scholarly journals Ecosystem fluxes of carbonyl sulfide in an old-growth forest: temporal dynamics and responses to diffuse radiation and heat waves

2018 ◽  
Vol 15 (23) ◽  
pp. 7127-7139 ◽  
Author(s):  
Bharat Rastogi ◽  
Max Berkelhammer ◽  
Sonia Wharton ◽  
Mary E. Whelan ◽  
Frederick C. Meinzer ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Temporal Dynamics ◽  
Heat Waves ◽  
Carbonyl Sulfide ◽  
Diffuse Radiation ◽  
Field Studies ◽  
Old Growth ◽  
Old Growth Forest ◽  
The Pacific ◽  
The Us

Abstract. Carbonyl sulfide (OCS) has recently emerged as a tracer for terrestrial carbon uptake. While physiological studies relating OCS fluxes to leaf stomatal dynamics have been established at leaf and branch scales and incorporated into global carbon cycle models, the quantity of data from ecosystem-scale field studies remains limited. In this study, we employ established theoretical relationships to infer ecosystem-scale plant OCS uptake from mixing ratio measurements. OCS fluxes showed a pronounced diurnal cycle, with maximum uptake at midday. OCS uptake was found to scale with independent measurements of CO2 fluxes over a 60 m tall old-growth forest in the Pacific Northwest of the US (45∘49′13.76′′ N, 121∘57′06.88′′ W) at daily and monthly timescales under mid–high light conditions across the growing season in 2015. OCS fluxes were strongly influenced by the fraction of downwelling diffuse light. Finally, we examine the effect of sequential heat waves on fluxes of OCS, CO2, and H2O. Our results bolster previous evidence that ecosystem OCS uptake is strongly related to stomatal dynamics, and measuring this gas improves constraints on estimating photosynthetic rates at the ecosystem scale.

scholarly journals Ecosystem fluxes of carbonyl sulfide in an old-growth forest: temporal dynamics and responses to diffuse radiation and heat waves

2018 ◽  
Author(s):  
Bharat Rastogi ◽  
Max Berkelhammer ◽  
Sonia Wharton ◽  
Mary E. Whelan ◽  
Frederick C. Meinzer ◽  
...  
Keyword(s):  
Temporal Dynamics ◽  
Heat Waves ◽  
Carbonyl Sulfide ◽  
Diffuse Radiation ◽  
Growing Season ◽  
Field Studies ◽  
Old Growth ◽  
Old Growth Forest ◽  
The Pacific ◽  
Global Carbon

Abstract. Carbonyl sulfide (OCS) has recently emerged as a tracer for terrestrial carbon uptake. While physiological studies relating OCS fluxes to leaf stomatal dynamics have been established at leaf and branch scales and incorporated in global carbon cycle models, the quantity of data from ecosystem-scale field studies remains limited. In this study we employ established theoretical relationships to infer ecosystem-scale OCS uptake from concentration measurements. OCS uptake was found to scale with independent measurements of CO2 fluxes over a 60-m-tall old-growth forest in the Pacific Northwestern U.S. (45°49′13.76′′ N; 121°57′06.88′′) at hourly and monthly timescales across the growing season in 2015. OCS fluxes tracked changes in soil moisture, and were strongly influenced by the fraction of downwelling diffuse light. Fluxes were also strongly affected by sequential heat waves during the growing season. Our results bolster previous evidence that ecosystem OCS uptake is strongly related to stomatal dynamics, and measuring this gas improves constraints on estimating photosynthetic rates at the ecosystem scale.

scholarly journals Influence of topography and fuels on fire refugia probability under varying fire weather conditions in forests of the Pacific Northwest, USA

2020 ◽  
Vol 50 (7) ◽  
pp. 636-647 ◽  
Author(s):  
Garrett W. Meigs ◽  
Christopher J. Dunn ◽  
Sean A. Parks ◽  
Meg A. Krawchuk
Keyword(s):  
Conditional Probability ◽  
Pacific Northwest ◽  
Weather Conditions ◽  
Fire Weather ◽  
Old Growth ◽  
Old Growth Forest ◽  
The Pacific ◽  
Live Fuels ◽  
Surrounding Areas ◽  
And Function

Fire refugia — locations that burn less severely or less frequently than surrounding areas — support late-successional and old-growth forest structure and function. This study investigates the influence of topography and fuels on the probability of forest fire refugia under varying fire weather conditions. We focused on recent large fires in Oregon and Washington, United States (n = 39 fires > 400 ha, 2004–2014). Our objectives were to (1) map fire refugia as a component of the burn severity gradient, (2) quantify the predictability of fire refugia as a function of prefire fuels and topography under moderate and high fire weather conditions, and (3) map the conditional probability of fire refugia to illustrate their spatial patterns in old-growth forests. Fire refugia exhibited higher predictability under relatively moderate fire weather conditions. Prefire live fuels were strong predictors of fire refugia, with higher refugia probability in forests with higher prefire biomass. In addition, fire refugia probability was higher in topographic settings with relatively northern aspects, steep catchment slopes, and concave topographic positions. Conditional probability maps revealed consistently higher fire refugia probability under moderate versus high fire weather scenarios. Results from this study inform conservation planning by determining late-successional forests most likely to persist as fire refugia despite increasing regional fire activity.

scholarly journals Radiocarbon Calibration around AD 1900 from Scots Pine (Pinus Sylvestris) tree rings from Northern Norway

Radiocarbon ◽  
2019 ◽  
Vol 61 (6) ◽  
pp. 1775-1784
Author(s):  
Helene Svarva ◽  
Pieter Grootes ◽  
Martin Seiler ◽  
Terje Thun ◽  
Einar Værnes ◽  
...  
Keyword(s):  
Pinus Sylvestris ◽  
Pacific Northwest ◽  
Scots Pine ◽  
Tree Rings ◽  
Fossil Fuels ◽  
Pacific Coast ◽  
Northern Norway ◽  
Pine Tree ◽  
The Pacific ◽  
The Us

ABSTRACTTo resolve an inconsistency around AD 1895 between radiocarbon (14C) measurements on oak from the British Isles and Douglas fir and Sitka spruce from the Pacific Northwest, USA, we measured the 14C content in single-year tree rings from a Scots pine tree (Pinus sylvestris L.), which grew in a remote location in Saltdal, northern Norway. The dataset covers the period AD 1864–1937 and its results are in agreement with measurements from the US Pacific coast around 1895. The most likely explanation for older ages in British oak in this period seems to be 14C depletion associated with the combustion of fossil fuels.

Canopy disturbances over the five-century lifetime of an old-growth Douglas-fir stand in the Pacific Northwest

2002 ◽  
Vol 32 (6) ◽  
pp. 1057-1070 ◽  
Author(s):  
Linda E Winter ◽  
Linda B Brubaker ◽  
Jerry F Franklin ◽  
Eric A Miller ◽  
Donald Q DeWitt
Keyword(s):  
Pacific Northwest ◽  
Variable Density ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Old Growth ◽  
The Pacific ◽  
History Of ◽  
Horizontal Heterogeneity ◽  
Restoration Strategies

The history of canopy disturbances over the lifetime of an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand in the western Cascade Range of southern Washington was reconstructed using tree-ring records of cross-dated samples from a 3.3-ha mapped plot. The reconstruction detected pulses in which many western hemlock (Tsuga heterophylla (Raf.) Sarg.) synchronously experienced abrupt and sustained increases in ringwidth, i.e., "growth-increases", and focused on medium-sized or larger ([Formula: see text]0.8 ha) events. The results show that the stand experienced at least three canopy disturbances that each thinned, but did not clear, the canopy over areas [Formula: see text]0.8 ha, occurring approximately in the late 1500s, the 1760s, and the 1930s. None of these promoted regeneration of the shade-intolerant Douglas-fir, all of which established 1500–1521. The disturbances may have promoted regeneration of western hemlock, but their strongest effect on tree dynamics was to elicit western hemlock growth-increases. Canopy disturbances are known to create patchiness, or horizontal heterogeneity, an important characteristic of old-growth forests. This reconstructed history provides one model for restoration strategies to create horizontal heterogeneity in young Douglas-fir stands, for example, by suggesting sizes of areas to thin in variable-density thinnings.

SPATIAL AND TEMPORAL DYNAMICS OF WOOD IN HEADWATER STREAMS OF THE PACIFIC NORTHWEST

2005 ◽  
Vol 41 (4) ◽  
pp. 899-919 ◽  
Author(s):  
Marwan A. Hassan ◽  
Dan L. Hogan ◽  
Stephen A. Bird ◽  
Christine L. May ◽  
Takashi Gomi ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Temporal Dynamics ◽  
Headwater Streams ◽  
Spatial And Temporal Dynamics ◽  
The Pacific

Astrosclereids In Needles Of Old-Growth Douglas-Fir Trees

1999 ◽  
Vol 5 (S2) ◽  
pp. 1240-1241
Author(s):  
M. Apple ◽  
A. Soeldner ◽  
R. Hamill ◽  
K. Tiekotfer
Keyword(s):  
Pacific Northwest ◽  
Cell Walls ◽  
Douglas Fir ◽  
Old Growth ◽  
Mesophyll Cells ◽  
Mesophyll Tissue ◽  
The Pacific ◽  
And Function ◽  
Development Structure

Old-growth Douglas-fir trees in the Pacific Northwest are venerable giants that often live for 500 years and reach heights of over 75 meters. Their needles are relatively ephemeral and small but have the important role of interacting with the atmosphere in order to transpire and photosynthesize. Within the photosynthetic mesophyll tissue of Douglas-fir needles, there are large, non-living cells with lignified secondary cell walls that are known as astrosclereids. Apparent channels in the secondary wall may provide a route for exchange or transport of materials between the astrosclereid lumen and mesophyll cells or the vascular cylinder. Astrosclereids may be involvev d in storage of secondary metabolites such as tannin and may develop in response to fungi, mistletoe, or other pathogens. More knowledge is needed about the development, structure and function of astrosclereids.Needles were collected from sapling and old-growth Douglas-fir, Pseudotsuga menziesii, (Mirb.) Franco, trees at the Wind River Canopy Crane in Carson, Washington and from three sites in the Cascade Mountains of Oregon in 1997 and 1998.

scholarly journals Tagging moisture sources with Lagrangian and inertial tracers: application to intense atmospheric river events

2018 ◽  
Vol 9 (2) ◽  
pp. 785-795 ◽  
Author(s):  
Vicente Pérez-Muñuzuri ◽  
Jorge Eiras-Barca ◽  
Daniel Garaboa-Paz
Keyword(s):  
Pacific Northwest ◽  
Wind Flow ◽  
Atmospheric Moisture ◽  
Atmospheric Rivers ◽  
Atmospheric River ◽  
Moisture Sources ◽  
The Pacific ◽  
The Us ◽  
Northwest Region ◽  
Thermodynamic Processes

Abstract. Two Lagrangian tracer tools are evaluated for studies on atmospheric moisture sources and pathways. In these methods, a moisture volume is assigned to each particle, which is then advected by the wind flow. Usual Lagrangian methods consider this volume to remain constant and the particle to follow flow path lines exactly. In a different approach, the initial moisture volume can be considered to depend on time as it is advected by the flow due to thermodynamic processes. In this case, the tracer volume drag must be taken into account. Equations have been implemented and moisture convection was taken into account for both Lagrangian and inertial models. We apply these methods to evaluate the intense atmospheric rivers that devastated (i) the Pacific Northwest region of the US and (ii) the western Iberian Peninsula with flooding rains and intense winds in early November 2006 and 20 May 1994, respectively. We note that the usual Lagrangian method underestimates moisture availability in the continent, while active tracers achieve more realistic results.

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