Climate change‐associated trends in net biomass change are age dependent in western boreal forests of Canada

Abstract

The impacts of climate change on forest net biomass change are poorly understood but critical for predicting forest's contribution to the global carbon cycle. Recent studies show climate change-associated net biomass declines in mature forest plots. The representativeness of these plots for regional forests, however, remains uncertain because we lack an assessment of whether climate change impacts differ with forest age. Using data from plots of varying ages from 17 to 210 years, monitored from 1958 to 2011 in western Canada, we found that climate change has little effect on net biomass change in forests ≤ 40 years of age due to increased growth offsetting increased mortality, but has led to large decreases in older forests due to increased mortality accompanying little growth gain. Our analysis highlights the need to incorporate forest age profiles in examining past and projecting future forest responses to climate change.

Climate change-associated trends in biomass dynamics are consistent across soil drainage classes in western boreal forests of Canada

“…Similar to previous studies (Chen and Luo 2015;Chen et al 2016;Hogg et al 2017;Searle and Chen 2017a), above-ground biomass for each individual stem was calculated for individual trees using species' specific allometric equations developed for all major boreal tree species (Lambert et al 2005;Ung et al 2008). The biomass of individual stems were summed across each plot to obtain stand-level estimates.…”

“…Although positive net biomass change of the world's forests is critical to offsetting global anthropogenic CO 2 emission, recent studies have demonstrated that the rate of positive aboveground biomass change has decreased with calendar year due to high biomass loss from mortality coupled with growth insufficient to offset these losses (Brienen et al 2015;Chen and Luo 2015;Chen et al 2016). The increased tree mortality in tropical forests has been attributed to shortened tree longevity associated with greater climate variability and feedbacks of faster growth on mortality (Brienen et al 2015).…”

“…Not only is it topographically diverse, but it has also been shown to be strongly affected by climate change. Studies generally demonstrate a loss in net above ground biomass change (Ma et al 2012;Chen and Luo 2015;Chen et al 2016) and increases in mortality either due to declining water availability (Peng et al 2011;Hember et al 2017). The effect of climate change on tree growth in the region is more complex, with studies demonstrating: increases in young stands but no change, or even decreases, in old stands (Chen et al 2016); a slight increase early successional conifer forest types but a decrease in latesuccessional and mixed forest types (Chen and Luo 2015); and, strongly spatially variable trends dominated by heat and drought stress (Girardin et al 2016).…”

“…Since aboveground biomass change and its components are strongly regulated by forest age in the boreal forest (Oliver and Larson 1990), and long-term temporal trends are forest age-dependent (Chen et al 2016), we modelled age as a continuous function, similar to previous studies (Chen and Luo 2015;Chen et al 2016). …”

Estimation of Winter Wheat Above-Ground Biomass Using Unmanned Aerial Vehicle-Based Snapshot Hyperspectral Sensor and Crop Height Improved Models

“…Therefore, AGB is considered one of the most important biochemical crop parameters [4][5][6], and correct estimation of AGB can help improve crop monitoring and yield prediction [7]. Estimation of AGB is also important for ecological research at regional and global scales [8] and has been employed in global carbon cycle [9][10][11] and climate change [12][13][14] studies.…”