Plant invasions

ECOLOGY LETTERS | Volume 21, Issue 2 | 2018 | Pages 217–224

Insu Jo, Kevin M. Potter, Grant M. Domke, Songlin Fei

Research highlight in ScienceDaily

DOI: 10.1111/ele.12884 | PDF | Supporting information PDF

Forest mycorrhizal type mediates nutrient dynamics, which in turn can influence forest community structure and processes. Using forest inventory data, we explored how dominant forest tree mycorrhizal type affects understory plant invasions with consideration of forest structure and soil properties. We found that arbuscular mycorrhizal (AM) dominant forests, which are characterised by thin forest floors and low soil C : N ratio, were invaded to a greater extent by non‐native invasive species than ectomycorrhizal (ECM) dominant forests. Understory native species cover and richness had no strong associations with AM tree dominance. We also found no difference in the mycorrhizal type composition of understory invaders between AM and ECM dominant forests. Our results indicate that dominant forest tree mycorrhizal type is closely linked with understory invasions. The increased invader abundance in AM dominant forests can further facilitate nutrient cycling, leading to the alteration of ecosystem structure and functions.

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JOURNAL OF ECOLOGY | Volume 105, Issue 4 | 2017 | Pages 1105–1110

Insu Jo, Jason D. Fridley, Douglas A. Frank

DOI: 10.1111/1365-2745.12732 | PDF | Supporting information PDF

Although it is widely believed that non‐native invasive species threaten the functional integrity of forest ecosystems, their impact on important ecosystem processes such as nitrogen (N) cycling is not well understood.

To examine how invasive species alter ecosystem N dynamics, we established monocultures of five phylogenetic pairs of native and non‐native invasive understory woody species common to Eastern U.S. forests.

After 3 years, we found invaders increased N cycling by enhancing the flow of N to the soil through greater litter N production and litter N content, and increased the uptake of available soil N, via greater fine root production and specific root length.

Our results highlight the importance of linking above‐ and below‐ground processes to better understand invader impacts on ecosystem nutrient processes. The rapid shifts in soil N processes as a result of invader dominance observed in our study suggest that invaders may be an important driver of forest ecosystem functioning.

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Monoculture plots of native and non-native invaders at Syracuse University experimental garden. Syracuse, NY (USA)

Hypothetical relationships between above- and below-ground resource use strategies using plant traits and soil attributes that affect soil N cycling

GLOBAL ECOLOGY AND BIOGEOGRAPHY | Volume 26, Issue 4 | 2017 | Pages 447–458

J. Mason Heberling, Insu Jo, Andrey Kozhevnikov, Hyohyemi Lee, Jason D. Fridley

DOI: 10.1111/geb.12551 | PDF | Supporting information XLSX, PDF 1, PDF 2, PDF 3

Modern species invasions result in the global reshuffling of regional floras, but biogeographical biases in floristic exchanges (origin effects) are underexplored. We compared habitat‐level invasion patterns in two environmentally similar regions, and ask whether plant exchanges are also similar or if one region largely invades the other.

We compiled a new dataset of the 1293 naturalized (i.e. non‐native, self‐sustaining) and invasive (i.e. spreading) plant taxa in EAS, including the habitats they invade and their native distributions. We tested for biases by biogeographical origin, growth form and habitat in EAS invasions, and compared them with those for ENA.

EAS contains 51% fewer naturalizations than ENA, but with a similar biogeographical representation. However, invasions in each region show large differences in biogeographical affinity, taxonomic representation and habitat. Invasions in ENA are biased from East Asia (29% invasive), while invaders in EAS come from a fairly uniform set of major temperate regions. Taxonomically, 54% of Asteraceae naturalizations in EAS are invasive compared with only 16% in ENA. Open habitats are highly invaded in both regions (75% of invasions), but forests are significantly more invaded in ENA than EAS (29% vs. 9%). Reciprocal invasions are asymmetric: EAS contributes more woody invaders to ENA than expected (56% woody, P < 0.001), while in EAS nearly all (91%) invaders from ENA are herbaceous.

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BIOLOGICAL INVASIONS | Volume 19, Issue 11 | 2017 | Pages 3287–3299

Gabriela C. Nunez-Mir, Andrew M. Liebhold, Qinfeng Guo, Eckehard G. Brockerhoff, Insu Jo, Kimberly Ordonez, Songlin Fei

DOI: 10.1007/s10530-017-1413-5 | PDF | Supplementary material DOCX

Biotic resistance, the ability of communities to resist exotic invasions, has long attracted interest in the research and management communities. However, inconsistencies exist in various biotic resistance studies and less is known about the current status and knowledge gaps of biotic resistance in forest ecosystems. In this paper, we provide a brief review of the history and mechanisms of the biotic resistance hypothesis, and summarize the central topics and knowledge gaps related to biotic resistance with a special emphasis on forest ecosystems. Overall, although the amount of research efforts on biotic resistance in forest ecosystems has increased since the mid-2000s, aspects such as resistance to exotic pests and pathogens remain understudied. In addition, we synthesize ecological and statistical explanations of observed inconsistencies and provide suggestions for future research directions. Some of the observed inconsistencies on biotic resistance can be attributed to (1) the interactive or additive effects of other ecological processes and (2) the statistical artifacts of modifiable areal unit problem. With the advancement of new statistical knowledge and tools, along with availability of big data, biotic resistance research can be greatly improved with the simultaneous consideration of key ecological processes, the attention to various scales involved, and the addition of understudied systems.

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NEW PHYTOLOGIST | Volume 209, Issue 1 | 2016 | Pages 115–122 or Virtual Issue

Insu Jo, Jason D. Fridley, Douglas A. Frank

Commentary article by Cindy E. Prescott, Jenna M. Zukswert | Included in the Virtual Issue on Root traits, edited by Richard J. Norby, Colleen M. Iversen

DOI: 10.1111/nph.13619 | This article is corrected by the authors (corrigendum) | PDF | Supporting information PDF

Invaders often have greater rates of production and produce more labile litter than natives. The increased litter quantity and quality of invaders should increase nutrient cycling through faster litter decomposition. However, the limited number of invasive species that have been included in decomposition studies has hindered the ability to generalize their impacts on decomposition rates. Further, previous decomposition studies have neglected roots.

We measured litter traits and decomposition rates of leaves for 42 native and 36 nonnative woody species, and those of fine roots for 23 native and 25 nonnative species that occur in temperate deciduous forests throughout the Eastern USA.

Among the leaf and root traits that differed between native and invasive species, leaf nitrogen and specific leaf area were significantly associated with decomposition rate. However, native and nonnative species did not differ systematically in leaf and root decomposition rates. We found that among the parameters measured, litter decomposer activity was driven by litter chemical quality rather than tissue density and structure.

Our results indicate that litter decomposition rate per se is not a pathway by which forest woody invasive species affect North American temperate forest soil carbon and nutrient processes.

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Litter bag experiment to determine leaf and root decomposition rates for native and non-native species in Eastern USA. Pompey, NY (USA)

BIOLOGICAL INVASIONS | Volume 17, Issue 5 | 2015 | Pages 1545–1554

Insu Jo, Jason D. Fridley, Douglas A. Frank

DOI: 10.1007/s10530-014-0814-y | PDF | Supplementary material DOCX

Non-native invasive species are often more productive aboveground than co-occurring natives. Because aboveground productivity is closely tied to plant nitrogen (N) uptake and use, high invader leaf productivity should be associated with root growth and plant N use strategies. However, little is known about the above- and belowground carbon (C) and N use strategies of native and invasive plants. We measured shoot and root attributes and soil properties associated with 10 native and 14 non-native invasive forest shrubs and lianas of the Eastern U.S. in a common garden in Syracuse, New York (USA), including leaf growth and chemistry (C, N), root growth, specific root length (SRL), root tissue density, and associated soil C and N concentration, each determined at 2-month intervals (July–November). Non-native species had greater leaf and root production, leaf N concentration, and SRL, but lower leaf N resorption rates and root N concentration than natives. Soil N concentration associated with non-natives was significantly lower than that of native species. Our results suggest that greater aboveground productivity of invasive forest species is linked to greater production of fine roots that may increase the capacity of invaders to take up soil resources. In addition, our findings suggest that invaders beget more rapid plant-soil N feedbacks by promoting N cycling compared to the strategy of slow growing native species that emphasizes recycled plant N. Such differences in N use strategy between native and non-native species would significantly impact forest soil nutrient cycling.

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