Effects of climate change on a subtropical montane peatland over the last two centuries: Evidence from diatom records

Abstract

Climate variability can induce rapid changes in peatland ecosystems, affecting both carbon cycling and vegetation succession. Diatoms are an important group of ubiquitous and diverse algae in peatlands. Until now, the responses of diatom communities to climate variability have rarely been explored in peatlands, especially in subtropical regions. In this study, monitoring and paleolimnological datasets were combined to decipher environmental changes of a subtropical montane peatland (central China) over the last two centuries. Seasonal monitoring data revealed that diatom communities were closely correlated with precipitation, depth to the water table, conductivity, nitrate and temperature. Sedimentary records revealed that temporal changes in diatom assemblages and geochemical elements displayed similar trends in two peat cores after the 1950s. The first gradient in diatom composition represented a shift from Pinnularia species to taxa preferring less-acidic habitats, which was closely linked to climate warming and the enrichment of inorganic elements (e.g. sodium and calcium) since the early 20th century. Meanwhile, changes in diatom communities were further related to precipitation variability, atmospheric deposition and local hydrogeomophic setting. Taken together, the succession of diatom communities was closely linked to climate-regulated availability of nutrients and moisture in this subtropical peatland over the last two centuries. In order to achieve sustainable management of these scarce peatlands, further biological monitoring and paleoecological studies are needed to improve our knowledge of peatland ecosystem evolution in response to future climate change.

Diatom‐inferred microtopography formation in peatlands

“…Electrical conductivity is a proxy for the total ionic concentration in natural waters (Rydin & Jeglum, 2013), and is often considered as the main factor responsible for diatom distribution in Sphagnum peatlands that are generally acidic and deficient in basic cations (e.g. Ca 2+ , Na + , K + and Mg 2+ ) (Chen et al, 2021; Fránková et al, 2009; Poulíčková et al, 2013). NH 4 + can be produced during microbial degradation of DOC and during grazing of bacteria by protozoa, and it is the key inorganic nutrient for diatom growth (cf.…”

“…In addition, the significant relationship between diatoms and altitude might represent potential effects of temperature (Gremmen et al, 2007). Previous studies have revealed that temperature is an important factor for the composition of moss‐inhabiting diatoms (Chen et al, 2021; Das et al, 2020; Gremmen et al, 2007). Nevertheless, the underlying relationship between diatoms and temperature is not clear.…”

“…Nevertheless, the underlying relationship between diatoms and temperature is not clear. One potential mechanism is that temperature might impose an effect on diatom distribution through mediating the availability of major cations (Chen et al, 2021; Passy, 2010). In this study, concentrations of Ca 2+ and Mg 2+ were negatively correlated with altitude ( r < −0.51, p < 0.001), probably due to weak weathering intensity in high‐elevation sites with cold climate.…”

“…Although water table was relatively stable during the growth season in the studied peatlands (Guo et al, 2017), extreme drought events probably influence diatom composition (Chen et al, 2021). It is essential to perform seasonal monitoring of diatom composition and environmental factors for establishing a robust transfer function.…”

“…Due to their dominance in algal communities, high diversity and unique microhabitat preferences (Gaiser & Rühland, 2010), diatoms have proven to be valuable indicators for hydrological alteration (e.g. drier/wetter) in peatlands (Carballeira & Pontevedra-Pombal, 2020;Chen et al, 2020Chen et al, , 2021Hargan et al, 2015;Ma et al, 2018;Poulíc ˇková et al, 2004).…”