scholarly journals Paludification reduces black spruce growth rate but does not alter tree water use efficiency in Canadian boreal forested peatlands

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Joannie Beaulne ◽  
Étienne Boucher ◽  
Michelle Garneau ◽  
Gabriel Magnan
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Tree Ring ◽  
Water Table ◽  
Black Spruce ◽  
Forest Growth ◽  
Peat Accumulation ◽  
Tree Water Use ◽  
Growth Decline ◽  
Use Efficiency

Abstract Background Black spruce (Picea mariana (Mill.) BSP)-forested peatlands are widespread ecosystems in boreal North America in which peat accumulation, known as the paludification process, has been shown to induce forest growth decline. The continuously evolving environmental conditions (e.g., water table rise, increasing peat thickness) in paludified forests may require tree growth mechanism adjustments over time. In this study, we investigate tree ecophysiological mechanisms along a paludification gradient in a boreal forested peatland of eastern Canada by combining peat-based and tree-ring analyses. Carbon and oxygen stable isotopes in tree rings are used to document changes in carbon assimilation rates, stomatal conductance, and water use efficiency. In addition, paleohydrological analyses are performed to evaluate the dynamical ecophysiological adjustments of black spruce trees to site-specific water table variations. Results Increasing peat accumulation considerably impacts forest growth, but no significant differences in tree water use efficiency (iWUE) are found between the study sites. Tree-ring isotopic analysis indicates no iWUE decrease over the last 100 years, but rather an important increase at each site up to the 1980s, before iWUE stabilized. Surprisingly, inferred basal area increments do not reflect such trends. Therefore, iWUE variations do not reflect tree ecophysiological adjustments required by changes in growing conditions. Local water table variations induce no changes in ecophysiological mechanisms, but a synchronous shift in iWUE is observed at all sites in the mid-1980s. Conclusions Our study shows that paludification induces black spruce growth decline without altering tree water use efficiency in boreal forested peatlands. These findings highlight that failing to account for paludification-related carbon use and allocation could result in the overestimation of aboveground biomass production in paludified sites. Further research on carbon allocation strategies is of utmost importance to understand the carbon sink capacity of these widespread ecosystems in the context of climate change, and to make appropriate forest management decisions in the boreal biome.

scholarly journals Paludification reduces black spruce growth rate but does not alter tree water use efficiency in Canadian boreal forested peatlands

2021 ◽  
Author(s):  
Joannie Beaulne ◽  
Étienne Boucher ◽  
Michelle Garneau ◽  
Gabriel Magnan
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Water Table ◽  
Black Spruce ◽  
Carbon Assimilation ◽  
Forest Growth ◽  
Peat Accumulation ◽  
Tree Water Use ◽  
Growth Decline ◽  
Use Efficiency

Abstract Background: Black spruce (Picea mariana (Mill.) BSP)-forested peatlands are widespread ecosystems in boreal North America in which peat accumulation, known as the paludification process, has been shown to induce forest growth decline. However, the ecophysiological mechanisms that lead to growth reductions in black spruce remain unexplored. Trees growing in paludified forests have to deal with continuously evolving environmental conditions (e.g., water table rise, increasing peat thickness) that may require growth mechanism adjustments over time. In this study, we investigated tree ecophysiological mechanisms along a paludification gradient in a boreal forested peatland of eastern Canada by combining peat-based and tree-ring analyses. Carbon and oxygen stable isotopes in tree rings were used to document changes in carbon assimilation rates, stomatal conductance, and water use efficiency. In addition, paleohydrological analyses were performed to evaluate the dynamical ecophysiological adjustments of black spruce trees to site-specific water table variations.Results: Increasing peat accumulation considerably impacted forest growth, but no significant differences in tree water use efficiency (iWUE) were observed between the study sites. Tree-ring isotopic analysis indicates no iWUE decrease over the last 100 years, but rather an important increase at each site up to the 1980s, before iWUE stabilized. Surprisingly, inferred basal area increments did not reflect such trends. Our results suggest that the slower growth rates observed at the most paludified sites are attributable, at least partially, to both lower carbon assimilation rates and stomatal conductance. These findings show that iWUE variations do not necessarily reflect tree ecophysiological adjustments required by changes in growing conditions. Local water table variations induced no changes in ecophysiological mechanisms, but the synchronous shift in iWUE observed at all sites in the mid-1980s suggests a tree response to regional or global factors, such as increasing atmospheric CO2 concentration.Conclusions: Our study shows that paludification induces black spruce growth decline without, however, altering tree water use efficiency in boreal forested peatlands. This is the first attempt in exploring the complex interactions between stem growth, ecophysiological mechanisms, and environmental conditions in paludified sites. Additional research on carbon allocation strategies is of utmost importance to understand the carbon sink capacity of these widespread ecosystems and better predict their response to future climate change.

scholarly journals Paludification reduces black spruce growth rate but does not alter ecophysiological mechanisms in Canadian boreal forested peatlands

2020 ◽  
Author(s):  
Joannie Beaulne ◽  
Étienne Boucher ◽  
Michelle Garneau ◽  
Gabriel Magnan
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Water Table ◽  
Tree Growth ◽  
Black Spruce ◽  
Stem Growth ◽  
Process Models ◽  
Organic Layer ◽  
Growth Decline ◽  
Use Efficiency

Abstract Background Paludification is widespread in the boreal biome, inducing tree growth decline in forested peatlands following the development of thick organic layers over the mineral soil. However, the ecophysiological processes involved remain poorly documented and little is known about the interactions between tree growth mechanisms and site conditions in these ecosystems. We investigated changes in stem growth and main ecophysiological processes in a black spruce forested peatland in eastern Canada by combining peat-based and tree-ring stable isotope analyses. These were conducted at three sampling sites located along a paludification gradient with different peat thicknesses.Results Organic layer thickening induces black spruce growth decline without altering tree ecophysiological mechanisms. A 40% increase in water use efficiency, or the ratio of carbon assimilated to water losses, was observed at the three sites from 1920 to the 1980s, but did not translate into enhanced tree growth. A clear shift in the 1980s revealed a decline in black spruce sensitivity to climate and rising atmospheric CO2 concentration, regardless of the organic layer thickness. Water table reconstructions revealed an important drawdown in the last few decades at the three sites, but we found no evidence of an influence of water table variations on stem growth.Conclusions This study shows that paludification induces black spruce growth decline without altering tree metabolism in boreal forested peatlands. This underlines that changes in water use efficiency are decoupled from changes in carbon allocation, which are constrained by site, or even tree-specific strategies to access water and nutrients from belowground. Our findings indicate that dynamic changes in edaphic conditions need to be considered in process models. Otherwise, failing to account for the degree of paludification can lead to misleading forest productivity predictions and result in considerable overestimations of aboveground carbon stocks from trees in the boreal regions.

scholarly journals Hot drought reduces the effects of elevated CO 2 on tree water‐use efficiency and carbon metabolism

2020 ◽  
Vol 226 (6) ◽  
pp. 1607-1621 ◽  
Author(s):  
Benjamin Birami ◽  
Thomas Nägele ◽  
Marielle Gattmann ◽  
Yakir Preisler ◽  
Andreas Gast ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Carbon Metabolism ◽  
Tree Water Use ◽  
Use Efficiency

Site-level soil moisture controls water-use efficiency improvement and climate response in sugar maple: a dual dendroisotopic study

2021 ◽  
pp. 1-12
Author(s):  
R. Dietrich ◽  
F.W. Bell ◽  
M. Anand
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Use ◽  
Tree Ring ◽  
Sugar Maple ◽  
Photosynthetic Capacity ◽  
Environmental Drivers ◽  
Tree Level ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency

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 CO2. 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, δ18O, and Δ13C 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 Δ13C and +0.8‰ for δ18O — across the tree life span. Additionally, we show that the physiological response of sugar maple to increasing atmospheric CO2 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.

Effects of climate change on tree water use efficiency, nitrogen availability and growth in boreal forest of northern China

2020 ◽  
Vol 20 (10) ◽  
pp. 3607-3614
Author(s):  
Amal Succarie ◽  
Zhihong Xu ◽  
Wenjie Wang ◽  
Tengjiao Liu ◽  
Xiting Zhang ◽  
...  
Keyword(s):  
Climate Change ◽  
Boreal Forest ◽  
Water Use Efficiency ◽  
Water Use ◽  
Nitrogen Availability ◽  
Northern China ◽  
Tree Water Use ◽  
Use Efficiency

scholarly journals Water use efficiency and yield of cowpea and nutrient loss in lysimeter experiment under varying water table depth, irrigation schedules and irrigation method

2017 ◽  
Vol 14 (2) ◽  
pp. 46-55 ◽  
Author(s):  
Binny Dasila ◽  
Veer Singh ◽  
HS Kushwaha ◽  
Ajaya Srivastava ◽  
Shri Ram
Keyword(s):  
Grain Yield ◽  
Water Use Efficiency ◽  
Nutrient Uptake ◽  
Water Use ◽  
Water Table ◽  
Root Length ◽  
Water Table Depth ◽  
Nutrient Loss ◽  
Lysimeter Experiment ◽  
Use Efficiency

Lysimeter experiment was conducted at Govind Ballabh Pant University of Agriculture & Technology, Pantnagar during summer season 2013 to study the effect of irrigation schedules and methods on yield, nutrient uptake and water use efficiency of cowpea as well as nutrient loss from silty clay loam soil under fluctuating water table conditions. The experiment was laid out in factorial randomized block design having three irrigation schedules at IW/CPE ratio of 0.3. 0.2 and 0.15 with two irrigation methods (flood and sprinkler) and at 30±1.5, 60±1.5 and 90±1.5 cm water tables replicated thrice. Maximum root length (129.4 cm) and root length density (0.395 cm/cm3) were obtained when irrigation was scheduled at IW: CPE 0.3 associated with 30±1.5 cm water table depth using sprinkler method. Increase in water table depth and IW: CPE ratio decreased water use efficiency where IW: CPE 0.3 produced highest grain yield (1411.6 kg ha-1) with the WUE of 1.15 kg ha mm-1. Significant nutrients uptake response was observed owing to variation in water table depth, irrigation schedules and methods. Analysis of lysimeter leached water showed that with deep drainage and more IW:CPE, leaching losses of N,P and K were more however water applied through sprinkler saved 20.1, 53.7 and 24.4% N, P and K, respectively, over flooded method. Irrigation given at IW: CPE 0.3 through sprinkler form at 60±1.5 cm water table depth favours the higher grain yield and nutrient uptake by crop whereas flooded irrigation with deep water table condition accelerated nutrient leaching.SAARC J. Agri., 14(2): 46-55 (2016)

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