The soil animal community as indicator of changes in the structure and functioning of Andean ecosystems with altitude and nutrient input
Ecology and Biodiversity of Plants and Ecosystems
Final Report Abstract
Investigating soil animal communities in tropical montane rainforests is of outstanding importance to better understand the functioning of tropical montane rainforests in face of global changes such as increased nutrient input and climate change. Since decomposer communities are exceptionally complex it is necessary to develop indicators which allow predicting changes in the functioning of the decomposer system. We investigated the effect of moderate nutrient addition, (NUMEX – nutrient manipulation experiment) and mycorrhizal fungi on soil microorganisms and soil invertebrates. Further, we investigated the phylogeny of tropical oribatid mites and methods for delineating species in tropical soil living testate amoebae. Nutrient addition increased the quality of the litter material and beneficially affected microbial communities thereby increasing decomposition rates. The results indicate that microorganisms are generally limited by nitrogen, but saprotrophic fungi also by phosphorus. Nutrient additions also strongly altered the community structure of testate amoebae. Testate amoebae benefited from the addition of nitrogen, but were detrimentally affected by phosphorus. The results suggests that testate amoeba communities are predominantly structured by abiotic factors and by antagonistic interactions with other microorganisms rather than by the availability of prey. Mycorrhizal fungi competed with other microorganisms and collembola benefitted from a reduction in mycorrhizal fungi whereas oribatid mites depended on root-/mycorrhiza-derived resources. Further, the results suggest that root-/mycorrhiza-derived resources are important for fuelling soil food webs, but that these resources are only available close to the roots and not channelled distant to roots via AMF. This indicates that in tropical rainforests the effect of root derived resources is limited to the close vicinity of roots, whereas in temperate forest root exudates are also available distant to the root system due to extraradical mycorrhizal hyphae. Abundance of microbial decomposers decreased significantly with increasing plant litter diversity, indicating that the interaction among litter types in mixtures facilitates the translocation of considerable amounts of secondary compounds resulting in a negative complementarity effect in leaf litter mixtures. The presence of low-quality leaf litter species enhanced the abundance of Oribatida and Collembola indicating that structurally more complex leaf litter appears to improve microhabitat conditions for the soil microarthropod community. Litter mixture effects have a strong impact on microbial decomposers, but individual litter features appear to be more important drivers of microarthropods abundance. Decomposition rates and soil fauna community structure were mainly influenced by the decompositional stage of the litter material and the surrounding environmental factors at different altitudes than by the initial quality and type of the litter material. Decompositional processes in could be separated into three phases characterised by the speed of decomposition as well as shifts in microbial biomass, soil fauna abundance and diversity and community structure of oribatid mites. This indicates that litter quality is not the main force structuring the tropical soil microarthropod community and that the relative importance of litter (leaf and root litter) and belowground plant derived resources (root exudates and mycorrhizal hyphae) shifts over the course of decomposition. Further, molecular analyses allowed to better understand the evolution and radiation of tropical soil animals. The results suggest that the high diversity of oribatid mites in tropical regions is based on the radiation of phylogenetically young lineages, supporting the hypothesis that the tropics function as cradle rather than museum of oribatid mite diversity. The results support the view that oribatid mites are a very old taxon which radiated intensively in tropical regions, their origin, however, predates the existence of tropical rainforests. To identify characters for morphology-based species delineation we investigated variations in shell size, pseudostome diameter and pseudostome form in Trigonopyxis arcula (testate amoebae) from three different sites of the Ecuadorian Andes. The results suggest that shell size is not an appropriate character for taxon delineation, but needs to be combined with other characters such as pseudostome form. Overall, the project provided novel insight into the morphological variability of the genus Trigonopyxis. Future studies need to combine morphological and phylogenetic approaches, but considerable further work is necessary for establishing the relevant molecular markers for these studies.
Publications
- (2014) Moderate changes in nutrient input alter tropical microbial and protist communities and belowground linkages. The ISME Journal 8, 1126-1134
Krashevska V, Sandmann D, Maraun M, Scheu S
(See online at https://doi.org/10.1038/ismej.2013.209) - (2017) Leaf and root litter decomposition is discontinued at high altitude tropical montane rainforests contributing to carbon sequestration. Ecology and Evolution 7, 6432–6443
Marian F, Sandmann D, Krashevska V, Maraun M, Scheu S
(See online at https://doi.org/10.1002/ece3.3189) - (2017) Leaf litter chemistry drives the structure and composition of soil testate amoeba communities in a tropical montane rainforest of the Ecuadorian Andes. Microbial Ecology 74, 681-690
Krashevska V, Sandmann D, Marian F, Maraun M, Scheu S
(See online at https://doi.org/10.1007/s00248-017-0980-4) - (2017) The tropics as ancient cradle of oribatid mite diversity. Acarologia 57, 309-322
Pachl P, Lindl AC, Krause A, Scheu S, Schaefer I, Maraun M
(See online at https://dx.doi.org/10.1051/acarologia/20164148) - (2018) Altitude and decomposition stage rather than litter origin structure soil microarthropod communities in tropical montane rainforests. Soil Biology and Biochemistry 125, 263-274
Marian F, Sandmann D, Krashevska V, Maraun M, Scheu S
(See online at https://doi.org/10.1016/j.soilbio.2018.07.017) - (2018) Evaluation of morphological characteristics to delineate taxa of the genus Trigonopyxis (Amoebozoa, Arcellinida). Protist 169, 190–205
Schulz G, Maraun M, Scheu S, Völcker E, Krashevska V
(See online at https://doi.org/10.1016/j.protis.2018.02.005) - (2019) Impacts of core rotation, defaunation and nitrogen addition on arbuscular mycorrhizal fungi, microorganisms and microarthropods in a tropical montane rainforest. Tropical Ecology
Sánchez-Galindo LM, Camenzind T, Maraun M, Scheu S
(See online at https://doi.org/10.1007/s42965-019-00038-9) - (2019) Parthenogenetic vs. sexual reproduction in oribatid mite communities. Ecology and Evolution 9, 7324-7332
Maraun M, Caruso T, Hense J, Lehmitz R, Mumladze L, Murvanidze M, Nae I, Schulz J, Seniczak A, Scheu S
(See online at https://doi.org/10.5061/dryad.gr6qb4h) - (2019) Roots, mycorrhizal fungi and altitude as determinants of litter decomposition and soil animal communities in tropical montane rainforests. Plant and Soil 438
Marian F, Brown L, Sandmann D, Maraun M, Scheu S
(See online at https://doi.org/10.1007/s11104-019-03999-x)
