Response to climate changes in radial growth of Picea crassifolia in the Qilian mountains of northwestern China

In order to investigate the response to climate changes in radial growth of Picea crassifolia at the lower tree line in the middle Qilian mountains in northwestern China, relationships of standardized chronologies of annual ring, earlywood and latewood widths with mean monthly temperature and total monthly precipitation were analyzed by ways of correlation and pointer year analyses. The results show that annual ring, earlywood and latewood widths are significantly negatively correlated with mean monthly temperature in June and July. Annual ring and earlywood widths are significantly and positively correlated with total monthly precipitation in March, May and June and negatively correlated with total monthly precipitation in September. Latewood width is less sensitive to climate changes than the width of earlywood and insignificantly sensitive to precipitation. The results of pointer year analysis revealed that when summer temperatures are higher than the mean summer temperature synchronization and the summer precipitation lower than mean summer precipitation synchronization, narrow annual rings are formed. Wide annual rings are formed when summer temperatures are lower than the mean summer temperature synchronization and summer precipitation higher than mean summer precipitation synchronization. The results indicate that more precipitation in the spring and summer is helpful for radial growth while warmer summer restricts radial growth of P. crassifolia at the lower tree line in the middle Qilian mountains.

Responsible Reaction To Climate Change

China calls for turning UNFCCC provisions into concrete actions Never before has climate change been as prominent on the public agenda as it is today.Its rele- vance was highlighted once again when more than 10,000 delegates from over 180 countries flocked to Bali early this month to discuss the topic.Environment officials as well as representatives from intergovernmental and nongovernmental organizations gath- ered on the Indonesian island on December 3-14 for the UN Climate Change Conference.

The spatiotemporal responses of Populus euphratica to global warming in Chinese oases between 1960 and 2015

Daily average temperature data from 48 meteorological stations in Chinese oases that are within the distribution area of Populus euphratica were analyzed to determine the spatiotemporal responses of this tree to climate change. Specifically, the start and end date as well as the number of days that comprised the growing season were analyzed with a multi-year trend line and using the Mann-Kendall mutation test, inverse distance weighted interpolation(IDW) in the software Arc GIS, a Morlet wavelet power spectrum, and correlation analysis. The results of this study show that, over the last 56 years, the start date of the P. euphratica growing season has advanced, while the end date has been postponed, and the number of days that comprise the growing season have gradually increased. The changing trend rates recovered in this analysis for these three time slices are –1.34 d/10 a, 1.33 d/10 a, and 2.66 d/10 a(α ≥ 0.001), respectively. Data show that while spatial disparity is extremely significant, it is nevertheless the case that along a southwest-to-northeast transect of Chinese oases, the later the start date of the P. euphratica season, the sooner the end data and the shorter the growing season. Mutations points in start and end date, as well as for the growing season overall were observed in 2001, 1989, and 1996, respectively, and the data presented in this paper show that, in particular, the date of this end of this period is most sensitive to climate warming. Growing season cycles for P. euphratica are between 3.56 years and 7.14 years, consistent with the periodicity of El Ni?o events, while a start date cycle between 3.56 years and 4.28 years is consistent with atmospheric circulation cyclicity. The causal analysis presented in this paper shows that the Asian polar vortex area index(APVAI), the Qinghai-Tibet Plateau index(TPI), the westerly circulation index(WCI), and carbon dioxide emissions(CDE) are the main factors influencing spatiotemporal changes in the growth of P. euphratica, the effect of latitude during the growing season is more significant than altitude, and the start date of the growing season is more significantly influenced by these factors than end date. In addition, data show that the start date, end date, and length of the growing season are all significantly correlated with their average corresponding monthly temperature(corre-lation coefficients are –0.875, 0.770, and 0.897; α≥0.001). Thus, if the average temperature in March increases by 1℃, the start date of the growing season will advance by 2.21 days, while if the average temperature in October increases by the same margin then the seasonal end date will be delayed by 2.76 days. Similarly, if the average temperature between March and October increases by 1℃, the growing season will be extended by 7.78 days. The results of this study corroborate the fact that changes in the P. euphratica growing are sensitive to regional warming and are thus of considerable theoretical significance to our understanding of the responses of Chinese vegetation to climate change as well as to ecological restoration.

Autumn NDVI contributes more and more to vegetation improvement in the growing season across the Tibetan Platea

Detecting changes in vegetation,distinguishing the persistence of changes,and seeking their causes during multiple periods are important to gaining a deeper understanding of vegetation dynamics.Using the Global Inventory Modeling and Mapping Studies Normalized Difference Vegetation Index(NDVI)version NDVI_(3g) dataset in the Tibetan Plateau,the trends in the seasonal components of NDVI and their linkage with climatic factors were analyzed over 14 asymptotic periods of 18–31 years since 1982.Dynamic trends in vegetation experienced an obvious increase at regional scale,but the increases of vegetation activity mostly tended to stall or slow down as the studied time period was extended.At pixel scale,areas with significant browning significantly expanded over 14 periods for all seasons,but for significant greening significantly increased only in autumn.The changes of vegetation activity in spring were the most drastic among three seasons.Increased increments of NDVI in summer,spring,and autumn took turns being the main reason for the enhanced vegetation activity in the growing season in the nested 14 periods.Vegetation activity was mainly regulated by a thermal factor,and the dominant climatic drivers of vegetation growth varied across different seasons and regions.We speculate that the increase of NDVI will continue but the increments will decline in all seasons except autumn.

Exploring the effect of Arctic perennial sea ice on modulation of local air temperature

Sea ice cover plays an important role in modulating local temperature through heat and moisture fuxes.The infuence of thin ice lead and polynya has been wellinvestigated,however,the effect of perennial ice(also called muliyear ice,MYI)has not.This study is motivated by it and investigated a hypothesis that changes in MYI concentration in winter triggers changes in short-term local 2-m air temperature.The hypothesis was tested using time series analysis of the two parameters and correlation between them.Data from the winters of 2004-2009 were used for the examination at three spatial scales.The hypothesis is found to be potentially accepted when MYI exists in a consolidated ice regime with negligible thin ice or open water in the surroundings,and the air temperature is low enough.Conditions for the acceptance of the hypothesis were quantitatively identified.The qualifications entail that the ice cell must experience daily change of MYI concentration meanwhile satisfy the criteria of total ice concentration(TIC),young ice concentration(YIC)and air temperature(Tar)in the surrounding area,which are TIC>88.3%,YIC<9.5%and T_(air)<-19.0℃.Inverse relationships between changes in MYI concentration and the corresponding changes in air temperature were developed retroactively using data that satisfied the acceptance conditions.The relationships varied with years,depending on ice conditions such as ice type distributions and snow cover.This study offers a first attempt to assess the effect of MYI on the same-day local surface air temperature using satelite observations,and provides evidence of this effect under quantitatively quanlifying conditions.