Soil salinity induces osmotic stress and ion toxicity in plants, detrimentally affecting their growth. Potato (So- lanum tuberosum) suffers yield reductions under salt stress. To understand salt-stress resilience mechanisms in potatoes, we studied three cultivars with contrasting salt sensitivity: Innovator, Desiree, and Mozart. Innovator emerged as the most resilient under salt stress, displaying minimal reductions in growth and plant tolerance index with no tuber yield loss, despite notable water loss. Conversely, Desiree experienced a significant tuber yield reduction but maintained better water retention. Mozart showed a low plant tolerance index and high water loss. Interestingly, ions measurement across different tissues revealed that, unlike chloride, sodium does not accumulate in tubers under salt stress in these cultivars, suggesting existence of an active sodium exclusion mechanism. A whole root transcriptomic analysis of these cultivars revealed a conserved salt stress response between potato and Arabidopsis. This response includes activation of various abiotic stress pathways and involves sequential activation of various transcription factor families. Root analyses showed that Innovator has lower suberin and lignin deposition, along with stronger K+ leakage in control conditions, resulting in a higher early stress response and increased ABA accumulation shortly after salt stress induction. This could explain Innovator has a more divergent transcriptomic response to salt stress compared to Desiree and Mozart. Nevertheless, Innovator displayed high suberin and lignin levels and ceased K+ leakage after salt stress, suggesting a high acclimation ability. Altogether, our results indicate that acclimation ability, rather than initial root protection against salt prevails in long-term salt-stress resilience of potato.

Winter reddening of young Douglas-fir (Pseudotsuga menziesii Mirb. Franco), triggered by large thermal fluctuations in late winter, is a critical problem for European forestry. A literature review identified certain climatic conditions that are characteristic of 'reddening' years, including warm daily temperatures, high daily temperature amplitude, low relative humidity, moderate wind speeds, as well as the occurrence of freeze-thaw cycles with cold night temperatures. By describing the triggering environmental and stand factors, we propose three hypotheses for the physiological processes leading to winter reddening, namely (i) hydraulic failure due to winter drought stress, (ii) photo-oxidative stress in shade-acclimated trees, and (iii) early cold deacclimation during warm periods. i) Low soil temperature, by reducing root water uptake, combined with anticyclonic conditions, by increasing water losses, can induce hydraulic failure in the xylem. Hydraulic failure may be further accelerated by night frosts. ii) Winter reddening can occur when low temperature and high irradiance coincide, disrupting photostasis. Overwhelming of winter photo-protection may lead to photodamage and subsequent reddening. iii) Warm periods, by inducing cold deacclimation, make trees susceptible to frost damage. Finally, the three processes may interact under atypical anticyclonic conditions in late winter (e.g. cold or dry soils, warm days, high irradiance and/or freezing nights). Indeed, trees under water stress would develop a higher sensitivity to freezing night and photooxidative stress. We therefore proposed mitigation actions to avoid exposing trees to stressful conditions based on e.g. stand characteristics, understorey vegetation and planting.

Global climate change is altering snow depth in winter, which could significantly affect soil respiration and microbial communities. However, belowground responses are still uncertain as they depend on the thermal effects on soils, the acclimation of soil microbial communities and ecosystem type. Here, we conducted a snow manipulation experiment including 50% removal of snowpack (mean snow depth after treatment was 3.1 +/- 0.7 cm), ambient snow (mean snow depth was 6.3 +/- 0.7 cm), and 50% increase of snowpack (mean snow depth after treatment was 9.6 +/- 1.5 cm) to explore the effects of altered snow depth on winter soil respiration and microbial communities in a mid-latitude plantation forest with continental climate with dry winters. Winter soil CO2 effluxes varied from 0.09 to 0.84 mu mol m(-2)S(-1) with a mean of 0.32 +/- 0.07 mu mol m(-2)s(-1). The cumulative soil CO2 effluxes from 11 December 2014 to 21 March 2015 were 27.3 +/- 1.1, 26.5 +/- 2.1, and 29.5 +/- 1.3 g Cm-2 under reduced, ambient and added snowpack, which corresponded to 5.7 +/- 0.2%, 5.5 +/- 0.3%, and 5.8 +/- 0.1% of the annual soil CO2 effluxes, respectively. Our one-year observation results suggested that although snow reduction decreased soil temperature, microbial biomass carbon (MBC) and soil respiration did not change, suggesting microbial adaptation to cold conditions between - 4 degrees C and -1 degrees C. In contrast, snow addition increased soil temperature, MBC, and soil respiration. Microbial community structure (F/B, ratio of fungi to bacteria) was also changed and soil enzymatic (beta-glucosidase) activities increased under snow addition. However, these effects were short-lived and disappeared when soil temperature did not differ between the addition and control plots at the 14th day after treatment. These results indicated that the responses of soil microbial communities and respiratory activities to changing soil temperature were rapid and the response of soil respiration to snow addition was transient. Consequently, altered snow depth did not affect cumulative soil CO2 effluxes. Our study suggests that wintertime soil respiration rates are generally low and snow manipulation has minor effects on soil CO2 efflux, soil temperature (the determinant driver of wintertime soil CO2 efflux) and soil microbial biomass at our site.

Assessments made over the past few decades have suggested that boreal forests may act as a sink for atmospheric carbon dioxide. However, the fate of the newly accumulated carbon in the living forest biomass is not well understood, and the estimates of carbon sinks vary greatly from one assessment to another. Analysis of remote sensing data has indicated that the carbon sinks in the Russian forests are larger than what has been estimated from forest inventories. In this study, we show that over the past four decades, the allometric relationships among various plant parts have changed in the Russian forests. To this end, we employ two approaches: (1) analysis of the database, which contains 3196 sample plots; and (2) application of developed models to forest inventory data. Within the forests as a whole, when assessed at the continental scale, we detect a pronounced increase in the share of green parts (leaves and needles). However, there is a large geographical variation. The shift has been largest within the European Russia, where summer temperatures and precipitation have increased. In the Northern Taiga of Siberia, where the climate has become warmer but drier, the fraction of the green parts has decreased while the fractions of aboveground wood and roots have increased. These changes are consistent with experiments and mathematical models that predict a shift of carbon allocation to transpiring foliage with increasing temperature and lower allocation with increasing soil drought. In light of this, our results are a possible demonstration of the acclimation of trees to ongoing warming and changes in the surface water balance. Independent of the nature of the observed changes in allometric ratios, the increase in the share of green parts may have caused a misinterpretation of the satellite data and a systematic overestimation by remote sensing methods of the carbon sink for living biomass of the Russian forest.