scholarly journals Emerging fungal pathogen on an invasive grass differentially affects native species

2020 ◽  
Author(s):  
Amy E. Kendig ◽  
Vida J. Svahnstrom ◽  
Ashish Adhikari ◽  
Philip F. Harmon ◽  
S. Luke Flory
Keyword(s):  
Community Composition ◽  
Plant Community ◽  
Indirect Effects ◽  
Fungal Pathogen ◽  
Native Species ◽  
Grass Species ◽  
Leaf Spot Disease ◽  
Plant Community Composition ◽  
Native Plant ◽  
Invasive Grass

AbstractInfectious diseases and invasive species are strong drivers of biological systems that may interact to shift plant community composition. Disease and invasion can each directly suppress native populations, but variation in responses among native species to disease, invasion, and their combined effects are not well characterized. Here, we quantified the responses of three native North American grass species to experimental inoculation with the fungal pathogen Bipolaris gigantea, which has recently emerged in populations of the invasive grass Microstegium vimineum, causing leaf spot disease. In a greenhouse experiment, we examined the direct effects of disease on the native species and the indirect effects of disease on the native species through altered competition with M. vimineum, which was planted at a range of densities. Pathogen inoculation directly affected each of the three native species in unique ways, by increasing, decreasing, or not changing their biomass relative to mock inoculation. Higher M. vimineum densities, however, reduced the biomass of all three native species, regardless of inoculation treatment, suggesting that disease had no indirect effects through altered competition. In addition, competition with M. vimineum suppressed native plant biomass to a greater extent than disease. The differential impacts of B. gigantea and the consistent impacts of M. vimineum on native species biomass suggest that disease may modify native plant community composition while plant invasion may suppress multiple native plant species in systems where these drivers co-occur.

scholarly journals Emerging fungal pathogen of an invasive grass: Implications for competition with native plant species

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0237894
Author(s):  
Amy E. Kendig ◽  
Vida J. Svahnström ◽  
Ashish Adhikari ◽  
Philip F. Harmon ◽  
S. Luke Flory
Keyword(s):  
Invasive Species ◽  
Plant Species ◽  
Fungal Pathogen ◽  
Native Species ◽  
Grass Species ◽  
Leaf Spot Disease ◽  
Native Plant ◽  
Invasive Grass ◽  
Native Plant Species ◽  
Species Specific

Infectious diseases and invasive species can be strong drivers of biological systems that may interact to shift plant community composition. For example, disease can modify resource competition between invasive and native species. Invasive species tend to interact with a diversity of native species, and it is unclear how native species differ in response to disease-mediated competition with invasive species. Here, we quantified the biomass responses of three native North American grass species (Dichanthelium clandestinum, Elymus virginicus, and Eragrostis spectabilis) to disease-mediated competition with the non-native invasive grass Microstegium vimineum. The foliar fungal pathogen Bipolaris gigantea has recently emerged in Microstegium populations, causing a leaf spot disease that reduces Microstegium biomass and seed production. In a greenhouse experiment, we examined the effects of B. gigantea inoculation on two components of competitive ability for each native species: growth in the absence of competition and biomass responses to increasing densities of Microstegium. Bipolaris gigantea inoculation affected each of the three native species in unique ways, by increasing (Dichanthelium), decreasing (Elymus), or not changing (Eragrostis) their growth in the absence of competition relative to mock inoculation. Bipolaris gigantea inoculation did not, however, affect Microstegium biomass or mediate the effect of Microstegium density on native plant biomass. Thus, B. gigantea had species-specific effects on native plant competition with Microstegium through species-specific biomass responses to B. gigantea inoculation, but not through modified responses to Microstegium density. Our results suggest that disease may uniquely modify competitive interactions between invasive and native plants for different native plant species.

Rehabilitating Downy Brome (Bromus tectorum)–Invaded Shrublands Using Imazapic and Seeding with Native Shrubs

2011 ◽  
Vol 4 (2) ◽  
pp. 223-233 ◽  
Author(s):  
Suzanne M. Owen ◽  
Carolyn Hull Sieg ◽  
Catherine A. Gehring
Keyword(s):  
Community Composition ◽  
Plant Community ◽  
Native Species ◽  
Developmental Stages ◽  
Growth Stages ◽  
Plant Community Composition ◽  
Downy Brome ◽  
Invasive Grass ◽  
Shrub Species ◽  
Native Shrubs

AbstractRehabilitation of downy brome–infested shrublands is challenging once this invasive grass dominates native communities. The effectiveness of imazapic herbicide in reducing downy brome cover has been variable, and there is uncertainty about the impacts of imazapic on native species. We used a before-after-control-impact (BACI) field experiment and greenhouse studies to (1) determine if imazapic herbicide applied at 132 g ai ha−1 (8 oz/ac−1) and seeding with two native shrub species (Wyoming big sagebrush [Artemisia tridentata] and Mexican cliffrose [Purshia mexicana]) reduced downy brome cover and promoted shrub establishment, (2) assess potential effects of imazapic on nontarget plant species and plant community composition, and (3) determine if imazapic affected downy brome or seeded shrub species when applied at different developmental stages. Seeding shrubs, alone, or in combination with imazapic application, did not significantly increase shrub density, possibly because of droughty conditions. In the field, imazapic reduced downy brome cover by 20% and nontarget forb cover by 25% and altered plant community composition the first year after treatment. Imazapic was lethal to downy brome at all growth stages in the greenhouse and reduced shrub germination by 50 to 80%, but older shrub seedlings were more tolerant of the herbicide. We conclude that a one-time application of imazapic combined with seeding shrubs was only slightly effective in rehabilitating areas with high downy brome and thatch cover and resulted in short-term impacts to nontarget species. These results highlight the need to treat downy brome infestations before they become too large. Also, removing thatch prior to treating with imazapic, although likely lethal to the native shrubs we studied, could increase the effectiveness of imazapic.

Effect of Aminopyralid on Canada Thistle (Cirsium arvense) and the Native Plant Community in a Restored Tallgrass Prairie

2010 ◽  
Vol 3 (2) ◽  
pp. 155-168 ◽  
Author(s):  
Travis L. Almquist ◽  
Rodney G. Lym
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Native Species ◽  
Cirsium Arvense ◽  
Grass Species ◽  
Stem Density ◽  
Native Plant ◽  
Canada Thistle ◽  
Native Plant Community ◽  
Restored Prairie

AbstractAminopyralid efficacy on Canada thistle (Cirsium arvense) and potential to injure native species was evaluated in a restored prairie at the Glacial Ridge Preserve managed by The Nature Conservancy in Polk County, MN. Canada thistle stem density was reduced from 17 to 0.1 stems m−2 10 mo after treatment (MAT) with aminopyralid applied in the fall at 120 g ha−1. Aminopyralid also altered the composition of both Canada thistle–infested and native plant communities. Aminopyralid controlled Canada thistle and removed or reduced several undesirable forb species from the restored prairie communities, such as absinth wormwood (Artemisia absinthium) and perennial sowthistle (Sonchus arvensis). A number of high seral forbs were also reduced or removed by aminopyralid, including maximilian sunflower (Helianthus maximiliani) and purple prairie clover (Dalea purpurea). Foliar cover of high seral forbs in the native plant community was reduced from 12.2 to 7% 22 MAT. The cover of high seral grass species, such as big bluestem (Andropogon gerardii) and Indiangrass (Sorghastrum nutans) increased after aminopyralid application in both the Canada thistle–infested and native plant communities and averaged 41.4% cover compared with only 19.4% before removal of Canada thistle. Species richness, evenness, and diversity were reduced after aminopyralid application in both Canada thistle–infested and native plant communities. However, the benefits of Canada thistle control, removal of undesirable species, and the increase in native grass cover should lead to an overall improvement in the long-term stability and composition of the restored prairie plant community, which likely outweigh the short-term effects of a Canada thistle control program.

scholarly journals Do No Harm: Efficacy of a Single Herbicide Application to Control an Invasive Shrub While Minimizing Collateral Damage to Native Species

Plants ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 426 ◽  
Author(s):  
David J. Gibson ◽  
Lindsay A. Shupert ◽  
Xian Liu
Keyword(s):  
Exotic Species ◽  
Community Composition ◽  
Plant Community ◽  
Native Species ◽  
Phylogenetic Diversity ◽  
Native Plant ◽  
Short Term ◽  
Seed Addition ◽  
Herbicide Treatments ◽  
Native Plant Community

Control of invasive exotic species in restorations without compromising the native plant community is a challenge. Efficacy of exotic species control needs to consider collateral effects on the associated plant community. We asked (1) if short-term control of a dominant exotic invasive, Lespedeza cuneata in grassland restorations allows establishment of a more diverse native plant community, and (2) if control of the exotic and supplemental seed addition allows establishment of native species. A manipulative experiment tested the effects of herbicide treatments (five triclopyr and fluroxypyr formulations plus an untreated control) and seed addition (and unseeded control) on taxonomic and phylogenetic diversity, and community composition of restored grasslands in three sites over three years. We assessed response of L. cuneata through stem density counts, and response of the plant community through estimates of canopy cover. Herbicide treatments reduced the abundance of the exotic in the first field season leading to a less dispersed community composition compared with untreated controls, with the exotic regaining dominance by the third year. Supplemental seed addition did not provide extra resistance of the native community to reinvasion of the exotic. The communities were phylogenetically over-dispersed, but there was a short-term shift to lower phylogenetic diversity in response to herbicides consistent with a decrease in biotic filtering. Native plant communities in these grassland restorations were resilient to short-term reduction in abundance of a dominant invasive even though it was insufficient to provide an establishment window for native species establishment.

scholarly journals Litter type affects the activity of aerobic decomposers in a boreal peatland more than site nutrient and water table regimes

2011 ◽  
Vol 8 (9) ◽  
pp. 2741-2755 ◽  
Author(s):  
P. Straková ◽  
R. M. Niemi ◽  
C. Freeman ◽  
K. Peltoniemi ◽  
H. Toberman ◽  
...  
Keyword(s):  
Community Composition ◽  
Plant Community ◽  
Indirect Effects ◽  
Enzyme Activities ◽  
Litter Quality ◽  
Plant Community Composition ◽  
Litter Type ◽  
Direct Effects ◽  
Short Term

Abstract. Peatlands are carbon (C) storage ecosystems sustained by a high water table (WT). High WT creates anoxic conditions that suppress the activity of aerobic decomposers and provide conditions for peat accumulation. Peatland function can be dramatically affected by WT drawdown caused by climate and/or land-use change. Aerobic decomposers are directly affected by WT drawdown through environmental factors such as increased oxygenation and nutrient availability. Additionally, they are indirectly affected via changes in plant community composition and litter quality. We studied the relative importance of direct and indirect effects of WT drawdown on aerobic decomposer activity in plant litter at two stages of decomposition (incubated in the field for 1 or 2 years). We did this by profiling 11 extracellular enzymes involved in the mineralization of organic C, nitrogen (N), phosphorus (P) and sulphur. Our study sites represented a three-stage chronosequence from pristine to short-term (years) and long-term (decades) WT drawdown conditions under two nutrient regimes (bog and fen). The litter types included reflected the prevalent vegetation: Sphagnum mosses, graminoids, shrubs and trees. Litter type was the main factor shaping microbial activity patterns and explained about 30 % of the variation in enzyme activities and activity allocation. Overall, enzyme activities were higher in vascular plant litters compared to Sphagnum litters, and the allocation of enzyme activities towards C or nutrient acquisition was related to the initial litter quality (chemical composition). Direct effects of WT regime, site nutrient regime and litter decomposition stage (length of incubation period) summed to only about 40 % of the litter type effect. WT regime alone explained about 5 % of the variation in enzyme activities and activity allocation. Generally, enzyme activity increased following the long-term WT drawdown and the activity allocation turned from P and N acquisition towards C acquisition. This caused an increase in the rate of litter decomposition. The effects of the short-term WT drawdown were minor compared to those of the long-term WT drawdown: e.g., the increase in the activity of C-acquiring enzymes was up to 120 % (bog) or 320 % (fen) higher after the long-term WT drawdown compared to the short-term WT drawdown. In general, the patterns of microbial activity as well as their responses to WT drawdown depended on peatland type: e.g., the shift in activity allocation to C-acquisition was up to 100 % stronger at the fen compared to the bog. Our results imply that changes in plant community composition in response to persistent WT drawdown will strongly affect the C dynamics of peatlands. The predictions of decomposer activity under changing climate and/or land-use thus cannot be based on the direct effects of the changed environment only, but need to consider the indirect effects of environmental changes: the changes in plant community composition, their dependence on peatland type, and their time scale.

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