中国西北干旱半干旱区是中国北方重要的生态屏障。在气候变化和人类活动双重影响下,开展该区域植被净生态系统生产力(NEP)时空变化特征及关键驱动因素的研究对区域生态安全与可持续发展意义重大。基于气象、植被、土壤和地形等多源遥感...中国西北干旱半干旱区是中国北方重要的生态屏障。在气候变化和人类活动双重影响下,开展该区域植被净生态系统生产力(NEP)时空变化特征及关键驱动因素的研究对区域生态安全与可持续发展意义重大。基于气象、植被、土壤和地形等多源遥感及再分析数据集,利用改进的CASA模型、土壤呼吸模型、地理探测器等方法,分析了2000-2022年中国西北干旱半干旱区植被NEP时空变化特征及其关键影响因子。主要研究结果表明:(1)研究区植被NEP多年均值为135.32g C/m^(2),整体呈碳汇功能,年内碳汇主要集中在5-9月份;碳源区主要集中在山前低植被覆盖区和东部沙地,面积占29%。(2)近23年研究区植被NEP以增加趋势为主,变化速率为3.98g C m^(-2) a^(-1)。空间上,呈增加趋势的面积占比为88.77%,减少趋势主要集中在天山山脉山前平原区。(3)LAI对植被NEP空间分布的解释力最强(0.75),其次是土壤湿度(0.42),不同要素交互对NEP均呈现双因子增强或非线性增强作用;LAI、降水和太阳辐射与研究区植被NEP主要呈显著正相关,显著正相关面积分别占73.79%、16.28%和15.10%,与降水呈显著正相关区域主要分布在西部山区、呼伦湖和东部沙地,与太阳辐射呈显著正相关区域主要分布在东部沙地。(4)西北干旱半干旱区气候变化对NEP的贡献度大于80%的地区占59.42%。人类活动对NEP的贡献率高于60%的区域占比为13.90%,集中分布在阿尔泰山和天山山脉的山前平原区,极少数散落分布在东部沙地。研究结果有助于了解植被NEP对气候变化的响应机制,为实现"双碳"目标提供理论依据。展开更多
Quantifying grassland changes and their drivers is essential to ensure the stability of grassland resources in China.We established a research framework with two primary objectives:to evaluate grassland degradation an...Quantifying grassland changes and their drivers is essential to ensure the stability of grassland resources in China.We established a research framework with two primary objectives:to evaluate grassland degradation and restoration over the past 30 years,and to quantify the contributions of climate change and anthropogenic activities to these changes across different grassland cover types.The results revealed that despite a net loss of 6.87×10^(4)km^(2)in China's total grassland area from 1990 to 2020,the proportion of high-coverage grassland increased by 2.45%,demonstrating an improvement in productivity per unit area.Conversion of grassland to cropland was the dominant land change type,with 80.83%occurring in the western part of the Northwest Ecological Region.Although the total degraded grassland area reached 3.33×10^(5)km^(2)during 1990-2020,this degradation was overwhelmingly dominated by the mild level(94.98%),with severe degradation accounting for only 5.02%.A comparison of the periods 2000-2010 and 1990-2000 revealed that grassland restoration became enhanced in the northeastern part of the Qinghai-Tibet Plateau Ecological Region but degradation intensified in the southwestern part.Moreover,mobile grazing emerged as the primary anthropogenic driver of grassland changes.These new findings provide an important scientific basis for adaptable grassland resource protection and grassland-livestock balanced management.展开更多
目的对比研究计算机辅助光学导航与电磁导航下精准牙种植手术的优缺点。方法 下颌牙列缺损拟行牙种植手术患者10例,采集患者颌骨CBCT影像,5例在计算机辅助光学导航下行牙种植手术,5例在计算机辅助电磁导航下行牙种植手术。术后拍摄CBCT...目的对比研究计算机辅助光学导航与电磁导航下精准牙种植手术的优缺点。方法 下颌牙列缺损拟行牙种植手术患者10例,采集患者颌骨CBCT影像,5例在计算机辅助光学导航下行牙种植手术,5例在计算机辅助电磁导航下行牙种植手术。术后拍摄CBCT进行种植位点评估。结果 两组患者均获得了良好的治疗效果,所有植体均植入理想的颌骨位置中。两组患者植体整体角度偏差范围不超过25°,植入深度偏差均不超过 1.4 mm;光学导航组植体植入角度偏差小于电磁导航组( t =3.5, P <0.05),两组患者植体植入深度差异无显著性( P >0.05)。结论 计算机辅助光学导航与电磁导航下均可完成精准牙种植手术,在应用过程中,两者各有优势和不足,电磁导航对于手术室环境要求较苛刻,在常规环境中精度略低于光学导航。在进一步研究中如果可以将光学导航和电磁导航相结合进行精准牙种植手术,将大大提高计算机辅助导航在牙种植领域的应用范围,特别是为复杂牙种植手术提供新的助力。展开更多
文摘中国西北干旱半干旱区是中国北方重要的生态屏障。在气候变化和人类活动双重影响下,开展该区域植被净生态系统生产力(NEP)时空变化特征及关键驱动因素的研究对区域生态安全与可持续发展意义重大。基于气象、植被、土壤和地形等多源遥感及再分析数据集,利用改进的CASA模型、土壤呼吸模型、地理探测器等方法,分析了2000-2022年中国西北干旱半干旱区植被NEP时空变化特征及其关键影响因子。主要研究结果表明:(1)研究区植被NEP多年均值为135.32g C/m^(2),整体呈碳汇功能,年内碳汇主要集中在5-9月份;碳源区主要集中在山前低植被覆盖区和东部沙地,面积占29%。(2)近23年研究区植被NEP以增加趋势为主,变化速率为3.98g C m^(-2) a^(-1)。空间上,呈增加趋势的面积占比为88.77%,减少趋势主要集中在天山山脉山前平原区。(3)LAI对植被NEP空间分布的解释力最强(0.75),其次是土壤湿度(0.42),不同要素交互对NEP均呈现双因子增强或非线性增强作用;LAI、降水和太阳辐射与研究区植被NEP主要呈显著正相关,显著正相关面积分别占73.79%、16.28%和15.10%,与降水呈显著正相关区域主要分布在西部山区、呼伦湖和东部沙地,与太阳辐射呈显著正相关区域主要分布在东部沙地。(4)西北干旱半干旱区气候变化对NEP的贡献度大于80%的地区占59.42%。人类活动对NEP的贡献率高于60%的区域占比为13.90%,集中分布在阿尔泰山和天山山脉的山前平原区,极少数散落分布在东部沙地。研究结果有助于了解植被NEP对气候变化的响应机制,为实现"双碳"目标提供理论依据。
基金The Postgraduate Research Innovation Project of Department of Education of Inner Mongolia Autonomous Region,No.KC2024029BThe Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA23100201The Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK0608。
文摘Quantifying grassland changes and their drivers is essential to ensure the stability of grassland resources in China.We established a research framework with two primary objectives:to evaluate grassland degradation and restoration over the past 30 years,and to quantify the contributions of climate change and anthropogenic activities to these changes across different grassland cover types.The results revealed that despite a net loss of 6.87×10^(4)km^(2)in China's total grassland area from 1990 to 2020,the proportion of high-coverage grassland increased by 2.45%,demonstrating an improvement in productivity per unit area.Conversion of grassland to cropland was the dominant land change type,with 80.83%occurring in the western part of the Northwest Ecological Region.Although the total degraded grassland area reached 3.33×10^(5)km^(2)during 1990-2020,this degradation was overwhelmingly dominated by the mild level(94.98%),with severe degradation accounting for only 5.02%.A comparison of the periods 2000-2010 and 1990-2000 revealed that grassland restoration became enhanced in the northeastern part of the Qinghai-Tibet Plateau Ecological Region but degradation intensified in the southwestern part.Moreover,mobile grazing emerged as the primary anthropogenic driver of grassland changes.These new findings provide an important scientific basis for adaptable grassland resource protection and grassland-livestock balanced management.
文摘目的对比研究计算机辅助光学导航与电磁导航下精准牙种植手术的优缺点。方法 下颌牙列缺损拟行牙种植手术患者10例,采集患者颌骨CBCT影像,5例在计算机辅助光学导航下行牙种植手术,5例在计算机辅助电磁导航下行牙种植手术。术后拍摄CBCT进行种植位点评估。结果 两组患者均获得了良好的治疗效果,所有植体均植入理想的颌骨位置中。两组患者植体整体角度偏差范围不超过25°,植入深度偏差均不超过 1.4 mm;光学导航组植体植入角度偏差小于电磁导航组( t =3.5, P <0.05),两组患者植体植入深度差异无显著性( P >0.05)。结论 计算机辅助光学导航与电磁导航下均可完成精准牙种植手术,在应用过程中,两者各有优势和不足,电磁导航对于手术室环境要求较苛刻,在常规环境中精度略低于光学导航。在进一步研究中如果可以将光学导航和电磁导航相结合进行精准牙种植手术,将大大提高计算机辅助导航在牙种植领域的应用范围,特别是为复杂牙种植手术提供新的助力。
