Presentation on theme: "Model of the Mineral Nutrient Cycle developed by P.F. Gersmehl in 1976 Soil is the top layer of the earth that is composed of disintegrated rock particles,"— Presentation transcript:
Model of the Mineral Nutrient Cycle developed by P.F. Gersmehl in 1976 Soil is the top layer of the earth that is composed of disintegrated rock particles, humus, water and air. Litter is organic matter in and on the soil, it includes humus and leaf litter. Biomass is the total mass of living organisms, mainly plant tissue, per unit area. It is a store of energy and is also known as standing crop. It can be measured in 3 ways: - dry weight (kg/metre squared) - ash weight - calorific value per unit area biomass litter soil Store of nutrients Transfer of nutrients The size of the circles and arrows is proportional to the amount of nutrients
a)Taiga (northern coniferous forest) biomass litter soil Large store because of low rate of decomposition due to cold temp. High runoff after snowmelt when ground still frozen Slow decomposition due to cold & thick cuticles Some leaching due to ppt. Slow chemical weathering of parent rock due to cold Small store of nutrients due to poor drainage and soil formed from glacial deposits which have low fertility Trees take up nutrients R elatively low as conifers form only one layer, little under growth, limited species, small needles Continual supply of litter Little ppt.
b) Steppe & Prairie (mid-latitude continental grassland) biomass litter soil High runoff as soils saturated High decomposition due to wet & dry seasons & bacteria Low ppt means less loss of nutrients from leaching Weather encourages chemical & physical weathering releasing nutrients to soil Large store of nutrients due to good drainage Small store due to climate, insufficient moisture to support trees & growing season reduced to 6 months by cold temps. Much of biomass beneath surface as rhizomes & roots High supply of litter, grasses die back in winter Little ppt. Litter store small as no trees, grasses die back quickly into soil Some plants store their own nutrients in rhizomes & roots so not as many nutrients taken up from soil
c) Selvas (tropical rainforest) biomass L soil Small store because of high rate of decomposition High runoff because of lots of rain, soil cannot absorb it all Rapid decay due to heat & moisture, ideal for bacterial action Rapid leaching due to ppt Rapid chemical weathering due to heat & humidity Small store due to leaching and soils inherent infertility The many plant roots take up vast amounts of nutrients Tall, dense & rapid growth of vegetation. Several layers & countless species. Continual supply of litter High ppt. all year