Nutrient optimization of tree growth alters structure and function of boreal soil food webs

Abstract

Nutrient optimization has been proposed as a way to increase boreal forest production, and involves chronic additions of liquid fertilizer with amounts of micro-and macro-nutrients adjusted annually to match tree nutritional requirements. We used a short-term (maintained since 2007) and a long-term (maintained since 1987) fertilization experiment in northern Sweden, in order to understand nutrient optimization effects on soil microbiota and mesofauna, and to explore the relationships between plant litter and microbial elemental stoichiometry. Soil microbes, soil fauna, and aboveground litter were collected from the control plots, and short-and long-term nutrient optimization plots. Correlation analyses revealed no relationships between microbial biomass and litter nutrient ratios. Litter C:N, C:P and N:P ratios declined in response to both optimization treatments; while only microbial C:P ratios declined in response to long-term nutrient optimization. Further, we found that both short-and long-term optimization treatments decreased total microbial, fungal, and bacterial PLFA biomass and shifted the microbial community structure towards a lower fungi:bacterial ratio. In contrast, abundances of most fungal-and bacterial-feeding soil biota were little affected by the nutrient optimization treatments. However, abundance of hemi-edaphic Collembola declined in response to the long-term nutrient optimization treatment. The relative abundances (%) of fungal-feeding and plant-feeding nematodes, respectively, declined and increased in response to both short-term and long-term treatments; bacterial-feeding nematodes increased relative to fungal feeders. Overall, our results demonstrate that long-term nutrient optimization aiming to increase forest production decreases litter C

Elemental stoichiometry (C, N, P) of soil in the Yellow River Delta nature reserve: Understanding N and P status of soil in the coastal estuary

“…This finding confirms that the long reclamation history with similar cultivation and fertilization management resulted in increased nutrient accumulation and decreased C:N ratios at the surface layer in the YNR. The findings were similar to those of Velthuis et al (2017), who found that nutrient addition consistently leads to decreased C:N ratios in submerged aquatic plants, and Maaroufi et al (2018) reported a decline in the total microbial and fungal biomass in forest plots where half of the total N added over 16 years of simulated N deposition was retained in the soil humus, thereby reducing the humus C:N ratio. As the soil-vegetation system is a synthesis, to complete this theory, we concluded that a longer reclamation and fertilization history leads to decreased C:N ratios in coastal estuary soils.…”

“…Soil microorganisms such as mycorrhizal fungi and symbiotic N-fixing bacteria provide nutrients to plants in exchange for photosynthetic C (Menge et al, 2017). Soil micro-and meso-biota biomass, community structure and function are constrained by the elemental C:N:P ratios of available litter resources (Maaroufi and Long, 2020;Maaroufi et al, 2018;Martinson et al, 2008;Ott et al, 2014). In return, soil animals, which have a wide range of stoichiometric requirements, alter the stoichiometry of leaf litter entering the soil by consumption and digestion processes (Buchkowski et al, 2019).…”

Metatranscriptomics captures dynamic shifts in mycorrhizal coordination in boreal forests

“…Sequencing this RNA (RNA-seq) revealed a significantly greater relative proportion of fungal RNA-seq reads in samples from NL compared to NE treatment ( Fig. 1 A ) ( P < 0.001; Wilcoxon signed-rank test), and supporting microbial phospholipid fatty acids data collected from soils at this site, which showed decreased fungal abundance in NE soils ( 31 ). NE conditions had a profound effect on the fungal community transcriptome at all time points throughout the growing season (349 up-regulated and 573 down-regulated differentially expressed [DE] Kyoto Encyclopedia of Genes and Genomes orthologs across the season; adjusted P < 0.01) while there was no apparent signal of seasonality ( Fig.…”

Nitrogen and phosphorus enrichment cause declines in invertebrate populations: a global meta‐analysis

“…As these two mechanisms are not mutually exclusive, unravelling their effect on invertebrate community dynamics would require evaluating both mechanisms simultaneously. Only two of the studies in our database (Pascal et al, 2013;Maaroufi et al, 2018) looked at both short-and long-term enrichment within the same study system. However, no clear pattern emerged as in both studies invertebrate abundance of different taxa increased and decreased relative to control plots in both acute and chronically enriched sites.…”