Point processes statistics of stable isotopes: analysing water uptake patterns in a mixed stand of Aleppo pine and Holm oak

  • Carles Comas Department of Mathematics, AGROTECNIO Center, Universitat de Lleida.
  • Jorge del Castillo Department of Crop and Forest Sciences, AGROTECNIO Center, Universitat de Lleida.
  • Jordi Voltas Department of Crop and Forest Sciences, AGROTECNIO Center, Universitat de Lleida.
  • Juan Pedro Ferrio Department of Crop and Forest Sciences, AGROTECNIO Center, Universitat de Lleida.


Aim of study: Understanding inter- and intra-specific competition for water is crucial in drought-prone environments. However, little is known about the spatial interdependencies for water uptake among individuals in mixed stands. The aim of this work was to compare water uptake patterns during a drought episode in two common Mediterranean tree species, Quercus ilex L. and Pinus halepensis Mill., using the isotope composition of xylem water (δ18O, δ2H) as hydrological marker.

Area of study: The study was performed in a mixed stand, sampling a total of 33 oaks and 78 pines (plot area= 888 m2). We tested the hypothesis that both species uptake water differentially along the soil profile, thus showing different levels of tree-to-tree interdependency, depending on whether neighbouring trees belong to one species or the other.

Material and Methods: We used pair-correlation functions to study intra-specific point-tree configurations and the bivariate pair correlation function to analyse the inter-specific spatial configuration. Moreover, the isotopic composition of xylem water was analysed as a mark point pattern.

Main results: Values for Q. ilex18O= -5.3 ±0.2‰, δ2H=-54.3±0.7‰) were significantly lower than for P. halepensis18O= -1.2±0.2‰, δ2H = -25.1±0.8‰), pointing to a greater contribution of deeper soil layers for water uptake by Q. ilex. Research highlights: Point-process analyses revealed spatial intra-specific dependencies among neighbouring pines, showing neither oak-oak nor oak-pine interactions. This supports niche segregation for water uptake between the two species.

Key words: Cross-pair correlation function; Deuterium; Mark correlation function; Oxygen-18; Point patterns; Xylem.

Abbreviations: d18O, oxygen isotope composition; d2H, hydrogen isotope composition; BA, basal area.


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Author Biographies

Carles Comas, Department of Mathematics, AGROTECNIO Center, Universitat de Lleida.
Department of Mathematics, Associate Professor
Jorge del Castillo, Department of Crop and Forest Sciences, AGROTECNIO Center, Universitat de Lleida.
Department of Crop and Forest Sciences, Ph.D student
Jordi Voltas, Department of Crop and Forest Sciences, AGROTECNIO Center, Universitat de Lleida.
Department of Crop and Forest Sciences, Professor
Juan Pedro Ferrio, Department of Crop and Forest Sciences, AGROTECNIO Center, Universitat de Lleida.
Department of Crop and Forest Sciences, Ramon y Cajal Researcher



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How to Cite
ComasC., del CastilloJ., VoltasJ., & FerrioJ. P. (2015). Point processes statistics of stable isotopes: analysing water uptake patterns in a mixed stand of Aleppo pine and Holm oak. Forest Systems, 24(1), e009. https://doi.org/10.5424/fs/2015241-05846
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