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Kourtev, Peter Stefanov; Huang, W. Z.; Ehrenfeld, Joan G.

doi:10.1023/a:1010048909563

Cited by 114 publications

(6 citation statements)

References 25 publications

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“…Given enough time, it is plausible that non-native earthworms from small areas of timber harvest may eventually spread throughout a watershed. However, non-native earthworms may be restricted to these small harvested plots and may not expand to the surrounding undisturbed forests (Kalisz and Dotson 1989). As harvest style has recently shifted to more selective logging, it will be interesting to see through time if lightly, selectively logged watersheds without riparian timber harvest will maintain low riparian earthworm populations or if all of the harvested sites will reach similar riparian earthworm densities.…”

Section: Discussionmentioning

confidence: 99%

Do non-native earthworms in Southeast Alaska use streams as invasional corridors in watersheds harvested for timber?

2010

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Exotic earthworms from Europe and Asia have invaded previously earthworm-free areas of North America where they consume leaf litter, mix soil horizons, and alter nutrient cycling. Primarily, earthworm introductions occur through human activities; we hypothesized that the combination of logging (i.e., road construction and soil disturbance) and stream transport (i.e., hydrochory) allows earthworms to invade new ecosystems and spread within watersheds. On Prince of Wales Island, AK, we surveyed riparian zones in 11 watersheds with varying timber harvest intensity for terrestrial oligochaetes. Additionally, common invasive earthworms were experimentally submerged in a local stream to test for tolerance to prolonged immersion: all taxa survived immersion for at least 6 days. Using principal components analysis, watershed and harvest variables describing the watersheds upstream of our sampled riparian areas were reduced to two principal components describing harvest intensity (PC1) and harvest style (PC2). Logistic models successfully predicted earthworm abundance (r 2 = 0.70) from PC1, which indicated that watersheds with older, intense upstream timber harvest contained larger earthworm populations. Earthworm species richness was best predicted by PC2 (r 2 = 0.39), which suggested that earthworm communities in watersheds containing large clear-cut stands were more species-rich. Collectively, these results suggest that (1) invasive earthworms may use streams for dispersal and (2) upstream introductions via timber harvest can initiate downstream earthworm invasions. Hydrochory would allow invasive earthworms to spread at rates (tens of km d -1 ) that are much greater than previously reported rates of terrestrial spread (5-10 m y -1 ). Effective control of exotic earthworms in riparian zones will require watershedlevel management and surveillance.

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Section: Discussionmentioning

confidence: 99%

Do non-native earthworms in Southeast Alaska use streams as invasional corridors in watersheds harvested for timber?

2010

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“…Mechanically, preferential NH 4 + uptake and assimilation were associated with the high energy cost of NO 3 − reduction and the potential for avoiding excessive NH 4 + accumulation (Kronzucker, Glass, & Siddiqi, 1999). In contrast, increases of soil N availability in many invaded ecosystems occurred in NO 3 − with preferential NO 3 − uptake in invasive plants (Ehrenfeld, Kourtev, & Huang, 2001;Gilliam, 2006;Kourtev, Huang, & Ehrenfeld, 1999), not NH 4 + . The mechanisms of plant N use such as N preference between NH 4 + and NO 3 − are important in driving invasion and influencing the potential coexistence of native species (Gilliam, 2006 (Ehrenfeld et al, 2001;Fargione & Tilman, 2005;Kourtev et al, 1999;McKane et al, 2002;Rossiter-Rachor et al, 2009).…”

Section: Plants N Sources and Preferencementioning

confidence: 99%

Plant nitrogen and phosphorus utilization under invasive pressure in a montane ecosystem of tropical China

Lei

Tan

et al. 2018

Journal of Ecology

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Exotic plant invasion has been changing the vegetation composition and function of terrestrial ecosystems. Nitrogen (N) and phosphorus (P) are often the limiting nutrients for terrestrial plants. However, under invasive pressure, in situ plant N and P usage mechanisms remain poorly understood but are pivotal for a better understanding of plant invasion and coexistence in invaded ecosystems. Nitrogen and P concentrations, natural 15N abundance (δ15N values) were investigated in leaves and soils under different invasive pressures (here expressed as the biomass percentages of invasive plants in each plot) for two invasive species (Chromolaena odorata and Ageratina adenophora) in Xishuangbanna in tropical China. Soil N and P concentrations revealed the relatively N‐rich but P‐poor status of our study site. Under invasion, soil inorganic N (dominated by ammonium) and available P did not increase significantly. The leaf N and P of invasive plants increased, while leaf N increased but P decreased for native species. Natural δ15N mass balance between leaves and soil inorganic N sources revealed that ammonium dominated N utilization in both natives and invaders. Invasive plants showed ammonium utilization with increasing leaf N levels, while native plants under no invasion showed nitrate utilization with increasing leaf N levels. Synthesis. Increased soil ammonium availability contributed to preferential ammonium utilization by invasive plants and elevated ammonium utilization in natives, but the P competition of natives decreased in invaded ecosystems. These novel insights into nutrient dynamics in invaded ecosystems enhance our understanding of plant invasion and coexistence mechanisms.

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“…Ecologists have often observed that nonnative earthworms and nonnative plants frequently occupy the same habitats, suggesting potential facilitation between earthworm and plant invaders (Kourtev et al 1999;Heneghan et al 2007). However, understanding causality of these patterns has been limited by the observational nature of the studies.…”

Section: Speciesmentioning

confidence: 99%

Tree leaf litter composition and nonnative earthworms influence plant invasion in experimental forest floor mesocosms

Belote

Jones

2008

Biol Invasions

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Dominant tree species influence community and ecosystem components through the quantity and quality of their litter. Effects of litter may be modified by activity of ecosystem engineers such as earthworms. We examined the interacting effects of forest litter type and earthworm presence on invasibility of plants into forest floor environments using a greenhouse mesocosm experiment. We crossed five litter treatments mimicking historic and predicted changes in dominant tree composition with a treatment of either the absence or presence of nonnative earthworms. We measured mass loss of each litter type and growth of a model nonnative plant species (Festuca arundinacea, fescue) sown into each mesocosm. Mass loss was greater for litter of tree species characterized by lower C:N ratios. Earthworms enhanced litter mass loss, but only for species with lower C:N, leading to a significant litter 9 earthworm interaction. Fescue biomass was significantly greater in treatments with litter of low C:N and greater mass loss, suggesting that rapid decomposition of forest litter may be more favorable to understory plant invasions. Earthworms were expected to enhance invasion by increasing mass loss and removing the physical barrier of litter. However, earthworms typically reduced invasion success but not under invasive tree litter where the presence of earthworms facilitated invasion success compared to other litter treatments where earthworms were present. We conclude that past and predicted future shifts in dominant tree species may influence forest understory invasibility. The presence of nonnative earthworms may either suppress of facilitate invasibility depending on the species of dominant overstory tree species and the litter layers they produce.

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Untitled

Cited by 114 publications

References 25 publications

Do non-native earthworms in Southeast Alaska use streams as invasional corridors in watersheds harvested for timber?

Do non-native earthworms in Southeast Alaska use streams as invasional corridors in watersheds harvested for timber?

Plant nitrogen and phosphorus utilization under invasive pressure in a montane ecosystem of tropical China

Tree leaf litter composition and nonnative earthworms influence plant invasion in experimental forest floor mesocosms

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