Variations in Leaf Area Index of Quercus brantii Trees in Response to Changing Climate

We aimed to find the meteorological parameters that affect variations in Leaf Area Index (LAI) of Persian oak (Quercus brantii var. persica) trees in the Zagros region of western Iran. Canopy developmental stage for five individual trees using a fish eye camera was monitored from August 2015 to August 2016. Meteorological parameters of Temperature (T), Precipitation (P), and Wind Speed (WS) were obtained from the nearest meteorological station during 1986-2016. FAO Penman-Monteith (PM) combination equation was employed to calculate daily reference Evapotranspiration (ET0). The nonparametric Mann–Kendall (MK) test was used to detect significant changes in yearly meteorological parameters and ET0. Over the study period, LAI varied from zero during the LeafLess Period (LLP), when the Woody Area Index (WAI) was 0.88, to 1.65 in Full Leaf Period (FLP). LAI showed relatively strong and significant positive linear correlations with T (R2= 0.71), Vapor Pressure Deficit (VPD) (R2= 0.58), and ET0 (R2= 0.33), such that higher LAI values were measured in warmer and drier days with higher ET0. No statistically significant trend was detected by MK test during 1986-2016 for yearly T and VPD (MK statistic, ZMK= 0.044 for T, and ZMK= 0.207 for VPD). Significant relationship between leaf area index of oak trees and temperature in the Zagros region can partially confirm the connection between declining oak trees and rising temperature.