Evidences of drought stress as a predisposing factor to Scots pine decline in Valle d’Aosta (Italy)

Abstract

12Scots pine (Pinus sylvestris L.) forests of many inner Alpine valleys have recently displayed a quick loss of 13 vitality. A decline disease has been suggested as the cause, with drought as the main predisposing factor and 14 the additional contribution of biotic agents inciting tree dieback. This study is focused on validated against ancillary ground truth. We: (1) tested whether EVI reductions in Scots pine forests were 19 significantly higher than those of a control species and of a wetter region for the same species, (2) analyzed 20 decline incidence as a function of site and topographic variables, and (3) assessed the relative influence of 21 site and stand structure on decline probability by means of path analysis. Mean EVI in the study area 22 increased due to an early onset of the 2007 growing season. Nevertheless, the incidence of decline was 6.3% 23 and significantly greater for Scots pine than the control species and site. Low-elevation, northerly exposed 24 sites exhibited the highest incidence of decline. 25Path analysis suggested that the most important determi-nants of decline probability were slope, solar 26 radiation, and stand sparseness. 27 28

An improved species distribution model for Scots pine and downy oak under future climate change in the NW Italian Alps

“…Drought is either a direct or a predisposing factor of mortality (Rebetez and Dobbertin 2004;Choat et al 2013). At low elevations, Scots pine reaches more rapidly decay stages, since trees weakened by drought are easily killed by "inciting" or "contributing" biotic agents (Dobbertin et al 2005;Bigler et al 2006;Vacchiano et al 2012). Also, land use change may eventually result in competitive exclusion of light-demanding Scots pine.…”

“…In order to distinguish reflectance anomalies from random or systematic error (Morisette and Khorram 2000), we classified as "decline" all pixels with ΔNDVI<(mean−3 standard deviations), as computed from the full scene (Fung and LeDrew 1988;Vacchiano et al 2012). Finally, we compared the modeled change in pine occurrence probability (2080-current) of decline vs. non-decline pixels by means of Wilcoxon signed-rank test (Sokal and Rohlf 1995).…”

“…Cloud cover of the MVC was between 1 and 4 % for the four images. Pixels with a quality analysis score of 2 and 3 (i.e., targets covered by snow/ice or cloudy pixel) as well as NDVI lower than 0.2 or null (open water) were filtered out (Vacchiano et al 2012).…”

“…Scots pine (Pinus sylvestris L.) forests at the southern edge of their distribution are currently facing decline and succession, resulting from a combination of climate warming, land use changes, and increased abiotic and biotic disturbances (Gimmi et al 2010;Vacchiano et al 2012).…”

Root architecture might account for contrasting establishment success of Pseudotsuga menziesii var. menziesii and Pinus sylvestris in Central Europe under dry conditions

“…In particular, Central Alpine populations are known for their high phenotypic plasticity, which enables them to grow in changing environments (Richter et al 2012). Nevertheless, Pinus sylvestris has suffered high mortality in dry Alpine valleys after the exceptional summer drought in 2003, for instance in the Valais, Switzerland (Bigler et al 2006;Rigling et al 2013) and the Aosta valley, Italy (Vacchiano et al 2012). As a result, adequate management measures (Vacchiano and Motta 2015) and potential alternatives to Pinus sylvestris, such as Pseudotsuga menziesii, have been investigated (Eilmann and Rigling 2012).…”