Abstract
Variation in resource acquisition strategies enables plants to adapt to different environments and may partly determine their responses to climate change. However, little is known about how belowground plant traits vary across climate and soil gradients. Focusing on interior Douglas-fir (Pseudotsuga menziesii var. glauca) in western Canada, we tested whether fine-root traits relate to the environment at the intraspecific level. We quantified the variation in commonly measured functional root traits (morphological, chemical, and architectural traits) among the first three fine-root orders (i.e., absorptive fine roots) and across biogeographic gradients in climate and soil factors. Moderate but consistent trait-environment linkages occurred across populations of Douglas-fir, despite high levels of within-site variation. Shifts in morphological traits across regions were decoupled from those in chemical traits. Fine roots in colder/drier climates were characterized by a lower tissue density, higher specific area, larger diameter, and lower carbon-to-nitrogen ratio than those in warmer/wetter climates. Our results showed that Douglas-fir fine roots do not rely on adjustments in architectural traits to adapt rooting strategies in different environments. Intraspecific fine-root adjustments at the regional scale do not fit along a single axis of root economic strategy and are concordant with an increase in root acquisitive potential in colder/drier environments.
Highlights
Functional traits of fine roots and mycorrhizal symbionts have become central to understanding belowground acquisition strategies and plant responses to environmental change from local to global scales [1,2,3,4,5]
In a complementary study across the same biogeographic gradient, we showed that root diameter was not related to patterns of ectomycorrhizal fungal exploration type and that fine roots with high
Across regional gradients of climate and edaphic factors in western Canada, the majority of Douglas-fir fine-root trait variance occurred within sites
Summary
Functional traits of fine roots and mycorrhizal symbionts have become central to understanding belowground acquisition strategies and plant responses to environmental change from local to global scales [1,2,3,4,5]. Recent syntheses of large-scale datasets have facilitated exploration of interspecific (i.e., among-species) fine-root functional trait variation. These studies have notably advanced our understanding of the fundamental constraints underlying fine-root trait variation (e.g., phylogeny and climate and growth form [4,6,7,8,9]). Most studies have focused on assessing fine-root functional trait variation among species, following the assumption that among species differences in root trait values are greater than those A multidimensional root trait framework has begun to emerge [13,14,15,16,17].
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