Climatic sensitivity, water‐use efficiency, and growth decline in boreal jack pine (Pinus banksiana) forests in Northern Ontario

Abstract

Rises in atmospheric carbon dioxide (atmCO2) levels are known to stimulate photosynthesis and increase intrinsic water‐use efficiency (iWUE) in trees. Stand‐level increases in iWUE depend on the physiological response of dominant species to increases in atmCO2, while tree‐level response to increasing atmCO2 depends on the balance between the direct effects of atmCO2 on photosynthetic rate and the indirect effects of atmCO2 on drought conditions. The aim of this study was to characterize the response of boreal jack pine (Pinus banksiana) stands in Northern Ontario to changes in atmCO2 and associated climatic change over the past 100 years. The impact of changes in growing season length, temperature, and precipitation, as well as atmCO2 on tree growth, was determined using stable carbon isotopes and dendrochronological analysis. Jack pine stands in this study were shown to be in progressive decline. As expected, iWUE was found to increase in association with rising atmCO2. However, increases in iWUE were not directly coupled with atmCO2, suggesting that the degree of iWUE improvement is limited by alternative factors. Water‐use efficiency was negatively associated with tree growth, suggesting that warming‐ and drought‐induced stomatal closure has likely led to deviations from expected atmCO2‐enhanced growth. This finding corroborates that boreal forest stands are likely to face continued stress under future climatic warming.

Coping With Extreme Events: Growth and Water‐Use Efficiency of Trees in Western Mexico During the Driest and Wettest Periods of the Past One Hundred Sixty Years

“…Since the industrial revolution, human-induced shifts in atmospheric composition and climate have impacted terrestrial ecosystems (Dietrich et al, 2016;Gomez-Guerrero et al, 2013;Silva & Anand, 2013a, 2013b. In western forests of Central and North America, despite great uncertainties with respect to changes in precipitation patterns, extreme events marked by atypically dry or wet periods have had measurable impacts on forest ecosystem structure and function (Cortés-Montaño et al, 2012;Van Mantgem et al, 2009).…”

Two Decades of Experimental Manipulation Reveal Potential for Enhanced Biomass Accumulation and Water Use Efficiency in Ponderosa Pine Plantations Across Climate Gradients

“…Accumulating observational evidence suggests that the availability of soil resources regulate the impact of climate variability on temperate forest ecosystems (Dietrich et al, 2016;Fernández-Martínez et al, 2014;Gómez-Guerrero et al, 2013;Maxwell et al, 2018). Few studies, however, have experimentally tested the long-term effect of competition for soil resources in forests across climatic stress gradients.…”

Untangling methodological and scale considerations in growth and productivity trend estimates of Canada’s forests

“…Throughout this systematic review, we shall refer to the terms 'growth' and 'productivity.' Here, we shall use the term 'growth' mainly to refer to secondary growth, i.e., the increase in tree diameter or basal area (e.g., Dietrich et al 2016, Girardin et al 2016a. Elsewhere, Assman (1970) defined 'forest productivity' as the increase in biomass or volume of wood per unit area and time.…”

“…An overall uncertainty rate was computed for each of the referenced studies, as the sum of uncertainty rates (i.e., values in table 2) potentially affecting the results that were reported in the study (table 3, last column). For example, Dietrich et al (2016) suggested that results could be biased both by stand-and treelevel sampling biases (both 30% uncertainty rates), and by biases from RCS detrending (15% uncertainty rate for the detection of negative trends), which leads to the assignment of an overall 75% uncertainty rate. These uncertainty rates were finally segregated into four classes, i.e.…”

“…Plot remeasurement provides information on temporal variation in stand productivity and permits the estimation of future (potential) productivity (Ciais et al 2008), an important management tool for adapting silvicultural practices to changing environmental conditions (Gillis 2011). A second field-based approach for studying growth trends relies upon dendrochronology, i.e., the measurement and dating of annual growth rings that allow linking spatiotemporal fluctuations in environmental factors to changes in tree growth rates (e.g., Berner et al 2011, Dietrich et al 2016.…”