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 ۲۰۱۵ to August ۲۰۱۶. Meteorological parameters of Temperature (T), Precipitation (P), and Wind Speed (WS) were obtained from the nearest meteorological station during ۱۹۸۶-۲۰۱۶. FAO Penman-Monteith (PM) combination equation was employed to calculate daily reference Evapotranspiration (ET۰). The nonparametric Mann–Kendall (MK) test was used to detect significant changes in yearly meteorological parameters and ET۰. Over the study period, LAI varied from zero during the LeafLess Period (LLP), when the Woody Area Index (WAI) was ۰.۸۸, to ۱.۶۵ in Full Leaf Period (FLP). LAI showed relatively strong and significant positive linear correlations with T (R۲= ۰.۷۱), Vapor Pressure Deficit (VPD) (R۲= ۰.۵۸), and ET۰ (R۲= ۰.۳۳), such that higher LAI values were measured in warmer and drier days with higher ET۰. No statistically significant trend was detected by MK test during ۱۹۸۶-۲۰۱۶ for yearly T and VPD (MK statistic, ZMK= ۰.۰۴۴ for T, and ZMK= ۰.۲۰۷ 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.

Keywords:

Evapotranspiration , Meteorological parameters , Oak trees , Zagros region.