The Rhizosphere and Soil Formation

Rhizosphere effect of three plant species of environment under periglacial conditions (Majella Massif, central Italy)

“…Helianthemum and Dryas had lower pH values in the rhizosphere than in the bulk, so confirming the acidifying action that the roots exert on the soil in contact with them (e.g., Hinsinger et al, 2003). The acidification of the rhizosphere can occur by different processes, other than the CO 2 produced by the root respiration (Richter et al, 2007): 1) excretion of H þ following the root absorption of cations in excess of anions (Haynes, 1990), and 2) release of organic acids to overcome nutrient deficiency (Rengel and Romheld, 2000;Hinsinger et al, 2003;Sandnes et al, 2005). For example, in P deficient soils, roots of natural and cultivated plants exude large amounts of low-molecular weight carboxylates that mobilize P by competing for the same adsorption sites in the soil matrix (Gerke et al, 2000;Fern andez Sanjurjo et al, 2003;Wouterlood et al, 2005).…”

Silicate weathering of soil-mantled slopes in an active Alpine landscape

“…This process acts to constantly refresh the groundwater, enhancing chemical weathering. (Berner et al, 1983;Richter et al, 2007). Additionally, symbiotic relationships are formed with mycorrhizal fungi, which excrete organic ligands and acids in order to mobilize essential nutrients from rock and soil to supply the to higher plants; amongst them the elements most important in rock weathering reactions .…”

Diversity and complexity of microbial communities from a chlor-alkali tailings dump

“…Rhizosphere soil, the thin layer of soil where roots and soil organisms interact in myriad ways (Richter et al, 2007), was sampled from seven Salicaceous trees in each area (tailings dumps and undisturbed soil) in April of 2013. All samples were obtained over a one-day period to reduce any heterogeneity imparted by climatic conditions.…”