title: Soil organic carbon stocks in estuarine and marine mangrove ecosystems are driven by nutrient colimitation of P and N.
abstract: Mangroves play an important role in carbon sequestration, but soil organic carbon (SOC) stocks differ between marine and estuarine mangroves, suggesting differing processes and drivers of SOC accumulation. Here, we compared undegraded and degraded marine and estuarine mangroves in a regional approach across the Indonesian archipelago for their SOC stocks and evaluated possible drivers imposed by nutrient limitations along the land-to-sea gradients. SOC stocks in natural marine mangroves (271-572 Mg ha(-1) m(-1)) were much higher than under estuarine mangroves (100-315 Mg ha(-1) m(-1)) with a further decrease caused by degradation to 80-132 Mg ha(-1) m(-1). Soils differed in C/N ratio (marine: 29-64; estuarine: 9-28), δ (15)N (marine: -0.6 to 0.7‰; estuarine: 2.5 to 7.2‰), and plant-available P (marine: 2.3-6.3 mg kg(-1); estuarine: 0.16-1.8 mg kg(-1)). We found N and P supply of sea-oriented mangroves primarily met by dominating symbiotic N2 fixation from air and P import from sea, while mangroves on the landward gradient increasingly covered their demand in N and P from allochthonous sources and SOM recycling. Pioneer plants favored by degradation further increased nutrient recycling from soil resulting in smaller SOC stocks in the topsoil. These processes explained the differences in SOC stocks along the land-to-sea gradient in each mangrove type as well as the SOC stock differences observed between estuarine and marine mangrove ecosystems. This first large-scale evaluation of drivers of SOC stocks under mangroves thus suggests a continuum in mangrove functioning across scales and ecotypes and additionally provides viable proxies for carbon stock estimations in PES or REDD schemes.
authors.affiliation: Institute of Soil Science Leibniz Universität Hannover Herrenhäuser Str. 2 D-30419 Hannover Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Weiss
authors.affiliation: Institute of Soil Science Leibniz Universität Hannover Herrenhäuser Str. 2 D-30419 Hannover Germany.
authors.forename: Joanna
authors.initials: J
authors.lastname: Weiss
authors.affiliation: Institute of Soil Science Leibniz Universität Hannover Herrenhäuser Str. 2 D-30419 Hannover Germany.
authors.forename: Jens
authors.identifier: 0000-0002-2751-957X
authors.initials: J
authors.lastname: Boy
authors.affiliation: Department of Soil Science and Land Resources Bogor Agricultural University Kampus IPB Dramaga Bogor 16680 Indonesia.
authors.forename: Issi
authors.initials: I
authors.lastname: Iskandar
authors.affiliation: Soil Science and Soil Protection Martin Luther Universität Halle Wittenberg Von-Seckendorff-Platz 3 D-06120 Halle (Saale) Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Mikutta
authors.affiliation: Institute of Soil Science Leibniz Universität Hannover Herrenhäuser Str. 2 D-30419 Hannover Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Guggenberger
keywords: Ecosystem functioning; Indonesia; global change; marine and estuarine mangroves; nitrogen; phosphorus; soil organic carbon; stable isotopes