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Alpine ecosystems are highly sensitive to global warming, and treeline shifts are a dramatic consequence of climate change. The alpine treelines are rapidly shifting upwards globally. We aimed to better understand what are the global warming effects behind the rapid upward shift of the alpine treeline. Specifically, we ask how climate change affects seedling recruitment and growth sensitivity. We found that summer warming attributed to rapid seedling recruitment beyond the alpine treeline, whereas stem radial growth sensitivity did not change with warming. Thus, the rapid upward migration of the alpine treeline is mainly caused by summer warming, and tree growth at and beyond treeline are likely to increase. The attached is the observed data and codes for figures and results in tables.

Changes in precipitation, and in particular heavy precipitation extremes, have wide-ranging implications for society particularly in a changing climate. However, the impacts of these changes can be sensitive to how precipitation accumulates over time and, for example, large-scale disastrous flooding is often associated with extreme precipitation persisting over several days. Little is known about how the temporal sequencing of precipitation is expected to change under global warming. This lack of knowledge is alarming given the link between multi-day extreme precipitation and flooding catastrophes.We address this gap, and focus on a previously neglected aspect of precipitation, by studying changes in temporally clustered extreme precipitation (that is, extreme precipitation occurring on consecutive days), based on a unique quasi-global database of observational records (5989 high-quality stations with long-term daily precipitation during 1961-2010) and climate model simulations. We now share the calculated monthly/seasonal/annual indices of precipitation so that our results can be easily be verified with these opened observationaldata. The specific definition and calculation of these indices could be found in the paper. Researchers who use these data are required to cite our paper.

Drought alters allocation patterns of carbon (C) and nutrients in trees and eventually impairs tree functioning. Elevated soil nutrient availability might alter the response of trees to drought. We hypothesize that increased soil nutrient availability stimulates root metabolism and carbon allocation to belowground tissues under drought stress. To test this hypothesis, we subjected three-year-old Pinus sylvestris saplings in open-top cambers during two subsequent years to drought using three different water treatments (100%, 20% and 0% plant available water in the soil) and two soil nutrient regimes (ambient and nitrogen-phosphorus-potassium (N-P-K) fertilization corresponding to 5 g N/m2/yr) and released drought thereafter. We conducted a 15N and 13C labelling experiment during the peak of the first-year drought by injecting 15N labelled fertilizer in the soil and exposing the tree canopies to 13C labelled CO2. The abundance of the N and C isotopes in the roots, stem and needles was assessed during the following year. C uptake was slightly lower in drought stressed trees, and extreme drought inhibited largely the N uptake and transport. Carbon allocation to belowground tissues was decreased under drought, but not in combination with fertilization. Our results indicate a potential positive feedback loop, where fertilization improved the metabolism and functioning of the roots, stimulating C allocation to belowground tissues. This way, soil nutrients compensated for drought-induced loss of root functioning, mitigating drought stress of trees.