@misc{PoradaTammRaggioetal.2019,
  author    = {Porada, Philipp and Tamm, Alexandra and Raggio, Jose and Yafang, Cheng and Kleidon, Axel and P{\"o}schl, Ulrich and Weber, Bettina},
  title     = {Global NO and HONO emissions of biological soil crusts estimated by a process-based non-vascular vegetation model},
  series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  number    = {746},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-43568},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-435682},
  pages     = {2003 -- 2031},
  year      = {2019},
  abstract  = {The reactive trace gases nitric oxide (NO) and nitrous acid (HONO) are crucial for chemical processes in the atmosphere, including the formation of ozone and OH radicals, oxidation of pollutants, and atmospheric self-cleaning. Recently, empirical studies have shown that biological soil crusts are able to emit large amounts of NO and HONO, and they may therefore play an important role in the global budget of these trace gases. However, the upscaling of local estimates to the global scale is subject to large uncertainties, due to unknown spatial distribution of crust types and their dynamic metabolic activity. Here, we perform an alternative estimate of global NO and HONO emissions by biological soil crusts, using a process-based modelling approach to these organisms, combined with global data sets of climate and land cover. We thereby consider that NO and HONO are emitted in strongly different proportions, depending on the type of crust and their dynamic activity, and we provide a first estimate of the global distribution of four different crust types. Based on this, we estimate global total values of 1.04 Tg yr⁻¹ NO-N and 0.69 Tg yr⁻¹ HONO-N released by biological soil crusts. This corresponds to around 20\% of global emissions of these trace gases from natural ecosystems. Due to the low number of observations on NO and HONO emissions suitable to validate the model, our estimates are still relatively uncertain. However, they are consistent with the amount estimated by the empirical approach, which confirms that biological soil crusts are likely to have a strong impact on global atmospheric chemistry via emissions of NO and HONO.},
  language  = {en}
}
@article{PoradaTammRaggioetal.2019,
  author    = {Porada, Philipp and Tamm, Alexandra and Raggio, Jose and Yafang, Cheng and Kleidon, Axel and P{\"o}schl, Ulrich and Weber, Bettina},
  title     = {Global NO and HONO emissions of biological soil crusts estimated by a process-based non-vascular vegetation model},
  series = {Biogeosciences},
  volume    = {16},
  journal   = {Biogeosciences},
  publisher = {Copernicus Publ.},
  address   = {G{\"o}ttingen},
  issn      = {1726-4170},
  doi       = {10.5194/bg-16-2003-2019},
  pages     = {2003 -- 2031},
  year      = {2019},
  abstract  = {The reactive trace gases nitric oxide (NO) and nitrous acid (HONO) are crucial for chemical processes in the atmosphere, including the formation of ozone and OH radicals, oxidation of pollutants, and atmospheric self-cleaning. Recently, empirical studies have shown that biological soil crusts are able to emit large amounts of NO and HONO, and they may therefore play an important role in the global budget of these trace gases. However, the upscaling of local estimates to the global scale is subject to large uncertainties, due to unknown spatial distribution of crust types and their dynamic metabolic activity. Here, we perform an alternative estimate of global NO and HONO emissions by biological soil crusts, using a process-based modelling approach to these organisms, combined with global data sets of climate and land cover. We thereby consider that NO and HONO are emitted in strongly different proportions, depending on the type of crust and their dynamic activity, and we provide a first estimate of the global distribution of four different crust types. Based on this, we estimate global total values of 1.04 Tg yr⁻¹ NO-N and 0.69 Tg yr⁻¹ HONO-N released by biological soil crusts. This corresponds to around 20\% of global emissions of these trace gases from natural ecosystems. Due to the low number of observations on NO and HONO emissions suitable to validate the model, our estimates are still relatively uncertain. However, they are consistent with the amount estimated by the empirical approach, which confirms that biological soil crusts are likely to have a strong impact on global atmospheric chemistry via emissions of NO and HONO.},
  language  = {en}
}
@misc{HargisGotschPoradaetal.2019,
  author    = {Hargis, Hailey and Gotsch, Sybil G. and Porada, Philipp and Moore, Georgianne W. and Ferguson, Briana and Van Stan, John T.},
  title     = {Arboreal epiphytes in the soil-atmosphere interface},
  series = {Geosciences},
  volume    = {9},
  journal   = {Geosciences},
  number    = {8},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2076-3263},
  doi       = {10.3390/geosciences9080342},
  pages     = {17},
  year      = {2019},
  abstract  = {Arboreal epiphytes (plants residing in forest canopies) are present across all major climate zones and play important roles in forest biogeochemistry. The substantial water storage capacity per unit area of the epiphyte "bucket" is a key attribute underlying their capability to influence forest hydrological processes and their related mass and energy flows. It is commonly assumed that the epiphyte bucket remains saturated, or near-saturated, most of the time; thus, epiphytes (particularly vascular epiphytes) can store little precipitation, limiting their impact on the forest canopy water budget. We present evidence that contradicts this common assumption from (i) an examination of past research; (ii) new datasets on vascular epiphyte and epi-soil water relations at a tropical montane cloud forest (Monteverde, Costa Rica); and (iii) a global evaluation of non-vascular epiphyte saturation state using a process-based vegetation model, LiBry. All analyses found that the external and internal water storage capacity of epiphyte communities is highly dynamic and frequently available to intercept precipitation. Globally, non-vascular epiphytes spend <20\% of their time near saturation and regionally, including the humid tropics, model results found that non-vascular epiphytes spend similar to 1/3 of their time in the dry state (0-10\% of water storage capacity). Even data from Costa Rican cloud forest sites found the epiphyte community was saturated only 1/3 of the time and that internal leaf water storage was temporally dynamic enough to aid in precipitation interception. Analysis of the epi-soils associated with epiphytes further revealed the extent to which the epiphyte bucket emptied-as even the canopy soils were often <50\% saturated (29-53\% of all days observed). Results clearly show that the epiphyte bucket is more dynamic than currently assumed, meriting further research on epiphyte roles in precipitation interception, redistribution to the surface and chemical composition of "net" precipitation waters reaching the surface.},
  language  = {en}
}
@misc{HargisGotschPoradaetal.2019,
  author    = {Hargis, Hailey and Gotsch, Sybil G. and Porada, Philipp and Moore, Georgianne W. and Ferguson, Briana and Van Stan II, John T.},
  title     = {Arboreal epiphytes in the soil-atmosphere interface},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {928},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-44199},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-441993},
  pages     = {19},
  year      = {2019},
  abstract  = {Arboreal epiphytes (plants residing in forest canopies) are present across all major climate zones and play important roles in forest biogeochemistry. The substantial water storage capacity per unit area of the epiphyte "bucket" is a key attribute underlying their capability to influence forest hydrological processes and their related mass and energy flows. It is commonly assumed that the epiphyte bucket remains saturated, or near-saturated, most of the time; thus, epiphytes (particularly vascular epiphytes) can store little precipitation, limiting their impact on the forest canopy water budget. We present evidence that contradicts this common assumption from (i) an examination of past research; (ii) new datasets on vascular epiphyte and epi-soil water relations at a tropical montane cloud forest (Monteverde, Costa Rica); and (iii) a global evaluation of non-vascular epiphyte saturation state using a process-based vegetation model, LiBry. All analyses found that the external and internal water storage capacity of epiphyte communities is highly dynamic and frequently available to intercept precipitation. Globally, non-vascular epiphytes spend <20\% of their time near saturation and regionally, including the humid tropics, model results found that non-vascular epiphytes spend ~1/3 of their time in the dry state (0-10\% of water storage capacity). Even data from Costa Rican cloud forest sites found the epiphyte community was saturated only 1/3 of the time and that internal leaf water storage was temporally dynamic enough to aid in precipitation interception. Analysis of the epi-soils associated with epiphytes further revealed the extent to which the epiphyte bucket emptied—as even the canopy soils were often <50\% saturated (29-53\% of all days observed). Results clearly show that the epiphyte bucket is more dynamic than currently assumed, meriting further research on epiphyte roles in precipitation interception, redistribution to the surface and chemical composition of "net" precipitation waters reaching the surface.},
  language  = {en}
}