The contributions of persistent organic pollutants (POPs) from the subtropical regions of China to pollution of the global environment have been paid great attention; however, little is known about the state of POPs...The contributions of persistent organic pollutants (POPs) from the subtropical regions of China to pollution of the global environment have been paid great attention; however, little is known about the state of POPs in agricultural ecosystems within these regions of China. This study primarily revealed the state of the contamination and distribution of polycyclic aromatic hydrocarbons (PAH) in agricultural soils in the subtropical regions. 115 surface soils (0-20 cm) were sampled in the breadbaskets of these regions. The concentrations and types of PAH were determined using gas chromatography linked to mass spectrometry (GC-MS). The total PAH concentrations ranged from 22.1 to 1 256.9 ng g^-1 with a mean of 318.2 ± 148.2 ng g^-1. In general terms, the current PAH concentrations were lower than most PAH levels reported in a number of investigations from different countries and regions. PAH isomer ratios indicated that pyrolytic origins, such as fossil fuel combustion related to vehicle tail gas and industrial emissions, were the dominant sources of PAH in the southern subtropical areas of China. Although PAH concentrations decreased with decreasing pollution, population, and traffic density, to a great extent PAH compositions were similar throughout subtropical soils, with naphthalene, phenanthrene, fluoranthene, and benzo(b)fluoranthene being dominant.展开更多
Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest was studied in the foothills of Eastern Himalaya, India. Tree species richness,density, basal area and...Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest was studied in the foothills of Eastern Himalaya, India. Tree species richness,density, basal area and the diversity indices were found significantly(P<0.05) decreased with the increasing level of disturbances whereas, shrub density, basal area and herb density significantly increased with increasing disturbance level. In case of shrubs, Simpson's dominance index significantly(P<0.007) increased along the disturbance gradient,whereas Pielou's evenness index significantly(P<0.005) decreased with an increasing level of disturbance. Shannon-Weiner diversity index for herbs significantly(P<0.016) increased with increasing disturbance whereas, Simpson's dominance index was significantly(P<0.013) declined along the disturbance gradient. Results revealed that10-50 cm dbh classes constituted the highest stem density, and highest basal area was recorded in the >100 cm dbh class in all three sites. Density of the matured trees decreased with increasing DBH whereas, tree basal area tended to increase with increasing DBH in all three sites. Tree species richness was highest in the lower DBH classes.62.07% of the total tree species regenerated in the largely undisturbed site followed by 50% in the mildly disturbed and 26.32% in the highly disturbed site.The overall regeneration condition was found to be good in the largely undisturbed site. Mildly disturbed site exhibited fair regeneration and so was in the highly disturbed site. Discernable variations in species composition, diversity, regeneration and tree population structure revealed the impact of anthropogenic disturbances on rainforest vegetation dynamics. Higher degree of disturbance was furtherly found not only affecting species diversity but also promoting the growth of invasive weed species.Dominance of Hydnocarpus kurzii and Crypteronia paniculata in the highly disturbed site also indicated that these less-valued timber species may benefit from the vegetation mosaic produced by the disturbance; so differences in abundance of these species may be useful for bio-indication. Furthermore,present study suggests the need of adequate biodiversity conservation measures and adaptation of sustainable forest management approaches in disturbed areas of lowland tropical rainforest in the foothills of eastern Himalaya, India.展开更多
The potential change of drought measured by the Palmer Drought Severity Index (PDSI) is projected by using a coupled climate system model under a Representative Pathway 8.5 (RCP8.5) scenario.The PDSI changes calcu...The potential change of drought measured by the Palmer Drought Severity Index (PDSI) is projected by using a coupled climate system model under a Representative Pathway 8.5 (RCP8.5) scenario.The PDSI changes calculated by two potential evapotranspiration algorithms are compared.The algorithm of Thomthwaite equation overestimates the impact of surface temperature on evaporation and leads to an unrealistic increasing of drought frequency.The PM algorithm based on the Penman-Monteith equation is physically reasonably and necessary for climate change projections.The Flexible Global Ocean-Atmosphere-Land System model,Spectral Version 2 (FGOALS-s2) projects an increasing trend of drought during 2051-2100 in tropical and subtropical areas of North and South America,North Africa,South Europe,Southeast Asia,and the Australian continent.Both the moderate drought (PDSI <-2) and extreme drought (PDSI <-4) areas show statistically significant increasing trends under an RCP8.5 scenario.The uncertainty in the model projection is also discussed.展开更多
Soil respiration (SR) Wis one of the largest contributors of terrestrial CO_2 to the atmosphere.Environmental as well as physicochemical parameters influence SR and thus, different land use practices impact the emissi...Soil respiration (SR) Wis one of the largest contributors of terrestrial CO_2 to the atmosphere.Environmental as well as physicochemical parameters influence SR and thus, different land use practices impact the emissions of soil CO_2. In this study, we measured SR, bi-monthly, over a one-year period in a terrace tea plantation, a forest tea plantation and a secondary forest, in a subtropical mountain area in Xishuangbanna, China. Along with the measurement of SR rates, soil characteristics for each of the land use systems were investigated. Soil respiration rates in the different land use systems did not differ significantly during the dry season, ranging from2.7±0.2 μmol m^(-2) s^(-1) to 2.8±0.2 μmol m^(-2) s^(-1). During the wet season, however, SR rates were significantly larger in the terrace tea plantation(5.4±0.5 μmol m^(-2)s^(-1)) and secondary forest(4.9±0.4 μmol m^(-2)s^(-1)) than in the forest tea plantation(3.7±0.2 μmol m^(-2) s^(-1)).This resulted in significantly larger annual soil CO_2 emissions from the terrace tea and secondary forest,than from the forest tea plantation. It is likely that these differences in the SR rates are due to the 0.5times lower soil organic carbon concentrations in thetop mineral soil in the forest tea plantation, compared to the terrace tea plantation and secondary forest.Furthermore, we suggest that the lower sensitivity to temperature variation in the forest tea soil is a result of the lower soil organic carbon concentrations. The higher SR rates in the terrace tea plantation were partly due to weeding events, which caused CO_2 emission peaks that contributed almost 10% to the annual CO_2 flux. Our findings suggest that moving away from heavily managed tea plantations towards low-input forest tea can reduce the soil CO_2 emissions from these systems. However, our study is a casestudy and further investigations and upscaling are necessary to show if these findings hold true at a landscape level.展开更多
Fossil reproductive structure from the Eocene of the Changchang Basin (Hainan Island,South China) is recognized as Chaneya hainanensis sp.nov.This new species is characterized by persistent corolla of five obovate pet...Fossil reproductive structure from the Eocene of the Changchang Basin (Hainan Island,South China) is recognized as Chaneya hainanensis sp.nov.This new species is characterized by persistent corolla of five obovate petals with three subparallel primary venation linked by arching secondary veins,circular central disk bearing two orbicular ovaries or fruit bodies.This discovery confirms the presence of the extinct fruit genus Chaneya in low-latitude tropical area,providing significant fossil evidence for investigating the origin,migration,and phytogeography of this genus and discussing the Tertiary floristic exchanges among North America,eastern Asia,and Europe.Considering the distribution of this genus and its extant relatives and the climate changes during the Cenozoic,we hypothesize that Chaneya was a widespread tropical or subtropical taxon,but,with climate cooling,became extinct in northern latitudes and evolved into Picrasma (Simaroubaceae) and Rutaceae mainly in modern tropics and subtropics.展开更多
The tropical Pacific is currently experiencing an El Nifio event. Various coupled models with different degrees of complexity have been used to make real-time E1 Nifio predictions, but large uncertainties exist in the...The tropical Pacific is currently experiencing an El Nifio event. Various coupled models with different degrees of complexity have been used to make real-time E1 Nifio predictions, but large uncertainties exist in the inten- sity forecast and are strongly model dependent. An intermediate coupled model (ICM) is used at the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), named the IOCAS ICM, to predict the sea surface temper- ature (SST) evolution in the tropical Pacific during the 2015-2016 E! Nifio event. One unique feature of the IOCAS ICM is the way in which the temperature of subsurface water entrained in the mixed layer (Te) is parameterized. Observed SST anomalies are only field that is utilized to initialize the coupled prediction using the IOCAS ICM. Examples are given of the model's ability to predict the SST conditions in a real-time manner. As is commonly evident in E1 Nifio- Southern Oscillation predictions using coupled models, large discrepancies occur between the observed and pre- dicted SST anomalies in spring 2015. Starting from early summer 2015, the model can realistically predict warming conditions. Thereafter, good predictions can be made through the summer and fall seasons of 2015. A transition to normal and cold conditions is predictecl to occur in rote spring 2016. Comparisons with other model predictions are made and factors influencing the prediction performance of the IOCAS ICM are also discussed.展开更多
基金Project supported by the State Environmental Protection Administration of China (No.2001-1-2)State Environmental Protection Administration of Guangdong (No.2001-08)Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control,and the National Natural Science Foundation of China(Nos.30170147 and 30270282)
文摘The contributions of persistent organic pollutants (POPs) from the subtropical regions of China to pollution of the global environment have been paid great attention; however, little is known about the state of POPs in agricultural ecosystems within these regions of China. This study primarily revealed the state of the contamination and distribution of polycyclic aromatic hydrocarbons (PAH) in agricultural soils in the subtropical regions. 115 surface soils (0-20 cm) were sampled in the breadbaskets of these regions. The concentrations and types of PAH were determined using gas chromatography linked to mass spectrometry (GC-MS). The total PAH concentrations ranged from 22.1 to 1 256.9 ng g^-1 with a mean of 318.2 ± 148.2 ng g^-1. In general terms, the current PAH concentrations were lower than most PAH levels reported in a number of investigations from different countries and regions. PAH isomer ratios indicated that pyrolytic origins, such as fossil fuel combustion related to vehicle tail gas and industrial emissions, were the dominant sources of PAH in the southern subtropical areas of China. Although PAH concentrations decreased with decreasing pollution, population, and traffic density, to a great extent PAH compositions were similar throughout subtropical soils, with naphthalene, phenanthrene, fluoranthene, and benzo(b)fluoranthene being dominant.
基金Department of Science & Technology, Government of India (GOI), New Delhi (Grant No. DST/ISSTAC/CO2-SR-227/14(G)-AICP-AFOLU-IV)
文摘Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest was studied in the foothills of Eastern Himalaya, India. Tree species richness,density, basal area and the diversity indices were found significantly(P<0.05) decreased with the increasing level of disturbances whereas, shrub density, basal area and herb density significantly increased with increasing disturbance level. In case of shrubs, Simpson's dominance index significantly(P<0.007) increased along the disturbance gradient,whereas Pielou's evenness index significantly(P<0.005) decreased with an increasing level of disturbance. Shannon-Weiner diversity index for herbs significantly(P<0.016) increased with increasing disturbance whereas, Simpson's dominance index was significantly(P<0.013) declined along the disturbance gradient. Results revealed that10-50 cm dbh classes constituted the highest stem density, and highest basal area was recorded in the >100 cm dbh class in all three sites. Density of the matured trees decreased with increasing DBH whereas, tree basal area tended to increase with increasing DBH in all three sites. Tree species richness was highest in the lower DBH classes.62.07% of the total tree species regenerated in the largely undisturbed site followed by 50% in the mildly disturbed and 26.32% in the highly disturbed site.The overall regeneration condition was found to be good in the largely undisturbed site. Mildly disturbed site exhibited fair regeneration and so was in the highly disturbed site. Discernable variations in species composition, diversity, regeneration and tree population structure revealed the impact of anthropogenic disturbances on rainforest vegetation dynamics. Higher degree of disturbance was furtherly found not only affecting species diversity but also promoting the growth of invasive weed species.Dominance of Hydnocarpus kurzii and Crypteronia paniculata in the highly disturbed site also indicated that these less-valued timber species may benefit from the vegetation mosaic produced by the disturbance; so differences in abundance of these species may be useful for bio-indication. Furthermore,present study suggests the need of adequate biodiversity conservation measures and adaptation of sustainable forest management approaches in disturbed areas of lowland tropical rainforest in the foothills of eastern Himalaya, India.
基金Carbon Budget and Related Issues of the Chinese Academy of Sciences(Grant No.XDA0 5110301)Public Science and Technology Research Funds Projects of Ocean(201105019-3)
文摘The potential change of drought measured by the Palmer Drought Severity Index (PDSI) is projected by using a coupled climate system model under a Representative Pathway 8.5 (RCP8.5) scenario.The PDSI changes calculated by two potential evapotranspiration algorithms are compared.The algorithm of Thomthwaite equation overestimates the impact of surface temperature on evaporation and leads to an unrealistic increasing of drought frequency.The PM algorithm based on the Penman-Monteith equation is physically reasonably and necessary for climate change projections.The Flexible Global Ocean-Atmosphere-Land System model,Spectral Version 2 (FGOALS-s2) projects an increasing trend of drought during 2051-2100 in tropical and subtropical areas of North and South America,North Africa,South Europe,Southeast Asia,and the Australian continent.Both the moderate drought (PDSI <-2) and extreme drought (PDSI <-4) areas show statistically significant increasing trends under an RCP8.5 scenario.The uncertainty in the model projection is also discussed.
基金financially supported by the Yunnan Department of Sciences and Technology of China (Grant No. 2012EB056)Further support was supplied by the CGIAR Research Program 6: Forests, Trees and Agroforestry
文摘Soil respiration (SR) Wis one of the largest contributors of terrestrial CO_2 to the atmosphere.Environmental as well as physicochemical parameters influence SR and thus, different land use practices impact the emissions of soil CO_2. In this study, we measured SR, bi-monthly, over a one-year period in a terrace tea plantation, a forest tea plantation and a secondary forest, in a subtropical mountain area in Xishuangbanna, China. Along with the measurement of SR rates, soil characteristics for each of the land use systems were investigated. Soil respiration rates in the different land use systems did not differ significantly during the dry season, ranging from2.7±0.2 μmol m^(-2) s^(-1) to 2.8±0.2 μmol m^(-2) s^(-1). During the wet season, however, SR rates were significantly larger in the terrace tea plantation(5.4±0.5 μmol m^(-2)s^(-1)) and secondary forest(4.9±0.4 μmol m^(-2)s^(-1)) than in the forest tea plantation(3.7±0.2 μmol m^(-2) s^(-1)).This resulted in significantly larger annual soil CO_2 emissions from the terrace tea and secondary forest,than from the forest tea plantation. It is likely that these differences in the SR rates are due to the 0.5times lower soil organic carbon concentrations in thetop mineral soil in the forest tea plantation, compared to the terrace tea plantation and secondary forest.Furthermore, we suggest that the lower sensitivity to temperature variation in the forest tea soil is a result of the lower soil organic carbon concentrations. The higher SR rates in the terrace tea plantation were partly due to weeding events, which caused CO_2 emission peaks that contributed almost 10% to the annual CO_2 flux. Our findings suggest that moving away from heavily managed tea plantations towards low-input forest tea can reduce the soil CO_2 emissions from these systems. However, our study is a casestudy and further investigations and upscaling are necessary to show if these findings hold true at a landscape level.
基金supported by National Natural Science Foundation of China (Grant Nos. 40972011,31070200)National Basic Research Program of China (973 Program) (Grant No. 2012CB822003)+2 种基金the joint Project of National Natural Science Foundation of China and Russian Foundation for Basic Research (Grant Nos. 41111120083,11-04-91175)Guangdong Natural Science Foundation (Grant No. 10151027501000020)Key Project of the Sun Yat-sen University for inviting foreign teachers and Scientific Research Fund, Hongda Zhang, Sun Yat-sen University
文摘Fossil reproductive structure from the Eocene of the Changchang Basin (Hainan Island,South China) is recognized as Chaneya hainanensis sp.nov.This new species is characterized by persistent corolla of five obovate petals with three subparallel primary venation linked by arching secondary veins,circular central disk bearing two orbicular ovaries or fruit bodies.This discovery confirms the presence of the extinct fruit genus Chaneya in low-latitude tropical area,providing significant fossil evidence for investigating the origin,migration,and phytogeography of this genus and discussing the Tertiary floristic exchanges among North America,eastern Asia,and Europe.Considering the distribution of this genus and its extant relatives and the climate changes during the Cenozoic,we hypothesize that Chaneya was a widespread tropical or subtropical taxon,but,with climate cooling,became extinct in northern latitudes and evolved into Picrasma (Simaroubaceae) and Rutaceae mainly in modern tropics and subtropics.
基金the National Natural Science Foundation of China(41490644,41475101 and41421005)the CAS Strategic Priority Project+1 种基金the Western Pacific Ocean System(XDA11010105,XDA11020306 and XDA11010301)the NSFC-Shandong Joint Fund for Marine Science Research Centers(U1406401)
文摘The tropical Pacific is currently experiencing an El Nifio event. Various coupled models with different degrees of complexity have been used to make real-time E1 Nifio predictions, but large uncertainties exist in the inten- sity forecast and are strongly model dependent. An intermediate coupled model (ICM) is used at the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), named the IOCAS ICM, to predict the sea surface temper- ature (SST) evolution in the tropical Pacific during the 2015-2016 E! Nifio event. One unique feature of the IOCAS ICM is the way in which the temperature of subsurface water entrained in the mixed layer (Te) is parameterized. Observed SST anomalies are only field that is utilized to initialize the coupled prediction using the IOCAS ICM. Examples are given of the model's ability to predict the SST conditions in a real-time manner. As is commonly evident in E1 Nifio- Southern Oscillation predictions using coupled models, large discrepancies occur between the observed and pre- dicted SST anomalies in spring 2015. Starting from early summer 2015, the model can realistically predict warming conditions. Thereafter, good predictions can be made through the summer and fall seasons of 2015. A transition to normal and cold conditions is predictecl to occur in rote spring 2016. Comparisons with other model predictions are made and factors influencing the prediction performance of the IOCAS ICM are also discussed.