Francisco Martín Huerta-Martínez

Vegetation ordination at the southern Chihuahuan Desert (San Luis Potosi, Mexico)

Cover data for 93 perennial plant species from fifty 1 ha sites, were used to ordinate desert vegetation in relation to 50 environmental variables at El Huizache Corridor. Cumulative variance recovered in the Bray and Curtis variance-regression ordination was substantial (80%). Community structure of desert plant communities at El Huizache Corridor may be influenced primarily by a combination of landscape and edaphic variables, which in turn may determine the distribution and abundance of moisture and nutrients, and perhaps promote habitat specialization and or competitive exclusion. Secondly, to a lesser extent, climate variables could be influencing community organization at small scale gradients, the longer the gradient the more relevant climatic factors become. First axis represented a landscape gradient; it was positively correlated to exposure, geology, slope angle, rocks, stoniness, iron, January mean temperature, and organic matter content; it was negatively correlated with latitude, longitude, soil depth, and potassium content. The second axis represented mainly a climatic gradient; it was positively correlated with mean precipitation of January, February, July, August, September, November, December, annual mean precipitation, Langs Index, organic matter content, and stoniness. The third axis represented an edaphic gradient; it was positively correlated with electrical conductivity, Mn, Zn and elevation, and negatively correlated with pH, nitrates, Ca, and disturbance. These findings should guide conservation efforts to maintain species diversity and endemism at this area.

Genetic diversity within a declining natural population of Ferocactus histrix (DC) Lindsay

Ferocactus histrix is a barrel cactus that is widespread in Mexico. A population located in Llanos de Ojuelos, a semiarid zone representative of many disturbed regions in north-central Mexico, was studied. Over a period of 10 years (1997 to 2007), the average number of individuals decreased from 21.95 to 3.53 plants per 300u2009m2. A change in population size structure was also registered over this period of time. In 2008, a plot selected on the basis of plant abundance was established within the population and a genetic analysis was conducted with ISTR and ISSR markers. This analysis revealed low levels of genetic diversity (expected heterozygosity (HE)u2009=u20090.073, Shannon index (I)u2009=u20090.113 and HEu2009=u20090.178, Iu2009=u20090.271, respectively) compared with those of most studied cacti species. The genetic diversity between the different life stages was also evaluated, and a gradual decrease in levels of genetic variation was observed from adults to juveniles and seedlings (HEu2009=u20090.130, Iu2009=u20090.192 to HEu2009=u20090.103, Iu2009=u20090.157). These differences, however, were not significant. Loci fixation and a decrease in the frequency of rare alleles were observed in seedling and juvenile classes. The decline in genetic variation may be associated with recent bottlenecks experienced by the population of F.u2009histrix. If the sizes of local populations of F.u2009histrix continue to decrease, genetic variation will be gradually lost, and the risk of extinction will increase.

Diet of Acorn Woodpeckers at La Primavera Forest, Jalisco, Mexico

Abstract We studied the diet of the Acorn Woodpeckers (Melanerpes formicivorus) at La Primavera Forest, Jalisco, Mexico. This resident species had a diverse diet throughout all seasons. The diet included acorns of Quercus viminea, Q. castanea, and Q. laeta, which were stored primarily in granaries in live trunks of pine (Pinus spp.) trees. They also consumed acorns of Q. magnoliifolia and Q. resinosa by piercing and eating just the central part of the seed. Acorn Woodpeckers did not use acorns from species of oak in the same proportion as available. They also fed seasonally on insects (Coleoptera and Lepidoptera) and tree sap.

The Deserts of China

This chapter provides features of environmental factors and phytogeographical divisions for desert vegetation in China. There are three kinds of desert vegetation in China: semi-desert, true desert, and extremely arid desert. The desert vegetation is distributed on different land forms with diversified soil feature, extending in NW China with mean annual precipitation less than 200 mm. Dominant species in the desert vegetation in China include eight life forms.

Vegetation and Environment

This chapter provides an overview of desert flora and plant communities. The vegetation-environment relationships were explained with two case studies, true desert in the Jungar Basin and extremely arid desert in the Anxi Extremely Arid Desert National Nature Reserve. There are 610 species in the desert of China, which can be classified into Central Asian element and Inner Asian element. The plant communities are abundant caused by diversified topography and soil features.

The Inland Eastern Desert of Egypt

The inland part of the Eastern Desert of Egypt forms an ecosystem with characteristic habitats: (1) rocky surface, (2) erosion pavement, (3) gravel desert, (4) slopes, (5) cliffs, and (6) desert wadi, which represents a drainage system collecting water from extensive catchment area. The geographic position of the mountainous range along the Red Sea coast is very conspicuous. The flora and vegetation of the Gebel Elba mountainous group is much richer than that of the other coastal mountain, where the Palaearctic and Afrotropical regions meet. The species composition of the Gebel Elba National Park was greatly influenced by disturbances such as severe cutting of trees and shrubs either for domestic fuel or charcoal production and browsing. In terms of classification and ordination, the vegetation and environment in northern wadis and southern wadis in four transects representing three different types of desert running from the Nile Valley to the Red Sea coast were investigated. Based on the current status of flora of the Eastern Desert, a biogeographical analysis and phytogeographical divisions of the were re-assessed.

The Coastal Desert of Egypt

The coastal deserts in Egypt are found along the Mediterranean (east and west), the Red Sea, and the Gulfs of Suez and Aqaba in Sinai Peninsula. The variations in their floristic composition and vegetation structure are varied considerably. The association between the landform units and their floristic features showed significant differences. In the meanwhile, the biological spectrum and chorological analyses of the flora exhibited a general trend in both dominance and structure. Climatic variations, especially rainfall, between the different geographical areas play a profound role in the species distribution patterns. The relationships between the vegetation and the prevailing environmental characteristics indicated the importance of certain soil factors such as coarse and fine sediments, moisture content, electrical conductivity, pH, and organic matter. The distance from the sea and altitude were other significant factors in delimiting species distribution.

The Sinai Desert

The Sinai Peninsula is currently recognized as one of the central regions for biodiversity in the Middle East by the World Conservation Union. It is rich both in the number of species and the high percentage of endemics. The roughness in geomorphology leads to differentiation of enormous number of microhabitats and landforms which resulted in relatively high diversity in ecosystems and flora. The most conspicuous inhabited oasis in south Sinai is Feiran Oasis which is considered as the largest receiving amounts of runoff water from the drainage system of Wadi Feiran. The small size of Feiran Oasis, the limited water resources, the rapid development due to increased touristic and population pressures, as well as the present serious socio-economic situation may cause the destruction of the remaining natural habitats in the near future. Recently, it is subjected to severe destruction and dryness of a great deal of its characteristic date palm orchards habitat. Out of the 33 species which recorded for the first time from Feiran Oasis, 13 were invading xerophytes, growing in fields and orchards, and behaving as field weeds. Floristic analysis, species distribution, and soil–vegetation correlations in Wadi Solaf, W. El-Akhdar, and W. Romana (as inland wadis) were compared to W. Kid (a coastal wadi). In the eastern sector of Central Sinai, plant communities and vegetation analysis were performed along four tracks (unpaved and unaccessible roads): Nekhel–Al-Qasimia, Al-Qasimia–Al-Kuntella, Al-Kuntella–Al-Thamad, and Nekhel–Al-Malha.

The Deserts of Pakistan

Pakistan is a subtropical country spread over an area of 79.6 million hectares (mha) lying between 24° and 37° N and 61° and 75° E. Most of the area is semiarid to arid, extending over 70 mha (87.94% of its land mass), receiving 250 mm annual rainfall. The deserts of Pakistan cover 11 mha (13.82%) of the land situated in the central and southeastern regions. These areas are broadly separated and are located between 100 and 1000 m above sea level. These deserts are monsoon in type, referring to a wind system marked with seasonal fluctuation in response to temperature variations between continents and oceans. The southeast-directed winds of the Arabian Sea supply heavy summer rains. The aridity is characteristic of a desert, with erratic rainfall occurring in clusters. The most dominant and frequent tree species in the desert habitat include Acacia senegal, Acacia nilotica, Azadirachta indica, Capparis decidua, Prosopis cineraria, Salvadora oleoides, Tamarix aphylla, and Tecomella undulata, with Prosopis cineraria being the most dominant and frequent. Among shrubs, Acacia jacquemontii, Aerva javanica, Calotropis procera, Calligonum polygonoides, Dipterygium glaucum, Euphorbia caducifolia, Fagonia indica, Haloxylon salicornicum, Leptadenia pyrotechnica, and Crotalaria burhia are dominant. Ephemerals are an important component of the desert habitat, here represented mostly by Boerhavia procumbens, Convolvulus prostratus, Gisekia pharnaceoides, Heliotropium strigosum, Indigofera argentea, Indigofera cordifolia, Indigofera linifolia, Limeum indicum, Mollugo cerviana, Senna ialica, and Tephrosia purpurea. Grasses are very prominent inhabitants in deserts, including Aristida spp., Cenchrus biflorus, Cenchrus ciliaris, Eragrostis spp., Panicum turgidum, Pennisetum divisum, Saccharum spontaneum, and Stipagrostis plumosa. Abutilon bidentatum, Abutilon pakistanicum, Alysicarpus monilifer, Alysicarpus tetragonolobus, Caralluma edulis, Cenchrus prieurii, Commiphora wightii, Convolvulus scindicus, Gisekia pharnacioides, Ephedra ciliata, Gynandropsis gynandra, Monsonia heliotropioides, Rhynchosia schimperi, and Tecomella undulata are some of the threatened species that are used by the inhabitants to meet their various socioeconomic needs. Pragmatic conservation measures are required to protect such habitats, because they represent threatened or rare and endemic species that are of economic importance to the local communities and thus are used unsustainably.

Arid Deserts of the World: Origin, Distribution, and Features

It is not easy to define the word ‘desert’. Botanicall, deserts could be defined as areas with little rainfall, and sparse vegetation made up of special plants having particular characteristics that enable them to avoid, resist, or tolerate harsh environments. Four major categories of derts are known: (1) subtropical deserts, (2) cool coastal deserts, (3) cold winter deserts, and (4) polar desert. Most arid deserts are found near the equator because of the plentiful daylight the location offers.The types of vegetation coincide with the pattern of the water resources othe habitat. As their diversity in landforms, soils, fauna, flora, water balances, and human activities, no particular definition of arid environments can be derived.However, the one binding element to all arid regions is aridity.