Research Summaries

Thorne, M. S., P. J. Meiman, Q. D. Skinner, M. A. Smith, and J. D. Dodd.
2005. clipping frequency affects canopy volume and biomass production in planeleaf willow (Salix planifolia). Journal of Range Management 58:41-50.

Willows (Salix spp.) are a key component of riparian ecosystems and are often browsed by both wildlife and livestock. However, little is understood about how the frequency of browsing affects aboveground and belowground willow production. The objectives of this study were to determine how the frequency of simulated browsing events in a controlled environment affected 1) the above, belowground, and total biomass production, and 2) the canopy volume of planeleaf willow (Salix planifolia) plants. The experiment was a completely randomized block design consisting of 2 groups of willow plants with different clipping histories. Within each group, plants were randomly assigned to 1 of 11 subgroups. Clipping events comprised of all combinations of early, middle, and late season periods were imposed on the treatment subgroups while 1 subgroup served as the control. Canopy volume measurements were made before and after each clipping event. Canopy volume change was related to the harvested twig length (cm) and weight (g). Results suggested that frequency of clipping alone did not explain differences in aboveground and belowground willow production. Instead, willow production was influenced by an accumulation of specific combinations of seasonal clipping events and was dependent on the clipping history of the plants. Early season clipping, along or in combination with other events, was more detrimental to willows with prior clipping histories than middle or late season clipping treatments. Willows with prior clipping histories treated in either the middle or late seasons, and the late/middle combination produced more than the controls. These results should be verified in willow communities subjected to natural environmental variations and browsing.