The document provides definitions and concepts related to ecosystems, including: 1. Definitions of ecosystems and their structure, including biomass and dead organic matter. 2. Functions of ecosystems, including energy and nutrient flows through photosynthesis, trophic levels, and nutrient recycling. 3. Plant succession and how plant communities change over time from pioneer to climax species in response to changing environmental conditions.

2. Amount of energy produced – energy needed for respiration 6CO + 6H 2 O + light energy = Glucose and Oxygen The rate of energy fixation – i.e. rate of production of new tissue – highest where there is an abundance of light, warmth, moisture and where key nutrients are made available e.g. TRF The total mass of living organisms in a plant community at any one moment (expressed as a dry weight per unit area or kg/m 2 The loss by plants of water from the soil via the plant to the atmosphere Sequence of energy transfer in the from of food, from one tropic level to another These consist of living organisms and their physical and chemical (non-living) environments which are interdependent and interacting. Total amount of energy fixed / absorbed by green plants BIOMASS PHOTOSYNTHESIS FOOD CHAIN ECOSYSTEM NPP (Net Primary Production) PRODUCTIVITY TRANSPIRATION GPP (Gross Primary Production) HOW WELL DO YOU KNOW YOUR KEY DEFINITIONS…. Which go with which? BACK

7. A simple example of Primary Succession: Source: Greg O’Hare p.66 Soils, Vegetation and Environment Back to Index

9. Sub-Climax At any point in the development of an ecosystem succession can be halted either temporarily or permanently by ARRESTING FACTORS. They can occur suddenly or gradually. This results in a sub-climax , where the plant community has been prevented from reaching its climax state (i.e. it is not in equilibrium with the environmental conditions). 1. TOPOCLIMAX – controlled by relief e.g. – landslide / volcanic eruption (e.g. Krakatoa; earthquake etc.) 2. HYDROCLIMAX – controlled by drainage 3. EDAPHIC CLIMAX – controlled by soil change – e.g. neolithic man (middle ages) – cutting down trees – soils become increasingly acidic – also Suertsey – salty wind – affected soil 4. BIOTIC CLIMAX – controlled by animals e.g. grazing goats (Mediterranean) 5. PLAGIOCLIMAX – controlled by man – e.g. grazing sheep on Welsh Mountains (man determining location); burning heather etc. see summary diagram of succession

11. Back to Krakatoa Notes Back to Index

12. Case study of Lithosere Succession: SURTSEY (and sub-climax) Surtsey – 1963 – a new island (climax vegetation = silver birch woodland) Covers an area of 2.5km 2 Slow colonisation – algae / fern and fruit spores (slower due to cooler conditions) Sources of colonisation: 1. Wind 2. Sea 3. Birds (seagull excreta acts as fertiliser) Sub-Climax – succession arrested due to salt spray and strong winds / heavy storms – developed a sub-climax vegetation of heath (moss, sedges, short willow) Back

13. Climax Theories MONO-CLIMAX THEORY It was in the 1930s that Clements et.al . put forward the belief that plant succession in any one region tended to up with a particular vegetation type – the climax vegetation. This climax vegetation had a fixed and predictable composition directly related to and in balance with the physical environment. It was believed that the climax vegetation of a region was dependent principally on one main factor – the climate (hence climatic climax community ) – this is known as the MONO CLIMAX THEORY POLYCLIMAX THEORY (sub-climax vegetation) Today we still recognised the importance of climate and its role in determining the climax vegetation is clearly true on a large-scale – e.g. tropical rainforest, desert etc. However, it has become increasingly recognised that the nature of a climax vegetation on a local scale will be determined by a lot of other factors (as well as climate) i.e. soil, relief, drainage, nature of parent rock, people / animal influence etc – this is known as the POLY CLIMAX THEORY Where vegetation is prevented from reaching its climatic climax vegetation due to the effect of a local factor, this is called a sub-climax. Back

14. Case Study: Succession in a Hydrosere (Sweetmere, Shropshire) B irch O ak Index 6 26 Number of Plant Species 18 10 Number of Plant Species 7.3 pH level 4.3 3.7 pH level A lder / Birch Woodland A lders Closed Wooded Fen W illows Open Wooded Fen S edges Marsh or Fen Bull Rushes Reed Swamp Algae & Lillies Open water

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21. Back to Index THE PROCESS OF SUCCESSION Retrogressive succession NEW ORGANIC SURFACE PIONEER COMMUNITY CLIMAX VEGETATION SERE name given to the whole series of communities that develop during succession from the pioneer species through to the climax vegetation PRIMARY SUCCESSION Involving a series of seral stages A series of possible interruptions which may result in sub-climaxes BIOTIC (animals grazing – e.g. Goats) EDAPHIC Soil Change (e.g. neolithic man – feeling trees - change of pH etc.) PLAGIO (Man cutting, grazing, burning) HYDROCLIMAX (impeded drainage) TOPOCLIMAX (changes in relief – e.g. land-slide) REGRESSIVE CLIMAX

22. KEY TERMS – PLANT SUCCESSION The group of species that is in equilibrium with the climatic conditions The group of species that is best able to exploit the prevailing environmental conditions The long-term evolution of a plant community from initial colonising species to the climax community The group of plant species living together in an ecosystem The group of species that exist in an ecosystem as a result of the influence of human activity Plant succession in a freshwater environment Plant succession on a bare rock surface The group of species found in an ecosystem found in an ecosystem that has not yet reached a state of equilibrium with the environmental conditions or which have been prevented from doing so. Plant Community Climax Community Hydrosere Plant Succession Lithosere Sub-climax community Plagioclimax Community Climatic Climax Community Can you mix and match the key words to the definitions? Back Next set of key words / definitions….

23. KEY TERMS – PLANT SUCCESSION The name given to the whole series of stages from pioneer species through to climax community Vegetation Community distinct from the one before and after it Changes in the environmental conditions bought about by the plant community itself that results in primary successsion Change in the environmental conditions caused by an external factor (e.g. human activity, fire etc.) – likely to lead to secondary succession Where a climatic climax vegetation reverts to a previous phase This is succession taking place on land that has been vegetated before but has been disturbed back to an earlier state Sere Seral Stage Allogenic Factors Autogenic Factors Secondary Succession Can you mix and match the key words to the definitions? Back Regressive Climax

24. Nutrient cycle GERSMEHLS MODEL BACK

28. Nutrient cycle BACK Remember the size of the circles and the arrows are proportional relative to each other. The size of the stores and flows varies with the type of ecosystem – you must know details of the nutrient cycles of a: FOREST BIOME and a GRASSLAND BIOME