Accidental Wilderness by Walter H. Kehm

Author:Walter H. Kehm
Language: eng
Format: epub
Publisher: University of Toronto Press
Published: 2020-03-15T00:00:00+00:00

Floristic Richness

Now that the overall pattern of vegetation colonization, community formation, and composition has been examined, it is worthwhile to take a closer look at the total flora and particular subsets of it.

The general pattern over the past 40 years has been an upward trend in plant species richness (Fig. 32). Accounting for the years in which full flora inventories took place at Tommy Thompson Park, the total number of plant species was roughly 155 in 1976. It increased to 285 in 1978, and then declined to 226 in 1982, possibly due to variation in survey intensity. In 2005–06, there were 352 plant species recorded. Finally, the most recent survey in 2017 yielded 407 species. The cumulative total (i.e., every plant that has ever been observed, whether or not it is still present) is 581 species (see the list of plant species).

The increase in floristic richness results from dispersal and colonization of the originally bare substrate at Tommy Thompson Park, followed by increasing complexity and interrelationships within the vegetation communities as they matured. Dispersal was initially by both natural and human means. Natural means included movement by wind, water, and birds. Human means included adhesion to vehicles and equipment or transport of propagules such as root pieces in fill material (Catling et al. 1977; MTRCA 1982).

After 1990, deliberate introduction of new species through plantings became a significant factor. There were 25 species identified as introduced through planting in 2005–06, and 53 in 2017. A few of these were random introductions by park users, such as the prickly-pear cactus (Opuntia cespitosa) observed in a sand barren in the late 1980s/early 1990s. Most of them are native species used in restoration plantings, such as tuberous white water lily, Indian grass (Sorghastrum nutans), and red oak (Quercus rubra). All of the conifers at Tommy Thompson Park, with the exception of common juniper (Juniperus communis) and possibly Scots pine (Pinus sylvestris), are planted (see the list of plant species).

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