THE OLDEST AND MOST COMPLEX LAND-BASED ECOSYSTEM ON OUR PLANET – THE TROPICAL RAINFOREST Show Tropical Rainforests are known for their complexity of interrelationships between plants and animals. Only about 1% of the light that is received at the uppermost canopy reaches the ground. Nearly all plants depend on sunlight for energy requirements as sunlight is converted into chemical energy in the form of carbohydrates through the process of photosynthesis. The ground level is therefore primarily composed of decomposing plant matter rather than living plants. Plants with similar structures belong to a specific synusia; the synusiae of a Tropical Rainforest include mechanically independent forms, which contain a supportive stem structure, saprophytes, which are plants, fungi, or microorganisms that live on dead or decomposing matter, and mechanically dependent species such as climbers and stranglers. The various-sized trees form canopies. The only chance for saplings to grow into maturity is the removal of overhanging vegetation or death or damage by wind to larger trees. Tropical Rainforests support the greatest number of species compared to any other biome on the planet. The high species diversity is brought about by warm temperatures and year-round rainfall – the average yearly rainfall is 100 inches – that ultimately allow for optimal growth. The high number of plant species can thus support a high number of animal species. The warm, wet conditions result in rapid decomposition and any nutrients that are present within the soil are used by the quickly growing plants, causing the soil to be left poor in nutrient content. Nutrients, however, continue to cycle through the ecosystem as long as no damage is inflicted. Gross Primary Productivity (GPP) is the total amount of organic matter synthesized by producers per unit area in unit time. Gross Primary Productivity refers to the total productivity including the energy that will ultimately be used for respiration, which is a chemical process in which energy is released from food substances such as glucose. Net Primary Productivity (NPP) is the total amount of energy converted from solar energy to chemical energy with the subtraction of the energy used for respiration. Net Primary Productivity is affected by temperature, water availability, carbon dioxide, and nutrients, all of which are abiotic factors. In Tropical Rainforests, water, sunlight, and high temperatures are consistent and a dense concentration of plants is present, causing both the GPP and NPP to be very high. So, high levels of productivity increase biomass. WHAT COVERS NEARLY 20% OF OUR PLANET’S SURFACE AREA? THAT’S RIGHT! DESERTS DO!  “Kamel” (CC BY-NC-SA 2.0) by Astrid Kopp A desert is often defined as any large, extremely dry area containing sparse vegetation that receives less than ten inches of average annual rainfall. Trees are few in number and the herbaceous plants that are present provide little ground cover. In some cases, extreme aridity causes deserts to be nearly completely devoid of plants. The low humidity, few bodies of water, and little vegetation absorb nearly all of the sunlight, heating the air at the soil’s surface. As the sun sets, however, nearly all of the heat present above and within the soil is released into the atmosphere, lowering the temperature drastically. Many desert species have adapted behavioural techniques to avoid extreme heat. Many, particularly mammals and reptiles, are crepuscular – they are only active at dusk and dawn. Others are nocturnal, seeking protection under the surface of the soil or sand, often blocking their burrows to prevent the entrance of hot air. The Round-Tailed Ground Squirrel, for example, is a diurnal mammal that hibernates during the hottest portions of the summer as well as during winter. In regards to the dissipation of heat, bird species often gape open-mouthed while quickly moving the throat region to evaporate water from mouth cavities while dark-colored vultures urinate on their legs to cool by evaporation. Other organisms have large ears or have pale feathers, fur, scales, or skin. Desert plants conserve water through deep and shallow-spreading roots, a reduced number of stomata, rolled leaves, waxy leaf cuticles, succulent tissue, and spines. The stomata are often open at night – reversed stomatal rhythm. Gross Primary Productivity and Net Primary Productivity are typically very low. Increases in productivity depend on nutrient distribution and the presence of moisture, which naturally allows for vegetation to grow before extreme arid conditions resume. The most fertile soil is often located beneath ground cover as shrub roots absorb nutrients and deposit them as plant litter on the surface, allowing for decomposition. The litter that is blown by the wind also allows for patchy, fertile areas to develop and thus increase productivity. So, depending on the amount of rainfall and nutrient distribution within a desert, certain areas may cause a larger GPP and NPP than others. Overall, the productivity of deserts is the lowest of all the biomes. Questions for Readers: (1) How does a Tropical Rainforest differentiate from a Desert? In your response, include your knowledge of the structure of these biomes and the organisms (with reference to their adaptations) that inhabit them.) (2) What are the proper definitions of Gross Primary Productivity and Net Primary Productivity? Why are these indicators important? (3) Why do Tropical Rainforests and Deserts have the productivity levels they do? (4) Can human influences – positive or negative – impact productivity within any biome? Provide your opinion with justification using real-world examples. CITATIONS
Which biome has highest net primary productivity?Tropical forests have the highest biodiversity and primary productivity of any of the terrestrial biomes. Net primary productivity ranges from 2–3 kg m-2 y-1 or higher.
Which is the most productive ecosystem in terms of net productivity?In terms of Net Primary Productivity (NPP) per unit area, the most productive systems are tropical rain forests.
Which of the following biomes is most productive?tropical rain forest is the most productive biome on earth.
Which biome is most productive in terms of net primary productivity NPP per unit area?In terms of NPP per unit area, the most productive systems are estuaries, swamps and marshes, tropical rain forests, and temperate rain forests (see Figure 4).
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Which of the following biomes are more productive in terms of net primary productivity?
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