ABSTRACT
Introduction: Under ongoing climate change, more frequent and severe drought periods accompanied by heat waves are expected in the future. Under these conditions, the tree's survival is conditioned by fast recovery of functions after drought release. Therefore, in the presented study, we evaluated the effect of long-term water reduction in soil on tree water use and growth dynamics of Norway spruce. Methods: The experiment was conducted in two young Norway spruce plots located on suboptimal sites at a low altitude of 440 m a.s.l. In the first plot (PE), 25% of precipitation throughfall was excluded since 2007, and the second one represented the control treatment with ambient conditions (PC). Tree sap flow, stem radial increment, and tree water deficit were monitored in two consecutive growing seasons: 2015-2016, with contrasting hydro-climatic conditions. Results: Trees in both treatments showed relatively isohydric behavior reflected in a strong reduction of sap flow under the exceptional drought of 2015. Nevertheless, trees from PE treatment reduced sap flow faster than PC under decreasing soil water potential, exhibiting faster stomatal response. This led to a significantly lower sap flow of PE, compared to PC in 2015. The maximal sap flow rates were also lower for PE treatment, compared to PC. Both treatments experienced minimal radial growth during the 2015 drought and subsequent recovery of radial growth under the more the humid year of 2016. However, treatments did not differ significantly in stem radial increments within respective years. Discussion: Precipitation exclusion treatment, therefore, led to water loss adjustment, but did not affect growth response to intense drought and growth recovery in the year after drought.
ABSTRACT
The aim of the work was to verify whether the fermentation of seed material is a suitable pre-sowing treatment of small-leaved lime. Seed material of two origins was treated for a period of 7, 14 and 21 days using anaerobic fermentation and for 10, 20 and 30 days using aerobic fermentation, the control treatment being the seed after warm-cold stratification. The water content, germination capacity and abscisic acid level of the seed were evaluated, together with the emergence and morphological parameters of annual lime seedlings that had emerged from the tested seeds. It was found that fermented seed had a low abscisic acid level (up to 700 pmol/g), a higher germination capacity (approx. 90%) than mature seed without fermentation and the morphological parameters of the seedlings that had emerged from seed after fermentation reached higher values, compared to those of the seedlings that had emerged from seed after warm-cold stratification. The seed material had to be collected green (e.g., immature seeds) and moistened. A suitable anaerobic fermentation time is 7 days; the aerobic phase can last 10, 20 or 30 days. The fermentation of seed material can shorten the preparation of seed for sowing by 1 year.
