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Different Ecosystems (different + ecosystem)
Selected AbstractsA cross-ecosystem comparison of the strength of trophic cascadesECOLOGY LETTERS, Issue 6 2002Jonathan B. Shurin Abstract Although trophic cascades (indirect effects of predators on plants via herbivores) occur in a wide variety of food webs, the magnitudes of their effects are often quite variable. We compared the responses of herbivore and plant communities to predator manipulations in 102 field experiments in six different ecosystems: lentic (lake and pond), marine, and stream benthos, lentic and marine plankton, and terrestrial (grasslands and agricultural fields). Predator effects varied considerably among systems and were strongest in lentic and marine benthos and weakest in marine plankton and terrestrial food webs. Predator effects on herbivores were generally larger and more variable than on plants, suggesting that cascades often become attenuated at the plant,herbivore interface. Top-down control of plant biomass was stronger in water than on land; however, the differences among the five aquatic food webs were as great as those between wet and dry systems. [source] Activity and diversity of methanotrophs in the soil,water interface and rhizospheric soil from a flooded temperate rice fieldJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009L. Ferrando Abstract Aims:, To combine molecular and cultivation techniques to characterize the methanotrophic community in the soil,water interface (SWI) and rhizospheric soil from flooded rice fields in Uruguay, a temperate region in South America. Methods and Results:, A novel type I, related to the genus Methylococcus, and three type II methanotrophs were isolated from the highest positive dilution steps from the most probable number (MPN) counts. Potential methane oxidation activities measured in slurried samples were higher in the rhizospheric soil compared to the SWI and were stimulated by N-fertilization. PmoA (particulate methane monooxygenase) clone libraries were constructed for both rice microsites. SWI clones clustered in six groups related to cultivated and uncultivated members from different ecosystems of the genera Methylobacter, Methylomonas, Methylococcus and a novel type I sublineage while cultivation and T-RFLP (terminal restriction fragment length polymorphism) analysis confirmed the presence of type II methanotrophs. Conclusions:, Cultivation techniques, cloning analysis and T-RFLP fingerprinting of the pmoA gene revealed a diverse methanotrophic community in the rice rhizospheric soil and SWI. Significance and Impact of the Study:, This study reports, for the first time, the analysis of the methanotrophic diversity in rice SWI and this diversity may be exploited in reducing methane emissions. [source] Ecosystem engineering across ecosystems: do engineer species sharing common features have generalized or idiosyncratic effects on species diversity?JOURNAL OF BIOGEOGRAPHY, Issue 2 2006Ernesto I. Badano Abstract Aim, To integrate the effects of ecosystem engineers (organisms that create, maintain or destroy habitat for other species) sharing the same archetype on species diversity, and assess whether different engineer species have generalized or idiosyncratic effects across environmentally similar ecosystems. Location, High-Andean habitats of Chile and Argentina, from 23° S to 41° S. Methods, We measured and compared the effects of eight alpine plants with cushion growth-form on species richness, species diversity (measured as the Shannon,Wiener index) and evenness of vascular plant assemblages across four high-Andean ecosystems of Chile and Argentina. Results, The presence of cushion plants always increased the species richness, diversity (measured as the Shannon,Wiener index) and evenness of high-Andean plant assemblages. However, while the presence of different cushion species within the same ecosystem controlled species diversity in the same way, these effects varied between cushion species from different ecosystems. Main conclusions, Results consistently supported the idea that increases in habitat complexity due to the presence of ecosystem engineers, in this case cushion plants, would lead to higher community diversity. Results also indicate that effects of the presence of different cushion species within the same ecosystem could be generalized, while the effects of cushion species from different ecosystems should be considered idiosyncratic. [source] Plant invasions in undisturbed ecosystems: The triggering attribute approachJOURNAL OF VEGETATION SCIENCE, Issue 6 2005Diego E. Gurvich The invasion of a target community by a non-indigenous plant species includes the stages of arrival, establishment and spread, which tend to depend on different characteristics of the invasive species and its context. While the mechanisms behind the invasion of highly disturbed ecosystems are well known, our understanding of the invasion process in undisturbed or weakly disturbed ecosystems is much more limited. Here we propose that, once a non-indigenous species has arrived to a new ecosystem and become established, the likelihood that it spreads, and thus becomes invasive, may depend on just one or very few characteristics, called,triggering attributes'(TA). We propose that a TA is a vegetative or regenerative attribute discontinuously distributed in comparison to the resident community. This attribute allows the species to benefit from a resource that is permanently or temporarily unused by the resident community. We present an original study case and examples from the literature to illustrate our approach, and we also propose some ways to test it in different ecosystems. [source] Cyclitols and carbohydrates in leaves and roots of 13 Eucalyptus species suggest contrasting physiological responses to water deficitPLANT CELL & ENVIRONMENT, Issue 11 2006ANDREW MERCHANT ABSTRACT In many tree species, physiological adaptations to drought include the accumulation of osmotically active substances and/or the presence of particular compatible solutes, among them cyclitols. Recently, the cyclitol quercitol was identified in species of Eucalyptus, a diverse genus whose speciation is probably driven by adaptation to water availability. We subjected seedlings of 13 Eucalyptus species from different ecosystems (,mesic' and ,xeric') and different sub-generic taxonomic groups to 10 weeks of water deficit (WD) treatment. Pre-dawn water potentials (,pdwn) and relative water content (RWC) were determined in shoots, and total osmolality, soluble low-molecular-weight carbohydrates and cyclitols were measured in leaves and roots. Responses to water deficit followed two distinct patterns: Eucalyptus species from ,mesic' environments adjusted concentrations of sucrose (through increased levels of sucrose and decreases in RWC) in response to water deficit, whereas ,xeric' species increased concentrations of quercitol (through reductions in RWC). In root tissues, only species from xeric environments contained high levels of quercitol and mannitol, increasing under WD conditions. We suggest that the former (mesic) strategy may be beneficial to respond to short-lasting drought conditions, because sucrose is easily metabolized, whereas the latter (xeric) strategy may relate to an effective acclimation to longer-lasting drought. These physiological response groups are also related to taxonomic groups within the genus. [source] | ||||||||||