Optimal season for discriminating C3 and C4 grass functional types using multi-date Sentinel 2 data

ABSTRACT

The ability of remote sensing systems to optimally discriminate and map C3 and C4 grass species varies over time, due to environmental changes, which influence their phenological, physiological and morphological characteristics. In this regard, the discrimination of C3 and C4 grasses is insufficient when using a single image acquired at a specific period. In this study, multi-date Sentinel 2A MultiSpectral Instrument (MSI) data were explored to determine the optimal period for classifying and mapping Festuca costata, C3 and Themeda Triandra, C4 grasses in the montane grasslands of South Africa. The study further assessed how seasonal variations in species classification can be explained by climatic variability (rainfall and temperature). Results showed that image acquisition dates influence the discrimination accuracy, spatial representation of the two grass species, as well as the performance of spectral bands. The winter period also presents a better temporal window for discriminating C3 and C4 target grass species, with higher overall classification accuracies (between 91.8% and 95.3%), than summer (between 81.4% and 90.3%). Lower omission (between 2.8% and 11.6%) and commission (between 2.5% and 14.2%) errors were also observed when discriminating using winter images, as compared to those acquired in summer. Summer images showed large grass species areal coverage (e.g. in November and March, C3 and C4 covered ±25%), whereas in winter (mainly August), a notable decrease was observed. Overall, findings of the study have demonstrated the relevance of multi-date Sentinel data in discriminating C3 and C4 grass species. There is, however, a need to explore the classification ability of Sentinel 2 derivatives, especially during early summer and winter fall.     

在垃圾焚烧厂规划中地理信息系统的应用

德国萨克森-安哈特州（Sachsen-Anhalt）州府玛葛得堡市（Magdeburg）计划在其北部2县4880km²的地域内建立一个垃圾焚烧厂,焚烧厂厂址规划要符合《环境质量影响评价法》.理想的厂址应该是一片包含环境质量影响评价要素最少的“空地”;为垃圾运输方便,厂址与主要交通干线的距离不应超过5km.由于规划区内土地利用覆盖复杂,常规的实地勘察和资料研究难以把各方面的评价要素信息考虑周全,因此利用地理信息系统（PC ARC/INFO）帮助解决问题,比如专题图件比例尺不统一的问题、信息叠加程度过高的问题等.通过多种比例尺机助制图、比较研究,共找出6个潜在的厂址,可以考虑建厂.编辑了6幅“潜在厂址”专题图,本文以其中1幅举例描述.     

Impact of anthropogenic activities on the sediment microbial communities of Baiyangdian shallow lake

Microorganisms are recognized as sensors of external disturbance in freshwater ecosystems.In this study,sediment samples from regions with strong human activity interference(four sites),moderate human activity interference(five sites) and minor human activity interference(five sites) in Baiyangdian Lake were collected;and their physiological and chemical properties and heavy metals contents were analyzed.The structures of bacterial and fungal communities were tested using 16 S ribosomal Ribonucleic Acid(rRNA) and Internal Transcribed Spacer 2(ITS2) high-throughput sequencing technologies.The results indicated that Proteobacteria was the most abundant bacterial phylum.Ascomycota,Basidiomycota and Ciliophora were the dominant phyla of fungi.Obvious differences of microbial genera among the three regions we re obse rved,especially fungal genera.With intensified disturbance by human activities,the Simpson and Shannon indices of bacteria significantly decreased.The fungal communities were clustered into three groups in accordance with the different human disturbance levels.The bacterial communities of sediment samples under moderate and minor human disturbance appeared similar,but different from those under strong human disturbance.Redundancy analysis indicated that zinc,total phosphorus,copper,and lead were the dominant factors that influenced the bacterial community.Nitrifiers and sulfate-reducing bacteria were influenced by pH,nitrate(NO3),and total nitrogen.The fungal community was significantly affected by total phosphorus.This study reveals that sediment microbial community structures among different regions of a shallow lake are mainly impacted by human activities.     

“全球环境变化与食物系统 (GECAFS)”科学框架与实施战略(英文)

文章从以下 6个方面概要介绍了IGBP、IHDP与WCRP的一项新的联合计划———“全球环境变化与食物系统 (GECAFS)”的科学框架与实施战略 :(1)背景 ;(2 )GECAFS的概念框架 ;(3)GECAFS的科学主题 ;(4 )GECAFS的研究类型与“示范性项目” ;(5 )科学新领域 ;(6 )GECAFS计划与其它组织的资助关系及战略伙伴关系。     

Aquaculture-related trace metals in sediments and lobsters and relevance to environmental monitoring program ratings for near-field effects

The study was undertaken to assess the marine environmental effects from feed and waste associated with aquaculture activities. Metal compositions of sediment, lobster, and feed were used to evaluate the extent of detectable effects at 0 m (under the cage) and 50 m distance. Sediments that were collected under the cages and were characterised as hypoxic or anoxic, showed elevated levels of Cu, Zn, organic carbon, and % <63 microm particles, and low Mn and Fe. At 50 m there was a major reduction in waste chemical impact. Using lobster, a bioindicator species, as a tool for detecting near-field impacts, showed accumulations of high Cu associated with active aquaculture sites. Chemical compositions and metal ratios normalised with organic carbon, were used to assess the sediment conditions associated with environmental monitoring program ratings (EMP--normal, hypoxic, and anoxic). Principal component analysis (PCA) was used to explore chemical data at all sites for differentiating normal, hypoxic and anoxic sediment conditions. Selected variables (Cu, Zn, Fe, Mn, organic carbon, and particles <63 microm) were sufficient for the PCA approach with >90% explainable variance of first two components. The groupings based on PCA and cluster analysis were similar to EMP classifications with some exceptions of mis-identification by EMP. The sediment chemistry components were valid indicators for evaluating marine environmental conditions and for assessing aquaculture operating sites. The developed techniques, using chemical variables in combination with EMP and the statistical approach should be useful to predict the effects of aquaculture practices and the suitability of aquaculture operations.     

环境剪应力场动态变化在施甸地震中短期预测中的应用

环境应力场是一个随时间和空间变化的动态场，追踪分析环境剪应力场时空动态调整变化，是强震危险性中，短期预测的有效途径之一。对追踪分析云南及邻区环境剪应力场年变化，2001年4月12日施甸5．9级地震的中期预测，以及追踪分析云南及邻区环境剪应力场月变化对该地震的短期预测实践作了论述。     

Characteristics of low frequency oscillations of the atmosphere-ocean coupling

The low frequency oscillation of latent heat flux over the tropical oceans has been studied. The NCEP reanalyzed fields of wind and humidity alongwith Reynolds SST are used to compute the instantaneous as well as monthly mean surface latent heat fluxes (LHF) for the year 1999. The procedure of LHF computation is based on bulk method. Spectral analysis shows that significant energy is contained in Madden Julian Oscillation band in the winds, SST, moisture and in the latent heat flux. The global distribution of wind, humidity, SST and LHF oscillation on the time scale of 30–50 days are analyzed. Maximum amplitude of oscillation on this time scale in all the above mentioned parameters were found over the Indian Ocean. The fluctuation of surface wind speed and moisture controls the latent heat flux on this time scale. The fluctuation of SST on this time scale does not seem to be important over most of the oceans.     

Anthropogenic impact on sediment composition and geochemistry in vertical overbank profiles of river alluvium from Belgium and Luxembourg

The geochemical study of alluvial sediments allows to reconstruct pollution through time. Geochemical and sedimentological variations recorded in 40 vertical overbank sediment profiles from Belgium and Luxembourg can be classified in three dominant pattern types:• type 1 profiles with dominantly non-anthropogenically influenced geochemical distribution patterns. These profiles are devoid of anthropogenic particles such as charcoal, plastic, brick and slag fragments, with the exception, in some cases, of their uppermost parts. Background concentrations thus are displayed throughout the profile (subtype 1A). However, in this group, profiles displaying anomalous values caused by the presence of heavy minerals (subtype 1B) or by base metal mineralisations in the catchment (subtype 1C) also occur;• type 2 profiles displaying clear evidence of anthropogenic influences. Most of these profiles display a gradual increase in heavy metal content in their upper part, with values doubling or tripling (subtype 2A). However, other profiles display a dramatic increase in pollution-related elements caused by past or present-day heavy industrial activities in the catchment (subtype 2B). Here also the sedimentological patterns reflect the influence of the industrial activities;• type 3 profiles contain features related to pedogenetic translocations of mobile elements. Apart from classical pedogenetic features such as illuviation/eluviation, the mobility of As and Cd is of particular importance. From a sedimentological point of view, these profiles do not necessarily differ from type 1 or 2 profiles.It should be noted that in some profiles, pattern types can be superimposed. Type 2B profiles are of particular environmental concern, because the potential release of heavy metals may have consequences for agricultural activities or groundwater contamination in the catchment. Furthermore, reworking of polluted sediments temporarily stored in the alluvial plain can also have negative effects on the ecosystem.     

Soft-sediment deformation structures in Late Miocene–Pleistocene sediments on the pediment of the Mátra Hills (Visonta, Atkár, Verseg): Cryoturbation, load structures or seismites?

The studied area, built up by silty clayey and partly sandy sediments and paleosols, lies on the tectonically active Northern margins of the Pannonian Basin. Wavy, sagging load casts can be observed in the upper part of the Late Miocene alluvial complex and larger scale sagging load casts, flame structures, drops and pillows detected in its Quaternary cover were studied in detail, in order to understand the origins of soft sediment deformation which characterized this young sedimentary suite. Sedimentological, paleopedological and mineralogical observations suggest that:

1. One of the reasons for the soft-sediment deformation might have been the relatively low cohesive strength of the predominantly smectitic sediment covering a gentle slope similar to the actual landscape.

2. On such a surface, the down-slope gravitational component of the mud-blanket might easily have been sufficient to overcome its cohesive strength.

3. Frost action traceable in the studied formations might also have contributed to the observed deformation, particularly along the eroded top of the Late Miocene sediments.

Combined evidence from field observations and laboratory analyses support the idea that liquefaction–fluidization was of prime importance in bringing about the observed structures. In conclusion two alternative Quaternary/Holocene scenarios are proposed, which might have resulted in the unusual behaviour of the sediments/paleosols. One is a seismic event, the other is the combined effect of freeze–thaw cycles and of the sloping foothill position, which might have resulted in episodic downslope transport and the associated deformation of the eroded soil material when its water content surpassed a certain threshold. We accept that the anomalous abundance of soft-sediment deformation in this marginal position may be causally related to paleo-earthquakes, but the obvious complexity of the phenomenon requires caution. In case the proposed scenarios would not have been alternatives but acted simultaneously, the analysed phenomena were to be interpreted as the joint results of tectonics and climate change.