c3.3.9 – Water table salinity, rainfall and water use by umbrella pine (Pinus pinea L.) trees

Teobaldelli M (1)*, Gandolfo GP (1), Mencuccini M (2), Piussi P (1)

(1) DISTAF, Università di Firenze, Italy, (2) IERM, University of Edinburgh
Collocazione: c3.3.9 – Tipo Comunicazione: Presentazione orale
3° Congresso SISEF *
Sessione 3: “Foreste e selvicoltura per la protezione del territorio” *

Contatto: Maurizio Teolbaldelli (teobaldelli@softhome.net)

Abstract: The interactions between environmental conditions (particularly precipitation and water table salinity) and pine water use were studied at the pinewood of Alberese (Grosseto), a coastal forest characterised by a sandy soil and a high water table level (ranging between 1.0 and 1.5 m depth). Data on soil water, water table (depth and salinity), sap flow (by heat pulse) and isotopic composition of water (using 18O in rainfall, seawater, soil water and tree sap) were compared between two contrasting sites (hereby referred to as A and B), characterised by differences in the salinity levels of the water table. Site A was located near the karstic Uccellina hills and was likely receiving lateral rainfall drainage. This site had values of water conductivity at the upper surface of the water table lower than 3.00 dS-m, i.e., fresh water. By contrast, the more typical site B, located further away from the hills, showed values of water conductivity of about 13-18 dS-m, half the value of seawater. Rainfall accumulates during winter forming a top layer of fresh water, which is then used by plants during the following spring-summer. When fresh water is exhausted or strongly reduced, upward movement by capillarity of the salty water salinises the entire soil profile at levels dangerous even for highly salt-tolerant plants. Based on isotope data, pines mainly used the fresh water stored at the top of the water table. When fresh water supplies were depleted, the pines drew from the underlying salty water with seasonal differences between the two sites. Pine sap flow declined in the summer when surface salinity of the water table increased at site B, but remained higher and more regular at site A. In agreement with the isotope and the sap flow data, tree ring analysis showed clear differences between site A, where growth was moderately dependent on temperatures but only slightly on rainfall and site B, where rainfall was the most important factor affecting radial growth.

Citazione: Teobaldelli M , Gandolfo GP , Mencuccini M , Piussi P (2001). Water table salinity, rainfall and water use by umbrella pine (Pinus pinea L.) trees . 3° Congresso Nazionale SISEF, Viterbo, 15 – 18 Ott 2001, Contributo no. #c3.3.9