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Fire (continued) • Chicago Wilderness – Passing the Drip torch In healthy woods and savannas, representatives of every age— seedlings, saplings, teenagers, and adults one community of “pioneer plants” prepares the way the growth of the next generation of oaks as “recruitment” http://www.chicagowildernessmag.org/issues/spring2007/editorsessay.html Healthy burns in the arboretum • Burns over large areas • Rotation of a 4-year burn schedule • Adjacent to areas not burned in the last 2 years • Seasonal rotation of burns The dry Plains were provided the perfect conditions for fires to start. The long hot summers left the Prairie Grass and the homesteaders’ crops bone dry. Accidental fires started by a spark or a bit of broken glass lying on the ground and reflecting the sun were a disaster for the homesteaders. Unless the fire could be stopped quickly by beating, it soon spread. Without any water to put out the fire, the homesteaders were forced to hide in their sod houses until their crops were destroyed and the fire died. Canopy fire Hot (300-400 F) Widespread mortality Strongly linked to fire weather Potentially large spatial scale Dominant vegetation removed Yellowstone National Park, 1988 Tallgrass prairie, Kansas Surface fires Grasses regenerate because growth tissues are underground Seedlings and saplings killed; adult trees spared Lower temperature than canopy fires Tall and short grass prairie http://climate.konza.ksu.edu/ Tall and short grass prairie • Disturbance agents: fire and drought, and historical grazing from bison. • 5-10 yr return intervals for tall grass prairie • Fires removes litter (or duff) and woody shrubs • Perennial grasses have greater seed production and germination rates following fire • Trees found on the eastern sides of rivers because of prevailing westerly winds. • Mowing is not a good replacement for fires, as it does not remove the litter. Grazing by domestic cattle is not a good replacement as it exerts a selective pressure on only a few species. • Burning is required for the restoration and maintenance of prairie reserves Is fire carbon Negative? Other physical effects of fire Creates environmental heterogeneity Promotes species coexistence, particularly between early and late successional species • Cerro Grande fire in New Mexico, 2000 – Controlled burn escapes and destroys homes in Los Alamos • Biscuit fire in southern Oregon, 2002 – Lightning-ignited fire burns uncontrollably over wide area and burns national forests and homes in local communities • Esperanza fire in southern California, 2006 – Arsonist starts fire at suburban-wildland interface in southern California • 1990’s-2006: increased pressure to suppress fire and thin forests in response to uncontrollable natural wildfires, escape of controlled burns, and a growing population at the suburban-wildland interface. • The recent Healthy Forests Restoration Act advocates salvage logging after fires to pre-emptively thin them • In-class short readings 2-4 Secrets of the Soil Chapter 4 Justin Borevitz • • • • • Fungal, bacterial, insect, nematodes Water Bear, Spring Tails Nitrogen Fixing Allelopathy Soil Microbe diversity A multi-disciplinary approach to research in soil related ecosystem services Soil ecology Soil science Environmental economics Resource economics Soil Biodiversity Ecosystem functions Soil processes Ecosystem services for human welfare Soil Organisms Sociology soil biology - microbiology Let me start with a challenge to soil science to Political sciences http://www.fao.org/ag/AGL/agll/soilbiod/default.stm KEY FUNCTIONAL GROUPS OF SOIL BIOTA Legume Maize Micro-symbionts mycorrhizal Fungi Macrofauna (Ecosystem Engineers) – Earthworms – Termites Source Swift (2002) Decomposers e.g. cellulose degraders N-fixing Bacteria Microregulators Nematodes Pests and Diseases e.g. fungi, invertebrates C&N transformers e.g.methanogens & nitrifiers What do fungi “eat?” • Decomposers break down complex molecules into sugars or consume sugars found in environment • Symbiotic fungi receive their energy (carbohydrates) directly from a plant or algal partner Examples: • mycorrhizal fungi (live on plant roots) • lichens (contain algae) Briana Timmerman [email protected] What else do fungi “eat?” • Predatory fungi, catch and digest other organisms (like nematodes) But still absorptive nutrition! Just have to catch it first… Briana Timmerman [email protected] Lichens Briana Timmerman [email protected] Mycorrhiza symbosis • A mycorrhiza (Greek for fungus roots) is the result of a mutualistic association between a fungus and a plant. This mutualism takes place at the root level, where individual hyphae extending from the mycelium of a fungus colonize the roots of a host plant, either intracellularly or extracellularly • Transport P, K from great distances • Extend the root system • Trade Minerals for sugars.. 95% of all plant families are predominantly mycorrhizal An ericoid mycorrhizal fungus isolated from Woollsia pungens [2]. Midgley, DJ, Chambers, SM & Cairney, JWG. 2002.. Australian Journal of Botany 50, 559-565 Mycorrhizae • “myco” = fungus and “rhiza” = root • Symbiotic association between plant roots and fungi • Several different types of association (defined by structure of fungus:plant interface) Briana Timmerman [email protected] Fungi can access more of the soil because 1. Hyphae are smaller than plant roots Root Hair Hyphae are 1/500th the diameter of a plant root hair hyphae Briana Timmerman [email protected] and fungi expand the surface area available for nutrient uptake Briana Timmerman [email protected] These connections can form forest-wide networks! •If mycorrhizae can move significant amounts of carbon (sugar) between different plant species, this could reduce competition and contribute to the stability and diversity of ecosystems. Briana Timmerman [email protected] Biological Nitrogen Fixation (BNF) • Plant receives ‘reduced’ nitrogen • Bacteria receives energy and other nutrients Root nodules Nitrogen fixation is the process by which atmospheric nitrogen gas is converted into ammonia. The ammonia is subsequently available for many important biological molecules such as amino acids, proteins, vitamins, and nucleic acids. The reaction can be presented as follows: N2 + 16 ATP + 8e- + 8H+ -> 2NH3 + 16 ADP + 16 Pi + H2 Biological Nitrogen Fixation (BNF) • Infection, nodule development, and fixation occurs when: Proper match occurs (strain specific) Surface chemistry conditions are met (Ca++, NO3levels) Bacteroid is formed capable of fixing N2 Synthesize nitrogenase Jointly with plant synthesize leghemoglobin N2 is reduced to NH3 NH3 is attached to glutamate Amino acid is made or transported as glutamine or ureide allelopathy • denotes the production of specific biomolecules by one plant that can harm, or give benefit to, another plant. However, it is most commonly used in the former sense - an interaction in which one plant causes suffering to another plant • Competition or toxicity • Direct or through microrhyzhoa • Some plants that use allelopathy are black walnut trees, sunflowers, wormwoods, sagebrushes, trees of heaven • Pine trees, Eucalyptus In 1 teaspoon of agricultural soil there are… Bacteria 100 million to 1 billion Fungi 6-9 ft fungal strands put end to end Protozoa Several thousand flagellates & amoeba One to several hundred ciliates Nematodes 10 to 20 bacterial feeders and a few fungal feeders Arthropods Up to 100 Earthworms 5 or more Mary Barbercheck Dept. of Entomology Penn State University Soil Health Indicator Some Factors Affected by Tillage • Soil Moisture • Soil Temperature • Range of Temperature and Moisture Fluctuations • Surface Residue • Soil Fauna Abundance and Diversity • Plant Diversity • Favors Bacteria > Fungi Tilled No Till Bacterial-based Fungal-based Soil Health Indicator Predatory Arthropods (0.0001x) Predatory Arthropods (0.01x) Predators of BFN (0.001x) BF Nemas (0.01x) FF Invertebrates (0.1x) Protozoa (0.1x) Bacteria (x) • • • Fungi (x) Densities are much lower than in unmanaged systems, regardless of level and types of inputs Favors bacteria over fungi (After Moldenke, 2002) Soil arthropods tend to consume fungi Effects of Cover Crop Rye Management in Reduced Tillage Corn Clark et al. 1993. J. Entomol. Sci. 28: 404-416 Mean Number Roll Paraquat 6 5 a Remove Fallow/Disk a a a 4 aa 3 ab bb 2 1 b b b 0 ae ae e lid a id el hi n ci p ny id in e ae id l hy a id s co ap oc C Li Ly St ab ar C Ave. #/Core Systems Experiment 1999-2002 Microarthropods Cumulative Average 180 160 140 120 100 80 60 40 20 0 Other Coll. Mites Pasture BMP CT Trees BMP NT Old Organic Field Barbercheck, unpubl.