高时空分辨率植被覆盖获取方法及其在土壤侵蚀监测中的应用

土壤侵蚀是全球性生态问题,准确监测区域土壤侵蚀状况是评估区域生态质量和生态保护成效的基础。准确获取高时空分辨率植被覆盖信息并与降水动态匹配是土壤侵蚀准确监测的关键。然而,受卫星传感器限制,大区域高时间分辨率与高空间分辨率遥感数据无法同时获取,高空间分辨率植被动态遥感监测面临巨大挑战。为解决这一问题,本研究提出了一套多源遥感数据融合的高时空分辨率绿色植被覆盖度(半月尺度,空间分辨率2 m)获取方法,并与半月尺度的降水因子匹配应用于CSLE开展了天津市蓟州区的土壤侵蚀监测。研究结果表明:1)降雨和植被覆盖度因子在一年之内变异较大,半月降雨量的平均值为43.32 mm,变异系数可达150%,绿色植被半月植被覆盖度的平均值为54.74%,变异系数为18%。考虑土地覆盖类型的高时空分辨率绿色植被覆盖度融合方法,可以获取合理的高空间分辨率绿色植被覆盖度动态,为高空间分辨率土壤侵蚀监测提供了一个有效手段;2)土壤侵蚀发生范围与强度与降水及植被因子在年内的动态匹配高度相关,土壤侵蚀发生范围最大为10月上半月,发生面积为137.55 km~2,土壤侵蚀发生强度最为严重为7月下半月,25 t/hm~2以上土壤侵蚀发生面积为12.70 km~2;3)高时空分辨率植被与降水因子耦合下的土壤侵蚀监测结果与地面一致性较好(判定系数可达0.88),明显好于仅用一期高空间分辨率植被因子的土壤侵蚀监测结果(判定系数仅为0.097),采用高时空分辨率植被与降水因子耦合的土壤侵蚀监测方法可以大幅度提高土壤侵蚀监测的准确性,本研究为其他区域准确开展土壤侵蚀监测提供了一套有效的方法。     

森林降水酸度及电导率的时空变化

在离大气污染源距离不同的两片杉木(Cunninghamia lanceolata)人工林中建立监测场,对降水化学进行了为期3年(1994～1996)的定位监测。降水通过林冠截留后,其酸度和电导率均明显增加,尤以树干径流为显著。在 FFC监测场,降雨、穿透雨和树干径流雨量加权平均pH值分别为6.13、6.06和4.18,在XQF监测场,其相应的数值分别为5.86、5.67和3.37;降雨和穿透雨的酸度表现出一定的季节变化动态,其最低月均pH值出现在夏委,最高值在冬季。在FFC监测场,降雨、穿透雨和树干径流雨量加权平均EC值分别为28.51μs·cm-1、63.71μs·cm-1、240.85μs·cm-1,在XQF监测场,其相应的数值分别为36.99μs·cm-1、66.41μs·cm-1、501.85μs·cm-1：降水电导率表现出显著一致的季节变化格局,其月均值均以夏季最低,冬季最高,春秋季居中,这种格局强烈受降雨量的影响。离污染源较近的XQF监测场,降水酸度和电导率明显高于相对未受污染的FFC监测场。     

基于Gash模型的青海云杉林降水截留模拟

选择Gash(1995)改进后的模型对祁连山东部青海云杉林冠层截留进行模拟。首先在2009年的5月底至9月期间对降水事件、降水截留和林冠结构进行观测,其次对林冠附加截留量进行计算,在不同的时间步长上利用Gash模型模拟截留量,最后对模型参数进行敏感性分析。结果表明:Gash模型对整个观测期间林冠截留模拟值比实测林冠总截留量偏低8.70%,15 d尺度和次降雨事件尺度上模拟值比观测值分别偏低18.92%和14.23%;附加截留占总截留的74.94%,吸附截留占总截留的25.06%;饱和林冠的平均蒸发强度和降雨强度的比值是模型的敏感性参数,精确获得平均蒸发强度是保证模型精度的前提条件,并且独立降水事件的界定是提高Gash模型的关键点。     

中国亚热带4个森林动态监测样地无人机可见光遥感影像数据集

常绿阔叶林是我国亚热带地区的地带性植被类型。由于亚热带森林植物群落垂直结构复杂、林冠郁闭度高, 对常绿阔叶林冠层的研究尚缺乏高质量的监测数据。本数据集包含浙江天童山、浙江百山祖、广东车八岭、广东鼎湖山4个大于20 ha的森林动态监测样地2014年8月或2016年9月采集的无人机可见光遥感影像。本数据集是通过将无人机影像、地面控制点和地面调查数据相结合而获得的。每个样地的数据集包括4个文件: ~5 cm空间分辨率的正射影像图和数字表面模型、1 m空间分辨率的森林冠层高度数据和正射影像质量报告。本数据集可为常绿阔叶林的林冠生态学、生物多样性、生态系统功能等研究提供数据支撑。     

基于地-空遥感耦合的冬小麦叶片氮积累量估算

利用不同冬小麦生态区同步的SPOT-5多光谱遥感影像、地面光谱数据和植株取样数据,提出一种基于波谱响应函数拟合和混合像元分解的纯净像元光谱提取方法,并对比分析了纯净像元光谱、模拟像元光谱和实测像元光谱与冬小麦叶片氮积累量（LNA）的定量关系.结果表明： 模拟像元光谱对叶片氮积累量的反演效果较好,纯净像元光谱反演效果次之,实测像元光谱最差;但基于模拟像元光谱的LNA监测模型不能直接外推至空间尺度.模型检验结果表明,基于纯净像元光谱的LNA监测模型在2个小麦生态区均具有较好的精度和稳定性,该方法综合利用了地-空遥感的优点,可以推广应用到其他不同空间分辨率和光谱分辨率的遥感数据,从而为区域性冬小麦氮素营养状况的遥感监测提供技术依据.     

对角膜细胞染色体的影响

随着微波技术在工业、国防、医疗、通讯等部门的广泛应用和空间电磁强度的不断增加,微波辐射已成为危害人们身体健康的一种因素,联合国人类环境会议已把微波列入必须控制的造成公害的主要污染物之一。关于首先微波导致人眼损害的研究,最早是由Hirsch在1952年报道:一名雷达技术工人,在1500—3000MHz频段,功率密度100毫瓦/厘米~2下工作一年后,发现二侧性白内障。此后,不少研究者表明,大强发暴露导致人眼晶状体混浊,患白内障发生。1978年Ya().K.T.S曾报道微波辐射对中国田鼠角膜上皮细胞染色体的影响,而国内至今未见有这方面的报道。我们用微波照射小白鼠角膜细胞,并就微波辐射对其染色体的影响作初步探讨。     

微波辐射对小白鼠的生物效应研究 Ⅲ.对角膜细胞染色体的影响

随着微波技术在工业、国防、医疗、通讯等部门的广泛应用和空间电磁强度的不断增加,微波辐射已成为危害人们身体健康的一种因素,联合国人类环境会议已把微波列入必须控制的造成公害的主要污染物之一。关于首先微波导致人眼损害的研究,最早是由Hirsch在1952年报道:一名雷达技术工人,在1500—3000MHz频段,功率密度100亳瓦/厘米~2下工作一年后,发现二侧性白内障。此后,不少研究者表明,大强度暴露导致人眼晶状体混浊,患白内障发生。1978年YaO,K.T.S曾报道微波辐射对中国田鼠角膜上皮细胞染色体的影响,而国内至今未见有这方面的报道。我们用微波照射小白鼠角膜细胞,并就微波辐射对其染色体的影响作初步探讨。     

基于光纤测温技术的城市地表温度精细化分析

城市景观空间构型与热岛效应关联性较强,研究高时空分辨率的城市不同下垫面地表温度变化,可以更加精细地掌握城市热环境的时空特征。光纤温度传感系统具有实时在线、测温精度高和不受电磁干扰等优点,具备实时、在线、连续开展城市地表温度在线监测的能力。在北京市通州某园区内,选择有太阳辐射的4个时段,对多种类型下垫面的地表温度进行了时间间隔为1 min、空间间隔为1 m的连续4 h、总长度为100 m的实时在线监测。通过对监测时间段内不同类型下垫面地表温度的变化分析,发现这种分布式光纤测温系统能够有效辨识小尺度下地表温度的时间变化性和空间变化性,能有效区分透水和不透水地面,并监测和评估沥青马路地表温度的升温速率以及遮荫效果对地表温度的降温作用。同时,这种监测模式获取的数据能够对地表温度空间序列开展自相关分析,进一步验证了地表温度空间序列在较小尺度上仍然具有自相关性,且距离越近,相关性越大。研究同时表明,光纤测温技术能直接地获取城市热环境的现场真实数据,可以有效应用于小尺度城市热环境的观测与研究。     

草地植物物种多样性测度方法及发展趋势

植物物种多样性是维持陆地生态系统多功能性和稳定性的关键要素之一.本文梳理了传统草地植物物种多样性的测度方法,结合无人机技术介绍了目前应用于草地植物物种多样性测度的新理念和新方法.传统的草地植物物种多样性测度方法依赖地面观测,需要投入大量的人力、物力且耗时,仅适合小范围的观测;卫星遥感方法受制于分辨率,难以直接对群落结构...     

基于多源遥感数据的荒漠植被覆盖度估测

以塔里木河下游为靶区,根据地面调查和不同分辨率的多源遥感数据,逐级建立荒漠植被覆盖度遥感估测模型,并对不同模型、不同估测方法的估测精度进行比较.结果表明: 随着遥感数据空间分辨率的提高,植被覆盖度遥感估测模型精度增加;基于高分辨率、中高分辨率及中低分辨率遥感数据建立的植被覆盖度模型的估测精度分别为89.5%、87.0%和84.6%;遥感模型法的估测精度高于植被指数法.不同分辨率遥感数据估测荒漠植被覆盖度的精度变化规律,实现了荒漠植被覆盖度估测的高、中、低分辨率遥感数据参数及尺度的定量转换,可为研究区生态恢复遥感综合监测方案的制定和实施提供直接依据.     

Geographic patterns and dynamics of Alaskan climate interpolated from a sparse station record

Data from a sparse network of climate stations in Alaska were interpolated to provide 1‐km resolution maps of mean monthly temperature and precipitation–‐variables that are required at high spatial resolution for input into regional models of ecological processes and resource management. The interpolation model is based on thin‐plate smoothing splines, which uses the spatial data along with a digital elevation model to incorporate local topography. The model provides maps that are consistent with regional climatology and with patterns recognized by experienced weather forecasters. The broad patterns of Alaskan climate are well represented and include latitudinal and altitudinal trends in temperature and precipitation and gradients in continentality. Variations within these broad patterns reflect both the weakening and reduction in frequency of low‐pressure centres in their eastward movement across southern Alaska during the summer, and the shift of the storm tracks into central and northern Alaska in late summer. Not surprisingly, apparent artifacts of the interpolated climate occur primarily in regions with few or no stations. The interpolation model did not accurately represent low‐level winter temperature inversions that occur within large valleys and basins. Along with well‐recognized climate patterns, the model captures local topographic effects that would not be depicted using standard interpolation techniques. This suggests that similar procedures could be used to generate high‐ resolution maps for other high‐latitude regions with a sparse density of data.     

Community Dynamics of Seed Rain in Mixed Evergreen Broad-leaved and Deciduous Forests in a Subtropical Mountain of Central China

Seed dispersal is a key process within community dynamics. The spatial and temporal variations of seed dispersal and the interspecific differences are crucial for understanding species coexistence and community dynamics. This might also hold for the mixed evergreen broadleaved and deciduous forests in the mountains of subtropical China, but until now little existing knowledge is available for this question. In 2001, we chose to monitor the seed rain process of our mixed evergreen broad-leaved and deciduous forest communities in Mount Dalaoling National Forest Park, Yichang, Hubei Province, China. The preliminary analyses show obvious variations in seed rain density, species compositions and timing of seed rain among four communities. The average seed rain densities of the four communities are 2.43 ± 5.15, 54.13 ±182.75, 10.05 ±19.30 and 24.91 ± 58.86 inds/m^2, respectively; about one tenth the values in other studies in subtropical forests of China. in each community, the seed production is dominated by a limited number of species, and the contributions from the others are generally minor. Fecundity of evergreen broadleaved tree species is weaker than deciduous species. The seed rain of four communities begins earlier than September, and stops before December, peaking from early September to late October. The beginning date, ending date and peak times of seed rain are extensively varied among the species, indicating different types of dispersal strategies. According to the existing data, the timing of seed rain is not determined by the climate conditions in the same period, while the density of seed rain may be affected by the disturbances of weather variations at a finer temporal resolution.     

中高纬度地区TRMM卫星降雨数据的精度评价

卫星降雨产品在降雨空间格局分析中扮演着重要角色,其中TRMM 3B42（3B42）是重要的产品之一,具有适宜的空间和时间尺度,已成为生态、气候、水文模型的重要驱动因子.当前对3B42 V7新版本数据的精度和误差认识仍然有限,尤其缺少中高纬度地区的数据精度评价研究,制约其在生态、气候和水文等领域的应用.本文基于内蒙古自治区1998—2012年3B42 V7产品和53个气象站点数据,评估其在中高纬度地区的精度,揭示了各精度评价指标的空间分布特征及其影响因子.总体精度评价结果表明： 3B42在年、月、日尺度上均高估降雨量,且误差随时间尺度增大而增加,日降雨量的平均误差和平均绝对误差分别为-0.06和0.88 mm;降雨事件侦测能力表现良好,公正预兆评分达到0.23,但对降雨事件总频率存在微弱高估.数据精度受海拔和多年平均降雨量影响,随海拔升高,降雨绝对误差减小,降雨事件探测能力减弱,多年平均降雨量对数据精度的影响则相反.     

基于地形和主风向效应模拟山区降水空间分布

在 ANUSPL IN和 GIS空间分析技术的支持下 ,采用岷江流域内及周边地区共计 5 1个雨量站的 1988～ 2 0 0 2年各月连续观测数据 ,模拟产生岷江上游面积达 2 2 919km2的流域范围内月平均降水量的空间分布栅格。为了体现当地季风方向和坡向之间的耦合效应 ,建立主风向效应指数 (PWEI) ,并从 DEM中提取海拔高度形成两个协变量 ,以雨量站的大地坐标位置作为独立变量。降水的模拟采用样条平滑技术 ,利用降水量值和 4个变量的统计关系拟合产生样条表面 ,并进而结合 DEM和 PWEI栅格产生空间分辨率达 5 0 0 m的降水量栅格。依据归一化交叉检验值 (GCV)确定平滑参数 ,并通过多次诊断运行实现平滑降噪 ,提高预测精度。统计结果表明 ,月平均降水量的预测误差变动在 15 %～ 4 2 %之间 ,是现有雨量站分布条件所能实现的较好的结果。雨季 (5～ 9月份 )的预测误差远小于旱季 ,表明东南季风对迎风坡面有明显的致雨效应 ,并因 PWEI的运用提高了模拟精度 ;旱季 PWEI效果不明显 ,降水分配主要依赖地形。和单纯利用海拔高度一个变量相比 ,增加 PWEI可使全年平均预测误差降低 3.0 %左右。     

Evaluation of High-Resolution Precipitation Estimates from Satellites during July 2012 Beijing Flood Event Using Dense Rain Gauge Observations

Satellite-based precipitation estimates products, CMORPH and PERSIANN-CCS, were evaluated with a dense rain gauge network over Beijing and adjacent regions for an extremely heavy precipitation event on July 21 2012. CMORPH and PEERSIANN-CSS misplaced the region of greatest rainfall accumulation, and failed to capture the spatial pattern of precipitation, evidenced by a low spatial correlation coefficient (CC). CMORPH overestimated the daily accumulated rainfall by 22.84% while PERSIANN-CCS underestimated by 72.75%. In the rainfall center, both CMORPH and PERSIANN-CCS failed to capture the temporal variation of the rainfall, and underestimated rainfall amounts by 43.43% and 87.26%, respectively. Based on our results, caution should be exercised when using CMORPH and PERSIANN-CCS as input for monitoring and forecasting floods in Beijing urban areas, and the potential for landslides in the mountainous zones west and north of Beijing.     

Weather conditions determine attenuation and speed of sound: Environmental limitations for monitoring and analyzing bat echolocation

Echolocating bats are regularly studied to investigate auditory‐guided behaviors and as important bioindicators. Bioacoustic monitoring methods based on echolocation calls are increasingly used for risk assessment and to ultimately inform conservation strategies for bats. As echolocation calls transmit through the air at the speed of sound, they undergo changes due to atmospheric and geometric attenuation. Both the speed of sound and atmospheric attenuation, however, are variable and determined by weather conditions, particularly temperature and relative humidity. Changing weather conditions thus cause variation in analyzed call parameters, limiting our ability to detect, and correctly analyze bat calls. Here, I use real‐world weather data to exemplify the effect of varying weather conditions on the acoustic properties of air. I then present atmospheric attenuation and speed of sound for the global range of weather conditions and bat call frequencies to show their relative effects. Atmospheric attenuation is a nonlinear function of call frequency, temperature, relative humidity, and atmospheric pressure. While atmospheric attenuation is strongly positively correlated with call frequency, it is also significantly influenced by temperature and relative humidity in a complex nonlinear fashion. Variable weather conditions thus result in variable and unknown effects on the recorded call, affecting estimates of call frequency and intensity, particularly for high frequencies. Weather‐induced variation in speed of sound reaches up to about ±3%, but is generally much smaller and only relevant for acoustic localization methods of bats. The frequency‐ and weather‐dependent variation in atmospheric attenuation has a threefold effect on bioacoustic monitoring of bats: It limits our capability (1) to monitor bats equally across time, space, and species, (2) to correctly measure frequency parameters of bat echolocation calls, particularly for high frequencies, and (3) to correctly identify bat species in species‐rich assemblies or for sympatric species with similar call designs.     

滇南红河地区现代花粉雨特征及其与气候因子的关系

我国低纬度热带亚热带地区现代花粉雨与气候关系的研究相对缺乏。本研究以滇南红河地区43个水体(湖泊、水库和池塘)的表层沉积物为对象,探讨研究区现代花粉雨与气候因子之间的关系。花粉分析结果表明,木本植物花粉含量高,占优势的是松属、桤木属和壳斗科;次为草本植物,主要为禾本科、菊科和莎草科;花粉谱中蕨类孢子以三缝孢为主,藻类的盘星藻也常见。同时,通过红河地区13个气象观测站1961—2010年月观测数据的线性插值,获得了各水体的现代气候数据(温度包括1月均温、7月均温、春、夏、秋、冬季均温,以及雨季、旱季和年均温;降水包括春、夏、秋和冬季降水量,雨季、旱季和年降水量),并对现代花粉和气候数据进行冗余分析,以揭示影响研究区现代花粉雨的气候因子。冗余分析结果表明,春季、旱季和年降水量及7月、雨季和年均温是控制滇南红河地区现代花粉雨的主要气候因子,温度的增加导致常绿阔叶林占优势,降水减少导致松林占主导。本研究结果能够为滇南红河地区利用化石花粉记录的古气候定量重建提供重要的理论支持。     

A simple Bayesian network to interpret the accuracy of armyworm outbreak forecasts

Forecasting of outbreaks of armyworm (larvae of the moth Spodoptera exempta) employs information from rain gauges and moth traps. Rainfall is an independent variable, but moth catch is affected by rainfall, and outbreak risk is affected by both moth catch and rainfall. A simple Bayesian network was used to describe these relationships and so derive conditional probabilities. The data were from a new initiative, community‐based forecasting of armyworm in Tanzania, in which outbreak risk for a village is determined locally from a single moth trap and rain gauge located within the village. It was found that, following a positive forecast, an armyworm outbreak was approximately twice as likely to occur as would be expected by chance. If the forecast was negative because of insufficient moths, outbreaks were half as likely as would be expected by chance. If the forecast was negative because of insufficient rain, however, the outbreak probability remained similar to chance: an aspect of the forecast that requires improvement. Overall, a high forecasting accuracy can be achieved by village communities using simple rules to predict armyworm outbreaks.     

Climate and climatic variability at Lake Myvatn

The climate of the Lake Myvatn region is examined through the use of weather station data, using the years from 1971 to 2000 as a reference period. Variations in mean monthly temperature and precipitation at Reykjahlid (Myvatn) are compared with variations at seven other weather stations in north east Iceland. The area is drier and colder than coastal stations and exhibits a seasonal cycle in temperature that is larger than found at the coast. The temperature is significantly influenced by the number of sunlight hours only during the summer months. During summer, the influence of a sea breeze circulation can be clearly identified.The variability of climate since 1936 is also examined in comparison with the seven other weather stations. It is found that temperature variations at the different stations are highly correlated, but for precipitation the correlation is significant but much weaker.The influence of the large scale atmospheric circulation on temperature and precipitation at Lake Myvatn is also examined. It is found that the air temperature at Lake Myvatn is most sensitive to an east-west dipole in the large scale sea surface pressure field, i.e. to a pattern that is very different from the spatial pattern associated with the North Atlantic Oscillation (NAO). Precipitation at Lake Myvatn is to some degree influenced by the NAO, but generally precipitation is associated with northerly winds and cold temperatures whereas southerly winds at Lake Myvatn are likely to be drier.