Environmental Settings/Biological Resources
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Chapter 3 Environment and Habitat Contents 3 ENVIRONMENT AND HABITAT 3-1 3.1 Introduction 3-1 3.2 Environmental Context 3-1 3.2.1 Climate and hydrology in the plan area 3-1 3.2.1.1 Climate 3-1 3.2.1.2 Stream flow and peak flow 3-2 3.2.1.2.1 Rain and flooding 3-2 3.2.1.2.2 Records on the Noyo and Navarro rivers 3-2 3.2.2 Geology and geomorphology of the plan area 3-3 3.2.2.1 Geologic features 3-3 3.2.2.2 Sediment inputs 3-3 3.2.2.3 Soil types 3-3 3.2.2.4 Mass wasting 3-4 3.2.2.4.1 Forest management practices affecting mass wasting 3-4 3.2.2.4.2 Effects of mass wasting on streams 3-5 3.2.2.4.3 Effects of mass wasting on anadromous salmonid habitat 3-5 3.2.3 Historical recap of the adjustment area 3-6 3.2.3.1 Land use 3-6 3.2.3.2 Historical location of roads and tractor trails 3-7 3.2.3.2.1 Impact of cable logging on road configurations 3-7 3.2.3.2.2 Impact of skid trails on sediment delivery 3-8 3.3 Aquatic Habitat 3-8 3.3.1 General concept of a watershed 3-8 3.3.2 Definition of watershed and watershed analysis 3-9 3.3.3 Watershed analysis units 3-9 3.3.4 Resource assessment report 3-10 3.3.5 Watershed analysis process 3-11 3.3.6 Summary of aquatic habitat conditions by major streams and rivers 3-11 3.3.6.1 Interpreting MRC data on streams and rivers 3-12 3.3.7 Regional summary of aquatic habitat conditions 3-32 3.3.7.1 Stream shade 3-32 3.3.7.2 Instream LWD conditions 3-33 3.3.7.3 Anadromous salmonid habitat conditions 3-34 3.3.7.4 Spawning habitat conditions 3-34 3.3.8 Summary of sediment input by planning watershed 3-35 3.3.8.1 Interpreting MRC data on sediment inputs 3-35 3.3.9 Summary of sediment input by source of erosion 3-39 3.3.9.1 Forest roads 3-39 3.3.10 Undersized culverts 3-41 3.3.11 Regional conclusions for aquatic habitat conditions 3-43 3.3.12 Predicting changes in peak flow 3-43 3.3.12.1 Impact of forest harvest on peak flow 3-44 3.3.12.2 Impact of increased peak flow on aquatic organisms 3-44 3.3.12.3 Snow and peak flow 3-44 3.3.12.4 Logging roads and peak flow 3-45 i 3.3.12.5 Prediction of peak flow increase from forest harvest 3-45 3.3.13 Fire impacts on aquatic habitat 3-46 3.4 Terrestrial Habitat 3-46 3.4.1 Vegetation distribution in the plan area 3-46 3.4.2 AMZ distribution within the plan area 3-47 3.4.3 Natural communities 3-49 3.4.3.1 North coast coniferous 3-50 3.4.3.2 Broadleaved upland 3-52 3.4.3.3 Closed-cone coniferous 3-54 3.4.3.4 Oak woodlands 3-55 3.4.3.5 Salt marsh 3-57 3.4.3.6 Deciduous riparian 3-58 3.4.3.7 Aquatic 3-59 3.4.4 Habitat elements 3-59 3.4.4.1 Old growth trees 3-59 3.4.4.2 Wildlife trees 3-60 3.4.4.3 Downed wood 3-60 3.4.4.4 Rocky outcrops 3-60 3.4.4.5 Hardwoods within conifer stands 3-60 3.4.4.6 Wetlands, watercourses, seeps, and springs 3-60 3.4.5 CWHR habitat classification system 3-61 3.4.6 Habitat quality for wildlife 3-62 3.4.7 Habitat sensitivity to land use 3-62 ii List of Tables Table 3-1 Watershed Analysis Units in the Plan Area 3-10 Table 3-2 Qualitative Indices 3-12 Table 3-3 Ratings for Canopy Cover 3-14 Table 3-4 Ratings for Effective Shade 3-16 Table 3-5 Ratings for LWD 3-16 Table 3-6 Ratings for Stream Gravel Permeability 3-17 Table 3-7 Ratings for Sediment 3-17 Table 3-8 Aquatic Habitat Conditions for Major Streams and Rivers: 1998-2008 3-19 Table 3-9 Summary of Aquatic Conditions by Watershed Analysis Unit 3-29 Table 3-10 LWD Projects in the Plan Area: 1998-2007 3-33 Table 3-11 Sediment Inputs (1963-2003) and Current Road Density by Planning Watershed 3-37 Table 3-12 Percent of Sediment Inputs by Source of Erosion 3-39 Table 3-13 Sediment Inputs 3-39 Table 3-14 Road Classes within AMZ 3-41 Table 3-15 Culverts at Watercourse Crossings 3-43 Table 3-16 Peak Flow Predictions for CalWater Planning Watersheds in the Plan Area 3-46 Table 3-17 Distribution of Forested and Non-Forested Areas 3-47 Table 3-18 Average Canopy Closure for AMZ Stands by Planning Watershed 3-47 Table 3-19 Acres of Hardwood and Conifer-Hardwood Stands by Major Drainage 3-48 Table 3-20 MRC Natural Communities 3-49 List of Figures Figure 3-1 General Illustration of a Watershed 3-9 Figure 3-2 Headwaters and Mouth 3-15 Figure 3-3 Effective Stream Shade in MRC Planning Watersheds as of 2005 3-32 Figure 3-4 LWD Conditions in MRC Planning Watersheds as of 2005 3-33 Figure 3-5 Anadromous Salmonid Habitat Condition by Life Stage 3-34 Figure 3-6 Spawning Gravel Quality from Long Term Monitoring Segments 3-35 iii Mendocino Redwood Company HCP/NCCP 3 ENVIRONMENT AND HABITAT 3.1 Introduction In order to evaluate the proposed conversation measures of our plan, you need an understanding of the past and present state of the plan area. Chapter 3, in effect, outlines where we have come from and where we are today. The conservation measures in Chapters 8-11 will focus on where we want to go. In reviewing the past and current conditions in the plan area, we distinguish between aquatic and terrestrial habitat. Habitat is the place where a specific species is commonly DEFINITION found because it provides the physical and biological resources required for its survival and reproduction. In the first half of this chapter, we examine environmental variables and physical processes related to aquatic habitat, as well as the conditions of such habitat in the plan area. Initially, we describe the environmental context of our landscape, including climate, geological features, pollution sources, stream temperatures, and mass wasting associated with roads and hillslope failure. Next, we focus on specific parameters related to riparian zone, canopy, LWD within stream channels, instream sediment, aquatic wildlife, and hydrology In the second half of the chapter, we turn our attention to terrestrial habitat, addressing topics such as natural communities, their distribution in California and in the plan area, and their ecological factors. After examining these broader habitat issues, we zero in on specific habitat elements—old growth, wildlife trees, downed wood, rocky outcrops, wetlands—and highlight their importance for covered species in our plan. These elements provide foraging, denning, and roosting sites; cover from predators; and other day-to-day needs for species survival. For management purposes, we may never fully and scientifically understand the relationship of any one species to all the environmental variables and processes we study on our landscape. However, we can sometimes manage or create what has been identified as its habitat and, in doing so, maintain or increase its numbers. This is a main thrust of our HCP/NCCP—to improve the quantity and quality of both aquatic and terrestrial habitat. 3.2 Environmental Context 3.2.1 Climate and hydrology in the plan area 3.2.1.1 Climate The climate of the plan area is Mediterranean, with warm dry summers and moderate winters. Mean annual precipitation ranges from 40 in. along the coast at Fort Bragg and Point Arena to 50 in. at Willits. Based on climate records,1 approximately 95% of the precipitation occurs during October through May. January is on average the wettest month, when about 18% of total annual precipitation is recorded. The driest month is July, with less than 1% of total annual precipitation. Precipitation occurs predominately in the form of rain. A small portion of precipitation falls as snow, but it rarely remains long. Snowmelt and rain-on-snow are not hydrologically significant in the plan area. 1 The records are from climate stations in Standish Hickey State Park (Station No. 8490), Willits 1NE (Station No. 9684), and Point Arena (Station No. 7009). 3-1 Mendocino Redwood Company HCP/NCCP 3.2.1.2 Stream flow and peak flow 3.2.1.2.1 Rain and flooding Stream flow in the plan area is responsive to rain, with high stream flows directly following high rainfall. Floods and variations in stream flow are stochastic and distributed throughout the year when rain occurs (October–May). Along the north coast, however, where our land is located, the greatest precipitation and flooding occur in late fall and winter (December–March). Within the last decade, there have been many intense storms in the plan area and, as a result, frequent flooding in its rivers. Floods have the capacity to re-shape river or stream channels and transport large sediment loads.