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201. Plant functional types and temperature control carbon input via roots in peatland soils.

Author: Zeh, Lilli, Limpens, Juul, Erhagen, Björn, Bragazza, Luca, and Kalbitz, Karsten
Subjects: *PEATLANDS, *GLOBAL warming, *CARBON compounds, *SOIL temperature, *STABLE isotopes
Abstract: Aims: Northern peatlands store large amounts of soil organic carbon (C) that can be very sensitive to ongoing global warming. Recently it has been shown that temperature-enhanced growth of vascular plants in these typically moss-dominated ecosystems may promote microbial peat decomposition by increased C input via root exudates. To what extent different plant functional types (PFT) and soil temperature interact in controlling root C input is still unclear. In this study we explored how root C input is related to the presence of ericoid shrubs (shrubs) and graminoid sedges (sedges) by means of a factorial plant clipping experiment (= PFT effect) in two peatlands located at different altitude (= temperature effect). Methods: By selective clipping of shrub and sedge shoots in mixed vegetation at two Alpine peatland sites we interrupted the above- to belowground translocation of C, thus temporarily inhibiting root C release. Subsequent measurements of soil respiration, dissolved organic carbon (DOC) concentration and stable isotope composition (13C) of DOC in pore water were used as proxies to estimate the above- to belowground transfer of C by different PFT. Results: We found that soil respiration rates and DOC concentrations temporarily decreased within 24 h after clipping, with the decrease in soil respiration being most pronounced at the 1.4 °C warmer peatland after clipping shrubs. The transient drop in DOC concentration coincided with a shift towards a heavier C isotope signature, indicating that the decrease was associated with inhibition of a light C source that we attribute to root exudates. Together these results imply that shrubs translocated more C into the peat than sedges, particularly at higher temperature. Conclusions: We showed that plant functional type and temperature interact in controlling root C input under field conditions in peatlands. Our results provide a mechanistic evidence that shrubs may potentially promote the release of stored soil C through root-derived C input. [ABSTRACT FROM AUTHOR]
Published: 2019
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202. Implications of belowground carbon allocation by vascular plants for peat decomposition in a warmer climate

Author: Zeh, Lilli, Kalbitz, Karsten, Limpens, Juul, Bragazza, Luca, Alewell, Christine, Glatzel, Stephan, and Technische Universität Dresden
Subjects: ddc:570, Peatland, Vascular plants, Hochmoor, Gefäßpflanzen
Abstract: Northern peatlands store large amounts of soil organic carbon that are extremely vulnerable to climate change. Direct environmental changes as temperature increase and water table drawdown might not only release more C as CO2 into the atmosphere, but will likely result in increasing vascular plants at the expense of Sphagnum mosses as well. Therefore, the question arises how different plant functional types (shrubs and sedges) with distinctly different functional strategies compared to Sphagnum mosses control C allocation in peatlands and what this means for peat decomposition. Therefore, the key objective of this thesis was to study the patterns of belowground C input by shrubs and sedges and how their above- to belowground C allocation might impact the decomposition of the present moss-dominated peat at different temperatures. To this aim, we applied a plant removal experiment on hummocks with mixed sedge-shrub vegetation in two moss-dominated peatlands located in the Italian Alps at different altitude, i.e. different temperatures. Subsequent measurements of soil respiration, dissolved organic carbon concentration and stable isotope composition (δ13C) of dissolved organic carbon in pore water were used as proxies to estimate the root derived C input by different plant functional type. With in situ 13C pulse-labelling, we assessed the above-to belowground C allocation by quantifying 13C in plant leaves and soil respiration and by measuring δ13C in dissolved organic carbon and in different depths of the peat. In additional peat cores taken under adjacent shrub and sedge plants, we used elemental analysis of carbon, nitrogen, their stable isotopes and analytical pyrolysis gas chromatography mass spectrometry to assess effects of vascular plants (sedge, shrub) on chemical properties and decomposition of the moss-dominated peat. The results provide a mechanistic evidence that plant functional types differ profoundly in their above- to belowground C allocation in peatlands. With shrubs, recently assimilated photosynthates are more likely to be allocated aboveground and turned over belowground than with sedges. Moreover, shrubs showed a fast and tightly coupled processes chain of C assimilation, subsequent C translocation to roots and finally C turnover to CO2, possibly supported by their mutualistic association to mycorrhizal fungi. Though sedges had a higher root-derived C input per unit of biomass than shrubs, the belowground C turnover of recently assimilated C was lower. At the same time, sedges allocated more C belowground to roots than shrubs. For sedges, belowground C turnover processes occurred decoupled from aboveground biomass. The temperature difference between sites did neither increase aboveground C allocation significantly nor belowground C allocation and turnover. However, a higher vascular plant biomass increased the root-derived C input, particularly with shrubs at higher temperatures. Multiple parameters also revealed a higher degree of decomposition of moss-dominated peat collected under sedges than under shrubs, particularly at the high temperature site. Temperature effects on peat decomposition were less pronounced than those of sedges. Eventually, it was not the higher belowground C turnover triggered by shrubs that accelerated decomposition of the present moss-dominated peat but likely the belowground C allocation to the roots by sedges. It can be concluded that the contribution of root exudates to belowground C allocation plays no decisive role in peat decomposition. Yet, the contribution of belowground biomass, particularly of sedges, but also litter of shrubs may impact decomposition processes in a changing climate. Hence, it can be expected that in northern peatlands with increasing shrub biomass, ancient C stores will not be mobilized, while with increasing sedge biomass, C stores are likely at risk.:Thesis at a glance 2 1 Introduction 5 1.1 Northern peatlands and climate change . . . . . . . . . . . . . . . . . . . . . 5 1.2 Vegetation and its impact on carbon cycling in northern peatlands in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3 In situ approaches to study plant functional type effects on peat decomposition in response to climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.4 Objectives, hypotheses and experimental approach . . . . . . . . . . . . . . . 14 2 Study I 21 2.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.4 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.5 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.9 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3 Study II 47 3.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.4 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.8 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4 Study III 75 4.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.3 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 4.7 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 5 Synthesis 97 5.1 Regulations of root-derived carbon input and above- to belowground carbon allocation by vascular plants in peatlands . . . . . . . . . . . . . . . . . . . . 97 5.2 The effect of different above- to belowground carbon allocation patterns of vascular plants on Sphagnum-derived peat decomposition at different temperatures103 6 Conclusions 105 6.1 Implications of belowground carbon allocation by vascular plants for peat decomposition in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.2 Towards a dynamic understanding of the impact of roots on peatland carbon cycling in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7 Acknowledgements 109 References 111 List of publications and license agreements 139 Curriculum Vitae 149 Moore der nördlichen Hemisphäre speichern große Mengen an organischem Kohlenstoff im Boden, der durch den Klimawandel extrem gefährdet ist. Direkte Umweltveränderungen wie ein Temperaturanstieg und die Absenkung des Grundwasserspiegels könnten nicht nur mehr Kohlenstoff als CO2 in die Atmosphäre freisetzen, sondern werden wahrscheinlich auch zu einer Zunahme von Gefäßpflanzen auf Kosten von Torfmoosen führen. Daher stellt sich die Frage, wie verschiedene funktionellen Pflanzengruppen (Sträucher und Seggen) mit deutlich unterschiedlichen funktionellen Strategien im Vergleich zu Torfmoosen die Kohlenstoff-Allokation in Mooren steuern und was dies für den Torfabbau bedeutet. Daher war das Hauptziel dieser Arbeit, die Muster des unterirdischen Kohlenstoff-Eintrags durch Sträucher und Seggen zu untersuchen und festzustellen, wie sich ihre ober- und unterirdische Kohlenstoff-Allokation auf die Zersetzung des moosdominierten Torfs bei unterschiedlichen Temperaturen auswirken könnte. Zu diesem Zweck haben wir ein Pflanzenentfernungs-Experiment auf Bulken mit gemischter Seggen- und Strauchvegetation in zwei moosdominierten Hochmooren in den italienischen Alpen auf unterschiedlichen Höhenlagen, d. h. bei unterschiedlichen Temperaturen, durchgeführt. Anschließende Messungen der Bodenatmung, der Konzentration des gelösten organischen Kohlenstoffs und der stabilen Isotopenzusammensetzung (δ13C) des gelösten organischen Kohlenstoffs im Porenwasser dienten als Indikatoren für den von den Wurzeln stammenden Kohlenstoff-Eintrag der verschiedenen funktionellen Pflanzengruppen. Mit Hilfe der In-situ-13C-Pulsmarkierung wurde die ober- und unterirdische Kohlenstoff-Allokation durch die Quantifizierung von 13C in den Pflanzenblättern und in der Bodenatmung sowie durch die Messung von δ13C im gelösten organischen Kohlenstoff und im Torf aus verschiedenen Tiefen festgestellt. In zusätzlichen Torfkernen, die unter benachbarten Strauch- und Seggenpflanzen entnommen wurden, haben wir Elementaranalyse von Kohlenstoff, Stickstoff und deren stabile Isotope sowie die analytische Pyrolyse-Gaschromatographie-Massenspektrometrie verwendet, um die Auswirkungen von Gefäßpflanzen (Seggen, Sträucher) auf die chemischen Eigenschaften und den Abbau des moosdominierten Torfs zu bewerten. Die Ergebnisse liefern einen mechanistischen Beweis dafür, dass sich funktionelle Pflanzengruppen in ihrer ober- und unterirdischen Kohlenstoff-Allokation in Mooren stark unterscheiden. Bei Sträuchern wird kürzlich assimilierter Kohlenstoff eher oberirdisch allokiert und unterirdisch umgesetzt als bei Seggen. Darüber hinaus wiesen Sträucher eine schnelle und eng gekoppelte Prozesskette aus Kohlenstoff-Assimilation, anschließender Kohlenstoff-Translokation in die Wurzeln und schließlich Kohlenstoff-Umsatz zu CO2 auf, was möglicherweise durch ihre mutualistische Beziehung zu Mykorrhiza Pilzen unterstützt wird. Obwohl Seggen gegenüber Sträuchern einen höheren Kohlenstoff-Eintrag aus den Wurzeln pro Biomasseeinheit hatten, war der unterirdische Kohlenstoff-Umsatz von kürzlich assimiliertem C geringer. Gleichzeitig bauten Seggen unterirdisch mehr Kohlenstoff in die Wurzeln ein als Sträucher. Bei Seggen fand der unterirdische Kohlenstoff-Umsatz entkoppelt von der oberirdischen Biomasse statt. Der Temperaturunterschied hatte weder Einfluss auf die oberirdische Kohlenstoff-Allokation noch auf die unterirdische Kohlenstoff-Verlagerung und -Umsatz. Ein höherer Anteil an Gefäßpflanzen, insbesondere an Sträuchern, erhöhte jedoch den aus den Wurzeln stammenden Kohlenstoffeintrag, insbesondere bei höheren Temperaturen. Mehrere Parameter zeigten einen höheren Abbaugrad des moosdominierten Torfs unter Seggen gegenüber Sträuchern an, insbesondere am Standort mit hohen Temperaturen. Die Auswirkungen des Temperaturanstiegs auf den Torfabbau waren weniger ausgeprägt als die Auswirkungen durch Seggen. Schlussendlich war es nicht der durch Sträucher ausgelöste höhere unterirdische Kohlenstoff-Umsatz, der die Zersetzung des vorhandenen moosdominierten Torfs beschleunigte, sondern wahrscheinlich die unterirdische Kohlenstoff-Allokation zu den Wurzeln der Seggen. Daraus lässt sich schließen, dass der Beitrag der Wurzelexsudate zur unterirdischen Kohlenstoff-Allokation bei der Torfzersetzung keine entscheidende Rolle spielt. Der Eintrag der unterirdischen Biomasse, insbesondere der Seggen, aber auch der Streu von Sträuchern, kann jedoch die Abbauprozesse in einem sich ändernden Klima beeinflussen. Daher ist zu erwarten, dass in Moore der nördlichen Hemisphäre mit zunehmender Strauchbiomasse alte Kohlenstoff-Speicher nicht mobilisiert werden, während mit zunehmender Seggenbiomasse die Kohlenstoff-Speicher wahrscheinlich gefährdet sind.:Thesis at a glance 2 1 Introduction 5 1.1 Northern peatlands and climate change . . . . . . . . . . . . . . . . . . . . . 5 1.2 Vegetation and its impact on carbon cycling in northern peatlands in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3 In situ approaches to study plant functional type effects on peat decomposition in response to climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.4 Objectives, hypotheses and experimental approach . . . . . . . . . . . . . . . 14 2 Study I 21 2.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.4 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.5 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.9 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3 Study II 47 3.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.4 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.8 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4 Study III 75 4.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.3 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 4.7 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 5 Synthesis 97 5.1 Regulations of root-derived carbon input and above- to belowground carbon allocation by vascular plants in peatlands . . . . . . . . . . . . . . . . . . . . 97 5.2 The effect of different above- to belowground carbon allocation patterns of vascular plants on Sphagnum-derived peat decomposition at different temperatures103 6 Conclusions 105 6.1 Implications of belowground carbon allocation by vascular plants for peat decomposition in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.2 Towards a dynamic understanding of the impact of roots on peatland carbon cycling in a warmer climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7 Acknowledgements 109 References 111 List of publications and license agreements 139 Curriculum Vitae 149
Published: 2022

203. Interaction of compost additives with phosphate solubilizing rhizobacteria improved maize production and soil biochemical properties under dryland agriculture.

Author: Shahzad, Sher Muhammad, Arif, Muhammad Saleem, Riaz, Muhammad, Ashraf, Muhammad, Yasmeen, Tahira, Zaheer, Ahmed, Bragazza, Luca, Buttler, Alexandre, and Robroek, Bjorn J.M.
Subjects: *PHOSPHORUS in soils, *RHIZOBACTERIA, *CORN, *SOIL biochemistry, *ARID regions agriculture
Abstract: Dry land soils from the Indo-Gangetic plains are inherently poor in organic matter content and phosphorus (P). Amendment of these soils with P-enriched compost, together with P solubilizing rhizobacterial (PSR) inoculation has been suggested to improve plant growth and P uptake. We performed 3 × 2 factorial experiment using compost i.e. control, raw saw dust P compost (RPC) and acidified saw dust P compost (APC), and PSR inoculation as factors. The pot study investigated the effects of compost and PSR on maize growth, yield, P nutrition and soil biochemical properties. PSR inoculation with APC enhanced shoot length, cob diameter, grain yield and plant P uptake compared to control. APC amendment, either alone or in combination with PSR, also improved root growth and caused extension of rhizosphere by increasing the root length density of the maize plants. Significant improvement in soil biochemical properties i.e. dehydrogenase (DHA), β-glucosidase (BGA), urease (UA) activity, dissolved organic carbon (DOC), soil organic carbon (SOC) and microbial biomass carbon (MBC) are due to the additive effect of compost amendments. A substantial increase in P availability and associated biochemical attributes reflect the significance of substrate quality, structural stability and optimized pH conditions of added compost that may have enhanced PSR performance, specifically with APC. Moreover, increased carboxylate secretions and PSR abundance in the root zone, lowering of pH and increase in rhizosphere fungal parameters, suggest PSR and APC to be synergetic driving of increased P availability for maize. We conclude that efficiency of P enriched compost could be increased with suitable compost additive in the presence of PSR in dry land soil. [ABSTRACT FROM AUTHOR]
Published: 2017
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204. Subfossil peatland trees as proxies for Holocene palaeohydrology and palaeoclimate.

Author: Edvardsson, Johannes, Stoffel, Markus, Corona, Christophe, Bragazza, Luca, Leuschner, Hanns Hubert, Charman, Dan J., and Helama, Samuli
Subjects: *PALEOHYDROLOGY, *HOLOCENE Epoch, *SPATIO-temporal variation, *ATMOSPHERIC carbon dioxide, *CLIMATE change
Abstract: Due to the scarcity of reliable and highly resolved moisture proxies covering much of the Holocene, there has been increased interest in the study of living and subfossil peatland trees sensitive to gradual and extreme changes in hydrology, precipitation, and related environmental processes. Peatland development and the associated carbon accumulation, which are strongly influenced by hydrological fluctuations, are also of prime importance as peatlands represent long-term sinks of atmospheric carbon. Improved knowledge of peatland development and soil moisture variability during the Holocene is therefore essential to our understanding of long-term hydroclimate changes, the terrestrial carbon cycle, and to enable more robust predictions of peatland response to future climate changes. Here, we review the existing mid- to late Holocene peatland tree-ring chronologies that have been used to study climate variability on (sub-)annual to centennial scales with a primary focus on northern Europe. Since the 1970s, absolutely dated tree-ring chronologies covering substantial parts of the Holocene have been developed from excavated remains of oak ( Quercus spp.) and pine ( Pinus sylvestris L.). The annual tree-ring patterns of these trees are often characterized by periods of depressed growth reflecting annual to decadal hydroclimatic changes. In addition, changes in the spatio-temporal distribution of trees throughout the Holocene are often found to reflect decadal to centennial climate and hydrological changes. Moreover, synchronicity between tree-ring chronologies and tree-population dynamics over larger geographical areas show periods of coherent regional climate forcing, especially during the mid-Holocene. This review (i) provides an overview of pioneering and recent studies presenting tree-ring chronologies developed from subfossil peatland trees, and (ii) presents recent developments in the fields of dendroecology (i.e. the response of tree growth and changes in vitality as a result of changes in climatic variables) and dendroclimatology (i.e. the reconstruction of climate fluctuations based on tree-ring analyses) in peatland regions. Moreover, we (iii) use long-term climate reconstructions based on alternative proxies for comparison, and (iv) present different ways to analyse tree-ring records to generate novel information on annual to centennial timescales. This analysis is based on an unprecedented network of tree-ring chronologies from Denmark, Finland, Germany, Great Britain, Ireland, Lithuania, the Netherlands, Poland, Sweden, and Canada, as well as a wealth of old and previously (un) published literature from Scandinavia and Germany, which has not been accessible to a wider audience in the past due to inaccessibility or linguistic barriers. Finally, a map of possible hotspots for the assessment of continuous peatland-tree studies is presented, along with suggestions for new research directions in the field. [ABSTRACT FROM AUTHOR]
Published: 2016
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205. Role of fertilization regime on soil carbon sequestration and crop yield in a maize-cowpea intercropping system on low fertility soils.

Author: Roohi, Mahnaz, Saleem Arif, Muhammad, Guillaume, Thomas, Yasmeen, Tahira, Riaz, Muhammad, Shakoor, Awais, Hassan Farooq, Taimoor, Muhammad Shahzad, Sher, and Bragazza, Luca
Subjects: *INTERCROPPING, *SOIL fertility, *FERTILIZERS, *CARBON sequestration, *CROP yields, *CROPPING systems
Abstract: [Display omitted] • Soil structural stability loss and carbon depletion instigate food security issues. • Suitable intercrops with balanced fertilization may reverse degradation processes. • Cowpea-maize leads grain yield advantage of intercrops with NPK enriched compost. • Compost boosted soil stability, NPK enriched compost had the highest C-storage. • Soil structural revitalization bids for higher C-storage and better crop yields. Achieving food security through intensive agricultural practices on low fertility soils is challenging as crop productivity is increasingly curtailed by the loss of soil structural stability and rapid depletion of soil organic carbon (SOC). As such, the conversion from traditional mono-cropping to legume-cereal intercropping, especially with integrated fertilization, may increase crop yields with the least ecological footprint. We set up a 2-year field experiment in a split-plot design with cowpea-maize monoculture and intercropping under different organic–inorganic fertilization regimes, including no fertilization (control), organic input only (compost), chemical input only (NPK), and multi-nutrient enriched compost (NPKEC). We observed that intercropped maize had a significantly higher biomass yield compared to the corresponding monoculture when fertilized with NPKEC fertilizer. However, cowpea biomass yield differences between monoculture and intercropped plots were comparable under all fertilization regimes. In contrast, the grain yield advantage of both maize and cowpea was significantly enhanced under the intercropping system compared to monoculture, with NPKEC showing the most significant effect among all fertilization regimes. When comparing the relative contribution of the fertilization regime to SOC, the NPKEC fertilizer provided the highest SOC-sequestration (0.30 Mg C/ha yr−1). At the same time, the effect of the cropping system on C-sequestration showed that intercropping provided the highest C-sequestration (0.17 Mg C/ha yr−1) compared to monocultures of both crops. Although compost application significantly increased mineral associated (MAOC) and particulate associated organic carbon (PAOC) concentrations compared to unfertilized control plots, NPKEC fertilization with intercropping system was the most effective combination causing the greatest increase of both soil C pools over time. Based on redundancy analysis (RDA), the positive association of MAOC and PAOC with C-sequestration suggests the importance of both organic fractions as primary C reservoirs conducting SOC storage. Importantly, although compost alone in association with intercropping had a lower C-sequestration, it was associated to a better soil structure as confirmed by its positive relationship with macro-and micro-aggregation, water stable aggregates (WSA), and mean weight diameter (MDA). Overall, our results indicate the importance of restoring soil structure in degraded soils through appropriate land management solutions, such as stoichiometrically balanced fertilization practices (NPKEC) and crop diversification (intercropping), in order to achieve significant gains in SOC storage and, ultimately, improve crop productivity. [ABSTRACT FROM AUTHOR]
Published: 2022
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206. Climate and human impacts inferred from a 1500-year multi-proxy record of an alpine peatland in the South-Eastern Alps.

Author: Fracasso, Ilaria, Dinella, Anna, Giammarchi, Francesco, Marinchel, Nadia, Kołaczek, Piotr, Lamentowicz, Mariusz, Marcisz, Katarzyna, Łokas, Edyta, Miecznik, Magdalena, Bragazza, Luca, Girardi, Matteo, Ventura, Maurizio, Borruso, Luigimaria, Tonon, Giustino, and Vernesi, Cristiano
Subjects: *RYE, *EUROPEAN beech, *EXPLOITATION of humans, *GENETIC barcoding, *MIDDLE Ages, *FOSSIL plants, *PEAT bogs
Abstract: [Display omitted] • All proxies showed a shift towards drier environmental conditions starting from 920 cal. CE. • Human activities and climate change left clear signatures in the Wölflmoor peat bog. • eDNA metabarcoding gave results with similar trends as the other proxies but highlighting some methodological limitations. In the last decades, climate and human activities significantly affected ecosystems, particularly in mountain areas. Whereas the Alps have been extensively studied for palaeoclimatic reconstructions, little information is available about ecological changes, especially in the Southeastern Alps. This study presents a palaeoclimatic and palaeoecological reconstruction from a 1500-years-old mountain peatland record: Wölflmoor, Bozen (Italy). Through Physico-chemical proxies, testate amoeba, pollen, plant macro-fossils, and environmental DNA (eDNA) analyses, we pursued a twofold objective: 1) reconstructing the palaeoenvironmental variations of the peatland and the surrounding environment to identify the main dry/wet periods, and their correlations with climate and human activities; 2) testing the use of eDNA from a peatland in palaeoecological reconstructions. The dating highlighted a distinct change of age at a depth of 55.5–50.5 cm (ca. 800–930 calibrated years), which suggests a depositional gap (hiatus), at least in this section, occurred during the Medieval Warm Period, due to the increase in air temperature. However, the possible exploitation of the peatland by humans cannot be excluded. Indeed, the increase of Poaceae, Cerealia type, and Secale cereale , and the reduction of Fagus sylvatica and Quercus presented a high human pressure starting around 720 cal. CE. Environmental DNA metabarcoding results showed similar trends. However, it gave limitations such as the preferential amplification of the most abundant species, leading to a relatively small number of detected taxa. This is one of the first studies of eDNA metabarcoding from peatland; thus, we argue that ample room for improvement is expected in a short time, making eDNA metabarcoding a valuable complementary approach, primarily when both flora and fauna taxa are targeted. [ABSTRACT FROM AUTHOR]
Published: 2022
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207. Peatland vascular plant functional types affect dissolved organic matter chemistry.

Author: Robroek, Bjorn, Albrecht, Remy, Hamard, Samuel, Pulgarin, Adrian, Bragazza, Luca, Buttler, Alexandre, and Jassey, Vincent
Subjects: *ATOMS, *BIOGEOCHEMICAL residence time, *HUMUS, *TRANSMUTATION (Chemistry), *MOLECULAR structure
Abstract: Background and aims: Northern peatlands are large repositories of carbon. Peatland vascular plant community composition has been functionally associated to a set of biogeochemical processes such as carbon cycling. Yet, we do not fully understand to what extent vascular plant functional types (PFTs) affect the quality of dissolved organic matter, and if there is any feedback on soil microbial activity. Methods: Using a longer-term plant removal experiment in a boreo-nemoral peatland in Southern Sweden, we relate the dominance of different vascular plant functional types (i.e. ericoids and graminoids) to the chemistry of the dissolved organic matter (DOM) and microbial enzymatic activities (fluorescein diacetate hydrolysis, FDA). Results: Our results show that PFTs modifies the composition of DOM moieties, with a decrease of low molecular weight organic compounds after vascular plant removal. The decrease of enzymatic activity by up to 68 % in the plant removal plots suggests a reduction in DOM mineralization in the absence of vascular plants. Conclusions: Our results show that plant-derived low molecular organic compounds enhance peatland microbial activity, and suggest that an increase of vascular plant cover in response to climate change can potentially destabilize the OM in peatlands, leading to increased carbon losses. [ABSTRACT FROM AUTHOR]
Published: 2016
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208. Environmental drivers of carbon and nitrogen isotopic signatures in peatland vascular plants along an altitude gradient.

Author: Gavazov, Konstantin, Hagedorn, Frank, Buttler, Alexandre, Siegwolf, Rolf, and Bragazza, Luca
Subjects: *PEATLANDS, *VASCULAR plants, *ATMOSPHERIC carbon dioxide, *CARBON isotopes, *CLIMATE change
Abstract: Peatlands are important sinks of atmospheric carbon (C) that, in response to climate warming, are undergoing dynamic vegetation succession. Here we examined the hypothesis that the uptake of nutrients by different plant growth forms (PGFs) is one key mechanism driving changes in species abundance in peatlands. Along an altitude gradient representing a natural climate experiment, we compared the variability of the stable C isotope composition (δC) and stable nitrogen (N) isotope composition (δN) in current-year leaves of two major PGFs, i.e. ericoids and graminoids. The climate gradient was associated with a gradient of vascular plant cover, which was parallelled by different concentrations of organic and inorganic N as well as the fungal/bacterial ratio in peat. In both PGFs the C natural abundance showed a marginal spatial decrease with altitude and a temporal decrease with progression of the growing season. Our data highlight a primary physical control of foliar δC signature, which is independent from the PGFs. Natural abundance of foliar N did not show any seasonal pattern and only in the ericoids showed depletion at lower elevation. This decreasing δN pattern was primarily controlled by the higher relative availability of organic versus inorganic N and, only for the ericoids, by an increased proportion of fungi to bacteria in soil. Our space-for-time approach demonstrates that a change in abundance of PGFs is associated with a different strategy of nutrient acquisition (i.e. transfer via mycorrhizal symbiosis versus direct fine-root uptake), which could likely promote observed and predicted dwarf shrub expansion under climate change. [ABSTRACT FROM AUTHOR]
Published: 2016
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209. Carbon storage in agricultural topsoils and subsoils is promoted by including temporary grasslands into the crop rotation.

Author: Guillaume, Thomas, Makowski, David, Libohova, Zamir, Elfouki, Saïd, Fontana, Mario, Leifeld, Jens, Bragazza, Luca, and Sinaj, Sokrat
Subjects: *CROP rotation, *SUBSOILS, *GRASSLANDS, *EMISSIONS (Air pollution), *GRASSLAND soils, *TOPSOIL, *SOIL sampling
Abstract: [Display omitted] • The role of temporary grasslands as negative emission technology was assessed. • A new approach to account for bias in bulk density is developed. • C-deficit in croplands decreases linearly with the increase of temporary grasslands. • SOC storage potential in top and subsoil are equivalent. • SOC storage potential corresponds to 1 year of GHG emissions from the same region. Atmospheric C sequestration in agricultural soils is viewed as one of the most promising negative emission technologies currently available. Nonetheless, it remains unclear how strongly soil organic carbon (SOC) stocks respond to agricultural practices, especially for subsoil. Here, we assess the SOC storage potential in croplands and how the presence of temporary grasslands (TG) in the crop rotation affects SOC stocks. We developed a new approach to correct for bias in bulk density (BD) induced by sampling conditions and land-use effects with a data-driven model to predict the BD of fine soil (<2 mm) for reference condition. Using 54 permanent grassland and cropland sites with various proportions of TG from a monitoring network in Switzerland, we showed that SOC stock differences down to 50-cm depth between cropland and permanent grasslands (maximum: 3.0 ± 0.8 kg C m−2) depend on the TG proportion in the crop rotation, regardless of clay content and pH. An increase of the TG proportion by 10% would induce a SOC gain of 0.40 ± 0.13 kg C m−2. The responses of topsoil (0–20 cm) and subsoil (20–50 cm) SOC stocks to TG proportion were linear and equivalent. The effect of TG on SOC storage would have been underestimated by 58% without accounting for subsoil stocks response and by 16% without BD corrections. The conversion of all croplands to permanent grasslands in the study region would potentially store a quantity of SOC equivalent to the anthropogenic greenhouse gas emissions generated by the same region during one year. Although the potential of agricultural soils as negative emission technology is relatively modest compared to former expectations, the findings demonstrate the potential to manage SOC and its associated ecosystem services at large scales and down to deep soil layers. [ABSTRACT FROM AUTHOR]
Published: 2022
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210. Experimental warming interacts with soil moisture to discriminate plant responses in an ombrotrophic peatland.

Author: Buttler, Alexandre, Robroek, Bjorn J.M., Laggoun‐Défarge, Fatima, Jassey, Vincent E.J., Pochelon, Cédric, Bernard, Gregory, Delarue, Frédéric, Gogo, Sébastien, Mariotte, Pierre, Mitchell, Edward A.D., Bragazza, Luca, and Morgan, John
Subjects: *SOIL moisture, *PEATLAND ecology, *EFFECT of global warming on plants, *BIOGEOCHEMISTRY, *ECOLOGICAL niche, *GROWING season
Abstract: Question A better understanding of the response of Sphagnum mosses and associated vascular plants to climate warming is relevant for predicting the carbon balance of peatlands in a warmer world. Open-top chambers ( OTCs) have been used to investigate the effect on soil biogeochemical processes in peatlands, but little information is available on the effects of OTCs on microclimate conditions and the associated response of the plant community. We aimed to understand how simulated warming and differences in soil moisture affect plant species cover. Location A Sphagnum-dominated peatlands in French Jura. Methods We used OTCs to measure the effect of a near-ground temperature increase (+1.5 °C on average) on vegetation dynamics over five growing seasons (2008-2012) in a Sphagnum-dominated peatland, in two adjacent microhabitats with different hydrological conditions - wet and dry. Microclimatic conditions and plant species abundance were monitored at peak biomass in years 1, 2, 3 and 5 and monthly during the plant growing season in year 5. Results The response to warming differed between vascular plants and bryophytes, as well as among species within these groups, and also varied in relation to soil moisture. Andromeda polifolia abundance responded positively to warming, while Vaccinium oxycoccus responded negatively, and Eriophorum vaginatum showed a high resistance. Conclusion Depth of rooting of vascular plants appeared to control the response in plant abundance, while moss abundance depended on various other interacting factors, such as shading by the vascular plant community, precipitation and soil moisture. [ABSTRACT FROM AUTHOR]
Published: 2015
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211. Snow cover manipulation effects on microbial community structure and soil chemistry in a mountain bog.

Author: Robroek, Bjorn, Heijboer, Amber, Jassey, Vincent, Hefting, Mariet, Rouwenhorst, T., Buttler, Alexandre, and Bragazza, Luca
Subjects: *SOIL microbiology, *FUNGAL communities, *CLIMATE change, *SOIL chemistry, *BIOGEOCHEMISTRY
Abstract: Background and Aims: Alterations in snow cover driven by climate change may impact ecosystem functioning, including biogeochemistry and soil (microbial) processes. We elucidated the effects of snow cover manipulation (SCM) on above-and belowground processes in a temperate peatland. Methods: In a Swiss mountain-peatland we manipulated snow cover (addition, removal and control), and assessed the effects on Andromeda polifolia root enzyme activity, soil microbial community structure, and leaf tissue and soil biogeochemistry. Results: Reduced snow cover produced warmer soils in our experiment while increased snow cover kept soil temperatures close-to-freezing. SCM had a major influence on the microbial community, and prolonged 'close-to-freezing' temperatures caused a shift in microbial communities toward fungal dominance. Soil temperature largely explained soil microbial structure, while other descriptors such as root enzyme activity and pore-water chemistry interacted less with the soil microbial communities. Conclusions: We envisage that SCM-driven changes in the microbial community composition could lead to substantial changes in trophic fluxes and associated ecosystem processes. Hence, we need to improve our understanding on the impact of frost and freeze-thaw cycles on the microbial food web and its implications for peatland ecosystem processes in a changing climate; in particular for the fate of the sequestered carbon. [ABSTRACT FROM AUTHOR]
Published: 2013
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212. Soil organic carbon saturation in cropland-grassland systems: Storage potential and soil quality.

Author: Guillaume, Thomas, Makowski, David, Libohova, Zamir, Bragazza, Luca, Sallaku, Fatbardh, and Sinaj, Sokrat
Subjects: *GRASSLAND soils, *SOIL quality, *CARBON in soils, *SOIL management, *CROP rotation, *SILT
Abstract: [Display omitted] • Mineral-associated organic C deficits in croplands and grasslands were estimated. • The relationship between soil C-saturation and soil physical quality was assessed. • Challenges to the C-saturation concept and the SOC:clay ratio were highlighted. • C-saturation in grassland was positively linked to SOC accrual history. • SOC accrual is more beneficial for soil physical quality in croplands. Reliable estimations of soil organic carbon (SOC) deficits in agroecosystems are crucial in evaluating the atmospheric C sequestration potential of agricultural soils and supporting management decisions. Nonetheless, the co-benefit on soil quality resulting from SOC accrual is rarely considered. Here, we assessed SOC saturation and soil physical quality in permanent grasslands (PG) and croplands (CR) by applying the C-saturation concept and the SOC:clay ratio as an indicator of soil physical quality to a set of long-term monitoring sites in western Switzerland. For this goal, we produced a new relationship between the silt + clay (SC) particles and the C stored in the mineral-associated fraction (MAOM C) and we assessed the assumption that grasslands can be used as C-saturated reference sites. The saturation in PG was not coincidental as it depended on the C accrual history. Hence, PG with the lowest MAOM C have not reached their C-saturation level and present a potential SOC storage under optimal management. The MAOM C saturation in CR was low (62 ± 4%) and corresponded to a deficit of −8.8 ± 1.2 mg C g−1 soil as compared to the current level in PG. The saturation was mainly affected by the proportion of temporary grassland in the crop rotation. The relative distribution of C between MAOM (∼80%) and the fine and coarse particulate organic matter (POM) was not affected by land-use types. The MAOM C saturation in this study (MAOM C = 0.372 × SC + 4.23) was similar to that reported in the litterature, but discrepancies appeared when the silt and clay contents were considered separately. SC was by far the main factor explaining MAOM C amount in PG (semi-partial R2: 0.66). In contrast to other studies, the C content of MAOM in PG (43 mg C g−1 SC) was not related to the SC content, suggesting a fixed maximal value in C-saturated soils. Nonetheless, MAOM C saturation may be underestimated as the least saturated PG might still accumulate MAOM C. Finally, the SOC:clay ratio was correlated with MAOM C saturation level in CR, but not in PG suggesting that targeting SOC accrual in CR optimizes the benefits between soil C storage and soil quality. [ABSTRACT FROM AUTHOR]
Published: 2022
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213. Biomass distribution of two subalpine dwarf-shrubs in relation to soil moisture and nutrient content.

Author: Gerdol, Renato, Anfodillo, Tommaso, Gulamini, Matteo, Cannone, Nicoletta, Bragazza, Luca, and Brancaleoni, Lisa
Subjects: *ABIES lasiocarpa, *FIR, *SOIL moisture, *SOIL physics, *PHOSPHORUS, *PLANT nutrition
Abstract: Question: Do soil water content and/or soil nitrogen (N) content and/or soil phosphorus (P) content affect the biomass of Vaccinium myrtillus and V. vitis-idaea in a sub-alpine heath? Location: Dolomites, northern Italy, 1800 m a.s.l. Methods: We determined above-ground and below-ground biomass of the shrubs at three sites, each on a different substrate type. At each site, we determined soil N- and P- contents. We also determined leaf water potential (ψ1), N- and P-concentrations in plant tissues and litter, as well as δ13C and δ15N in mature leaves. Results: V. myrtillus biomass was highest at the silicate site, V. vitis-idaea biomass was highest at the carbonate site. Both shrubs had low biomass at the peat site, possibly due to a toxic effect of waterlogging in wet soils. For both species, pre-dawn ψ1 indicated optimal hydration and midday ψ1 did not show any sign of water stress. Water use efficiency (WUE) did not differ among sites for any species. Whole-plant nutrient concentrations showed that, with increasing biomass, N was diluted in V. myrtillus tissues while P was diluted in V. vitis- idaea tissues. Foliar N-concentration was higher overall for V. myrtillus. Foliar P-concentration in V. myrtillus peaked at the silicate site. Foliar N : P ratios suggested that V. myrtillus was primarily P-limited and V. vitis-idaea primarily N-limited. Conclusions: Water content affected the distribution of the two shrubs in a similar way, higher P-availability in the soil enhanced V. myrtillus rather than V. vitis-idaea. [ABSTRACT FROM AUTHOR]
Published: 2004
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214. Plant–environment interactions through a functional traits perspective: a review of Italian studies

Author: Maurizio Cutini, Silvia Del Vecchio, Enrico Simonetti, Adriano Stinca, Carlo Ricotta, Sabina Burrascano, Giovanni Bacaro, Simone Orsenigo, Thomas Abeli, Consolata Siniscalco, Chiara Montagnani, Anna Rita Frattaroli, Daniela Ciccarelli, Alicia Teresa Rosario Acosta, Sandra Citterio, Giandiego Campetella, Gabriella Buffa, Marcello Tomaselli, Renato Benesperi, Michele Carbognani, Michele Dalle Fratte, Elena Barni, Marco Caccianiga, Alessandro Bricca, Michele Di Musciano, Juri Nascimbene, Graziano Rossi, Bruno Paura, Francesco Petruzzellis, Antonio Montagnoli, Giovanna Aronne, Andrea Catorci, Guido Incerti, Stefano Chelli, Antonio Slaviero, Federico Maria Tardella, Rossano Bolpagni, Simon Pierce, Veronica De Micco, Camilla Wellstein, Paolo Giordani, Bruno Enrico Leone Cerabolini, Luisa Conti, Simonetta Bagella, Valentina Calabrese, Marta Carboni, Andrea Mondoni, Elisabetta Sgarbi, Michele Lussu, Loretta Gratani, Rodolfo Gentili, Alessandro Chiarucci, Eleonora Giarrizzo, Stefano Mazzoleni, Giacomo Puglielli, Roberto Canullo, Giulietta Bernareggi, Giuliano Bonanomi, Alessandro Petraglia, Edy Fantinato, Renato Gerdol, Luciano Di Martino, Rossella Speranza Filigheddu, Maria Laura Carranza, Luca Bragazza, Michela Marignani, Angela Stanisci, Stefania Pisanu, Guido Brusa, Chelli S., Marignani M., Barni E., Petraglia A., Puglielli G., Wellstein C., Acosta A.T.R., Bolpagni R., Bragazza L., Campetella G., Chiarucci A., Conti L., Nascimbene J., Orsenigo S., Pierce S., Ricotta C., Tardella F.M., Abeli T., Aronne G., Bacaro G., Bagella S., Benesperi R., Bernareggi G., Bonanomi G., Bricca A., Brusa G., Buffa G., Burrascano S., Caccianiga M., Calabrese V., Canullo R., Carbognani M., Carboni M., Carranza M.L., Catorci A., Ciccarelli D., Citterio S., Cutini M., Dalle Fratte M., De Micco V., Del Vecchio S., Di Martino L., Di Musciano M., Fantinato E., Filigheddu R., Frattaroli A.R., Gentili R., Gerdol R., Giarrizzo E., Giordani P., Gratani L., Incerti G., Lussu M., Mazzoleni S., Mondoni A., Montagnani C., Montagnoli A., Paura B., Petruzzellis F., Pisanu S., Rossi G., Sgarbi E., Simonetti E., Siniscalco C., Slaviero A., Stanisci A., Stinca A., Tomaselli M., Cerabolini B.E.L., Chelli, S., Marignani, M., Barni, E., Petraglia, A., Puglielli, G., Wellstein, C., Acosta, Atr., Bolpagni, R., Bragazza, L., Campetella, G., Chiarucci, A., Conti, L., Nascimbene, J., Orsenigo, S., Pierce, S., Ricotta, C., Tardella, Fm., Abeli, T., Aronne, G., Bacaro, G., Bagella, S., Benesperi, R., Bernareggi, G., Bonanomi, G., Bricca, A., Brusa, G., Buffa, G., Burrascano, S., Caccianiga, M., Calabrese, V., Canullo, R., Carbognani, M., Carboni, M., Carranza, Ml., Catorci, A., Ciccarelli, D., Citterio, S., Cutini, M., Dalle Fratte, M., De Micco, V., Del Vecchio, S., Di Martino, L., Di Musciano, M., Fantinato, E., Filigheddu, R., Frattaroli, Ar., Gentili, R., Gerdol, R., Giarrizzo, E., Giordani, P., Gratani, L., Incerti, G., Lussu, M., Mazzoleni, S., Mondoni, A., Montagnani, C., Montagnoli, A., Paura, B., Petruzzellis, F., Pisanu, S., Rossi, G., Sgarbi, E., Simonetti, E., Siniscalco, C., Slaviero, A., Stanisci, A., Stinca, A., Tomaselli, M., Be, L. Cerabolini., Chelli, S, Marignani, M, Barni, E, Petraglia, A, Puglielli, G, Wellstein, C, Acosta, A, Bolpagni, R, Bragazza, L, Campetella, G, Chiarucci, A, Conti, L, Nascimbene, J, Orsenigo, S, Pierce, S, Ricotta, C, Tardella, F, Abeli, T, Aronne, G, Bacaro, G, Bagella, S, Benesperi, R, Bernareggi, G, Bonanomi, G, Bricca, A, Brusa, G, Buffa, G, Burrascano, S, Caccianiga, M, Calabrese, V, Canullo, R, Carbognani, M, Carboni, M, Carranza, M, Catorci, A, Ciccarelli, D, Citterio, S, Cutini, M, Dalle Fratte, M, De Micco, V, Del Vecchio, S, Di Martino, L, Di Musciano, M, Fantinato, E, Filigheddu, R, Frattaroli, A, Gentili, R, Gerdol, R, Giarrizzo, E, Giordani, P, Gratani, L, Incerti, G, Lussu, M, Mazzoleni, S, Mondoni, A, Montagnani, C, Montagnoli, A, Paura, B, Petruzzellis, F, Pisanu, S, Rossi, G, Sgarbi, E, Simonetti, E, Siniscalco, C, Slaviero, A, Stanisci, A, Stinca, A, Tomaselli, M, Cerabolini, B, Chelli, Stefano, Marignani, Michela, Barni, Elena, Petraglia, Alessandro, Puglielli, Giacomo, Wellstein, Camilla, Acosta, Alicia T. R., Bolpagni, Rossano, Bragazza, Luca, Campetella, Giandiego, Chiarucci, Alessandro, Conti, Luisa, Nascimbene, Juri, Orsenigo, Simone, Pierce, Simon, Ricotta, Carlo, Tardella, Federico M., Abeli, Thoma, Aronne, Giovanna, Bacaro, Giovanni, Bagella, Simonetta, Benesperi, Renato, Bernareggi, Giulietta, Bonanomi, Giuliano, Bricca, Alessandro, Brusa, Guido, Buffa, Gabriella, Burrascano, Sabina, Caccianiga, Marco, Calabrese, Valentina, Canullo, Roberto, Carbognani, Michele, Carboni, Marta, Carranza, Maria L., Catorci, Andrea, Ciccarelli, Daniela, Citterio, Sandra, Cutini, Maurizio, Dalle Fratte, Michele, De Micco, Veronica, Del Vecchio, Silvia, Di Martino, Luciano, Di Musciano, Michele, Fantinato, Edy, Filigheddu, Rossella, Frattaroli, Anna Rita, Gentili, Rodolfo, Gerdol, Renato, Giarrizzo, Eleonora, Giordani, Paolo, Gratani, Loretta, Incerti, Guido, Lussu, Michele, Mazzoleni, Stefano, Mondoni, Andrea, Montagnani, Chiara, Montagnoli, Antonio, Paura, Bruno, Petruzzellis, Francesco, Pisanu, Stefania, Rossi, Graziano, Sgarbi, Elisabetta, Simonetti, Enrico, Siniscalco, Consolata, Slaviero, Antonio, Stanisci, Angela, Stinca, Adriano, Tomaselli, Marcello, Cerabolini, Bruno E. L., Stefano, Chelli, Michela, Marignani, Elena, Barni, Alessandro, Petraglia, Giacomo, Puglielli, Camilla, Wellstein, Rossano, Bolpagni, Luca, Bragazza, Giandiego, Campetella, Alessandro, Chiarucci, Luisa, Conti, Simone, Orsenigo, Simon, Pierce, Carlo, Ricotta, Giovanna, Aronne, Simonetta, Bagella, Renato, Benesperi, Giulietta, Bernareggi, Giuliano, Bonanomi, Alessandro, Bricca, Guido, Brusa, Gabriella, Buffa, Sabina, Burrascano, Marco, Caccianiga, Valentina, Calabrese, Roberto, Canullo, Michele, Carbognani, Marta, Carboni, Andrea, Catorci, Daniela, Ciccarelli, Sandra, Citterio, Maurizio, Cutini, Michele Dalle Fratte, Veronica De Micco, Silvia Del Vecchio, Luciano Di Martino, Michele Di Musciano, Edy, Fantinato, Rossella, Filigheddu, Anna Rita Frattaroli, Rodolfo, Gentili, Renato, Gerdol, Eleonora, Giarrizzo, Loretta, Gratani, Michele, Lussu, Stefano, Mazzoleni, Andrea, Mondoni, Chiara, Montagnani, Antonio, Montagnoli, Bruno, Paura, Stefania, Pisanu, Graziano, Rossi, Elisabetta, Sgarbi, Enrico, Simonetti, Siniscalco, Maria Consolata, Antonio, Slaviero, Angela, Stanisci, Adriano, Stinca, and Marcello, Tomaselli
Subjects: 0106 biological sciences, land use change, Evolution, CSR plant strategy theory, plant trait, Forest management, forest management, Climate change, Intraspecific variability, Land use change, Plant traits, Terrestrial and Freshwater environments, Plant Science, KEYWORDS Climate change, intraspecific variability, plant traits, terrestrial and freshwater environments, 010603 evolutionary biology, 01 natural sciences, Behavior and Systematics, Land use, land-use change and forestry, Ecology, Evolution, Behavior and Systematics, Plant traits, Plant diversity, Italian studies, Climate change, CSR plant strategy theory, forest management, intraspecific variability, land use change, plant traits, terrestrial and freshwater environments, Ecology, Settore BIO/02 - Botanica Sistematica, Perspective (graphical), Ambientale, Geography, Trait, 010606 plant biology & botany, Settore BIO/03 - Botanica Ambientale e Applicata
Abstract: Italy is among the European countries with the greatest plant diversity due to both a great environmental heterogeneity and a long history of man–environment interactions. Trait-based approaches to ecological studies have developed greatly over recent decades worldwide, although several issues concerning the relationships between plant functional traits and the environment still lack sufficient empirical evaluation. To draw insights on the association between plant functional traits and direct and indirect human and natural pressures on the environmental drivers, this article summarizes the existing knowledge on this topic by reviewing the results of studies performed in Italy adopting a functional trait approach on vascular plants, bryophytes and lichens. Although we recorded trait measurements for 1418 taxa, our review highlighted some major gaps in plant traits knowledge: Mediterranean ecosystems are poorly represented; traits related to belowground organs are still overlooked; traits measurements for bryophytes and lichens are lacking. Finally, intraspecific variation has been little studied at community level so far. We conclude by highlighting the need for approaches evaluating trait–environment relationship at large spatial and temporal scales and the need of a more effective contribution to online databases to tie more firmly Italian researchers to international scientific networks on plant traits.
Published: 2019

215. Critical plant phosphorus for winter wheat assessed from long-term field experiments.

Author: Fontana, Mario, Bélanger, Gilles, Hirte, Juliane, Ziadi, Noura, Elfouki, Saïd, Bragazza, Luca, Liebisch, Frank, and Sinaj, Sokrat
Subjects: *WINTER wheat, *PHOSPHATE rock, *CROP yields, *GRAIN yields, *PHOSPHORUS, *WHEAT
Abstract: Optimizing the use of phosphorus (P) fertilizers is essential considering the environmental issues linked to over fertilization and the limited rock phosphate reserve. Diagnosing the crop P status by calculating a phosphorus nutrition index (PNI) based on the plant critical P concentration (P c) could help determine the minimum amount of P fertilizer to ensure maximum crop yield. This study investigated (i) the effect of P fertilization on winter wheat (Triticum hybernum L.) shoot biomass and grain yield after several decades of different annual P fertilization rates, (ii) the stability over several site-years of the P c expressed either as a function of shoot biomass or shoot nitrogen (N) concentration, and (iii) the possibility of using the PNI or the shoot N-to-P c ratio as nutritional indicators to diagnose P deficiency and predict the expected response to P fertilization. Shoot biomass and its P and N concentrations were measured weekly at five site-years along with grain yield after several decades of P fertilization treatments that ranged between 0 and 5/3 of the theoretical P crop uptake. The P fertilization did not affect the grain yield, but it generally increased shoot biomass especially at the CD 27- -37 developmental stages. The P c expressed either as a function of shoot biomass or shoot N concentration differed among site-years and this was attributed to differences in crop N status. When N was not deficient, we developed a P c dilution curve as a function of shoot biomass (SB) (4.56 × SB−0.279) along with a linear relationship (P c = 1.10 + 0.061 × N) and a power function (P c = 0.34 × N0.632) between P c and shoot N concentration. The N-to-P c ratio was related to shoot biomass accumulation according to a power function, but the relationship also differed among site-years. The relative shoot biomass responded positively to the PNI up to different thresholds for limiting and non-limiting N conditions. The relative grain yield, however, was not related to the PNI. The PNI, based on the P c dilution curve, has potential as a nutritional indicator to diagnose P deficiency and the expected response to P fertilization, but more research is needed to clarify the effect of N deficiencies on the P c dilution curve. [ABSTRACT FROM AUTHOR]
Published: 2021
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216. Peat Decomposition Rates from Managed Organic Soils in Switzerland

Author: Bader, Cédric, Schulin, Rainer, Leifeld, Jens, and Bragazza, Luca
Subjects: priming effect, Stable carbon isotopes, ORGANIC SOILS + BOG SOILS + PEAT SOILS (PEDOLOGY), CO2 emissions, Peat decomposition, C14, radiocarbon, carbon accumulation, ddc:630, Agriculture
Abstract: Organic soils develop under waterlogged conditions, leading to a reduced decomposition of biomass. Over the last millennia this led to the development of a large carbon (C) pool in the global C cycle. Drainage, necessary for agriculture and forestry, triggers rapid decomposition of soil organic matter (SOM). While undisturbed organic soils are C-sinks, drainage transforms them into C-sources. Climate, drainage depth and land-use are considered the main factors controlling SOM decomposition. However, there is still a large variation in decomposition rates among organic soils, even when climate, drainage and land-use conditions are similar. This thesis investigates the role of SOM composition on peat decomposability in a variety of differently managed drained organic soils. Peat samples from 21 organic soils managed as cropland, grassland and forest soils situated in Switzerland were incubated at 10 and 20 °C for more than 6 months. During incubation, we monitored CO2 emissions and related them to soil characteristics, including bulk density, soil pH, soil organic carbon (SOC) content, and elemental ratios (C/N, H/C and O/C). The incubated samples lost between 0.6 to 1.9% of their SOC at 10 °C and between 1.2 to 42% at 20 °C over the course of 10,000 h (>1 yr). This huge variation occurring under controlled conditions suggests that, besides drainage depth, climate and management, SOM composition is an underestimated factor that determines CO2 fluxes measured in field experiments. In contrast, correlations between the investigated soil characteristics and CO2 emissions were weak. Furthermore, there were no land-use effects. Such effects were expected based on the measured SOM characteristics and IPCC data. Temperature sensitivity of decomposition decreased with depth, indicating an enrichment of recalcitrant SOM in topsoils. This finding stands in contrast to findings in studies of undisturbed organic soils and Further it suggests that future C loss from agriculturally managed organic soils will be similar considering warmer climate conditions. Cultivation of organic soils is accompanied by inputs of young organic carbon (YOC) from plant residues. The amount of YOC inputs, their potential to compensate for oxidative peat loss as well as their lability are unknown. Studying the δ13C signatures in the topsoil of a managed organic soil revealed that at least 19 ± 2.4% of the SOC originate from YOC being accumulated recently. Yet, the accumulation rates are substantially smaller than average peat loss rates on the studied soils. Remarkably, the percentage of YOC in decomposing SOC was 53 ± 0.1%, indicating that YOC is more labile than bulk SOC. These findings are supported by the 14C age of emitted CO2 being younger than that of SOC. Inputs of fresh organic matter (FOM) to soil are known to induce priming effects, i.e. an altered decomposition of resident SOM. The effect of FOM addition on peat decomposition of agriculturally used organic soils has seldom been quantified experimentally. Therefore, we incubated soil samples from managed organic soils over three weeks with and without adding corn straw as FOM. The 13C and 14C signatures of SOC and emitted CO2 enabled us to apportion the amount of decomposed corn, as well as to estimate relative effects of corn addition on the decomposition of SOC from old peat and from YOC. FOM addition induced negative, positive and neutral priming of SOC decomposition. Further, the relative contribution of peat SOC to the overall CO2 release consistently decreased after FOM addition, suggesting that young and old C pools in managed organic soils respond differently to the addition of fresh plant residues. A combination of those two findings indicates that FOM addition can effectively reduce the decomposition of old peat. The results of this thesis suggest that agricultural use of organic soils has a tremendous effect on the composition and decomposability of SOC in organic soils. Furthermore, they show that also crop species known for their carbon sequestration potential are not likely to counteract peat losses caused by drainage. Therefore, agricultural management of organic soils without the risk of losing vast amounts of SOC seems unrealistic and thus, CO2 emissions from organic soils are not likely to decrease in the future. This means that they remain a big issue of concern for future generations in order to counteract climate change.
Published: 2017

217. Effects of cropping system and fertilization regime on soil phosphorous are mediated by rhizosphere-microbial processes in a semi-arid agroecosystem.

Author: Roohi, Mahnaz, Arif, Muhammad Saleem, Yasmeen, Tahira, Riaz, Muhammad, Rizwan, Muhammad, Shahzad, Sher Muhammad, Ali, Shafaqat, and Bragazza, Luca
Subjects: *CROPPING systems, *INTERCROPPING, *FERTILIZERS, *RHIZOSPHERE, *FERTILIZER application, *SOIL fertility, *SUPERPHOSPHATES, *SOIL amendments
Abstract: In semi-arid regions, soil phosphorus (P) dynamics in cereal-legume intercropping are not yet fully elucidated, particularly in relation to integrated application of fertilizers. To this aim, we investigate the effects of different fertilizers on various P fractions in relation to the rhizosphere-microbial processes in a cowpea/maize intercropping system. Field experiments were conducted during two consecutive years (2016–2017) in a split-plot design by establishing cowpea/maize alone or intercropped onto the main plot, while the sub-plot was treated with four types of fertilization, i.e. no fertilizer addition (control), organic amendment (compost), mineral fertilizers (NPK) and multi-nutrient enriched compost (NPKEC). Our results showed that NPKEC fertilizer increased NaHCO 3 -P i by 69% in maize, 62% in cowpea and 93% in intercropped plots compared to control plots. Similarly, a significant increase in the NaHCO 3 -P o fraction was also recorded with NPKEC treatment in all cropping systems. In case of moderately labile P, NPKEC fertilizer caused the highest increase of NaOH-P o (12.87 ± 0.50 mg P kg−1 soil) and NaOH-P i (22.29 ± 0.83 mg P kg−1 soil) fractions in intercropped plots. Except for intercropping, NPK application caused an increase in the non-available P fraction (HCl-P i), while the use of NPKEC decreased the HCl-P i concentration in all cropping systems, suggesting stronger merits both for intercropping and NPKEC. Surprisingly, maize exhibited substantially higher phosphatases activity compared to cowpea in monoculture amended with compost, implying distinct crop strategies for adaptation under low P conditions. Based on the multi-factor analysis, the close association of NaHCO 3 –P with P solubilizing bacteria, root carboxylates and pH indicated that rhizosphere processes are the strongest predictors of immediately available P. Since alkaline phosphatase (ALP) is a P-degrading enzyme of microbial origin, rhizosphere related ALP association may have originated from root-associated microflora promoting P mobilization. Furthermore, the strong association of microbial biomass P (MBP) and acid phosphates (ACP) with NaOH–P fraction indicated moderately available P cycle in soil was mainly driven by microbial-related processes. Factor analysis map and two-way ANOVA confirmed that fertilization regime had a stronger effect on all tested variables compared to cropping system. Altogether, our results suggest that a combination of microbial-rhizosphere processes controls the dynamics of P fertility in semi-arid soils. In the broader context of improving soil P fertility, it is highly recommended the use of environmentally sustainable sources of fertilizer, such as NPKEC, which can enhance the competitive performance of legume-cereal intercropping under semi-arid agroecosystems. Image 1 • Multi-nutrient compost (NPKEC) was tested for P fertility under cowpea-maize cropping. • In all cropping systems, NPKEC increased labile inorganic P ~62–93% than control. • Intercropping with NPKEC reduced non-available inorganic P by 29% over NPK fertilizers. • Type of fertilization steers intercropping related rhizosphere-microbial P processes. • Multi-nutrient compost enhanced competitiveness of intercrops in semi-arid agroecosystem. [ABSTRACT FROM AUTHOR]
Published: 2020
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218. Carbon dynamics in peatlands under changing hydrology: Effects of water level drawdown on litter quality, microbial enzyme activities and litter decomposition rates

Author: Petra Straková, University of Helsinki, Faculty of Agriculture and Forestry, Department of Forest Sciences, Finnish Forest Research Institute (METLA), Helsingin yliopisto, maatalous-metsätieteellinen tiedekunta, metsatieteiden laitos, Helsingfors universitet, agrikultur-forstvetenskapliga fakulteten, institutionen för skogsvetenskaper, Bragazza, Luca, and Laiho, Raija
Subjects: Hydrology, geography, Peat, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, biology, Wetland, Plant community, metsätieteet, 04 agricultural and veterinary sciences, 15. Life on land, Plant litter, biology.organism_classification, 01 natural sciences, Sphagnum, 13. Climate action, Forest ecology, 040103 agronomy & agriculture, 0401 agriculture, forestry, and fisheries, Environmental science, Ecosystem, Cycling, 0105 earth and related environmental sciences
Abstract: Pristine peatlands are carbon (C) accumulating wetland ecosystems sustained by a high water level (WL) and consequent anoxia that slows down decomposition. Persistent WL drawdown as a response to climate and/or land-use change directly affects decomposition: increased oxygenation stimulates decomposition of the old C (peat) sequestered under prior anoxic conditions. Responses of the new C (plant litter) in terms of quality, production and decomposability, and the consequences for the whole C cycle of peatlands are not fully understood. WL drawdown induces changes in plant community resulting in shift in dominance from Sphagnum and graminoids to shrubs and trees. There is increasing evidence that the indirect effects of WL drawdown via the changes in plant communities will have more impact on the ecosystem C cycling than any direct effects. The aim of this study is to disentangle the direct and indirect effects of WL drawdown on the new C by measuring the relative importance of 1) environmental parameters (WL depth, temperature, soil chemistry) and 2) plant community composition on litter production, microbial activity, litter decomposition rates and, consequently, on the C accumulation. This information is crucial for modelling C cycle under changing climate and/or land-use. The effects of WL drawdown were tested in a large-scale experiment with manipulated WL at two time scales and three nutrient regimes. Furthermore, the effect of climate on litter decomposability was tested along a north-south gradient. Additionally, a novel method for estimating litter chemical quality and decomposability was explored by combining Near infrared spectroscopy with multivariate modelling. WL drawdown had direct effects on litter quality, microbial community composition and activity and litter decomposition rates. However, the direct effects of WL drawdown were overruled by the indirect effects via changes in litter type composition and production. Short-term (years) responses to WL drawdown were small. In long-term (decades), dramatically increased litter inputs resulted in large accumulation of organic matter in spite of increased decomposition rates. Further, the quality of the accumulated matter greatly changed from that accumulated in pristine conditions. The response of a peatland ecosystem to persistent WL drawdown was more pronounced at sites with more nutrients. The study demonstrates that the shift in vegetation composition as a response to climate and/or land-use change is the main factor affecting peatland ecosystem C cycle and thus dynamic vegetation is a necessity in any models applied for estimating responses of C fluxes to changes in the environment. The time scale for vegetation changes caused by hydrological changes needs to extend to decades. This study provides grouping of litter types (plant species and part) into functional types based on their chemical quality and/or decomposability that the models could utilize. Further, the results clearly show a drop in soil temperature as a response to WL drawdown when an initially open peatland converts into a forest ecosystem, which has not yet been considered in the existing models. Luonnontilaiset suot ovat hiiltä sitovia ekosysteemejä. Niissä maaperän märkyydestä johtuva hapen niukkuus hidastaa orgaanisen aineen hajotusta. Ilmaston tai maankäytön muutos voi aiheuttaa suon pitkäkestoisen kuivumisen. Se vaikuttaa sekä suorasti että epäsuorasti hajotukseen ja sitä kautta hiilen kiertoon ja hiilitaseeseen. Merkittävin suora vaikutus on maaperän hapekkuuden lisääntyminen, mikä nopeuttaa hajotusta. Epäsuorasti kuivuminen vaikuttaa muuttamalla suon kasviyhteisöä: tyypillisten suokasvien, kuten rahkasammalten ja sarojen, biomassa, tuotos ja karikesyöte vähenevät, kun taas varpujen ja puiden lisääntyvät. Kasviyhteisössä ja sen karikesyötteessä tapahtuvilla muutoksilla voi olla suurempi vaikutus hiilen kiertoon kuin vedenpinnan alenemisella sinänsä. Näiden muutosten suuntaa ja merkitystä koko ekosysteemin hiilitaseelle ei kuitenkaan vielä tunneta riittävästi. Tässä työssä tarkasteltiin vedenpinnan tason vaikutusta suohon tulevan karikkeen määrään, kemiallisiin ominaisuuksiin, mikrobiaktiivisuuteen ja hajoamisnopeuteen, ja näiden lopputulemana tapahtuvaan uuden orgaanisen aineen kertymään. Kuivumisen suorien ja epäsuorien vaikutusten merkitystä arvioitiin vertailemalla ympäristötekijöiden (vedenpinnan taso sekä maan lämpötila ja kemialliset ominaisuudet) ja kasvillisuuden koostumuksen selitysvoimaa. Tätä tietoa tarvitaan, kun mallinnetaan soiden hiilen kiertoa muuttuvissa olosuhteissa. Lyhyt- (muutamia vuosia) ja pitkäkestoisen (muutamia vuosikymmeniä) kuivumisen vaikutuksia tutkittiin kolmella eri ravinteisuustasolla. Ilmaston vaikutusta arvioitiin lisäksi vertailemalla Pohjois- ja Etelä-Suomessa sekä Virossa sijaitsevia koealoja. Karikkeen kemiallisen koostumuksen ja hajotettavuuden arviointiin kokeiltiin perinteisten uuttomenetelmien ja regressiomallien lisäksi nopeaa ja edullista infrapunaspektroskopiaa ja monimuuttuja-analyysiä. Vedenpinnan aleneminen vaikutti kasvilajitasolla karikkeen laatuun, kariketta hajottavaan mikrobiyhteisöön ja karikkeen hajoamisnopeuteen. Nämä kuivumisen suorat vaikutukset olivat kuitenkin vähäisiä verrattuina karikkeen määrän ja koostumuksen muutosten epäsuoriin vaikutuksiin. Lyhytkestoisen kuivumisen vaikutukset tutkittuihin tunnuksiin olivat kaikkinensa melko vähäisiä. Pitkäkestoisen kuivumisen aikana karikesyöte kasvoi merkittävästi. Se johti orgaanisen aineen kertymän lisääntymiseen, vaikka hajotus samalla nopeutui. Kertyvän aineen laatu myös poikkesi selvästi luonnontilaisten soiden kertymän laadusta. Vaste vedenpinnan alenemiseen sekä nopeutui että voimistui suon ravinteisuustason noustessa. Tulokset osoittavat, että metsäojituksesta ja ilmaston kuivumisesta aiheutuvat muutokset soiden kasviyhteisöissä vaikuttavat oleellisesti hiilen kiertoon. Siksi kasvillisuusmuutokset on sisällytettävä malleihin, joilla arvioidaan hiilivirtojen vasteita muuttuviin olosuhteisiin. Muutokset on myös huomioitava riittävän pitkällä aikajänteellä. Työssä esitetään karikkeen kemiallisiin ominaisuuksiin ja hajoamisnopeuteen perustuvat soille tyypillisten kasvien toiminnalliset ryhmät, joita malleissa voidaan hyödyntää. Lisäksi työ osoittaa kuivumisen alentavan maan lämpötilaa huomattavasti, mitä malleissa ei ole otettu huomioon.
Published: 2010

219. Ericoid shrub encroachment shifts aboveground-belowground linkages in three peatlands across Europe and Western Siberia.

Author: Buttler A, Bragazza L, Laggoun-Défarge F, Gogo S, Toussaint ML, Lamentowicz M, Chojnicki BH, Słowiński M, Słowińska S, Zielińska M, Reczuga M, Barabach J, Marcisz K, Lamentowicz Ł, Harenda K, Lapshina E, Gilbert D, Schlaepfer R, and Jassey VEJ
Subjects: Ecosystem, Siberia, Europe, Soil, Water, Tracheophyta, Sphagnopsida
Abstract: In northern peatlands, reduction of Sphagnum dominance in favour of vascular vegetation is likely to influence biogeochemical processes. Such vegetation changes occur as the water table lowers and temperatures rise. To test which of these factors has a significant influence on peatland vegetation, we conducted a 3-year manipulative field experiment in Linje mire (northern Poland). We manipulated the peatland water table level (wet, intermediate and dry; on average the depth of the water table was 17.4, 21.2 and 25.3 cm respectively), and we used open-top chambers (OTCs) to create warmer conditions (on average increase of 1.2°C in OTC plots compared to control plots). Peat drying through water table lowering at this local scale had a larger effect than OTC warming treatment per see on Sphagnum mosses and vascular plants. In particular, ericoid shrubs increased with a lower water table level, while Sphagnum decreased. Microclimatic measurements at the plot scale indicated that both water-level and temperature, represented by heating degree days (HDDs), can have significant effects on the vegetation. In a large-scale complementary vegetation gradient survey replicated in three peatlands positioned along a transitional oceanic-continental and temperate-boreal (subarctic) gradient (France-Poland-Western Siberia), an increase in ericoid shrubs was marked by an increase in phenols in peat pore water, resulting from higher phenol concentrations in vascular plant biomass. Our results suggest a shift in functioning from a mineral-N-driven to a fungi-mediated organic-N nutrient acquisition with shrub encroachment. Both ericoid shrub encroachment and higher mean annual temperature in the three sites triggered greater vascular plant biomass and consequently the dominance of decomposers (especially fungi), which led to a feeding community dominated by nematodes. This contributed to lower enzymatic multifunctionality. Our findings illustrate mechanisms by which plants influence ecosystem responses to climate change, through their effect on microbial trophic interactions., (© 2023 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)
Published: 2023
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220. Effects of Sphagnum Leachate on Competitive Sphagnum Microbiome Depend on Species and Time.

Author: Hamard S, Robroek BJM, Allard PM, Signarbieux C, Zhou S, Saesong T, de Baaker F, Buttler A, Chiapusio G, Wolfender JL, Bragazza L, and Jassey VEJ
Abstract: Plant specialized metabolites play an important role in soil carbon (C) and nutrient fluxes. Through anti-microbial effects, they can modulate microbial assemblages and associated microbial-driven processes, such as nutrient cycling, so to positively or negatively cascade on plant fitness. As such, plant specialized metabolites can be used as a tool to supplant competitors. These compounds are little studied in bryophytes. This is especially notable in peatlands where Sphagnum mosses can dominate the vegetation and show strong interspecific competition. Sphagnum mosses form carpets where diverse microbial communities live and play a crucial role in Sphagnum fitness by regulating C and nutrient cycling. Here, by means of a microcosm experiment, we assessed to what extent moss metabolites of two Sphagnum species ( S. fallax and S. divinum ) modulate the competitive Sphagnum microbiome, with particular focus on microbial respiration. Using a reciprocal leachate experiment, we found that interactions between Sphagnum leachates and microbiome are species-specific. We show that both Sphagnum leachates differed in compound richness and compound relative abundance, especially sphagnum acid derivates, and that they include microbial-related metabolites. The addition of S. divinum leachate on the S. fallax microbiome immediately reduced microbial respiration (-95%). Prolonged exposition of S. fallax microbiome to S. divinum leachate destabilized the food web structure due to a modulation of microbial abundance. In particular, leachate addition decreased the biomass of testate amoebae and rotifers but increased that of ciliates. These changes did not influence microbial CO 2 respiration, suggesting that the structural plasticity of the food web leads to its functional resistance through the replacement of species that are functionally redundant. In contrast, S. fallax leachate neither affected S. divinum microbial respiration, nor microbial biomass. We, however, found that S. fallax leachate addition stabilized the food web structure associated to S. divinum by changing trophic interactions among species. The differences in allelopathic effects between both Sphagnum leachates might impact their competitiveness and affect species distribution at local scale. Our study further paves the way to better understand the role of moss and microbial specialized metabolites in peatland C dynamics.
Published: 2019
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221. Plant functional types define magnitude of drought response in peatland CO2 exchange.

Author: Kuiper JJ, Mooij WM, Bragazza L, and Robroek BJ
Subjects: Carbon Dioxide chemistry, Carbon Dioxide metabolism, Droughts, Plant Physiological Phenomena, Plants classification, Soil
Abstract: Peatlands are important sinks for atmospheric carbon (C), yet the role of plant functional types (PFTs) for C sequestration under climatic perturbations is still unclear. A plant-removal experiment was used to study the importance of vascular PFTs for the net ecosystem CO2 exchange (NEE) during (i.e., resistance) and after (i.e., recovery) an experimental drought. The removal of PFTs caused a decrease of NEE, but the rate differed between microhabitats (i.e., hummocks and lawns) and the type of PFTs. Ericoid removal had a large effect on NEE in hummocks, while the graminoids played a major role in the lawns. The removal of PFTs did not affect the resistance or the recovery after the experimental drought. We argue that the response of Sphagnum mosses (the only PFT present in all treatments) to drought is dominant over that of coexisting PFTs. However, we observed that the moment in time when the system switched from C sink to C source during the drought was controlled by the vascular PFTs. In the light of climate change, the shifts in species composition or even the loss of certain PFTs are expected to strongly affect the future C dynamics in response to environmental stress.
Published: 2014
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222. Heatwave 2003: high summer temperature, rather than experimental fertilization, affects vegetation and CO2 exchange in an alpine bog.

Author: Gerdol R, Bragazza L, and Brancaleoni L
Subjects: Nitrogen pharmacology, Phosphorus pharmacology, Rain, Sphagnopsida drug effects, Sphagnopsida metabolism, Carbon Dioxide metabolism, Fertilizers, Hot Temperature, Photosynthesis, Sphagnopsida growth & development, Wetlands
Abstract: Nitrogen and phosphorus were added experimentally in a bog in the southern Alps. It was hypothesized that alleviating nutrient limitation will increase vascular plant cover. As a consequence, more carbon will be fixed through higher rates of net ecosystem CO(2) exchange (NEE). The vascular cover did increase at the expense of Sphagnum mosses. However, such vegetation changes were largely independent of the treatment and were probably triggered by an exceptional heatwave in summer 2003. Contrary to the tested hypothesis, NEE was unaffected by the nutrient treatments but was strongly influenced by temperature and water-table depth. In particular, ecosystem respiration in the hot summer of 2003 increased dramatically, presumably owing to enhanced heterotrophic respiration in an increased oxic peat layer. At the end of the experiment, the Sphagnum cover decreased significantly in the nitrogen-fertilized treatment at hummock microhabitats. In the long term, this will imply a proportionally greater accumulation of vascular litter, more easily decomposable than the recalcitrant Sphagnum litter. As a result, rates of carbon fixation may decrease because of stimulated respiration.
Published: 2008
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223. Atmospheric nitrogen deposition promotes carbon loss from peat bogs.

Author: Bragazza L, Freeman C, Jones T, Rydin H, Limpens J, Fenner N, Ellis T, Gerdol R, Hájek M, Hájek T, Iacumin P, Kutnar L, Tahvanainen T, and Toberman H
Subjects: Europe, Phosphorus analysis, Spectrum Analysis, Atmosphere chemistry, Carbon Dioxide analysis, Greenhouse Effect, Models, Biological, Nitrogen analysis, Soil analysis, Wetlands
Abstract: Peat bogs have historically represented exceptional carbon (C) sinks because of their extremely low decomposition rates and consequent accumulation of plant remnants as peat. Among the factors favoring that peat accumulation, a major role is played by the chemical quality of plant litter itself, which is poor in nutrients and characterized by polyphenols with a strong inhibitory effect on microbial breakdown. Because bogs receive their nutrient supply solely from atmospheric deposition, the global increase of atmospheric nitrogen (N) inputs as a consequence of human activities could potentially alter the litter chemistry with important, but still unknown, effects on their C balance. Here we present data showing the decomposition rates of recently formed litter peat samples collected in nine European countries under a natural gradient of atmospheric N deposition from approximately 0.2 to 2 g.m(-2).yr(-1). We found that enhanced decomposition rates for material accumulated under higher atmospheric N supplies resulted in higher carbon dioxide (CO2) emissions and dissolved organic carbon release. The increased N availability favored microbial decomposition (i) by removing N constraints on microbial metabolism and (ii) through a chemical amelioration of litter peat quality with a positive feedback on microbial enzymatic activity. Although some uncertainty remains about whether decay-resistant Sphagnum will continue to dominate litter peat, our data indicate that, even without such changes, increased N deposition poses a serious risk to our valuable peatland C sinks.
Published: 2006
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224. Nutritional constraints in ombrotrophic Sphagnum plants under increasing atmospheric nitrogen deposition in Europe.

Author: Bragazza L, Tahvanainen T, Kutnar L, Rydin H, Limpens J, Hájek M, Grosvernier P, Hájek T, Hajkova P, Hansen I, Iacumin P, and Gerdol R
Abstract: • We studied the effects of increasing levels of atmospheric nitrogen (N) deposition on nutrient limitation of ombrotrophic Sphagnum plants. • Fifteen mires in 11 European countries were selected across a natural gradient of bulk atmospheric N deposition from 0.1 to 2 g/m 2 year -1 . Nutritional constraints were assessed based on nutrient ratios of N, phosphorus (P), and potassium (K) in Sphagnum plants collected in hummocks (i.e. relatively drier microhabitats) and in lawns (i.e. relatively wetter microhabitats). • Nutrient ratios in Sphagnum plants increased steeply at low atmospheric N input, but above a threshold of N deposition of c. 1 g/m 2 year -1 the N : P and N : K ratios tended to saturation. Increasing atmospheric N deposition was also accompanied by a reduced retention of Ca and Mg in Sphagnum plants and a decreased stem volumetric density in hummock Sphagnum plants. • We suggest a critical load of N deposition in Europe of 1 g/m 2 year -1 above which Sphagnum plants change from being N-limited to be K + P colimited, at N : P > 30 and N : K > 3.
Published: 2004
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224 results on '"Bragazza, Luca"'

201. Plant functional types and temperature control carbon input via roots in peatland soils.

202. Implications of belowground carbon allocation by vascular plants for peat decomposition in a warmer climate

203. Interaction of compost additives with phosphate solubilizing rhizobacteria improved maize production and soil biochemical properties under dryland agriculture.

204. Subfossil peatland trees as proxies for Holocene palaeohydrology and palaeoclimate.

205. Role of fertilization regime on soil carbon sequestration and crop yield in a maize-cowpea intercropping system on low fertility soils.

206. Climate and human impacts inferred from a 1500-year multi-proxy record of an alpine peatland in the South-Eastern Alps.

207. Peatland vascular plant functional types affect dissolved organic matter chemistry.

208. Environmental drivers of carbon and nitrogen isotopic signatures in peatland vascular plants along an altitude gradient.

209. Carbon storage in agricultural topsoils and subsoils is promoted by including temporary grasslands into the crop rotation.

210. Experimental warming interacts with soil moisture to discriminate plant responses in an ombrotrophic peatland.

211. Snow cover manipulation effects on microbial community structure and soil chemistry in a mountain bog.

212. Soil organic carbon saturation in cropland-grassland systems: Storage potential and soil quality.

213. Biomass distribution of two subalpine dwarf-shrubs in relation to soil moisture and nutrient content.

214. Plant–environment interactions through a functional traits perspective: a review of Italian studies

215. Critical plant phosphorus for winter wheat assessed from long-term field experiments.

216. Peat Decomposition Rates from Managed Organic Soils in Switzerland

217. Effects of cropping system and fertilization regime on soil phosphorous are mediated by rhizosphere-microbial processes in a semi-arid agroecosystem.

218. Carbon dynamics in peatlands under changing hydrology: Effects of water level drawdown on litter quality, microbial enzyme activities and litter decomposition rates

219. Ericoid shrub encroachment shifts aboveground-belowground linkages in three peatlands across Europe and Western Siberia.

220. Effects of Sphagnum Leachate on Competitive Sphagnum Microbiome Depend on Species and Time.

221. Plant functional types define magnitude of drought response in peatland CO2 exchange.

222. Heatwave 2003: high summer temperature, rather than experimental fertilization, affects vegetation and CO2 exchange in an alpine bog.

223. Atmospheric nitrogen deposition promotes carbon loss from peat bogs.

224. Nutritional constraints in ombrotrophic Sphagnum plants under increasing atmospheric nitrogen deposition in Europe.

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