封育对干热河谷Savanna植物群落种间关联性的影响

为探讨封育措施对干热河谷稀树灌草丛(Savanna)群落种间关系的影响,在金沙江干热河谷实施水土保持封育20年的区域及其周边区域设置封育区和干扰区样地开展植被调查,应用方差比率(VR)法、χ2检验结合Jaccard指数法以及Spearman秩相关系数法对25个优势物种的种间关系进行比较分析。结果表明:封育导致稀树灌草丛群落组成及结构发生明显变化,有助于橘草等多年生乡土禾草的生长,促进假杜鹃(Bc)、清香木(Pw)和地檀香(Gf)等一些木质化程度较高的物种留存,同时抑制一年生物种、杂草类物种和外来物种的出现,在群落中形成多个建群物种;干热河谷稀树灌草丛群落总体种间联结以正联结为主,封育促进群落形成更加复杂的种间联结关系;相较于封育区,干扰区群落物种间存在较高的资源竞争或生态关系的相互排斥,促进一年生物种、杂草类物种和外来物种间形成较强的正联结关系,形成以黄茅为代表的单优势建群种群落,而封育区群落总体种间关系呈现显著正联结状态,促进豆科物种、木质化物种、乡土物种间形成正联结关系,优势物种间正负相关关系同时加强。以上结论表明,封育措施对干热河谷稀树灌草丛优势植物种间关系有重要影响,通过影响植物群落物种组成、功能群结构等强化优势种间的相互作用是其重要影响途径。

昆明强降水对城市化和热环境变化的响应研究

局部气候变化下的城市化往往对强降水的发生发展产生重大影响,为探究城市化和热环境对昆明强降水的作用,文中利用昆明市1991—2021年湿季(5—10月)城区昆明站与郊区晋宁站的逐时降水数据进行分析,在揭示不同城市化阶段城郊站点之间的强降水差异和变化趋势基础上,结合MODIS地表温度遥感数据,从快速城市化背景的角度,进一步探讨昆明主城区湿季昼夜城市热环境时空分布情况及其与城区强降水指标之间的定量关系。结果表明,近31年来城郊两站点的强降水量和强降水频次均呈现上升趋势。其中,城区强降水量与强降水频次总体增长速率大于郊区,城郊差异较大,城市化对城区强降水量和强降水频次的贡献率分别达到47%以及40%。昆明城区进入21世纪以来总降水量减少,城区强降水量与强降水频次的贡献率不断上升,其线性趋势均在快速城市化阶段表现出更高的显著性。昆明城区强降水主要活跃在19时至次日05时,属于夜间活跃型单峰结构,强降水峰值出现在凌晨04时,“夜雨”特性显著,强降水频次对强降水量具有主要贡献。在1991—2021年期间,白天城郊站点强降水均无明显变化趋势,而夜间城区的强降水量与强降水频次的贡献率趋势上升,并显著表现在近17年快速城市化阶段。快速城市化时期夜间城市热环境指数相比白天显著升高,城市热效应明显。通过相关分析发现,城市热环境对城区强降水具有正向促进作用,而这种作用以高显著性主要表现在夜间。

昆明市干季碳气溶胶污染特征及来源解析

为研究西南高原城市昆明的碳气溶胶浓度特征及其来源,2018年11月20日—2019年3月23日,在昆明主城区采集PM_(2.5)样品共117个,测定有机碳(OC,organic carbon)和元素碳(EC,elemental carbon)的质量浓度,对其进行源解析。结果显示:昆明市PM_(2.5)平均浓度为72.31±26.19μg/m^(3),碳气溶胶浓度(TC,total carbon)为38.04±18.74μg/m^(3),约占PM_(2.5)的53%。碳气溶胶以有机碳排放为主,OC约占TC的75%,EC平均质量为9.15±4.02μg/m^(3)。OC/EC值为3.23,二次有机碳(SOC,secondary organic carbon)约占有机碳的40%左右,存在二次有机污染物。碳组分浓度排序为:OC3>OC4>OPC>EC1>OC2>OC1>EC2>EC3,以汽油车尾气排放、燃煤、扬尘、生物质燃烧源占主导。外源气团影响了昆明市碳质气溶胶浓度水平和组成,与局地排放相比,西南风时OC3、OP占比较高,EC1占比降低;偏南风时OP占比增加;东北风时OC4占比增加明显。昆明碳气溶胶的潜在外源输入主要来自西南方向,如红河、玉溪及缅北等地,部分来自东南(文山)、东北(曲靖)方向,生物质燃烧和工业排放是区域传输的主要来源。

纳板河流域不同植被类型下土壤肥力综合评价

为了解不同植被类型土壤肥力差异,通过检测土壤自然含水率、土壤容重、pH、有机质、全氮、全磷、全钾和速效钾等土壤肥力指标,运用主成分分析对西双版纳纳板河流域20 a茶树林、甘蔗地、5 a橡胶林、8 a橡胶林、15—20 a橡胶林、火龙果地和香蕉地等不同植被类型土壤肥力进行评价。结果表明:纳板河流域土壤自然含水率变异系数除8 a橡胶林和15—20 a橡胶林外均属于中等强度变异;土壤容重除甘蔗地变异系数为18.12%,属中等强度变异,其他植被类型变异系数均低于10%,属弱变异;土壤pH变异系数均属于弱变异;有机质变异系数除香蕉地外均属于中等强度变异;全氮变异系数也均属于中等强度变异;全磷变异系数除甘蔗地和火龙果地均属于弱变异;甘蔗地、5 a橡胶林和香蕉地全钾变异系数属于弱变异,其他植被类型均属于中等强度变异;而速效钾变异系数均属于中等强度变异。通过对纳板河流域不同植被类型土壤肥力研究,将其肥力排序为:甘蔗地>20 a茶树林>5 a橡胶林>香蕉地>火龙果地>15—20 a橡胶林>8 a橡胶林。

滇池主要入湖河流水化学特征及其环境意义

为了给滇池流域水污染治理及水环境修复提供理论依据,选取滇池4条主要入湖河流(盘龙江、宝象河、柴河、捞渔河)为研究对象,同时采集农田排污口5个、城市排污口5个、雨水3个共计13个水样,按照河流流经区的不同土地类型,共布设28个样点,对其水化学特征进行了系统调查,并结合流域土地利用类型,探讨了流域水化学特征对环境的指示意义。结果表明,滇池流域4条主要入湖河流的pH值为6.50～7.77,均值为7.03;电导率(EC)为6.3～85.0 mS/m,均值为33.0 mS/m;总溶解固体(TDS)为40～540 mg/L,均值为210 mg/L,空间上均表现出沿河流自上游向下游递增的趋势;4条主要入湖河水中阳离子以Ca^(2+)为主,占主要阳离子的65%,阴离子则以HCO^-_3为主,占主要阴离子的84%,入湖河流的水化学类型为HCO^-_3-Ca^(2+)型;河道径流主要离子浓度均表现为自上游向下游增加的趋势。Ca^(2+)、Mg^(2+)和HCO^-_3主要指示了研究区地质条件对水环境的作用,K^+、NO^-_3、SO■主要指示了农业活动对水环境的影响,Na^+、Cl^-主要指示城市生活污水排放对水环境的影响。

基于GF-1与Sentinel-2融合数据的地膜识别方法研究

随着我国地膜使用面积的增加和人们对土壤微塑料污染问题的日益关注,大尺度的地膜遥感识别已成为农业生产管理、土壤污染防治的必要手段。针对地膜光谱反射特征的复杂性以及基于单一遥感影像光谱特征识别方法错分率高等问题,该文以河北省邯郸市邱县为试验区,利用GF-1数据的空间细节与Sentinel-2数据的光谱信息进行NN Diffuse Pan Sharpening融合,据此建立地膜识别的特征矩阵(NDVI、MNDWI、NDBI、IBI、PSI),基于该特征矩阵可实现自动阈值地膜分层分类识别。多种方法的地膜识别结果精度对比表明:多源光学遥感数据融合方法的总体精度为94.87%,Kappa系数达0.89,显著优于基于单一数据源的深度学习法的精度(93.14%)以及基于传统机器学习分类方法的支持向量机(85.91%)和随机森林分类法(86.78%)的精度;通过与Sentinel-2多光谱影像融合,弥补了GF-1数据光谱分辨率低的缺陷,实现了多源数据在地膜识别中的优势互补,可为相关部门农业规划与管理以及生态环境保护等研究提供大尺度、高精度的地膜分布参考数据。

Landscape structures of different rural landscape connectivity in typical plateau karst regions: Taking the Houzhai River area of Anshun City, Guizhou Province as an example

Landscape connectivity is important for energy and material flow in ecosystems as well as for the survival of species. The landscape structure influences and reflects the degree of landscape connectivity. In order to study the coupling relationship between landscape structure and connectivity and reveal the succession relationship between its structure and connectivity in the typical karst plateau area. The study analyzed the typical area of Houzhai River in Puding County, Anshun City, Guizhou Province, according to the landscape pattern index and probability landscape connectivity index. The results show:(1) The landscape structure of the study area A is mainly characterized by large patches and uniform distribution. The main land is woodland and cultivated land, and the overall landscape is low fragmentation.(2) The landscape structure of the study area B is mainly characterized by the clustering of a certain type of land cover and the uneven distribution of the patches, for example, cultivated land. Other types of patches are scatteredly distributed, and the overall landscape is highly fragmented.(3) The study area A, B in 100, 500, 1000, 2000, 3000, 5 distance thresholds of landscape connectivity were 1.55, 1.99, 2.26, 2.49, 2.58 and 0.02, 0.10, 0.15, 0.19, 0.20, respectively. The average landscape connectivity is 2. 18 and 0. 13, respectively. Study Area A has a higher degree of landscape connectivity than B. Landscape pattern indicators can represent the landscape structure and probability landscape connectivity index calculates the landscape connectivity in the study area. The results of the study can provide a basis for ecological restoration of plateau karst regions and well-oriented rural development planning.

Response of artificial lake algae growth to water quality and meteorological conditions in plateau area

The problem of water environment caused by algal blooms is very common and serious.Effective methods of algal bloom control are one of the focuses of current research.Compared to natural lakes,the artificial lake environment is relatively simple,and it is a good place to study the effects of meteorology and water quality on algae growth.The study selected three typical artificial lakes in Kunming City of Yunnan province as research areas.The water quality,meteorology and algae growth characteristics of these three artificial lakes were monitored and analyzed,the response relationship of artificial lake algae growth to water quality and meteorological conditions were revealed.Results showed that nitrogen nutrients,N/P ratio and the temperature of water environment,air CO2 concentration are the mainly factors affecting the growth of algae in these three lakes,and the total phosphorus concentration has no significant effect on algae growth.The research conclusions can provide a basis for exploring the mechanism of environmental factors affecting algae growth and the governance of eutrophication of lakes in the plateau.

Nitrogen forms and pollution load of Dianchi Lake inflow river runoff in rainy season

With the control of point source pollution in Dianchi Lake basin, and the expansion of Kunming city, non-point source pollution has become the main source pollution of urban water environment and Dianchi Lake. To reveal the nitrogen pollution characteristics in watershed, this research selected key monitoring points and sections at Baoxiang river basin in rainy season which is the peak transported time of non-point source pollution, the nitrogen and hydrological indicators are monitored systematically. The different forms of nitrogen are analyzed, the pollution load of nitrogen are calculated and studied at cardinal sections; combined with the literature data, we compared the water nitrogen characteristics of Dianchi basin and Taihu basin, the main results are as follows:(1) In summer, water nitrogen form of Baoxiang river in the Caohe area is dominated by nitrate nitrogen, while in other areas it is dominated by ammonia nitrogen which is accounted for 31%-50% of total nitrogen;(2) The water pollution loads of Baoxiang river tended to increase from upstream to downstream, from June to August the total nitrogen pollution mainly comes from urban areas and the pollution load is 166.408 t;(3) In Dianchi Lake watershed and Taihu Lake watershed nitrogen concentration of inflow river is higher than that of the lake, nitrate nitrogen concentration between inflow river and lake shows a little difference, while ammonia nitrogen concentration of inflow river is higher than that of the lake. The results can provide the theoretical basis for nonpoint source pollution control and urban water environment planning and improvement in Dianchi Lake Basin.

Effect of Inflow and Outflow Angles on the Computational Hemodynamics in Abdominal Aortic Aneurysm

To help the clinical screening and diagnosis of abdominal aortic aneurysm(AAA), we evaluated the effect of inflow angle (IA) and outflow bifurcation angle(BA) on the distribution of blood flow and wall shear stress(WSS) in an idealized AAA model. A 2D incompressible Newtonian flow is assumed and the computational simulation is performed using finite volume method. The results showed that the largest WSS often located at the proximal and the distal end of the AAA. An increase in IA resulted in an increase in maximum WSS. We also found that WSS was maximal when BA was 90°. IA and BA are two important geometrical factors, they may help AAA risk assessment along with the commonly used AAA diameter.