[Radial growth response of Populus euphratica to climate change in the Cele desert oasis ecotone, China]. / ç­–å‹’æ²™æ¼ ç»¿æ´²è¿‡æ¸¡å¸¦èƒ¡æ¨å¾„å‘ç”Ÿé•¿å¯¹æ°”å€™å˜åŒ–çš„å“åº”.

Populus euphratica is an important tree species in the arid regions of Northwest China, which is sensitive to climate changes. Climate of the Northwest China is changing to be "warm and humid", but how it would affect the regional forest growth is not clear. In this study, the radial growth response of P. euphratica to major climatic factors and their temporal changes during 1984-2021 were analyzed by using dendrochronology method in the desert oasis ecotone of Cele in the southern Tarim basin. The results showed that tree-ring width index of P. euphratica had a significant negative correlation with temperature in September of the previous year, and in February and May of current year, had significant positive correlation with precipitation in September of previous year and March and May of current year, and had significant positive correlations with SPEI in February and May of current year. The relationships between tree-ring width index and combined month climatic factors were more obvious. The results of moving correlation analysis showed that the correlation between tree-ring width index and temperature in the growing season tended to be strengthened in recent years, while the correlation between tree-ring width index and precipitation, SPEI tended to be declined or remain stable. The variations of the relationships between tree-ring width index and combined month climatic factors were more obvious compared that with single month. Current regional climate is conducive to the growth and development, as well as the improvement of ecological shelter function of P. euphratica forest in the desert oasis ecotone of Cele.

[Spatial-temporal variation of vegetation water use efficiency and its relationship with climate factors over the Qinghai-Tibet Plateau, China]. / é’è—é«˜åŽŸæ¤è¢«æ°´åˆ†åˆ©ç”¨æ•ˆçŽ‡æ—¶ç©ºå˜åŒ–åŠä¸Žæ°”å€™å› å­çš„å ³ç³».

Water use efficiency (WUE) is an effective index to study the coupling of land carbon and water cycle. The Qinghai-Tibet Plateau is the most important ecological security barrier in China. Understanding the characteristics and mechanism of WUE is important for the carbon cycle and water resources rational utilization in the plateau. Based on MODIS data of gross primary productivity (GPP) and evapotranspiration (ET), we analyzed the spatial-temporal variations of WUE over the Qinghai-Tibet Plateau and the effects of climate factors. The results showed that WUE in the Qinghai-Tibet Plateau had an upward trend under the combined action of GPP and ET during 2001-2020. The southeast and northeast of the Plateau had the highest WUE value, while the central part had the lowest WUE value. WUE of grassland, marsh and alpine vegetation showed an increasing trend, while that of shrub land, broadleaved forest and coniferous forest showed a decreasing trend. There was a significant positive correlation between WUE and annual air temperature, and the sensitivity increased with the increases of air temperature. The relationship between WUE and annual precipitation was non-linear. When precipitation was less than 700 mm, the sensitivity of WUE to precipitation decreased with the increases of precipitation. When precipitation was more than 700 mm, the sensitivity of precipitation increased with the increases of precipitation. However, WUE was negatively correlated with precipitation in more than 75% of regions, and was affected by precipitation in a larger area. In the future, warm and humid climate would lead to a decrease in WUE.

[Research advances in shrub dendroecology]. / çŒæœ¨å¹´è½®ç”Ÿæ€å­¦ç ”ç©¶è¿›å±•.

The ecological value of shrub-ring data has received more and more attention. The tree-ring data of shrub species have been increasingly used to reveal growth dynamics of regional shrub vegetation and its sensitivity to climate change. Up to now, nearly 70 species of shrubs have been used in the studies of shrub dendrochronology, which considerably broadened the traditional tree-ring research network, enriched the research scope and object of dendrochronology, and certainly with great significance in revealing the characteristics of regional climate fluctuation and annual dynamics of structure, function and service for shrubland ecosystems. In this study, we systematically collected dendrochronological studies based on shrub species during the 1996-2021, and reviewed research progress in four main subfields (physiology, climatology, ecology and hydrology) in dendrochronology for shrub species. The characteristics of shrub growth and xylem anatomy under different environmental stresses were expounded. The main limiting factors for shrub growth in different climatic conditions and the history of regional climate fluctuations based on shrub-ring data were revealed. The individual growth and population dynamics of shrub species driven by climate and the changes in ecosystems caused by non-climatic factors were assessed, and the reconstructions of regional hydrological histories were compiled using tree-ring data of shrub species. Under the context of global warming, dendrochronological studies of shrub species in China should pay more attention to the responses of shrub species radial growth to drought stress under different moisture conditions in the semi-arid and arid regions and the transforming feature of distribution pattern and climate response sensitivity for shrub species under the background of climate change.

[Response differences of radial growth of Larix gmelinii and Pinus sylvestris var. mongolica to climate change in Daxing'an Mountains, Northeast China]. / å¤§å ´å®‰å²­å ´å®‰è½å¶æ¾å’Œæ¨Ÿå­æ¾å¾„å‘ç”Ÿé•¿å¯¹æ°”å€™å˜åŒ–çš„å“åº”å·®å¼‚.

Daxing'an Mountains is one of regions in China with the most significant climate change. Larix gmelinii and Pinus sylvestris var. mongolica are the most important species in this area. The study of their radial growth response to climate change would provide a scientific basis for predicting the dynamics of boreal forests under climate change. A total of 451 tree-ring cores of L. gmelinii and P. sylvestris var. mongolica were collected from six sites in the Daxing'an region, and 12 standard chronologies were established. We compared the tree growth trend since 1900, and analyzed their response to the climate factor in each site using Pearson correlation analysis. Effects of temperature and precipitation on the annual radial growth of L. gmelinii and P. sylvestris var. mongolica were investigated by linear mixed models. The time stability of the relationship between two species growth-climate was compared by moving correlation. The results showed that the radial growth of L. gmelinii was negatively correlated with mean temperature in March and positively correlated with precipitation in the previous winter and July of current year. The radial growth of P. sylvestris var. mongolica was positively correlated with temperature in August and precipitation in the growing season (from May to September) of current year. Snow in winter played an important role in promoting the radial growth of L. gmelinii, whereas precipitation in summer limited the radial growth of P. sylvestris var. mongolica. The responses of L. gmelinii and P. sylvestris var. mongolica to climate change were significantly different, which affected tree growth, species composition, and spatial distribution in the boreal forests.

[Comparing the responses of radial growth between Quercus mongolica and Phellodendron amurense to climate change in Xiaoxing'an Mountains, China.] / å°å ´å®‰å²­è’™å¤æ Žå’Œé»„è èå¾„å‘ç”Ÿé•¿å¯¹æ°”å€™å˜åŒ–çš„å“åº”æ¯”è¾ƒ.

Quercus mongolica and Phellodendron amurense are two important broad-leaved species in temperate forests of Northeast China. It is critical to explore their responses to climate change for supporting management, protection, and restoration of the broad-leaved forest in Northeast China under the future climate change scenario. Three sampling sites along a longitude gradient, Heilun, Tieli and Yichun, were set up in the Xiaoxing'an Mountains. Dendrochronological methods were used to establish standard chronologies for Q. mongolica and P. amurense. Correlation analyses were conducted between these chronologies and local climatic factors to establish the spatial and temporal variations in growth-climate relationship of Q. mongolica and P. amurense. The results showed that the radial growth of P. amurense was sensitive to temperature, while that of Q. mongolica was limi-ted by both temperature and precipitation. The temperature sensitivities of these two species were different. High spring temperature inhibited the radial growth of Q. mongolica, but promoted that of P. amurense. The limiting effect of high maximum temperature in summer on radial growth of Q. mongolica was significantly higher than that of P. amurense. With the increases of longitude (water availability), the correlation coefficients between radial growth of Q. mongolica and precipitation gradually weakened, while P. amurense didn't change. The physiological characteristics of those tree species was the key factors affecting their growth-climate relationship. With the significant warming since the 1976, the growth trend of P. amurense increased, whilst that of Q. mongolica decreased. Deteriorated drought stress caused by warming and difference in the species' ability to cope with water deficits might be the main reasons for different responses of two species, and for the divergence phenomenon occurring for Q. mongolica. If warming continues or worsens in the future, the growth of Q. mongolica may decline due to the intensified drought stress, while that of P. amurense may be less affected or be slightly enhanced.

[Ecological and physiological mechanisms of growth decline of Robinia pseudoacacia plantations in the Loess Plateau of China: A review.] / 黄土高原人工刺槐林生长衰退的生态生理机制.

Robinia pseudoacacia has been widely planted in the Loess Plateau of China for soil and water conservation. The growth decline of R. pseudoacacia plantations has become a recently emerging challenge for the revegetation program and sustainable forest management in this region. As to the scientific definition, identified criteria and quantitative indices have not yet been comprehensively quantified, our current understanding of the ecological and physiological mechanisms for growth decline of R. pseudoacacia plantations is limited. The knowledge could enrich the basic theories of vegetation restoration and benefit the sustainable development of the afforestation project in the Loess Plateau. Through the comprehensive compilation of literatures on forest decline and tree mortality in the Loess Plateau and other regions across the world, this review summarized the mechanisms and recent research progress on growth decline for R. pseudoacacia plantations in the Loess Plateau, primarily demonstrated from ecological (e.g., climatic change, soil desiccation, the imbalance of community structure and the misconduct of forest management) and physiological (e.g., hydraulic failure, carbon starvation, genetic and molecular regulation) perspectives. Finally, we highlighted the research gap with regard to growth decline of R. pseudoacacia plantations in the Loess Plateau.

[Seagrass ecosystems: contributions to and mechanisms of carbon sequestration].

The ocean's vegetated habitats, in particular seagrasses, mangroves and salt marshes, each capture and store a comparable amount of carbon per year, forming the Earth's blue carbon sinks, the most intense carbon sinks on the planet. Seagrass meadows, characterized by high primary productivity, efficient water column filtration and sediment stability, have a pronounced capacity for carbon sequestration. This is enhanced by low decomposition rates in anaerobic seagrass sediments. The carbon captured by seagrass meadows contributes significantly to the total blue carbon. At a global scale, seagrass ecosystems are carbon sink hot spots and have profound influences on the global carbon cycle. This importance combined with the many other functions of seagrass meadows places them among the most valuable ecosystems in the world. Unfortunately, seagrasses are declining globally at an alarming rate owing to anthropogenic disturbances and climate change, making them also among the most threatened ecosystems on the Earth. The role of coastal systems in carbon sequestration has received far too little attention and thus there are still many uncertainties in evaluating carbon sequestration of global seagrass meadows accurately. To better assess the carbon sequestration of global seagrass ecosystems, a number of scientific issues should be considered with high priorities: 1) more accurate measurements of seagrass coverage at national and global levels; 2) more comprehensive research into species- and location-specific carbon sequestration efficiencies; 3) in-depth exploration of the effects of human disturbance and global climate change on carbon capture and storage by seagrass ecosystems.

The potential influence of seasonal climate variables on the net primary production of forests in eastern China.

Knowledge of the effects of climate factors on net primary production (NPP) is pivotal to understanding ecosystem processes in the terrestrial carbon cycle. Our goal was to evaluate four different categories of effects (physical, climatic, NDVI, and all effects[global]) as predictors of forest NPP in eastern China. We developed regression models with data from 221 NPP in eastern China and identified the best model with each of the four categories of effects. Models explained a large part of the variability in NPP, ranging from 46.8% in global model to 36.5% in NDVI model. In the most supported global model, winter temperature and sunshine duration negatively affected NPP, while winter precipitation positively affected NPP. Thus, winter climate conditions play an important role in modulating forest NPP of eastern China. Spring temperature had a positive affect on NPP, which was likely because a favorable warm climate in the early growing season promotes forest growth. Forest NPP was also negatively affected by summer and autumn temperatures, possibly because these are related to temperature induced drought stress. In the NDVI model, forest NPP was affected by NDVI in spring (positive), summer (negative) and winter (negative) seasons. Our study provides insight into seasonal effects of climate and NPP of forest in China, as well as useful knowledge for the development of climate-vegetation models.