Tillandsia Usneoides (L.) L. (Spanish Moss) Water Storage and Leachate Characteristics From Two Maritime Oak Forest Settings

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Along subtropical and tropical coastlines, Tillandsia usneoides L. (Spanish moss) can heavily cover tree crowns, altering the volume, timing and chemical composition of rainwater reaching soils as throughfall. It is well-established that throughfall amount, dissolved ion and dissolved organic matter (DOM) enrichment, as well as the chemical character of DOM, can influence a host of ecological processes – e.g. litter decomposition and fine root patterns. However, no study known to the authors has holistically examined the water storage capacity, dissolved ions and DOM derived from T. usneoides. This study examined 60 T. usneoides samples from two maritime live oak (Quercus virginiana Mill.) forest settings for water absorbency, maximum water storage capacity, dissolved solutes (Na+, NH4+, K+, Mg2+, Ca2+, F−, Cl−, NO3−, PO43−, SO42−, dissolved organic carbon, total dissolved nitrogen) and DOM optical properties using ultraviolet-visible and fluorescence spectrophotometry. Thirty samples were collected from each study site: downtown Savannah (SAV) and St. Catherine's Island (SCI), GA, USA. Results show that T. usneoidescoverage can increase canopy water storage more markedly (up to 3 mm) than most other epiphyte communities, tree leaf forms or bark structures previously studied. Ion wash off/leaching was greater for N species from SAV samples; yet, base cation macronutrients (Mg2+, Ca2+) and sea salts (Na+, Cl−) were more enriched from SCI samples. Spectrophotometry revealed that T. usneoides leachates contained DOM with low-specific UV absorbance at 254 nm per unit carbon (SUVA254) and high percentage of protein-like fluorescent material compared with literature values for other throughfall and vegetation leachates. In other natural waters, these optical characteristics indicate highly biolabile DOM, suggesting that T. usneoides DOM may also be highly biolabile (i.e. highly relevant to soil microbial functions, like mineralization). Cluster analysis linked fluorescent DOM (FDOM) to ion concentrations of primarily anthropogenic source (F−, SO42−). Correlation analyses including both sites' data indicated that log-transformed FDOM intensities indirectly relate (p < 0.01, r = −0.5) – and enrichment of major sea salt ions directly relate (Na+: p < 0.000001, r = 0.83; Cl−: p < 0.000001, r = 0.80) – to T. usneoides maximum water absorbency.