Fruit characteristics, defoliation, forest floor and soil properties of sweet chestnut (Castanea sativa Mill.) forests in IIstanbul-Turkey

Abstract

The defoliation and fruit characteristics of natural Castanea sativa Mill. forests were annually monitored between 2014 and 2016 in Istanbul, Turkey. The soil and forest floor properties were also investigated and evaluated according to the stand development stages. Comparisons were made with ANOVA and Tukey HSD tests; the relationship between fruit yield and the properties of the soil and forest floor were tested with correlation analysis; and allometric regression models were developed for fruit yield with DBH (diameter at breast height) and (DBH)H-2. The total mass was 509-652 g/m(2), N mass was 7.67-9.70 g/m(2) and C mass was between 165.75 g/m(2) and 183.28 g/m(2) in the forest floor in the development stages. The soil texture was loam-clay loam, soil C concentration was between 0.3% and 1.92%, N concentration was 0.08-0.32%, the EC was very low (33-84 mu S/cm), and the pH was acidic (5 pH). The properties of the forest floor and soil were not significantly different from the development stages. The defoliation rates increased significantly every year in each development stage. The fruit yield was between 183.51 kg/ha and 298.27 kg/ha, and fruit was not detected in the smallest development stage (SDF). The fruit yields were quite low in comparison with other natural C. sativa forests. However, in each year in the study period, fruit yields were negatively correlated with mass and C and N content and positively correlated with N concentration in the H layer of the forest floor. There was not a significant difference in fruit yield over the years, and it had a low relation with DBH and (DBH)H-2 (R-2 = 0.34 and R-2 = 0.23, respectively). The fruits' characteristics significantly fluctuated over the years. As a result, low fruit yield and low relationships with properties of the forest floor and soil might be attributed to the former coppice management and possible health problems.