从技能培养到综合育人:以自然地理与资源环境专业西北野外实习为例

野外实习是很多高等院校地理类专业的必修课程,是使学生接触自然现象、理解专业知识、锻炼野外技能的绝佳机会.在当前“立德树人”培养理念的引领下,如何利用好野外实习的机会,实现从技能培养到综合育人的提升,是高校地理教育者需要重点思考的问题.本文以自然地理与资源环境专业近年来开展的西北野外实习为例,重点介绍了在实习动员、实习路线和实习作业3个阶段的育人举措.通过这些举措的实施,使课程思政育人理念贯穿整个实习过程,让学生完全融入其中,不仅学会了野外实践的技能,还真正“爱”上了地理学.通过学生的成绩和反馈发现,野外实习培养了他们团队协作的品质和合作交流的能力,并坚定了他们深入创新的科研志趣,达到了良好的培养效果.据此提出了野外实习在综合育人方面的三大优势,可以作为未来设计、组织和实施野外实习时的切入点.

四川稻城海子山方枝柏树轮宽度与气候因子的响应关系研究

对四川稻城县海子山高原上的方枝柏进行树芯采集,经交叉定年后建立林线上限位置的方枝柏树轮宽度年表。标准化年表与气象资料的响应分析结果揭示了该地区树木生长主要受当年生长季前期温度条件的控制。轮宽指数与前一年9月到当年2月的平均气温呈显著正相关(R=0.56,P<0.01)。由此重建了该地区1850—2019年这170 a的前一年9月到当年2月平均气温的变化,转换函数方差解释量31.7%。重建结果与邻近地区树轮记录的温度变化具有较好的一致性。重建序列显示工业革命以来,研究区经历较冷的时期有:1870—1890年和1960—1980年;较暖的时期有:1884—1892年、1919—1925年、1940—1960年以及1980—2019年。1940—1960年是20世纪最暖的时期,20世纪60年代后温度呈现下降趋势,1980年开始气温保持持续升高,2010年之后气温有小幅下降。重建气温序列与太阳黑子数变化和北大西洋多年代际涛动AMO有较强的响应,揭示了太阳活动、海温等因子可能对该区温度变化产生重要影响。

南京地区降水稳定同位素场季节尺度变化特征

基于1987年6月至1992年12月全球大气降水同位素观测网(GNIP)数据和2015年1月至2019年6月南京地区大气降水的连续采样数据,探究场降水和月降水 δ^18O变化的水汽源指示意义.结果表明,南京地区的降水稳定同位素δD的变化范围为-142.50‰^+42.91‰,δ^18O的变化范围为-19.16‰^+3.94‰,并且利用场降水稳定同位素数据建立了南京地区大气降水方程:δD=7.42δ^18O+8.07(n=330,R^2=0.95).天气尺度上,对单一水汽源场降水氧同位素分析,将水汽来源地主要分为五类(A^E),其降水 δ^18O平均值分别为-3.66‰、-6.65‰、-6.45‰、-1.64‰和-8.97‰;在持续性降水过程中,受雨除效应影响,δ^18O值呈现逐渐负偏的趋势,水汽源地的变化可能使降水δ^18O值波动加剧,其振幅可达11.14‰,而水汽源稳定的降水δ^18O值波动要相对小的多.在月尺度上,降水δ^18O值呈现春季偏正,夏季偏负的特征,d-excess与温度和降水均呈明显反相位关系;这种现象的原因是南京地区不同季节降水水汽来源存在差异,即夏季以印度洋、南海和西太平洋水汽源(B、E类)为主,冬季降水主要来源于欧亚大陆和西风带来的水汽(A、C类),而春季则是西风远源和局地水汽源(C、D类)占优势,这与上述五类降水的 δ^18O具有很好的对应.

陕西地洞河高分辨率石笋记录的DO18季风增强事件

千年尺度事件的结构特征和区域响应是理解和认识冰期气候变化及动力机制的关键.本文基于陕西汉中宁强县地洞河一支长417 mm石笋DDH1的11个U-Th年代和417个氧同位素(δ^18O)数据,重建了末次冰期(64.8~33.2 ka B.P.)亚洲季风演化历史.石笋 δ^18O记录在64.7±0.2 ka B.P.和59.3±0.1 ka B.P.快速负偏,分别指示了DO18事件的开始和H6事件的结束.在DO18事件结束过程,石笋 δ^18O记录在64.0~60.4 ka B.P.持续正偏,振幅达2.9‰,反应季风逐渐减弱,但未出现明显转型阶段.其总体形态与大西洋Cariaco盆地岩芯反射率、南极冰芯的记录较为一致,但是不同于格陵兰冰芯的记录.因地洞河所处青藏高原、 秦岭叠加影响的区域,纬度和地形的双重影响使得其石笋 δ^18O记录较其他地区偏负,振荡幅度更大.因地形阻挡了高纬信号,使得低纬甚至南半球的信号突现出来,ITCZ的移动、南半球温度和水汽潜热的释放作用在这一区域尤为显著.

Long-term trend and abrupt events of the Holocene Asian monsoon inferred from a stalagmiteδ^(18)O record from Shennongjia in Central China

A high-resolution oxygen-isotope record from a thorium-uranium-dated stalagmite from Shanbao Cave at Shennongjia reflects variations in the amount of monsoon precipitation for the period from 11.5 to 2.1 ka (1 ka = 1000 cal aBP). Between 11.5 and 9.3 ka, a sharp decrease in δ18O indicates a rapid increase in monsoon precipitation. An interval of generally high monsoon precipitation is observed between 9.3 and 4.4 ka. An arid period has prevailed between 4.4 and 2.1 ka. The long-term trend of Shanbao record appears to follow summer insolation at 33°N latitude. An abrupt decrease in monsoon precipitation around 4.3 ka is synchronous with the collapse of Neolithic culture in central China. This abrupt change could have resulted from the amplifi- cation of the gradually decreased summer insolation by the positive vegetation-atmosphere-aerosol feed- back. The weakened Asian monsoon events were in concert with decreased Greenland temperature dur- ing the early Holocene, centered at 8.2, 8.6, 9.3, 10.2 and 11.0 ka. This correlation suggests that changes in low-latitude monsoon are connected with climate change in high-latitude polar region.

Abrupt climate change of EastAsian Monsoon at 130 kaBP inferred from a high resolu-tion stalagmite δ^(18)O record

230Th ages and oxygen isotope data of a stalagmite from Shanbao Cave in Hubei Province characterize thEast Asian Monsoon precipitation from 133 to127 ka. Thdecadal-scale high-resolution δ18O record reveals a detailedtransitional process from the Penultimate Glaciation to thLast Interglaciation. As established with 230Th dates, the agof the Termination II is determined to be 129.5±1.0 kaBPwhich supports the Northern Hemisphere insolation as thtriggers for the ice-age cycles. In our δ18O record, the glacialinterglacial fluctuation reaches about 4‰, almost the samlevel as in other Asian Monsoon cave stalagmite δ18O recordThe transition of the glacial/interglacial period in our recordcan be recognized as four stepwise stages, among which, arapid rise of monsoon precipitation follows the stage o“Termination II pause”. The rapid rise is synchronous withthe abrupt change of global methane concentration, whichreflects that an increase in both Asian Monsoon precipitationand tropical wetland plays an important role in the globaclimate changes.

Stalagmite-inferred Holocene precipitation in northern Guizhou Province, China, and asynchronous termination of the Climatic Optimum in the Asian monsoon territory

An absolute-dated, bi-decadal-resolution, stalagmite oxygen-isotopic time series from Shigao Cave reveals the evolution of summer monsoon precipitation over the past 9.9 ka BP in northern Guizhou Province, Southwest China. The 18O-inferred climate conditions are divisible into three distinct stages: (1) a maximum humid era from 9.9-6.6 ka BP; (2) a gradual declining precipitation interval between 6.6-1.6 ka BP; and (3) a relatively low precipitation time window after 1.6 ka BP. Consistency of contemporaneous stalagmite Holocene 18O records between Shigao and other caves in the Indian and East Asian monsoon realms support the effect of primary orbital solar forcings on monsoonal precipitation. However, statistical analysis shows a significant spatial asynchroneity of the Holocene Optimum termination in the Asian monsoon territory. The Holocene Optimum ended at 7.2-7.4 ka BP in Oman, located in the Indian monsoon region, and at 5.6-5.8 ka BP in Central China, in the East Asian monsoon zone. In Southwest China, the termination occurred between these periods, at 6.6-7.0 ka BP, and was influenced by both monsoon systems. We propose that this spatially asynchronous ending of Holocene Optimum in Asia may be attributed to sea surface temperature changes in the western tropical Pacific, which is a primary moisture source for the East Asian monsoon.

Precise dating of East-Asian-Monsoon D/O events during 95―56 ka BP:Based on stalagmite data from Shanbao Cave at Shennongjia,China

Based on 23 U/Th analyses and 532 oxygen isotopic data, an averaged 80-a stalagmite oxygen isotopic composition series was established through 95 to 56 thousand years before present (ka BP) from two speleothems in Shanbao Cave, Shennongjia, central China. Shanbao Cave record (referred to as SB record) replicates well with Hulu Cave record, extending the characteristics of millennial oscillations in East-Asian-Summer-Monsoon (EASM) to the past 95 ka. The trend of the SB record generally follows mid-July solar insolation at 65°N, suggesting that mid-high northern latitude insolation, in the first or- der, controls changes of EASM intensity. Millennial oscillations of EASM recorded in the stalagmites are well related to the Greenland interstadials referred to as Dansgaard/Oeschger (D/O) events from 1 to 22, indicating that rapid ocean-atmosphere reorganization in North Atlantic has a remote effect in EASM. The well-dated D/O events by stalagmites probably provide an absolute calibration for chro- nologies of Greenland ice cores. The timings of D/O events in the SB record are different variously from those in Greenland ice cores. For D/O 19 and 20, the age offsets between the stalagmites' and the Greenland ice cores' record are significant, larger than the uncertainties of uranium-series dating. The two events in the SB record are younger than those in North GRIP time scale by 1―2 ka, and older than the counterparts in GISP2 by approximately 3―4 ka. A comparison between the SB and Brazil stalag- mite record shows an anti-phase relation in millennial-scale monsoon precipitation between the two localities. This supports a mode for the coupled ocean-atmosphere "See-saw".