Mammalian herbivory in post-fire chaparral impacts herbaceous composition but not N and C cycling

2020 ◽  
Author(s):  
Lindsey Hendricks-Franco ◽  
Scott L Stephens ◽  
Wayne P Sousa
Keyword(s):  
Relative Abundance ◽  
Plant Litter ◽  
N Cycling ◽  
Herbaceous Plant ◽  
N Availability ◽  
Mammalian Herbivores ◽  
C Cycling ◽  
Mammalian Herbivory ◽  
The Impact ◽  
Native Herbs

Abstract Aims Classical theory predicts that herbivores impact herb assemblages and soil nitrogen (N) cycling through selective plant consumption and the deposition of N-rich waste, with effects dependent upon ecosystem N availability. Herbivores are predicted to accelerate N cycling when N availability is high and decelerate cycling when availability is low. However, experimental tests of these theories in natural systems are limited and have yielded contradictory results. California’s widespread chaparral shrublands provide a tractable system in which to test these theories. They are prone to periodic crown-fire, which temporarily removes living shrub cover, deposits mineral N on soils, and allows diverse herbaceous assemblages to dominate the landscape for 3-5 years. Chaparral is also increasingly vulnerable to herbaceous invasion; mammalian herbivory may limit the establishment of non-native herbs in the shrub understory. Methods We implemented a two-year herbivore-exclosure experiment (Hopland, California) to assess the impact of mammalian herbivory during early post-fire chaparral succession, both on herbaceous plant assemblages and soil N and C cycling. We predicted that, in high-N post-fire conditions, mammalian herbivory would not demonstrate a strong preference for N-fixing herbs, would accelerate N cycling, and would reduce the abundance of non-native herbs. Important Findings Excluding mammalian herbivores increased herb standing biomass by 54%, but changed neither the relative abundance of N-fixing vs. non-N-fixing herbs nor any measure of N or C cycling. Herbivore impacts on nutrient cycling may not be significant over the two-year time scale of the experiment and physical effects of herbivore activity could have counteracted the influence of plant litter and animal dung/urine inputs. Mammalian herbivores concentrated their feeding on typical non-native herbs, slightly decreasing their relative abundance; however, mammalian herbivory was not sufficient to stem the invasion of chaparral by invasive herbs or alter C and N cycling over the first two years after fire.

scholarly journals Nitrogen Cycling Potential of a Grassland Litter Microbial Community

2015 ◽  
Vol 81 (20) ◽  
pp. 7012-7022 ◽  
Author(s):  
Michaeline B. Nelson ◽  
Renaud Berlemont ◽  
Adam C. Martiny ◽  
Jennifer B. H. Martiny
Keyword(s):  
Global Change ◽  
Plant Litter ◽  
N Cycling ◽  
N Availability ◽  
Microbial Composition ◽  
Content Type ◽  
Plant Litter Decomposition ◽  
N Utilization ◽  
Over Time ◽  
Microbial N

ABSTRACTBecause microorganisms have different abilities to utilize nitrogen (N) through various assimilatory and dissimilatory pathways, microbial composition and diversity likely influence N cycling in an ecosystem. Terrestrial plant litter decomposition is often limited by N availability; however, little is known about the microorganisms involved in litter N cycling. In this study, we used metagenomics to characterize the potential N utilization of microbial communities in grassland plant litter. The frequencies of sequences associated with eight N cycling pathways differed by several orders of magnitude. Within a pathway, the distributions of these sequences among bacterial orders differed greatly. Many orders within theActinobacteriaandProteobacteriaappeared to be N cycling generalists, carrying genes from most (five or six) of the pathways. In contrast, orders from theBacteroideteswere more specialized and carried genes for fewer (two or three) pathways. We also investigated how the abundance and composition of microbial N cycling genes differed over time and in response to two global change manipulations (drought and N addition). For many pathways, the abundance and composition of N cycling taxa differed over time, apparently reflecting precipitation patterns. In contrast to temporal variability, simulated global change had minor effects on N cycling potential. Overall, this study provides a blueprint for the genetic potential of N cycle processes in plant litter and a baseline for comparisons to other ecosystems.

scholarly journals The impact of fixed orthodontic appliances on oral microbiome dynamics in Japanese patients

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Isamu Kado ◽  
Junzo Hisatsune ◽  
Keiko Tsuruda ◽  
Kotaro Tanimoto ◽  
Motoyuki Sugai
Keyword(s):  
Relative Abundance ◽  
Japanese Patients ◽  
Oral Microbiome ◽  
Orthodontic Appliances ◽  
Periodontal Pathogens ◽  
Supragingival Plaque ◽  
Fixed Orthodontic Appliances ◽  
Microbial Dna ◽  
The Impact ◽  
Level Analysis

AbstractFixed orthodontic appliances are common and effective tools to treat malocclusion. Adverse effects of these appliances, such as dental caries and periodontitis, may be associated with alteration of the microbiome. This study investigated the impact of these appliances on the dynamics of the oral microbiome. Seventy-one patients were selected. Supragingival plaque samples were collected before placement (T0) and six months after placement (T1). Saliva samples were collected at T0 and T1, and then when appliance removal (T2). Microbial DNA was analyzed by 16S rRNA meta-sequencing. The diversity analysis indicated dynamic changes in the structure of the oral microbiome. Taxonomic analysis at phylum level showed a significant increase in Bacteroidetes and Saccharibacteria (formally TM7) and decrease in Proteobacteria and Actinobacteria over time, in both plaque and saliva. Genus level analysis of relative abundance indicated a significant increase in anaerobic and facultative anaerobes in both plaque and saliva. Fixed orthodontic appliances induced measurable changes in the oral microbiome. This was characterized by an increase in relative abundance of obligate anaerobes, including periodontal pathogens. It can be concluded that this dysbiosis induced by fixed orthodontic appliances is likely to represent a transitional stage in the shift in microbiome from healthy to periodontitis.

Interactions between invasive plants and heavy metal stresses: a review

2021 ◽  
Author(s):  
Jian Li ◽  
Zhanrui Leng ◽  
Yueming Wu ◽  
Yizhou Du ◽  
Zhicong Dai ◽  
...  
Keyword(s):  
Invasive Species ◽  
Invasive Plants ◽  
Native Plants ◽  
Escape Behavior ◽  
Negative Influence ◽  
Plant Litter ◽  
Global Changes ◽  
Native Plant ◽  
Anthropogenic Contamination ◽  
The Impact

Abstract Global changes have altered the distribution pattern of the plant communities, including invasive species. Anthropogenic contamination may reduce native plant resistance to the invasive species. Thus, the focus of the current review is on the contaminant biogeochemical behavior among native plants, invasive species and the soil within the plant-soil ecosystem to improve our understanding of the interactions between invasive plants and environmental stressors. Our studies together with synthesis of the literature showed that a) the impacts of invasive species on environmental stress were heterogeneous, b) the size of the impact was variable, and c) the influence types were multidirectional even within the same impact type. However, invasive plants showed self-protective mechanisms when exposed to heavy metals (HMs) and provided either positive or negative influence on the bioavailability and toxicity of HMs. On the other hand, HMs may favor plant invasion due to the widespread higher tolerance of invasive plants to HMS together with the “escape behavior” of native plants when exposed to toxic HM pollution. However, there has been no consensus on whether elemental compositions of invasive plants are different from the natives in the polluted regions. A quantitative research comparing plant, litter and soil contaminant contents between native plants and the invaders in a global context is an indispensable research focus in the future.

Effect of fire regime on the grass community of the humid savanna of Lamto, Ivory Coast

2018 ◽  
Vol 35 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Kouamé Fulgence Koffi ◽  
Aya Brigitte N’Dri ◽  
Jean-Christophe Lata ◽  
Souleymane Konaté ◽  
Tharaniya Srikanthasamy ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Ivory Coast ◽  
Fire Regime ◽  
Fire Regimes ◽  
Abundant Species ◽  
Grass Species ◽  
The Third ◽  
Humid Savanna ◽  
The Impact ◽  
Tussock Grasses

AbstractThis study assesses the impact of four fire treatments applied yearly over 3 y, i.e. early fire, mid-season fire, late fire and no fire treatments, on the grass communities of Lamto savanna, Ivory Coast. We describe communities of perennial tussock grasses on three replicated 5 × 5-m or 10 × 5-m plots of each fire treatment. Tussock density did not vary with fire treatment. The relative abundance of grass species, the circumference of grass tussocks and the probability of having a tussock with a central die-back, varied with fire treatment. Mid-season fire had the highest proportion of tussocks with a central die-back while the late fire had the smallest tussocks. Tussock density, circumference, relative abundance and probability of having a central die-back varied with species. Andropogon canaliculatus and Hyparrhenia diplandra were the most abundant of the nine grass species. They had the largest tussocks and the highest proportion of tussock with a central die-back. Loudetia simplex was the third most abundant species but was very rare in no fire plots. The distribution of tussock circumferences was right skewed and dominated by small tussocks. The proportion of the tussocks with a central die-back strongly increased with circumference, which could lead to tussock fragmentation. Taken together, this study suggests that fire regimes impact grass demography and that this impact depends on grass species and tussock size.

scholarly journals Carbon losses from pyrolysed and original wood in a forest soil under natural and increased N deposition

2014 ◽  
Vol 11 (18) ◽  
pp. 5199-5213 ◽  
Author(s):  
B. Maestrini ◽  
S. Abiven ◽  
N. Singh ◽  
J. Bird ◽  
M. S. Torn ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Forest Soil ◽  
N Deposition ◽  
Main Process ◽  
N Availability ◽  
N Losses ◽  
Mineral N ◽  
C Cycling ◽  
Carbon Losses

Abstract. Pyrogenic organic matter (PyOM) plays an important role as a stable carbon (C) sink in the soils of terrestrial ecosystems. However, uncertainties remain about in situ turnover rates of fire-derived PyOM in soil, the main processes leading to PyOM-C and nitrogen (N) losses from the soil, and the role of N availability on PyOM cycling in soils. We measured PyOM and native soil organic carbon losses from the soil as carbon dioxide and dissolved organic carbon (DOC) using additions of highly 13C-labelled PyOM (2.03 atom %) and its precursor pinewood during 1 year in a temperate forest soil. The field experiment was carried out under ambient and increased mineral N deposition (+60 kg N-NH4NO3 ha−1 year−1). The results showed that after 1 year: (1) 0.5% of PyOM-C and 22% of wood-C were mineralized as CO2, leading to an estimated turnover time of 191 and 4 years, respectively; (2) the quantity of PyOM and wood lost as dissolved organic carbon was negligible (0.0004 ± 0.0003% and 0.022 ± 0.007% of applied-C, respectively); and (3) N additions decreased cumulative PyOM mineralization by 43%, but did not affect cumulative wood mineralization and did not affect the loss of DOC from PyOM or wood. We conclude that mineralization to CO2 was the main process leading to PyOM losses during the first year of mineralization in a forest soil, and that N addition can decrease PyOM-C cycling, while added N showed no effect on wood C cycling.

Response of benthic macroinvertebrate communities to El Niño related drought events in six upland streams in south-central Ontario

2008 ◽  
Vol 65 (5) ◽  
pp. 890-905 ◽  
Author(s):  
Beth Gilbert ◽  
Peter J Dillon ◽  
Keith M Somers ◽  
Ron A Reid ◽  
Lem Scott
Keyword(s):  
Relative Abundance ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Benthic Macroinvertebrate ◽  
Macroinvertebrate Communities ◽  
South Central ◽  
Effects Of Drought ◽  
One Year ◽  
The Impact

We examined the effects of extreme drought events on benthic macroinvertebrate (BMI) community structure in six forested upland streams in south-central Ontario, Canada, during a 9-year period. Variation in the mean winter El Niño – Southern Oscillation Index was strongly correlated with drought conditions (zero flow days) in the study streams. Drought onset and duration varied among study streams and among years. Below-average precipitation coincided with the occurrence of drought, although it remains unclear if snowfall and rainfall contributed equally to the impact of decreased precipitation. Increased relative abundance of Ephemeroptera, Plecoptera, and Trichoptera (EPT) one year following drought and decreased relative abundance two years after drought indicated high resistance but poor resilience. In contrast, chironomids showed poor resistance and high resilience. Although these patterns were not consistent across all streams, temporal coherence among streams was found in percent EPT, percent chironomids, and percent dipterans, suggesting that drought acts as a disturbance mechanism that simplifies benthos community assemblages. Biocriteria developed from 22 nearby reference streams indicated that abnormal BMI communities occurred only after recurring episodes of drought, indicating that the effects of drought are cumulative. Headwater streams may prove to be sentinel ecosystems for monitoring the impacts of climate change.

Effects of balsam poplar (Populus balsamifera) tannins and low molecular weight phenolics on microbial activity in taiga floodplain soil: implications for changes in N cycling during succession

1996 ◽  
Vol 74 (1) ◽  
pp. 84-90 ◽  
Author(s):  
Joshua P. Schimel ◽  
Keith Van Cleve ◽  
Rex G. Cates ◽  
Thomas P. Clausen ◽  
Paul B. Reichardt
Keyword(s):  
Molecular Weight ◽  
Secondary Compounds ◽  
N Cycling ◽  
Low Molecular Weight ◽  
N Fixation ◽  
N Availability ◽  
Populus Balsamifera ◽  
Floodplain Soil ◽  
Balsam Poplar ◽  
River Floodplains

The transition from alder (Alnus tenuifolia) to balsam poplar (Populus balsamifera) is a critical turning point in primary succession on river floodplains in interior Alaska. Associated with the change in plant species are large changes in N cycling. N-fixation and nitrification decrease and the system becomes N-limited, with NH4+ dominating the inorganic N pool. Balsam poplar leaves contain large quantities of tannins and low molecular weight phenolic compounds. We evaluated the effect of these compounds on microbial respiration and N cycling in laboratory assays on soils from an alder-dominated site. Plant compounds were purified and applied to silica gel as an inert carrier. Both tannins and phenolics caused net N-immobilization over a 30-day assay. However, tannins inhibited respiration while phenolics stimulated it. There were no specific effects on nitrification. Thus, tannins acted as a general microbial inhibitor, while phenolics acted as a growth substrate. By inhibiting mineralization while stimulating immobilization, poplar secondary compounds may reduce soil N-availability during the transition betwen alder and poplar stages in succession. Keywords: respiration, mineralization, tannins, secondary chemicals, succession, plant–microbe interactions.

scholarly journals The influence of a new water infrastructure development on the relative abundance of two Australian freshwater turtle species

2018 ◽  
Vol 66 (1) ◽  
pp. 57 ◽  
Author(s):  
Natalie J. Clark ◽  
Courtenay E. Mills ◽  
Nicolette A. Osborne ◽  
Kerry M. Neil
Keyword(s):  
Relative Abundance ◽  
Temporal Variability ◽  
Monitoring Program ◽  
Freshwater Turtle ◽  
Spatial And Temporal Variability ◽  
Main Body ◽  
Water Infrastructure ◽  
Turtle Species ◽  
Australian Freshwater ◽  
The Impact

Development of water infrastructure benefits water security and agriculture but poses risks to habitat and aquatic fauna. Wyaralong Dam was constructed on Teviot Brook in 2010 to provide future urban water supplies for South East Queensland, Australia. Construction of the dam created a large impoundment area and environmental impact assessment predicted significant impacts upon resident freshwater turtle species and their habitats. Differences in habitat requirements, life-history characteristics and sensitivity to change between the Macquarie River turtle (Emydura macquarii macquarii) and the common saw-shelled turtle (Myuchelys latisternum) were expected to influence the impact of the dam on the spatial and temporal abundance of these species. The relative abundance of each species was monitored at sites located within, upstream and downstream of the impoundment across wet and dry seasons during the dam’s first five years of operation. The results of this monitoring program indicate that spatial and temporal variability in the relative abundance of E. macquarii macquarii and M. latisternum occurred during the study but not all expected impacts were realised. Contrary to expectation, the relative abundance of E. macquarii macquarii did not increase over time within, upstream or downstream of the dam. M. latisternum showed greater temporal variability at some sites; however, no clear relationship between relative abundance and operational years was observed during the monitoring program. Spatial variability in relative abundance between sites was dependent upon season, with trends generally consistent across both turtle species. Where differences between species were observed, these are suspected to have resulted from the influence of environmental conditions on species-specific movement behaviours. The monitoring program confirmed the use of the upper limits of the impoundment and the plunge pool below the dam wall by both turtle species but relative abundance within the main body of the impoundment remained low throughout monitoring. The results of the study allow for consideration of the suitability of predefined management measures and the development of recommendations for future monitoring programs prescribed for water infrastructure developments.

scholarly journals Comparison of eddy covariance CO<sub>2</sub> and CH<sub>4</sub> fluxes from mined and recently rewetted sections in a northwestern German cutover bog

2020 ◽  
Vol 17 (10) ◽  
pp. 2853-2874 ◽  
Author(s):  
David Holl ◽  
Eva-Maria Pfeiffer ◽  
Lars Kutzbach
Keyword(s):  
Carbon Dioxide ◽  
Land Use ◽  
Time Series ◽  
Eddy Covariance ◽  
Relative Difference ◽  
Plant Litter ◽  
Absolute Difference ◽  
Data Set ◽  
Ch4 Flux ◽  
The Impact

Abstract. With respect to their role in the global carbon cycle, natural peatlands are characterized by their ability to sequester atmospheric carbon. This trait is strongly connected to the water regime of these ecosystems. Large parts of the soil profile in natural peatlands are water saturated, leading to anoxic conditions and to a diminished decomposition of plant litter. In functioning peatlands, the rate of carbon fixation by plant photosynthesis is larger than the decomposition rate of dead organic material. Over time, the amount of carbon that remains in the soil and is not converted back to carbon dioxide grows. Land use of peatlands often goes along with water level manipulations and thereby with alterations of carbon flux dynamics. In this study, carbon dioxide (CO2) and methane (CH4) flux measurements from a bog site in northwestern Germany that has been heavily degraded by peat mining are presented. Two contrasting types of management have been implemented at the site: (1) drainage during ongoing peat harvesting on one half of the central bog area and (2) rewetting on the other half that had been taken out of use shortly before measurements commenced. The presented 2-year data set was collected with an eddy covariance (EC) system set up on a central railroad dam that divides the two halves of the (former) peat harvesting area. We used footprint analysis to split the obtained CO2 and CH4 flux time series into data characterizing the gas exchange dynamics of both contrasting land use types individually. The time series gaps resulting from data division were filled using the response of artificial neural networks (ANNs) to environmental variables, footprint variability, and fuzzy transformations of seasonal and diurnal cyclicity. We used the gap-filled gas flux time series from 2 consecutive years to evaluate the impact of rewetting on the annual vertical carbon balances of the cutover bog. Rewetting had a considerable effect on the annual carbon fluxes and led to increased CH4 and decreased CO2 release. The larger relative difference between cumulative CO2 fluxes from the rewetted (13±6 mol m−2 a−1) and drained (22±7 mol m−2 a−1) section occurred in the second observed year when rewetting apparently reduced CO2 emissions by 40 %. The absolute difference in annual CH4 flux sums was more similar between both years, while the relative difference of CH4 release between the rewetted (0.83±0.15 mol m−2 a−1) and drained (0.45±0.11 mol m−2 a−1) section was larger in the first observed year, indicating a maximum increase in annual CH4 release of 84 % caused by rewetting at this particular site during the study period.

scholarly journals The Impact of Dietary Grape Seed Meal on Healthy and Aflatoxin B1 Afflicted Microbiota of Pigs after Weaning

Toxins ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 25 ◽  
Author(s):  
Iulian A. Grosu ◽  
Gina C. Pistol ◽  
Ionelia Taranu ◽  
Daniela E. Marin
Keyword(s):  
Large Intestine ◽  
Relative Abundance ◽  
Aflatoxin B1 ◽  
Illumina Miseq ◽  
Grape Seed ◽  
Antagonistic Effect ◽  
Seed Meal ◽  
Control Group ◽  
The Individual ◽  
The Impact

The study investigated the effect of grape seed (GS) meal, aflatoxin (AFB1), or their combination on the large intestine microbiota of weanling piglets. Twenty-four piglets were allocated into four groups based on diet composition: (1) Control group; (2) AFB1 (320 g/kg feed) group; (3) GS group (8% inclusion in the diet); (4) AFB1 + GS group. After 30 days of experiment, the colon content was used for microbiota analyses; after isolation of total bacterial genomic DNA, V3/V4 regions of the 16S rRNA amplicons were sequenced using the Illumina MiSeq platform. The raw sequences were analyzed using the v.1.9.1 QIIME pipeline software. 157 numbers of OTUs were identified among all four dietary groups with 26 of them being prevalent above 0.05% in the total relative abundance. GS and AFB1 increase the relative abundance of phylum Bacteroidetes and Proteobacteria, while decreasing the Firmicutes abundance in a synergic manner as compared with the individual treatments. An additive or synergistic action of the two treatments was identified for Lactobacillus, Prevotella and Campylobacter, while rather an antagonistic effect was observed on Lachnospira. The action mechanisms of aflatoxin B1 and grape seed meal that drive the large intestine microbiota to these changes are not known and need further investigations.

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