Modern pollen-vegetation relationships along a steep temperature gradient in the Tropical Andes of Ecuador

The characterization of modern pollen rain assemblages along environmental gradients is an essential prerequisite for reliable interpretations of fossil pollen records. In this study, we identify pollen-vegetation relationships using modern pollen rain assemblages in moss polsters (n = 13) and lake sediment surface samples (n = 11) along a steep temperature gradient of 7°C (3100–4200 m above sea level) on the western Andean Cordillera, Ecuador. The pollen rain is correlated to vascular plant abundance data recorded in vegetation relevées (n = 13). Results show that pollen spectra from both moss polsters and sediment surface samples reflect changes in species composition along the temperature gradient, despite overrepresentation of upper montane forest taxa in the latter. Estimated pollen transport distance for a lake (Laguna Llaviucu) situated in a steep upper montane forest valley is 1–2 km, while a lake (Laguna Pallcacocha) in the páramo captures pollen input from a distance of up to 10–40 km. Weinmannia spp., Podocarpus spp., and Hedyosmum sp. are indicators of local upper montane forest vegetation, while Phlegmariurus spp. and Plantago spp. are indicators for local páramo vegetation.

Post-fire dispersal characteristics of charcoal particles in the Daxing'an Mountains of north-east China and their implications for reconstructing past fire activities

A wildfire with many ignition points took place in the Daxing’an Mountains of north-east China in June 2010. After the fire, moss polsters and particle traps were collected from burnt and unburnt areas a few kilometres away from four ignition points. Charcoal extracted from the samples was divided into macroscopic charcoal >125 μm and microscopic charcoal <125 μm. Our results showed that the average amount of charcoal deposited in the burnt areas was statistically greater than the amount deposited in unburnt areas. The microscopic charcoal concentration inside the burnt areas rose as the size of the burnt area increased. However, the sampling points within the largest burnt area did not have the highest macroscopic charcoal concentration. We found that only limited amounts of charcoal were transported over a long distance and that the primary charcoal produced during or shortly after a fire event was much more abundant than the secondary charcoal produced during the non-fire period. This suggested that primary charcoal is the dominant signal in charcoal records, and that the charcoal Z-score values inside the burnt areas were clearly higher than the surroundings. Our observations indicate that multiple-size charcoal records may be a robust tool for reconstructing fire histories.