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Peatlands are one of the most significant carbon reservoirs in the terrestrial ecosystem. Understanding past peatland carbon accumulation processes and their responses to varying external and internal forcing factors would help reveal the general development patterns of peatland ecosystems and provide useful insights into projecting the fate of carbon reservoirs into the future. In this paper, the basal ages of 17 peat cores were used to explore the lateral expansion processes of the Laolike peatland, northeast China. Two cores were selected to calculate carbon accumulation rates (CAR) and reconstruct moisture/precipitation records based on δ13C and grain size analyses. The basal ages show that the peatland was initiated at 12.1 cal kyr BP, then laterally expanded with its fastest rate occurring during the early Holocene, and reached its largest area around 6 cal kyr BP. The time-weighted mean CAR in the Laolike peatland ranged from 31.1 to 52.9 g C/m2/yr (with an average of 42 g C/m2/yr) during the Holocene. The peatland experienced a high CAR of 52.5 g C/m2/yr from 11.7 to 5 cal kyr BP, followed by a low CAR of 35.1 g C/m2/yr after 5 cal kyr BP. Both lateral expansion and vertical accretion are consistent with the summer insolation, climate seasonality, and the strength of the East Asia summer monsoon (EASM) over multi-millennium timescales, where the CAR correlated well with δ13C and grain size, implying moisture/precipitation might be the primary factors controlling carbon accumulation over millennium timescales. Local conditions, such as topography and hydrology, also played an important role in the process of peatland initiation and lateral expansion, as well as the discrepant CAR within the peatland. This study reveals the roles of climate and local conditions in peatland initiation, expansion, and CAR during the Holocene. In addition, we provide a window for a better understanding of the driving factors of peatland development in the temperate zones of the Northern Hemisphere. • Climate conditions are the primary control on the lateral expansion and vertical accretion of Laolike peatland over multi-millennium timescales. • Moisture/precipitation affects carbon accumulation of Laolike peatland over millennium timescales. • Local conditions play an important role in the lateral expansion and the internal differences of carbon accumulation rate. [ABSTRACT FROM AUTHOR]

Testate amoebae (TA) are a common and diverse group of protists and are especially abundant in peatlands. The structure of peatland TA communities is well correlated to surface moisture and water table depth (WTD). For that reason, TA are widely used as proxy indicators in ecological and palaeoecological studies. Peatlands are abundant across Asia, but the diversity and ecology of the TA that inhabit these systems are poorly documented. It is therefore unclear whether TA can be used as palaeohydrological indicators in the manner in which they commonly are in Europe and North-America. There is particular uncertainty as to the efficacy of this approach in the lower latitudes. We compiled existing and new data on testate amoebae from 1124 Sphagnum -dominated samples from 42 individual peatlands covering broad latitudinal (25°–66° N) and longitudinal (68°–129° E) ranges. Using a consensus taxonomic framework, we built a checklist of TA and developed TA-based hydrological transfer functions for Asian peatlands. The results showed that three models, weighted averaging (WA), weighted average partial least squares (WA-PLS), and maximum likelihood (ML), predicted similar WTD values for full samples, while the modern analogue technique (MAT) produced the strongest (R2 boot = 0.58) relationship between observed and estimated water-table depths (WTDs). Removing outlier samples improved the R2 values of observed vs. estimated WTDs, with ML then demonstrating the strongest predictive power (R2 boot = 0.68, RMSEP boot = 8.98 cm). The predictive capability of the developed WTD transfer function is comparable to equivalent models for Europe and North America and thus can be used for palaeohydrological reconstructions for boreal to subtropical peatlands in Asia. • A testate amoebae taxonomic checklist was compiled from Asian peatlands. • We developed continental scale testate amoeba-based hydrological transfer functions. • The water-table depth transfer functions can be used for paleohydrological reconstructions. [ABSTRACT FROM AUTHOR]