18 research outputs found
Barriers against wear affect the spatial distribution of tree saplings in urban woodlands
http://www.elsevier.com/locate/issn/16188667In order to maintain indigenous, self-regenerating tree populations in urban woodlands, it is essential to identify factors affecting the survival of tree seedlings and saplings. In densely populated areas, intensive recreational use may
cause considerable wear of the vegetation and soil, and decrease the total number of saplings. At the same time trees,
high stones and other structural elements in a woodland patch can act as natural barriers and give shelter against wear.
Hence, we hypothesised that with an increasing amount of wear, a greater proportion of tree saplings survive, and is
thus found, close to these natural barriers. We tested this hypothesis with observational data, and described the
microhabitat associations of different sapling species in detail to define the most favourable or unfavourable
microhabitats. We recorded the microhabitats of saplings and randomly chosen points in 30 medium-fertile Picea abies
dominant woodlands in Helsinki and the surroundings, Finland. The description included location in relation to
physical objects (stones, trees, topography, etc.), other saplings, vegetation and canopy. We then compared the sapling
microhabitats to those available (the random points). Our results suggest that the microhabitat associations of saplings
change with increasing wear: Sorbus aucuparia, Populus tremula, Rhamnus frangula, Picea abies and Acer platanoides
saplings grew more often close to natural barriers (obstacles X30 cm high excluding other saplings), the first three
showing a statistically significant response to wear in logistic regression models. The saplings were able to grow in a
variety of microhabitats, but the species also differed in their microhabitat associations. In general, saplings grew in
groups, and in worn sites the grouping was more pronounced. With increasing wear the saplings associated more
positively with trees, canopy cover and lush vegetation