scholarly journals Changes in the Cerrado vegetation structure: insights from more than three decades of ecological succession

Web Ecology ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 55-64
Author(s):  
Rogério Victor S. Gonçalves ◽  
João Custódio F. Cardoso ◽  
Paulo Eugênio Oliveira ◽  
Denis Coelho Oliveira
Keyword(s):  
Vegetation Structure ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Progressive Increase ◽  
Plant Management ◽  
Brazilian Cerrado ◽  
Cerrado Vegetation ◽  
Management Plans ◽  
Over Time

Abstract. Changes in the vegetation of Brazilian Cerrado may occur over time. However, long-term dynamics are not fully understood yet, especially woody plant encroachment (WPE). The objective of this study was to examine changes in vegetation structure in a preserved area in Triângulo Mineiro region, within the southern Brazilian Cerrado domain, over 32 years (1987, 2005, and 2019). We based the study on field and literature surveys, as well as satellite imagery, and hypothesized that, due to the absence of periodic fires or grazing, Cerrado open formations (i.e., grassland or savanna) tend to become denser due to WPE. Shrubby grassland cover assessed in 1987 disappeared in the following periods (from 30.0 % to 0.0 % in 2019) while forest formations increased (from 7.0 % in 1987 to 11.0 % in 2019). Changes between 2005 and 2019 occurred within the stricto sensu cerrado subdivisions, with reduction of sparse cerrado (from 34.2 % to 7.7 %) and an increase in dense cerrado (from 6.9 % to 39.8 %). Normalized difference vegetation index (NDVI) applied for similar periods indicates a progressive increase of values over time (from 1986 (0.61±0.10) to 2004 (0.65±0.06) and 2018 (0.78±0.05)) and corroborates the WPE process. These patterns imply the loss of biodiversity in open plant formation. Another major consequence was the reduction of wetlands and possible impact on water supply. Such patterns are important to support plant management plans for the threatened Cerrado open plant formations.

scholarly journals Drought Analysis for the Seyhan Basin with NDVI and VCI Vegetation Indices

2021 ◽  
Author(s):  
Murat Aksel ◽  
Mehmet Dikici
Keyword(s):  
Climate Change ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Vegetation Indices ◽  
Condition Index ◽  
Drought Indices ◽  
Drought Risk ◽  
Vegetation Condition Index ◽  
Management Plans

Abstract Various drought indices have been developed to monitor the drought, which is one of the results of climate change and mitigates its adverse effects on water resources, especially agriculture. Vegetation indices determined by remote sensing have been the subject of many studies in recent years and shed light on drought risk management. This study is examined in the Seyhan River Basin, a basin with Turkey’s considerable population density counts and is situated south of the country. Normalized Difference Vegetation Index (NDVI) and Vegetation Condition Index (VCI) are the most widely used vegetation indices and are very useful because they give results only based on satellite images. This study examined the Seyhan Basin by using satellite data in which the vegetation transformation occurring due to the decline of agricultural and forest areas was also seen. An increase in drought frequency was detected in the Seyhan Basin using NDVI and VCI indices. It was determined that climate change and drought increased with a linear uptrend. It is recommended that decision-makers should take the necessary measures by considering the drought risk maps and that long-term drought management plans should be made and implemented.

scholarly journals Forage Production of the Argentine Pampa Region Based on Land Use and Long-Term Normalized Difference Vegetation Index Data

2009 ◽  
Vol 62 (2) ◽  
pp. 163-170 ◽  
Author(s):  
Carlos M. Di Bella ◽  
Ignacio J. Negri ◽  
Gabriela Posse ◽  
Florencia R. Jaimes ◽  
Esteban G. Jobbágy ◽  
...  
Keyword(s):  
Land Use ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Forage Production ◽  
Index Data ◽  
Pampa Region

Inter-comparison of remotely-sensed actual evapotranspiration products in the Zayandehrud river basin, Iran

2021 ◽  
Author(s):  
Neda Abbasi ◽  
Hamideh Nouri ◽  
Sattar Chavoshi Borujeni ◽  
Pamela Nagler ◽  
Christian Opp ◽  
...  
Keyword(s):  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Field Measurements ◽  
Water Shortage ◽  
Remotely Sensed ◽  
Irrigation Scheduling ◽  
Accurate Estimation ◽  
Agricultural Areas ◽  
Eta Products

<p>Accurate estimation of evapotranspiration (ET) helps to create a better understanding of water allocation, irrigation scheduling, and crop management especially in arid and semiarid regions where agricultural areas are far more affected by water shortage and drought events. Remote sensing (RS) facilitates estimating the ET in regions where long-term field measurements are missed.  In this study, we compare the performance of free open-access remotely sensed actual ET products at eleven counties of the Zayandehrud basin. The Zayandehrud basin, one of the major watersheds of Iran, suffers from recurrent droughts and long-term impacts of aridity. The RS products used in this study are namely WaPOR (2009-2019), MOD16A2 (2003-2019), SSEBOp (2003-2019). We also merged the two products of SSEBOp and WaPOR and assessed its performance. To prepare the Merged ETa Product (MEP), WaPOR was resampled to the spatial resolution of SSEBOp. Then, the average pixel values of the resampled ETa product and SSEBOp were calculated. To compare ETa estimations over croplands in each county, maximum Normalized Difference Vegetation Index (NDVI) maps at annual scale (2003-2019) were prepared using LANDSAT 5, 7, and 8 images. Annual mean ETa estimations were then extracted over croplands by using annual maximum NDVI layers. We compared the RS-based ETa with reported long-term ETa values extracted from the local available literature. Our results showed a consistent underestimation of MOD16A2 in all counties. The MEP and WaPOR outperformed other products in the estimation of ETa in seven. Estimations of WaPOR and SSEBOp agreed in most of the counties. Our analysis displayed that, although MOD16A2 underestimated ETa values, it could together with SSEBOp capture the drought better than that of WaPOR and MEP in the lower reaches of the basin. Further study is needed to evaluate the monthly and seasonal performance of RS-based ETa products.</p>

scholarly journals Phenological behavior of Atlas cedar (Cedrus atlantica) forest to snow and precipitation variability in Boutaleb and Babors Mountains, Algeria

2019 ◽  
Vol 21 (1) ◽  
Author(s):  
Khaled Missaoui ◽  
Rachid Gharzouli ◽  
Yamna Djellouli ◽  
Frençois Messner
Keyword(s):  
Time Series ◽  
Satellite Images ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Descriptive Analysis ◽  
Precipitation Variability ◽  
Monthly Precipitation ◽  
Cedrus Atlantica ◽  
The Past

Abstract. Missaoui K, Gharzouli R, Djellouli Y, Messner F. 2020. Phenological behavior of Atlas cedar (Cedrus atlantica)  forest to snow and precipitation variability in Boutaleb and Babors Mountains, Algeria. Biodiversitas 21: 239-245. Understanding the changes in snow and precipitation variability and how forest vegetation response to such changes is very important to maintain the long-term sustainability of the forest. However, relatively few studies have investigated this phenomenon in Algeria. This study was aimed to find out the response of Atlas cedar (Cedrus atlantica (Endl.) G.Manetti ex Carrière) forest in two areas (i.e Boutaleb and Babors Mountains) and their response to the precipitation and snow variability. The normalized difference vegetation index (NDVI) generated from satellite images of MODIS time series was used to survey the changes of the Atlas cedar throughout the study area well as dataset of monthly precipitation and snow of the province of Setif (northeast of Algeria) from 2000 to 2018. Descriptive analysis using Standarized Precipitation Index (SPI) showed the wetter years were more frequent in the past than in the last two decades. The NDVI values changes in both areas with high values were detected in Babors Mountains with statistically significant differences. Our findings showed important difference in Atlas cedar phenology from Boutaleb mountains to Babors Mountains which likely related to snow factor.

scholarly journals ÍNDICE DE VEGETAÇÃO POR DIFERENÇA NORMALIZADA ASSOCIADO ÀS VARIÁVEIS PLUVIOMÉTRICAS PARA A SUB-BACIA DO RIO ESPINHARAS – PB/RN

Nativa ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 106-114
Author(s):  
Ewerton Medeiros Simões ◽  
Joedla Rodrigues de Lima ◽  
Izaque Francisco Candeia de Mendonça
Keyword(s):  
Rainy Season ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Progressive Increase ◽  
Limiting Factor ◽  
Landsat 8 ◽  
Dry Period ◽  
Rainy Period ◽  
Brazilian Semiarid ◽  
Weather Stations

No semiárido brasileiro, onde se insere o bioma caatinga, a precipitaçãos é um dos fator limitante para seu desenvolvimento sócioeconômico e ambiental, este estudo avaliou a correlação existente entre o nível de cobertura vegetal e as variáveis pluviométricas locais, considerando a climatologia de 2005 e 2015, utilizando-se imagens dos sensores TM e OLI dos satélites Landsat 5 e Landsat 8, respectivamente. O ano de 2005 apresentou maiores valores de NDVI em relação a 2015, com valores máximos de 0,71 e 0,78 no período seco e úmido, respectivamente. No ano de 2015, os valores máximos são de 0,64 e 0,61, para o período seco e úmido, respectivamente. Os maiores valores foram observados no período chuvoso de 2005, nas áreas de influência das estações meteorológicas de Matureia, Salgadinho e Areia de Baraúnas. No período seco, nota-se a baixa variabilidade dos valores de NDVI, sendo as maiores leituras observadas nas estações de Matureia, Salgadinho e Teixeira. As estações que apresentaram as maiores reduções nos valores de NDVI de 2005 para 2015, no período chuvoso, foram Matureia, Santa Teresinha e Salgadinho, com reduções de 41,9%, 38,2% e 32,7%, respectivamente. As correlações mais significativas foram estabelecidas para os períodos secos. As menores correlações foram verificadas no período chuvoso. A elevação dos níveis pluviométricos na região não implicou o aumento progressivo nos valores de NDVI. Palavras-chave: semiárido; geoprocessamento; índice de vegetação normalizada.   Normalized difference vegetation index associated with pluviometric variables for Espinharas River sub-basin - PB/RN States   ABSTRACT: In the Brazilian semiarid, where the caatinga biome is inserted, precipitation is a limiting factor for its socioeconomic and environmental development, This study evaluated the correlation between the level of vegetation cover and the local rainfall variables, considering the climatology of 2005 and 2015, using images from the TM and OLI sensors of the Landsat 5 and Landsat 8 satellites, respectively. The year 2005 presented higher NDVI values compared to 2015, with maximum values of 0.71 and 0.78 in the dry and wet periods, respectively. In 2015, the maximum values are 0.64 and 0.61, for the dry and wet periods, respectively. The highest values were observed in the rainy period of 2005, in the weather stations of Matureia, Salgadinho and Areia de Baraúnas. In the dry period, the low variability of NDVI values is noted, with the highest readings observed in the Matureia, Salgadinho and Teixeira platforms. The platforms that showed the greatest reductions in NDVI values from 2005 to 2015, in the rainy season, were Matureia, Santa Teresinha and Salgadinho, with reductions of 41.9%, 38.2% and 32.7%, respectively. The most significant correlations were established for the dry periods. The smallest correlations were found in the rainy season. The increase in rainfall levels in the region did not imply a progressive increase in NDVI values. Keywords: semiarid; geoprocessing; normalized difference vegetation index.

scholarly journals INVESTIGATING MANGROVE FRAGMENTATION CHANGES USING LANDSCAPE METRICS

2019 ◽  
Vol XLII-4/W18 ◽  
pp. 159-162
Author(s):  
M. Baharlouii ◽  
D. Mafi Gholami ◽  
M. Abbasi
Keyword(s):  
Climate Change ◽  
Landscape Metrics ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Landsat Images ◽  
Surrounding Water ◽  
Maximum Likelihood Classification ◽  
High Degree ◽  
Drought Occurrence

Abstract. Generally, investigation of long-term mangroves fragmentation changes can be used as an important tool in assessing sensitivity and vulnerability of these ecosystems to the multiple environmental hazards. Therefore, the aim of this study was to reveal the trend of mangroves fragmentation changes in Khamir habitat using satellite imagery and Fragstats software during a 30-year period (1986–2016). To this end, Landsat images of 1986, 1998, and 2016 were used and after computing the normalized difference vegetation index (NDVI) to distinguish mangroves from surrounding water and land areas, images were further processed and classified into two types of land cover (i.e., mangrove and non-mangrove areas) using the maximum likelihood classification method. By determining the extent of mangroves in the Khamir habitat in the years of 1986, 1998 and 2017, the trend of fragmentation changes was quantified using CA, NP, PD and LPI landscape metrics. The results showed that the extent of mangroves in Khamir habitat (CA) decreased in the period post-1998 (1998–2016). The results also showed that, the NP and PD increased in the period of post-1998 and in contrast, the LPI decrease in this period. These results revealed the high degree of vulnerability of mangroves in Khamir habitat to the drought occurrence and are thus threatened by climate change. We hope that the results of this study stimulate further climate change adaptation planning efforts and help decision-makers prioritize and implement conservative measures in the mangrove ecosystems on the northern coasts of the PG and the GO and elsewhere.

scholarly journals Assessing the Effectiveness for Achieving Policy Objectives of Land Consolidation in China: Evidence from Project Practices in Jiangsu Province from 2001 to 2017

2021 ◽  
Vol 13 (24) ◽  
pp. 13891
Author(s):  
Yan Sun ◽  
Xiaojun Song ◽  
Jing Ma ◽  
Haochen Yu ◽  
Xiaoping Ge ◽  
...  
Keyword(s):  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
National Level ◽  
Jiangsu Province ◽  
Land Consolidation ◽  
Investment Funds ◽  
Strategic Factors ◽  
Implementation Scheme ◽  
Policy Objectives

Land consolidation (LC) is an important measure taken to increase the quantity and productivity of farmland while reducing land fragmentation and ensuring food security. However, long-term land consolidation project (LCP) practices are rarely analyzed to assess the effectiveness for achieving current policy objectives of LC in China. Taking the practices of LCPs in Jiangsu Province from 2001 to 2017 as a case study, we used the spatial self-related analysis, the consistency analysis, and the redundant analysis (RDA), and found that the construction scale and the investment amount of LC in Jiangsu Province displayed varying trends, and that the newly increased farmland rate is clearly divided into three stages and gradually decreases. The newly increased farmland area, the investment funds, and reserved land resources for farmlands are not spatially synchronized in Jiangsu Province. Only the positive relationship between the LC rate and the Normalized Difference Vegetation Index (NDVI) growth rate continue to rise. The earlier stage of land consolidation projects (LCPs)’s practices is mainly affected by natural and social factors, and the late stage is mainly affected by economic and strategic factors. Finally, a new implementation scheme framework of LC planning has been proposed. This framework provides reference for top-level design, planning, and management of LC policies at the national level in China and other developing countries. Check meaning retained.

Application of Mann-Kendall trend test and Normalized Difference Vegetation Index (NDVI) in hydroclimatological change detection – A Case Study of Urmia Lake watershed, Iran

2020 ◽  
Author(s):  
Roshanak Tootoonchi ◽  
Vahid Nourani ◽  
Soghra Andaryani ◽  
Faranak Tootoonchi
Keyword(s):  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Urmia Lake ◽  
Trend Test ◽  
Vegetation Changes ◽  
Agricultural Activities ◽  
Increasing Trend ◽  
West Azerbaijan ◽  
East Azerbaijan

<p>Urmia Lake watershed, which is located at the northwest of Iran has gone through crucial hydroclimatological changes that resulted in Urmia Lake Desiccation. Long term average temperature and precipitation trends, precipitation pattern transition and changes in precipitation-snow timing are some of the hydroclimatological changes that have occurred in this watershed. Aforementioned changes are provoked by anthropogenic activities such as land cover changes, booming urbanization, unauthorized exploitations of Urmia Lake and inefficient crop management, followed by natural factors that could be caused by climate change.</p><p>In this study we aim to address contributing hydroclimatological factors and vegetation changes that resulted in Urmia Lake desiccation. In order to examine the vegetation changes in this watershed, we analyzed remote sensing data. In this regard, normalized difference vegetation index (NDVI)-based models for two sub-basins in East Azerbaijan province and West Azerbaijan -located at two sides of Urmia Lake watershed- are developed by an ensemble of satellite data from 1990 to 2019. Data of Landsat 5 TM satellite from 1990 to 2013 and Landsat 8 OLI/TIRS satellite from 2013 to 2019, are collected and analyzed to consider vegetation changes. Hydrological data for precipitation, temperature and Urmia Lake water level elevation are also considered for analyzing hydroclimatic impacts. The adequacy of NDVI-based models and long term hydrological time series are checked by Mann-Kendall trend test.</p><p>The evaluation of NDVI-based models shows an increasing trend in vegetation. In comparison, the studied sub-basin in West Azerbaijan province has a higher level of increasing trend than the sub-basin in East Azerbaijan province. The evaluation of precipitation time series shows a decreasing trend and temperature data exhibit an increasing trend. The trend pattern changes validates the hypothesis that increasing trend of vegetation in Urmia Lake watershed is in proportion to the escalating agricultural activities. Furthermore, the escalation of land use is higher in West Azerbaijan province where there exists more agricultural activities.</p>

scholarly journals Satellite-Derived Estimation of Grassland Aboveground Biomass in the Three-River Headwaters Region of China during 1982–2018

2021 ◽  
Vol 13 (15) ◽  
pp. 2993
Author(s):  
Ruiyang Yu ◽  
Yunjun Yao ◽  
Qiao Wang ◽  
Huawei Wan ◽  
Zijing Xie ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Aboveground Biomass ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Growth Period ◽  
Spatiotemporal Variation ◽  
Coefficient Of Determination ◽  
Gradient Boosting ◽  
Ancillary Data

The long-term estimation of grassland aboveground biomass (AGB) is important for grassland resource management in the Three-River Headwaters Region (TRHR) of China. Due to the lack of reliable grassland AGB datasets since the 1980s, the long-term spatiotemporal variation in grassland AGB in the TRHR remains unclear. In this study, we estimated AGB in the grassland of 209,897 km2 using advanced very high resolution radiometer (AVHRR), MODerate-resolution Imaging Spectroradiometer (MODIS), meteorological, ancillary data during 1982–2018, and 75 AGB ground observations in the growth period of 2009 in the TRHR. To enhance the spatial representativeness of ground observations, we firstly upscaled the grassland AGB using a gradient boosting regression tree (GBRT) model from ground observations to a 1 km spatial resolution via MODIS normalized difference vegetation index (NDVI), meteorological and ancillary data, and the model produced validation results with a coefficient of determination (R2) equal to 0.76, a relative mean square error (RMSE) equal to 88.8 g C m−2, and a bias equal to −1.6 g C m−2 between the ground-observed and MODIS-derived upscaled AGB. Then, we upscaled grassland AGB using the same model from a 1 km to 5 km spatial resolution via AVHRR NDVI and the same data as previously mentioned with the validation accuracy (R2 = 0.74, RMSE = 57.8 g C m−2, and bias = −0.1 g C m−2) between the MODIS-derived reference and AVHRR-derived upscaled AGB. The annual trend of grassland AGB in the TRHR increased by 0.37 g C m−2 (p < 0.05) on average per year during 1982–2018, which was mainly caused by vegetation greening and increased precipitation. This study provided reliable long-term (1982–2018) grassland AGB datasets to monitor the spatiotemporal variation in grassland AGB in the TRHR.

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