Effects of climate change on leaf litter decomposition across post-fire plant regenerative groups

Saura-Mas S., Estiarte M., Peñuelas J., Lloret F. (2012) Effects of climate change on leaf litter decomposition across post-fire plant regenerative groups. Environmental and Experimental Botany. 77: 274-282.
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Doi: 10.1016/j.envexpbot.2011.11.014

Resum:

Decomposition is a determining factor for the functioning of ecosystems because litter dynamics (litter fall and litter decomposition) constitute a key process in the regulation of the recycling of carbon and nutrients. We studied the litter decomposition properties of a set of 19 Mediterranean-basin woody species with different post-fire regenerative strategies (resprouters and non-resprouters), under experimental climate manipulation (simulating warming and drought) over a 2-year period. We show that climate change modifies litter decomposition of these Mediterranean woody species as litter contributions to the soil (g/year) were lower under drought experimental conditions. Species with different post-fire regeneration performance showed different leaf decomposition patterns, though these patterns were influenced by the taxonomical affiliation of the species. As expected, the mass loss of the non-resprouter litter, after 2 years, was higher than in resprouters. Non-resprouters showed higher nutrient concentration per mass of leaf litter after 2 years of experiment than resprouters, possibly because they have lost more C-rich biomass, allowing high nutrients concentration in the remaining litter. That would apply particularly to P as litter N:P ratio was lower in non-resprouters than in resprouters. This study suggests that, in Mediterranean ecosystems, nutrients' return from leaf litter to the soil will be slower under the projected future drier conditions. Furthermore, changes in fire regimes that lead to modifications in the abundance of post-fire regenerative groups are likely to affect ecosystem's functional properties. Thus, if new fire regimes enhance non-resprouters' abundance, we can expect a greater return of organic matter contributions to the soil and a lower litter N:P. © 2011 Elsevier B.V.

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Effect of experimentally induced climate change on the seed bank of a Mediterranean shrubland

del Cacho M., Saura-Mas S., Estiarte M., Peñuelas J., Lloret F. (2012) Effect of experimentally induced climate change on the seed bank of a Mediterranean shrubland. Journal of Vegetation Science. 23: 280-291.
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Doi: 10.1111/j.1654-1103.2011.01345.x

Resum:

Questions: We studied the soil seed bank under field-simulated climate change conditions and addressed the following questions: Is the effect of climate change on seed banks more evident in areas without vegetation? Are short-lived species more sensitive to this directional climate change than long-lived species? Location: A Mediterranean shrubland in the Garraf Natural Park, NE Spain. Methods: Directional climate change was induced through manipulating temperature and rainfall over almost 9 yr. Soil seed banks were assessed using the seedling emergence method. Results: Under drought and warming treatments, the total number of germinating seeds decreased by 47% and 43%, respectively, in non-vegetated areas. In contrast, no effect was found for areas with vegetation cover. Reduced seed bank density was particularly pronounced for short-lived species (therophytes plus hemicryptophytes), which dropped by 60% and 69%, respectively, in the drought and warming treatments in open areas, while no significant changes were observed under vegetation. In non-vegetated areas, the reduction in seed bank density was similar in all species. In contrast, a shift in the relative abundance of seed bank species was apparent under shrub canopies. Conclusions: As experimental climatic manipulations of Mediterranean shrublands demonstrate a trend towards an increase in open areas under drought conditions, a decrease in the seed bank of short-lived species in these areas may potentially result in a positive feedback that would accentuate the loss of vegetation cover under predicted future climate conditions. © 2011 International Association for Vegetation Science.

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