Wet but dry: interpreting contrasting proxy evidence during a high accumulation event in Draftinge mosse (Sweden)

• Main Authors: Silva-Sanchez, Noemi, Mighall, Tim, Kylander, Malin E., Sjostrom, Jenny K., Hansson, Agda Sophia Veronica, Martinez-Cortizas, A
• Format: Conference Object
• Language: English
• Published: 2018
• Subjects: North Atlantic
• Online Access: https://pure.au.dk/portal/da/publications/wet-but-dry-interpreting-contrasting-proxy-evidence-during-a-high-accumulation-event-in-draftinge-mosse-sweden(2c976025-6c25-443d-9184-6d8af4d75a64).html

Reconstructing surface wetness in peatlands is a challenging issue that, more often than desired, gives contrasting proxy evidence, making it difficult to clearly differentiate between dry and wet periods. The differences inherent to the different methods and their intrinsic weaknesses may be behind this situation. However, other circumstances such as seasonal contrast or microtopography development could account for some of the apparent disagreement. Draftinge Mosse is a raised peat bog located in south-central Sweden close to the extensively studied “Great Bog” (Store Mosse). Here, contrasting proxy evidence for moisture conditions was found for the period between ~5600 and ~4600 cal.BP. At this time, a high peat accumulation event (HPAE, with a maximum of 294 g m-2 y-1, also found at Store Mosse by Kylander et al., 2013) was accompanied by increased carbohydrates/lipids ratio indicating less decomposed peat and pointing to wetter conditions. In contrast, in the same peat section supposed dry NPP indicators also showed a large increase in abundance, suggesting that drier conditions prevailed. To complicate the interpretation further, suggested wet NPP indicators also increase from ~5000 cal. yr BP to present (with ups and downs). The sudden boost in peat accumulation, that started coinciding with warming in the North Atlantic right after the termination of Bond Event 4, suggests that changes in microtopography might have played a role in the creation of different microhabitats (drier hummocks and wetter hollows) and this would explain the variable response in some of the proxies. Although other factors affecting the ecological behavior of the detected NPP cannot be neglected, our hypothesis is that during the HPAE, despite generally wetter conditions in the region, the surface of the peatland might have been locally isolated of the water table because of the rapid peat growth, resulting in the creation of dry microhabitats.