Biology 2483A Lecture Notes - Lecture 21: Cyanobacteria, Plant Litter, Azolla Filiculoides
8 Dec 2017
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Document Summary
All nutrients are ultimately derived from abiotic sources: Precipitation over rocks and extracts essential nutrients, one being phosphorus. Elements are released from rock minerals by weathering. Freeze-thaw and drying rewetting cycles break rocks into smaller pieces. Chemical weathering: chemical reactions release soluble forms of the mineral elements. Soil is a mix of mineral particles, organic matter (mostly decomposing plant matter), water, and organisms matter), water, and organisms. The water contains dissolved organic minerals, as gases. Soils with a high proportion of sand have large spaces between the particles and do not hold water well. Parent material: rock or mineral matter that was broken down by weathering to form a soil. May be bedrock or sediment deposited by glaciers (till), wind (loess), or water. Soils derived from limestone have high levels of ca2+, k+, mg2+ Soils derived from granite have lower levels of these elements and lower ph. Lower ph reduced availability of n and p to plants.
