Past Disturbance–Present Diversity: How the Coexistence of Four Different Forest Communities within One Patch of a Homogeneous Geological Substrate Is Possible

Abstract

Understanding the relationship between disturbance and forest community dynamics is a key factor in sustainable forest management and conservation planning. The study aimed to determine the main factors driving unusual differentiation of forest vegetation into four communities, all coexisting on the same geological substrate. The fieldwork, conducted on the fluvioglacial sand area in Central Poland, consisted of vegetation sampling, together with soil identification and sampling, up to depths of 150 cm. Additional soil parameters were measured in the laboratory. A Geographical Information System was applied to assess variables related to topography and forest continuity. Vegetation was classified and forest communities identified. Canonical Correspondence Analysis indicated significant effects of organic horizon thickness, forest continuity, soil disturbance and soil organic matter content on vegetation composition. We found that the coexistence of four forest communities, including two Natura 2000 habitats, a Cladonia-Scots pine forest and an acidophilous oak forest (codes–91T0 and 9190 respectively), resulted from former agricultural use of the land followed by secondary succession. The lowest soil-disturbance level was observed within late-successional acidophilous oak forest patches. Nearly complete soil erosion was found within the early-successional Cladonia-Scots pine forest. We propose that both protected habitat types may belong to the same successional sere, and discuss the possibility of replacement of the early-and late-successional forest habitat types in the context of sustainable forest management and conservation.