The Ponderosa Pine (PP) zone occurs in
valley bottoms above the BG zone (where present) to approximately
900m and is situated beneath the IDF zone. This is the driest forested
zone in the province (Meidinger and Pojar 1991). Lloyd et. al. (1990)
reports that the mean annual precipitation ranges between 250-400mm
and the mean annual temperature ranges between 5.4 and 9.0C.
There are two subzones recognized in the
PP zone. The very dry, hot subzone (PPxh) occupies valley bottom between
Lytton, Lilloet, Nicola and Thompson rivers and the Okanagan Valley.
The dry, hot subzone (PPdh) is found along the Kettle River near Grand
Forks, drier portions of the East Kootenay Trench near Cranbrook and
the Kootenay River along the Koocanusa reservoir (Meidinger and Pojar
1991).
Soils are typically Chernozemic or Brunisolic
with thin mull humus forms. Parent material are often glaciofluvial,
fluvial, glaciolacustrine, morainal, colluvial or eolian.
Ecosystems
The following ecosystem information is
summarized from Braumandl and Curran (1992), Lloyd et. al. (1990),
Meidinger and Pojar (1991) and Steen and Coupé (1997).
Zonal ecosystems in the PPxh subzone consist
of Ponderosa pine, Bluebunch wheatgrass (Pseudoroegneria spicata),
and Idaho fescue (Festuca idahoensis). Dry sites consist of Ponderosa
pine, Big sage (Artemesia tridentata) and Bluebunch wheatgrass. Douglas-fir
(Pseudotsuga menziesii) and Trembling aspen are more common on wetter
sites or cool aspects. Understory species on theses sites includes
Snowberry (Symphoricarpos albus), Pinegrass (Calamagrostis rubescens)
and Birch-leaved spirea (Spiraea betulifolia).
In the PPdh, zonal sites are occupied by
ponderosa pine, Bluebunch wheatgrass and junegrass (Koeleria macrantha).
Dry sites are typified by compact selaginella (Selaginella densa),
Bluebunch wheatgrass and blue-eyed Mary (Collinsia parvifora). Isolated
pockets of dense forest occur in wet sites near riparian areas and
depressions. These sites have vegetation such as trembling aspen,
black cottonwood, snowberry (Symphoricarpos albus) and horsetail (Equisetum
spp.).
Very dry sites
commonly have association of arrow-leaved balsamroot (Balsamorhiza
sagittata) and prickly pear cactus (Opuntia fragilis).
Resources
This zone is used extensively for cattle
grazing in the spring and provides ideal ungulate winter range habitat.
Additional agricultural crops include a variety of fruits from orchards,
wine production from vineyards in the southern end of the range and
ginseng.
Due to the population density and rolling
topography, urban development is common and widespread in some areas
particularly the Okanagan valley.
Forestry activities are often limited due
to poor productivity and sparse coverage of commercial trees.
Recreational activities include hiking,
mountain biking, hunting and fishing. Water sports are common near
large water bodies such as Okanagan Lake.
References
Braumandl, T.F. and M.P. Curran. 1992.
A field guide for site identification and interpretation for the Nelson
Forest Region. B.C. Min. For., Res. Br., Victoria, B.C., Land Manage.
Handb. No. 20. http://www.for.gov.bc.ca/hfd/pubs/docs/lmh/lmh20.htm
Lloyd, D., K. Angove, G. Hope, and C. Thompson.
1990. A guide to site identification and interpretation for the Kamloops
Forest Region. B.C. Min. For., Res. Br., Victoria, B.C., Land Manage.
Handb. No. 23. http://www.for.gov.bc.ca/hfd/pubs/docs/lmh/lmh23.htm
Meidinger, D. and Pojar, J. 1991. Ecosystems
of British Columbia. British Columbia Ministry of Forests. 330 pp.
http://www.for.gov.bc.ca/hfd/pubs/Docs/Srs/SRseries.htm
Steen, O.A., and R.A. Coupé. 1997.
A field guide to forest site identification and interpretation for
the Cariboo Forest Region. B.C. Min. For., Res. Br., Victoria, B.C.,
Land Manage. Handb. No. 39. http://www.for.gov.bc.ca/hfd/pubs/docs/lmh/lmh39.htm
Images © Derek Marcoux
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