Document Details
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Title |
Effects of Cumulative Disturbances on an Endangered Whitebark Pine ? Cladina Lichen Ecosystem | ||||||
Author |
Haeussler, Sybille | ||||||
Date |
2008 | ||||||
Abstract |
Maintaining biodiversity & ecosystem integrity requires understanding the relationships between natural disturbance, ecosystem structure, composition & pattern & the habitat requirements of organisms within the ecosystem. The unprecedented scale of the current mountain pine beetle (MPB) epidemic is expected to cause system-wide reorganization of ecosystem structure & function in Interior BC, with major consequences for biodiversity & ecosystem integrity at stand & landscape scales. This research project uses low elevation, peripheral occurrences of the blue-listed Whitebark Pine(Pa)-Cladina Lichen ecosystem (ESSFmk/02) near the Burnie River in northwest BC as a model system to demonstrate how loss of ecosystem diversity occurs in response to cumulative disturbance & shifts in climatic regimes, even in areas untouched by forest management activities. Understanding how such shifts in ecosystem diversity occur in natural landscapes is a prerequisite for projecting the effects of forest management on landscape diversity. The endangered Pa-Lichen ecosystems lie on the east slopes of the Kitimat Ranges within the traditional territories of the Wet?suwet?en Nation & were an important source of nutritious pine nuts for indigenous peoples & wildlife (including grizzly bear) as well as serving as habitat for caribou. Detailed ecosystem descriptions were prepared during original biogeoclimatic ecosystem classification (BEC) fieldwork in 1978-80. Since then, we hypothesize that a rapid shift from a Pa-Lichen to a more typical Subalpine fir(Bl)-Mountain hemlock(Hm)-Moss ecological community has taken place, resulting in lower wildlife habitat value & reduced ecosystem diversity at the landscape scale. We hypothesize that the shift in ecosystem states was precipitated by Pa mortality from exotic white pine blister rust & 1980-90s MPB attack, coinciding with wetter, milder climatic conditions since the 1977 Pacific Decadal Oscillation shift in the North Pacific. We will test this hypothesis by: 1) contrasting climatic conditions in the study area during four PDO regime intervals 1901-1923, 1923-1946, 1946-1977 & 1977-2002, with emphasis on climatic conditions before & after the major 1977 shift (Gedalof & Smith 2001). We will use the simulation model ClimateBCv3.1 (Wang et al.2006), which interpolates climate between existing stations, to predict climatic variables for each time interval. We hypothesize that 1977-2002 was milder with wetter summers than pre-1977. 2) contrasting stand, vegetation & soil conditions before & after the 1977 PDO shift by remeasuring 1978/80 BEC plots in stands with low to high Pa mortality. We hypothesize that Hm, Bl, ericaceous shrubs & mosses have increased more, & Cladina lichens have decreased more, in stands with high levels of overstory Pa mortality than in stands that have so-far experienced lower mortality. 3) reconstructing stand dynamics in the large Burnie River Pa-Lichen ecosystem with ~80% mortality of overstory Pa by sampling live & dead trees, saplings, seedlings & woody debris using standard dendrochronological & stand reconstruction techniques. We hypothesize that release & ingrowth of shade tolerant Hm & Bl is correlated with mortality of overstory Pa & the PDO index. 4) reconstructing stand dynamics in a 1974 wildfire adjacent to the Burnie old growth stand that appears to lack Pa regeneration. We believe the wildfire is regenerating to a Bl-Hm-Moss ecosystem rather than Pa-lichen because of insect & disease impacts in the adjacent Pa stand & mild weather. Peripheral ecosystems demonstrate lower ecological resilience to environmental change than more contiguous ecosystems (Peterson 2002) and can be considered as ?canaries in the coal mine? for assessing the effects of cumulative environmental change on ecosystems. Whitebark pine ecosystems are threatened throughout their range & have been extensively researched in the US (Tomback et al. 2001). But little work has been published in Canada, & ... | ||||||
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