Chapter 2 Chapter 2 – Mountain and Foothills Ecosystems To understand the fashion of any life, one must know the land it is lived in and the procession of the year. — Mary Austin (1903) Key Questions • What are the major ecological known multitude of invertebrate animals and communities in the coastal nonvascular plants. We know very little about mountains of southern California? the specific habitat needs of the majority of • What is known about the status and these species. So how do we address all of this distribution of each? biological diversity in a feasible manner? Until recently, wildlife management • How have they changed in the last tended to focus on the needs of a few, high- 100 to 200 years? profile species (mostly game animals and • What rare communities exist and endangered species). Now the potential im- what are their status and trends? portance of all members of an ecosystem has been recognized and the focus has shifted away This chapter provides a large-scale over- from single-species management and towards view of landscape patterns and ecological ecosystem-based conservation (Hansen et al. communities within the assessment area. A 1993; Manley et al. 1995; Haufler et al. 1996). more detailed description of the specific eco- The idea that conserving broad ecological logical processes and human land uses affecting communities may be the most efficient way these ecosystems is presented in chapter 3. to maintain species diversity has gained wide- Here we focus on the extent and distribution spread acceptance and is implicit in the of each type, its current condition, and its rep- so-called coarse-filter approach (Noss 1987). resentation on public lands across the different Originally developed by The Nature Con- mountain ranges. Much of this information servancy, the coarse-filter approach assumes that is based on our GIS vegetation data. How- a representative array of ecological communities ever, first we describe the coarse-filter analysis will sustain the vast majority of species, includ- approach that is a major component of this ing many of the ones we know little about (fig assessment. 2.1)(Hunter et al. 1988). By relying on reten- tion of community types and providing an array The Coarse-Filter, Habitat- of structures and compositions, we hope to “cap- ture” most of the diversity in the system. Based Approach However, we know that some species, subspe- According to the California Wildlife Habi- cies, and rare communities have characteristics tat Relationships System (CWHR, version that make them “fall through the mesh” of the 5.2) and the California Flora Database coarse filter and these need special attention (i.e., (CALFLORA), the mountains and foothills a finer filter). The fine-filter approach focuses of southern California are inhabited by 18 on learning the specific needs of individual spe- amphibian, 61 reptile, 299 bird, 104 mam- cies and then providing for those needs, mal, and 2,900 vascular plants species (CDFG potentially through intensive management. 1996; Dennis 1995). Added to that is an un- 15 sarily require specific management attention. Rather, it suggests that their status and needs warrant individual consideration before decid- ing on a course of action. Based on the fine-filter screening criteria, 184 animals and 256 plants made the focal species list. These species are addressed in chapters 4 and 5, “Species at Risk,” and chap- ter 6, “Species of High Public Interest.” All other plants and animals occurring within the assessment area will only be addressed indi- rectly, via the coarse-filter, community-level analysis. The coarse-filter analysis procedure is quite simple: Current conditions are compared to reference conditions (based on how the landscape would look and function if people were not altering it), differences between the two are identified, the significance of the change is analyzed, and this information is fed into the decision-making process. However, the application of these ideas can be quite com- plicated (Sampson et al. 1997). Figure 2.1. The coarse-filter approach to The reference conditions represent our maintaining biological diversity focuses on best attempt to describe the ecological condi- protecting a representative array of communities tions, including their variability over space and and is based on the assumption that these time, under which native species evolved. If communities will encompass the vast majority of species. The fine-filter approach focuses on saving individual species that slip through the coarse filter. Figure 2.2. Fine-filter criteria used to identify As illustrated here, the coarse filter has been used species that should receive individual consideration to save a tract of Zaire’s forest, while the fine-filter in this assessment. A species or subspecies made approach has been employed for the pygmy the list if it met one or more of the criteria. chimpanzee and Congo peafowl (from Hunter et al. 1988). Species Potentially at Risk: • A Threatened, Endangered, or Proposed In this assessment we employed a com- Species (federal and state) bined coarse-filter/fine-filter approach. • A former USFWS Candidate (C1 or C2) Species Fine-filter criteria were used to identify spe- • A Forest Service, Region 5 Sensitive Species cies that would receive individual consideration (fig 2.2). The criteria primarily • A California Species of Special Concern target species that are rare and vulnerable. • A Riparian Obligate Species of Concern (as However, we also identified species that have defined by California Partners in Flight) a heightened status due to the high public in- • A species determined to have viability concerns terest that they generate. Thus, the fine-filter at a local level list is really divided into two distinct catego- Species of High Public Interest: ries: (1) species potentially at risk and (2) • A major game animal species of high public interest. Each species • A species that has particular public interest (e.g., identified in the fine-filter list does not neces- mountain lion) 16 Chapter 2 today’s conditions are similar to the reference In between the patches and corridors is the conditions, we are confident that adequate habi- surrounding matrix — a dominant vegetation tat is present for most species. The greater the or land type, such as chaparral in the foothills deviation from the reference conditions, the more or urbanized land in the Los Angeles Basin. species may be at risk. (Sampson et al. 1997). Across the southern California mountains An inherent difficulty with this approach and foothills region there are a few broad-scale is that it is usually difficult to determine the landscape mosaics that are clearly recognizable “true” reference conditions and the natural and repeatedly encountered. In the coastal range of variability. They must be inferred foothills the matrix is coastal scrub and chap- based on our knowledge of historic habitat arral interspersed with riparian corridors, oak conditions and on our understanding of key woodlands, and grasslands. Above the foot- ecological processes such as fire, succession, hills on often-steep lower mountain slopes, the and flooding. Since the historic record is fre- mosaic shifts to patches of mixed hardwood/ quently sketchy and inconclusive, there are conifer forest scattered between large expanses usually several plausible theories on how the of chaparral. As you move into the upper historic landscape might have looked and mountain region, pine and fir forests domi- functioned. nate the landscape and are punctuated with These problems are compounded by the patches of black oak woodland, montane fact that we will often be managing outside meadows, and chaparral. On the desert side the range of conditions that native species of the mountain crest is another distinct land- encountered in the past. In some places, the scape, dominated by sparse pinyon forests, ecological systems are so altered that we will juniper woodlands, desert scrub, and exten- typically be outside the range of conditions sive areas of bare rock. that occurred historically (e.g., in dammed Key physical factors that seem to trigger river systems or in grasslands that are now broad-scale changes in the vegetation mosaic dominated by non-native species). Social con- are elevation, distance from the coast, topog- siderations (e.g., reducing fire hazards near raphy, and position on either the coastal or towns) and economic factors also affect our desert side of the mountain crest. These fac- ability to remain in (or move toward) more tors have a strong influence on precipitation “natural” landscapes. The farther we move amounts and temperature regimes, which in from those conditions, the less successful we turn greatly influence the type of vegetation can expect the coarse-filter approach to be that grows. Today, human land use also plays (Sampson et al. 1997). a key role in shaping these land mosaics. Despite these difficulties, the coarse filter Below we describe and present a map (fig. can be an effective approach for (1) retaining 2.3) of the six large-scale vegetation mosaics biological diversity in its broadest sense, (2) that characterize the mountains and foothills retaining critical but little understood pro- of southern California. In reality these mosa- cesses (such as roles played by soil microbes), ics, or “landscapes” as we refer to them here, and (3) sustaining species that we currently do not have distinct boundaries but rather have know little about. broad transition zones where different vegeta- tion assemblages intergrade. However, each Broad-Scale Landscape landscape has unifying characteristics that have important implications for resource manage- Mosaics ment. These characteristics transcend the From an airplane, land usually appears as particulars of which mountain range or wa- a mosaic of patches, corridors, and matrix tershed the landscape may be found in. There (Forman 1995). Woodlands, fields, and hous- are clear differences in the way each landscape ing tracts often stand out as conspicuous type has historically been affected and shaped patches.