Summer Vegetation Research Articles

Monitoring LULC changes and its impact on the LST and NDVI in District 1 of Shiraz City

Today, immediate and long-term change detection and monitoring using remote sensing (RS) data and geographical information system (GIS) is of paramount importance in generating information about the latest land use/land cover (LULC), land surface temperature (LST), and normalized difference vegetation index (NDVI) in accordance with spatial and temporal changes. Therefore, to obtain these components, a multi-temporal dataset was used consisting of two sets of Landsat Thematic Mapper (TM) images from 1986 to 2011 period across District 1 of Shiraz. Additionally, to investigate the relationship between LST and NDVI over seasons, four Landsat images were used. LULC, LST, and NDVI components were retrieved using Landsat image in ERDAS IMAGINE 9.2 image processing software. Results showed that during the study period, the city had experienced a massive urban (residential) growth. Moreover, change detection suggested that residential areas had increased by 13.17 km2 and vegetation zones (garden) and barren lands had decreased by 4.6 and 8.63 km2, respectively, during 1985–2011 period. The study of the relationship between vegetation index (land cover) and vegetation (land use) in District 1 showed that with reduced vegetation zone (land use), the quality of vegetation (land cover) had deteriorated. These findings indicate that reduced quality of vegetation cover and consequently its Reduction can have a positive effect on the temperature patterns. In general, the negative correlation between vegetation and LST caused by lower vegetation quality was less significant in 2011 compared to 1986, while there the correlation between vegetation and LST in summer was higher than other seasons.

A Polarimetric SAR and Multispectral Remote Sensing Approach for Mapping Salt Diapirs: Axel Heiberg Island, NU, Canada

Remote sensing has revolutionized resource exploration by enabling quick surveillance of large areas. Quad-polarimetric synthetic aperture radar (SAR) is useful for assessing surface roughness, but few studies have applied it for geological mapping. Located in the Canadian Arctic, Axel Heiberg Island is a suitable site for exploring remote predictive geologic mapping techniques that combine quad-polarimetric SAR and multispectral datasets. The island has extensive rock exposure, with little interference from vegetation and snow in late summer. Axel Heiberg Island has the second highest concentration of salt diapirs globally. As a result, it also hosts extensive secondary salt deposits that have been weathered and precipitated away from their source. Because diapirs frequently provide structural traps for petroleum reservoirs, it is important to distinguish between diapiric and non-diapiric salt during early exploration. This study maps diapirs and secondary salts using multispectral data and characterizes them in polarimetric SAR. Diapirs appear rough in C-Band and L-Band radar, whereas the secondary salts appear smooth at both (cm–dm) scales. Field observations confirm salt diapirs are rough at the millimeter–meter scales, whereas secondary salts precipitate on smoother surfaces. These results show that radar can help differentiate between diapiric and secondary salt exposures, which will assist in future resource exploration.

Application of unmanned aircraft system (UAS) for monitoring bank erosion along river corridors

Excessive streambank erosion is a significant source of fine sediments and associated nutrients in many river systems as well as poses risk to infrastructure. Geomorphic change detection using high-resolution topographic data is a useful method for monitoring the extent of bank erosion along river corridors. Recent advances in an unmanned aircraft system (UAS) and structure from motion (SfM) photogrammetry techniques allow acquisition of high-resolution topographic data, which are the methods used in this study. To evaluate the effectiveness of UAS-based photogrammetry for monitoring bank erosion, a fixed-wing UAS was deployed to survey 20 km of river corridors in central Vermont, in the northeastern United States multiple times over a two-year period. Digital elevation models (DEMs) and DEMs of difference allowed quantification of volumetric changes along selected portions of the survey area where notable erosion occurred. Results showed that UAS was capable of collecting high-quality topographic data at fine resolutions even along vegetated river corridors provided that the surveys were conducted in early spring, after snowmelt but prior to summer vegetation growth. Longer term estimates of streambank movements using the UAS showed good comparison to previously collected airborne lidar surveys and allowed reliable quantification of significant geomorphic changes along rivers.

Genetic diversity of leafy amaranth (Amaranthus tricolor L.) resources in Vietnam.

Leafy amaranths, which are consumed as traditional food in Asia and Africa, are now considered among the most promising vegetables. In Vietnam, leafy amaranths, particularly Amaranthus tricolor L., are important summer vegetables due to their excellent nutritional values and high tolerance to biotic and abiotic stresses. However, this species has not been subjected to systematic breeding. Here we describe species identification and evaluation of the genetic diversity of Vietnamese amaranth collection by using matK and simple sequence repeats (SSR) markers. Our phylogenetic analysis based on the matK marker classified the species of 68% of the accessions, of which 120 belonged to A. tricolor. We developed 21 SSR markers, which amplified a total of 153 alleles in 294 A. tricolor accessions originating from Vietnam and overseas, with a mean allelic richness of 7.29 per marker, observed heterozygosity of 0.14, expected heterozygosity of 0.38, and polymorphic information content of 0.35. The STRUCTURE and FST analysis indicated a positive relationship between geographic distance and genetic differentiation among most of the overseas groups and the Vietnamese collection, but not among geographic groups within the Vietnamese collection. Vietnamese amaranths could be divided into two major types, one common in East Asia and the other one unique to Vietnam.

A transdisciplinary framework for predictive disease ecology based on cross-scale interactions: Insights from long-term data

A transdisciplinary framework for predictive disease ecology based on cross-scale interactions: Insights from long-term data

Effect of intercropping on the incidence of Jassid (Amrasca biguttula biguttula Ish.) and Whitefly (Bemesia tabaci Guen.) in Okra (Abelmoschus esculentus L. Moench)

Okra is one of the most important summer vegetables in South Asian countries including Nepal. However, the damage by insects like Jassid (Amrasca biguttula Ish.) and whitefly (Bemisia tabaci Guen) has resulted in significant reduction of its production. An experiment was conducted based on intercropping taking okra (Abelmoschus exculentus L. Moench) as the main crop in Arghau, Lekhnath-27, Kaski, Nepal from March 4 to May 24, 2018. The intercrops used were coriander (Corriander sativum), carrot (Daucas carota), fennel (Foeniculum vulgare) and parsley (Petroselinum crispum). The population of jassid and whitefly was recorded from three leaves representing the different strata (bottom, middle and top) of the vegetative parts; and related yield parameters were also observed to correlate with the level of population incidence of these pests. Least numbers of jassids (5.50±0.29, 6.94±0.43, 8.00±0.41 and 3.69±0.76) were observed respectively at 30, 40, 50 and 60 days after sowing (DAS) in okra+ coriander. Likewise, okra + coriander intercropping was effective in inhibiting the population of whitefly (7.50±0.59, 8.56±0.19, 10.25±0.66 and 7.06±0.42) at 30, 40, 50 and 60 days after sowing (DAS) respectively. In contrary, the highest number of jassids and whiteflies were observed in okra + parsley and control (okra only). Both pod length (cm) and yield (t/ha) were the highest (17.92±0.57 and 28.20±0.49 respectively) in okra + coriander and were the lowest (16.42±0.21 and 27.58±0.39 respectively) in okra + carrot. The benefit-cost ratio was in order okra + coriander > okra + carrot > okra + fennel > okra + parsley > control (okra only). Among the different intercrop combinations, the okra + coriander was found most effective that could be suggested as one of the alternative strategies to limit the population of pests; jassid and whitefly in okra.

Emerging negative impact of warming on summer carbon uptake in northern ecosystems

Most studies of the northern hemisphere carbon cycle based on atmospheric CO2 concentration have focused on spring and autumn, but the climate change impact on summer carbon cycle remains unclear. Here we used atmospheric CO2 record from Point Barrow (Alaska) to show that summer CO2 drawdown between July and August, a proxy of summer carbon uptake, is significantly negatively correlated with terrestrial temperature north of 50°N interannually during 1979–2012. However, a refined analysis at the decadal scale reveals strong differences between the earlier (1979–1995) and later (1996–2012) periods, with the significant negative correlation only in the later period. This emerging negative temperature response is due to the disappearance of the positive temperature response of summer vegetation activities that prevailed in the earlier period. Our finding, together with the reported weakening temperature control on spring carbon uptake, suggests a diminished positive effect of warming on high-latitude carbon uptake.

Disentangling the carbon budget of a vineyard: The role of soil management

The environmental sustainability of viticulture can be enhanced with the application of conservative management practices (e.g. resident vegetation or cover crop on the inter-row), which can lead to an increase of soil carbon (C) sequestration. However, studies disentangling the vineyard C budget are still very scarce. In this context, comparing vineyard net ecosystem CO2 exchange (NEE) with soil fluxes is especially useful. From January 2015 to August 2016, we continuously monitored vineyard NEE with the eddy covariance method and ground CO2 fluxes with an automated chamber system in a commercial vineyard in North Eastern Italy. At the site, inter-rows are covered with resident herbaceous vegetation, however, due to low soil permeability, soil cultivation (ripping or tillage) was performed on alternate alleys in autumn and, sometimes, spring in order to improve water infiltration. Measured annual soil respiration was comparable, but lower, to values estimated by previous studies in vineyards and the net uptake of the grass cover laid in the middle of yearly C budget range reported in the literature for grasslands. At the end of the measurement period, the vineyard ecosystem showed to be a net sink of CO2, absorbing around −233 gC m−2. However, the C sequestration could have been much greater if no soil cultivation had been applied. Indeed, the ground compartment was a source of CO2, but without inter-row cultivation it could have been a net sink, with an overall vineyard C budget of about −421 gC m−2. This confirms that grass cover of the inter-rows can play an important role in the C budget of woody crops. Additionally, the pattern of C fluxes reveals that the activity of herbaceous vegetation in summer decreased well before vines, thus reducing water competition during dry periods. These results provide important information for the tuning of management practices aimed at improving the environmental sustainability of viticulture.

Soil and climate differently impact NDVI patterns according to the season and the stand type

Several studies use satellite-based normalized difference vegetation index (NDVI) to monitor the impact of climate change on vegetation covers. Good understanding of the drivers of NDVI patterns is hindered by the difficulties in disentangling the effects of environmental factors from anthropogenic changes, by the limited number of environmental predictors studied, and by the diversity of responses according to periods and land covers. This study aims to improve our understanding of the different environmental drivers of NDVI spatial variations for different stand type characteristics of mountain and Mediterranean biomes. Using NDVI values extracted from MODIS Terra time series, we calculated Spring Greenness (SG) and annual Relative Greenness (RGRE) to depict spring and summer vegetation activity, respectively, in a contrasted area of 10,255 km2 located in the south of France. We modeled SG and RGRE at different scales, using 20 environmental predictors characterizing available energy, water supply, and nutrient supply calculated for different periods of the year. In spring, high minimum temperatures, good nitrogen availability, and acidic or neutral pH turned out to be determining for greenness, particularly for stand types located in altitude. In summer, an important soil water reserve and low temperatures promoted vegetation dynamics, particularly for stands located in areas with a Mediterranean climate. Our results show that NDVI dynamics was not only driven by climatic variability, and should not be studied using only mean temperature and rainfall. They highlight that different environmental factors act complementarily, and that soil parameters characterizing water stress and soil nutrition should be taken into account. While the factors limiting NDVI values varied according to the season and the position of the stands along the ecological gradients, we identified a global temperature and water-stress threshold when considering the whole vegetation.

Evolution of Crop Water Productivity in the Nile Delta over Three Decades (1985–2015)

Estimating crop water productivity (CWP) for spatially variable climatic conditions in Egypt is important for the redistribution of crop planting to optimize production per unit of water consumed. The current paper aims to estimate maximum CWP trends under conditions of the Northern Nile Delta over three decades to choose crops that exhibit a higher productivity per unit of water and positive trends in the CWP. The Kafr El Sheikh Governorate was selected to represent the Northern Nile Delta Region, and mean monthly weather data for the period of 1985 to 2015 were collected to calculate standardized reference evapotranspiration and crop water use for a wide array of crops grown in the region using the CROPWAT8.0 model. The CWP was then calculated by dividing crop yield by seasonal water consumption. The CWP data range from 0.69 to 13.79 kg·m−3 for winter field crops, 3.40 to 10.69 kg·m−3 for winter vegetables, 0.29 to 6.04 kg·m−3 for summer field crops, 2.38 to 7.65 kg·m−3 for summer vegetables, 1.00 to 5.38 kg·m−3 for nili season crops (short-season post summer), and 0.66 to 3.35 kg·m−3 for orchards. The crops with the highest CWP values (kg·m−3) over three decades in descending order are: sugar beet (13.79), potato (w2) (10.69), tomato (w) (10.58), eggplant (w) (10.05), potato (w1) (9.98), cucumber (w) (9.81), and cabbage (w) (9.59). There was an increase in CWP of 41% from the first to the second and 22% from the second to the third decade. The CWP increase is attributed to a small decrease in water consumption and to a considerable increase in crop yield. The yield increases are attributed mainly to the planting of higher yielding varieties and/or the application of better agronomic practices.

Identifying Critical Climate Periods for Vegetation Growth in the Northern Hemisphere

AbstractVegetation‐climate relationships have been extensively investigated in previous studies, yet the critical seasons and corresponding climate factors influencing annual vegetation growth in a changing climate remain unclear. Relying on Global Inventory Modeling and Mapping Studies NDVI3g data and climate data from 1982 to 2013, this study explored the responses of vegetation growth to climate changes in the Northern Hemisphere (NH), with an emphasis on vegetation changes and legacy effects during different seasons. We further identified the most critical season in terms of vegetation growth. We found an apparent seasonal shift in the influence of climate change on vegetation growth in the NH. In addition, we observed legacy effects of climate change on vegetation growth throughout the seasons. Winter temperatures exerted a positive impact on vegetation growth during the following spring in Europe and central North America. Spring precipitation was an important factor for summer vegetation growth in dry areas. Using partial least squares regression, the relative importance of seasonal climatic factors on annual vegetation growth conditions were determined. This study finds that the vegetation in more than 40% of the NH is controlled by temperature, especially spring temperatures (12.8%). Precipitation and solar radiation were the dominant climate factors influencing vegetation growth in 29.9% and 29.1% of vegetated regions, respectively. Furthermore, compared with the period from 1983 to 1997, the influence of seasonal solar radiation on vegetation growth increased in the NH during the period from 1998 to 2013. This phenomenon was accompanied by reductions in the influence of spring and summer temperatures.

Constraints affecting summer vegetable cultivation

ABSTRACT The demand for summer vegetables continues to increase with many vegetables being cultivated in many countries all year round. Despite this, there is a decrease in cultivated area and production of vegetables in Iraq. The study was conducted in Al-Taleiaa district, Babylon Province, Iraq, to identify constraints faced in vegetables cultivation. One hundred and sixty vegetable farmers were randomly selected. A list of 4 categories affecting summer vegetable cultivation: production, financial, technical, and marketing, covering 35 constraints was prepared. About half of the vegetable farmers indicated that there was a high level of constraint impeding production. Competition from imported vegetables, soil salinity, water shortage, high cost of improved seed, poor extension service, and lack of knowledge of recommended cultivation practices were the most cited. The area cultivated with summer vegetable crops, number of cultivated summer vegetable crops, and seasonal income from summer vegetable crops were positively correlated with constraints. Vegetable producers have problems, and those problems need to be solved. It is necessary to use appropriate planning to overcome constraints facing vegetable producers. Restricting vegetable imports, availability of irrigation water, improved, affordable, seed, effective extension services, and adequate information about recommended cultivation practices are needed to improve vegetable production.

Dynamics of vegetation autumn phenology and its response to multiple environmental factors from 1982 to 2012 on Qinghai-Tibetan Plateau in China

Autumn phenological shifts induced by environmental change have resulted in substantial impacts on ecosystem processes. However, autumn phenology and its multiple related controlling factors have not been well studied. In this study, the spatiotemporal patterns of the end date of the vegetation growing season (EGS) and their multiple controls (climate change, summer vegetation growth and human activities) over the Qinghai-Tibetan Plateau (QTP) were investigated using the satellite-derived normalized difference vegetation index (NDVI) based on GIMMS3g datasets during 1982–2012. The results showed that there was no significant temporal trend in the EGS during the period of 1982–2012. Spatially, there was a notable advancing trend in the southwest region and a delayed trend in the other regions of the QTP during 1982–2000, and this spatial trend was reversed during 2001–2012. We found average temperature, precipitation and sunshine duration of autumn exerted positive effects on EGS on the QTP, while average temperature and sunshine duration of summer exerted negative effects. Our results indicated that vegetation growth in summer tends to induce an earlier EGS in alpine vegetation, whereas summer vegetation degradation could delay the EGS on the QTP. In contrast, moderate grazing delays vegetation browning in autumn, while overgrazing leads to advancement of grass senescence. This study improves our understanding of how multiple environmental variables jointly affect autumn phenology and highlights the importance of biotic controls for autumn phenology on the QTP.

Assessment of actual evapotranspiration over a semiarid heterogeneous land surface by means of coupled low-resolution remote sensing data with an energy balance model: comparison to extra-large aperture scintillometer measurements

Abstract. In semiarid areas, agricultural production is restricted by water availability; hence, efficient agricultural water management is a major issue. The design of tools providing regional estimates of evapotranspiration (ET), one of the most relevant water balance fluxes, may help the sustainable management of water resources. Remote sensing provides periodic data about actual vegetation temporal dynamics (through the normalized difference vegetation index, NDVI) and water availability under water stress (through the surface temperature Tsurf), which are crucial factors controlling ET. In this study, spatially distributed estimates of ET (or its energy equivalent, the latent heat flux LE) in the Kairouan plain (central Tunisia) were computed by applying the Soil Plant Atmosphere and Remote Sensing Evapotranspiration (SPARSE) model fed by low-resolution remote sensing data (Terra and Aqua MODIS). The work's goal was to assess the operational use of the SPARSE model and the accuracy of the modeled (i) sensible heat flux (H) and (ii) daily ET over a heterogeneous semiarid landscape with complex land cover (i.e., trees, winter cereals, summer vegetables). SPARSE was run to compute instantaneous estimates of H and LE fluxes at the satellite overpass times. The good correspondence (R2 = 0.60 and 0.63 and RMSE = 57.89 and 53.85 W m−2 for Terra and Aqua, respectively) between instantaneous H estimates and large aperture scintillometer (XLAS) H measurements along a path length of 4 km over the study area showed that the SPARSE model presents satisfactory accuracy. Results showed that, despite the fairly large scatter, the instantaneous LE can be suitably estimated at large scales (RMSE = 47.20 and 43.20 W m−2 for Terra and Aqua, respectively, and R2 = 0.55 for both satellites). Additionally, water stress was investigated by comparing modeled (SPARSE) and observed (XLAS) water stress values; we found that most points were located within a 0.2 confidence interval, thus the general tendencies are well reproduced. Even though extrapolation of instantaneous latent heat flux values to daily totals was less obvious, daily ET estimates are deemed acceptable.

Nutrition and husbandry conditions of Palearctic tortoises (Testudo spp.) in captivity

ABSTRACTMediterranean and Russian tortoises (Testudo spp.) are popular companion animals (pets), despite ongoing controversy concerning privately keeping reptiles. The arguments used during these controversial discussions have often been based on outdated facts. Therefore, a survey was developed to evaluate the current population structure, husbandry conditions, diet regime, and health status of Testudo species in captivity. More than 75% of the 1075 respondents housed their tortoises in an outdoor enclosure containing a greenhouse or cold frame, which is considered the most species-appropriate way of husbandry. Of the respondents, 67.7% fed their tortoises with the optimum diet of more than 80% grasses and weeds during the summer vegetation period. Only 8.2% of respondents owned a tortoise with a diagnosed disease. According to the results, the likelihood of tortoises developing pyramidal growth syndrome, which can be used as an indicator of the quality of tortoise husbandry, was high in tortoises kept in a terrarium and/or fed a diet of less than 80% grasses and weeds in summer. This likelihood varied among species, with a higher incidence in Hermann’s tortoises (Testudo hermanni).

Seasonal divergence in the responses of vegetation growth to PDO in Tibetan Plateau, China

Regional-scale normalized difference vegetation index (NDVI) derived from satellite remote sensing observations and gridded climate data were used to study the seasonal responses and underlying mechanisms of vegetation growth over Tibetan Plateau to Pacific Decadal Oscillation (PDO) at period of 1982-2015, by performing Spearman correlation analysis and enhanced multivariate regression model: structural equation model (SEM). The results showed that there was significant negative correlation between PDO index and mean growing-season (April-October) NDVI over Tibetan Plateau; however, marked seasonal divergence in the relationship between PDO and vegetation growth existed among different seasons. It characterized with stronger negative correlation between PDO and NDVI in autumn than in summer, and winter PDO had significant effect on consequent summer vegetation growth. Additionally, it showed great divergence in control processes of PDO on vegetation growth among different seasons, with significant control of PDO on both temperature and precipitation in summer, and significant control of PDO on temperature only in autumn.

Peculiarities of growth and lipoxygenase activity of wild fern Dryopteris filix-mas (L.) Schott

<p>We studied the peculiarities of growth, localization and dynamics of lipoxygenase activity in sporophyte organs of wild fern <em>Dryopteris filix-mas </em>(L.) Schott at various stages: intensive growth; sori ripening; spore release; summer vegetation, and vegetation termination. Morphometric analysis showed that the weight of one plant during sporophyte ontogenesis varied from 130 to 150 g. Frond length varied from 11 to 85 cm. Diameter of the overground part of rhizome was 9-10 cm. In the stage of spore release and during the summer vegetation we mentioned 7 fronds on plant, and in the phase of vegetation termination – 18. The plants had the biggest weight in phase of spore release. Following spore release and at the beginning of vegetation termination, the frond weight diminished almost by two times. An intensive elongation of fronds was observed prior to the start of spore release. When fronds unfold and grow the number of segments of the first order increase from 39 to 47 pairs. Frond length in the stage of summer vegetation increased from 4.3 to 11.2 cm (9 pairs), and then it gradually decreased from 10.2 to 0.1 cm (39 pairs) that resulted in the formation of a lanceolate lamina. In the stage of vegetation termination, the fern had 18 fronds, 12 of which remained green, while the rest dried and turned greyish-brown. The frond lamina contained 47 pairs of segments of the first order whose length increased from 4.5 to 10.5 cm, and then it diminished from 9.5 to 0.05 cm. The rhizome weight was in the range of 110.2–115.7 g in all the stages except vegetation termination. The morphological analysis showed that plants had successfully passed all developmental phases, reached their normal dimensions, had a mass spore formation, no external signs of suppression and damages, and this was generally consistent with the highest level of life state assessment. Localization and dynamics of lipoxygenase (LOX) activity in organs of the sporophyte of <em>D. filix-mas </em>have been studied. We registered that fronds contained 13-LOX with рН<sub>opt. </sub>values of 7.2, rhizomes – 9-LOX (рН<sub>opt. </sub>6.5). Peculiarities that were mentioned in localization and dynamics of LOX isoforms catalytic activity in the fern organs at various phases of development suggest that the enzyme might be involved in the regulation of lipid metabolism of growth processes that ensure plant adaptation to the environment. </p><p> </p>

Фотосинтетичні пігменти й ультраструктура хлоропластів папороті Dryopteris filix-mas (L.) Schott на різних фенологічних фазах розвитку

A comparative analysis of the photosynthetic pigments content, frond anatomic structure and chloroplast ultrastructure in the various developmental phases of the sporophyte of the leptosporangial fern Dryopteris filix-mas (L.) Schott that belongs to the lower layer plants and grows in shade was carried out. Observations were conducted in the phase of an intensive growth (April), sori ripening (May), spores dissemination (June), summer vegetation (July) as well as vegetation completion and aboveground part die-off (October). The chlorophyll a and b content in fronds was found to increase during the first three phenological phases and reached its maximum in the phase of spores dissemination. A specific feature turned out to be a relatively high content of carotenoids in the first four phases of development. In the phase of vegetation completion and aboveground part die-off the pigments content in frond tissues significantly decreased. The pigments content in fronds of summer green fern D. filix-mas was lower than that of winter green fern Polystichum aculeatum (L.) Roth. The frond anatomic structure was studied by means of the scanning electron microscope using freeze-dried cross-sections. The frond parenchyma was found to be divided into palisade and spongy tissues. The chloroplast ultrastructure was studied using the transmission electron microscope. It was revealed that in the phase of sori ripening the frond mesophyll cells contained elongated lens-like chloroplasts with an electron-dense stroma, which had big starch grains and sometimes plastoglobules. In the parenchyma cells, chloroplasts are in close proximity to the plasmalemma. In the phase of vegetation completion and aboveground part die-off, chloroplasts in cells of the assimilating parenchyma showed a partial deformation in the stroma lamellae and emergence of numerous plastoglobules. The number of starch grains in plastids significantly reduced. The comparison analysis of the photosynthetic pigments composition and content and chloroplast ultrastructure in the various developmental phases of the sporophyte of the Dryopteris filix-mas indicated that the successful existence in shade conditions and changes in the temperature regime along with other features provide a specific structural-functional organization of the photosynthetic apparatus.

Research on Current Situation and Strategy of Online Marketing of Plateau Summer vegetables in Gansu

This paper pointed out that there were a series of problems in the development of Gansu plateau summer-vegetables online marketing such as the lagging online marketing subject, the low application rate of rural internet and the low standardization and branding of products as well as the imperfect product distribution system and so on. In order to deal with these problems effectively, this paper suggested that Gansu province not only should cultivate the online marketing awareness of all relevant parties and improve the popularization rate of rural networks, but also should build a standardized system and a high-qualified plateau summer food brand. In addition, it is also of much importance to perfect the plateau summer vegetables distribution mode.

基于MODIS-EVI的重庆植被覆盖时空分异特征研究

PDF HTML阅读 XML下载 导出引用 引用提醒 基于MODIS-EVI的重庆植被覆盖时空分异特征研究 DOI: 10.5846/stxb201709131650 作者: 作者单位: 西南大学 地理科学学院,西南大学 地理科学学院,重庆师范大学 GIS应用研究重庆市高校重点实验室,西南大学 地理科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技支撑计划项目（2006BAC01A16，2011BAC09B01）；重庆市自然科学基金重点项目（CSTC2009BA0002） Study on the spatial-temporal variability of vegetation coverage based on MODIS-EVI in Chongqing Author: Affiliation: School of Geographic Sciences, Southwest University,School of Geographic Sciences, Southwest University,, Fund Project: National Key Technology Research and Development Program of the Ministry of Science and Technology of China, NO. 2006BAC01A16 and 2011BAC09B01; Key Program of the Natural Science Foundation of Chongqing, NO. CSTC2009BA0002. 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用MODIS-EVI数据，采用像元二分模型结合距平百分率、变异系数和分布指数对2000-2015年重庆植被覆盖度变化时空分异特征进行了分析，结果表明：（1）重庆植被年际、夏、秋季和2008-2015年春季以中覆盖度为主，冬季以及2000-2007年春季以低覆盖度为主。（2）植被覆盖年际变化不明显；劣覆盖度在2000、2002、2003年春季，2001、2006年秋季以及2011年冬季异常偏多；低覆盖度在2000、2001年秋季异常偏多；高覆盖度在2000、2008年秋季和2014年春季异常偏少。（3）植被的波动变化除了冬季以中度为主外，年际、春、夏、秋季均以轻度为主；稳定比例最高为夏季，轻度比例最高为秋季，中度和重度比例最高为冬季。（4）稳定和轻度波动类型主要分布在山地森林和草地区，中度和重度波动类型主要是城镇、水域及其周边区域。在400m以下，植被变化为重度波动；在400-800m，植被年际和夏季趋于稳定分布，而春、秋、冬季为轻度波动；在800-1300m，植被年际和夏季为中度波动，春、秋、冬季为稳定分布；在1300m以上，植被年际和夏季呈现轻度波动，春季为中度波动，秋、冬季为稳定分布。 Abstract:The spatial-temporal variability of vegetation coverage in Chongqing was studied based on the MODIS-EVI datasets using the method of dimidiate pixel modeling and anomaly percentage and variance coefficient and distribution indexes from 2000-2015. The results showed that:(1) the vegetation coverage was dominated by medium coverage annually and in summer and autumn. In spring, the vegetation coverage was dominated by low coverage from 2000-2007, while it was dominated by medium coverage from 2008-2015. (3) The annual coverage did not changed significantly. Little coverage was much more than normal in the springs of 2000, 2002, and 2003, and in the autumns of 2001 and 2006, and in the winter of 2011. Low coverage was much greater than normal in the autumns of 2000 and 2001. High coverage was much less than normal in the autumns of 2000 and 2008 and in the spring of 2014. (3) Priority was given to the fluctuation of vegetation coverage with low fluctuation annually and in spring, summer, and autumn, while priority was given to moderate fluctuation in winter. The highest percentage stability was recorded during summer and low fluctuation was in autumn, while the moderate and serious fluctuations were in winter. (4) The stable and low fluctuations were mainly distributed in the forest and grass on mountains, while the moderate and serious fluctuations were mainly distributed in the town, water, and the surrounding region. With the increase in elevation, the serious fluctuation was mainly distributed below 400m. The vegetation was stable annually and during summer, while in spring, autumn, and winter there was low fluctuation for vegetation between 400-800m. The annual and summer vegetation showed moderate fluctuation, while in spring, autumn, and winter it was stable between 800-1300m. Annual and summer vegetation showed low fluctuation, while in spring there was moderate fluctuation, but was stable in autumn and winter above 1300m. 参考文献 相似文献 引证文献