Leaf Development of Native Bluestem Grasses in Relation to Degree-Day Accumulation

Abstract

Degree-day accumulation is commonly used to predict crop development and harvest dates. Relationships between degree-day accumulation and phenological development of range forage grasses have received less attention. This research tested the hypotheses that leaf development by big bluestem [Andropogon gerur-&Vitman] and little bluestem [Scfiac~yrium scopuriuu~ (Michx.) Nash] is related to degree-day accumulation and that these relationships are stable over environments and years within environments. Study environments included native prairie, a spaceplanted garden, and a growth chamber. Individual tillers of big and little bluestem were permanently marked and fully developed leaves were counted once or twice weekly over 3 growing seasons and 1 growth chamber trial. Quadratic regression models accounted for 94 to 99% of the observed variation in leaf development for all species-environment-year combinations. Regression models were significantly different (p= 0.05) among environments and between years within environments. Lack of model stability over years was a result of high variation in total leaves produced per tiller relative to annual variation in degree-day accumulation. The simple lndo pendent variable, day of year, predicted leaf development equally as well as degree-day accumulation.

Morphological Development of 2 Warm-Season Grasses in the Nebraska Sandhills

“…In grasses, developmental morphology determines plant architectural organization, influences accessibility and palatability to herbivores, and affects regrowth following defoliation (Briske 1991 (Gillen and Ewing 1992). Both growing degree day (GDD) and day of the year (DOY) appear to be valuable predictors of grass morphological development.…”

Simulating Growth and Root-shoot Partitioning in Prairie Grasses Under Elevated Atmospheric CO2and Water Stress

“…Thus we tested a null model of partitioning, in which the partitioning coefficient lsh is linearly related to plant size. However, grass phenological development is usually related to time or ' growing degree days ' rather than size (Gillen and Ewing, 1992). We therefore tested a second null model, another expression of ontogenetic drift which relates lsh linearly to time.…”

Use of Degree-Days in Multiple-Temperature Experiments

“…Base temperatures can be determined by regressing germination or growth on temperature (Arnold 1959), or if base temperatures are not known, 0?C can be used (e.g. Bauer et al 1984, Frank and Hoffmann 1989, Gillen and Ewing 1992, Romo et al 1991, Grilz et al 1994). Caution must be exercised when comparing species, genotypes, and different stages of growth for they have different base temperature thresholds (Wang 1960).…”

“…Degree-days or thermal units have been successfully utilized to describe or predict insect phenology (Dennis et al 1986, Dennis andKemp 1988), bud burst in trees (Thomson andMoncrieff 1982, Hunter andLechowicz 1992), pollen shedding (Boyer 1973), flowering in several range plants (White 1979), anthesis and maturity of wheat (Triticurni aestivum L.) and com (Zea mays L.) (Gilmore and Rodgers 1958, Cross and Zuber 1972, Davidson and Campbell 1983, Bauer et al 1984), growth of forage species (Holt and Haferkamp 1987, Frank and Hofmann 1989, Frank 1991, Gillen and Ewing 1992, Harrison and Romo 1994) and germination and emergence of several species (Carberry andCampbell 1989, Jordan andHaferkamp 1989). Degree-days have, however, received limited use as time limits where results are compared from experiments conducted at different temperatures.…”