Seasonal trends of gross N mineralization in a natural calcareous grassland

Jamieson, N. D.; Monaghan, Rachel; Barraclough, D.

doi:10.1046/j.1365-2486.1999.00232.x

Cited by 39 publications

(30 citation statements)

References 31 publications

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“…The weak presence of Glo8 in September and October is difficult to explain but may be related to seasonal fluctuations in N mineralization. This mineralization seems to reach the highest levels at the beginning of the growth season in spring, the lowest levels in summer, and relatively high levels in autumn (32,40), but it is not known how G. intraradices responds in relation to these seasonal flushes. The genus Acaulospora has been shown to occur more frequently in spring in arable fields (29).…”

Section: Discussionmentioning

confidence: 99%

Seasonal Dynamics of Arbuscular Mycorrhizal Fungal Communities in Roots in a Seminatural Grassland

Santos-González

Finlay²,

Tehler

2007

Appl Environ Microbiol

131

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Symbiotic arbuscular mycorrhizal fungi (AMF) have been shown to influence both the diversity and productivity of grassland plant communities. These effects have been postulated to depend on the differential effects of individual mycorrhizal taxa on different plant species; however, so far there are few detailed studies of the dynamics of AMF colonization of different plant species. In this study, we characterized the communities of AMF colonizing the roots of two plant species, Prunella vulgaris and Antennaria dioica, in a Swedish seminatural grassland at different times of the year. The AMF small subunit rRNA genes were subjected to PCR, cloning, sequencing, and phylogenetic analysis. Nineteen discrete sequence types belonging to Glomus groups A and B and to the genus Acaulospora were distinguished. No significant seasonal changes in the species compositions of the AMF communities as a whole were observed. However, the two plant species hosted significantly different AMF communities. P. vulgaris hosted a rich AMF community throughout the entire growing season. The presence of AMF in A. dioica decreased dramatically in autumn, while an increased presence of Ascomycetes species was detected.In temperate and boreal regions, seminatural grasslands are some of the most species-rich plant communities (37). Grasslands in Europe have been managed during the last millennia by grazing and haymaking. The total area and connectivity of grasslands have decreased dramatically during the last hundred years (77). This decline is one of the major threats to diversity for many groups of organisms (44).Arbuscular mycorrhizal fungi (AMF), belonging to the phylum Glomeromycota, are obligate symbiotic fungi forming mutualistic associations with the roots of most land plants. Increased access to low-mobility soil mineral nutrients has been considered to be the main beneficial effect of AMF on their host plants (61). Experimental greenhouse studies have shown that AMF diversity can affect the diversity and productivity of the host plant communities and, therefore, the functioning of the whole ecosystem (21,33,74,76,78). Other benefits to host plants arising from the presence of AMF include a reduction in the occurrence of pathogenic infections (5, 41), the improvement of water relations (9), and the limitation of heavy-metal uptake (39). The effects of AMF diversity and species composition are thought to arise through differential effects of different AMF taxa on the growth of individual plant species (47), but descriptive ecological data on the structure of AMF communities are still few in comparison with the available information on the structure and dynamics of plant communities (52).Investigations of the phenology, diversity, and functioning of natural AMF communities have traditionally been based on root colonization estimates and spore counts. The extension of the intraradical mycelia gives information on the mycorrhizal status of the plant but can provide hardly any information about the identities of the fungi. Soil spore anal...

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Section: Discussionmentioning

confidence: 99%

Seasonal Dynamics of Arbuscular Mycorrhizal Fungal Communities in Roots in a Seminatural Grassland

Santos-González

Finlay²,

Tehler

2007

Appl Environ Microbiol

131

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“…Individual studies report that mineralization increases with soil moisture (Pilbeam et al 1993, Fisk et al 1998, Willison et al 1998b, Jamieson et al 1999, though under saturated conditions, mineralization continues but assimilation is inhibited (Nishio et al 1994). Nitrification may respond positively to increasing soil moisture up to Ϫ0.01 MPa Firestone 1995, Low et al 1997) and then decline as the soil becomes saturated (Breuer et al 2002, Corre et al 2003.…”

Section: Nhmentioning

confidence: 99%

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

Booth

Stark

Rastetter

2005

Ecological Monographs

914

105

729

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Abstract. Isotope pool dilution studies are increasingly reported in the soils and ecology literature as a means of measuring gross rates of nitrogen (N) mineralization, nitrification, and inorganic N assimilation in soils. We assembled data on soil characteristics and gross rates from 100 studies conducted in forest, shrubland, grassland, and agricultural systems to answer the following questions: What factors appear to be the major drivers for production and consumption of inorganic N as measured by isotope dilution studies? Do rates or the relationships between drivers and rates differ among ecosystem types? Across a wide range of ecosystems, gross N mineralization is positively correlated with microbial biomass and soil C and N concentrations, while soil C:N ratio exerts a negative effect on N mineralization only after adjusting for differences in soil C. Nitrification is a log-linear function of N mineralization, increasing rapidly at low mineralization rates but changing only slightly at high mineralization rates. In contrast, NH 4 ϩ assimilation by soil microbes increases nearly linearly over the full range of mineralization rates. As a result, nitrification is proportionately more important as a fate for NH 4 ϩ at low mineralization rates than at high mineralization rates. Gross nitrification rates show no relationship to soil pH, with some of the fastest nitrification rates occurring below pH 5 in soils with high N mineralization rates. Differences in soil organic matter (SOM) composition and concentration among ecosystem types influence the production and fate of mineralized N. Soil organic matter from grasslands appears to be inherently more productive of ammonium than SOM from wooded sites, and SOM from deciduous forests is more so than SOM in coniferous forests, but differences appear to result primarily from differing C:N ratios of organic matter. Because of the central importance of SOM characteristics and concentrations in regulating rates, soil organic matter depletion in agricultural systems appears to be an important determinant of gross process rates and the proportion of NH 4 ϩ that is nitrified. Addition of 15 N appears to stimulate NH 4 ϩ consumption more than NO 3 Ϫ consumption processes; however, the magnitude of the stimulation may provide useful information regarding the factors limiting microbial N transformations.

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“…Warming generally increased net or gross N mineralization and immobilization rates (Rustad et al 2001, Shaw andHarte 2001), while the response of nitrification to increased temperature was highly variable, and the response of denitrification was generally non-significant (Barnard et al 2005). Changes in precipitation regimes, through changes in soil moisture, significantly altered rates of N cycling processes in field studies (Barnard et al 2006, Dijkstra et al 2010, Larsen et al 2010: in particular, increased soil moisture can result in enhanced N mineralization, N immobilization, and nitrification rates under water-limiting conditions (Jamieson et al 1999, Avrahami and Bohannan 2007, Dijkstra et al 2010, or in increased denitrification rates by enhancing anaerobic conditions (Barnard et al 2006). Finally, enhanced N deposition increased gross and potential N mineralization rates through increases in primary productivity and decreases in C/N ratio of the organic matter (Booth et al 2005, Vourtilis et al 2007) and enhanced gross and potential nitrification and denitrification rates through increases in soil inorganic N availability (Barnard et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Testing interactive effects of global environmental changes on soil nitrogen cycling

et al. 2011

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Abstract. Responses of soil nitrogen (N) cycling to simultaneous and potentially interacting global environmental changes are uncertain. Here, we investigated the combined effects of elevated CO 2 , warming, increased precipitation and enhanced N supply on soil N cycling in an annual grassland ecosystem as part of the Jasper Ridge Global Change Experiment (CA, USA). This field experiment included four treatments-CO 2 , temperature, precipitation, nitrogen-with two levels per treatment (ambient and elevated), and all their factorial combinations replicated six times. We collected soil samples after 7 and 8 years of treatments, and measured gross rates of N mineralization, N immobilization and nitrification, along with potential rates of ammonia oxidation, nitrite oxidation and denitrification. We also determined the main drivers of these microbial activities (soil ammonium and nitrate concentrations, soil moisture, soil temperature, soil pH, and soil CO 2 efflux, as an indicator of soil heterotrophic activity). We found that gross N mineralization responded to the interactive effects of the CO 2 , precipitation and N treatments: N addition increased gross N mineralization when CO 2 and precipitation were either both at ambient or both at elevated levels. However, we found limited evidence for interactions among elevated CO 2 , warming, increased precipitation, and enhanced N supply on the other N cycling processes examined: statistically significant interactions, when found, tended not to persist across multiple dates. Soil N cycling responded mainly to single-factor effects: long-term N addition increased gross N immobilization, potential ammonia oxidation and potential denitrification, while increased precipitation depressed potential nitrite oxidation and increased potential ammonia oxidation and potential denitrification. In contrast, elevated CO 2 and modest warming did not significantly affect any of these microbial N transformations. These findings suggest that global change effects on soil N cycling are primarily additive, and therefore generally predictable from single factor studies.

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Seasonal trends of gross N mineralization in a natural calcareous grassland

Cited by 39 publications

References 31 publications

Seasonal Dynamics of Arbuscular Mycorrhizal Fungal Communities in Roots in a Seminatural Grassland

Seasonal Dynamics of Arbuscular Mycorrhizal Fungal Communities in Roots in a Seminatural Grassland

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

Testing interactive effects of global environmental changes on soil nitrogen cycling

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