Relationships between tree-ring cell features of Pinus koraiensis and climate factors in the Changbai Mountains,Northeastern China

Anatomical characteristics have been proven useful for extracting climatic signals. To examine the climatic signals recorded by tree-ring cell features in the Changbai Mountains, we measured cell number and cell lumen diameter, in addition to ring widths, of Korean pine （Pinus koraiensis） tree rings at sites of varied elevation, and we developed chronologies of cell number （CN）, mean lumen diameter （MLD）, maximum lumen diameter （MAXLD） and tree-ring width （TRW）. The chronologies were correlated with climatic factors monthly mean tem- perature and the sum of precipitation. As shown by our analysis, the cell parameter chronologies were suitable for dendroclimatology studies. CN and TRW shared relatively similar climatic signals which differed from MLD and MAXLD, and growth-climate relationships were elevation- dependent, as shown by the following findings： （1） at each elevation, MLD and MAXLD recorded different monthly climatic signals from those recorded by TRW for the same climatic factors; and （2） MLD and MAXLD recorded cli- matic factors that were absent middle elevations. Cell lumen effective archive for improving for this study area. from TRW at lower and diameter proved to be an the climate reconstruction

High-resolution reconstruction of April-September precipitation and major extreme droughts in China over the past∼530 years

Extreme drought events have increased,causing serious losses and damage to the social economy under current warming conditions.However,short-term meteorological data limit our understanding and projection of these extremes.With the accumulation of proxy data,especially tree-ring data,large-scale precipitation field reconstruction has provided opportunities to explore underlying mechanisms further.Using point-by-point regression,we reconstructed the April-September precipitation field in China for the past~530 years on the basis of 590 proxy records,including 470 tree-ring width chronologies and 120 drought/flood indices.Our regression models explained average 50%of the variance in precipitation.In the statistical test on calibration and verification,our models passed the significance level that assured reconstruction quality.The reconstruction data performed well,showing consistency and better quality than previously reported reconstructions.The first three leading modes of variability in the reconstruction revealed the main distribution modes of precipitation over China.Wet/drought and extremely wet/drought years accounted for 12.81%/10.92%(68 years/58 years)and 1.69%/3.20%(9 years/17 years)of the past~530 years in China,respectively.Major extreme drought events can be identified explicitly in our reconstruction.The detailed features of the Chongzhen Great Drought(1637-1643),the Wanli Great Drought(1585-1590),and the Ding-Wu Great Famine(1874-1879),indicated the existence of potentially different underlying mechanisms that need further exploration.Although further improvements can be made for remote uninhabited areas and large deserts,our gridded reconstruction of April-September precipitation in China over the past~530 years can provide a solid database for studies on the attribution of climate change and the mechanism of extreme drought events.

Spatially explicit reconstruction of cropland cover in Europe from AD 1800 to 2000

One of the challenges in global change research is the significant uncertainty in global historical land use and land cover(LUCC)datasets,which are widely used as foundational data.In addition to the regional cropland area reconstructions,improving the grid allocation method is another feasible way to raise the reliability of historical LUCC data.In this study,an integrated reconstruction of the national cropland areas over the past 200 years was developed for 36 European countries.After that,the allocation algorithm was built using physiogeographic variables and historical city sites for accounting for land suitability and cultivation preferences,respectively.Finally,cropland data in Europe with a spatial resolution of 5′×5′at five time sections from AD 1800 to 2000 were generated using the optimal allocation algorithm in accordance with the stages of the regional history.The results were as follows:(1)The dominant factors governing the distribution of croplands in Europe vary at different agricultural stages,but the results can be merged together.Land suitability was more optimal for allocation during the modern agricultural stage(AD 1950 and 2000);the priority index combined with land suitability and cultivation preference was more reasonable for allocation during the traditional agricultural stage(AD 1800).The average of the allocations by priority index and the land suitability could be adopted as the allocation results during the transitional stage(AD 1850 and 1900)because the grids for absolute differences within±10 and±20 percentage points between the results obtained from the above two allocations were above 80% and 95%,respectively,which means the two allocation results could be merged.(2)Over the past 200 years,the total cropland area in Europe first increased to a peak in AD 1900 and then decreased.Spatially,the centre of the higher cropland fraction shifted from the western part of Europe in AD 1800 to the eastern part of the continent after AD 1950.(3)Both the cropland area and the spatial distribution in this study are more reasonable than the global dataset HYDE3.2.

Methodology for credibility assessment of historical global LUCC datasets

Land use-induced land cover change(LUCC)is an important anthropogenic driving force of global change that has influenced,and is still influencing,many aspects of regional and global environments.Accurate historical global land use/cover datasets are essential for a better understanding of the impacts of LUCC on global change.However,there are not only evident inconsistencies in current historical global land use/cover datasets,but inaccuracies in the data in these global dataset revealed by historical record-based reconstructed regional data throughout the world.A focus in historical LUCC and global change research relates to how the accuracy of historical global land cover datasets can be improved.A methodology for assessing the credibility of existing historical global land cover datasets that addresses temporal as well as spatial changes in the amount and distribution of land cover is therefore needed.Theoretically,the credibility of a global land cover dataset could be assessed by comparing similarities or differences in the data according to actual land cover data(the"true value").However,it is extremely difficult to obtain historical evidence for assessing the credibility of historical global land cover datasets,which cannot be verified through field sampling like contemporary global land cover datasets.We proposed a methodological framework for assessing the credibility of global land cover datasets.Considering the types and characteristics of the available evidence used for assessments,we outlined four methodological approaches:(1)accuracy assessment based on regional quantitative reconstructed land cover data,(2)rationality assessment based on regional historical facts,(3)rationality assessment based on expertise,and(4)likelihood assessment based on the consistency of multiple datasets.These methods were illustrated through five case studies of credibility assessments of historical cropland cover data.This framework can also be applied in assessments of other land cover types,such as forest and grassland.

Plasma-enabled healing of graphene nano-platelets layer

Graphene platelet networks (GPNs) were deposited onto silicon substrates by means of anodic arc discharge ignited between two graphite electrodes.Substrate temperature and pressure of helium atmosphere were optimized for the production of the carbon nanomaterials.The samples were modified or destroyed with different methods to mimic typical environments responsible of severe surface degradation.The emulated conditions were performed by four surface treatments,namely thermal oxidation,substrate overheating,exposition to glow discharge,and metal coating due to arc plasma.In the next step,the samples were regenerated on the same substrates with identical deposition technique.Damaging and re-growth of GPN samples were systematically characterized by scanning electron microscopy and Raman spectroscopy.The full regeneration of the structural and morphological properties of the samples has proven that this healing method by arc plasma is adequate for restoring the functionality of2D nanostructures exposed to harsh environments.

Rising grain prices in response to phased climatic change during 1736–1850 in the North China Plain

Grain price volatility during historical periods is regarded as an important indicator of the impact of climate change on economic system, as well as a key link to adjust food security and social stability. The present study used the wheat prices in Baoding Prefecture, China, during 1736–1850 to explore connections between climatic transition and grain price anomalies in the North China Plain. The main findings were as follows:(1) The grain price change showed an apparent correspondence with climatic transition. The period 1781–1820 was a transition phase, with more extremes and decreased precipitations when the climate shifted from a warm phase to a cold one. Corresponding with the climatic transition, the grain price during 1781–1820 was characterized by that the mean of the original grain price series was significantly higher(lower) than the previous(later)phase, and the variance and anomaly amplitude of the detrended grain price series was the highest during 1736–1850.(2) The correspondence between grain price extremes and drought events occurred in phases. Five grain price extremes occurred following drought events during 1781–1810, while extreme droughts were the direct cause of the grain price spike during 1811–1820.(3) Social stability affected by climate change also played an important role in the grain price spike between 1811 and 1820. Paralleling the pathway of "precipitation-grain production-grain price", climate change could have an impact on grain price via the pathway of "precipitation-grain production-grain price-famine-uprising-grain price", as shown during the Tianli Uprising in 1813. These findings could contribute to an improved understanding of the interaction between climate change and human society during the historical period.

Impacts of inter-sectoral trade on carbon emissions --a case of China in 2007

With the increase in international trade, more attention has been given to quantifying the impacts of international trade on energy use and carbon emissions. Input-output analysis is a suitable tool for assessing resources or pollutants embodied in trade and it has become a critical tool for performing such analysis. This study estimated the national and sectoral carbon emissions embodied in Chinese international trade using the latest available China input-output table of 2007. The results showed that a significant exporting behavior of embodied carbon emissions existed in China＇s trade. Over 1/3 of the emissions in Chinese domestic production processes were generated for exports in 2007. The net balance of emissions embodied in exports and imports accounted for nearly 30% of China＇s domestic emissions, which means that any policy made to increase the exports would result in a significant growth of China＇s domestic emissions. Since over half of China＇s export trade is processing trade, the re-exported emissions could not be overlooked; otherwise, it would hard to capture the actual emissions generated abroad to obtain China＇s domestic consumption. The enlargement of export scale is a primary driven factor to the rapid growth of China＇s exported emissions. It is necessary for China to adjust its economic and industrial structure to reduce the dependence of economic growth on the export trade. However, when adjusting industry structures or making policies on carbon emission reduction, it will be more reasonable to consider the relationship between production and consumption, rather than just focus on the emission values of sectors＇ direct production, as a large part of carbon emissions emitted by the principal direct polluters were generated to obtain the products which were required by other sectors.