ISSN:
1432-1939
Keywords:
Key words Nitrate
;
Nitrogen utilisation
;
Tropical woodland
;
Tropical monsoon forest
;
Xylem sap
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Nitrogen relations of natural and disturbed tropical plant communities in northern Australia (Kakadu National Park) were studied. Plant and soil N characteristics suggested that differences in N source utilisation occur at community and species level. Leaf and xylem sap N concentrations of plants in different communities were correlated with the availability of inorganic soil N (NH+ 4 and NO− 3). In general, rates of leaf NO− 3 assimilation were low. Even in communities with a higher N status, including deciduous monsoon forest, disturbed wetland, and a revegetated mine waste rock dump, levels of leaf nitrate reductase, xylem and leaf NO− 3 levels were considerably lower than those that have been reported for eutrophic communities. Although NO− 3 assimilation in escarpment and eucalypt woodlands, and wetland, was generally low, within these communities there was a suite of species that exhibited a greater capacity for NO− 3 assimilation. These “high- NO− 3 species” were mainly annuals, resprouting herbs or deciduous trees that had leaves with high N contents. Ficus, a high-NO− 3 species, was associated with soil exhibiting higher rates of net mineralisation and net nitrification. “Low-NO− 3 species” were evergreen perennials with low leaf N concentrations. A third group of plants, which assimilated NO− 3 (albeit at lower rates than the high-NO− 3 species), and had high-N leaves, were leguminous species. Acacia species, common in woodlands, had the highest leaf N contents of all woody species. Acacia species appeared to have the greatest potential to utilise the entire spectrum of available N sources. This versatility in N source utilisation may be important in relation to their high tissue N status and comparatively short life cycle. Differences in N utilisation are discussed in the context of species life strategies and mycorrhizal associations.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004420050636
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