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Media type:
E-Article
Title:
Effects of land use on ¹⁵N natural abundance of soils in Ethiopian highlands
Contributor:
Eshetu, Zewdu;
Högberg, Peter
Published:
Kluwer Academic Publishers, 2000
Published in:
Plant and Soil, 222 (2000) 1/2, Seite 109-117
Language:
English
ISSN:
0032-079X;
1573-5036
Origination:
Footnote:
Description:
<p>We used the natural abundance of ¹⁵N in soils in forests, pastures and cultivated lands in the Menagesha and Wendo-Genet areas of Ethiopia to make inferences about the N cycles in these ecosystems. Since we have described the history of these sites based on variations in ¹³C natural abundance, patterns of δ¹⁵N and δ¹³C values were compared to determine if shifts of ¹⁵N correlate with shifts of vegetation. At Menagesha, a > 500-yr-old planted forest, we found (δ¹⁵N values from —8.8 to +3.5‰ in litter, from —3.5 to +4.5‰ in 0-10 cm soil layer, and from —1.5 to +6.8‰ at > 20 cm soil depth. The low δ¹⁵N in litter and surface mineral soils suggests that a closed N cycle has operated for a long time. At this site, the low δ¹³C of the surface horizon and the high δ¹³C of the lower soil horizons is clear evidence of a long phase of C₄ grass dominance or cultivation of C₄ crops before the establishment of the forest > 500 years ago. In contrast, at Wendo-Genet, high δ¹³C of soils reveals that most of the land has been uncovered by forests until recently. Soil δ¹⁵N was high throughout (3.4-9.8‰), and there were no major differences between forested, cultivated and pasture soils in δ¹⁵N values of surface mineral soils. The high δ¹⁵N values suggest that open N cycles operate in the Wendo-Genet area. From the points of view of soil fertility management, it is interesting that tall forest ecosystems with relatively closed N cycling could be established on the fairly steep slopes at Menagesha after a long period of grass vegetation cover or cultivation.</p>