Impact of land use/cover changes on carbon storage in a river valley in arid areas of Northwest China

Soil carbon pools could become a CO_2 source or sink, depending on the directions of land use/cover changes. A slight change of soil carbon will inevitably affect the atmospheric CO_2 concentration and consequently the climate. Based on the data from 127 soil sample sites, 48 vegetation survey plots, and Landsat TM images, we analyzed the land use/cover changes, estimated soil organic carbon（SOC） storage and vegetation carbon storage of grassland, and discussed the impact of grassland changes on carbon storage during 2000 to 2013 in the Ili River Valley of Northwest China. The results indicate that the areal extents of forestland, shrubland, moderate-coverage grassland（MCG）, and the waterbody（including glaciers） decreased while the areal extents of high-coverage grassland（HCG）,low-coverage grassland（LCG）, residential and industrial land, and cultivated land increased. The grassland SOC density in 0–100 cm depth varied with the coverage in a descending order of HCG〉MCG〉LCG.The regional grassland SOC storage in the depth of 0–100 cm in 2013 increased by 0.25×1011 kg compared with that in 2000. The regional vegetation carbon storage（S_（rvc）） of grassland was 5.27×10~9 kg in2013 and decreased by 15.7% compared to that in 2000. The vegetation carbon reserves of the under-ground parts of vegetation（S_（ruvb）） in 2013 was 0.68×10~9 kg and increased by approximately 19.01%compared to that in 2000. This research can improve our understanding about the impact of land use/cover changes on the carbon storage in arid areas of Northwest China.

Special Issue on "Response of Polar Organisms and Natural Environment to Global Changes"

High altitude and high latitude regions on Earth are experiencing rapid changes in climate, with impacts on polar organisms and the environment. The persistent cold and sometimes inhospitable conditions create unique ecosystems and habitats for polar organisms.

Inviting Contributions to a Special Issue on "Response of Polar Organisms and Natural Environment to Global Changes"

Dear Colleagues, We would like to invite you to submit manuscripts to a special issue of the journal Advances in Polar Science （APS） on ＂Response of Polar Organisms and Natural Environment to Global Changes＂.

Spatio-temporal variability in microfossil and geochemical records of Cenomanian-Turonian oceanic anoxic event-2:a review

The Cenomanian-Turonian boundary oceanic anoxic event(OAE-2;Bonarelli event;~94 Ma)is associated with a species turnover in the marine calcareous microfossil record,widespread marine anoxia,black shale deposition and positiveδ13C excursions.This study reviews 141 CTBE sites globally,aiming to understand micropaleontological,geochemical,and sedimentological expressions of OAE-2.There is a clear palaeogeographic and palaeobathymetric heterogeneity in the development of OAE-2 marine anoxia.A majority of the documented OAE-2 sites are from deep marine environments.The calcareous nannoplankton and benthic foraminifera record a diversity decline,while planktic foraminifera shows community level shifts and no major mass extinction.The variability of total organic carbon in OAE-2 sediments across sites(<1 to>10 wt.%)and theδ13C profiles(diachronous)have been attributed to different mechanisms of anoxia development.The increased primary“productivity model”gains support from productivity proxies(e.g.,Ba,P,Cu,Ni),redox-sensitive elements(e.g.,Mn,Mo,U,V,As),and eutrophic genera(e.g.,benthic foraminifera Gabonita spp.,calcareous nannofossils Biscutum spp.and Zeugrhabdotus erectus).The enhanced organic carbon“preservation model”in stratified(semi)restricted basins gains support from sites with lower enrichment of redox-sensitive elements and oligotrophic flora and fauna in the OAE-2 records.Geochronology of the Caribbean and the High Atlantic Large Igneous Province events(CLIP and HALIP)mark them as likely triggers of the OAE-2 related global perturbation of marine biogeochemistry.Volcanic triggers may have caused climate warming,altered hydrological cycles,enhanced continental weathering,shifts in ocean circulation,and nutrient flows.Addressing knowledge gaps,further research is urged,utilizing innovative proxies,and exploring underrepresented depositional systems to comprehensively understand OAE-2 onset and biotic crisis.