Responses of a shallow temperate lake ecosystem to major late-Holocene terrestrial vegetation shifts

Abstract

Major terrestrial vegetation shifts (MTVSs) resulting from either human activities or natural processes can exert substantial pressure on lakes mainly through impacts on catchment biogeochemical cycles and groundwater circulation. To better understand the links between terrestrial vegetation dynamics and lake ecosystem structure and functions over long temporal scales, in this study, we reconstructed the responses of shallow Lake Spore (N Poland) to major late-Holocene vegetation shifts. We combined newly acquired data from pollen and spores, Cladocera, TOC/N, δ13C, and δ15N analyses of bulk organic matter with the already published results from sediment dating and analyses of several biotic and geochemical proxies. Statistical analysis of the abundance data for all the major terrestrial pollen taxa and reconstruction of vegetation openness derived from the REVEALS model indicated five MTVSs, each followed by a change in the lake environment. Changes in Lake Spore trophic status at MTVS1 (~2.82 kyr BP) and MTVS2 (~2.17 kyr BP) were attributed to the reorganization of the catchment’s nutrient cycling associated with a decline (MTVS1) and subsequent regeneration (MTVS2) of deciduous tree stands in the area. A distinct drop in the CaCO3 content of the lake sediments that started at MTVS4 (~0.57 kyr BP) likely occurred due to the substantial depletion of the water calcium pool following an abrupt transition from a tree-dominated to an herb-dominated landscape. Our record also suggested slight lake acidification following a spread of Pinus sylvestris at MTVS1 (~2.82 kyr BP) and MTVS3 (~1.10 kyr BP) and a lake level rise concurrent with the sharp increase in landscape openness at MTVS4 (~0.57 kyr BP).