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Relatively unmanaged interstitial areas at the residential–wildland interface can support the development of novel woody plant communities. Community assembly processes in urban areas involve interactions between spontaneous and cultivated species pools that include native, introduced (exotic/non-native) and invasive species. The potential of these communities to spread under changing climate conditions has implications for the future trajectories of forests within and beyond urban areas. We quantified woody vegetation (including trees and shrubs) in relatively unmanaged "interstitial" areas at the residential–wildland interface and in exurban reference natural areas in six metropolitan regions across the continental USA. In addition, we analyzed soil N and C cycling processes to ensure that there were no major anthropogenic differences between reference and interstitial sites such as compaction, profile disturbance or fertilization, and to explore effects of novel plant communities on soil processes. We observed marked differences in woody plant community composition between interstitial and reference sites in most metropolitan regions. These differences appeared to be driven by the expanded species pool in urban areas. There were no obvious anthropogenic effects on soils, enabling us to determine that compositional differences between interstitial and reference areas were associated with variation in soil N availability. Our observations of the formation of novel communities in interstitial spaces in six cities across a very broad range of climates, suggest that our results have relevance for how forests within and beyond urban areas are assessed and managed to provide ecosystem services and resilience that rely on native biodiversity. [ABSTRACT FROM AUTHOR]

Leaf trait networks (LTNs) visualize the intricate linkages reflecting plant trait-functional coordination. Typical karst vegetation, developed from lithological dolomite and limestone, generally exhibits differential communities, possibly due to habitat rock exposure, soil depth, and soil physicochemical properties variations, leading to a shift from plant trait variation to functional linkages. However, how soil and habitat quality affect the differentiation of leaf trait networks remains unclear. LTNs were constructed for typical dolomite and limestone habitats by analyzing twenty-one woody plant leaf traits across fifty-six forest subplots in karst mountains. The differences between dolomite and limestone LTNs were compared using network parameters. The network association of soil and habitat quality was analyzed using redundancy analysis (RDA), Mantle's test, and a random forest model. The limestone LTN exhibited significantly higher edge density with lower diameter and average path length when compared to the dolomite LTN. It indicates LTN differentiation, with the limestone network displaying a more compact architecture and higher connectivity than the dolomite network. The specific leaf phosphorus and leaf nitrogen contents of dolomite LTN, as well as the leaf mass and leaf carbon contents of limestone LTN, significantly contributed to network degree and closeness, serving as crucial node traits regulating LTN connectedness. Additionally, both habitat LTNs significantly correlated with soil nitrogen and phosphorus, stoichiometric ratios, pH, and organic carbon, as well as soil depth and rock exposure rates, with soil depth and rock exposure showing greater relative importance. Soil depth and rock exposure dominate trait network differentiation, with the limestone habitat exhibiting a more compact network architecture than the dolomite habitat. [ABSTRACT FROM AUTHOR]

Urbanization has a profound impact on the ecological processes and plant diversity of remnant forests. To understand the relationship between urbanization and woody plant communities in remnant forests, we conducted a study in Guiyang, China, where we sampled 120 plots in 15 remnant forest patches along an urbanization gradient. We evaluated the functional diversity of woody plants based on four functional diversity indices and nine functional traits. We compared the functional diversity among different types of woody plants and between interior and edge communities, and analyzed the changes in functional diversity and individual functional traits along the urbanization gradient. Our results indicate that urbanization significantly decreases the functional diversity of woody plant communities. Additionally, urbanization leads to shifts in functional composition, particularly in shrub species, with an increase in leaf N content and a decrease in leaf C content, leaf C/N ratio, seed germination rate and seed mass. These findings suggest that increasing urbanization reduces the values of high resource-conserving traits of woody plants in remnant forests. Therefore, it is crucial to limit additional urban expansion around remnant forest patches to protect the functional diversity and crucial plant species with strong resource-conserving traits.

Understanding the change in vegetation composition along elevational gradients is critical for species conservation in a changing world. We studied the species richness, tree height, and floristic composition of woody plants along an elevation gradient of protected habitats on the eastern slope of Mount Meru and analyzed how these vegetation variables are influenced by the interplay of temperature and precipitation. Vegetation data were collected on 44 plots systematically placed along five transects spanning an elevational gradient of 1600 to 3400 m a.s.l. We used ordinary linear models and multivariate analyses to test the effect of mean annual temperature and precipitation on woody plant species richness, tree height, and floristic composition. We found that species richness, mean tree height, and maximum tree height declined monotonically with elevation. Models that included only mean annual temperature as an explanatory variable were generally best supported to predict changes in species richness and tree height along the elevation gradient. We found significant changes in woody plant floristic composition with elevation, which were shaped by an interaction of mean annual temperature and precipitation. While plant communities consistently changed with temperature along the elevation gradient, levels of precipitation were more important for plant communities at lower than for those at higher elevations. Our study suggests that changes in temperature and precipitation regimes in the course of climate change will reshape elevational gradients of diversity, tree height, and correlated carbon storage in ecosystems, and the sequence of tree communities on East African mountains. [ABSTRACT FROM AUTHOR]

Globally, temperate deciduous forests are threatened by invasion of non‐native (exotic) plant species. In the eastern United States, Rosa multiflora is a dominant shrub invader in forests, which often forms dense thickets that reduce sunlight availability in the understory, where decreased native plant diversity and abundance are observed. Management and restoration are difficult but desirable, especially when invasion intensity is still low. Few studies have examined the relative success of different management strategies under varying invasion intensities. Our study objectives were to conduct a R. multiflora removal experiment in three forest sites experiencing different invasion intensities and to restore native plant biodiversity while preventing secondary invasion. We utilized three management strategies: invasive plant removal, removal followed by native seed addition, and removal plus native seed and mulched invasive stem addition. We investigated the similarity between seed bank species composition and existing vegetation before and after removal to assess the potential for passive restoration. Two seasons after removal, we found that simply removing roses increased native species richness, native floristic quality assessment (FQAIN), and native shrub abundance in our medium invasion site, and total species richness in our low and medium invasion sites. Compared to removal alone, native seed addition, with and without mulch addition, resulted in larger native and total species richness and FQAIN increases at all sites, larger increases in native shrub abundance and exotic species richness in our medium invasion site, and larger reductions in exotic and total shrub abundance in our low and medium invasion sites. Following removal, species similarity between the seed bank and vegetation improved for all three sites. Our results indicate that removal of R. multiflora alone increased native plant biodiversity in the medium invasion scenario, but the seed bank may not provide a large native species pool. Additional management strategies lead to improved outcomes, especially in our most invaded forest, demonstrating the need to conduct multiple plant removal treatments across forests with varying site conditions and plant invasion intensity to improve management recommendations. [ABSTRACT FROM AUTHOR]

Abstract Globally, temperate deciduous forests are threatened by invasion of non‐native (exotic) plant species. In the eastern United States, Rosa multiflora is a dominant shrub invader in forests, which often forms dense thickets that reduce sunlight availability in the understory, where decreased native plant diversity and abundance are observed. Management and restoration are difficult but desirable, especially when invasion intensity is still low. Few studies have examined the relative success of different management strategies under varying invasion intensities. Our study objectives were to conduct a R. multiflora removal experiment in three forest sites experiencing different invasion intensities and to restore native plant biodiversity while preventing secondary invasion. We utilized three management strategies: invasive plant removal, removal followed by native seed addition, and removal plus native seed and mulched invasive stem addition. We investigated the similarity between seed bank species composition and existing vegetation before and after removal to assess the potential for passive restoration. Two seasons after removal, we found that simply removing roses increased native species richness, native floristic quality assessment (FQAIN), and native shrub abundance in our medium invasion site, and total species richness in our low and medium invasion sites. Compared to removal alone, native seed addition, with and without mulch addition, resulted in larger native and total species richness and FQAIN increases at all sites, larger increases in native shrub abundance and exotic species richness in our medium invasion site, and larger reductions in exotic and total shrub abundance in our low and medium invasion sites. Following removal, species similarity between the seed bank and vegetation improved for all three sites. Our results indicate that removal of R. multiflora alone increased native plant biodiversity in the medium invasion scenario, but the seed bank may not provide a large native species pool. Additional management strategies lead to improved outcomes, especially in our most invaded forest, demonstrating the need to conduct multiple plant removal treatments across forests with varying site conditions and plant invasion intensity to improve management recommendations.

The Mediterranean Basin has distinct vegetation types shaped by fire, herbivory, and various human activities. Based on data from 83 belt transects of 10 × 40 m in 28 study sites for five physiognomic vegetation types (semi-closed forest, open forest, closed shrubland, open shrubland, and scrubland) in southwestern Anatolia (Turkey), we analyzed woody species diversity, woody community composition, and vegetation structure of study sites. We used the growth form and regeneration strategy for functional comparisons of physiognomic vegetation types. We found clear distinctions in diversity, species composition, and functional structure of woody plant community across five physiognomic vegetation types. The forest-shrubland-scrubland distinction was the most apparent one. Despite similarities in the woody species richness and Shannon diversity, open and closed vegetation states of forests and shrublands also differed regarding the density and cover of mature individuals and the density of saplings in different functional groups. Non-metric multidimensional scaling analyses and indicator species analyses also indicated clear distinctions among physiognomic vegetation types and openness states. Our findings indicate the necessity of a more complex description of vegetation types in the Mediterranean Basin. The results suggest that open and closed vegetation states of forests and shrublands are functionally distinct vegetation types. Supplemental data for this article is available online at https://doi.org/10.1080/11263504.2022.2036845. [ABSTRACT FROM AUTHOR]

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.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.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 non-native 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.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. [ABSTRACT FROM AUTHOR]