Effects of size, shape, and edge on vegetation in remnants of the upland boreal mixed-wood forest in agro-environments of Alberta, Canada

2007 ◽  
Vol 85 (3) ◽  
pp. 273-284 ◽  
Author(s):  
L. Dennis Gignac ◽  
Mark R.T. Dale

Forty-one remnants of the aspen-dominated upland forest in three subregions of the dry boreal mixed-wood in Alberta were studied to determine effects of fragment size and shape on native and alien plant species richness and abundance in agro-environments. The percent cover of all vascular plant species was visually estimated in 5 m diameter circular plots along transects that covered the length and the width of each fragment. A subset of 12 of the largest fragments (>900 m2) that had distinct interiors (portions of the fragment >15 m from any edge) was used to measure edge effects on the vegetation. Regression analyses revealed significant positive relationships between species richness and area regardless of the subregion. Species richness stabilized in fragments that were larger than 11 ha. Edges did not affect shrub species richness and only affected herbaceous species richness on west- and south-facing aspects. Shrub abundance decreased and herb abundance increased up to 20 m from the edges regardless of orientation. Edges did not support a different suite of species than interiors, although several species occurred more frequently in the interior than along the edges. Alien species richness and abundance reached their highest values between 5 and 15 m from the edge, and some of those species could be found up to 40 m from the edge. Although larger fragments generally supported more alien species than smaller fragments, the smallest fragments had the greatest number of species per metre squared. Results from this study indicated that it would be preferable to conserve larger woodlots rather then several smaller woodlots on the landscape.

2015 ◽  
Vol 19 (2) ◽  
pp. 30-36 ◽  
Author(s):  
Binoj Kumar Shrestha ◽  
Dharma Raj Dangol

This research investigated the invasion of the alien plant Mikania micrantha H.B.K. and its impact on plant species richness and abundance in Chitwan National Park (CNP) forest. Stratified sampling technique was used to collect the information using the nested quadrats in the Mikania invaded and not invaded sites in July 2011. The study revealed that the invasion highly related with the vegetation structure of the habitat; higher the tree crown cover lower the invasion. On the other hand, the invasion in terms of cover percent of Mikania irrespective of the biomass (fresh weight) decreased plant species richness. Species richness showed unimodal response to the Mikania cover percent with the decrease after 35% of Mikania cover. Journal of Institute of Science and Technology, 2014, 19(2): 30-36


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