Spatial analysis of Prosopis Juliflora trees, its environmental and developmental effects on Wadi Yiba in the southwest of Saudi Arabia: التحليل المكاني لأشجار البرسوبس وآثاره البيئية والتنموية على وادي يــبة جنوب غرب المملكة العربية السعودية

Prosopis Juliflora is an invasive shrub or tree native to South American countries. It is one of the most important exotic and invasive organisms that are spread in the Kingdom of Saudi Arabia. This study concentrates on investigating the widespread of Prosopis Juliflora in Wadi Yiba، located in the southwest of the Kingdom، and given the possibilities offered by geographic information system (GIS) and remote sensing to help determine the areas of spread of the plant and its size، and to take the best capabilities، especially with regard to processing and analyzing large and diverse spatial information، the present research aims to use this in evaluating the current and future situation of the spread of plants in Wadi Yiba، and the extent of its impact on the environment، while suggesting appropriate ways to manage it. The research relied on the use of Landsat images، working with the subtraction method، and subjecting the images to the object-oriented classification، by taking 30 specimens for each cover and merging these specimens، and the layers of vegetation cover were derived using the normalized difference vegetation index (NDVI) for each year. The research concluded that there is a concentration in the spread of Prosopis Juliflora in the center and north of Wadi Yiba، especially in the city of Therban and villages of Al-Balqa’a، Al-Tala’i، Sabt Al-Jara، and Khamis Harb، with a spread along the valley to the estuary. At the end، the research recommended the establishment of a research center for the study of Prosopis Juliflora in Assir region، and an attempt to develop economic plans to benefit from Prosopis Juliflora in Wadi Yiba.

SHADING AND LIGHT INTERCEPTION IN THICKETS OF INVASIVE ACER NEGUNDO AND SORBARIA SORBIFOLIA

The aim of the work is to establish how greatly the light conditions change under the leaf canopy of two invasive plant species in the Middle Urals - Acer negundo and Sorbaria sorbifolia . In June - August 2020, using a portable light meter, 8370 measurements of illumination were performed in forest parks (at a height of 1.5 and 0.5 m, i.e. above and below the canopy of the leaves of the invasive shrub S. sorbifolia and the native shrub Rubus idaeus ; in random points under the canopies of Pinus sylvestris ; on glades, paths and forest edges) and in urban habitats (at a height of 1.5 m and 0.5 m in dense thickets of the invasive tree A. negundo and other tree species). The average illumination intensity was as following: under S. sorbifolia - 4 ± 1 lux × 10; under R. idaeus - 7 ± 1 lux × 10; in A. negundo thickets - 13 ± 2 lux × 10; in thickets of other tree species - 25 ± 4 lux × 10; under the canopies of urban pine forests - 80 ± 10 lux × 10; in the forest edges - 96 ± 14 lux × 10. In dense thickets, A. negundo intercepts about 94% of the light falling on its canopies, S. sorbifolia - about 93%. This is significantly higher than the light interception level in habitats used as control: other tree species canopies of greatly urbanized habitats intercept about 89%, the thickets of R. idaeus - about 82%. Thus, invasive plants reduce the amount of light available to other plant species in communities significantly more than native plants.

Exploring the role of fungal endophytes in the sudden death syndrome of the invasive shrub Chrysanthemoides monilifera subsp. rotundata in Australia

Pathogens that attack invasive plants can positively affect the integrity and functioning of ecosystems. Stem-tip dieback and extensive wilting followed by sudden death have been observed in Chrysanthemoides monilifera subsp. rotundata (bitou bush), one of Australia’s worst invasive shrubs. Metabarcoding and culturing methods were used to investigate if fungi are implicated in this syndrome. Metabarcoding results revealed significantly different endophytic fungal communities within healthy and diseased bitou bush, and co-located native plants. There was no difference in fungal communities between soil sampled in the root zone of healthy and diseased bitou bush at the same site. Two Diaporthe sp. operational taxonomic units (OTUs), dominant at sites with extensive wilting, explained 30% of the similarity between diseased bitou bush across all sites. Two other OTUs, Austropleospora osteospermi and Coprinellus sp., explained 20 and 40% of the similarity between diseased plants, respectively, and were only dominant at sites with dead or stunted, partially defoliated but not wilted bitou bush. A Penicillium sp. OTU explained 90% of the similarity between healthy bitou bush. Various Diaporthe spp. dominated isolations from diseased bitou bush. Manipulative experiments confirmed Diaporthe spp. pathogenicity on bitou bush excised and in-situ stems. In another experiment, Diaporthe masirevicii infected flowers and from there colonized stems endophytically, but wilting and sudden death of bitou bush did not occur within the experimental timeframe. Our study provides circumstantial evidence that bitou bush sudden death syndrome is the result of a shift in the composition of its endophytic fungal community, from mutualist to pathogenic species.

Plant diversity and community composition in managed humid coastal dune slacks in NW England

Humid coastal dune slacks are an endangered habitat in Northwestern Europe. In the UK, dune slacks are currently classified as being in ‘unfavourable’ condition, with projected decrease in England of up to 30% by 2036. Studies in mainland Europe suggest that regional factors (e.g. slack area, age, and isolation) are more important than local factors (e.g. soil, pH, soil nutrient and water status) in driving successional vegetation processes in coastal slacks. However, this has never been tested for the UK, where approximately 14% of European slacks occur. We used previously established survey protocols to test whether regional factors are more important than local factors in UK coastal slacks, along the Sefton Coast in NW England. We found that slack area and slack age were more important than local factors in driving plant community composition and species richness. We also showed that higher levels of management, such as active grazing and invasive shrub and tree removal, are effective in increasing soil moisture levels in slacks. Our results suggest that similar successional processes are likely to be important in slacks in the NW of England, compared to mainland Europe.

Soil texture and other site-level factors differentially affect growth of Scotch broom (Cytisus scoparius) and Douglas-fir (Pseudotsuga menziesii) seedlings in the western Pacific Northwest

The invasive shrub Scotch broom (Cytisus scoparius (L.) Link) is a pervasive threat to regenerating Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stands in the Pacific Northwest, USA. Field observations indicate that the susceptibility of areas to Scotch broom invasion and dominance can vary by site. We selected ten sites throughout the western Pacific Northwest that spanned a gradient of soil textures and other factors to test the site-specific susceptibility of Douglas-fir to overtopping by Scotch broom. We expected to find that the ability of Scotch broom to dominate a site was mediated by site-level factors, particularly those influencing soil water – the most limiting factor to growth in the region. We found Scotch broom and Douglas-fir were inversely affected by site-level factors. In general, Douglas-fir absolute height growth rates were more competitive with those of Scotch broom on fine-textured soils than on more coarsely textured soils. We also found Douglas-fir to have a more dramatic response to increasing down woody material than Scotch broom. Scotch broom height growth approached an asymptote at 3 m. Sites with fast-growing Douglas-fir were able to surpass this height six to seven years after planting and appear likely to avoid suppression by Scotch broom.

Morphological, anatomical and preliminary phytochemical characterization of Buddleja madagascariensis Lam.

Buddleja madagascariensis Lam. is a perennial invasive shrub distributed in tropical and sub-tropical regions of the world. The present study was conducted on morphological, anatomical and phytochemical characterization of Buddleja madagascariensis and the results revealed that plant height varied from about 188-191 cm, and the whole plant was covered with trichome which may be glandular and eglandular and unicellular or, multicellular. Inflorescence was terminal and axillary in position, thyrsoid panicle. Anatomical and histo-chemical studies of the transverse section of various parts of the plant revealed the presence of steller tissues, starch in cortical and pith region. Phytochemical analysis of the crude extract showed the presence of carbohydrates, proteins, saponins, flavonoids, phenolic compounds and tannins. But alkaloids, glycosides and free amino acids were absent. Thus, characterization of plants on the basis of these parameters could be used as tools to distinguish the crude drugs of plants from adulterants, used in the preparation of traditional medicines and used as diagnostic keys. Also, it is useful in the future for revealing the importance of plants and phytochemical resources for the conservation of resources.