Costimulation of soil glycosidase activity and soil respiration by nitrogen addition

Abstract

Unprecedented levels of nitrogen (N) have been deposited in ecosystems over the past century, which is expected to have cascading effects on microbially mediated soil respiration (SR). Extracellular enzymes play critical roles on the degradation of soil organic matter, and measurements of their activities are potentially useful indicators of SR. The links between soil extracellular enzymatic activities (EEAs) and SR under N addition, however, have not been established. We therefore conducted a meta-analysis from 62 publications to synthesize the responses of soil EEAs and SR to elevated N. Nitrogen addition significantly increased glycosidase activity (GA) by 13.0%, α-1,4-glucosidase (AG) by 19.6%, β-1,4-glucosidase (BG) by 11.1%, β-1,4-xylosidase (BX) by 21.9% and β-D-cellobiosidase (CBH) by 12.6%. Increases in GA were more evident for long duration, high rate, organic and mixed N addition (combination of organic and inorganic N addition), as well as for studies from farmland. The response ratios (RRs) of GA were positively correlated with the SR-RRs, even when evaluated individually for AG, BG, BX and CBH. This positive correlation between GA-RR and SR-RR was maintained for most types of vegetation and soil as well as for different methods of N addition. Our results provide the first evidence that GA is linked to SR under N addition over a range of ecosystems and highlight the need for further studies on the response of other soil EEAs to various global change factors and their implications for ecosystem functions.

Responses of growing‐season soil respiration to water and nitrogen addition as affected by grazing intensity

“…Under each grazing intensity, the nitrogen addition‐induced declines in soil respiration were similar and resulted mostly from the adverse effects of nitrogen addition on microbial biomass and F/B ratio in the semi‐arid grassland of the current study. In highly nitrogen‐limited plots under moderate or heavy grazing in previous studies, the increase in soil nitrogen availability enhanced the quality and quantity of plant biomass and soil extracellular enzymatic activities, and thus increased soil respiration (Chen, Luo, et al., ; LeBauer & Treseder, ; Liu & Greaver, ; Wang et al., ). In the present study, however, nitrogen addition probably reduced soil respiration across grazing intensities because its negative effect on microbial respiration was greater than its positive effect on root respiration (Harpole, Potts, & Suding, ; Phillips & Fahey, ); in the present study, these effects were accompanied by substantial declines in soil pH and hence in microbial biomass and F/B ratio.…”

Differential responses of carbon‐degrading enzyme activities to warming: Implications for soil respiration

“…Warming‐induced redistribution of N from soils to vegetation could progressively lead to microbial N limitation, particularly in high C:N regions (Bai et al., ; Beier et al., ; Melillo et al., ). In that case, soil microorganisms are expected to invest C and energy to acquire N through decomposition of N‐containing molecules (Chen, Luo et al., ; Sinsabaugh et al., ), which are often physically or chemically protected by other aromatic macromolecules such as lignin (Hobbie, ; Weedon et al., ; Zhao et al., ). This explanation is supported by the positive correlation between warming effects on ligninase activity and soil C:N, while no clear relationship is found for the responses of cellulase activity (Supporting information Figure S6).…”

“…It is specific that there is a lack of information regarding the degree to which soil extracellular enzymes (EEs), which catalyze the rate‐limiting step in SOM decomposition (Allison, Wallenstein, & Bradford, ; Jing et al., ; Sinsabaugh, ; Stone et al., ), are affected by warming. These enzymes, primarily produced by microbes, are considered proximate agents of SR because they lower the activation energy of key reactions and speed up the breakdown of polymers (Chen, Luo et al., ; Chen et al., ; Janssens et al., ; Suseela, Tharayil, Xing, & Dukes, ). Although the rates at which these enzymes are produced and degraded are sensitive to temperature (Allison & Treseder, ; German, Marcelo, Stone, & Allison, ; Papanikolaou, Britton, Helliwell, & Johnson, ; Steinweg, Dukes, Paul, & Wallenstein, ), it is still unclear how warming responses of enzymes affect SR.…”

Understory Plants Regulate Soil Respiration through Changes in Soil Enzyme Activity and Microbial C, N, and P Stoichiometry Following Afforestation

“…Plants affect SR in many ways, one of which is soil enzyme activities [15,16]. Enzyme activity is the most basic driving factor of SR. More than 50% of SR is produced by the enzyme-related decomposition of litter and soil organic matter (SOM) [17,18].…”