Browsing by Subject "allometry"

Now showing 1 - 3 of 3
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    Earlywood vessel area analysis of Quercus macrocarpa tree rings at the Cedar Creek Ecosystem Science Reserve in Minnesota
    (2021-07) Crawford, Daniel
    Quantification of various wood anatomical characteristics in annually resolved tree rings has been shown to reveal environmental information on seasonal or shorter timescales that is often not present in ring width alone. The genus Quercus is particularly important to dendroclimatology, and Q. macrocarpa tree rings are particularly useful for studies of regional climate. Further, the ring-porous anatomy of this species positions it as a prime candidate for quantitative wood anatomy. To date, the majority of dendroclimate studies involving Q. macrocarpa have been based purely on ring width. Very few quantitative wood anatomy studies have been conducted in North America, and virtually none in the Western Great Lakes states. Measurement of earlywood vessel area may provide an avenue for extracting information on past environmental conditions, even at forest interior locations which fall outside the typical schema of dendrochronology site selection. When related to tree height measurements, earlywood vessel area can provide key insights into the hydraulic properties of individual plants, water use strategies, and the history of tree height throughout ontogenesis.This study examines the interannual variability in mean vessel area as well as the reliance of vessel area on tree height in savanna and woodland habitat types at the Cedar Creek Ecosystem Science Reserve, in Minnesota. The relationship between vessel area and tree height is statistically and practically significant, and far stronger at this site than the relationship between inter-annual mean vessel area variability and climate, for which no clear process-based relationships were detected. This finding holds true when other metrics than mean vessel area are explored, including percentiles of mean vessel area, hydraulic diameter, and vessel area variance. The overall positive trend in vessel area throughout ontogenesis and the adherence of this trend to a functional allometric power curve further support the body of literature showing that tree height is a deterministic driver of vessel size in these individuals. Given the clear dependence of hydraulic characteristics on tree height, and the possible role of tree height as a factor in plant vulnerability to myriad factors associated with global environmental change, I advocate for tree height to become a standard datum in dendrochronological sampling, and encourage future studies involving quantitative wood anatomy to further examine the role of tree height on individual trends in xylem size through time.
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    How does biomass distribution change with size and differ among species? An analysis for 1200 plant species from five continents
    (Elsevier, 2015) Poorter, Hendrik; Jagodzinski, Andrzej M; Oleksyn, Jacek; Ruiz-Peinado, Ricardo; Kuyah, Shem; Luo, Yunjian; Reich, Peter B; Usoltsev, Vladimir A; Buckley, Thomas N; Sack, Lawren
    We compiled a global database for leaf, stem and root biomass representing c. 11 000 records for c. 1200 herbaceous and woody species grown under either controlled or field conditions. We used this data set to analyse allometric relationships and fractional biomass distribution to leaves, stems and roots. We tested whether allometric scaling exponents are generally constant across plant sizes as predicted by metabolic scaling theory, or whether instead they change dynamically with plant size. We also quantified interspecific variation in biomass distribution among plant families and functional groups. Across all species combined, leaf vs stem and leaf vs root scaling exponents decreased from c. 1.00 for small plants to c. 0.60 for the largest trees considered. Evergreens had substantially higher leaf mass fractions (LMFs) than deciduous species, whereas graminoids maintained higher root mass fractions (RMFs) than eudicotyledonous herbs. These patterns do not support the hypothesis of fixed allometric exponents. Rather, continuous shifts in allometric exponents with plant size during ontogeny and evolution are the norm. Across seed plants, variation in biomass distribution among species is related more to function than phylogeny. We propose that the higher LMF of evergreens at least partly compensates for their relatively low leaf area : leaf mass ratio.
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    Mean mass-specific metabolic rates are strikingly similar across life’s major domains: Evidence for life’s metabolic optimum
    (National Academy of Sciences, 2008) Makarieva, Anastassia M; Gorshkova, Victor G; Li, Bai-Lian; Chown, Steven L; Reich, Peter B; Gavrilov, Valery M
    A fundamental but unanswered biological question asks how much energy, on average, Earth’s different life forms spend per unit mass per unit time to remain alive. Here, using the largest database to date, for 3,006 species that includes most of the range of biological diversity on the planet—from bacteria to elephants, and algae to sapling trees—we show that metabolism displays a striking degree of homeostasis across all of life. We demonstrate that, despite the enormous biochemical, physiological, and ecological differences between the surveyed species that vary over 1020-fold in body mass, mean metabolic rates of major taxonomic groups displayed at physiological rest converge on a narrow range from 0.3 to 9 W kg 1. This 30-fold variation among life’s disparate forms represents a remarkably small range compared with the 4,000- to 65,000-fold difference between the mean metabolic rates of the smallest and largest organisms that would be observed if life as a whole conformed to universal quarterpower or third-power allometric scaling laws. The observed broad convergence on a narrow range of basal metabolic rates suggests that organismal designs that fit in this physiological window have been favored by natural selection across all of life’s major kingdoms, and that this range might therefore be considered as optimal for living matter as a whole.