Co-Authors:
Calev, A., Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel, Judean Mountains Forest Region, KKL, Givat Yeshiayah, Israel, Department of Natural Resources, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet-Dagan, Israel
Zoref, C., Judean Mountains Forest Region, KKL, Givat Yeshiayah, Israel
Tzukerman, M., Judean Mountains Forest Region, KKL, Givat Yeshiayah, Israel
Moshe, Y., Department of Natural Resources, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet-Dagan, Israel
Zangy, E., Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel, Department of Natural Resources, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet-Dagan, Israel
Osem, Y., Department of Natural Resources, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet-Dagan, Israel
Abstract:
Pinus halepensis plantations are widespread throughout semiarid–subhumid landscapes of the Mediterranean. Recently, drought-induced decline has often been reported raising concerns with regard to the future of these man-made ecosystems. The study was set out to investigate thinning as a means to alleviate water stress and improve performance of mature P. halepensis plantations experiencing prolonged drought. The study was conducted in a 40-year-old P. halepensis forest in the Jerusalem Mountains of Israel (rainfall: 550 mm year−1). Declining stands (stand basal area increment, BAIstand ≈ −3 % year−1) were treated by thinning: (1) intense thinning—tree density, BAstand, and leaf area index (LAI) reduced by 81, 68, and 59 %, respectively; (2) moderate—56, 48, and 26 %, respectively; (3) control (~560 tree ha−1). Plots of 70 × 70 m were used in four replicates. Individual tree- to stand-level variables were monitored during 4 years through stem and leaf area metrics alongside with predawn shoot water potential (ψPD) and tree mortality. Thinning ameliorated drought stress, reduced mortality, and improved individual tree growth (ψPD = −1.7, −1.8, and −2.0 MPa; mortality = 0.2, 2, and 5 % year−1; BAItree = 3.4, 2.0, and 1.4 % year−1 in intense, moderate, and control treatments, respectively). Thinning effects became more pronounced with time. LAI and individual tree leaf area (LAtree) fluctuated with association to annual rainfall. Higher LAtree caused by thinning reflected a “selection effect” while increased leaf area efficiency (BAI per unit LAtree) was attributed to a “release effect” of thinning. © 2016, Springer-Verlag Berlin Heidelberg.
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