A field comparison of indicators of sublethal stress in the salt-marsh grassSpartina patens

There is a need for research into bioindicators of stress in threatened plant communities such as coastal wetlands. Land subsidence, diversion of sediment, and salt-water intrusion produce stresses associated with waterlogging, elevated salinity, and nutrient depletion. Temporal and spatial environmental variation (soil redox potential, interstitial water salinity, pH, ammonium and phosphorus, and cation and trace metal concentrations) was analyzed near Lake de Cade, Louisiana, in a brackish marsh which is a mosaic of healthy plant communities interspersed with areas where wetland loss is occurring. Environmental variation was related to indicators of stress inSpartina patens, which included variables derived from the adenine nucleotide levels in plants, leaf spectral reflectance, leaf proline concentrations, and shoot elongation. In a comparison of burned and unburned sites, streamside and inland marsh, and along a salinity gradient, among-site differences were found in spectral reflectance and adenine-nucleotide-related indicators. Although it was difficult to relate a single causal environmental variable to the response of a specific indicator, spectral reflectance in the visible light range responded to salinity or to elements borne in seawater, and adenine-nucleotide indices were sensitive to nutrient availability. The ability of indicators to detect plant responses changed during the growing season, suggesting that they were responding to the changing importance of different environmental factors. In addition, some reflectance indicator responses occurred along salinity gradients when salinity differences were less than those that were found to have ecologically meaningful effects in greenhouse experiments. A multivariate numerical approach was used to relate environmental variation with indicator responses. We concluded that factors which in combination cause the degradation and loss of Louisiana wetlands produce environmental conditions that are only subtly different from those in vigorously growing marsh communities.     

Identification of the best spectral indices to remotely trace the diurnal course of water use efficiency of <Emphasis Type="Italic">Tamarix ramosissima</Emphasis> in the Gurbantunggut Desert,China

Water availability is one of the most important factors limiting photosynthetic assimilation of carbon dioxide and growth of individual plants in terrestrial ecosystems. Water use efficiency (WUE) of plants has been widely assessed using ecological methods in field measurements; however, approaches for remotely sensing WUE are still lacking, particularly in arid ecosystems. In this study, a comprehensive analysis of diurnal WUE via spectral indices in arid ecosystems was assessed. Analyses were conducted on a native dominant desert shrub, Tamarix ramosissima, in its original habitat on the southern periphery of the Gurbantunggut Desert, China. Based on diurnal measurements of spectral reflectance, photosynthesis, and micrometeorological variables, simple and useful spectral indices for estimating diurnal WUE at the assimilative organ scale were explored. From six types of spectral indices, ranging from simple to sophisticated, the best wavelength domains for a given type of index were determined by screening all combinations using correlation analysis. The coefficient of determination (R ²), ranging from 0.19 to 0.60, for WUE was calculated for all indices derived from spectra taken from the assimilative organs. With only two wavelengths and a significant correlation coefficient (R ² = 0.60, P < 0.001), the simple ratio (SR) type index was the most sensitive to WUE among all of the indices. Furthermore, SR is a useful indicator to determine the dynamic and diurnal processes of photosynthesis and transpiration of T. ramosissima. Although it has a few weaknesses, SR serves as a simple and robust indicator of WUE in arid ecosystems.     

Evaluating the progress of restored cordgrass (Spartina foliosa) marshes: Belowground biomass and tissue nitrogen

We report the first data on belowground tissue mass and nitrogen (N) concentration forSpartina foliosa in southern California, assessing one natural and two constructed marshes on San Diego Bay. Biomass at the natural marsh was low compared to that of otherSpartina spp., but higher than values reported forS. foliosa in northern California. In sandy constructed marshes planted 5 and 10 years before this study,S. foliosa had lower belowground tissue N, lower N crop (%N×biomass), and shallower roots than in the adjacent natural marsh. We took advantage of a 2-yr, large-scale fertilization project being performed in the older constructed marsh and examined biomass and N storage after N additions. Although there was a trend toward N accumulation with fertilization, N crop remained at approximately 50% of natural marsh levels, unlike the large aboveground responses to N addition in our previous studies. Lower belowground reserves help to explain poor aerial growth in the created marshes and suggest the need for finer sediments (with greater potential for holding and supplying nutrients) to sustain (S. foliosa. While fine sediments are beginning to accumulate on the surface of the created marshes, vertical accretion is more likely to shift the plant community toward other species than to enhanceS. foliosa growth. We suggest salvaging and importing fine, organic marsh sediments or providing organic amendments to establish proper substrate conditions. Overexcavating and allowing fine sediments to accumulate remains an option, although the time scale is unpredictable due to the stochasticity of accretion events.     

Site conditions, not parental phenotype, determine the height ofSpartina foliosa

The effect of parental growth form on ramets introduced to new sites has broad implications for ecological restoration. We asked whether transplants ofSpartina foliosa need to come from tall parents in order to produce tall stands for nesting by the light-footed clapper rail, one of southern California’s many endangered, salt-marsh-dependent species. Tall and shortS. foliosa transplants, collected from local salt marshes, were grown in a common garden and in microcosms, with different results. In the common garden, which had hypersaline soil, offspring of tall versus short clones did not differ, but they did respond to soil variations among blocks. In blocks with less sandy soil, stems were taller and up to 5 times more numerous, and patch sizes were up to 3 times larger. After two years in low-salinity microcosms, transplants receiving nitrogen additions produced more stems and over twice the total stem length of controls, regardless of parental height form. A slight parental effect was seen in this benign environment; the maximum height of tall-form transplants was 15 cm taller than that of short-form transplants, but the effect did not persist through year 2. Results indicate that both height forms ofS. foliosa grew better (taller and more dense) with less environmental stress (lower salinity, more nutrients). We conclude that environmental differences are more important than parental height form in determiningS. foliosa growth. This means that, for restoration purposes,S. foliosa ramets can and should be collected from short clones, rather than from existing, prime nesting habitat.     

Using hyperspectral plant signatures for CO<Subscript>2</Subscript> leak detection during the 2008 ZERT CO<Subscript>2</Subscript> sequestration field experiment in Bozeman,Montana

Hyperspectral plant signatures can be used as a short-term, as well as long-term (100-year timescale) monitoring technique to verify that CO₂ sequestration fields have not been compromised. An influx of CO₂ gas into the soil can stress vegetation, which causes changes in the visible to near-infrared reflectance spectral signature of the vegetation. For 29 days, beginning on July 9, 2008, pure carbon dioxide gas was released through a 100-m long horizontal injection well, at a flow rate of 300 kg day⁻¹. Spectral signatures were recorded almost daily from an unmown patch of plants over the injection with a “FieldSpec Pro” spectrometer by Analytical Spectral Devices, Inc. Measurements were taken both inside and outside of the CO₂ leak zone to normalize observations for other environmental factors affecting the plants. Four to five days after the injection began, stress was observed in the spectral signatures of plants within 1 m of the well. After approximately 10 days, moderate to high amounts of stress were measured out to 2.5 m from the well. This spatial distribution corresponded to areas of high CO₂ flux from the injection. Airborne hyperspectral imagery, acquired by Resonon, Inc. of Bozeman, MT using their hyperspectral camera, also showed the same pattern of plant stress. Spectral signatures of the plants were also compared to the CO₂ concentrations in the soil, which indicated that the lower limit of soil CO₂ needed to stress vegetation is between 4 and 8% by volume.     

浅析泥石流堆积物的光谱特征——以蒋家沟泥石流堆积物为例

作者运用100BXMTS野外光谱仪探测了小江支流蒋家沟新、老泥石流堆积物的光谱反射率,总结了新、老堆积物的反射光谱特征,进一步分析了影响泥石流堆积物反射光谱特性的因素（岩性、水分含量、植被覆盖）,最后讨论了应用高空间分辨率遥感图像解译泥石流堆积物的可能性。     

Spectrometric analyses in comparison to the physiological condition of heavy metal stressed floodplain vegetation in a standardised experiment

Floodplain ecosystems are affected by flood dynamics, nutrient supply as well as anthropogenic activities. Heavy metal pollution poses a serious environmental challenge. Pollution transfer from the soil to vegetation is still present at the central location of Elbe River, Germany. The goal of this study was to assess and separate the current heavy metal contamination of the floodplain ecosystem, using spectrometric field and laboratory measurements. A standardized pot experiment with floodplain vegetation in differently contaminated soils provided the basis for the measurements. The dominant plant types of the floodplains are: Urtica dioica, Phalaris arundinacea and Alopecurus pratensis, these were also chemically analysed. Various vegetation indices and methods were used to estimate the red edge position, to normalise the spectral curve of the vegetation and to investigate the potential of different methods for separating plant stress in floodplain vegetation. The main task was to compare spectral bands during phenological phases to find a method to detect heavy metal stress in plants. A multi-level algorithm for the curve parameterisation was developed. Chemo-analytical and ecophysiological parameters of plants were considered in the results and correlated with spectral data. The results of this study show the influence of heavy metals on the spectral characteristics of the focal plants. The developed method (depth CR1730) showed significant relationship between the plants and the contamination.     

半干旱区内陆湖泊透明度高光谱估测模型研究——以松嫩平原查干湖为例

通过实测查干湖高光谱数据,建立透明度(Secchi Disk Depth,SDD)单波段估测模型、比值估测模型以及神经网络高光谱估测模型,并以确定性系数R2以及剩余残差RMSE为指标进行了验证.通过对单波段估测模型和比值估测模型进行比较发现,单波段模型估测结果与比值模型相差无几,而水体透明度经对数处理有利于模型精度提高,但是神经网络模型是三者中最优的.查干湖透明度高光谱定量估测模型的建立,有利于今后利用遥感影像,对查干湖水体透明度进行全面估测,对于研究和监测查干湖水体水质状况有重要意义.     

Vegetation recovery and landscape change assessment at Chiufenershan landslide area caused by Chichi earthquake in central Taiwan

This study discusses vegetation recovery and land cover change with reference to the Chiufenershan landslide, a major disaster caused by the Chichi earthquake, 21 September 1999. Image classification technology, landscape indicators from multi-temporal remotely sensed data and a field survey provide the data. Image differencing methods and threshold values coupled with pre- and post-quake satellite images were used. Multi-temporal images in combination with various vegetation indices were drawn on to classify land cover patterns and discuss differences and suitability of indices. Landscape indicators and field investigations fed into an investigation of vegetation recovery and landscape change. The study results show that the best image classification system is original wavebands coupled with a cropping management factor index (CMFI). The land cover analysis shows that areas of forest and grass are increasing and areas of landslide are decreasing. From the field investigation, because the left and right sides of the landslide area were not disturbed by the earthquake, their calculated similarity index is the highest (30.08%). Miscanthus floridulus is the most dominant pioneer plant at the landslide collapse area with an importance value index (IVI) of 63.6%.     

表征海相烃源岩有机质成熟度的若干重要指标的对比与研究

对目前表征海相烃源岩有机质成熟度的几个重要指标（镜质体反射率,沥青反射率,镜状体反射率、动物有机碎屑反射率及牙形刺色变指数等）进行了探讨与对比,并在总结它们各自优缺点的基础上,提出了选择海相烃源岩有机质成熟度评价指标的原则,进而提出牙形刺相对荧光强度（Ｉ５４６）是表征海相烃源岩有机质成熟度的良好指标,其具有较广泛的适用性。     

Optical spectrum based measurement of flotation slurry contents

Monitoring and control of a flotation circuit is mainly based on the information gained by assaying the process slurry lines. In flotation plants, usually an X-ray fluorescence analyzer is used to obtain the on-line assays. This article introduces the visual and near-infrared reflectance spectroscopic analysis of the process slurries as a supplementary method which complements the on-line assay information available from an X-ray fluorescence analyzer. It is shown that the spectral information can be used to accurately predict the element contents in the slurry in between successive XRF analyses. Since the spectral measurements can be taken with high frequency as opposed to the sparse X-ray fluorescence analysis, a practically continuous on-line estimate of the slurry contents is reached. These estimates can be used in the plant control to improve the overall performance of the circuits and to yield also economical savings. Additionally, the frequent monitoring of the grades can provide means to eliminate rapid disturbances in the circuits, thus improving the stability of the process.     

Multi-spectral imaging of vegetation for detecting CO<Subscript>2</Subscript> leaking from underground

Practical geologic CO₂ sequestration will require long-term monitoring for detection of possible leakage back into the atmosphere. One potential monitoring method is multi-spectral imaging of vegetation reflectance to detect leakage through CO₂-induced plant stress. A multi-spectral imaging system was used to simultaneously record green, red, and near-infrared (NIR) images with a real-time reflectance calibration from a 3-m tall platform, viewing vegetation near shallow subsurface CO₂ releases during summers 2007 and 2008 at the Zero Emissions Research and Technology field site in Bozeman, Montana. Regression analysis of the band reflectances and the Normalized Difference Vegetation Index with time shows significant correlation with distance from the CO₂ well, indicating the viability of this method to monitor for CO₂ leakage. The 2007 data show rapid plant vigor degradation at high CO₂ levels next to the well and slight nourishment at lower, but above-background CO₂ concentrations. Results from the second year also show that the stress response of vegetation is strongly linked to the CO₂ sink–source relationship and vegetation density. The data also show short-term effects of rain and hail. The real-time calibrated imaging system successfully obtained data in an autonomous mode during all sky and daytime illumination conditions.     

Estimation of winter wheat biomass based on remote sensing data at various spatial and spectral resolutions

Biomass can indicate plant growth status, so it is an important index for plant growth monitoring. This paper focused on the methodology of estimating the winter wheat biomass based on hyperspectral field data, including the LANDSAT TM and EOS MODIS images. In order to develop the method of retrieving the wheat biomass from remote sensed data, routine field measurements were initiated during periods when the LANDSAT satellite passed over the study region. In the course of the experiment, five LANDSAT TM images were acquired respectively at early erecting stage, jointing stage, earring stage, flowering stage and grain-filling stage of the winter wheat, and the wheat biomass was measured at each stage. Based on the TM and MODIS images, spectral indices such as NDVI, RDVI, EVI, MSAVI, SIPI and NDWI were calculated. At the same time, the hyperspectral field data was used to compute the normalized difference in spectral indices, red-edge parameters, spectral absorption, and reflection feature parameters. Then the correlation coefficients between the wheat biomass and spectral parameters of the experiment sites were computed. According to the correlation coefficients, the optimal spectral parameters for estimating the wheat biomass were determined. The bestfitting method was employed to build the relationship models between the wheat biomass and the optimal spectral parameters. Finally, the models were used to estimate the wheat biomass based on the TM and MODIS data. The maximum RMSE of estimated biomass was 66.403 g/m².     

风化面、荒漠漆及地衣在岩矿表面对高光谱遥感的影响

地表风化产生的表面覆盖层、风吹送的尘埃、胶结物或附着物在岩矿表面形成的外壳是影响地表高光谱遥感识别和反演的重要和关键因素。本研究区位于干旱缺水的新疆西准噶尔包古图地区,对岩矿表面的风化面、胶结物形成的荒漠漆、附着于岩面的地衣和原岩的新鲜面进行了波谱测定分析、X射线荧光元素分析和光薄片镜下观察。结果表明：该地区的大部分岩石表面有风化层覆盖,主要为物理风化,少部分岩石表面发生了化学风化;荒漠漆波谱在可见光波段改变原岩本身的波谱形态,但在短波红外波段,保持原岩波谱特征只改变了反射率大小,并不影响对原岩矿物质的高光谱探测;地衣附着于岩表的波谱特征不仅改变了波谱反射率,还完全改变了原岩的波谱形态,对原岩表面波谱有混淆干扰作用。岩矿表面的研究是波谱测量从实验室走向野外实际应用的基础,也是利用高光谱遥感技术直接进行矿物识别、相似矿物的区分以及提取矿物含量和化学成分研究的最初和关键一步。     

Natural Cycles and Transfer of Mercury Through Pacific Coastal Marsh Vegetation Dominated by Spartina foliosa and Salicornia virginica

The potential for marsh plants to be vectors in the transport of mercury species was studied in the natural, mature, tidal China Camp salt marsh on San Pablo Bay. The fluxes of organic matter, mercury (THg), and monomethylmercury (MeHg) were studied in natural stands of Spartina foliosa and Salicornia virginica. Seasonal fluxes from the sediment into aboveground biomass of live plants and subsequent transfer into the dead plant community by mortality were measured. Loss of THg and MeHg from the dead plant community through fragmentation, leaching, and excretion were calculated and were similar to net uptake. Seasonal data were added up to calculate annual mass balances. In S. foliosa, annual net production was 1,757 g DW m^?2, and the annual net uptakes in the aboveground biomass were 305 μg THg m^?2 and 5.720 μg MeHg m^?2. In S. virginica, annual net production was 2,117 g DW m^?2, and the annual net uptakes in aboveground biomass were 99.120 μg THg m^?2 and 1.990 μg MeHg m^?2. Of both plant species studied, S. foliosa had a slightly lower production rate but greater mercury species uptake and loss rates than S. virginica, and, consequently, it is to be expected that S. foliosa matter may affect the local and possibly the regional food web relatively more than S. virginica. However, the actual effects of the input of mercury-species-containing plant-derived particulate matter into the food webs would depend on trophic level, food preference, seasonal cycle of the consumer, total sediment surface area vegetated, location of the vegetation in the marsh landscape, and estuary bay landscape. Since the levels of mercury species in dead plant material greatly exceed those in live plant material (on a dry weight basis), detritivores would ingest greater mercury species concentrations than herbivores, and consumers of S. foliosa would ingest more than consumers of S. virginica. The greatest THg and MeHg losses of both plant species due to mortality and to fragmentation–leaching–excretion occurred in late spring and early autumn, which corresponds to peak MeHg levels observed in sediments of coastal systems of previous studies, suggesting enhanced THg–MeHg export from the marsh to the nearshore sediment.     

Relationship of intertidal surface sediment chlorophyll concentration to hyperspectral reflectance and chlorophyll fluorescence

Estimating biomass of microphytobenthos (MPB) on intertidal mud flats is extremely difficult due to their patchy occurrence, especially at the scale of an entire mud flat. We tested two optical approaches that can be applied in situ: spectral reflectance and chlorophyll fluorescence. These two approaches were applied in 4 European estuaries with different sediment characteristics. At each site, paired replicate measurements of hyperspectral reflectance, chlorophyll fluorescence (after 15 min dark adaptation, F_o ¹⁵), sediment water content, and chlorophylla concentrations were taken (including breakdown products: [chla+phaeo]). Sediments were further characterized by grain size and organic content analysis. The spectral signatures of tidal flats dominated by benthic microalgae, mainly diatoms, could be easily distinguished from sites dominated by macrophytes; we present a 3 waveband algorithm that can be used to detect the presence of macrophytes. The normalized difference vegetation index (NDVI) was found to be most strongly correlated to sediment [chla+phaeo], except for the predominantly sandy Sylt stations. F_o ¹⁵ was also significantly correlated to sediment [chla+phaeo] in all but one grid (Sylt grid A). Our results suggest that the functional relationships (i.e., the slopes) between NDVI or fluorescence and [chla+ phaeo] were not significantly different in the muddier grids, although the intercepts could differ significantly, especially for F_o ¹⁵. This suggests a mismatch of the optical depth seen by the reflectometer or fluorometer and the depth sampled for pigment analysis. NDVI appears to be a robust proxy for sediment [chla+phaeo] and can be used to quantify MPB biomass in muddy sediments of mid latitude estuaries.     

矿物蚀变区典型地物光谱特征初步研究——以内蒙古突泉县-扎鲁特旗成矿带为例

文章基于野外的实测光谱数据,对岩石、土壤和植被的光谱反射特征以及它们在统计空间的分布关系进行分析研究,总结中等植被覆盖的矿物蚀变区典型地物的光谱反射特征以及不同地物在光谱空间的分布规律,为矿物的遥感蚀变信息提取提供一定的科学依据,有利于改进蚀变信息提取的方法。     

Studies on the reflectance spectral features of saline soil along the middle reaches of Tarim River: a case study in Xinjiang Autonomous Region, China

There has been growing interest in the use of reflectance spectroscopy as a rapid and inexpensive tool for soil characterization. In this study, 53 soil samples were collected from the oasis in the Weigan and Kuqa River delta along the middle reaches of Tarim River to investigate the level of soil chemical components in relation to soil spectral. An approach combining spectral technology and multi-variant statistical analysis was used to determine the reflectance spectral features of saline soil. The spectral data was first pretreated to remove noises and absorption bands from water, which eliminated influence from instrument errors and other external background factors. Several spectral absorption features were calculated for several saline soil samples to confirm that soil at the same salinity level had similar absorption spectral properties. Secondly, a correlation relationship between reflectance spectra and salinity factors was estimated by bivariate correlation method. Fourteen salinity factors including eight major ions and soil electrical conductivity (EC), soil salt content (SSC), pH, and total dissolved solid (TDS) in the saline soil were evaluated. Datasets of the salinity factors that correlated significantly with field data measurements of reflectance rate and the corresponding spectrum data were used to construct quantitative regression models. According to the multiple linear regression analysis, SSC, SO₄ ^2?, TDS, and EC had a correlation coefficient at 0.746, 0.908, 0.798, and 0.933 with the raw spectral data, respectively, which confirmed strong correlation between salinity factors and soil reflectance spectrum. Findings from this study will have significant impact on characterization of spectral features of saline soil in oasis in arid land.     

Designing of the perpendicular drought index

In this paper, a simple, effective drought monitoring method is developed using two dimensional spectral space obtained from reflectance of near-infrared (NIR) and Red wavelengths. First, NIR–Red reflectance space is established using atmospheric and geometric corrected ETM+ data, which is manifested by a triangle shape and in which different surface targets possess certain spatial distribution rules. Second, perpendicular drought index (PDI) is developed on the basis of spatial characteristics of moisture distribution in NIR–Red space, as well as the relationships between PDI and soil moisture is examined. Validation work includes: comparison of PDI with in-situ drought index obtained from field measured data in the study area which includes bulk soil moisture content at different soil depths, field moisture capacity and wilting coefficient, etc.; and comparison of PDI with other recognized drought monitoring methods such as LST/NDVI and vegetation temperature condition index (VTCI). It is evident from the results that graph of PDI of field measured plots demonstrates very similar trends with ground truth drought data, LST/NDVI and VTCI. PDI is highly correlated with in-situ drought values calculated from 0 to 20 cm mean soil moisture with correlation coefficients of R ² = 0.49 (r = 0.75). This paper concludes that PDI has a potential in remote estimation of drought phenomenon as a simple, effective drought monitoring index.     

Catastrophic events reveal the dynamic nature of salt-marsh vegetation in Southern California

Recent hydrological disturbances, including flooding, dry-season streamflow, and drought, greatly altered coastal wetland habitats in sourthern California. At Tijuana Estuary, a six-year study of salt-marsh vegetation patterns during these rare conditions documented substantial temporal variability in plant growth and distribution. Important to cordgrass (Spartina foliosa Trin.) dynamics were the amount and timing of streamflows, which reduced soil salinity and alleviated stresses on plant growth. Poorest growing conditions occurred in 1984 when both river and tidal flows were lacking; soils had low moisture and extreme salinities (avg.=104‰ in September). Plant stress was documented in 1984 as high mortality (62% fewer stems than in 1983) and reduced height (19% less than in 1983). Cordgrass height was greatest in 1980 following winter flooding (20% increase over 1979); densities were greatest in 1983 with summer freshwater influxes (60% increase over 1982). A carbon allocation model is proposed to explain the varied responses.