Walt Klenner. 1998. Changing Landscapes in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

CHANGING LANDSCAPES

Monitoring forested habitats in the Montane Cordillera Ecozone
across large spatial and temporal scales

Walt Klenner
Ministry of Forests, Kamloops Region
515 Columbia St.
Kamloops, B.C.
V2C 2T7

ABSTRACT

Approaches to monitoring landscape changes in the Montane Cordillera Ecozone are discussed in the context of the need to quantify indicators of habitat change across large spatial and temporal scales. The monetary and technical resources required to track changes in community structure or even the population of a single species across its range in relation to human or natural disturbances are formidable. Although direct measures of species or community level changes may be preferred, a hierarchical approach to assessing ecosystem changes over time is proposed. To provide a context and overall picture within which more detailed measures of changes in biological diversity can be interpreted, several landscape features need to be tracked on an extensive basis, and complemented with more detailed sampling at selected monitoring installations to relate habitat changes with impacts on biota. Five landscape characteristics are identified that can serve as general indicators of overall landscape change in forested ecosystems: 1. seral stage distribution of forests, 2. patch size mosaic of forest and openings, 3. tree species composition, 4. density and dispersion of roads, and 5. landbase status. Monitoring approaches and the relevance of these features to biological diversity is discussed.

Introduction

The Montane Cordillera Ecozone (MCE) is a vast and complex landscape composed of 13 recognized biogeoclimatic zones (Meidinger and Pojar 1991, Harding and McCullum 1994b, Scudder and Smith, this volume), ranging from dry, valley-bottom bunchgrass ecosystems to alpine tundra. Although the MCE represents only about 5% of the terrestrial landmass of Canada (Lowe et al. 1996), the combination of a high average timber volume (204.6 m3/ha) and a high percentage of timber producing land in the ecozone (65%) creates a valuable natural resource that forms the basis for a large timber harvesting and manufacturing industry. For example, in 1995 approximately 75 million m3 of timber was harvested in BC (BC Ministry of Forests 1996), and about 80% of this came from the area within the MCE.

Maintaining biological diversity has become a recognized and important land management objective at the local and global scale (Wilson 1988, Salwasser 1990, Fenger et al. 1993). The increasing human population, an increasing demand for forest commodities and sophisticated resource extraction technologies have created an environment where non-timber resources could easily be compromised.

Resource extraction has been practiced by native peoples for centuries, but it has largely been since 1870 (Harding 1994) that forests have been harvested at a commercial scale or extensively impacted by human settlements and agriculture. Forestry is now a major industry in BC and elsewhere in Canada, with harvests in excess of 40 million m3 each year since 1965 (Harding 1994). Recent legislative changes in British Columbia have defined specific habitat targets to address biological diversity concerns (BC Forest Service and BC Environment 1995a, 1995b, Fenger 1996). Whether forests are managed for defined habitat characteristics, or with an ecosystem management approach (Grumbine 1994) that seeks to maintain habitat parameters within their historic range, a monitoring program will be necessary to determine if specific habitat targets are being achieved, and if defined targets are adequate.

Prior to the management of forests for timber commodities, a wide range of natural disturbances (e.g. wildfire, insect attack, windthrow, etc.; Canham and Marks 1985, Runkle 1985, Agee 1991) and aboriginal burning (Kay 1995) influenced forest ecosystems. These events created a diverse mosaic of seral stages and patch sizes across the landscape (Lehmkuhl et al. 1991, Mladenoff et al. 1993), and within stands, an abundance of habitat structures such as snags and downed wood was maintained (Franklin and Spies 1991a,b, Spies and Franklin 1991). This complex and heterogeneous mosaic of habitat structures and patterns is important in maintaining high levels of biodiversity (Miller 1982, Denslow 1985, Karr and Freemark 1985).

Forest harvesting will modify the temporal and spatial distribution of habitat types that formerly originated through natural disturbances. Increased amounts of edge, a decrease in the complexity of edges, and an increase in the interspersion of early and late seral habitats may have both short and long-term implications for maintaining biodiversity (Franklin and Forman 1987, Saunders et al. 1991, Lehmkuhl and Ruggiero 1991, Mladenoff et al. 1993). These changes will benefit some species and be detrimental to others, as the foraging, breeding or cover capabilities of the habitats are modified. Along with changes in habitat patterns, the abundance and distribution of several habitat structures will likely differ between managed and natural forests (Cline et al. 1980, Zarnowitz and Manuwal 1985, Spies and Cline 1988, Spies and Franklin 1991, Lee et al. 1995). The numerous large declining green trees, snags and abundant downed wood characteristic of old growth forests will decline in managed forests unless special practices are implemented to maintain these features (Swanson and Franklin 1992). Many species use or depend on these habitat features for food, breeding sites or cover. In British Columbia, for example, more than 90 species of vertebrates use large declining trees or snags for nesting, foraging or cover (Backhouse and Lousier 1991). Other habitat structures such as downed wood (Anderson 1986, Barnum et al. 1992), a deep layer of forest floor litter, terrestrial moss and lichens (Seastsdt and Crossley 1987) and arboreal lichens (Stevenson and Hatler 1985, Rominger and Oldemeyer 1989) provide important habitat for other biota. Tracking these complex habitat changes, and the extirpation of species or changes in ecosystem productivity is a formidable challenge to any monitoring program.

Ecological responses to natural and managed (anthropogenic) habitat disturbances are diverse, including a reduction in the population abundance and possible extirpation of one or more species (Thomas et al. 1990, Verner et al. 1992, Ralph et al. 1995), to shifts in a predator-prey complex (Seip and Cichowski 1996) that lead to depressed prey populations. Tracking all of the habitats and species in an ecosystem is not possible with any monitoring program, especially if the size of the MCE or other ecozones in Canada is considered. It is therefore important to choose a monitoring program and indicators that: 1. can be evaluated across the spatial scale of interest, 2. are precise (sensitive) and accurate and which will provide advanced warning of changes that will likely have undesirable ecological consequences, 3. use procedures that are repeatable and compatible between administrative jurisdictions in the area being evaluated, 4. are cost-effective to collect and report, and 5. Are causally related or correlated with the ecological issues of interest (adapted from Noss 1990).

There are currently a large number of individual research and monitoring projects that investigate the details of ecological interactions and responses to natural or managed disturbances at the species, population or community level. These studies form the basis of our ability to assess and predict ecological responses to change. At the other end of the spatial scale, the North American breeding bird survey (Robbins et al. 1986, Sauer et al. 1997) and the monitoring of air quality or weather patterns are examples of extensive monitoring programs that have been established for decades (see CENR 1997 for other examples). In Canada, the Canadian forest inventory program is a good example of an extensive monitoring program that periodically reports on the status of forests (Lowe et al. 1996), but the indicators presented largely reflect economic rather than ecological issues. This program is complemented by initiatives to periodically assess the status of biological diversity in specific regions in Canada (e.g. Harding and McCullum 1994a) and the EMAN program (Smith 1996) which reports on the status of a range of taxa in specific ecozones. Individually, these programs form valuable contributions to our ability to assess and predict the ecological consequences of natural and managed disturbances. Two innovations would help to markedly increase the utility of these programs: 1. the integration of research studies across spatial scales, and 2. a periodic and systematic evaluation of landscape habitat features at the regional or national level. The first issue, integration across spatial scales, is being addressed by several initiatives that are seeking approaches to assemble individual studies or extensive monitoring programs into an integrated framework (e.g. CENR 1997, Schneider 1997). As funds to manage natural resources become increasingly scarce, these initiatives are crucial and need to be undertaken in the Montane Cordillera Ecozone to develop the ability to assess the magnitude and rate of change, and to focus attention on priority areas.

I now review the importance of several habitat parameters that, if assessed systematically, would enhance our ability to assess and predict the ecological consequences of landscape habitat changes over time. I focus on large scale features that are best addressed at the regional, provincial or ecozone scale. Although the monitoring system I describe is suggested for the Montane Cordillera Ecozone, the results are applicable to any forested lands for which inventory information is available. This approach does not imply that monitoring and research efforts at other scales are unimportant, but the perspective that activities at different scales should complement each other. A complementary monitoring system will need to be developed for aquatic habitats, grasslands, or other non-forested habitats that are not evaluated in most forest inventories. I focus on five landscape characteristics that can be monitored by remote sensing technologies (satellites or aerial photography) or information captured in existing administrative or inventory databases: 1. seral stage distribution of forests, 2. patch size mosaic of forest and openings, 3. tree species composition, 4. density and dispersion of roads, and 5. landbase status. Other landscape features are undoubtedly important in their effects on ecological processes, and I present and discuss the above list as a first approximation. Although the current ability to systematically evaluate the status of these or other indicators is limited, a monitoring and assessment strategy could readily be developed to use currently available information, in addition to new monitoring approaches that utilize developing technologies.

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