Cacti–shrub interactions in the coastal desert of northern Sinaloa, Mexico

Spatial patterns and replacement in ten cacti were studied on an island of the coastal desert of Sinaloa, México. Four platyopuntias had 74–92% of their individuals beneath shrub canopies, whereas three globose cacti, one columnar cactus and two cylindropuntias had similar or higher percentages of individuals in open spaces. This study advances the idea that open-space colonization is enhanced by less harsh physical and biotic conditions in coastal deserts, and by certain morphological and physiological adaptations of cacti. The absence of nurse-shrub replacement is understood as a result of induced co-existence by physical damage from cyclones in the coastal zone.     

Distribution and floristics of desert plant communities in the lower reaches of Tarim River, southern Xinjiang, People's Republic of China

The distribution and abundance of desert plant communities were examined in the lower reaches of the Tarim River, southern Xinjiang. Eighteen plant species were collected at 18 sites along a sequence of increasing ground-water depths in six transects. Except for Tamarix ramosissima and Populus euphratica, which were distributed across nearly all sites, most of the investigated species had low frequency of occurrence. Correspondence analysis (CA) of the 18 species revealed a separation of growth forms into distinct groups corresponding to different ground-water levels. Three clearly defined groups of growth forms were strongly associated with three distinct ground-water zones, ranging from <3, 3–5 and >5 m, respectively. Four taxa groups were found to correspond to the three ground-water zones and to several other environmental factors. Canonical correspondence analysis (CCA) of the 18 species and seven environmental variables would suggest a major botanical gradient exists relating to ground-water depth and secondary gradients exists that include soil moisture, pH and to a lesser extent alkalinity and mineralization.     

Effect of vegetation with different evolution degree on soil organic matter in a semi-arid environment (Cabo de Gata-Níjar Natural Park, SE Spain)

The organic matter of the surface horizons of soils developed below scrub vegetation in a Mediterranean semi-arid area of great environmental interest (Cabo de Gata-Níjar Natural Park, SE Spain) has been studied. The study mainly concentrates on examining the influence of two vegetation types, one evolved (according to its successional stage), and the other clearly degraded as a result of prior removal of vegetation. In spite of the homogeneity in the results obtained from the analysis of the organic matter from the soils studied, a relationship may be established between vegetation biotype and characteristics and evolution of the soil organic matter. The evolved vegetation results in the presence in the soil of a somewhat more evolved and stable organic matter (demonstrated by certain chemical and microbiological aspects), resulting in a greater degree of humification, thus favouring the protection of the soil and the ecosystem as a whole. Hence, the presence of degraded vegetation might lead to soil degradation, something that is unsustainable in semi-arid areas that are particularly fragile in nature.