Shade/Microclimate a. Technical overview: riparian vegetation influence on shade function Riparian areas can have microclimates that differ from upland areas and which influence physical and biological conditions at a local scale. Marine riparian areas are strongly influenced by marine water temperatures during both summer and winter months (warmer in the winter and cooler in the summer than upland areas). Living riparian (overstory trees, understory shrubs, and ground) vegetation, in turn, can intercept solar inputs and affect microclimate conditions such as soil and ambient air temperature, soil moisture, wind speeds, and humidity (XXXXX 1993; Xxxxxxx and Xxxx 1997; May 2003; Xxxxxx 2004). Terrestrial and aquatic microclimates are influenced by shade, and temperature fluctuations that can negatively impact both aquatic and terrestrial organisms, particularly those that can only survive within a relatively narrow range of temperature and moisture conditions. Solar radiation has long been considered an important limiting factor for organisms in the upper intertidal zone of marine environments. Solar radiation affects distribution, abundance, and species composition (e.g., Xxxxxxxx and Xxxxxx 1968; Xxxxxxx 1972). Although research is limited, studies have quantified the influence of shade on marine organisms such as surf smelt (eggs) and talitrids (amphipods) on Puget Sound beaches. In their literature review of causes of spatial and temporal patterns in intertidal communities, Xxxxxx et al. (1986) found that desiccation is the most commonly reported factor responsible for setting the upper elevational limits of survival for intertidal animals. More recent studies (Pentilla 2001; Xxxx 2006) showed that a lack of shade on surf smelt spawning beaches results in higher temperatures, drier conditions, and increased egg mortality.
Shade/Microclimate. The shade function of riparian areas is affected by many activities in the riparian area, particularly those occurring near the water’s edge. Vegetation removal can decrease shade (Xxxxxxxxx et al. 1994; Xxxx et al. 1994; Xxxxxxxxx 1995; Xxxxxxxx 1996; Xxxxxxxx and Xxxx 2001) and increase water and beach substrate temperatures (Xxxxxxx et al. 1987; Xxxxxxxx and Xxxx 2001; Bereitschaft 2007). Xxxx (2006) and Xxxxxxxxxx et al. (2003) demonstrated that shoreline modifications (such as boat ramps, bulkheads, roads, and parking lots) that involve vegetation removal close to the water’s edge not only reduce shade but also lower species diversity and abundance. Maintaining native vegetation in the form of mature trees in riparian areas can provide more shade than low-lying shrubs and grasses. Decreased shade, via removal of trees can result in increased egg mortality of beach-spawning forage fishes (Pentilla 2001; Rice 2006) and reductions in diversity and abundance of invertebrate species, as well as loss of habitat structure that supports climate sensitive species (Xxxxxxxxxx et al. 2003; Xxxxxxx and Xxxxxxxxxx 2004; Tonnes 2008).
Shade/Microclimate. Removal of trees within marine riparian areas reduces the amount of shade available (Hashim and Xxxxxxx 2005). Shade and temperature influence photosynthesis rates of plants and metabolic rates of animals. Fluctuations in temperature can alter fish community structure and composition (Xxxxx et al. 1987; Xxxxxxxxx 1991; Xxxxxxx 1991; Xxxxxx et al. 1987). High water temperatures can cause behavioral changes in fish by affecting migration timing and patterns (Xxxxxx et al. 1996).
Shade/Microclimate. The removal of canopy through logging and thinning practices opens the understory and ground to increased light and air flow. The resulting microclimate changes can change the character of the plant species, expose soils and beach sediment to desiccation, and/or alter the temperature of water bodies below through the removal of shade-inducing foliage. Timber harvesting within riparian areas reduces shade and can increase water temperatures (Hashim and Xxxxxxx 2005).
