Nutritional Effects of Complemental Specie Assemblages and Potential for Ecological Restoration of Post-Fire Soils
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abstract
Human induced large wildfire is a relatively new and growing conservation threat for Chilean temperate forests. Since forest fires can severely modify soil condition and nutritional status different techniques have been proposed for ecological restoration of these ecosystems. Among them assemblages of tree species planted in nucleus have been proposed as option to aid ecological restoration by improving early tree establishment and facilitating regeneration. In this study, we evaluated the nutritional changes in plants and soils resulting from a combination of plant assemblages. The selected species display complementary nutrient acquisition mechanisms. Nothofagus obliqua (NO), Lomatia dentata (LD) y Sophora cassioides (SC) were planted in pots containing a post-fire surface soil under a full factorial design. NO is a deciduous oak specie with mycorrhizal association, while LD is a proteacea shrub (cluster roots), and SC is a leguminous shub (symbiotic nitrogen fixation). In addition, we added a mirror experiment to test the potential subsidy of nutrients effects by fertilizing the pots with a complete balanced nutrient solution. Our results showed that complementary fertilization enhance the growth of all three species independently if they were growing in or out of an assemblage. Biomass of all species was significantly reduced by the presence of other species in the assemblage, the lower being the assemblage with three species together. Differences in plant growth between species growing in the various plant assemblages suggest these species may use complementation or competition strategies depending on the other species present. Growth was generally greater in NO-SC than NO-LD assemblages suggesting complementation of strategies without fertilization. This was supported by 15N and 13C analysis that showed potential transference of nutrients. Soil pH was significantly higher for SC (6.60.1) and lower for NO (6.3 0.2). The form of available N (NH4+ and NO3-) and P availability differed greatly between assemblages (e.g. SC has the lowest NH4+ and the highest NO3. In general, N availability and acquisition was enhanced by the presence of SC and LD, indicating an improvement of the overall nutritional status. The results of our investigation support the use of plant assemblages as a potentially effective restauration strategy in low-nutrient post-fire soils.
