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Glencoe, IL, United States

Larkin D.J.,Plant Science and Conservation
Biological Invasions

There are often lag phases in plant invasions, seemingly dormant periods between arrival in a new range and rapid population growth. Lags impede prioritization of invasive-species control efforts: when eradication is most feasible, it is often unclear whether a species is benign or a potentially harmful "sleeper weed." I used herbarium records to estimate lag phases for invasive or potentially invasive plant species in three regions of the upper Midwest. I tested whether factors related to species' invasion epidemiology, traits, or the habitats they invade were correlated with lag lengths. From an initial pool of 151 species, there were sufficient records to test for lags in 76 for northern Wisconsin, 90 for southern Wisconsin, and 91 for the southern Lake Michigan region. Lags were identified in 77% (197) of these 257 datasets and ranged from 3-140 years with a mean of 47.3 ± 34.6 (SD). Lags differed by native range, introduction pathway, growth form and habit, dispersal mode, flowering phenology, pollination mode for a subset of species, and breadth, light availability, and water availability of invaded habitats. However, estimated lags were highly variable and tested factors did not have strong explanatory power. Exotic species comprised an increasing proportion of total herbarium records. Of the species with known introduction pathways, 85% were intentionally introduced, mainly as ornamentals. The long durations, high variability, and low predictability of lags, along with human culpability for an increasingly non-native flora, support a cautious approach to species introductions. © 2011 Springer Science+Business Media B.V. Source

Larkin D.J.,Plant Science and Conservation | Lishawa S.C.,Loyola University Chicago | Lishawa S.C.,University of Michigan | Tuchman N.C.,Loyola University Chicago | Tuchman N.C.,University of Michigan
Aquatic Botany

A 15N-addition mesocosm experiment was used to study competition for nitrogen (N) between the aggressive cattail species Typha×glauca (T. latifolia×T. angustifolia) Godr. (hybrid cattail) and a suite of native plant species often found in marshes Typha invades. Plant uptake of 15N released from labeled Typha and native-species litter was then measured in a pot experiment with new cohorts of two native plant species (Juncus balticus Willd. and Schoenoplectus acutus Muhlenberg ex Bigelow) grown with and without Typha. In both experiments, species differed in their above- and belowground uptake of 15N, with Typha outperforming the other species (1.7-5.0-times greater mean uptake, P=<0.0001-0.007). Typha then held on more strongly to the N it acquired: newly grown native plants in the pot experiment acquired more 15N from native litter than from Typha litter (1.4-12.0-times greater mean uptake, P=0.0006-0.017). In contrast, Typha showed no differences in N uptake by litter type (P=0.16-0.54). There were no main effects of live Typha on native-plant N uptake (P=0.64-0.86), but there were modest interactions between Typha presence and litter type (P=0.030-0.091). Where native plants and Typha co-occurred, native species matched Typha in recovering 15N from native litter (P=0.17-0.33) but recovered 90-96% less 15N from Typha litter (P=0.020-0.021). Typha's higher overall N recovery was due to both greater biomass production and uptake efficiency ( 15N per unit dry weight). Typha's greater N uptake and retention, repeated over multiple cycles of senescence and new growth, should lead to an increasing appropriation of N away from native species and into living and dead Typha biomass. © 2012 Elsevier B.V. Source

Barak R.S.,Plant Science and Conservation | Barak R.S.,Northwestern University | Hipp A.L.,Herbarium | Cavender-Bares J.,University of Minnesota | And 7 more authors.
International Journal of Plant Sciences

Historical information spanning different temporal scales (from tens to millions of years) can influence restoration practice by providing ecological context for better understanding of contemporary ecosystems. Ecological history provides clues about the assembly, structure, and dynamic nature of ecosystems, and this information can improve forecasting of how restored systems will respond to changes in climate, disturbance regimes, and other factors. History recorded by humans can be used to generate baselines for assessing changes in ecosystems, communities, and populations over time. Paleoecology pushes these baselines back hundreds, thousands, or even millions of years, offering insights into how past species assemblages have responded to changing disturbance regimes and climate. Furthermore, archeology can be used to reconstruct interactions between humans and their environment for which no documentary records exist. Going back further, phylogenies reveal patterns that emerged from coupled evolutionary-ecological processes over very long timescales. Increasingly, this information can be used to predict the stability, resilience, and functioning of assemblages into the future. We review examples in which recorded, archeological, paleoecological, and evolutionary information has been or could be used to inform goal setting, management, and monitoring for restoration. While we argue that longview historical ecology has much to offer restoration, there are few examples of restoration projects explicitly incorporating such information or of research that has evaluated the utility of such perspectives in applied management contexts. For these ideas to move from theory into practice, tests performed through research-management partnerships are needed to determine to what degree taking the long view can support achievement of restoration objectives. © 2015 by The University of Chicago. All rights reserved. Source

Price A.L.,Plant Science and Conservation | Price A.L.,Northwestern University | Fant J.B.,Plant Science and Conservation | Larkin D.J.,Plant Science and Conservation

Rapid spread of Phragmites australis(common reed) in North American wetlands is widely attributed to cryptic invasion by an introduced lineage. However, in the Midwestern U.S., the native subspecies (subsp. americanus) may also exhibit rapid expansion. Where both lineages occur, wetland managers are sometimes unsure whether they should limit management activities to the introduced lineage or control both. We conducted field studies to contrast the ecology of native and introduced Phragmites by pairing patches of each with native reference vegetation. We measured each lineage's association with environmental conditions, their growth metrics (stem heights, stem densities, and plant cover), and their invasiveness as indicated by the diversity and composition of associated plant communities. Introduced Phragmites exhibited more robust growth than the native, and its growth was more positively correlated with increases in soil nutrient availability and salinity. Areas with introduced Phragmites had lower plant diversity and altered species composition relative to reference vegetation.We did not observe similar evidence of invasiveness in native Phragmites. We encourage wetland managers to differentiate populations by lineage and, unless there is compelling evidence to do otherwise, restrict control efforts to the introduced lineage. ©Society of Wetland Scientists 2013. Source

Larkin D.J.,Plant Science and Conservation | Steffen J.F.,Plant Science and Conservation | Gentile R.M.,Plant Science and Conservation | Gentile R.M.,University of Notre Dame | And 2 more authors.
Restoration Ecology

Shifts in plant-community composition following habitat degradation and species invasions can alter ecosystem structure and performance of ecosystem services. In temperate North American woodlands, invasion by aggressive Eurasian shrubs has produced dense thickets with depauperate understory vegetation and increased rates of litter decomposition and nutrient cycling, attributes that could impair storage of carbon as soil organic matter (SOM). It is important to know if such impairment has occurred and, if so, the extent to which restoration can return this service. We used an oak-woodland restoration chronosequence in northeastern Illinois to contrast structural and functional attributes of unrestored areas dominated by Rhamnus cathartica (common buckthorn) with areas that had undergone buckthorn removal and ongoing, active management for less than 1 to 14years. With increasing age, restored areas had higher understory plant diversity and cover (p < 0.0001 and 0.005, respectively) and higher litter mass (p = 0.018). These structural differences were associated with some evidence of reduced soil erosion (p = 0.027-0.135) but greater soil CO2 efflux (p = 0.020-0.033). Total particulate organic matter (POM) in the soil increased with restoration age, which was driven by increases in the slow-turnover, mineral-associated SOM fraction. However, variance was high and relationships were only weakly significant (p = 0.082 and 0.083 for total POM and mineral-associated SOM, respectively). Our results suggest that, in addition to better documented biodiversity benefits, beneficial changes to ecosystem properties and processes may also occur with active, long-term restoration of degraded woodlands. © 2013 Society for Ecological Restoration. Source

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