Altitudinal variation of leaf area index of Corylus avellana L. Along mountainous agricultural landscapes in Ordu, Turkey

Abstract

Monitoring the phenology and ecophysiology of Corylus avellana L. is significant in respect to its growth, health, productivity and overall agricultural landscape ecology. Leaf area index (LAI) is a multi-purpose vegetation parameter that indicates one-sided area of the leaves of the canopy over the projected area of that canopy. LAI can be used as an effective indicator parameter particularly for deciduous trees and shrubs such as C. avellana. In this study, the altitudinal alteration of C. avellana LAI was investigated along the mountainous landscapes of Ordu, Turkey. The agricultural landscapes are within the Ordu province of Eastern Black Sea Region of Turkey. The agricultural landscapes from Perşembe and Gölköy sub-provinces constitute two different transects from each altitudinal gradients of mean 335 and 1,135 m a.s.l., respectively. The lapse rate between the altitudinal gradients was estimated as 0.5°C 100 m-1. A hemispherical photographing technique was used to determine the LAI. Hemispherical photographs were taken with a fisheye objective mounted on a digital SLR camera in mid-May 2017. They were analyzed with an image processing software. From each transect, 10 hemispherical photographs were taken being 20 hemispherical photographs from each altitudinal gradient. In total, 40 hemispherical photographs were taken from the agricultural landscapes covered by C. avellana. Based on the lapse rate of 0.5°C 100 m-1, the mean temperature ranged between 15.0 and 10.9°C along the 800 m altitudinal difference. The onset of the leaves at the lower gradients was earlier than that at the higher altitudes where the foliation process was delayed temporal. Therefore, the LAI changed between 0.80 and 2.86 m2 m-2 being higher within the lower altitudinal gradient compared to the higher altitudinal gradient. There was no major diversity among the transects of the altitudinal gradients. Gölköy sub-province where the higher altitudinal gradient of this study exists, is relatively the spatial upper limits of the C. avellana orchards in the region. Hence, the forested landscapes accompany agricultural landscapes within those limits. In order to account for the possible climate change in the region, the ecophysiology and shifting phenology of the agricultural areas should be evaluated at the landscape scale. Consequently, the sustainable management objectives for these agricultural land uses can be achieved under the potential climate change phenomenon. © 2019 Elsevier B.V., All rights reserved.