Peatlands are remarkable for their specific biodiversity, crucial role in carbon cycling and climate change. Their deposits preserve organism remains that can be used to reconstruct long-term ecosystem and environmental changes as well as human impact in the prehistorical and historical past. This study presents a new multi-proxy reconstruction of the peatland and vegetation development investigating climate dynamics and human impact at the border between mixed and boreal forests in the Valdai Uplands (the East European Plain, Russia) during most of the Holocene. We performed plant macrofossil, pollen, testate amoeba, Cladocera, diatom, peat humification, loss on ignition, carbon and nitrogen content, δ¹³C and δ¹⁵N analyses supported by radiocarbon dating of the peat deposits from the Krivetskiy Mokh mire. The results of the study indicate that the wetland ecosystem underwent a classic hydroserial succession from a lake (8300 BC–900 BC) terrestrialized through a fen (900 BC–630 AD) to an ombrotrophic bog (630 AD–until present) and responded to climate changes documented over the Holocene. Each stage was associated with clear changes in local diversity of organisms responding mostly to autogenic successional changes during the lake stage and to allogenic factors at the fen-bog stage. The latter can be related to increased human impact and greater sensitivity of peatland ecosystems to external, especially climatic, drivers as compared to lakes.

The paper describes a dataset, comprising 236 surface moss samples and 143 testate amoeba taxa. The samples were collected in 11 Sphagnum-dominated bogs during frost-free seasons of 2004, 2007, 2009, 2017, and 2022. For the whole dataset, the sampling effort was sufficient in terms of observed species richness (143 species in total), though a regional species pool is deemed to be discovered incompletely (143 species is its lower 95 % confidence limit using Chao’s estimator). The local community composition demonstrated high heterogeneity in a reduced ordination space. It supports the opinion that the high versatility of bog ecosystems should be taken into account during ecological studies.

Testate amoebae are widely used in palaeoecological studies as indicators (proxies) of environmental conditions in mires and freshwater ecosystems. The goal of this work was to identify patterns in the dynamics of the species composition of testate amoeba assemblages during a “waterbody–mire” succession. This study was performed using multiproxy analysis of the deposits in Mochulya Bog, Kaluga oblast, European Russia. To explain changes in the species composition of testate amoebae, we used data on the plant macrofossil composition, peat humification, and the loss on ignition, together with the results of radiocarbon dating and pollen analysis. The deposit was formed by the sediments of the waterbody, with rich fen and poor fen. The age at the base of the deposits was 4100 cal. yr. BP. Changes in the species composition of testate amoeba assemblages were largely determined by local vegetation, especially Sphagnum mosses, which significantly transform the environment. The transformation of the waterbody into a rich fen may have most likely occurred as a result of climatic (allogeneic) factors: short-term drying and wildfires that might have led to the overgrowth of the shore. The transformation of the rich fen to a poor fen could have been related to the effects of both autogenic (accumulation of the deposits) and allogeneic factors (decrease in human activity in the adjacent area).