Herbivory and Soil Properties as Ecological Constraints to Willow Growth in a Restored Riparian Ecosystem in Coastal California

Herbivory and Soil Proper- ties as Ecological Constraints to Willow Growth in a Restored Riparian Ecosystem in Coastal California. J Environ Sci 2: 003. Abstract This study investigated stunted arroyo willow ( Salix lasiolepis ) cuttings planted along a restored riparian corridor in Marin County, California. Restoration activities along this corridor included channel realignment, bank stabilization, and placement of streambed material and large woody debris, which required the use of heavy ma- chinery and compacted soils. Additionally, evidence of deer browsing indicated that predation may be significantly affecting cutting growth and survivorship. In our field study, we measured effects of deer browsing and physical soil characteristics (i.e., soil moisture, com- paction, texture, and total organic content) on the change in willow growth (i.e., height, mean canopy diameter, estimated aerial percent cover, and volume) of 160 recently planted willow cuttings (in their second and third year of growth following planting) to better under- stand stunted growth. Growth and health attributes of the cuttings were further analyzed in relation to three factors: 1) presence of ex- clusionary deer fencing; 2) location on left or right bank and 3) age of the cutting. Results of the study indicated deer herbivory was a critical stressor limiting survivorship and growth of willow cuttings. Exclusionary fencing resulted in significantly higher growth for all four metrics compared to unfenced willows with the greatest bene-ficial effect on younger willows in their second growing season. Sig - nificantly higher soil moisture and lower soil compaction were found in reference sites compared to restoration study sites. However, the influence of physical soil characteristics on willow growth revealed weak correlations. Exclusionary fencing is a cost-efficient method for restricting browsing by wild herbivores on recently planted willow cuttings, most effective when implemented during the first two growing seasons or until willow cuttings are resilient to the effects of herbivory.