Rangeland Plant Communities Research Articles

Action Windows for Optimum Control of Rangeland Grasshoppers (Orthoptera: Acrididae)

Different assemblages of primary and secondary pest grasshopper species were found in 5 different rangeland plant communities in western North Dakota. The action window for their control (i.e., the interval when control is likely to be efficacious) with short-lived insecticides can be visualized in terms of time, grasshopper phenology, or plant phenology. Action windows ranged from 14 d duration in habitats dominated by western wheatgrass to 38 d duration in habitats dominated by needle-and-thread or by crested wheatgrass. Action windows opened 11-15 d later in rhizominous grass habitats than in bunchgrass habitats because of increased presence of late-hatching secondary pest species. In all habitat types, action windows closed primarily in response to imminent oviposition by a ubiquitous primary pest species, Melanoplus sanguinipes (F.). In all habitat types, action windows tended to open during seed development of 2 common and conspicuous grasses, needle-and-thread and green needlegrass. No such consistent indicator for closure of action windows was detected.

Response of texas bluegrass to season of nitrogen fertilization on the Louisiana coastal plain

Texas bluegrass (Poa arachnifera Torr.) has shown potential for use as a cool‐season perennial pasture grass in the southern Great Plains, where it occurs as a natural component of rangeland plant communities, and into the western Coastal Plain. Responsiveness of this grass to nitrogen (N) fertilization appeared to be limited to the spring growing period in initial evaluations in Louisiana. A field plot experiment was conducted to assess forage production and quality responses to season of N fertilization on the Syn‐1 population of Texas bluegrass. Winter forage production responses to 50 kg N ha‐1 were obtained in the 1997–98 growing season but not in 1998–99 after stands had been depleted by summer drought. Greatest yield increases resulted from spring N application, however, fall plus winter fertilization provided the most uniform distribution of forage through the cool season. Forage fiber fractions, in vitro digestibility, and crude protein were not affected by N fertilization. Both amount and distribution of Texas bluegrass forage, but not forage quality, can be manipulated by time of N fertilization.

Gradient Analysis of Infiltration and Environmental Variables as Related to Rangeland Vegetation

Rangeland plant communities and the hydrologic cycle associated with them are multivariate in nature and are affected by many interacting biotic and abiotic components. A rotating boom rainfall simulator was used to apply rainfall in three applications (dry run, wet run, and very wet run) to paired 3.05- 10.7-m runoff plots. Representative plant community types were tall-grass, mixed-grass, short-grass prairie, and sagebrush steppe. Indirect gradient analysis was used to summarize relationships between rangeland plant communities, infiltration, and soil variables. Effective terminal infiltration rate (fe) was consistently higher in sagebrush communities. The best coefficient of determination of fe for the pooled data set (144 runoff plots, 24 sites, 10 states) was R2 = 0.45. Infiltration equations which represented rangeland community types (short-grass, mixed-grass, tall-grass, and sagebrush-grass) were more robust (R2 values > 0.71). The inclusion of endemic plant species in the model building process also improved fe rates. For example, in the tall-grass prairie, the inclusion of above-ground indiangrass (Sorghastrum nutans) biomass, an endemic native grass species, and other plants as independent variables increased regression coefficients of determination from 0.71 to 0.82.

MODELING WATER BALANCE WITH THE ERHYM MODEL ON SOUTH TEXAS RANGELANDS1

ABSTRACT: Understanding the hydrologic processes of rangeland plant communities is essential to determine if water augmentation through shrub management is feasible. Vegetation manipulation studies are costly, difficult to accurately replicate, and often require more than 10 years to determine treatment effect on the water budget. If properly applied, hydrologic simulation models are an attractive alternative for assessing vegetation manipulation practices. The ERHYM‐II model was evaluated to determine if it was capable of simulating the water balance for honey mesquite shrub clusters, grass interspaces, and bare soil in south Texas. The simulated water budget was within 2 percent of the measured evapotranspiration for the shrub clusters and grass interspaces. The model underestimated the number of runoff events and overestimated runoff volume for the grass interspace and shrub clusters. Simulated runoff was overestimated by approximately twofold for the grass interspace and threefold for the shrub clusters. Although simulated runoff was substantially overestimated, observed and simulated runoff only accounted for 3 to 6 percent of annual rainfall for the grass and shrub dominated areas, respectively. Simulated evapotranspiration was underestimated by 18 percent and soil water content was overestimated by 82 percent for the bare soil. The model underestimated evapotranspiration for the bare soil as a result of restricting evaporative losses to the first soil layer. Based on our analysis, the ERHYM‐II model has the potential for simulating the annual water balance for semiarid rangeland plant communities where runoff and deep drainage are limited components of the water balance.

Growth, Photosynthesis, and Stomatal Conductance in Gutierrezia sarothrae Associated with Hydraulic Conductance and Soil Water Extraction by Deep Roots

We hypothesize that predominance of Gutierrezia sarothrae in the rangeland plant community depends on its ability to take up water more effectively from soil depths below 30 cm. Gutierrezia seedlings grown in 30-cm-deep pots were allowed to develop deep lateral roots out of pots into subsoil. The deep laterals were then excised and photosynthesis and stomatal conductance of the test plants measured before and after root pruning. Photosynthesis (A) and stomatal conductance (g) were at least 49% greater (P < .05) before than after root pruning. Photosynthesis and g were more affected by the removal of four deep roots 30 cm below the surface than by the removal of four shallow roots in the top 30 cm of soil. The soil water extraction patterns in Gutierrezia plants grown in 60-cm soil columns were determined for the upper 30 cm and 30 to 60 cm of soil. Water extraction was significantly greater (P < .05) from the wetter, lower section of the soil column than from the drier, upper column. Higher photosynthesis...

Soil Climate and Plant Community Relationships on Some Rangelands of Northeastern Nevada

Soil temp. and moisture data were collected in 1983-86 on one forest and eleven sagebrush-dominated rangeland plant community types of the Humboldt National Forest in NE Nevada. Six soil parameters were used to contrast differences between the community types studied: mean annual soil temp., mean summer soil temp., starting date (when soil temperature at 0.5 m depth exceeded 5°C), growing period (number of days when soil temp. and moisture were not limiting to growth), soil degree days (number of days that soil temp. at 0.5 m depth exceeded 5° C), and growing period percentage (i.e., growing period/soil degree days). These soil parameters were effective in discriminating between most plant community types, yet their effectiveness varied considerably among types. Certain community types (e.g. Artemisia tridentata subsp. vaseyana - Agropyron spicatum) occupied a wide range in soil temp. and moisture, which limited their indicator significance for predicting soil climate. Short growing periods of 25-150 d characterized the rangeland plant community types studied. The onset of the growing period (starting date) occurred between 6 March and 1 July. Such information facilitated the determination of rangeland readiness by plant community type in the study area.

A multi-species model for rangeland plant communities

A plant growth model has been developed as a component of a general rangeland production and utilization model (SPUR). The carbon and nitrogen content of standing green, live roots, propagules, standing dead, litter, dead roots, soil organic matter and soil inorganic nitrogen are simulated. The model can simultaneously simulate up to seven plant species or species groups on a total of nine heterogeneous range sites. It incorporates processes which are common to C 3 and C 4 plants but does not consider plants with Crassulacean Acid Metabolism. When coupled with the other components of the SPUR model, the plant component allows testing of grazing management, environmental variation, and fertilizer application.

Aerial and ground spectral characteristics of rangeland plant communities in Nevada

Visible and near infrared spectral reflectance values were recorded from Nevada rangeland plant communities using both low flying aircraft and ground measurement approaches. The individual spectrum values, four-band signatures and infrared: red scatterplots were used to compare 5 × 5 m aerial pixels with data from various ground components. Results show that vegetation and soil do not account for the integrated aerial spectra. The composite ground signatures indicate that spectrally dark components exist in rangeland plant communities which decrease the brightness of a scene measured from the air. Shadow and litter are presumed to be the primary sources of spectral darkening. An estimate of the overall signature of the shadow/fitter component was calculated.

Cultural Practices for Establishing Fourwing Saltbush within Perennial Grass Stands

Cultural Practices for Establishing Fourwing Saltbush within Perennial Grass Stands

Response of Vegetation of the Northern Great Plains to Precipitation Amount and Grazing Intensity

Changes in basal cover of vegetation were predicted in response to variation in precipitation and grazing intensity. Multiple regression analysis was used with basal cover as a dependent variable and precipitation parameters as independent variables to develop predictive equations. Predicted cover values were used to develop three dimensional response surfaces which describe individual species responses to fluctuating precipitation and different grazing intensities. Results indicate that each species reacts to precipitation regimes and grazing pressure in a unique manner. Continual changes in basal cover can be expected in the plant community as the precipitation regime changes. Moderate grazing intensity, approximately 0.92 ha (2.3 acres) per AUM, appears to be most conducive for maintaining vegetative cover that is desirable for livestock production. However, stocking rate changes need to be anticipated and planned to coincide with available forage because of large fluctuations in cover due to varying precipitation. Climate appears to be the major factor controlling plant growth in the Great Plains. Whitman et al. (1943) stated that drought is the primary influence of vegetational change. Reed and Peterson (1961) Hurtt (1951) and Clark et al. (1943) stated that major trends in vegetation are primarily determined by fluctuations in climatic conditions, and that changes within these major trends are influenced by grazing intensity. Authors are former graduate student, Department of Animal and Range Sciences, Montana State University. Bozeman 597 17; research plant physiologist, USDA-ARS. Livestockand Range Research Station, Route. I Box 2021, MilesCity, Mont. 59301; and assistant professor. Department of Animal and Range Sciences. Montana State University, Bozeman 59717, respectively. The research is a contribution from the Western Region. USDA-ARS, Livestock and Range Research Station and the Montana Agricultural Experiment Station, Journal Series No. J-1445. Manuscript accepted January 2. 1985. JOURNAL OF RANGE MANAGEMENT 38(4), July 1985 There is a close relationship between time and amount of precipitation and plant growth (Albertson et al. 1953). One wet or dry year will affect production, but 2 or more wet or dry years are required to change the basal cover (Johnson 1981). Abrupt and fundamental changes in the amount and kind of living plant crown area may result from severe drought and last longer than anticipated (Reed and Peterson 1961). Both frequency and duration of drought are important in determining the severity of effects of climate on vegetation (Cook and Sims 1975, Herbel et al. 1972). Native vegetation has developed under conditions of wide climatic variation (Albertson et al. 1957). Marked changes in botanical composition occur, but plant populations are seldom completely destroyed by climatic fluctuation (Cook and Sims 1975). These changes are slow, whether for better or worse (Sarvis 1941). Native grass species will remain dominant in prairies unless they are severely grazed or buried by dust (Cook and Sims 1975, Schumacher 1974, Albertson et al. 1957). A more comprehensive understanding of the responses of range ecosystems to weather and grazing is desirable for good management (Reed and Peterson 1961). Drought cannot be controlled, but its impact can be moderated by proper livestock management. To do this, changes in plant communities need to be better defined so that effects of both drought and above average precipitation can be anticipated on the range. There are general ideas of the influence of precipitation and grazing intensity on rangeland plant communities, but only limited effort has been made to predict the responses within plant communities to fluctuating precipitation regimes and different grazing intensities. Models have been developed to predict forage production at different levels of precipitation (Smoliak 1956, Sneva and Hyder 1962, Abel et al. 1962) but similar endeavors that evaluate plant cover response to fluctuating precipitation

An In-Depth Examination of the Philip Equation for Cataloging Infiltration Characteristics in Rangeland Environments

The objective of this study was to investigate the use of Philip's equation coefficients (which have, in theory, direct physical meaning) to characterize infiltration on rangelands. It was found that a least squares regression approach to estimating Philip equation parameters (S and A) essentially reduces A, and perhaps S, to empirical coefficients. However, the Philip equation does provide a model that fits infiltrometer data reasonably well and reflects signiflcant differences between infiltration curves. The effects of land management and temporal variables (e.g., soil moisture, season) may be associated with changes in S and A for particular sites. Indexing of inflltration curves by model coefficients allows for infiltrometer data from different researchers to be pooled and provides a basis for simulation modeling of infiltration and runoff on small watersheds. Coefficients are tabulated for a variety of rangeland plant communities for easy reference by practicing rangeland hydrologists. Researchers who present infiltration data in the future are urged to represent their data, at least in part, in the form of S and A coefficients to expand results tabulated from this study. Authors are graduate research assistant and professor, respectively, Watershed Science Unit, College of Natural Resources, Utah State University, Logan. Mr. Jaynes is currently attending law school at the University of Utah. This work was supported jointly by the Utah Agricultural Experiment Station (Proj. 749) and the United States Department of the Interior, Office of Water Research and Technology, Project No. E143-Utah, Agreement No. 14-34-0001-7193, as authorized under the Water Resources Research Act of 1964, as amended. Technical paper No. 2483, Utah Agricultural Experiment Station, Logan, 84322. Thanks are due Dr. Will Blackburn, Texas A&M University, for use of data relative to Nevada plant communities. Manuscript received November 14, 1979. Water movement through the soil-air interface (or infiltration) may be regarded as one of the most important processes on rangeland watersheds. Indeed, in an environment where convective rainstorms produce the majority of watershed runoff and erosion events, infiltration characteristics are key factors in determining the extent of soil loss, gully formation, and stream sedimentation. Since soil moisture on rangelands is often the most limiting resource for plant growth, the occurrence of surface runoff inhibits storm precipitation from promoting on-site forage production. In many instances, the main goal of rangeland watershed management is to simply prevent overland flow. Therefore, the variability in infiltration characteristics among plant communities and as a consequence of land management becomes an important item of study. The ability to understand and predict infiltration characteristics and runoff events on rangeland watersheds (where extensive rainfall-runoff data rarely exists) is of great value to watershed hydrologists. There exists a variety of empirical techniques which are intended to simulate individual processes as well as the overall infiltration phenomenon. The development of infiltration models based on physically meaningful quantitative theories may well provide rangeland hydrologists with infiltration and runoff indexes which are more interpretable. Such models present the opportunity of utilizing infiltration characteristics of individual plant communities to predict watershed runoff events. The two major objectives of this study were: (1) to investigate utilizing the well-known Philip infiltration model to index infiltration characteristics of rangeland communities (i.e., spatial variability both within and among different soil-plant complexes), and (2) JOURNAL OF RANGE MANAGEMENT 34(4), July 1981 285 This content downloaded from 207.46.13.48 on Wed, 12 Oct 2016 05:48:34 UTC All use subject to http://about.jstor.org/terms to determine what magnitude of change (or +) must be experienced in equation coefficients before temporal changes affecting community infiltration characteristics are deemed significant (e.g., the effects of land management, season, and antecedent soil moisture). The Philip Equation: Philip's infiltration equation is: I(t) = St 12 + A T (1) where: I(t) is cumulative infiltration at a given time (t) (cm), S is (cm/ hr1/2), and A is a permeability coefficient or gravity term (cm/hr). Chapter 7 of Kirkham and Powers(1972)containsa detailed analysis of the mathematics of the Philip equation. The first term of equation (1) describes the uptake of water by porous media via forces and dominates infiltration when time is small (Philip 1957a, b). This term contains a coefficient S, or (cm/hr1/2 ), which bears resemblance to the terms permeability, capillary conductivity, and absorptivity. The term sorptivity is preferred by Philip (1 957b) because it embraces both the concepts of absorption and desorption (i.e., the ability of the soil pores to absorb and release water by capillarity). Sorptivity may also be discussed in terms of pore-liquid geometry (Philip 1957b). Although the parameter is not a directly measurable soil attribute, it may be derived from actual soil properties (Hanks and Ashcroft 1976). The differential form of equation (1) is:

Studies of Central Australian Semidesert Rangelands. I. Range Condition and the Biomass Dynamics of the Herbage Layer and Litter.

Following a sequence of years of above-average rainfall, standing biomass, rates of production and quantities of litter were high in the ground storey of three central Australian rangeland plant communities. Standing biomass was of the order of 4000 kg ha-1 in Astrebla grasslands, 2600 kg ha-1 in open woodlands and 1300 kg ha-1 in Acacia shrublands, and litter biomass was c. 1300 kg ha-1, 1600 kg ha-1 and 4000 kg ha-1 respectively. Levels of biomass and production rates were comparable with those of some semiarid and temperate sown pastures in average seasons, but they appeared to have reached their natural limit. Total standing biomass, production rates, species diversity, litter biomass and decomposition rates were not correlated with range condition assessments of the experimental sites. Species frequency was the only characteristic measured which was related to range condition other than botanical composition, the basis of site selection.

Use of Infiltration Equation Coefficients as an Aid in Defining Hydrologic Impacts of Range Management Schemes

Highlight: Based on infiltrometer data from 13 pinyon-juniper sites in Utah, the relationship of selected rangeland vegetation characteristics and soil physical properties to the various infiltration coeffkients contained in three well-known algebraic infiltration equations was determined. Coefftcients in Kostiakov’s equation were related more to vegetation factors than to soil &actors while coefficients in Philip’s equation were more related to soil factors than to vegetation factors. The single coefficient in Horton’s equation was somewhat intermediate, representing both vegetation and soil influences. It is conceivable that changes in rangeland use activities or intensity of use may be detected through changes encountered in infiltration coefficients, with emphasis on either vegetation or soil factors or both, depending on the equation or model used. The relationship of infiltration in native and “disturbed” rangeland plant communities to soil and vegetation parameters has been of interest to hydrologists for many years. Many devices have been designed to measure infiltration rates, and these range from ring-type infiltrometers to sprinkling-type devices that attempt to duplicate certain characteristics of natural rainfall. Based on actual measurements, various researchers have found that the results of infiltrometer trials may be expressed in terms of specific models or equations. Examples include Kostiakov’s equation (1932), Horton’s equation (1940)) and Philip’s equation (1957). Each of these equations contains various coefficients, most of which are speculatively related in some (perhaps unidentified) way to factors that may be controlling the infiltration process. The objective of this study was to determine, to the extent possible, the relationship of selected rangeland vegetation characteristics and soil physical properties to the various infiltration coefficients contained in the three well known algebraic infiltration equations mentioned above. This objective is especially pertinent in terms of possible interpretations of long- or short-term temporal changes in infiltration rates as a function of specific management plans, and especially in those circumstances where supplemental data are minimal or completely lacking. soil and vegetation

Applicability of some infiltration formulae to rangeland infiltrometer data

Three algebraic infiltration equations (Kostiakov's, Horton's and Philip's) were examined to determine which one would best fit infiltrometer data collected from a variety of mostly semi-arid rangeland plant communities from both Australia and the United States. Approximately 1,100 infiltrometer plots were included in the analysis. Results indicated that, in every instance, Horton's equation best fit the infiltrometer data. Variability of “point” measures of short-term infiltration rates were never satisfactorily accounted for by using either Kostiakov's or Philip's equation. Though Horton's equation provided a best fit to the overall infiltration data, R 2 values indicated a potential usefulness of this equation only under the certain conditions that were sampled in several rangeland plant communities in the Northern Territory, Australia. The equation could not be considered consistently useful under conditions sampled on rangelands in the United States.

Infiltrometer studies in rangeland plant communities of the Northern Territory.

Infiltrometer studies were conducted within several plant communities near Alice Springs, Northern Territory. Plant commu- nities studied included mulga-perennial, mulga-shortgrass, savanna woodland, gilgai, flood-plain grassland, and scalded areas (no vegetation). Attempts were made to quantify the impact of surface crusting, antecedent soil moisture conditions, and time of year on infiltration rates and potential sediment yields. Results indicate that the infiltration process within certain plant communities is often complex, and hydrologic differences which occur both within and among the plant communities should be acknowledged. Sediment yields from a floodplain-grassland unit and a scald situation were about 2 and 5 times greater, respectively, than those from various mulga communities, woodland, or gilgai circumstances. With one exception, antecedent soil moisture had little influence on sediment yields. Removal of surface soil crusts significantly increased sediment yields, regardless of antecedent soil moisture conditions. The relationship between soil movement and loss and ecosystem stability needs to be established for most rangeland environments, but little has been done to satisfy this need.