Intra-annual Course of Canopy Parameters and Phenological Patterns for a Mixed Deciduous Forest Ecosystem Along the Altitudinal Gradients Within a Dam Reservoir Landscape

Abstract

Abstract Context: Following the introduction of the dams into the river basins, altitudinal gradients of forest ecosystems experience different alternations within their reservoir landscapes, where the deciduous tree canopies display particular physiological and phenological characteristics. Therefore, monitoring already intra-annual or seasonal patterns of their physiological and phenological parameters not only supports determining current eco-physiological characteristics of these deciduous forest ecosystems but also will promote projecting prospective status of these characteristics and also will provide comparing them with those previous observations and analyses. Objectives: Within a mixed deciduous forest ecosystem of a dam reservoir landscape in Western Black Sea Region of Turkey, a dense young-mature stand composed of oriental beeches, European hornbeams, sessile oaks, and silver lindens, was chosen as the study field in order to monitor and analyse some canopy parameters and determine phenological patterns along the altitudinal gradients. Referring and correlating also to the air-soil temperature and precipitation data, intra-annual and seasonal eco-physiological characteristics of that stand tree canopies, were aimed to be determined having regard to the altitudinal gradients. Methods: From 100 m asl. to 280 m asl., 10 altitudinal gradients were defined and for each of these altitudinal gradients, the mixed deciduous stand canopy physiological characteristics were monitored and analysed by hemispherical photographing, and associated canopy parameters were acquired from those digital hemispherical photographs, which were also confirmed with the secondary LAI data from the LAI-2200C device. The Leaf Area Index (LAI), Light Transmission (LT), Canopy Openness (CO) and Gap Fraction (GF) were these canopy parameters obtained during the total 21 study field visits throughout the monitoring year (2021-2022). Results: Beginning from the leafless stage with 0.51 m2 m-2, the average LAI increased to 0.89 m2 m-2 during the budburst stage, and then gradually up to 3.60 m2 m-2 during the climax leaf period, and then to 1.38 m2 m-2 during the during the senescence period, gradually down to 0.50 m2 m-2 again during the next leafless period. On the other hand, during the same periods, the average LT (64%, 61%, 9%, 36%, 74%), CO (65%, 62%, 9%, 37%, 75%) and GF (18%, 14%, 1%, 8%, 14%) percentages followed the opposite patterns. However, any definite increasing or decreasing trend from the lowest to the highest altitudinal gradient, could not be determined for any of those canopy parameters. Furthermore, there were significant correlations between all those canopy parameters and, both the air and soil temperatures. Conclusions: Although obvious intra-annual patterns emerged for these canopy parameters following particularly that annual air-soil temperature data course, any increasing or decreasing trend was not valid for these canopy parameters from the lowest to the highest altitudinal gradient.