Fungi exposed to chronic nitrogen enrichment are less able to decay leaf litter

Abstract

Abstract. Saprotrophic fungi are the primary decomposers of plant litter in temperate forests, and their activity is critical for carbon (C) and nitrogen (N) cycling. Simulated atmospheric N deposition is associated with reduced fungal biomass, shifts in fungal community structure, slowed litter decay, and soil C accumulation. Although rarely studied, N deposition may also result in novel selective pressures on fungi, affecting evolutionary trajectories. To directly test if long-term N enrichment reshapes fungal responses to N, we isolated decomposer fungi from a long-term (28 yr) N-addition experiment and used a common garden approach to compare growth rates and decay abilities of isolates from control and N-amended plots. Both growth and decay were significantly altered by long-term exposure to N enrichment. Changes in growth rates were idiosyncratic, as different species grew either more quickly or more slowly after exposure to N, but litter decay by N isolates was consistent and generally lower compared to control isolates of the same species, a response not readily reversed when N isolates were grown in control (low N) environments. Changes in fungal responses accompany and perhaps drive previously observed N-induced shifts in fungal diversity, community composition, and litter decay dynamics.

Resistant Soil Microbial Communities Show Signs of Increasing Phosphorus Limitation in Two Temperate Forests After Long-Term Nitrogen Addition

“…The core of this conceptual model is well-supported by observations that added N often reduces soil microbial biomass and alters soil microbial community composition, particularly by decreasing the abundance of fungi (Frey et al, 2004;van Diepen et al, 2007van Diepen et al, , 2016Edwards et al, 2011;Morrison et al, 2016). Decreases in fungal abundance often co-occurred with reduced activities of the lignin-modifying enzymes (LMEs) phenol oxidase and peroxidase, which are mainly produced by white rot fungi to oxidize lignin and SOM (Carreiro et al, 2000;Baldrian, 2006;Sinsabaugh, 2010;Hatakka and Hammel, 2011;Frey et al, 2014).…”

Carbon:Nitrogen:Phosphorus Stoichiometry in Fungi: A Meta-Analysis

“…Indeed, Cleveland and Liptzin (2007) suggested that an average soil microbial N:P ratio might be a more appropriate index of ecosystem nutrient limitation than plant N:P ratios. A recent study showed that the biogeochemical consequences of N deposition in temperate forests may be driven by the stoichiometry of the dominant trees and their associated microbes (Midgley and Phillips, 2016) while van Diepen et al (2017) found that fungi exposed to chronic nitrogen enrichment are less able to decay leaf litter. All of these studies point to the importance of multi-resource interactions in nutrient cycling in soils.…”

A plant virus (BYDV) promotes trophic facilitation in aphids on wheat

“…Previous work has established that the order and timing of species colonization can influence the structure and dynamics of communities through facilitation in different types of organisms ranging from bacteria to vertebrates 3 , 8 , 10 , 12 – 17 . In the case of aphids, for example, small species such as Rhopaloshipum padi are first to colonize grasses (e.g., wheat), while others like the larger R .…”