Record ID No. |
1925 |
Author(s) |
Kahmen, A; Wanek, W; Buchmann, N. , 2008 |
Affiliation |
Kahmen A, Univ Calif Berkeley, Dept Integrat Biol, Ctr Stable Isotope Biogeochem, Berkeley,CA 94720 USA |
Title |
Foliar delta N-15 values characterize soil N cycling and reflect nitrate or ammonium preference of plants along a temperate grassland gradient |
Source. Vol.(no):Page |
Oecologia, 156(4): 861-870 |
Categories |
Mycorrhiza General |
Subjects |
Biochemistry |
Sub-subjects |
Miscellaneous |
Country |
USA, North America |
Abstracts |
The natural abundance of stable N-15 isotopes in soils and plants is potentially a simple tool to assess ecosystem N dynamics. Several open questions remain, however, in particular regarding the mechanisms driving the variability of foliar delta N-15 values of non-N-2 fixing plants within and across ecosystems. The goal of the work presented here was therefore to: ( 1) characterize the relationship between soil net mineralization and variability of foliar Delta delta N-15 (delta(15)Nleaf - delta(15) Nsoil) values from 20 different plant species within and across 18 grassland sites; (2) to determine in situ if a plant's preference for NO3- - or NH4+ uptake explains variability in foliar Delta delta N-15 among different plant species within an ecosystem; and (3) test if variability in foliar Delta delta N-15 among species or functional group is consistent across 18 grassland sites. Delta delta N-15 values of the 20 different plant species were positively related to soil net mineralization rates across the 18 sites. We found that within a site, foliar Dd15N values increased with the species' NO3- to NH4+ uptake ratios. Interestingly, the slope of this relationship differed in direction from previously published studies. Finally, the variability in foliar Delta delta N-15 values among species was not consistent across 18 grassland sites but was significantly influenced by N mineralization rates and the abundance of a particular species in a site. Our findings improve the mechanistic understanding of the commonly observed variability in foliar Delta delta N-15 among different plant species. In particular we were able to show that within a site, foliar delta N-15 values nicely reflect a plant's N source but that the direction of the relationship between NO3- to NH4+ uptake and foliar Delta delta N-15 values is not universal. Using a large set of data, our study highlights that foliar Delta delta N-15 values are valuable tools to assess plant N uptake patterns and to characterize the soil N cycle across different ecosystems. |