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  • 1. Baker, Paul A.
    et al.
    Fritz, Sherilyn C.
    Dick, Christopher W.
    Eckert, Andrew J.
    Horton, Brian K.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Ribas, Camila C.
    Garzione, Carmala N.
    Battisti, David S.
    The emerging field of geogenomics: Constraining geological problems with genetic data2014In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 135, p. 38-47Article in journal (Refereed)
    Abstract [en]

    The development of a genomics-derived discipline within geology is timely, as a result of major advances in acquiring and processing geologically relevant genetic data. This paper articulates the emerging field of geogenomics, which involves the use of large-scale genetic data to constrain geological hypotheses. The paper introduces geogenomics and discusses how hypotheses can be addressed through collaboration between geologists and evolutionary biologists. As an example, geogenomic methods are applied to evaluate competing hypotheses regarding the timing of the Andean uplift, the closure of the Isthmus of Panama, the onset of trans-Amazon drainage, and Quaternary climate variation in the Neotropics.

  • 2. Baskaran, Preetisri
    et al.
    Hyvönen, Riitta
    Berglund, S. Linnea
    Clemmensen, Karina E.
    Ågren, Göran I.
    Lindahl, Björn D.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Modelling the influence of ectomycorrhizal decomposition on plant nutrition and soil carbon sequestration in boreal forest ecosystems2017In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 213, no 3, p. 1452-1465Article in journal (Refereed)
    Abstract [en]

    Tree growth in boreal forests is limited by nitrogen (N) availability. Most boreal forest trees form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve the uptake of inorganic N and also have the capacity to decompose soil organic matter (SOM) and to mobilize organic N (ECM decomposition'). To study the effects of ECM decomposition' on ecosystem carbon (C) and N balances, we performed a sensitivity analysis on a model of C and N flows between plants, SOM, saprotrophs, ECM fungi, and inorganic N stores. The analysis indicates that C and N balances were sensitive to model parameters regulating ECM biomass and decomposition. Under low N availability, the optimal C allocation to ECM fungi, above which the symbiosis switches from mutualism to parasitism, increases with increasing relative involvement of ECM fungi in SOM decomposition. Under low N conditions, increased ECM organic N mining promotes tree growth but decreases soil C storage, leading to a negative correlation between C stores above- and below-ground. The interplay between plant production and soil C storage is sensitive to the partitioning of decomposition between ECM fungi and saprotrophs. Better understanding of interactions between functional guilds of soil fungi may significantly improve predictions of ecosystem responses to environmental change.

  • 3. Brangari, Albert C.
    et al.
    Fernandez-Garcia, Daniel
    Sanchez-Vila, Xavier
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ecological and soil hydraulic implications of microbial responses to stress - A modeling analysis2018In: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 116, p. 178-194Article in journal (Refereed)
    Abstract [en]

    A better understanding of microbial dynamics in porous media may lead to improvements in the design and management of a number of technological applications, ranging from the degradation of contaminants to the optimization of agricultural systems. To this aim, there is a recognized need for predicting the proliferation of soil microbial biomass (often organized in biofilms) under different environments and stresses. We present a general multi-compartment model to account for physiological responses that have been extensively reported in the literature. The model is used as an explorative tool to elucidate the ecological and soil hydraulic consequences of microbial responses, including the production of extracellular polymeric substances (EPS), the induction of cells into dormancy, and the allocation and reuse of resources between biofilm compartments. The mechanistic model is equipped with indicators allowing the microorganisms to monitor environmental and biological factors and react according to the current stress pressures. The feedbacks of biofilm accumulation on the soil water retention are also described. Model runs simulating different degrees of substrate and water shortage show that adaptive responses to the intensity and type of stress provide a clear benefit to microbial colonies. Results also demonstrate that the model may effectively predict qualitative patterns in microbial dynamics supported by empirical evidence, thereby improving our understanding of the effects of pore-scale physiological mechanisms on the soil macroscale phenomena.

  • 4. Buendía, Corina
    et al.
    Kleidon, Axel
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Reu, Björn
    Porporato, Amilcare
    Evaluating the effect of nutrient redistribution by animals on the phosphorus cycle of lowland Amazonia2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 1, p. 279-295Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) availability decreases with soil age and potentially limits the productivity of ecosystems growing on old and weathered soils. Despite growing on ancient soils, ecosystems of lowland Amazonia are highly productive and are among the most biodiverse on Earth. P eroded and weathered in the Andes is transported by the rivers and deposited in floodplains of the lowland Amazon basin creating hotspots of P fertility. We hypothesize that animals feeding on vegetation and detritus in these hotspots may redistribute P to P-depleted areas, thus contributing to dissipate the P gradient across the landscape. Using a mathematical model, we show that animal-driven spatial redistribution of P from rivers to land and from seasonally flooded to terra firme (upland) ecosystems may sustain the P cycle of Amazonian lowlands. Our results show how P imported to land by terrestrial piscivores in combination with spatial redistribution of herbivores and detritivores can significantly enhance the P content in terra firme ecosystems, thereby highlighting the importance of food webs for the biogeochemical cycling of Amazonia.

  • 5. Capek, Petr
    et al.
    Kotas, Petr
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Santruckova, Hana
    Drivers of phosphorus limitation across soil microbial communities2016In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 30, no 10, p. 1705-1713Article in journal (Refereed)
    Abstract [en]

    Nutrient limitation of soil microbial communities controls the rates of plant litter and soil organic matter decomposition and nutrient mineralization, and as such, it is central to soil and ecosystem models. According to ecological stoichiometry theory, when the carbon (C)-to-nutrient (E) ratio of resources used by a microbial community is higher than a critical ratio (C:E-CR), that nutrient is limiting. The C-to-phosphorus (P) critical ratio (C:P-CR) that determines P limitation is largely unknown for soils, and thus, it is the subject of our study. Our results show that the C:P-CR in widely different soils ranges from 26<bold></bold>6 to 465<bold></bold>1 or from 20<bold></bold>9 to 740<bold></bold>7 when accounting for 95% confidence intervals. Using constant or narrowly fluctuating C:P-CR in ecosystem models is therefore inaccurate. The C:P-CR cannot be simply predicted from microbial community C:P or available soil P. C:P-CR was only related to relative abundance of phospholipid fatty acids, which reflects microbial community structure and physiology. Our data suggest complex controls over microbial community C:P-CR. We further propose that using P storage compounds that allow the microbial community to temporarily buffer variability in available P can represent a widely adopted strategies across soils.

  • 6. D'Orangeville, Loic
    et al.
    Maxwell, Justin
    Kneeshaw, Daniel
    Pederson, Neil
    Duchesne, Louis
    Logan, Travis
    Houle, Daniel
    Arseneault, Dominique
    Beier, Colin M.
    Bishop, Daniel A.
    Druckenbrod, Daniel
    Fraver, Shawn
    Girard, Francois
    Halman, Joshua
    Hansen, Chris
    Hart, Justin L.
    Hartmann, Henrik
    Kaye, Margot
    Leblanc, David
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ouimet, Rock
    Rayback, Shelly
    Rollinson, Christine R.
    Phillips, Richard P.
    Drought timing and local climate determine the sensitivity of eastern temperate forests to drought2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 6, p. 2339-2351Article in journal (Refereed)
    Abstract [en]

    Projected changes in temperature and drought regime are likely to reduce carbon (C) storage in forests, thereby amplifying rates of climate change. While such reductions are often presumed to be greatest in semi-arid forests that experience widespread tree mortality, the consequences of drought may also be important in temperate mesic forests of Eastern North America (ENA) if tree growth is significantly curtailed by drought. Investigations of the environmental conditions that determine drought sensitivity are critically needed to accurately predict ecosystem feedbacks to climate change. We matched site factors with the growth responses to drought of 10,753 trees across mesic forests of ENA, representing 24 species and 346 stands, to determine the broad-scale drivers of drought sensitivity for the dominant trees in ENA. Here we show that two factors-the timing of drought, and the atmospheric demand for water (i.e., local potential evapotranspiration; PET)-are stronger drivers of drought sensitivity than soil and stand characteristics. Droughtinduced reductions in tree growth were greatest when the droughts occurred during early-season peaks in radial growth, especially for trees growing in the warmest, driest regions (i.e., highest PET). Further, mean species trait values (rooting depth and psi(50)) were poor predictors of drought sensitivity, as intraspecific variation in sensitivity was equal to or greater than interspecific variation in 17 of 24 species. From a general circulation model ensemble, we find that future increases in earlyseason PET may exacerbate these effects, and potentially offset gains in C uptake and storage in ENA owing to other global change factors.

  • 7. Hoeber, Stefanie
    et al.
    Fransson, Petra
    Prieto-Ruiz, Ines
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Weih, Martin
    Two Salix Genotypes Differ in Productivity and Nitrogen Economy When Grown in Monoculture and Mixture2017In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 8, article id 231Article in journal (Refereed)
    Abstract [en]

    Individual plant species or genotypes often differ in their demand for nutrients; to compete in a community they must be able to acquire more nutrients (i.e., uptake efficiency) and/or use them more efficiently for biomass production than their competitors. These two mechanisms are often complementary, as there are inherent trade-offs between them. In a mixed-stand, species with contrasting nutrient use patterns interact and may use their resources to increase productivity in different ways. Under contrasting nutrient availabilities, the competitive advantages conferred by either strategy may also shift, so that the interaction between resource use strategy and resource availability ultimately determines the performance of individual genotypes in mixtures. The aim was to investigate growth and nitrogen (N) use efficiency of two willow (Salix) genotypes grown in monoculture and mixture in a fertilizer contrast. We explored the hypotheses that (1) the biomass production of at least one of the involved genotypes should be greater when grown in mixture as compared to the corresponding monoculture when nutrients are the most growth-limiting factor; and (2) the N economy of individual genotypes differs when grown in mixture compared to the corresponding monoculture. The genotypes 'Tora' (Salix schwerinii x S. viminalis) and 'Loden' (S. dasyclados), with contrasting phenology and functional traits, were grown from cuttings in a growth container experiment under two nutrient fertilization treatments (high and low) in mono-and mixed-culture for 17 weeks. Under low nutrient level, 'Tora' showed a higher biomass production (aboveground biomass, leaf area productivity) and N uptake efficiency in mixture than in monoculture, whereas 'Loden' showed the opposite pattern. In addition, 'Loden' showed higher leaf N productivity but lower N uptake efficiency than 'Tora.' The results demonstrated that the specific functional trait combinations of individual genotypes affect their response to mixture as compared to monoculture. Plants grown in mixture as opposed to monoculture may thus increase biomass and vary in their response of N use efficiency traits. However, young plants were investigated here, and as we cannot predict mixture response in mature stands, our results need to be validated at field scale.

  • 8. Hunt, Allen G.
    et al.
    Stefano, Manzoni
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Networks on Networks: The physics of geobiology and geochemistry2015Book (Other academic)
    Abstract [en]

    This book presents research into the physical rules that can underlie the behaviour of biota, as well as the geochemistry of soil development. It addresses both nutrient and water transport limitations of processes from chemical weathering to vascular plant growth. It attempts to bring order to the question of the extent to which soils can facilitate plant growth, and what limitations on plant sizes, metabolism, occurrence and correlations can be formulated thereby.

  • 9.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Flexible Carbon-Use Efficiency across Litter Types and during Decomposition Partly Compensates Nutrient Imbalances-Results from Analytical Stoichiometric Models2017In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 8, article id 661Article in journal (Refereed)
    Abstract [en]

    Mathematical models involving explicit representations of microbial processes have been developed to infer microbial community properties from laboratory and field measurements. While this approach has been used to estimate the kinetic constants related to microbial activity, it has not been fully exploited for inference of stoichiometric traits, such as carbon-use efficiency (CUE). Here, a hierarchy of analytically-solvable mass-balance models of litter carbon (C) and nitrogen (N) dynamics is developed, to infer decomposer CUE from measured C and N contents during litter decomposition. The models are solved in the phase space-expressing litter remaining N as a function of remaining C-rather than in time, thus focusing on the stoichiometric relations during decomposition rather than the kinetics of degradation. This approach leads to explicit formulas that depend on CUE and other microbial properties, which can then be treated as model parameters and retrieved via nonlinear regression. CUE is either assumed time-invariant or as a function of the fraction of remaining litter C as a substitute for time. In all models, CUE tends to increase with increasing litter N availability across a range of litter types. When temporal trends in CUE are considered, CUE increases during decomposition of N-poor litter cohorts, in which decomposers are initially N-limited, but decreases in N-rich litter possibly due to C-limitation. These patterns of flexible CUE that partly compensate stoichiometric imbalances are robust to moderate shifts in decomposer C: N ratio and hold across wide climatic gradients.

  • 10.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Integrating plant hydraulics and gas exchange along the drought-response trait spectrum2014In: Tree Physiology, ISSN 0829-318X, E-ISSN 1758-4469, Vol. 34, no 10, p. 1031-1034Article in journal (Refereed)
  • 11.
    Manzoni, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Capek, Petr
    Mooshammer, Maria
    Lindahl, Björn D.
    Richter, Andreas
    Santruckova, Hana
    Optimal metabolic regulation along resource stoichiometry gradients2017In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 20, no 9, p. 1182-1191Article in journal (Refereed)
    Abstract [en]

    Most heterotrophic organisms feed on substrates that are poor in nutrients compared to their demand, leading to elemental imbalances that may constrain their growth and function. Flexible carbon (C)-use efficiency (CUE, C used for growth over C taken up) can represent a strategy to reduce elemental imbalances. Here, we argue that metabolic regulation has evolved to maximise the organism growth rate along gradients of nutrient availability and translated this assumption into an optimality model that links CUE to substrate and organism stoichiometry. The optimal CUE is predicted to decrease with increasing substrate C-to-nutrient ratio, and increase with nutrient amendment. These predictions are generally confirmed by empirical evidence from a new database of c. 2200 CUE estimates, lending support to the hypothesis that CUE is optimised across levels of organisation (microorganisms and animals), in aquatic and terrestrial systems, and when considering nitrogen or phosphorus as limiting nutrients.

  • 12.
    Manzoni, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Katul, G.
    Invariant soil water potential at zero microbial respiration explained by hydrological discontinuity in dry soils2014In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, no 20, p. 7151-7158Article in journal (Refereed)
    Abstract [en]

    Soil microbial respiration rates decrease with soil drying, ceasing below water potentials around -15MPa. A proposed mechanism for this pattern is that under dry conditions, microbes are substrate limited because solute diffusivity is halted due to breaking of water film continuity. However, pore connectivity estimated from hydraulic conductivity and solute diffusivity (at Darcy's scale) is typically interrupted at much less negative water potentials than microbial respiration (-0.1 to -1MPa). It is hypothesized here that the more negative respiration thresholds than at the Darcy's scale emerge because microbial activity is restricted to microscale soil patches that retain some hydrological connectivity even when it is lost at the macroscale. This hypothesis is explored using results from percolation theory and meta-analyses of respiration-water potential curves and hydrological percolation points. When reducing the spatial scale from macroscale to microscale, hydrological and respiration thresholds become consistent, supporting the proposed hypothesis.

  • 13.
    Manzoni, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Swedish University of Agricultural Sciences, Sweden.
    Katul, Gabriel
    Porporato, Amilcare
    A dynamical system perspective on plant hydraulic failure2014In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, no 6, p. 5170-5183Article in journal (Refereed)
    Abstract [en]

    Photosynthesis is governed by leaf water status that depends on the difference between the rates of transpiration and water supply from the soil and through the plant xylem. When transpiration increases compared to water supply, the leaf water potential reaches a more negative equilibrium, leading to water stress. Both high atmospheric vapor pressure deficit and low soil moisture increase the water demand while decreasing the supply due to lowered soil-to-root conductance and xylem cavitation. Therefore, dry conditions may eventually reduce the leaf water potential to the point of collapsing the plant hydraulic system. This hydraulic failure is shown to correspond to a fold bifurcation where the environmental parameters (vapor pressure deficit and soil moisture) trigger the loss of a physiologically sustainable equilibrium. Using a minimal plant hydraulic model, coordination among plant hydraulic traits is shown to result in increased resilience to environmental stresses, thereby impeding hydraulic failure unless hydraulic traits deteriorate due to prolonged water shortage or other damages.

  • 14.
    Manzoni, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Moyano, F.
    Kätterer, T.
    Schimel, J.
    Modeling coupled enzymatic and solute transport controls on decomposition in drying soils2016In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 95, p. 275-287Article in journal (Refereed)
    Abstract [en]

    Mechanistic descriptions of microbial processes are difficult to embed in ecosystem models because they require complex mathematical formulations. The interactions between microbes, soil carbon (C), and water availability are particularly complex, as they involve coupled physical (advection and diffusion in unsaturated media) and biochemical processes (enzymatic reactions, C uptake by microbes). Here we propose an approximated equation based on a quasi-equilibrium assumption that describes microbial uptake of soil C as a function of soil moisture and organic matter content during soil drying. The equation predicts that uptake depends on two terms, one dependent on soil organic C concentration and enzyme availability (analogous to a Michaelis-Menten equation) and one dependent on soil moisture via its effects on enzyme and solute mass transfer, and microbial uptake kinetics. Assuming that uptake is proportional to microbial respiration, model results are compared to measured respiration water potential curves. Using independently estimated parameter values (except for the calibrated microbial uptake efficiency), the theoretical model captures well the respiration decline during drying and provides an explanation of respiration pulses at rewetting. Thus, this simple formulation could be employed in ecosystem models as an alternative to empirical respiration-moisture response functions.

  • 15.
    Manzoni, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Swedish University of Agricultural Sciences.
    Schaeffer, S. M.
    Katul, G.
    Porporato, A.
    Schimel, J. P.
    A theoretical analysis of microbial eco-physiological and diffusion limitations to carbon cycling in drying soils2014In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 73, p. 69-83Article in journal (Refereed)
    Abstract [en]

    Soil microbes face highly variable moisture conditions that force them to develop adaptations to tolerate or avoid drought. Drought conditions also limit the supply of vital substrates by inhibiting diffusion in dry conditions. How these biological and physical factors affect carbon (C) cycling in soils is addressed here by means of a novel process-based model. The model accounts for different microbial response strategies, including different modes of osmoregulation, drought avoidance through dormancy, and extra-cellular enzyme production. Diffusion limitations induced by low moisture levels for both extracellular enzymes and solutes are also described and coupled to the biological responses. Alternative microbial life-history strategies, each encoded in a set of model parameters, are considered and their effects on C cycling assessed both in the long term (steady state ahalysis) and in the short term (transient analysis during soil drying and rewetting). Drought resistance achieved by active osmoregulation requiring large C investment is not useful in soils where growth in dry conditions is limited by C supply. In contrast, dormancy followed by rapid reactivation upon rewetting seems to be a better strategy in such conditions. Synthesizing more enzymes may also be advantageous because it causes larger accumulation of depolymerized products during dry periods that can be used upon rewetting. Based on key model parameters, a spectrum of life-history strategies thus emerges, providing a possible classification of microbial responses to drought.

  • 16.
    Manzoni, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Vico, G.
    Thompson, S.
    Beyer, F.
    Weih, M.
    Contrasting leaf phenological strategies optimize carbon gain under droughts of different duration2015In: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 84, p. 37-51Article in journal (Refereed)
    Abstract [en]

    In most ecosystems, plants face periods with limited water availability, during which stomatal conductance is reduced to maintain hydration. However, prolonged dry spells might require more drastic strategies to conserve water, such as drought-deciduousness. If drought-related changes in leaf area are adaptive, it can be hypothesized that leaf area is optimized to maximize the growing-season carbon (C) gain. Different phenological strategies during drought have been proposed: (i) leaf area index (L) declines when net photosynthetic rates (A(net)) reach zero to maintain a non-negative A(net); (ii) L adjusts to avoid water potentials with negative impacts on A(net); (iii) a constant leaf water potential is maintained (isohydric behavior); and (iv) leaf area remains unaltered (i.e., summer-evergreen leaf habit). However, whether these strategies are optimal in terms of growing season C gains has not been assessed. Here we consider these theories in a unified framework using the same set of equations to describe gas exchanges and water transport in the soil plant atmosphere continuum, and quantify the effect of the leaf phenological strategy on plant C gain over the entire growing season in different climates. Longer dry periods tend to favor drought-deciduous rather than summer-evergreen habit. Deciduous plants that allow leaf water potential to fluctuate (anisohydric) while preventing negative A(net) assimilate more carbon than deciduous plants with fixed leaf water potentials (isohydric). Increased rooting depth allows evergreens to more effectively compete with drought-deciduous species. Moreover, increasing leaf nitrogen concentrations and thus photosynthetic capacity can be an effective acclimation strategy when dry periods are relatively short.

  • 17.
    Manzoni, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Swedish University of Agricultural Sciences, Sweden.
    Vico, Giulia
    Katul, Gabriel
    Palmroth, Sari
    Porporato, Amilcare
    Optimal plant water-use strategies under stochastic rainfall2014In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, no 7, p. 5379-5394Article in journal (Refereed)
    Abstract [en]

    Plant hydraulic traits have been conjectured to be coordinated, thereby providing plants with a balanced hydraulic system that protects them from cavitation while allowing an efficient transport of water necessary for photosynthesis. In particular, observations suggest correlations between the water potentials at which xylem cavitation impairs water movement and the one at stomatal closure, and between maximum xylem and stomatal conductances, begging the question as to whether such coordination emerges as an optimal water-use strategy under unpredictable rainfall. Here mean transpiration <E> is used as a proxy for long-term plant fitness and its variations as a function of the water potentials at 50% loss of stem conductivity due to cavitation and at 90% stomatal closure are explored. It is shown that coordination between these hydraulic traits is necessary to maximize <E>, with rainfall patterns altering the optimal range of trait values. In contrast, coordination between ecosystem-level conductances appears not necessary to maximize <E>. The optimal trait ranges are wider under drier than under mesic conditions, suggesting that in semiarid systems different water use strategies may be equally successful. Comparison with observations across species from a range of ecosystems confirms model predictions, indicating that the coordinated functioning of plant organs might indeed emerge from an optimal response to rainfall variability.

  • 18. Porporato, A.
    et al.
    Feng, X.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mau, Y.
    Parolari, A. J.
    Vico, G.
    Ecohydrological modeling in agroecosystems: Examples and challenges2015In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 51, no 7, p. 5081-5099Article, review/survey (Refereed)
    Abstract [en]

    Human societies are increasingly altering the water and biogeochemical cycles to both improve ecosystem productivity and reduce risks associated with the unpredictable variability of climatic drivers. These alterations, however, often cause large negative environmental consequences, raising the question as to how societies can ensure a sustainable use of natural resources for the future. Here we discuss how ecohydrological modeling may address these broad questions with special attention to agroecosystems. The challenges related to modeling the two-way interaction between society and environment are illustrated by means of a dynamical model in which soil and water quality supports the growth of human society but is also degraded by excessive pressure, leading to critical transitions and sustained societal growth-collapse cycles. We then focus on the coupled dynamics of soil water and solutes (nutrients or contaminants), emphasizing the modeling challenges, presented by the strong nonlinearities in the soil and plant system and the unpredictable hydroclimatic forcing, that need to be overcome to quantitatively analyze problems of soil water sustainability in both natural and agricultural ecosystems. We discuss applications of this framework to problems of irrigation, soil salinization, and fertilization and emphasize how optimal solutions for large-scale, long-term planning of soil and water resources in agroecosystems under uncertainty could be provided by methods from stochastic control, informed by physically and mathematically sound descriptions of ecohydrological and biogeochemical interactions.

  • 19.
    Thorslund, Josefin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Jawitz, James W.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Basu, Nandita B.
    Chalov, Sergey R.
    Cohen, Matthew J.
    Creed, Irena F.
    Goldenberg, Romain
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hylin, Anna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kalantari, Zahra
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Koussis, Antonis D.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mazi, Katerina
    Mård, Johanna
    Persson, Klas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Pietroń, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Quin, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    van Meter, Kimberly
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wetlands as large-scale nature-based solutions: Status and challenges for research, engineering and management2017In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 108, no Part B, p. 489-497Article in journal (Refereed)
    Abstract [en]

    Wetlands are often considered as nature-based solutions that can provide a multitude of services of great social, economic and environmental value to humankind. Changes in land-use, water-use and climate can all impact wetland functions and services. These changes occur at scales extending well beyond the local scale of an individual wetland. However, in practical applications, engineering and management decisions usually focus on individual wetland projects and local site conditions. Here, we systematically investigate if and to what extent research has addressed the large-scale dynamics of landscape systems with multiple wetlands, hereafter referred to as wetlandscapes, which are likely to be relevant for understanding impacts of regional to global change. Although knowledge in many cases is still limited, evidence suggests that the aggregated effects of multiple wetlands in the landscape can differ considerably from the functions observed at individual wetland scales. This applies to provisioning of ecosystem services such as coastal protection, biodiversity support, groundwater level and soil moisture regulation, flood regulation and contaminant retention. We show that parallel and circular flow-paths, through which wetlands are interconnected in the landscape, may largely control such scale-function differences. We suggest ways forward for addressing the mismatch between the scales at which changes take place and the scale at which observations and implementation are currently made. These suggestions can help bridge gaps between researchers and engineers, which is critical for improving wetland function-effect predictability and management.

  • 20. Vico, Giulia
    et al.
    Dralle, David
    Feng, Xue
    Thompson, Sally
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    How competitive is drought deciduousness in tropical forests? A combined eco-hydrological and eco-evolutionary approach2017In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 12, no 6, article id 065006Article in journal (Refereed)
    Abstract [en]

    Drought-deciduous and evergreen species are both common in tropical forests, where there is the need to cope with water shortages during periodic dry spells and over the course of the dry season. Which phenological strategy is favored depends on the long-term balance of carbon costs and gains that leaf phenology imposes as a result of the alternation of wet and dry seasons and the unpredictability of rainfall events. This study integrates a stochastic eco-hydrological framework with key plant economy traits to derive the long-term average annual net carbon gain of trees exhibiting different phenological strategies in tropical forests. The average net carbon gain is used as a measure of fitness to assess which phenological strategies are more productive and more evolutionarily stable (i.e. not prone to invasion by species with a different strategy). The evergreen strategy results in a higher net carbon gain and more evolutionarily stable communities with increasing wet season lengths. Reductions in the length of the wet season or the total rainfall, as predicted under climate change scenarios, should promote a shift towards more drought-deciduous communities, with ensuing implications for ecosystem functioning.

  • 21. Vico, Giulia
    et al.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Nkurunziza, Libere
    Murphy, Kevin
    Weih, Martin
    Trade-offs between seed output and life span - a quantitative comparison of traits between annual and perennial congeneric species2016In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 209, no 1, p. 104-114Article in journal (Refereed)
    Abstract [en]

    Perennial plants allocate more resources belowground, thus sustaining important ecosystem services. Hence, shifting from annual to perennial crops has been advocated towards a more sustainable agriculture. Nevertheless, wild perennial species have lower seed production than selected annuals, raising the questions of whether there is a fundamental trade-off between reproductive effort and life span, and whether such trade-off can be overcome through selection. In order to address these questions and to isolate life span from phylogenetic and environmental factors, we conducted a meta-analysis encompassing c. 3000 congeneric annual/perennial pairs from 28 genera. This meta-analysis is complemented with a minimalist model of long-term productivity in perennial species. Perennials allocate more resources belowground and less to seeds than congeneric annuals, independently of selection history. However, existing perennial wheat and rice could achieve yields similar to annuals if they survived three years and each year doubled their biomass, as other perennial grasses do. Selected perennial crops maintain the large belowground allocation of wild perennials, and thus can provide desired regulatory ecosystem services. To match the seed yield of annuals, biomass production of perennial grains must be increased to amounts attained by some perennial grasses - if this goal can be met, perennial crops can provide a more sustainable alternative to annuals.

  • 22. Vico, Giulia
    et al.
    Thompson, Sally E.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Swedish University of Agricultural Sciences (SLU), Sweden .
    Molini, Annalisa
    Albertson, John D.
    Almeida-Cortez, Jarcilene S.
    Fay, Philip A.
    Feng, Xue
    Guswa, Andrew J.
    Liu, Hu
    Wilson, Tiffany G.
    Porporato, Amilcare
    Climatic, ecophysiological, and phenological controls on plant ecohydrological strategies in seasonally dry ecosystems2015In: Ecohydrology, ISSN 1936-0584, E-ISSN 1936-0592, Vol. 8, no 4, p. 660-681Article, review/survey (Refereed)
    Abstract [en]

    Large areas in the tropics and at mid-latitudes experience pronounced seasonality and inter-annual variability in rainfall and hence water availability. Despite the importance of these seasonally dry ecosystems (SDEs) for the global carbon cycling and in providing ecosystem services, a unifying ecohydrological framework to interpret the effects of climatic variability on SDEs is still lacking. A synthesis of existing data about plant functional adaptations in SDEs, covering some 400 species, shows that leaf phenological variations, rather than physiological traits, provide the dominant control on plant-water-carbon interactions. Motivated by this result, the combined implications of leaf phenology and climatic variability on plant water use strategies are here explored with a minimalist model of the coupled soil water and plant carbon balances. The analyses are extended to five locations with different hydroclimatic forcing, spanning seasonally dry tropical climates (without temperature seasonality) and Mediterranean climates (exhibiting out of phase seasonal patterns of rainfall and temperature). The most beneficial leaf phenology in terms of carbon uptake depends on the climatic regime: evergreen species are favoured by short dry seasons or access to persistent water stores, whereas high inter-annual variability of rainy season duration favours the coexistence of multiple drought-deciduous phenological strategies. We conclude that drought-deciduousness may provide a competitive advantage in face of predicted declines in rainfall totals, while reduced seasonality and access to deep water stores may favour evergreen species. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

  • 23. Wang, Lixin
    et al.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ravi, Sujith
    Riveros-Iregui, Diego
    Caylor, Kelly
    Dynamic interactions of ecohydrological and biogeochemical processes in water-limited systems2015In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 6, no 8, article id 133Article in journal (Refereed)
    Abstract [en]

    Water is the essential reactant, catalyst, or medium for many biogeochemical reactions, thus playing an important role in the activation and deactivation of biogeochemical processes. The coupling between hydrological and biogeochemical processes is particularly evident in water-limited arid and semi-arid environments, but also in areas with strong seasonal precipitation patterns (e.g., Mediterranean) or in mesic systems during droughts. Moreover, this coupling is apparent at all levels in the ecosystems-from soil microbial cells to whole plants to landscapes. Identifying and quantifying the biogeochemical hot spots'' and hot moments'', the underlying hydrological drivers, and how disturbance-induced vegetation transitions affect the hydrological-biogeochemical interactions are challenging because of the inherent complexity of these interactions, thus requiring interdisciplinary approaches. At the same time, a holistic approach is essential to fully understand function and processes in water-limited ecosystems and to predict their responses to environmental change. This article examines some of the mechanisms responsible for microbial and vegetation responses to moisture inputs in water-limited ecosystems through a synthesis of existing literature. We begin with the initial observation of Birch effect in 1950s and examine our current understanding of the interactions among vegetation dynamics, hydrology, and biochemistry over the past 60 years. We also summarize the modeling advances in addressing these interactions. This paper focuses on three opportunities to advance coupled hydrological and biogeochemical research: (1) improved quantitative understanding of mechanisms linking hydrological and biogeochemical variations in drylands, (2) experimental and theoretical approaches that describe linkages between hydrology and biogeochemistry (particularly across scales), and (3) the use of these tools and insights to address critical dryland issues of societal relevance.

  • 24. Way, Danielle A.
    et al.
    Katul, Gabriel G.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Swedish University of Agricultural Sciences, Sweden.
    Vico, Giulia
    Increasing water use efficiency along the C-3 to C-4 evolutionary pathway: a stomatal optimization perspective2014In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 65, no 13, p. 3683-3693Article in journal (Refereed)
    Abstract [en]

    C-4 photosynthesis evolved independently numerous times, probably in response to declining atmospheric CO2 concentrations, but also to high temperatures and aridity, which enhance water losses through transpiration. Here, the environmental factors controlling stomatal behaviour of leaf-level carbon and water exchange were examined across the evolutionary continuum from C-3 to C-4 photosynthesis at current (400 mu mol mol(-1)) and low (280 mu mol mol(-1)) atmospheric CO2 conditions. To this aim, a stomatal optimization model was further developed to describe the evolutionary continuum from C-3 to C-4 species within a unified framework. Data on C-3, three categories of C-3-C-4 intermediates, and C-4 Flaveria species were used to parameterize the stomatal model, including parameters for the marginal water use efficiency and the efficiency of the CO2-concentrating mechanism (or C-4 pump); these two parameters are interpreted as traits reflecting the stomatal and photosynthetic adjustments during the C-3 to C-4 transformation. Neither the marginal water use efficiency nor the C-4 pump strength changed significantly from C-3 to early C-3-C-4 intermediate stages, but both traits significantly increased between early C-3-C-4 intermediates and the C-4-like intermediates with an operational C-4 cycle. At low CO2, net photosynthetic rates showed continuous increases from a C-3 state, across the intermediates and towards C-4 photosynthesis, but only C-4-like intermediates and C-4 species (with an operational C-4 cycle) had higher water use efficiencies than C-3 Flaveria. The results demonstrate that both the marginal water use efficiency and the C-4 pump strength increase in C-4 Flaveria to improve their photosynthesis and water use efficiency compared with C-3 species. These findings emphasize that the advantage of the early intermediate stages is predominantly carbon based, not water related.

  • 25. Zhang, Quan
    et al.
    Katul, Gabriel G.
    Oren, Ram
    Daly, Edoardo
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Yang, Dawen
    The hysteresis response of soil CO2 concentration and soil respiration to soil temperature2015In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 120, no 8, p. 1605-1618Article in journal (Refereed)
    Abstract [en]

    Diurnal hysteresis between soil temperature (T-s) and both CO2 concentration ([CO2]) and soil respiration rate (R-s) were reported across different field experiments. However, the causes of these hysteresis patterns remain a subject of debate, with biotic and abiotic factors both invoked as explanations. To address these issues, a CO2 gas transport model is developed by combining a layer-wise mass conservation equation for subsurface gas phase CO2, Fickian diffusion for gas transfer, and a CO2 source term that depends on soil temperature, moisture, and photosynthetic rate. Using this model, a hierarchy of numerical experiments were employed to disentangle the causes of the hysteretic [CO2]-T-s and CO2 flux T-s (i.e., F-T-s) relations. Model results show that gas transport alone can introduce both [CO2]-T-s and F-T-s hystereses and also confirm prior findings that heat flow in soils lead to [CO2] and F being out of phase with T-s, thereby providing another reason for the occurrence of both hystereses. The area (A(hys)) of the [CO2]-T-s hysteresis near the surface increases, while the A(hys) of the R-s-T-s hysteresis decreases as soils become wetter. Moreover, a time-lagged carbon input from photosynthesis deformed the [CO2]-T-s and R-s-T-s patterns, causing a change in the loop direction from counterclockwise to clockwise with decreasing time lag. An asymmetric 8-shaped pattern emerged as the transition state between the two loop directions. Tracing the pattern and direction of the hysteretic [CO2]-T-s and R-s-T-s relations can provide new ways to fingerprint the effects of photosynthesis stimulation on soil microbial activity and detect time lags between rhizospheric respiration and photosynthesis.

  • 26. Zhang, Quan
    et al.
    Phillips, Richard P.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Scott, Russell L.
    Oishi, A. Christopher
    Finzi, Adrien
    Daly, Edoardo
    Vargas, Rodrigo
    Novick, Kimberly A.
    Changes in photosynthesis and soil moisture drive the seasonal soil respiration-temperature hysteresis relationship2018In: Agricultural and Forest Meteorology, ISSN 0168-1923, E-ISSN 1873-2240, Vol. 259, p. 184-195Article in journal (Refereed)
    Abstract [en]

    In nearly all large-scale terrestrial ecosystem models, soil respiration is represented as a function of soil temperature. However, the relationship between soil respiration and soil temperature is highly variable across sites and there is often a pronounced hysteresis in the soil respiration-temperature relationship over the course of the growing season. This phenomenon indicates the importance of biophysical factors beyond just temperature in controlling soil respiration. To identify the potential mechanisms of the seasonal soil respiration-temperature hysteresis, we developed a set of numerical models to demonstrate how photosynthesis, soil moisture, and soil temperature, alone and in combination, affect the hysteresis relationship. Then, we used a variant of the model informed by observations of soil respiration, soil temperature, photosynthesis, and soil moisture from multiple mesic and semi-arid ecosystems to quantify the frequency of hysteresis and identify its potential controls. We show that the hysteresis can result from the seasonal cycle of photosynthesis (which supplies carbon to rhizosphere respiration), and soil moisture (which limits heterotrophic respiration when too low or too high). Using field observations of soil respiration, we found evidence of seasonal hysteresis in 9 out of 15 site-years across 8 diverse biomes. Specifically, clockwise hysteresis occurred when photosynthesis preceded seasonal soil temperature and counterclockwise hysteresis occurred when photosynthesis lagged soil temperature. We found that across all sites, much of the respiration-temperature lag was explained by the decoupling of photosynthesis and temperature, highlighting the importance of recently assimilated carbon to soil respiration. An analysis of observations from 129 FLUXNET sites revealed that time lags between gross primary productivity (a proxy for canopy photosynthesis) and soil temperature were common phenomena, which would tend to drive counterclockwise hysteresis at low-latitude sites and clockwise hysteresis at high-latitude sites. Collectively, our results show that incorporating photosynthesis and soil moisture in the standard exponential soil respiration-temperature model (i.e., Q(10) model) improves the explanatory power of models at local scales.

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