Contrasting Nutritional Acclimation of Sugar Maple (Acer saccharum Marsh.) and Red Maple (Acer rubrum L.) to Increasing Conifers and Soil Acidity as Demonstrated by Foliar Nutrient Balances

Abstract

Sugar maple (Acer saccharum Marshall, SM) is believed to be more sensitive to acidic and nutrient-poor soils associated with conifer-dominated stands than red maple (Acer rubrum L., RM). Greater foliar nutrient use efficiency (FNUE) of RM is likely the cause for this difference. In the context of climate change, this greater FNUE could be key in favoring northward migration of RM over SM. We used the concept of foliar nutrient balances to study the nutrition of SM and RM seedlings along an increasing gradient in forest floor acidity conditioned by increasing proportions of conifers (pH values ranging from 4.39 under hardwoods, to 4.29 under mixed hardwood-conifer stands and 4.05 under conifer-dominated stands). Nutrients were subjected to isometric log-ratio (ilr) transformation, which views the leaf as one closed system and considers interactions between nutrients. The ilr method eliminates numerical biases and weak statistical inferences based on raw or "operationally" log-transformed data. We analyzed foliar nutrients of SM and RM seedlings and found that the [Ca,Mg,K| P,N] and [Ca,Mg| K] balances of SM seedlings were significantly different among soil acidity levels, whereas they did not vary for RM seedlings. For SM seedlings, these differences among soil acidity levels were due to a significant decrease in foliar Ca and Mg concentrations with increasing forest floor acidity. Similar differences in foliar balances were also found between healthy and declining SM stands estimated from literature values. Conversely, foliar balances of RM seedlings did not differ among soil acidity levels, even though untransformed foliar nutrient concentrations were significantly different. This result highlights the importance of using ilr transformation, since it provides more sensitive results than standard testing of untransformed nutrient concentrations. The lower nutrient Collin et al. Contrasting Foliar Nutrient Balance in Acer spp. requirements of RM and its greater capacity to maintain nutrient equilibrium are factors that could explain its competitive success and recent northward expansion. This study underscores the importance of using nutrient balances to study the redistribution of plant species in natural ecosystems under climate change.

Can sugar maple establish into the boreal forest? Insights from seedlings under various canopies in southern Quebec

“…In St. Hippolyte, Collin et al. () showed a similar foliar imbalance caused by a decrease in foliar Ca and Mg levels with the increasing presence of conifers and soil acidity. Also, while pH of the mineral soil was relatively similar between forest types, conifer‐dominated stands without maple regeneration distinguished themselves by having a significantly more acidic mineral soil (Table ).…”

Unravelling potential northward migration pathways for tree species under climate change

“…The transition from the temperate to boreal forest, however, is particularly challenging for species that will need to cope with strong gradients in soil conditions and competition with boreal species. By investigating baseline conditions at migration sites as well as potential interspecific influences on species establishment, our study complements others examining site and/or biotic constraints to migration (Brown & Vellend, 2014;Carteron et al, 2020;Collin et al, 2016;Solarik et al, 2020). Site conditions are important because failure to establish at unsuitable sites will result in species distribution lagging behind suitable climate (i.e.…”

“…Acer saccharum and A. rubrum show negative association across their range, implying spatial segregation, but were found to co-occur in up to 52% of migration sites. Field studies at the ecotone have shown that A. rubrum seedlings, more so than Acer saccharum, can tolerate low soil pH at sites where needle litter is abundant while also mobilizing nutrients from the soil better (Collin et al, 2016), characteristics that are important for breaking into the boreal forest. With time, A. rubrum could promote suitable soil conditions for a species like A. saccharum through increased pH and nutrient mineralization (Collin et al, 2016(Collin et al, , 2017 and/or the promotion of favourable soil biota (Brown & Vellend, 2014).…”

“…In the closed canopy of mixed or boreal forests, resident conifers may constrain the establishment and growth of temperate migrants (De Frenne et al, 2013;Solarik et al, 2020) through their effect on light, litter and decomposition, influencing in turn nutrient availability, soil pH and soil fungal communities (Collin et al, 2017;Fisichelli et al, 2013;Hobbie, 1996;Nagati et al, 2018). Conversely, the presence of deciduous species in the canopy of migration sites could further promote suitable soil conditions for migrating temperate species through increased pH and nutrient mineralization (Bradley & Fyles, 1995;Collin et al, 2016) and/or the promotion of favourable soil biota (Brown & Vellend, 2014). Such interactions can result in competitive exclusion, release or facilitation and determine species distribution when propagules are available (Lenoir et al, 2010;Wisz et al, 2013).…”

Increasing atmospheric CO2 concentrations correlate with declining nutritional status of European forests

“…N deposition can cause deficiencies in other nutrients than N and nutrient imbalances due to a range of effects, including stimulation of plant growth (dilution effect) and negative effects on tree nutrient acquisition by modifying mycorrhizal associations 24,66 . Increasing mean annual temperature (MAT) also contributed to the decrease in Mg and the increase in Ca and N:P. Ca Moreover, in general, increases in soil pH translate into higher foliar cation concentrations [67][68][69] . The higher temperatures at the northern European sites favoured longer growing seasons, biological activity and nutrient up-take, thus accounting for the lower general decreases in foliar nutrient concentrations and even the increase in N. In contrast, the increases in temperature and consequently in drought (decreases in mean annual precipitation (MAP) in southern Europe could account for the decline in soil fertility and capacity of nutrient uptake, all of which contribute to a decrease in foliar nutrient concentration, as in experimental drought studies conducted in Mediterranean forests where mineralisation, soil enzymatic activity and plant growth also decreased, thus leading to a large decrease in aboveground nutrient mineralomasses 9,35,[70][71][72] .…”