Tuber melanosporum Vittad. abundance and specific soil parameters predict soil enzymatic activity in wild and managed truffle producing systems

Abstract

Soil microorganisms are able to produce extracellular enzymes and are crucial for ecosystem processes like decomposition and nutrient cycling. The black truffle (Tuber melanosporum Vittad.) is a highly valued ectomycorrhizal edible fungus. It exerts a strong allelopathic effect, creating a burnt area around the host tree that impacts soil biotic and abiotic properties, and likely affects soil functioning as well. This study investigated the influence of black truffle abundance on soil functions, at different seasons and truffle-producing systems. A regional field design was set up in black truffle productive plantations and forests across the natural distribution area of this fungus in Spain. Physico-chemical soil properties, potential soil enzymatic activities related with carbon, phosphorus and nitrogen cycling, and soil fungal richness and abundance were determined. Black truffle-producing forests generally exhibited lower enzymatic activity compared to plantations, except for chitinase. Besides greater soil enzymatic activity —mainly related with rapid carbon and nitrogen turnover— was observed in late spring than autumn, independently of the type of truffle producing system. Our findings revealed a significant negative impact of black truffle abundance on soil enzymatic activities, and particularly on those involved in carbon and nitrogen mobilisation. Besides the strong local site effect, other biotic and abiotic factors differently impacted soil functioning in truffle forests (Mg) and plantations (Ascomycetes richness, CaCO3, Na). These results offer insights into the ecology and functionality of host-truffle-soil interactions and provide valuable information for optimising management practices in black truffle plantations.