Global air temperature has increased and continues to increase, especially in high latitude and high altitude areas, which may affect plant resource physiology and thus plant growth and productivity. The resource remobilization efficiency of plants in response to global warming is, however, still poorly understood. We thus assessed end-season resource remobilization from leaves to woody tissues in deciduous Betula ermanii Cham. trees grown along an elevational gradient ranging from 1700 m to 2187 m a.s.l. on Changbai Mountain, northeastern China. We hypothesized that end-season resource remobilization efficiency from leaves to storage tissues increases with increasing elevation or decreasing temperature. To test this hypothesis, concentrations of non-structural carbohydrates (NSCs), nitrogen (N), phosphorus (P), and potassium (K) during peak shoot growth (July) were compared with those at the end of growing season (September on Changbai Mt.) for each tissue type. To avoid leaf phenological effects on parameters, fallen leaves were collected at the end-season. Except for July-shoot NSC and July-leaf K, tissue concentrations of NSC, N, P, and K did not decrease with increasing elevation for both July and September. We found that the end-season leaf-to-wood reallocation efficiency decreased with increasing elevation. This lower reallocation efficiency may result in resource limitation in high-elevation trees. Future warming may promote leaf-to-wood resource reallocation, leading to upward shift of forests to higher elevations. The NSC, N, P, and K accumulated in stems and roots but not in shoots, especially in trees grown close to or at their upper limit, indicating that stems and roots of deciduous trees are the most important storage tissues over winter. Our results contribute to better understand the resource-related ecophysiological mechanisms for treeline formation, and vice versa, to better predict forest dynamics at high elevations in response to global warming. Our study provides resource-related ecophysiological knowledge for developing management strategies for high elevation forests in a rapidly warming world.

Climate change and human activities are important factors driving changes in wetland ecosystems. It is therefore crucial to quantitatively characterize the relative importance of these stressors in wetlands. Previous such analyses have generally not distinguished between wetland types, or have focused on individual wetland types. In this study, three representative wetland areas of the upper, middle and lower reaches of the Heilongjiang River Basin (HRB) were selected as the study area. An object-based classification was used with Landsat TM data to extract the spatial distribution of wetland in 1990, 2000 and 2010. We then quantified the relative importance of climate change and human activities on the wetlands by using the R package “relaimpo” package. The results indicated that: (1) the effects of human activities on wetland changes were greater (contribution rate of 63.57%) than climate change in the HRB. Specifically, there were differences in the relative importance of climate change and human activities for wetlands in different regions. Wetlands of the upper reaches were more affected by climate change, while wetlands in the middle and lower reaches were more affected by human activities; (2) climate change had a greater impact (contribution rate of 65.72%) on low intensity wetland loss, while human activities had a greater impact on moderate and severe intensity wetland loss, with respective contribution rates of 57.22% and 70.35%; (3) climate change had a larger effect on the shrub and forested wetland changes, with respective contribution rates of 58.33% and 52.58%. However, human activities had a larger effect on herbaceous wetland changes, with a contribution rate of 72.28%. Our study provides a useful framework for wetland assessment and management, and could be a useful tool for developing wetland utilization and protection approaches, particularly in sensitive environments in mid- and high-latitude areas.

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Precipitation extremes occurring on consecutive days may be of crucial importance for the formation of extensive and long-lasting flooding. Changes in such consecutive extreme precipitation (CEP) events between different regions (i.e., dry and wet regions) still remain unclear in China, which may result in different impacts on human livelihoods and ecosystems. Here, the changes in CEP frequency between dry and wet regions of China were studied by utilizing an observation-based gridded precipitation dataset. We further determined the driving factors of the changes in CEP frequency by separating the effects of precipitation intensification and temporal clustering of daily extreme precipitation. Our results showed that the CEP frequency in dry regions increased faster (9.73%Ádecade −1 ) compared with wet regions (1.14%Ádecade −1 ) during the last $60 years. The increasing precipitation intensity primarily (over 90%) resulted in the increases of CEP events. However, changes in the temporal clustering of daily extreme precipitation can benefit the effects of the changes in precipitation intensity in dry regions but can reverse these effects in wet regions. In dry regions, the regression relationship of precipitation intensity and temperature (7.38%Á C −1 ) was stronger than that in wet regions (3.44%Á C −1 ), suggesting that the same magnitude of warming would cause greater precipitation intensity and consequently cause more frequent CEP events in dry regions. Therefore, as the intensification of precipitation and the increasing temporal clustering of daily extreme precipitation, more CEP events may increase the flooding risk in dry regions over China with a stronger warming signal.climate warming, consecutive extreme precipitation, dry and wet regions, precipitation intensity, temporal clustering | INTRODUCTIONGlobal climate warming is expected to enhance the hydrological cycle (Allen and Ingram, 2002;Durack et al., 2012;Zahn and Allan, 2013), accompanying with an increase of the frequency and magnitude of extreme precipitation events (Allan and Soden, 2008;Papalexiou and Montanari, 2019). Short-duration extreme precipitation events often lead to sudden and small-scale natural hazards, such as flash flooding (Norbiato et al., 2008). However, if daily extreme precipitation occurs consecutively, with great potential to cause large-scale and long-lasting

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