SOIL ECOLOGY the general patterns, and the particular

Transkript

1 Soil Biology topic No. 5: SOIL ECOLOGY the general patterns, and the particular patterns

2 SOIL ECOLOGY is an applied scientific discipline dealing with living components of soil, their activities and THEIR INTERRELATIONSHIPS Microbiology Soil Science Soil Ecology Environmental Science Soil Biology Zoology Plant Physiology Biochemistry

3 In general, irrespectively of The First Law of Thermodynamics, i) the energy in soil is degradated from chemical energy to heat which is not recycled, ii) ultimately, nutrients are excreted by organisms (as a whole) and, they are recycled via plant root uptake.

4 (ultimately, net immobilisation has to be zero... microbial dead cells and humic substances are decomposed as well!)

5 Notes

6 Which ecological factors favour soil biological activity? There are five the essential ones: oxygen availability (whenanexcessofwatercanresultin O 2 limitations; obligate aerobes vs. micro aerophils vs. facultative anaerobes vs. obligate anaerobes) presence of water (as both i) the principal component of protoplasm, and ii) the carrier of nutrients into the living cells) nutrients osmotic pressure temperature (psychrophiles vs. mesophiles vs. thermophiles).

7 In addition, there are five more ones: 1. ph level 2. toxicity of the soil 3. heavy metals content in the soil 4. molecular structure 5. co metabolism

8 Notes

9 A. there are hundreds of ecological strategies of soil biota, e.g. the reaction of temperature changings: winter spring time: capsule formation enables it to survive at reduced temperatures and grow as the temperature increases; B. there are hundreds of ecological strategies of plants in terms of their root systems, e.g. the reaction to dry conditions: in permanently dry soils, plants invest a larger fraction of their primary production below ground... to obtain sufficient water, in seasonally dry soils, they do the same... to survive this season;

10 C. there are hundreds of ecological interrelationships among plants and soil biota, e.g. the reaction to infertile soils: on infertile sites, plants have not enough nutrients to make new tissues, ie. not enough nutrients to translate their photosynthetic production into new tissues thus, they give a great deal of the photosynthetical products to mycorrhizal fungi whose growth increases the plant uptake capacities for nutrients.

11 Notes

12 Dealing with soil ecology, there are three substantial questions:

13 A. Which way plant roots influence soil itself? There are three main mechanisms working on very different time level: (1) measurable within days, via uptake of water and nutrients ie., soil moisture and soil nutrient content is directly influenced by plant uptake (2) measurable within years, via penetration of soil bodies ie., a formation of soil pores (3) measurable within centuries, via rate of parrent material weathering ie., the amount of nutrients bounds in mineral is directly influenced by biological weathering

14 B. Which way soil organisms influence soil itself? There are three main mechanisms, as well: (1) defragmentation of plant litter (2) consuming of soil organic matter (3) bioturbation

15 C. Which way soil organic matter influences soil itself? There are fourmain mechanisms the fourwaysof increase in: (1) a simple storage of nutrients in thelitter(firstofall, N + P + S; secondly, Ca, Mg and K), (2) a soil structural stability the formation of soil aggregates (small aggregates are formed by inorganic binding agents; large aggregates come from organic binding agents), (3) a water holding capacity, (4) exchange capacity (CEC in particular).

16 Notes