Definitions Flashcards
Complementarity
- descriptor of niche or resource partitioning
- positive effects attributable to mixing species, including facilitation
- the extent to which two or more parts are complementary or fit together without overlap
Stem Biomass Overyielding
the difference in stem biomass between a mixture and the average of its constituent monocultures; equivalent to the net biodiversity effect
Leader height to lateral branch growth ratio
reported for a variety of shade-tolerant conifer species; is the variation from a conical crown in full light to a more umbrella shaped or flat topped form in understory conditions b/c of reduced height growth relative to lateral branch extensions as well as to the death of lower branches
Conifer morphological plasticity
e.g. number of branches per whorl, crown depth, leader height to lateral branch growth ratio
coexistence via relative non-linearity
Chesson (1994) showed that stable coexistence could result from variation in limiting resource when at least one species has a non-linear response to it. i.e. one spp. is a superior competitor for the resource when it is stable, vs one which is superior when its fluctuating
coexistence via successional niche differentiation
driven by two parameters: disturbance rate (return interval and intensity) and successional rate (speed of succession). High disturbance rate + low successional rate = coexistence
The R* rule of competitive exclusion
assumes that all species have access to a resource (i.e. access is not limited by spatial or temporal constraints). after a disturbance, there is a finite window of time where resources are underexploited. if an inferior competitor is successful at colonizing the resource, this transient pulse provides an opportunity for temporal partitioning of the resource
Coexistence via the storage effect
a mechanism of coexistence based on the storage of the benefits that accrue during periods of high recruitment, and this process prevents dramatic population losses during periods of low recruitment
Name the stand development stages listed in the Franklin 2002 review
Disturbance + Legacy Creation (yr 0) Cohort Establishment (20) Canopy Closure (30) Biomass Accumulation/Competitive Exclusion (80) Maturation (150) Vertical Diversification (300) Horizontal Diversification (800) Pioneer Cohort Loss (1200)
Regime Shift (as defined in Raffa et al 2008)
as abrupt changes into different domains and trajectories beyond which prior controls no longer function
Explain how bark beetles change forest structure
Raffa et al 2008:
- bb’s change structure, function and composition; reduced canopy cover -> increased ratios of light loving to shade loving spp. than can persist for decades.
- For mixed stands, conversion to nonhost tree spp. can speed up normal successional pathways; or conversions to nonforest can also occur following severe outbreaks (this may represent threshold changes)
- stand primary productivity goes down initially then increases as surviving plants release
- additionally: increased coarse woody debris, increased stream flow, sig interactions between fire, changes to carbon cycling
name critical thresholds in population dynamics of bark beetles + some internal and external controls for each threshold/stage
Raffa et al 2008
1. Host entry
a. internal: beetle behavior, physiology, host
defense chemistry
b. external: Temp, drought, biotic stresses on host
2. Aggregation
a. internal: resin flow, local beetle density, canopy
density
b. external: drought, biotic stresses on host
3. Establishment
a. internal: induced defenses, attack density + rate,
microbial symbionts
b. external: drought, biotic stresses on host
4. Reproduction
a. internal: phloem thickness, predators,
competitors, microbial symbionts,
beetle physiology
b. external: Temp
5. Stand meso-scale eruption
a. internal: beetle density, stand hetero, host
availability, age, density
b. external: ecophysical processes, stand
dynamics, succession, disturbance
6. Landscape level eruption
a. internal: dispersal, proximity of suitable stands,
landscape heterogeneity
b. external: Temp, geophysical barriers,
anthropogenic activities
7. Regime Shift
a. internal: artificially favorable habitats, altered
selection pressures, access to new
hosts
b. external: anthropogenic activities
compare and contrast the direct and indirect and interaction likelihoods for insects and fire (Siedl et al 2017 paper)
Insects: direct (29.9%), indirect (29.3%), interactions (40.8%)
Fire: direct (63.5%), indirect (25.3%), interactions (11.2%)
Siedl paper got these %s from reviewed literature. most interaction effects occur within <6yrs, direct next, then indirect being the slowest response with most taking >25 yrs
Name common biological mechanisms that drive insect population cycles
- Predator-prey interactions
- Host-disease interactions
- Induction of host-plant defenses or changes in plant nutritional quality
- Intrinsic changes in individual traits
- Changes in population allele frequencies
- Induction of maternal effects
what is the common consensus that causes population harmonic cycles?
Berryman (1978, 2002) harmonic cycles in density of insect populations are the result of delayed, negative feedbacks between the insect and its environment
