Epsilon Archive for Student Projects

Abstract

The development of secondary forest on abandoned agricultural lands has proven significant to land cover changes, especially in marginal areas across Europe. It is therefore important to quantify secondary forest succession in order to sustainably manage forest and agricultural resources, and also for modelling climate change. This study aimed to access secondary forest succession on abandoned agricultural land and its carbon stock compared to a nearby agricultural field and old-growth forest. The study was conducted at three sites (secondary forest, old-growth forest and an agricultural field) in Göttingen, Germany, where field inventory of the vegetation was carried out in the secondary forest alone. The top litter and soil were also sampled to a depth of 30cm to estimate the soil carbon stocks of all three land uses. To estimate the total carbon of the secondary forest, the aboveground biomass (ABG) was estimated from tree volume and wood density, and the estimated values converted to C stock estimates (C = AGB * 0.47).
A total of 304 trees belonging to 11 tree species were identified in the secondary forest, with Populus tremula and Fraxinus excelsior been the most abundant species. The total basal area per ha and volume per ha were 20 (m2/ha) and 129 (m3/ha), respectively. From the high proportion of pioneer species and relatively small average stand DBH (15.8 cm) of the secondary forest, an intermediate successional stage can be implied. Cornus sanguinea was found to be the most frequent understorey vegetation. A ring width analysis of the understorey vegetation showed an average decline in growth rate of the understorey trees, which may be a result of competition for available resources. The largest total carbon stock for this study was recorded in the old-growth forest, followed by the secondary forest and the agricultural field. However, the largest soil carbon stock was recorded in the secondary forest. This study has shown the potential of abandoned agricultural land in supporting tree diversity as well as contributing to the global carbon budget, alongside other ecosystem services. However, the reported soil carbon stocks for the three land uses may have been overestimated, due to the low sampling density. It is therefore recommended that future studies on the study sites increase the sampling density.