How do soil biota impact plant communities? Flashcards
Name abiotic characteristics of soil ecosystems
Moisture, temperature, solar radiation, light, space, allelopathy
What are the two major pathways of soil feedback for soil biota to impact plant communities
Direct and indirect
What is allelopathy?
The production of chemicals that are detrimental to neighbouring species
Describe direct soil feedback of soil biota on plant communities
Occurs via root herbivores, pathogens, and symbionts
Describe indirect soil feedback of soil biota on plant communities
Via the effect of the soil decomposer subsystem on the supply of nutrients
What has an increase arbuscular mycorrhizal fungi diversity been shown to result in?
Increased plant diversity
What is the role of mycorrhizal fungi?
Provide phosphorus for plant growth and increase direct nitrogen absorption in collaboration with nitrogen-fixing microbes
Describe the relationship between a plant and mycorrhizal fungi
The fungi penetrates there root of the cell. The plant give the fungi carbon, the fungi extend into the soil, transferring nutrients from the soil to the place
How do arbuscular mycorrhizal fungi lead to increased plant biodiversity?
They increase the survivorship of herbs, reducing the dominance of grasses. There is a more efficient exploitation of soil P reserves.
Why do rare plants show a negative feedback that limits their growth and spread when invasive species show a positive feedback loop?
Invasive species accumulate pathogens more slowly. This enforces their dominance.
How do plants modify the soil biota?
They change the quantity and quality of resources that enter the soil
What are two resources that enter the soil that can affect the soil biota?
Root exudates and plant litter
How can resources entering the soil affect the soil biota?
It can either stimulate or inhibit microbial activity and affect the soil nitrogen availability to plants
Describe the carbon donor hypothesis
AM hyphae network interconnects species and carbon and nutrient supply is shared between herb species
What did a 1998 study conclude about the diversity of AM fungi?
AM diversity enhanced plant diversity and productivity (ecosystem function) because high AM diversity increases external hyphae length.
What did a 1993 study conclude about the degradation of Marram grass?
It degraded as it moves inland due to the build up of parasitic nematodes and soil-borne fungi
What is the name of the marram grass genus suppressed by soil organisms and what species takes over?
Ammophila is suppressed and Festuca takes over
What did a 2002 study find when studying rare and invasive species?
Rare plants showed -tive feedback in their own soil and invasive plants show +tive feedback in their own soil
What did the same 2002 study conclude about soil organisms and their feedback effects?
That soil organisms and their feedback effects strongly influence the relative abundance within a community
What do invasive species do to result in a positive feedback of growth?
Modify the soil biota in a way that modifies their growth
What is DON?
Dissolved organic nitrogen
What did a 1995 study conclude about how conifers have a competitive advantage in boreal forests?
Pine litter increases the ratio of DON to inorganic nitrogen. Pines take up DON by mycorrhizal associations.
Before the 1995 study, what was thought about nutrients used by plants?
That plants only used inorganic forms of nutrients
What was thought of the richness of polyphenols in pine litter?
Would inhibit the availability of inorganic nitrogen and enhance the production of DON.
What have conifers (pines) adapted to and how?
Adapted to nitrogen limitation by monopolised the nitrogen economy
What did Bowman et al (2004) study?
How slow-growing, phenol-rich herbs can coexist with fast-growing grasses in alpine meadows
What did Bowman et al (2004) conclude?
Phenol-rich herb litter increases the soil microbial activity because they are a carbon source for microbes. Microbes uptake nitrogen, reducing the availability. Less N for grasses, reducing their dominance.
How do herbaceous plants in alpine meadows enhance their persistence?
Modifying their environment
