Subjects: Geosciences >> Geography submitted time 2023-06-28 Cooperative journals: 《干旱区地理》
Abstract：基于准噶尔盆地西部46个样方的植被调查和表土花粉资料，估算了19种主要花粉类型的联合指数（A）、低代表性指数（U）、超代表性指数（O）、代表性系数（R）、区内无植被出现时某花粉类型百分比的平均值（Ma）、区内有植被出现时某花粉类型百分比的平均值（Mp）、样方花粉组合与植物群落间相似系数（CC），定量描述花粉对植被的指示性。结果表明：第1组包括藜科，A 值为1.0，O、U 值均为0，R 值为12.5，Mp远大于Ma，对植被指示意义明显；第2组包括蒿属和麻黄属，A 值在0.1~0.4之间，O 值在0.6~0.9之间，U 值均为0，R 值大于18.5，Mp与Ma相差3.6%~12.1%，对植被具较明显指示意义；第3组包括白刺属、百合科、唇形科、豆科、禾本科、菊科、蓼科、毛茛科、蔷薇科、伞形科、莎草科、十字花科、石竹科、旋花科、荨麻科和紫草科，A 值小于0.6，U 值在0.2~0.9之间，O 值在0.1~1.0之间，R 值小于4.0，Mp与Ma相差小于4.9%，对植被指示意义不明。研究结果可为利用化石花粉资料准确恢复古植被提供参考依据。
Subjects: Geosciences >> Hydrology submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： Climate change and human activities are the main driving forces of river runoff variation. Under the similar weather condition (SWC), human activities are the dominant factors for change of discharge in the basin that quantitative identification on the action mechanism of human activities on runoff change has great significance to further explore the change characteristics of runoff. This study was conducted in the Yue River basin of the Qinling Mountains. Combined with Land-Use and Land-Cover Change (LUCC) as well as Normalized Difference Vegetation Index (NDVI), human activities’impacts on runoff is quantified by analyzing runoff changes in the Yue River basin with similar weather condition. The results show that: the average runoff value from 1960 to 2018 is 8.3×108 m3. The discharge shows a decreasing trend as a whole, and the change trend is not significant. Under the similar weather condition, this research obtains 6 paired- years. Among them, the annual runoff of 3 paired-years increased and that of 2 paired-years decreased. Taking the third paired-year (2000 and 2016) as an example to quantitatively distinguish the impact of climate change and human activities on runoff which reduced by 4.7 × 108 m3 in 2016 compared with 2000. In the third paired- year (2000 and 2016), 25751.4 hm2 of arable land was converted into forest land, and the forest land area increased by 24998.9 hm2. The NDVI change is mainly caused by human activities. The area increased by NDVI in 2016 was 242652.0 hm2 compared with that in 2000. The change trend of NDVI is opposite to that of runoff. This study can provide a theoretical basis for quantitative evaluation for human activities’impact on river runoff changes within the Qinling Mountains.
Subjects: Geosciences >> Atmospheric Sciences submitted time 2023-03-13 Cooperative journals: 《干旱区研究》
Abstract： In recent decades, an unusual reduction in forest radial growth and temperature sensitivity has been widely observed in the northern high latitudes. Several studies have also suggested that unstable and nonlinear relationships exist between tree growth and its climatic drivers at mid-latitudes and even globally. However, this relationship remains poorly understood, particularly in the mid-latitudes. The climate response and growth process before and after the temperature abrupt change were investigated using dendroclimatological methods and the Vaganov- Shashkin model in order to research the variations and mechanisms of response of radial growth of Pinus tabulaeformis to climate factors in Maijishan Mountain, Tianshui, during 1980- 2019. The findings revealed that: (1) According to the Mann-Kendall test, temperature changed abruptly in 1997 and then increased significantly. During 1980-1997 and 1998-2019, there were three patterns of response in radial growth to climate factors revealed in the variation in correlation with climatic factors: decline (Temperature in May), increase (Temperature and precipitation in October, precipitation in July and temperature in December), and fluctuation (Precipitation in June and temperature in July). (2) The Vaganov- Shashkin model estimated chronologies are significantly correlated with the measured tree- ring chronologies before and after the abrupt change (P<0.05). According to simulation results, significant climate warming resulted in more abundant heat supply for growth in spring and autumn, thereby significantly extending the growing season and potentially causing a change in response patterns in May and October. Furthermore, summer high temperatures and water scarcity impacted growth, potentially leading to a change in response patterns in July. (3) The change in response patterns to climate factors is primarily caused by climate warming and the lengthening of the growing season. If the climate continues to warm, the response patterns are expected to change, even more, and similar behavior may exist in other areas where the species is found.
Subjects: Geosciences >> Geography submitted time 2022-06-09 Cooperative journals: 《干旱区地理》
Abstract：为了定量划分分散式乡村聚落的形状类型并探究其形成原因，以陕北黄土丘陵沟壑区米脂 县龙镇为例，尝试使用Alpha Shape算法对聚落形状进行提取，通过Boyce-Clark指数计算并划分聚 落形状类型，最后结合多元线性回归和回归树的方法探究影响聚落形状的因素。结果表明：100 m 滚动半径下，Alpha Shape算法能够提取76.1%聚落的精确轮廓；研究区乡村聚落形状类型可以分为 块状矩形及其变种、延伸形、哑铃形和串珠形、带状矩形及其组合、线形5种，Boyce-Clark指数依次 增加；高程和Boyce-Clark指数呈显著正相关，水资源可获取性与Boyce-Clark指数在高海拔地区呈 负相关，聚落面积与Boyce-Clark指数先呈负相关后呈正相关。研究结果可为分散式聚落生活空间 边界的划定提供参考，增进对黄土丘陵沟壑区分散式聚落形态的认识。
Subjects: Geosciences >> Geography submitted time 2022-06-09 Cooperative journals: 《干旱区地理》
Abstract：社会-生态系统恢复力理论为可持续发展研究提供了新视角。从社会、经济、生态三大子 系统，脆弱性和适应能力两大要素着手，建立社会-生态系统恢复力评价指标体系，采用集对分析 法测度黄土高原20002018年各子系统及社会-生态系统恢复力，利用探索性空间数据分析法进 行时空演变格局分析，并甄别社会-生态系统恢复力的主要影响因素。结果表明：（1）20002018 年社会-生态系统恢复力由0.522增强至0.721。社会恢复力由0.548增强至0.629后减弱至0.525； 经济恢复力由0.401持续增强至0.850；生态恢复力由0.725减弱至0.607后增强至0.734，子系统恢 复力演化趋势均不协同，经济系统与社会-生态系统恢复力演化趋势协同。经济系统恢复力的增 强对于社会-生态系统恢复力增强具有显著促进作用。（2）社会-生态系统恢复力出现显著空间集 聚趋势，较高地区除省会城市和包头等能源富集区外，关中平原地区始终呈现高-高（H-H）集聚格 局，其余地区恢复力普遍相对偏低。（3）2000年以来黄土高原地区社会-生态系统恢复力生态维度 障碍度始终高于社会和经济维度，不同地区指标层首要影响因素为人均GDP。
Subjects: Geosciences >> Geography submitted time 2020-01-06 Cooperative journals: 《干旱区地理》
Abstract：基于秦巴山商洛地区农户问卷调查数据，在可持续生计框架下，聚焦不同群体之间生计资本状况，并探讨其农户生计资本对生计策略选择的影响以及生计资本的耦合性。结果表明：（1） 山区农户生计策略出现明显分化，依据非农收入比重分为纯务工型、务工主导型、兼业型和纯农型4种类型。（2） 调研样本中农户生计资本有限和不均衡，呈现金融资本和社会资本相对较高，自然资本、人力资本偏低的特征。非贫困户中兼业型生计资本总值最高，务工主导型、纯务工型次之，纯农型最低；贫困户中务工主导型生计资本总值最高，纯务工型、兼业型次之，纯农型最低。（3） 非贫困户中人均耕地面积、人均林地面积、耕地质量、职业技能水平、政治资源、就业网络对纯务工型农户向务工主导型、兼业型转变有着积极影响，家庭人均收入、男性劳动力比例则具有负向影响；家庭人均收入和职业技能水平对于纯务工型向纯农型转变有负向影响。贫困户中人均耕地面积、人均林地面积、政治资源对纯务工型农户向务工主导型、兼业型和纯农型转变具有正向影响，家庭人均收入、劳动力教育水平、职业技能水平、联系成本则具有负向影响。（4） 非贫困农户生计资本耦合度依次为兼业型＞务工主导型＞纯务工型＞纯农型；贫困农户则为兼业型＞纯务工型＞务工主导型＞纯农型。因此，开展农户可持续性生计研究，对于农户减贫、促进乡村地区发展具有重要意义。
Subjects: Geosciences >> Geography submitted time 2020-01-06 Cooperative journals: 《干旱区地理》
Abstract：等高线曲率是一个重要的地形属性，反应了地形表面在水平方向的凹凸性，表达了地表物质运动的发散和汇合模式。基于安塞县县南沟小流域的矢量等高线数据和DEM，分别利用圆拟合算法（相邻三点法、间隔三点法和最小二乘法）和曲面拟合模型（E模型、S模型和Z模型）提取等高线曲率，通过对实地地形的对比分析，结果表明：（1） 在矢量等高线数据的计算结果中，三点拟合法计算结果相比最小二乘法结果差异大，对等高线曲率空间格局分布描述更准确；（2） 最小二乘法计算的结果频数分布集中程度最高，两种三点拟合法计算结果频数曲线差别微小；（3） 在栅格数字高程模型的计算结果中，基于S模型计算结果在空间格局上较E模型和Z模型的结果差别大，基于E模型的计算结果对等高线曲率描述效果更好。结果能准确说明采用不同算法计算等高线曲率的差别，对在实际数字地形分析中有重要的意义，可为等高线曲率计算提供重要参考。
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