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MeaSUring FUnC[iOn and DiSfUnCIiOn in ECOSYS[emS ALICIA I. BREYMEYER Institute of Geography and Spatial Organization Polish Academy of Sciences Debates over the forms of environmental damage caused by increasing and hasty human activity often revolve around a central question: How should these deviations be measured? 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. The behavior and condition of particular species do not necessarily reflect the condition of the whole ecosystem, unless the system is dominated by only one producer species. Except for agriculture, monocultures are rather rare today; however, in Europe, until quite recently, pine cultures had been maintained for several generations, i.e., for several hundred years. Over such a long period, a specific ecosystem based on only one producer species is formed. Such a system will be fundamentally altered if the main producer of organic matter (e.g., pine) is devastated, and only in such a case can the state of an ecosystem be evaluated through the condition of a single species. Usually, however, there are many producers in an ecosystem, and the state of the ecosystem cannot be recognized from the condition of only one species of plant or animal. Some very specific types of ecosystems function with one or few con- sumers, such as the case of a tundra ecosystem described by Klekowski and Opalinski (1984~. The tundra in the Fugleberget catchment on Spitsber- gen, north of Norway, is supplied with allochthonous organic matter and 116

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HUMAN EFFECTS ON THE TERRESTRIAL ENVIRONMENT 117 nutrients from breeding colonies of marine birds feeding in the near-shore waters and nesting on land. The excrement of birds is distributed by surface waters and fertilizes a thin layer of soil. However, there are usually many consumers in an ecosystem, and their condition is not in itself a sufficient indicator of the state of the ecosystem. Similarly, particular plant species commonly used as bioindicators are not adequate to diagnose the condition of an ecosystem They may indicate the contamination of air, soil, or water, and therefore, work as live instruments to measure concentrations of differ- ent chemical compounds (Chapter 14, this volume). However, they do not answer questions about the response of an ecosystem to these substances, nor do they characterize its condition. ECOSYSTEMS: DEFINITION AND FUNCTION In order to make further discussions more explicit, we should define what is meant by an ecosystem (Breymeyer, 1981b). An ecosystem is an ecological system in which organic matter produced within this system (or partially from outside) is transformed at successive trophic levels according to known and described patterns of matter cycling and energy flow. This definition is consistent with the hierarchical approach presented by O'Neill et al. (1986~. The ecosystem is treated as a "medium number system," consisting of a number of smaller functional components. Such an explicitly functional definition of an ecosystem makes its delimitation difficult; generally speak- ing, so-called "small cycles" of basic elements are included in this system as they are conditioned by biotic components of the ecosystem. "Large cycles" of energy, water, and elements are dependent on atmosphere, ge- ology, and other physical and chemical factors. These are external and can be considered only as an environment in which the ecosystem functions. The main inputs from this environment to the ecosystem are solar energy, 02, C02, and water solutions of essential elements. Main outputs are gases, the energy dispersed in metabolic processes, and the remains of organic matter falling into the soil or sediments. Interpreted in this way, the boundaries of an ecosystem are designated in the diagram of carbon cycling (Figure 1~. The ecological system operates within these limits; its environment is outside. The creation and transformations of organic matter through a network of functioning trophic levels are the basic ecosystem processes. 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 defi- nition of an ecosystem is necessary for the self-restoration of an ecosystem and for its theoretically unlimited duration. Under conditions of increasing

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118 CO2 recRperai ~ \ _ _ ~ 1 1 ~ ~ Wateratm~ ~ ,~ / equilibrium ~~= ~~.~ ~ AM Fossil energetic sources 1_~: ., plants and~nima~ ~ ~ Icanism ~ ~ (mu) S a?: ~J~/ ~/Dr ~: ECOLOGICAL RISKS |lU[~ bit ; r MU; 'art et totem, A Decompositiop7~7' as rock' FIGURE 1 Carbon cycle and ecosystem boundanes. The "small" carbon cycle is framed by the ecosystem boundary (IIIIII); the "large" carbon pycle connects the ecosystem with the outside environment (Duvigneaud and linghe, 1962, adapted). human impact, fewer ecosystems function solely on the basis of internal production of organic matter. 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 ecosys- tem processes are intensified or limited from outside, the fundamental ecosystem function is still the same: energy flow and cycling of matter. The functional definition of an ecosystem provides a convenient ba- sis to determine the limits of ecosystem capacity for pollutants and other stresses, i.e., the limits of ecosystem resilience can be estimated by the resilience of ecosystem processes. These processes can obviously be inten- sified or reduced; and the proportions among production, decomposition,

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HUMAN EFFECTS ON THE TERRESTRIAL ENVIRONMENT 119 and consumption can vary in each ecosystem. However, these processes must continue. If any of them disappear, the ecosystem by definition no longer exists. The disappearance of ecosystem processes is measurable, so the capacity (vulnerability) of an ecosystem can be measured as well. How can we determine the level at which the rates and the character of ecosystem processes are altered from their ~`natural'' state, resulting in dis- turbances in the functioning of the whole ecosystem? Comparative analyses provide a useful starting point. The natural range of rates of ecosystem processes should be determined in presently existing, ecologically stable ecosystems operating at different levels of production and decomposition. Comparative ecology of ecosystems provides the opportunity to utilize both older data from literature and recent information collected intensively at several ecological centers. Examples are the current studies of Berg et al. in Sweden, Meentemeyer and Box in the United States, Singh in India, and Parkinson et al. in Canada. In Poland, investigations of pine forests are carried out on a rather wide scale; data from these studies have yet to be published, but they are partly used in this chapter. NATURAL INFLUENCES ON ECOSYSTEMS Climate is the basic factor of the exterior environment that conditions the production and decomposition of organic matter in ecosystems. Mate- rials from the International Biosphere Program (IBP) and the older studies compiled by O'Neill and DeAngelis (1981) show the dependence of forest productivity upon two basic components of climate: temperature and pre- cipitation (Figure 2~. These comparisons are based on a wide range of both elements of climate comprising the whole earth, so that the extreme values of forest productivity are represented. A similar, distinct pattern exists for the productivity of grassland ecosystems over a wide range of precipita- tion (Figure 3~. The allocation of aboveground (green) and underground biomass in grassland ecosystems shows distinct dependence on the quan- tity 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 Swe- den to central Poland seems to react to lower average temperatures by decline in the decay rate (Figure 5~. Stands examined along the transect were chosen with great care; pine forests of similar age growing on similar sandy soil were selected. The range of precipitation is not wide, although the two Spanish sites are situated in much drier conditions. The differen- tiation of temperature can be assumed to be the primary limiting factor, although the dependence is not simple, as can be seen in the variability of measurements.

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120 ECOLOGICAL RISKS 30 25 >, 20 _ . 1,~ 15 10 5 (_) O 1 i- o ~ -13 -10 C 30 At: 25 llJ 20 Hi: ~ 10 C) 15 5 o ~0 oo o Off Otp ~ 00 10 20 TEMPERATURE (C) oo o ~:e l 1~ o . 30 0 1000 2000 3000 4000 PRECIPITATION ~ MM ~ FIGURE 2 Forest productivity in relation to temperature and precipitation. Open and closed circles show two sources of information (IBP data after Reichle measurements, cited by Lieth, 1975). Meentemeyer (1984) calculated the index of evapotranspiration and showed its correlation with decomposition. The question of the dependence of litter decomposition on its lignin content has provoked heated debate. Initial calculations made on measurements from the temperate zone suggest that the rate of litter decomposition could be precisely predicted by lignin content. Very high correlations of both these values were recorded in subsequent studies. This index was not applicable to a desert environment in which the rate of litter decay was found not to depend on lignin content (Schaefer et al., 1985~. Berg (1986) surveyed the research on the dependence of litter de- composition 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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HUDSON EFFECTS ON THE TERRESTRIAL ENVIRONMENT ~ 1600 1200 `, 800 Om: I;: - 400 1 . . 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). ~ 2000 - Z 1600 ~ 1200 tL (3 800 or 400 f . . . . e ~ . ~ S - 4 8 12 16 20 24 28 32 36 40 UNDERGROUND TO GREEN BIOMASS RATIO FIGURE 4 Ratio of underground/green biomass in relation to precipitation for types of grasslands (Breymeyer, 1981).

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122 60 To of Oh CO o ~ 40 CD LL 20 ECOLOGICAL RISKS f 2 3 . . . ~ D 45 50 55 LATITUDE FIGURE 5 Litter decomposition as percent weight loss (litter-bag method) in first year of exposure in coniferous forests of different latitudes. 1=Spain, 2=Sweden, 3=Poland (according to data from Berg et al., 1983; Alvera, 1981; Breymeyer, in preparation). stages. Meentemeyer and Berg (1986) attempted to link chemical and cli- matic factors in their map of the rate of decomposition of pine needles for all of Scandinavia (Figure 6~. The map predicts the rates of decomposition of the material with known, constant chemical composition, using the index of actual evapotranspiration as the driving variable. On a geographic scale, one of the best known indices of production is the fall of litter. 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 pro- duction, particularly in monitoring programs (Breymeyer 1981, 1984) or

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HUM 4N EFFECTS ON THE TERRESTRIAL ENVIRONMENT A / - 30 ~ ~00 i JO JU ~ r~30 ry o Con f ALL a' ~ 1 rid 20 123 FIGURE 6 Isolines of decomposition rates for Scandinavia. The first-year needle-litter mass loss cloy was predicted on the basis of similar initial chemical composition of needles (N=0.41~o, P=0.022~o, lignin=25.7~o) with changing actual evapotranspiration (AEI) value (Meentmeyer and Berg, 1986, amended). in modeling (Ajtay et al., 1979), since the complete estimation of forest productivity is quite laborious. Theoretically, it can be assumed that all biomass produced in an ecosys- tem 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. In forest ecosystems, this error can be neglected. According to the estimates of different authors, the consumption of crown herbivores does not exceed a few percent of a canopy biomass, except in conditions of pest outbreaks. Hence, litter fall the measure of "annual green production" of a forest~an be assumed to be a good index of total aboveground produc- tion of a forest ecosystem. As an example, the production and production

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124 2000 1500 cat 18 _ 1000 as - - - 500 to ECOLOGICAL RISKS - _ / / / i- S . / X~- ~ . / of- ~ I / ~- / . - ~ . 500 1000 1500 2000 Above ground net primary production {gm I' FIGURE 7 Annual litterfall as a function of aboveground net primary production. The solid line shows the situation when the loopy of production falls down (O'Neill and DeAngelis, 1981; Debazac, 1983; Grodzinski et al., 1984~. efficiency in four mixed-pine forests in Poland and the United States can be analyzed (Table 13. 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~. (It is worth mentioning that only a small number of research centers have undertaken studies of complete forest productivity.) A large number of measurements show that the amount of organic matter delivered to the soil in forests decreases with nothward movement from the equator. This dependence is unquestionable within the gradient from 0 to 70N latitude. However, at a smaller scale, such as the size of the territory of Poland (6 in latitude, 49 to 50N), variance is relatively large and the data do not show any correlation with latitude.

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HUMAN EFFECTS ON THE TERRESTRL4L ENY7RONMENT TABLE 1 Production and production effiacocy in four stands of mid pine forest. MEASUREMENTS FOREST STANDS 1 2 3 4 Tree production Tdw ha-1 ye % of total: 2.5 4.7 7.9 14.3 Leaves, fruits, twigs. 40.4 53.7 24.7 57.4 Production efficiency (PIB) Trees Leaves 1 - - - 5% 50 - - - 53% SOURCE: Reiger et al., lS84; Whittaker and Marks, 1975. 125 On the basis of this information, one could conclude that the minimum north-south span for observing litter fall must be 20. Does this also mean that the total production of these ecosystems reacts to changes in macroclimate only when the area comprises 20? Some data suggest that such areas may be even more extensive. The measurements of wood production collected during the IBP are noted in Figure 8. Although the values maintain the general increasing trend from the north toward the equator, they show no such clear tendency between 30 and 60N; in these latitudes, wood production may actually increase as one moves northwards. These measurements are not numerous, so it is not yet known whether this tendency is definitive or not. Nevertheless, it is an indication that climate regulates the wood production only over large areas. Some idea of the variability of organic matter on a global scale is offered bv the man bv Olson et al. fl9831 entitled "Major World Ecosvstem ~ ~ , ~ , ~ _ , Complexes Ranked by Carbon in live Vegetation." The Eurasian continent is reproduced from this map in Figure 9. The biome of temperate needle- leaf forests is marked according to the UNESCO-Udvardy (1975) blame map. This biome covers four classes of the complexes defined by Olson et al. (1983~: tundra; northern and maritime taiga; main and southern taiga; and cool conifer. According to the measurements collected by Olson et al., tundra is characterized by the smallest biomass (i.e., carbon accumulation) 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. Zonal distribution of these ecosystem complexes is distinct, especially in the case of two -taiga complexes. Further analysis of the map shows that this natural variability of needle-leaf forest takes place in the span of 20 North-South. Does this mean that living carbon in ecosystems is more

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126 ~1 a: ECOLOGICAL RISKS 18 16 14 12 10 8 6 4 2 1 o o X o XX xx o X o XX X X _~ ~ _ X 2 - 3 x 4 0 5 + 6= 7. o ~0 AX X . x X ~ Ibex ~~ 4,1 X Act; Xl it X 0 o++ ~ O ~ 0 ~ ~ ~ o + ~ 60 70. N 0 10 20 30 40 50 LATITUDE FIGURE 8 Annual litterfall in relation to latitude. 1=Bray and Gorham, 1984; 2=IBP Woodland Data Bank (Reichle, 1981~; 3=Vogt et al., 1986 (broadleaved forest); 4Vogt et al., 1986 (needle forest); 5=Breymeyer et al.(unpublished data); 6=Alvera, 1980; 7=means and standard errors of measurements of wood production according to Woodland Data Bank. Vogt et al. data are collected for northern and southern latitudes, the others for northern latitudes only.

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130 ECOLOGICAL RISINGS T , S A I II III IV SEASONS I . II III IV FIGURE 10 Biomass of various groups of soil fauna (g fw m~2) in three grassland ecosystems: T=non-polluted meadow of medium fertility in Poland (data from literature), S=Szc~yglowice meadow in Silesia (moderately polluted); A=industrial Aniolki meadow (heavily polluted). Circle size is proportional to the total biomass of soil fauna (for a non-polluted meadow the biomass 135 g fw m-2 was assumed). In each circle three groups of fauna are shown as percentages of total biomass: 1=microfauna, 2=oligochaeta, 3=other invertebrates. Samples were collected in four seasons and three years (spring, summer, fall, and winter 1978-1980) (Cianciara and Pilarska, 1984, amended). TABLE 2 Increase in content of selected elements in the bodies of three main groups of consumers in a NPK fertilized meadow. Calculated on the basis of consumer biomass evaluated on fertilized and Fertilized plots (ma m~3. Invertebrate bodies Elements Fertilized from trophic groups analyzed Non-fertilized Phytophagans C 1.55 N 1.70 K+Na 1.72 Saprophagans C 1.71 N 1.69 K+Na 2.00 Predators C 2.73 N 2.88 K+Na 3.00 SOURCE: Machnacka-Lawacz and Olechowicz, 1978. there was a kind of nitric fertilization which caused substantial elongation of needles and sprouts (shoots), but also induced their flabbiness and early dropping from the trees (Jakubczak and Pieta, 1968~. Several years later, the first portions of the forest began to die, and the border of living forest moved away from the factory. Investigations on the production and decomposition of organic matter in the area were carried out in the period 1980-1982. 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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HUAf4N EFFECTS ON THE TERRESTRIAL ENVIRONMENT 131 ~ _~.% ~] ~ Hi , ~- d., ~~%~.~% -,: ~ FIGURE 11 Distribution of coniferous and mined forests and air pollution in Poland. The map was elaborated at the Institute of Geodesy and Cartography in Wa maw under the supervision of Andrzej Ciolkosz on the basis of L~dsat MSS and Salut-6 images acquired in 1978. The isolines delimit the area with SO2 mean annual concentration equal/higher than 50 micrograms per m3; dark areas show regions above 150 micrograms. Data on pollution Mom the map predicting air pollution in Poland in 1990 lay J. Juda et al., 1982 (manuscnpt). and the forest wall. 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) suggested that this was probably abiotic decomposition, as the litter was dissolved in the solution of nitric and sulfur compounds in rainwater. Let us move on to the territory of Poland as a whole and the condition of coniferous forests as demonstrated by scientists and foresters. Satellite pictures of pine and mixed-pine forests in Poland are shown in Figure 11. The simulated isolines of contamination by sulfur oxides delimit the area of real danger for conifers as projected to 1990. Present evaluations by forestry services of the state of these forests are shown in Figures 12 and

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132 , , to ~ ~ , ''art: ECOLOGICAL RISKS NOx FIGURE 12a Pollution of Polish coniferous forests by NOT in 1986 measured 1,800 points as dry sediments on specifically prepared filter paper exposed for 30 days in the canopy. Contamination expressed as mg m 2 d 1 in four classes: 1=0.000-0.200 ma; 2=0.201 - 0.5000 ma; 3=0.501-1.000 ma; 4=higher than 1.001 ma. A=winter pollution, B=summer pollution. 13. Comparison of winter (i.e., heating season) and summer contamination of forests provides a basis for some optimism: in many regions, forests are not as stressed during the warm season when heating is not used. STATUS OF FOREST ECOSYSTEMS IN POLAND According to maps of potential vegetation and the knowledge of geo- botanists, Poland should be covered with a mixture of forest types. 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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HIJAL4N EFFECTS ON THE TERRESTRIAL ENVIRONMENT 133 E zczecln . NOx FIGURE 12b L . ~ ~ ,., _; ~ I,' ,, ., ., Polish forests, conifers make up 74%, and pine alone is 54.4% (Figure 14~. 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~. There is.still no single answer as to which mechanisms are responsible for the dying of coniferous forests, but some are particularly worthy of analysis. Coniferous forests, and pine forests in particular, are in general ecosystems of cool climates and poor soils. Matter cycling is rather slow in these ecosystems, and the rate of organic matter decomposition is distinctly slower than. in deciduous forests (%ble 34. Interesting mechanisms for saving essential elements in these ecosystems are described in Figure 15.

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134 A ECOLOGICAL RISKS FIGURE 13a Pollution of Polish forests by SO2. Description as for Figure 12. Masses of contamination: 1=0.000-10.000 mg m-2 dot; 2=10.001-30.000; 3=30.001-50.000; 4=above 50.000 ma. A = winter pollution, B = summer pollution. 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. Moreover, conifers shed their needles two or three times slower than do other plants in similar climates. Consequently, pine forests can be considered to be the ecosystems that retain in their biomass a relatively large proportion of the elements taken from the abiotic environment. This tendency to accumulate the elements which are difficult to acquire can be seen as an evolutionary strategy. However, this strategy may turn against coniferous ecosystems. When the chemical composition of the atmosphere and water changes rapidly in the surrounding environment,

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HUMAN EFFECTS ON THE TERRESTRIAL ENVIRONMENT 135 R ~~ ART;- ! _ so2 FIGURE 13b / "sparing" (nutrient-conserving) ecosystems are more susceptible to gradual poisoning than are others that dispose of toxic substances more rapidly. With respect to control mechanisms, the tendencies recorded in forest ecosystems are similar to those observed in grasslands in heavy stress sit- uations, the number of species often decreases, the percentage of predators increases, and the dominance structure becomes more uneven (i.e., fewer species are dominant). These tendencies were recorded by Lesniak (in press) in his investigations of soil and epigeic (soil surface) invertebrates carried out in 52 forest districts distributed over the entire territory of Poland. 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), the percentage of predators was only 28% The regulatory mechanisms induced by an increasing share of predators

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136 ECOLOGICAL RISKS :~: ]~ 1~' me -'5~-~( -~U=: 4_~ --I am-_ ~= FIGURE 14 Composition of forests in geographical units in Poland. The portion of tree species expressed as percent of surface covered by this species. 1=pine; 2=spruce; 3=fir, 4=beach; 5=oak; 6=birch and hornbeam; 7=alder and aspen (1tampler et al., 1982, prepared from Forestry Service Data). and their increased metabolism rate are strengthened in stress conditions; perhaps this is the first distinct, repeatable reaction of an ecosystem noted in the case of changing conditions. Is the ecosystem trying to defend and adapt itself in this way? And how does it influence the pattern of matter circulation and the budget of production/decompostion? 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 de- fined 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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HUMAN EFFECTS ON THE TERRESTRIAL ENVIRONMENT TABLE 3 Weight loss of litter in central Poland. Litter bags exposed on 28 stands (10-30 bags per stand) during warm season. Decomposition rate expressed as percent of initial weight. Site Forest type Number of stands Daily decomposition rate (%) Bolimow Malogoszcz Pulawy Bialoleka Dw. Pine and mined 6 0.08-0.30 Pine 7 0.10-0.24 Pine ~ 0.20-0.24 Pine and mined 2 0.22 Coniferous 20 0.08-0.30 20 Bialoleka Dw. Bialoleka Dw. Bialoleka Dw. 2 Alder Birch l Oak hornbeam 5 Broadleaved 8 0.34 0.44 0.51 0.34-0.51 SOURCE: Unpublished data, Breymeyer and Grabinska. PINE FOREST NUTRIENTS C N K P IN GREEN LEAVES (kg/ha) 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 . ~ 2291. ~1 1 L-l 1 7,. l ~ l I I t I I P K N L4.6 10.8 85fi oil V C .0 1 l FIGURE l5 Pattern of nutrient transfer to soil in pine and alder forests (Stachu~ki and Zimka, 1981; modified). characteristics as do species? They have no mechanisms of heredity, since they are not organisms provided with sets of features coded in their genes. However, it appears that ecosystems adjust so as to permit the recurrence of the composition of species (or the communities of ecologically redundant species) worked out during long-term evolution. And perhaps ecosystems evolve by even simpler means than the do cogeneric populations.

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138 ECOLOGICAL RISKS If, for example, a sand dune is colonized, the first group of colonizers is selected; there are only a small number of pioneer species that are fit for living on dune sand. They prepare the environment for succeeding species, which in turn do the same for the next generation. A layer of soil appears and it grows thicker, pine seedlings attach in it, and the succession proceeds In the same way, only to reach the climax stage as one of the forest associations common to the climatic zone. Just as in the case of populations where conditions select the fittest of overabundant progeny, it can be assumed in the case of an ecosystem that only certain groups of the overabundant seeds, spores, or juvenile forms of plants and animals which expand in different ways and are ready to colonize a given area will be accepted there. 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). It is not proven how much time is needed to develop the complex trophic structure registered in contemporary forest stands. Probably many generations of trees produce the pool of organic matter in the forest soil as detritivores gradually enter the soil and put in motion the circulation of elements. Can this be recognized as a beginning of ecosystem function? And how many years are needed to develop sets of species ready to replace or complete each other In all points of the trophic net? Kornas (1972) dis- cussed the historical background of European and North American conifers (genus Pinus, Picea, Abies, Lards) from the boreal zone of coniferous taiga. The author believes that Eurasiatic and North American lowlands were colonized by taiga-type forest not earlier than in the Holocene. The taiga trees have had their long, early history in primary centers in the moun- tains of Eastern Asia and Pacific North America, and they dispersed in lowlands after Pleistocene glaciation (before the Tertiary Holarctic realm divided). Moreover, there is some proof that pairs of close, vicariant taxa of American and European flora still show distinct ecological correspondence: Nearly all series of closely related taxa in the forests of temperate Eurasia and North America consist of ecologically corresponding components which have similar ranges of tolerance, occupy similar habitats, and grow in strictly analogous plant communities. The ecological constitution of such groups must be very ancient and very rigid. Even those nemoral taxa which are separated

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HUAL4N EFFECTS ON THE TERRESTRIAL ENVIRONMENT 139 into morphologically distinct species have undergone no noticeable ecological changes since their isolation some 1~15 million Yeats ago (Kornas, 19723. Thus, contemporary boreal coniferous forest ecosystems began their evolution in the Holocene 10,000 years ago, but they consist of some very conservative taxa which did not change ecological habits for millions of years. REFERENCES Allay, G.K, P. Ketner, and P. Duvigneaud. 1979. Terrestrial primary production and phytomass. Pp. 129-181 in The Global Carbon Cycle, B. Bolin, R.T. Degnas, S. Kempe, P. Ketner, eds. SCOPE 13 (Wiley ~ Sons). Alvera, B. 1981. Decomposition de hojas en un pinar altoaragones. Ann. Edafol. Agrobiol. Madrid 40:37-46. Berg, B., P.E. Jansson, and V. Meentemeyer. 1984. Litter decomposition and climate-regional and local models. Pp. 389 404 in State and Change in Forest Ecosystems, G.I. Agren, ed. Report 13 Swed. Univ. Agric. Sci. Bray, J.R., and E. Gorham. 1964. Litter production in forests of the world. Ad. ecol. Res. 2:101-157. Breymeyer, A. 1981a. Comparative studies on trophic structure of grassland ecosystems. Glad. Ekol. 27:116-147 On Polish with summary in English). . 1981b. Monitoring of the functioning of ecosystems. Environmental Monitoring and Assessment 1:173-183. . 1984. Ecological monitoring as a method of land evaluation. Geographia Polonica 50:371-384. 1986. Pine forests in Poland, their productivity, distribution, and degradation. Geographia Polonica 52:101-109. Bulla, L^, J. Pacheco, and R. Miranda. 1981. Ciclo estacional de la biomass verde, muerta y raices en una sabana inundate de estero en Mantecal (Venezuela). Acta Cient. Venezolana 31:339-344. Bulla, L~, J. Pacheco, and G. Morales. In press. Seasonally flooded meotropical savanna closed by dikes. In Damaged Grasslands, A. Breymeyer, ed. Elsevier. Cianciara, S., and J. Pilarska. 1983. Numbers and structures of soil fauna communities in tow meadows in Upper Silesia. Ekol. Poll 31,4:947-997. Debazac, E.F. 1983. Temperate broad-leaved evergreen forest of the Mediterranean region and Middle East. Pp. 107-122 in Temperate Broad-Leaved Evergreen Forests, J.D. Ovington, ed. Elsevier. Duvigneaud, P., and M. Dinghy. 196Z Ecosystems et biosphere. Itavaux du Centre d'Ecologe Generate. BnrYelles. Grabinska, B. 1985. The rate of organic matter decomposition and stands characteristics in coniferous forests of Central Poland. Dissertation in Polish. Inst. of Geography, Polish Academy of Sciences. Warsaw. Grodzinski, W., J. Weiner, and P.F. Maycock, eds. 1984. Forest ecosystems in industrial regions. Springer Verlag. Jakubczak, A., and J. Pieta. 1968. Some morphological variation of the needles and shoots of Scotch pine (Pibus sylYes~is L) in the polluted surroundings of nitrogen plant at Pulawy. P. 68 in the Proceedings of the VI International Conference, "Influence of air pollution on forests". Research Laboratory GOP, Polish Academy of Sciences. Juda, J., S. Chrosciel, J. Jednejowski, M. Nowicki, and W. Jaworski. 198Z The influence of fossil fuel combustion on environment in the perspective of the year 2000 in Poland. typescript in Polish. Klekowski, Z.R., and KW. Opalinski. 1984. Matter and energy flow in Spitzbergen tundra. Glad. Ekol. 30143-166 (in Polish with summary in English).

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140 ECOLOGICAL RISKS Koalas, J. 1972. Corresponding taxa and their ecological background in the forest of temperate Eurasia and North America. Pp. 37-59 in Taxonomy, Phytogeography, and Evolution, D.H. Valentine, ed. Academic Press. Lesniak, A. 1988. Monitoring of soil fauna on 52 stands of coniferous forest in Poland. Institute of Zoology, Polish Academy of Sciences. Warsaw (manuscript in Polish). Lieth, H. 1975. Modelling the primary production of the world. Pp. 237-242 in Primary Productivity of the Biosphere, H. Lieth and R.H. Whittaker, eds. Springer Verlag,. Meentemeyer, V. 1984. The geography of organic decomposition rates. Ann. Assoc. American Geographem 74~4~:551-560. Meentemeyer, V., and B. Berg. 1986. Regional variation in rate of mass loss of Pibus silvesms needle litter in Swedish pine forests as influenced by climate and litter quality. Scand. J. For. res. 1:167-180. Mochnacka-Lawacz, H., and E. Olechowicz. 1978. The role of selected heterotrophic groups in the nutrient economy of a meadow ecosystem. Poll Ecol. Stud. 4~1~:243-257. Molski, B.N, and W. Dmuchowski. 1986. Effects of acidification on forest and natural vegetation, wild animals, and insects. Pp. 29-51 in Acidification and its Policy Implications, T.S. Schneider, ed. Proceedings of the International Conference, Elsevier Studies in Environmental Science 30. Okruszko, H. 1978. Meliorations and changes in the environment. Pp. 38~5 in The Role of Meliorations in Management of Natural Environment. Proceedings of the Conference, IMUZ-Falenty (in Polish). Olson, J.S., J.N Watts, and ~J. Allison. 1983. Carbon in live vegetation of major world ecosystems. Oak Ridge National Laboratory. O'Neill, R.V., and D.L~ DeAngelis. 1981. Comparative productivity and biomass relations of forest ecosystems. Pp. 411449 in Dynamic properties of forest ecosystems, D.E. Reichle, ed. Boston: Cambridge University Press. O'Neill, R.V., D.L. DeAngelis, J.B. Waide, and T.F.H. Allen. 1986. A hierarchical concept of ecosystems. Monographs in Population Ecology 23, Princeton University Press. Reichle, D., ed. 1981. Dynamic properties of forest ecosystems. Boston: Cambridge University Press. Rieger, R., S. Grabczynski, S. Orzel, and J. Ramier. 1984. Primary production in the Niepolomice forest ecosystems. Pp. 70-78 in Growing Stock and Increasing of liee Stands in Forest Ecosystems in Industrial Regions, W. Grodzinski, J. Weiner, and P.F. Maycock, eds. Springer Verlag. Schaefer, D., Y. Steinberger, and W.G. Whitford, 1985. The failure of nitrogen and lignin control of decompositoin in a North American desert. Oecologia 65:382-386. Stachurski, A., and J. Zimka. 1981. The patterns of nutrient cycling in forest ecosystems. Bull. Acad. Poll Sci., CI. II, 29, 3 4:141-147. Itampler, T., A. Girzda, and E. Dmyterko. 1986. Di~erentiation of biomass and production of coniferous forests in Poland. Institute of Geography and Spatial Organization. Warsaw (typescnpt in Polish). Trampler, T., E. Dmyterko, and B. Lonkiewicz. 1987. State and prognosis of forest damages in Poland. Bull. of ForestIy Institute 3,87:10-18 (in Polish). Udvardy, M.D.F. 1975. A classification of the biogeographical provinces of the world. IUCN occasional paper No. 18. Morges, Switzerland. Vogt, K^, C.C. Grier, and D. J. Vogt. 1986. Production, turnover, and nutrient dynamics of above- and belowground detritus of world forests. Advances in Ecologial Res. 15:303-377. Whittaker, R.H., and P.L~ Marks. 1975. Methods of assessing terrestrial productivity. Pp. 55-118 in Primary productivity of biosphere, H. Lieth and R.H. Whittaker, eds. Springer Verlag. Zurek, S. 1987. Peat deposits in Poland on the background of European peat zones. Dok. Geogr. 3:85 (in Polish with summa~y in English).