Palmer June /13/01

Transcription

1 7/3/

2 Day 4_Ecosystem Functions_intro + OM processes Ecosystem Function = Ecosystem or Ecological Processes Primary Production Whole Stream metabolism Organic matter processing (Decomposition and use of OM) Nutrient Dynamics (uptake/release/transformations) Shifting the focus to restoration of function (hydrogeomorphic and ecological processes) Sediment supply Hydrologic regime Organic matter processing Nutrient Processing Primary production Processes Flood control Water quality Fish Inverts SERVICES

3 What people want from rivers: Ecosystem goods & services clean water - drinking, irrigation climate control temperature regulation minimize floods - absorb storm energy food - fisheries recreation angling, canoeing, hiking Objectives What needs to be restored: Processes that support ecosystem services nutrient & contaminant processing e.g., denitrification Water availability - diacharge water storage - groundwater recharge heat capacity condensation, evaporation primary & secondary production photosynthesis, growth Organic matter processing nutrient regeneration; decomp What restoration designs can address: Controlling factors Floodplain connectivity Channel morphology & interaction with flow Channel complexity & retentiveness Riparian vegetation Energy inputs organic matter, sunlight Streambed D 5, D 5 /D 84 Sediment transport Flow regime frequency, intensity of floods & baseflows Location Palmer of Source June 6Populations, Cumulative Watershed Impacts Options Why include functional measures? They assess how ecosystems work, recognizing that processes support structure Need for additional tools for water resource managers Belief that function may be a better measure of resilience (e.g., Schindler, D.W. 99. Oikos 57: 5-4) May indicate direction of change after restoration function MUST come back before structure (so may detect change more rapidly due to species redundancy, we may be able to determine that management practices are working more quickly than if we wait for a species to return) More integrative, less variable 3

4 Is there an ideal level of functioning?? No the ideal goal is to get: Biophysical processes within the range of natural variability for least impacted systems so, the river system provides ecosystem services supports native flora and fauna is more self-sustaining Most likely when focus is on restoration of dynamic processes (e.g., river-floodplain reconnection) Activities should minimize physical disturbance and harm to native vegetation Activities should avoid channel designs or hardening that could force river adjustments up- and downstream Acknowledge Palmer June it may 6take time What supports stream Ecosystems? Autotrophic vs. Heterotrophic systems SUN: autochthonous streams = primary production. OM inputs: allochthonous streams = inputs like leaves 4

5 The River Continuum Concept Heterotrophy System is supported by breakdown of OM C 6 H O O 6 H O + 6 CO + energy animals, fungi, plants, most bacteria aerobic or anaerobic decomposition 5

6 Allochthonous streams Organic matter inputs are the primary energy source animals, fungi, plants, most bacteria break the OM down, making energy available for higher trophic levels Sources/Types of OM Coarse-Particulate Organic Matter (CPOM) Fine Particulate Organic Matter (FPOM) Dissolved Organic Matter (DOM) 6

7 Controls on OM Processing Leaf chemistry (species) Invertebrate Activity Microbes Water Chemistry Breakdown of CPOM: start to finish 7

8 Leaf Chemistry & Decomposition C:N high C:N means lower decomposition Secondary Compounds Tannin Tannins Polyphenolics Alkaloids Lignin Nutrients N, P, micronutrients Leaf Chemistry and Decomposition C:N high C:N means lower decomposition Secondary Compounds Tannins, Polyphenolics, Alkaloids, Lignin Nutrients N, P, micronutrients willow birch alder Haapala et al., 8

9 Invertebrate Processing of POM Functional Feeding Groups Grazers and scrapers consume algae and biofilm from stones and other surfaces Shredders consume leaves with their associated microbes Collector-gatherers consume fine particles of OM from the water column (suspension-feeders) and from the stream bed Predators feed on smaller macroinvertebrates Importance of shredders & fungi in OM processing Sponseller & Benfield,, JNABS Hieber & Gessner, 9

10 What happens if you reduce CPOM? Study of litter exclusion in headwater streams in N.C. Wallace et al., 997 Change Quality of CPOM? Less phenols & more lignin at senesce Elevated CO leads to lower quality litter C:N phenols lignin Tuchman et al.,

11 Decomposition as a metric of ecosystem function? integral to food web in stream ecosystems represents the flow of energy through the heterotrophic part of the ecosystem OM processing is linked to downstream consumption and biogeochemistry Quantification of decomposition rates yields an integrative measure of ecosystem function Litter Decomposition Rates in northern Sweden streams Reference = forested watersheds Restored = walls removed, banks regraded, natural wood input allowed Channelized = rock walls and homogenous streambed Lepori et al. 5. Journal of Applied Ecology Volume 4 Page 8

12 Litter Decomposition Rates in northern Sweden streams Näreträskbäcken Vatjokbäcken Storkvarnbäcken Videbäcken Krycklan Vällingträskbäcken Dergabäcken Abmobäcken Staggbäcken Tannbäcken Ramsan Maltan Channelized Restored Reference (degraded) (undegraded) Leaf mass loss (%) 5 Lepori et al. 5. Journal of Applied Ecology Volume 4 Page 8 Shredder richness Channelized Restored Reference Shredder abundance Channelized Restored Reference Litter Decomposition Rates Agricultural vs. Urban Headwaters This work and others show that in general excess nutrients and elevated flows enhance breakdown Decomposition Rate (k) vs. % Ag y =.x +.9 R = Palmer et al. unpub Decomposition rate vs. % Dev (Urban) y =.66x -.6 R = Palmer.8 June 6 Palmer et al. unpub Meyer et al. 5. JNABS, Vol 4

13 Setting aside the detritivorous fish and insects why is OM important in streams? It plays a huge role in biogeochemical processes such as production and nutrient processes! Moving on to production Whole Stream metabolism Autotrophic System is supported by photosynthesis 6 CO + 6 H O + light C 6 H O O Autotrophs: algae, macrophytes, bacteria Heterotrophic System is supported by microbial respiration (breakdown) of organic matter C 6 H O O 6 H O + 6 CO + energy animals, fungi, plants, most bacteria aerobic or anaerobic decomposition 3

14 Biofilm is a gel-like substance and is a mixture of sugars, enzymes, diatoms (attached and loose), bluegreen algae, bacteria, fungus, microinvertebrates i.e., protozoans and early stages of insects. It absorbs Dissolved Organic Matter (DOM) from the water and collects Fine Particulate Matter (FPOM) in the matrix. PRIMARY SITE OF PRODUCTION & HETEROTROPHIC METABOLISM Benthic primary production and whole stream metabolism CONTROLS: Amount of sunlight Nutrients (ratio of N: P: C) Flow Temperature Herbivory Biofilm on rocks Measuring benthic production:. Biomass accural on tiles (measure chlorohpyll). Palmer Measure June 6 diel changes in oxygen by deploying sondes with O probe 4

15 Diel Δ oxygen method for measuring primary production (if we only had photosynthetic organisms) GPP* = NPP + respiration of O produced due to photosynthesis during day (oxygen is released in the light but some also used by respiration which you estimate using night measurements) produce O Algae Macrophytes of all O consumption during night time (oxygen taken up in the dark) use O Algae but Microbes, inverts, fish also use O so we really estimate community respiration 3. Whole stream metabolism method at reach scales NDM* = GPP community respiration Average daytime O production (includes losses due to heterotrophic respiration) 8. Average night-time O use Dissolved O diel curve used to estimate whole stream metabolism* O (mg/l) TIME *Net Daily Metabolism or Whole Stream Metabolism = the net oxygen change per day resulting from biological activity; it takes into account the costs of autotrophic & heterotrophic production 5

16 Method Sondes deployed upstream & downstream to measure dissolved O for 48 hr Determine re-aeration coefficient using a propane evasion experiment Hydrolab mini Sonde (temp, conductivity, ph, O, etc). Now plot oxygen use per unit time and stream length When change in oxygen = then there is no Net Production (respiration = production) Mg/L 7. Mg O L - hr Respiration CR (measured at night) : : 4: Time (hr) GPP 6

17 GPP - highest in biomes with little riparian vegetation; lowest in forested biomes - land-use influences GPP across all biomes, with agriculturally influenced sites having higher rates than urban-influenced or reference sites CR - highly variable within and among biomes but often positively correlated with watercolumn nutrient concentrations and stream transient storageacross all biomes. Prairie stream in Kansas Forested stream in Tennessee Ratio of Pre vs. Post restoration Production and Respiration in Restored (dark bars) vs. Degraded streams* 4 3 PRODUCTION a) winter Control (n = 4) Manipulated (n = 4) * a) winter MS RESPIRATION * GPP A:B ratio b) spring c) summer d) autumn MS * Respiration A:B ratio 3 b) spring 4 c) summer 3 MS 4 3 d) autumn * Control (n = 4) Manipulated (n = 4) *Effects of in-stream restoration on ecosystem metabolism in headwater streams along a gradient of upland soil and vegetation disturbance. Brian Roberts Pat Mulholland, and Jeff Houser * * ** 7

18 Measuring Decomposition (litter bags, leaf packs) W t = W o e -kt Where W t = weight (mass) at time t, W o = initial mass And k is the rate coefficient (units are /time usually days) Log e (mass) days 8

19 How do you know the right direction to push (restore) a stream? window of natural variability Ecosystem Function Restoration Time Space 9