Interstorm Variability in the Biolability of Tree-Derived Dissolved Organic Matter (Tree-DOM) in Throughfall and Stemflow

Abstract

Dissolved organic matter (DOM) drives carbon (C) cycling in soils. Current DOM work has paid little attention to interactions between rain and plant canopies (including their epiphytes), where rainfall is enriched with tree-derived DOM (tree-DOM) prior to reaching the soil. Tree-DOM during storms reaches soils as throughfall (drip through canopy gaps and from canopy surfaces) and stemflow (rainwater drained down the trunk). This study (1) assessed the susceptibility of tree-DOM to the consumption by microbes (biolability); (2) evaluated interstorm variability in the proportion and decay kinetics of biolabile tree-DOM (tree-BDOM), and (3) determined whether the presence of arboreal epiphytes affected tree-BDOM. Tree-BDOM from Juniperus virginiana L. was determined by subjecting throughfall and stemflow samples from five storms to 14-day microbial incubations. Tree-DOM was highly biolabile, decreasing in concentration by 36-73% within 1-4 days. Tree-BDOM yield was 3-63 mg-C m −2 mm −1 rainfall, which could represent 33-47% of annual net ecosystem exchange in Georgia (USA) forests. Amount and decay kinetics of tree-BDOM were not significantly different between throughfall versus stemflow, or epiphyte-covered versus bare canopy. However, epiphyte presence reduced water yields which reduced tree-BDOM yields. Interstorm proportions, rates and yields of tree-BDOM were highly variable, but throughfall and stemflow consistently contained high tree-BDOM proportions (>30%) compared to previously-published litter and soil leachate data (10-30%). The high biolability of tree-DOM indicates that tree-BDOM likely provides C subsidies to microbial communities at the forest floor, in soils and the rhizosphere.

addition to reply to Refree #1

“…With a cumulative degradation of up to 40 % of the initial DOC concentration as well as the highest degradation rates, DOM from SF samples was most bioavailable. TF samples with BDOC up to 36 % contained DOM that seemed slightly less bioavailable This corresponded to the results of Howard et al (2018) reporting BDOC in an interquartile range of 36 %-73 % for cedar throughfall and stemflow samples. The lowest degradation rates and, thus, the most stable DOM were found in LL (8 %-18 %), comparable with results of Kalbitz et al (2003), who reported mean values of 8 % BDOC when incubating extracts from spruce and beech forest fermentation layers (Oa horizons).…”

Host Tree Identity Influences Leaf Nutrient Relations of the Epiphyte Dendrobium guamense Ames.

“…The presence of epiphytes in a tree canopy can significantly reduce the volume of throughfall and stemflow [33,34] illuminating the ability of epiphytes to intercept rainfall, throughfall, and stemflow. The orchid velamen is highly efficient in capturing nutrients within solutions that are ephemerally available on stem surfaces.…”

Precipitation Partitioning—Hydrologic Highways Between Microbial Communities of the Plant Microbiome?

“…Microbiota may rely on dissolved nutrients in net precipitation waters, having been found to consume ~90% of dissolved organic matter transported by throughfall and stemflow within 1-4 days, for example (Howard et al 2018). Finally, evaporation from wet canopy and litter surfaces exerts a significant influence over humidity dynamics throughout the plant microbiome (Pypker et al 2017;Van Stan et al 2017b).…”