Temperate deciduous forests embedded across developed landscapes: Younger forests harbour invasive plants and urban forests maintain native plants

Abstract

1. Temperate deciduous forests in the United States are located in the most densely populated states across the northern and mid-Atlantic east coast. Land development and associated human activities result in small forests that are susceptible to anthropogenic influences, such as urbanization and non-native plant invasion. 2. The overall objective of this study was to assess spatial and temporal drivers of forest vegetation structure and diversity in small forests embedded across developed landscapes. We assessed woody plant composition across spatial gradients (i.e., urbanization and non-native plant invasion) and a temporal gradient (i.e., time since canopy closure) across 38 forests along the east coast of the United States in northern Delaware and southeastern Pennsylvania. 3. Surprisingly, we found the invasion gradient was not related to the urban gradient across our forests. Across all forests, the canopy consisted of native species (98% of all trees), whereas the forest understory was most vulnerable to nonnative plant invasion (65% of all woody plant stems). Greater native species richness in forest canopies and understories with increasing urbanization supports the conclusion that urban forests maintain native species and are not inherently degraded ecosystems. Non-native plant invasion has a strong influence on understory plant communities, and the duration of intact forest canopy had a strong negative correlation with non-native plant invasion suggesting intact forests can resist invasion. 4. Synthesis. This is the first study to compare simultaneously the importance of invasion and urbanization in determining plant community composition in forests embedded across developed landscapes, and to discover that younger forests harbor more invasive plants and urban forests maintain native plants. K E Y W O R D S nonmetric multidimensional scaling, non-native plant invasion, temperate deciduous forest, urban forests, urbanization, woody plant community | 2367

Photosynthesis, fluorescence, and biomass responses of white oak seedlings to urban soil and air temperature effects

“…Urban forest patches of the eastern United States are largely made up of native canopy species (Groffman et al, 2006;Templeton et al, 2019;Trammell et al, 2020), which may provide the seed source for natural forest regeneration. Furthermore, urban forest restoration plantings are costly, and many cities are not able to support these activities on a regular basis .…”

Sensitivity of Stomate Size in Red Maple (Acer rubrum L.) Trees in Deciduous Forests to Urban Conditions

“…The FRAME traverses an urban gradient extending across Newark, DE (small city) and Philadelphia, PA (large city). Philadelphia has a population density (4,405 people km-2) three times higher and a total population (1,526,006 people) nearly fifty times larger than that of Newark (density = 1,403 people km-2; total population = 31,454), yet the urban intensity (e.g., impervious surface area, population density) surrounding the forest patches (within 1000 m of forest patch) is similar across the forests in both Newark and Philadelphia [36]. The magnitude of urban intensity at the regional scale is referred to as metro-scale impacts (proxy for urban intensity) that can stimulate growth and/or induce stress in plants in urban forests (e.g., regional urban heat island).…”

“…The magnitude of urban intensity at the regional scale is referred to as metro-scale impacts (proxy for urban intensity) that can stimulate growth and/or induce stress in plants in urban forests (e.g., regional urban heat island). The forest canopy of the FRAME is dominated by native tree species in both cities [36]: red maple (Acer rubrum), American beech (Fagus grandifolia), black gum (Nyssa sylvatica), sweetgum (Liquidambar styraciflua), tulip poplar (Liriodendron tulipifera), and 9 of 13 red oak (Quercus rubra). The forest understory is dominated by non-native and native species: multiflora rose (Rosa multiflora), spicebush (Lindera benzoin), greenbrier (Smilax rotundifolia), Japanese honeysuckle (Lonicera japonica), southern arrowwood (Viburnum dentatum), autumn olive (Elaegnus umbellata), and sweet pepperbush (Clethra alnifolia).…”

“…The morphology and growth characteristics of red maple in forest stands in the eastern U.S. have resulted in wide scale cultivation because of its aesthetics, marketability, and adaptability in many urban landscapes [33][34][35]. Importantly, red maple trees are a dominant tree across urban forests [36] and demonstrate healthy growth and function despite potentially harsh environmental conditions in cities [3,32].The purpose of this study was to determine changes in red maple leaf morphology and anatomy in response to urban conditions. To understand the combined impacts of different magnitudes of urban intensity (i.e., large versus small city; hereafter metro-scale impacts) on leaf anatomy and morphology, we investigated red maple trees in forests embedded in two cities (i.e., Newark, DE and Philadelphia, PA).…”

“…The morphology and growth characteristics of red maple in forest stands in the eastern U.S. have resulted in wide scale cultivation because of its aesthetics, marketability, and adaptability in many urban landscapes [33][34][35]. Importantly, red maple trees are a dominant tree across urban forests [36] and demonstrate healthy growth and function despite potentially harsh environmental conditions in cities [3,32].…”