Assessment of Forage Utilization in Jicarilla Apache Range Lands.

Grazing monitoring on rangelands is crucial for its conservation, sustainability and ecosystem functions. The Jicarilla Apache Nation in Northern New Mexico has 879,661 acres, primarily rangelands for cattle, sheep, horse and wild life grazing. The primary objective of this study is to assess forage utilization based on the grazed stubble height measurements. Residual dry matter (RDM), the dry grass biomass left on the ground at the end of the grazing season, is a commonly used proxy for rangeland condition. Moderate levels of RDM (50 - 59% forage left) are correlated with soil stability, forage production, wildlife habitat, and diversity of native plants. Considering 120 range units, three range use types, 10 forage species and their interactions as independent variables, forage utilization percentage was analyzed using GLM procedure in SAS. Results indicated that average forage utilization percentage ranged from 9 to 64 on summer ranges, 7 to 48 on winter ranges and 4 to 62 on continuous ranges. Range units with Crested Wheatgrass (Agropyron cristatum), Blue Grama (Bouteloua gracilis) and Western Wheatgrass (Pascopyrum smithii) were heavily utilized (> 50%) and have major soil erosion implications. Average utilization percentage ranged from 21 to 58 for crested wheatgrass, 9 to 63 for Blue Grama and 5 to 62 for Western Wheatgrass. Other grasses such as Squirrel tail (Elymus elymoides), Galleta (Pleuraphis jamesii), and Alkali Sacaton (Sporobolus airoides) were utilized only 11 to 28%. Regression models to calculate optimum animal unit months were developed.