BIOS 5445: Human Ecology Dr. Stephen Malcolm, Department of Biological Sciences

Transcription

1 BIOS 5445: Human Ecology Dr. Stephen Malcolm, Department of Biological Sciences Week 11. Survivorship: energy flow Lecture summary: Energy. Productivity. Web flow. Human energy flow: Examples Week 11: Slide - 1

2 2. Matter and energy: All organisms require matter for construction, and energy for activity, at individual, population and community levels of organization. Communities interact with the abiotic environment as ecosystems which include: primary producers, decomposers and detritivores, a pool of dead organic matter, herbivores, carnivores and parasites, plus the physicochemical environment that provides living conditions and acts both as a source and a sink for energy and matter. Begon et al. (2006). Week 11: Slide - 2

3 3. Productivity: The primary productivity of a community is: The rate at which biomass is produced per unit area by plants (primary producers) as energy (J m -2 day -1 ) or dry organic matter (kg ha -1 year -1 ). Gross primary productivity (GPP) Total fixation of energy by photosynthesis Net primary productivity (NPP) GPP - energy lost to respiration» = actual rate of biomass accumulation available for consumption by heterotrophs. Secondary productivity Rate of biomass production by heterotrophs. Week 11: Slide - 3

4 4. Net primary productivity: Global terrestrial NPP: x 10 9 tonnes dry weight per year. Global marine NPP (Fig. 18.1, Table 18.1): x 10 9 tonnes per year: despite being 67% of the earth's surface. Productivity (P) and biomass (B): (Fig. 18.5): P:B ratios (kg/year/kg biomass) average: for forests for other terrestrial systems. 17 for aquatic communities. Ratios also change with successional shifts (Fig. 18.6). Week 11: Slide - 4

5 5. Community trophic structure: Energy moves through communities via trophic (feeding) interactions. Primary productivity generates secondary productivity in heterotrophic consumers once they consume autotrophs with a measurable efficiency: The slope of Fig at about 0.1. Generates the classical view of a broad-based productivity pyramid or biomass pyramid: After Elton (1927) and later Lindemann (1942). Week 11: Slide - 5

6 6. Community trophic structure: Basic trophic structure of communities: (Figs & 18.19). Energy flow through different components of a grassland community (Fig ). Predicted vs observed values of productivity: (Fig ). Energy flow & nutrient cycling links between decomposer & grazer systems & return of free inorganic nutrients released by decomposers from dead organic matter (DOM) back to net primary production (NPP): (Fig. 19.1). Week 11: Slide - 6

7 7. NPP and global climate change Climate models predict that increased greenhouse gases will lead to an increase in temperature of C. Altered CO 2, temperature, cloud cover and rainfall will dramatically change the NPP of earth's communities: Table Week 11: Slide - 7

8 8. Flux of matter: If plants, and their consumers, were not eventually decomposed, the supply of nutrients would become exhausted and life on earth would cease. So the matter cycling (fueled by energy) of Fig is essential. Week 11: Slide - 8

9 9. The Hubbard Brook experiments: How important is nutrient cycling within a terrestrial community in relation to the through-put of nutrients? The Hubbard Brook experiment in the temperate deciduous forest of the White Mountains in New Hampshire is the best test of this question: 6 small catchments with input and output measured: (Table 19.2). Most nutrients were held in biomass: Like N 2 in Fig But sulfur was released in excess of input because it was a major pollutant in the area (acid rain). Week 11: Slide - 9

10 10. The Hubbard Brook experiments: Experimentally, one catchment was deforested: The rate of nutrient loss rose x13 in comparison with a control catchment. Two reasons for the lost nutrients: (1) Through increased water flow (less water held by trees) - see Fig (2) Within-system nutrient cycling was lost by uncoupling the decomposition process from the plant-uptake process: Nutrients made available by decomposition were lost to leaching in the increased stream flow (Fig. 19.6). Week 11: Slide - 10

11 11. Examples - Dobe San foraging system (Fig. 14-3): animal source green plant storage heat sink work gate Week 11: Slide - 11

12 12. Examples - Ngisonyoka Turkana pastoral system (Fig. 14-6): Week 11: Slide - 12

13 13. Examples - Tsembaga Maring horticultural system (Fig ): Week 11: Slide - 13

14 14. Daily energy consumption in different societies (kcal/person/day)(fig ): Week 11: Slide - 14

15 15. Week 11: Slide - 15

16 16. Week 11: Slide - 16

17 Figure 18.1: Distribution of global terrestrial and marine net primary productivity Week 11: Slide - 17

18 Week 11: Slide - 18

19 Figure 18.5: Relationship between average net primary productivity and average standing crop biomass for communities in Table 18.1 Week 11: Slide - 19

20 Figure 18.6: Change in net primary productivity (P), standing crop biomass (B) and P:B ratio during forest succession on Long Island Week 11: Slide - 20

21 Figure 18.17: Secondary productivity plotted against primary productivity in three communities. Week 11: Slide - 21

22 Figure 18.18: Energy flow through a trophic compartment. Week 11: Slide - 22

23 Figure 18.19: Model of trophic structure and energy flow for a terrestrial community. Week 11: Slide - 23

24 Figure 18.22: Patterns of energy flow through the different trophic compartments of Fig Week 11: Slide - 24

25 Figure 18.23: Predicted heterotroph productivity plotted against observed productivity in a range of communities. Week 11: Slide - 25

26 Figure 19.1: Energy flow (pink) and nutrient cycling of organic matter (red) and inorganic matter (white). Week 11: Slide - 26

27 Week 11: Slide - 27

28 Table 19.2: Week 11: Slide - 28

29 Figure 19.5: Annual nitrogen budget for control forest at Hubbard Brook (kg N 2 /ha). Week 11: Slide - 29

30 Figure 19.4: Annual loss of major nutrients in streamflow. Week 11: Slide - 30

31 Figure 19.6: Concentrations of ions in stream water from control and deforested watersheds at Hubbard Brook. Week 11: Slide - 31

32 32. References: Begon, M., C.R. Townsend, & J.L. Harper Ecology: From individuals to ecosystems. 4 th edition. Blackwell Science, Oxford, 738 pp. Elton, C Animal ecology. Sidgwick & Jackson, London. Kormondy, E.J., & D.E. Brown Fundamentals of Human Ecology. Prentice Hall. Lindemann, R.L The trophic-dynamic aspect of ecology. Ecology 23: Week 10: Slide - 32