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The decomposition of dead organic matter in natural ecosystems and field in forest steppe zone — The role of separate factors
Zentralbl. Mikrobiol. 145 (1990), 47-49 VEB Gustav Fischer Verlag lena
[Institute of LandscapeEcology, Czechoslovak Akademy of Sciences, Ceske Budejovice, Czechoslovakia, Institute of Evolutionary Morphology and Ecology of Animals, USSR Academy of Sciences, Moscow, USSR]
The Decomposition of Dead Organic Matter in Natural Ecosystems and Field in Forest Steppe Zone - the Role of Separate Factors JAROSLAV BOHAt , ANDREI POKARZH EVSKI and ALEXANDER GUSEV Key words: decomposition of dead organic matter, steppe, forest, barley field, ploughed field, soil macro- and mesofauna
Summary Field experiments with the decomposition of dead organic matter in various ecosystems (unmown steppe, oak forest, barley field, ploughedfield) indicated that soil macro- and mesofauna had a variable but generally significant effect on litter decomposition. Decomposition rate was higher in forest than in open ecosystems owing to better hydrothermical regime. Decomposition rate inopenecosystems was the highest in the ploughed field and in the steppe. Decomposition rate in barley field was lower than in the above mentioned ecosystems. The decomposition in ploughed field was provided by a high activity of soil microorganisms because the abundanceof soil animals was insignificant.
Zusammenfassung Freilandversuche zur Zersetzung abgestorbener organischer Substanz in verschiedenen Okosystemen (ungemahte Steppe, Eichenwald, Gcrstenfeld, Ackerland) deuten darauf hin, daB die Bodenmakro- und -mesofauna einen unterschiedlichen. aber im allgemeinen bedeutenden EinfluBauf die Zersetzungsrate ausiibt. Die Geschwindigkeit des Abbaus war im Waldhoher als indenoffenenOkosystemen, bedingt durch ein bessereshydrothermisches Regime. Bei den offenen Okosysternen lag die Zersetzungsrate im Ackerland hoher als in der Steppe. 1mGerstenfeld wurden die niedrigsten Wertebeobachtel. DerAbbauderorganischenSubstanz im Ackerland warvora llembedingtdurcheine hohe mikrobielle Aktivitat ; die Bodentiere spielten hier nur eine untergeordnete Rolle.
The vast majority of ener gy and nutrient s of plants is eventu ally incorporated in dead organic matter or detritus. Both the decomposition of this material and release of inorganic elements that are bound in detritus (i.e. mineralization) are critical to the continued productivity of terrestrial ecosystems. The accumulation of dead organic matter not only locks away plant nutrients, but in certain ecosystems it reduces the amount of energy available for plant metabolism and photosynthesis because of the insulating and shading effects of litter. As a result , terrestrial decomposition and mineral ization processes have been the subject of a considerable scientific effort of biochemists, soil scientists , bacteriologi sts, mycologists, invertebrate zoologists, and ecologists. The concept that soil fauna regulat es the decomposition proce ss has become increasingly popular in spite of the fact that the amount of soil metabolism (C0 2 produ ction) that can beattributed to all soil animals is 10% or less of the total amount. Fungi and bacteria are directly responsible for most of the organic matter breakdown , but a diverse assamblage of protozoas, nematodes , annel ids and arthropods greatly influen ce the functions of the decomposing flora as a direct results of their feedin g activities . On the other side , little is known about the role of soil fauna in the decomposition process in vario us natural and man-m ade ecosys tems. The purpose of this study was to find out : I ) the rate of the decomposition of plant rem ains in vario us ecosys tems in forest steppe zone , 2) the share of soil fauna in the decomp osition proce ss, 3) factors causing differences in the decomposition rate in various ecosystems.
48
J. BOHAC et al.
Material and Methods The relation of soil fauna and decomposition process was studied in the forest steppe biosphere reserve and in the Agricultural Experimental Station near Kursk in the period April-September 1982. The typical chernozem soil is developed in the studied area. The decomposition of various plant remains was studied in the following ecosystems: I) unmown steppe (steppe grasses roots and litter), 2) oak forest (oak roots and leaves), 3) barley field (barley roots and straw), 4) all-year ploughed field (barley roots and straw). Roots, leaves and straw were washed and dried at 60 DC to constant weight. 5 g portions of plant remains were placed to the bags with various sizes of meshes (0.8 and 16mm). The litterbag method has been used for excluding soil macrofauna from the decomposition process. The bags with roots, leaves and straw were buried in the soil. A part of the bags was treated by naftalin to repell microarthropods. The use of the litterbag method and naftalin was the reason of 3 variants of our experiment: 1) decomposition with all biotic components (soil fauna and microflora), 2) decomposition without soil macrofauna participation, 3) decomposition without soil macrofauna and mesofauna participation. After the experiment the plant remains were cleaned and weighed. The difference between the initial weight and the weight after finishing the experiment was determined. Simultaneously with the experiment, the species diversity and abundance of soil macrofauna and mesofauna was followed. The temperature and humidity of soil in various depths were measured.
Results and Discussion The ecological characteristics of the studied ecosystems are different (Table 1). Oak forest differs from unmown steppe by a higher amount of phytomass and mass of leaf litter and roots. For that reason in the oak forest soil fauna feeds mainly on leaf litter, while in the steppe on roots with mycorrhiza. The barley field has not any the litter. Phytomass and mass of roots are lower than in natural ecosystems. The mass of microorganisms is higher in the field than in natural ecosystems. Plants and litter are absent in ploughed field. The quantity of microorganisms in ploughed field is comparable with that in barley field. Table 1. The ecological characteristics of the studied ecosystems. Mass (kglha)
Unmown steppe
Oak forest
Barley field
Ploughed field
Soil Litter Phytomass Roots living Roots dead Microorganisms
2250000 3800 3300 7805 11725 1000
2200000 15350 160000 20000 20600 1200
2607000
2305000
7000 4000 4000 3780
3780
135
125 6 2
Invertebrates: Saprophages Predators Phytophages
1.5 3
13.8 0.4 0.2
2.8 0.4
The biomass of soil animals in natural ecosystems is very similar. The biomass of soil fauna in barley field is about 10 times lower than in natural ecosystems, and in ploughed field it is insignificant. The reasons of the low abundance of soil fauna in agroecosystems are: absence of food (plant remains with fungi and microorganisms), unstable microclimatic conditions (deepfrozen soil in winter and drying of soil in summer) and the negative influence of man (harvesting and ploughing) (POKARZHEVSKYI et al. 1987). The sesonal dynamics of soil fauna were different in the studied ecosystems. There were two peaks in the seasonal dynamics of the soil macrofauna in natural ecosystems (steppe and forest) and in the barley field. In the all-year ploughed field we found only one peak in the seasonal dynamics of the soil macrofauna. Peaks of seasonal dynamics of the macrofauna in the barley field and oak forest were slightly shifted (by 1-2 weeks) in comparison with the steppe. This fact is caused by the later
The Decomposition of Dead Organic Matter
49
Table 2. The percent rate of decomposed mass from the starting point in various ecosystems of forest steppe. Variant of experiment
Unmown steppe
Oak forest
Barley field
Ploughed field
58 42 38
45 32
49 54 36
67 60 63
59 56 34
74 27 7
47 42 23
62 60 65
Roots: all biotic components without macrofauna without soil fauna
40
Straw, Leaves: all biotic components without macrofauna without soil fauna
warming of soil in the forest which influences the later finishing of hibernation of invertebrates and later activity of soil fauna. The reason of the different types of seasonal dynamics in the barley field is the later development of vegetation cover in the field. The rate of root decomposition with eliminated soil fauna is reduced in all ecosystems except the ploughed field (Table 2). The soil fauna considerable accelerated root decomposition in the steppe (about 16%). The influence of soil mesofauna on root decomposition is in all ecosystems lower than the influence macrofauna. The rates of decomposition in the ploughed field are similar both in the presence and absence of soil fauna. Soil fauna influences the rate of leaf and straw decomposition in all ecosystems except the ploughed field. The rate of decomposition was the highest in forest, and soil macrofauna and mesofauna had a considerable influence on the decomposition rates (47 % and 20 %). We believed that the constant microclimatical conditions in forest are more advantageous for soil fauna than in other studied ecosystems. Straw decomposition in open ecosystems is secured mainly by the diet of soil mesofauna (15-22%). The influence of the soil fauna on decay rates in ploughed field is minimal.
References POKARZHEVSKYI, A., GORDIENKO, S., BOHAC, J., ZABOYEV, L.: Resourcesof aminoacidsin the food of soil fauna andthe problemof the originof the useful soilfaunain agroecosystems. In: "Soil faunaof northernEurope" (D. A. KRIVOLUTSKYI, ed.). Nauka, Moscow 1987, 139-149 (in Russ.). Authors' address: Dr. JAROSLAv BOHAC, Institute of LandscapeEcology, CzechoslovakAcademy of Sciences, Na sadkach 7, 37005 Ceske Budejovice, Czechoslovakia" Dr. A. POKARZHEVSKYI, Dr. A. GUSEV, Institute of EvolutionaryMorphology and Ecology of Animals, USSR Academyof Sciences, 117071 Moscow, Leninskipr. 33, USSR.
4 ZentraIbl. Milaobiol., Bd. 145, 1
[Institute of LandscapeEcology, Czechoslovak Akademy of Sciences, Ceske Budejovice, Czechoslovakia, Institute of Evolutionary Morphology and Ecology of Animals, USSR Academy of Sciences, Moscow, USSR]
The Decomposition of Dead Organic Matter in Natural Ecosystems and Field in Forest Steppe Zone - the Role of Separate Factors JAROSLAV BOHAt , ANDREI POKARZH EVSKI and ALEXANDER GUSEV Key words: decomposition of dead organic matter, steppe, forest, barley field, ploughed field, soil macro- and mesofauna
Summary Field experiments with the decomposition of dead organic matter in various ecosystems (unmown steppe, oak forest, barley field, ploughedfield) indicated that soil macro- and mesofauna had a variable but generally significant effect on litter decomposition. Decomposition rate was higher in forest than in open ecosystems owing to better hydrothermical regime. Decomposition rate inopenecosystems was the highest in the ploughed field and in the steppe. Decomposition rate in barley field was lower than in the above mentioned ecosystems. The decomposition in ploughed field was provided by a high activity of soil microorganisms because the abundanceof soil animals was insignificant.
Zusammenfassung Freilandversuche zur Zersetzung abgestorbener organischer Substanz in verschiedenen Okosystemen (ungemahte Steppe, Eichenwald, Gcrstenfeld, Ackerland) deuten darauf hin, daB die Bodenmakro- und -mesofauna einen unterschiedlichen. aber im allgemeinen bedeutenden EinfluBauf die Zersetzungsrate ausiibt. Die Geschwindigkeit des Abbaus war im Waldhoher als indenoffenenOkosystemen, bedingt durch ein bessereshydrothermisches Regime. Bei den offenen Okosysternen lag die Zersetzungsrate im Ackerland hoher als in der Steppe. 1mGerstenfeld wurden die niedrigsten Wertebeobachtel. DerAbbauderorganischenSubstanz im Ackerland warvora llembedingtdurcheine hohe mikrobielle Aktivitat ; die Bodentiere spielten hier nur eine untergeordnete Rolle.
The vast majority of ener gy and nutrient s of plants is eventu ally incorporated in dead organic matter or detritus. Both the decomposition of this material and release of inorganic elements that are bound in detritus (i.e. mineralization) are critical to the continued productivity of terrestrial ecosystems. The accumulation of dead organic matter not only locks away plant nutrients, but in certain ecosystems it reduces the amount of energy available for plant metabolism and photosynthesis because of the insulating and shading effects of litter. As a result , terrestrial decomposition and mineral ization processes have been the subject of a considerable scientific effort of biochemists, soil scientists , bacteriologi sts, mycologists, invertebrate zoologists, and ecologists. The concept that soil fauna regulat es the decomposition proce ss has become increasingly popular in spite of the fact that the amount of soil metabolism (C0 2 produ ction) that can beattributed to all soil animals is 10% or less of the total amount. Fungi and bacteria are directly responsible for most of the organic matter breakdown , but a diverse assamblage of protozoas, nematodes , annel ids and arthropods greatly influen ce the functions of the decomposing flora as a direct results of their feedin g activities . On the other side , little is known about the role of soil fauna in the decomposition process in vario us natural and man-m ade ecosys tems. The purpose of this study was to find out : I ) the rate of the decomposition of plant rem ains in vario us ecosys tems in forest steppe zone , 2) the share of soil fauna in the decomp osition proce ss, 3) factors causing differences in the decomposition rate in various ecosystems.
48
J. BOHAC et al.
Material and Methods The relation of soil fauna and decomposition process was studied in the forest steppe biosphere reserve and in the Agricultural Experimental Station near Kursk in the period April-September 1982. The typical chernozem soil is developed in the studied area. The decomposition of various plant remains was studied in the following ecosystems: I) unmown steppe (steppe grasses roots and litter), 2) oak forest (oak roots and leaves), 3) barley field (barley roots and straw), 4) all-year ploughed field (barley roots and straw). Roots, leaves and straw were washed and dried at 60 DC to constant weight. 5 g portions of plant remains were placed to the bags with various sizes of meshes (0.8 and 16mm). The litterbag method has been used for excluding soil macrofauna from the decomposition process. The bags with roots, leaves and straw were buried in the soil. A part of the bags was treated by naftalin to repell microarthropods. The use of the litterbag method and naftalin was the reason of 3 variants of our experiment: 1) decomposition with all biotic components (soil fauna and microflora), 2) decomposition without soil macrofauna participation, 3) decomposition without soil macrofauna and mesofauna participation. After the experiment the plant remains were cleaned and weighed. The difference between the initial weight and the weight after finishing the experiment was determined. Simultaneously with the experiment, the species diversity and abundance of soil macrofauna and mesofauna was followed. The temperature and humidity of soil in various depths were measured.
Results and Discussion The ecological characteristics of the studied ecosystems are different (Table 1). Oak forest differs from unmown steppe by a higher amount of phytomass and mass of leaf litter and roots. For that reason in the oak forest soil fauna feeds mainly on leaf litter, while in the steppe on roots with mycorrhiza. The barley field has not any the litter. Phytomass and mass of roots are lower than in natural ecosystems. The mass of microorganisms is higher in the field than in natural ecosystems. Plants and litter are absent in ploughed field. The quantity of microorganisms in ploughed field is comparable with that in barley field. Table 1. The ecological characteristics of the studied ecosystems. Mass (kglha)
Unmown steppe
Oak forest
Barley field
Ploughed field
Soil Litter Phytomass Roots living Roots dead Microorganisms
2250000 3800 3300 7805 11725 1000
2200000 15350 160000 20000 20600 1200
2607000
2305000
7000 4000 4000 3780
3780
135
125 6 2
Invertebrates: Saprophages Predators Phytophages
1.5 3
13.8 0.4 0.2
2.8 0.4
The biomass of soil animals in natural ecosystems is very similar. The biomass of soil fauna in barley field is about 10 times lower than in natural ecosystems, and in ploughed field it is insignificant. The reasons of the low abundance of soil fauna in agroecosystems are: absence of food (plant remains with fungi and microorganisms), unstable microclimatic conditions (deepfrozen soil in winter and drying of soil in summer) and the negative influence of man (harvesting and ploughing) (POKARZHEVSKYI et al. 1987). The sesonal dynamics of soil fauna were different in the studied ecosystems. There were two peaks in the seasonal dynamics of the soil macrofauna in natural ecosystems (steppe and forest) and in the barley field. In the all-year ploughed field we found only one peak in the seasonal dynamics of the soil macrofauna. Peaks of seasonal dynamics of the macrofauna in the barley field and oak forest were slightly shifted (by 1-2 weeks) in comparison with the steppe. This fact is caused by the later
The Decomposition of Dead Organic Matter
49
Table 2. The percent rate of decomposed mass from the starting point in various ecosystems of forest steppe. Variant of experiment
Unmown steppe
Oak forest
Barley field
Ploughed field
58 42 38
45 32
49 54 36
67 60 63
59 56 34
74 27 7
47 42 23
62 60 65
Roots: all biotic components without macrofauna without soil fauna
40
Straw, Leaves: all biotic components without macrofauna without soil fauna
warming of soil in the forest which influences the later finishing of hibernation of invertebrates and later activity of soil fauna. The reason of the different types of seasonal dynamics in the barley field is the later development of vegetation cover in the field. The rate of root decomposition with eliminated soil fauna is reduced in all ecosystems except the ploughed field (Table 2). The soil fauna considerable accelerated root decomposition in the steppe (about 16%). The influence of soil mesofauna on root decomposition is in all ecosystems lower than the influence macrofauna. The rates of decomposition in the ploughed field are similar both in the presence and absence of soil fauna. Soil fauna influences the rate of leaf and straw decomposition in all ecosystems except the ploughed field. The rate of decomposition was the highest in forest, and soil macrofauna and mesofauna had a considerable influence on the decomposition rates (47 % and 20 %). We believed that the constant microclimatical conditions in forest are more advantageous for soil fauna than in other studied ecosystems. Straw decomposition in open ecosystems is secured mainly by the diet of soil mesofauna (15-22%). The influence of the soil fauna on decay rates in ploughed field is minimal.
References POKARZHEVSKYI, A., GORDIENKO, S., BOHAC, J., ZABOYEV, L.: Resourcesof aminoacidsin the food of soil fauna andthe problemof the originof the useful soilfaunain agroecosystems. In: "Soil faunaof northernEurope" (D. A. KRIVOLUTSKYI, ed.). Nauka, Moscow 1987, 139-149 (in Russ.). Authors' address: Dr. JAROSLAv BOHAC, Institute of LandscapeEcology, CzechoslovakAcademy of Sciences, Na sadkach 7, 37005 Ceske Budejovice, Czechoslovakia" Dr. A. POKARZHEVSKYI, Dr. A. GUSEV, Institute of EvolutionaryMorphology and Ecology of Animals, USSR Academyof Sciences, 117071 Moscow, Leninskipr. 33, USSR.
4 ZentraIbl. Milaobiol., Bd. 145, 1