Based on: Plant nutri0on Soils and Soil Minerals 1. O 2 2. CO 2 3. H 2 O 4. inorganic minerals Too little! Just fine Too much! Remember, most things can be too little or too much. Micro Macro 1
Source of essen0al elements CO 2, O 2 from atmosphere H 2 0, O 2, minerals from soil NH 4, SO 4 can vola0lize and be transported dry deposi0on can be cri0cal in nutrient poor areas or near the coast rainfall can bring materials from the atmosphere, from smoke, vola0liza0on, volcanoes, pollu0on, etc Soils are cri0cal for Supplies mineral nutrients Support and anchorage Supplies water Allows gas exchange (especially O 2 and CO 2, also ethylene and other gasses) Soil Soil results from Soil is a dynamic feature of systems containing organisms Soil results from the interac0on of climate, substrate and organisms (principally plants and associated microbes) ShiOs in any one of these 3 inter- actors can change the dynamics and characteris0cs of soil Geological Substrate Plants Dynamic, constantly evolving process Climate 2
Rock Residual Soil Forming Factors - Substrate Transport water gravity ice wind Deposition lakes streams oceans downslope ice water wind wind Parent Material Lacustrine Alluvial Marine Colluvial Till, Moraine Outwash Lacustrine Alluvial Marine Eolian Soil Forming Factors - Climate Temperature Warmer - > faster soil development Cooler - > slower soil development Precipita0on Higher rainfall - > greater leaching in profile Leaching zone determined by CaCO3 in soil profile (caliche layer in arid zones) Soil Forming Factors Bio0c Plants Add organic mazer Leach and deposit considerable chemicals (especially organic acids ph determinate) Animals & micro- organisms Mix horizons Modify and transform organic mazer Soils are not created equal Strong varia0on among soils in their mineral content, water holding ability, depth, and other characteris0cs. Strong determinant of plant (community) distribu0on pazerns Soils are not created equal Substrate Climate Biotic Texture Coarse to fine Minerals Acidity Toxicity Temperature Rainfall Roo0ng depth ph of detritus Site produc0vity Cri0cal Features of Soil Source of resources (minerals, water) and support Resources adsorb to surfaces of soil par0cles. Surface Area per Volume Rela0onships as a quan0ta0ve dimension for resource availability Soil Texture (propor0ons of par0cle size classes) Soil Structure (% of soil organics that bind soil together into larger par0cles) Herb- woody 3
1. Soil Texture Texture refers to the propor0ons of different size classes of par0cles decomposed from rock. 3 classes are recognized that can make up soil clay (<0.002 mm) silt (0.02-0.002 mm) sand (2.0-0.02 mm) Different types of rocks yield different soil materials Silt or Sand particles Clay crystals Water adsorbed to surfaces PORE Proportions of clay vs. silt vs. sand modify the size and frequency of soil pores, and consequently influence characteristics of water and mineral retention. Important issues Texture defined by par0cle sizes Soil pores cri0cal characteris0c Suggests large par0cles important 4
Available water varies greatly by soil type. Clay soils can hold more cations because of clay s negative charges and high surface area. Clay is classified into different types depending on its chemistry, structure and other characteristics. Montmorillonite, for example, holds more minerals and water because of its charges and the larger distance between its crystal lattice layers Characteris0cs of soils Depend on soil texture Clay has high surface area and nega-ve charges in its crystalline structure which can readily adsorb minerals and water At the other extreme, sand is a large par0cle with rela0vely lizle surface area (per unit volume), but it can create large soil pores (spaces), which are cri0cal for gas and water movement Important issues Texture defined by par0cle sizes Soil pores cri0cal characteris0c Suggests large par0cles important Surface area cri0cal for holding water and minerals Suggests small par0cles important 5
2. Soil Structure Structure refers to the ability of organic mazer to bind par0cles into larger soil aggregates dissolved organics react with each other forming large carbon compounds that can glue par0cles together into larger aggregates Aggregates act as if they were larger par0cles, crea0ng large soil pores, but also having high surface area Soil Structure Soil Aggregate - soil particles bound together into larger structures High Surface Area due to small particles Hig`h Soil Porosity due to large aggregates yielding large pores Important issues Soil organic mazer combines the characteris0cs of small and large soil par0cles Both increased soil porosity and increased mineral and water holding capacity Generalized Soil Profile Soils vary with distance from source of organic matter (litter) and depending on ability (amount) of rainfall to leach materials to depth. Generalized soil profile associated with a northern forest. Soil development Dependent on climate, vegeta0on and substrate, topography Key aspect is soil organic mazer Addi0on of organic mazer modifies soil characters due to acidity, ability to adsorb minerals, tendency of organic mazer to bind and react. 6
Topography, location and texture: As water empties from a mountain stream, its velocity starts to decrease. The largest size particles, like sand, are the first to drop out of suspension (Site A). Fine, clay size particles can be carried further away from the base of the slope before they are deposited. As a result, coarse textured soils tend to be found near the base of a mountain and fine textured soils are located farther away (Site C). In the context of soils: Vegeta0on responds to Varia0on in texture (e.g., sandy vs clayey soils (NE Pine Barrens; chaparral- clay interfaces in coast ranges) Varia0on in geological substrate serpen0ne (low in N, P, high in heavy metals) granites (low nutrients, degrade to acidic soils) limestones (very high in Ca) Unusual geology often results in unusual plant communities Toxic or imbalanced mineral content restricts plant communities to those that can adapt or tolerate conditions Significant shift in soil texture will shift communities Soils above the yellow line made from uplifted crust high in magnesium, coarse textured. Below, clay soils with fine soils covered by grassland. White Mountains Serpentine Soil the state rock Bristlecone pine on dolomite outcrops Dolomite is a Calcium & Magnesium rich substrate. Like limestone, it is a carbonate based mineral. Often contain restricted or rare species. Serpentine Soils contain large numbers of endemic species. Low in N, high in heavy metals. 7
N. Calif. Sierran Granites Pismo Beach Death Valley Vegetation of Sandy Substrates Many places in California experience the deposition of sand as a major process. Some of these areas are active, like beaches and desert dunes; others more historic, like the sandy soils at Bonny Doon. Bonny Doon area Kelso Dunes The percentage composi0on of feldspar varies between 65-90%, quartz can range from 10 to 60% and that of bio0te lies between 10 to 15%. Feldspar breaks down into clays Quartz into sand Bio0te (mica) into clays Anzo-Borrego Sierran Soils: Mostly Grani0cs and Volcanics Sedimentary soils at lower eleva0ons Things to remember Plant nutri0on depends on soil minerals Soils- cri0cal for: minerals, water, gas exchange, support, anchorage Soils are constantly dynamic: climate, vegeta0on, substrate Soil Texture: par0cle size Soil Structure: organic mazer and soil aggregates Soil porosity: size and density of soil pores 8