Pinus contorta understory vegetation dynamics following clearcutting in west-central Alberta, Canada

Understory vegetation-environment relationships of lichen-rich forests in north-central British Columbia.

“…Manipulative experiments are often limited to using overstory removal as a treatment, which has been useful in demonstrating the effects of disturbance, but falls short of being able to establish a cause-and-effect pattern of overstory on understory development (Harris 1996, Miege et al 2001, Bainbridge and Strong 2005, Nelson and Halpern 2005, Dovciak et al 2006, Kembel et al 2008. The converse type of experiment, whereby a forest canopy is added to an otherwise disturbed site, is limited by the slow growth of trees, and the difficulty in determining direct or indirect influences on the understory.…”

“…Yet, greater light means both greater photosynthetic potential and greater evaporation of water from the soil surface, so it can be difficult to separate competition for water from competition for light (Tilman 1988). Because of this, much of the ecological research on lichen-rich communities has focused on combining or partitioning resource gradients of light and moisture as related to the forest canopy (Yarranton 1975, Maikawa and Kershaw 1976, Coxson and Marsh 2001, Gilliam and Roberts 2003, Bainbridge and Strong 2005, Kembel and Dale 2006. It is true that the amount of light reaching the ground can significantly influence nutrient and moisture supply through the regulation of soil temperature, and therefore, of microbial respiration and decomposition (Bonan and Shugart 1989, Bonan 1990, Balisky and Burton 1993, Stark et al 2000, Nilsson and Wardle 2005.…”

“…Many studies have used a chronosequence approach to document the successional development of lichen-rich forests (Maikawa and Kershaw 1976, Carroll and Bliss 1982, Oksanen 1986, Morneau and Payette 1989, Crites and Dale 1998, Coxson and Marsh 2001, Bainbridge and Strong 2005, while a small number have used long-term observations of stands in varying initial serai stages (Hunt et al 2003), or employed sedimentary pollen records and dendrochronological methods McDonald 1998, Pitkanen andHuttunen 1999). Though none have documented the development of a single stand from initiation to maturity, a general theoretical sequence of successional development has evolved.…”

“…and mosses as distinct functional groups when examining environment relationships (Pharo and Vitt 2000, Bainbridge and Strong 2005, Lang et al 2009). Others have used finer division of moss and lichen groups, such as generic-level separation of lichens and growth-form separation of mosses, on the basis of their association with successional stages (Coxson and Marsh 2001).…”

“…The first is to examine environmental variables that affect habitat suitability and growth rates of lichens and feathermosses; variables such as canopy closure, leaf area index, stand age, and organic layer depth often show strong positive relationships with feathermoss dominance and negative relationships with lichen dominance (Oksanen 1986, Coxson and Marsh 2001, DeLuca et al 2002, Hunt et al 2003, Bainbridge and Strong 2005, Uotila et al 2005. The second approach is to explain the presence of one understory group by the absence of another; matforming lichens are generally regarded as poor competitors, and are often overgrown by the competitively superior feathermosses as woodlands age (Frego and Carleton 1995a, Pharo and Vitt 2000, Williston et al 2006).…”