`Tree-grass´ ecosystems. Mixed tree-grass systems are widely distributed (~16-35% of global land-surface) vegetation formations such as tropical and Mediterranean savannas, the “waldsteppe” in Eurasia and culturally influenced vegetation types such as agro-forestry systems or grazed open-forests in Europe (Hanan & Hill 2011). Semi-arid tree-grass systems are considered one of the major contributors to the interannual variability of the global carbon cycle (Poulter et al., 2014). Despite their wide distribution, Earth observation systems, and associated land-surface modeling development have been so far poorly adapted to the key structural and functional characteristics of tree-grass ecosystems. As consequence a significant uncertainty and bias in the assessments of energy, carbon, water and biogeochemical dynamics is often observed (Hanan & Hill 2011; Beringer et al. 2011).
Nutrient (N, P) imbalance. Human induced CO2 and N fertilization leads to a stoichiometric imbalance, which confers an important role to P availability and leads to shifts in C-N-P ratios and balances (Peñuelas et al. 2012).
N/P imbalances are particularly important in water-limited ecosystems (Sardans et al., 2012), where the synergistic effect of water and nutrient (N and P) availability/imbalance could impact ecosystem functioning, structure, allocation patterns and the nutrient and carbon cycling, and ultimately how the ecosystem will respond to extreme drought events.
Hence it is important to study the effects of N and P imbalances under different water regimes, in particular in mixed tree-grass at ecosystem scale.
MaNiP project offers an original experimental design integrating cutting-edge approaches to study the combined effect of nutrient and water limiting factors on fundamental ecosystem, plant and soil processes.
1. Long-term experiment in a Mediterranean tree-grass systems
2. Focus on interaction and effects of different N/P stoichiometry and water availability on ecosystem processes
Map of the MaNiP experimental site and location of the 3 EC sites.
Blue squares represent the 3 EC sites in the “WET” cluster (established in April 2014). Orange squares represent the EC sites in the DRY cluster. (not yet implemented)
Experimental facilities and instruments installed in the „WET“ cluster. Picture lysimiter (http://www.ugt-online.de/en/produkte/lysimetertechnik/lysimeter.html). Picture spectral signatures (Rossini et al., 2011).
SMANIE experimental facility. Right panel EVI and MTCI retrieved with the CASI hyperspectral flight (April 2014, 10 days after fertilization)
Tarek S. El-Madany, Markus Reichstein, Oscar Perez-Priego, Arnaud Carrara, Gerardo Moreno, M. Pilar Martín, Javier Pacheco-Labrador, Georg Wohlfahrt, Hector Nieto, Ulrich Weber, Olaf Kolle, Yun-Peng Luo, Nuno Carvalhais, Mirco Migliavacca, (2018). Drivers of spatio-temporal variability of carbon dioxide and energy fluxes in a Mediterranean savanna ecosystem, Agricultural and Forest Meteorology, Volume 262, Pages 258-278, link
Sippel, S., El-Madany, T. S., Migliavacca, M., Mahecha, M. D., Carrara, A., Flach, M., Kaminski, T., Otto, F. E. L., Thonicke, K., Vossbeck, M., Reichstein, M. (2018). Warm winter, wet spring, and an extreme response in ecosystem functioning on the Iberian Peninsula. Bulletin of the American Meteorological Society, 99(1), S80-S85. doi:10.1175/BAMS-D-17-0135.1.
Hilman, B., Muhr, J., Trumbore, S. E., Carbone, M. S., Yuval, P., Wright, S. J., Moreno, G., Pérez-Priego, O., Migliavacca, M., Carrara, A., Grünzweig, J. M., Osem, Y., Weiner, T., Angert, A. (2018). Comparison of CO2 and O2 fluxes demonstrate retention of respired CO2 in tree stems from a range of tree species. Biogeosciences Discussions. doi:10.5194/bg-2018-256.
Perez-Priego, O., El-Madany T.S., Migliavacca, M., Kowalski A.S., Jung M., Carrara A. ,Kolle O., Martín M. P., Pacheco-Labrador J., Moreno G. , Reichstein, M. (2017) Evaluation of eddy covariance latent heat fluxes with independent lysimeter and sapflow estimates in a Mediterranean savannah ecosystem. Agricultural and Forest Meteorology, 236 DOI: 10.1016/j.agrformet.2017.01.009
Migliavacca, M. , Perez-Priego, O., Rossini, M., El-Madany T.S., Moreno, G., van der Tol, C., Rascher, U., Berninger, A., Bessenbacher, V., Burkart, A. .. , Reichstein, M., '(2017). Plant functional traits and canopy structure control the relationship between photosynthetic CO2 uptake and far-red sunâ€induced fluorescence in a Mediterranean grassland under different nutrient availability, New Phytologist, 214, 3, 1078-1091.
Perez-Priego, O., Guan, J., Rossini, M., Fava, F., Wutzler, T., Moreno, G., Carvalhais, N., Carrara, A., Kolle, O., Julitta, T., Schrumpf, M., Reichstein, M., Migliavacca, M. (2015). Sun-induced Chlorophyll fluorescence and PRI improve remote sensing GPP estimates under varying nutrient availability in a typical Mediterranean savanna ecosystem. Biogeosciences, 12(14), 11891-11934. doi:10.5194/bgd-12-11891-2015