TY - JOUR
T1 - Biogeochemical indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems
AU - Ochoa-Hueso, Raúl
AU - Arróniz-Crespo, María
AU - Bowker, Matthew A.
AU - Maestre, Fernando T.
AU - Pérez-Corona, M. Esther
AU - Theobald, Mark R.
AU - Vivanco, Marta G.
AU - Manrique, Esteban
N1 - Funding Information:
Acknowledgments This research was financially supported by the Spanish Ministerio de Economía y Competitividad (CGL-2009-11015; CTM2009-12838-CO4-O3) and the Comunidad de Madrid (S-0505/AMB/0335). ROH was funded by a FPU fellowship (AP2006-04638). The work of FTM is supported from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no. 242658 (BIOCOM). We are very thankful to Octavio Cedenilla, Luis Ayala, and Cristina Paradela for helping with the field and lab work. Emi Martin-Queller is especially thanked for her great contribution during the field sampling.
PY - 2014/9
Y1 - 2014/9
N2 - Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha-1 year-1). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha -1 year-1. Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution.
AB - Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha-1 year-1). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha -1 year-1. Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution.
KW - Acidification
KW - Biocrusts
KW - Bioindicators
KW - C and N storage
KW - Cryptogams
KW - N deposition
KW - Nitrate reductase
KW - Phosphomonoesterase
KW - Semiarid Mediterranean
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U2 - 10.1007/s10661-014-3822-6
DO - 10.1007/s10661-014-3822-6
M3 - Article
C2 - 24894911
AN - SCOPUS:84905972271
SN - 0167-6369
VL - 186
SP - 5831
EP - 5842
JO - Environmental Monitoring and Assessment
JF - Environmental Monitoring and Assessment
IS - 9
ER -