Plant-soil interactions - day 2 Flashcards
What are soil physical properties?
- Soil texture - soil particles
- Soil structure - soil layering
- Bulk density - soil dry mass divided by soil volume (high bulk = more soil compaction, less aeriation and reduced biological activity and more water stagnation)
What are the chemical properties of soil?
- pH - acidity of the soil;
- nutrient concentration - N, P + base cations;
- Nitrogen concentration
- Phosphorous concentration
- Base cations concentrations
- Cation exchange capacity (CEC)
What are the components of soil biological properties?
- Bacteria
- Fungi
- Mesofauna
- Macrofauna
What are the soil layers from top to bottom?
- Litter layer - ectorganic layer, intact, complete litter;
- Fragmentation layer - ectorganic layer of fragmented litter;
- Humus layer - ectorganic humus layer, origin opf organic materials not recognisable;
Ah: Layer where the mineral soil is mixed with humus - Endorganic layer - mineral soil is mixed with organic matter;
- Elluviation layer - layer from which humus and/or clay particles
and/or Fe or Al have gone into solution and percolated to lower soil layers; - Illuviation layer - thin layer of precipitated iron oxides and/or/humus, and/or clay –> form a hardened, impenetrable layer = water stagnation
- Parent material - consist of sand/silt clay or of bedrock
What are the three types of soil recognised based on the humus layer?
- Mor - poor + infertile soil –> only ectorganic layer
- Moder - intermediate fertility –> Ah + humus incorporated in mineral layer
- Mull - rich and fertile soil –> bioturbation = well-mixed soil
How do Above-belowground linkages differ between ‘fast’ communities on fertile soils, versus
‘slow’ communities on infertile soils?
Plant species adapted to fertile conditions are geared towards fast growth, and have different traits than species adapted to infertile conditions, and are geared towards slow growth and persistence.
Fertile species make thin, productive, metabolically active leaves with high nutrient
concentrations of leaves and roots –> support high herbivore densities, with more than 50% of net primary productivity being returned to the soil as labile fecal material, litter with high nutrient concentrations and low defenses, support soil food webs in which the bacteria-based energy channel, microfauna, and earthworms play an important role in nutrient cycling.
What are the three drivers of decomposition?
- Litter - quantity and quality of litter input;
- Environment - environmental conditions that speed
up decomposer metabolism and activity (i.e., high water and oxygen availability, and high temp) - Decomposers - composition of the decomposer community (i.e., whether it mainly consists bacteria and macrofauna that can decompose high quality litter, or of fungi and microarthropods that can decompose recalcitrant low quality litter)
What are the two different types of litter?
- Leaves - high-quality litter with nutrient rich leaves;
- Deadwood - low-quality litter, nutrient-poor but carbon and lignin-rich wood.
How does leaf litter change with latitude?
Leaf litter production increases from the pole to the tropics. Leaf litter production in forest ecosystems is strongly related to global patterns in climate. Leaf litter production is low at high latitudes near the pole where short growing seasons limit plant growth; it increases toward the equator and the tropics where plant growth can occur throughout the entire year
How does the amount of litter on the floor change with latitude?
Litter on the forest floor increases from the tropics to the poles. Tropical forests: high litterfall –> longer growing season = higher productivity. Amount of litter on
forest floor is very low –> fast decomposition rate, as a result of benign environmental conditions (high temperature, water) and a
longer growing season where decomposers are active.
How do leaves lose nutrients?
- Leaching
- Retranslocation
- Senescence
What is the feedback loop of nutrient species and litter?
Species with nutritive litter enrich the soil. Because tree species with fast life styles produce large amount of leaf litter of high nutritional quality that are easily decomposable, they have the ability to modify their soil conditions.
What is the importance of dead wood?
Dead wood is a source of life as it provides a habitat and substrate for a wide range of organisms, ranging from bacteria, fungi, plants, and insects to mammal species.
Fungal abundance and richness were higher for Angiosperm trees than for Gymnosperm trees (Fig. 9A), higher for tree species with more acquisitive stem trait strategies (i.e., high nutritional value and low physical defence) (Fig. 9B), and peaked after four years of decay.
What are the management implications for plant-soil interactions?
- Use an ecosystem approach to manage your system;
- Soil is the long-term capital of your site that maintains site productivity, so maintain your soils healthy;
- Create a diversity of dead wood to increase insect and fungal diversity;
- Plant nitrogen-fixing tree species to restore the fertility of sites with degraded soils;
- Add inoculum of relevant mycorrhizae in planting holes to enhance the success of tree
plantations; - Increase decomposition of thick litter layer to facilitate diversity of the understory layer;
- Increase long-term site fertility by planting or enhancing regeneration of tree species with high litter quality.
What are the causes of Nitrogen deposition?
Acid rain was mainly driven by S, now by N.
Reduced and oxidized nitrogen; different sources, different impact. –> reduced nitrogen (ammonia, from agriculture, larger impact on ecosystems) + oxidised nitrogen (NOx)
–> High nitrogen emissions driven by agriculture.
