Impact of pre-dispersal predation by red squirrels (Tamiasciurus hudsonicus) and cone insects on balsam fir (Abies balsamea) seed production in eastern Newfoundland

• Main Author: Boa-Antwi, Kofi
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2009
• Subjects: Canada; Bonavista Bay; Newfoundland
• Online Access: https://research.library.mun.ca/9707/; https://research.library.mun.ca/9707/1/Boa-Antwi_Kofi.pdf

Predispersal seed predation is a critical factor limiting population recruitment among a number of coniferous species in natural systems. Introduced species, a major threat to biodiversity, can cause high levels of predispersal seed predation. Balsam fir (Abies balsamea) regeneration and establishment has been an ongoing challenge for land managers on the island of Newfoundland due to paucity of adult trees producing female cones, and the fact that fir recruitment requires annual seed production as there is no seed bank. This study focused on the combined impact of a mammal and a suite of insects on pre-dispersal cone and seed mortality of balsam fir through investigation of ecological impacts of non-native red squirrels (Tamiasciurus hudsonicus) and a variety of predispersal cone/seed insects on this dominant tree species. Specifically, the impact of red squirrels and cone/seed insects were compared between balsam fir stands with different disturbance types and stem densities: Intact sites with no recent history of insect-infestation; and Insect Kill sites with recent history of insect infestation, around a range of stem densities (286-3100 trees/ha). The study was conducted within Terra Nova National Park and the surrounding forest management area in the southern Bonavista Bay region of the island of Newfoundland, Canada. -- The percentage of pollen cones lost to red squirrels (3.5 ± 7.3% to 84.6 ± 9.3%), with an average loss of 47.6 ± 3.9%, was significantly higher in study sites with low balsam fir stem densities (229 ± 76 trees/ha) than in sites with high balsam fir stem densities (826 ± 189 trees/ha). Pollen cone loss to red squirrels showed no significant variation between disturbance types and among sites with respect to tree height and diameter at breast height (DBH). The percentage of seed cone loss to red squirrels (33.0 ± 15.7% to 93.5 ± 3.3%), with an average loss of 58.9 ± 15.5%, was not significantly between high and low stem density sites, nor between disturbance types. The number of female cones ...