Illig, Jens (2007)
Structure and functioning of oribatid mite communities along an elevational gradient of tropical mountain rainforests.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
Tropical mountain rain forests are among the most species rich regions in the world. The RBSF (Reserva Biológica San Francisco) area in southern Ecuador is a hotspot of biodiversity. To characterise this exceptional high diversity it is essential to investigate the complex interactions between the organisms and their abiotic environment. A number of groups of organisms, including birds, moths, orchids and mosses, have been investigated, whereas knowledge on others, including soil invertebrates, is minute. This study focuses on (1) the characterisation of the hidden diversity of soil animal species, in particular that of oribatid mites (Oribatida), (2) the composition and function of soil microarthropods including their trophic relationship, (3) decomposition processes including altitude (temperature, moisture), litter type (low and high quality) and microarthropods (small and large mesh of litterbags). (1) At the study site 193 species of 48 families of oribatid mites were determined which is high but compared to temperate forest ecosystems not extraordinary divers. The proportion of not described species is assumed to be around 40 %. Nine new species of ptyctimous oribatid mites were described. Many species are restricted to tropical regions indicating specific community structures in the tropics. Furthermore, the oribatid mite community differed along the elevation gradient from 1850 to 2270 m indicating distinct oribatid mite communities at different altitudes. (2) The high diversity of oribatid mites and decomposer soil animals in general, is one of the great riddles in soil ecology. Whereas in deciduous forests the soil microarthropods are well characterised, taxonomical knowledge in tropical rainforests and especially in mountain regions is low. One aim of this study was to investigate the microarthropod soil community. The density of microarthropods and oribatid mite communities at three horizons (L, F/H, Ah) and on the bark of adjacent trees along an elevation gradient (1850, 2020, 2200 and 2270 m) in the RBSF forest were studied. Oribatid mites were the most abundant group followed by Collembola and Gamasina. The compared to temperate forests generally low number of microarthropods declined with elevation in the order 1850 > 2020 > 2270 ~ 2200 m and with soil depth (L, F/H, Ah). Microarthropods on bark were less abundant than in soil. Declining numbers of soil microarthropods with altitude is concluded to be due to harsh abiotic conditions (e.g. lower temperatures, waterlogging, solar radiation). Low microbial biomass and resource quality presumably also contribute to the low abundances of soil microarthropods. The trophic structure of 32 species and potential basal food resources (litter of Graffenrieda emarginata) was investigated by analysing natural variations in stable isotope ratios (15N/14N; 13C/12C). The results indicate that the soil food web is similar to that of temperate forests and spans about four trophic levels. Primary decomposers, i.e. litter feeding species, were rare, potentially reflecting low litter quality. A large number of ‘decomposer’ animals were in fact predatory or necrophagous, suggesting that various putative decomposer soil animal species (especially in oribatid mites) presumably feed on other soil invertebrates, in particular nematodes or animal carcasses. (3) We studied leaf litter decomposition of two abundant tree species with higher and lower litter quality (Graffenrieda emarginata, Purdiaea nutans) and a mixture of both in a litterbag field experiment at two altitudes (1850 and 2280 m). Litter quality was measured as microbial biomass and N content. Decomposition rates at the studied tropical mountain rain forest were generally low (average of 32 % y-1). The slow decomposition rates may have been due to low litter quality (e.g. high C-to-N ratios) but also due to low temperatures. Litter generally decomposed slower at higher elevation supporting our assumption that temperature is a major driving force for litter decomposition at our study sites and indicating that organic matter accumulates at high altitudes. P. nutans litter after 2 and 6 months of exposure decomposed slower than that of G. emarginata, but not at the end of the experiment, after twelve months. We suggest that litter chemistry affect decomposition mainly at early stages of decomposition. After 12 months the mixture of G. emarginata and P. nutans litter decomposed significantly faster than both single litter types indicating that combining the two litter types accelerates decomposition processes ('non-additive effect'). Soil microarthropods contributed little to decomposition processes. Microbial biomass and density of microarthropods in the litterbags were higher at 1850 than at 2280 m indicating higher biological activity at lower altitudes. Species composition was similar in both litter types supporting previous findings that the structure of soil decomposer microarthropod communities is little affected by litter type.
| Typ des Eintrags: |
Dissertation
|
| Erschienen: |
2007 |
| Autor(en): |
Illig, Jens |
| Art des Eintrags: |
Erstveröffentlichung |
| Titel: |
Structure and functioning of oribatid mite communities along an elevational gradient of tropical mountain rainforests |
| Sprache: |
Englisch |
| Referenten: |
Galuske, Prof. Dr. Ralf ; Hinderer, Prof. Dr. Matthias |
| Berater: |
Scheu, Prof. Dr. Stefan ; Brose, Dr. Ulrich |
| Publikationsjahr: |
27 November 2007 |
| Ort: |
Darmstadt |
| Verlag: |
Technische Universität |
|
Datum der mündlichen Prüfung: |
26 Oktober 2007 |
| URL / URN: |
urn:nbn:de:tuda-tuprints-8947 |
| Kurzbeschreibung (Abstract): |
Tropical mountain rain forests are among the most species rich regions in the world. The RBSF (Reserva Biológica San Francisco) area in southern Ecuador is a hotspot of biodiversity. To characterise this exceptional high diversity it is essential to investigate the complex interactions between the organisms and their abiotic environment. A number of groups of organisms, including birds, moths, orchids and mosses, have been investigated, whereas knowledge on others, including soil invertebrates, is minute. This study focuses on (1) the characterisation of the hidden diversity of soil animal species, in particular that of oribatid mites (Oribatida), (2) the composition and function of soil microarthropods including their trophic relationship, (3) decomposition processes including altitude (temperature, moisture), litter type (low and high quality) and microarthropods (small and large mesh of litterbags). (1) At the study site 193 species of 48 families of oribatid mites were determined which is high but compared to temperate forest ecosystems not extraordinary divers. The proportion of not described species is assumed to be around 40 %. Nine new species of ptyctimous oribatid mites were described. Many species are restricted to tropical regions indicating specific community structures in the tropics. Furthermore, the oribatid mite community differed along the elevation gradient from 1850 to 2270 m indicating distinct oribatid mite communities at different altitudes. (2) The high diversity of oribatid mites and decomposer soil animals in general, is one of the great riddles in soil ecology. Whereas in deciduous forests the soil microarthropods are well characterised, taxonomical knowledge in tropical rainforests and especially in mountain regions is low. One aim of this study was to investigate the microarthropod soil community. The density of microarthropods and oribatid mite communities at three horizons (L, F/H, Ah) and on the bark of adjacent trees along an elevation gradient (1850, 2020, 2200 and 2270 m) in the RBSF forest were studied. Oribatid mites were the most abundant group followed by Collembola and Gamasina. The compared to temperate forests generally low number of microarthropods declined with elevation in the order 1850 > 2020 > 2270 ~ 2200 m and with soil depth (L, F/H, Ah). Microarthropods on bark were less abundant than in soil. Declining numbers of soil microarthropods with altitude is concluded to be due to harsh abiotic conditions (e.g. lower temperatures, waterlogging, solar radiation). Low microbial biomass and resource quality presumably also contribute to the low abundances of soil microarthropods. The trophic structure of 32 species and potential basal food resources (litter of Graffenrieda emarginata) was investigated by analysing natural variations in stable isotope ratios (15N/14N; 13C/12C). The results indicate that the soil food web is similar to that of temperate forests and spans about four trophic levels. Primary decomposers, i.e. litter feeding species, were rare, potentially reflecting low litter quality. A large number of ‘decomposer’ animals were in fact predatory or necrophagous, suggesting that various putative decomposer soil animal species (especially in oribatid mites) presumably feed on other soil invertebrates, in particular nematodes or animal carcasses. (3) We studied leaf litter decomposition of two abundant tree species with higher and lower litter quality (Graffenrieda emarginata, Purdiaea nutans) and a mixture of both in a litterbag field experiment at two altitudes (1850 and 2280 m). Litter quality was measured as microbial biomass and N content. Decomposition rates at the studied tropical mountain rain forest were generally low (average of 32 % y-1). The slow decomposition rates may have been due to low litter quality (e.g. high C-to-N ratios) but also due to low temperatures. Litter generally decomposed slower at higher elevation supporting our assumption that temperature is a major driving force for litter decomposition at our study sites and indicating that organic matter accumulates at high altitudes. P. nutans litter after 2 and 6 months of exposure decomposed slower than that of G. emarginata, but not at the end of the experiment, after twelve months. We suggest that litter chemistry affect decomposition mainly at early stages of decomposition. After 12 months the mixture of G. emarginata and P. nutans litter decomposed significantly faster than both single litter types indicating that combining the two litter types accelerates decomposition processes ('non-additive effect'). Soil microarthropods contributed little to decomposition processes. Microbial biomass and density of microarthropods in the litterbags were higher at 1850 than at 2280 m indicating higher biological activity at lower altitudes. Species composition was similar in both litter types supporting previous findings that the structure of soil decomposer microarthropod communities is little affected by litter type. |
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Alternatives oder übersetztes Abstract: |
|
Alternatives Abstract | Sprache |
|---|
Tropische Bergwälder gehören zu den artenreichsten Regionen der Welt. Das in dieser Arbeit untersuchte Gebiet in Südecuador, RBSF (Reserva Biológica San Francisco), gilt als "hotspot" der Biodiversität. Neben dem Ziel diese herausragende Vielfalt zu erfassen, gilt es vor allem die komplexen Interaktionen zwischen den Organismen und das Zusammenwirken der biotischen und abiotischen Faktoren des Ökosystems tropischer Bergregenwäldern zu entschlüsseln. In der Region des RBSF sind außergewöhnlich diverse Gruppen, wie z.B. Vögel, Spanner, Orchideen und andere Epiphyten untersucht worden. Die Diversität vieler untersuchter Tier- und Pflanzengruppen ist wesentlich höher als in den gemäßigten Breiten, bei einigen Gruppen liegt die maximale Diversität aber vermutlich in tiefer gelegenen Regionen. Die hohe Artenfülle der Hornmilben (Acari: Oribatida) und anderer Bodenbewohner gilt als eines der großen Rätsel in der Bodenökologie. Während in den gemäßigten Breiten deren Gemeinschaft gut untersucht ist, sind in den tropischen Regenwäldern und speziell in den Bergregionen nur wenige Arten taxonomisch erfasst. Ziel der vorliegenden Arbeit war es, die Gemeinschaft der Bodenmikroarthropoden qualitativ und quantitativ zu erfassen. Im Wald der RBSF wurde entlang eines Höhengradienten von 1850 bis 2270 m die Gemeinschaft der Mikroarthropoden in verschiedenen Bodenhorizonten (L, F/H, Ah) und auf Borke angrenzender Bäume untersucht. Die Dichte war bei den Hornmilben (Oribatida) am höchsten, gefolgt von Raubmilben (Gamasina) und Springschwänzen (Collembola). Die generell geringe Dichte der Mikroarthropoden nahm von 1850 nach 2200 m ab, stieg aber auf 2270 m wieder leicht an. Die Siedlungsdichte von Mikroarthropoden im Boden war wesentlich höher als auf Borke und nahm mit der Bodentiefe ab. Die geringere Dichte mit zunehmender Höhe ist vermutlich auf "strengere" abiotische Faktoren, wie z.B. niedrigere Temperatur, stärkere Sonneneinstrahlung und Staunässe zurückzuführen. Die Gemeinschaft der Hornmilben unterschied sich zwischen den Höhenstufen. Geringere Streuqualität und mikrobielle Biomasse sind vermutlich die Hauptursache für die Abnahme der Dichte der Mikroarthropoden mit der Meereshöhe und auch für die unterschiedliche Struktur der Gemeinschaften. Die zahl- und auch artenreichste Gruppe, die Hornmilben (Oribatida), wurden genauer untersucht. Insgesamt wurden 193 Arten aus 48 Familien nachgewiesen. Neun für die Wissenschaft neue Hornmilbenarten aus der Gruppe der Ptyctima wurden beschrieben. Der geschätzte Anteil unbestimmter Arten liegt bei etwa 40 %. Die Diversität der Hornmilben ist hoch, jedoch nicht wesentlich höher als in temperierten Wäldern. Die Hornmilbengemeinschaft änderte sich entlang eines Höhengradienten von 1850 bis 2270 m. Entlang des Höhengradienten war die Untergruppe der Poronota die häufigste, gefolgt von Pycnonotic Apheredermata. Um das Nahrungsnetz mit seinen trophischen Gilden in tropischen Bergregenwäldern besser zu verstehen, wurden die δ15N und δ13C Signaturen von 32 Bodenarthropoden und von einer basalen Resource, Laubstreu von Graffenrieda emarginata, ermittelt. Die untersuchten Arten lagen innerhalb von vier trophischen Ebenen. Ähnlich wie in den gemäßigten Breiten, bildeten sie einen Gradienten von Pflanzenfressern über Zersetzer bis zu Aasfressern und Räubern. Wider Erwarten zeigte sich, dass der überwiegende Teil der "Zersetzergemeinschaft" nicht direkt an totem organischen Material frisst, sondern sich vermutlich vor allem von Pilzen und Tieren ernährt. In einem Freilandexperiment wurde die Bedeutung der Mikroarthropoden für die Zersetzungsprozesse der Laubstreu untersucht. In Streubeuteln wurden zwei Streutypen (Graffenrieda emarginata und Purdiaea nutans) und eine gleiche Mischung aus beiden auf 1850 und 2280 m ein Jahr lang ausgelegt. Generell war die Streuabbaurate gering. Nach einem Jahr war durchschnittlich noch 68 % der Trockenmasse der eingesetzten Streu in den Streubeuteln. Dies deutet darauf hin, dass in tropischen Bergregenwäldern andere Einflussgrößen von Bedeutung sind als in tropischen Tiefland-Regenwäldern, in denen die Streu schneller abgebaut wird. Die Streu wurde auf 1850 m schneller abgebaut als auf 2280 m, vermutlich auf Grund von höheren Temperaturen und erhöhter mikrobieller Biomasse. Nach 12 Monaten war die Zersetzung der Mischstreu weiter vorangeschritten als bei den beiden Einzelstreutypen, ("nicht-additiver" Effekt). Der Einfluss der Bodenmikroarthropoden auf die Zersetzung der Streu war eher gering. Höhere Dichten von Mikroarthropoden und höhere mikrobielle Biomasse in den Streubeuteln auf 1850 m im Vergleich zu 2280 m unterstützen die Hypothese höherer biotischer Aktivität auf geringerer Meereshöhe. Die Zusammensetzung der Hornmilbengemeinschaft unterschied sich nicht wesentlich in den beiden Streutypen. Dies deutet auf eine wenig spezialisierte Lebensweise der Mikroarthropoden hin. | Deutsch |
|
| Freie Schlagworte: |
Oribatida, stabile Isotope, Mikroarthropoden, Streuzersetzung, Regenwald, Biodiversität |
| Schlagworte: |
| Einzelne Schlagworte | Sprache |
|---|
| Decomposition, Oribatida, Microarthropods, stable Isotopes, Tropics, Biodiversity | Englisch |
|
| Sachgruppe der Dewey Dezimalklassifikatin (DDC): |
500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie |
| Fachbereich(e)/-gebiet(e): |
10 Fachbereich Biologie |
| Hinterlegungsdatum: |
17 Okt 2008 09:22 |
| Letzte Änderung: |
30 Jul 2017 21:18 |
| PPN: |
|
| Referenten: |
Galuske, Prof. Dr. Ralf ; Hinderer, Prof. Dr. Matthias |
|
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: |
26 Oktober 2007 |
| Schlagworte: |
| Einzelne Schlagworte | Sprache |
|---|
| Decomposition, Oribatida, Microarthropods, stable Isotopes, Tropics, Biodiversity | Englisch |
|
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