Syed Shahid Shaukat

Population structure and dynamics oi Juniperus excelsa in Balouchistan, Pakistan

. 60 monospecific stands of Juniperus excelsa were sampled at four locations in Balouchistan. Density, basal area and height of individuals were recorded. Soils were analysed for selected physical and chemical characteristics and the degree of disturbance due to logging and burning was noted. The density of juniper trees (> 6 cm dbh) ranged from 56 to 332 stems / ha (average 174 stems / ha). Higher densities were recorded for relatively undisturbed stands and on west facing slopes. Density of seedlings and saplings (< 6 cm dbh) was strongly correlated with tree density and tree basal area. Among the edaphic variables CaC03 was correlated with juniper density and basal area. Diameter distributions within stands were mostly skewed and unimodal with gaps appearing in large size classes. The male to female ratio was close to 1. Cross-sections of 16 trees were used to determine age and growth rate. Number of rings in trees with 20 to 30 cm dbh ranged from 95 to 221 (x = 160 ± 38). Diameter and age were not related. Mean annual diameter increment ranged from 6 to 16 yr / cm x = 10 ± 3 yr / cm). It is concluded that size class gaps and low seedling / sapling densities are the consequence of anthropogenic disturbance.

Vegetation-environment relationships in the forests of Chitral district Hindukush range of Pakistan

We investigated the composition of plant communities to quantify their relationships with environmental parameters in the Chitral Hindukush range of Pakistan. We sampled tree vegetation using the Point Centered Quarter (PCQ) method while understory vegetation was sampled in 1.5-m circular quadrats. Cedrus deodara is the national symbol of Pakistan and was dominant in the sampled communities. Because environmental variables determine vegetation types, we analyzed and evaluated edaphic and topographic factors. DCA-Ordination showed the major gradient as an amalgam of elevation (p<0.05) and slope (p<0.01) as the topographic factors correlated with species distribution. Soil variables were the factors of environmental significance along DCA axes. However, among these factors, Mg2+, K+ and N2+ contributed not more than 0.054% 0.20% and 0.073%, respectively, to variation along the first ordination axis. We conclude that the principal reason for weak or no correlation with many edaphic variables was the anthropogenic disturbance of vegetation. The understory vegetation was composed of perennial herbs in most communities and was most dense under the tree canopy. The understory vegetation strongly regulates tree seedling growth and regeneration patterns. We recommend further study of the understory vegetation using permanent plots to aid development of forest regeneration strategies.

Nematicidal and allelopathic responses of Lantana camara root extract

The impact of root leachates of Lantana camara L., a tropical weed, against Meloidogyne javanica, the root-knot nematode, was tested under laboratory and pot conditions. Concentrated and diluted root leachate caused substantial mortality of M. javanica juveniles. Significant suppression of the nematode was achieved when soil was treated with a full-strength concentration of the leachate. Whilst this high concentration retarded plant height and shoot fresh weight, more diluted concentrations actually enhanced plant growth. To establish whether this inhibition of plant growth from the leachate was the result of depleted nitrogen levels in the soil due to the leachate, soil treated with such leachates was given urea as an additional nitrogen source. Urea not only enhanced nematode suppression activity of the root leachates but also increased seedling emergence and growth of mungbean. Application of the L. camara root leachates in combination with Pseudomonas aeruginosa, a plant growth-promoting rhizobacterium, significantly reduced nematode population densities in roots and subsequent root-knot infection, and enhanced plant growth. While a high concentration of root leachate slightly reduced P. aeruginosa colonization in the rhizosphere and inner root tissues, the nematicidal efficacy of the bacterium was unaffected. The root leachate of L. camara was found to contain phenolic compounds, including p-hydroxybenzoic acid, vanillic acid, caffeic acid, ferulic acid and a quercetin glycoside, 7-glucoside. It also contained weak enzymic hydrogen cyanide.

Avicennia marina (mangrove) soil amendment changes the fungal community in the rhizosphere and root tissue of mungbean and contributes to control of root-knot nematodes

The effect of soil amendment with Avicennia marina (mangrove) on mungbean growth and mungbean infestation with Meloidogyne javanica was determined in greenhouse pot experiments. Galling and final nematode population densities were reduced by all soil amendments with mangrove. To better understand whether nematode suppression by A. marina was caused directly by the release of nematicidal factor(s) into the soil, or was due indirectly to changes in the fungal community, the diversity of the rhizosphere populations of culturable fungi was assessed before organic amendment (day 0), after decomposition but before seed sowing (day 15) and at harvest (day 73). Thirteen out of 20 fungal species were isolated from both A. marina-amended and unamended soils, the most frequent genera being Alternaria, Aspergillus, Fusarium, Penicillium, Trichoderma, Mucor, Myrothecium and Rhizoctonia. The other seven were found only in amended soils. At different times in the course of the experiment amended and unamended soils differed significantly in the fungi isolated from the rhizosphere and/or in the concentrations of A. marina. Trichoderma viride was isolated only from surface-sterilized mungbean roots grown in amended soils, whereas Chaetomium sp. was isolated only from unamended soils.

Trigonella foenum-graecum (fenugreek)-mediated suppression of meloidogyne javanica in Mungbean

Soil amendments with powered seeds of Trigonella foenum graecum (fenugreek) caused soil suppressiveness against Meloidogyne javanica. Decomposed seeds of fenugreek caused marked reduction in nematode population densities and subsequent root-knot development as compared to the aqueous extract of the seeds, indicating that some indirect factors are involved in the suppression of root-knot nematode. Both decomposed seeds and aqueous extracts enhanced plant height and fresh weights of shoot, whereas root growth remained uninfluenced. Changes in fungal communities associated with nematode control were studied by comparing population numbers of fungi in the soil and in internal root tissues (endorhiza) in non-amended and fenugreek-amended soils. Acremonium coenophialum, Chaetomium globosum, Fusarium solani, Macrophomina phaseolina and Rhizoctonia solani were found to colonize inner root tissues of mungbean. A. coenophialum, C. globosum and F. solani were isolated in a relatively higher frequency from roots growing in the amended soils, while M. phaseolina and R. solani colonized greatly in roots growing in non-amended soil. Of the fungi isolated from soils, Penicillium brefaldianum caused maximum juvenile mortality, whereas F. solani caused greatest inhibition of egg hatch.

Vulnerability to climate change of surface water resources of coastal areas of Sindh, Pakistan

AbstractThe coastal district Thatta of Sindh Province is the area where availability of freshwater is a critical factor for the human survival and livelihood. As such, there are no perennial surface water resources available in the district except of River Indus and its canal system. In view of the changing climate change scenario of the coastal areas of Sindh, this study was undertaken to determine the availability and quality of surface water available in Thatta district. Results of the present investigation indicate that the water from the canals was not suitable for drinking as per WHO guidelines and National Standards for Drinking Water Quality Pakistan. Agriculture run-off, sewage leaks and metals quite often contaminate the surface water resources. However, users have no method to judge its quality except for the taste. Thus, most of the residents drink polluted water unknowingly, and do not question its quality. Increasing variability in rainfall pattern and reduced flow in the River Indus at down...

Factors influencing the effectiveness of non-pathogenic Fusarium solani strain Fs5 in the suppression of root-knot nematode in tomato

Four experiments were carried out under greenhouse conditions to evaluate the effectiveness of Fusarium solani strain Fs5 against the root-knot nematode Meloidogyne javanica. The effect of population densities of M. javanica, various application rates of F. solani, moisture regimes and levels of benzaldehyde, a volatile compound of plant origin affecting the plant-nematode-fungus interaction, were also studied. F. solani parasitized eggs and females of M. javanica and thereby reduced root-knot severity in tomato. Although the fungus was frequently isolated from root tissues, it did not produce phytotoxic symptoms; instead, there was enhanced plant growth. At higher nematode densities, inner root colonization by the fungus increased. The rates of fungal infection on M. javanica eggs and females also increased with increasing nematode densities and fungal inoculum levels. Nematode invasion and subsequent root-knot increased with increasing soil moisture, in both F. solani-treated and untreated plants. However, root-knot development was lower at all moisture regimes when F. solani was applied to the soil. Root colonization by F. solani and parasitism on female nematodes was highest at 50% moisture holding capacity (MHC) whereas egg parasitism by the fungus was greatest at 75% MHC. With increasing concentration of benzaldehyde in soil, nematode penetration and subsequent root-knot infection were progressively reduced. Root colonization by F. solani was greatest in soil treated with benzaldehyde at 2 µg g-1 of soil in the presence of M. javanica. Increasing benzaldehyde concentrations resulted in increased parasitism of M. javanica females by F. solani but in lower parasitism of the eggs. Treatments with F. solani led to better plant growth when they were combined with benzaldehyde at 2 µg g-1 of soil.