Cold Soils Research Articles

Selenium nanoparticles with boron salt-based compound act synergistically against the brown-rot Serpula lacrymans

The spherical polyvinylpyrrolidone (PVP) stabilized red Se NPs (PVP–Se NPs) with a mean size of ∼45 nm were prepared via upgraded one-step wet chemical reduction by L-cysteine, which considerably shortened the synthesis procedure. Their morphological features were characterized by high-resolution scanning transmission electron microscopy, UV-VIS spectroscopy, and small-angle X-ray scattering method. The toxicological properties of PVP-Se NPs were analyzed by colorimetric cell viability assay based on the reduction of a yellow tetrazolium salt (XTT) in mitochondria, a further assay based on the measurement of lactate dehydrogenase (LDH) release from damaged cell membrane, and finally by cell proliferation assay. The antifungal effect of PVP-Se NPs alone, or in a mixture of commercial fungicide containing 2% of boric acid, 2% alkylbenzyldimethylammonium chloride, and ∼0.9% ethanolamine in distilled water was tested on the brown-rot fungus Serpula lacrymans The fungus belongs to important basidiomycetes causing economically significant decay of wood, mainly in houses and particularly cold soil cellars. The average mass loss tests performed on spruce wood blocks after four months of inoculation with S. lacrymans showed an enhanced antifungal effect of the mixture of PVP-Se NPs with a commercial fungicide than a PVP-Se NPs or commercial fungicide alone, which proved their synergistic effect on inhibiting fungi growth. Finally, scanning electron microscopy analysis of outer and inner parts of wood blocks treated with our novel mixture was performed.

Moisture Fluctuations Modulate Abiotic and Biotic Limitations of H2 Soil Uptake

AbstractSoil uptake by H2‐oxidizing bacteria is the main sink of the global hydrogen cycle, accounting for nearly 80% of the atmospheric H2 consumption. Although the H2 uptake is strongly influenced by soil moisture, little attention has been paid to coherently couple the water and hydrogen dynamics in soils. Toward this goal, we improve the mechanistic representation of the H2 uptake as a function of soil moisture and highlight the role of the moisture temporal fluctuations on the biotic consumption of H2. The results show that, due to the strongly nonlinear relationship between soil moisture and H2 uptake, addressing the dry‐wet sequences is necessary to characterize the H2 uptake in semi‐arid regions correctly. From novel analytical relationships validated with field data, we also infer the biotic and abiotic limitations in the global soil H2 uptake. It is shown that, diffusion generally limits the uptake in humid temperate and tropical regions, while biotic limitations tend to occur in very arid or cold soils. Finally, we discuss the implications that climate change may have on the H2 soil sink.

Temperature sensitivity of Antarctic soil-humic substance degradation by cold-adapted bacteria.

Heteropolymer humic substances (HS) are the largest constituents of soil organic matter and are key components that affect plant and microbial growth in maritime Antarctic tundra. We investigated HS decomposition in Antarctic tundra soils from distinct sites by incubating samples at 5°C or 8°C (within a natural soil thawing temperature range of -3.8°C to 9.6°C) for 90 days (average Antarctic summer period). This continuous 3-month artificial incubation maintained a higher total soil temperature than that in natural conditions. The long-term warming effects rapidly decreased HS content during the initial incubation, with no significant difference between 5°C and 8°C. In the presence of Antarctic tundra soil heterogeneity, the relative abundance of Proteobacteria (one of the major bacterial phyla in cold soil environments) increased during HS decomposition, which was more significant at 8°C than at 5°C. Contrasting this, the relative abundance of Actinobacteria (another major group) did not exhibit any significant variation. This microcosm study indicates that higher temperatures or prolonged thawing periods affect the relative abundance of cold-adapted bacterial communities, thereby promoting the rate of microbial HS decomposition. The resulting increase in HS-derived small metabolites will possibly accelerate warming-induced changes in the Antarctic tundra ecosystem.

The statistical sensitivity of highway project cost to geo-heterogeneity in the tropics

PurposeThe study is carried out to analytically reconnoiter geotechnical index properties of subgrade soils as key variables that shape the cost profile of road infrastructure projects in a tropical geographic setting with starkly heterogenous ground conditions.Design/methodology/approachUsing the Niger Delta region, as a point of reference, data on geotechnical index properties of subgrade soils at spatially dispersed locations for 61 completed highway projects are collated. Exploratory statistical tests were carried out to infer significant associations with final project costs before regression analysis. Regression analysis is principally deployed as an explanatory analytical tool, relevant to quantify the sensitivity of highway project costs to the individual and collective impact of geotechnical variables.FindingsSeveral parameters of expansivity and compressibility exhibited significantly strong associations with the final costs recorded on the highway projects. The statistical analysis further established a cause-effect relationship, whereby small changes in the geotechnical properties of sub-grade soils at project locations, would result in disproportionately large changes in the cost of road construction.Practical implicationsThe study findings provide insight into the sensitivity of road construction costs to geotechnical variables, which can serve as a useful input in financial risk analysis for development appraisal and the generation of location adjustment factors.Originality/valueThe study statistically demonstrates location-induced construction cost profiles, triggered in response to the spatial geotechnical variability and occurrence of problem subgrade soils in the humid tropics, which may be different from those traditionally established in studies of cold and temperate climate soils.

TILLING-by-Sequencing+ Reveals the Role of Novel Fatty Acid Desaturases (GmFAD2-2s) in Increasing Soybean Seed Oleic Acid Content.

Soybean is the second largest source of oil worldwide. Developing soybean varieties with high levels of oleic acid is a primary goal of the soybean breeders and industry. Edible oils containing high level of oleic acid and low level of linoleic acid are considered with higher oxidative stability and can be used as a natural antioxidant in food stability. All developed high oleic acid soybeans carry two alleles; GmFAD2-1A and GmFAD2-1B. However, when planted in cold soil, a possible reduction in seed germination was reported when high seed oleic acid derived from GmFAD2-1 alleles were used. Besides the soybean fatty acid desaturase (GmFAD2-1) subfamily, the GmFAD2-2 subfamily is composed of five members, including GmFAD2-2A, GmFAD2-2B, GmFAD2-2C, GmFAD2-2D, and GmFAD2-2E. Segmental duplication of GmFAD2-1A/GmFAD2-1B, GmFAD2-2A/GmFAD2-2C, GmFAD2-2A/GmFAD2-2D, and GmFAD2-2D/GmFAD2-2C have occurred about 10.65, 27.04, 100.81, and 106.55 Mya, respectively. Using TILLING-by-Sequencing+ technology, we successfully identified 12, 8, 10, 9, and 19 EMS mutants at the GmFAD2-2A, GmFAD2-2B, GmFAD2-2C, GmFAD2-2D, and GmFAD2-2E genes, respectively. Functional analyses of newly identified mutants revealed unprecedented role of the five GmFAD2-2A, GmFAD2-2B, GmFAD2-2C, GmFAD2-2D, and GmFAD2-2E members in controlling the seed oleic acid content. Most importantly, unlike GmFAD2-1 members, subcellular localization revealed that members of the GmFAD2-2 subfamily showed a cytoplasmic localization, which may suggest the presence of an alternative fatty acid desaturase pathway in soybean for converting oleic acid content without substantially altering the traditional plastidial/ER fatty acid production.

Comparative Genomic Analysis of Arctic Permafrost Bacterium Nesterenkonia sp. PF2B19 to Gain Insights into Its Cold Adaptation Tactic and Diverse Biotechnological Potential

Nesterenkonia sp. PF2B19, a psychrophile was isolated from 44,800-year-old permafrost soil. This is the first report on comparative genomics of Nesterenkonia sp. isolated from Arctic. Genome of PF2B19 exhibited the presence of a vast array of genetic determinants involved in cold adaptation i.e., response to cold-associated general, osmotic, and oxidative stress. These genomic attributes proved to be valuable in unraveling the adaptive tactics employed by PF2B19 for survival in the cold permafrost soils of the Arctic. Genomic analysis of PF2B19 has given some valuable insight into the biotechnological potential of this strain, particularly as a source of cold-active enzymes, as a bioremediating agent and as plant growth-promoting bacteria.

Efficacy of nonfumigant nematicides against Meloidogyne javanica as affected by soil temperature under pasteurized and natural soil conditions.

Biotic and abiotic factors such as microbes and soil temperature can affect nematicide efficacy. Two experiments were conducted to test the effect of three soil temperatures on the efficacy of nonfumigant nematicides (fluopyram, fluensulfone, oxamyl and fluazaindolizine) against Meloidogyne javanica in pasteurized and natural soil in planta. The results showed that all tested nematicides were more efficacious in pasteurized than in natural soil. Temperature affected the nematicides differently with no effect of soil temperature on oxamyl and fluazaindolizine, whereas fluopyram and fluensulfone had greater efficacy at higher soil temperatures. Temperature effects were noted for some but not all nonfumigant nematicides. Fluopyram and fluensulfone were less effective when applied in cold soil, whereas oxamyl and fluazaindolizine were not affected by soil temperature. Although all nematicides resulted in almost complete control of M.javanica in pasteurized soil, this was not the case in natural soil, and much more root damage and nematode reproduction was noted in the latter. © 2021 Society of Chemical Industry.

Feasibility studies of protective sub-ballast soil-cement layers at heavy-train traffic

The development of ways to create a solid base for laying the track structure becomes especially relevant in conditions of the heavy-train traffic. This work presents feasibility studies of using a cold regeneration soil method for strengthening the main subgrade site. The advantages of this method are identified by the creation of models of production processes for soil-cement layers of various thickness. The main performance indicators are analyzed and compared with similar indicators of the most used engineering solutions for strengthening the subgrade working area: soft soil replacing and creation of a protective layer from a rubble-sand-gravel mixture reinforced with a geocell.The obtained results allow determining the following parameters: the number of employees, length of employment, outputs, productivity, labor costs, wages, costs of machine and mechanism operation, materials and works.Based on the results, a conclusion is made that there is an obvious advantage of the cold regeneration soil method for all parameters.

Soil bacterial communities vary more by season than with over two decades of experimental warming in Arctic tussock tundra

High latitude ecosystems are characterized by cold soils and long winters, with much of their biogeochemistry directly or indirectly controlled by temperature. Climate warming has led to an expansion of shrubby plant communities across tussock tundra, but whether these clear aboveground shifts correspond to changes in the microbial community belowground remains less certain. Using bromodeoxyuridine to label growing cells, we evaluated how total and actively growing bacterial communities varied throughout a year and following 22 years of passive summer warming. We found that changes in total and actively growing bacterial community structures were correlated with edaphic factors and time point sampled, but were unaffected by warming. The aboveground plant community had become more shrub-dominated with warming at this site, and so our results indicate that belowground bacterial communities did not track changes in the aboveground plant community. As such, studies that have used space-for-time methods to predict how increased shrub cover has altered bacterial communities may not be representative of how the microbial community will be affected by in situ changes in the plant community as the Arctic continues to warm.

Long‐term changes in layered soil temperature based on ground measurements in Jiangsu Province, China

AbstractWhile air temperature has been widely investigated to better understand the recent climate changes, the importance of soil temperature has been underestimated and rarely studied. Here, the long‐term soil temperature changes and the occurrence of extreme heats have been studied based on daily measurements in Jiangsu Province for 1970–2017. A general warming trend in soil temperature is observed at most stations, and these trends are more pronounced in the cold seasons than the warm seasons. Due to the asymmetric warming of maximum and minimum soil temperatures over the past 48 years, the diurnal range shows a long‐term decreasing trend with a rate of −0.34°C/10a. The occurrences of extreme soil temperatures have been analysed based on the probability density functions. It is found that the hot soil days have increased and cold soil days have decreased significantly, and these changes are particularly significant in the most recent decades.

Using floristic gradient mapping to assess seasonal thaw depth in interior Alaska

AbstractQuestionsIs it possible to map floristic gradients in heterogeneous boreal vegetation by using remote‐sensing data? Does a continuous vegetation map enable the creation of a spatially continuous map of seasonal permafrost soil thaw depth?LocationBonanza Creek LTER, Fairbanks, Alaska, USA.MethodsVegetation records are subjected to an ordination to extract the predominant floristic gradient. The ordination scores are then extrapolated using Sentinel 2 imagery and a digital elevation model (DEM). As the relation between vegetation pattern and seasonal thaw depth was confirmed in this study, the spatial distribution of ordination scores is then used to predict seasonal thaw depth over the same area.ResultsThe first dimension of the ordination space separates species corresponding to moist and cold soil conditions from species associated with well‐drained soils. This floristic gradient was successfully mapped within the sampled plant communities. The extrapolated thaw depths follow the typical distribution along a topographical and geomorphological gradient for this region. Besides vegetation information also DEM derivatives show high contributions to the thaw depth modeling.ConclusionWe demonstrate that floristic gradient mapping in boreal vegetation is possible. The accuracy of the thaw depth prediction model is comparable to that in previous analyses but uses a more parsimonious set of predictors, underlining the efficacy of this approach.

Effects of Nitrogen Addition and Reproductive Effort on Nutrient Resorption of a Sand-Fixing Shrub.

Caragana microphylla is a sand-fixing leguminous shrub with strong resistance to drought, cold, and low soil fertility. As a result, it plays an essential role in combating desertification in northern China, but little is known about its nutrient budget. Nutrient resorption is a key process in plant nutrient conservation and has marked ecological implications for plant fitness and ecosystem nutrient cycling. We studied the effects of both nitrogen (N) addition and reproductive effort on leaf N resorption of C. microphylla in a temperate semi-arid sandy land in China. The results showed that sprouting of the early leaves from over-wintered buds employs a strategy for slow returns on nutrient investment with smaller specific leaf area (SLA) and higher N resorption efficiency, whereas the late leaves, which sprout from current-year buds, employ a strategy for quick returns on nutrient investment with higher SLA and lower N resorption efficiency. N addition significantly increased the N resorption efficiency from early leaves while exerting no impact on late leaves, suggesting that the increased N recovery from early leaves is done to sustain the high N demands of late leaves. Reproductive effort did not affect the N resorption from early or late leaves due to the temporal separation between fruit production and leaf senescence. Taken together, our results demonstrate that C. microphylla has evolved different investment strategies for leaf N in early and late leaves to conserve nutrients and facilitate its growth in desertified environments.

Impact of Linseed Variety, Location and Production Year on Seed Yield, Oil Content and Its Composition

Linseed (Linum usitatissimum L.) is a traditional oilseed crop in Europe that represents a valuable alternative for cropping systems because of the high quality of the seed oil, which is being increasingly appreciated by consumers, food, cosmetic and ecomaterials industries. The aim of this study was to evaluate the influence of linseed variety and year of production in relation to weather conditions on seed yields, oil content and its quality, with a focus on human nutrition value, through a field study carried at four different locations in Slovenia. Six early French linseed varieties were studied: Recital, Niagara, Princess, Altess, Comtess and Duchess. The seed yield was significantly affected by the year of production (413 kg/ha higher in 2012 compared to 2013), the location and the variety. The environmental factors that negatively affect seed yield are high temperatures in summer, water shortage and wet and cold soil in spring. The highest seed yield was reached at mid-heavy soil (1907 kg/ha) in the region with higher precipitation amount, while the lowest on light soil (1052 kg/ha) in the region with a lower precipitation amount. Comtess and Altess varieties, followed by Duchess, would be recommendable for Slovenian environmental conditions. Comtess variety gave the significantly highest oil yield. There were no significant differences in oil content between varieties. The content of α-linolenic acid was highly related to genetic and environmental factors. The ratio of omega-3 and omega-6 fatty acids was recognized as favorable for human health for all studied varieties. The content of α-linolenic acid in seeds from the Altess, Comtess and Duchess varieties exceeded the averages of 2012 and 2013, at 50.3% and 51.6%, respectively. The omega-3:omega-6 ratio ranged from 3:1 to 4:1 among varieties.

15N tracer enrichment in response to winter soil temperature manipulation differs between canopy trees and juveniles

Juveniles and canopy trees may not exhibit similar nitrogen acquisition responses to soil temperature change caused by variation in snow cover over winter. The use of 15N tracer is a powerful tool for tracking the effects of variation in soil frost on plant nitrogen acquisition. While the responses of juvenile trees to environmental change are often used to infer the responses of canopy trees, the 15N enrichment responses of juveniles and mature canopy trees may not be comparable. We conducted a winter soil temperature manipulation study (snow exclusion, ambient snow or soil insulation) in a lowland Fagus sylvatica forest. 15N tracer was applied the following spring and the 15N enrichments of soil, juvenile and mature canopy trees were examined in late fall. Within canopy trees and juveniles, the relative treatment effects on 15N enrichment were consistent among all sampled tissues (roots, stem cores, leaves, buds and the current year’s shoot growth). For juveniles, 15N enrichment was highest under snow exclusion (coldest soil) and lowest under soil insulation (warmest soil), and lower 15N enrichment occurred under ambient conditions than under snow exclusion. For canopy trees, 15N enrichment also was highest under snow exclusion and lowest under soil insulation, but there was no difference in 15N enrichment between ambient conditions and the snow exclusion treatment. Therefore, our results indicate that sampling of juveniles may overestimate the nitrogen acquisition responses of mature trees to winter temperature variation.

Greenhouse gas emission from the cold soils of Eurasia in natural settings and under human impact: Controls on spatial variability

The annual balance of biogenic greenhouse gases (GHGs; carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) in the atmosphere is well studied. However, the contributions of specific natural land sources and sinks remain unclear, and the effect of different human land use activities is understudied. A simple way to do this is to evaluate GHG soil emissions. For CO2, it usually comprises 60–75% of gross respiration in natural terrestrial ecosystems, while local human impact can increase this share to almost 100%. Permafrost-affected soils occupying 15% of the land surface mostly in the Eurasia and North America contain approximately 25% of the total terrestrial carbon. The biogenic GHG soil emissions from permafrost are 5% of the global total, which makes these soils extremely important in the warming world. Measurements of CO2, methane, and nitrous oxide, from eighteen locations in the Arctic and Siberian permafrost, across tundra, steppe, and north taiga domains of Russia and Svalbard, were conducted from August to September during 2014–2017 in 37 biotopes representing natural conditions and different types of human impact. We demonstrate that land use caused significant alteration in soil emission and net fluxes of GHGs compared to natural rates, regardless of the type and duration of human impact and the ecosystem type. The cumulative effect of land use factors very likely supported an additional net-source of CO2 into the atmosphere because of residual microbial respiration in soil after the destruction of vegetation and primary production under anthropogenic influence. Local drainage effects were more significant for methane emission. In general, land use factors enforced soil emission and net-sources of CO2 and N2O and weakened methane sources. Despite the extended heat supply, high aridity caused significantly lower emissions of methane and nitrous oxide in ultra-continental Siberian permafrost soils. However, these climatic features support higher soil CO2 emission rates, in spite of dryness, owing to the larger phytomass storage, presence of tree canopies, thicker active layer, and greater expressed soil fissuring. Furthermore, the “Birch effect” was much less expressed in ultra-continental permafrost soils than in permafrost-free European soils. Models and field observations demonstrated that the areal human footprint on soil CO2 fluxes could be comparable to the effect of climate change within a similar timeframe. Settlements and industrial areas in the tundra function as year-round net CO2 sources, mostly owing to the lack of vegetation cover. As a result, they could compensate for the natural C-balance on significantly larger areas of surrounding tundra.

Treatment of bell pepper (Capsicum annuum L.) seeds with chitosan increases chitinase and glucanase activities and enhances emergence in a standard cold test

Pepper (Capsicum annuum), as a warm-season crop, germinates poorly under wet and cold soils due in part to seed fungal diseases. The objective of this study was to test whether seed treatment with chitosan improved low temperature germination by increasing chitinase and glucanase activities. Pepper seeds were imbibed in 0.01, 0.05, 0.1, 0.3, and 0.5 % chitosan solutions, 1 % acetic acid, 1 % Benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazole] fungicide, or hydroprimed in distilled water for comparison with dry-untreated seeds. After treatment, all seeds were slowly dried back to their original moisture content and evaluated for germination percentage, mean time to germination (MTG), seedling growth in a warm germination test and for seedling emergence in a standard cold test. Chitinase and glucanase activities were also measured for seeds after treatment and for germinating seedlings. Seeds treated with chitosan or hydroprimed germinated faster with decreased MTG compared to untreated seeds germinated at 25 °C and produced longer seedlings with greater fresh weights. Treatment of seeds with chitosan significantly improved final germination percentage by 8% in the second lab experiments (≥90 %). Seed treatment with chitosan or hydropriming improved seedling emergence in the cold test by 29 %. Seed treatment with chitosan increased chitinase and glucanase activities in both seeds and seedlings compared to untreated seeds. In conclusion, treatment of pepper seeds with chitosan improved seed germination under wet and cold conditions, which might be due to the induction of systemic acquired resistance in seeds by increasing chitinase and glucanase activities. Greater chitinase and glucanase activities in chitosan-treated seeds might protect seedlings from fungal diseases under cold conditions.

EFFECT OF THE SOIL TEMPERATURE AND AIR TEMPERATURE ON THE GROWTH OF SILVER BIRCH SEEDLINGS AND THEIR GASEOUS CO₂ EXCHANGE

Gaseous CO2 exchange and shoot growth over a growing season were studied in 3‑yearold seedlings of silver birch (Betula pendula Roth) growing in 10‑litre pots with different soil temperatures. Initially, activation of growth and an increase of CO ₂ exchange were observed in seedlings experiencing higher soil temperatures compared to seedlingsgrowing in colder soil. Also, an increase in stomatal conductance and a higher pigment content were detected. In the seedlings growing in cold soil, a consistent rise of CO ₂ exchange and dark respiration was observed as the air temperature and soil temperature were growing. In the period before intensive growth, the total leaf area in seedlings rooted in warmer soil was more than three times higher than that of seedlings in cold soil. Until July, air temperatures were not high enough to initiate intensive growth. Therefore, a great deal of assimilates in the seedlings growing under higher soil temperature were largely being deposited, particularly in roots and bark. In the absence of powerful attracting points, assimilates were in excess, and photosynthesis was inhibited. A significant difference in CO ₂ exchange and stomatal conductance between the two groups of seedlings was seen at the beginning of the growing season. Later on, as the air temperature was rising, CO ₂ exchange increased insignificantly in seedlings growing in soil of higher temperature. Warming up of the soil smoothed down the difference in CO2 exchange between the two groups of seedlings. In the period of intensive growth in July, CO ₂ exchange in seedlings growing naturally in the field was higher than in pot-grown seedlings. We suppose that the increase in soil temperature early in the growing season results in a rise in the concentration of sucrose in the phloem exudate, and promotes bark thickening. This process is quite pronounced in Karelian (curly) birch – an ecological form of silver birch (Betula pendula Roth var. carelica (Merclin) Hämet Ahti).

The Integration of Spring and Winter Wheat Genetics With Agronomy for Ultra-Early Planting Into Cold Soils

Early seeding has been suggested as a method of increasing the grain yield and grain yield stability of wheat (Triticum aestivum L.) in the Northern Great Plains. The point at which early seeding results in a decrease in grain yield has not been clearly identified. Changes in climatic conditions have increased frost-free periods and increased temperatures during grain filling, which can either be taken advantage of or avoided by seeding earlier. Field trials were conducted in western Canada from 2015 to 2018 to evaluate an ultra-early wheat planting system based on soil temperature triggers as opposed to calendar dates. Planting began when soil temperatures at 5 cm depth reached 0°C and continued at 2°C intervals until 10°C, regardless of calendar date. Conventional commercial spring wheat genetics and newly identified cold tolerant spring wheat lines were evaluated to determine if ultra-early wheat seeding systems required further development of specialized varieties to maintain system stability. Ultra-early seeding resulted in no detrimental effect on grain yield. Grain yield increased at sites south of 51° latitude N, and was unaffected by ultra-early seeding at sites north of 51° latitude N. Grain protein content, kernel weight, and bulk density were not affected by ultra-early seeding. Optimal seeding time was identified between 2 and 6°C soil temperatures. A greater reduction in grain yield was observed from delaying planting until soils reached 10°C than from seeding into 0°C soils; this was despite extreme environmental conditions after initial seeding, including air temperatures as low as −10.2°C, and as many as 37 nights with air temperatures below 0°C. Wheat emergence ranged from 55 to 70%, and heads m−2 decreased with delayed seeding while heads plant−1 did not change. Cold tolerant wheat lines did not increase stability of the ultra-early wheat seeding system relative to the conventional spring wheat check, and are therefore not required for growers to adopt ultra-early seeding. The results of this study indicate that growers in western Canada can successfully begin seeding wheat earlier, with few changes to their current management practices, and endure less risk than delaying seeding until soil temperatures reach 10°C or greater.

Precipitation extremes influence patterns and partitioning of evapotranspiration and transpiration in a deciduous boreal larch forest

High latitude boreal forests are experiencing dramatic changes in climate and hydrology. It is not clear how boreal forests will adapt to hydrological change or how stable they will be to extreme climate fluctuations and shifts in ecosystem water availability (EWA; residuals between precipitation and evapotranspiration). Although there have been numerous studies in North American and European boreal forests, the Siberian boreal region is underrepresented. Moreover, Siberia is dominated by deciduous conifers (larch) that may have different response to shifting hydrology than boreal evergreens do. We observed evapotranspiration (ET) by eddy covariance technique and transpiration (T) by sap-flow probes on a subsample of trees within the flux-tower footprint through two growing seasons in a larch forest in northernmost China. Ecosystems at the margins of their zone could be amongst the first to experience significant shifts in structure and function. At this site there have already been signs of permafrost degradation and more frequent temperature and precipitation anomalies. The canopy-dominant larch accounted for half the total T fluxes. The remaining 50% was distributed evenly among intermediate and suppressed trees. T is the dominant subcomponent in ET, where overall T/ET varies of 66%–84% depending on precipitation patterns. In dormant and early growing seasons, T still constitutes a majority of ET even though the canopy foliage is not fully developed because cold soil creates a negative soil to air vapor pressure gradient that impedes evaporation. However, in the peak growing season, excess precipitation reduces T while providing sufficient wetness for surface evaporation. ET from standard data product based on MODIS satellite reflectance underestimates tower ET by 17%–29%. Solar-induced chlorophyll fluorescence measured by satellite is well correlated with tower ET (r2 = 0.69–0.73) and could provide a better basis for regional ET extrapolations. A global comparison of data for 2000–2018 period reveals that boreal forests not only have the smallest annual MODIS ET but also the least EWA compared to temperate and tropical forests. Also, even though boreal deciduous and evergreens have comparable annual ET, their T/ET and EWA are distinct. This work highlights how short-term precipitation extremes may shift ecosystem function and structure by changing EWA through exported runoff. Sites along boreal ecotones are critical to observe for signs of shifts in their structure, function, and response to climate anomalies.

Influence of soil temperature and moisture on micronutrient supply, plant uptake, and biomass yield of wheat, pea, and canola

Crop yield response to micronutrient fertilization is difficult to predict, particularly under unfavorable environmental conditions as these may alter both crop nutrient demand and the soil micronutrient supply to plant roots. The research objective was to evaluate the effect of various soil temperature and moisture conditions on crop growth response to added micronutrient copper (Cu), zinc (Zn), and boron (B) along with soil micronutrient supply and distribution among fractions. Brown and Dark Brown farm soils collected from southern Saskatchewan were used to grown wheat, pea and canola within controlled environment chambers. The biomass yields of all crops decreased under cold soil temperature and moisture stress (drought and saturated) conditions. Greater plant uptake of Cu, Zn, and B was associated with optimum (i.e., field capacity) soil moisture and warm temperature (23°C) growing conditions, compared to drought (i.e., 50% field capacity), saturated, and cold (5°C) temperature conditions. Environmental stress had the greatest impact on pea growth, reducing crop yield and micronutrient utilization efficiency more than 95%. Soil supplies of Cu and Zn were most negatively impacted by drought stress due to reduced mobility of these diffusion limited nutrients. The extractable micronutrients levels and chemical speciation fractions of Cu, Zn, and B indicating that bioavailability and micronutrient transformation were not affected during our short-term (i.e., six-weeks) study. However, it is suggested that assessments of micronutrient forms also be conducted on soil samples under actual moisture and temperature conditions as they exist in the experiment, as well as on dried, processed samples.