ENVS 151 - midterm

Facilitation vs inhibition models of disturbances

Facilitation - pioneering plants create the abiotic conditions needed for the next seral stage of succession.

Inhibition - pioneering plants soak up all the resources and inhibit the next level of succession. Disturbance regime rattles this cage, allowing for later succession species to move in.

Stakeholder motivations besides biodiversity

improves ecosystem services: flood protection, water quality, benefits to fisheries etc. Public access to nature. Complying with legislature.

Hyrdochory and Serotiny

Seeds dispersed by water and seeds dispersed by fire

Major disturbance regimes

fire, flooding, drought, landslides, tides, seasons, tree fall

What are the differences in key life history traits between early vs. late successional plants?

Early succession plants: fast growing, highly fecund, light demanding, reproduce quickly, spread fast (these plants are highly dominate without disturbance regime)

Later succession plants: Slower growing, can live in low light setting, low fecundity.

Intermediate disturbance hypothesis

Periodic amounts of disturbance creates conditions for high biodiversity. Too much / little lowers biodiversity. Graph shape is a bell curve, biodiversity on y, disturbance frequency on x.

What is habitat heterogeneity and why is it important?

The presence of varying abiotic factors in an ecosystem, creating the conditions needed for a variety of organisms to live. High heterogeneity correlates with high biodiversity.

What are alpha, beta, and gamma diversity?

Alpha - diversity at local scale

Beta - diversity at regional scale

Gamma - diversity at landscape scale

Be able to contrast niche-based assembly rules and neutral theory of biodiversity

Neutral theory - organisms exist in an area randomly, by stochastic chances. All animals in a trophic scale are equal in ecosystem function. (ex. plants exists in a forest randomly, controlled by chance and extinction trends)

Niche based assembly theory - the opposite. It is not random. Species are better suited to live in certain environments than others. They fill a niche which helps to reduce competition and use of resources. (ex. plants in a desert live there because they are drought tolerant)

What are some major hurdles imposed by anthropogenic disturbances on normal successional dynamics?

Fire suppression, channelization and levee erection, soil compaction, pollution, Severity of disturbances (droughts), Deforestation

Be able to distinguish between local vs. landscape-scale drivers of community assembly

local drivers - biotic filters (competition, predation, grazing pressure, mutualism etc) and abiotic filters (temp, light availability, moisture availability, soil pH etc)

landscape drivers - connectivity between patches, patch size (edge effects vs core), Anthropogenic matrix.

What are the major spatial considerations when thinking about the landscape context and restoration?

There must be connectivity to your patch, otherwise how will a desired species be able to return to it. ex. creating a wetland in the middle of a city is likely futile, because it may be difficult for your desired flor and fauna to reach said patch

Be able to relate at least a few of the “myths” of restoration ecology to our discussion of disturbance and recovery at multiple spatial scales.

Carbon copy - Trying to revert an ecosystem to exactly what it was previously. Applies to local scale - Abiotic conditions are likely not the same, meaning the original system may not be the best goal to achieve for a project. Carbon copy myth fails to factor in change

Field of Dreams - If you create the necessary abiotic conditions, species will always return. Need to consider anthropogenic matrix and other connectivity factors which play a role in this

What do we need to consider when choosing a reference system?

Location - how close is it to our restoration site?

Size - Is it big enough to have all levels of ecological succession and all desired ecosystem functions

Conditions - How similar are abiotic conditions between two sites?

Disturbance - How present are humans?

Why is it difficult to pick a reference site?

How do you define pre-disturbed… meaning what is your reference from a historic perspective?

Maybe there is no system that meets all of the desired criteria: large enough, close enough, not disturbed much, similar abiotic conditions etc

In what situations would we not want to use a historical reference system to guide our restoration efforts?

If conditions of our current site have changed so much or are predicted to change (climate change), to the point where our reference site is no longer completely viable for our purposes anymore. In other words the reference site is no longer compatible with our restoration site, despite being historically similar.

What is an alternative stable state?

A ecosystem state that has changed from its historic norm often due to a stressor. Removal of that stressor alone will not revert back an ecosystem to what it was originally (hence the word stable) Ex. novel ecosystem.

Know how to defend the arguments for and against the novel ecosystem concept.

Defense for - Defense for: conditions change - climate change, shifting baseline, hybridization occurs, it may not be financially feasible to revert an ecosystem so its important to consider if its novelty still provides all the ecosystem functions we need and supports biodiversity

Defense against - Can be used as a scapegoat for environmental degradation, hard to define, we have many examples of successful restoration of highly degraded ecosystems.

How are reclamation and remediation different from true restoration?

They really only have one goal in mind (say revegetation) vs true restoration takes a more holistic approach with the aim of returning an entire ecosystem.

Be able to contrast broad restoration strategies from passive to active restoration: natural regeneration, assisted regeneration, and reconstruction. What ecological considerations inhibit the ability of a system to be restored passively?

Passive vs active is a gradient

Natural regeneration - Ex. put up fence so cattle don’t graze on species, allowing it to regrow.

Assisted regeneration - completely remove a competitor and let the other species return on their own (sort of like you create the disturbance regime). ex. remove urchins from kelp beds

reconstruction - Change the hydrology or topography of an area such that traditional abiotic conditions can return an ecosystem can recover.

what inhibits passive restoration - significant / prolonged land use change, removal of disturbance regime, highly altered hydrology/topography

Know the characteristics of wetlands and how they are delineated: level of inundation, soils, vegetation.

Transition zones, making them hard to define.

Inundation - how periodically is a wetlands soil submerged underwater (constantly, daily, seasonally)

Soils - wetlands have highly anoxic soil (low oxygen and hydric) and high amounts of organic matter.

Vegetation - Plants in wetland vary significantly in terms of being obligate vs facultative based on the plants adaptation to inundation and low oxygen levels.

What is meant by obligate vs. facultative wetland plants?

Obligate: They are wetland or upland plants that prefer high or low inundation.

Facultative: Its a gradient, but plants that are accustomed to periodic changes in inundation.

What are the general types of wetlands and how do they differ in periodicity/ salinity?

Salt Marsh: High salinity, daily inundation

Estuary: brackish water, daily inundation

Riparian: fresh water, seasonal inundation

Swamp: fresh water, constant inundation

Vernal pool: freshwater, seasonal inundation

Peat bog: freshwater, constant inundation

Know the major drivers of wetland degradation. 

Land use change (coastal development and ag land - fertile soil)

eutrophication

Why are wetlands important from an ecosystem services perspective?

Major carbon sink: lots of organic matter and anoxic soil means not much of that matter is decomposing - so it all stays underground (swamp - peat- lignite - coal -graphite)

Flood / tidal protection

Water filtration / purification from ag runoff

What’s the most important abiotic factor to restore in wetlands before using other tactics like revegetation?

Hydrology - this drives the inundation periodicity, flow rates, salinity, sedimentation -aka a bunch of abiotic factors

Generally, what tactics do restoration practitioners employ when restoring wetlands? (Week 4)

Altered hydrology - breach levees, dam them to prevent water loss after drained

Altered sedimentation - erosion control using mats, mulch or something, and restore upstream processes

Reduced infiltration - revegetate riparian to flow water flow and increase groundwater infiltration

What is the general policy landscape of wetland regulation (compensatory mitigation, gov agencies involved, Clean Water Act 404)

Clean Water Act 404 - prohibits dredging or filling of navigable waters without permit from USACE

Agencies involved - USACE, EPA, USFWS

compensatory mitigation - Requirement to restore wetlands by companies who do receive permission to dredge/fill

What is mitigation banking and why is it a concerning approach to wetland conservation?

You destroy a wetland and site A, you restore a wetland at Site B often at a high ratio.

Issues:

• the site restored is in a different location (different people reap benefits)

• Site A plays a different role in connectivity that Site B cannot replicate.

• Legislation only requires monitoring of site for 5 years, but ecologically this time line needs to be longer.

Know the important components of heterogeneity at the local scale that drive biodiversity and ecosystem function

Sinuosity: curving nature of river. Allows for more base flow and creates point bars and cut banks

point bar: Areas of slow water flow and high sediment deposit (convex side of river)

Cut bank: Areas of fast moving water and low sediment deposit

Riffle: Shallow areas of river with fast flow, and high O2 rate

Pool: Deeper areas of river with lower flow, and low O2 amount

What is the major disturbance regime associated with riverine systems and why is it important?

Flooding - facilitates seeds that are hydrochory, deposits sedimentation and nutrient into floodplain, inundates plants that have adapted to seasonal inundation.

What are the major anthropogenic disturbances to riverine systems and how do they affect river dynamics / heterogeneity?

Dams - reduce water flow and sedimentation downstream. (Shifts hydrograph right, lower peak discharge, gradual rising and falling limbs)

Channelized rivers / encroachment of riparian - little to no sinuosity which has huge effect on heterogeneity, less base flow infiltration due to reduced river length, faster flow rate, less ground recharge. (Shifts hydrograph left, higher peak discharge, steeper rising and falling limbs, reduced base flow)

What are the key restoration strategies for ameliorating anthropogenic disturbances? Know specifically which effect from disturbance each strategy addresses and some of their limitations / drawbacks.

Dam removal - improves hydrology, takes time, and expensive

Set back levee - allows river to flood a bit, its a compromise (not ideal)

Re-meandering - An attempt to revert a channelized river to its normal sinuosity

Restore riparian and wetlands - reconnect areas cutoff from the channel

Why do the best strategies for restoring lake and marine systems not rely on in-site restoration techniques? Put another way, what are the specific challenges that impede restoration of lakes and marine ecosystems?

• In-site restoration addresses the effects on a system but not the sources. They are band-aids not cures.

• Once a source of pollution or an invasive species has reached an aquatic system it becomes much harder to deal with

What is one in-site strategy for reducing lake eutrophication?

Introduce herbaceous fish to help reduce algae and plant growth before it decomposes.

Add aluminum to water to render the phosphorus inorganic.

Name and describe the major drivers of coral reef degradation.

Warming waters and ocean acidification

What are the general strategies for restoring reefs?

• Establishing substrates

• coral rearing

• spreading gametes

Name and describe the major drivers of kelp forest degradation.

• Sea urchin overpopulation

What are the general strategies for restoring kelp forests?

• urchin control

• adding substrates (rocky reefs)