Search

The southern part of northeast China has experienced a marked warming and drying climate. We provide dendrochronological evidence for atmospheric CO fertilization and the impacts of warming on Chinese pine ( Pinus tabulaeformis) growth. The results of this study show that increased temperature has a negative effect on pine growth during a major part of the growing season and a weakly positive effects on growth during the remaining portion of the year. The monthly temperatures explain ca. 20 % of the total variance in the annual radial growth of Chinese pine from 1901 to 2009. An increase of approximately 3-5 °C is the maximum that Chinese pine can tolerate in this region with an annual rainfall of 500-700 mm. Our results suggest a that there is a proportional response to warming only up to a maximum of 1 °C warming, and indicate the complexitiesof succession in forest ecosystems in terms of adaptation and evolution in local pine populations under a rapid warming condition. In addition, increasing atmospheric CO concentrations have a positive effect on tree growth. This effect can be detected with conventional dendrochronological methods. [ABSTRACT FROM AUTHOR]

The frequency, intensity, and duration of extreme droughts, with devastating impacts on tree growth and survival, have increased with climate change over the past decades. Assessing growth resistance and resilience to drought is a crucial prerequisite for understanding the responses of forest functioning to drought events. However, the responses of growth resistance and resilience to extreme droughts with different durations across different climatic zones remain unclear. Here, we investigated the spatiotemporal patterns in growth resistance and resilience in response to extreme droughts with different durations during 1901–2015, relying on tree‐ring chronologies from 2389 forest stands over the mid‐ and high‐latitudinal Northern Hemisphere, species‐specific plant functional traits, and diverse climatic factors. The findings revealed that growth resistance and resilience under 1‐year droughts were higher in humid regions than in arid regions. Significant higher growth resistance was observed under 2‐year droughts than under 1‐year droughts in both arid and humid regions, while growth resilience did not show a significant difference. Temporally, tree growth became less resistant and resilient to 1‐year droughts in 1980–2015 than in 1901–1979 in both arid and humid regions. As drought duration lengthened, the predominant impacts of climatic factors on growth resistance and resilience weakened and instead foliar economic traits, plant hydraulic traits, and soil properties became much more important in both climatic regions; in addition, such trends were also observed temporally. Finally, we found that most of the Earth system models (ESMs) used in this study overestimated growth resistance and underestimated growth resilience under both 1‐year and 2‐year droughts. A comprehensive ecophysiological understanding of tree growth responses to longer and intensified drought events is urgently needed, and a specific emphasis should be placed on improving the performance of ESMs. [ABSTRACT FROM AUTHOR]

ABSTRACT Possible future climate change can be projected by general circulation models ( GCMs), and the future geographic distribution of global climate zones can be projected based on these GCM simulations. In this study, the performance of 33 GCMs in simulating the distribution of global climate zones was evaluated using Kappa values. The results show that certain models are more skillful than other models in simulating the present distribution of global climate zones. The ensemble mean of all the GCMs showed worse performance than some individual models in simulating the present distribution of climate zones. The ensemble mean based on the three GCMs that showed superior performance achieved the optimum results in simulating the future distribution of climate zones. Based on the simulations of the ensemble mean of these three GCMs, the distributions of global climate zones in the future were projected for three scenarios (Representative Concentration Pathways, RCP) ( RCP2.6, RCP4.5, and RCP8.5). The climate types in the temperate zone were susceptible to climate changes under the three scenarios. The shift in the distribution of climate zones was mainly caused by the joint variations of temperature and precipitation among different climate zones. [ABSTRACT FROM AUTHOR]

A method was developed, based on Bayesian model averaging (BMA), to reconstruct regional mean temperature. Different from the arithmetic mean, which gives equal weight to each chronology, BMA weights the chronologies according to their contributions to the actual temperature variances. Thus, BMA holds advantages in integrating chronologies to reconstruct the regional mean temperature. The regional mean temperature for the Yunnan-Guizhou Plateau was reconstructed for the past four centuries (1628-2005) using BMA, which performed better than the simple arithmetic mean. The reconstruction explained 41.33% of total observed temperature variances during the period of 1961-2005. The warmest decade was found to be 1840-50 and the coldest 1810-20 prior to the instrumental period. The reconstructed temperature showed a high correlation ( r > 0.7, p < 0.001) with gridded observed temperatures in most grid cells of the Yunnan-Guizhou Plateau, suggesting that the regional temperature changes were captured well by the reconstruction. [ABSTRACT FROM AUTHOR]

Abstract Forests are sensitive to climate change at high altitude and high latitude. Dahurian larch (Larix gmelinii Rupr.) has experienced an unprecedented forest retreat northward during the last century. Whether the response of growth to climate has dissimilar patterns at different altitudes, and what the "altitudinal trends" of forest development will be in the future, remains unclear. We dendroclimatically investigated the impacts of climate change on the growth of larch forests along an altitudinal gradient. In total, 721 trees from 25 forest stands, representing an altitudinal range from 400 to 950 m a.s.l. in the Great Xing'an Mountains, northeast China, were sampled and used to develop tree-ring width chronologies. The results suggest that warming caused a decline in larch growth at low altitude, while tree growth increased at high altitude. The growth–climate relationships indicate that October–February temperatures were positively correlated with larch growth at low- and high-altitude sites, but negatively correlated at medium-altitude sites (ca. 600–700 m a.s.l.). April–May (early spring) temperatures and October–January precipitation had positive effects on growth in general (ca. 75% of all sites). The effects of summer temperature/precipitation on larch growth at high-altitude sites were opposite to that at low-altitude sites. This change of response from significantly positive/negative correlation to significantly negative/positive correlation occurred gradually along the altitudinal gradient. The relationships varied significantly with altitude both in the case of temperature (R 2 = 0.425, P < 0.001) and precipitation (R 2 = 0.613, P < 0.001). The shift in response of larch forest to changes in summer temperature and precipitation occurred in the areas with a mean annual temperature of ca. −4 °C and ca. −5 °C, respectively; larch growth at temperatures lower or higher than these thresholds was limited by temperature and precipitation, respectively. Graphical abstract Unlabelled Image Highlights • The larch growth decline at low altitude and increase at high altitude. • Effects of summer temperature/precipitation on growth at high altitude was opposite to that at low altitude. • The response shift threshold of larch to temperature and precipitation of ca. –4 °C and ca. –5 °C, respectively. • The larch radial growth changed from the temperature limit at high altitude to the drought limit at low altitude. [ABSTRACT FROM AUTHOR]

ABSTRACT Vegetation types are generally classified based only on remote sensing vegetation data, and yet they cannot reflect their connection with climate. Climatic vegetation types reflect the regional vegetation characteristics in terms of climate. The distribution of global climatic vegetation types were identified by K-means method based on vegetation and climate data. Fourteen climatic vegetation types were classified based on vegetation and climate data. Every type had distinct climate and vegetation characteristics. The regions with similar normalized difference vegetation index ( NDVI) values but with different climate values such as tropical desert and temperate desert could be distinguished. Our new updated climatic vegetation types agreed 'fair' with Koeppen climate types and climate type of Zhang and Yan while agreed 'good' with vegetation types when checked with Kappa test. [ABSTRACT FROM AUTHOR]

The Changbaishan volcano, located in northeast China, produced a large amount of charcoal during the "Millennium Eruption" (c. 946 CE). In this paper, we report a high-resolution date for the eruption using multiple methods applied to the fossil charcoal and living trees, including wood anatomy, radiocarbon dating and tree-ring cross-dating. In addition, we develop a new floating annual-resolution tree-ring chronology spanning nearly 200 years that provides information about paleoclimate conditions. In our study, we identified 60 samples of charcoal as Larix olgensis based on anatomical characteristics and geographical location. Using these materials, we dated the eruption to the winter of 946 CE based on a combination of radiocarbon dating, traditional dendrochronological cross-dating and cambial cell growth status. This allowed us to develop an L. olgensis tree-ring width chronology covering 764–946 CE and 1715–2016 CE, with significant sensitivities to April–September temperature (p < 0.05). The tree-ring data have great potential to indicate extreme climate events; for example, we identify an extremely cold year in 903 CE. Such marker years can improve the reliability and accuracy of tree-ring data. Our study provides direct and precise tree-ring evidence for volcanic eruptions and anomalous climate years in the Middle Ages. [Display omitted] • Cambial activity enables us to date the Millennium Eruption to winter 946 CE. • The first chronology reaching the Middle Ages so far developed in northeastern China. • The chronology was assembled from volcanic charcoal and living larch. • This chronology is sensitive to temperature. [ABSTRACT FROM AUTHOR]