Estimating global nitrous oxide emissions by lichens and bryophytes with a process-based productivity model

Abstract

Abstract. Nitrous oxide is a strong greenhouse gas and atmospheric ozone-depleting agent which is largely emitted by soils. Recently, lichens and bryophytes have also been shown to release significant amounts of nitrous oxide. This finding relies on ecosystem-scale estimates of net primary productivity of lichens and bryophytes, which are converted to nitrous oxide emissions by empirical relationships between productivity and respiration, as well as between respiration and nitrous oxide release. Here we obtain an alternative estimate of nitrous oxide emissions which is based on a global process-based non-vascular vegetation model of lichens and bryophytes. The model quantifies photosynthesis and respiration of lichens and bryophytes directly as a function of environmental conditions, such as light and temperature. Nitrous oxide emissions are then derived from simulated respiration assuming a fixed relationship between the two fluxes. This approach yields a global estimate of 0.27 (0.19-0.35) (Tg N 2 O) year −1 released by lichens and bryophytes. This is lower than previous estimates but corresponds to about 50 % of the atmospheric deposition of nitrous oxide into the oceans or 25 % of the atmospheric deposition on land. Uncertainty in our simulated estimate results from large variation in emission rates due to both physiological differences between species and spatial heterogeneity of climatic conditions. To constrain our predictions, combined online gas exchange measurements of respiration and nitrous oxide emissions may be helpful.

Desiccation and rehydration of mosses greatly increases resource fluxes that alter soil carbon and nitrogen cycling

“…Additionally, the rate of cellular repair following rehydration directly determines the duration of bryotic pulses, but the duration of this period of repair is known for only a few moss species for which repair rates varied from 30 min to 12 hr (Coxson et al, ; Oliver, Mishler, & Quisenberry, ; Wilson & Coxson, ). Integration of such data with existing models of moss effects on ecosystems (e.g., Delgado‐Baquerizo et al, ; Porada et al, ; Sun et al, ) could allow us to determine the effects of mosses on soil C and N pools and fluxes and understand how changing environmental patterns will influence moss‐mediated nutrient cycling. This may be of particular importance in systems where predicted increases in temperature and changes in precipitation patterns may cause widespread increases in moss mortality and yield large changes in C and N budgets (Barker, Stark, Zimpfer, Mcletchie, & Smith, ; Belnap, Phillips, Flint, Money, & Caldwell, ; Coe, Belnap, & Sparks, ; Li, Jia, Zhang, Zhang, & Hui, ; Reed et al, ).…”

Effects of short-term variability of meteorological variables on soil temperature in permafrost regions

“…The Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg (JSBACH) is the land surface scheme for the Max Planck Institute Earth System Model (MPI-ESM) (Raddatz et al, 2007;Reick et al, 2013). It runs coupled to the atmosphere inside the ESM or offline forced by observation-based or projected climate input data.…”

“…This model is designed to predict lichen and bryophyte net primary productivity (NPP) in a process-based way from available light, surface temperature, atmospheric carbon dioxide concentration, and water content of lichens and bryophytes. Furthermore, it is applicable when estimating various impacts of lichens and bryophytes on biogeochemical cycles (Lenton et al, 2016;Porada et al, 2016bPorada et al, , 2017. The model includes a dynamic representation of the surface cover which depends on the balance of growth due to NPP and reduction by disturbance, such as fire (Porada et al, 2016a).…”

Contrasting effects of reindeer grazing on CO2, CH4, and N2O fluxes originating from the northern boreal forest floor

“…The role of cryptogams as sources of N 2 O and CH 4 has also been demonstrated recently (Lenhart et al, ). By affecting ground vegetation composition and soil temperatures, reindeer grazing could significantly impact the N 2 O and CH 4 fluxes from the forest floor (Porada, Pöschl, Kleidon, Beer, & Weber, ).…”