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Soil organic matter quality along rotations in acacia and eucalypt plantations in the Congolese coastal plains

TitoloSoil organic matter quality along rotations in acacia and eucalypt plantations in the Congolese coastal plains
Tipo di pubblicazioneArticolo su Rivista peer-reviewed
Anno di Pubblicazione2019
AutoriKoutika, Lydie-Stella, Ngoyi Sylvain, Cafiero Lorenzo M., and Bevivino Annamaria
RivistaForest Ecosystems
Volume6
Start Page39
Data di pubblicazione09/2019
ISSN20956355
Parole chiaveParticulate organic matter; Nitrogen; Carbon; Phosphorus; Sulphur; Nitrogen-fixing species; Fast growing tree; Climate change mitigation
Abstract

Background

Afforestation of savannas in the Congolese coastal plains with eucalypt has provided wood pulp for industry and fuel energy for the local population. Typically, following afforestation, Acacia mangium are introduced to improve soil fertility and sustain productivity. Through investigations of particulate organic matter (POM), potential soil organic matter (SOM) quality was assessed in acacia and eucalypt plantations along rotations.

Methods

Nutrients in POM (4000–50 μm) in the 0–5 cm soil layer were measured after five years into the second rotation (R2Y5) in relation to soil pH and P availability. Data were compared to those at the end of the first 7-year-rotation (R1Y7) and after two years into the second rotation (R2Y2) to evaluate overall SOM quality in the topsoil.

Results

At R2Y5, soil pH was higher in the pure eucalypt stands (100E) than in stands containing acacia, either in monoculture (100A) or evenly mixed with eucalypt (50A50E). Coarse POM (cPOM, 4000–250 μm) beneath 100A had the highest N concentration (1.71%), followed by those beneath 50A50E (1.42%) and 100E (1.30%). Higher N was always found in the stands containing acacia. Lower sulphur (S) concentrations and P availabilities were observed in cPOM (50A50E). The greatest amount of coarse (414.7 g) and fine (214.5 g) forest floor litter were found in 100A stands, whereas higher C concentrations were found in the 100E stands for coarse forest floor litter (36.5%) and in the 50A50E stands for fine forest floor litter (38.7%). The decrease in cPOM N and C concentrations were lower than 20% (R1Y7) and 26% (R2Y5) relative to the younger stage (R2Y2). This tendency was more pronounced in fine POM (250–50 μm) and organo-mineral fraction (< 50 μm).

Conclusions

The main changes occurred in cPOM beneath stands containing acacia while higher weight of forest floor litter was found in 100A. Soil pH decreased in stands containing acacia. Overall N and C dynamics was enhanced in older stands (R2Y5) than in the younger stands (R2Y2). This may reveal a creation of more labile SOM with lower N and C concentrations in POM fractions in the surface layer, i.e., an ecosystem with a lower potential to mitigate climate change along rotations.

Note

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URLhttps://www2.scopus.com/inward/record.uri?eid=2-s2.0-85071945849&doi=10.1186%2fs40663-019-0197-8&partnerID=40&md5=e5e9124e37e1732d37cdd4e19b7b4368
DOI10.1186/s40663-019-0197-8
Citation Key7651