The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system ...The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.展开更多
Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the ...Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the close relationship between the soil cracking process and water movement in such semi-arid regions. Here we report regular changes on surface morphology of soil cracks with decreasing water in four different soils (Typ-Ustic Ferrisols,Ver-Ustic Ferrisols,Tru-Ustic Vertisols and Typ-Ustic Vertisols) through simulation experiments. Our results indicate the following: 1) Different soils ultimately have different development degrees of soil cracks,according to their various values of crack area density. Soil cracks in Typ-Ustic Ferrisols can only develop to the feeble degree,while those in the other three soils are capable of developing into the intensive degree,and even into the extremely intensive degree. 2) Soil crack complexity,as expressed by the value of the area-weighted mean of crack fractal dimension (AWMFRAC),is found to continuously decrease as a whole through the whole cracking process in all the studied soils. 3) Soil crack connectivity shows a uniform trend in the studied soils,that is to say,connectivity gradually increases with soil crack development.展开更多
为明确种植密度对地膜覆盖谷子干物质的分配、转运和产量的影响,本研究以‘陇谷13’为材料,于2021—2022年,在甘肃省平凉市崆峒区草峰镇进行地膜覆盖穴播种植试验,共设置3个密度梯度,行距均为30 cm,穴距分别为:20.2 cm (T1)、16.5 cm (...为明确种植密度对地膜覆盖谷子干物质的分配、转运和产量的影响,本研究以‘陇谷13’为材料,于2021—2022年,在甘肃省平凉市崆峒区草峰镇进行地膜覆盖穴播种植试验,共设置3个密度梯度,行距均为30 cm,穴距分别为:20.2 cm (T1)、16.5 cm (T2)、13.75 cm (T3);以传统露地条播种植(CK)为对照,播种量等同T3,通过测定谷子单株干物质积累量,量化个体和群体干物质积累量之间关系,分析茎鞘和叶的转运量及其对籽粒的贡献和水平。结果显示,本研究中Logistic拟合曲线(R~2>0.99)有效反映各处理干物质积累过程。覆膜谷子单株干物质积累量随着密度的增加而降低,T1有利于谷子获得较高单株干物质积累量;增加密度可使覆膜谷子提前进入快速增长期,提高最大增长速率,实现群体干物质积累量增加,T3较T1群体干物质积累量显著提高11.71%;覆膜和密度处理对谷子的千粒重影响不显著,穗粒重T1较T2、T3处理显著提高8.99%~39.03%;T2处理可显著提高茎鞘对籽粒产量的贡献率,T2较T1、T3处理显著提高365.71%、9.71%;T2模式在各因素协调作用下,表现出最高的产量和收获指数,为5 350.90 kg/hm~2和26.64%。本研究为陇东旱作区谷子高产栽培措施的优化提供一定的参考。展开更多
A novel species of Rhamnaceae,Colubrina zhaoguangii,is discovered in Sichuan,China,during the biodiversity investigations of the Second Tibetan Plateau Scientific Expedition and Research.Detailed descriptions and illu...A novel species of Rhamnaceae,Colubrina zhaoguangii,is discovered in Sichuan,China,during the biodiversity investigations of the Second Tibetan Plateau Scientific Expedition and Research.Detailed descriptions and illustrations of the new species are presented herein.To date,the new species is only found in dry-warm river valleys of the Jinsha River basin in the Hengduan Mountains region(HDM).Compared with the other two known Chinese Colubrina species,C.zhaoguangii features by the habit of twisted shrub and tiny leaves with emarginate apex.In morphology,the new species highly resembles C.alluaudii endemic in Madagascar and C.viridis in northwestern Mexico,whereas it is distinguished from these two relatives by its minutely white scales on the leaf blades.The discovery of C.zhaoguangii reminds us again that the bottom region is also important for biodiversity conservation in HDM and should be a flora survey priority.展开更多
Background:Global modeling of carbon storage and sequestration often mischaracterizes unique ecosystems such as the seasonally dry tropical forest of the central region of the Gulf of Mexico,because species diversity ...Background:Global modeling of carbon storage and sequestration often mischaracterizes unique ecosystems such as the seasonally dry tropical forest of the central region of the Gulf of Mexico,because species diversity is usually underestimated,as is their carbon content.In this study,aboveground and soil carbon stocks were estimated to determine the climate mitigation potential of this highly degraded landscape(<25%of forest cover).Results:Tree species in the study area had carbon content values that were 30%–40%higher than the standard value proposed by the IPCC(i.e.,50%).Tropical oak forest in the region,despite its restricted distribution and low species richness,accounted for the highest mean carbon stocks per unit area.The main factors driving spatial variability in carbon stocks were:maximum precipitation,soil organic matter,clay and silt content.No strong relationship was found between aboveground carbon stocks and soil organic carbon in the study area.Quanti-fication of carbon stocks is an important consideration in the assessment of the conservation value of remnants of native vegetation in human-modified landscapes.Conclusions:This study demonstrates the importance of the highly fragmented tropical dry regions of the Neo-tropics in maintaining landscape functionality and providing key ecosystem services such as carbon sequestration.Our results also highlight how crucial field-based studies are for strengthening the accuracy of global models.Furthermore,this approach reveals the real contribution of ecosystems that are not commonly taken into account in the mitigation of climate change effects.展开更多
More than 240 items of historical records containing climatic information were retrieved from official historical books, local chronicles, annals and regional meteorological disaster yearbooks. By using moisture index...More than 240 items of historical records containing climatic information were retrieved from official historical books, local chronicles, annals and regional meteorological disaster yearbooks. By using moisture index and flood/drought （F/D） index obtained from the above information, the historical climate change, namely wet-dry conditions in borderland of Shaanxi Province, Gansu Province and Ningxia Hui Autonomous Region （BSGN, mainly included Ningxialu, Hezhoulu, Gongchanglu, Fengyuanlu and Yan＇anlu in the Yuan Dynasty） was studied. The results showed that the climate of the region was generally dry and the ratio between drought and flood disasters was 85/38 during the period of 1208-1369. According to the frequencies of drought-flood disasters, the whole period could be divided into three phases. （1） 1208-1240： drought dominated the phase with occasional flood disasters. （2） 1240-1320： long-time drought disasters and extreme drought events happened frequently. （3） 1320-1369： drought disasters were less severe when flood and drought disasters happened alternately. Besides, the reconstructed wet-dry change curve revealed obvious transition and periodicity in the MongoI-Yuan Period. The transitions occurred in 1230 and 1325. The wet-dry change revealed 10- and 23-year quasi-periods which were consistent with solar cycles, indicating that solar activity had affected the wet-dry conditions of the study region in the Mongol-Yuan Period. The reconstructed results were consistent with two other study results reconstructed from natural evidences, and were similar to another study results from historical documents. All the above results showed that the climate in BSGN was characterized by long-time dry condition with frequent severe drought disasters during 1258 to 1308. Thus, these aspects of climatic change, might have profound impacts on local vegetation and socio-economic system.展开更多
基金Project supported by the State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences (No. 035109)the National Natural Science Foundation of China (No. 30390080).
文摘The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.
基金Under the auspices of National Natural Science Foundation of China (No. 40901009)National Key Technologies Research and Development Program in the Eleventh Five-Year Plan of China (No. 2008BAD98B02, 2006BAC01A11)+1 种基金the Western Light Program of Talents Cultivating of Chinese Academy of Sciences (2008)the Foundation of Key Laboratory of Mountain Hazards and Surface Process, Chinese Academy of Sciences
文摘Soil cracking is an important process influencing water and solutes transport in the Yuanmou Dry-hot Valley region of Southwest China. Studying the morphological development of soil cracks helps to further reveal the close relationship between the soil cracking process and water movement in such semi-arid regions. Here we report regular changes on surface morphology of soil cracks with decreasing water in four different soils (Typ-Ustic Ferrisols,Ver-Ustic Ferrisols,Tru-Ustic Vertisols and Typ-Ustic Vertisols) through simulation experiments. Our results indicate the following: 1) Different soils ultimately have different development degrees of soil cracks,according to their various values of crack area density. Soil cracks in Typ-Ustic Ferrisols can only develop to the feeble degree,while those in the other three soils are capable of developing into the intensive degree,and even into the extremely intensive degree. 2) Soil crack complexity,as expressed by the value of the area-weighted mean of crack fractal dimension (AWMFRAC),is found to continuously decrease as a whole through the whole cracking process in all the studied soils. 3) Soil crack connectivity shows a uniform trend in the studied soils,that is to say,connectivity gradually increases with soil crack development.
文摘为明确种植密度对地膜覆盖谷子干物质的分配、转运和产量的影响,本研究以‘陇谷13’为材料,于2021—2022年,在甘肃省平凉市崆峒区草峰镇进行地膜覆盖穴播种植试验,共设置3个密度梯度,行距均为30 cm,穴距分别为:20.2 cm (T1)、16.5 cm (T2)、13.75 cm (T3);以传统露地条播种植(CK)为对照,播种量等同T3,通过测定谷子单株干物质积累量,量化个体和群体干物质积累量之间关系,分析茎鞘和叶的转运量及其对籽粒的贡献和水平。结果显示,本研究中Logistic拟合曲线(R~2>0.99)有效反映各处理干物质积累过程。覆膜谷子单株干物质积累量随着密度的增加而降低,T1有利于谷子获得较高单株干物质积累量;增加密度可使覆膜谷子提前进入快速增长期,提高最大增长速率,实现群体干物质积累量增加,T3较T1群体干物质积累量显著提高11.71%;覆膜和密度处理对谷子的千粒重影响不显著,穗粒重T1较T2、T3处理显著提高8.99%~39.03%;T2处理可显著提高茎鞘对籽粒产量的贡献率,T2较T1、T3处理显著提高365.71%、9.71%;T2模式在各因素协调作用下,表现出最高的产量和收获指数,为5 350.90 kg/hm~2和26.64%。本研究为陇东旱作区谷子高产栽培措施的优化提供一定的参考。
基金This study was supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0301)National Natural Science Foundation of China(31860167 and 32101234)Wild Plants Sharing and Service Platform of Sichuan Province.
文摘A novel species of Rhamnaceae,Colubrina zhaoguangii,is discovered in Sichuan,China,during the biodiversity investigations of the Second Tibetan Plateau Scientific Expedition and Research.Detailed descriptions and illustrations of the new species are presented herein.To date,the new species is only found in dry-warm river valleys of the Jinsha River basin in the Hengduan Mountains region(HDM).Compared with the other two known Chinese Colubrina species,C.zhaoguangii features by the habit of twisted shrub and tiny leaves with emarginate apex.In morphology,the new species highly resembles C.alluaudii endemic in Madagascar and C.viridis in northwestern Mexico,whereas it is distinguished from these two relatives by its minutely white scales on the leaf blades.The discovery of C.zhaoguangii reminds us again that the bottom region is also important for biodiversity conservation in HDM and should be a flora survey priority.
基金This study was funded by The Rufford Foundation(Rufford small grant#206761,to N.M.-S.)the Instituto de Ecologia,A.C.(project INECOL,20030-10281,to J.L.)the Consejo Nacional de Ciencia y Tecnologia(CONACYT,Scholarship#263474,to N.M.-S.).
文摘Background:Global modeling of carbon storage and sequestration often mischaracterizes unique ecosystems such as the seasonally dry tropical forest of the central region of the Gulf of Mexico,because species diversity is usually underestimated,as is their carbon content.In this study,aboveground and soil carbon stocks were estimated to determine the climate mitigation potential of this highly degraded landscape(<25%of forest cover).Results:Tree species in the study area had carbon content values that were 30%–40%higher than the standard value proposed by the IPCC(i.e.,50%).Tropical oak forest in the region,despite its restricted distribution and low species richness,accounted for the highest mean carbon stocks per unit area.The main factors driving spatial variability in carbon stocks were:maximum precipitation,soil organic matter,clay and silt content.No strong relationship was found between aboveground carbon stocks and soil organic carbon in the study area.Quanti-fication of carbon stocks is an important consideration in the assessment of the conservation value of remnants of native vegetation in human-modified landscapes.Conclusions:This study demonstrates the importance of the highly fragmented tropical dry regions of the Neo-tropics in maintaining landscape functionality and providing key ecosystem services such as carbon sequestration.Our results also highlight how crucial field-based studies are for strengthening the accuracy of global models.Furthermore,this approach reveals the real contribution of ecosystems that are not commonly taken into account in the mitigation of climate change effects.
基金National Natural Science Foundation of China, No.40471047 No.40871033The Knowledge Innovation Program of Chinese Academy of Sciences, No.KZCX2-YW-315
文摘More than 240 items of historical records containing climatic information were retrieved from official historical books, local chronicles, annals and regional meteorological disaster yearbooks. By using moisture index and flood/drought （F/D） index obtained from the above information, the historical climate change, namely wet-dry conditions in borderland of Shaanxi Province, Gansu Province and Ningxia Hui Autonomous Region （BSGN, mainly included Ningxialu, Hezhoulu, Gongchanglu, Fengyuanlu and Yan＇anlu in the Yuan Dynasty） was studied. The results showed that the climate of the region was generally dry and the ratio between drought and flood disasters was 85/38 during the period of 1208-1369. According to the frequencies of drought-flood disasters, the whole period could be divided into three phases. （1） 1208-1240： drought dominated the phase with occasional flood disasters. （2） 1240-1320： long-time drought disasters and extreme drought events happened frequently. （3） 1320-1369： drought disasters were less severe when flood and drought disasters happened alternately. Besides, the reconstructed wet-dry change curve revealed obvious transition and periodicity in the MongoI-Yuan Period. The transitions occurred in 1230 and 1325. The wet-dry change revealed 10- and 23-year quasi-periods which were consistent with solar cycles, indicating that solar activity had affected the wet-dry conditions of the study region in the Mongol-Yuan Period. The reconstructed results were consistent with two other study results reconstructed from natural evidences, and were similar to another study results from historical documents. All the above results showed that the climate in BSGN was characterized by long-time dry condition with frequent severe drought disasters during 1258 to 1308. Thus, these aspects of climatic change, might have profound impacts on local vegetation and socio-economic system.
