中国地理科学学科体系浅析

新的国际和国内形势为地理科学带了新的发展机遇,同时也提出了更高的要求。以《中国学科及前沿领域发展战略研究（2021—2035）》地理科学的学科规划为契机,本文系统梳理了新时期地理科学的学科体系。根据地理科学现状和发展趋势,中国地理科学可划分为综合地理学、自然地理学、人文地理学和信息地理学4个二级学科,各二级学科下的三级学科也基本成熟,有些三级学科下的四级学科名称也在普遍使用。我们希望以这一新的学科体系为支点,完善地理科学的学科分支,推动地理科学框架下新兴学科的发展,更好地服务于新时期国际及国家的战略需求。     

摇蚊亚化石记录的苏干湖近千年来盐度变化研究

利用摇蚊亚化石重建湖泊古盐度进而分析区域干湿变化已成为国际上古气候重建研究的热点之一。本文利用苏干湖SG03I孔的摇蚊亚化石组合变化分析了湖泊水体近千年来的盐度波动过程,沉积序列可划分为3个摇蚊组合带,通过高咸水属种Orthocladius/Cricotopus和Psectrocladius barbimanus,以及低咸水属种Psectrocladius sordidellus和Procladius的相对丰度变化实现盐度重建。结果表明,990～1450A.D.期间高咸水种处于绝对优势,湖泊盐度较高;1450～1850A.D.期间低咸水种显著增加,指示了小冰期期间较高的入湖水量与蒸发量之比;1850～2002A.D.期间低咸水种丰度回落,湖泊水体盐度逐渐增加至现代水平。SG03I孔岩芯摇蚊指标与其他代用指标的结果有很好的对应关系,摇蚊亚化石组合变化揭示的苏干湖区小冰期相对湿润的气候状况在干旱区其他记录中也有反映,证实了摇蚊亚化石分析在西北干旱区古环境研究中的有效性。     

中国西北干旱区小冰期的湿度变化特征

选取中国西北干旱区11 条具有明确古湿度指示意义的气候记录, 结合冰芯、地层沉积、 湖泊沉积、树木年轮、河流阶地等各种研究资料和历史记载, 研究中国西北干旱区小冰期的湿 度变化。结果表明研究区小冰期(1400-1920 AD) 从整体而言处于相对湿润的阶段: 区内高大 山系降水处于较高时段- -西昆仑山古里雅冰芯积累量增大, 天山山间湖泊水位回升, 祁连山 敦德冰芯孢粉总浓度增加; 而盆地内流系统水量也出现了相应的变化- -塔里木盆地克里雅 河和塔里木河流量增大, 准噶尔盆地艾比湖水位上升, 巴丹吉林沙漠地下水补给量上升, 居延 海入湖水量增大, 湖面扩展, 青海湖盆地降水增加, 有效湿度增大, 苏干湖水体盐度降低, 入湖 水量/ 蒸发量之比升高。同时, 较高分辨率的湿度资料显示, 研究区东-南边缘地带在小冰期 内部存在次一级的干湿波动, 两个湿度较高的时期出现在16 世纪和18 世纪, 分别与小冰期内 部的两个相对温暖时期有很好的对应。中国西北相对湿润的小冰期主要是西风带强度增加和 位置南移造成该区域降水增多和全球性普遍降温导致有效湿度增大两个因素共同作用的结果, 研究区边缘地带小冰期内部冷干暖湿的配置则主要体现了夏季风的影响。     

阿尼玛卿山地祁连圆柏径向生长对气候的响应

通过对阿尼玛卿山地5 个坡面20 个祁连圆柏树轮宽度标准年表的分析, 发现公共区间内各树木年轮宽度标准年表中的信噪比SNR 和样本总解释量EPS 值都较高, 说明年表中都含有较强的环境信息; 树轮宽度年表之间的平均相关为0.35 (大多达到95%的置信程度), 具有较好的区域一致性。聚类分析使树木年轮宽度年表分成东、西两大部分, 而年表的第一主分量显示出: 西部树轮的指数序列明显长于东部即树木生长有自西向东扩展的趋势, 并且东、西区域树木生长变化的特征年变化具有同步性。东、西树轮宽度年表中第一主分量和第二主分量与气候因子的相关和响应都表现出一定的相似性, 但第二主分量对气候因子响应的差异性更显著。西部树木生长PCI 的主要限制因子是温度, 尤其当年春末夏初及前一年秋季温度影响最大, 同样降水也起着重要的作用, 西部树木生长PC2 的主要限制因子是降水量; 而东部树木生长PC1 主要受降水的制约, 第二主分量PC2 的响应分析显示出气候的滞后影响(树木前期生长) 是非常重要的限制因子。     

青海苏干湖表层沉积物粒度分布模式 与大气粉尘记录

位于干旱区柴达木盆地具有年纹层的苏干湖是以地下水补给为主的内陆封闭湖泊, 其表层沉积物粒度具有多组分峰态分布特征, Weibull 函数的拟合结果发现, 其粒度分布全部具 有4 个基本组分: 超细粒组分, 众数粒径在1 μm 上下; 细粒组分, 众数粒径在5~10 μm; 粗粒组分, 众数粒径在50~100 μm; 砂组分, 众数粒径在500 $m 左右。粒度主峰出现在细 粒组分或者粗粒组分。直接来自大气粉尘的冬季湖泊冰面样品及当地尘暴样品的Weibull 函数粒度拟合也显现出了相似的分布模式, 冰面样品的粒度主峰位于众数粒径在15~20 μmm 的 细粒组分, 砂组分(众数粒径452.9μm) 的出现指示出砂粒在冬半年沿冰面而进入湖泊中心。 尘暴降尘样品在尘暴季节(5 月份) 和非尘暴季节(11 月份) 的粒度分布普遍具有3 个组分, 缺少砂组分, 强沙尘暴事件样品则由4 个组分组成, 粒度主峰均位于众数粒径在100~200 μm 的粗粒组分。结果显示, 苏干湖湖泊沉积能够较好记录当地大气粉尘, 砂组分与湖泊周边干旱地表经历的近地面强沙尘活动有关, 粗粒组分记录了区域性的尘暴事件, 细粒组分主要反映 流域径流状况, 超细粒组分代表干旱区的大气背景粉尘和气溶胶。研究表明, 苏干湖内陆湖 泊沉积客观记录了区域大气粉尘和尘暴事件, 具有重建干旱区大气粉尘变化历史的潜在优势。     

柴达木盆地苏干湖表层沉积与尘暴事件——元素示踪的初步结果

通过分析苏干湖地区10个地表表层沉积物、9个大气降尘(含2个尘暴降尘)、16个湖泊表层沉积物等样品的8种常量-微量元素和11种稀土元素的含量,以及同类沉积不同元素含量和不同沉积同一元素含量的相关性,结果表明,在湖泊沉积体系中Al、Fe、Sc含量的变化与强风-尘暴过程有关,指示了湖泊沉积碎屑颗粒风成输入的可能性．元素Fe、Sc含量在3种不同的沉积物中差异不大,与尘暴事件的强度和频次有关．稀土元素结果显示3类沉积具有同源性．苏干湖沉积可以用来重建研究区尘暴演化历史．     

Consistent long-term Holocene warming trend at different elevations in the Altai Mountains in arid central Asia

Recent results indicate contrasting Holocene moisture histories at different elevations in arid central Asia (ACA). However, relatively little is known about Holocene temperature changes at different elevations. Here we report an independently dated peat brGDGTs-based MBT'_5ME record from the Narenxia peatland (NRX) in the southern Altai Mountains. The record suggests a long-term warming trend since ~7.7 cal. kyr bp , with a warmer stage during ~7–5.5 cal. kyr bp , a cold stage during ~5.5–4 cal. kyr bp , and a warming trend over the last ~4 kyr. The long-term warming trend indicated by the NRX MBT'_5ME record is largely consistent with Holocene temperature records from nearby sites covering an altitudinal range of ~1700–4100 m above sea level. This consistent long-term warming trend at different elevations differs from the long-term Holocene drying/wetting trends at high/low elevations of the Altai Mountains. We propose that the warming trend and consequent permafrost thawing at high elevations could have resulted in increased meltwater runoff, which would have contributed to the long-term wetting trend at low elevations. Our findings potentially provide an improved understanding of regional climate change and associated water resource availability, with implications for their possible future status.     

伊朗黄土高原表土磁性特征与古气候指示意义

全球变化研究中的现代过程研究越来越成为定量重建工作的先决前提,而由于如黄土等气候记录载体沉积分布的全球性与沉积环境的多样性,更需要就具体的研究区进行有针对性的现代过程工作以最大程度地保证重建工作的可靠性.西起地中海、东至帕米尔的广大区域是丝路文明演化的关键地区,其过去气候变化也是了解北半球中纬度气候演化与机制的重要拼图...     

Stable carbon isotope characteristics of different plant species and surface soil in arid regions

The stable carbon isotope composition in surface soil organic matter (δ¹³Csoil) contains integrative information on the carbon isotope composition of the standing terrestrial plants (δ¹³Cleaf). In order to obtain valuable vegetation information from the δ¹³C of terrestrial sediment, it is necessary to understand the relationship between the δ¹³C value in modern surface soil and the standing vegetation. In this paper, we studied the δ¹³C value in modern surface soil organic matter and standing vegetation in arid areas in China, Australia and the United States. The isotopic discrepancy between δ¹³Csoil and δ¹³Cleaf of the standing dominant vegetation was examined in those different arid regions. The results show that the δ¹³Csoil values were consistently enriched compared to the δ¹³Cleaf. The δ¹³Cleaf values were positively correlated with δ¹³Csoil, which suggests that the interference of microorganisms and hydrophytes on the isotopic composition of surface soil organic matter during soil organic matter formation could be ignored in arid regions. The averaged discrepancy between δ¹³Csoil and δ¹³Cleaf is about 1.71%in Tamarix L. in the Tarim Basin in China, 1.50% in Eucalytus near Orange in Australia and 1.22% in Artemisia in Saratoga in the United States, which are different from the results of other studies. The results indicate that the discrepancies in the δ¹³C value between surface soil organic matter and standing vegetation were highly influenced by the differences in geophysical location and the dominant species of the studied ecosystems. We suggest that caution should be taken when organic matter δ¹³C in terrestrial sediment is used to extract paleovegetation information (C₃/C₄ vegetation composition), as the δ¹³C in soil organic matter is not only determined by the ratio of C₃/C₄ species, but also profoundly affected by climate change induced variation in the δ¹³C in dominant species.     

Rill erosion processes on a constantly saturated slope

Rill erosion processes on saturated soil slopes are important for understanding erosion hydrodynamics and determining the parameters of rill erosion models. Saturated soil slopes were innovatively created to investigate the rill erosion processes. Rill erosion processes on saturated soil slopes were modelled by using the sediment concentrations determined by sediment transport capacities (STCs) measurement and the sediment concentrations at different rill lengths. Laboratory experiments were performed under varying slope gradients (5°, 10°, 15°, and 20°) and unit-width flow rates (0.33, 0.67, and 1.33 × 10⁻³ m³ s⁻¹ m⁻¹) to measure sediment concentrations at different rill lengths (1, 2, 4, and 8 m) on saturated soil slopes. The measured sediment concentrations along saturated rills ranged from 134.54 to 1,064.47 kg/m³, and also increased exponentially with rill length similar to non-saturated rills. The model of the rill erosion process in non-saturated soil rills was applicable to that in saturated soil rills. However, the sediment concentration of the rill flow increased much faster, with the increase in rill length, to considerably higher levels at STCs. The saturated soil rills produced 120–560% more sediments than the non-saturated ones. Moreover, the former eroded remarkably faster in the beginning section of the rills, as compared with that on the non-saturated soil slopes. This dataset serves as the basis for determining the erosion parameters in the process-based erosion models on saturated soil slopes.