Unst 180 a 4.18


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Unst 180 a 4.18

  1. 1. “Does management for enhancing recreational values in suburban woodlands affect the intensity of bird predation on canopy-living arthropods?”<br />Erik Heyman & BengtGunnarsson<br />KhanhDuong,MarkGriffith,AliciaMcCuskerUNST 181 A 4/20/2011<br />
  2. 2. History<br /> Previous studies show Insectivorous birds aid in controlling the population of the arthropods on which they preyMany suburban forests are clearing understory for aesthetic and recreation value Increase in leaf damage Ultimately question asked and studied in two Swedish forests <br />
  3. 3. Methods<br />2 similar sites were chosen<br />The Hultaberg site (area 8.0 ha)<br />The Ryaåsar site (7.2 ha)<br />Understory clearance was conducted at both sites<br />4.0 ha at Hultaberg site<br />3.9 ha at Ryaåsar site<br />
  4. 4. Methods: Experimental Procedure<br />44 Oak trees were randomly selected.<br />24 trees were located at the Hultaberg site<br />20 trees were located at the Rya åsar site<br />4 branches were randomly selected for each tree<br />2 low branches (3-5 m above ground)<br />2 high branches (12-15 m above ground)<br />Each height had one plastic anti-bird net<br />
  5. 5. Experimental setup. The experiment was replicated at two sites. Each site was divided in two plots of equal area which were randomly assigned to either understory clearance or no management (control). Bird enclosures were placed in 10-12 trees in each plot, at two height levels in each tree. <br />
  6. 6. Methods: Collection<br />Net-enclosed and control branches were cut and stored in bags<br />Arthropods were collected and preserved<br />All leaves were removed from branches and weighed<br />Control for differences in branch size<br />
  7. 7. Results<br />Arthropod biomass of the six largest orders in relation to experimental treatment and management <br />dotted line - dense understory<br />full line - understory clearance<br />
  8. 8. Results Cont.<br />
  9. 9. Conclusion<br />Insectivorous birds significantly decrease arthropod populations in forest and agricultural ecosystems.<br />Population control of arthropods is higher in the areas with dense understory.<br />Human activity in less dense understory could have disrupted the birds.<br />Negative effects on recreation because arthropod increase tree leaf damage.<br />
  10. 10. Extended and future research suggestion: <br />The effect of human presence on the birds feeding  Times that they feed Where nest are built in correlation to foot trails<br />Density of arthropods around foot trails and human activity<br />
  11. 11. Better Explanation<br />Arthropod- invertebrate with exoskeleton, segmented body and appendages.<br />How many?<br />Wood understory- group of small trees, shrubs and vines that grow under the taller trees. <br />Didn't give any other reasons why the birds left.<br />Example of arthropods<br />
  12. 12. Relevance to Sustainability<br /><ul><li>Reduces pest population of ecosystem.
  13. 13. Allows agriculture and forestry to flourish.
  14. 14. Without birds increase leaf damage has been found.</li>