Plant source and soil interact to determine characteristics of dissolved organic matter leached into waterways from riparian leaf litter

Hannah M Franklin; Anthony R Carroll; Chenrong Chen; Paul Maxwell; Michele A Burford

doi:10.1016/j.scitotenv.2019.134530

Plant source and soil interact to determine characteristics of dissolved organic matter leached into waterways from riparian leaf litter

Sci Total Environ. 2020 Feb 10:703:134530. doi: 10.1016/j.scitotenv.2019.134530. Epub 2019 Oct 25.

Authors

Hannah M Franklin¹, Anthony R Carroll², Chenrong Chen³, Paul Maxwell⁴, Michele A Burford³

Affiliations

¹ Australian Rivers Institute, Griffith University, Nathan, 4111 Brisbane, Queensland, Australia. Electronic address: h.franklin@griffith.edu.au.
² Environmental Futures Research Institute, Griffith University, Southport 4222 Gold Coast, Queensland, Australia; Griffith Institute for Drug Discovery, Griffith University, Nathan, 4111 Brisbane, Queensland, Australia.
³ Australian Rivers Institute, Griffith University, Nathan, 4111 Brisbane, Queensland, Australia; School of Environment and Sciences, Griffith University, Nathan, 4111 Brisbane, Queensland, Australia.
⁴ Healthy Land and Water, 4000 Brisbane, Queensland, Australia.

PMID: 31757551
DOI: 10.1016/j.scitotenv.2019.134530

Abstract

Wetting of leaf litter accumulated in riparian zones during rainfall events provides pulses of dissolved organic matter (DOM) to rivers. Restoring riparian vegetation aims to reduce sediment and nutrient transport into rivers, however DOM from leaf litter can stimulate phytoplankton growth and interfere with water treatment processes. Improved understanding of the loads and chemical composition of DOM leached from leaf litter of different plant species, and how subsequent leaching through soils affects DOM retention or transformation, is needed to predict the outcomes of riparian revegetation. To investigate this, we simulated rapid leaching of rainfall through the leaf litter of two riparian tree species with and without subsequent leaching through soil, comparing dissolved organic carbon (DOC) and nitrogen (DON) loads, and DOM chemical composition (via spectroscopic and novel NMR-fingerprinting techniques). Plant source affected the load and composition of DOM leaching, with Eucalyptus tereticornis leaching more DOC than Casuarina cunninghamiana. Additionally, E. tereticornis DOM had a higher sugar, myo-inositol, benzoic acid, flavonoid and oxygenated aromatic content. More than 90% of leaf litter DOM was retained in the soil under simulated repeated heavy rainfall. The DOM chemistry of these species determined the total loads and changes in DOM composition leaching through soil. Less E. tereticornis DOM was retained by the soil than C. cunninghamiana DOM, with sugars, myo-inositol and amino acids being poorly retained compared to fatty acids and aromatic compounds. It also appears that DOM from E. tereticornis litter primed the soil, resulting in more DON being leached compared with bare soil. In comparison, C.cunninghamiana litter resulted in greater retention of DON, oxygenated aromatic compounds and the amino acid tryptophan. This study provides new information on how a range of DOM sources and transformations affect the DOM ultimately leached into waterways, key to developing improved models of DOM transformations in catchments.

Keywords: Dissolved organic carbon; Dissolved organic nitrogen; Humic substances; NMR-fingerprinting; Rainfall events; Riparian restoration.

MeSH terms

Carbon
Nitrogen
Plant Leaves*
Soil*
Trees

Substances

Soil
Carbon
Nitrogen