Changes in the microbial community in a forest soil amended with aluminium in situ

Abstract

Considerable knowledge exists about the effect of aluminium (Al) on root vitality, but whether elevated levels of Al affect soil microorganisms is largely unknown. We thus compared soils from Al-treated and control plots of a field experiment with respect to microbial and chemical parameters, as well as root growth and vitality. The field experiment was established in a 50-year-old Norway spruce (Picea abies L.) stand where no Al or low concentrations of Al had been added every 7-10 days during the growth season for 7 years. Analysis of soil solutions collected using zero tension lysimeters and porous suction cups showed that Al treatment lead to increased concentrations of Al, Ca and Mg and lower pH and [Ca + Mg + K/Al] molar ratio. Corresponding soil analyses showed that soil pH remained unaffected (pH 3.8), that exchangeable Al increased, while exchangeable Ca and Mg decreased due to the Al treatment. Root in-growth into cores placed in the upper 20 cm of the soil during three growth seasons was not affected by Al additions, neither was nutrient concentration or mortality of these roots. The biomass of some taxonomic groups of soil microorganisms, analyzed using specific membrane components (phospholipid fatty acids; PLFAs), was clearly affected by the imposed Al treatment, both in the organic soil horizon and in the underlying mineral soil. Microbial community structure in both horizons was also clearly modified by the Al treatment. Shifts in PLFA trans/cis ratios indicative of short term physiological stress were not observed. Yet, aluminium stress was indicated both by changes in community structure and in ratios of single PLFAs for treated/untreated plots. Thus, soil microorganisms were more sensitive indicators of subtle chemical changes in soil than chemical composition and vitality of roots.

Evidence that acidification‐induced declines in plant diversity and productivity are mediated by changes in below‐ground communities and soil properties in a semi‐arid steppe

“…Secondly, soil acidification leads to an increase in Al 3+ concentration, which has been considered to be the main factor inhibiting soil microbial biomass and structure (Piña & Cervantes 1996;Illmer, Obertegger & Schinner 2003;Joner et al 2005). In this study, we found that low Al 3+ concentration of 37-60 mg kg À1 (0.…”

“…In this study, we found that low Al 3+ concentration of 37-60 mg kg À1 (0. (Piña & Cervantes 1996;Joner et al 2005). Similarly, Rousk et al (2010a) found that, below pH 4.5, the universal inhibition of all microbial variables derived from increased release of free aluminium.…”

Changes in land use alter the structure of bacterial communities in Western Amazon soils

“…pH is a master variable in the soil environment and it is related to changes in other soil attributes, such as Al concentration and nutrient availability (McBride, 1994). Al toxicity has long been known to affect microbes as well as plants in tropical soils (Wood, 1995;Joner et al, 2005), and has been especially problematic in some regions for effective Rhizobium-legume symbioses (Hungria and Vargas, 2000). Soils in the studied area are rich in Al due to the presence of minerals with Al interlayers (Marques et al, 2002).…”

Land-use system shapes soil bacterial communities in Southeastern Amazon region

“…Our results show that Al saturation index and Al were the factors that presented correlation with more number of bacterial phyla. Aluminum toxicity has long been reported to affect microbial communities as well plants in tropical soils (Joner et al, 2005). Therefore, several parameters other than pH are correlated to specific bacterial groups and are altered by the land-use conversion.…”