North American Grasslands Research Articles

The Structure and Function of Ten Western North American Grasslands: I. Abiotic and Vegetational Characteristics

(1) Data collected from coordinated comparative studies on the structure and function of ten central and western United States grasslands are presented and analysed. The ten study areas encompassed six major grassland types: mountain grassland, northwest bunchgrass, mixed-grass prairie, shortgrass prairie, tallgrass prairie and desert grassland. Experimental design at each location included two replications of ungrazed (i.e. long-term absence of grazing by large domestic herbivores) and grazed treatments. (2) Structural characteristics studied included quantities of cool- and warm-season plants at each site, and magnitude and seasonality of primary producer compartments. (3) The environmental variables measured at each site were precipitation, temperature and solar radiation. These variables were calculated as both annual and growing-season values, along with annual and growing-season potential and actual evapotranspiration. (4) The seasonal mean live biomass averaged 94 g m -2 for the ten grasslands, with a mean of 98 g m -2 on ungrazed grasslands and 89 g m -2 for grazed grasslands. Ungrazed grasslands averaged about 160 g m -2 of recent and old dead plant material, compared to approximately 70 g m -2 on grazed grasslands. Ungrazed grasslands had about 50 and 150% more recent and old dead material, respectively, than grazed grasslands. Generally, grazing in previous seasons decreased the standing crop of dead material across the grasslands. (5) The mean total shoot standing crop averaged 203 g m -2 for all grasslands across all treatments; ungrazed grasslands averaged 245 g m -2 , compared to 161 g m -2 for grazed grasslands. The magnitude of litter corresponded in general to the amount of total shoot standing crop. (6) Generally, the shortgrass prairie had the maximum amount of crown material, followed by the mixed-grass prairie, with the tallgrass prairie least. Crown material averaged c. 275 g m -2 for the mixed- and shortgrass prairie, compared to c. 200 g m -2 for the tallgrass prairie. Although grazing did not significantly influence the amount of crown material, crown material tended to increase under grazing in mixed-grass and shortgrass prairies. (7) Root biomass ranged from 156 g m -2 in the desert grassland to as much as 2000 g m -2 in the mixed-grass prairie, while other grasslands were intermediate between these two extremes. (8) There was an inverse relationship between root biomass and dynamics and mean annual temperature. Grazing generally resulted in an increase in the root/shoot ratios, particularly on the cooler grasslands.

AN EXPLORATORY METHOD FOR FRACTIONATION OF ORGANIC PHOSPHORUS FROM GRASSLAND SOILS

A high percentage of the P in grassland soils is organic. Where the NaHCO3- extractable P is below the adequate level, plants must rely on mineralization of organic P. This paper attempts to show the nature, transformations, and relative sizes of the organic P pools for five North American grassland soils. We evaluated four such pools: (1) a labile pool, extracted with 0.5 M NaHCO3 (pH 8.5); (2) a moderately libile pool, consisting of acid-soluble organic P and alkali-soluble inorganic P; (3) a moderately resistant fraction (fulvi-acid P); and (4) a highly resistant fraction (humic-acid P). Recovery of organic P from the extracts averaged 7, 34, 47, and 12 percent in the labile, moderately labile, moderately resistant, and highly resistant fractions, respectively. The P in phytic acid was not recoverable in either acid or alkali extractions, although ribonucleic acid was recovered in the labile fraction.

Model estimation of energy flow in North American grassland bird communities.

The energy demands and general food consumption rates of bird populations breeding in North American grasslands are estimated using a simulation model which employs information on population natural history and individual metabolism gathered from several study locations. The total breeding season energy demand of the grassland/shrub-steppe avifaunas ranged from 0.89 kcal m-2 season-1 in arid shrub-steppe to 2.92 kcal m-2 season-1 in a mesic tallgrass prairie. There was substantial variation between years and between census plots, however, and in general the average avian community energy demands did not differ significantly over the range of locations. Production accounted for 0.9 to 1.5% of the total seasonal energy demand. Roughly 11 to 18% of the seasonal energy flow was required in the production of eggs and maintenance and growth of nestlings and fledglings.On the average, between 209 and 386 kg dry wt km-2 of prey were consumed by the bird communities breeding in the grassland locations. Seeds contributed more to the total biomass consumed at the drier plots, but in general, animal prey types comprised roughly 80% of the total biomass eaten. Phytophagous insects were the major component of the animal prey.These low magnitudes of energy flow and biomass consumption attest to the relatively minor role of birds in the processing of energy and biomass in grassland ecosystems. If these populations do play an 'importnat' role in the functioning of grassland ecosystems, it must be quite subtle and indirect.

Nitrogen Fixation in Some Prairie Legumes

Acetylene reduction was compared in five important leguminous species of the central North American grasslands. Nodulated seedlings were obtained by natural or artificial means, watered with nitrogen-free nutrient solution, and maintained under uniform conditions in growth chambers. Seedlings 9-13 weeks old were assayed weekly by the C2H2 C24 technique using gas chromatography. Most species differed significantly in total N2 fixation expressed as ,u moles of C24 daily/plant, and in nodule efficiency expressed as v1 moles of C2H4 hourly/mg fresh nodules. Using the ranges of the weekly assay means as indicators, the species ranked in total N2 fixation as follows: Cassia fasciculata (25.9-87.0), Lespedeza capitata (7.7-16.6), Schrankia uncinata (3.1-8.9), Amorpha canescens (3.5-7.0) and Psoralea argophylla (1.1-1.9). The order for nodular efficiency was L. capitata (6.2-1 1.1),, C. fasciculata (3.1-4.7), A. canescens (2.6-4.2), S. uncinata (1.3-4.1) and P. argophylla (1.52.7). Measurements of growth rates in most cases paralleled the fixation rates. The results of this study suggest the possibility that species (C. fasciculata and L. capitata) which occupy niches in pioneer through late seral stages of grassland succession have a greater N2-fixing capacity than species more limited to the climax (A. canescens, S. uncinata, P. argophylla). INTRODUCTION Domestic legumes have been widely studied in regard to nitrogenfixing capacity and stimulation of pasture and forage production (Stewart, 1966). Similar information on legumes of native grasslands of the world is lacking (Coaldrake, 1962), although legumes reach high densities in the central North American grasslands (Weaver, 1954; Weaver and Albertson, 1956). In the true prairie of eastern Nebraska, Warren (1909) studied the extent of nodulation of various species, and Alway and Pinckney (1909) estimated that various legumes added 9.4 kg N/ha/year to the soil. This estimate was based on the harvest method and Kjeldahl analysis of total N of the tops; no data were given for N added from nodules or from root decay. In central Oklahoma, Kneebone (1959) studied nodulation of prairie legume seedlings and found nodules in all species examined; however, in mature individuals there was often a paucity or absence of nodules indicating absence of fixation. In the mixed prairie of Kansas and Nebraska, Weaver and Albertson (1956) reported nodules from depths

Climatic Instability and the "Ecological Saturation" of Bird Communities in North American Grasslands

Journal Article Climatic Instability and the “Ecological Saturation” of Bird Communities in North American Grasslands Get access John A. Wiens John A. Wiens Department of Zoology Oregon State University Corvallis, Oregon 97331 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 76, Issue 4, 1 October 1974, Pages 385–400, https://doi.org/10.2307/1365813 Published: 01 October 1974 Article history Accepted: 20 August 1973 Published: 01 October 1974

Habitat Heterogeneity and Avian Community Structure in North American Grasslands

In a variety of environments, patchiness of habitat structure appears related to faunal diversity. I examined the relations between vegetational heterogeneity and several attributes of avian communities over a range of North American grassland and shrub steppe situations. Habitat heterogeneity was measured by assessing the variability in vertical density of vegetation within clustered point samples, and an index to express this horizontal patchiness was derived. Heterogeneity was directly related to the areal coverage of bare ground and woody vegetation and to patchiness in litter distribution of sample plots, and inversely related to grass coverage and litter depth. Heterogeneity generally increased with decreasing annual precipitation and primary production, tall grass-prairie sites being the least and western shrub steppe the most heterogeneous. Analysis of breeding bird population censuses from these plots revealed no apparent relationships between habitat heterogeneity and the diversity of breeding avifaunas or the extent of spatial (territorial) overlap between species. The density of breeding bird populations decreased slightly witth increasing vegetation patchiness; the standing crop biomass of the avian community, however, decreased markedly as heterogeneity increased. This pattern appeared to result from a replacement of largesized species by medium-sized species in the transition from tall grass to short grass areas and an increasing dominance of small-sized species in the western Palouse and shrub steppe sites. INTRODUCTION Many workers have recently drawn attention to the relation between habitat structure and faunal diversity. In deciduous forests in eastern North America, for example, the diversity of breeding bird species in a community increases with increasing patchiness or vertical layering of the vegetation (MacArthur and MacArthur, 1961; MacArthur, 1965), and a correlation between increasing habitat complexity and diversity in breeding bird faunas seems most general (e.g., Karr and Roth, 1971; Cody, 1970; Orians, 1969). Diversity in lizard faunas also may be related to habitat complexity (Pianka, 1967; Schoener and Schoener, 1971), and the structure of some small mammal communities may be closely tied to structural heterogeneity of the environment (Rosenzweig and Winakur, 1969). These observations and others have led to the development of a rather extensive body of theory of habitat heterogeneity (e.g., Levins, 1968; MacArthur and Levins, 1964, 1967; MacArthur and Pianka, 1966), although a good deal of this theory remains untested. In forest communities a good share of the increase in bird species diversity with increasing patchiness in the vertical distribution of foliage may be due to an increased vertical layering of the bird species. Spatial overlap between species, as projected on a single horizontal plane, may thus be extensive. In structurally simple habitats such as

Nutritional Strategies of Myomorph Rodents in North American Grasslands

Grass-eating and seed-eating myomorphs associate in temperate North American grassland environments. These two groups have distinctive nutritional specializations as expressed by different morphological, physiological, and behavioral characteristics. There seems to be opportunity for many more species of seed-eaters than grass-eaters to occupy a single grassland community, at least in the American area discussed herein.

Global Water Balance According to the Penman Approach*

Global Water Balance According to the Penman Approach*

Biogeographic Extensions into a Coniferous Forest Plantation in the Nebraska Sandhills

A plantation in the Nebraska sandhills, representing an expanded forest ecosystem in a prairie region, is effecting a changed biota. Dates, origins, and sites of the forest plantations are well docu- mented, thereby allowing biogeographic correlation of animal species with the natural distribution and origin of the tree species. Distribu- tional data for sixty species new to Nebraska are recorded, most of which represent insects. A lichen and a pseudoscorpion are included in the new locality data. Several new insect species plus a variety of undescribed insect forms provide evidence that the area has good poten- tial for further taxonomic and biogeographic investigation. (Nebraska National Forest, Bessey Division), presents unique oppor- tunities for biological studies. The sandhills in which it occurs repre- sent the largest single, continuous tract of dune sand originating in their peculiar manner in the United States. Weathering of Tertiary alluvial sediments from the Rocky Mountains produced the sandhills of Nebraska and adjacent states during Pleistocene times (Lugn and Lugn, 1955). Nebraska lies in the middle of the North American Grassland Formation of Weaver and Clements (1938). The Nebraska sandhills, a phytogeographic region in itself, is considered an edaphic postclimax tall-grass prairie. Climatically and longitudinally most of it should belong to the mixed prairie, which touches it on the south, southeast, and north (Weaver and Bruner, 1954). A smaller eastern portion is regarded as true prairie and directly east the great extent of North American true prairie begins. Immediately west of the sand- hills are the short-grass plains. Trees, with the possible exception of Populus tremuloides, are not native to the upland regions of the area; however, various species of the genera Pinus and Juniperus have been imported from the following natural coniferous forest associations of North America: the montane forest climax of the Rocky Mountain region; the lake forest of the territory from the Great Lakes eastward to New England; various outlying portions of other coniferous asso- ciations in New England and the Southwest. Some experimental attempts have involved European imports, and some Pinus ponderosa (scopulorum) native to areas peripheral to the sandhills have been introduced.

Aspects of Needed Research on North American Grasslands: By a Committee of the Grassland Research Foundation

Aspects of Needed Research on North American Grasslands: By a Committee of the Grassland Research Foundation

The North American Grassland in Historical Perspective

The North American Grassland in Historical Perspective

The Climate of the Central North American Grassland

The Climate of the Central North American Grassland

The Climate of the Central North American Grassland

The Climate of the Central North American Grassland

Studies of Plants in the Black Hills of South Dakota

Previous articleNext article No AccessStudies of Plants in the Black Hills of South DakotaHerman E. HaywardHerman E. Hayward Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 85, Number 4Jun., 1928 Article DOIhttps://doi.org/10.1086/333852 Views: 5Total views on this site Citations: 1Citations are reported from Crossref Journal History This article was published in the Botanical Gazette (1876-1991), which is continued by International Journal of Plant Sciences (1992-present). PDF download Crossref reports the following articles citing this article:Robert F. Whitcomb, James Kramer, Michael E. Coan, Andrew L. Hicks Ecology and Evolution of Leafhopper—Grass Host Relationships in North American Grasslands, (Jan 1987): 121–178.https://doi.org/10.1007/978-1-4612-4712-8_5