Forest Heterogeneity
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Increase heterogeneity of forest structure
Data collection in progress
Iron Curtain to Green Belt
Bulgaria
Problem: The forestry sector has historically focused on planting non-native coniferous tree species in highly homogeneous plantations. These plantations have a lack of deciduous trees and multiple species mixtures, which also leads to a lack of vegetation in the forest floor and shrub layers. This leads to a lack of diversity of habitats and environmental conditions that do not support the high levels of biodiversity which would be present in natural forests.
Action: The project is opening the canopy of pine plantations to increase the amount of light that reaches the forest floor. This will allow the understorey, particularly native deciduous species, to grow, and will eventually increase the heterogeneity and structural complexity of the forest towards that of a natural forest. In time, these stands will transform from non-native plantations back to native oak forests.
Indicator: The change in forest heterogeneity over time will mark the structural changes of forest stands as they transform from pine plantations to forests that also contain mixed, native deciduous species.
An example of a monoculture pine plantation. Notice a lack of mixed species and no understory. Photo: Veronika Ferdinandova
An example of a mixed-species forest, with natural regeneration occurring in the understory and broadleaved trees of different ages growing under the canopy. Photo: Veronika Ferdinandova
Methods
Forty-seven forest stands of coniferous plantations in the age groups of 0-20, 21-40 and 41-60 years were selected in 2023 to create a chronosequence study design. In each stand, 16 circular plots with a 5 m radius were established in a grid pattern, each 30 m apart, and were used to measure forest structural and biological elements within the radius. These elements include the size of gaps and the percentage of their overlap with the 5 m radius plot, percentage of canopy closure, percentage of the grass cover within the plot, number and species of tree and shrub species within three height categories (<30, 31-80 and 80-130 cm), volume of standing and lying dead wood, and tree basal area per tree species. The project will establish plots in old-growth forests within the same landscape, where the same variables will be collected to understand the desired target state of these individual elements, as a reference.
Surveys were carried out between July and October in the first year of the project (2023) before openings in the canopy were made, and this baseline data will be used to create a heterogeneity index, enabling the project to assess the developing structural heterogeneity of each stand over time. The project aims to reassess the heterogeneity index in the future, once the forest stands have a chance to develop, but that will take many years. In the meantime, the project will compare the 2023 assessment to the heterogeneity index of old-growth stands, which provide target values, to help them understand how far their baseline measurements are from ideal levels of structural complexity found in old-growth native forests.
Results
This page will be updated once the baseline data is available to share.
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