Soil wetting-drying and water-retention properties in a mine-soil treated with composted and thermally-dried sludges

Ojeda G., Mattana S., Bonmatí M., Woche S.K., Bachmann J. (2011) Soil wetting-drying and water-retention properties in a mine-soil treated with composted and thermally-dried sludges. European Journal of Soil Science. 62: 696-708.
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Doi: 10.1111/j.1365-2389.2011.01378.x

Resum:

The main objective of this study was to analyse how different sewage sludges influence soil wetting and drying dynamics. Three composted and three thermally-dried municipal sludges from different wastewater plants located in Catalonia (NE Spain) were mixed with a mine-soil obtained from a limestone quarry. Measurements of the time required to reach zero contact angle () and water holding time (WHT) provided information on the time required for a mine-soil to reach its complete wettability and the residence time of water stored between -0.75 and -25 MPa of soil suction, respectively. One month after sludge amendments, one composted and one thermally-dried sludge significantly increased WHT was increased in the mine-soil treated by composted sludges (50.6% by Blanes' sludge, 65.5% by Manresa's sludge and 52.5% by Vilaseca's sludge) one month after sludge amendments. The amount of water retained in the mine-soil was increased by all composted sludges and one thermally-dried sludge after one month (by 42.3% with Blanes' sludge, 42.3% with Manresa's sludge, 65.7% with Vilaseca's sludge and 23.9% with Mataró's sludge) and one year after sludge amendments and at a small suction. Increments in WHT corresponded with the amount of water retained so the time-scale of soil water availability should also be considered. The value was modified mainly by increments in carbon stock and microbial biomass, while the WHT was modified mainly by increments in pH and electrical conductivity. Under similar air-drying conditions, mine-soil treated with composted sludges retained more water for longer compared with thermally-dried sludges. © 2011 The Authors. Journal compilation © 2011 British Society of Soil Science.

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Drought-resistant fungi control soil organic matter decomposition and its response to temperature

Yuste J.C., Peñuelas J., Estiarte M., Garcia-Mas J., Mattana S., Ogaya R., Pujol M., Sardans J. (2011) Drought-resistant fungi control soil organic matter decomposition and its response to temperature. Global Change Biology. 17: 1475-1486.
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Doi: 10.1111/j.1365-2486.2010.02300.x

Resum:

Microbial-mediated decomposition of soil organic matter (SOM) ultimately makes a considerable contribution to soil respiration, which is typically the main source of CO2 arising from terrestrial ecosystems. Despite this central role in the decomposition of SOM, few studies have been conducted on how climate change may affect the soil microbial community and, furthermore, on how possible climate-change induced alterations in the ecology of microbial communities may affect soil CO2 emissions. Here we present the results of a seasonal study on soil microbial community structure, SOM decomposition and its temperature sensitivity in two representative Mediterranean ecosystems where precipitation/throughfall exclusion has taken place during the last 10 years. Bacterial and fungal diversity was estimated using the terminal restriction fragment length polymorphism technique. Our results show that fungal diversity was less sensitive to seasonal changes in moisture, temperature and plant activity than bacterial diversity. On the other hand, fungal communities showed the ability to dynamically adapt throughout the seasons. Fungi also coped better with the 10 years of precipitation/throughfall exclusion compared with bacteria. The high resistance of fungal diversity to changes with respect to bacteria may open the controversy as to whether future 'drier conditions' for Mediterranean regions might favor fungal dominated microbial communities. Finally, our results indicate that the fungal community exerted a strong influence over the temporal and spatial variability of SOM decomposition and its sensitivity to temperature. The results, therefore, highlight the important role of fungi in the decomposition of terrestrial SOM, especially under the harsh environmental conditions of Mediterranean ecosystems, for which models predict even drier conditions in the future. © 2010 Blackwell Publishing Ltd.

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