Physiology-phenology interactions in a productive semi-arid pine forest

• Published in: The New phytologist Vol. 178; no. 3; pp. 603 - 616
• Main Authors: Maseyk, Kadmiel S., Lin, Tongbao, Rotenberg, Eyal, Grünzweig, José M., Schwartz, Amnon, Yakir, Dan
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.05.2008; Blackwell Publishing; Blackwell Publishing Ltd
• Subjects: Drought; Ecosystem; Forest ecology; Forest ecosystems; maximum carboxylation rate; maximum electron transport rate; nitrogen; Nitrogen - metabolism; Phenology; Photosynthesis; Pine trees; Pinus - physiology; Pinus halepensis; Plant Leaves - growth & development; Plant Transpiration; Plants; Productivity; Seasons; Soil - analysis; Soil water; Soil water content; stomatal regulation; Time Factors; Trees - physiology; vapour pressure deficit; Water
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2008.02391.x

This study explored possible advantages conferred by the phase shift between leaf phenology and photosynthesis seasonality in a semi-arid Pinus halepensis forest system, not seen in temperate sites. Leaf-scale measurements of gas exchange, nitrogen and phenology were used on daily, seasonal and annual time-scales. Peak photosynthesis was in late winter, when high soil moisture, mild temperatures and low leaf vapour pressure deficit (DL) allowed high rates associated with high water- and nitrogen-use efficiencies. Self-sustained new needle growth through the dry and hot summer maximized photosynthesis in the following wet season, without straining carbon storage. Low rates of water loss were associated with increasing sensitivity of stomatal conductance (gs) to soil moisture below a relative extractable water (REW) of 0.4, and decreased gs sensitivity to DL below REW of approx. 0.2. This response was captured by the modified Ball-Berry (Leuning) model. While most physiological parameters and responses measured were typical of temperate pines, the photosynthesis-phenological phasing contributed to high productivity under warm-dry conditions. This contrasts with reported effects of short-term periodical droughts and could lead to different predictions of the effect of warming and drying climate on pine forest productivity.