Browsing by Author "Purnima Raizada"

Now showing 1 - 5 of 5

Comparative response of seedlings of selected native dry tropical and alien invasive species to CO2 enrichment
(2009) Purnima Raizada; Anamika Singh; A.S. Raghubanshi
Aims Global climate change and ongoing plant invasion are the two prominent ecological issues threatening biodiversity world wide. Among invasive species, Lantana camara and Hyptis suaveolens are the two most important invaders in the dry deciduous forest in India. We monitored the growth of these two invasive species and seedlings of four native dry deciduous species (Acacia catechu, Bauhinia variegata, Dalbergia latifolia and Tectona grandis) under ambient (375-395 μ mol mol-1) and elevated CO2 (700-750 μ mol mol-1) to study the differential growth response of invasive and native seedlings. Methods Seedlings of all the species were exposed to ambient and elevated CO2. After 60 days of exposure, seedlings were harvested and all the growth-related parameters like plant height; biomass of root, stem and leaves; total seedling biomass; R/S ratio; allocation parameters; net assimilation rate (NAR) and relative growth rate (RGR) were determined. Important Findings Biomass, RGR and NAR of all the species increased under elevated CO2 but the increase was higher in invasive species and they formed larger seedlings than natives. Therefore under the CO 2-enriched future atmosphere, competitive hierarchies could change and may interfere with the species composition of the invaded area.
Effect of water stress on seedling growth of four tropical dry deciduous tree species under an elevated CO2 regime
(2007) Anamika Singh; Purnima Raizada; A.S. Raghubanshi
[No abstract available]
Impact of invasive alien plant species on soil processes: A review
(2008) Purnima Raizada; A.S. Raghubanshi; J.S. Singh
Majority of research papers dealing with the impact of invasive plant species have addressed autecoiogy of invasive species, factors facilitating the spread of these species, change in community structure and economic losses. Soil processes which change in response to plant invasion and, in turn, affect the recruitment and growth of both native as well as invasive species, are often ignored. The authors review the existing literature on the impact of invasive plant species to show that several soil properties and processes are substantially altered. These changes support feed back mechanisms, which could reverberate up to landscape level and affect ecosystem structure and biogeochemical cycles. Evidently, studies need to focus on soil processes for better understanding of the invasion process so that appropriate management strategy could be developed to combat the onslaught of biological invasion.
Ingress of lantana in dry tropical forest fragments: Edge and shade effects
(2008) Purnima Raizada; Gyan P. Sharma; A.S. Raghubanshi
[No abstract available]
Seed germination behaviour of Lantana camara in response to smoke
(2010) Purnima Raizada; Akhilesh S. Raghubanshi
Lantana camara, a native of the New World tropics, has invaded tropical and subtropical ecosystems across the world. Its growth is stimulated by disturbances such as mild fire, cutting, pruning, and grazing. We investigated the effects of smoke on seed germination of L. camara. Smoked seeds started germinating earlier than non-smoked seeds. The proportion of seeds that germinated, and values of the Germination Velocity Index (GVI) and Vigour Index (VI) were also higher in the smoke treatment compared to the control treatment. Further, seedling mortality was lower in the case of smoked seeds. Our experiment indicates that fire could enhance seed germination in L. camara. Besides mechanical and chemical control methods, burning is used as a method to control L. camara. This practice needs to be discouraged because it could promote - rather than check - the spread of L. camara in burnt areas. © International Society for Tropical Ecology.