Genetic variability of wild Agave angustifolia populations based on AFLP: A basic study for conservation

Agave angustifolia is taken from wild populations in the desert of Sonora, Mexico, to make the alcoholic drink known as “bacanora”. An increase in the demand for this beverage has led to overexploitation of these agaves. We used AFLP to measure the genetic variability within and between natural populations of the species. The fixation index (FST) and population genetic distances (GD) were determined for three populations of A. angustifolia. At the clonal level, the expected heterozygosis (HE), the proportion of polymorphic loci (P), and the genetic similarity indices (GSIs) were lower in one population. Total GSI for adults and offshoots was 0.924. There were no differences in the GSI within or between the populations and dendrogram showed three groups that partially reflect the geographical distribution of the populations. Some degree of genetic variation between mother plants and their vegetatively produced rhizomes was observed. At the species level, total expected heterozygosity was high (HT = 0.314) with a P value of 78%, and intermediate gene flow (Nm = 1.18), giving rise to a moderate fixation index (FST = 0.175). Nm, FST and GD values observed, indicate that urgent measures must be implemented to preserve the genetic diversity.     

中国粮食生产时空演变规律与耕地可持续利用研究

随着全球粮食贸易格局的日益紧张,如何利用有限的耕地资源保证中国粮食安全成为新阶段的难题。本文从耕地可持续利用视角提出粮食稳产、增产策略,以期为粮食安全、耕地保护等国家战略提供理论支撑。基于1985—2015年中国31个省（自治区、直辖市）统计数据,以农业生态区为基本单元,采用比较分析法和GIS空间分析法,对中国粮食生产时空演变及其影响因素进行规律性探究。研究结果表明：（1）中国粮食产量呈“波动-上升”的趋势,但长江中下游区、江南和华南区粮食增长率较低,甚至出现减产现象。（2）中国粮食产量主产区逐渐由长江中下游区、江南和华南区向东北区、黄淮海区转移。（3）中国粮食生产的影响因素呈现阶段性和区域性规律。例如,东北区、西北区粮食生产主要受粮食单产、耕地面积等影响;黄淮海区、内蒙古高原和黄土高原区、云贵高原和横断山区主要受粮食单产影响。（4）中国各区耕地存在不同类型和不同程度的耕地非持续问题,在西北区、内蒙古高原和黄土高原等生态脆弱区域较严重。     

The karstlands of Antigua, their land use and conservation

The northeastern 110 km², or nearly 40%, of Antigua is underlain by impure limestones of the Oligocene-aged Antigua Formation, on which has developed a subdued karst landscape consisting essentially of shallow enclosed depressions (dolines), intermittently active stream valleys and widely scattered residual hills. The dispersed dolines are broad, shallow and clustered, especially in the central and southeastern sections of the limestone belt, where they attain densities of 7/km². The widely spaced residual hills attain heights of up to 40 m and localized densities of over 4/km². Five main valley systems up to 6 km in length traverse the limestone in a broadly northeast direction, carrying both autogenic drainage from within the karst area and allogenic drainage from the non-carbonate Central Plain. Karst and cave development has been constrained by the low purity of the limestones. Of the four types of carbonate islands identified within the Carbonate Island Karst Model, Antigua most closely resembles the Composite Island type. The karst has been much influenced by human activities, particularly agriculture and quarrying, and is now a focus of the burgeoning tourism industry. Virtually none of the karst is designated as protected areas, but several sites warrant protection, and several conservation strategies have been suggested.     

Genetic diversity of wild barley (Hordeum vulgare ssp. spontaneum) and its utilization for barley improvement

Wild barley (Hordeum vulgare spp. spontaneum) is the undisputed progenitor of cultivated barley and offers considerable potential as a genetic resource for barley improvement. Naturally occurring populations are distributed primarily across the Fertile Crescent, but secondary areas of diversity are also found in central Asia and Tibet. The pattern of its genetic diversity is non-random, and is structured on a global, regional and local scale. On a global scale, diversity follows ecogeography, while on a regional and local scale, it is more strongly determined by ecology. Populations growing in areas where the climate is unreliable and/or the soil is heterogeneous tend to retain the most diversity. A large number of accessions are currently conserved ex situ, but a high proportion of these have originated from the Fertile Crescent. Given the likelihood of future climate change, conserving germplasm both in situ and ex situ in the various regions where the species’ currently existing is a research priority. The value of H. vulgare spp. spontaneum for the improvement of cultivated barley lies largely in its potential contribution to the levels of attainable pathogen resistance and abiotic stress tolerance.     

The karstlands of Trinidad and Tobago, their land use and conservation

The karst landscapes of Trinidad and Tobago, although restricted in area, present a previously undocumented array of tropical karst landforms, including karren, caves, springs, valley systems, and a range of dolines or sinkholes, including an area of polygonal cockpit karst. The karstlands are located primarily in the Northern and Central Ranges of Trinidad and in the southwestern portion of Tobago, and they have developed on carbonate rocks ranging in age from Jurassic to Quaternary. Associated with them is a range of vegetation types and faunal communities, many of which have been much altered by human land management, including forestry and agriculture. Quarrying has destroyed much of the karst in the western part of Trinidad, and urban development and tourism have taken their toll too, especially in the Lowlands of western Tobago. Little of the karst is incorporated within existing protected areas.     

The development and application of a land use diversity index for Oklahoma City,OK

Characteristics of land use and land use diversity play an integral part in determining how a city develops, and also can influence the allocation of funds for urban redevelopment, crime prevention, and civic and transportation projects. With the rise of the sustainability movement and concern about environmental degradation, more cities are interested in optimizing transportation routes and utilizing their budgets to accommodate high-priority projects that benefit the most people. This paper develops a method for measuring land use diversity for Oklahoma City, Oklahoma, and explores the relationship between land use diversity and a suite of demographic variables. To accomplish this, a land use diversity index (LUDI) was developed to examine spatial patterns in diversity of land use. The analysis shows that areas with a higher LUDI are near interstates and main corridors while areas with a lower LUDI are located closer to where newer residential areas have been developed. A multivariate statistical approach was then used to identify those variables that might explain the specific spatial patterns of the LUDI in Oklahoma City. The results identify the relationship between the demographic variables and land use across the city, and illustrate the most interesting and significant spatial patterns. By coupling the land use diversity index and demographic data, Oklahoma City planners can apply the information to help make important decisions for the city, and it will provide quantifiable data to support their decisions.     

Gendered production spaces and crop varietal selection: Case study in Yucatán, Mexico

This paper examines the influence of gender relations and gendered domains on maize and squash varietal selection in a village in Yucatán State, southeast Mexico. Results of the exploratory study indicate that the traditional production spaces of homegardens and agricultural fields are complementary gendered domains of varietal maintenance for both crops although with different cropping patterns, while a 'new' space, of land allocated to some families for future residential construction ( terreno ) is in the meantime a jointly worked agricultural domain. Women's labour, knowledge and preferences predominate in post-harvest processes. Fieldwork revealed that neither men nor women are independent decision-makers, planning what to grow, where and in what amounts, but that in most aspects of farming the interests of both are accommodated within the household's production spaces.     

Hydrophytes of the oases in the Sierra de la Giganta of Central Baja California Sur, Mexico: Floristic composition and conservation status

One of the features of the Sierra de la Giganta mountain range is the existence of many small riparian wetlands (oases) along drainage channels. There are no geohydrological studies from which to determine their dynamics in the arid environment, but these areas confront increasing water extraction to satisfy demands of small local settlements. This study compiled a checklist of the hydrophytes from 12 representative oases, and discusses their current status on the basis of composition, richness, and species characteristics. Floristic composition (absence–presence of 57 hydrophytes) at each location was classified by using UPGMA to represent a dendrogram of group cohesivity. Two major kinds of locations are present. By analysing individual site characteristics, we found that one group occurs in places under “good conservation conditions” and the other composed of locations that are “impacted” in several ways. The former group contains oases that are relatively rich in species, including most of the aquatic forms, which are sensitive to disturbance. Geographical affinity of the floristic list reveals that most species have a broad distribution, mostly in tropical America.     

A synthesis of sociological and biological perspectives on sustainable land use in Namaqualand

A transdisciplinary synthesis, grouped into four main themes, of the key papers in this Special Issue on Namaqualand is provided. Perspectives on current environmental, economic and social issues in the region are interpreted in the context of the past and are used to inform future trajectories of change and development needs within the region. Firstly, in terms of the climatic and biophysical environment, Namaqualand's rich biodiversity is not uniformly distributed and is explained in terms of the spatially heterogeneous geological, pedological and topographical gradients that characterize the region. Spatial and temporal variation in rainfall over long time frames would also have promoted speciation within isolated, poorly-dispersed, leaf succulent populations. Future climate models propose a decrease in rainfall across the region with an associated reduction in livestock production. The second theme provides an historical perspective on changing land use practices in Namaqualand over the last 2000 years. It suggests that they have frequently been influenced by events originating far from the region such as colonial expansion, apartheid legislation and globalization. Local people, particularly marginalised communal farmers have had to adapt to these outside influences within an increasingly confined landscape that has progressively eroded their mobility and restricted their ability to utilise the spatial and temporal variability inherent in semi-arid environments. The third theme shows how livelihood diversification has been one of the key ways in which local people from communal areas have adapted to change. While farming makes up a relatively small part of the income of most households it enhances the resilience of livelihoods in the region. The fourth theme is concerned with land reform, conservation and restoration in Namaqualand. While a significant amount of land has been transferred to previously-marginalised groups, equitable access to these resources is lacking. An exclusively commercial orientation within the extension and development programmes of the Department of Agriculture further hampers the effectiveness of land reform as a tool for reducing levels of poverty in the majority of households in the region. Conservation initiatives could enhance livelihood options in Namaqualand but are viewed by some as being in competition with the state's land reform programme and are too recent to reflect significant regional benefits at this stage. While restoration is possible in severely degraded lands, the costs and operational difficulties in these event-driven, semi-arid systems are emphasised. Finally, this synthesis suggests that the important exogenous drivers of change in the 21st century are likely to be climate, biodiversity conservation initiatives, land redistribution and continued processes of de-agrarianisation as a result of macro-economic change. A focus on building institutions, encouraging livestock mobility within a significantly expanded commons and supporting livelihood diversification are some of the approaches necessary to address the development needs of Namaqualand.     

An assessment of land use and other factors affecting sediment loads in the Rio Puerco watershed, New Mexico

Rapid channel erosion in the Rio Puerco watershed of northwest New Mexico has been attributed to land use, climate changes, and internal channel adjustments. The objectives of this study were to assess (1) the impacts of land uses on sediment load, (2) the quantitative relationships between land use and sediment load, and (3) the effectiveness of different erosion control methods. The impacts of land uses on sediment load were assessed via hypotheses that, holding other erosion-related variables constant, sediment load correlates positively with grazing intensity and with density of unpaved roads, and correlates negatively with the number of erosion control treatments. We calculated the average annual sediment load for 17 subbasins of 0.67–17.97 km² by comparing sediment accumulation at two points in time (mid-1960s and 1999) behind intact sediment retention structures. We assessed land use via grazing records and measurements of unpaved roads generated from aerial photographs. Soil characteristics, vegetation, and physical factors were quantified for each subbasin. Using 18 variables for each subbasin, we employed Mallow's C_p as a selection criterion. We used six statistical models, including multiple regression and principal components analysis, to determine inherent mathematical relationships between significant independent variables and sediment load. The results indicate that sediment load does not correlate with grazing intensity except in small, relatively low-relief basins with fewer bedrock exposures. However, this interpretation may be compromised by the low quality of data available to quantify grazing. Sediment load is highly sensitive to the presence of unpaved roads, which serve as high gradient, channelized conduits of water and sediment during storms. Sediment load does not correlate with erosion control except in the subset of small, relatively low-relief subbasins that also proved sensitive to grazing intensity. Overall, the statistical analyses suggest that the impact of land uses on sediment load can be assessed using the data available although physical factors appear more significant than land use in producing high sediment loads in the Rio Puerco subbasins. Historical erosion control techniques, as implemented in the Rio Puerco watershed, prove largely ineffective against accelerated sediment loads because they have not been appropriately implemented or maintained.     

Spatial distribution of nitrate health risk associated with groundwater use as drinking water in Merida,Mexico

Water containing nitrate levels above 45 mg/l is not recommended for human consumption and its prolonged intake is associated with various health conditions. In Merida city, Mexico, the only source for water supply is a karstic aquifer, but the absence of sewerage and drainage networks makes it highly vulnerable to anthropogenic contamination. In this work, the concentration and spatial distribution of nitrate in the Merida's karstic aquifer were assessed by statistical and geostatistical techniques. The sources of nitrate contamination were tracked by making statistical correlations between nitrate concentrations and key ions; the potential risk to human health was also estimated by using the Hazard Index (HI). A total of 177 groundwater samples were collected from the four water supply systems serving Merida, during 2012 and 2013. Nitrate concentrations from collected samples varied between 15.51 and 70.61 mg/l, with maximum and minimum concentrations per sampling point ranging from 47.47 to 70.61 mg/l and from 15.51 to 17.32 mg/l, respectively. Significant positive correlations (P < 0.05) between nitrates and chlorides, sulphates and potassium were found, which may indicate potential contamination from domestic wastewater and agricultural activities. The spatial distribution of nitrate concentrations in the aquifer revealed an increase in nitrates following a trajectory South–North West, towards central and northwestern zones within Merida Metropolitan Area. From the health risk analysis, it was found that infants exposed at current nitrate levels are at a higher risk (HI_MAX = 1.40) than adults (HR < 1.0) and therefore, there is a clear need for implementing effective strategies to protect groundwater quality and to better manage and control nitrate pollution sources.     

Effects of land use,slope gradient,and soil and water conservation structures on runoff and soil loss in semi-arid Northern Ethiopia

April lightning production in Richmond County, Georgia, from 1995 to 2003 is considered with regard to the associated risk to golfers and spectators at the Master's Golf Tournament and courses throughout the county. An examination of the April lightning climatology of Georgia, focusing on Richmond County, reveals a minimum in lightning activity during the time of the tournament (the first full week of April). A discriminant analysis of Richmond County lightning production utilizes several meteorological variables in order to discern between three categories of April lightning days: little or no lightning activity, minimal lightning activity, and high lightning activity. The analysis distinguishes relatively well between the categories with only 13.5% of the events misclassified. A composite regional analysis of the three lightning categories illustrates the environmental differences between these events. Although the little or no lightning and high lightning categories are somewhat similar environmentally, the intensity of features separates these events and allows for interpretation. The statistical and synoptic analyses together emphasize the importance of low-level instability and frontal proximity and intensity in enhancing lightning production in thunderstorms during April in and surrounding Richmond County. A multitude of meteorological conditions can lead to thunderstorm development. Localized studies of these environments, especially during times of major outdoor sporting events, are needed to help mitigate the risk associated with lightning.     

Land use and land cover change in Greater Dhaka, Bangladesh: Using remote sensing to promote sustainable urbanization

This study evaluates land use/cover changes and urban expansion in Greater Dhaka, Bangladesh, between 1975 and 2003 using satellite images and socio-economic data. Spatial and temporal dynamics of land use/cover changes were quantified using three Landsat images, a supervised classification algorithm and the post-classification change detection technique in GIS. Accuracy of the Landsat-derived land use/cover maps ranged from 85 to 90%. The analysis revealed that substantial growth of built-up areas in Greater Dhaka over the study period resulted significant decrease in the area of water bodies, cultivated land, vegetation and wetlands. Urban land expansion has been largely driven by elevation, population growth and economic development. Rapid urban expansion through infilling of low-lying areas and clearing of vegetation resulted in a wide range of environmental impacts, including habitat quality. As reliable and current data are lacking for Bangladesh, the land use maps produced in this study will contribute to both the development of sustainable urban land use planning decisions and also for forecasting possible future changes in growth patterns.     

Land use/cover, landforms and fragmentation patterns in a tropical dry forest in the southern Pacific region of Mexico

In spite of widely documented studies of deforestation rates and land use/cover changes in tropical dry forests in Mexico, relatively little is known about fragmentation patterns in such forests. This study defines the spatial distribution of landforms and land use/cover types the lower Papagayo River basin and examines their influence on fragmentation patterns and biological diversity in a tropical dry forest in that southern Pacific region. The land use/cover map was constructed from aerial photographs, Landsat TM imagery (2000) and fieldwork. Landform units were defined based on altitude, slope, lithology and morphology. Landscape fragmentation parameters were obtained using FRAGSTATS (version 3.3) considering the numbers of patches, mean, minimum and maximum patch size, edge density, total edge and connectivity. Results show tropical dry forest to be remnant vegetation (~11 per cent), characterized by isolation and low connectivity. Land use/cover types have different effects on fragmentation patterns. Agriculture and cattle raising produce similar numbers of patches, but with a different mean size; and human settlements have a scattered distribution pattern. The abandonment of rural agricultural livelihoods has favoured the expansion of secondary tropical dry forest characterized by continuity and high connectivity, which suggests a high regeneration potential from land abandonment. It can be concluded that tropical dry forest fragmentation and recovery at regional scales depend on such landscape attributes as lithology, slope, geomorphology and management.     

From the kitchen and the field: Gender and maize diversity in the Bajío region of Mexico

The conservation of crop genetic diversity in farmers' fields is important for future food security. Recent research on women and biodiversity has emphasized the importance of women's knowledge in plant domestication and biodiversity conservation. This paper presents a case study of the differences in women's and men's knowledge of maize landraces in four different environments in the Bajío region of Mexico. We argue that research on crop diversity and conservation needs to include both men and women farmers' knowledge. Gendered knowledge results from men and women in a household being responsible for different tasks and sometimes for farming separate plots. In addition, as economic pressures increasingly force men to work away from their communities for extended periods, women become the primary agricultural decision-makers.     

Biomass production, evapotranspiration and water use efficiency of arid rangelands in the Northern Cape, South Africa

Annual above-ground net primary production (ANPP), evapotranspiration (ET) and water use efficiency (WUE) of rangeland have the potential to provide an objective basis for establishing pricing for ecosystem services. To provide estimates of ANPP, we surveyed the biomass, estimated ET and prepared a water use efficiency for dwarf shrublands and arid savanna in the Riemvasmaak Rural Area, Northern Cape, South Africa. The annual production fraction was surveyed in 33 MODIS 1 km² pixels and the results regressed against the MODIS f_PAR product. This regression model was used to predict the standing green biomass (kg DM ha⁻¹) for 2009 (dry year). Using an approach which combines potential evapotranspiration (ET₀) and the MODIS f_PAR product, we estimated actual evapotranspiration (ET_a). These two models (greening standing biomass and ET_a) were used to calculate the annual WUE for 2009. WUE was 1.6 kg DM mm⁻¹ ha⁻¹ yr⁻¹. This value may be used to provide an estimate of ANPP in the absence of direct measurements of biomass and to provide a comparison of the water use efficiency of this rangeland with other rangeland types.     

Soil quality and sustainable land use in urban-rural marginal area: a case study of Kaifeng

Soil quality is closely related to the sustainability of environment and development[1], hence people have paid more and more attention to soil quality research in recent years, and have made a thorough inquiry of the definition of soil quality as well as the method and theory of its expression[2-4]. As a zone devoting to most intensive modern agricultural land use, urban-rural marginal area has become a region where intensity of soil quality change is most remarkable. Moreover, with the devel…     

Soil quality and sustainable land use in urbanrural marginal area: a case study of Kaifeng

By using the basic theories of physical geography, land resources and ecology, this article analyzes the soil quality of the rural-urban marginal area in Kaifeng. Computer techniques, based on soil samples analysis, are used to study soil quality changes in the Kaifeng’s rural-urban marginal area. While focusing on nutrient circle key links of input and output in soil, relying on numerous practical survey data, this article reveals clearly the impact of land use change on soil quality.