利用Landsat热红外遥感调查广西平果县石漠化现状和变化特征

喀斯特石漠化是我国西南地区严重的生态问题,通过对喀斯特地区岩石热特性的探究,提出基于热红外遥感的石漠化监测方法.以平果县为研究区,利用2006年Landsat 5和2014年Landsat 8热红外遥感影像计算亮温,参考高分影像建立典型样本区并分析样本区亮温,确定不同石漠化等级的亮温阈值,最后对全县石漠化进行等级划分,并分析平果县石漠化变化.平果县2014年石漠化分级结果显示:非石漠化占18.47％;潜在石漠化32.9％;轻度石漠化占24.8％;中度石漠化占18.94％;重度石漠化占4.89％.平果县2014年石漠化整体情况较2006年有所好转,局部区域石漠化有恶化的趋势.本研究通过确定适当的夏冬季亮温差阈值可以有效地对石漠化程度进行分级划分,该方法与已有方法相比,具有物理意义明确、方法简单有效、结果客观等优点,具有推广应用价值.

Landsat thermal remote sensing to investigate the present situation and variation characteristics of karst rocky desertification in Pingguo County of Guangxi,Southwest China

Background] Karst rocky desertification is a serious ecological problem in the southwest of China,and the degradation of ecosystems limits the regional social and economic development,which attracts extensive attention.Remote sensing technology shows many advantages,such as rapidness and economy.It is an indispensable means for rapid,large-scale,qualitative evaluation and quantitative information extraction of rocky desertification.The traditional remote sensing monitoring method of Karst rocky desertification (KRD) is mainly based on visual interpretation and comprehensive index method.Both methods need large workload but in low efficiency.The KRD monitoring method based on thermal infrared remote sensing was proposed to explore the thermal characteristics of Karst rock.The method has the advantages of clear physical meaning concise method and less subjectivity.Methods] The method is based on the limestone reflectivity different from vegetation reflectivity in the vicinity of 11 μm in the thermal infrared band,where limestone is a reflectance peak and the vegetation reflectivity low.A typical sample area of KRD was established with reference to the high resolution image of Google Earth,and the threshold temperature of typical desertification area was determined.The research covers the determination of grading index of rocky desertification,the extraction of Karst area in Pingguo County,the extraction of construction land,the determination of rocky desertification grade threshold,the classification of KRD,the distribution characteristics of KRD at various levels,and dynamic analysis of KRD.Results] In 2014 each level of KRD accounted for the total Karst area in Pingguo County:none KRD was 18.47％,mainly distributed in the gentle areas;potential KRD was 32.90％,widely distributed in Pingguo karst area;slight KRD was 24.80％,was striped in the middle and southwest of Pingguo County karst area;moderate KRD accounted for 18.94%,showed a strip along the mountain trend distribution;severe KRD accounted for 4.89％,was flat or dotted distribution of Pingguo County southeast and central.Classification results of KRD in 2006:none KRD was 16.08％,potential was 33.24％,slight accounted for 22.18％;moderate KRD accounted for 20.63％;severe KRD accounted for 7.15％.The analysis of KRD change in Pingguo County shows that the overall situation of KRD in 2014 is better than that in 2006,but the KRD in some areas has a tendency of deterioration.Conclusions] Compared with other methods,the method proposed in this paper reduced the artificially subjectivity of traditional visual interpretation and improved the efficiency of interpretation.Compared with KRD index,the method is more concise and needs less data.The method can obtain more objective and accurate karst rock desertification information and can be popularized and applied.