Andy Moldenke - Insects in Early Seral Habitats


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Andy Moldenke - Insects in Early Seral Habitats

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  • 30 m buffer (100ft buffer in SH ranger district)
  • Chose 4 forest-floor invertebrate groups Intended to represent a broad range of functional groups: herbivores (weevils and gastropods), predators (other beetles and spiders), detritivores (millipedes) 34 families in all Some are known to be useful indicator taxa (carabids),taxonomy well known (lycosids) Mollusks chosen because over 40 gastropods on the survey & manage list associated with the NW Forest Plan. Millipedes because they’re an important functional group
  • Sampling design. Each site had a transect on either side of the stream, with pairs of traps at 1m, 5m, 10m, 20m, 50-70m from the stream. Traps offset, so no two traps closer than 10m to each other. This meant that at buffer site, first four rows of traps were within the buffer, 70 m traps were in the clearcut. Trapping conducted in 6 discrete 2-week sampling periods, between August 2000 and July 2002
  • I’m going to be showing a series of ordinations (Alan will have explained?) The data that went into these ordinations is a matrix of species by sample units. Using combined data from all sampling periods, adults to species only.
  • Again, same ordination as previous slide, but missing 5m distance. I created 3 (arbitrary) microclimate classes again, and the two ends of the horizontal axis are distinctly cool/humid or warm/dry, with some mixing inbetween. Range was much larger (18.0-44.1 C, 16-93%RH) than for forests only (18-31 C, 30-95%RH) Those samples in Swamp Peak buffer were warm/dry, and the samples circled in green are all clearcut 1m distance—span the range of microclimate classes (talk about near-stream vegetation BP vs. 2G) There were 3 shared indicator species for cool/humid and forest/buffer (3 beetles, one spider, one snail, one millipede), and 14 shared species for warm/dry and clearcut (6 beetles, 10 spiders)(no medium indicators) So, it does appear that having a riparian buffer is a more effective management treatment than harvesting to the stream edge for preserving the riparian forest community, but to how similar are the forest and buffer?… So microclimate does seem to be strongly associated with these distributions. Gradient from stream-side to forest/buffer to clearcut. How similar are the forest and the buffer?
  • This ordination shows 75 sample units in all 3 treatments Samples are coded a different color for each treatment, the 70 m samples from buffer sites are coded as clearcuts. Samples at 1 m from the stream (in all treatments) are unfilled triangles. Again, you see elevation driving the ordination along the vertical axis. Now, I’ve rotated the ordination so that treatment is aligned with the horizontal axis. The green clearcut samples are all at one end of the axis, while forest and buffer sites are more mixed together on the left side of the ordination. Interestingly, the samples at 1 m distance from the stream are almost all at the extreme left side, this includes samples from all treatments. Two of the clearcut samples from next to the stream do not cluster with the rest. Also evident that at higher elevations, buffer and forest are more separate (vertically, diagonally?) Partially, due to a windthrown buffer…
  • I’ve paired up the forest and buffer sites for each block, and lifted them right out of the ordination. This is just purely a visual analysis When we look at the individual block pairs of real data, no clear pattern emerges. In 2G, there appears to be no stream effect in the forest (because it’s a flat site, and seepy damp areas up to 10 m from stream?), while in the buffer, 5,10, and 20m samples are close together, but quite a bit further on the right of the axis. In MM, very similar patterns. SP also pretty similar, although the whole buffer transect is shifted to the right. TC quite similar. BP, more of stream effect in the forest. All in all, although this is all just visual, doesn’t show much effect at a community level I did an Indicator Species Analysis with buffer and forest as groups, and there was one millipede forest indicator, and 4 spider buffer indicators (two of which are very abundant in clearcuts). Might be good to look at some individual species…
  • Andy Moldenke - Insects in Early Seral Habitats

    1. 1. Bug Communities and Forest Structure Modification Andy Moldenke Carolyn Ver Linden
    2. 2. Bugs, bugs, bugs and more bugs! “Bugs rule!!”
    3. 3. Shade versus sun <ul><li>On an individual species preference basis: </li></ul><ul><li>Climatic </li></ul><ul><ul><li>Bombus mixtus </li></ul></ul><ul><ul><ul><li>Thermoregulation – easier to locomote in open-canopy environment </li></ul></ul></ul><ul><ul><li>Eukiefferiella spp (flying adults) </li></ul></ul><ul><ul><ul><li>Visibility – easier to find mate in open-canopy environment </li></ul></ul></ul><ul><li>Resource </li></ul><ul><ul><li>For both, easier to find more food </li></ul></ul>
    4. 4. <ul><li>Individual species preference basis: </li></ul><ul><ul><li>Is this interesting only for ‘endangered’ species? </li></ul></ul><ul><ul><ul><li>(after all who cares about a single species of arthropod?) </li></ul></ul></ul><ul><ul><ul><li>Bombus mixtus is probably a ‘keystone species’ </li></ul></ul></ul>
    5. 5. Shade versus sun <ul><li>On a functional guild preference basis: </li></ul><ul><ul><li>Herbivores prefer sunny conditions </li></ul></ul><ul><ul><ul><li>More photosynthesis </li></ul></ul></ul><ul><ul><ul><li>More young leaves </li></ul></ul></ul><ul><ul><ul><li>More broadleafed plants </li></ul></ul></ul><ul><ul><ul><li>Higher caloric status </li></ul></ul></ul><ul><ul><ul><li>Lower % poisonous secondary compounds </li></ul></ul></ul><ul><ul><ul><ul><li>(but less nitrogen) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>(but higher vertebrate predator populations) </li></ul></ul></ul></ul>
    6. 6. Shade versus sun <ul><li>A whole taxon preference basis: </li></ul><ul><ul><li>Bees </li></ul></ul><ul><ul><ul><li>Nesting requirement = sunny bare ground </li></ul></ul></ul><ul><ul><li>Jumping spiders </li></ul></ul><ul><ul><li>Wolf-spiders </li></ul></ul><ul><ul><ul><li>Visual pursuit hunting diurnal predators </li></ul></ul></ul><ul><ul><li>Butterflies </li></ul></ul>
    7. 7. <ul><li>Whole taxon basis: </li></ul><ul><ul><li>Bees </li></ul></ul><ul><ul><li>Responsible for pollination </li></ul></ul><ul><ul><li>Responsible for fruit/seed resource (vertebrate food) </li></ul></ul><ul><ul><li>Diurnal activity </li></ul></ul><ul><ul><ul><li>Responsible for shift from mammals & amphibian predators to birds and reptiles </li></ul></ul></ul>
    8. 8. Shade versus sun <ul><li>Total community species richness basis: </li></ul><ul><ul><li>On a localized basis, much higher in early succession </li></ul></ul><ul><ul><li>Basic reason: </li></ul></ul><ul><ul><ul><li>Nearly all closed-canopy taxa PLUS open-canopy obligates too (if not trashed) </li></ul></ul></ul>
    9. 9. Shade versus sun <ul><li>Continental-scale distribution of </li></ul><ul><li>Madrotertiary and Arctotertiary biota: </li></ul><ul><li>Glacial cycles of migration of taxa </li></ul>Add north america map
    10. 10. Californian biota – summer-dry adapted; thermophilic; largely open-canopy preference <ul><li>Prefer: </li></ul><ul><li>open-canopy meadows </li></ul><ul><li>savanna (oak & ponderosa) </li></ul><ul><li>Willamette Valley grasslands </li></ul><ul><li>(often disturbance & fire-adapted) </li></ul><ul><li>(not very important in mesic west-side Douglas-fir forests) </li></ul>
    11. 11. <ul><li>The macroevolutionary scale: </li></ul><ul><ul><li>Evolutionary plug for open-canopy species </li></ul></ul><ul><ul><ul><li>Small populations </li></ul></ul></ul><ul><ul><ul><li>Rapid local extinctions </li></ul></ul></ul><ul><ul><ul><li>Northern edge of species distributions </li></ul></ul></ul><ul><ul><ul><li>Important for: adaptation to climatic changes </li></ul></ul></ul><ul><ul><ul><li>exposure to novel biotic interactions </li></ul></ul></ul><ul><ul><ul><li>(with both native & introduced taxa) </li></ul></ul></ul>
    12. 12. Ecosystem function changes with clearcutting <ul><li>#1 – Changing the position of the photosyn- </li></ul><ul><li>thetic biomass (canopy to herb/shrub layer) </li></ul><ul><ul><li>and changing the edibility of the photosynthetic biomass (awful distasteful evergreen needles to short-term edible deciduous leaves) </li></ul></ul>
    13. 13. <ul><li>This change in plant species composition results in a HUGE change in the species composition of animals – and their biomass increases (because of increased edibility of food) </li></ul>
    14. 14. Opening the canopy Open-canopy Forest
    15. 15. <ul><li>Functional guild basis: </li></ul><ul><ul><li>Herbivorous caterpillars </li></ul></ul><ul><ul><ul><li>Joan’s birds run on herbivorous caterpillars </li></ul></ul></ul><ul><ul><li>Collector/gatherer aquatic midges + </li></ul></ul><ul><ul><ul><li>Flycatchers and bats; and fish too </li></ul></ul></ul><ul><ul><ul><ul><li>(and more important things like web-spinning spiders too) </li></ul></ul></ul></ul>
    16. 16. Opening the canopy Open-canopy versus closed-canopy foodwebs
    17. 17. How open is open? <ul><li>Effect of 1 acre gap openings </li></ul><ul><li>Forest Canopy </li></ul><ul><li>Indicator Species 11% </li></ul><ul><li>Open Canopy </li></ul><ul><li>Indicator Species 42% </li></ul><ul><li>The presence of open canopy species is logical (even though the gap is very small; but the % is surprisingly high!) </li></ul>
    18. 18. Ecosystem function changes with clearcutting <ul><li>#2 – Fundamental alteration of soil water </li></ul><ul><li>relations </li></ul><ul><li>Trees (all plants, but especially trees) are like fountains pumping water out of the ground and back into the atmosphere </li></ul>
    19. 19. Remove the trees (w of the mountains) and there is plenty of water to go around during the summer months <ul><li>Plants can fix photosynthetic carbon all summer long (instead of shutting down in August-September) </li></ul><ul><li>Soil microbes have water so they can metabolize all summer long (and the bugs that eat them also) – so they can provide nutrients for plant growth all summer long </li></ul><ul><ul><li>(no stop/start as in control forested sites) </li></ul></ul>
    20. 20. You have to judge by ‘ecological function’ <ul><li>In a thinning the flush of annual vegetation is initially mineralized (decomposed) at the start of the fall rainy season – the pulse of soluble nutrients are picked up by the remaining tree roots and mycorrhizae </li></ul><ul><li>(more available; nothing lost – good + good) </li></ul><ul><li>In the clearcut ( especially if followed by a hot burn and herbicides ) there are few/no live roots to absorb the fall nutrient flush – nutrients are lost to ground water </li></ul><ul><li>(more available; most lost – good + bad) </li></ul>
    21. 21. Opening the canopy <ul><li>Open versus closed canopy faunas </li></ul><ul><li>1. many years of Andrews Forest studies reveals that the two are nearly entirely distinct </li></ul><ul><li>2. both faunas VERY diverse </li></ul><ul><li>3. about 50% of species of total arthropod fauna of forested regions is restricted to the short temporal windows (15-30 yrs.) of open canopy </li></ul><ul><li> WOW! Surprising! </li></ul>
    22. 22. Opening the canopy <ul><ul><ul><ul><ul><li>Species Richness Total Abundance </li></ul></ul></ul></ul></ul><ul><li>Forested Canopy 318 9575 </li></ul><ul><li>Clearcut 489 7942 </li></ul><ul><li>(per 250 samples each) </li></ul><ul><li>Clearcuts are unsightly-- </li></ul><ul><li>but clearcuts very speciose </li></ul><ul><li> clearcuts very productive </li></ul>
    23. 23. <ul><li>Total species richness basis: </li></ul><ul><ul><li>Spiders: ½ of total fauna only in first 15 years post-harvest </li></ul></ul><ul><ul><li>Bees: 1-2 under closed-canopy versus 250 post-harvest (other groups too: butterflies, grasshoppers, etc.) </li></ul></ul><ul><ul><li>Pitfall-trapping fauna: richness increases 1.5 – 2.0x. </li></ul></ul>
    24. 24. Aquatic environments <ul><li>Density and biomass of emergent aquatics increases (1.5-2.5x)(fixed sunlight) </li></ul><ul><li>Biggest response is in Diptera (esp. midges, not EPTs) </li></ul><ul><li>Richness shows very modest increase </li></ul><ul><ul><li>(few, if any, forest canopy taxa are lost entirely) </li></ul></ul><ul><ul><li>(in contrast with terrestrial fauna, little turnover in species) </li></ul></ul><ul><ul><li>(more emergent biomass results in higher percentage of predaceous species) </li></ul></ul>
    25. 25. Ecosystem function changes with clearcutting <ul><li>Canopy removal increases light </li></ul><ul><li>Allows plants to fix more energy </li></ul><ul><li>Allows plants to make flowers & fruits </li></ul><ul><li>Canopy removal increases light </li></ul><ul><li>Allows air temperature to increase for cold-blooded </li></ul><ul><li>insect activity of pollinators </li></ul><ul><li>Logging disturbance provides nesting opportunities </li></ul><ul><li>Plants get pollinated </li></ul><ul><li>Seeds & fruits provide additional resources for vertebrates </li></ul>#3 – Pollination of the flora (& reproduction)
    26. 26. So… open- and closed-canopy bugs are different <ul><li>What makes any one open-canopy stand ‘better’ than any other? </li></ul>
    27. 27. <ul><li>Predaceous species respond in basically the same manner to all types of canopy openings (probably the same as most vertebrates species) </li></ul><ul><li>The driving environmental variable is productivity (total photosynthetic biomass; deciduous/conifer ratio) </li></ul><ul><li>native predators; introduced predators; individual plant species present – no difference </li></ul>
    28. 28. <ul><li>For herbivores and shredders it is a different story: </li></ul><ul><li>Amount and species of CWD and types of individual plant species are crucial for determining insect assemblages. </li></ul>
    29. 29. Let’s hear it for ‘clearcuts’! <ul><li>industrial-grade clearcuts with low-to-moderate burn site prep have the highest diversity of insects (esp. if some slash is piled) </li></ul><ul><ul><li>Usually highest herbaceous component </li></ul></ul><ul><ul><li>(burn removes litter) </li></ul></ul><ul><ul><li>Greatest growth rate of shrubs </li></ul></ul><ul><ul><li>(burn mineralizes nitrogen) </li></ul></ul><ul><ul><li>Best pollination and seed set </li></ul></ul><ul><ul><li>(burn produces bee nesting sites) </li></ul></ul>
    30. 30. However, <ul><li>If burn is too hot </li></ul><ul><li>If legacy of dead wood is not left </li></ul><ul><li>If herbicides are used </li></ul><ul><li>then legacy is gone </li></ul><ul><li>introduced weeds/pests flourish </li></ul><ul><li>erosion ensues </li></ul>
    31. 31. Caveat: <ul><li>Nearly all post-harvest changes have short half-lives, BUT </li></ul><ul><li>1) ‘Natural’ post-harvest foodweb change shifts system towards more bacterial-based energy flow. </li></ul><ul><li>2) If soil ecosystem is shifted too far towards a bacterial-based foodweb, then a certain class of microbes may develop which prevents the recolonization of ectomycorrhizal fungi and subsequent conifer recolonization. </li></ul>
    32. 35. Riparian Zone Fauna Composition <ul><li>How far does riparian influence extend away from stream? </li></ul>
    33. 36. Riparian Hotspots <ul><ul><ul><li>Species Richness Total Abundance </li></ul></ul></ul><ul><ul><ul><li>Forest Floor 13.6c 32.6c </li></ul></ul></ul><ul><ul><ul><li>Veg break 15.8b 44.4b </li></ul></ul></ul><ul><ul><ul><li>Riparian 19.0a 65.6a </li></ul></ul></ul><ul><ul><ul><li>(p = <0.004) (p=<0.00001) </li></ul></ul></ul><ul><ul><ul><li>(Green Peak – August) </li></ul></ul></ul>
    34. 37. Forest floor Riparian Riparian Zone Fauna Composition
    35. 38. Riparian Zone Fauna Composition <ul><li>Indicator species numerous </li></ul><ul><li>Example: Pterostichus crenicollis </li></ul><ul><li>Big, easy to identify, abundant, widespread </li></ul><ul><li>geographically, active most of the year </li></ul><ul><li>With several such indicator species, can assay for </li></ul><ul><li>effect of management activities in riparian zone </li></ul><ul><li>(=extra margin of safety for aquatic portion) </li></ul><ul><ul><li>(fish lobby; drinking water) </li></ul></ul>
    36. 40. Forest-floor invertebrates: Spiders Beetles Mollusks Millipedes
    37. 42. <ul><li>Individual species preference basis: </li></ul><ul><ul><li>Is this interesting only for ‘endangered’ species? </li></ul></ul><ul><ul><ul><li>(after all who cares about a single species of arthropod?) </li></ul></ul></ul><ul><ul><ul><li>Bombus mixtus is probably a ‘keystone species’ </li></ul></ul></ul>
    38. 43. Forest (97 species) 1 m 5-70 m (2 species) (1 species @ 20 m) F. Köhler Distance from stream 1m 5 m 10 m 20 m 50-70 m Total r 2 = .92 Axis 1 = .12 Axis 2 = .66 DISTANCE ELEVATION
    39. 44. Management treatments Microclimate classes 18.0-23.9 C 45-93% RH 24.0-31.9 C 31-61% RH 32.0-44.1 C 16-36% RH Cool/humid (6 species) Warm/dry (16 species) AIR TEMP SOIL TEMP % RH
    40. 45. Buffer/Forest (9 species) Clearcut (19 species) Management treatments (134 species) Total r 2 = .84 Axis 1 = .18 Axis 2 = .51 Buffer Clearcut Forest
    41. 46. Buffer vs. Forest edge effects? 2G SP MM Edge effect Stream effect TC BP Buffer Forest