Hypothetical Responses of Pine Forests to Climate Change Based on Manipulation Experiments

Tree physiology/Tree physiology (Dordrecht) · 2026-01-01

Shoot Architecture: A Crown Attribute Regulating Biosphere-Atmosphere Exchanges Via Coordinated Light Absorption and Water Delivery

Tree physiology/Tree physiology (Dordrecht) · 2026-01-01

Similar response of canopy conductance to increasing vapor pressure deficit and decreasing soil conductivity with drought among five morphologically contrasting but co-occurring pine species

Agricultural and Forest Meteorology · 2025-03-09 · 5 citations

Leaf transpiration decreases similarly among five pine species as height increases over stand development

Tree Physiology · 2025-07-26 · 3 citations

With increasing tree height, leaf transpiration (EL) is increasingly restricted by path-length resistance and gravity's discount of the driving force of xylem water flow. The effect of height on leaf transpiration is nearly always assessed using chronosequence data; however, in this long-term, dynamic study, we assessed increasing height's effects on EL using continuous monitoring of sap-flux for five Pinus species growing in a common-garden and experiencing a wide range of environmental conditions. We assessed how three drivers of EL-path-length (h), water-potential gradient (ΔΨ) and sapwood-to-leaf area ratio (AS:AL)-affect transpiration of the five Pinus species ranging five-fold in needle length by performing gas-exchange and water potential measurements and monitoring tree biometrics, sap-flux and soil and atmospheric conditions over 5 years at the Duke Forest, NC. With our methods controlling for all but the effect of tree hydraulics on transpiration, we found that EL, derived early in the study based on gas-exchange and later based on sap-flux measurements, were similar among species under both wet and dry soil moisture conditions. When soil moisture was not limiting, ΔΨ decreased across species with increasing needle length while whole-plant conductance (kplant) increased, leading to similar EL among species. Under soil drought, the trends with needle length of both variables became weaker as shorter-needle species showed a greater decrease in ΔΨ, while longer-needle species had a greater decline in kplant, again resulting in similar EL among species. Increasing h over time reduced EL similarly in all species, in part owing to similar annual minima of AS:AL among species and its invariance over a four-fold range in h. Controlling for non-hydraulic sources of variation showed that EL decreased with h similarly in five Pinus spp. of a wide range in leaf and crown characteristics.

Increasing Pathlength Resistance and Within-Canopy Shading Similarly Attenuate Transpiration in Accruing Collocated Stands of Five Pine Species

SSRN Electronic Journal · 2025-01-01

Hydraulic conductivity‐induced systematic parameter variation in a widely used thermal dissipation sap‐flow technique

New Phytologist · 2025-08-25

The Granier-type thermal-dissipation method (TDM) is the most widely used sap-flow technique. However, its original calibration coefficients often underestimate high flow rates, limiting their generality. We derived TDM coefficients (scaling factors and exponents) for 31 species, including 18 diffuse-porous, two ring-porous, six palms, and five lianas, representing a broad range of wood properties. Factors influencing the coefficients and their accuracy were also investigated. Furthermore, we compiled 119 published coefficients for 88 additional species covering seven major xylem types. Most recalibrated and published coefficient values were substantially different from the original values, particularly in ring-porous and liana species with high hydraulic conductivity. The coefficient values depend on the statistical models and the applied maximum pressure during the calibration process. Vessel-lumen area fraction and hydraulic conductivity explained the interspecific variation in two coefficients at both segment and species levels. We applied recalibrated and original coefficients to a rubber plantation and found that the original coefficients produced unreasonably low transpiration estimates, while recalibrated coefficients yielded reasonable values. Uncertainties in scaling processes, including sapwood-area and radial and azimuth effects, also contributed significantly to the overall estimates. Our study demonstrates that accurate transpiration estimation must also address scaling-related sources of variation, as they contribute equally to uncertainty as poor calibration.

Xylem Hydraulic Properties of Five <i>Pinus</i> Species Grown in Common Environment Vary From Needles to Roots With Needle Length and Native‐Range Climate

Plant Cell & Environment · 2025-06-19 · 3 citations

Plant hydraulics govern water transport linking root to mesophyll surfaces, affecting gas-exchange, survival and growth. Xylem and leaf structural and functional characteristics vary widely among Pinus species, even when growing under similar conditions. We quantified the variation of xylem anatomy, hydraulic function, and within-tree hydraulic resistivity distribution, among five widely ranging southern US species: Pinus echinata, Pinus elliottii, Pinus palustris, Pinus taeda and Pinus virginiana. We found that, across species, needle length (NL) explained most of the variation in needle hydraulic properties. Resistivity to water flow in needles through tracheids' bordered-pits decreased linearly from ~99% to 8% with increasing NL; total tracheid resistivity in branches and roots was partitioned between bordered-pits and lumens similarly regardless of NL. Mean annual precipitation typical of the species' climatic range (CR) accounted for the variation in root hydraulic properties. Despite strong root-to-branch correlations of several attributes, neither NL nor CR explained the variation of any branch attribute. The results suggest that NL dominates needle xylem anatomy and function in a manner consistent with increasing hydraulic efficiency with NL, but CR produces genetic differences resulting in increased resistance to more negative xylem pressures with decreasing precipitation, at a cost of reduced hydraulic efficiency.

Overlooked branch turnover creates a widespread bias in forest carbon accounting

Proceedings of the National Academy of Sciences · 2024 · 9 citations

• Environmental science
• Forestry
• Ecology

globally), of similar magnitude to the observed global forest carbon sinks. In addition, reallocating carbon to branch turnover in model simulations reduced stem wood biomass, a long-lasting carbon storage, by 7 to 17%. This prevailing neglect of branch turnover suggests widespread biases in carbon flux estimates across global datasets and model simulations. Branch litterfall, sometimes used as a proxy for branch turnover, ignores carbon lost from attached dead branches, underestimating branch C turnover by 38% in a pine forest. Modifications to field measurement protocols and existing models are needed to allow a more realistic partitioning of wood production and forest carbon storage.

Xylem hydraulic properties of five Pinus species grown in common environment vary from needles to roots with needle length and native-range climate

2024-12-09

Plant hydraulics govern water transport linking root to mesophyll surfaces, affecting gas-exchange, survival, and growth. Xylem and leaf structural and functional characteristics vary widely among Pinus species, even when growing under similar conditions. We quantified the variation of xylem anatomy, hydraulic function, and within-tree hydraulic resistivity distribution, among five widely ranging southern US species: Pinus echinata , P. elliottii , P. palustris , P. taeda , and P. virginiana . We found that, across species, needle length (NL) explained most of the variation in needle hydraulic properties. Resistivity to water flow in needles through tracheids’ bordered-pits decreased from ~99% to 8% with increasing NL; total tracheid resistivity in branches and roots was partitioned between bordered-pits and lumens similarly regardless of NL. Mean annual precipitation typical of the species’ climatic range (CR) accounted for the variation in root hydraulic properties. Despite strong root-to-branch correlations of several attributes, neither NL nor CR explained the variation of any branch attribute. The results suggest that NL dominates needle xylem anatomy and function in a manner consistent with increasing hydraulic efficiency with NL, but CR produces genetic differences resulting in increased resistance to more negative xylem pressures with decreasing precipitation, at a cost of reduced hydraulic efficiency.

Increased leaf area index and efficiency drive enhanced production under elevated atmospheric [<scp>CO₂</scp>] in a pine‐dominated stand showing no progressive nitrogen limitation

Global Change Biology · 2024-02-01 · 4 citations

Abstract Enhancement of net primary production (NPP) in forests as atmospheric [CO 2 ] increases is likely limited by the availability of other growth resources. The Duke Free Air CO 2 Enrichment (FACE) experiment was located on a moderate‐fertility site in the southeastern US, in a loblolly pine ( Pinus taeda L.) plantation with broadleaved species growing mostly in mid‐canopy and understory. Duke FACE ran from 1994 to 2010 and combined elevated [CO 2 ] (eCO 2 ) with nitrogen (N) additions. We assessed the spatial and temporal variation of NPP response using a dataset that includes previously unpublished data from 6 years of the replicated CO 2 × N experiment and extends to 2 years beyond the termination of enrichment. Averaged over time (1997–2010), NPP of pine and broadleaved species were 38% and 52% higher under eCO 2 compared to ambient conditions. Furthermore, there was no evidence of a decline in enhancement over time in any plot regardless of its native site quality. The relation between spatial variation in the response and native site quality was suggested but inconclusive. Nitrogen amendments under eCO 2 , in turn, resulted in an additional 11% increase in pine NPP. For pine, the eCO 2 ‐induced increase in NPP was similar above‐ and belowground and was driven by both increased leaf area index ( L ) and production efficiency (PE = NPP/ L ). For broadleaved species, coarse‐root biomass production was more than 200% higher under eCO 2 and accounted for the entire production response, driven by increased PE. Notably, the fraction of annual NPP retained in total living biomass was higher under eCO 2 , reflecting a slight shift in allocation fraction to woody mass and a lower mortality rate. Our findings also imply that tree growth may not have been only N‐limited, but perhaps constrained by the availability of other nutrients. The observed sustained NPP enhancement, even without N‐additions, demonstrates no progressive N limitation.