Application of the Ancient Forest Concept to Potential Natural Vegetation Mapping in Flanders, A Strongly Altered Landscape in Northern Belgium

Abstract

Construction of potential natural vegetation (PNV) poses particular challenges in landscapes heavily altered by human activity and must be based on transparent, repeatable methods. We integrated the concept of ancient forest (AF) and ancient forest species (AFS) into a four-step procedure of PNV mapping: 1) classification of forest vegetation relevés; 2) selection of those vegetation types that can serve as PNV units, based on AF and AFS; 3) merging of selected vegetation types into five PNV units that can be predicted from a digital morphogenetic soil map; 4) mapping of three additional PNV units based on additional environmental data. The second step, concerning the selection of reference forest vegetation, is of particular interest for PNV construction in Flanders (northern Belgium), where forest Folia Geobot cover has been subject to temporal disruption and spatial fragmentation. Among the variety of extant forest recovery states, we chose as PNV units those vegetation types for which a high proportion of relevés had been located in AF and that contained many AFS. As the frequency of AFS depends on site conditions, we only compared and selected vegetation types that are found on similar sites according to average Ellenberg indicator values. While succession is irrelevant for the definition of PNV, colonization rates of AFS can be used to estimate the time required for PNV to be restored in a site.

Distribution of Natural and Planted Forests in the Yanhe River Catchment: Have We Planted Trees on the Right Sites?

“…The concept of Potential Natural Vegetation (PNV), introduced by Tüxen [25], is defined as vegetation that would ultimately develop under a dominant set of site conditions if human interference was removed [26]. PNV units can be derived from existing actual vegetation and its relationships with site conditions [27].…”

Diverging effects of two contrasting tree species on soil and herb layer development in a chronosequence of post-agricultural forest

“…Poplars and oaks, being the most frequently used trees in afforestations within the study region, were selected because of their contrasting ecology. Since many ancient forest species are acid intolerant and specialised in light limited conditions De Keersmaeker et al, 2012) neither homogenous oak and poplar stands may be ideal for understory restoration on silty soils.…”

“…For this purpose we selected a chronosequence (space for time substitution) of stands with two frequently used tree species with contrasting characteristics on well drained silty soils which are vulnerable for acidification (Baeten et al, 2009a;De Schrijver et al, 2011a;Van Calster et al, 2007). This soil type potentially harbours a high number of ancient forest species, but forest cover has been strongly reduced on these sites in Flanders (De Keersmaeker et al, 2012). This makes them of focal interest for restoration purposes.…”

Dark Ages woodland recovery and the expansion of beech: a study of land use changes and related woodland dynamics during the Roman to Medieval transition period in northern Belgium

“…It is situated on a small and low coversand ridge, at c. 5 m above mean sea level, with dry to wet sandy and loamy sand soils, and surrounded by lower-lying wet to very wet sandy and loamy sand soils. The potential natural vegetation in the area is alder carr (Alnion glutinosae) on waterlogged soil, beech-dominated (Fagion sylvaticae) or oak-hornbeam forest (Carpinion betuli) on dryer soils with high silt content, and English and sessile oak forest (Quercion robori-petraeaea) on sandy soils (Bohn et al, 2003;De Keersmaeker et al, 2013).…”