Lubrecht Forest, Montana NREM 301 Forest Ecology & Soils Day 23 – Nov 10, 2009 Nutrient Cycling (Chapters 16-18) Lab today – Finish Inventory work at Rest Area Site Quiz on Thursday Take a plot every 50 ft Teams 1- 4 Azimuth Teams 5-8Azimuth Plot 1m2 o o 0 or 360 or N 330o Identify by: 1. Warm-season grasses 2. Cool-season grasses 3. Forbs 4. Woody species 5. Litter 6. Bare ground 7. Standing dead woody material For Each of the above use an 8- point scale (0, Trace, 3%, 16%, 38%, 63%, 85%, 96%) Total can be more than 100% Set meter stick vertical in center of the plot – at 4 m from the stick and at 1 m above the ground write down the decimeter on stick that is 50% covered Also record trees & shrubs that cross the tape – note distance measure where they cross – keep track of total distance % classes for the following cover types: 0, Trace, 3, 16, 38, 63, 85, 96 Team Number in m2 plots (can exceed 100% total because of multiple canopies) Total Robel Reading Plot Distance Warm‐ Cool‐season Woody Standing 4 m away 1 m Numberfrom start season Grass Grass Forbs Species Litter Bare Ground dead wood above ground 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Team Number Tree/shrub Inventory ‐ note whenever a tree or shrub stem or branch crosses your transect ‐ list at least shrub or tree & if you can ID please do ‐ start in 2 left columns and down then move right Distance from Tree or shrub species Distance from Tree or shrub species Distance from Tree or shrub species beginning beginning beginning Group Activity Diagram the general nutrient cycle for an ecosystem Think of nutrients cycling in an ecosystem box a) Inputs (how do nutrients get into an ecosystem) b) Outputs (how are nutrients lost from the ecosystem) c) Internal Cycling (how do nutrients move around in the ecosystem Biochemical General Nutrient Cycle Geochemical Biogeochemical Page 525 Textbook Ability of fresh OM to be incorporated into the soil helps dictate rate of cycling Oi (L) Oe (F) Oa (H) Mineral soil Bogs 1. Northern or high elevation climates 2. Water source – precip – bowl with not other in or outputs 3. Anaerobic water 4. Low pH < 5 5. Slows decomposition 6. Sphagnum moss Histisol Organic Soil Fens 1. Similar locations 2. Water source is groundwater or stream – moving into & out of fen 3. Higher pH 4. More nutrients 5. More plant diversity Major Trees – Black & White Spruce Less water than Eastern Deciduous Forest Permafrost What Can Happen Without Disturbance Bogs – absence of disturbance Forest Decline Group Activity Two Concave Depression Sites Both within about 10 miles of each other in Wyoming - one is at about 6,000 ft the other at 9,000 ft elevation What reasons cause the difference you see? Salt Flat pH very basic Fen pH very acid Low precipitation, high ET Higher precipitation, lower ET, more Plant growth – conifers dominate Fall is here and the leaves have fallen off of the trees Group Activity These leaves play an important role in maintaining the organic matter in the soil. How do you think they become part of the OM? Please use this figure to expand your answer Group Activity A) What % of the aspen leaves is water? B) What % of the aspen leaves are C, H, O and ash? Lignins & phenolic compounds C) Rank the compounds from Cellulose fastest decomposition to Sugars, starches & simple proteins slowest. Hemicellulose Fats, waxes, etc. Crude proteins Composition of typical green plant material Sugars, starches & simple proteins Rapid decomposition Crude proteins Hemicellulose Cellulose Fats, waxes, etc. Lignins & phenolic compounds Slow decomposition Soil – a very complex ecosystem – 1,000’s of organisms that are critical to global cycles. The most densely packed ecosystem on the planet. Macrofauna - > 2 mm – termites, ants, earthworms, beetles, etc. – can dig through soil & create structures for their movement and habitat (burrows, galleries, nests, etc.) Mesofauna – 0.2-2mm – collembolas, acarids – live in air-filled pores Microfauna - <0.2mm – protozoa, nematodes, rotifers – live in water-filled pores Soil Meso & Microfauna Over 1000 species in a single m2 of forest soil Many of the world’s terrestrial insect species are soil dwellers for at least some stage of their life-cycle A single gram of soil may contain millions of individuals and several thousand species of bacteria A typical, healthy soil might contain: a) several species of vertebrate animals – moles, shrews, etc. b) several species of earthworms, c) 20-30 species of mites, d) 50-100 species of insects, e) tens of species of nematodes, f) hundreds of species of fungi g) thousands of species of bacteria and actinomycetes. Group Activity A) What is meant by the term detrital food web? B) How is this food web similar, different from the traditional terrestrial food web? C) What are the major steps of decomposition? Soil (Detrital) Food Web Decomposition 1. OM is oxidized to water & CO2 2. Heat energy released 3. Nutrients released (mineralized) 4. Resistant compounds produced by organisms C/N Dry Plant OM 42% = C 1-2% = N 1. Microbes need 8 C for 1N to build cells 2. Need 16 C for Rs 3. Need C/N = 24/1 4. If OM > 24:1 C/N = 30:1 microbes take N from NO C/N = 120:1 3 in soil 5. So lack of N can C/N = 300:1 slow decomposition Soil pH Microbial activity & Nutrient availability Decomposition slowed at low pH – fewer bacteria High pH also limits availability of some – note especially P and micro-nutrients Many nutrients limited by low pH – some micros - not Temperature & Moisture Influences on SOM What does this figure show? Higher temperature decreases SOM • faster decomposition • higher respiration Higher moisture increases SOM • more production of OM • possibly slower decomposition Page 29 Soil & Plant Handout Compare the mean residence time of OM, N & P in the FF of tropical, boreal & warm temperate forests Soil Chemistry Cation Exchange Capacity (CEC) Clay & Humus have negative charges to which cations are adsorbed. Cations adsorbed to CE sites do not leach – but can be taken up by plants Clay & Humus CE sites can hold 100’s to 1,000’s of lbs of nutrients per acre furrow slice (6” deep over 1 acre – weight ~ 2 million lbs) Base Saturation = % of CEC occupied by cations other than H+ Heavily leached soils have low BS – low fertility pH & Base Saturation are related If CEC is mainly occupied by H+ pH is more acid Forest soils that are acid have most nutrients in biomass Old soils that are highly leached because of high rainfall have lost cations – soil is acid.