The coordination of plant leaf water potential (ΨL) regulation and xylem vulnerability to embolism is fundamental for understanding the tradeoffs between carbon uptake and risk of hydraulic damage. ...There is a general consensus that trees with vulnerable xylem more conservatively regulate ΨL than plants with resistant xylem. We evaluated if this paradigm applied to three important eastern US temperate tree species, Quercus alba L., Acer saccharum Marsh. and Liriodendron tulipifera L., by synthesizing 1600 ΨL observations, 122 xylem embolism curves and xylem anatomical measurements across 10 forests spanning pronounced hydroclimatological gradients and ages. We found that, unexpectedly, the species with the most vulnerable xylem (Q. alba) regulated ΨL less strictly than the other species. This relationship was found across all sites, such that coordination among traits was largely unaffected by climate and stand age. Quercus species are perceived to be among the most drought tolerant temperate US forest species; however, our results suggest their relatively loose ΨL regulation in response to hydrologic stress occurs with a substantial hydraulic cost that may expose them to novel risks in a more drought‐prone future.
Summary Statement
Across 10 diverse eastern US stands, anisohydric Quercus alba possessed more embolism‐vulnerable stems than isohydric Acer saccharum and Liriodendron tulipifera. Although oaks are often considered drought‐tolerant species, Q. alba sustains gas exchange by operating with heightened risk for hydraulic dysfunction.
Mercury (Hg) in the environment has been receiving considerable attention in recent years, but little is known about Hg accumulation in trees. We analyzed Hg in tree rings from four tree species at ...the Hubbard Brook Experimental Forest in New Hampshire to determine whether Hg concentrations are more influenced by soil Hg concentrations, which have been stable or increasing due to the cumulative retention of historical atmospheric Hg deposition, or by atmospheric Hg deposition, which has declined in recent decades. Declining concentrations from the top to the bottom of the bole (
p
< 0.001) and from older to newer tree rings (
p
= 0.001) suggest that foliar uptake of Hg is more important than root uptake. Ten sugar maple clones planted in six blocks at the Heiberg Forest in New York State showed significant genetic control of sap Hg concentration (
p
= 0.02), which was not related to soil Hg concentration differences across blocks. Clones could differ in stomatal uptake, root uptake, or translocation of Hg. Better understanding of the source of Hg in wood is needed to forecast future changes in Hg cycling in forested ecosystems.
Global warming is affecting plant phenology, with potential consequences on the dynamics of growth reactivation of sugar maple and the timings of maple syrup production. In this study, we assess the ...temperatures inducing the daily reactivation or cessation of sap production. We selected 19 sugarbushes across Quebec, Canada, using a tapping method associated with the tubing system, we recorded the daily timings of onset and ending of sap production during winter and spring 2018, and we associated the hourly temperatures at each site. Sap production occurred from mid-February to the end of April, starting on average between 10 and 11 AM, and ending from 6 to 8 PM. We observed a seasonal pattern in the onset and ending of sap production during spring, with the onset showing a greater change than the ending. Onset and ending of sap production occurred mostly under temperatures ranging between –2 and 2 °C. The production of sap in maple is closely related to circadian freeze–thaw cycles and occurs under nighttime and daytime temperatures fluctuating below and above 0 °C. The daily lengthening of the duration of sap production mirrors the changes in the timings of freeze and thaw events and can be explained by the physical properties of the water and the physiological processes occurring during growth reactivation. The ongoing warming will result in earlier and warmer springs, which may anticipate the cycles of freeze and thaw and advance sap production in sugar maple.
Research Highlights: In central Ontario, large quantities of non-industrial wood ash (NIWA) are generated and could be used as a forest soil amendment to counteract soil acidification and base cation ...depletion caused by decades of acid deposition. Background and Objectives: The properties and biogeochemical responses of NIWA have not been thoroughly explored, and field experiments must be conducted before NIWA can be regulated as a forest soil amendment in Ontario. Materials and Methods: In this study, soil chemistry and sugar maple (Acer saccharum, Marsh.) seedling growth and chemistry were measured in an acidic sugar bush over twelve months following a NIWA field experiment. Plots (2 m by 2 m) were established with sugar maple, white pine (Pinus strobus L.), and yellow birch (Betula alleghaniensis Britt.) NIWA treatments applied at rates of 6 Mg ha−1 along with untreated control plots. Results: Ash chemistry varied significantly among species and yellow birch ash generally had much higher metal concentrations compared with other species. Following ash application, significant increases in soil pH and calcium and magnesium concentrations were observed, however the level of response varied by treatment. Foliar concentrations of base cations in sugar maple seedlings significantly increased in ash treatments and there was no significant treatment effect on foliar metal concentrations or seedling growth. In roots and shoots, concentrations of several metals (manganese, aluminum, iron, boron, arsenic, cadmium, zinc, copper, lead, chromium, and nickel) increased after ash application, however response was most pronounced in yellow birch ash. Conclusions: These results suggest that application of NIWA can counteract the lasting effects of acid rain by increasing soil pH and base cation concentrations, as well as increasing sugar maple seedling foliar nutrient concentrations, but ashes from species with high metal contents may also increase metal availability to vegetation, at least in the short-term.
Given the large contribution of forests to terrestrial carbon storage, there is a need to resolve the environmental and physiological drivers of tree-level response to rising atmospheric CO
2
. This ...study examines how site-level soil moisture influences growth and intrinsic water-use efficiency in sugar maple (Acer saccharum Marsh.). We construct tree-ring, δ
18
O, and Δ
13
C chronologies for trees across a soil moisture gradient in Ontario, Canada, and employ a structural equation modelling approach to ascertain their climatic, ontogenetic, and environmental drivers. Our results support previous evidence for the presence of strong developmental effects in tree-ring isotopic chronologies — in the range of −4.7‰ for Δ
13
C and +0.8‰ for δ
18
O — across the tree life span. Additionally, we show that the physiological response of sugar maple to increasing atmospheric CO
2
depends on site-level soil moisture variability, with trees only in relatively wet plots exhibiting temporal increases in intrinsic water-use efficiency. These results suggest that trees in wet and mesic plots have experienced temporal increases in stomatal conductance and photosynthetic capacity, whereas trees in dry plots have experienced decreases in photosynthetic capacity. This study is the first to examine sugar maple physiology using a dendroisotopic approach and broadens our understanding of carbon–water interactions in temperate forests.
Measurements of tree tissue chemistry are influenced by the precision and accuracy of laboratory analyses, sampling position within the tree, variation among replicate trees of the same species, and ...variation from year to year. We characterized these sources of uncertainty for six northern hardwood species and compared them with observed rates of long-term change. Uncertainty associated with laboratory quality control was small (1%–5%) and differed among elements, with K concentrations exhibiting the lowest accuracy and precision. Sampling position within the tree was more important for branches (the coefficient of variation was 23%) and wood (37%) than for foliage or bark (12% for both) (p < 0.001). Foliar N and P concentrations in leaves were less variable than other elements or tissue types both from tree to tree (p = 0.02) and from year to year (p = 0.03), which means that more samples would be needed to detect differences over space or time for Ca, Mg, or K in branches or wood. Concentrations of foliar N increased over 25 years at the Huntington Forest (p ≤ 0.03) by > 16%. Uncertainty analysis can be used to guide the allocation of sampling effort, depending on the elements and tissue types of interest and the objectives of the study.
Measuring mercury in wood: challenging but important Yang, Yang; Yanai, Ruth D.; Montesdeoca, Mario ...
International journal of environmental analytical chemistry,
04/2017, Volume:
97, Issue:
5
Journal Article
Peer reviewed
Mercury (Hg) in tree wood has been overlooked, in part because concentrations are so low as to be below detection limits of some analytical methods, but it is potentially important to forest ...ecosystem processes and budgets. We tested methods for the preparation and determination of Hg in tree wood by analysing samples of four tree species at the Hubbard Brook Experimental Forest, New Hampshire, USA, using thermal decomposition, catalytic conversion, amalgamation and atomic absorption spectrophotometry (USEPA Method 7473). Samples that were freeze-dried or oven-dried at 65°C were suitable for determination of Hg, whereas oven-drying at 103°C resulted in Hg losses, and air-drying resulted in Hg gains, presumably due to sorption from indoor air. Mean (±SE) concentrations of Hg tree bole wood were 1.75 ± 0.14 ng g
−1
for American beech, 1.48 ± 0.23 ng g
−1
for sugar maple, 3.96 ± 0.19 ng g
−1
for red spruce and 4.59 ± 0.06 ng g
−1
for balsam fir. Based on these concentrations and estimates of wood biomass by species based on stand inventory, we estimated the Hg content of wood in the reference watershed at Hubbard Brook to be 0.32 g ha
−1
, twice the size of the foliar Hg pool (0.15 g ha
−1
). Mercury in wood deserves more attention and is feasible to measure using appropriate techniques.
Designs for litterfall sampling can be improved by understanding the sources of uncertainty in litterfall mass and nutrient concentration. We compared the coefficient of variation of leaf litterfall ...mass and nutrient concentrations (nitrogen, phosphorus, calcium, magnesium, and potassium) at different spatial scales and across years for six northern hardwood species from 23 stands in the White Mountains of New Hampshire, USA. Stands with steeper slopes (P = 0.01), higher elevations (P = 0.05), and more westerly aspect (P = 0.002) had higher interannual variation in litter mass, probably due to a litter trap design that allowed litter to blow into traps in windy years. The spatial variation of nutrient concentrations varied more across stands than within stands for all elements (P < 0.001). Phosphorus was the most spatially variable of all nutrients across stands (P < 0.001). Litter nutrient concentrations varied less from year to year than litter mass, but the magnitude of difference depended on the element and tree species. We compared the relative importance of variation in mass vs. concentration to estimates of nutrient flux by simulating different sampling intensities of one while holding the other constant. In this dataset, interannual variability of leaf litter mass contributed more to uncertainty in litterfall flux calculations than interannual variation in nutrient concentrations. Optimal sampling schemes will depend on the elements of interest and local factors affecting spatial and temporal variability.
Measurements of tree tissue chemistry are influenced by the precision and accuracy of laboratory analyses, sampling position within the tree, variation among replicate trees of the same species, and ...variation from year to year. We characterized these sources of uncertainty for six northern hardwood species and compared them with observed rates of long-term change. Uncertainty associated with laboratory quality control was small (1%â5%) and differed among elements, with K concentrations exhibiting the lowest accuracy and precision. Sampling position within the tree was more important for branches (the coefficient of variation was 23%) and wood (37%) than for foliage or bark (12% for both) (p < 0.001). Foliar N and P concentrations in leaves were less variable than other elements or tissue types both from tree to tree (p = 0.02) and from year to year (p = 0.03), which means that more samples would be needed to detect differences over space or time for Ca, Mg, or K in branches or wood. Concentrations of foliar N increased over 25 years at the Huntington Forest (p ⤠0.03) by > 16%. Uncertainty analysis can be used to guide the allocation of sampling effort, depending on the elements and tissue types of interest and the objectives of the study.
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