Biomass and Defoliation Tolerance of 12 Populations of Pseudoroegneria spicata at Two Densities

• Published in: Rangeland ecology & management Vol. 66; no. 6; pp. 706 - 713
• Main Authors: Mukherjee, Jayanti Ray, Jones, Thomas A., Monaco, Thomas A.
• Format: Journal Article
• Language: English
• Published: Lawrence the Society for Range Management 01.11.2013; Elsevier Inc; Allen Press Publishing Services; Elsevier Limited
• Subjects: Biomass; Biomass production; bluebunch wheatgrass; cool season grasses; cultivars; Defoliation; feeding preferences; field experimentation; genotype; germplasm; Grasses; Grazing; grazing compensation; Herbivores; Hypotheses; indigenous species; Intermountain West; plant density; Plant roots; Plants; Population density; Pseudoroegneria spicata; rangelands; Research s; Root biomass; Seeds; semiarid zones; shoot biomass; shoots; Stomatal conductance; Intermountain West; shoot biomass; bluebunch wheatgrass; grazing compensation; root biomass
• ISSN: 1550-7424; 1551-5028; 1551-5028
• DOI: 10.2111/REM-D-13-00049.1

Pseudoroegneria spicata (Pursh.) A. Löve is an important native grass of the rangelands of the Intermountain West, USA and is widely used in this region for restoration applications. High grazing preference, together with high grazing sensitivity, has reduced the abundance of this species, indicating the need for the development of grazing-tolerant plant materials. While a genotype may be defoliation tolerant at low density, e.g., in an experimental setting, an effective grazing-tolerant genotype must also display this trait at higher densities resembling those found in natural and restoration settings. We compared 12 restoration plant materials for response to spring-defoliation at high (25 plants · m−2) and low (8 plants · m−2) plant densities in a field experiment. Two consecutive years of spring-defoliation reduced shoot biomass 19% compared to the nonspring-defoliated control, and this reduction was similar for the two densities examined. Two populations, P-3 and Acc:238, were able to compensate for shoot biomass after 2 yr of spring-defoliation, while the remaining 10 populations undercompensated, as is commonly reported for cool-season grasses in arid and semiarid regions. While the association between control and spring-defoliated shoot biomass was marginally positive (R2 = 0.26; P < 0.10), we found a stronger negative association (R2 = 0.36; P < 0.05) between spring-defoliation tolerance and control shoot-biomass production. This suggests a possible trade-off between growth and defoliation tolerance (calculated as percentage of control biomass) among populations. Of the four commercially available plant materials in our study, the more recent prevariety germplasm, P-7, exhibited higher control shoot biomass and higher spring-defoliation tolerance than the older cultivars, Whitmar and Goldar. Anatone germplasm was intermediate but not statistically different from these other plant materials for these two traits.