Nutrient supply and belowground interaction alter responses to CO2 elevation in black spruce and white spruce

High nutrient supply and interspecific belowground competition enhance the relative performance of Picea mariana (Mill). B.S.P seedlings over Picea glauca [Moench] Voss. under elevated CO2

“…Since elevated CO 2 increases nutrient use efficiency (Ainsworth and Long 2005;Cao et al 2007;Huang et al 2007;Ambebe et al 2010), we further hypothesize that low nutrient would be less limiting to photosynthesis under elevated than under ambient CO 2 . In a previous study (Dang et al 2020), we have found that belowground competitions reduce whole seedling photosynthesis, seedling growth, and biomass allocation to leaves as well as influence their responses to nutrient supply and elevated CO 2 ; nutrient supply affects the responses of photosynthesis and leaf morphology to elevated CO 2 and the effect differs between the two species. However, there are several key issues that are not addressed in our previous study: while whole seedling photosynthesis gives us a big picture of how the carbon sequestration of the seedling responds to the treatments, the results have little use beyond the measurement environmental conditions because they cannot be used to estimate trees' photosynthesis under other environmental conditions or to be scaled up to estimate the response at the forest stand or ecosystem levels.…”

“…Dang-supervisor of Marfo, initiated the research, advised Marfo in the entire process of the research, adapted this manuscript from Marfo's dissertation, re-wrote substantial amount of the text, revised figures, and made some new figures Du: contributed to the development of the manuscript Newaz: re-analyzed some of the results, updated the literature and some part of the introduction and discussions photosynthesis (Dang et al 2020), at least in the short term. However, the responses and interactions may be modified by other environmental factors such as nutrient availability (Danyagri and Dang 2013, Li et al 2013, Li et al 2015, Danyagri and Dang, 2014a, b, c, Newaz et al 2016, Newaz et al 2017, Tedla et al 2020); e.g., low nutrient supply reduces the stimulation of photosynthesis by elevated CO 2 (Zhang et al 2006;Cao et al 2007;Ambebe et al 2010;Danyagri and Dang 2014b).…”

“…In this study, we examined two photosynthetic parameters that are commonly used in computer models for estimating tree carbon sequestration at different space and time scales: the maximum Rubisco carboxylation capacity (V cmax ) and maximum photosynthetic electron transport rate (J max ). Furthermore, Dang et al (2020) gives no information on the mechanisms of belowground competition. Belowground competition can occur physiologically (including allelopathic) and morphologically (Lambers and Oliveira 2019).…”

“…In this study, we examined various root morphological characteristics that influence tree's competitiveness in belowground competitions. The last important issue that Dang et al (2020) did not address is resource use efficiency. Adjusting resource use efficiencies is a key acclimation strategy that plants use in response to changes in environmental conditions, particularly environmental stresses.…”

“…Table 1 provides average height and root collar diameter for each treatment combination from Dang et al 2020.…”