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Lecture 6

REN R440 Lecture 6: Guest
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Department
Renewable Resources
Course Code
REN R440
Professor
Nadir Erbilgin

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Ren R 440: Guest lecture
Ecological impacts of forest diseases
-can be applied to most situations where large numbers of trees die (forestry, insect outbreaks etc.)
-physical characteristics defining structure and altering microclimate: vertical stratification (can have
different amounts of vertical structure, more continuous or just one layer), horizontal structure
(gradients as you go through the forest), temperature, humidity (shading from veg, less
evapotranspiration)
-tissue chemistry and biomass contribute to ecosystem processes: nutrient cycling, primary productivity
(accumulation of plant biomass, carbon sequestration increases with pp)
-trees as foundation species: create and define an entire ecological community by virtue of their
structure and functional attributes, primary producers, locally and regionally abundant, create stable
conditions that support many other organisms, not keystone species (don’t have to be abundant, just
have to be present and have significant impacts on ecosystem even in small numbers eg wolves)
-directly and indirectly impact ecosystem function (by supporting other species)
-high mortality severs ecological linkages between trees, other organisms and ecosystem functions, or if
it doesn’t sever them, changes them down the road
-diseases can alter ecosystem functions, change the habitat for secondary species, will recover but not
necessarily with the same species
-pathogens can be ecosystem engineers/ regulators, indirectly alter the resource availability for other
species and alter the abiotic environment
-disease induced mortality can alter light levels (opening up of cover from loss of trees), stand hydrology
(more light so more evaporation from soil, plants evaporate water from the soil so if large numbers of
trees die, less water being pulled from ground water so ground water table will rise), nutrient cycling
(increased temperature causes increased decomposition and release of minerals to soil)
-pathogen comes through and kills hemlock, area increases radially with time, occurs in nitrogen poor
soil, so were trees died, light levels increase, so soil nitrogen mineralization/availability increases, so
hemlock regeneration with increased vigor, nutrition leading to disease resistance, so part of cycling
-disease associated stress and mortality can help define species spatial distributions
-especially important for regeneration layer: see Janzen-Connell hypothesis majority of seeds fall close
to tree producing the seeds, but survivability of seedlings increases further from tree, this is because of
the pathogens occupying the roots of the parent tree, killing the seedlings near the roots of the parent
tree, so less pathogen density further from the tree, the pathogens are driving the spatial distribution of
these trees
-diseases can impact the local genetics of a tree population as only resistant trees remain in infected
sites, susceptible trees are forced to grow in drier areas where the bacteria doesn’t grow shows effect
on species distribution
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Description
Ren R 440: Guest lecture Ecological impacts of forest diseases -can be applied to most situations where large numbers of trees die (forestry, insect outbreaks etc.) -physical characteristics defining structure and altering microclimate: vertical stratification (can have different amounts of vertical structure, more continuous or just one layer), horizontal structure (gradients as you go through the forest), temperature, humidity (shading from veg, less evapotranspiration) -tissue chemistry and biomass contribute to ecosystem processes: nutrient cycling, primary productivity (accumulation of plant biomass, carbon sequestration increases with pp) -trees as foundation species: create and define an entire ecological community by virtue of their structure and functional attributes, primary producers, locally and regionally abundant, create stable conditions that support many other organisms, not keystone species (don’t have to be abundant, just have to be present and have significant impacts on ecosystem even in small numbers eg wolves) -directly and indirectly impact ecosystem function (by supporting other species) -high mortality severs ecological linkages between trees, other organisms and ecosystem functions, or if it doesn’t sever them, changes them down the road -diseases can alter ecosystem functions, change the habitat for secondary species, will recover but not necessarily with the same species -pathogens can be ecosystem engineers/ regulators, indirectly alter the resource availability for other species and alter the abiotic environment -disease induced mortality can alter light levels (opening up of cover from loss of trees), stand hydrology (more light so more evaporation from soil, plants evaporate water from the soil so if large numbers of trees die, less water being pulled from ground water so ground water table will rise), nutrient cycling (increased temperature causes increased decomposition and release of minerals to soil) -pathogen comes through and kills hemlock, area increases radially with time, occurs in nitrogen poor soil, so were trees died, light levels increase, so soil nitrogen mineralization/availability increases, so hemlock regeneration with increased vigor, nutrition leading to disease resistance, so part of cycling -disease associated stress and mortality can help define species spatial distributions -especially important for regeneration layer: see Janzen-Connell hypothesis majority of seeds fall close to tree producing the seeds, bu
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