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Legume and Non-legume Trees Increase Soil Carbon Sequestration in Savanna

Abstract

Savanna ecosystems are increasingly pressured by climate and land-use changes, especially around populous areas such as the Mt. Kilimanjaro region. Savanna vegetation consists of grassland with isolated trees or tree groups and is therefore characterized by high spatial variation and patchiness of canopy cover and aboveground biomass. Both are major regulators for soil ecological properties and soil-atmospheric trace gas exchange (CO2, N2O, CH4), especially in water-limited environments. Our objectives were to determine spatial trends in soil properties and trace gas fluxes during the dry season and to relate above- and belowground processes and attributes. We selected a Savanna plain with vertic soil properties, south east of Mt. Kilimanjaro. Three trees were chosen from each of the two most dominant species: the legume Acacia nilotica and the non-legume Balanites aegyptiaca. For each tree, we selected one transect with nine sampling points, up to a distance of 4 times the crown radius from the stem. At each sampling point, we measured carbon (C) and nitrogen (N) content, δ13C of soil (0–10, 10–30 cm depth) and in plant biomass, soil C and N pools, water content, available nutrients, cation exchange capacity (CEC), temperature, pH, as well as root biomass and greenhouse-gas exchange. Tree species had no effect on soil parameters and gas fluxes under the crown. CEC, C, and N pools decreased up to 50% outside the crown-covered area. Tree leaf litter had a far lower C:N ratio than litter of the C4 grasses. δ13C in soil under the crown shifted about 15% in the direction of tree leaf litter δ13C compared to soil in open area reflecting the tree litter contribution to soil organic matter. The microbial C:N ratio and CO2 efflux were about 30% higher in the open area and strongly dependent on mineral N availability. This indicates N limitation and low microbial C use efficiency in the soil of open grassland areas. We conclude that the spatial structure of aboveground biomass in savanna ecosystems leads to a spatial redistribution of nutrients and thus C mineralization and sequestration. Therefore, the capability of savanna ecosystems to act as C sinks is both directly and indirectly dependent on the abundance of trees, regardless of their N-fixing status.

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References

  • Appelhans T, Mwangomo E, Otte I, Detsch F, Nauss T, Hemp A. 2014. Monthly and annual climate data averaged from 2011 to 2013 for 79 research plots on the southern slopes of Mt. Kilimanjaro - V 1.0: ZENODO.

  • Beck T, Joergensen RG, Kandeler E, Makeschin F, Nuss E, Oberholzer HR, Scheu S. 1997. An inter-laboratory comparison of ten different ways of measuring soil microbial biomass C. Soil Biol Biochem 29:1023–32.

    CAS  Article  Google Scholar 

  • Belsky AJ. 1994. Influences of trees on savanna productivity: tests of shade, nutrients, and tree-grass competition. Ecology 75:922.

    Article  Google Scholar 

  • Belsky AJ, Mwonga SM, Amundson RG, Duxbury JM, Ali AR. 1993. Comparative effects of isolated trees on their undercanopy environments in high-and low-rainfall savannas. J Appl Ecol 30:143.

    Article  Google Scholar 

  • Belsky AJ, Amundson RG, Duxbury JM, Riha SJ, Ali AR, Mwonga SM. 1989. The effects of trees on their physical, chemical and biological environments in a semi-arid savanna in Kenya. J Appl Ecol 26:1005.

    Article  Google Scholar 

  • Bernhard-Reversat F. 1982. Biogeochemical cycle of nitrogen in a semi-arid savanna. Oikos 38:321.

    Article  Google Scholar 

  • Blagodatskaya E, Blagodatsky S, Anderson T-H, Kuzyakov Y. 2014. Microbial growth and carbon use efficiency in the rhizosphere and root-free soil. PLOS ONE 9:e93282.

    Article  PubMed  PubMed Central  Google Scholar 

  • Bradford MA, Crowther TW. 2013. Carbon use efficiency and storage in terrestrial ecosystems. New Phytol 199:7–9.

    CAS  Article  PubMed  Google Scholar 

  • Burton AJ, Pregitzer KS, Crawford JN, Zogg GP, Zak DR. 2004. Simulated chronic NO3− deposition reduces soil respiration in northern hardwood forests. Glob Chang Biol 10:1080–91.

    Article  Google Scholar 

  • Ceccon C, Panzacchi P, Scandellari F, Prandi L, Ventura M, Russo B, Millard P, Tagliavini M. 2011. Spatial and temporal effects of soil temperature and moisture and the relation to fine root density on root and soil respiration in a mature apple orchard. Plant Soil 342:195–206.

    CAS  Article  Google Scholar 

  • Cerling TE, Harris JM, MacFadden BJ, Leakey MG, Quade J, Eisenmann V, Ehleringer JR. 1997. Global vegetation change through the Miocene/Pliocene boundary. Nature 389:153–8.

    CAS  Article  Google Scholar 

  • Chen C, Cleverly J, Zhang L, Yu Q, Eamus D. 2016. Modelling seasonal and inter-annual variations in carbon and water fluxes in an arid-zone acacia savanna woodland, 1981–2012. Ecosystems 19(4):625–44.

    CAS  Article  Google Scholar 

  • Chen H, Billen N, Stahr K, Kuzyakov Y. 2007. Effects of nitrogen and intensive mixing on decomposition of 14C-labelled maize (Zea mays L.) residue in soils of different land use types. Soil Tillage Res 96:114–23.

    Article  Google Scholar 

  • Chesworth W. 2008. Encyclopedia of soil science. Dordrecht: Springer.

    Book  Google Scholar 

  • Diallo A, Agbangba EC, Ndiaye O, Guisse A. 2013. Ecological structure and prediction equations for estimating tree age, and dendometric parameters of acacia senegal in the senegalese semi-arid zone—ferlo. AJPS 04:1046–53.

    Article  Google Scholar 

  • Garcia-Moya E, McKell CM. 1970. Contribution of shrubs to the nitrogen economy of a desert-wash plant community. Ecology 51:81–8.

    Article  Google Scholar 

  • Goldewijk KK. 2001. Estimating global land use change over the past 300 years: The HYDE Database. Global Biogeochem Cycles 15:417–33.

    Article  Google Scholar 

  • Grace J, Jose JS, Meir P, Miranda HS, Montes RA. 2006. Productivity and carbon fluxes of tropical savannas. J Biogeogr 33:387–400.

    Article  Google Scholar 

  • Hertel D, Leuschner C. 2002. A comparison of four different fine root production estimates with ecosystem carbon balance data in a Fagus-Quercus mixed forest. Plant Soil 239:237–51.

    CAS  Article  Google Scholar 

  • Hibbard KA, Archer S, Schimel DS, Valentine DW. 2001. Biogeochemical changes accompanying woody plant enchroachment in a subtropical savanna. Ecology 82:1999–2011.

    Article  Google Scholar 

  • Horton JL, Hart SC. 1998. Hydraulic lift. A potentially important ecosystem process. Trends Ecol Evol 13:232–5.

    CAS  Article  PubMed  Google Scholar 

  • Huntley BJ, Walker BH. 1982. Ecology of tropical savannas. Berlin: Springer.

    Book  Google Scholar 

  • IPCC. 2013. Climate change 2013: the physical science basis. contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change. Cambridge: Cambridge University Press

  • Joergensen RG. 1996. The fumigation-extraction method to estimate soil microbial biomass. Calibration of the kEC value. Soil Biol Biochem 28:25–31.

    CAS  Article  Google Scholar 

  • Joergensen RG, Mueller T. 1996. The fumigation-extraction method to estimate soil microbial biomass. Calibration of the kEN value. Soil Biol Biochem 28:33–7.

    CAS  Article  Google Scholar 

  • Kühnel A. 2015. Variability of physical, chemical and hydraulic parameters in soils of Mt. Kilimanjaro across different land uses. Dissertation. Bayreuth, Germany.

  • Lambin EF, Geist HJ, Lepers E. 2003. Dynamics of land-use and land-cover change in tropcial regions. Annu Rev Environ Resourc 28:205–41.

    Article  Google Scholar 

  • Ludwig F, de Kroon H, Berendse F, Prins HH. 2004. The influence of savanna trees on nutrient, water and light availability and the understorey vegetation. Plant Ecol 170:93–105.

    Article  Google Scholar 

  • Ludwig F, Kroon H, Prins HH, Berendse F. 2001. Effects of nutrients and shade on tree-grass interactions in an East African savanna. J Veg Sci 12:579–88.

    Article  Google Scholar 

  • Meyer KM, Wiegand K, Ward D. 2009. Patch dynamics integrate mechanisms for savanna tree–grass coexistence. Basic Appl Ecol 10:491–9.

    Article  Google Scholar 

  • Meyer KM, Wiegand K, Ward D, Moustakas A. 2007. The rhythm of savanna patch dynamics. J Ecol 95:1306–15.

    Article  Google Scholar 

  • Miranda AC, Miranda HS, Lloyd J, Grace J, Francey RJ, McIntyre JA, Meir P, Riggan P, Lockwood R, Brass J. 1997. Fluxes of carbon, water and energy over Brazilian cerrado. An analysis using eddy covariance and stable isotopes. Plant Cell Environ 20:315–28.

    CAS  Article  Google Scholar 

  • Nicolardot B, Recous S, Mary B. 2001. Simulation of C and N mineralisation during crop residue decomposition: A simple dynamic model based on the C: N ratio of the residues. Plant Soil 228:83–103.

    CAS  Article  Google Scholar 

  • Otieno D, Ondier J, Arnhold S, Okach D, Ruidisch M, Lee B, Kolb A, Onyango J, Huwe B. 2015. Patterns of CO2 exchange and productivity of the herbaceous vegetation and trees in a humid savanna in western Kenya. Plant Ecol 216:1441–56.

    Article  Google Scholar 

  • Otieno DO, Schmidt M, Kinyamario JI, Tenhunen J. 2005. Responses of Acacia tortilis and Acacia xanthophloea to seasonal changes in soil water availability in the savanna region of Kenya. J Arid Environ 62:377–400.

    Article  Google Scholar 

  • Perakis SS, Kellogg CH. 2007. Imprint of oaks on nitrogen availability and δ15N in California grassland-savanna. A case of enhanced N inputs? Plant Ecol 191:209–20.

    Article  Google Scholar 

  • R Core Team. 2013. R. A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing.

  • Rascher KG, Hellmann C, Máguas C, Werner C. 2012. Community scale 15 N isoscapes: tracing the spatial impact of an exotic N2 -fixing invader. Ecol Lett 15:484–91.

    Article  PubMed  Google Scholar 

  • Raz-Yaseef N, Rotenberg E, Yakir D. 2010. Effects of spatial variations in soil evaporation caused by tree shading on water flux partitioning in a semi-arid pine forest. Agric For Meteorol 150:454–62.

    Article  Google Scholar 

  • Schleicher J, Wiegand K, Ward D. 2011. Changes of woody plant interaction and spatial distribution between rocky and sandy soil areas in a semi-arid savanna, South Africa. J Arid Environ 75:270–8.

    Article  Google Scholar 

  • Scholes RJ, Archer SR. 1997. Tree-grass interactions in savannas. Annu Rev Ecol Syst 28:517–44.

    Article  Google Scholar 

  • Scholes RJ, Walker BH. 1993. An African savanna. Cambridge: Cambridge University Press.

    Book  Google Scholar 

  • Scholes RJ. 1990. The influence of soil fertility on the ecology of southern African dry savannas. J Biogeogr 17:415.

    Article  Google Scholar 

  • Sinsabaugh RL, Manzoni S, Moorhead DL, Richter A. 2013. Carbon use efficiency of microbial communities: stoichiometry, methodology and modelling. Ecology letters 16:930–9.

    Article  PubMed  Google Scholar 

  • Sitters J, Edwards PJ, Suter W, Olde Venterink H. 2015. Acacia tree density strongly affects N and P fluxes in savanna. Biogeochemistry 123:285–97.

    CAS  Article  Google Scholar 

  • Spohn M. 2015. Microbial respiration per unit microbial biomass depends on litter layer carbon-to-nitrogen ratio. Biogeosciences 12:817–23.

    Article  Google Scholar 

  • Staver AC, Archibald S, Levin S. 2011. Tree cover in sub-Saharan Africa. Rainfall and fire constrain forest and savanna as alternative stable states. Ecology 92:1063–72.

    Article  PubMed  Google Scholar 

  • Vance ED, Brookes PC, Jenkinson DS. 1987. An extraction method for measuring soil microbial biomass C. Soil Biol Biochem 19:703–7.

    CAS  Article  Google Scholar 

  • Varella RF, Bustamante MMC, Pinto AS, Kisselle KW, Santos RV, Burke RA, Zepp RG, Viana LT. 2004. Soil Fluxes of CO2, CO, NO, and N2O from an Old Pasture and from Native Savanna in Brazil. Ecol Appl 14:221–31.

    Article  Google Scholar 

  • Veenendaal EM, Kolle O, Lloyd J. 2004. Seasonal variation in energy fluxes and carbon dioxide exchange for a broad-leaved semi-arid savanna (Mopane woodland) in Southern Africa. Global Chang Biol 10:318–28.

    Article  Google Scholar 

  • Vetaas OR. 1992. Micro-site effects of trees and shrubs in dry savannas. J Veg Sci 3:337–44.

    Article  Google Scholar 

  • Virginia RA, Jenkins MB, Jarrell WM. 1986. Depth of root symbiont occurrence in soil. Biol Fertil Soils 2(3):127–30.

    Article  Google Scholar 

  • Vitousek PM, Walker LR. 1989. Biological invasion by Myrica faya in Hawai’i: plant demography, nitrogen fixation, ecosystem effects. Ecol Monogr 59:247–65.

    Article  Google Scholar 

  • Werner C, Reiser K, Dannenmann M, Hutley LB, Jacobeit J, Butterbach-Bahl K. 2014. N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia. An incubation experiment with intact soil cores. Biogeosciences 11:6047–65.

    Article  Google Scholar 

  • Yelenik SG, Stock WD, Richardson DM. 2004. Ecosystem level impacts of invasive Acacia saligna in the South African fynbos. Restor Ecology 12:44–51.

    Article  Google Scholar 

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Acknowledgements

We thank the Tanzanian Commission for Science and Technology (COSTECH), the Tanzania Wildlife Research Institute (TAWIRI), and the Ministry of Natural Resources and Tourism (MNRT) for supporting this research. Further thanks go to Emanueli Ndossi (University of Göttingen) as well as to our local workers Ayubu Mtaturu, Jumanne Mwinyi, Jubilate Maruchu, Richard Mrema, and our laboratory staff for their help. This study was funded by the German Research Foundation (DFG) within the Research-Unit 1246 (KiLi).

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Correspondence to Joscha N. Becker.

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All authors contributed to the study design. Fieldwork and data processing were conducted by JNB, AG, and NSC. Data were analyzed by JNB. JNB led data interpretation and wrote the paper with contributions of all authors.

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Becker, J.N., Gütlein, A., Sierra Cornejo, N. et al. Legume and Non-legume Trees Increase Soil Carbon Sequestration in Savanna. Ecosystems 20, 989–999 (2017). https://doi.org/10.1007/s10021-016-0087-7

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Keywords

  • carbon use efficiency
  • Balanites aegyptiaca
  • Acacia nilotica
  • soil respiration
  • spatial variability
  • C:N stoichiometry