Effects of grazing exclusion on spring and autumn pastures in arid regions of China: Insights from field surveys and landsat images

2021 ◽  
Vol 310 ◽  
pp. 107302
Author(s):  
Xiaoli Tai ◽  
Howard E. Epstein ◽  
Bo Li
2020 ◽  
Author(s):  
Giovanni Martino Bombelli ◽  
Daniele Bocchiola ◽  
Federica Camin ◽  
Paolo Maria Ossi

<p>Depiction of glaciers’ dynamics in the high altitudes of Himalaya, and hydrological fluxes therein is often limited, and yet necessary to assess their contribution to overall water budget in the downstream areas. Information about glaciers in these remote regions is often based on satellite data, which routinely document the retreat or advance of ice-covered areas, while volume changes are less easy to quantify, and require local assessment of weather, and hydrology. <br>Here, we report investigation of snow accumulation, ice melt, and mass balance of the West Khangri Nup (WKN) glacier (mean altitude 5494 m a.s.l., 0.23 km<sup>2</sup>), a part of the Khumbu glacier in the Everest region. The glaciers of the area have experienced negative mass balances in the last three decades, and accordingly investigation of their recent, and prospective dynamics seems necessary. <br>Weather, glaciological, snow pits, hydrologic, and isotopic data gathered during some field campaigns (2010-2014) on the glacier, and at the EVK2CNR pyramid site are used here to set up the Poli-Hydro glacio-hydrological model, to depict ice and snow melt and hydrological flows, and investigate seasonal snow dynamics on this high region of the glacier.   <br>Coupling ice ablation data, and Poli-Hydro simulation for ca. 5 years (January 2010-June 2014), we estimated that WKN depleted ca. -10.46 m of ice water equivalent IWE (i.e. annually ca. -2.32 m IWEy<sup>-1</sup>). Using then snowpack density, and isotopic (δ<sup>18</sup>O) profiles on the WKN, we demonstrate that local snowpack during field surveys was recent (Fall-Winter 2013-2014), and that significant snow accumulation did not occur recently. Analysis of recent snow cover from LANDSAT images also confirms snow dynamics as depicted. <br>We present original data and results, and complement present studies covering glaciers’ mass balance, and investigation of accumulation zones in the Everest region, and the Himalayas, also potentially helpful in the assessment of future dynamics under ongoing climate change.     </p>


2021 ◽  
Author(s):  
Aicha Seifelislam-Schreiber ◽  
Elfatih AbdelRahman ◽  
Christina Bogner

<p><strong>Introduction</strong> African wetlands in arid and semi-arid regions provide a multitude of ecosystem services and have been described as the “heart of Sahelian life systems". The Khor Abu Habil alluvial wetlands (Khor is the name given to ephemeral rivers in Sudan) are situated in the semi-arid zone in the southern part of the Sudan. These ephemeral wetlands are fed by seasonal wadi streams and remain for several months. They provide a habitat for migratory water birds and play a fundamental role in supporting the human population (agriculture, grazing, fishing, hunting and construction).</p><p><strong>Goals</strong> In this study we analyse the Land Use and Land Cover (LUL) dynamics related to wetlands and the agricultural activities.</p><p><strong>Material and Methods</strong> Landsat images between 1982 and 2018 were used to run a LULC analysis in the Khor Abu Habil alluvial fan using random forests (RF) and change vector analysis (CVA). Due to the political and the COVID-19 pandemic situations in the study area,  the field work aiming at collecting ground reference points could not be completed. Therefore, we decided to identify training data on different types of LULC classes that were dominant in the study area for the last 30 years using CVA, in addition to the collected ground reference points. High resolution images (Quickbird, Geoeye, WorldView) and expert knowledge were used for the selection of training data. For Landsat images acquired before 2018, the present training data were used where CVA showed no change in LULC. After creating accurate training data, the classification of the different Landsat images was run in R using RF.</p><p><strong>Results </strong>Different types of LULC classes were detected over the past 30 years: Wetlands, Vegetation, Agriculture, Arenosols, Cambisols, Clays.  Our results show that many of those classes were "transformed" into other classes over the past years. We observe that many of those changes are related to different anthropological activities such as the expansion of agriculture or construction of dams.</p><p><strong>Conclusions</strong> Wadis or Khors are particular ecosystems that occur in semi-arid regions. In our study area, the economic activities show a relationship between LULC and different human communities. It is crucial to understand those activities and their effects on an ecosystem, especially if the ecosystem is aimed to be protected. Our research is part of the FAO-supported project RESSOURCE with the overall goal to localise and study wetlands of international importance in the sub-saharan Africa and to possibly declare them as Ramsar protected zones.</p>


2020 ◽  
Vol 12 (15) ◽  
pp. 2398
Author(s):  
Mingxing Cha ◽  
Mengmeng Li ◽  
Xiaoqin Wang

An accurate estimation of evapotranspiration (ET) from crops is crucial in irrigation management, crop yield assessment, and optimal allocation of water resources, particularly in arid regions. This study explores the estimation of seasonal evapotranspiration for crops using multisource remote sensing images. The proposed estimation framework starts with estimating daily evapotranspiration (ETd) values, which are then used to calculate ET estimates during the crop growing season (ETs). We incorporated Landsat images into the surface energy balance algorithm over land (SEBAL) model, and we used the trapezoidal and sinusoidal methods to estimate the seasonal ET. The trapezoidal method used multitemporal ETd images, while the sinusoidal method employs time-series Moderate Resolution Imaging Spectroradiometer (MODIS) images and multitemporal ETd images. Experiments were implemented in the agricultural lands of the Kai-Kong River Basin, Xinjiang, China. The experimental results show that the obtained ETd estimates using the SEBAL model are comparable with those from the Penman–Monteith method. The ETs obtained using the trapezoidal and sinusoidal methods both have a relatively high spatial resolution of 30 m. The sinusoidal method performs better than the trapezoidal method when using low temporal resolution Landsat images. We observed that the omission of Landsat images during the middle stage of crop growth has the greatest impact on the estimation results of ETs using the sinusoidal method. Based on the results of the study, we conclude that the proposed sinusoidal method, with integrated multisource remote sensing images, offers a useful tool in estimating seasonal evapotranspiration for crops in arid regions.


Author(s):  
A. H. Ngandam Mfondoum ◽  
P. G. Gbetkom ◽  
R. Cooper ◽  
S. Hakdaoui ◽  
M. B. Mansour Badamassi

Abstract. Drought affects all human activities and ecosystems. Nearly 40 percent of the world’s population inhabit Drylands, and they depend on agriculture for their food, security and livelihoods. Among the remote sensing indices developed, the Land Surface General Drought Index (LSGDI) was recently proposed. This paper proposes an improved model of LSGDI to face the issue of drought in semi-arid and arid regions. The experiment was conducted for the Maga’s floodplain, in North-Cameroon. The method uses satellite images of Landsat in 1987, 2003 and 2018, for January and March or April, corresponding to the middle and the end of the dry season. A Vegetation Moisture Index (VMI) and a Normalized Difference Soil Drought Index (NDSoDI) are both developed. On an orthogonal plan, their projections give a drought line that expresses the improved LSGDI (LSGDI2) as the root sum square of the NDSoDI and the VMI. The LSGDI2 results are ranged in [0.09 – 0.14] interval, which is used to define the threshold and ease the qualifiers for drought classes. The visual patterns easily match the sandy areas of the original Landsat images with the highest values, while the vegetation and water areas match the lowest values. Compared with the LSGDI and Second Modified Perpendicular drought Index (MPDI1), the new index reflectance values are higher. Finally, although LSGDI2 curve’s evolution follows the NDSoDI one at 94%, the new spectral index values depends on the both components, helping to map highest values of drought and moisture in Maga’s floodplain, for a sustainable rice culture expansion.


TERRITORIO ◽  
2020 ◽  
pp. 148-163
Author(s):  
Luca Fondacci

In the 1970s, the fragile historical centre of the city of Perugia was a key area where the binomial of sustainable mobility and urban regeneration was developed and applied. At the turn of the xxi century, the low carbon automatic people-mover Minimetrò broadened that application from the city's historical centre to the outskirts, promoting the enhancement of several urban environments. This paper is the outcome of an investigation of original sources, field surveys and direct interviews, which addresses the Minimetrò as the backbone of a wide regeneration process which has had a considerable impact on the economic development of a peripheral area of the city which was previously devoid of any clear urban sense. The conclusion proposes some solutions to improve the nature of the Minimetrò as an experimental alternative means of transport.


2020 ◽  
Vol 4 (1) ◽  
pp. 27-42
Author(s):  
Wiyoga Triharto ◽  
Bambang Perkasa Alam

Ratu harbor beach is one of the mainstay tourist sites for the Regional Government of Sukabumi Regency in bringing PAD, besides public transportation facilities and terminals have a major role in supporting the queen port as a tourist attraction so that tourists are comfortable and facilitated in accessing through public transportation. The condition of the Pelabuhan Ratu Terminal, Sukabumi Regency is currently very poor, poorly maintained, and many supporting facilities are damaged and inadequate. This study aims to identify problems and formulate the type B terminal arrangement in Sukabumi Regency. The method used is descriptive qualitative in order to get a picture of the problems of the situation and conditions currently taking place or occurring in the present and the study of policies. Collecting data by field surveys, literature studies and interviews. The results in this study get a terminal B type terminal design concept Sukabumi Regency according to current and future needs.


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