Towards a better understanding of soil- and tree stem-atmosphere exchanges of greenhouse gases, i.e. CO2, CH4, N2O, in a tropical rainforest

The importance of greenhouse gas (GHG) emissions in global climate change is undisputed, but our understanding of the daily and seasonal variations of the GHG fluxes is far from complete and detailed flux estimates are unequally distributed among ecosystems worldwide. Carbon dioxide (77%; CO2), methane (14%; CH4) and nitrous oxide (8%; N2O) are the three main GHGs that trap infrared radiations and contribute to climate change. While CO2 has been largely studied, a considerable effort is still required to quantify the magnitude and drivers of CH4 and N2O, which have radiative effects 25 and 298 times greater than CO2, respectively. Tropical forests play a pivotal role in global carbon (C) balance and climate change mitigation, accounting for 68% of global C stock and representing up to 30% of total forest soil C sink. In the tropics, soils are main contributors to the ecosystem GHG fluxes. In fact, tropical forest soils are the largest natural source of soil CO2 and N2O and are overwhelmingly reported as important sink of CH4. More recently, studies reported that tree stems can also emit CO2, CH4 and N2O and act, via passive transport through the soil xylem stream, as a pathway for these gas emissions to the atmosphere.Although accurate estimates of GHG sources and sinks are of great importance for reducing the uncertainties of C cycle - climate feed-backs, we are only just beginning to understand the role of tropical tree stems as producers and / or conduits of soil-produced GHG.I present first results of soil and tree stem GHG fluxes estimated over a six-month period, including a dry and a wet season, of continuous high frequency measurements with automated GHG flux systems in a tropical rainforest, in French Guiana. We adapted and extended an existing soil GHG flux system, combining a commercial automated soil CO2 flux chamber system (LI-8100A) and CH4 and N2O analyser (Picarro G2308), to include tree stem chambers. Different closure times were applied to ensure reliable flux estimates, especially for low CH4 and N2O fluxes. I show that the new automated system operated successfully, allowing for robust long-term measurements to examine temporal variations and ultimately calculate budgets of CO2, CH4 and N2O fluxes at soil and tree stem levels. Our results indicated that soils and tree stems acted exclusively as source for CO2, whereas soils and tree stems exhibited distinct patterns for both CH4 and N2O, which highlights the importance of partitioning GHG fluxes to better determine environmental controls regulating ecosystem GHG exchanges.

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Contrasting capabilities of two ungulate species to cope with extremes of aridity

Scientific Reports ◽

10.1038/s41598-021-83732-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Melinda Boyers ◽

Francesca Parrini ◽

Norman Owen-Smith ◽

Barend F. N. Erasmus ◽

Robyn S. Hetem

Keyword(s):

Climate Change ◽

High Water ◽

Future Climate Change ◽

Body Temperatures ◽

Wet Season ◽

Trade Off ◽

Ambient Temperatures ◽

Mammalian Herbivores ◽

Dry Seasons ◽

Connochaetes Taurinus

AbstractSouthern Africa is expected to experience increased frequency and intensity of droughts through climate change, which will adversely affect mammalian herbivores. Using bio-loggers, we tested the expectation that wildebeest (Connochaetes taurinus), a grazer with high water-dependence, would be more sensitive to drought conditions than the arid-adapted gemsbok (Oryx gazella gazella). The study, conducted in the Kalahari, encompassed two hot-dry seasons with similar ambient temperatures but differing rainfall patterns during the preceding wet season. In the drier year both ungulates selected similar cooler microclimates, but wildebeest travelled larger distances than gemsbok, presumably in search of water. Body temperatures in both species reached lower daily minimums and higher daily maximums in the drier season but daily fluctuations were wider in wildebeest than in gemsbok. Lower daily minimum body temperatures displayed by wildebeest suggest that wildebeest were under greater nutritional stress than gemsbok. Moving large distances when water is scarce may have compromised the energy balance of the water dependent wildebeest, a trade-off likely to be exacerbated with future climate change.

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Surface Water Temperature Predictions at a Mid-Latitude Reservoir under Long-Term Climate Change Impacts Using a Deep Neural Network Coupled with a Transfer Learning Approach

Water ◽

10.3390/w13081109 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1109

Author(s):

Nobuaki Kimura ◽

Kei Ishida ◽

Daichi Baba

Keyword(s):

Climate Change ◽

Surface Water ◽

Water Temperature ◽

Transfer Learning ◽

Air Temperature ◽

Climate Models ◽

Temporal Variations ◽

Training Data ◽

Surface Water Temperature

Long-term climate change may strongly affect the aquatic environment in mid-latitude water resources. In particular, it can be demonstrated that temporal variations in surface water temperature in a reservoir have strong responses to air temperature. We adopted deep neural networks (DNNs) to understand the long-term relationships between air temperature and surface water temperature, because DNNs can easily deal with nonlinear data, including uncertainties, that are obtained in complicated climate and aquatic systems. In general, DNNs cannot appropriately predict unexperienced data (i.e., out-of-range training data), such as future water temperature. To improve this limitation, our idea is to introduce a transfer learning (TL) approach. The observed data were used to train a DNN-based model. Continuous data (i.e., air temperature) ranging over 150 years to pre-training to climate change, which were obtained from climate models and include a downscaling model, were used to predict past and future surface water temperatures in the reservoir. The results showed that the DNN-based model with the TL approach was able to approximately predict based on the difference between past and future air temperatures. The model suggested that the occurrences in the highest water temperature increased, and the occurrences in the lowest water temperature decreased in the future predictions.

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Spatio and temporal variations in population abundance and distribution of peach fruit fly, Bactrocera zonata (Saunders) during future climate change scenarios based on temperature driven phenology model

Climate Risk Management ◽

10.1016/j.crm.2021.100277 ◽

2021 ◽

Vol 32 ◽

pp. 100277

Author(s):

Jaipal S. Choudhary ◽

Santosh S. Mali ◽

Naiyar Naaz ◽

Sandip Malik ◽

Bikash Das ◽

...

Keyword(s):

Climate Change ◽

Fruit Fly ◽

Temporal Variations ◽

Future Climate Change ◽

Climate Change Scenarios ◽

Population Abundance ◽

Peach Fruit ◽

Bactrocera Zonata ◽

Phenology Model ◽

Abundance And Distribution

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Persistence of the Swiss Needle Cast Outbreak in Oregon Coastal Douglas-Fir and New Insights from Research and Monitoring

Journal of Forestry ◽

10.1093/jofore/fvab011 ◽

2021 ◽

Author(s):

David C Shaw ◽

Gabriela Ritóková ◽

Yung-Hsiang Lan ◽

Doug B Mainwaring ◽

Andrew Russo ◽

...

Keyword(s):

Climate Change ◽

Regional Scale ◽

Emerging Diseases ◽

Douglas Fir ◽

Landscape Patterns ◽

Needle Cast ◽

Plantation Management ◽

Environmental Controls ◽

Swiss Needle Cast ◽

Improvement Programs

Abstract Swiss needle cast (SNC), caused by Nothophaeocryptopus gaeumannii, is a foliage disease of Douglas-fir (Pseudotsuga menziesii), that reduces growth in native stands and exotic plantations worldwide. An outbreak of SNC began in coastal Oregon in the mid-1990s and has persisted since that time. Here we review the current state of knowledge after 24 years of research and monitoring, with a focus on Oregon, although the disease is significant in coastal Washington and has recently emerged in southwestern British Columbia. We present new insights into SNC distribution, landscape patterns, disease epidemiology and ecology, host-pathogen interactions, trophic and hydrologic influences, and the challenges of Douglas-fir plantation management in the presence of the disease. In Oregon, the SNC outbreak has remained geographically contained but has intensified. Finally, we consider the implications of climate change and other recently emerged foliage diseases on the future of Douglas-fir plantation management. Study Implications: Douglas-fir tree growers need to consider Swiss needle cast (SNC) and other emerging foliage diseases as SNC has not abated over the past 24 years, and along with other emerging diseases, it continues to pose a threat to Douglas-fir plantation productivity. Douglas-fir management in western Oregon remains important, such that a knowledge of disease impacts and effective silvicultural responses is key. Managers should carefully consider whether alternative species may be ecologically or economically beneficial in some situations while tree improvement programs must continue to breed for tolerance to SNC. Research shows that regional scale foliage disease outbreaks can result in trophic cascades and hydrologic changes that affects more than just the trees. The environmental controls on the SNC epidemic imply that climate change could strongly influence future directions of the outbreak, with the greatest threats to trees at higher elevations.

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Projections for Mexico’s Tropical Rainforests Considering Ecological Niche and Climate Change

Forests ◽

10.3390/f12020119 ◽

2021 ◽

Vol 12 (2) ◽

pp. 119

Author(s):

Antonio Fidel Santos-Hernández ◽

Alejandro Ismael Monterroso-Rivas ◽

Diódoro Granados-Sánchez ◽

Antonio Villanueva-Morales ◽

Malinali Santacruz-Carrillo

Keyword(s):

Climate Change ◽

Ecological Niche ◽

Potential Distribution ◽

Tropical Rainforest ◽

Statistical Significance ◽

Climate Change Scenarios ◽

Climate Conditions ◽

Tropical Regions ◽

Temperature And Precipitation ◽

Ecological Importance

The tropical rainforest is one of the lushest and most important plant communities in Mexico’s tropical regions, yet its potential distribution has not been studied in current and future climate conditions. The aim of this paper was to propose priority areas for conservation based on ecological niche and species distribution modeling of 22 species with the greatest ecological importance at the climax stage. Geographic records were correlated with bioclimatic temperature and precipitation variables using Maxent and Kuenm software for each species. The best Maxent models were chosen based on statistical significance, complexity and predictive power, and current potential distributions were obtained from these models. Future potential distributions were projected with two climate change scenarios: HADGEM2_ES and GFDL_CM3 models and RCP 8.5 W/m2 by 2075–2099. All potential distributions for each scenario were then assembled for further analysis. We found that 14 tropical rainforest species have the potential for distribution in 97.4% of the landscape currently occupied by climax vegetation (0.6% of the country). Both climate change scenarios showed a 3.5% reduction in their potential distribution and possible displacement to higher elevation regions. Areas are proposed for tropical rainforest conservation where suitable bioclimatic conditions are expected to prevail.

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Spatial and temporal variations of faecal indicator bacteria in Lake Bunyonyi, South-Western Uganda

SN Applied Sciences ◽

10.1007/s42452-021-04684-4 ◽

2021 ◽

Vol 3 (7) ◽

Author(s):

Alex Saturday ◽

Thomas J. Lyimo ◽

John Machiwa ◽

Siajali Pamba

Keyword(s):

Health Risks ◽

Rank Correlation ◽

Temporal Variations ◽

Indicator Bacteria ◽

Spatial And Temporal Variations ◽

Wet Season ◽

Recreational Waters ◽

Faecal Indicator Bacteria ◽

E Coli ◽

Spearman’S Rank Correlation

AbstractBackground Microbial water quality serves to indicate health risks associated with the consumption of contaminated water. Nevertheless, little is known about the microbiological characteristics of water in Lake Bunyonyi. This study was therefore undertaken to examine the spatial and temporal variations of faecal indicator bacteria (FIB) in relation to physicochemical parameters in Lake Bunyonyi. Result The FIB concentration was consistently measured during sampling months and correlated with each other showing the presumed human faecal pollution in the lake. The highest concentration values for E. coli (64.7 ± 47.3 CFU/100 mL) and enterococci (24.6 ± 32.4 CFU/100 mL were obtained in the station close to the Mugyera trading centre. On a temporal basis, the maximum values were recorded during the rainy season in October 2019 (70.7 ± 56.5 CFU/100 mL for E. coli and 38.44 ± 31.8 CFU/100 mL for enterococci. FIB did not differ significantly among the study stations (p > 0.05) but showed significant temporal variations among the months (p < 0.05) with concentrations being significantly high in wet season than dry season (U = 794, p < 0.0001 for E. coli; U = 993.5, p = 0.008 for enterococci). Spearman’s rank correlation revealed that FIB concentrations were significantly positively correlated with turbidity and DO concentration levels (p < 0.05). Approximately 97.2% of the water samples had E. coli and enterococci concentrations levels below USEPA threshold for recreational waters. Likewise, 98.1 and 90.7% of samples recorded E. coli and enterococci counts exceeding the UNBS, APHA, WHO and EU threshold values for drinking water. Conclusion The FIB counts show that the Lake Bunyonyi water is bacteriologically unsuitable for drinking unless it is treated since the FIB pose health risks to consumers. Besides, the water can be used for recreational purposes.

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Comparative Analysis or Precipitation Variation Characteristics between Subtropical Monsoon Climate and Temperate Monsoon Climate-Take Changsha and Chengde for Example

Tobacco Regulatory Science ◽

10.18001/trs.7.5.29 ◽

2021 ◽

Vol 7 (5) ◽

pp. 1113-1122

Author(s):

Bo Chen ◽

Shi-jun Xu ◽

Xin-ping Zhang ◽

Yi Xie

Keyword(s):

Climate Change ◽

Extreme Precipitation ◽

Precipitation Intensity ◽

Annual Precipitation ◽

Wet Season ◽

Precipitation Frequency ◽

Extreme Precipitation Events ◽

Average Precipitation ◽

Autumn And Winter ◽

Average Annual Precipitation

Using the methods of literature review, regression analysis and moving average, this paper selects the daily precipitation of Changsha and Chengde from 1951 to 1986 as samples, and analyzes the average precipitation, precipitation frequency, precipitation intensity, extreme precipitation time and other indicators of Changsha and Chengde from the perspective of interannual and seasonal changes Trends. The researches show that: the average precipitation of Changsha in the 36 years is 1151.2mm, spring is the wet season, autumn and winter are the dry seasons, and the maximum average precipitation is in spring; the average annual precipitation, precipitation frequency in spring, summer and winter, annual precipitation frequency, annual precipitation intensity and extreme precipitation events show a decreasing trend. The average annual precipitation of Chengde city is 454.1 mm, wet season in summer and dry season in spring, autumn and winter; the average annual precipitation, precipitation in four seasons, annual precipitation frequency, precipitation frequency in spring, autumn and winter, annual precipitation intensity and extreme precipitation events show a decreasing trend, while the precipitation frequency in summer shows an increasing trend. The study of regional climate change based on the time series data of this stage is of great significance to comprehensively understand the law of regional climate change and predict the future trend of climate change.

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Subsoil organic carbon turnover is dominantly controlled by soil properties in grasslands across China

10.5194/egusphere-egu21-2413 ◽

2021 ◽

Author(s):

Yuehong Shi ◽

Xiaolu Tang ◽

Peng Yu ◽

Li Xu ◽

Guo Chen ◽

...

Keyword(s):

Climate Change ◽

Organic Carbon ◽

Soil Properties ◽

Soil Carbon ◽

Carbon Turnover ◽

Area Index ◽

Important Indicator ◽

Environmental Controls ◽

Biogeochemical Models ◽

Soc Stock

Soil carbon turnover time (&#964;, year) is an important indicator of soil carbon stability, and a major factor in determining soil carbon sequestration capacity. Many studies investigated &#964; in the topsoil or the first meter underground, however, little is known about subsoil &#964; (0.2 &#8211; 1.0 m) and its environmental drivers, while world subsoils below 0.2 m accounts for the majority of total soil organic carbon (SOC) stock and may be as sensitive as that of the topsoil to climate change. We used the observations from the published literatures to estimate subsoil &#964; (the ratio of SOC stock to net primary productivity) in grasslands across China and employed regression analysis to detect the environmental controls on subsoil &#964;. Finally, structural equation modelling (SEM) was applied to identify the dominant environmental driver (including climate, vegetation and soil). Results showed that subsoil &#964; varied greatly from 5.52 to 702.17 years, and the mean (&#177; standard deviation) subsoil &#964; was 118.5 &#177; 97.8 years. Subsoil &#964; varied significantly among different grassland types that it was 164.0 &#177; 112.0 years for alpine meadow, 107.0 &#177; 47.9 years for alpine steppe, 177.0 &#177; 143.0 years for temperate desert steppe, 96.6 &#177; 88.7 years for temperate meadow steppe, 101.0 &#177; 75.9 years for temperate typical steppe. Subsoil &#964; significantly and negatively correlated (p < 0.05) with vegetation index, leaf area index and gross primary production, highlighting the importance of vegetation on &#964;. Mean annual temperature (MAT) and precipitation (MAP) had a negative impact on subsoil &#964;, indicating a faster turnover of soil carbon with the increasing of MAT or MAP under ongoing climate change. SEM showed that soil properties, such as soil bulk density, cation exchange capacity and soil silt, were the most important variables driving subsoil &#964;, challenging our current understanding of climatic drivers (MAT and MAP) controlling on topsoil &#964;, further providing new evidence that different mechanisms control topsoil and subsoil &#964;. These conclusions demonstrated that different environmental controls should be considered for reliable prediction of soil carbon dynamics in the top and subsoils in biogeochemical models or earth system models at regional or global scales.

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Equilibrium Spin-up of Cold and Warm Permafrost Models

10.5194/egusphere-egu21-13922 ◽

2021 ◽

Author(s):

Cameron Ross ◽

Ryley Beddoe ◽

Greg Siemens

Keyword(s):

Climate Change ◽

Temperature Response ◽

Ground Temperature ◽

Future Climate Change ◽

Climate Projections ◽

Multiple Model ◽

Climate Data ◽

Ground Temperatures ◽

C Cycle ◽

Warm Permafrost

Initialization (spin-up) of a numerical ground temperature model is a critical but often neglected step for solving heat transfer problems in permafrost. Improper initialization can lead to significant underlying model drift in subsequent transient simulations, distorting the effects on ground temperature from future climate change or applied infrastructure. &#160;In a typical spin-up simulation, a year or more of climate data are applied at the surface and cycled repeatedly until ground temperatures are declared to be at equilibrium with the imposed boundary conditions, and independent of the starting conditions.Spin-up equilibrium is often simply declared after a specified number of spin-up cycles. In few studies, equilibrium is visually confirmed by plotting ground temperatures vs spin-up cycles until temperatures stabilize; or is declared when a certain inter-cycle-temperature-change threshold is met simultaneously at all depths, such as &#8710;T &#8804; 0.01oC per cycle. In this study, we investigate the effectiveness of these methods for determining an equilibrium state in a variety of permafrost models, including shallow and deep (10 &#8211; 200 m), high and low saturation soils (S = 100 and S = 20), and cold and warm permafrost (MAGT = ~-10 oC and >-1 oC). The efficacy of equilibrium criteria 0.01oC/cycle and 0.0001oC/cycle are compared. Both methods are shown to prematurely indicate equilibrium in multiple model scenarios. &#160;Results show that no single criterion can programmatically detect equilibrium in all tested models, and in some scenarios can result in up to 10oC temperature error or 80% less permafrost than at true equilibrium. &#160;A combination of equilibrium criteria and visual confirmation plots is recommended for evaluating and declaring equilibrium in a spin-up simulation.Long-duration spin-up is particularly important for deep (10+&#160;m) ground models where thermal inertia of underlying permafrost slows the ground temperature response to surface forcing, often requiring hundreds or even thousands of spin-up cycles to establish equilibrium. Subsequent transient analyses also show that use of a properly initialized 100 m permafrost model can reduce the effect of climate change on mean annual ground temperature of cold permafrost by more than 1 oC and 3 oC under RCP2.6 and RCP8.5 climate projections, respectively, when compared to an identical 25 m model. These results have important implications for scientists, engineers and policy makers that rely on model projections of long-term permafrost conditions.

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Reconstruction of recent climate change in Alaska from the Aurora Peak ice core, central Alaska

Climate of the Past ◽

10.5194/cp-11-217-2015 ◽

2015 ◽

Vol 11 (2) ◽

pp. 217-226 ◽

Cited By ~ 8

Author(s):

A. Tsushima ◽

S. Matoba ◽

T. Shiraiwa ◽

S. Okamoto ◽

H. Sasaki ◽

...

Keyword(s):

Climate Change ◽

Accumulation Rate ◽

Ice Core ◽

Chemical Species ◽

Volcanic Eruptions ◽

Gulf Of Alaska ◽

Temporal Variations ◽

Storm Activity ◽

Alaska Range ◽

Recent Climate

Abstract. A 180.17 m ice core was drilled at Aurora Peak in the central part of the Alaska Range, Alaska, in 2008 to allow reconstruction of centennial-scale climate change in the northern North Pacific. The 10 m depth temperature in the borehole was −2.2 °C, which corresponded to the annual mean air temperature at the drilling site. In this ice core, there were many melt–refreeze layers due to high temperature and/or strong insolation during summer seasons. We analyzed stable hydrogen isotopes (δD) and chemical species in the ice core. The ice core age was determined by annual counts of δD and seasonal cycles of Na+, and we used reference horizons of tritium peaks in 1963 and 1964, major volcanic eruptions of Mount Spurr in 1992 and Mount Katmai in 1912, and a large forest fire in 2004 as age controls. Here, we show that the chronology of the Aurora Peak ice core from 95.61 m to the top corresponds to the period from 1900 to the summer season of 2008, with a dating error of ± 3 years. We estimated that the mean accumulation rate from 1997 to 2007 (except for 2004) was 2.04 m w.eq. yr-1. Our results suggest that temporal variations in δD and annual accumulation rates are strongly related to shifts in the Pacific Decadal Oscillation index (PDOI). The remarkable increase in annual precipitation since the 1970s has likely been the result of enhanced storm activity associated with shifts in the PDOI during winter in the Gulf of Alaska.

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