Topic%204%20Forest%20Disturbance%20slides

Topic%204%20Forest%20Disturbance%20slides - Forest...

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Unformatted text preview: Forest Disturbance Acid Deposition Ozone Global climate change Fire Wind/Hurricane/Ice storms Insects/Disease/Invasive species Harvest/Thinning/Land clearing Fertilization/Biosolids Mining Volcanoes Oak trees create "Islands of Soil Fertility" Organic Matter & Nutrient Enrichment Occurs beneath Oak Canopy Atmosphere Hydrosphere Biosphere Soil Zone Geosphere Atmosphere Accumulation of wet & dry deposition Dissolved Gases Dust Biosphere Prevent deep leaching of nutrients Steal nutrients from beyond canopy Lichens on canopy and bark fix N Mycorrhizae enhance nutrient availability & chemical weathering Return organic matter to soil – litterfall and roots 1 Geosphere Enhanced chemical weathering Carbonic acid (CO2) Organic acids Chelates Increased cation exchange from soil organic matter 35 Loss of Organic Carbon (Mg/ha) 30 25 20 15 10 5 0 1.5 SFREC HREC Hydrosphere Increased E.T. = Less leaching 23% canopy interception 7% increase in transpiration Loss of organic carbon and nitrogen following oak tree removal Lower bulk density → Increased macropores → Increased infiltration → Less runoff & erosion Loss of Nitrogen (Mg/ha) 1.0 0.5 0.0 0 5 10 15 20 25 30 35 40 Years Since Tree Removal Desertification 2 Clearcutting Litter and SOM Increased - above & below ground Soil temperature Increased - solar radiation Soil moisture Increased - transpiration & canopy interception Soil microbial activity Increased - temp, food & H2O Plant nutrient uptake Decreased Gaseous Inputs/Outputs Atmospheric Deposition Atmosphere Decomposition Dry Wet Microbes Im mo bil Mi iza ner tio n al i zat i on Litterfall Litter Ex ud Vegetation Mycorrhizae Soil Organic Matter fw ati o n as h& Primary minerals Secondary minerals Weathering Synthesis Soil Solution Le a Geosphere Up t Biosphere Exchan ak e ge Exchangeable Ions Hydrosphere Leaching (Surface & Ground Waters) Gaseous Inputs/Outputs Atmospheric Deposition Atmosphere Decomposition Clearcutting of Northern Hardwood Forest, NH Dry Wet Microbes Im m Litterfall Litter ob iliz ati Ex ud Vegetation Mycorrhizae Soil Organic Matter on Le a fw Geosphere Primary minerals Secondary minerals tio n Weathering Synthesis Soil Solution Up t Mi ner al iza X Exchan ati o n as h& Biosphere ak e ge Exchangeable Ions Hydrosphere Leaching (Surface & Ground Waters) Streamwater Chemistry Northern Hardwood Forest: Clearcut + 3 Years Herbicide Forest Clearcut Coastal Redwood 3 1 ppm Clearcut Bole-only harvest Coastal Redwood Forest Control Very low nitrate leaching Whole-tree harvest Skid Trail Compaction Open-Canopy Forest (Surface Fires) Closed-Canopy Forest (Crown Fires) 2000o F & 100 mile/hr winds Stand replacement fires Closed-canopy forest – increased competition for light, water and nutrients; increases stress leading to increased disease & insect damage Ladder Fuels – dead trees and dead branches help pull the fire into the canopy 4 Pyro-denitrification (Fire) Volatilized as NH3, N2, N2O & NOx 100 to 300 kg/ha lost Up to 90% of leaf and twig N can be volatilized by hot fire Increased N mineralization Lower lignin, tannins and C/N Total loss in gas and particulate forms Carbon dioxide emissions - A single fire released 5 million tons of CO2 - equivalent to annual emissions of 970,000 vehicles or one coal-fired power plant N>> K > Mg > Ca > P Increased pH Loss of Nutrients Volatilization & Particulate (surface) (crown) (major wildfire) Runoff & Erosion Leaching Soluble nutrients in ash of longleaf pine Soil Erosion What is the fate this nitrate in soil? • Plant uptake • Leaching • Denitrification 5 Creation of hydrophobic layers – water repelling Unburned Partially Hydrophobic Litter Burned We ttab le Hy lay dro er ph obi We c la tta yer ble low er soi l Hydrophobic layer Water saturation le lay er Hy dro ph obi We c la tta yer ble low er soi l We ttab Erosion and Deposition in Stream Habitat Mass movement of surface layer Tree Roots Reinforce Hillslopes Acidic Deposition Nitric acid – HNO3 Sulfuric acid – H2SO4 Ammonium – NH4+ + O2 → HNO3 6 Gaseous Inputs/Outputs Atmospheric Deposition Atmosphere Decomposition Dry Wet Microbes Deciduous Litterfall Litter Im mo bil Mi iza ner tio n al i zat i on Ex ud Vegetation Mycorrhizae Soil Organic Matter fw ati o n as h& Conifer Primary minerals Secondary minerals Weathering Synthesis Soil Solution Le a Geosphere Up t Biosphere Exchan ak e ge Exchangeable Ions Hydrosphere Leaching (Surface & Ground Waters) Ozone Damage Spruce-fir decline in the northeastern USA 1963 1983 Spruce and fir grow in the higher elevations and receive large fog inputs 7 Lake Acidification in Canada Adding sulfuric acid Non-acidified Acidified A starving lake trout captured in acidified lake when the pH was 5.1. Most of the trout's food supply had been killed off by the acid Effects of Acid Deposition Toxicity from H+ and/or Al3+ Nutrient deficiencies (Ca2+, Mg2+ and K+) Nitrogen saturation NO3 leaching Decreased soil microbial activity and diversity Tree susceptibility to freezing and insects Affects aquatic food web dynamics and diversity Model of Forest Ecosystem Response to Nitrogen Saturation by Atmospheric Deposition Biosolids – Sewage Sludge • • • • • Total N NH4-N Total P pH EC 7% 3% 2.5% 7.4 5 dS/m Benefits of Biosolids • • • • Source of nutrients – N & P Increased organic matter Improved physical properties Soil acidity modification 8 Biosolid Slurry being Stored for Land Application Sludge Application in Forest Ecosystems No Sludge Applied Sludge application greatly increases growth rate Volcanic Eruptions Sludge Applied Apatite in volcanic ash deposits rejuentatives soil fertility by adding fresh minerals New volcanics Old volcanics a AP Disturbance gradient 9 Free-Air CO2 Enrichment Annual C Increment Response to Elevated CO2 Annual C increment in woody tissue Water-Use Efficiency WUE = CO2 fixed / water lost (mmoles) (moles) Guard cell Forest Carbon Balance – CO2 Sequestration 10 ...
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This note was uploaded on 04/22/2011 for the course PLS 144 taught by Professor Rice during the Fall '08 term at UC Davis.

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Topic%204%20Forest%20Disturbance%20slides - Forest...

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