Riparian woody plant diversity and forest structure along an urban-rural gradient

Abstract

Changes in riparian woody plant assemblages are anticipated in the southeastern United States due to increases in urbanization rates. Because riparian forests serve important roles in maintaining water quality and biodiversity, understanding how they respond to urbanization is crucial. The objective of this study was to examine forest structure and woody vegetation diversity indices of riparian communities in response to an urbanization gradient in West Georgia, USA. Measures of forest structure and diversity were compared to measures of urbanization and land cover. Although Liquidambar styraciflua and Quercus nigra were dominant species in the forest stand and regeneration layer for all riparian communities, the invasive, non-native shrub Ligustrum sinense was the most dominant species observed in the regeneration layer for urban, developing, and agriculture communities. The proportion of non-native species in the forest stand and regeneration layer decreased and Shannon diversity of the regeneration layer increased with increasing distance from the urban center. Shifts in diversity indicate that anthropogenic disturbance may subdue the ability of diverse communities to resist non-native plant invasions.

Alien Species Invasion and Diversity of Riparian Forest According to Environmental Gradients and Disturbance Regime

“…These differences express the variable environmental conditions in the adjacent segments of the moisture gradient. Burton et al (2005) found significant decrease in basal area and forest cover along the urban gradient. They ascribed this phenomenon to decreasing forest productivity and history of timber harvesting.…”

“…Burton et al (2005) reported that the proportion of non-native species in the canopy and regeneration layer decreased and diversity of the regeneration layer increased along an urban gradient of the riparian forest studied. They assigned this pattern to the anthropogenic disturbance that may subdue the ability of diverse communities to resist non-native plant invasions.…”

Does urbanization explain differences in interactions between an insect herbivore and its natural enemies and mutualists?

“…Model selection was made by comparing all candidate models using Akaike's Information Criteria (Burnham and Anderson 2003) by developing a series of alternative mixed effect models that include different combinations of the explanatory variables (Zuur et al 2009 , Table 1), by fitting the full model with the set of all possible explanatory variables and taking out the least significant term on each step (Crawley 2007). We then ranked the models according to AIC differences (Δ i = AIC i -AIC min , where AIC i is the model i value and AIC min is the best model value).…”

“…Models with Δ i < 2 provide substantial support for a candidate model, whereas values of Δ i between 4 and 7 provide less support and Δ i > 10 indicates that the model is unlikely. We also calculated Akaike weights for all models, where these model weights are used to indicate the importance of a model, with increasing weights indicating the likelihood of a particular model as the overall best model (Burnham and Anderson 2003). Aikaike weights can also be used to calculate the relative importance of a variable by summing the Akaike weights of all models that include that variable (Burnham and Anderson 2003).…”

Riparian corridor vegetation structure and soil function along urban, suburban, and rural streams in Louisville, KY, USA.

“…Most trees ranged between 2.5-and 25-cm in diameter at breast height (DBH) ( Table 2- Species richness of woody vegetation can differ dramatically along an urban-torural gradient (Burton et al 2005, Burton andSamuelson 2008). As such, species richness for woody plant communities was computed as one measure of species diversity and was computed individually for trees, saplings, tree seedlings, and shrubs.…”