Quaking aspen (Populus tremuloides Michx.), a widespread and keystone tree species in North America, experienced heat and drought stress in the years 2002 and 2003 in the southwestern United States. This led to widespread aspen mortality that has altered the composition of forests, and is expected to occur again if...
Because iso- and anisohydric species differ in stomatal regulation
of the rate and magnitude of fluctuations in shoot
water potential, they may be expected to show differences in
the plasticity of their shoot water relations components, but
explicit comparisons of this nature have rarely been made.
We subjected excised shoots...
Because iso- and anisohydric species differ in stomatal regulation
of the rate and magnitude of fluctuations in shoot
water potential, they may be expected to show differences in
the plasticity of their shoot water relations components, but
explicit comparisons of this nature have rarely been made.
We subjected excised shoots...
Stored non-structural carbohydrates (NSCs) could play an important role in tree survival in the face of a changing climate and
associated stress-related mortality. We explored the effects of the stomata-blocking and defoliating fungal disease called
Swiss needle cast on Douglas-fir carbohydrate reserves and growth to evaluate the extent to which...
Stored non-structural carbohydrates (NSCs) could play an important role in tree survival in the face of a changing climate and
associated stress-related mortality. We explored the effects of the stomata-blocking and defoliating fungal disease called
Swiss needle cast on Douglas-fir carbohydrate reserves and growth to evaluate the extent to which...
First-year tree seedlings represent a particularly vulnerable life stage and successful seedling establishment is crucial for forest
regeneration. We investigated the extent to which Pinus ponderosa P. & C. Lawson populations from different climate zones
exhibit differential expression of functional traits that may facilitate their establishment. Seeds from two populations...
First-year tree seedlings represent a particularly vulnerable life stage and successful seedling establishment is crucial for forest
regeneration. We investigated the extent to which Pinus ponderosa P. & C. Lawson populations from different climate zones
exhibit differential expression of functional traits that may facilitate their establishment. Seeds from two populations...
Recent work has suggested that plants differ in their relative
reliance on structural avoidance of embolism versus maintenance
of the xylem water column through dynamic traits such
as capacitance, but we still know little about how and why
species differ along this continuum. It is even less clear how
or...
Recent work has suggested that plants differ in their relative
reliance on structural avoidance of embolism versus maintenance
of the xylem water column through dynamic traits such
as capacitance, but we still know little about how and why
species differ along this continuum. It is even less clear how
or...
Rising atmospheric [CO₂], cₐ, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO₂],...
First-year tree seedlings represent a particularly vulnerable life stage and successful seedling establishment is crucial for forest regeneration. We investigated the extent to which Pinus ponderosa P. & C. Lawson populations from different climate zones exhibit differential expression of functional traits that may facilitate their establishment. Seeds from two populations...
Leaf hydraulics, gas exchange and carbon storage in Pinus edulis and Juniperus monosperma, two tree species on opposite ends of the isohydry–anisohydry spectrum, were analyzed to examine relationships between hydraulic function and carbohydrate dynamics. Leaf hydraulic vulnerability, leaf water potential (Wl), leaf hydraulic conductance (Kleaf), photosynthesis (A), stomatal conductance (gs)...
Because iso- and anisohydric species differ in stomatal regulation
of the rate and magnitude of fluctuations in shoot
water potential, they may be expected to show differences in
the plasticity of their shoot water relations components, but
explicit comparisons of this nature have rarely been made.
We subjected excised shoots...
Swiss needle cast (SNC) is a fungal disease of Douglas-fir
(Pseudotsuga menziesii) that has recently become prevalent
in coastal areas of the Pacific Northwest. We used growth
measurements and stable isotopes of carbon and oxygen in
tree-rings of Douglas-fir and a non-susceptible reference
species (western hemlock, Tsuga heterophylla) to evaluate...
Stored non-structural carbohydrates (NSCs) could play an important role in tree survival in the face of a changing climate and associated stress-related mortality. We explored the effects of the stomata-blocking and defoliating fungal disease called Swiss needle cast on Douglas-fir carbohydrate reserves and growth to evaluate the extent to which...
Recent work has suggested that plants differ in their relative reliance on structural avoidance of embolism versus maintenance of the xylem water column through dynamic traits such as capacitance, but we still know little about how and why species differ along this continuum. It is even less clear how or...
Tree-ring characteristics are commonly used to reconstruct climate variables, but divergence from the assumption of a single biophysical control may reduce the accuracy of these reconstructions. Here, we present data from bur oaks (Quercus macrocarpa Michx.) sampled within and beyond the current species bioclimatic envelope to identify the primary environmental...
Stomata control tree transpiration by sensing and integrating environmental signals originating in the atmosphere and soil, and co-occurring species may differ in inherent stomatal sensitivity to these above- and belowground signals and in the types of signals to which they respond. Stomatal responsiveness to environmental signals is likely to differ...
• Premise of the Study: Tropical liana abundance has been increasing over the past 40 yr, which has been associated with reduced
rainfall. The proposed mechanism allowing lianas to thrive in dry conditions is deeper root systems than co-occurring trees,
although we know very little about the fundamental hydraulic physiology...
• Premise of the study: The pathway of radial water movement in tree stems presents an unknown with respect to whole-tree
hydraulics. Radial profi les have shown substantial axial sap fl ow in deeper layers of sapwood (that may lack direct connection
to transpiring leaves), which suggests the existence of...
Paleoclimate proxies based on the measurement of xylem cell anatomy have rarely been developed across the temperature range of a species or applied to wood predating the most recent millennium. Here we describe wood anatomy-based proxies for spring temperatures in central North America from modern bur oaks (Quercus macrocarpa Michx.)....
Angiosperm and coniferous tree species utilize a continuum of hydraulic strategies. Hydraulic safety margins (defined as differences between naturally occurring xylem pressures and pressures that would cause hydraulic dysfunction, or differences between pressures resulting in loss of hydraulic function in adjacent organs (e.g., stems vs. leaves) tend to be much...
Co-occurring species often have different strategies for tolerating daily cycles of water stress. One underlying parameter that can link together the suite of traits that enables a given strategy is wood density. Here we compare hydraulic traits of two pioneer species from a tropical forest in Panama that differ in...
Hydraulic redistribution is the process of passive water movement from deeper moist soil to shallower dry soil layers using plant roots as conduits. Results from this study indicate that this phenomenon exists among two shrub species (Guiera senegalensis and Piliostigma reticulatum) that co-exist with annual food crops in Sahelian agro-ecosystems....
Hydraulic conductance of leaves (K[subscript leaf]) typically decreases with increasing water stress and recent studies have proposed different mechanisms responsible for decreasing K[subscript leaf]. We measured K[subscript leaf] concurrently with ultrasonic acoustic emissions (UAEs) in dehydrating leaves of several species to determine whether declining K[subscript leaf] was associated with xylem...
Transgenic down-regulation of the Pt4CL1 gene family encoding 4-coumarate:coenzyme A ligase (4CL) has been reported as a
means for reducing lignin content in cell walls and increasing overall growth rates, thereby improving feedstock quality for
paper and bioethanol production. Using hybrid poplar (Populus tremula 3 Populus alba), we applied this...
Plant hydraulic architecture (PHA) has been linked to water transport sufficiency, photosynthetic rates, growth form and attendant carbon allocation. Despite its influence on traits central to conferring an overall competitive advantage in a given environment, few studies have examined whether key aspects of PHA are indicative of successional stage, especially...
• Reduced lignin content in perennial crops has been sought as a means to
improve biomass processability for paper and biofuels production, but it is unclear
how this could affect wood properties and tree form.
• Here, we studied a nontransgenic control and 14 transgenic events containing
an antisense 4-coumarate:coenzyme...
Of 14 transgenic poplar genotypes (Populus tremula × Populus alba) with antisense 4-coumarate:coenzyme A ligase that were grown in the field for 2 years, five that had substantial lignin reductions also had greatly reduced xylem-specific conductivity compared with that of control trees and those transgenic events with small reductions in...
Given the fundamental importance of xylem safety and efficiency for plant survival and fitness, it is not surprising that these are among the most commonly studied features of hydraulic architecture. However, much remains to be learned about the nature and universality of conflicts between hydraulic safety and efficiency. Although selection...
We studied xylem anatomy and hydraulic architecture in 14 transgenic insertion events and a control line of hybrid poplar (Populus spp.) that varied in lignin content. Transgenic events had different levels of down‐regulation of two genes encoding 4‐coumarate:coenzyme A ligase (4CL). Two‐year‐old trees were characterized after growing either as free‐standing...
In the Pacific north-west, the Cascade Mountain Range blocks much of the precipitation and maritime influence of the Pacific Ocean, resulting in distinct climates east and west of the mountains. The current study aimed to investigate relationships between water storage and transport properties in populations of Douglas-fir (Pseudotsuga menziesii) and...
Premise of the study: The Pacific Northwest of North America experiences relatively mild winters and dry summers. For the
tall coniferous trees that grow in this region, we predicted that loss in the hydraulic conductivity of uppermost branches would
be avoided because of difficulty reversing accumulated emboli in xylem that...
The gravitational component of water potential and frictional resistance during transpiration lead to substantial reductions in leaf water potential (Ψl) near the tops of tall trees, which can influence both leaf growth and physiology. We examined the relationships between morphological features and gas exchange in foliage collected near the tops...
Use of Granier-style heat dissipation sensors to measure sap flow is common in plant physiology, ecology and hydrology. There has been concern that any change to the original Granier design invalidates the empirical relationship between sap flux density and the temperature difference between the probes. Here, we compared daily water...
This study investigated the mechanisms involved in the
regulation of stomatal closure in Douglas-fir and evaluated
the potential impact of compensatory adjustments in
response to increasing tree height upon these mechanisms.
In the laboratory, we measured leaf hydraulic conductance
(Kleaf) as leaf water potential (Yl) declined for comparison
with in...
The volume and complexity of their vascular systems make the dynamics of long‐distance water transport in large trees difficult to study. We used heat and deuterated water (D₂O) as tracers to characterize whole‐tree water transport and storage properties in individual trees belonging to the coniferous species Pseudotsuga menziesii (Mirb.) Franco...
We determined the axial and radial xylem tension gradients in trunks of young Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. Axial specific conductivity (ks-a) and sap flux density (Js) were measured at four consecutive depths within the sapwood at a stem height of 1 m. By definition, at a given position...
1. The xylem pressure inducing 50% loss of hydraulic conductivity due to embolism
widely used for comparisons of xylem vulnerability among species and across aridity
However, despite its utility as an index of resistance to catastrophic xylem failure
drought, P5o may have no special physiological relevance in the context of...
Our goals were to quantify how non-embolism-inducing pressure gradients influence trunk sapwood specific conductivity (ks) and to compare the impacts of constant and varying pressure gradients on ks with KCl and H2O as the perfusion solutions. We studied six woody species (three conifers and three angiosperms) which varied in pit...
• Hydraulic vulnerability of Douglas-fir (Pseudotsuga menziesii) branchlets
decreases with height, allowing shoots at greater height to maintain hydraulic
conductance (Kshoot) at more negative leaf water potentials (Ψl).
• To determine the basis for this trend shoot hydraulic and tracheid anatomical
properties of foliage from the tops of Douglas-fir trees...
• Coniferous, diffuse‐porous and ring‐porous trees vary in their xylem anatomy, but the functional consequences of these differences are not well understood from the scale of the conduit to the individual.
• Hydraulic and anatomical measurements were made on branches and trunks from 16 species from temperate and tropical areas,...
• There are two optima for maximizing hydraulic conductance per vasculature volume in plants. Murray's law (ML) predicts the optimal conduit taper for a fixed change in conduit number across branch ranks. The opposite, the Yarrum optimum (YO), predicts the optimal change in conduit number for a fixed taper.
•...
The air‐seeding hypothesis predicts that xylem embolism resistance is linked directly to bordered pit functioning. We tested this prediction in trunks, roots, and branches at different vertical and radial locations in young and old trees of Pseudotsuga menziesii. Dimensions of bordered pits were measured from light and scanning electron micrographs,...
Despite renewed interest in the nature of limitations on maximum tree height, the mechanisms governing ultimate and species-specific height limits are not yet understood, but likely involve water transport dynamics. Tall trees experience increased risk of xylem embolism from air-seeding because tension in their water column increases with height due...
The cohesion-tension theory of water transport states that hydrogen bonds hold water molecules together and that they are pulled through the xylem under tension. This tension could cause transport failure in at least two ways: collapse of the conduit walls (implosion), or rupture of the water column through air-seeding. The...
Little is known of wood properties in trees that were initially suppressed and subsequently released from suppression. The purpose of this study was to assess differences in growth ring width, specific conductivity (Ks), tracheid dimensions, moisture content, and wood density in suppressed Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock...