EEMB/ES 171 Vitousek & Reiners. 1975. BioScience1. How do the authors define “ecosystem”? Give an example of an ecosystem input, including both a potential source and sink for this.In this article, the authors describe an ecosystem as an open biogeochemical system that consists of inputs, outputs, and internal recycling to a certain extent. The inputs are stated to come from a variety of different sources, which lead to various sinks (ouputs). In this article, the authors give the example of a Sand Dune ecosystem in which precipitation (input) will be equally lost more or less due to hydrologic outputs, which with time will be outnumbered by precipitationand elemental nutrients will be stored in biomass (sink).2. Can you give an example of a biological system that is closed? (Hint: this doesn’t have to be a naturally occurring system, and light can keep entering).An example of a biological system that is closed would be a bottle garden. A bottle garden would be an example of this because no outside energy or matter is able to enter the system once closed. This becomes a self-sustaining system in which the initial water and nutrient rich soil are cycled within the system, as well as the outside source of light, which aids these biological processes.3. What does it mean when an ecosystem is in steady state?When an ecosystem in steady state, it means that the ecosystem must show the same balance of inputs to outputs as an unoccupied system would show. In other words, theinputs and outputs of a system are proportional as elements (inputs) enter and exit the system (outputs) and elements are inputted again for production. 4. Explain Figure 1.Figure 1, shows that the rate at which a particular element is incorporated into the net biomass increment for a system will determine the difference between net input and output of a certain element, which will be proportional to the increment. Figure 1A shows that nutrient incorporation into biomass increases very rapidly before reaching a maximum and slowly declining to zero. Figure 1B on the other hand shows that depending on the element, whether non-essential, essential or limiting, determines theextent to which ecosystems retain these elements. Non-essential elements output will vary very little over the succession of time. Essential and limiting elements outputs will vary significantly, limiting element outputs may reach near zero, while essential elements will be strongly retained, but not to the extent of limiting elements. 5. How does the age of an ecosystem affect nutrient retention or leakage? The age of an ecosystem affects nutrient retention or leakage by the amount of nutrients it retains. It was found that intermediate-aged successional ecosystems showed the lowest nutrient loss in comparison to very young or very old (mature)EEMB/ES 171 Vitousek & Reiners. 1975. BioScienceecosystems. However it is advised that a good understanding of changes in net increment with time and consideration of developmental postion should be taken to analyze ecosystems