Mycorrhizal fungi and roots are complementary in foraging within nutrient patches.

The roots of the majority of tree species are associated with either arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. The absorptive roots of tree species also vary widely in their diameter. The linkages between root thickness, mycorrhiza type and nutrient foraging are poorly understood. We conducted a large root ingrowth experiment in the field to investigate how absorptive roots of varying thickness and their associated fungi (AM vs. EM) exploit different nutrient patches (inorganic and organic) in a common garden. In nutrient-rich patches, thin-root tree species more effectively proliferated absorptive roots than thick-root tree species, whereas thick-root tree species proliferated more mycorrhizal fungal biomass than thin-root tree species. Moreover, nutrient patches enriched with organic materials resulted in greater root and mycorrhizal fungal proliferation compared to those enriched with inorganic nutrients. Irrespective of root morphology, AM tree species had higher root foraging precision than mycorrhizal hyphae foraging precision within organic patches, whereas EM tree species exhibited the opposite. Our findings that roots and mycorrhizal fungi are complementary in foraging within nutrient patches provide new insights into species coexistence and element cycling in terrestrial ecosystems.

Cheng L ，Chen W ，Adams TS ，Wei X ，Li L ，McCormack ML ，DeForest JL ，Koide RT ，Eissenstat DM ... -  《ECOLOGY》

Complementarity in nutrient foraging strategies of absorptive fine roots and arbuscular mycorrhizal fungi across 14 coexisting subtropical tree species.

In most cases, both roots and mycorrhizal fungi are needed for plant nutrient foraging. Frequently, the colonization of roots by arbuscular mycorrhizal (AM) fungi seems to be greater in species with thick and sparsely branched roots than in species with thin and densely branched roots. Yet, whether a complementarity exists between roots and mycorrhizal fungi across these two types of root system remains unclear. We measured traits related to nutrient foraging (root morphology, architecture and proliferation, AM colonization and extramatrical hyphal length) across 14 coexisting AM subtropical tree species following root pruning and nutrient addition treatments. After root pruning, species with thinner roots showed more root growth, but lower mycorrhizal colonization, than species with thicker roots. Under multi-nutrient (NPK) addition, root growth increased, but mycorrhizal colonization decreased significantly, whereas no significant changes were found under nitrogen or phosphate additions. Moreover, root length proliferation was mainly achieved by altering root architecture, but not root morphology. Thin-root species seem to forage nutrients mainly via roots, whereas thick-root species rely more on mycorrhizal fungi. In addition, the reliance on mycorrhizal fungi was reduced by nutrient additions across all species. These findings highlight complementary strategies for nutrient foraging across coexisting species with contrasting root traits.

Liu B ，Li H ，Zhu B ，Koide RT ，Eissenstat DM ，Guo D ... -  《-》

Linking root traits to nutrient foraging in arbuscular mycorrhizal trees in a temperate forest.

The identification of plant functional traits that can be linked to ecosystem processes is of wide interest, especially for predicting vegetational responses to climate change. Root diameter of the finest absorptive roots may be one plant trait that has wide significance. Do species with relatively thick absorptive roots forage in nutrient-rich patches differently from species with relatively fine absorptive roots? We measured traits related to nutrient foraging (root morphology and architecture, root proliferation, and mycorrhizal colonization) across six coexisting arbuscular mycorrhizal (AM) temperate tree species with and without nutrient addition. Root traits such as root diameter and specific root length were highly correlated with root branching intensity, with thin-root species having higher branching intensity than thick-root species. In both fertilized and unfertilized soil, species with thin absorptive roots and high branching intensity showed much greater root length and mass proliferation but lower mycorrhizal colonization than species with thick absorptive roots. Across all species, fertilization led to increased root proliferation and reduced mycorrhizal colonization. These results suggest that thin-root species forage more by root proliferation, whereas thick-root species forage more by mycorrhizal fungi. In mineral nutrient-rich patches, AM trees seem to forage more by proliferating roots than by mycorrhizal fungi.

Eissenstat DM ，Kucharski JM ，Zadworny M ，Adams TS ，Koide RT ... -  《-》

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

Chen W ，Koide RT ，Adams TS ，DeForest JL ，Cheng L ，Eissenstat DM ... -  《-》

Foraging speed and precision of arbuscular mycorrhizal fungi under field conditions: An experimental approach.

To better understand the ecology of arbuscular mycorrhizal (AM) symbiosis, we need to measure functional traits of individual fungal virtual taxa under field conditions. The efficiency of AM fungi in locating nutrient-rich patches in soil space is one of their central traits in this symbiotic relationship. We used plots of a long-term field experiment in grassland with manipulated functional group composition of host plant community to establish ingrowth patches with substrate free of roots and fungi and with varying nutrient availability. Comparison of the original AM fungal community before patch creation with that present 9 weeks after patch establishment enabled us to estimate relative hyphal foraging speed for 41 fungal taxa, and a comparison of the fungal community in neighbouring patches differing in nutrient availability provided estimates of hyphal foraging precision for 22 taxa. Members of two dominant fungal families, Glomeraceae and Claroideoglomeraceae, differed in their foraging speed and precision. Glomeraceae taxa responded more slowly, but with a higher focus on enriched patches. We further demonstrated the usefulness of the obtained fungal functional traits by testing the differences between grass and dicotyledonous plant hosts using a data set obtained in another experiment at the same plots. Grass species hosted AM fungal communities with higher foraging speed, but lower foraging precision than the dicotyledonous species. Our study results support the use of field experiments for measuring comparative characteristics of AM fungi, which are highly elusive (or misrepresented) under controlled conditions.

Šmilauer P ，Šmilauerová M ，Kotilínek M ，Košnar J ... -  《-》