scholarly journals Seasonally frozen soil modifies patterns of boreal peatland wildfire vulnerability

2018 ◽  
Author(s):  
Simon J. Dixon ◽  
Max C. Lukenbach ◽  
Nicholas Kettridge ◽  
Kevin J. Devito ◽  
Richard M. Petrone ◽  
...  
Keyword(s):  
Water Balance ◽  
Water Table ◽  
High Water ◽  
Vital Role ◽  
Frozen Soil ◽  
Near Surface ◽  
Smoldering Combustion ◽  
Global Carbon ◽  
Frost Layer ◽  
Water Contents

Abstract. Peatlands play a vital role in the global carbon cycle, acting as one of the most important global carbon sinks. However, an understanding of their environmental processes, particularly in relation to a changing climate, remains inchoate. In particular, the role seasonal ice or frost layers play in altering spring water balance, and thus vulnerability to deep smoldering combustion during wildfire is not fully understood. Continental boreal peatlands are characterized by periodic wildfire disturbance, which releases carbon, but can also inhibit short-term peat productivity and carbon sequestration as the peatland recovers, with recovery timescales linked to the severity or depth of burning. The presence of seasonal frost layers coincides with drier spring conditions and an enhanced risk of wildfire. Two-dimensional numerical modelling was conducted using HYDRUS-2D, a variably saturated flow model, to simulate water balance in the vadose zone and assess vulnerability to fire during prolonged rain free periods in the presence of continuous and discontinuous frost. Our results show there is a lack of horizontal water transfer which increases spatial variability in water balance and leads to pronounced heterogeneity in the risk of smoldering combustion and the potential for deep combustion at hummock-hollow interfaces. Peatlands are broadly divided into areas which are characterized by a dry near-surface and high water contents at depth (water conserving), and those with a wetter near-surface, but comparatively lower water contents at depth (productive). Those areas with dry near-surfaces will be more vulnerable to wildfire and characterize around 50 % of hummocks and 25 % of hollows. In the presence of a seasonal frost layer productive peat layers in hollows will show substantial drying out due to the frost layer disconnecting the surface from the water table; this approximately doubles the proportion of hollows vulnerable to wildfire. Breaks in the frost layer allows areas to maintain hydrological connectivity to a falling water table, but this connectivity is limited in lateral extent and can drive further spatial heterogeneity in vulnerability to wildfire ignition in the weeks when the frost layer begins to thaw.

scholarly journals Estimation of potential evapotranspiration with shallow lysimeters in a forest tree nursery

1995 ◽  
Vol 71 (6) ◽  
pp. 755-758 ◽  
Author(s):  
Jean Stein ◽  
Richard Caissy ◽  
André P. Plamondon ◽  
Pierre Y. Bernier
Keyword(s):  
Water Balance ◽  
Picea Glauca ◽  
Potential Evapotranspiration ◽  
Black Spruce ◽  
White Spruce ◽  
High Water ◽  
Forest Tree ◽  
Irrigation Scheduling ◽  
Daily Evapotranspiration ◽  
Water Contents

Daily evapotranspiration values (ETL) were obtained during three consecutive summers from water balance measurements on eight shallow drainable lysimeters in similarly planted nursery beds of either white spruce [Picea glauca (Moench) Voss] or black spruce [Picea mariana (Mill) B.S.P.]. Values of ETL and of potential evapotranspiration (PET), calculated with the Penman equation, were nearly equal for most of the sampled days during the first two years. During the last year of study, the ratio ETL/PET was reduced to 0.8 due to a lack of water input (precipitation and irrigation) to the lysimeters. Water balance measurements from the surrounding seedling beds showed that values of actual evapotranspiration (AET) for the first two years were 0.61 times those of either PET or ETL. Rates of evapotranspiration in the lysimeters remained high because of the high water contents in the shallow lysimeters induced by the presence of a zero tension plane at the base of the lysimeters, above the drainage holes. Results indicate that well-watered shallow lysimeters can be used to estimate values of PET and be used directly for the purpose of driving water balance models for irrigation scheduling. Key words: water relations, irrigation scheduling, lysimeters, evapotranspiration, white spruce, black spruce

scholarly journals Stratigraphy, chronology and palaeontology of the Tertiary rocks of the Cheringoma Plateau, Mozambique

2021 ◽  
Vol 77 (1) ◽  
pp. 187-213
Author(s):  
Marion Bamford ◽  
Martin Pickford
Keyword(s):  
Water Table ◽  
High Water ◽  
Late Eocene ◽  
Rift System ◽  
Fossil Plants ◽  
Near Surface ◽  
Marine Molluscs ◽  
History Of Interpretation ◽  
History Of ◽  
African Rift

The discovery of fossil plants, marine molluscs and mammals in the Mazamba Formation, Cheringoma Plateau, Mozambique, opens a new chapter in the study of this part of the African Rift System. The evidence suggests that the Mazamba Formation is older than previously reported, probably late Eocene rather than Miocene. The fossil wood and stems indicate a frost-free tropical humid environment and a high water table soon after deposition, and the marine molluscs and mammals indicate proximity to the sea. There is also evidence for the occurrence of pans in the area during the late Eocene which also suggest a near-surface water table. This paper discusses the history of interpretation of the geology of the Cheringoma Plateau and describes and interprets the fossil plants, molluscs and mammals collected in 2012 and 2013. It is concluded that the Mazamba Formation, which overlies the fully marine Lutetian-Bartonian Cheringoma Limestone, is a coastal facies (fluvio-deltaic, lagoonal and onshore deposits) that accumulated on top of the marine limestones as sea level dropped late in the Bartonian. Mammalian bones from the White Patch sites represent a heavily built species about the dimensions of a pygmy hippopotamus, probably belonging to the order Embrithopoda. If so, then the Mazamba Formation is likely to correlate to the latest Bartonian or early Priabonian rather than to the Miocene as previously assumed.

A review of the composition and evolution of hydrocarbon gases during solidification of the Ilímaussaq alkaline complex, South Greenland

2001 ◽  
pp. 159-166 ◽  
Author(s):  
Jens Konnerup-Madsen
Keyword(s):  
Nepheline Syenite ◽  
Subsequent Development ◽  
High Water ◽  
Vapour Phase ◽  
Low Carbon ◽  
Low Oxygen ◽  
Alkaline Complex ◽  
Hydrocarbon Gases ◽  
Wide Range ◽  
Water Contents

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Konnerup-Madsen, J. (2001). A review of the composition and evolution of hydrocarbon gases during solidification of the Ilímaussaq alkaline complex, South Greenland. Geology of Greenland Survey Bulletin, 190, 159-166. https://doi.org/10.34194/ggub.v190.5187 _______________ Fluid inclusions in minerals from agpaitic nepheline syenites and hydrothermal veins in the Ilímaussaq complex and in similar agpaitic complexes on the Kola Peninsula, Russia, are dominated by hydrocarbon gases (predominantly methane) and hydrogen. Such volatile compositions differ considerably from those of most other igneous rocks and their formation and entrapment in minerals reflects low oxygen fugacities and a wide range of crystallisation temperatures extending to a low-temperature solidus. Their composition reflects initial low carbon contents and high water contents of the magma resulting in the exsolution of a waterrich CO2–H2O dominated vapour phase. Fractionation of chlorides into the vapour phase results in high salinities and the subsequent development of a heterogeneous vapour phase with a highly saline aqueous-rich fraction and a methane-dominated fraction, with preferential entrapment of the latter, possibly due to different wetting characteristics. The light stable isotope compositions support an abiogenic origin for the hydrocarbons in agpaitic nepheline syenite complexes.

scholarly journals Structure, Diversity, and Environmental Determinants of High-Latitude Threatened Conifer Forests

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 775
Author(s):  
Carlos Esse ◽  
Francisco Correa-Araneda ◽  
Cristian Acuña ◽  
Rodrigo Santander-Massa ◽  
Patricio De Los Ríos-Escalante ◽  
...  
Keyword(s):  
Water Table ◽  
Environmental Variables ◽  
National Park ◽  
High Water ◽  
Forest Communities ◽  
Competitive Effect ◽  
Forest Patches ◽  
Last Glaciation ◽  
The World ◽  
Local Topography

Pilgerodendron uviferum (D. Don) Florin is an endemic, threatened conifer that grows in South America. In the sub-Antarctic territory, one of the most isolated places in the world, some forest patches remain untouched since the last glaciation. In this study, we analyze the tree structure and tree diversity and characterize the environmental conditions where P. uviferum-dominated stands develop within the Magellanic islands in Kawésqar National Park, Chile. An environmental matrix using the databases WorldClim and SoilGrids and local topography variables was used to identify the main environmental variables that explain the P. uviferum-dominated stands. PCA was used to reduce the environmental variables, and PERMANOVA and nMDS were used to evaluate differences among forest communities. The results show that two forest communities are present within the Magellanic islands. Both forest communities share the fact that they can persist over time due to the high water table that limits the competitive effect from other tree species less tolerant to high soil water table and organic matter. Our results contribute to knowledge of the species’ environmental preference and design conservation programs.

Constraints on the formation of the giant Daheishan porphyry Mo deposit (NE China) from whole-rock and accessory mineral geochemistry

2021 ◽  
Author(s):  
Kai Xing ◽  
Qihai Shu ◽  
David R Lentz
Keyword(s):  
High Water ◽  
Accessory Mineral ◽  
Ne China ◽  
Accessory Minerals ◽  
Slab Rollback ◽  
Continental Arc ◽  
Arc Setting ◽  
Porphyry Mo Deposit ◽  
T Values ◽  
Water Contents

Abstract There are more than 90 porphyry (or skarn) Mo deposits in northeastern China with Jurassic or Cretaceous ages. These are thought to have formed mainly in a continental arc setting related to the subduction of the Paleo-Pacific oceanic plate in the Jurassic and subsequent slab rollback in the early Cretaceous. The Jurassic Daheishan porphyry Mo deposit is one of the largest Mo deposits in NE China, which contains 1.09 Mt Mo with an average Mo grade of 0.07%. To better understand the factors that could have controlled Mo mineralization at Daheishan, and potentially in other similar porphyry Mo deposits in NE China, the geochemical and isotopic compositions of the ore-related granite porphyry and biotite granodiorite, and the magmatic accessory minerals apatite, titanite and zircon from the Daheishan intrusions, were investigated so as to evaluate the potential roles that magma oxidation states, water contents, sulfur and metal concentrations could have played in the formation of the deposit. Magmatic apatite and titanite from the causative intrusions show similar εNd(t) values from -1.1 to 1.4, corresponding to TDM2 ages ranging from 1040 to 840 Ma, which could be accounted for by a mixing model through the interaction of mantle-derived basaltic melts with the Precambrian lower crust. The Ce and Eu anomalies of the magmatic accessory minerals have been used as proxies for magma redox state, and the results suggest that the ore-forming magmas are highly oxidized, with an estimated ΔFMQ range of + 1.8 to + 4.1 (+2.7 in average). This is also consistent with the high whole-rock Fe2O3/FeO ratios (1.3–26.4). The Daheishan intrusions display negligible Eu anomalies (Eu/Eu* = 0.7–1.1) and have relatively high Sr/Y ratios (40–94) with adakitic signatures; they also have relatively high Sr/Y ratios in apatite and titanite. These suggest that the fractionation of amphibole rather than plagioclase is dominant during the crystallization of the ore-related magmas, which further indicates a high magmatic water content (e.g., >5 wt%). The magmatic sulfur concentrations were calculated using available partitioning models for apatite from granitoids, and the results (9–125 ppm) are indistinguishable from other mineralized, subeconomic and barren intrusions. Furthermore, Monte Carlo modelling has been conducted to simulate the magmatic processes associated with the formation of the Daheishan Mo deposit, and the result reveals that a magma volume of ∼280 km3 with ∼10 ppm Mo was required to form the Mo ores containing 1.09 Mt Mo in Daheishan. The present study suggests that a relatively large volume of parental magmas with high oxygen fugacities and high water contents is essential for the generation of a giant porphyry Mo deposit like Daheishan, whereas a specific magma composition (e.g., with unusually high Mo and/or S concentrations), might be less critical.

scholarly journals Sensitivity of groundwater recharge using climatic analogues and HYDRUS-1D

2012 ◽  
Vol 16 (8) ◽  
pp. 2485-2497 ◽  
Author(s):  
B. Leterme ◽  
D. Mallants ◽  
D. Jacques
Keyword(s):  
Water Balance ◽  
Groundwater Recharge ◽  
Potential Evapotranspiration ◽  
Future Climate ◽  
Annual Precipitation ◽  
Balance Model ◽  
Subtropical Climate ◽  
Northern Spain ◽  
Near Surface ◽  
Hydrus 1D

Abstract. The sensitivity of groundwater recharge to different climate conditions was simulated using the approach of climatic analogue stations, i.e. stations presently experiencing climatic conditions corresponding to a possible future climate state. The study was conducted in the context of a safety assessment of a future near-surface disposal facility for low and intermediate level short-lived radioactive waste in Belgium; this includes estimation of groundwater recharge for the next millennia. Groundwater recharge was simulated using the Richards based soil water balance model HYDRUS-1D and meteorological time series from analogue stations. This study used four analogue stations for a warmer subtropical climate with changes of average annual precipitation and potential evapotranspiration from −42% to +5% and from +8% to +82%, respectively, compared to the present-day climate. Resulting water balance calculations yielded a change in groundwater recharge ranging from a decrease of 72% to an increase of 3% for the four different analogue stations. The Gijon analogue station (Northern Spain), considered as the most representative for the near future climate state in the study area, shows an increase of 3% of groundwater recharge for a 5% increase of annual precipitation. Calculations for a colder (tundra) climate showed a change in groundwater recharge ranging from a decrease of 97% to an increase of 32% for four different analogue stations, with an annual precipitation change from −69% to −14% compared to the present-day climate.

A comprehensive review on the medicinal importance; biological and therapeutic efficacy of Lagenaria siceraria (Mol.) (bottle gourd) Standley fruit

2021 ◽  
Vol 21 ◽  
Author(s):  
Muhammad Zahoor ◽  
Muhammad Ikram ◽  
Nausheen Nazir ◽  
Sumaira Naz ◽  
Gaber El-Saber Batiha ◽  
...  
Keyword(s):  
Herbal Medicines ◽  
High Water ◽  
Bottle Gourd ◽  
Herbal Remedies ◽  
Lagenaria Siceraria ◽  
Synthetic Drugs ◽  
Domestic Plant ◽  
Phytochemical Constituents ◽  
Cucurbitaceae Family ◽  
Water Contents

: Herbal remedies have been employed for the treatment and management of different diseases for ages. Herbal medicines are a promising choice over modern synthetic drugs because of their low side effects and are thus considered safe and effective in treating human diseases. Lagenaria siceraria (Mol.) Standley fruit (Bottle gourd) belongs to the Cucurbitaceae family that has been used in a different system of traditional medication to treat various diseases. This is a domestic plant that provides food as well as medication. This vegetable has low caloric values and high water contents. The edible portion of it contains phytochemicals like vitamins, proteins, choline, minerals, terpenoids, flavonoids etc. Several bioactive compounds have been isolated from L. siceraria, including triterpenoids, sterols, cucurbitacins, flavones, C-glycosides and β-glycosides. Researchers have evaluated various parts of this plant viz., fruit, root, flowers, and leaves for pharmacological activities like antianxiety, antidepressant, diuretic, antimicrobial, cytotoxic, antihyperlipidemic, cardioprotective, analgesic, anti-inflammatory, anthelmintic, anti-hyperglycemic, antihepatotoxic, anti-urolithiatic, antistress, antiulcer, anticancer, hepatoprotective, anthelmintic, immunomodulatory, and antioxidant. In this review, an attempt has been made to explore its phytochemical constituents, traditional, medicinal, and pharmacological uses to highlight the therapeutic importance of this well-known plant. This would be helpful in reviving its importance and highlight its several promising aspects to encourage researchers for further research on L. siceraria.

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