Bud dormancy of plants has traditionally been explained either by physiological growth arresting conditions in the bud or by unfavourable environmental conditions, such as non-growth-promoting low air temperatures. This conceptual dichotomy has provided the framework also for developing process-based plant phenology models. Here, we propose a novel model that in addition to covering the classical dichotomy as a special case also allows the quantification of an interaction of physiological and environmental factors. According to this plant-environment interaction suggested conceptually decades ago, rather than being unambiguous, the concept of "non-growth-promoting low air temperature" depends on the dormancy status of the plant. We parameterized the model with experimental results of growth onset for seven boreal plant species and found that based on the strength of the interaction, the species can be classified into three dormancy types, only one of which represents the traditional dichotomy. We also tested the model with four species in an independent experiment. Our study suggests that interaction of environmental and physiological factors may be involved in many such phenomena that have until now been considered simply as plant traits without any considerations of effects of the environmental factors.

The transition from Eocene to Oligocene and its implications in the terrestrial realm has been a focal target for Cenozoic climate and environment research as it is widely considered the most dramatic climatic shift of the past 50 million years. Tibetan Plateau and proximal areas have been of utmost interest since the biogeographic relationships and understanding of the depositional environments in the region have remained unsettled during and after the Eocene-Oligocene transition (EOT). This study derives a first chronostratigraphic framework for Ulantatal, a fossiliferous area in Inner Mongolia, China. Based on paleomagnetic reversal stratigraphy and the constraints of faunal correlations, the time spanned in the strata is between ca. 35 and 27 Ma, thus exposing a long sedimentary succession ranging from the latest Eocene to late Oligocene. The lithological characteristics reveal these extensive fine-grained sediments mainly originate from eolian dust deposition, the onset of which is constrained at the latest Eocene (ca. 34.8 Ma). The presence of post "Mongolian Remodeling" fauna already in the late Eocene of Ulantatal demonstrates unequivocally that the major faunal turnover preceded the Eocene-Oligocene boundary, earlier to what has been recorded from other East Asian localities. The faunal composition predominated by rodents and lagomorphs remains strikingly stable across the Eocene-Oligocene boundary, suggesting the EOT related change in the animal communities was gradual or stepwise rather than abrupt. Moreover, the turnover into this environment dominated by small mammals can be linked with Eocene acidification of Asia, highlighting the dynamic responses of terrestrial systems to changing environment and climate associated with the EOT. (C) 2020 The Author(s). Published by Elsevier B.V.

Transpiration from the Amazon rainforest generates an essential water source at a global and local scale. However, changes in rainforest function with climate change can disrupt this process, causing significant reductions in precipitation across Amazonia, and potentially at a global scale. We report the only study of forest transpiration following a long-term (>10 year) experimental drought treatment in Amazonian forest. After 15 years of receiving half the normal rainfall, drought-related tree mortality caused total forest transpiration to decrease by 30%. However, the surviving droughted trees maintained or increased transpiration because of reduced competition for water and increased light availability, which is consistent with increased growth rates. Consequently, the amount of water supplied as rainfall reaching the soil and directly recycled as transpiration increased to 100%. This value was 25% greater than for adjacent nondroughted forest. If these drought conditions were accompanied by a modest increase in temperature (e.g., 1.5°C), water demand would exceed supply, making the forest more prone to increased tree mortality.

Phytoplankton cell death is an important process in marine food webs, but the viability of natural phytoplankton communities remains unexplored in many ecosystems. In this study, we measured the viability of natural pico- and nanophytoplankton communities in the central and southern parts of the Baltic Sea (55°21′ N, 17°06′ E–60°18′ N, 19°14′ E) during spring (4th–15th April 2016) to assess differences among phytoplankton groups and the potential relationship between cell death and temperature, and inorganic nutrient availability. Cell viability was determined by SYTOX Green cell staining and flow cytometry at a total of 27 stations representing differing hydrographic regimes. Three general groups of phytoplankton (picocyanobacteria, picoeukaryotes, and nanophytoplankton) were identified by cytometry using pigment fluorescence and light scatter characteristics. The picocyanobacteria and picoeukaryotes had significantly higher cell viability than the nanophytoplankton population at all depths throughout the study area. Viability correlated positively with the photosynthetic efficiency (Fv/Fm, maximum quantum yield of photosystem II) as measured on the total phytoplankton community. However, an anticipated correlation with dissolved organic carbon was not observed. We found that the abiotic factors suggested to affect phytoplankton viability in other marine ecosystems were not as important in the Baltic Sea, and other biotic processes, e.g. processes related to species succession could have a more pronounced role.