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991.
Sentinel-2卫星落叶松林龄信息反演 总被引:1,自引:0,他引:1
林龄结构信息能够有效反映区域森林群落不同生长阶段的固碳能力,对于评估森林生态系统的健康状况具有重要意义。本研究以中国温带典型优势树种落叶松林为研究对象,分别选择其芽萌动期、展叶期和落叶期时段的Sentinel-2影像,采用多元线性回归(MLR)、随机森林(RF)、支持向量机回归(SVR)、前馈反向传播神经网络(BP)以及多元自适应回归样条(MARS)等5种方法依次构建落叶松林龄反演模型。通过相关性分析首先确定最佳遥感反演物候期,并在此基础上根据相关性差异筛选出5个最优特征变量用于模型反演,分别为冠层含水量(CWC),归一化水体指数(NDWI),叶面积指数(LAI),光合有效辐射吸收率(FAPAR)和植被覆盖度(FVC)。研究结果表明,展叶期为落叶松林最佳遥感反演物候期。除植被衰减指数(PSRI)以及落叶期的NDVI、RVI外,落叶松林龄与各指标之间均呈负相关关系,其中与冠层含水量(CWC)的相关性最高,pearson相关系数达到-0.74(p<0.01)。此外,不同模型反演结果表明,随机森林模型(RF)为最佳落叶松林龄估测模型,其平均决定系数R2和平均均方根误差RMSE分别为0.89和2.91 a;多元线性回归模型(MLR)的林龄估测结果最差,其平均决定系数R2和平均均方根误差RMSE仅为0.57和5.69 a,非线性模型能更好的解释林龄与建模变量之间的关系。 相似文献
992.
993.
为探讨TiO2光催化法处理微污染水中腐殖酸的规律,利用悬浮状的TiO2颗粒在紫外光的照射下催化降解含有腐殖酸污染物的水样,设计正交试验研究pH值、TiO2的投加量、腐殖酸溶液初始浓度、曝气量和温度等对腐殖酸降解效果的影响及规律。结果表明:pH=3.5时,TiO2的投加量为1.0 g/L、曝气量为0.12 m3/h、温度为18℃时,最佳有机物降解效果为96.83%;TiO2光催化法对微污染水中的腐殖酸能够有效降解。 相似文献
994.
The automatic extraction of information content from remotely sensed data is always challenging. We suggest a novel fusion approach to improve the extraction of this information from mono-satellite images. A Worldview-2 (WV-2) pan-sharpened image and a 1/5000-scaled topographic vector map (TOPO5000) were used as the sample data. Firstly, the buildings and roads were manually extracted from WV-2 to point out the maximum extractable information content. Subsequently, object-based automatic extractions were performed. After achieving two-dimensional results, a normalized digital surface model (nDSM) was generated from the underlying digital aerial photos of TOPO5000, and the automatic extraction was repeated by fusion with the nDSM to include individual object heights as an additional band for classification. The contribution was tested by precision, completeness and overall quality. Novel fusion technique increased the success of automatic extraction by 7% for the number of buildings and by 23% for the length of roads. 相似文献
995.
Manuel Hernández Fernández 《Quaternary Research》2006,65(2):308-323
This paper presents a quantitative reconstruction of the European late Pleistocene paleoclimate based on 72 rodent assemblages of five sequences from France, Germany and Bulgaria, covering the last interglacial-glacial cycle. They show a pattern of severe changes in temperature, with reduced precipitation during the coldest periods. A tentative correlation between the isotopic and palynological records and the paleotemperature changes is shown. These changes are consistent with variations in atmospheric circulation patterns in response to an expanding-retracting Fennoscandian ice-sheet. They can be attributed to the enhancement-weakening of the Scandinavian-Polar anticyclone and its associated dry winds, the south-north shifting of the North Atlantic Polar Front, and the varying supply of moist air from the Atlantic. Qualitative paleoenvironmental analysis shows broadleaved-deciduous forests in France and Bulgaria during most of the studied period. Taiga and tundra appeared in eastern France during the lower Würm. The German sequence indicates the presence of coniferous forests. These results are broadly consistent with other paleobiological records (mammalian, avian and insect faunas, isotopic record in dental tissue, palynology). The main discrepancies with the paleoclimate inferred from the palynological record are found during the coldest periods and are probably due to the interaction between vegetation, climate, and atmospheric CO2 levels. 相似文献
996.
997.
David March Josep Als Amlia Grau Miquel Palmer 《Estuarine, Coastal and Shelf Science》2011,92(4):251-587
The short-term movements of a small temperate fish, the annular seabream Diplodus annularis (Linnaeus 1758), were examined using standard tag-recapture and passive acoustic telemetry in Palma Bay (NW Mediterranean), a marine protected area (MPA). The study aimed to provide valuable information for assessing the recreational fishery and its results suggest that MPAs can be used to protect the adult stock of D. annularis. All the fish tagged with standard tags were recaptured near the release locations, with a maximum distance of ∼300 m. The maximum time between release and recapture was 185 d. Two different arrays of acoustic receivers were deployed, one in 2008 and another in 2009, within the MPA. Twenty adults were surgically tagged with acoustic transmitters. Fish monitored in 2008 (n = 12) were translocated from the point of capture to analyse the movement behaviour after artificial displacement. Upon release at displaced locations, 67% of the fish moved towards the original capture location using a time of return that ranged from 0.75 to 15.25 h. Fish monitored in 2009 (n = 8) were released at the point of capture. They showed high site fidelity with a maximum period of 27 d between the first time and the last time they were detected. 相似文献
998.
Planting a cover crop between the main cropping seasons is an agricultural management measure with multiple potential benefits for sustainable food production. In the maize production system of the Netherlands, an effective establishment of a winter cover crop is important for reducing nitrogen leaching to groundwater. Cover crop establishment after maize cultivation is obliged by law for sandy soils and consequently implemented on nearly all maize fields, but the winter-time vegetative ground cover varies significantly between fields. The objectives of this study are to assess the variability in winter vegetative cover and evaluate to what extent this variability can be explained by the timing of cover crop establishment and weather conditions in two growing seasons (2017–2018). We used Sentinel-2 satellite imagery to construct NDVI time series for fields known to be cultivated with maize within the province of Overijssel. We fitted piecewise logistic functions to the time series in order to estimate cover crop sowing date and retrieve the fitted NDVI value for 1 December (NDVIDec). We used NDVIDec to represent the quality of cover crop establishment at the start of the winter season. The Sentinel-2 estimated sowing dates compared reasonably with ground reference data for eight fields (RMSE = 6.6 days). The two analysed years differed considerably, with 2018 being much drier and warmer during summer. This drought resulted in an earlier estimated cover crop sowing date (on average 19 days) and an NDVIDec value that was 0.2 higher than in 2017. Combining both years and all fields, we found that Sentinel-2 retrieved sowing dates could explain 55% of the NDVIDec variability. This corresponded to a positive relationship (R2 = 0.50) between NDVIDec and the cumulative growing degree days (GDD) between sowing date and 1 December until reaching 400 GDD. Based on cumulative GDD derived from two weather stations within Overijssel, we found that on average for the past three decades a sowing date of 19 September (± 7 days) allowed to attain these 400 GDD; this provides support for the current legislation that states that from 2019 onwards a cover crop should be sown before 1 October. To meet this deadline, while simultaneously ascertaining a harvest-ready main crop, in practice implies that undersowing of the cover crop during spring will gain importance. Our results show that Sentinel-2 NDVI time series can assess the effectiveness and timing of cover crop growth for small agricultural fields, and as such has potential to inform regulatory frameworks as well as farmers with actionable information that may help to reduce nitrogen leaching. 相似文献
999.
位于中亚造山带北缘的喀拉通克早二叠世铜镍硫化物矿区是新疆规模最大的铜镍矿山,包含13个岩体,相当部分为隐伏岩体,其中1号、2号、3号、9号矿床为主力矿床,经过30余年持续开发,最大开采深度已达740 m,已面临后备资源不足的危机。已知矿体主要产于辉长岩、苏长岩、辉长苏长岩以及橄榄苏长岩中,甚至角闪辉长岩局部也含矿,未见超镁铁岩产出,具有显著的磁性(200 nT)、重力(0.29×10~(-5)m/s~2)、激化率异常,以镁铁岩含矿、岩体规模小且成群成带、分异演化程度高、富铜(Cu/Ni约3:2)、PGE较高、块状硫化物贯入矿体普遍发育为特色。其围岩为含炭质板岩、片岩和凝灰岩,变形强烈,常规电法受到炭质层的干扰。依据岩石学、地球化学研究,岩浆源于软流圈地幔,基于与东天山同期铜镍矿床含矿岩相及其比例和剩余重力异常的比较,推断其应发育有相当比例的超镁铁岩,因而深部出现超基性岩的可能性很高,且含矿性应更好。这一推断得到坑道钻探的证实,2013年矿区在Y2岩体东段650~740 m深度和Y2岩体西段400~500 m深度发现隐伏超镁铁岩且含矿,局部见贯入块状矿体。橄榄辉石岩、辉石橄榄岩系矿区首次发现,粒度很细,发育强烈的蛇纹石化、纤闪石化,推测只是隐伏超基性岩的头部。结合控岩控矿构造的追溯及南、北岩带的侧伏和倾伏方向判断,硫化物珠滴构造的发现与系统观测统计,围岩烘烤边和角岩化的研究分析,提出南岩带主岩浆通道位于Y2与Y3岩体之间,而不是原普遍认为的岩浆通道位于Y1与Y2岩体之间。结合矿区的现状,提出采用高分辨率浅层地震、CSAMT和瞬变电磁地-井测量,结合传统的高精度重力勘探、磁法勘探和激发极化法来勘探和预测南岩带深部隐伏含矿超镁铁岩的空间位置和产状,圈定岩浆通道和隐伏铜镍矿体,进而推动北岩带和外围G21、22号岩体的深部探矿工作。 相似文献
1000.