TY - JOUR

T1 - Roots and rhizospheric soil microbial community responses to tree species mixtures

AU - Ribbons, Relena R.

AU - Del Toro, Israel

AU - Smith, Andy R.

AU - Healey, John R.

AU - Vesterdal, Lars

AU - McDonald, Morag A.

N1 - Publisher Copyright: © 2022 Elsevier B.V.

PY - 2022

Y1 - 2022

N2 - Below-ground processes are crucial in determining the effects of plants on ecosystem function. The root-soil interface is a highly active zone due to root exudation and nutrient uptake. However, its role in determining effects of tree species and their interactions on the soil microbial community, ecosystem function and above-ground growth is less well known. We compared the effects of tree species monocultures and their mixture on rhizospheric microbial communities, specific functional genetic markers associated with processes in the nitrogen (N) cycle, and above-ground and below-ground growth and nutrient allocation. Two pairs of tree species were grown: Pseudotsuga menziesii and Alnus rubra; Acer pseudoplatanus and Quercus robur. Tree establishment altered soil microbial composition, but after 26 months differences amongst tree species and effects of species mixture were minor, suggesting functional redundancy in microbial communities. A greater abundance of fungi, bacteria, and specifically ammonia oxidising and denitrifying bacteria in the rhizospheric soil of the N-fixing A. rubra was the most notable trend. Mixing A. rubra with P. menziesii did produce overyielding: trees grown in mixture attained a two-fold greater (Relative Yield Total 2.03 ± 0.52) above-ground biomass than in a mixture predicted from trees grown in monoculture. We did not observe strong trends in overyielding for A. psuedoplatanus and Q. robur. Inclusion of the N-fixing species A. rubra in admixture with P. menziesii promoted N cycling, and decreased the C:N ratios of leaf, branch, and root tissues but not soil C:N ratio for P. menziesii. Given the observed overyielding in the A. rubra with P. menziesii mixtures, we explored potential mechanistic links between functional genetic markers for nitrification and ammonification, however we found no statistically significant effects attributable to these genetic markers. We found root area index was significantly lower in A. rubra monocultures than in admixture with P. menziesii. For both P. menziesii and A. rubra, the number of root tips was lower in mixture than monoculture, indicating physical partitioning of soil space as a result of growing in mixture. We documented additive and synergistic effects of tree species identity on above and belowground productivity, and rhizospheric microbial community development in these four tree species.

AB - Below-ground processes are crucial in determining the effects of plants on ecosystem function. The root-soil interface is a highly active zone due to root exudation and nutrient uptake. However, its role in determining effects of tree species and their interactions on the soil microbial community, ecosystem function and above-ground growth is less well known. We compared the effects of tree species monocultures and their mixture on rhizospheric microbial communities, specific functional genetic markers associated with processes in the nitrogen (N) cycle, and above-ground and below-ground growth and nutrient allocation. Two pairs of tree species were grown: Pseudotsuga menziesii and Alnus rubra; Acer pseudoplatanus and Quercus robur. Tree establishment altered soil microbial composition, but after 26 months differences amongst tree species and effects of species mixture were minor, suggesting functional redundancy in microbial communities. A greater abundance of fungi, bacteria, and specifically ammonia oxidising and denitrifying bacteria in the rhizospheric soil of the N-fixing A. rubra was the most notable trend. Mixing A. rubra with P. menziesii did produce overyielding: trees grown in mixture attained a two-fold greater (Relative Yield Total 2.03 ± 0.52) above-ground biomass than in a mixture predicted from trees grown in monoculture. We did not observe strong trends in overyielding for A. psuedoplatanus and Q. robur. Inclusion of the N-fixing species A. rubra in admixture with P. menziesii promoted N cycling, and decreased the C:N ratios of leaf, branch, and root tissues but not soil C:N ratio for P. menziesii. Given the observed overyielding in the A. rubra with P. menziesii mixtures, we explored potential mechanistic links between functional genetic markers for nitrification and ammonification, however we found no statistically significant effects attributable to these genetic markers. We found root area index was significantly lower in A. rubra monocultures than in admixture with P. menziesii. For both P. menziesii and A. rubra, the number of root tips was lower in mixture than monoculture, indicating physical partitioning of soil space as a result of growing in mixture. We documented additive and synergistic effects of tree species identity on above and belowground productivity, and rhizospheric microbial community development in these four tree species.

KW - Below-ground biodiversity

KW - Forest diversity

KW - Functional genetic markers

KW - Root traits

KW - Soil microbial communities

U2 - 10.1016/j.apsoil.2022.104509

DO - 10.1016/j.apsoil.2022.104509

M3 - Journal article

AN - SCOPUS:85129733380

VL - 176

JO - Applied Soil Ecology

JF - Applied Soil Ecology

SN - 0929-1393

M1 - 104509

ER -