Soil ecology explained

Soil ecology studies interactions among soil organisms, and their environment.[1] It is particularly concerned with the cycling of nutrients, soil aggregate formation and soil biodiversity.[2]

Overview

Soil is made up of a multitude of physical, chemical, and biological entities, with many interactions occurring among them. It is a heterogenous mixture of minerals and organic matter with variations in moisture, temperature and nutrients. Soil supports a wide range of living organisms and is an essential component of terrestrial ecology.

Features of the ecosystem

Soil fauna

Soil fauna is crucial to soil formation, litter decomposition, nutrient cycling, biotic regulation, and for promoting plant growth. Yet soil organisms remain underrepresented in studies on soil processes and in existing modeling exercises. This is a consequence of assuming that much below ground diversity is ecologically redundant and that soil food webs exhibit a higher degree of omnivory. However, evidence is accumulating on the strong influence of abiotic filters, such as temperature, moisture and soil pH, as well as soil habitat characteristics in controlling their spatial and temporal patterns.

Soils are complex systems and their complexity resides in their heterogeneous nature: a mixture of air, water, minerals, organic compounds, and living organisms. The spatial variation, both horizontal and vertical, of all these constituents is related to soil forming agents varying from micro to macro scales.[13] Consequently, the horizontal patchy distribution of soil properties (soil temperature, moisture, pH, litter/nutrient availability, etc.) also drives the patchiness of the soil organisms across the landscape,[14] and has been one of the main arguments for explaining the great diversity observed in soil communities. Because soils also show vertical stratification of their elemental constituents along the soil profile as result of microclimate, soil texture, and resource quantity and quality differing between soil horizons, soil communities also change in abundance and structure with soil depth.[15]

The majority of these organisms are aerobic, so the amount of porous space, pore-size distribution, surface area, and oxygen levels are crucial to their life cycles and activities. The smallest creatures (microbes) use the micropores filled with air to grow, whereas other bigger animals require bigger spaces, macropores, or the water film surrounding the soil particles to move in search for food. Therefore, soil textural properties together with the depth of the water table are also important factors regulating their diversity, population sizes, and their vertical stratification. Ultimately, the structure of the soil communities strongly depends not only on the natural soil forming factors but also on human activities (agriculture, forestry, urbanization) and determines the shape of landscapes in terms of healthy or contaminated, pristine or degraded soils.

Macrofauna

Since all these drivers of biodiversity changes also operate above ground, it is thought that there must be some concordance of mechanisms regulating the spatial patterns and structure of both above and below ground communities. In support of this, a small-scale field study revealed that the relationships between environmental heterogeneity and species richness might be a general property of ecological communities.[16] In contrast, the molecular examination of 17,516 environmental 18S rRNA gene sequences representing 20 phyla of soil animals covering a range of biomes and latitudes around the world indicated otherwise, and the main conclusion from this study was that below-ground animal diversity may be inversely related to above-ground biodiversity.[17]

The lack of distinct latitudinal gradients in soil biodiversity contrasts with those clear global patterns observed for plants above ground and has led to the assumption that they are indeed controlled by different factors.[18] For example, in 2007 Lozupone and Knight found salinity was the major environmental determinant of bacterial diversity composition across the globe, rather than extremes of temperature, pH, or other physical and chemical factors.[19] In another global scale study in 2014, Tedersoo et al. concluded fungal richness is causally unrelated to plant diversity and is better explained by climatic factors, followed by edaphic and spatial patterns.[20] Global patterns of the distribution of macroscopic organisms are far poorer documented. However, the little evidence available appears to indicate that, at large scales, soil metazoans respond to altitudinal, latitudinal or area gradients in the same way as those described for above-ground organisms.[21] In contrast, at local scales, the great diversity of microhabitats commonly found in soils provides the required niche portioning to create hot spots of diversity in just a gram of soil.

Spatial patterns of soil biodiversity are difficult to explain, and its potential linkages to many soil processes and the overall ecosystem functioning are debated. For example, while some studies have found that reductions in the abundance and presence of soil organisms results in the decline of multiple ecosystem functions,[22] others concluded that above-ground plant diversity alone is a better predictor of ecosystem multi-functionality than soil biodiversity.[23] Soil organisms exhibit a wide array of feeding preferences, life-cycles and survival strategies and they interact within complex food webs.[24] Consequently, species richness per se has very little influence on soil processes and functional dissimilarity can have stronger impacts on ecosystem functioning.[25] Therefore, besides the difficulties in linking above and below ground diversities at different spatial scales, gaining a better understanding of the biotic effects on ecosystem processes might require incorporating a great number of components together with several multi-trophic levels[26] as well as the much less considered non-trophic interactions such as phoresy, passive consumption.[27]) In addition, if soil systems are indeed self-organized, and soil organisms concentrate their activities within a selected set of discrete scales with some form of overall coordination,[28] there is no need for looking for external factors controlling the assemblages of soil constituents. Instead we might just need to recognize the unexpected and that the linkages between above and below ground diversity and soil processes are difficult to predict.

Microfauna

Recent advances are emerging from studying sub-organism level responses using environmental DNA[29] and various omics approaches, such as metagenomics, metatranscriptomics, proteomics and proteogenomics, are rapidly advancing, at least for the microbial world.[30] Metaphenomics has been proposed recently as a better way to encompass the omics and the environmental constraints.[31]

Soil microbes

See main article: article and Soil microbiology. Soil harbors many microbes: bacteria, archaea, protist, fungi and viruses.[32] A majority of these microbes have not been cultured and remain undescribed.[33] Development of next generation sequencing technologies open up the avenue to investigate microbial diversity in soil. [34] One feature of soil microbes is spatial separation which influences microbe to microbe interactions and ecosystem functioning in the soil habitat. [35] Microorganisms in soil are found to be concentrated in specific sites called 'hot spots' which is characterized by an abundance of resources such as moisture or nutrients. [36] An example is the rhizosphere, and areas with accumulated organic matter such as the detritusphere.[37] These areas are characterized by the presence of decaying root litter and exudates released from plant roots which regulates the availability of carbon and nitrogen and in consequence modulate microbial processes. Apart from labile organic carbon, spatial separation of microbes in soil may be influenced by other environmental factors such as temperature and moisture. Other abiotic factors like pH and mineral nutrient composition may also influence the distribution of microorganisms in soil. [38] Variability of these factors make soil a dynamic system. [39] Interactions between members of the soil microhabitat takes place via chemical signaling which is mediated by soluble metabolites and volatile organic compounds, in addition to extracellular polysaccharides. [40] Chemical signals enable microbes to interact, for example bacterial peptidoglycans stimulate growth of Candida albicans.[41] Reciprocally, C. albicans production of farnesol modulates the expression of virulence genes and influences bacterial quorum sensing. [42] Trophic interactions by microbes in the same environment is driven by molecular communication.[43] Microbes may also exchange metabolites to support each other's growth, e.g., the release of extracellular enzymes by ectomycorrhiza decomposes organic matter and releases nutrients which then benefits other members of the population, in exchange organic acids from bacteria stimulate fungal growth [44] These examples of trophic interactions especially metabolite dependencies drive species interactions and are important in the assembly of soil microbial communities. [45]

Soil food web

See main article: soil food web.

Diverse organisms make up the soil food web. They range in size from one-celled bacteria, algae, fungi, and protozoa, to more complex nematodes and micro-arthropods, to the visible earthworms, insects, small vertebrates, and plants. As these organisms eat, grow, and move through the soil, they make it possible to have clean water, clean air, healthy plants, and moderated water flow.

There are many ways that the soil food web is an integral part of landscape processes. Soil organisms decompose organic compounds, including manure, plant residues, and pesticides, preventing them from entering water and becoming pollutants. They sequester nitrogen and other nutrients that might otherwise enter groundwater, and they fix nitrogen from the atmosphere, making it available to plants. Many organisms enhance soil aggregation and porosity, thus increasing infiltration and reducing surface runoff. Soil organisms prey on crop pests and are food for above-ground animals.

Research

Research interests span many aspects of soil ecology and microbiology, Fundamentally, researchers are interested in understanding the interplay among microorganisms, fauna, and plants, the biogeochemical processes they carry out, and the physical environment in which their activities take place, and applying this knowledge to address environmental problems.

Example research projects are to examine the biogeochemistry and microbial ecology of septic drain field soils used to treat domestic wastewater, the role of anecic earthworms in controlling the movement of water and nitrogen cycle in agricultural soils, and the assessment of soil quality in turf production.[46]

Of particular interest is to understand the roles and functions of arbuscular mycorrhizal fungi in natural ecosystems. The effect of anthropic soil conditions on arbuscular mycorrhizal fungi, and the production of glomalin by arbuscular mycorrhizal fungi are both of particular interest due to their roles in sequestering atmospheric carbon dioxide.

Bibliography

External links

Notes and References

  1. Access Science: Soil Ecology . Url last accessed 2006-04-06
  2. Web site: Soil Ecology Crop and Soil Sciences NC State University . 2024-11-13 . cals.ncsu.edu . en.
  3. Orth . Rene . Denissen . Jasper M.C. . Li . Wantong . Oh . Sungmin . 2023-05-15 . Increasing water limitation of global ecosystems in a changing climate . Egu General Assembly Conference Abstracts . 2024-11-13 . 10.5194/egusphere-egu23-1422. free . 2023EGUGA..25.1422O .
  4. Šťovíček . Adam . Kim . Minsu . Or . Dani . Gillor . Osnat . 2017-04-06 . Microbial community response to hydration-desiccation cycles in desert soil . Scientific Reports . en . 7 . 1 . 45735 . 10.1038/srep45735 . 2045-2322 . 5382909 . 28383531. 2017NatSR...745735S .
  5. Liang . Guopeng . Reed . Sasha C. . Stark . John M. . Waring . Bonnie G. . October 2023 . Unraveling mechanisms underlying effects of wetting–drying cycles on soil respiration in a dryland . Biogeochemistry . en . 166 . 1 . 23–37 . 10.1007/s10533-023-01085-0 . 2023Biogc.166...23L . 0168-2563. free .
  6. Singh . Shikha . Mayes . Melanie A. . Kivlin . Stephanie N. . Jagadamma . Sindhu . 2023-04-01 . How the Birch effect differs in mechanisms and magnitudes due to soil texture . Soil Biology and Biochemistry . 179 . 108973 . 10.1016/j.soilbio.2023.108973 . 2023SBiBi.17908973S . 0038-0717.
  7. Kulish . T . 2022-06-01 . Spatial variation of soil temperature fields in a urban park . IOP Conference Series: Earth and Environmental Science . 1049 . 1 . 012056 . 10.1088/1755-1315/1049/1/012056 . 2022E&ES.1049a2056K . 1755-1307. free .
  8. Bourletsikas . Athanassios . Proutsos . Nikolaos . Michopoulos . Panagiotis . Argyrokastritis . Ioannis . 2023-04-14 . Temporal Variations in Temperature and Moisture Soil Profiles in a Mediterranean Maquis Forest in Greece . Hydrology . en . 10 . 4 . 93 . 10.3390/hydrology10040093 . free . 2306-5338.
  9. Bulgakov . Volodymyr . Pascuzzi . Simone . Adamchuk . Valerii . Gadzalo . Jaroslav . Nadykto . Volodymyr . Olt . Jüri . Nowak . Janusz . Kaminskiy . Viktor . 2022-03-23 . Dynamics of Temperature Variation in Soil under Fallow Tillage at Different Depths . Agriculture . en . 12 . 4 . 450 . 10.3390/agriculture12040450 . free . 2077-0472.
  10. Maier . Martin . Osterholt . Laurin . Schindler . Dirk . 2022-03-28 . Blowing in the wind: a review of wind and air- pressure-related effects on soil gas transport  . Egu General Assembly Conference Abstracts . 2024-11-14 . 10.5194/egusphere-egu22-8713. free . 2022EGUGA..24.8713M .
  11. Letey . J . 1991 . The study of soil structure - Science or art . Soil Research . en . 29 . 6 . 699 . 10.1071/SR9910699 . 1838-675X.
  12. Leuther . Frederic . 2023-05-15 . Soil structure – a dynamic soil property which effects multiple soil functions . Egu General Assembly Conference Abstracts . 2024-11-17 . 10.5194/egusphere-egu23-15721. free . 2023EGUGA..2515721L .
  13. 10.1016/j.ecolmodel.2004.04.006. Assessment of soil spatial variability at multiple scales. 2005. Lin. Hangsheng. Wheeler. Dan. Bell. Jay. Wilding. Larry. Ecological Modelling. 182. 3–4. 271–290. 2005EcMod.182..271L .
  14. Book: Soil Ecology and Ecosystem Services. 978-0-19-957592-3. Wall. Diana H.. 14 June 2012. OUP Oxford .
  15. 10.1111/j.0030-1299.2007.15748.x. Temporal and spatial variability in soil food web structure. 2007. Berg. Matty P.. Bengtsson. Janne. Oikos. 116. 11. 1789–1804. 2007Oikos.116.1789B .
  16. 10.1371/journal.pone.0011567. free. The Enigma of Soil Animal Species Diversity Revisited: The Role of Small-Scale Heterogeneity. 2010. Nielsen. Uffe N.. Osler. Graham H. R.. Campbell. Colin D.. Neilson. Roy. Burslem. David F. R. P.. Van Der Wal. René. PLOS ONE. 5. 7. e11567. 20644639. 2903492. 2010PLoSO...511567N.
  17. 10.1073/pnas.1103824108. Molecular study of worldwide distribution and diversity of soil animals. 2011. Wu. T.. Ayres. E.. Bardgett. R. D.. Wall. D. H.. Garey. J. R.. Proceedings of the National Academy of Sciences. 108. 43. 17720–17725. 22006309. 3203765. 2011PNAS..10817720W. free .
  18. 10.1038/nature13855. Belowground biodiversity and ecosystem functioning. 2014. Bardgett. Richard D.. Van Der Putten. Wim H.. Nature. 515. 7528. 505–511. 25428498. 2014Natur.515..505B. 4456564.
  19. 10.1111/j.0030-1299.2007.15748.x. Temporal and spatial variability in soil food web structure. 2007. Berg. Matty P.. Bengtsson. Janne. Oikos. 116. 11. 1789–1804. 2007Oikos.116.1789B .
  20. 10.1126/science.1256688. Global diversity and geography of soil fungi. 2014. Tedersoo. Leho. Bahram. Mohammad. Põlme. Sergei. Kõljalg. Urmas. Yorou. Nourou S.. Wijesundera. Ravi. Ruiz. Luis Villarreal. Vasco-Palacios. Aída M.. Thu. Pham Quang. Suija. Ave. Smith. Matthew E.. Sharp. Cathy. Saluveer. Erki. Saitta. Alessandro. Rosas. Miguel. Riit. Taavi. Ratkowsky. David. Pritsch. Karin. Põldmaa. Kadri. Piepenbring. Meike. Phosri. Cherdchai. Peterson. Marko. Parts. Kaarin. Pärtel. Kadri. Otsing. Eveli. Nouhra. Eduardo. Njouonkou. André L.. Nilsson. R. Henrik. Morgado. Luis N.. Mayor. Jordan. Science. 346. 6213. 25430773. 11336/20627 . 206559506. 1.
  21. 10.1111/j.1466-8238.2009.00517.x. Macroecological patterns in soil communities. 2010. Decaëns. Thibaud. Global Ecology and Biogeography. 19. 3. 287–302. free. 2010GloEB..19..287D .
  22. 10.1073/pnas.1320054111. Soil biodiversity and soil community composition determine ecosystem multifunctionality. 2014. Wagg. C.. Bender. S. F.. Widmer. F.. Van Der Heijden. M. G. A.. Proceedings of the National Academy of Sciences. 111. 14. 5266–5270. 24639507. 3986181. 2014PNAS..111.5266W. free .
  23. 10.1038/ncomms9159. The links between ecosystem multifunctionality and above- and belowground biodiversity are mediated by climate. 2015. Jing. Xin. Sanders. Nathan J.. Shi. Yu. Chu. Haiyan. Classen. Aimée T.. Zhao. Ke. Chen. Litong. Shi. Yue. Jiang. Youxu. He. Jin-Sheng. Nature Communications. 6. 8159. 26328906. 4569729 . 2015NatCo...6.8159J. 10933025.
  24. 10.3389/fenvs.2014.00007. free. Soil fauna and soil functions: A jigsaw puzzle. 2014. Briones. Marãa Jesãºs I.. Frontiers in Environmental Science. 2.
  25. 10.1126/science.1101865. Biodiversity Effects on Soil Processes Explained by Interspecific Functional Dissimilarity. 2004. Heemsbergen. D. A.. Berg. M. P.. Loreau. M.. Van Hal. J. R.. Faber. J. H.. Verhoef. H. A.. Science. 306. 5698. 1019–1020. 15528441. 2004Sci...306.1019H. 39362502.
  26. 10.1038/nature09492. Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment. 2010. Scherber. Christoph. Eisenhauer. Nico. Weisser. Wolfgang W.. Schmid. Bernhard. Voigt. Winfried. Fischer. Markus. Schulze. Ernst-Detlef. Roscher. Christiane. Weigelt. Alexandra. Allan. Eric. Beßler. Holger. Bonkowski. Michael. Buchmann. Nina. Buscot. François. Clement. Lars W.. Ebeling. Anne. Engels. Christof. Halle. Stefan. Kertscher. Ilona. Klein. Alexandra-Maria. Koller. Robert. König. Stephan. Kowalski. Esther. Kummer. Volker. Kuu. Annely. Lange. Markus. Lauterbach. Dirk. Middelhoff. Cornelius. Migunova. Varvara D.. Milcu. Alexandru. Nature. 468. 7323. 553–556. 20981010. 2010Natur.468..553S. 4304004. 1.
  27. 10.1086/523945. Nontrophic Interactions, Biodiversity, and Ecosystem Functioning: An Interaction Web Model. 2008. Goudard. Alexandra. Loreau. Michel. The American Naturalist. 171. 1. 91–106. 18171154. 5120077.
  28. 10.1097/SS.0000000000000155. Ecosystem Engineers in a Self-organized Soil. 2016. Lavelle. Patrick. Spain. Alister. Blouin. Manuel. Brown. George. Decaëns. Thibaud. Grimaldi. Michel. Jiménez. Juan José. McKey. Doyle. Mathieu. Jérôme. Velasquez. Elena. Zangerlé. Anne. Soil Science. 181. 3/4. 91–109. 2016SoilS.181...91L. 102056683.
  29. 10.1016/j.biocon.2014.11.019. Environmental DNA – an emerging tool in conservation for monitoring past and present biodiversity. 2015. Thomsen. Philip Francis. Willerslev. Eske. Biological Conservation. 183. 4–18. 27384537 . free. 2015BCons.183....4T .
  30. 10.6092/issn.2281-4485/4541. 2014. Nannipieri. Paolo. Soil as a Biological System and Omics Approaches. EQA - International Journal of Environmental Quality. 13. 61–66.
  31. 10.1016/j.mib.2018.01.013. The soil microbiome — from metagenomics to metaphenomics. 2018. Jansson. Janet K.. Hofmockel. Kirsten S.. Current Opinion in Microbiology. 43. 162–168. 29454931. 3377418 . free.
  32. Nannipieri . Paolo . 2014-12-01 . Soil as a Biological System and Omics Approaches . EQA - International Journal of Environmental Quality . 13 . en . 61–66 Pages . 10.6092/ISSN.2281-4485/4541.
  33. Fierer . Noah . 2017-08-21 . Embracing the unknown: disentangling the complexities of the soil microbiome . Nature Reviews Microbiology . en . 15 . 10 . 579–590 . 10.1038/nrmicro.2017.87 . 28824177 . 1740-1534 . Springer Nature.
  34. Chaudhary . Dhiraj Kumar . Khulan . Altankhuu . Kim . Jaisoo . 2019-04-30 . Development of a novel cultivation technique for uncultured soil bacteria . Scientific Reports . en . 9 . 1 . 6666 . 10.1038/s41598-019-43182-x . 31040339 . 6491550 . 2019NatSR...9.6666C . 2045-2322.
  35. Cao . Tingting . Kong . Xiangshi . He . Weihua . Chen . Yunru . Fang . You . Li . Qiang . Chen . Qi . Luo . Yunchao . Tian . Xingjun . 2022-09-01 . Spatiotemporal characteristics of enzymatic hotspots in subtropical forests: In situ evidence from 2D zymography images . CATENA . 216 . 106365 . 10.1016/j.catena.2022.106365 . 2022Caten.21606365C . 0341-8162.
  36. Kuzyakov . Yakov . Blagodatskaya . Evgenia . 2015-04-01 . Microbial hotspots and hot moments in soil: Concept & review . Soil Biology and Biochemistry . 83 . 184–199 . 10.1016/j.soilbio.2015.01.025 . 2015SBiBi..83..184K . 0038-0717.
  37. Sieradzki . Ella T. . Nuccio . Erin E. . Pett-Ridge . Jennifer . Firestone . Mary K. . 2023-10-26 . Makhalanyane . Thulani P. . Rhizosphere and detritusphere habitats modulate expression of soil N-cycling genes during plant development . mSystems . en . 8 . 5 . e0031523 . 10.1128/msystems.00315-23 . 2379-5077 . 10654102 . 37754554.
  38. Zhalnina . Kateryna . Dias . Raquel . de Quadros . Patricia Dörr . Davis-Richardson . Austin . Camargo . Flavio A. O. . Clark . Ian M. . McGrath . Steve P. . Hirsch . Penny R. . Triplett . Eric W. . 2014-11-14 . Soil pH Determines Microbial Diversity and Composition in the Park Grass Experiment . Microbial Ecology . 69 . 2 . 395–406 . 10.1007/s00248-014-0530-2 . 25395291 . 0095-3628.
  39. Nannipieri . P. . Ascher . J. . Ceccherini . M. T. . Landi . L. . Pietramellara . G. . Renella . G. . January 2017 . Microbial diversity and soil functions . European Journal of Soil Science . 68 . 1 . 12–26 . 10.1111/ejss.4_12398 . 2017EuJSS..68...12N . 1351-0754.
  40. Cao . Tingting . Luo . Yunchao . Shi . Man . Tian . Xingjun . Kuzyakov . Yakov . 2024-01-01 . Microbial interactions for nutrient acquisition in soil: Miners, scavengers, and carriers . Soil Biology and Biochemistry . 188 . 109215 . 10.1016/j.soilbio.2023.109215 . 2024SBiBi.18809215C . 0038-0717.
  41. Cugini . Carla . Calfee . M. Worth . Farrow . John M. . Morales . Diana K. . Pesci . Everett C. . Hogan . Deborah A. . 2007-07-19 . Farnesol, a common sesquiterpene, inhibits PQS production in Pseudomonas aeruginosa . Molecular Microbiology . 65 . 4 . 896–906 . 10.1111/j.1365-2958.2007.05840.x . 17640272 . 0950-382X.
  42. Cugini . Carla . Morales . Diana K. . Hogan . Deborah A. . 2010 . Candida albicans-produced farnesol stimulates Pseudomonas quinolone signal production in LasR-defective Pseudomonas aeruginosa strains . Microbiology . 156 . 10 . 3096–3107 . 10.1099/mic.0.037911-0 . free . 1465-2080 . 3068698 . 20656785.
  43. Zelezniak . Aleksej . Andrejev . Sergej . Ponomarova . Olga . Mende . Daniel R. . Bork . Peer . Patil . Kiran Raosaheb . 2015-05-19 . Metabolic dependencies drive species co-occurrence in diverse microbial communities . Proceedings of the National Academy of Sciences . en . 112 . 20 . 6449–6454 . 10.1073/pnas.1421834112 . free . 0027-8424 . 4443341 . 25941371. 2015PNAS..112.6449Z .
  44. Olsson . PÃ¥l Axel . Wallander . HÃ¥kan . October 1998 . Interactions between ectomycorrhizal fungi and the bacterial community in soils amended with various primary minerals . FEMS Microbiology Ecology . en . 27 . 2 . 195–205 . 10.1111/j.1574-6941.1998.tb00537.x.
  45. Zelezniak . Aleksej . Andrejev . Sergej . Ponomarova . Olga . Mende . Daniel R. . Bork . Peer . Patil . Kiran Raosaheb . 2015-05-19 . Metabolic dependencies drive species co-occurrence in diverse microbial communities . Proceedings of the National Academy of Sciences . en . 112 . 20 . 6449–6454 . 10.1073/pnas.1421834112 . free . 0027-8424 . 4443341 . 25941371. 2015PNAS..112.6449Z .
  46. http://www.uri.edu/cels/nrs/seml/ Laboratory of Soil Ecology and Microbiology