Browsing Journal of Range Management, Volume 46, Number 3 (May 1993) by Subjects
Now showing items 1-3 of 3
Bluegrass billbug feeding response to perennial triticeae grassesIn a 4-year field study, 25 perennial triticeae grasses, representing a wide range of genomes and genome combinations, were evaluated as potential hosts for the bluegrass billbug (Sphenophorus parvulus Gyllenhal [Coleoptera: Curculionidae]). Root-sample data suggested that Russian wildrye (Psathyrostachys juncea [Fischer] Nevski) was unsuitable for billbug reproduction. Numbers of immatures varied significantly among remaining entries. Rhizomatous entries were more tolerant of billbug injury than caespitose entries. Plant mortality rates were frequently 50% or higher for self-pollinated caespitose entries with the SH genome complement (Elymus spp.). Losses to billbugs among the remaining species, particularly those with the J, N, and P genomes, were insignificant. Billbugs did not discriminate between native and introduced grasses, as resistant and susceptible entries were identified in both groups. The results obtained here may aid in selecting triticeae grasses for reseeding in areas where billbugs have damaged stands in the past.
Forage response to N, P, and S fertilization on clearcut lodgepole pine sitesThe response of selected plant species to a single application of factorial combinations of nitrogen (N), phosphorus (P), and sulfur (S) on 2 lodgepole pine (Pinus contorta Dougl.) clearcut-logged sites in British Columbia was evaluated over 3 years. Increasing N rates typically resulted in higher forage standing crop on both sites, in all years. but standing crop at Fly Creek was nearly double that at Beaverdam Lake. On both sites, forage yields peaked at 400 kg N/ha in 1982 and carry-over of the fertilizer effect lasted for 3 years although yields declined annually. Addition of P to N applications enhanced (P < 0.05) total standing crop, other grass standing crop, and pinegrass (Calamagrostis rubescens Buckl.) standing crop at Beaverdam Lake and grass standing crop at Fly Creek, but had no effect (P > 0.05) on other species and groups. Sulfur, added to N applications, enhanced total yields compared to control on both clearcuts although at Fly Creek this response nearly doubled that produced at Beaverdam Lake. Nitrogen fertilization increased (P < 0.05) pinegrass crude protein (CP) content, particularly in the first year after fertilization. Acid detergent fiber (ADF) generally increased in response to increasing N levels in 1982, but declined compared to control in 1983 and 1984. Elevated forage CP levels, litter N concentrations, and soil N levels in 1984 indicated that the carry-over response on these forest sites resulted directly from N remaining in the soil or again becoming available for plant growth.
Viewpoint: Selection for improved drought response in cool-season grassesWater limits the establishment, growth, and production of cool-season grasses on semiarid rangelands, and plant improvement programs for these areas must be capable of screening breeding lines for response to drought. Although many techniques to evaluate various morphological and physiological characteristics have been proposed, few have been used successfully in plant breeding programs. Consequently, a need exists to identify and develop rapid, reliable screening techniques that can assess integrated plant response to drought in large plant populations. Improved seedling emergence has been achieved in Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] by selecting for emergence from a deep seeding depth and long coleoptiles. Water uptake by roots is critical, and screening for enhanced seedling root growth in cool-season grasses offers considerable promise. In spite of the important role that stomatal control has in regulating plant water loss, limited success has been achieved in incorporating desirable stomatal characteristics into improved grass cultivars. Although osmotic adjustment appears beneficial in some crop species, more research is needed before cool-season grasses should be selected based on osmotic adjustment. Selection for improved water-use efficiency in cool-season grasses based on carbon isotope discrimination is a promising approach. Successful incorporation of these various traits into improved cool-season grass cultivars necessitates close cooperation between breeders and physiologists.