soil and water Flashcards
soil
organic (rare) or inorganic
complex, heterogenous environment and immense microbial diversity
soil formation
complex, takes 1000s of years, affected by microbial (metabolic products = organic acids, co2), plant and animal activities, and physical and chemical processes (freeze-thaw, wind/water erosion, dissolution)
primary producers in aquatic env
microbes (eg phytoplankton)
organic soil
created by decomposition of organic matter in bogs and marshes, much higher level of organic matter than inorganic matter, fairly rare but v productive
inorganic soil
most common
microbial activites in soil
metabolic products, organic acids, CO2
animal contribution to soil
mixing and aerating upper layers
plant contribution to soil
taking up water, releasing organics into soil (as they die)
soil profile layers
O: exposed organic matter on surface
A: topsoil, lots of minerals, root zone, lots of microbes, active
B: subsoil, less available minerals, some microbes (spare populations), somewhat active
C: mostly inorganic matter, resembled bedrock (crumbled), sometimes have microbes (spare and metabolically inactive mostly)
Bedrock
microenvironments in soil aggregates
clay, mineral, organic matter sufaces
water, air-filled pores
determinants of microbial activity in soil
water –> affects o2 (which will affect aerobes!)
nutrient status –> microbial activity limited by C, N, or P availability
how the soil aggregate microenvironments can change
introduction of organic matter (eg fungi)
is the oxygen [] of a microenvironment constant
no; the aerobic microbes will quickly use up the O content, and then O-dependent microbes will die, or have to switch to a different form of metabolism
do all soil have the same microbial communities?
v few microbes are common to all soil samples, immense diversity
rhizosphere
soil that surrounds plant roots, significantly different than bulk soil environment –> known as rhizosphere effect
large amounts of organic carbon due to plant excretion, therefore a higher number of microbes can grow here
rhizosphere effect
the difference in bulk soil env. vs plant soil env. bc plants greatly influence soil habitat + serve as potential habitat
rhizoplane
actual root surface
source of root exudates –> sugar, AAs, hormones, vitamins