Variability within a Native Stand of Blue Grama

Abstract

Considerable variability and patchiness have been observed within sites of native range dominated by blue grama [Botielow gra&z(H.B.K.) GrIffItha] range at the Central Plains Experhuental Range, Weld County, Colorado. Patches contalnhtg tall plants of blue grama with many seedstalks were interspersed with patches of short plants with few seedstalks. Differences in plant height were not entirely related to soil properties. Relative differences ln plant height among plants collected in the field were maintained when these plants were grown in a greenhouse environment. "Dry spots" (usually 2 to 4 m in dlameter) that contain dark-colored, wllted plants have s&o been observed during dry, hot weather. We found several differences in soil properties that could be responsible for the dry spots. Ail differences in soil properties were within the range for the soil series of the experimental site, an Ascalon flne sandy loam (Arldic Arglustoll). Sixty-two plants of blue grama were collected based on their variability from a single pasture, increased vegetatively in the greenhouse, and transplanted into a spaced-plant nursery. In the third growing season following transplanting, mean v8lues for measurements on replicated clones ranged from 202 to 719 reproductive culms per ramet, 25 to 46 cm height of reproductive cuhus, 17 to 24 cm basal diameter, 39 to 93 grams dry matter per remet, and from 11 June to 20 July for first anthesls. Somatic chromosome numbers were determined for 60 plants and 55 were tetraploids (4x = 40), 3 were pentaploids (5x = SO), and 2 were hexrploids (6x q 60). We concluded that the observed variablllty and patchlness apparently result from a comblnatlon of both gene& and edaphic f&on.

Effects of simulated grazing on different genotypes of Bouteloua gracilis : how important is morphology?

“…We used plants which differed genetically with respect to potentially important morphological characters. Initial differences among our genotypes were significant and often large (1.5-6 fold); in their original study of the set of clones from which ours were drawn, McGinnies et al (1988) reported similar magnitudes of variation for numbers of culms (54-287 per plant), culm height (26-48 cm), plant weight (9-54 g), and basal diameter (8-17 cm). Though all grazing syndrome characters need not occur in the same plant, we found characters relating to plant stature (leaf height, culm height, culm number) tended to co-vary among genotypes; these are likely to be the characters that most directly influence tissue losses to grazing.…”

“…Each was subdivided into replicate clones, which were placed in a common garden at the CPER in 1982. Different genotypes maintained significantly different morphologies under these common garden conditions, suggesting a genetic basis (McGinnies et al 1988). …”

“…The genotypes used in this experiment originally were collected in 1981 for the study of McGinnies et al (1988). Samples were gathered from a 7 ha area within a single 2.5-km 2 section of the CPER (Section 17).…”

“…This area has never been ploughed (McGinnies et al 1988), and has been subject to variable but moderate levels of cattle grazing for many years; on an evolutionary timescale, it is small enough that all plants presumably shared similar grazing histories. Plants were chosen to maximize variation in a range of morphological characters, including culm height, number of culms, leaf length, leaf colour, "bunchiness", and "general plant appearance" (McGinnies et al 1988). Each was subdivided into replicate clones, which were placed in a common garden at the CPER in 1982.…”

“…This morphological variability might be maintained in part by variation in soil properties and other microenvironmental characteristics (Coughenour 1985;McGinnies et al 1988;Belsky et al 1993;Rosenthal and Kotanen 1994); however, it has the potential to affect the ability of these plants to tolerate or escape grazing. Experimentally separating tolerance and escape requires designs that remove constant fractions of tissue from different genotypes (Oesterheld and McNaughton 1991;also Strauss and Agrawal 1999).…”