![\"\"](\"https:\/\/sites.warnercnr.colostate.edu\/larryr\/wp-content\/uploads\/sites\/83\/2017\/04\/ecosyste-300x154.gif\")
<\/p>\nCENTRAL ORGANIZING QUESTION\/IDEA: What is an ecosystem? All organisms in a bounded area interacting with the physical environment so that a flow of energy leads to a clearly defined trophic structure and mineral cycling. An ecosystem has boundaries. Cannot be defined outside of an issue.<\/p>\n
About 80% of students indicate information is redundant with material in
\nother classes they have taken.
\nBased on past student surveys, this unit is distributed for information. You are responsible.
\nAssign Chapter 6, Heady and Child
\nView video – Ecosystems<\/p>\n
Teaching objectives [numbers in brackets cross-reference goals]:<\/p>\n
1. [2,5,6]to provide an overview of ecosystems, including terms, processes and
\ninteractions.
\n2. [1,2,6]To justify the ecosystem as a rationale construct or paradigm for
\ndeveloping management alternatives and making management decisions;
\ncompeting paradigms might include the organism or population or
\ncommunity.
\n3. [1]To link biological\/ecological systems with human systems<\/p>\n
Teaching points:
\nGeneral: This section is designed to help students understand the importance of the paradigm we use to explain variation in the natural world and the spatial scale we chose to delineate the boundaries of the system we are dealing with.
\n[2,3] The paradigm we use to approach management does make a difference. The ecosystem is a reasonable construct for explaining the functional relationships in a system. The landscape is a relevant scale for most management decisions. Regional variability can have an effect on global issues like air-born particulates, changes in atmospheric gases, and even climate.<\/p>\n
[2,3] Rangeland Ecosystem managers deal with biotic and abiotic stressors and strainers at both the organism and community level in an environment of uncertainty.<\/p>\n
[2,3] Rangeland Ecosystem managers manage succession. They worry about levels of soil nutrients and turnover rates; they worry about colonization; they worry about organism performance. Dr. Redente and I will spend 6 to 8 class periods discussing succession.<\/p>\n
[1,2,3] Range managers manage aboveground nutrients and their rate of depletion by herbivores. They control the amount of energy\/biomass that is stored in different trophic levels and the efficiency of energy transfer. They control the amount of biomass that follows the grazer vs decomposer pathway.<\/p>\n
[1,2] Resources are distributed both above and below ground. Talk about the relative amount of biomass above and below ground and implications to management. The amount of total biomass belowground is inversely related to ppt, while the amount of total biomass aboveground is directly related to ppt.<\/p>\n
[1,3] Range managers consider the whole system. They worry about linking human and biological systems; i.e., dealing with the complexity of human values and potential resource uses. It would be quite simple to say, “we will manage based on good science.” The implication is that politics will be removed from decision making. The fact is most natural resource issues are political. For example, the biology of a system may determine the suitability of habitat for deer or elk or sage hens or grouse or sheep or feral horses or flycatchers; but, politics will decide the mix.<\/p>\n
TASK 1: View video – “Understanding Ecosystems”
\nWords from the video presentation:<\/p>\n
TASK 2: On your own<\/p>\n
<\/p>\n
<\/p>\n
DRIVING VARIABLES ARE HIGHLY INDEPENDENT on reasonable time-scales, e.g., climate, soils, exposure
\nSYSTEM COMPONENTS ARE VARIABLY INTERDEPENDENT on a wide range of time-scales, e.g., organisms, nutrients
\nAn ecosystem is made up of the biotic and the abiotic
\nabiotic = mineral soil, water, non-living
\nbiotic = organismal, living<\/p>\n
autotrophs – green plants or primary
\n producers
\nheterotrophs – secondary producers or
\n secondary or higher consumers
\n Herbivores, Omnivores,
\n Carnivores<\/p>\n
decomposers – microbes, fungi<\/p>\n
A word about trophic ecology.
\n– A trophic level is a level of carbon, energy or dry matter storage.
\n– Some energy is dissipated when transferred to the next trophic level
\n– So, we say energy flows through the system
\n– Minerals cycle, hence the CO2 cycle, the P cycle, the S cycle, the N cycle, etc.
\nTASK 3: more review of ecosystem terminology and comparison to other disciplines; most of this
\n you can review on your own; tie these to Odum, page 6.
\nPG = gross productivity<\/p>\n
C = consumption<\/p>\n
D = decomposition<\/p>\n
Rp = respiration in the process of photosynthesis<\/p>\n
Net Primary Production = NPP
\nNPP = PG – Rp<\/p>\n
RC = respiration as a result of transfer of energy to the next
\n storage level<\/p>\n
RD = respiration as a result of all decomposition, i.e., both
\n primary and secondary producers<\/p>\n
Net Community Production = NCP
\nNCP = PG – Rp – RC – RD <\/p>\n
TASK 5: Study Figure 6-1, page 76. Review the Nitrogen, Sulfur, Phosphorus and Potassium
\n cycles. Where is the water cycle?<\/p>\n
Some more fundamental definitions that are really important:<\/p>\n
ECOSYSTEM BOUNDARY. A system is confined to a definite place in space by the boundary of the system, whether this is natural or arbitrary. It is a defined system of matter plus energy content of that system of matter. The boundary separates it from the rest of the universe. But, energy, carbon or dry matter may be transported across boundaries.<\/p>\n
Within the boundary the system has 3 properties:<\/p>\n
1. ELEMENTS. Elements of the system are the kinds of substance composing the
\n system. They be atoms or molecules, or larger bodies of matter like grains of
\n sand, raindrops, grass plants, rabbits, etc, but each is a unit which exists in both
\n time and space.
\n2. ATTRIBUTES. Each element has a set of attributes or states. These elements
\n and their attributes may be perceived by the senses, or be made perceptable by
\n measurement or experiment.<\/p>\n
3. VALUE. In the case of measurable attributes as number, size pressure, volume,
\n temperature, color, or age, a numerical value can be assigned by direct or indirect
\n comparison with a standard.<\/p>\n
The most important concept is that the RELATIONSHIP among 2 or more elements or states or 2 or more states which serves to define the states of aggregation of the elements or THE ORGANIZATION OF THE SYSTEM. One of the first questions in the field is, “what organizes this system?”
\nThe state of the system is defined when each of its properties, i.e., elements, attributes and relationships, has a definite value.<\/p>\n
KNOW AND UNDERSTAND THE NEXT 2 PARAGRAPHS; these may be the most important ideas presented during this semester.<\/p>\n
Systems organize because of negative feedback mechanisms. These are things that damp-down change and become control mechanisms. The process is homeostasis. Positive feedbacks disorganize systems. The process is homeorhesis.<\/p>\n
So, it is the interplay of these negative and positive feedbacks that determines the state of the system. Where negative feedbacks predominate, the system tends toward a pseudo steady state. Positive feedback can lead to increase in order and complexity of the system state which results in “developement” of the system; or, positive feedback can progressively destroy organization and lead to a retrogressive and often irreversible change in state. <\/p>\n
TASK 6: Read and study syllabus tables on page 6 and 7. Don’t get too up-tight about this now; it is an
\n important introduction to the unit on why plants grow where they grow and succession. It is mostly
\n here to get you to thinking about attributes of ecosystems.<\/p>\n
Ecosystem Attributes in relation to succession and ecosystem structure and processes. From Odum 1969. [Brackets are my modification.] <\/p>\n
Ecosystem Attributes\tDevelopmental stages\tMature stages
\nCommunity energetics
\n1. Gross production\/community respiration (P\/R ratio)\tGreater or less than 1\tApproaches 1
\n2. Gross production\/standing crop biomass (P\/B ratio)\tHigh\tLow
\n3. Biomass supported\/unit energy flow (B\/E ratio)\tLow\tHigh
\n4. Net community productivity (yield)\tHigh\tLow
\n5. Food chains\tLinear, predominately grazing\tWeblike [Complex], predominately detritus
\nCommunity structure
\n6. Total organic matter\tSmall\tLarge
\n7. Inorganic nutrients\tExtrabiotic\tIntrabiotic
\n8. Species diversity-variety component\tLow\tHigh
\n9. Species diversity-equitability component\tLow\tHigh
\n10. Biochemical diversity\tLow\tHigh
\n11. Stratification and spatial heterogeneity (pattern diversity)\tPoorly organized\tWell-organized
\nLife history
\n12. Niche separation\tBroad\tNarrow
\n13. Size of organism\tSmall\tLarge
\n14. Life cycles\tShort, simple\tLong, complex
\nNutrient cycling
\n15. Mineral cycles\tOpen\tClosed
\n16. Nutrient exchange rate, between organisms and environment\tRapid\tSlow
\n17. Role of detritus in nutrient regeneration\tUnimportant\tImportant
\nSelection pressure
\n18. Growth form\tFor rapid growth (“r” selected)\tFor feedback control (“K” selected)
\n19. Production\tQuantity\tQuality
\nOverall homeostasis
\n20. Internal symbiosis\tUndeveloped\tDeveloped
\n21. Nutrient conservation\tPoor\tGood
\n22. Stability (resistance to internal perturbations)\tPoor\tgood
\n23. Entropy\tHigh\tLow
\n24. Information\tLow\tHigh
\n[25. ]
\nThe following table is from E.P. Odum (1985) Trends expected in stressed ecosystems, BioScience 35:419-422. <\/p>\n
Trends Expected in Stressed Ecosystems
\nEnergetics<\/p>\n
1. Community respiration increases
\n 2. P\/R (production\/respiration) becomes unbalanced ( 1)
\n 3. P\/B and R\/B (maintenance:biomass structure) ratios increase
\n 4. Importance of auxiliary energy increases
\n 5. Exported or unused primary production increases
\nNutrient Cycling
\n 6. Nutrient turnover increases
\n 7. Horizonal transport increases and vertical cycling of nutrients decreases
\n 8. Nutrient loss increases (system becomes more leaky)
\nCommunity Structure
\n 9. Proportion of r-strategists increases
\n10. Size of organisms decreases
\n11. Lifespans of organisms or parts (leaves, for example) decrease
\n12. Food chains shorten because of reduced energy flow at higher trophic levels
\n and\/or greater sensitivity of predators to stress
\n13. Species diversity decreases and dominance increases; if original diversity is low,
\n the reverse may occur; at the ecosystem level, redundancy of parallel processes
\n theoretically declines.
\nGeneral System-Level Trends
\n14. Ecosystem becomes more open (i.e., input and output environments become
\n more important as internal cycling is reduced).
\n15. Autogenic successional trends reverse (succession reverts to earlier stages)
\n16. Efficiency of resource use decreases
\n17. Parasitism and other negative interactions increases, and mutualism and other
\n positive interactions decreases
\n18. Functional properties (such as community metabolism) are more robust
\n (homeostatic-resistant to stressors) than are species composition and other
\n structural properties
\nTASK 6: More thoughts on management challenges. Are organisms important? You bet they are.
\n Are populations important? You bet they are. Are communities important? You bet
\n they are. Are landscapes important? You bet they are. Then why do I emphasize the
\n ecosystem and landscape scales?
\nHierarchy of scales and how things are related, e.g., individual to community to landscape to regions to continents to global systems. Hierarchy theory states that organization at a given level is the aggregate of organisms and processes at the next lowest level. And, what happens at any level is constrained by the level above. For example, the grazing pattern I observe on a unit of land is the aggregate of grazing activity within the area, but some areas may not be grazed because they are not accessible.<\/p>\n
Resources are distributed on multiple temporal and spatial scales. Rangeland Ecosystem managers often have viewed this heterogeneity as a management challenge, especially as it related to animal distribution and utilization. Management typically strives for uniformity in utilization of nutrients with minimum impact on other components of the system. <\/p>\n
– sometimes management for “uniformity” over large spatial scales is appropriate. Note Chapter 13, “Animal
\nDistribution.”
\n– sometimes management for “non-uniformity” at multiple or pre-determined scales is appropriate. Note Heady and Child do not have a counterpart to Chapter 13 that might be entitled, “methods of using livestock to create heterogeneous environments on multiple scales.<\/p>\n
– Different fauna, on different trophic levels, respond to variability in resources in different ways. Bottom line is how animals respond to that variability in relation to risk, especially during life-cycle bottlenecks, e.g., nesting. Some fauna respond best to heterogeneous environments at both small and large scales; others respond best to uniformity on small scales and heterogeneity at large scales; with all combinations in between.<\/p>\n","protected":false},"excerpt":{"rendered":"
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