Pregunta | Respuesta |
Microbial symbiont with grasses | Arbuscular mycorrhizae |
Microbial symbiont with Azolla | Anabaena |
Microbial symbiont with pine trees | Ectomycorrhizae |
Microbial symbiont with Lichen | blue-green alga |
Microbial symbiont with actinorhizal plants | Frankia |
Microbial symbiont with leguminous plants | Rhizobium |
Ochric | Pale, thin, low in organic C |
Natric | accumulation of silicate clays and <15% of exchangeable Na |
Umbric | similar to mollic but has a lower base cation saturation |
Histic | organic material (20-60cm) overlying mineral soil |
Spodic | accumulation of illuvial humus and aluminum oxides |
Kandic | accumulation of Fe and Al oxides and kaolinite |
Oxic | highly weathered, high in Fe and Al oxides and kaolinite, humid tropical regions |
Albic | light colored eluvial horizon, Fe and Al oxides have been removed |
Xeric | Cool, moist winters and warm dry summers with drought conditions. “Mediterranean” climate |
Aridic | Soil dry for at least half the growing season and moist for <90 consecutive days. |
Ustic | Soil moisture intermediate between Udic and Aridic. Some plant available water during growing season but drought may occur. |
Udic | Soil moisture is sufficient for plant needs year-round |
Aquic | Soil is saturated with water and anaerobic for long enough to show soil indicators of poor aeration |
subordinate horizon designation "p" | plowed |
subordinate horizon designation "t" | accumulation of clay |
subordinate horizon designation "h" | concentration of humus |
subordinate horizon designation "k" | accumulation of carbonates |
subordinate horizon designation "g" | gleyed -prolonged wetness |
Histosol | • Layered organic materials •Cool, wet environments at high latitudes or in wetlands • Histic epipedon* • No permafrost |
Entisol | • Little or no horizon development • Characteristics reflect varied parent materials • Very dry or cool climates, unstable landscape positions, or resistant parent material |
Andisol | • Form in recent (5,000 – 10,000 yrs) volcanic ejecta •Generally high in natural fertility • Easily wind eroded |
Inceptisol | • Beginning horizon development • Often found in mountainous areas |
Aridisol | • Arid climates • Ochric A • Often CaCO3 or Na salt accumulations • May have Bt formed during wet climate |
Vertisol | • High content of shrinking/swelling clays • Ca and Mg rich parent materials • Contain ‘slickenslides’ - smooth surfaces created as the subsoil masses move past each other and smear the clay. • Fertile; high CEC; high OM |
Mollisol | • Highly fertile soils of grasslands • Mollic A • Bt (argillic) • Often calcic (Ck) horizons |
Alfisol | • Form mainly under deciduous forests • Ochric A horizon • Often E horizon • Argillic horizon (Bt) |
Ultisol | • Form on old stable land surfaces • Usually tropical forest vegetation • Warm humid climate • Umbric or ochric A; Bt; often E |
Spodosol | • Form in sandy materials under coniferous forests • Usually in wet, cool climates • Albic and spodic horizons |
Oxisol | • Most highly weathered soils • Form in hot, humid climates • Oxic B • Low natural fertility and high soil acidity |
Immobilization | ammonium-N and nitrate-N are incorporated into living tissue |
Mineralization | releases soluble nitrogen as the result of the breakdown of nitrogen-rich organic compounds |
Nitrification | NH4 is changed to NO3 by bacteria |
Volatilization | loss of N by the conversion of NH4 to N gas |
Denitrification | reduction of NO3 to nitrogen gas by microorganisms occurring under anaerobic conditions |
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