Pinus halepensis Mill. plantations did not restore organic carbon,microbial biomass and activity levels in a semi-arid Mediterranean soil |
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| Institution: | 1. The University of British Columbia, British Columbia Children''s Hospital Research Institute, V6H 3V4, Canada;2. ETH Zurich, Mobile Health Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Sciences and Technology, BAA, Lengghalde 5, 8092 Zurich, Switzerland;3. Department of Anesthesia, British Columbia Children''s Hospital, Vancouver BC V6H 3V4, Canada;1. School of Geographical Sciences, Guangzhou University, Guangzhou 510006, China;2. Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;3. Institute of Water Resources Protection in Yangtze River, Wuhan 430051, China;4. Department of Ecology, South China Agricultural University, Guangzhou 510642, China |
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| Abstract: | Maquis is a dense evergreen shrub layer which, in semi-arid Mediterranean lands, is commonly linked to the presence of well-conserved soils with large contents of mineralizable substrates. It was our aim to test whether: (i) maquis promotes soil microbial biomass and activity, and (ii) mature pine plantations without a shrubby understory support microbial biomass and activity levels comparable to those of stands with maquis. Surface soil samples were taken in four sites that sustain pine plantations (PP), maquis with pines (MP), maquis (MQ) and grasslands (GS). Microbial biomass was inferred from the C content in the soil microbiota. The ATP content in fresh samples and the CO2–C production from incubated samples were used to assess microbial activity, as was the activity of β-glucosidase and alkaline phosphatase. Topsoils under maquis (MP and MQ) were the most fertile, both chemically (high organic carbon contents) and physically (low bulk density, high aggregate stability) and showed by far the largest levels of microbial biomass and activity. These levels in soils under PP, which sustained a successful plantation in terms of tree canopy density but lacked the shrubby understory, were significantly smaller than those of the adjacent shrubland with pines (MP). Redundancy analysis extracted a main axis explaining 67% of the variation of the microbiological soil properties, which was interpreted as an environmental gradient of soil fertility. Along this axis, the samples were separated according to the presence or absence of a maquis dominated by late-successional species; other factors such as soil type, slope position and aspect were less influential. The effects of afforestation practices on the detritus-based system should be considered in the design of future forest restoration strategies in desertification-threatened lands. |
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