Are boreal ecosystems susceptible to invasion by alien plants? : a case study of Gros Morne National Park

Rose, Michael David (2002) Are boreal ecosystems susceptible to invasion by alien plants? : a case study of Gros Morne National Park. Masters thesis, Memorial University of Newfoundland.

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Abstract

Invasion by alien species is one of the major contributors to the local and global loss of indigenous biological diversity, and a concern to managers of protected areas. The objectives of this study were to document and evaluate the distribution and abundance o( alien plant species in boreal ecosystems of Gros Morne National Park of Canada (GMNP). In areas susceptible to invasion by alien plants the physical parameters contributing to their presence or absence were determined. The importance of disturbance to alien plant invasion in boreal ecosystems was examined by evaluating how environmental conditions and diversity of alien species change as a function of disturbance regime. Functional characteristics contributing to successful invasion in GMNP were also examined. -- Alien plants were found in areas of anthropogenic and natural disturbance throughout GMNP with the greatest abundance and diversity of species occurring in disturbances close to high anthropogenic activity. Although alien plants were absent from undisturbed areas, their unexpected occurrence in disturbed areas remote from human activity is of great concern because they may alter ecosystem properties and displace native species in these areas. -- Vegetation types vulnerable to alien plant invasion in GMNP include forests, riparian areas, fens, and alpine meadows. Disturbance occurring in these vegetation types caused increases in bare ground and or light availability which allowed alien plants to invade these areas. Although high soil pH was associated with alien plants in these areas, disturbance was not found to cause changes in soil pH. This implies that areas susceptible to mv asion bv alien plants may be pre-determined by bedrock geology or other factors influencing soil pH. -- The abundance of alien plants changed from high to undisturbed disturbance regimes. The greatest percentage of alien species occurred at high disturbance regimes, while the total number of alien species was greatest at intermediate disturbance regimes. Moose (Alecs ulcus), a non-native herbivore, acted as the primary conduit for alien plant invasion in GMNP by dispersal of propagules and creating or prolonging disturbance bv trampling and browsing vegetation. Hiking trails were also found to be conduits for alien plant dispersal into natural areas. Areas no longer experiencing disturbance by anthropogenic activity required long periods of time to recover. These areas acted as foci in which alien species could persist and spread to other areas of GMNP. -- Species of concern in GMNP include Ranunculus repens. Tussdago farfara. Lvlhrum salicana. Digitalis purpurea. Hicracium spp.. Taraxacum officinale. Cirsium anense. and Mvosons scorpioules. -- Alien species able to successfully invade areas remote from human activity differed from alien species unable to invade these areas by exhibiting both vegetative reproduction and dispersal of asexually produced propagules. -- Boreal ecosystems can be invaded by alien plants. Management plans must monitor the presence and potential spread of alien plants in GMNP.

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