Comparing integrated stable isotope and eddy covariance estimates of water-use efficiency on a Mediterranean successional sequence

• Published in: Oecologia 2014-10, Vol.176 (2), p.581-594
• Main Authors: Scartazza, Andrea, Vaccari, Francesco Primo, Bertolini, Teresa, Di Tommasi, Paul, Lauteri, Marco, Miglietta, Franco, Brugnoli, Enrico
• Format: Article
• Language: English
• Subjects: Agroecosystems; Agronomy. Soil science and plant productions; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Brackish; Carbon dioxide; Carbon Isotopes - analysis; Covariance; Drought; Droughts; Dry matter; Dry season; Ecology; Ecosystem; ECOSYSTEM ECOLOGY; Ecosystem ecology - Original research; Ecosystems; eddy covariance; energy; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; General aspects; Generalities. Agricultural and farming systems. Agricultural development; Hydrology/Water Resources; Islands; Isotopes; Italy; Leaves; Life Sciences; Maquis; Marine; Marine ecosystems; Mediterranean Region; Photosynthesis; Plant communities; Plant Leaves - chemistry; Plant Leaves - physiology; Plant Sciences; Plants; primary productivity; seasonal variation; Seasonal variations; Seasons; shrublands; Species; Stable isotopes; Stomatal conductance; Sugar; sugars; Terrestrial ecosystems; Water; Water relations; Water use; water use efficiency
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-014-3027-2

Water-use efficiency (WUE), thought to be a relevant trait for productivity and adaptation to water-limited environments, was estimated for three different ecosystems on the Mediterranean island of Pianosa: Mediterranean macchia (SMM), transition (STR) and abandoned agricultural (SAA) ecosystems, representing a successional series. Three independent approaches were used to study WUE: eddy covariance measurements, C isotope composition of ecosystem respired CO₂, and C isotope discrimination (Δ) of leaf material (dry matter and soluble sugars). Seasonal variations in C–water relations and energy fluxes, compared in SMM and in SAA, were primarily dependent on the specific composition of each plant community. WUE of gross primary productivity was higher in SMM than in SAA at the beginning of the dry season. Both structural and fast-turnover leaf material were, on average, more enriched in ¹³C in SMM than SAA, indicating relatively higher stomatal control and WUE for the long-lived macchia species. This pattern corresponded to ¹³C-enriched respired CO₂ in SMM compared to the other ecosystems. Conversely, most of the annual herbaceous SAA species (terophytes) showed a drought-escaping strategy, with relatively high stomatal conductance and low WUE. An ecosystem-integrated Δ value was weighted for each ecosystem on the abundance of different life forms, classified according to Raunkiar’s system. Agreement was found between ecosystem WUE calculated using eddy covariance and those estimated using integrated Δ approaches. Comparing the isotopic methods, Δ of leaf soluble sugars provided the most reliable proxy for short-term changes in photosynthetic discrimination and associated shifts in integrated canopy-level WUE along the successional series.