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Changing Vegetation Patterns in Yobe State Nigeria: An Analysis of the Rates of Change, Potential Causes and the Implications for Sustainable Resource Management  [PDF]
Ali I. Naibbi, Brian Baily, Richard G. Healey, Peter Collier
International Journal of Geosciences (IJG) , 2014, DOI: 10.4236/ijg.2014.51007
Abstract:

The exploitation of natural resources for timber production, fuelwood use and conversion to agricultural land is increasing to such an extent that the sustainable use of many areas of the world is in doubt. This paper examines three decades of freely available Landsat satellite images of the northeastern part of Nigeria using a supervised classification based technique to create maps of vegetation change in Yobe State. The maps are then used to examine the temporal and spatial aspects of changes which have occurred in the context of previous evidence and literature. The results indicate that the vegetation of the area has drastically reduced since the 1970’s. However, as this study shows, the pattern of these changes is complicated and cannot be explained by any single physical or anthropogenic causal factor. Similarly, evidence from ground truthing investigation indicates the importance of fuelwood collection to the deforestation process within the region. This article shows the value of an existing remote sensing and image processing methodology for the assessment of vegetation change in developing countries in relation to the sustainable management of natural resources. The study also discusses the overall change within the study area and discusses several potential causative factors of the observed patterns of change.

Design, Efficiency and Influence of a Multiple-Row, Mix-Species Shelterbelt on Wind Speed and Erosion Control in Arid Climate of North Sudan
M.D. Dafa-Alla,Nawal K.N. Al-Amin
Research Journal of Environmental and Earth Sciences , 2011,
Abstract: The study aimed at assessing the design and efficiency of Alhudi shelterbelts in Semi arid zone of Northern Sudan in protecting soil erosion, suppressing moving sand and suggesting a suitable and appropriate shelterbelt design to be applicable in similar conditions at national and regional levels. Alhudi is an irrigated shelterbelt composed of six rows of tree species: Acacia seyal, Acacia ehrenbergiana, Ziziphus spina-christi, Azadirechta indica, Conicarpus lancifolius and Acacia amplicips. Based on shelterbelt configuration two well defined segments on the shelterbelt were recognized (termed belt 1 and belt 11). Wind speeds were measured on windward of both belts during north prevailing wind using CR800 programmable data logger connected to cup anemometer. Vertical measurements were taken at 0.25 and 0.5 h, horizontal measurements were taken at 0.25, 0.5, 1, and 2 h from the shelterbelt upwind and a control anemometer was placed in an open area for the two levels and distances. Ten-minute average wind speeds were recorded. The measurements were aimed to evaluate the influence of the shelters on capability of wind to erode the soil windward and create dust and sand storm or to reduce the coming wind's load capability to deposit its load (sand deposit). The capability of each belt were estimated and predicted by applying a protection efficiency model. Results indicate that species of Acacia ehrenbergiana and Acacia seyal or other species of this family are not suitable for first row of the windward of a shelterbelt. The appropriate shelterbelt design to protect buildings and cultivated fields from sand storm in arid climate of Sudan is recommended to be irrigated, of at least three rows with its height increased from outside to inside, to decrease turbulence. Shelterbelt proper management is crucial for better growth and efficiency.
The ecohydrology of the soil–vegetation system restoration in arid zones: a review
XinRong Li,ZhiShan Zhang,Lei Huang,LiChao Liu,XinPing Wang
寒旱区科学 , 2009,
Abstract: Arid zones, which cover approximately 40 percent of the earth’s land surface, support complicated and widely varied ecological systems. As such, arid zones are an important composition of the global terrestrial ecosystem, and water is the key and abiotic limited factor in ecosystem-driven processes in these areas. Ecohydrology is a new cross discipline that provides, in an objective and comprehensive manner, novel ideas and approaches to the evaluation of the interaction and feedback mechanisms involved in the soil–vegetation systems in arid zones. In addition, ecohydrology provides a theoretical basis of ecological restoration that is centered on vegetation construction. In this paper, long-term monitoring and local observations in the transitional belt between a desertified steppe and a steppified desert at the Shapotou Desert Research and Experiment Station, Tengger Desert, in northern China, were evaluated. The primary achievements and related research progress regarding ecohydrology in arid zones were analyzed and summarized, as a keystone, and the response of soil ecohydrological processes to the changes in the species composition, structure, and function of sandland vegetation was discussed. Meanwhile, the long-term ecological effects and mechanism of regulation of vegetation on soil habitat and on water-cycling were considered. As a vital participant in the ecohydrological processes of soil–vegetation systems, the studies on biological soil crusts was also summarized, and related theoretical models of restoration based on the water balance was reviewed
Succession of potential vegetation in arid and semi-arid area of China
中国干旱半干旱区潜在植被演替

LI Fei,ZHAO Jun,ZHAO Chuanyan,ZHANG Xiaoqiang,
李飞
,赵军,赵传燕,张小强

生态学报 , 2011,
Abstract: The study of vegetation background has become preliminary and infrastructural work toward the ecological environment construction in arid and semi-arid area of northwest China.Potential vegetation,as a final state of succession when one vegetation achieves the balance with its site,is the climax vegetation type at the site without human interference characterizing with high stability and full mature,and is the trend of the regional existing vegetation development.It has great significance regarding to the r...
Analysis of Vegetation Behavior in a North African Semi-Arid Region, Using SPOT-VEGETATION NDVI Data  [PDF]
Rim Amri,Mehrez Zribi,Zohra Lili-Chabaane,Benoit Duchemin,Claire Gruhier,Abdelghani Chehbouni
Remote Sensing , 2011, DOI: 10.3390/rs3122568
Abstract: The analysis of vegetation dynamics is essential in semi-arid regions, in particular because of the frequent occurrence of long periods of drought. In this paper, multi-temporal series of the Normalized Difference of Vegetation Index (NDVI), derived from SPOT-VEGETATION satellite data between September 1998 and June 2010, were used to analyze the vegetation dynamics over the semi-arid central region of Tunisia. A study of the persistence of three types of vegetation (pastures, annual agriculture and olive trees) is proposed using fractal analysis, in order to gain insight into the stability/instability of vegetation dynamics. In order to estimate the state of vegetation cover stress, we propose evaluating the properties of an index referred to as the Vegetation Anomaly Index (VAI). A positive VAI indicates high vegetation dynamics, whereas a negative VAI indicates the presence of vegetation stress. The VAI is tested for the above three types of vegetation, during the study period from 1998 to 2010, and is compared with other drought indices. The VAI is found to be strongly correlated with precipitation.
A conceptual dynamic vegetation-soil model for arid and semiarid zones
D. I. Quevedo,F. Francés
Hydrology and Earth System Sciences Discussions , 2007,
Abstract: Plant ecosystems in arid and semiarid zones show high complexity from the point of view of water resources, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development. The available water in the system results from a water balance where the soil, vegetation and the atmosphere are the key issues; but it is the vegetation which modulates (to a great extent) the total balance of water and the mechanisms of the feedback between soil and atmosphere, being the knowledge about soil moisture quite relevant for assessing available water and, as a consequence, for growth and plants maintenance and the final water balance in the system. A conceptual dynamic vegetation-soil model (CDVSM) for arid and semiarid zones was developed. This model based in a tank type conceptualization represents in a suitable way, for Mediterranean climate, the vegetation responses to soil moisture fluctuations. Two tanks interconnected were considered using the water balance equation and the appropriate dynamic equation for all considered fluxes. The first one corresponds to the interception process done by the vegetation. The second one models the upper soil moisture determination. In this tank parameters are based on soil and vegetation properties. The transpiration of the vegetation is a function of the soil moisture, the vegetation type and the biomass. Once all water state variables are evaluated at each time step, the modifications in the biomass are made as a function of transpiration rate and water stress. Simulations for monoculture of Quercus Coccifera L. were carried out. Results shows that CDVSM is able to represent the vegetation dynamic, reflecting how the monoculture is stabilized around 0.7 of relative biomass, with adaptation to the soil moisture fluctuations in the long term. The model shows the vegetation adaptation to the variability of the climatic conditions, demonstrating how either in the presence or shortage of water, the vegetation regulates its biomass as well as its rate of transpiration trying to minimize the total water stress.
A conceptual dynamic vegetation-soil model for arid and semiarid zones
D. I. Quevedo ,F. Francés
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2008,
Abstract: Plant ecosystems in arid and semiarid climates show high complexity, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development and its dynamic evolution. The available water-soil content results from the water balance in the system, where the key issues are the soil, the vegetation and the atmosphere. However, it is the vegetation, which modulates, to a great extent, the water fluxes and the feedback mechanisms between soil and atmosphere. Thus, soil moisture content is most relevant for plant growth maintenance and final water balance assessment. A conceptual dynamic vegetation-soil model (called HORAS) for arid and semi-arid zones has been developed. This conceptual model, based on a series of connected tanks, represents in a way suitable for a Mediterranean climate, the vegetation response to soil moisture fluctuations and the actual leaf biomass influence on soil water availability and evapotranspiration. Two tanks were considered using at each of them the water balance and the appropriate dynamic equation for all considered fluxes. The first one corresponds to the interception process, whereas the second one models the evolution of moisture by the upper soil. The model parameters were based on soil and vegetation properties, but reduced their numbers. Simulations for dominant species, Quercus coccifera L., were carried out to calibrate and validate the model. Our results show that HORAS succeeded in representing the vegetation dynamics and, on the one hand, reflects how following a fire this monoculture stabilizes after 9 years. On the other hand, the model shows the adaptation of the vegetation to the variability of climatic and soil conditions, demonstrating that in the presence or shortage of water, the vegetation regulates its leaf biomass as well as its rate of transpiration in an attempt to minimize total water stress.
Eco-geomorphology and vegetation patterns in arid and semi-arid regions
P. M. Saco,G. R. Willgoose,G. R. Hancock
Hydrology and Earth System Sciences Discussions , 2006,
Abstract: The interaction between vegetation and hydrologic processes is particularly tight in water-limited environments where a positive-feedback links water redistribution and vegetation. The vegetation of these systems is commonly patterned, that is, arranged in a two phase mosaic composed of patches with high biomass cover interspersed within a low-cover or bare soil component. These patterns are strongly linked to the redistribution of runoff and resources from source areas (bare patches) to sink areas (vegetation patches) and play an important role in controlling erosion. In this paper a new modeling framework that couples landform evolution and dynamic vegetation for water-limited ecosystems is presented. The model explicitly accounts for the dynamics of runon-runoff areas that controls the evolution of vegetation and erosion/deposition patterns in water limited ecosystems. The analysis presented here focuses on the interaction between vegetation patterns, flow dynamics and sediment redistribution for areas with mild slopes where sheet flow occurs and banded vegetation patterns emerge. Model results successfully reproduce the dynamics of both migrating and stationary banded vegetation patterns (commonly known as tiger bush). Modeling results show strong feedbacks effects between vegetation patterns, runoff redistribution and geomorphic changes. The success at generating not only the observed patterns of vegetation but also patterns of runoff and erosion redistribution, which gives rise to modeled microtopography similar to that observed in several field sites, suggests that the hydrologic and erosion mechanisms represented in the model are correctly capturing the essential processes driving these ecosystems.
An integrated assessment of the impact of precipitation and groundwater on vegetation growth in arid and semiarid areas  [PDF]
Lin Zhu,Huili Gong,Zhenxue Dai,Tingbao Xu,Xiaosi Su
Physics , 2014,
Abstract: Increased demand for water resources together with the influence of climate change has degraded water conditions which support vegetation in many parts of the world, especially in arid and semiarid areas. This study develops an integrated framework to assess the impact of precipitation and groundwater on vegetation growth in the Xiliao River Plain of northern China. The integrated framework systematically combines remote sensing technology with water flow modeling in the vadose zone and field data analysis. The vegetation growth is quantitatively evaluated with the remote sensing data by the Normalized Difference Vegetation Index (NDVI) and the simulated plant water uptake rates. The correlations among precipitation, groundwater depth and NDVI are investigated by using Pearson correlation equations. The results provide insights for understanding interactions between precipitation and groundwater and their contributions to vegetation growth. Strong correlations between groundwater depth, plant water uptake and NDVI are found in parts of the study area during a ten-year drought period. The numerical modeling results indicate that there is an increased correlation between the groundwater depth and vegetation growth and that groundwater significantly contributes to sustaining effective soil moisture for vegetation growth during the long drought period. Therefore, a decreasing groundwater table might pose a great threat to the survival of vegetation during a long drought period.
Formation of Vegetation Patterns and Hysteresis Phenomena in Arid and Semiarid Zones
HUA Da-Yin,WANG Lie-Yan,
华达银
,王烈衍

中国物理快报 , 2007,
Abstract: Considering the spatial effect of the complicated interactions between plant and resource (soil water) and the stochastic character of the complicated ecological processes in an ecosystem, we introduce a lattice gas model to investigate the vegetation pattern formation in the arid and the semiarid ecosystems with Monte Carlo simulations. With consistency of some previousmean-field models, the model reproduces a wide range of patterns observed in the arid and the semiarid regions. The sequences of vegetation states are also investigated with scanning three parameters, i.e., the precipitation and the plant growth rate, and then the parameter ranges are identified where a hysteresis loop appears and two different stable states coexist. The simulation results denote that the complex structures occur only when theprecipitation parameter decreases. Moreover, based on the model, it is found that an increase of the competition of the plant for the resource along the slope direction results in the regular stripes parallel to the hill's contours. The model provides an interesting mechanism to understand the formation of the other regular vegetation stripe in a limited resource condition.
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