Predicting the decline in daily maximum transpiration rate of two pine stands during drought based on constant minimum leaf water potential and plant hydraulic conductance

Remko A. Duursma, Pasi Kolari, M. Perämäki, Eero Nikinmaa, Pertti Hari, Sylvain Delzon, Denis Loustau, Hannue Ilvesniemi, Jukka Pumpanen, Annikki Makela

    Research output: Contribution to journalArticle

    86 Citations (Scopus)

    Abstract

    The effect of drought on forest water use is often estimated with models, but comprehensive models require many parameters, and simple models may not be sufficiently flexible. Many tree species, Pinus species in particular, have been shown to maintain a constant minimum leaf water potential above the critical threshold for xylem embolism during drought. In such cases, prediction of the relative decline in daily maximum transpiration rate with decreasing soil water content is relatively straightforward. We constructed a soil–plant water flow model assuming constant plant conductance and daily minimum leaf water potential, but variable conductance from soil to root. We tested this model against independent data from two sites: automatic shoot chamber data and sap flow measurements from a boreal Scots pine (Pinus sylvestris L.) stand; and sap flow measurements from a maritime pine (Pinus pinaster Ait.) stand. To focus on soil limitations to water uptake, we expressed daily maximum transpiration rate relative to the rate that would be obtained in wet soil with similar environmental variables. The comparison was successful, although the maritime pine stand showed carry-over effects of the drought that we could not explain. For the boreal Scots pine stand, daily maximum transpiration was best predicted by water content of soil deeper than 5 cm. A sensitivity analysis revealed that model predictions were relatively insensitive to the minimum leaf water potential, which can be accounted for by the importance of soil resistance of drying soil. We conclude that a model with constant plant conductance and minimum leaf water potential can accurately predict the decline in daily maximum transpiration rate during drought for these two pine stands, and that including further detail about plant compartments would add little predictive power, except in predicting recovery from severe drought.
    Original languageEnglish
    Pages (from-to)265-276
    Number of pages12
    JournalTree Physiology
    Volume28
    Issue number2
    DOIs
    Publication statusPublished - 2008

    Keywords

    • Pinas pinaster
    • Pinus sylvestris
    • plant-soil interactions
    • process-based model
    • water stress
    • water uptake

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