| dc.description.abstract | Mediterranean forests are water limited. While understanding that the growth and survival of these systems are strongly influenced by water availability, the interactive effects of precipitation and other edaphic and topographic factors on forest performance and the importance of these environmental abiotic factors in light of heavy human influence is less clear. The purpose of this project was to (1) assess how abiotic factors such as precipitation, elevation, bedrock and aspect affect the structure and function of Israel’s mature (> 30 years) Pinus halepensis and Pinus brutia forests, (2) determine whether the growth and performance of both species was different in response to abiotic factors and (3) assess how abiotic factors and overstory canopy coverage influence understory growth and development. Inventory data of ninety-six P. halepensis and seventy-four P. brutia stands were analyzed that were planted throughout Israel. Tree growth such as height, stem diameter, and mean basal area increment and stand-level characteristics such as stem density, basal area, and Landsat NDVI were analyzed. In addition, understory volume data such as total, pine, and oak volume, was collected and analyzed from a subset of the same stands, specifically forty-eight P. halepensis and thirty-two P. brutia stands.
Stepwise multiple linear regression models were produced. For P. halepensis, precipitation was the determining factor influencing forest performance for all models produced (40 - 92% of explained variation) with an additional positive influence of north vs. south facing aspects, while for P. brutia forests the results were more complicated, as interacting effects between the four abiotic factors were prevalent, mostly aspect × elevation for individual tree characteristics and precipitation × bedrock for stand-level ones. No conclusive explanation was found that would account for these discrepancies, but temperature limitation, or possibly management, might have important contributing effects. Understory development in both forests was positively related to precipitation, while overstory canopy coverage had a minimal effect. The conclusions of this study highlight the need to consider site-specific water based management regimes. In addition, future management decisions should account for the sensitivity to changes in water availability for both species, and temperature for P. brutia. | en |
