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Lecture 3 Soil Engineers Learning Objectives Lecture 3 – Soil Engineers Lecture 3 – Soil Engineers – Explain why earthworms, ants and termites are called.

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Presentation on theme: "Lecture 3 Soil Engineers Learning Objectives Lecture 3 – Soil Engineers Lecture 3 – Soil Engineers – Explain why earthworms, ants and termites are called."— Presentation transcript:

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2 Lecture 3 Soil Engineers

3 Learning Objectives Lecture 3 – Soil Engineers Lecture 3 – Soil Engineers – Explain why earthworms, ants and termites are called soil engineers – Describe earthworms as an example for the importance of functional diversity and the impact of invasive species (both negative and positive) – Discuss the benefits of managing soil to encourage a healthy, diverse soil community.

4 Lecture 3 - Topics Intro Soil Engineers Intro Soil Engineers Earthworms Earthworms Summary of Soil Organisms Summary of Soil Organisms

5 Organisms that make major alterations to the physical environment that influences the habitats for many other organisms within the ecosystem Ecosystem Engineers Microorganisms that create impermeable surface microbiotic crust that spatially concentrates scarce nutrient and water supplies in certain arid and semi-arid ecosystems. Microorganisms that create impermeable surface microbiotic crust that spatially concentrates scarce nutrient and water supplies in certain arid and semi-arid ecosystems. Burrowing animals that create air and water movement in soil as well as create root passages through dense surface soils. Earthworms are natures tillers. Ants and termites create passage ways and mounds. Burrowing animals that create air and water movement in soil as well as create root passages through dense surface soils. Earthworms are natures tillers. Ants and termites create passage ways and mounds. Humans Humans

6 What Do Earthworms Do? 1.Stimulate microbial activity Earthworms derive nutrition from microbes Earthworms derive nutrition from microbes Organic matter is fragmented and inoculated in gut Organic matter is fragmented and inoculated in gut Greater microbial biomass in feces and casts than in surrounding soil – microbial hotspot Greater microbial biomass in feces and casts than in surrounding soil – microbial hotspot

7 What Do Earthworms Do? (cont) Soil passed through the earthworm gut is expelled as casts. Soil passed through the earthworm gut is expelled as casts. During the passage through the gut, organic materials are shredded and mixed with mineral soil materials. The casts enhance the aggregate stability of the soil. During the passage through the gut, organic materials are shredded and mixed with mineral soil materials. The casts enhance the aggregate stability of the soil. Carry organic matter down into deeper soil layers Carry organic matter down into deeper soil layers 2.Mix and aggregate soil

8 What Do Earthworms Do? (cont) 3.Increase infiltration 4.Improve water holding capacity Burrow Increase porosity Increase porosity Burrows become preferential flow paths Burrows become preferential flow paths Help minimize surface water erosion Help minimize surface water erosion By fragmenting organic matter and increasing soil porosity and aggregation - earthworms improve water holding capacity By fragmenting organic matter and increasing soil porosity and aggregation - earthworms improve water holding capacity

9 What Do Earthworms Do? (cont) 1.Stimulate microbial activity 2.Mix and aggregate soil 3.Increase infiltration 4.Improve water holding capacity 5.Provide channels for roots growth 6.Bury and shred plant residue Pulling corn leaf into burrow

10 Earthworm Functional Diversity Epigeic Surface soil and litter species Endogeic Upper soil species Anecic Deep burrowing species

11 Earthworm Video

12 Abundance and Distribution Native Earthworm Distributions Distributions (Proulx 2003 risk assessment of non-indigenous earthworms) The majority of temperate and many tropical soils support significant earthworm populations

13 Abundance and Distribution Native Earthworm Distributions Distributions (Proulx 2003 risk assessment of non-indigenous earthworms) L. terrestrus and L. rubellus Invasive Earthworm Distributions Distributions

14 Active Invasion on Local Scales (Bohlen et al. 2004, Ecosystems) L. rubellus in Cornells Arnot Forest, NY Box 10.1 in text

15 Smithsonian Forest 3 old forest sites ( y) 3 young forest sites (50-70 y) Macroinvertebrate activity Litter decay Organic matter inputs

16 Dominant earthworms Late Mid Consume litter layer, can leave 60% of soil surface bare Even when native earthworms are present, invasives make major alterations to the soil environment Earthworm biomass (g/m 2 ) Successional Stage (Filley et al. 2008, Global Biogeochemical Cycles) L. rubellus

17 Invaded Forests Biomass and density was highBiomass and density was high Species diversity was lowSpecies diversity was low Functional diversity was lowFunctional diversity was low

18 Earthworms and Agriculture Croplands in the US can contain earthworms/yd 2 Croplands in the US can contain earthworms/yd 2 Grasslands and temperate forests can have earthworms/yd2 Grasslands and temperate forests can have earthworms/yd2 Based on total biomass, earthworms predominate the soil invertebrates Based on total biomass, earthworms predominate the soil invertebrates Lumbricidae is the most important family of earthworms enhancing agricultural soils*. Only 2 species are native, the rest are from Europe and Asia

19 Putting Invasives to Work BUG BIOGRAPHY: Night Crawlers and Tillage The substitution of conventional tillage by no-till or conservation tillage is increasingly common and widely adopted in the United States and elsewhere. In these situations, earthworms, particularly the night crawler, Lumbricus terrestris L., are especially important. Earthworms become the main agent for incorporating crop residue into the soil by pulling some into their burrows and by slowly burying the remainder under casts laid on the soil surface. In reduced tillage systems, surface residue builds up and triggers growth in earthworm populations. Earthworms need the food and habitat provided by surface residue, and they eat the fungi that become more common in no-till soils. As earthworm populations increase, they pull more and more residue into their burrows, helping to mix organic matter into the soil, improving soil structure and water infiltration.

20 Summary – Ecosystem Engineers Organisms that make major alterations to the physical environment that influences the habitats for many other organisms within the ecosystem Organisms that make major alterations to the physical environment that influences the habitats for many other organisms within the ecosystem Earthworms dominate the soil invertebrates, occur at every trophic level Earthworms dominate the soil invertebrates, occur at every trophic level – Native populations are biodiverse, species and functional diversity – Invasive populations are more likely to have greater biomass but less diversity – Invasive earthworms can be damaging in forest floors but beneficial in some agricultural systems

21 Summary – Its Alive Soil is a complex, diverse ecosystem Soil is a complex, diverse ecosystem Organisms incorporate plant residues into soil, return CO 2 to the atm where it can be re-fixed into plants. In the process, soil organic matter is formed and essential plant nutrients are released.Organisms incorporate plant residues into soil, return CO 2 to the atm where it can be re-fixed into plants. In the process, soil organic matter is formed and essential plant nutrients are released % of metabolic activity in soil food web is bacteria and fungi 80-90% of metabolic activity in soil food web is bacteria and fungi The activity of organisms is more important than the identity. Functional diversity vs. species diversity. The activity of organisms is more important than the identity. Functional diversity vs. species diversity.

22 Summary – Beneath the Surface Rhizosphere Rhizosphere Hyphae Hyphae Mycorrhizae Mycorrhizae Biological N fixation Biological N fixation – Inoculants to be sure that crops have the right symbiosis cost $3 /ha; fertilizer costs $87 /ha – Nearly as much N fixed into fertilizers than BNF annually

23 Summary – Soil Organisms In every healthy system or watershed, the soil food web is critical to major soil functions In every healthy system or watershed, the soil food web is critical to major soil functions – Sustaining biological diversity – Regulating flow of water and dissolved nutrients – Storing and recycling nutrients and elements – Filtering, buffering, degrading, immobilizing, detoxifying potential pollutants Complexity, that is, interactions among organisms and high functional diversity within the soil food web, enhances these functions Complexity, that is, interactions among organisms and high functional diversity within the soil food web, enhances these functions Microorganisms and earthworms dominate the life of most soils (Table 10.4) Microorganisms and earthworms dominate the life of most soils (Table 10.4)


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