Ecological Risks Perspectives from Poland and the United States (1990) / Chapter Skim
Currently Skimming:
Measuring Function and Disfunction in Ecosystems
Measuring Function and Disfunction in Ecosystems
Pages 116-140
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From page 116... ...
This is an especially difficult issue in moving from simple situations where injury can be easily observed to more complicated ecological systems, i.e., ecosystems composed of hundreds or even thousands of species which, within their trophic groups, are disposed to take over the niches and functions of eliminated competitors. These deviations should be recognized early, when adverse effects begin to occur in an ecosystem and when remediation is still possible; belated recognition of dying ecosystems signals both ecological disaster and the defeat of ecologists who have not foreseen them.
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From page 117... ...
These are the production of organic matter, its consumption and incorporation into the bodies of successive consumers, and its breakdown by decomposers. This sequence of basic ecosystem processes included in the functional definition of an ecosystem is necessary for the self-restoration of an ecosystem and for its theoretically unlimited duration.
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From page 118... ...
Similarly, the process of decomposition, which releases nutrients necessary for biomass production and subsequent recycling, is often supplemented by intended or unintended fertilization from human activities. However, in spite of the fact that basic ecosystem processes are intensified or limited from outside, the fundamental ecosystem function is still the same: energy flow and cycling of matter.
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From page 119... ...
and underground biomass in grassland ecosystems shows distinct dependence on the quantity of water available to the site (Figure 4~: the fraction of underground biomass increases with decreasing precipitation. Litter decomposition measured along the transect from northern Sweden to central Poland seems to react to lower average temperatures by decline in the decay rate (Figure 5~.
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From page 120... ...
Berg (1986) surveyed the research on the dependence of litter decomposition rate on its chemical composition, suggesting that different stages of decomposition are controlled by different factors and that there are "lignin-controlled" as well as "nitrogen- and phosphorus-controlled"
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From page 121... ...
. D 400 800 1200 1600 2000 2400 2800 3200 DRY WEIGHT 9 m~2 y-1 121 FIGURE 3 Annual precipitation and aboveground production of grasslands (Breymeyer, 1981)
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From page 122... ...
This is a good comparative measure of forest productivity, though it is known that the correlation between litter fall and production becomes less direct in more productive forests (Figure 7~. Nevertheless, measurement of litter fall is commonly used as a measure of forest production, particularly in monitoring programs (Breymeyer 1981, 1984)
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From page 123... ...
, since the complete estimation of forest productivity is quite laborious. Theoretically, it can be assumed that all biomass produced in an ecosystem must at some time die and fall into the soil or sediments; error in this estimation results from ignoring the loss of biomass eaten by consumers, as some portion of organic matter produced is always consumed before it falls down.
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From page 124... ...
According to these measurements, it can be assumed that half of aboveground forest production falls to the soil annually; in the years when cones are produced, this percentage is considerably higher. Let us analyze the dependence of litter fall on climatic conditions (Figure 8~.
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From page 125... ...
at 0-1 kg cm~2. Northern and maritime taiga accumulates at 3-6 kg cm-2; and the main and southern taiga and cool conifer complexes are both characterized by a wide range of carbon accumulation at 4-25 kg cm-2.
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From page 126... ...
; 5=Breymeyer et al.(unpublished data) ; 6=Alvera, 1980; 7=means and standard errors of measurements of wood production according to Woodland Data Bank.
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From page 127... ...
ANTHROPOGENIC INFLUENCES ON ECOSYSTEMS In addition to analyses of the natural variability of ecosystems, let us consider variability induced by humans by analyzing two examples of human-provoked disfunction in grassland ecosystems which were subjected to drastic changes in water conditions. Irrigation Bulla et al.
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From page 128... ...
128 o to ~D 1L o to .
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From page 129... ...
Effect of Industrial Emissions on Grassland and Forest Ecosystems Very large disturbances in the functioning of grassland ecosystems can be observed in Polish Silesia, which is heavily polluted by coal mining and other extractive industries. Local stimulation and growth of plant production have been recorded in the region; however, decomposition rates decreased at the same time.
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From page 130... ...
In successive zones moving away from the factory, a whole range of changes could be observed a zone of bare soil; a zone of thick litter composed of very long needles and twigs; a zone of dwarf pines;
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From page 131... ...
Living but strongly damaged forest was characterized by already small organic fall from balding trees and a high rate of litter decomposition. Grabinska (dissertation, 1985)
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From page 132... ...
Due to various factors, however, Poland is covered primarily with coniferous forests, which constitute more than 75% of total aboveground biomass of forests in the country (pine alone covers 62%~. Of the total production of
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From page 133... ...
Of the three species of conifers grown in Poland, pine shows the lowest productivity and yet provides the greatest wood production in the country, since pine forests occupy the largest area. Coniferous forests are considered to be the terrestrial ecosystems most imperiled by air pollution; they are affected particularly by sulfur and nitric oxides, whose concentrations in the air have recently increased considerably (Figure 12~.
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From page 134... ...
Pine trees translocate some essential elements from the needles before leaf fall. In this way, the forest accumulates a larger portion of elements in plant tissue instead of losing them from litter and sandy soil.
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From page 135... ...
In plots situated in pine forests of southwest Poland (which are heavily polluted) , 71% of all predators were registered in epigeic fauna, while in northeast Poland (which is least polluted)
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From page 136... ...
These are still open questions, but the answers must come soon as the demands of society and the interest of scientists grow simultaneously. EVOLUTION OF ECOSYSTEMS Considering the functioning and the character of ecosystems as defined above, we often pause on the question of their evolution: How do ecosystems make evolutionary progress since they do not inherit their
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From page 137... ...
17780 s7.4 3Q3 As RET RAN SLOCATI ON INTENSITY LEAF FALL I 1 12072 1 ~ 1 11 p6~/.l ~ ~ 435 57DE 1 1 1 1 ~ V N al P 13.9 2s 1.2 - o.s1 3~0 67 Lit 137 BROADLEAVED FOREST (P 1[ N C I I 55 138 92.3 1721.0 ~~~ 1 .
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From page 138... ...
These sets of species or communities: · accept the physical conditions of an area; · can produce organic matter or feed on organic matter produced there; and · can defy competition or other ecological dependences which grow in number and intensify as the colonization of niches increases. In the conditions of a cool temperate climate, forest succession must take more than 200-300 years to reach a climax forest stage (assuming that the forest attains maturity at an age of about 100-150 years, and all of the intermediary stages can develop and last for shorter penods)
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From page 139... ...
1985. The rate of organic matter decomposition and stands characteristics in coniferous forests of Central Poland.
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From page 140... ...
1986. Regional variation in rate of mass loss of Pibus silvesms needle litter in Swedish pine forests as influenced by climate and litter quality.
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