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68 results for “nitrogen limitation”
Fire Self-Limitation (FiSL) Experiment: Quantifying Wildfire Carbon Combustion Losses in boreal Deciduous and Mixed Forests in Interior Alaska and the Boreal Cordillera IV: Organic Soil Carbon and Nitrogen Content from Organic Soil Samples 2022
This dataset contains lab-quantified (and some field-measured) characteristics for post-fire residual organic soil samples collected in the field for plots in 8 fire scars in Interior Alaska and the Yukon. Data was collected in the summer of 2022. Fire scars sampled included Shovel Creek (2019), Aggie Creek (2015), Hess Creek (2019), Baker (2015), Munson Creek (2021), Isom Creek (2020), 2019MA014 (2019), and 2019BC005 (2019). Lab analyses were conducted in summer and fall of 2022 at UAF and NAU.
Data and Code in support of Nitrogen and phosphorus co-limitation of forest growth in northern hardwood forests; Blumenthal et al. 2025
The Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE) project studies N and P acquisition and limitation of forest productivity through a series of nutrient manipulations in northern hardwood forests. This data set is published in support of a manuscript titled "Nitrogen and phosphorus co-limitation of forest growth in northern hardwood forests" and includes data and code used in the analysis. The primary diameter breast height dataset can be found in: Fisk, M.C., R.D. Yanai, and T.J. Fahey. 2025. Tree DBH response to nitrogen and phosphorus fertilization in the MELNHE study, Hubbard Brook Experimental Forest, Bartlett Experimental Forest, and Jeffers Brook ver 2. Environmental Data Initiative. https://doi.org/10.6073/pasta/fb8f8d5b903627bee9ad6aa4c32f2289. Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=344 These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
Chlorophyll data from experiments testing for nitrogen, phosphorus, and thiamine limitation of phytoplankton in 39 Ohio lakes of varying trophic status during the growing seasons (April – October) of 2008–2009
Although nitrogen and phosphorus deficiency of algal blooms have been the focus of substantial attention, organic nutrients can limit algal growth in aquatic systems. Growing evidence indicates thiamine (vitamin B1) can influence the community of primary producers in marine systems, but comparatively little is known about the effect of thiamine on freshwater algal productivity. We conducted 106 nutrient deficiency experiments with water from 39 Ohio lakes of varying trophic status during the growing seasons (April – October) of 2008–2009. Specifically, we tested the response of phytoplankton biomass (as chlorophyll a, chl-a) relative to controls to added nitrogen (N), phosphorus (P), thiamine (Th), or combinations of N+P and N+P+Th in integrated surface water collected from the inflow and outflow of each lake. The data presented here show the average chl-a of two replicate samples of each treatment (control, N, P, Th, N+P, N+P+Th), ratio of treatment/control response, and growth response ratio as ln(treatment chl-a/control chl-a). Each entry also includes lake surface water pH at time of collection and the initial chl-a concentration at time of experiment start.
Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE): Root biomass and growth responses to nitrogen and phosphorus
The Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE) project studies N , P, and Ca acquisition and limitation of forest productivity through a series of nutrient manipulations in northern hardwood forests. This data set includes data testing effects of elevated N and P availability on fine root growth (using ingrowth cores) and biomass in the MELNHE project. Subsets of ingrowth cores were treated with nutrients differing from the plot-scale nutrient treatments to test fine root foraging. Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=344 These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE): Nitrogen and phosphorus additions affect fruiting of ectomycorrhizal fungi in a temperate hardwood forest, 2018
The functioning of mycorrhizal symbioses is tied to soil nutrient status, suggesting that nutrient availability should influence the reproduction of mycorrhizal fungi. To quantify the effects of nitrogen (N) and phosphorus (P) availability on ectomycorrhizal fungal fruiting, we collected > 4,000 epigeous sporocarps representing 19 families during the course of a season in a full factorial NxP addition experiment in six replicate forest stands. Nutrient effects on fruiting shifted as the season progressed, with early fruiting species responding more to P and late-fruiting species responding more to N. The composition of species fruiting in young successional forests differed more with nutrient addition than in mature forests. Sporocarp abundance and species richness were suppressed by N addition. This work shows that N and P availability affect ectomycorrhizal fungal fruiting, with these effects taking place within a context defined by stand age and the progression of fruiting across the season. The data table in this data package contains the sprorocarp observation counts and biomass. Corresponding DNA sequences can be found in GenBank at: https://www.ncbi.nlm.nih.gov/nuccore/?term=MT345178%3AMT345282%5Baccn%5D Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-hbr.344.2 These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
Nutritional constraints on brain evolution: sodium and nitrogen limit brain size
Nutrition has been hypothesized as an important constraint on brain evolution. However, it is unclear whether the availability of specific nutrients or the difficulty of locating high quality diets limits brain evolution, especially over long periods of time. We show that dietary nutrient content predicted brain size across 42 species of butterflies. Brain size, relative to body size, was associated with the sodium and nitrogen content of a species' diet. There was no evidence that host plant apparency (measured by plant height) was related to brain evolution. The timing of diet shifts varied from 3.5 to 90 million years ago, but nutritional constraints did not lessen over time as species adapted to a diet. While nutrition was linked to overall brain volume, there was no evidence that nutrition was related to the relative size of individual brain regions. Lab rearing experiments confirmed the underlying assumption of most comparative studies that the majority of interspecific trait variation stems from species differences rather than an individual's current developmental environment. This study highlights a novel role of sodium and nitrogen in brain evolution, which is additionally interesting given current anthropogenic change in the availability of these nutrients.
data for paper: Predator-induced defense decreases growth rate and photoprotective capacity in a nitrogen-limited dinoflagellate
<p>this is the data for paper "Predator-induced defense decreases growth rate and photoprotective capacity in a nitrogen-limited dinoflagellate" </p>
CESM model results - Effect of nitrogen limitation and soil processes on Holocene greening of the Sahara
<p>The model results are made in EAPL, Yonsei University, South Korea (https://eapl.yonsei.ac.kr). The purpose of the simulations were to find out the effect of nitrogen limitation and soil processes on Holocene greening of the Sahara. CESM model v1.2 was used for this simulation.</p>
Limited legacy effects of extreme multi-year drought on carbon and nitrogen cycling in a mesic grassland
<p>The intensification of drought throughout the US Great Plains has the potential to have large impacts on grassland functioning, as has been shown with dramatic losses of plant productivity annually. Yet, we have a poor understanding of how grassland functioning responds after drought ends. This study examined how belowground nutrient cycling responds after drought and whether legacy effects persist post-drought. We assessed the two-year recovery of nutrient cycling processes following a four-year experimental drought in a mesic grassland by comparing two different growing season drought treatments - chronic (each rainfall event reduced by 66%) and intense (all rain eliminated until 45% of annual rainfall was achieved) – to the control (ambient precipitation) treatment. At the beginning of the first growing season post-drought, we found that in situ soil CO<sub>2</sub> efflux and laboratory-based soil microbial respiration were reduced by 42% and 22% respectively in the intense drought treatment compared to the control, but both measures had recovered by mid-season (July) and remained similar to the control treatment in the second post-drought year. We also found that extractable soil ammonium and total inorganic N were elevated throughout the growing season in the first year after drought in the intense treatment. However, these differences in inorganic N pools did not persist during the growing season of the second year post-drought. The remaining measures of C and N cycling in both drought treatments showed no post-drought treatment effects. Thus, although we observed short-term legacy effects following the intense drought, C and N cycling returned to levels comparable to non-droughted grassland within a single growing season regardless of whether the drought was intense or chronic in nature. Overall, these results suggest that key aspects of C and N cycling in mesic tallgrass prairie do not exhibit persistent legacies from four years of experimentally-induced drought.</p>
How nitrogen and phosphorus supply to nutrient-limited autotroph communities affects herbivore growth: testing stoichiometric and co-limitation theory across trophic levels
<p><span>Primary producer communities are often growth-limited by essential nutrients such as nitrogen (N) and phosphorus (P). The magnitude of </span><span>limitation and whether N, P, or both elements are limiting autotroph </span><span>growth depends on the supply and ratios of these essential nutrients. </span><span>Previous studies identified single, serial or co-limitation as predominant </span><span>limitation outcomes in autotroph communities by factorial nutrient </span><span>additions. Little is known about potential consequences of such scenarios </span><span>for herbivores and whether their growth is primarily affected by changes </span><span>in autotroph quantity or nutritional quality. We grew a community of </span><span>phytoplankton species differing in various food quality aspects in </span><span>experimental microcosms at varying N and P concentrations resulting in </span><span>three different N:P ratios. At carrying capacity, N, P, both nutrients or </span><span>none were added to reveal which nutrients were limiting. The nutrient supplied </span><span>communities were fed to the generalist herbivorous rotifer </span><span>Brachionus calyciflorus to investigate how changing phytoplankton </span><span>biomass and community composition affect herbivore abundance. We </span><span>found phytoplankton being growth-limited either by N alone (single </span><span>limitation) or serially, i.e. primarily by N and secondarily by P, altering </span><span>available food quantity for rotifers. Rotifer growth showed a different </span><span>response pattern compared to phytoplankton, suggesting that apart from </span><span>food quantity food quality aspects played a substantial role in the </span><span>transfer from primary to secondary production. The combined addition of </span><span>N and P to phytoplankton had generally a positive effect on herbivore </span><span>growth, whereas adding non-limiting nutrients had a rather detrimental </span><span>effect probably due to stoichiometrically imbalanced food in terms of </span><span>nutrient excess. Our experiment shows that adding various nutrients to </span><span>primary producer communities will not always lead to increased </span><span>autotroph and herbivore growth, and that differences between autotroph </span><span>and herbivore responses under co-limiting conditions can be partly well </span><span>explained by concepts of ecological stoichiometry theory.</span></p>
Model output for "Impact of intensifying nitrogen limitation of ocean net primary production is fingerprinted by nitrogen isotopes"
<p><strong>Description.</strong></p> <p>The data included in this repository is output of simulations performed with the NEMO-PISCESv2 global ocean-biogeochemical model. Simulations involved forcing the NEMO-PISCESv2 with global warming associated with historical and future emissions, as well as the historical and future trends in atmospheric nitrogen deposition. Future climate change was according to the Representative Concentration Pathway 8.5 scenario (Dufresne et al., 2013; Riahi et al., 2011), which sees rapid warming during the 21<sup>st</sup> century. Historical and future atmospheric nitrogen deposition fields were created via linear interpolation of fields produced by Hauglustaine et al. (2014) at years 1850, 2000, 2030, 2050 and 2100. To represent the amplification of deposition since 1950 (Galloway 2014), 60 % of the increase between 1850 and 2000 occurred from 1950 onwards.</p> <p>In this study, we quantified the effect anthropogenic climate change and anthropogenic increases in atmospheric nitrogen deposition on the marine nitrogen cycle. The response of the marine nitrogen cycle to these combined stressors is highly uncertain, and we therefore employed this complex model with a strong representation of nitrogen cycling in an attempt to constrain the global behaviour of this important cycle. In addition, through the addition of nitrogen isotopes to the ocean-biogeochemical model, we also explored and described how the isotopes responded to these anthropogenic forcings, and if the isotopes uniquely fingerprinted the response for potential monitoring/detection purposes.</p> <p>Our abstract reads:</p> <p>“The open ocean nitrogen cycle is being altered by increases in anthropogenic atmospheric nitrogen deposition and climate change. How the nitrogen cycle responds will determine long-term trends in net primary production (NPP) in the nitrogen-limited low latitude ocean, but is poorly constrained by uncertainty in how the source-sink balance will evolve. Here we show that intensifying nitrogen limitation of phytoplankton, associated with near-term reductions in NPP, causes detectable declines in nitrogen isotopes (δ<sup>15</sup>N) and constitutes the primary perturbation of the 21<sup>st</sup> century nitrogen cycle. Model experiments show that ~75% of the low latitude twilight zone develops anomalously low δ<sup>15</sup>N by 2060, predominantly due to the effects of climate change that alter ocean circulation, with implications for the nitrogen sources-sink balance. Our results highlight that δ<sup>15</sup>N changes in the low latitude twilight zone may provide a useful constraint on emerging changes to nitrogen limitation and NPP over the 21<sup>st</sup> century.”</p> <p> </p> <p><strong>Coordinates</strong></p> <p>Spatial resolution is global (90°S-90°N, 180°W-180°E, surface ocean to 5000 metres depth) and temporal resolution runs from years 1801 to 2100.</p> <p> </p> <p><strong>Citation.</strong></p> <p>Buchanan PJ, Aumont O, Bopp L, Mahaffey C, and Tagliabue A (2021): An isotopic fingerprint of increasingly nitrogen-limited phytoplankton in a changing oceanic nitrogen cycle. Nature Communications.</p> <p> </p> <p><strong>Files provided.</strong></p> <p>The data files provided are those that are required to create the figures for this study and/or perform key analyses (i.e. the time of emergence calculations). In the following, each figure or analysis has an associated python script and we list the data files needed to run that script.</p> <p>Python scripts can be found the lead authors GitHub at <a href="https://github.com/pearseb/PISCESiso_Ncycle_analysis">https://github.com/pearseb/PISCESiso_Ncycle_analysis</a>. </p> <p> </p> <p>Put δ<sup>15</sup>N<sub>NO3</sub> observations on model grid (<em>process-d15Nno3_observations_on_model_grid.py</em>):</p> <ul> <li>“RafterTuerena_watercolumn_d15N_no3.txt”</li> </ul> <p>Model assessment (<em>process-model_assessment.py</em>):</p> <ul> <li>“ETOPO_spinup_d15Nno3.nc”</li> <li>“ETOPO_ORCA2.0_Basins_float.nc”</li> <li>“ETOPO_ORCA2.0.full_grid.nc”</li> <li>“RafterTuerena_watercolumn_d15N_no3_gridded.npz”</li> </ul> <p>Time of emergence calculations (<em>process-compute_toe.py</em>):</p> <ul> <li>“ETOPO_picontrol_1y_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_1y_nst_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_1y_d15n_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_1y_d15n_pom_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_ndep_1y_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_ndep_1y_nst_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_ndep_1y_d15n_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_ndep_1y_d15n_pom_ez_utz_ltz.nc”</li> <li>“ETOPO_future_1y_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_future_1y_nst_ez_utz_ltz.nc”</li> <li>“ETOPO_future_1y_d15n_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_future_1y_d15n_pom_ez_utz_ltz.nc”</li> <li>“ETOPO_future_ndep_1y_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_future_ndep_1y_nst_ez_utz_ltz.nc”</li> <li>“ETOPO_future_ndep_1y_d15n_no3_ez_utz_ltz.nc”</li> <li>“ETOPO_future_ndep_1y_d15n_pom_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_1y_temp_ez_utz_ltz.nc”</li> <li>“ETOPO_future_1y_temp_ez_utz_ltz.nc”</li> <li>“ETOPO_picontrol_1y_npp.nc”</li> <li>“ETOPO_picontrol_ndep_1y_npp.nc”</li> <li>“ETOPO_future_1y_npp.nc”</li> <li>“ETOPO_future_ndep_1y_npp.nc”</li> <li>“ETOPO_picontrol_1y_nfix.nc”</li> <li>“ETOPO_picontrol_ndep_1y_nfix.nc”</li> <li>“ETOPO_future_1y_nfix.nc”</li> <li>“ETOPO_future_ndep_1y_nfix.nc”</li> </ul> <p>Figure 1 (<em>fig-main1.py</em>):</p> <ul> <li>“ncycle_changes.nc”</li> <li>“sources_and_sinks.nc”</li> </ul> <p>Figure 2 (<em>fig-main2.py</em>):</p> <ul> <li>“figure2D_ndep_d15nno3_signal_usingPAR.nc”</li> <li>“figure2D_ndep_d15npom_signal_usingPAR.nc”</li> <li>“figure2D_cc_d15nno3_signal_usingPAR.nc”</li> <li>“figure2D_cc_d15npom_signal_usingPAR.nc”</li> <li>“figure2D_picdep_d15nno3_signal_usingPAR.nc”</li> <li>“figure2D_picdep_d15npom_signal_usingPAR.nc”</li> <li>“ETOPO_ToE_futndep_depthzones.nc”</li> <li>“ETOPO_ToE_fut_depthzones.nc”</li> <li>“ETOPO_ToE_picndep_depthzones.nc”</li> <li>“ToE_futndep_curves.txt”</li> <li>“ToE_fut_curves.txt”</li> <li>“ToE_picndep_curves.txt”</li> </ul> <p>Figure 3 (<em>fig-main3.py</em>):</p> <ul> <li>“figure2D_cc_d15npom_signal_usingPAR.nc”</li> <li>“ETOPO_fluxanalysis_results.nc”</li> <li>“figure2D_cc_din_e15n.nc”</li> </ul> <p>Figure 4 (<em>fig-main4.py</em>):</p> <ul> <li>“ETOPO_direct_indirect_effects.nc”</li> </ul> <p>Supp Figure 1 (<em>fig-supp1.py</em>):</p> <ul> <li>“figure_d15Nmaps.nc”</li> </ul> <p>Supp Figure 2 (<em>process-model_assessment.py</em>):</p> <ul> <li>Produced by <em>process-model_assessment.py </em>(see data above)</li> </ul> <p>Supp Figure 3 (<em>fig-supp3.py</em>):</p> <ul> <li>“d15nstats.txt”</li> </ul> <p>Supp Figure 4 (<em>fig-supp4.py</em>):</p> <ul> <li>“ndep_Tg_yr.nc”</li> </ul> <p>Supp Figure 5 (<em>fig-supp5.py</em>):y</p> <ul> <li>“ncycle_changes_climatechangeonly.nc”</li> </ul> <p>Supp Figure 6 (<em>fig-supp6.py</em>):</p> <ul> <li>“ncycle_changes_ndeponly.nc”</li> </ul> <p>Supp Figure 7 (<em>fig-supp7.py</em>):</p> <ul> <li>“figure_depthzones.nc”</li> </ul> <p>Supp Figure 8 (<em>fig-supp8.py</em>):</p> <ul> <li>“figure2D_ndep_d15nno3_signal_usingPAR.nc”</li> <li>“figure2D_ndep_d15npom_signal_usingPAR.nc”</li> <li>“figure2D_cc_d15nno3_signal_usingPAR.nc”</li> <li>“figure2D_cc_d15npom_signal_usingPAR.nc”</li> <li>“figure2D_picdep_d15nno3_signal_usingPAR.nc”</li> <li>“figure2D_picdep_d15npom_signal_usingPAR.nc”</li> <li>“BGCP_ETOPO_merged_alt.nc”</li> <li>“ETOPO_ToE_futndep_depthzones.nc”</li> <li>“ETOPO_ToE_fut_depthzones.nc”</li> <li>“ETOPO_ToE_picndep_depthzones.nc”</li> <li>“BGCP_ETOPO_merged_alt.nc”</li> <li>“ToE_fut_curves.txt”</li> <li>“ToE_futndep_curves.txt”</li> <li>“ToE_picndep_curves.txt”</li> </ul> <p>Supp Figure 9 (<em>fig-supp9.py</em>):</p> <ul> <li>“figure2D_ndep_no3_utz.nc”</li> </ul> <p>Supp Figures 10 and 11 (<em>process-0D_model_phyto_frac.py</em>):</p> <ul> <li>Produced by <em>process-0D_model_phyto_frac.py</em> and no data required.</li> </ul> <p>Supp Figure 12 (<em>process-compute_toe.py</em>):</p> <ul> <li>Produced by <em>process-compute_toe.py </em>(see data above)</li> </ul> <p> </p> <p><strong>References.</strong></p> <p>Dufresne, J. L., Foujols, M. A., Denvil, S., Caubel, A., Marti, O., Aumont, O., et al. (2013). <em>Climate change projections using the IPSL-CM5 Earth System Model: From CMIP3 to CMIP5</em>. <em>Climate Dynamics</em> (Vol. 40). https://doi.org/10.1007/s00382-012-1636-1</p> <p>Galloway, J. N. (2014). The Global Nitrogen Cycle. In <em>Treatise on Geochemistry</em> (2nd ed., Vol. 10, pp. 475–498). Elsevier. https://doi.org/10.1016/B978-0-08-095975-7.00812-3</p> <p>Hauglustaine, D. A., Balkanski, Y., & Schulz, M. (2014). A global model simulation of present and future nitrate aerosols and their direct radiative forcing of climate. <em>Atmospheric Chemistry and Physics</em>, <em>14</em>(20), 11031–11063. https://doi.org/10.5194/acp-14-11031-2014</p> <p>Riahi, K., Rao, S., Krey, V., Cho, C., Chirkov, V., Fischer, G., et al. (2011). RCP 8.5—A scenario of comparatively high greenhouse gas emissions. <em>Climatic Change</em>, <em>109</em>(1–2), 33–57. https://doi.org/10.1007/s10584-011-0149-y</p>
Water limitation drives species loss in grassland communities after nitrogen addition and warming
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Limited legacy effects of extreme multi-year drought on carbon and nitrogen cycling in a mesic grassland
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How nitrogen and phosphorus supply to nutrient-limited autotroph communities affects herbivore growth: testing stoichiometric and co-limitation theory across trophic levels
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Nutritional constraints on brain evolution: sodium and nitrogen limit brain size
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Decomposition Model Parameters : Nitrogen limitation in decomposition
Modern agriculture and fossil fuel combustion contribute to the transfer of N from largely inert pools (atmospheric N2, fossil fuel reserves) to biologically reactive forms that can be transported downwind from agricultural or industrial areas to ecosystems that historically may have experienced low levels of N inputs. Understanding how increased N inputs alter the cycling of another biologically important element, C, has been impeded by uncertainties about N effects on the process of decomposition. To date, ecologists remain unable to predict when, where, and in what forms N addition stimulates rates of decomposition. For example, recent work showed that in eight low-N sites in Central Minnesota, litter N was positively correlated with decomposition, suggesting N limitation of decomposition, yet addition of inorganic N fertilizer increased decomposition in only two of eight sites. These paradoxical results call into question the assumption that the often-observed correlation between substrate N concentration and decomposition arises because N limits decomposition. Research is addressing three interrelated questions:* (1) Why do litter N and externally supplied N have contrasting effects on decomposition in low-N ecosystems? (2) Do different forms of N (organic vs. inorganic; substrate vs. externally supplied) affect the activity, function and composition of the decomposer community differently, and, if so, what are the consequences for decomposition? (3) What are temporal dynamics of the activity, function, and composition of the decomposer community and do these dynamics depend upon the amount and forms of N supplied to the decomposer community?* These questions will be addressed using a 4-y decomposition experiment manipulating the quantity and form of N available to decomposers via use of substrates ranging in N concentrations and of inorganic (ammonium nitrate) and organic (amino acids) N fertilizers. The response of microbial biomass, stoichiometry, efficiency
Siliceous and non-nutritious: nitrogen limitation increases anti-herbivore silicon defenses in a model grass
<p>Silicon (Si) accumulation alleviates a diverse array of environmental stresses in many plants, including conferring physical resistance against insect herbivores. It has been hypothesised that grasses, in particular, utilise 'low metabolic cost' Si for structural and defensive roles under nutrient limitation. While carbon (C) concentrations often negatively correlate with Si concentrations, the relationship between nitrogen (N) status and Si is more variable. Moreover, the impacts of N limitation on constitutive physical Si defences (e.g. silica and prickle cells) against herbivores are unknown. We determined how N limitation affected Si deposition in the model grass <i>Brachypodium distachyon</i> and how changes in these constitutive defences impacted insect herbivore (<i>Helicoverpa armigera</i>) growth rates. We used scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry in conjunction with X-ray mapping (XRM) to quantify physical structures on leaves and determine Si deposition patterns. We also determined how N limitation and Si supply impacted the jasmonic acid (JA) pathway, the master-regulator of induced defences against arthropod herbivores. N limitation reduced shoot growth by over 40%, but increased root mass (+21%), leaf Si concentrations (+50%) and the density of silica (+28%) and flattened prickle (+76%) cells. EDS and XRM established that Si was being deposited in these structures, together with hooked prickle cells and macro-hairs. Herbivore relative growth rates (RGR) were more than 115% lower in Si supplied plants compared to plants without Si supply and negatively correlated with leaf Si concentration and silica cell density. RGR was further reduced by N limitation and positively correlated with leaf N concentrations. Increases in JA concentrations following induction of the JA pathway were at least doubled by N limitation. Si accumulation and deposition were highly regulated by N availability, with N limitation promoting both constitutive Si physical defences and induction of the JA defensive pathway, in line with the resource availability hypothesis. These results indicate that grasses use 'low cost Si' when resources are limited and suggests that plant productivity may benefit from optimising conventional fertilisers and Si fertilisation.</p>
Global warming enhances nitrogen-limitation in a temperate reservoir system under consistent external load.
<p>Data belonging to AGU<em>:Water Resources Research</em> submission:</p> <p>Global warming and continued external loading increase nitrogen limitation in a temperate reservoir system.</p> <p>Climate change impacts hydrology, geochemistry, and biology of lakes and reservoirs worldwide, also affecting surface water concentrations of the essential nutrients nitrogen (N) and phosphorus (P). Few studies have illustrated climate change’s impact on nutrient processing due to compounded effects of both climate change and catchment inputs. In this study, we have evaluated monitoring data from the years 2000 to 2019 in the Franconian Lake District (FLD), which consists of one shallow (hypertrophic) and three deep reservoirs (meso- to eutrophic), interconnected by a transfer canal. The cascade configuration and consistent external load buffer catchment variations, making nutrient trends attributable to internal processing. Mass balances were set up and statistical analyses were conducted for trends in stratification, hypolimnetic anoxia and nutrient concentrations. Warming significantly increased water temperature (+0.35-1.0°C decade<sup>−1</sup> ), stratification (+7-18 days decade<sup>−1</sup>), and hypolimnetic anoxia (+15-35 days decade<sup>−1</sup>). TP increased in deep reservoirs (+0.006-0.01 mg-P L<sup>−1</sup> decade<sup>−1</sup> ) and TN decreased in all reservoirs (−0.2-0.4 mg-N L<sup>−1</sup> decade<sup>−1</sup> ). The increased rates of NO<sub>3</sub>-loss could be related to enhanced denitrification rates and earlier algal uptake. Increased TP-concentrations were attributable to increased sediment P-release, induced by prolonged stratification and hypolimnetic anoxia. Primarily, the decrease in TN drove a strong decrease in TN:TP-ratio (-4 to -15 mol:mol decade<sup>−1</sup>), triggering a biogeochemical regime shift towards N-limitation, associated with proliferation of harmful algae blooms. The identified impacts emphasizes the need to consider the potential disruptive effects of intensifying climate change on the health and restoration efforts for temperate, eutrophic lakes worldwide.</p>
Data for: Phosphorus limitation of early growth differs between nitrogen-fixing and non-fixing dry tropical forest tree species
<p>Tropical forests are often characterized by low soil phosphorus (P) availability, suggesting that P limits plant performance. However, how seedlings from different functional types respond to soil P availability is poorly known but important for understanding and modeling forest dynamics under changing environmental conditions.</p> <p>We grew four nitrogen (N)-fixing Fabaceae and seven diverse non-N-fixing tropical dry forest tree species in a shade house under three P fertilization treatments, and evaluated carbon (C) allocation responses, P demand, P-use, investment in P acquisition traits, and correlations among P acquisition traits.</p> <p>N-fixers grew larger with increasing P addition in contrast to non-N-fixers, which showed fewer responses in C allocation and P-use. Foliar P increased with P addition for both functional types, while P acquisition strategies did not vary among treatments but differed between functional types, with N-fixers showing higher root phosphatase activity (RPA) than non-fixers.</p> <p>Growth responses suggest that N-fixers are limited by P, but non-fixers may be limited by other resources. However, regardless of limitation, P acquisition traits such as mycorrhizal colonization and RPA were non-plastic across a steep P gradient. Differential limitation among plant functional types has implications for forest succession and earth system models.</p>
Long-term nitrogen deposition inhibits soil priming effects by enhancing phosphorus limitation in a subtropical forest
<p class="MsoNormal"><span>It is widely accepted that phosphorus (P) limits microbial metabolic processes and thus soil organic carbon (SOC) decomposition in tropical forests.</span><span> Global change factors like elevated atmospheric nitrogen (N) deposition can enhance P limitation, raising concerns about the fate of SOC. However, how elevated N deposition affects the soil priming effect (PE) (<em>i</em>.<em>e</em>., fresh C inputs induced changes in SOC decomposition) in tropical forests remains unclear. We incubated soils exposed to nine years of experimental N deposition in a subtropical evergreen broadleaved forest with two types of <sup>13</sup>C-labeled substrates of contrasting bioavailability (glucose and cellulose) with and without P amendments. We found that N deposition decreased soil total P and microbial biomass P, suggesting enhanced P limitation. In P unamended soils, N deposition significantly inhibited the PE. In contrast, adding P significantly increased the PE under N deposition and by a larger extent for the PE of cellulose (PE<sub>cellu</sub>) than the PE of glucose (PE<sub>glu</sub>). Relative to adding glucose or cellulose solely, adding P with glucose alleviated the suppression of soil microbial biomass and C-acquiring enzymes induced by N deposition, whereas adding P with cellulose attenuated the stimulation of acid phosphatase induced by N deposition. Across treatments, the PE<sub>glu</sub> increased as C-acquiring enzyme activity increased, whereas the PE<sub>cellu</sub> increased as acid phosphatase activity decreased. This suggests that P limitation, enhanced by N deposition, inhibits the soil PE through varying mechanisms depending on substrate bioavailability; that is, P limitation regulates the PE<sub>glu</sub> by affecting soil microbial growth and investment in C acquisition, whereas regulates the PE<sub>cellu</sub> by affecting microbial investment in P acquisition. These findings provide new insights for tropical forests impacted by N loading, suggesting that expected changes in C quality and P limitation can affect the long-term regulation of the soil PE.</span></p>
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