Buckley, Thomas N.http://hdl.handle.net/10211.1/14602024-03-28T22:36:18Z2024-03-28T22:36:18ZCapacity of Old Trees to Respond to Environmental ChangePhillips, Nathan G.Buckley, Thomas N.Tissue, David T.http://hdl.handle.net/10211.3/1978162019-12-12T20:37:08Z2008-11-01T00:00:00ZCapacity of Old Trees to Respond to Environmental Change
Phillips, Nathan G.; Buckley, Thomas N.; Tissue, David T.
Atmospheric carbon dioxide [CO2] has increased dramatically within the current life spans of long-lived trees and old forests. Consider that a 500-year-old tree in the early twenty-first century has spent 70% of its life growing under pre- industrial levels of [CO2], which were 30% lower than current levels. Here we address the question of whether old trees have already responded to the rapid rise in [CO2] occurring over the past 150 years. In spite of limited data, aging trees have been shown to possess a substantial capacity for increased net growth after a period of post-maturity growth decline. Observations of renewed growth and physiological function in old trees have, in some instances, coincided with Industrial Age increases in key environmental resources, including [CO2], suggesting the potential for continued growth in old trees as a function of continued global climate change.
This is the pre-peer reviewed version of the following article: Phillips, N. G., Buckley, T. N. and Tissue, D. T. "Capacity of Old Trees to Respond to Environmental Change." Journal of Integrative Plant Biology. 50 (2008): 1355–1364, which has been published in final form at https://doi.org/10.1111/j.1744-7909.2008.00746.x. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
2008-11-01T00:00:00ZNocturnal Water Loss in Mature Subalpine Eucalyptus delegatensis Tall Open Forests and Adjacent E. pauciflora WoodlandsBuckley, Thomas N.Turnbull, Tarryn L.Pfautsch, SebastianAdams, Mark A.http://hdl.handle.net/10211.1/14802018-11-21T00:05:00Z2011-01-01T00:00:00ZNocturnal Water Loss in Mature Subalpine Eucalyptus delegatensis Tall Open Forests and Adjacent E. pauciflora Woodlands
Buckley, Thomas N.; Turnbull, Tarryn L.; Pfautsch, Sebastian; Adams, Mark A.
We measured sap flux (S) and environmental variables in four monospecific stands
of alpine ash (Eucalyptus delegatensis R. Baker, AA) and snowgum (E. pauciflora
Sieb. ex Spreng., SG) in Australia’s Victorian Alps. Nocturnal S was 11.8 ± 0.8%
of diel totals.We separated transpiration (E) and refilling components of S using a
novel modeling approach based on refilling time constants. The nocturnal fraction
of diel water loss (fn) averaged 8.6 ± 0.6% for AA and 9.8 ± 1.7% for SG; fn differed
among sites but not species. Evaporative demand (D) was the strongest driver of
nocturnal E (En). The ratio En/D (Gn) was positively correlated to soil moisture in
most cases, whereas correlations between wind speed and Gn varied widely in sign
and strength. Our results suggest (1) the large, mature trees at our subalpine sites
have greater fn than the few Australian native tree species that have been studied at
lower elevations, (2) AA and SG exhibit similar fn despite very different size and life
history, and (3) fn may differ substantially among sites, so future work should be
replicated across differing sites.Our novel approach to quantifying fn can be applied
to S measurements obtained by any method.
The definitive version of this article is available at https://doi.org/10.1002/ece3.44. All Ecology and Evolution articles are published under the terms of the Creative Commons Attribution License (CC BY) which allows users to copy, distribute and transmit an article, adapt the article and make commercial use of the article. The CC BY license permits commercial and non-commercial re-use of an open access article, as long as the author is properly attributed.
2011-01-01T00:00:00ZThe Role of Bundle Sheath Extensions and Life Form in Stomatal Responses to Leaf Water StatusBuckley, Thomas N.Gilbert, Matthew E.Sack, Lawrenhttp://hdl.handle.net/10211.1/14752013-09-11T15:58:36Z2011-01-01T00:00:00ZThe Role of Bundle Sheath Extensions and Life Form in Stomatal Responses to Leaf Water Status
Buckley, Thomas N.; Gilbert, Matthew E.; Sack, Lawren
Bundle sheath extensions (BSEs) are key features of leaf structure with currently little-understood functions. To test the hypothesis that BSEs reduce the hydraulic resistance from the bundle sheath to the epidermis (rbe) and thereby accelerate hydropassive stomatal movements, we compared stomatal responses with reduced humidity and leaf excision among 20 species with heterobaric or homobaric leaves and herbaceous or woody life forms. We hypothesized that low rbe due to the presence of BSEs would increase the rate of stomatal opening (V) during transient wrong-way responses, but more so during wrong-way responses to excision (Ve) than humidity (Vh), thus increasing the ratio of Ve to Vh. We predicted the same trends for herbaceous relative to woody species given greater hydraulic resistance in woody species. We found that Ve, Vh, and their ratio were 2.3 to 4.4 times greater in heterobaric than homobaric leaves and 2.0 to 3.1 times greater in herbaceous than woody species. To assess possible causes for these differences, we simulated these experiments in a dynamic compartment/resistance model, which predicted larger Ve and Ve/Vh in leaves with smaller rbe. These results support the hypothesis that BSEs reduce rbe. Comparison of our data and simulations suggested that rbe is approximately 4 to 16 times larger in homobaric than
heterobaric leaves. Our study provides new evidence that variations in the distribution of hydraulic resistance within the leaf
and plant are central to understanding dynamic stomatal responses to water status and their ecological correlates and that
BSEs play several key roles in the functional ecology of heterobaric leaves.
Published by and copyright by American Society of Plant Biologists. Refer to definitive publisher's version for full text of article: http://www.plantphysiol.org/content/156/2/962
2011-01-01T00:00:00ZHow Should Leaf Area, Sapwood Area and Stomatal Conductance Vary with Tree Height to Maximize Growth?Buckley, Thomas N.Roberts, David W.http://hdl.handle.net/10211.1/15102013-07-20T09:17:56Z2006-01-01T00:00:00ZHow Should Leaf Area, Sapwood Area and Stomatal Conductance Vary with Tree Height to Maximize Growth?
Buckley, Thomas N.; Roberts, David W.
Conventional wisdom holds that the ratio of leaf
area to sapwood area (L/S) should decline during height (H)
growth to maintain hydraulic homeostasis and prevent stomatal
conductance (gs) from declining. We contend that L/S
should increase with H based on a numerical simulation, a
mathematical analysis and a conceptual argument: (1) numerical
simulation—a tree growth model, DESPOT (Deducing
Emergent Structure and Physiology Of Trees), in which carbon
(C) allocation is regulated to maximize C gain, predicts L/S
should increase during most of H growth; (2) mathematical
analysis—the formal criterion for optimal C allocation, applied
to a simplified analytical model of whole tree carbon–
water balance, predicts L/S should increase with H if leaf-level
gas exchange parameters including gs are conserved; and (3)
conceptual argument—photosynthesis is limited by several
substitutable resources (chiefly nitrogen (N), water and light)
and H growth increases the C cost of water transport but not
necessarily of N and light capture, so if the goal is to maximize
C gain or growth, allocation should shift in favor of increasing
photosynthetic capacity and irradiance, rather than sustaining
gs. Although many data are consistent with the prediction that
L/S should decline with H, many others are not, and we discuss
possible reasons for these discrepancies.
Published by and copyright by Heron Publishing.
2006-01-01T00:00:00Z