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Affected by the pressure and constraints of available resources, plant growth and development, as well as plant life history strategies, usually vary with environmental conditions. Plant buds play a crucial role in the life history of woody plants. Nitraria tangutorum is a common dominant woody species in desertified areas of northern China and its growth is critical to the desert ecosystem. Revealing the allometry of N. tangutorum aboveground bud fates and the linkage between bud traits and plant nutrient contents and stoichiometric ratios can be useful in understanding plant adaptation strategy. We applied seven nitrogen and phosphorus fertilizer addition treatments to natural N. tangutorum ramets in Ulan Buh Desert in three consecutive years. We surveyed three types of aboveground buds (dormant buds, vegetative buds, and reproductive buds) in each N. tangutorum ramet, then measured the plant carbon (C), nitrogen (N), and phosphorus (P) contents and ratios during three consecutive years. We specified that reserve growth potential (RGP), vegetative growth intensity (VGI) and sexual reproduction effort (SRE) are the three indices of bud dynamic pattern. The results showed that the bud dynamic pattern of N. tangutorum ramets differed significantly among different fertilizer addition treatments and sampling years. The allometry of RGP, VGI, and SRE was obvious, showing size dependence. The allometric growth relationship fluctuated among the sampling years. The linkage between bud traits and plant stoichiometric characteristics of N. tangutorum ramets showed close correlation with plant P content, C:P and N:P ratios, no significant correlation with plant C content, N content and C:N ratio. These results contribute to an improved understanding of the adaptive strategies of woody plants growing in desert ecosystems and provide insights for adoption of effective measures to restore and conserve plant communities in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

Abstract The evolutionary stability of mutualistic interactions involving multiple partners requires “sanctioning”–the ability to influence the fitness of each partner based on its respective contribution. Sanctions must be sensitive to even small differences if even slightly less‐beneficial partners could gain a fitness advantage by diverting resources away from the mutualistic service toward their own reproductive fitness. Here, we test whether legume hosts sanction even mediocre N2‐fixing rhizobial strains by influencing either nodule growth (which limits rhizobial cell numbers) or carbon accumulation (polyhydroxybutryate or PHB) per rhizobial cell. We also test whether sanctions depend on the availability of less‐expensive nitrogen alternatives, either as nitrate or coinoculation with a more‐efficient isogenic strain. We found that nitrate eliminated differences in nodule size between the mediocre and more‐efficient strains, suggesting that host sanctions were compromised. However, nitrate additions also decreased PHB accumulation by the mediocre strain, which may eliminate any fitness advantages of diverting resources from N2 fixation. Coinoculation with a more‐efficient strain could also compromise host sanctions if reduction in fitness from smaller nodules does not offset the potential fitness gain from greater PHB accumulation that we observed in the mediocre strain. Hence, a host's ability to sanction mediocre strains depends not only on alternative sources of nitrogen but also the relative importance of different components of rhizobial fitness.

Rising concentrations of carbon dioxide (CO2) is likely to have important effects on growth and development of plants and on their relationship with symbiotic microbes. A rise in CO2 could increase demand by plant hosts for nutrient resources, which may increase host investments in beneficial symbionts. In the legume-rhizobia mutualism, while elevated CO2 is often associated with increased nodule growth and investment in N2-fixing rhizobia, it is yet unclear if this response depends on the mutualistic quality of the rhizobia. To test if host carbon allocation towards more-beneficial nodules are similar to less-beneficial (but still effective) nodules when plant N demand changes, we manipulated plant C and N status with elevated CO2 and additional nitrate. We used two isogenic Rhizobium etli strains that differ in their ability to synthesize an energy reserve compound, poly-beta-hydroxybutyrate (PHB), as well as their efficiencies for nitrogen fixation and nodulation rates, resulting in two Phaseolus vulgaris host groups with either large number of small nodules or small number of large nodules. The addition of nitrate negatively affected carbon allocation towards nodules, and elevated CO2 reversed this effect, as expected. However, this alleviation of nodule inhibition was greater on plants that started with greater numbers of smaller nodules. If smaller nodules indicate less-efficient or low-fixing rhizobia, this study suggests that increased demand for nitrogen in the face of elevated CO2 has the potential to disproportionately favor less-beneficial strains and increase variation of nitrogen fixation quality among rhizobia. [ABSTRACT FROM AUTHOR]

Any management practice that results in greater carbon (C) return to the soil, increases stabilization of soil C, or reduces C losses may lead to soil organic carbon (SOC) storage in soil. Therefore, SOC dynamics in soil are dictated by a balance between input and output of C in the soil, and C sequestration occurs only when the input exceeds the output. Primarily, greater C input can occur by enhancing biomass production using fertilizers with irrigation, stubble retention, crop rotation, minimum tillage, and by improving soil properties including having the appropriate pH, cation exchange capacity (CEC), and osmotic pressure. Conventional farming with intensive plowing leads to SOC decomposition, whereas conservation farming with no or minimum tillage with stubble retention may retard the decomposition of soil native organic C. Fertilizer addition may influence the decomposition of SOC. The effect of fertilizer on decomposition of soil organic matter (SOM) differs with and without the presence of organic matter as crop residues, labile C, or easily degradable C in soil. This effect of fertilizer is mostly dominated by the presence/addition of organic matter in soil rather crop management or what the pH, CEC, or osmotic pressure are. However, decomposition of crop residues or organic matter depends on their quality (biochemical properties), soil types, soil environment, the microbial community, and nutrient availability. More microbial activity with organic matter decomposition means more production of stabilized C, which is relatively recalcitrant to microbial degradation. Therefore, nutrient addition in soil may be helpful in increasing SOM stock. At least, it can maintain the SOM level if the C (energy source) for microbial growth is external like stubble or added organic matter rather than internal (native) SOM. [ABSTRACT FROM AUTHOR]

The evolutionary stability of mutualistic interactions involving multiple partners requires "sanctioning"–the ability to influence the fitness of each partner based on its respective contribution. Sanctions must be sensitive to even small differences if even slightly less‐beneficial partners could gain a fitness advantage by diverting resources away from the mutualistic service toward their own reproductive fitness. Here, we test whether legume hosts sanction even mediocre N2‐fixing rhizobial strains by influencing either nodule growth (which limits rhizobial cell numbers) or carbon accumulation (polyhydroxybutryate or PHB) per rhizobial cell. We also test whether sanctions depend on the availability of less‐expensive nitrogen alternatives, either as nitrate or coinoculation with a more‐efficient isogenic strain. We found that nitrate eliminated differences in nodule size between the mediocre and more‐efficient strains, suggesting that host sanctions were compromised. However, nitrate additions also decreased PHB accumulation by the mediocre strain, which may eliminate any fitness advantages of diverting resources from N2 fixation. Coinoculation with a more‐efficient strain could also compromise host sanctions if reduction in fitness from smaller nodules does not offset the potential fitness gain from greater PHB accumulation that we observed in the mediocre strain. Hence, a host's ability to sanction mediocre strains depends not only on alternative sources of nitrogen but also the relative importance of different components of rhizobial fitness. [ABSTRACT FROM AUTHOR]

Almost all natural terrestrial ecosystems are nutrient limited in terms of growth, and we expect treeline vegetation to be no exception. However, direct constraints of low temperature on tissue formation may superimpose effects of low nutrient availability.We examined growth responses of two tree (Larix decidua and Pinus uncinata) and two dwarf shrub species (Vaccinium myrtillus and Vaccinium gaultherioides) to 12 years of moderate fertilizer addition (NPK applied at a rate of 15 and 30 kg nitrogen ha−1 a−1) along an elevation gradient within the treeline ecotone in the Swiss Alps (2,083 to 2,225 m a.s.l.). We measured annual top‐ and side‐shoot increments as well as stem ring width in trees and shoot increments in dwarf shrubs.Fertilizer addition increased soil nutrient availability, indicated by enhanced soil extractable N, higher concentrations of N, P and K in leaves and higher foliar δ15N.Fertilizer addition stimulated annual growth of all four species: by 11%–20% for L. decidua and 15%–36% for P. uncinata (depending on trait) and by 8%–16% for the two dwarf shrub species. Growth stimulation by the higher fertilizer dose was not significantly stronger than by the lower dose (except for V. gaultherioides), suggesting an overall low nutrient demand for growth and saturation at a rather low nutrient input.Synthesis. Even slightly enhanced nutrient availability can stimulate growth of trees and dwarf shrubs in an alpine treeline ecosystem. Ongoing atmospheric nutrient deposition, in conjunction with global warming, may accelerate plant growth at the treeline. Twelve years of low‐dose nutrient addition showed that even slightly enhanced nutrient availability stimulates growth of two tree (Larix decidua and Pinus uncinata) and two dwarf shrubs species (Vaccinium myrtillus and Vaccinium gaultherioides) in an alpine treeline ecosystem. Ongoing atmospheric nutrient deposition, in conjunction with global warming, may therefore accelerate plant growth at the treeline. [ABSTRACT FROM AUTHOR]

We manipulated nutrient concentrations in 14 channels adjacent to a forested headwater stream to examine the influence of nutrient enrichment on detrital and algal pathways. Our fertilization experiment increased the average water concentration of N up to a maximum of ~2 times and of P up to ~7 times relative to control channels, levels considered as moderate enrichment. We measured algal biomass and leaf mass loss as a proxy measure of primary production and leaf decomposition, respectively. We determined the effects of nutrients on the quantity and quality of food resources and tested whether these effects influenced biotic structure and stoichiometry. Our results indicate that algal pathways showed significant and consistent responses across treatments by increasing epilithon quantity and quality. Moreover, despite an increase in quality of leaves, its quantity and loss rate were unaltered. Importantly, changes to detritivore densities were subtle, but they showed a hump-shaped response along the induced nutrient gradient. This trend suggests the existence of nutrient limitation at low nutrient concentrations and the existence of negative biotic interactions and/or sublethal toxic effects at higher concentrations, while enhancing detritivore densities at intermediated enriched conditions (threshold at ~10 µg/l of P-PO in water and 0.10% of leaf-P). This study reveals the complexity of connections between algal and detritus pathways with implications in the study of transfer of matter and energy in oligotrophic, forested headwater streams. [ABSTRACT FROM AUTHOR]

Affected by the pressure and constraints of available resources, plant growth and development, as well as plant life history strategies, usually vary with environmental conditions. Plant buds play a crucial role in the life history of woody plants. Nitraria tangutorum is a common dominant woody species in desertified areas of northern China and its growth is critical to the desert ecosystem. Revealing the allometry of N. tangutorum aboveground bud fates and the linkage between bud traits and plant nutrient contents and stoichiometric ratios can be useful in understanding plant adaptation strategy. We applied seven nitrogen and phosphorus fertilizer addition treatments to natural N. tangutorum ramets in Ulan Buh Desert in three consecutive years. We surveyed three types of aboveground buds (dormant buds, vegetative buds, and reproductive buds) in each N. tangutorum ramet, then measured the plant carbon (C), nitrogen (N), and phosphorus (P) contents and ratios during three consecutive years. We specified that reserve growth potential (RGP), vegetative growth intensity (VGI) and sexual reproduction effort (SRE) are the three indices of bud dynamic pattern. The results showed that the bud dynamic pattern of N. tangutorum ramets differed significantly among different fertilizer addition treatments and sampling years. The allometry of RGP, VGI, and SRE was obvious, showing size dependence. The allometric growth relationship fluctuated among the sampling years. The linkage between bud traits and plant stoichiometric characteristics of N. tangutorum ramets showed close correlation with plant P content, C:P and N:P ratios, no significant correlation with plant C content, N content and C:N ratio. These results contribute to an improved understanding of the adaptive strategies of woody plants growing in desert ecosystems and provide insights for adoption of effective measures to restore and conserve plant communities in arid and semi-arid regions., Competing Interests: The authors declare there are no competing interests., (©2023 Li et al.)

The study was undertaken to determine the decomposition of pineapple leaf residue (PLR) char produced by controlled combustion in the laboratory (CL) and by field burning (FB) with and without added fertilizer in tropical peat over 12 months. Decompositions of both chars with and without added fertilizer fit the three-parameter single exponential decay model. Fertilizer treatment significantly reduced the weight and lignin remainings in the CL and CF biochars after 12 months. Total C remaining in the biochar showed an increase in this order: CF + fertilizer < CF < CL + fertilizer < CL. The aliphatic functional groups of both chars transformed to aromatic groups 12 months after application to the peat. The pot study indicates that the total C, recalcitrant fractions and lignin content of char made by CL were higher than the char made by FB. The results suggest that to produce biochar for carbon sequestration purposes, the PLR should be carbonized in a CL process rather than by FB. [ABSTRACT FROM AUTHOR]

Question There are contrasting opinions about how communities assemble along a productivity gradient, particularly in relation to competitive interactions. One view is that functionally similar, and closely related species, are less likely to co-exist (limiting similarity). Alternatively, competitive exclusion may act on dissimilar species because species bearing traits associated with low competitive ability are excluded (weaker competitor exclusion). We ask if patterns of functional and phylogenetic diversity are related to changes in species diversity in response to fertility manipulations. Location Species-rich mesophytic grassland in Estonia. Methods The grassland has been manipulated from 2002 to 2011 to increase (fertilizer addition) and decrease productivity (sucrose addition) in small-scale (50 cm × 50 cm) plots. We linked annual increases and decreases in species diversity to changes in functional and phylogenetic diversity. We used abundance-weighted mean pair-wise functional or phylogenetic distance of all possible species pairs. Results We found convergence in four traits (plant height, leaf distribution, lateral spread, type of reproduction) and a decrease in mean functional and phylogenetic diversity, in support of weaker competitor exclusion or habitat filtering. There was less support for limiting similarity, with divergence found for two traits associated with decreasing species diversity (leaf distribution in the sucrose treatment and lateral spread in the fertilizer treatment). Conclusions Our results support the view that competition can lead to the exclusion of weaker competitors, rather than increasing functional and phylogenetic diversity, as expected from the principle of limiting similarity. However, multiple assembly processes, which are generally seen as mutually exclusive, are operating simultaneously, albeit on different traits and at different stages of community assembly. [ABSTRACT FROM AUTHOR]

Seasonal growth responses of plants and soil microorganisms to additions of nitrogen (N), phosphorus (P) and carbon (C) were examined in goose-grazed and exclosed plots in an Arctic salt marsh. Plants showed strong growth responses to N and NP additions but not to P. Nitrogen levels in the shoots and roots of Puccinellia phryganodes declined as summer progressed. Microbial biomass was low in spring in spite of N and P additions, likely due to C limitation, but values rose in autumn, independent of nutrient treatment, as dissolved organic carbon (DOC) increased. Glucose addition (C source) elicited a transitory increase in microbial biomass. Multiple plant defoliations by geese had a negative effect on microbial biomass, in spite of the presence of DOC and added N and P, possibly because hypersalinity restricted growth. Plants appear to limit soil inputs of C in summer and compete effectively for resources in contrast to autumn, indicating a temporal partitioning of resources. [ABSTRACT FROM AUTHOR]

The ultramafic sites at Meikle Kilrannoch, Scotland, have small sparsely colonized patches with soils which have highly toxic (to many non-indigenous plants) concentration of Mg and Ni. These toxic metals are unlikely to be the main cause of the open vegetation as the indigenous plants are at least partially tolerant of them. The hypothesis that low soil nutrients were a likely cause of the open vegetation was tested by a fertilization experiment in which major nutrients and Ca were added in August 1991 and July 1992 to replicated quadrats which initially had 5.3-6.6% plant cover. There was a large increase in plant cover on major nutrient addition. The increase in rosette size, flowering, seed production, and recruitment if the dominant semelparous Cochlearia pyrenaica DC. ssp. alpina (Bab.) Dalby was studied in detail. The increased growth of Cochlearia (and some other native species at the site) in nutrient addition strengthens the argument that a major nutrient deficiency rather than a metal toxicity limits plants growth at Meikle Kilrannoch and shows that at least some stress tolerators respond with rapid growth and reproduction when nutrient limitation is removed. A small-scale experiment set up in June 1993, in which the major nutrients were added separately, suggested that P and not N, or K was the limiting element. The effects of P seem to be unrelated to any possible reduction in the availability of the toxic ions Mg2+ and Ni2+. [ABSTRACT FROM AUTHOR]