Soil C and N dynamics in a Mediterranean oak woodland with shrub encroachment
Background and aims
Intensive land use has led to degradation and abandonment of Portuguese oak woodlands, and subsequent shrub encroachment may have altered the spatial heterogeneity of soil C and N pools. The aim of this study was to evaluate the effects of shrub invasion on soil C and N dynamics in an oak woodland in Southern Portugal.
Soil was sampled beneath and outside scattered Quercus suber L. canopies, considering non-encroached areas and areas encroached by shrubs (Cistus ladanifer L. or Cistus salviifolius L.).
The spatial heterogeneity of soil C and N contents was mainly associated with tree presence. Outside tree canopies, the labile C pools were larger (mainly beneath C. ladanifer) and C cycling was faster in encroached areas than in non-encroached areas. Net and gross N mineralization and urease and protease activities were also higher in encroached than in non-encroached areas; however, the metabolic quotient and the Cmicrobial/Corganic ratio were not significantly affected. Beneath the tree canopy, significant effects of encroachment included a small increase in soil labile C and the enzymatic activity beneath C. ladanifer.
The results indicate the potential capacity of shrub encroachment to accumulate soil organic C in the long term. The rate of soil C and N turnover promoted by shrub encroachment may depend on the Cistus species present.
Keywords15N isotope dilution technique Gross N mineralization Hot water-soluble C Particulate organic matter Soil respiration
The study was conducted within the activities of the Centro de Estudos Florestais (FCT), Instituto Superior de Agronomia. Part of the funding for the isotopic ratio mass spectrometer was obtained from the European Regional Development Fund (EU). The first author is grateful to the Portuguese Science and Technology Foundation for financial support for this postdoctoral research (SFRH/BPD/27067/2006). We thank Paula Simões for assistance in sampling design and Paulo Marques for help with fieldwork. We also acknowledge laboratory staff in the Departamento de Ciências do Ambiente (Instituto Superior de Agronomia) for technical assistance with analytical work. The authors also thank Ana Carla Madeira for comments on the text of an earlier version of the manuscript.
- Egnér H, Riehm H, Domingo WR (1960) Untersuchungen über die chemische Bodenanalyse als Grundlage für die Beurteilung des Nährstoff-zustandes der Böden. II Chemische Extraktionmethod zur Phosphor-und Kaliumbestimmung. Kungl Lantbr Högsk Ann 26:199Google Scholar
- Escudero A, García B, Gómez JM, Luís E (1985) The nutrient cycling in Quercus rotundifolia and Quercus pyrenaica ecosystems (dehesas) of Spain. Acta Oecol 6:73–86Google Scholar
- Gómez-Rey MX, Garcês A, Madeira M (2011) Organic C distribution and N mineralization in soil of oak woodlands with improved pastures. Revista de Ciências Agrárias 34(1):80–92Google Scholar
- IFN (2006) Inventário Florestal Nacional (2005–2006). Divisão de Inventário e Estatísticas Florestais. Direcção Geral das Florestas, LisboaGoogle Scholar
- IUSS Working Group WRB (2006) World Reference Base for Soil Resources 2006. World Soil Resources Report, vol 103. FAO, RomeGoogle Scholar
- Nunes JMSD (2004) Interacção solo-árvore isolada em montados de azinho (Quercus rotundifolia Lam.): processos fundamentais. Ph D Dissertation. Universidade de Évora.Google Scholar
- Pérez-Bejarano A, Mataix-Solera J, Zornoza R, Guerrero C, Arcenegui V, Mataix-Beneyto J, Cano-Amat S (2010) Influence of plant species on physical, chemical and biological soil properties in a Mediterranean forest soil. Eur J Forest Res 129:15–24. doi: 10.1007/s10342-008-0246-2 CrossRefGoogle Scholar
- Reis RMM, Gonçalves MZ (1987) Clima de Portugal, Fascículo XXXIV. Caracterização climática da região agrícola do Alentejo. Instituto Nacional de Meteorología e Geofísica, LisboaGoogle Scholar
- Rivest D, Rolo V, López-Díaz ML, Moreno G (2011) Shrub encroachment in Mediterranean silvopastoral systems: Retama sphaerocarpa and Cistus ladanifer induce contrasting effects on pasture and Quercus ilex production. Agr Ecosyt Envir 141:447–454. doi: 10.1016/j.agee.2011.04.018 CrossRefGoogle Scholar
- Sá C, Madeira M, Gazarini L (2001) Produção e decomposição da folhada de Quercus suber L. Revista de Ciências Agrárias 24(3, 4):245–256Google Scholar
- Silva de Sá CMM (2001) Influência do coberto arbóreo (Quercus suber L.) em processos ecofisiológicos da vegetação herbácea em áreas de montado. Ph D Dissertation, Universidade de ÉvoraGoogle Scholar
- Simões MP (2002). Dinâmica de biomassa (carbono) e nutrientes em Cistus salvifolius L. e Cistus ladanifer L.. Influência nas características do solo. Ph D Dissertation, Universidade de ÉvoraGoogle Scholar
- Tabatabai MA (1982) Soil enzymes. In: Page AL, Miller RH, Keeney DR (eds) Methods of soil analysis. Part 2. Chemical and microbiological properties, 2nd edn. ASA, SSAJ, Wisconsin, pp 903–947Google Scholar
- Thomas GW (1982) Exchangeable cations. In: Page AL, Miller RH, Keeney DR (eds) Methods of soil analysis, part 2. Chemical and microbiological properties, 2nd edn. ASA, SSAJ, Wisconsin, pp 159–165Google Scholar