Biology subjects

Griffin, K. L.

Publications and source records attributed to Griffin, K. L..

3 recordsLinked to original sources

bioRxiv2021

Variation in white spruce needle respiration across the species range

White spruce (Picea glauca) spans a massive range from arctic treeline to temperate forests, yet the variability in respiratory physiology and related implications for tree carbon balance at the extremes of this distribution remain as enigmas. Working at both the most northern and southern extents of the white spruce distribution range more than 5000 km apart, we measured the short- term temperature response of dark respiration (R/T) at upper and lower canopy positions. R/T curves were fit to both polynomial and thermodynamic models so that model parameters could be compared among locations, canopy positions, and with previously published data. Respiration measured at 25{degrees}C (R25) was 68% lower at the southern location than at the northern location (0.73{+/-}0.15 vs. 2.27{+/-}0.02 mol m-2 s-1), resulting in a significantly lower (p< 0.01) intercept in R/T response in temperate trees. Only at the southern location did upper canopy leaves have a steeper temperature response than lower canopy leaves, likely reflecting steeper canopy gradients in light. No differences were observed in the maximum temperature of respiration. At the northern range limit respiration is nearly twice that of the average R25 reported in a global leaf respiration database. This large carbon cost likely challenges tree survival and contributes to restricting the location of the northern treeline. We predict that without significant thermal acclimation, foliage respiration will increase with projected end-of-the-century warming and will likely constrain the future range limits of this important boreal species. Summary StatementWhite spruce (Picea glauca) needle respiration at the northern limit of the species range is three times higher than at the southern range limit (when measured at 25 {degrees}C). This high carbon cost likely challenges tree survival and contributes to the location of the northern treeline.

plant biology↗

bioRxiv2021

High Leaf Respiration Rates May Limit the Success of White Spruce Saplings growing in The Kampfzone at the Arctic Treeline

Arctic Treeline is the transition from the boreal forest to the treeless tundra and may be determined by growing season temperatures. The physiological mechanisms involved in determining the relationship between the physical and biological environment and the location of treeline are not fully understood. In Northern Alaska we studied the relationship between temperature and leaf respiration in 36 white spruce (Picea glauca) trees, sampling both the upper and lower canopy, to test two research hypotheses (H0). The first H01 is that canopy position will not influence leaf respiration. The associated alternative hypothesis (HA) is that the upper canopy leaves which are more directly coupled to the atmosphere will experience more challenging environmental conditions and thus have higher respiration rates to facilitate metabolic function. The second H02 is that tree size will not influence leaf respiration. The associated HA is that saplings (stems that are 5-10 cm DBH (diameter at breast height)) will have higher respiration rates than trees (stems [≥] 10 cm DBH) since saplings represent the transition from seedlings growing in the more favorable aerodynamic boundary layer, to trees which are fully coupled to the atmosphere but of sufficient size to persist. Respiration did not change with canopy position, however respiration at 25{degrees}C was 42% higher in saplings compared to trees (3.43 {+/-} 0.19 vs. 2.41 {+/-} 0.14 mol m-2 s-1). Furthermore, there were significant differences in the temperature response of respiration, and seedlings reached their maximum respiration rates at 59{degrees}C, more than two degrees higher than trees. Our results demonstrate that the respiratory characteristics of white spruce saplings at treeline are extreme, imposing a significant carbon cost that may contribute to their lack of perseverance beyond treeline. In the absence of thermal acclimation, the rate of leaf respiration could increase by 57% by the end of the century, posing further challenges to the ecology of this massive ecotone. This paper is dedicated to the memory of James N. Siedow, Professor of Botany at Duke University. I am honored to have learned from, and to have been inspired by Jim. I will always be grateful for the time he spent helping me, the depth of education he gave me, and his steady mentoring as part of my thesis committee. His devotion to science and push for deeper knowledge of plant respiration set an example for all of us, particularly those who were lucky enough to study with him. Jim was also a memorable Father Christmas at the departmental holiday parties, always keeping us laughing with his particular brand of quick wit and sarcasm. - Kevin L. Griffin

ecology↗

bioRxiv2020

Novel insights from point-dendrometers in an urban setting: linking environmental variation to fluctuations in stem radius.

BackgroundReal-time monitoring of tree growth can provide novel information about trees in urban/suburban areas and the myriad ecosystem services they provide. By monitoring irrigated specimen trees we test the hypothesis that in trees with sufficient water, growth is governed by environmental factors regulating energy gain rather than by factors related to water use. MethodsInternet enabled, high-resolution dendrometers were installed on three trees in Southampton, NY. The instruments, along with a weather station, streamed data to a project web page that was updated once an hour. (https://ecosensornetwork.com). Growing periods were determined using a Hidden Markov Model based on Zweifel et al.s (2016) zero-growth model. Linear models and conditional inference trees correlated environmental variables to growth magnitude and rate of growth. ResultsGrowth was governed by the interacting environmental variables of air temperature, soil moisture, VPD and took place primarily at night. Radial growth of spruce began April 14 after the accumulation of 69.7 {degrees}C growing degrees days and ended September 7th. Cedar growth began later (April 26th), after the accumulation of 160.6 {degrees}C and ended later (November 3rd). During the observation period, these three modest suburban trees sequestered 108.3 kg of CO2. ConclusionsThough irrigated, residential tree growth in our experiment was affected by environmental factors relating to both water use and energy gain through photosynthesis. Linking tree growth to fluctuations in environmental conditions facilitates the development of a predictive understanding useful for ecosystem management and growth forecasting across future altering climates.

ecology↗