to determine what environmental factors most influence plant species composition within a given community type.
The end product of our efforts will be a publication detailing riparian plant community types along with the environmental and management factors influencing plant species composition. Information gained from this effort should allow managers to more accurately separate the influences of management actions and site conditions on plant community dynamics, and should serve as a useful reference for stream rehabilitation/re-vegetation efforts.
If you are interested in this study, contact Chad Boyd.
Dr. Boyd is a member of the Oregon Sage-grouse planning team, and organized a diverse group of authors in developing and invited synthesis paper on the ecology and management of sage-grouse for the Journal of Range Management. He currently serves on the technical review panel for the Natural Resource Conservation Service’s “Sage-grouse Restoration Project”.
Research activities (Livestock grazing study)
Livestock grazing has been indirectly related to sage-grouse declines in the western United States and southern Canada; however, there is a lack of scientific research that directly relates the two. We used grazing trials conducted in the summer of 2003 and 2004 to determine the level of utilization at which cattle begin to access herbaceous vegetation adjacent to and under the canopy of sagebrush. This vegetation is thought to provide important screening cover for nesting sage-grouse, providing a degree of protection from potential nest predators. Four pastures 15 acre pastures were fenced in a Wyoming big sagebrush community and each stocked with 3 to 4 yearling heifers. Within each pasture 30 sagebrush plants were randomly located and a randomly selected perennial grass was permanently marked under the canopy of each sagebrush and a second marked in the interspace between shrubs. Visual obstruction for a potential nest site was measured using a modified Robel pole to document changes in screening cover with increasing herbaceous utilization. Grass plants were checked every second day and given a grazed or ungrazed score. Changes in standing crop and utilization (by weight) were assessed weekly by clipping 20 random 1-m² plots in each pasture. Grazing of under-canopy plants was negligible at light to moderate levels of utilization (e.g. < 10% of under canopy plants were grazed at 30% pasture utilization). At utilization levels >30% by weight, under canopy plants were used with increasing frequency. There was no statistical effect on visual obscurity with consumption of forage for this environment. Overall, our data suggest that sagebrush constituted the bulk of screening cover at this site and that utilization of understory grasses will be minimal with light grazing.
Crawford, J.A., R.A. Olson, N.E. West, J.C. Mosley, M.A. Schroeder, T.D. Whitson, R.F. Miller, M.A. Gregg, and C.S. Boyd. 2004. Ecology and management of sage-grouse and sage-grouse habitat. Journal of Range Management 57:2-19.
France, K.A. 2005. Interspace/Under-canopy Foraging Patterns of Beef Cattle in Sagebrush Communities: Implications to Sage-grouse Nesting Habitat. M.S. Thesis, Oregon State University, Corvallis.
If you are interested in this study, contact Chad Boyd.
Few logistically feasible techniques exist for monitoring changes in the biomass of willow and other woody riparian species. In this ongoing project, we are attempting to develop a method for monitoring changes in willow biomass which is based on evaluating percent visual obstruction and incorporates the use of scanned 35mm images. The relationship between visual obstruction and willow biomass is determined using a sequential removal technique. Harvested willow branches are placed in a holding device such that they are oriented perpendicular to the ground and located in front of a 70 x 50cm photoboard. The leaves obstructing view of the photoboard are then incrementally removed, with each successive removal representing an approximately 25% decrease in visual obstruction of the photoboard. A photo is taken, before and after each removal, and harvested leaf material is dried and weighed. Camera placement is 3.5 meters from the photoboard with a lens focal length of 80mm. Slides are then scanned and cropped to encompass the dimensions of the photoboard. Visual obstruction is estimated for all scanned images, using Sigma Scan 5.0 computer software, by determining the amount of the photoboard visible in the image and comparing that to its' actual area. The relationship between percent visual obstruction and leaf biomass is evaluated by regressing the amount of leaf biomass covering the photoboard against percent visual obstruction. Preliminary results indicate a strong relationship between visual obstruction and willow leaf biomass.
We are currently exploring the idea of using permanent photo monitoring stations to evaluate changes in willow biomass over time. Each monitoring station will consist of two 2 x 12" boards placed behind a willow clump (Figure 1).
The boards will be placed at roughly 1/2 and 2/3 the height of the willow clump. If the clump is immature, an average willow height of nearby mature willows will be used to determine height placement of boards. Annual photographs will be taken from a permanent photo point located perpendicular to the visual obstruction boards. We will use a minimum focal length of 50mm to minimize distortion of scale, and the photo-point will be located just far enough from the willow clump to frame the mounting posts in the photograph. Photos will be scanned and visual obstruction of each board will be determined. This setup will facilitate determination of visual obstruction at two levels in the tree canopy. Changes in these readings from year to year can be used to imply changes in biomass of the willow clump. The boards will be of known length and can be used as scale references for determining the height and width of the clump.
If you are interested in this study, contact Chad Boyd at this location.
Current Livestock and Forage Research at EOARC
Many cattle in the western United States consume low-quality forage ( < 6% Crude Protein) from late summer through winter. Digestible crude protein is normally insufficient to maintain cow weight and body condition during this period.
Supplementation with protein increases cow weight gain and body condition score, forage intake and digestibility, and can improve reproductive performance. However, winter supplementation can be very expensive. In addition to actual supplement costs, winter supplementation includes other expenses such as the labor, time, and equipment associated with supplement delivery.
Decreasing the frequency of protein supplementation is one management practice that decreases labor and time costs. It has been suggested that recycling of absorbed N to the rumen may support fermentation between times of supplementation. In addition, research has shown that protein supplements can be fed at infrequent intervals and still maintain acceptable levels of performance. However, data is limited comparing the effects of degradable intake protein (DIP) and undegradable intake protein (UIP) supplemented at infrequent intervals on forage intake, forage digestibility, microbial protein synthesis, and efficiency of N use. Therefore, current studies include:
Influence of protein Degradability and Supplementation Frequency on Lambs Consuming Low-Quality Forage: Efficiency of Nitrogen Use
Influence of Rumen Protein Degradability and Supplementation Frequency on Steers Consuming Low-Quality Forage: Ruminal Fermentation, Site and Extent of Nutrient Digestibility, and Microbial Efficiency
Influence of Rumen Protein Degradability and Supplementation Frequency on Cows Consuming Low-Quality Forage: Cow Performance
Influence of Protein Supplementation Frequency on Cows Consuming Low-Quality Forage: Performance, Intake, Harvest Efficiency, and Pasture Utilization
The objective of this research is to determine the influence of ruminal protein degradability and supplementation frequency on utilization of low-quality forage by ruminants. This knowledge will assist in developing management strategies that help reduce winter feed costs while maintaining acceptable levels of production
For more information about this research contact Dave Bohnert.
To a high degree, both wild and domestic herbivores are creatures of habit, and they typically choose to occupy only small portions of the entire landscape that is available to them. In extensive rangeland settings, intensively used areas may be associated with the presence of scarce but necessary resources like water, shade, hiding cover, or mineral sources, and animals will center their activities about those areas. One problem associated with these uneven patterns of distribution is that preferred forages in some areas may endure repeated and eventually detrimental use, while similar forages in many unused areas may never be grazed. A positive aspect of this, however, is that on a landscape basis, a greater diversity of plants and animals may occur where patches of grazed and ungrazed vegetation co-exist.
The inexpensive forages of rangeland pastures have the capacity to support many more animals if the herbivores can be lured into previously unused areas. Historically, water developments, fencing, herders, and mineral supplements have been used to encourage or discourage livestock grazing on rangelands. These are costly and occasionally prohibited methods of influencing livestock distribution in extensive settings, and less expensive and more environmentally sensitive techniques are needed to manipulate livestock dispersal patterns.
To assist with this problem several studies have been designed to more thoroughly understand which plant, animal, and landscape features most heavily influence livestock grazing behavior. At the plant level we have found that beef cattle can be extremely selective foragers, extracting as much as 80 percent of their diet from only 3 percent of the forage base. Cattle are also quite aware of standing-dead stems in their forages, and they prefer to use plants or areas that require little if any sorting of old and new growth.
Presently GPS collars and GIS software are being used to investigate spatial patterns of beef cattle distribution at landscape levels. Effects of salt and water manipulations are currently being researched, and the influences of previous grazing history of the landscape and the spatial patterns of forage quality will be studied in the near future.
If you are interested in these projects, contact Dave Ganskopp.
The objective of this research is to determine if a source of fermentable fiber (beet pulp) can increase the performance of steers and heifers grazing native flood meadows. In addition, if beet supplementation positively effects animal performance, this study will determine what level of beet pulp supplementation is used most efficiently.
For more information about this research contact Dave Bohnert.
Current Wildlife/Forestry Research at EOARC.
In the Intermountain West where summer precipitation does not generally occur, grasses normally mature early in the summer. When mature, grasses usually have rather poor nutritional quality. Mule deer and pronghorn seldom use mature grasses in their diets during fall, winter and early spring for this reason. Elk will utilize them but nutrient content of the grasses will not meet the nutritional requirements of elk. Controlled grazing with livestock provides a potential method of improving both protein and energy content of grasses as well as improving the palatability of them for mule deer, pronghorn and elk.
Livestock grazing in the spring when grasses are in the boot stage, just as the seed heads are forming in the sheaths of the plants, removes most of the plant material. This forces the grass plants to begin again. As this regrowth develops, soil moisture is being depleted. If timing is correct there is insufficient soil moisture available to complete the growth cycle of the grass and the plants will go into dormancy in an immature stage. This immature stage is higher in nutrient content than if the plants were allowed to complete their life cycle and produce seed. The lack of reproductive stems also improves the palatability of the grasses to wild ungulates. This same management strategy can also be used to enhance the growth of desirable shrubs like bitterbrush. The trick is to remove the livestock when sufficient soil moisture remains to provide regrowth of the grasses or additional growth by shrubs. This system must not be used annually, as the grasses need to be rested every other year and allowed to complete their life cycle.
A multiple pasture grazing system that provides both rest and deferment as well as spring use treatments will provide high quality conditioned grasses for wildlife use later in the year, rest for regaining vigor and seed production of the grasses, and seasonal forage for livestock during spring and early summer. Forage produced in the rested pasture will also be available for use by wildlife. The deferred pasture will be used by livestock after soil moisture is low enough so that spring regrowth will not occur. However, if fall rains occur, regrowth may develop at this time and be readily available to wildlife.
In forests, the kind and amount of overstory vegetation is influenced by both the tree canopy and the season and intensity of ungulate herbivory. As tree canopy increases, the trees are able to outcompete understory vegetation for available moisture and soil nutrients. Shading is also important in thicker overstories. Additionally, grazing animals like mule deer, elk and cattle consume understory vegetation, sometimes to the extent that the plants drop out of the understory. This understory vegetation is important to a variety of small mammals and birds. Therefore, the interaction of overstory density and grazing pressure is important to maintaining biodiversity at the landscape level in forested ecosystems.
This research project is just beginning. We will be observing and evaluating the influence of various logging methods and the influence of grazing animals on the composition and production of forest understory vegetation.
For more information about this research contact Marty Vavra.
Our ability to prescribe management actions to optimize the nature, extent, and distribution of favorable habitat conditions for bird populations across successional stages of juniper woodlands is extremely limited. Juniper woodlands have expanded at unprecedented rates during the past 120 years in the Intermountain west. In order to conserve or create optimal breeding habitats for a large number of birds, we must understand which successional stages are necessary, and to what extent.
The overall goal of this program is to investigate avian populations along a successional gradient of juniper woodland communities during breeding season and in the winter. Information will available for incorporation into planning prescribed burns, juniper tree harvest, and other landscape treatments across shrub-western juniper landscapes toward optimizing the extent and distribution of various successional stages for bird species.
Breeding season sampling was conducted at 3 study areas in 1996, 7 in 1997, 5 in 1998, and 1 in 1999. In1996, we observed 2947 birds of 60 species. Diversity, number of species, and number of individuals observed was higher in the cut plots than in the uncut. When contrasting old growth woodland with adjacent shrubland, diversity was similar, while the number of species and the number of individuals was higher in shrub sites.
In 1997, we counted 5991 birds of 67 species. The 10 most common species comprised 2/3 of all observations. A similar pattern in density, abundance, and species richness emerged from the mid-aged woodland versus cut unit comparisons. Results from old-growth versus shrub site comparisons were somewhat inconsistent between the 2 study areas, although all measures were relatively high in both types of site. In a comparison of burned versus unburned shrubland in Nevada, little difference was found except that number of individuals observed was higher in burned than unburned blocks, possibly due to large aggregations of horned larks in the burned sites.
In 1998, 3298 birds of 64 species were encountered. Initial summarization indicates a similar trend in measures among treatments. We plan to compare changes over time with this year's data.
Winter bird surveys were conducted monthly in the pumice zone of central Oregon from December through April, 1998-99 in four community structural types. Structural types were: 1) recently burned (grassland), 2) shrub steppe, 3) mid-successional woodland (juniper –shrub steppe), and 4) open old growth woodland. Over the winter , 776 individuals of 24 species were enumerated. American Robins and Townsend's Solitaires were the most common species encountered with 132 observations each . The number of species observed in each monthly sampling session increased after January, peaking at 18 in April. The number of observations was higher in the latter 2 sampling periods. The number of species found in the 4 cover types was quite similar across the sampling period. However, there were large seasonal differences among structural types. During mid-winter the greatest abundance of birds were observed in the two juniper structural types, with few birds measured in the shrub steppe and grassland communities. The number of observations, however, was highly variable, with the most birds found in the mid-successional stands (275 birds). Within the grassland community, the number of birds and species seen generally increased through the winter. In the shrub steppe, no birds were observed during the second session. The Number observed was quite high during the last 2 sessions compared to the first 2. In the mid successional juniper woodland community, the number of species generally increased, while the number of birds observed showed no apparent pattern. In the old growth juniper woodland sites, the number of species encountered was apparently unrelated to time while the number of individuals observed generally increased
Work on this project will continue through winter 1999-2000.