Patterns of Biogeochemistry in Alaskan Boreal Forests

2006 ◽  
Author(s):  
David W. Valentine ◽  
Knut Kielland
Keyword(s):  
Boreal Forest ◽  
Boreal Forests ◽  
General Circulation ◽  
Plant Productivity ◽  
Parent Material ◽  
Forest Types ◽  
Element Cycling ◽  
Soil C ◽  
Growing Seasons ◽  
Data Gap

As the northernmost forest on Earth, boreal forests endure a combination of environmental challenges common only in subalpine forests elsewhere: extremely cold winters, short growing seasons, cold soils, and limited nutrient availability. Consequently, decomposition has lagged plant production, making circumpolar boreal forest soils one of the largest terrestrial reservoirs of carbon (C). Soil organic matter also constitutes a major source of nutrients, particularly nitrogen (N), that promote plant productivity when released during decomposition. If current trends in high-latitude warming continue (Chapter 4), how will accelerated soil C losses from decomposition compare to the C gains from enhanced plant productivity? This remains an open question of great interest to climate modelers seeking to incorporate biological feedbacks into future generations of general circulation models. This chapter builds on earlier chapters on plants (Chapters 11 and 12), herbivores (Chapter 13), and soil microbes (Chapter 14) to describe the patterns and processes of C and N dynamics in Alaska’s boreal forest, paying particular attention to responses of these processes to the interacting influences of disturbance and climatic variations that occur across the landscape and through time. Other nutrients have received less attention in Alaskan research, and that data gap is reflected in this chapter. Interior Alaska’s boreal forest is a patchwork of successional forest types. The major physiographic zones into which we categorize them reflect the contrasting influences of two major disturbance types: fire in upland and lowland areas results in multiple secondary successional pathways, while a more ordered array of forest types results from a combination of primary succession and variation in flooding frequency during succession on active floodplains (Chapter 7). Within each general physiographic zone (uplands and lowlands, floodplains), differences in the postdisturbance environment further influence vegetation establishment, plant species composition, and, ultimately, element cycling. The state factor approach has proven useful in understanding landscape variation in biogeochemistry (Chapter 1; Van Cleve et al. 1991). As with other aspects of ecosystem function, element cycling reflects control exerted by major state factors: climate, parent material, potential vegetation, topography, and time since the most recent disturbance event.

scholarly journals The Dynamics of Transpiration to Evapotranspiration Ratio under Wet and Dry Canopy Conditions in a Humid Boreal Forest

Forests ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 237 ◽  
Author(s):  
Bram Hadiwijaya ◽  
Steeve Pepin ◽  
Pierre-Erik Isabelle ◽  
Daniel F. Nadeau
Keyword(s):  
Boreal Forest ◽  
Sap Flow ◽  
Boreal Forests ◽  
Cold Climate ◽  
Thermal Dissipation ◽  
Evaporative Demand ◽  
Sap Flux Density ◽  
Flow Measurements ◽  
Growing Seasons ◽  
The Impact

Humid boreal forests are unique environments characterized by a cold climate, abundant precipitation, and high evapotranspiration. Transpiration ( E T ), as a component of evapotranspiration (E), behaves differently under wet and dry canopy conditions, yet very few studies have focused on the dynamics of transpiration to evapotranspiration ratio ( E T / E ) under transient canopy wetness states. This study presents field measurements of E T / E at the Montmorency Forest, Québec, Canada: a balsam fir boreal forest that receives ∼ 1600 mm of precipitation annually (continental subarctic climate; Köppen classification subtype Dfc). Half-hourly observations of E and E T were obtained over two growing seasons using eddy-covariance and sap flow (Granier’s constant thermal dissipation) methods, respectively, under wet and dry canopy conditions. A series of calibration experiments were performed for sap flow, resulting in species-specific calibration coefficients that increased estimates of sap flux density by 34 % ± 8 % , compared to Granier’s original coefficients. The uncertainties associated with the scaling of sap flow measurements to stand E T , especially circumferential and spatial variations, were also quantified. From 30 wetting–drying events recorded during the measurement period in summer 2018, variations in E T / E were analyzed under different stages of canopy wetness. A combination of low evaporative demand and the presence of water on the canopy from the rainfall led to small E T / E . During two growing seasons, the average E T / E ranged from 35 % ± 2 % to 47 % ± 3 % . The change in total precipitation was not the main driver of seasonal E T / E variation, therefore it is important to analyze the impact of rainfall at half-hourly intervals.

Snow-mass intercomparisons in the boreal forests from general circulation models and remotely sensed data sets

Polar Record ◽  
1996 ◽  
Vol 32 (182) ◽  
pp. 199-208 ◽  
Author(s):  
James Foster ◽  
Randy Koster ◽  
Helga Behr ◽  
Lydia Dümenil ◽  
Judah Cohen ◽  
...  
Keyword(s):  
North America ◽  
Boreal Forest ◽  
Boreal Forests ◽  
General Circulation ◽  
General Circulation Models ◽  
Passive Microwave ◽  
Data Sets ◽  
Climatological Data ◽  
Study Results ◽  
Snow Mass

ABSTRACTIn much of the boreal forests, snow covers the ground for half of the year. Since these boreal forests comprise approximately 15% of the land normally covered by snow during the winter and upwards of 40% of the land surface normally snow-covered during the spring and autumn, reliable measures of snow cover and snow mass are required for improved energy-balance and water-balance estimates. In this study, results from snow-depth climatological data (SDC), passive microwave satellite data, and output from general circulation models (GCMs) have been intercompared for the boreal forests of both North America and Eurasia. In Eurasia, during the winter months, snowmass estimates from these data sets correspond rather well; however, in North America, the passive microwave estimates are smaller than the estimates from the climatological data and the modeled data. The underestimation results primarily from the effects of vegetation on the microwave signal. The reason why the underestimation is a bigger problem in North America than in Eurasia is likely due to the use of global microwave algorithms that have not accounted for regional differences in the size of snow grains. The GCMs generally produce too much snow in the spring season. This is a result of the models having moisture amounts that are greater and temperatures that are slightly lower than observed, in the late winter and early spring periods. The models compare more favorably with the SDC in the Eurasian boreal forest than in the forests of North America during the winter season. However, in the spring, the model results for the North America boreal forest are in better agreement with the SDC than are the forests of Eurasia.

scholarly journals Spatial Variability of Throughfall in a Larch (Larix gmelinii) Forest in Great Kingan Mountain, Northeastern China

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 393
Author(s):  
Houcai Sheng ◽  
Tijiu Cai
Keyword(s):  
Spatial Variability ◽  
Boreal Forest ◽  
Boreal Forests ◽  
Temporal Stability ◽  
Canopy Structure ◽  
Terrestrial Ecosystem ◽  
Rainfall Amount ◽  
Larix Gmelinii ◽  
Forest Types ◽  
Area Index

Larix gmelinii forest is one of the dominant forest types in boreal forest and plays a unique eco-hydrological role in the terrestrial ecosystem. However, the throughfall variability in boreal forest ecosystems, which plays a crucial role in regulating hydrology, remains unclear. Here, we investigated the spatial variability and temporal stability of throughfall within a Larix gmelinii forest in the full leaf stage in Great Kingan Mountain, Northeast China, and the effects of rainfall properties and canopy structure on throughfall variability were systematically evaluated. The results indicate that throughfall represented 81.26% of the gross rainfall in the forest. The throughfall CV (coefficient of variation of throughfall) had a significant and negative correlation with the rainfall amount, rainfall intensity, rainfall duration, and distance from the nearest trunk, whereas it increased with increasing canopy thickness and LAI (leaf area index). The correlation analysis suggested that the throughfall variability was mainly affected by the rainfall amount (R2 = 0.7714) and canopy thickness (R2 = 0.7087). The temporal stability analysis indicated that the spatial distribution of the throughfall was temporally stable. Our findings will facilitate a better understanding of the spatiotemporal heterogeneity of throughfall and help the accurate assessment of throughfall and soil water within boreal forests.

scholarly journals The undetected loss of aged carbon from boreal mineral soils

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Geert Hensgens ◽  
Hjalmar Laudon ◽  
Mark S. Johnson ◽  
Martin Berggren
Keyword(s):  
Organic Carbon ◽  
Boreal Forest ◽  
Soil C ◽  
Earth Systems ◽  
Nuclear Bomb ◽  
C Cycle ◽  
Water Extractable Organic Carbon ◽  
High Lability ◽  
Mineral Soils ◽  
Terrestrial Biomes

AbstractThe boreal forest is among the largest terrestrial biomes on earth, storing more carbon (C) than the atmosphere. Due to rapid climatic warming and enhanced human development, the boreal region may have begun transitioning from a net C sink to a net source. This raises serious concern that old biogenic soil C can be re-introduced into the modern C cycle in near future. Combining bio-decay experiments, mixing models and the Keeling plot method, we discovered a distinct old pre-bomb organic carbon fraction with high biodegradation rate. In total, 34 ± 12% of water-extractable organic carbon (WEOC) in podzols, one of the dominating boreal soil types, consisted of aged (~ 1000 year) labile C. The omission of this aged (i.e., Δ14C depleted) WEOC fraction in earlier studies is due to the co-occurrence with Δ14C enriched modern C formed following 1950s nuclear bomb testing masking its existence. High lability of aged soil WEOC and masking effects of modern Δ14C enriched C suggests that the risk for mobilization and re-introduction of this ancient C pool into the modern C cycle has gone undetected. Our findings have important implications for earth systems models in terms of climate-carbon feedbacks and the future C balance of the boreal forest.

scholarly journals Boreal Forest Songbird Communities of the Liard Valley, Northwest Territories, Canada

The Condor ◽  
2003 ◽  
Vol 105 (1) ◽  
pp. 27-44 ◽  
Author(s):  
Craig S. Machtans ◽  
Paul B. Latour
Keyword(s):  
Boreal Forest ◽  
Northwest Territories ◽  
Boreal Forests ◽  
Bird Community ◽  
Deciduous Forests ◽  
Zonotrichia Albicollis ◽  
Catharus Ustulatus ◽  
Regional Patterns ◽  
Dendroica Coronata ◽  
Spizella Passerina

Abstract Songbird communities in the boreal forest of the Liard Valley, Northwest Territories, Canada, are described after three years of study. Point count stations (n = 195) were placed in six types of forest (mature deciduous, coniferous, and mixedwood; young forests; wooded bogs; clearcuts) in a 700-km2 area. Vegetation characteristics at each station were also measured. Eighty-five species of birds (59 passerine species) occurred in 11 647 detections. Mixedwood forests had the highest richness of songbirds (∼41 species per 800 individuals) of the six forest types, and contained approximately 30% more individuals than nearly pure coniferous or deciduous forests. Species richness and relative abundance was 10–50% lower than in comparable forests farther south and east, and the difference was most pronounced in deciduous forests. Communities were dominated by a few species, especially Tennessee Warbler (Vermivora peregrina), Magnolia Warbler (Dendroica magnolia), Swainson's Thrush (Catharus ustulatus), Yellow-rumped Warbler (Dendroica coronata) and Chipping Sparrow (Spizella passerina). White-throated Sparrow (Zonotrichia albicollis), a dominant species in boreal forests farther south, was notably scarce in all forests except clearcuts. Clearcuts and wooded bogs had the simplest communities, but had unique species assemblages. Canonical correspondence analysis showed that the bird community was well correlated with vegetation structure. The primary gradient in upland forests was from deciduous to coniferous forests (also young to old, respectively). The secondary gradient was from structurally simple to complex forests. These results allow comparisons with other boreal areas to understand regional patterns and help describe the bird community for conservation purposes. Comunidades de Aves Canoras de Bosques Boreales del Valle de Liard, Territorios del Noroeste, Canadá Resumen. Luego de tres años de estudio, se describen las comunidades de aves canoras de bosques boreales del Valle de Liard, Territorios del Noroeste, Canadá. Se ubicaron estaciones de conteo de punto (n = 195) en seis tipos de bosque (maduro caducifolio, conífero y de maderas mixtas; bosques jóvenes; pantanos arbolados; zonas taladas) en un área de 700 km2. Las características de la vegetación en cada estación también fueron medidas. Se registraron 85 especies de aves (59 especies de paserinas) en 11 647 detecciones. Los bosques mixtos presentaron la mayor riqueza de aves canoras (∼41 especies por 800 individuos) de los seis tipos de bosque, y contuvieron aproximadamente 30% individuos más que los bosques de coníferas y los caducifolios. La riqueza de especies y la abundancia relativa fue 10–50% menor que en bosques comparables más al sur y al este, y la diferencia fue más pronunciada en los bosques caducifolios. Las comunidades estuvieron dominadas por unas pocas especies, especialmente Vermivora peregrina, Dendroica magnolia, Catharus ustulatus, Dendroica coronata y Spizella passerina. Zonotrichia albicollis, una especie dominante en bosques boreales más al sur, fue notablemente escasa en todos los bosques, excepto en las zonas taladas. Las áreas taladas y los pantanos arbolados tuvieron las comunidades más simples, pero presentaron ensamblajes únicos. Análisis de correspondencia canónica mostraron que la comunidad de aves estuvo bien correlacionada con la estructura de la vegetación. El gradiente primario en bosques de zonas altas fue de bosque caducifolio a conífero (también de joven a viejo, respectivamente). El gradiente secundario fue de bosques estructuralmente simples a bosques complejos. Estos resultados permiten hacer comparaciones con otros bosques boreales para entender los patrones regionales y ayudar a describir las comunidades de aves con fines de conservación.

Interspecific root interactions enhance photosynthesis and biomass of intercropped millet and peanut plants

2019 ◽  
Vol 70 (3) ◽  
pp. 234
Author(s):  
Xiaojin Zou ◽  
Zhanxiang Sun ◽  
Ning Yang ◽  
Lizhen Zhang ◽  
Wentao Sun ◽  
...  
Keyword(s):  
Crop Yields ◽  
Positive Root ◽  
Foxtail Millet ◽  
Phosphoglycerate Kinase ◽  
Plant Productivity ◽  
Photosynthetic Rates ◽  
Interspecific Facilitation ◽  
Growing Seasons ◽  
Root Interactions ◽  
Root Barrier

Intercropping is commonly practiced worldwide because of its benefits to plant productivity and resource-use efficiency. Belowground interactions in these species-diverse agro-ecosystems can greatly contribute to enhancing crop yields; however, our understanding remains quite limited of how plant roots might interact to influence crop biomass, photosynthetic rates, and the regulation of different proteins involved in CO2 fixation and photosynthesis. We address this research gap by using a pot experiment that included three root-barrier treatments with full, partial and no root interactions between foxtail millet (Setaria italica (L.) P.Beauv.) and peanut (Arachis hypogaea L.) across two growing seasons. Biomass of millet and peanut plants in the treatment with full root interaction was 3.4 and 3.0 times higher, respectively, than in the treatment with no root interaction. Net photosynthetic rates also significantly increased by 112–127% and 275–306% in millet and peanut, respectively, with full root interaction compared with no root interaction. Root interactions (without barriers) contributed to the upregulation of key proteins in millet plants (i.e. ribulose 1,5-biphosphate carboxylase; chloroplast β-carbonic anhydrase; phosphoglucomutase, cytoplasmic 2; and phosphoenolpyruvate carboxylase) and in peanut plants (i.e. ribulose 1,5-biphosphate carboxylase; glyceraldehyde-3-phosphate dehydrogenase; and phosphoglycerate kinase). Our results provide experimental evidence of a molecular basis that interspecific facilitation driven by positive root interactions can contribute to enhancing plant productivity and photosynthesis.

The distribution of organic carbon in major components of forests located in five life zones of Venezuela

1997 ◽  
Vol 13 (5) ◽  
pp. 697-708 ◽  
Author(s):  
M. Delaney ◽  
S. Brown ◽  
A. E. Lugo ◽  
A. Torres-Lezama ◽  
N. Bello Quintero
Keyword(s):  
Tropical Forests ◽  
Aboveground Biomass ◽  
Dead Wood ◽  
Clear Trend ◽  
Soil C ◽  
Forest Inventories ◽  
Biomass Components ◽  
Life Zone ◽  
Data Gap

ABSTRACTOne of the major uncertainties concerning the role of tropical forests in the global carbon cycle is the lack of adequate data on the carbon content of all their components. The goal of this study was to contribute to filling this data gap by estimating the quantity of carbon in the biomass, soil and necromass for 23 long-term permanent forest plots in five life zones of Venezuela to determine how C was partitioned among these components across a range of environments. Aboveground biomass C ranged from 70 to 179 Mg ha−1 and soil C from 125 to 257 Mg ha−1, and they represented the two largest C components in all plots. The C in fine litter (2.4 to 5.2 Mg ha−1), dead wood (2.4 to 21.2 Mg ha−1) and roots (23.6 to 38.0 Mg ha−1) accounted for less than 13% of the total C. The total amount of C among life zones ranged from 302 to 488 Mg ha−1, and showed no clear trend with life zone. In three of the five life zones, more C was found in the dead (soil, litter, dead wood) than in the live (biomass) components (dead to live ratios of 1.3 to 2.3); the lowland moist and moist transition to dry life zones had dead to live ratios of less than one. Results from this research suggest that for most life zones, an amount equivalent to between 20 and 58% of the aboveground biomass is located in necromass and roots. These percentages coupled with reliable estimates of aboveground biomass from forest inventories enable a more complete estimation of the C content of tropical forests to be made.

The stock and age of pyrogenic carbon in boreal forest soils of the Mackenzie Basin, Northern Canada

2021 ◽  
Author(s):  
Marcus Schiedung ◽  
Philippa Ascough ◽  
Severin-Luca Bellè ◽  
Samuel Abiven
Keyword(s):  
Boreal Forest ◽  
Forest Soils ◽  
Boreal Forests ◽  
Radiocarbon Dating ◽  
Bulk Soil ◽  
Northern Canada ◽  
Pyrogenic Carbon ◽  
Discontinuous Permafrost ◽  
Soc Stocks ◽  
Mackenzie River

<p>Wildfires occur regularly in the boreal forests of Northern Canada and an increasing frequency and intensity due to the global climate change is projected. A by-product of these forest fires is pyrogenic carbon (PyC) as a residue of incomplete combustion. The quantity and age of PyC in boreal forest soils, however, are largely unknown although boreal soils contribute to a large extent to the global soil organic carbon (SOC) stocks. The Mackenzie River is a major export pathway for PyC between terrestrial and marine environments, with exported PyC ages on geological timescales. This indicates that soil may play an important role as an intermediate pool prior to the PyC export. We sampled eleven forest soils (with nine replicates) in the Canadian Taiga Plains and Shield within the Mackenzie River basin. Our sample sites were located in regions with soils under continuous permafrost in the Inuvik region (northern sites) and under sporadic and discontinuous permafrost in the South Slave Lake regions (southern sites). All sites were unaffected by fire for at least four decades. We used the hydrogen pyrolysis (HyPy) method to separate the PyC<sub>HyPy</sub> from the non-fire-derived SOC in the upper 0-15 cm to determine PyC<sub>HyPy</sub> stocks and performed radiocarbon dating upon both bulk soil and isolated PyC<sub>HyPy</sub>. The total SOC stocks were lower in the soil from the southern sites with on average 26 ± 20 Mg ha<sup>-1</sup> (10-153 Mg ha<sup>-1</sup>) compared to 57 ± 29 Mg ha<sup>-1</sup> (16-188 Mg ha<sup>-1</sup>) in the northern sites. The radiocarbon dating revealed much older PyC<sub>HyPy</sub> compared to the bulk soil SOC radiocarbon age, supporting the persistent nature of PyC and stabilization in soils. The PyC<sub>HyPy </sub>found in the soil of the southern sites, however, was much younger with ages in the range of 495-3 275 radiocarbon years BP than in the northern sites with ages on the range of 2 083-10 407 radiocarbon years BP. The larger SOC stocks and higher ages of PyC<sub>HyPy</sub> in the soils of the northern sites indicate the importance of permafrost conditions for the whole carbon cycle of boreal forests soils.</p>

scholarly journals Splitting in Fire-Killed Trees in the Boreal Forest of Alberta

2003 ◽  
Vol 20 (4) ◽  
pp. 167-174
Author(s):  
Nobutaka Nakamura ◽  
Paul M. Woodard ◽  
Lars Bach
Keyword(s):  
Boreal Forest ◽  
Boreal Forests ◽  
Black Spruce ◽  
Lodgepole Pine ◽  
White Spruce ◽  
Balsam Fir ◽  
Crown Fire ◽  
In Fire ◽  
Solar Angle

Abstract Tree boles in the boreal forests of Alberta, Canada will split once killed by a stand-replacing crown fire. A total of 1,485 fire-killed trees were sampled, 1 yr after burning, in 23 plots in 14 widely separated stands within a 370,000 ha fire. Sampling occurred in the Upper and Lower Foothills natural subregions. The frequency of splitting varied by species but averaged 41% for all species. The order in the frequency of splitting was balsam fir, black spruce, white spruce and lodgepole pine. The type of splitting (straight, spiral, or multiple) varied by species, as did the position of the split on the tree bole. Aspect or solar angle was not statistically related to the type or occurrence of splitting.

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