Vegetation Management and Maintenance Plan - Watsonville ...

CHAPTER 1.0
INTRODUCTION
The Watsonville Wetlands Trail System encompasses approximately six miles of multi-use
recreational trails in the City of Watsonville. The trails traverse portions of Watsonville Slough
and Struve Slough and abut multiple urban land uses, including residential areas, commercial
developments, school facilities, and City recreational areas. The trail system and slough areas
addressed in this manual are depicted on Figure 1.
The Watsonville Wetlands Trail Vegetation Management and Maintenance Manual (VMMM)
identifies the location and treatment methods to be used by the City’s maintenance personnel,
contractors, and/or volunteer groups to remove and/or control the growth of weeds and invasive,
non-native plant species within the trail system project area. The manual also outlines strategies
to encourage native plant growth that will reduce the need for long-term weed control.
The City of Watsonville has implemented several riparian and wetland plantings along the slough
trails, providing mitigation for bridge and trail improvement projects. The VMMM identifies
these areas and the specific maintenance and monitoring requirements that are applicable to these
mitigation plantings.
1.1 STUDY METHODOLOGY
1.1.1 Existing Vegetation Types and Management Areas
The existing vegetation types in the VMMM project area were mapped during the City’s
preparation of the Trail Plan (Swanson Hydrology & Geomorphology, 2002). Nine plant
community types were observed within the trail study area. These plant communities are nonnative
grassland, blackberry scrub, ruderal (weedy) scrub, coyote brush scrub, non-native
trees/tree groves, willow riparian woodland, freshwater marsh, and seasonal wetlands. Field
surveys conducted for the VMMM confirmed the current distribution of these habitat types and
identified recent City-designated riparian and wetland mitigation and enhancement areas; the
distribution of the vegetation types and mitigation/enhancement areas is shown on Figures 2, 3,
and 4.
1.1.2 Existing Invasive Weeds, Infestation Areas, and Threat Rankings
The occurrence of invasive weeds (i.e., invasive, non-native species) within the project area was
identified and mapped during field surveys conducted in February, March, May, and June 2007.
The infestations were mapped as line features, polygons, or spot locations by GPS or hand drawn
onto aerial photos. The GPS and hand drawn data was supplied to the City’s GIS coordinator to
develop a GIS data layer (i.e., “distribution of invasive weeds”). Potential vegetation management
or maintenance areas were also identified, such as vegetation types or plant species that may
require periodic maintenance (e.g., willow riparian woodland that abuts a trail and pruning or
other maintenance may be required now or in the future).
Based on the type and extent of invasive weeds in the project area, the species/species locations
were categorized as high, moderate, or low threat. A species growth pattern, extent within the
project area, effect on native vegetation, and ability to spread into uninfected areas were used to
Vegetation Management and Maintenance Manual
Draft 1 July 27, 2007