Root morphology and mycorrhizal symbioses together shape nutrient foraging strategies of temperate trees

Abstract

Photosynthesis by leaves and acquisition of water and minerals by roots are required for plant growth, which is a key component of many ecosystem functions. Although the role of leaf functional traits in photosynthesis is generally well understood, the relationship of root functional traits to nutrient uptake is not. In particular, predictions of nutrient acquisition strategies from specific root traits are often vague. Roots of nearly all plants cooperate with mycorrhizal fungi in nutrient acquisition. Most tree species form symbioses with either arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. Nutrients are distributed heterogeneously in the soil, and nutrient-rich "hotspots" can be a key source for plants. Thus, predicting the foraging strategies that enable mycorrhizal root systems to exploit these hotspots can be critical to the understanding of plant nutrition and ecosystem carbon and nutrient cycling. Here, we show that in 13 sympatric temperate tree species, when nutrient availability is patchy, thinner root species alter their foraging to exploit patches, whereas thicker root species do not. Moreover, there appear to be two distinct pathways by which thinner root tree species enhance foraging in nutrient-rich patches: AM trees produce more roots, whereas EM trees produce more mycorrhizal fungal hyphae. Our results indicate that strategies of nutrient foraging are complementary among tree species with contrasting mycorrhiza types and root morphologies, and that predictable relationships between below-ground traits and nutrient acquisition emerge only when both roots and mycorrhizal fungi are considered together. mycorrhizal fungi | plant traits | root proliferation | soil heterogeneity | symbioses

Climate, soil and plant functional types as drivers of global fine‐root trait variation

“…Fine‐root traits give us critical information on plant resource acquisition abilities (Chen et al . ), plant resource economics (Roumet et al . ), as well as plant impacts on ecosystem carbon and nutrient cycling (Freschet et al .…”

“…growth rate, sensu Eissenstat ; Chen et al . ). Fine‐roots with high tissue density also show higher longevity, at least for non‐woody species (Ryser ; Tjoelker et al .…”

Arbuscular Mycorrhizal Fungus Rhizophagus irregularis Increased Potassium Content and Expression of Genes Encoding Potassium Channels in Lycium barbarum

“…The changed reliance might due to the potassium stimulated systemic lateral root growth improved water and mineral nutrients absorption (Drew, 1975). Another possibility might be the nutrient foraging strategy of L. barbarum , which relied on root growth rather than AM fungal mycelium (Chen et al, 2016). Combined with the higher efficiency of root hair in nutrient absorption (Brown et al, 2013) and substitution of AM fungal mycelium on root hair (Jakobsen et al, 2005), this might be another potential explanation for the changed reliance.…”

Ideas and perspectives: Strengthening the biogeosciences in environmental research networks

“…The biogeosciences can potentially enrich CZOs by bringing novel and advanced biological and ecological research to the otherwise predominant Earth science focus of CZOs (e.g., Chen et al, 2016;Brantley et al, 2017a). The critical zone is called "critical" because all of Earth's diverse life-forms depend entirely on the structure and function of the critical zone.…”