scholarly journals PLANT COMMUNITY CHANGE ACROSS THE PALEOCENE-EOCENE BOUNDARY IN THE GULF COASTAL PLAIN, CENTRAL TEXAS

2019 ◽  
Author(s):  
Jennifer D. Wagner ◽  
Daniel J. Peppe ◽  
Jennifer M.K. O'Keefe ◽  
Christopher Dennison
Keyword(s):  
Global Warming ◽  
Plant Community ◽  
Plant Communities ◽  
Coastal Plain ◽  
Community Change ◽  
Northern Great Plains ◽  
Gulf Coastal Plain ◽  
High Turnover ◽  
Future Global Warming ◽  
Central Texas

During the early Paleogene the Earth experienced long-term global warming punctuated by several short-term ‘hyperthermal’ events, the most pronounced of which is the Paleocene-Eocene Thermal Maximum (PETM). During this time, tropical climates expanded into extra-tropical areas potentially forming a wide band of ‘paratropical’ forests that are hypothesized to have expanded into the mid-latitude Northern Great Plains (NGP). Relatively little is known about these ‘paratropical’ floras, which would have extended across the Gulf Coastal Plain (GCP). This study assesses the preserved floras from the GCP in Central Texas before and after the PETM to define plant ecosystem changes associated with the hyperthermal event in this region. These floras suggest a high turnover rate, change in plant community composition, and uniform plant communities across the GCP at the Paleocene-Eocene boundary. Paleoecology and paleoclimate estimates from Central Texas PETM floras suggest a warm and wet environment, indicative of tropical seasonal forest to tropical rainforest biomes. Fossil evidence from the GCP combined with data from the NGP and modern tropics suggest that warming during the PETM helped create a ‘paratropical belt’ that extended into the mid-latitudes. Evaluating the response of plant communities to rapid global warming is important for understanding and preparing for current and future global warming and climate change.

scholarly journals Species turnover reveals hidden effects of decreasing nitrogen deposition in mountain hay meadows

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6347 ◽  
Author(s):  
Tobias Roth ◽  
Lukas Kohli ◽  
Christoph Bühler ◽  
Beat Rihm ◽  
Reto Giulio Meuli ◽  
...  
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Climate Warming ◽  
Species Turnover ◽  
Monitoring Program ◽  
Community Change ◽  
N Deposition ◽  
Indicator Values ◽  
Hay Meadows ◽  
Random Expectation

Nitrogen (N) deposition is a major threat to biodiversity in many habitats. The recent introduction of cleaner technologies in Switzerland has led to a reduction in the emissions of nitrogen oxides, with a consequent decrease in N deposition. We examined different drivers of plant community change, that is, N deposition, climate warming, and land-use change, in Swiss mountain hay meadows, using data from the Swiss biodiversity monitoring program. We compared indicator values of species that disappeared from or colonized a site (species turnover) with the indicator values of randomly chosen species from the same site. While oligotrophic plant species were more likely to colonize, compared to random expectation, we found only weak shifts in plant community composition. In particular, the average nutrient value of plant communities remained stable over time (2003–2017). We found the largest deviations from random expectation in the nutrient values of colonizing species, suggesting that N deposition or other factors that change the nutrient content of soils were important drivers of the species composition change over the last 15 years in Swiss mountain hay meadows. In addition, we observed an overall replacement of species with lower indicator values for temperature with species with higher values. Apparently, the community effects of the replacement of eutrophic species with oligotrophic species was outweighed by climate warming. Our results add to the increasing evidence that plant communities in changing environments may be relatively stable regarding average species richness or average indicator values, but that this apparent stability is often accompanied by a marked turnover of species.

scholarly journals Species turnover reveals hidden effects of decreasing nitrogen deposition in mountain hay meadows

2018 ◽  
Author(s):  
Tobias Roth ◽  
Lukas Kohli ◽  
Christoph Bühler ◽  
Beat Rihm ◽  
Reto Giulio Meuli ◽  
...  
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Climate Warming ◽  
Species Turnover ◽  
Monitoring Program ◽  
Community Change ◽  
N Deposition ◽  
Indicator Values ◽  
Hay Meadows ◽  
Random Expectation

Nitrogen (N) deposition is a major threat to biodiversity in many habitats. The recent introduction of cleaner technologies in Switzerland has led to a reduction in the emissions of nitrogen oxides, with a consequent decrease in N deposition. We examined different drivers of plant community change, i.e. N deposition, climate warming, and land-use change, in Swiss mountain hay meadows, using data from the Swiss biodiversity monitoring program. We compared indicator values of species that disappeared from or colonized a site (species turnover) with the indicator values of randomly chosen species from the same site. While oligotrophic plant species were more likely to colonize, compared to random expectation, we found only weak shifts in plant community composition. In particular, the average nutrient value of plant communities remained stable over time (2003-2017). We found the largest deviations from random expectation in the nutrient values of colonizing species, suggesting that N deposition or other factors that change the nutrient content of soils were important drivers of the species composition change over the last 15 years in Swiss mountain hay meadows. In addition, we observed an overall replacement of species with lower indicator values for temperature with species with higher values. Apparently, the community effects of the replacement of eutrophic species with oligotrophic species was outweighed by climate warming. Our results add to the increasing evidence that plant communities in changing environments may be relatively stable regarding average species richness or average indicator values, but that this apparent stability is often accompanied by a marked turnover of species.

scholarly journals CO<sub>2</sub> and CH<sub>4</sub> budgets and global warming potential modifications in <i>Sphagnum</i>-dominated peat mesocosms invaded by <i>Molinia caerulea</i>

2019 ◽  
Vol 16 (20) ◽  
pp. 4085-4095 ◽  
Author(s):  
Fabien Leroy ◽  
Sébastien Gogo ◽  
Christophe Guimbaud ◽  
Léonard Bernard-Jannin ◽  
Xiaole Yin ◽  
...  
Keyword(s):  
Global Warming ◽  
Plant Communities ◽  
Global Warming Potential ◽  
Ecosystem Respiration ◽  
Vascular Plant ◽  
Community Change ◽  
Ch4 Emission ◽  
Molinia Caerulea ◽  
Sphagnum Mosses ◽  
Emission Models

Abstract. Plant communities play a key role in regulating greenhouse gas (GHG) emissions in peatland ecosystems and therefore in their ability to act as carbon (C) sinks. However, in response to global change, a shift from Sphagnum-dominated to vascular-plant-dominated peatlands may occur, with a potential alteration in their C-sink function. To investigate how the main GHG fluxes (CO2 and CH4) are affected by a plant community change (shift from dominance of Sphagnum mosses to vascular plants, i.e., Molinia caerulea), a mesocosm experiment was set up. Gross primary production (GPP), ecosystem respiration (ER) and CH4 emission models were used to estimate the annual C balance and global warming potential under both vegetation covers. While the ER and CH4 emission models estimated an output of, respectively, 376±108 and 7±4 g C m−2 yr−1 in Sphagnum mesocosms, this reached 1018±362 and 33±8 g C m−2 yr−1 in mesocosms with Sphagnum rubellum and Molinia caerulea. Annual modeled GPP was estimated at -414±122 and -1273±482 g C m−2 yr−1 in Sphagnum and Sphagnum + Molinia plots, respectively, leading to an annual CO2 and CH4 budget of −30 g C m−2 yr−1 in Sphagnum plots and of −223 g C m−2 yr−1 in Sphagnum + Molinia ones (i.e., a C sink). Even if CH4 emissions accounted for a small part of the gaseous C efflux (ca. 3 %), their global warming potential value makes both plant communities have a climate warming effect. The shift of vegetation from Sphagnum mosses to Molinia caerulea seems beneficial for C sequestration at a gaseous level. However, roots and litter of Molinia caerulea could provide substrates for C emissions that were not taken into account in the short measurement period studied here.

scholarly journals Comparing stability in random forest models to map Northern Great Plains plant communities in pastures occupied by prairie dogs using Pleiades imagery

2020 ◽  
Vol 17 (5) ◽  
pp. 1281-1292
Author(s):  
Jameson R. Brennan ◽  
Patricia S. Johnson ◽  
Niall P. Hanan
Keyword(s):  
Random Forest ◽  
Plant Community ◽  
Plant Communities ◽  
Plant Biomass ◽  
Error Rates ◽  
Cynomys Ludovicianus ◽  
Prairie Dogs ◽  
Northern Great Plains ◽  
Prairie Dog ◽  
The Impact

Abstract. Black-tailed prairie dogs (Cynomys ludovicianus) have been described as a keystone species and are important for grassland conservation, yet many concerns exist over the impact of prairie dogs on plant biomass production and consequently livestock production. The ability to map plant communities in pastures colonized by prairie dogs can provide land managers with an opportunity to optimize rangeland production while balancing conservation goals. The aim of this study was to test the ability of random forest (RF) models to classify five plant communities located on and off prairie dog towns in mixed-grass prairie landscapes of north central South Dakota, assess the stability of RF models among different years, and determine the utility of utilizing remote sensing techniques to identify prairie dog colony extent. During 2015 and 2016, Pleiades satellites were tasked to image the study site for a total of five monthly collections each summer (June–October). Training polygons were mapped in 2016 for the five plant communities and used to train RF models. Both the 2015 and 2016 RF models had low (1 %) out-of-bag error rates. However, comparisons between the predicted plant community maps using the 2015 imagery and one created with the 2016 imagery indicate over 32.9 % of pixels changed plant community class between 2015 and 2016. The results show that while RF models may predict with a high degree of accuracy, overlap of plant communities and interannual differences in rainfall may cause instability in fitted models. A final RF model combining both 2015 and 2016 data yielded the lowest error rates and was also highly accurate in determining prairie dog colony boundaries.

scholarly journals Warming, euxinia and sea level rise during the Paleocene–Eocene Thermal Maximum on the Gulf Coastal Plain: implications for ocean oxygenation and nutrient cycling

2014 ◽  
Vol 10 (4) ◽  
pp. 1421-1439 ◽  
Author(s):  
A. Sluijs ◽  
L. van Roij ◽  
G. J. Harrington ◽  
S. Schouten ◽  
J. A. Sessa ◽  
...  
Keyword(s):  
Global Warming ◽  
Nutrient Cycling ◽  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Plain ◽  
Continental Margins ◽  
Gulf Coastal Plain ◽  
Thermal Maximum ◽  
Organic Carbon Burial ◽  
Phosphorus Regeneration

Abstract. The Paleocene–Eocene Thermal Maximum (PETM, ~ 56 Ma) was a ~ 200 kyr episode of global warming, associated with massive injections of 13C-depleted carbon into the ocean–atmosphere system. Although climate change during the PETM is relatively well constrained, effects on marine oxygen concentrations and nutrient cycling remain largely unclear. We identify the PETM in a sediment core from the US margin of the Gulf of Mexico. Biomarker-based paleotemperature proxies (methylation of branched tetraether–cyclization of branched tetraether (MBT–CBT) and TEX86) indicate that continental air and sea surface temperatures warmed from 27–29 to ~ 35 °C, although variations in the relative abundances of terrestrial and marine biomarkers may have influenced these estimates. Vegetation changes, as recorded from pollen assemblages, support this warming. The PETM is bracketed by two unconformities. It overlies Paleocene silt- and mudstones and is rich in angular (thus in situ produced; autochthonous) glauconite grains, which indicate sedimentary condensation. A drop in the relative abundance of terrestrial organic matter and changes in the dinoflagellate cyst assemblages suggest that rising sea level shifted the deposition of terrigenous material landward. This is consistent with previous findings of eustatic sea level rise during the PETM. Regionally, the attribution of the glauconite-rich unit to the PETM implicates the dating of a primate fossil, argued to represent the oldest North American specimen on record. The biomarker isorenieratene within the PETM indicates that euxinic photic zone conditions developed, likely seasonally, along the Gulf Coastal Plain. A global data compilation indicates that O2 concentrations dropped in all ocean basins in response to warming, hydrological change, and carbon cycle feedbacks. This culminated in (seasonal) anoxia along many continental margins, analogous to modern trends. Seafloor deoxygenation and widespread (seasonal) anoxia likely caused phosphorus regeneration from suboxic and anoxic sediments. We argue that this fueled shelf eutrophication, as widely recorded from microfossil studies, increasing organic carbon burial along many continental margins as a negative feedback to carbon input and global warming. If properly quantified with future work, the PETM offers the opportunity to assess the biogeochemical effects of enhanced phosphorus regeneration, as well as the timescales on which this feedback operates in view of modern and future ocean deoxygenation.

scholarly journals Species turnover reveals hidden effects of decreasing nitrogen deposition in mountain hay meadows

2018 ◽  
Author(s):  
Tobias Roth ◽  
Lukas Kohli ◽  
Christoph Bühler ◽  
Beat Rihm ◽  
Reto Giulio Meuli ◽  
...  
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Climate Warming ◽  
Species Turnover ◽  
Monitoring Program ◽  
Community Change ◽  
N Deposition ◽  
Indicator Values ◽  
Hay Meadows ◽  
Random Expectation

Nitrogen (N) deposition is a major threat to biodiversity in many habitats. The recent introduction of cleaner technologies in Switzerland has led to a reduction in the emissions of nitrogen oxides, with a consequent decrease in N deposition. We examined different drivers of plant community change, i.e. N deposition, climate warming, and land-use change, in Swiss mountain hay meadows, using data from the Swiss biodiversity monitoring program. We compared indicator values of species that disappeared from or colonized a site (species turnover) with the indicator values of randomly chosen species from the same site. While oligotrophic plant species were more likely to colonize, compared to random expectation, we found only weak shifts in plant community composition. In particular, the average nutrient value of plant communities remained stable over time (2003-2017). We found the largest deviations from random expectation in the nutrient values of colonizing species, suggesting that N deposition or other factors that change the nutrient content of soils were important drivers of the species composition change over the last 15 years in Swiss mountain hay meadows. In addition, we observed an overall replacement of species with lower indicator values for temperature with species with higher values. Apparently, the community effects of the replacement of eutrophic species with oligotrophic species was outweighed by climate warming. Our results add to the increasing evidence that plant communities in changing environments may be relatively stable regarding average species richness or average indicator values, but that this apparent stability is often accompanied by a marked turnover of species.

scholarly journals CO<sub>2</sub> and CH<sub>4</sub> budgets and global warming potential modifications in <i>Sphagnum</i>-dominated peat mesocosms invaded by <i>Molinia caerulea</i>

2017 ◽  
Author(s):  
Fabien Leroy ◽  
Sébastien Gogo ◽  
Christophe Guimbaud ◽  
Léonard Bernard-Jannin ◽  
Xiaole Yin ◽  
...  
Keyword(s):  
Global Warming ◽  
Plant Communities ◽  
Global Warming Potential ◽  
Ecosystem Respiration ◽  
Vascular Plant ◽  
Community Change ◽  
Ch4 Emission ◽  
Molinia Caerulea ◽  
Sphagnum Mosses ◽  
Emission Models

Abstract. Plant communities play a key role in regulating greenhouse gas (GHG) emissions in peatland ecosystems and therefore in their ability to act as carbon (C) sinks. However, in response to global change, a shift from Sphagnum to vascular plant-dominated peatlands may occur, with a potential alteration in their C-sink function. To investigate how the main GHG fluxes (CO2 and CH4) are affected by a plant community change (shift from dominance of Sphagnum mosses to vascular plants, i.e. Molinia caerulea), a mesocosm experiment was set up. Gross primary production (GPP), ecosystem respiration (ER) and CH4 emission models were used to estimate the annual C balance and global warming potential under both vegetation covers. While the ER and CH4 emission models estimated an output of, respectively, 376 and 7 gC m−2 y−1 in Sphagnum mesocosms, this reached 1018 and 33 gC m−2 y−1 in mesocosms with Sphagnum rubellum and Molinia caerulea. Annual modelled GPP was estimated at −414 and −1273 gC m−2 y−1 in Sphagnum and Sphagnum + Molinia plots, respectively, leading to an annual CO2 and CH4 budget of −30 gC m−2 y−1 in Sphagnum plots and of −223 gC m−2 y−1 in Sphagnum + Molinia ones (i.e., a C-sink). Even if, CH4 emissions accounted for a small part of the gaseous C efflux (ca. 3 %), their global warming potential value makes both plant communities have a climate warming effect. The shift of vegetation from Sphagnum mosses to Molinia caerulea seems beneficial for C sequestration at a gaseous level. However, roots and litters of Molinia caerulea could provide substrates for C emissions that were not taken into account in the short measurement period studied here.

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