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Pyrus calleryana (Callery pear) is an invasive plant that threatens ecosystems in the eastern United States. We investigated the efficacy of various control techniques on P. calleryana invasion in grasslands. Treatments were applied to (a) P. calleryana stems that had experienced mowing annually for several years and were sprouting (n = 100 stems; "trees-sprouting") and (b) stems that had established ca. 10 years earlier, had never been cut, and were single-stemmed trees (n = 40 stems; "trees-intact"). In both experiments, existing stems were cut and randomly assigned one of the following treatments: cut only (control), burning, freezing, or herbicide, and in the trees-sprouting experiment there was also a negative control of monitoring existing sprouts. All trees in which the cut stumps were treated with herbicide were effectively killed, whereas stems in all other treatments, in both experiments, generated a vigorous sprout response. In the trees-sprouting experiment, there was a strong overall effect of treatments (RMANOVA; p < 0.001) and prescribed fire created a statistically significant increase in sprout number in relationship to the negative control (post-hoc test; p = 0.036). In the trees-intact experiment, there was vigorous sprouting in response to all treatments other than herbicide. Stump freezing resulted in a delay in sprout response; however, all frozen stems eventually sprouted. The ability of this species to sprout vigorously, even after experiencing frequent and intense ecological disturbance, creates the potential for a fundamental alteration of old-field succession in habitats where this species is present. [ABSTRACT FROM AUTHOR] more...

Urban natural area forests provide cities with crucial ecosystem services, including carbon storage and sequestration. Although previous work from a single city has suggested that urban natural area forests may be carbon‐rich and dominated by native species, it is unclear if that pattern is widespread. Indeed, little is known about the species composition and carbon storage in these green spaces, or how urban natural area forests compared with similar rural forests. Here, we use data collected by the Forests in Cities network to quantify carbon stored in urban natural area forests across 1852 plots in eight of the most populous US cities and examine patterns in woody vegetation carbon storage by tree species composition and size class. We also compare the carbon storage in these urban natural area forests to similar rural forests using USDA FS Forest Inventory and Analysis data. We found that urban natural area forests store between 214 and 267 Mg C ha−1, with the majority (on average 55%) in the above‐ground portion of live trees and shrubs. This carbon was primarily stored by native trees and increased with the proportion of native species, as native trees tended to be larger. The proportion of non‐native species was higher in smaller size classes. Overall, the woody vegetation carbon density in urban natural area forests was higher than similar forest types in rural settings, a phenomenon driven by the presence of more large trees. Synthesis and applications: Together these results demonstrate the importance of urban natural area forests as carbon‐dense ecosystems and havens for native tree species. However, because of the greater number of non‐native species in smaller size classes, these forests may also be at risk of transitioning away from native‐dominated systems. Therefore, greater monitoring efforts and increased management activities such as non‐native species removal will be crucial to maintaining the high carbon storage and health of these ecosystems. [ABSTRACT FROM AUTHOR] more...