Plant and soil microbe responses to light, warming and nitrogen addition in a temperate forest

Abstract

Temperate forests across Europe and eastern North America have become denser since the 1950s due to less intensive forest management and global environmental changes such as nitrogen deposition and climate warming. Denser tree canopies result in lower light availability at the forest floor. This shade may buffer the effects of nitrogen deposition and climate warming on understorey plant communities. We conducted an innovative in situ field experiment to study the responses of co‐occurring soil microbial and understorey plant communities to nitrogen addition, enhanced light availability and experimental warming in a full‐factorial design. We determined the effects of multiple environmental drivers and their interactions on the soil microbial and understorey plant communities, and assessed to what extent the soil microbial and understorey plant communities covary. High light led to lower biomass of the soil microbes (analysed by phospholipid fatty acids), but the soil microbial structure, i.e. the ratio of fungal biomass to bacterial biomass, was not affected by light availability. The composition of the soil bacterial community (analysed by high‐throughput sequencing) was affected by both light availability and warming (and their interaction), but not by nitrogen addition. Yet, the number of unique operational taxonomic units was higher in plots with nitrogen addition, and there were significant interactive effects of light and nitrogen addition. Light availability also determined the composition of the plant community; no effects of nitrogen addition and warming were observed. The soil bacterial and plant communities were co‐structured, and light availability explained a large part of the variance of this co‐structure. We provide robust evidence for the key role of light in affecting both the soil microbial and plant communities in forest understoreys. Our results advocate for more multifactor global change experiments that investigate the mechanism underlying the (in) direct effects of light on the plant–soil continuum in forests. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13061/suppinfo is available for this article.

Agricultural land‐use history and restoration impact soil microbial biodiversity

“…As a consequence, underlying site properties might be mistakenly interpreted as agricultural legacy effects, when in fact they are simply consequences of the land-use decision-making process. Controlling for these land-use biases is particularly important for resolving how soil microbial communities respond to land-use legacies, given soil microbes' responsiveness to soil conditions (Fierer & Jackson, 2006;Lauber, Strickland, Bradford, & Fierer, 2008;Ma, De Frenne, Vanhellemont, et al, 2019;Ma et al, 2018;Xue et al, 2018). Here, we control for land-use biases through a study design where post-agricultural plots and remnant plots with no known history of agriculture are paired in space, resulting in no bias in underlying soil types (Brudvig, Grman, Habeck, Orrock, & Ledvina, 2013).…”

Plant–bacteria–soil response to frequency of simulated nitrogen deposition has implications for global ecosystem change

“…Zavaleta et al (), Harpole, Potts, and Suding (), and Fornara and Tilman () amended N twice per year, and Reich et al () and Bowman, Cleveland, Halada, Hresko, and Baron () amended N three times per year. Second (b), N is applied throughout a growing season four to six times per year (Contosta, Frey, & Cooper, ; Langley, J., Megonigal, & Patrick, J., ; Ma et al, ) and sometimes (c) up to monthly (12X) N additions per year (Phoenix et al, ). Overwhelmingly, N deposition simulation experiments used the first way (a) of N addition frequency and tended to focus amendment during vigorous plant‐growth stages.…”

Nitrogen addition accelerates the nitrogen cycle in a young subtropical Cunninghamia lanceolata (Lamb.) plantation

“…Such changes in productivity are important as they reflect the quantity and quality of litter and soil organic matter, all of which eventually feed back to the rate and pathways of the N cycle (Dawes et al 2017). Soil microbes are sensitive to environmental conditions, including temperature, N deposition, moisture, and vegetation (de Vries et al 2012;Sugihara et al 2015;Xu et al 2015;Yang et al 2015;Ma et al 2018). Nitrogen addition is considered to enhance microbial biomass by increasing C and N resources availability in most terrestrial ecosystems limited by N (Zhou et al 2017).…”