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Waterlogging and fire impacts on nitrogen availability and utilization in a subtropical wet heathland (wallum)
Author(s) -
SCHMIDT S.,
STEWART G.R.
Publication year - 1997
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1997.d01-20.x
Subject(s) - waterlogging (archaeology) , subtropics , environmental science , nitrogen , agronomy , tropical and subtropical moist broadleaf forests , agroforestry , ecology , biology , chemistry , wetland , organic chemistry
Protein, amino acids and ammonium were the main forms of soluble soil nitrogen in the soil solution of a subtropical heathland (wallum). After fire, soil ammonium and nitrate increased 90‐ and 60‐fold, respectively. Despite this increase in nitrate availability after fire, wallum species exhibited uniformly low nitrate reductase activities and low leaf and xylem nitrate. During waterlogging soil amino acids increased, particularly γ‐aminobutyric acid (GABA) which accounted for over 50% of amino nitrogen. Non‐mycorrhizal wallum species were significantly ( P < 0.05) 15 N‐enriched (0.3–4.3‰) compared to species with mycorrhizal associations (ericoid‐type, ecto‐, va‐mycorrhizal) which were strongly depleted in 15 N (‐6.3 to ‐1.8‰). Lignotubers and roots had δ 15 N signatures similar to that of the leaves of respective species. The exceptions were fine roots of ecto‐, ecto/va‐, and ericoid type mycorrhizal species which were enriched in 15 N (0.1–2.4‰). The 5 15 N signatures of δ 15 N total soil N and δ 15 N soil NH4+ were in the range 3.7–4.5‰, whereas δ 15 N soil NO3− was significantly ( P < 0.05) more enriched in 15 N (9.2–9.8‰). It is proposed that there is discrimination against 15 N during transfer of nitrogen from fungal to plant partner. Roots of selected species incorporated nitrogen sources in the order of preference: ammonium > glycine > nitrate. The exception were proteoid roots of Hakea (Proteaceae) which incorporated equal amounts of glycine and ammonium.