Statement from Ukrainian leader of the Ultra-Nationalist group Bratstvo on Kazakhstan — says Ukrainian militias will penetrate Kazakhstan and assist the armed gangs that have been wreaking havoc on the population for the last few days.l distribution and diversity of mangrove forests is greatly influenced by the frequency and intensity of winter air temperature extremes. However, our understanding of how different mangrove species respond to winter temperature extremes has been lacking because extreme freezing and chilling events are, by definition, relatively uncommon and also difficult to replicate experimentally. In this study, we investigated species-specific variation in mangrove responses to winter temperature extremes in China. In 10 sites that span a latitudinal gradient, we quantified species-specific damage and recovery following a chilling event, for mangrove species within and outside of their natural range (i.e., native and non-native species, respectively). To characterize plant stress, we measured tree defoliation and chlorophyll fluorescence approximately one month following the chilling event. To quantify recovery, we measured chlorophyll fluorescence approximately nine months after the chilling event. Our results show high variation in the geographic- and species-specific responses of mangroves to winter temperature extremes. While many species were sensitive to the chilling temperatures (e.g., Bruguiera sexangula and species in the Sonneratia and Rhizophora genera), the temperatures during this event were not cold enough to affect certain species (e.g., Kandelia obovata, Aegiceras corniculatum, Avicennia marina, and Bruguiera gymnorrhiza). As expected, non-native species were less tolerant of winter temperature extremes than native species. Interestingly, tidal inundation modulated the effects of chilling. In comparison with other temperature-controlled mangrove range limits across the world, the mangrove range limit in China is unique due to the combination of the following three factors: (1) Mangrove species diversity is comparatively high; (2) winter air temperature extremes, rather than means, are particularly intense and play an important ecological role; and (3) due to afforestation and restoration efforts, several species of non-native mangroves have been introduced beyond their natural range limits. Hence, from a global perspective, mangroves in China provide valuable opportunities to advance understanding of the effects of freezing and chilling temperatures on mangroves. Within the context of climate change, our findings provide a foundation for better understanding and preparing for mangrove species-specific responses to future changes in the duration and intensity of winter temperature extremes.
Introduction
Within the context of climate change, ecologists and natural resource managers are increasingly challenged to better understand and prepare for the ecological implications of changes in the duration and intensity of climate extremes (Jentsch et al. 2007, Glick et al. 2011, Smith 2011, Hoover et al. 2014). Near the transition between tropical and temperate climates, the frequency and intensity of winter air temperature extremes (i.e., freezing and chilling air temperatures) are particularly important because they greatly influence species' distributions and the structure and functioning of ecosystems (Woodward 1987, Boucek et al. 2016, Osland et al. 2017a). Tropical and
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ΑπάντησηΔιαγραφή