12-14: Soils Flashcards

Question

Wherever you go, how many organisms will be the same in the soil?

Answer 1

909 | Eg. clay, sandy, organic etc

Answer 2

88 endangered | 17 extinct

Answer 3

``` Introduction of invasive species Soil sealing (building over land) Climate change Organic matter decline Extensive human exploitation ```

Answer 4

Decrease diversity in soil functional groups (eg. earthworms) Decrease the average number of trophic levels in the soil food web

Answer 5

Redundancy hypothesis Rivot hypothesis Idiosyncratic hypothesis

Answer 6

Can lose a species as long as there are others that can do the same job

Answer 7

All species have a role If you lose one, there will be a drop in function If you lose too many, the whole system will collapse

Answer 8

It depends on which species you lose- some have a bigger impact

Answer 9

Keystone species | Engineer species

Answer 10

Alter material transfer via trophic relations Impact on community composition Eg. Enchytraeid worms

Answer 11

Influence ecosystem processes through physical disturbance | Eg. moles and earthworms

Answer 12

Idiosyncratic

Answer 13

Grew birch in sterilised soil Added microbes to some Increased growth and nutrient content when microbes present Fewer fungal taxa = slower rate of decomposition and lower N availability in soil Significant decline if under 10 species Supports REDUNDANCY theory

Answer 14

Manipulated the complexity of soil systems Less simplistic than boreal forest one 3 systems, one with microfauna, one with micro and mesofauna, one with micro, meso, and macrofauna No detectable effect of soil biodiversity on aboveground plant productivity- REDUNDANCY After 9 months, different plants growing in different soils- affects plant community

Answer 15

Tested in field Soil samples from most major ecosystem types Assessed bacterial and fungal diversity, measured soil functions eg. nutrient cycling Multifunctionality index calculated Abiotic and biogeographic factors found to be as important as microbial diversity Positive relationship between bacterial diversity and eco. multi. Lose diversity of soil = decline in system function

Answer 16

Moisture, temperature Competition for nutrients, light, water, space Allelopathy Dispersal

Answer 17

Chemical inhibition of one plant by another due to release of substances acting as germination/growth inhibitors

Answer 18

Direct- via root herbivores, pathogens, symbionts | Indirect- through effect of soil decomposer subsystem on supply of nutrients

Answer 19

Used a mesocosm- outdoor experiment system, natural environment under controlled conditions Looked at 20 species in a developing community Reducing dominant grasses and increasing herbs increases diversity Some with AM, some without After 6 months, +AM 50% herb seedlings survive vs -AM 18% +AM 23% were over 5mm height, -AM was 0% So AM fungi promotes plant diversity

Answer 20

Different AM fungi induce different growth responses in plants- species specific Manipulated AM species in grassland (mesocosm) Each plot had randomly selected AM from pool of 23 species, gradient of 1 to 14 species Each replicate had different combinations of AM, so effects were independent of which species added Found that AM diversity enhances plant diversity and productivity Increased AM diversity = greater P uptake by plants, enhanced plant biomass AM diversity promotes ecosystem function

Answer 21

Looked at the 3 coastal succession zones- marram grass is first, degraded and replaced, then changes as closer in land Theory that degraded marram grass is associated with the build up of host specific pathogens in stable dunes Festuca (another plant) is favoured when marram is exposed to soil pathogens Planted Ammophila and Festuca in sterilised vs unsterilised soil Transplanted soil of each species Growth of ammophila was lower in unsterilised than sterilised soil Growth of festuca was not reduced in unsterilised soil from ammophila Ammophila was out-competed by festuca in non-sterilised soil So soil pathogen-driven competition is an important mechanism in the succession of fordune vegetation

Answer 22

Theory that rare plants accumulate pathogens that limit their growth Highly invasive plants modify soil biota to promote their growth Found that rare plants show negative feedback in own soil, whereas invasive show positive- ie. invasive perform better in own soil, rare perform worse (compared to other soils)

Answer 23

Crop rotation

Answer 24

Parasitic plants stimulate microbial activity and nutrient cycling Hayrattle infects fast-growing grasses, reducing their competitive dominance Root death and C leakage = stimulates microbes So enhanced N cycling and plant N supply More nutrients! But bad for farmers as less grass for livestock

Answer 25

Theory that tannic acid production from pine litter controls N release as organic N- used by dominant pine trees Tannins enhance production of dissolved organic nitrogen (DON), inhibit availability of inorganic N Pine trees control soil N availability to benefit their growth and competitive ability in N limited ecosystems

Answer 26

How slow-growing herbs and fast-growing grass coexist in alpine meadows Herb increases soil microbial activity, less N available