Effect of irrigation on needle morphology, shoot and stem growth in a drought-exposed Pinus sylvestris forest

Abstract

In Valais, Switzerland, Scots pines (Pinus sylvestris L.) are declining, mainly following drought. To assess the impact of drought on tree growth and survival, an irrigation experiment was initiated in 2003 in a mature pine forest, approximately doubling the annual precipitation. Tree crown transparency (lack of foliage) and leaf area index (LAI) were annually assessed. Seven irrigated and six control trees were felled in 2006, and needles, stem discs and branches were taken for growth analysis. Irrigation in 2004 and 2005, both with below-average precipitation, increased needle size, area and mass, stem growth and, with a 1-year delay, shoot length. This led to a relative decrease in tree crown transparency (-14%) and to an increase in stand LAI (+20%). Irrigation increased needle length by 70%, shoot length by 100% and ring width by 120%, regardless of crown transparency. Crown transparency correlated positively with mean needle size, shoot length and ring width and negatively with specific leaf area. Trees with high crown transparency (low growth, short needles) experienced similar increases in needle mass and growth with irrigation than trees with low transparency (high growth, long needles), indicating that seemingly declining trees were able to 'recover' when water supply became sufficient. A simple drought index before and during the irrigation explained most of the variation found in the parameters for both irrigated and control trees.

Inter- and transdisciplinary perspective on the integration of ecological processes into ecosystem services analysis in a mountain region

“…findings from local ecological field studies and drought experiments (Brunner et al 2009;Dobbertin et al 2010;Eilmann and Rigling 2012;Eilmann et al 2009Eilmann et al , 2013Rigling et al 2013) were analyzed to improve the existing mechanistic forest model LandClim (Schumacher et al 2004). LandClim is a spatially explicit processbased model that incorporates competition-driven forest dynamics and landscape-level disturbances to simulate forest dynamics at a landscape scale.…”

Sustainable Land-use Practices in European Mountain Regions under Global Change: an Integrated Research Approach

“…In Davos, data from a long-term experiment at the treeline on Stillberg were analyzed (Martin et al 2010). In the case study region Valais, field studies and drought experiments investigated the germination, growth, and mortality of different tree species (Brunner et al 2009, Eilmann et al 2009, Dobbertin et al 2010, Eilmann and Rigling 2012, Rigling et al 2013). These experimental findings were used to improve existing mechanistic models (Schumacher et al 2004, Lischke et al 2006, Gillet 2008 in the corresponding area.…”

The conditions of forests in Italy. Results from the extensive surveys of Level I (1997-2010)

“…In particolare il pino silvestre mostra costantemente un livello di defogliazione particolarmente elevato. E' noto che il 11 Forest@ 11: 8-12 (2014) pino silvestre, soprattutto nei siti più caldi della sua distribuzione alpina è soggetto a forme di deperimento probabilmente dovuto a motivi climatici (Dobbertin et al 2010). Comparazioni spaziali degli andamenti delle singole specie sono possibili solo per quanto riguarda il faggio, grazie alla sua uniforme distribuzione.…”