Pattern,phenology and sex ratio of Egyptian Thymelaea hirsuta populations

The distributional pattern, phenology and sex structure of the desert shrub Thymelaea hirsuta (L.) Endl. were evaluated in six major habitat types in the Mediterranean desert of Egypt.The distributional pattern changes from contagious in the less arid-to random in the more arid habitats.Soil salinity, low content of soil moisture, and extremes of temperature are of importance for the phenological activity.The plant is mainly dioecious. Males are more abundant in two of the habitats and are characterized by larger sizes compared with the females in all but one habitat.     

Factors affecting habitat selection in a specialist fossorial skink

Habitat specialists maximize their fitness by using a subset of the habitats that are potentially available to them and fare poorly if they move elsewhere. The factors that constrain habitat use are diverse and often difficult to identify, but are important to distinguish if we are to understand the trade-offs that drive species to become specialists. In the present study, we investigated habitat use in a fossorial skink, Lerista labialis , and explore the factors that confine it to the crests of sand dunes in the Simpson Desert, central Australia. Models positing that L. labialis selects dune crests because of their sparse cover of vegetation, more favourable temperatures, and greater abundance of preferred prey, received no support. Instead, a model positing that dune crests provide soft and less compacted sand that facilitates movement by L. labialis , was strongly supported. Sand on the crests was consistently softer that that on the sides and swales of the dunes; the skinks preferred soft rather than hard sand for movement in captivity, and were captured more often on experimentally softened sand than on compacted sand in the field. There was no evidence that L. labialis responds to attributes of the substrate other than softness because captive animals used loose sand from the dune crests, sides, and swales equally. We suggest that the dune crest environment allows L. labialis to reduce the energetic costs of locomotion, provides priority of access to the subterranean galleries of its termite prey, and also a secure refuge from surface-active predators and extreme surface temperatures.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 531–544.     

Vegetation zonation along the desert-wetland ecosystem of Taif Highland,Saudi Arabia

Saudi Arabia has no permanent lakes or rivers but has wet meadows, which are desert wetlands temporarily formed due to the seasonal rainfall. This work investigates the environmental variables' impact on the vegetation pattern in the desert-wetland ecosystem in Taif highlands. Forty-one stands were randomly selected representing three main habitats (wet meadows, slopes, and terraces) to study their floristic features and vegetation analysis. A total of 142 species were recorded belonging to 111 genera and 45 families in the desert wetlands of Taif Province. About 64.1% were natural plants, while 25.4% were segetal weeds, 7.7% were aquatic plants, and 2.8% were plants that escaped from cultivation. Therophytes dominated over the other life forms, and mono-regional taxa were the dominant chorotype. Multivariate analysis of the recorded plants produced eight vegetation groups; four of them (A: Potamogeton nodosus-Nasturtium officinale, B: Lemna gibba-Leptochloa fusca, C: Typha domingensis- Xanthium strumarium and D: Conyza stricta- Cyperus longus) represented the wet meadows, while two (E: Acacia gerrardii- Commicarpus plumbagineus and H: Osteospermum vaillantii- Eragrostis Pilosa) for slopes and other two (F: Argemone ochroleuca-Cyperus rotundus and G: Pulicaria undulata- Solanum incanum) for the desert terraces. The vegetation zonation was clear, which started from real aquatic species in the wet meadows passing through mixed vegetation in the slopes and ended with proper xerophytic vegetation in the terraces. Conyza stricta- Cyperus longus community had the highest species diversity, while that of Potamogeton nodosus-Nasturtium officinale had the lowest. The principal component analysis indicated that HCO₃, NO₃, Mg, Cl, Ca, and pH values were the most effective soil variable. The presence of several segetal weeds suggests the alteration of the natural status of the desert-wetland ecosystem, and thus the conservation of these natural habitats becomes urgent.     

Spacing and Competition Between Planted Grass Plugs and Preexisting Perennial Grasses in a Restoration Site in Oregon

Planting native species into restoration settings where other natives already occur is a common practice. However, the competitive consequences of such plantings are rarely studied. Planting density also affects restoration costs. Here we examined the effects of established individuals of Lemmon's needlegrass (Achnatherum lemmonii) on plugs of bluebunch wheatgrass (Pseudoroegneria spicata) and Idaho fescue (Festuca idahoensis) in a restoration site in Oregon. All three of these grasses are local native perennials. Plugs were planted at 6, 12, and 18 cm from established A. lemmonii bunchgrasses and also in plots without A. lemmonii neighbors. Plug survival was uniformly high, averaging more than 98%. Plugs planted at 6 cm from established grasses showed significantly lower growth and reproduction than plugs planted at 18 cm, which had similar values to plugs not planted in the vicinity of A. lemmonii. These results suggest that interplanting distances of as little as 18 cm were sufficient to greatly reduce competitive effects on newly planted plugs, at least in early establishment at this site.     

Western Desert and Native Title: How Models Become Myths

A number of litigated Australian native title cases concern lands located within the area of Australia known as the Western Desert. In these cases, legal arguments concerning the nature of the land‐owning group and the ‘society’ at the time of colonisation have inevitably drawn on anthropological writings about Western Desert local and social organisation. The impetus for this paper was provided by the Yulara case, a compensation claim over the township of Yulara near Uluru, in which the trial judge concluded that land tenure systems in the Western Desert are based on patrilineal principles. One of the significant factors in the Court's decision was an apparently uncritical acceptance of early anthropological models and data, which had reported supposedly patrilineal socio‐territorial organisation in the Western Desert. Researchers currently working in this region and Indigenous peoples themselves, however, reject this model. In this paper, we question the validity of some of the earlier investigations, and propose an alternative understanding of Western Desert territorial organisation based on data gathered from one of the Pitjantjatjara‐speaking people's neighbouring dialectal groups, which is also consistent with most of the other recent and extensive work done in this cultural bloc.     

Correspondence Analysis of species by environmental variable matrices

Abstract. Correspondence Analysis of species by environmental variables matrices is a relatively simple method for handling matrices which include many species and variables. If columns represent species and rows represent the states in which the environmental variables have been divided, each element of the matrix shows the number of releves in which the simultaneous occurrence of that species and that environmental variable state have been recorded. In this paper the use of the method for presence-absence data is considered. The method is appropriate for studies whose main purpose is to look for broad correlations between groups of environmental variables and groups of species. It is particularly useful for handling heterogeneous data sets including rare species and species-poor releves, a situation in which Correspondence Analysis and Canonical Correspondence Analysis are frequently complicated by the production of axes explaining the relationship between rare species and species-poor releves. Examples are presented with artificial data as well as with real data collected in the Mexican portion of the Chihuahuan Desert (Bolsón de Mapimi). It is shown for the Mapimi data that the method is robust to the partition of variables into different numbers of states.