Seedbed micro-sites and their role in post-fire succession of the lichen-black spruce woodland in Terra Nova National Park, Newfoundland

Power, Randal Gerard (2005) Seedbed micro-sites and their role in post-fire succession of the lichen-black spruce woodland in Terra Nova National Park, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Effects of a recent wildfire in the lichen-black spruce woodland in Terra Nova National Park, Newfoundland, were investigated to determine the interaction between fire intensity and fire severity; plus effects on forest-floor disturbance, on canopy seed banks, and on black spruce regeneration. As there was much exposed mineral soil from ant activity on this site, the potential for enhanced post-fire black spruce recruitment due to ants was also investigated. A seeding trial considered four potential seedbeds available: areas of high severity; areas of low severity; active ant nests; and abandoned ant nests. In addition, the amount and distribution of seed rain in the burned area was measured in an attempt to assess factors that affect the pattern and success of black spruce recruitment following fire. Duff depths were reduced by fire by as much as 50% while lichen depth by up to 88%. Ant nests occurred at a density of 6.15 per 100m² in the burned areas compared to 2 per 100m² in the unburned forest. Black spruce seed-fall, while low at 16 539 seeds per ha in the year following the fire, was sufficient for re-establishing the lowdensity lichen woodland community at an initial density of 524 seedlings per ha by 2003. However, a mean cone removal of 52% by non-native red squirrels may be limiting the establishment of a higher-density forest. Available seedbed was limited by the extensive caribou-lichen mat, but over 40% of successful black spruce seedlings in the seeding trial germinated in this substrate, compared with 33% for inactive ant nests and 26% for high severity bum. Seedlings were most likely to become established and survive in desiccation fractures in the lichen mat. The presence of abandoned ant nests did result in germination, but did not necessarily result in establishment as seedling survival was reduced from 89% to 44% after winter. Seedling mortality on scorched organic soil substrate under former spruce canopies was highest at 71 %. Active ant nests produced no germinants in the trial and were the least suitable for germination. Drier and warmer than normal conditions in 2003, resulting in soil moisture deficits, appeared to be the main limiting factor for black spruce germination and survival. The next several years will be critical for subsequent black spruce germination and survival and in determining if reestablishment of the recently burned lichen woodland in TNNP will be successful.

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