Estimating global carbon uptake by lichens and bryophytes with a process-based model

[摘要] Lichens and bryophytes are abundant globally and they may even form thedominant autotrophs in (sub)polar ecosystems, in deserts and at highaltitudes. Moreover, they can be found in large amounts as epiphytes inold-growth forests. Here, we present the first process-based model whichestimates the net carbon uptake by these organisms at the global scale, thusassessing their significance for biogeochemical cycles. The model usesgridded climate data and key properties of the habitat (e.g. disturbanceintervals) to predict processes which control net carbon uptake, namelyphotosynthesis, respiration, water uptake and evaporation. It relies onequations used in many dynamical vegetation models, which are combined withconcepts specific to lichens and bryophytes, such as poikilohydry or theeffect of water content on CO₂ diffusivity. To incorporate the greatfunctional variation of lichens and bryophytes at the global scale, the modelparameters are characterised by broad ranges of possible values instead of asingle, globally uniform value. The predicted terrestrial net uptake of 0.34to 3.3 Gt yr⁻¹ of carbon and global patterns of productivity are inaccordance with empirically-derived estimates. Considering that theassimilated carbon can be invested in processes such as weathering ornitrogen fixation, lichens and bryophytes may play a significant role inbiogeochemical cycles.

[学科分类] 地球化学与岩石