Weed Characteristics
What Characteristics would a super weed have? Name at least 3
-high plasticity- velvetleaf can ba 2-10' tall
-quick development- germ to flower- chickweed
-multiple ways of reproducing- seeds, rhyzomes
-broad germination requirements
-broad germination over time
-herbicide resistance
Why is it important to use adaptive management?
Management could lead to unintended consequences so should be evaluated (ex: erosion control leading to invasion). It also leads to more efficient management.
What are four things that determine a population’s size?
Births, deaths, immigration, emigration
What is competition?
The direct or indirect interaction of organisms that leads to a change in fitness when they share a resource such as light, water, or nutrients.
Maxwell 1998- How is the modeling of leafy spurge populations informing management decisions?
Found the most sensitive stage for control was basal bud transition. Also knowing rates to graze sheep, herbicide application rates, density thresholds for cattle grazing.
What is the difference between a simple and creeping perennial? Why are they important to distinguish for management?
Creeping- predominately vegetative reproduction. Informs decisions on whether to till or what herbicide to use.
What is sustainable agriculture?
Integrated system of plant and animal production having site-specific application that will over the long-term:
What is a metapopulation? Why is it important for management?
A population of populations, connected with dispersal. This is important because management can target source populations to better focus methods and go after more plants with less labor.
How does the quality of light impact plant competition for light?
Far red and red light signal different physiochemical processes. The canopy of a forest generally receives more red light and the ground more far-red. So far red light often indicates competition and can lead to plant responses such as inhibiting germination or growing up fast.
Westerman et al 2005- How is a diversified cropping system exemplifying the "many little hammers" approach to weed management?
Four year rotation exposed weeds to many stress factors, better buffered against sudden increases in new weed species with greater weed diversity
Compare and contrast the characteristics of R and K selected species and provide an example weed of each.
K- perennial vegetative growth, fewer seeds, survival focus. canada thistle
R- annual, reproduciton focus, lots of seeds. cheatgrass
Thinking about propagule pressure, what is the relationship between distance from parent plant and probability of establishment? Why is this important to consider for management?
Plants are more likely to establish farther from their parent. This leads to a focus in managing small recruitment satellites with early detection and rapid response.
What is the equation of exponential growth? Logistic growth? What is the predominate difference?
Exponential: dN/dt=rN where r is the rate of growth of species in the population and N is the number of individuals.
Logistic: dN/dt=((K-N)/K)rN where K is the carrying capacity of the population
predominant difference is carrying capacity
What are the two characteristics that make up the competitive ability of a plant? How do they differ? What is an example of each?
Competitive effect- The plant’s offense. Ex: a plant grows quickly or germinates early
Competitive response- The plant’s defense. Ex: plasticity of a plant to grow differently in shade or sun
Merfield 2022: What is the post-herbicide era?
Starting to think about managing weeds without herbicides due to the large problems with their resistance and pollution. Thinking integrated weed managment.
Compare and contrast the seedbanks of an arable field and a secondary forest.
Compare priority 1A and priority 2A/2B weeds
1A should be eradicated. Would use early detection and rapid response. ex:yellow starthistle
2A/B More wide spread, generally focus is on containment
What are the two equations for measuring population growth rates? How do you interpret their results?
Lambda= Nt/N(t-1) greater than 1 growing, less than 1 going extinct, =1 stable
dN/dt=Nt-N(t-1) greater than zero- growing, less than zero going extinct, =0 stable
What is the critical period of weed control and how is it determined? Aside from environmental conditions, why do we see differences in the length of cpwc between crops?
The time period when removing weeds will avoid significant economic loss. It is determined by weeding plants up to and after certain time points and measuring resulting yields. We see differences because there are different competitive abilities of different crops.
Jordan and Vavotec 2004: What are the proposed principles in designing and implementing a weed restoration program?
-spatial and temporal location of weeds is determined by the set of ecological benefits that’s desired from weeds in a particular cropping system
-The farm(or ecosystem) as a whole is the instrument of restoration- pattern analysis
-situating weeds along ecological boundaries my be an important design consideration in determining the advantageous location of weed patches
-refuges from various disturbances may help maintain desirable weed species
-ongoing monitoring and ‘data-poor’ adaptive management are necessary to guide restoration
How does Merfield define a weed?
A plant, or population of plants,
in a specific time and place,
causing significant harm,
either immediately or in the longer term,
based on a holistic analysis of both their positive and
negative attributes
When monitoring, what are the four questions we need to ask and why?
These are important to make sure the management is being targeted to populations that are invasive and causing ecosystem harm and that the management is effective and helping the system.
What is sensitivity analysis used for?
In population modeling it is used to see where in a plant’s life cycle is most susceptible to management.
What is physiological, physical, and morphological
dormancy? What is the advantage of seeds having
dormancy?
Dormancy allows dispersal through time.
physiological- inhibiting mechanisms in the embryo (light, oxygen, moisture)
physical- seed coat impenetrable
morphological- undeveloped embryo needs time to grow
Little et al 2020- What are the four scenarios of the framework on the effects of fertility amendments on weeds? what is an example of each scenario?