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The Twig Length Removal Method is a way of measuring utilization of browse where utilization is defined as the amount of plant material removed by livestock or wildlife. According to Utilization Studies and Residual Measurements reference, “With the Twig Length Measurement Method, utilization is determined by measuring twigs on 25 to 50 browse plants after full annual growth has occurred and again after the period of use.” The difference between the before and after measurements estimates the amount of browse that has been used. Plants to sample are selected at fixed intervals along a transect and tagged so they can be relocated. Different transects are selected for different browse species. This technique is most often used on wildlife winter range.
Two important considerations when implementing methods for quantifying utilization are selection of areas that have been utilized and selection of key species for measurement. Factors to take into account for site selection include whether the objective is to sample a critical area or to sample key areas that are representative of a larger landscape. For selecting key species, it is important to consider the forage value of each species, when during the year it is utilized, and the potential for the key species to reflect changes in the whole plant community.
From the Utilization Studies and Residual Measurements manual:
and/or wild burros. The degree of direct forage competition among different kinds of animals can be determined where there are discrete periods of use by different animals. Growth and use indexes can also be determined.
results will vary with species due to twig growth characteristics.
and browsed-twig methods of determining browse utilization. J. Range Manage. 30:64-67.
bitterbrush utilization from twig diameter-length-weight relations. J. Range Manage. 30:231-236.
Method of determining utilization of browse. Utah State Dept. of Fish & Game. Publication No. 62-9. 35p.
Monitoring - Utilization Studies, TR4400-3.