AIMS Great Plains approach3 Ash-free Dry Mass (AFDM)

This study was conducted in the South Fork of King’s Creek at Konza Prairie Biological Station, one of the most well-studied prairie streams in the world. At the USGS gage located on the mainstem (06879560; est. 1979), Kings Creek is a 5th order intermittent stream draining 1059-ha of tallgrass prairie in the Kansas Flint Hills.
This synoptic survey was designed in support of the sampling goals of the Aquatic Intermittency effects on Microbiomes in Streams (AIMS) Project. During June, July, and August 2021, a field team co-collected datasets characterizing the hydrology and biogeochemistry across 50 locations within a sub-drainage of the South Fork of Kings’ Creek. The 50 sites were selected to balance multiple competing priorities: (i) strategically targeting existing monitoring infrastructure with long-term data (n=14); (ii) including sites near several known springs and tributary junctions (n=9); and (iii) including a range of drainage area and topographic wetness index (TWI) values (n=27), both of which have been correlated with flow permanence elsewhere. Briefly, the sites selected based on drainage area and TWI were chosen by binning drainage area into 10 bins and then binning TWI into quintiles within each drainage area bin (Supplemental Info 1). We then randomly selected a point in each bin after accounting for points selected based on existing infrastructure, springs, and tributaries;, and enforcing a minimum spacing of 100 m between locations. We then made minor adjustments to points to account for field conditions, for instance adjusting locations with respect to a road crossing. For a detailed description of the site selection process, please see (Swenson et al., 2023)
This data comprises the ash free dry mass (AFDM) of four sample type namely water, biofilm, leaf litter and sediment. AFDM of water and biofilm was measured by filtering (42.5 mm Whatman GF/F filter) a known volume of each sample, then the dry mass of the samples was determined by weighing the filters before (wet mass), and after drying at 70ºC for 48 hours. The dried filters were then combusted at 500ºC for 2 hours in a muffle furnace and AFDM was calculated as the ratio of the organic matter combusted to the dry mass of each sample. As for the other sample types, the wet mass of subsamples of leaf litter or sediment were recorded, and the subsamples dried at 70 °C for 48 h and re-weighed. Dry subsamples were combusted at 500 °C for 2 h and re-weighed. AFDM was determined in the same manner as for water and biofilm.