Major Plant Types Research Articles

Evaluating the Impact of Different Vegetation Types on NEE: A Case Study of Banni Grasslands, India

Estimation of NEE of Grasslands ecosystems becomes mandatory as these grasslands with their wide spread (almost 40% of land of the earth) and high plant diversity play a major role in global carbon balances and NEE at both local and global scale. The present study has been focused on understanding the role of different plant species responsible for variation in NEE of the Banni Grasslands of India. These grasslands form a belt of arid grassland having low growing forbs, graminoids and scattered tree cover. Due to its wide spread and inaccessibility of Banni, this study utilized spatial approach for evaluating carbon emissions and NEE. Landsat data was utilized for vegetation type classification and SMAP data for extraction of NEE values proved their potential for categorising vegetation type and generating NEE values precisely. Three major plant types were identified from the study area viz., Grasslands, Land with Acacia and Land with Prosopis. Grasses were dominant covering 77% and the rest of the area was occupied by the other two classes, i.e. Acacia and Prosopis. The NEE values were higher for the grasses when compared to the other two plant species proving to be the active sinks when compared to other plants. The differential contribution of NEE by species has been depicted in the present work.

Relationship between airborne pollen assemblages and major meteorological parameters in Zhanjiang, South China.

Pollen is an important component of bioaerosol and the distribution of pollen and its relationship with meteorological parameters can be analyzed to better prevent hay fever. Pollen assemblages can also provide basic data for analyzing the relationship between bioaerosol and PM. We collected 82 samples of airborne pollen using a TSP large flow pollen collector from June 1, 2015 to June 1, 2016, from central Zhanjiang city in South China. We also conducted a survey of the nearby vegetation at the same time, in order to characterize the major plant types and their flowering times. We then used data on daily temperature, relative humidity, precipitation, vapor pressure and wind speed from a meteorological station in the center of Zhanjiang City to assess the relationship between the distribution of airborne pollen and meteorological parameters. Our main findings and conclusions are as follows: (1) We identified 15 major pollen types, including Pinus, Castanopsis, Myrica, Euphorbiaceae, Compositae, Gramineae, Microlepia and Polypodiaceae. From the vegetation survey, we found that the pollen from these taxa represented more than 75% of local pollen, while the pollen of Podocarpus, Dacrydium and other regional pollen types represented less than 25%. (2) The pollen concentrations varied significantly in different seasons. The pollen concentrations were at a maximum in spring, consisting mainly of tree pollen; the pollen concentrations were at an intermediate level in autumn and winter, consisting mainly of herb pollen and fern spores; and the pollen concentrations in summer were the lowest, consisting mainly of fern spores. (3) Analysis of the relationship between airborne pollen concentrations and meteorological parameters showed that variations in the pollen concentrations were mainly affected by temperature and relative humidity. In addition, there were substantial differences in these relationships in different seasons. In spring, pollen concentrations were mainly affected by temperature; in summer, they were mainly affected by the direction of the maximum wind speed; in autumn, they were mainly affected by relative humidity and temperature; and in winter, they were mainly affected by relative humidity and wind speed. Temperature and relative humidity promote plant growth and flowering. Notably, the variable wind direction in summer and the increased wind speed in winter and spring are conductive to pollen transmission. (4) Of the 15 major pollen types, Moraceae, Artemisia and Gramineae are the main allergenic pollen types, with peaks in concentration during April-May, August-September, and October-December, respectively. (5) Atypical weather conditions have substantial effects on pollen dispersal. In South China, the pollen concentrations in the sunny day were usually significantly higher than that of the rainy day. The pollen concentrations increased in short rainy days, which usually came from the Herb and Fern pollen. The pollen concentrations decreased in continuous rainy days especially for the Tree and Shrub pollen. the pollen concentrations in the sunny days were usually significantly higher than that in the rainy days. The pollen concentrations increased in short and strong rainfall.

Time Is Not Money: Income Is More Important Than Lifestage for Explaining Patterns of Residential Yard Plant Community Structure and Diversity in Baltimore

Plant biodiversity is affected by limiting resources such as water, nutrients, and sunlight. In urban settings, such as residential yards, however, limiting resources may also include the social factors of time and money spent on yard care. To examine the role that these precious human resources play in determining plant community structure and diversity, we surveyed homeowners and their yards in 12 neighborhoods across Baltimore City and Baltimore County, Maryland, visiting a total of 96 residential properties. We chose neighborhoods based on residents’ median income (a proxy for money) and lifestage (a proxy for time) as determined by ESRI's Tapestry dataset [older (>65 and most likely retired with more free time) versus younger (<65 and most likely working with less free time)]. At each residential yard, we studied four major plant types: lawn species, flowering herbaceous plants (excluding grasses), trees, and invasive species. For the flowering plants, we documented the number, size, and color of flowers, and calculated total floral area. We found that residential yards harbored high plant diversity with 89 tree species, 82 lawn species, and 80 flowering plant genera. Lawn richness was not related to the neighborhood-level lifestage of the residents or their income,; rather, all lawns were equally weedy. Consistently, we found that yards in higher income neighborhoods and larger yards had greater abundance of plants and greater diversity of flowering herbaceous plants, trees, and invasive species, whereas lifestage was rarely associated with plant diversity. Additionally, we found front yards had greater floral area than back yards, while back yards had greater tree abundance and tree diversity than front yards. Finally, we found that residents who spent more time doing yard work had more flowering plants, flower colors, and floral genera. Overall, yards in highincome neighborhood, and large yards had the greatest plant biodiversity, indicating that money is the more precious human resource for creating and maintaining biodiverse residential yards.

English

Ethnobotanical study on medicinal plants was conducted in Tenta District, South Wollo, Ethiopia from December 2016 to May 2017. Data were collected using guided field walk, semi-structured interview, group discussion and direct field observation. Data were analysed using descriptive statistics and response compared with chi-square test. The results documented 121 species of medicinal plants under 98 genera and 53 families based on local medicinal values. Of the total species recorded, Fabaceae contributed higher number (12) of medicinal plant species. Majority of plants (63.5%) were harvested from wild habitat and 16.5% from home garden. Shrubs (44.1%) were the major plant types followed by herbs (30.5%) and trees (12.7%). Pearson correlation analysis (r = 0.44) indicated that there was significant increase of knowledge about medicinal plants as age increases. According to the present study, the existence of a number of medicinal plants is an indication of the presence of ample traditional medicinal knowledge among the community but these curative medicinal plant species decline from time to time. This calls for urgent and collaborative actions to keep the balance between medicinal plants availability and their utilization by the community. Key words: Ethnobotany, indigenous knowledge, medicinal plants, Tenta District, traditional healers.

A synthesis of empirical plant dispersal kernels

Summary Dispersal is fundamental to ecological processes at all scales and levels of organization, but progress is limited by a lack of information about the general shape and form of plant dispersal kernels. We addressed this gap by synthesizing empirical data describing seed dispersal and fitting general dispersal kernels representing major plant types and dispersal modes. A comprehensive literature search resulted in 107 papers describing 168 dispersal kernels for 144 vascular plant species. The data covered 63 families, all the continents except Antarctica, and the broad vegetation types of forest, grassland, shrubland and more open habitats (e.g. deserts). We classified kernels in terms of dispersal mode (ant, ballistic, rodent, vertebrates other than rodents, vehicle or wind), plant growth form (climber, graminoid, herb, shrub or tree), seed mass and plant height. We fitted 11 widely used probability density functions to each of the 168 data sets to provide a statistical description of the dispersal kernel. The exponential power (ExP) and log‐sech (LogS) functions performed best. Other 2‐parameter functions varied in performance. For example, the log‐normal and Weibull performed poorly, while the 2Dt and power law performed moderately well. Of the single‐parameter functions, the Gaussian performed very poorly, while the exponential performed better. No function was among the best‐fitting for all data sets. For 10 plant growth form/dispersal mode combinations for which we had &gt;3 data sets, we fitted ExP and LogS functions across multiple data sets to provide generalized dispersal kernels. We also fitted these functions to subdivisions of these growth form/dispersal mode combinations in terms of seed mass (for animal‐dispersed seeds) or plant height (wind‐dispersed) classes. These functions provided generally good fits to the grouped data sets, despite variation in empirical methods, local conditions, vegetation type and the exact dispersal process. Synthesis. We synthesize the rich empirical information on seed dispersal distances to provide standardized dispersal kernels for 168 case studies and generalized kernels for plant growth form/dispersal mode combinations. Potential uses include the following: (i) choosing appropriate dispersal functions in mathematical models; (ii) selecting informative dispersal kernels for one's empirical study system; and (iii) using representative dispersal kernels in cross‐taxon comparative studies.

Microbiome and Exudates of the Root and Rhizosphere of Brachypodium distachyon, a Model for Wheat.

The rhizosphere microbiome is regulated by plant genotype, root exudates and environment. There is substantial interest in breeding and managing crops that host root microbial communities that increase productivity. The eudicot model species Arabidopsis has been used to investigate these processes, however a model for monocotyledons is also required. We characterized the rhizosphere microbiome and root exudates of Brachypodium distachyon, to develop it as a rhizosphere model for cereal species like wheat. The Brachypodium rhizosphere microbial community was dominated by Burkholderiales. However, these communities were also dependent on how tightly they were bound to roots, the root type they were associated with (nodal or seminal roots), and their location along the roots. Moreover, the functional gene categories detected in microorganisms isolated from around root tips differed from those isolated from bases of roots. The Brachypodium rhizosphere microbiota and root exudate profiles were similar to those reported for wheat rhizospheres, and different to Arabidopsis. The differences in root system development and cell wall chemistry between monocotyledons and eudicots may also influence the microorganism composition of these major plant types. Brachypodium is a promising model for investigating the microbiome of wheat.

Harvesting Effects on Species Composition and Distribution of Cover Attributes in Mixed Native Warm-Season Grass Stands

Managing grasslands for forage and ground-nesting bird habitat requires appropriate defoliation strategies. Subsequent early-summer species composition in mixed stands of native warm-season grasses (Indiangrass (IG, Sorghastrum nutans), big bluestem (BB, Andropogon gerardii) and little bluestem (LB, Schizachyrium scoparium)) responding to harvest intervals (treatments, 30, 40, 60, 90 or 120 d) and durations (years in production) was assessed. Over three years, phased May harvestings were initiated on sets of randomized plots, ≥90 cm apart, in five replications (blocks) to produce one-, two- and three-year-old stands. Two weeks after harvest, the frequencies of occurrence of plant species, litter and bare ground, diagonally across each plot (line intercept), were compared. Harvest intervals did not influence proportions of dominant plant species, occurrence of major plant types or litter, but increased that of bare ground patches. Harvest duration increased the occurrence of herbaceous forbs and bare ground patches, decreased that of tall-growing forbs and litter, but without affecting that of perennial grasses, following a year with more September rainfall. Data suggest that one- or two-year full-season forage harvesting may not compromise subsequent breeding habitat for bobwhites and other ground-nesting birds in similar stands. It may take longer than a year’s rest for similar stands to recover from such changes in species composition.

Seasonal Patterns of Forage Availability in the Fescue Grasslands Under Contrasting Grazing Histories

Grazing by large herbivores has been shown to condition vegetation in a manner that improves grassland quality for subsequent herbivory. Fescue grasslands evolved with disturbance from fire and winter grazing by bison but are now grazed primarily by cattle during summer. We examined the effect of long-term summer grazing on the seasonal forage production and quality of fescue grasslands in an examination of the hypothesis that long-term grazing had conditioned fescue grasslands to benefit livestock. This hypothesis was examined by comparing, between grazed and ungrazed plots, the biomass and composition of herbage components, concentrations of nitrogen (N) and acid detergent fiber (ADF) therein, and the ability of major plant types to maintain their biomass and quality throughout the growing season. The study was conducted in southern Alberta at five sites that had long-term exclosures (20+ yr) on grasslands that had been moderately grazed. Grazing had no effect on the N concentration of associated grasses, but grasses had lower N concentration than forbs. Concentrations of ADF followed a reciprocal trend to N. Grazing increased the mass of forbs from about 10% to 20% as a proportion of total biomass, which in turn, was not affected by grazing history. However, this grazing-induced shift to a higher quality vegetation type was not sufficient to affect total mass of N or total digestible nutrients at the community level. Rather than changes in current growth and quality, the predominant effect of summer grazing was in reducing litter mass, which also had the potential for affecting forage production and selection by herbivores. Finally, grazing reduced the relative contribution of rough fescue to total biomass by about 30%, and despite no significant effect on the potential to support summer grazing, this change could reduce the quality of these grasslands for winter grazing. El Pastoreo por grandes herbívoros ha demostrado que mejora la vegetación incrementando la calidad de los pastizales para un pastoreo subsecuente. Los pastizales de Festucas evolucionaron con perturbaciones de fuego y pastoreo por el búfalo durante el invierno, pero ahora son pastoreados principalmente durante el verano por ganado doméstico. Examinamos el efecto a largo plazo del pastoreo de verano sobre la producción de forraje estacional y la calidad de los pastizales de Festuca, y probamos la hipótesis de que el pastoreo a largo plazo ha acondicionado los pastizales de Festuca en beneficio del ganado doméstico. Esta hipótesis se examinó por comparación entre parcelas pastoreadas y no pastoreadas, la biomasa y la composición de componentes del forraje, las concentraciones de nitrógeno (N) y fibra detergente ácido (ADF) y en la capacidad de la mayoría de tipos de plantas para mantener su biomasa y calidad a lo largo de la temporada de crecimiento. El estudio se realizó en el sur de Alberta en cinco sitios que tenían exclusiones a largo plazo (más de 20 años) en pastizales ha habían sido pastoreado moderadamente. El pastoreo no tuvo ningún efecto en la concentración de N de los pastos asociados, pero las gramíneas tenían una menor concentración de N que las herbáceas. Las concentraciones de ADF siguieron una tendencia recíproca al N. El pastoreo aumentó la masa de herbáceas de alrededor del 10% al 20% como proporción de la biomasa total, que a su vez, no se afectó por la historia de pastoreo. Sin embargo, este cambio inducido por el pastoreo a un tipo de vegetación de mejor calidad, no fue suficiente para afectar la masa total de N o TDN a nivel de la comunidad. En lugar de los cambios en el crecimiento real y en la calidad, el efecto predominante de pastoreo de verano fue en la reducción de la masa del mantillo, que también tenía el potencial de afectar la producción de forraje y selección por herbívoros. Finalmente, el pastoreo redujo la contribución relativa de Festuca aproximadamente un 30%, de la biomasa total a pesar de no mostrar ningún efecto significativo sobre el potencial de apoyar el pastoreo de verano, este cambio podría reducir la calidad de estos pastizales para el pastoreo durante el invierno.

Cost and performance of fossil fuel power plants with CO 2 capture and storage

CO 2 capture and storage (CCS) is receiving considerable attention as a potential greenhouse gas (GHG) mitigation option for fossil fuel power plants. Cost and performance estimates for CCS are critical factors in energy and policy analysis. CCS cost studies necessarily employ a host of technical and economic assumptions that can dramatically affect results. Thus, particular studies often are of limited value to analysts, researchers, and industry personnel seeking results for alternative cases. In this paper, we use a generalized modeling tool to estimate and compare the emissions, efficiency, resource requirements and current costs of fossil fuel power plants with CCS on a systematic basis. This plant-level analysis explores a broader range of key assumptions than found in recent studies we reviewed for three major plant types: pulverized coal (PC) plants, natural gas combined cycle (NGCC) plants, and integrated gasification combined cycle (IGCC) systems using coal. In particular, we examine the effects of recent increases in capital costs and natural gas prices, as well as effects of differential plant utilization rates, IGCC financing and operating assumptions, variations in plant size, and differences in fuel quality, including bituminous, sub-bituminous and lignite coals. Our results show higher power plant and CCS costs than prior studies as a consequence of recent escalations in capital and operating costs. The broader range of cases also reveals differences not previously reported in the relative costs of PC, NGCC and IGCC plants with and without CCS. While CCS can significantly reduce power plant emissions of CO 2 (typically by 85–90%), the impacts of CCS energy requirements on plant-level resource requirements and multi-media environmental emissions also are found to be significant, with increases of approximately 15–30% for current CCS systems. To characterize such impacts, an alternative definition of the “energy penalty” is proposed in lieu of the prevailing use of this term.

Evapotranspiration on western U.S. rivers estimated using the Enhanced Vegetation Index from MODIS and data from eddy covariance and Bowen ratio flux towers

We combined remote sensing and in-situ measurements to estimate evapotranspiration (ET) from riparian vegetation over large reaches of western U.S. rivers and ET by individual plant types. ET measured from nine flux towers (eddy covariance and Bowen ratio) established in plant communities dominated by five major plant types on the Middle Rio Grande, Upper San Pedro River, and Lower Colorado River was strongly correlated with Enhanced Vegetation Index (EVI) values from the Moderate Resolution Imaging Spectrometer (MODIS) sensor on the NASA Terra satellite. The inclusion of maximum daily air temperatures ( T a) measured at the tower sites further improved this relationship. Sixteen-day composite values of EVI and T a were combined to predict ET across species and tower sites ( r 2 = 0.74); the regression equation was used to scale ET for 2000–2004 over large river reaches with T a from meteorological stations. Measured and estimated ET values for these river segments were moderate when compared to historical, and often indirect, estimates and ranged from 851–874 mm yr − 1 . ET of individual plant communities ranged more widely. Cottonwood ( Populus spp.) and willow ( Salix spp.) stands generally had the highest annual ET rates (1100–1300 mm yr − 1 ), while mesquite ( Prosopis velutina) (400–1100 mm yr − 1 ) and saltcedar ( Tamarix ramosissima) (300–1300 mm yr − 1 ) were intermediate, and giant sacaton ( Sporobolus wrightii) (500–800 mm yr − 1 ) and arrowweed ( Pluchea sericea) (300–700 mm yr − 1 ) were the lowest. ET rates estimated from the flux towers and by remote sensing in this study were much lower than values estimated for riparian water budgets using crop coefficient methods for the Middle Rio Grande and Lower Colorado River.

Life cycle issues of power plant in Australia and New Zealand

Australia and New Zealand have markedly different energy mixes. In Australia over 90% of electricity is generated from non-renewable energy sources, predominantly coal. In contrast, New Zealand uses little fossil fuel and the main power generation is provided by hydro with a significant contribution from geothermal resources. This paper presents a brief history and description of the different types of fuel powered plant in use in these two countries, identifies some of the local life cycle issues and discusses research and development and management plans associated with these local renewable and fossil fuelled plant. Additionally brief case histories for the three major plant types are presented and future options in power generation are considered.

Life cycle issues of power plant in Australia and New Zealand

Australia and New Zealand have markedly different energy mixes. In Australia over 90% of electricity is generated from non-renewable energy sources, predominantly coal. In contrast, New Zealand uses little fossil fuel and the main power generation is provided by hydro with a significant contribution from geothermal resources. This paper presents a brief history and description of the different types of fuel powered plant in use in these two countries, identifies some of the local life cycle issues and discusses research and development and management plans associated with these local renewable and fossil fuelled plant. Additionally brief case histories for the three major plant types are presented and future options in power generation are considered.

Assessment of spectral vegetation indices for riparian vegetation in the Colorado River delta, Mexico

This study tested the relationship between three, commonly-used vegetation indices (VIs), percent vegetation cover (% cover) and leaf area index (LAI) over a complex riparian landscape in the Colorado River delta, Mexico. Our objective was to correlate vegetation and soil features with VIs using low-level aerial photography, in preparation for scaling up to analysis of vegetation features using satellite imagery. We used a three-band digital imaging camera (Dycam) to collect data from an aircraft flying at 150 m. A series of 84 images (67×100 m) were analysed. Nine of these sites were ground-truthed; the species, % cover, and LAI were determined. Measured LAI (nine sites) from tree, shrub, and groundcover categories were used to determine a global (GLAI) value for 63 images. We conducted both VIs:% cover and VIs:GLAI regression analyses. The normalized difference vegetation index (NDVI) was the VI that best predicted % cover (r2=0·837), but the soil adjusted vegetation index (SAVI) and enhanced vegetation index (EVI) gave nearly equal results (r2=0·807 and 0·796, respectively). Normalized difference vegetation index, SAVI and EVI were less useful in predicting GLAI (r2=0·73, 0·65, 0·64, respectively). Variability in GLAI was due mainly to differences in % cover among images rather than differences in LAI among vegetation types. We also measured reflectance values of the major plant types between 450 and 900 nm, and found small but significant (p<0·05) differences among some of the species. The results support the conclusion that vegetation indices are most simply related to % vegetation cover, rather than species differences in LAI or VIs, even in this mixed riparian biome. There was also a near 1:1 correspondence between the Dycam and Thematic Mapper (TM) NDVI values over a wide range of landcover types (water, bare soil, partial and complete vegetation cover), which indicate that reflectance-based NDVI values can be scaled from low-level aerial Dycam images to satellite images for this ecosystem.

Plant functional types and climate at the global scale

Abstract. Globally applicable sets of terrestrial plant functional types (PFTs) have been identified as a major need in the development of dynamic global vegetation models for use with global atmospheric models. Global sets of PFTs should represent the world's most important plant types; characterize them through their functional behavior; and provide complete, geographically representative coverage of the world's land areas. Three main schools of thought on PFTs have emerged: (1) a physiological focus on internal function, especially at the level of basic metabolism; (2) an ecological focus on function in relation to plant form and environmental conditions; and (3) a geophysical focus on how plant functions affect the adjacent atmosphere. A structural approach based on pheno‐physiognomy permits ready identification of relatively familiar, recognizable plant types. Many of the criteria cited by other approaches also are intimately related to structure and its seasonal changes. An earlier global system of structural‐functional PFTs and their climatic relations has been improved, including addition of less well‐known plant types, and is briefly described. A more strictly ‘functional’ approach is proposed, in which major aspects of plant function, initially metabolism and water balance, are used to classify functional types and suggest how these are constrained by climate. Such functional considerations, however, are closely linked to structural manifestations ‐ but also require other functional criteria for more completely functional classifications. A recent global model of potential natural vegetation types suggested ca. 15 major plant types as necessary to cover the world's main terrestrial vegetation patterns. These essential types correspond well with a first‐cut set of structural types implied by metabolic considerations.

Morphological and isozyme characterisation of Arachis pintoi Krap. et Greg. nom. nud. germplasm

Arachis pintoi, a wild perennial relative of the peanut, originated in Brazil, is of increasing importance to pasture improvement in the tropics. Its available genetic base, however, is very narrow, and intensive collection is being carried out. This study aimed to characterise the existing eight accessions in the CIAT germplasm collection in order to describe the existing variation, identify plant types, and discover possible duplicates. Morphological characterisation, based on 60 morphological descriptors, demonstrated that variation exists. Numerical taxonomic techniques were used to rank the importance of these descriptors. Cluster analysis, conducted on those pre-selected morphological characters, grouped the accessions into two major plant types: one homogenous, and the other falling into four distinct subgroups. Polyacrylamide gel electrophoresis (PAGE) was applied to root-tip tissue. Isozyme characterisation by PAGE showed polymorphisms in the isozymes α-EST, ACP, GOT, and DIA. When analysed together, the four isozymes could uniquely distinguish every accession of A. pintoi held in the CIAT germplasm collection. Correspondence and cluster analyses of these isozyme patterns showed the morphologically homogenous plant type to be heterogenous, and the heterogenous morphotype to have similar banding patterns. The lack of continuous patterns of variation in both morphology and isozymes manifests the need for further germplasm collection of A. pintoi.

Laser-induced fluorescence of green plants 3: LIF spectral signatures of five major plant types

A technique amenable to remote sensing use which utilizes laser-induced fluorescence (LIF) properties of plants has been successfully used in the laboratory to identify five major plant types. These included herbaceous dicots, herbaceous monocots, conifers, hardwoods, and algae. Each of these plant types exhibited a characteristic LIF spectra when excited by a pulsed N2 laser emitting at 337 nm. Although monocots and dicots possess common fluorescence maxima at 440, 685, and 740 nm, they could be differentiated from one another by using the ratio of the square of the fluorescence intensity at 440 nm to the nonsquared intensity at 685 nm, i.e., (440)2/685. In all cases, monocots yielded a significantly higher ratio. Conifers have fluorescence maxima at 440, 525, and 740 nm but none at 685 nm. Hardwoods exhibited fluorescence at 440, 525, 685, and 740 nm. Algae had very low fluorescence at 440 nm, no fluorescence at 525 nm, and fluorescence maxima at 685 and 740 nm. For algae, the ratio of the fluorescence intensity at 685 nm to that at 740 nm was much greater than that for monocots, dicots, and hardwoods. The potential use of the LIF technique for individual species identification is suggested.

Response to Tebuthiuron by Utah Juniper and Mountain Big Sagebrush Communities

The herbicide tebuthiuron was applied aerially in replicated parallel strips at rates of 0, 1.3, 2.0, and 2.7 kg/ha a.i. (active ingredient) in 40% pellets on a Utah juniper stand, and at rates of 0, 0.6, 1.0, and 1.3 kg/ha a.i. in 10% pellets on a mountain big sagebrush stand. Crown kill on Utah juniper was nearly 100% at application rates of 2.0 kg/ha or greater. Control of mountain big sagebrush was obtained at rates of 0.6 kg/ha and above. Antelope bitterbrush, hairy low rabbitbrush, and gray horsebrush responded to the herbicide similarly to Utah juniper. Rubber rabbitbrush was not controlled by tebuthiuron. Total understory production had changed little 3 years after application, although compensating decreases in production of perennial plants and increases in production of annual grasses occurred. Seldom does rangeland offer an array of plants that is ideal for a particular purpose (Stoddart et al. 1975). The species mixes are often changing as part of successional trends and such changes are often not in the direction that the land user desires. In pinyonjuniper and sagebrush ecosystems, the trend is often an increase in woody plants at the expense of herbaceous plants useable as ruminant forage. Such a trend may occur as a result of some action by man or his grazing animals or may be part of a normal progression toward a climatic climax. If a rangeland is to be held at a particular stage, periodic manipulation of vegetation may be required to reset the successional clock. Tebuthiuron (N_ES-( 1 , ldimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N'dimethylurea) has shown promise for controlling many woody plants. South Texas mixed brush (Scifres et al. 1979), blackjack oak (Quercus marilandica Muenchh.) and winged elm (Ulmus alata Michx.) (Shroyer et al. 1979), sand shinnery oak (Quercus havardii Rydb.) (Pettit 1979), and various other hardwood species (Nolte et al. 1982) have been successfully controlled by tebuthiuron. Control of woody overstory species often has resulted in substantial increases in forage plants about 2 years after application of tebuthiuron (Scifres and Mutz 1978, Scifres et al. 198 1 b, Jones and Pettit 1982). Generally, the junipers have been unresponsive to tebuthiuron. Negative results have been reported on western juniper (Juniperus occidentalis Hook.) (Britton and Sneva 198 I), eastern red cedar (J. virginiana L.) (Scifres et al. 198 la), and redberry juniper (J. pinchotii Sudw.) (Ueckert and Whisenant 1982). However, tebuthiuron has been shown to be effective in controlling Utah juniper (J. osteosperma (Torr.) Little) at rates of 2.2-4.5 kg/ha (Johnsen 1977, 1979). Sand sagebrush (Artemisia filijiolia Torr.) has been effectively controlled (Jones and Pettit 1982). Control of big sagebrush has been obtained at rates of 1.1 to 2.2 kg/ha (Britton and Sneva 1983, Klauzer and Arnold 1975). Authors are supervisory range scientist and range conservationist, Shrub Sciences Laboratory, Intermountain Forest and Range Experiment Station, Provo, Utah 846Ol;and rangeconservationist, Fillmore Ranger District, Fishlake National Forest, Fillmore, Utah 8463 I. Authorsacknowledge Richard Bjerregaard and Eli Lilly and Co. for theircontributions to this research. The use of trade, firm. or corporation names in this article is for the information and convenience of the reader. Such does not constitute an official endorsement or approval by the U.S. Department of Agriculture of any product or service to the exclusion of others that mav be smtable. This article reoorts research involvinn pesticides. It does not contain recommendations for their “‘se! nor does it imply thay the uses discussed here have been registered. All uses of pestlcldes must be registered by appropriate State and/or Federal agencies before they can be recommended. Manuscript accepted April 17, 1984. 56 Cool-season herbaceous plants typical of the Intermountain region appear to be sensitive to tebuthiuron and may be strongly repressed by rates of 2 kg/ha (Britton and Sneva 1981, 1983). The pinyon-juniper zone, dominated by Utah juniper, and the sagebrush zone, dominated by big sagebrush (Artemisia tridentata Nutt.), are major plant types in the Intermountain region. Combined, they occupy 34% and 4.5% of’Utah and Nevada, respectively (USDA Forest Service 1972). These plant types, whose historic use has been dominated by the grazing of livestock, have experienced increases in amounts of woody plants and diminished amounts of herbaceous forage plants. In an effort to reverse this trend, managers have tried fire, mechanical, chemical, and biological means to manipulate vegetation. The objectives of this study were to determine the effectiveness of tebuthiuron in controlling woody plants on Utah juniper and mountain big sagebrush (Artemisia tridentata ssp. vaseyana (Rydb.) Beetle) dominated sites and evaluate response of herbaceous species.