| Summary: | The main objectives of this study were (1) to determine how yearly changes in climate
affects phenology at sites in the Bunchgrass (BG) and the Sub-Boreal Spruce (SBS)
Biogeoclimatic Zones of the Cariboo-Chilcotin region of British Columbia, (2) to clarify how
phenology varies among plant associations which are related to soil moisture gradients in
grasslands, (3) to clarify how phenology varies among plant associations which are related to
soil moisture and canopy cover gradients in forested range, and (4) to describe and compare
the phenological patterns found in riparian areas and surrounding uplands at sites in the BG
and SBS.
A set of permanent plots was established in each of the riparian and upland plant
associations at the two BG sites and one SBS site. I observed and recorded the phenology
of each species growing in each plot from April to September in 1995 and 1996. Soil
moisture and degree day totals at each site were also measured. Hierarchial cluster analysis
and ordering species by flowering dates were used to group species with similar phenologies.
Spring degree day totals were close to 20 year averages in 1995, but in 1996, they were
only 69% of average at the BG sites and 73% of average at the SBS site. Changes in
phenology between 1995 and 1996 reflected these differences. Forty percent of the species at
the three sites flowered two or more weeks later in 1996 than in 1995. Twenty-four percent
of the species dispersed fruit later in 1996. The higher levels of winter precipitation in 1996
increased the time in spring that soils were saturated, and changes in phenology were greatest
in the species growing in the transition areas between riparian and upland habitats. More
species growing in these areas flowered two weeks later in 1996 than species growing in other areas.
I categorized species into five general phenological groups based on flowering dates
(Early Spring, Spring, Early Summer, Mid Summer, and Late Summer). The Early Spring
and Late Summer groups each had distinct, uniform phenologies. The three mid season
groups (Spring, Early Summer, and Mid Summer) overlapped in both flowering and fruit
dispersal times and included a variety of phenologies. Individual upland and riparian plant
associations differed in at least one aspect of their phenological patterns related to dates of
flowering and fruit dispersal and/or proportion of species included in each phenological group.
In addition, the phenology of some species growing in several associations varied among
associations. These differences suggested that species growing in each plant association had
phenological adaptations related to the habitat and microclimate where each association grew.
The use of indicator species clarified the differences in upland and riparian phenologies.
At the BG sites, only one riparian species flowered in early spring compared to 17% of the
upland species. By early summer, only 50% of the riparian species had flowered compared to
63% of the upland species. Fruit dispersal was three weeks later in respective riparian
phenological groups than in upland groups. At the SBS site, flowering times were similar in
the riparian areas and uplands, but species in respective phenological groups dispersed fruit
two to four weeks later in the riparian area than species growing in the upland areas.
Many BG species common across the uplands flowered up to two weeks later growing
in the associations with higher soil moisture (transition and deep swale plant associations).
At the SBS site, species generally flowered earlier in the clear cut (low levels of canopy
cover) than in the other upland forest associations (higher levels of canopy cover). === Land and Food Systems, Faculty of === Graduate
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