Contrasting nitrogen fluxes in African tropical forests of the Congo Basin

被引：36

作者：

Bauters, Marijn ^{[1
,2
]}

Verbeeck, Hans ^{[2
]}

Rutting, Tobias ^{[3
]}

Barthel, Matti ^{[4
]}

Mujinya, Basile Bazirake ^{[5
]}

Bamba, Fernando ^{[6
]}

Bode, Samuel ^{[1
]}

Boyemba, Faustin ^{[7
]}

Bulonza, Emmanuel ^{[6
]}

Carlsson, Elin ^{[3
]}

Eriksson, Linnea ^{[3
]}

Makelele, Isaac ^{[6
]}

Six, Johan ^{[4
]}

Ntaboba, Landry Cizungu ^{[6
]}

Boeckx, Pascal ^{[1
]}

机构：

[1] Univ Ghent, Dept Green Chem & Technol, Isotope Biosci Lab ISOFYS, Coupure Links 653, B-9000 Ghent, Belgium

[2] Univ Ghent, Computat & Appl Vegetat Ecol, CAVElab, Dept Environm, Coupure Links 653, B-9000 Ghent, Belgium

[3] Univ Gothenburg, Dept Earth Sci, Box 460, S-40530 Gothenburg, Sweden

[4] Swiss Fed Inst Technol, Sustainable Agroecosyst, Dept Environm Syst Sci, Tannenstr 1, CH-8092 Zurich, Switzerland

[5] Univ Lubumbashi, Lab Soil Sci, Dept Gen Agr Sci, POB 1825, Lubumbashi, DEM REP CONGO

[6] Univ Catholique Bukavu, Fac Agron, Ave Mission,Box 285, Bukavu, DEM REP CONGO

[7] Univ Kisangani, Plant Dept, Fac Sci, Kisangani, DEM REP CONGO

来源：

ECOLOGICAL MONOGRAPHS | 2019年 / 89卷 / 01期

关键词：

N-15; tracing; central African tropical forest; Congo Basin; gross N rates; N balance; N deposition; N losses; nitrogen cycle; organic nitrogen; tropical forests; TRACE GAS EMISSIONS; NUTRIENT LIMITATION; RAIN-FOREST; INORGANIC NITROGEN; ORGANIC NITROGEN; ISOTOPE PATTERNS; SOUTH-AMERICAN; SOIL; CARBON; LOWLAND;

D O I：

10.1002/ecm.1342

中图分类号：

Q14 [生态学（生物生态学）];

学科分类号：

071012 ; 0713 ;

摘要：

The observation of high losses of bioavailable nitrogen (N) and N richness in tropical forests is paradoxical with an apparent lack of N input. Hence, the current concept asserts that biological nitrogen fixation (BNF) must be a major N input for tropical forests. However, well-characterized N cycles are rare and geographically biased; organic N compounds are often neglected and soil gross N cycling is not well quantified. We conducted comprehensive N input and output measurements in four tropical forest types of the Congo Basin with contrasting biotic (mycorrhizal association) and abiotic (lowland-highland) environments. In 12 standardized setups, we monitored N deposition, throughfall, litterfall, leaching, and export during one hydrological year and completed this empirical N budget with nitrous oxide (N2O) flux measurement campaigns in both wet and dry season and in situ gross soil N transformations using N-15-tracing and numerical modeling. We found that all forests showed a very tight soil N cycle, with gross mineralization to immobilization ratios (M/I) close to 1 and relatively low gross nitrification to mineralization ratios (N/M). This was in line with the observation of dissolved organic nitrogen (DON) dominating N losses for the most abundant, arbuscular mycorrhizal associated, lowland forest type, but in contrast with high losses of dissolved inorganic nitrogen (DIN) in all other forest types. Altogether, our observations show that different forest types in central Africa exhibit N fluxes of contrasting magnitudes and N-species composition. In contrast to many Neotropical forests, our estimated N budgets of central African forests are imbalanced by a higher N input than output, with organic N contributing significantly to the input-output balance. This suggests that important other losses that are unaccounted for (e.g., NOx and N-2 as well as particulate N) might play a major role in the N cycle of mature African tropical forests.

引用

页数：17

共 114 条

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