TY - JOUR
T1 - Topographical influences on foliar nitrogen concentration and stable isotope composition in a Mediterranean-climate catchment
AU - Xu, Xiang
AU - Guan, Huade
AU - Skrzypek, Grzegorz
AU - Williams, David G.
N1 - Funding Information:
Data analysis of this study was funded by the National Natural Science Foundation of China (41807148), the Open Foundation of MOE Key Laboratory of Western China's Environmental System, Lanzhou University and the Fundamental Research Funds for the Central Universities (lzujbky-2019-kb01). The field experiments were funded by National Centre for Groundwater Research and Training (Australia SR08000001), China Scholarship Council, and a Future Fellowship from the Australian Research Council (FT110100352). The authors thank Hailong Wang for his assistance of fieldwork, and Langdon Badger's permission of the field site. Ashleigh Pitman from Willunga Environment Centre and Paul Green from Flinders University kindly help the identification of tree species.
Funding Information:
National Natural Science Foundation of China , Grant/Award Number: 41807148 ;
Publisher Copyright:
© 2022
PY - 2022/5
Y1 - 2022/5
N2 - Nitrogen (N) oligotrophication is increasing globally across terrestrial ecosystems and manifested in decreasing nitrogen concentration ([N]) and changes in the stable nitrogen isotope composition (δ15N) of foliage. Heterogeneity in plant nitrogen sources makes it challenging to detect the effects of N oligotrophication even at a small catchment scale with complex topography. Understanding the spatial and temporal variation of foliar δ15N and [N] at such a scale is required to develop useful ecological indicators and monitoring methods to support catchment management with a potential N oligotrophication problem. This study examined spatial and high-resolution temporal variation of foliar δ15N and [N] and their influencing factors in ten trees grouped by Eucalyptus and Acacia in a native forest vegetation catchment. Over 16 sampling campaigns within a 12-month period, foliar δ15N and [N] increased in Eucalyptus but were constant in the N2-fixing Acacia. The higher foliar [N] and δ15N in Acacia reflected its N2-fixation ability. Topographic flow accumulation area (NDVI) explained 46% (77%) of spatial variation in dry-season Eucalyptus foliar δ15N ([N]). For Eucalyptus, foliar δ15N was higher at the downslope than the upslope locations, but no hillslope location differences were observed for foliar [N]. These results suggest that in the non-N2-fixing Eucalyptus, seasonal water stress related nitrogen availability may be reflected in foliar δ15N rather than foliar [N]. As such, foliar δ15N of non-N2-fixing plants potentially is a more sensitive indicator of seasonal or topographical N availability than foliar [N].
AB - Nitrogen (N) oligotrophication is increasing globally across terrestrial ecosystems and manifested in decreasing nitrogen concentration ([N]) and changes in the stable nitrogen isotope composition (δ15N) of foliage. Heterogeneity in plant nitrogen sources makes it challenging to detect the effects of N oligotrophication even at a small catchment scale with complex topography. Understanding the spatial and temporal variation of foliar δ15N and [N] at such a scale is required to develop useful ecological indicators and monitoring methods to support catchment management with a potential N oligotrophication problem. This study examined spatial and high-resolution temporal variation of foliar δ15N and [N] and their influencing factors in ten trees grouped by Eucalyptus and Acacia in a native forest vegetation catchment. Over 16 sampling campaigns within a 12-month period, foliar δ15N and [N] increased in Eucalyptus but were constant in the N2-fixing Acacia. The higher foliar [N] and δ15N in Acacia reflected its N2-fixation ability. Topographic flow accumulation area (NDVI) explained 46% (77%) of spatial variation in dry-season Eucalyptus foliar δ15N ([N]). For Eucalyptus, foliar δ15N was higher at the downslope than the upslope locations, but no hillslope location differences were observed for foliar [N]. These results suggest that in the non-N2-fixing Eucalyptus, seasonal water stress related nitrogen availability may be reflected in foliar δ15N rather than foliar [N]. As such, foliar δ15N of non-N2-fixing plants potentially is a more sensitive indicator of seasonal or topographical N availability than foliar [N].
KW - Flow accumulation area
KW - Foliar nitrogen concentration
KW - Foliar δC
KW - Foliar δN
KW - Mediterranean climate
KW - NDVI
UR - http://www.scopus.com/inward/record.url?scp=85123712770&partnerID=8YFLogxK
U2 - 10.1016/j.ecoinf.2022.101569
DO - 10.1016/j.ecoinf.2022.101569
M3 - Article
AN - SCOPUS:85123712770
SN - 1574-9541
VL - 68
JO - Ecological Informatics
JF - Ecological Informatics
M1 - 101569
ER -
