Forest harvesting reduces the soil metagenomic potential for biomass decomposition

Abstract

Soil is the key resource that must be managed to ensure sustainable forest productivity. Soil microbial communities mediate numerous essential ecosystem functions, and recent studies show that forest harvesting alters soil community composition. From a long-term soil productivity study site in a temperate coniferous forest in British Columbia, 21 forest soil shotgun metagenomes were generated, totaling 187 Gb. A method to analyze unassembled metagenome reads from the complex community was optimized and validated. The subsequent metagenome analysis revealed that, 12 years after forest harvesting, there were 16% and 8% reductions in relative abundances of biomass decomposition genes in the organic and mineral soil layers, respectively. Organic and mineral soil layers differed markedly in genetic potential for biomass degradation, with the organic layer having greater potential and being more strongly affected by harvesting. Gene families were disproportionately affected, and we identified 41 gene families consistently affected by harvesting, including families involved in lignin, cellulose, hemicellulose and pectin degradation. The results strongly suggest that harvesting profoundly altered below-ground cycling of carbon and other nutrients at this site, with potentially important consequences for forest regeneration. Thus, it is important to determine whether these changes foreshadow long-term changes in forest productivity or resilience and whether these changes are broadly characteristic of harvested forests.

Differential Effects of Coarse Woody Debris on Microbial and Soil Properties in Pinus densiflora Sieb. et Zucc. Forests

“…Combining our results with their finding, we suggested that CWD could be considered to be spots where both pedogenic and microbial processes are concentrated. It could confirm the importance of appropriate CWD management in the context of sustaining soil functioning and fertility [9][10][11][12].…”

“…Recent studies have found negative effects of CWD removal on soil nitrogen (N) availability and C pool as well as soil microbial communities and metabolic potential [10][11][12]. However, the interaction between CWD and soils remains one of the most unknown subjects in forest ecology.…”

Microbial energy and matter transformation in agricultural soils

“…Total OC (%) plays a strong role in shaping the relative abundance of GH families in situ, as shown by greater richness of GH families involved in cellulose, hemicellulose, lignin and pectin degradation in relatively C rich organic soil layers compared to a greater relative abundance of phenol and protein degradation in C poor mineral soil layers (Cardenas et al, 2015;de Menezes et al, 2015;Uroz et al, 2013). Comparative analysis of a relatively C rich grassland soil showed preferential enrichment of GH families involved in cellobiose and amine degradation while a relatively C poor wheat cropping soil enriched for GH families involved in chitin, b-N-acetylglucosamine and glycoside degradation (Manoharan et al, 2015).…”

Long-Term Warming Alters Carbohydrate Degradation Potential in Temperate Forest Soils

“…Forest soil profiles typically consist of a root-entangled mat of partially decomposed plant litter (organic horizon) that sits atop a less-carbon-rich mineral soil. The functional (13) and taxonomic (14) compositions of microbial communities are similarly stratified, with the organic horizon more enriched in fungi and carbohydrate-degrading genes than the mineral soil (15). Forest organic horizon communities have previously been shown to respond to environmental stressors with greater functional (15) and taxonomic (16) shifts than those of the mineral soil, indicating that evaluating the horizon-specific responses to warming may provide insight into altered microbial carbon cycling capacity.…”