Doctoral Dissertation Research: High-Resolution Climate and Land-Use Records from Cave Stalagmites and County Gazetters for China Over the Last 2,000 Years

当代科学家关注的一个主要问题是如何区分与自然气候变化有关的全球环境变化与由人类活动引起的全球环境变化。土地利用和土地覆盖的变化是人类引起的最重要的变化之一，但对这些变化的研究一般限于过去10至30年，与人类活动的历史相比，这是一个非常短的时期。因此，迫切需要过去几千年的高分辨率气候数据以及同一时期土地利用和土地覆盖变化的信息。这个博士论文研究项目将探索洞穴石笋在多大程度上可以为洞穴附近和上面的地区提供高分辨率的气候和土地利用数据，从而可以更准确地评估人类在环境变化中的作用。在中国中南部的贵州省工作，这是一个以喀斯特地貌为主的地区，包括许多洞穴。博士候选人将研究仍然有自然植被覆盖的地区的石笋，这些地区没有直接受到人类活动，特别是农业活动的影响。采用石笋年层厚度、灰度、稳定同位素、紫外激光致发光等气候代用措施，并与2000多年气象资料的县志气象记录进行对比。这些比较将用于确定哪些变量最能反映降雨和温度的变化。然后将适当的代理措施与处理极端气候事件（如洪水和干旱、冰雹、河流和湖泊冻结以及降雪）的地名词典数据进行比较。对一根石笋的初步研究已经确定了夏季降雨的变化，并显示了大约公元1430年发生大洪水的证据。根据卫星图像、航空照片、历史地图和对当地居民的采访，研究人员还将对农业地区洞穴中的石笋进行调查，特别是在过去已知时期土地利用发生重大变化的地区。该项目的这一部分将旨在确定是否可以从洞穴记录中确定有关洞穴上方土地利用和土地覆盖的信息，从而延长在可靠的历史记录之外推断土地利用的时间。除了提供有关中国南方长期气候、土地利用和自然植被过程之间关系的宝贵信息外，该项目还将通过评估洞穴沉积物在多大程度上可以用于提供高分辨率的气候、土地利用和土地覆盖数据，从而在方法上做出重大贡献。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

A major concern of contemporary scientists is distinguishing global environmental changes associated with natural variations in climate from those that resulting from human activities. Land-use and land-cover changes are among the most important changes instigated by humans, but studies of these changes generally have been limited to the last 10 to 30 years, a very short period compared with the history of human activity. An urgent need therefore exists for high-resolution climate data over the last few thousand years and for information on land-use and land-cover changes over the same time period. This doctoral dissertation research project will explore the degree to which cave stalagmites can provide both high-resolution climate and land-use data for the areas near and above caves, thereby allowing a more accurate assessment of the role of humans in environmental change. Working in Guizhou Province of south central China, a region dominated by karst features, including many caves with speleothems. The doctoral candidate will study stalagmites from areas that still have natural vegetation cover and that have not been affected directly by human activities, particularly agriculture. Stalagmite annual layer thickness, gray-scale, stable isotope, and UV laser-induced luminescence proxy measures of climate will be taken and compared with meteorological records drawn from county gazetteers, which provide meteorological information for periods of more than 2,000 years. These comparisons will be used to determine which variables best reflect variations in rainfall and temperature. Appropriate proxy measures then will be compared with gazetteer data dealing with extreme climate events, such as floods and droughts, hail, freezing of rivers and lakes, and snow. Preliminary studies of one stalagmite have identified variations in summer rainfall and shown evidence of major floods back to ca. AD 1430. Investigations also will be made of stalagmites from caves in agricultural areas, particularly locations for which there have been significant changes in land use at a known times in the past, as determined from satellite images, aerial photographs, historical maps, and interviews with local residents. This part of the project will aim at identifying whether information about land use and land cover above the caves can be determined from speleothem records, thereby lengthening the periods over which land uses can be inferred back in time beyond reliable historical records. In addition to providing valuable information about relationships among climate, land-use, and natural vegetative processes over long periods for southern China, the project will make significant methodological contributions by assessing the degree to which cave deposits can be used to provide high-resolution climate and land-use and land-cover data. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.