Spatio-temporal patterns and driving mechanism of farmland fragmentation in the Huang-Huai-Hai Plain

Exploring the spatio-temporal variations of farmland landscape patterns in a traditional agricultural region can provide scientific support for decision-making on sustainable rural land use and rural vitalization development. This study established a comprehensive evaluation index for farmland fragmentation with multiple aspects (dominance, integrity, aggregation, regularity, and connectivity) at the county scale. The goal was to identify the evolution of farmland fragmentation in the traditional agricultural region of the Huang-Huai-Hai Plain during 2000-2015 and investigate underlying drivers using panel data of 359 counties. Results showed an accelerating but fluctuating fragmentation pattern of the farmland landscape. The indexes of dominance, integrity, and aggregation of farmland decreased most sharply, while the index of connectivity increased. Furthermore, the evolution of the farmland fragmentation pattern showed significant spatio-temporal heterogeneity, which is similar to the trajectory of urbanization and land use transition. Farmland fragmentation in municipal districts also emerged earlier and was more severe than in county-level cities and counties. Factors influenced by advancing urbanization include the proportion of artificial land, population density, and proportion of primary industry; these factors drove the evolution of farmland fragmentation. In contrast, the increase in income of rural residents and production efficiency of farmland were the key factors contributing to the improvement in farmland connectivity.     

BRINCK JACKSON IN THE REALM OF THE EVERYDAY*

ABSTRACT. Academic geography is dotted with fly-specks from the fashion conscious who have skittered from one enthusiasm to another like aggravating bugs in midroom flight. Our disciplinary history in fact abounds in dead-end roads entered at fatally high speed, theoretical turns not negotiated, crossroads oracles proved dismally inaccurate. By contrast, the formidable cultural geographer and landscape historian J. B. “Brinck” Jackson (1909–1996) conceived of a more slowly developing world, replete with enduring geographies. Although firmly Brahmin by origin, Jackson was chary of the fleeting fashions and power tropes of what he sometimes dubbed the Establishment. He was inclined instead to attend to the structures of the everyday, emphasizing community and connection over didactic fashion. With writing grounded in daily experience and a consummate ability to witness pattern, he urged geographers to think and envision.     

喀斯特石漠化小流域景观的空间因子分析——以贵州清镇王家寨小流域为例

以贵州喀斯特地区的王家寨小流域为研究对象,基于多源信息,依托RS和GIS技术获取2005年该流域石漠化景观格局信息,以此为基础进行石漠化景观分布指数、石漠化综合指数、 -s平面分析模型以及三次曲线拟合等分析,旨在从小流域尺度上探讨石漠化景观在坡度、坡向、高程和与村庄距离等空间因子上的分布规律。结果表明:潜在、轻度石漠化景观受坡度影响最显著;其他类型石漠化景观受坡向影响最明显。石漠化程度先随坡度的增大而加重,27°后呈缓解趋势;各坡向中南、东南坡石漠化最严重;随高程增加石漠化加剧;距村庄越远石漠化越严重。初步推断各空间因子对石漠化程度的影响由强至弱的顺序为:坡度、坡向、高程、与村庄的距离。     

遥感影像云检测网络泛化性能研究：以DeepLabv3+为例

近年来,深度学习算法得到了长足的发展,并开始应用于云检测。但是深度神经网络模型参数众多,依赖大量训练样本,因此理解其泛化性能对于深度学习在不同遥感影像的实际应用具有重要的参考价值。本文以深度语义分割算法DeepLabv3+为例,以一组广泛使用的云标记数据集"L8 Biome"为验证数据,探讨该算法用于云检测时在不同的地表景观、空间分辨率和光谱波段组合的遥感影像上的泛化性能。云标记数据集"L8Biome"包含96景具有全球代表性的Landsat 8 OLI影像及相应的人工云掩膜,被广泛用于测试云和云阴影检测算法性能。首先,利用Landsat 8 OLI云标记数据集"L8 Biome",构建不同类型景观、不同空间分辨率、不同波段组合的训练影像集和测试影像集;其次基于不同训练样本集和测试集,评估了DeepLabv3+算法在不同情况下的云检测精度,并与Fmask算法作对比分析。研究结果表明:(1)使用全混合景观类型的训练集训练出来的云检测网络在总体检测精度(92.81%)与稳定度(标准差12.08%)上都优于使用单一景观类型的训练集训练得到的云检测网络,也优于Fmask的总体精度(88.75%)与稳定度(标准差17.34%),说明在构建深度学习算法的训练集时,应该尽可能包含多类型的地表景观;(2)将全混合景观训练集中剔除一类景观的样本(冰/雪景观除外)构建的"混合-1"训练集与全混合景观训练集训练的DeepLabv3+网络的云检测精度也相差不大,说明现有训练样本集已具备较强的景观泛化能力;(3)基于30 m空间分辨率的全混合景观训练样本集训练得到的DeepLabv3+云检测网络在不同分辨率(30 m、60 m、120 m、240 m)的测试集上云检测精度差异不大,都取得较好的效果,说明DeepLabv3+能够泛化应用于不同空间分辨率的遥感影像,相反Fmask直接应用于低分辨率影像时精度明显下降;(4) DeepLabv3+能充分自适应不同波段的信息用于云检测,总体来说更多的光谱波段输入能够提高DeepLabv3+的云检测的精度和稳定度,其中短波红外波段对于DeepLabv3+区分冰/雪与云具有重要价值,而热红外波段对DeepLabv3+云检测网络的性能提升很微小。以上结果说明利用现有数据集"L8 Biome"训练的DeepLabv3+云检测网络能够适用于多种类型的遥感影像,并优于Fmask算法。     

基于景观格局的黑河中游土地利用冲突时空分析

以黑河中游为研究区,在分析土地利用变化的基础上,构建了由外部压力、脆弱性和稳定性表征土地利用冲突强度的模型,分析了1980—2015年土地利用冲突的时空变化特征。结果表明:①土地利用冲突强度的空间分布在不同时期虽有不同,但冲突强度较高的区域集中在甘州、临泽2个人类活动较为活跃的区县,且指数最高的区域呈围绕城市四周分布的特点;②土地利用冲突在不同时期变化显著,1995—2005年是土地利用冲突强度增加较为明显的时段,中部的甘州区、南部的山丹县两地增加最为明显;2005—2015年虽然冲突强度增大区域的面积少于上一时段,但冲突增加幅度高于上一时段,尤其民乐县和高台县增加较为明显;③土地利用冲突与自然因素的相关性极弱,与道路和河流等用地条件的相关性较强,而与人口密度和GDP为代表的社会经济因素的相关性最强;④土地利用冲突与土地利用变化的阶段性特征一致,1995—2000年是土地利用变化程度最为剧烈的时期,而1995—2005年也是土地利用冲突面积增加最多的时段;耕地和建设用地的增长极为活跃,对生态用地产生侵占,反映了耕地、建设用地和生态用地三者之间的矛盾是黑河中游土地利用冲突的主要表现形式。     

松嫩平原中部农业区域土地景观动态研究

松嫩平原中部作为我国重要的农业生产区域之一,随着农业生产的发展变化土地景观也发生着变化,对区域土地景观动态的分析研究有利于保持土地合理利用和土地景观系统的生态平衡.卫星遥感信息与统计资料结合进行分析可以宏观、定位、定量地得出土地景观动态.     

基于RS和GIS的西双版纳土地覆被动态变化

人口增加、经济发展导致滇南热带地区西双版纳土地利用/土地覆被发生显著变化,这些变化对该区的生态环境及生物多样性保护有着重要影响。基于RS和GIS方法,通过对1976、1988和2003年三个时期遥感影像解译分析,试图了解西双版纳近27 a间土地利用/土地覆被时空变化特征及影响因素。结果表明,近27 a间有林地在西双版纳分布最广、占绝对优势,其中以亚热带常绿阔叶林面积最大;但在研究时段内,有林地面积不断减少、呈现破碎化,尤其是热带季节雨林、山地雨林面积减少最为明显和破碎化最为严重。相应,橡胶园、灌木林面积不断扩大并聚集成片,其中橡胶园在1988~2003年间是面积增长最快、最多的地类,其面积扩张主要来源于对热带季节雨林的砍伐。轮歇地面积在1976~1988年是所有地类中增长最快、最多的,在1988~2003年由于向橡胶园转变而大幅度减小。粗放式的刀耕火种和橡胶种植园的不断扩大是主导本区土地利用/土地覆被变化的主要因素,土地利用变化导致了本区生态环境的退化和生物多样性的丢失。     

塔里木河干流区土地覆被变化与景观格局分析

在GIS和遥感技术支持下,结合景观格局数量分析方法,利用1973年MSS、1983年航空遥感土地利用图、1990年TM、2000年TM和2005年CBERS遥感影像对新疆塔里木河干流区土地利用/覆被变化过程进行了定量分析.结果表明,1973-2005年塔里木河干流区土地利用/覆被发生了显著变化,耕地和城乡居民及建设崩地面积显著增加,林地、草地和湿地面积减少,未利用地表现出先增加后减小的趋势.研究区土地利用类型转移的主要方向是林地和草地转化为耕地、耕地转化为城乡居民及建设用地、草地转化为未利用地.土地利用变化经历了"显著变化-缓慢变化-显著变化-急剧变化"的过程.景观格局分析表明,在人类活动的影响下,研究区景观破碎度、多样性增大,优势度减小.草地和未利用地对整个景观的控制作用减小,景观结构趋于多样和均匀.驱动力分析表明,人口增长和经济发展因素是塔里木河干流区土地利用/覆被变化的最直接驱动力,同时还受产业结构因素和政策因素及人类干扰强度的影响.     

Improved simulation of river water and groundwater exchange in an alluvial plain using the SWAT model

Hydrological interaction between surface and subsurface water systems has a significant impact on water quality, ecosystems and biogeochemistry cycling of both systems. Distributed models have been developed to simulate this function, but they require detailed spatial inputs and extensive computation time. The soil and water assessment tool (SWAT) model is a semi‐distributed model that has been successfully applied around the world. However, it has not been able to simulate the two‐way exchanges between surface water and groundwater. In this study, the SWAT‐landscape unit (LU) model – based on a catena method that routes flow across three LUs (the divide, the hillslope and the valley) – was modified and applied in the floodplain of the Garonne River. The modified model was called SWAT‐LUD. Darcy's equation was applied to simulate groundwater flow. The algorithm for surface water‐level simulation during flooding periods was modified, and the influence of flooding on groundwater levels was added to the model. Chloride was chosen as a conservative tracer to test simulated water exchanges. The simulated water exchange quantity from SWAT‐LUD was compared with the output of a two‐dimensional distributed model, surface–subsurface water exchange model. The results showed that simulated groundwater levels in the LU adjoining the river matched the observed data very well. Additionally, SWAT‐LUD model was able to reflect the actual water exchange between the river and the aquifer. It showed that river water discharge has a significant influence on the surface–groundwater exchanges. The main water flow direction in the river/groundwater interface was from groundwater to river; water that flowed in this direction accounted for 65% of the total exchanged water volume. The water mixing occurs mainly during high hydraulic periods. Flooded water was important for the surface–subsurface water exchange process; it accounted for 69% of total water that flowed from the river to the aquifer. The new module also provides the option of simulating pollution transfer occurring at the river/groundwater interface at the catchment scale. Copyright © 2015 John Wiley & Sons, Ltd.     

基于Landsat遥感数据的长岛南部岛群景观格局演化研究

为了了解长岛南部岛群在经济发展背景下的景观格局及未来变化趋势,利用1990~2015年6景Landsat TM5、TM7和OLI8影像数据源,基于地理信息系统(GIS)平台采用决策树分类的方法对长岛南部岛群的景观类型进行了分类,并结合Frag-stats软件提取7种不同的景观格局指数,对长岛南部岛群的景观格局演化特征进行了系统分析。结果显示,人为活动是近年来长岛南部岛群景观格局演化的主要驱动力,该岛群景观类型变化以建设用地、水产养殖用地增加和林地减少为特征,建设用地斑块聚集度指数较高,斑块的聚集度指数逐年增加,整体上斑块的聚集度和连通性很好。不同景观指数(SHDI(景观斑块多样性)、PAFRAC(周长面积分维数)、PD(斑块密度指数)、LSI(斑块形状指数)、CA(斑块面积指数)、AI(景观聚集度指数)、COHESION(斑块结合度指数))对人为扰动因子均具有良好的表征。相关研究结论可为长岛南部岛群综合管理和生态红线划定提供有效依据。