Biogeographic Patterns of Leaf Stoichiometry and Adaption Strategy of Stellera Chamaejasme L. in Degraded Grasslands Across Northern China

Background: Plant leaf stoichiometry reflect its adaptations to environments. Leaf stoichiometry variations across different environments have been extensively studied among grassland plants, but little is known about intraspecific leaf stoichiometry, especially for widely distributed species, such as Stellera chamaejasme L. We present the first study on the leaf stoichiometry of S. chamaejasme, and evaluate their relationships with environmental variables by collecting S. chamaejasme leaf and soil samples from 29 invaded sites in the two plateaus of distinct environments [the Inner Mongolian Plateau (IM) and Qinghai-Tibet Plateau (QT)] in Northern China. Leaf C, N, P, and K and their stoichiometric ratios, and soil physicochemical properties were determined, together with climate information from each sampling sites. Results: Results showed that mean leaf C, N, P, and K concentrations were 498.60, 19.95, 2.15, and 6.57 g · kg-1, respectively; the C/N, C/P, and N/P ratios were 25.46, 246.22, and 9.84, respectively. Soil physicochemical properties of S. chamaejasme invaded area varied wildly, and few significant correlations between S. chamaejasme leaf ecological stoichiometry and soil physicochemical properties were observed. Except for C and N in leaves, the P and K had higher homeostasis than 1, between 4.17 and 13.21. Moreover, C and N content of S. chamaejasme leaves were unaffected by any climate factors. However, the correlation between leaf P and climate factors was significant in IM only, while leaf K in QT. Finally, partial least squares path modeling suggested that leaf P or leaf K were affected by different mechanisms in QT and IM regions. Conclusions: Our results indicated that S. chamaejasme tend to be insensitive to variation in soil nutrient availability, resulting in their broad distributions in China grasslands. Moreover, S. chamaejasme adapt to changing environments by adjusting its relationships with climate or soil factors to improve their chances of survival and spread in degraded grasslands.

Fertilization management strategies for ‘Agata’ potato production

ABSTRACT Fluctuations in potato prices and invariably rising production costs need sustainable fertilization strategies. For this purpose, two experiments were conducted in the southwestern region of São Paulo state to evaluate fertilization management strategies for the ‘Agata’ potato cultivar. The treatments consisted of the producer’s standard fertilization (1700 kg ha-1 NPK 4-30-10 at planting + 100 kg ha-1 urea and 150 kg ha-1 KCl at hilling) and combinations of two P rates at planting (standard rate and half of the rate), as monoammonium phosphate (MAP) with two forms of KCl application (total rate in the post-planting phase or half of the rate in the post-planting phase and half at hilling). The application of half the P rate (255 kg ha-1 P2O5) as the MAP at planting and the transfer of K from planting to applications in the post-planting phase or in the post-planting phase and at hilling, despite having provided a lower leaf P concentration, maintained the total tuber yield with higher operational yield of planting fertilization. It also increased the yield of tubers with a diameter >4.5 cm under conditions of lower water availability in the vegetative stages of the crop and soil with medium availability of P and K. Such a fertilization strategy is valuable for cost reductions and possible environmental liabilities.

Climatic Rather than Edaphic Variables Determine Leaf C, N, P Stoichiometry of Deciduous Quercus Species

Purpose Leaf elemental stoichiometry is indicative of plant nutrient limitation, community composition, ecosystem function. Understanding the variations of leaf carbon (C), nitrogen (N), and phosphorus (P) stoichiometry at genus-level across large geographic regions and identifying their driving factors are important to predict species’ distribution range shifts affected by climate change.MethodsHere, we determined the patterns of leaf concentrations ([ ]) and ratios ( / ) of C, N, P of five deciduous oaks species (Quercus) across China covering ~ 20 latitude (~21–41˚ N) and longitude (~99–119˚ E) degrees, and detected their relationships with climatic, edaphic variables. ResultsLeaf [C], [N] and N/P, C/P significantly increased, while leaf [P] and C/N decreased with the increasing latitude. Leaf stoichiometry except for leaf [C] had no significant trends along the longitude. Climatic variables, i.e. mean annual temperature, mean annual precipitation, the maximum temperature of the warmest month, temperature seasonality, aridity index, and the potential evapo-transpiration were the determinants of the geographic patterns of leaf C, N, P stoichiometry. The mean annual precipitation and the maximum temperature of the warmest month indirectly regulated leaf C/N, C/P and N/P via altering leaf [P]. Edaphic variables had non-significant effects on leaf C, N, and P stoichiometry at the broad geographic range.ConclusionsClimatic variables have more important effects than edaphic properties on leaf C, N, P stoichiometry of the studied deciduous Quercus species, which imply the ongoing climate change will alter nutrient strategies and potentially shift the distribution range of this eurytopic species.

The Effect of Microbial Inoculation under Various Nitrogen Regimes on the Uptake of Nutrients by Apple Trees

The European Green Deal strategy currently implemented in the EU aims to, among others, reduce the negative impact of fertilization on the environment. One of the solutions influencing the nutritional status of plants and the improvement of soil quality is the use of plant symbiosis with microorganisms. Thus, in this study we investigated the effect of arbuscular mycorrhizal fungi (AMFs) and plant-growth-promoting rhizobacteria (PGPR) colonization on the nutritional status of apple leaves and fruit, depending on the nitrogen treatment. In a fully factorial experiment, trees were grown for nine years with or without AMFs and PGPR. We compared several ammonium nitrate treatments as well as growth without fertilization as a control. The interactions between inoculation and doses of nitrogen fertilization were observed. AMF + PGPR significantly increased the concentration of nitrogen (N), phosphorus (P), and potassium (K) in leaves up to 5%, 23%, and 19%, respectively, depending on the N dosage. Conversely, in uninoculated trees, the nitrogen treatment had a negative impact on the leaf P mineral status. On the other hand, under microbial inoculation conditions, the dose of 100 kg N∙ha−1 diminished the leaf phosphorus content in comparison to other N doses, by a maximum of 9.6%. AMF + PGPR, depending on the N treatment, either did not influence or it decreased the Mg and Ca concentrations in the leaves by maximums of 8% and 15%, respectively. Microbial inoculation had no effect on the acquisition of Ca and Mg by fruits, except for the coupled negative influence of the 100 kg N∙ha−1 treatment. Symbiosis positively conditioned the K in fruits under a specific N regime—100 kg N∙ha−1 divided into two applications during the season and 50 kg N∙ha−1 applied to the herbicide strip, increasing the concentration by approximately 4% and 8%, respectively. This study greatly contributes to our understanding of the benefits of AMF and PGPR on perennials and encourages the future exploration of their effects on apple yield and fruit quality.

Effect of Drip Fertigation under Different Fertilizer Levels on Nutrient Status in Coconut (Cocos nucifera L) Leaf

A study was conducted during 2017-18 under the All India Co-ordinated Research Project initiated in 2009 at research farm of Bihar Agricultural University, Sabour, Bhagalpur. The aim of this study was compare the nutrient concentration of coconut leaves at different nutrient levels through drip fertigation in a Randomized Block Design (RBD) with four (4) replications. Result was observed that leaf Nitrogen, Phosphorous, Sulphur, Iron, Manganese, Copper and Boron content under different fertigation treatments were not significantly different from each other. The content of micronutrients in leaf were found to increase with increasing levels of fertilizer in the treatments. Cation Exchange Capacity was positively correlated with all the leaf nutrients. Organic carbon did not show remarkable relation with plant nutrient parameters. Soil K content of all three depths was positively correlated with all the leaf nutrient elements. Soil pH value was positively correlated with leaf P content in coconut which explains that leaf P content is directly proportional to the soil pH value. Electrical conductivity (EC) of soil was also positively correlated with P, K and B concentration in coconut leaf. Correlation coefficient value between CEC and leaf nutrient contents explains that 2nd depth of soil is more important for mineral nutrition of coconut palm. Correlation coefficient values between soil P content and leaf nutrient content. Higher correlation coefficient value was found at lower soil depth between available sulphur content in soil and sulphur content in leaf of coconut. This result suggests that inherent supplying capacity of micronutrient of experimental soil is not so influential for higher plant growth, but application of N, P and K fertilizers trigger the absorption capacity for micronutrient from soil. Under different NPK levels, the applied NPK does not have significant effect on leaf N, P, S, Zn content after five (5) years of experimentation while the effect was found to be significant for few elements like K, Fe, Mn, Cu, and B. An increasing trend was observed for leaf nutrient content with increasing levels of fertilizer application.

Solar radiation effects on leaf nitrogen and phosphorus stoichiometry of Chinese fir across subtropical China

Background Solar radiation (SR) plays critical roles in plant physiological processes and ecosystems functions. However, the exploration of SR influences on the biogeochemical cycles of forest ecosystems is still in a slow progress, and has important implications for the understanding of plant adaption strategy under future environmental changes. Herein, this research was aimed to explore the influences of SR on plant nutrient characteristics, and provided theoretical basis for introducing SR into the establishment of biochemical models of forest ecosystems in the future researches. Methods We measured leaf nitrogen (N) and phosphorus (P) stoichiometry in 19 Chinese fir plantations across subtropical China by a field investigation. The direct and indirect effects of SR, including global radiation (Global R), direct radiation (Direct R) and diffuse radiation (Diffuse R) on the leaf N and P stoichiometry were investigated. Results The linear regression analysis showed that leaf N concentration had no association with SR, while leaf P concentration and N:P ratio were negatively and positively related to SR, respectively. Partial least squares path model (PLS-PM) demonstrated that SR (e.g. Direct R and Diffuse R), as a latent variable, exhibited direct correlations with leaf N and P stoichiometry as well as the indirect correlation mediated by soil P content. The direct associations (path coefficient = − 0.518) were markedly greater than indirect associations (path coefficient = − 0.087). The covariance-based structural equation modeling (CB-SEM) indicated that SR had direct effects on leaf P concentration (path coefficient = − 0.481), and weak effects on leaf N concentration. The high SR level elevated two temperature indexes (mean annual temperature, MAT; ≥ 10 °C annual accumulated temperature, ≥ 10 °C AAT) and one hydrological index (mean annual evapotranspiration, MAE), but lowered the soil P content. MAT, MAE and soil P content could affect the leaf P concentration, which cause the indirect effect of SR on leaf P concentration (path coefficient = 0.004). Soil N content had positive effect on the leaf N concentration, which was positively and negatively regulated by MAP and ≥ 10 °C AAT, respectively. Conclusions These results confirmed that SR had negatively direct and indirect impacts on plant nutrient status of Chinese fir based on a regional investigation, and the direct associations were greater than the indirect associations. Such findings shed light on the guideline of taking SR into account for the establishment of global biogeochemical models of forest ecosystems in the future studies.

Phosphorus uptake and toxicity is delimited by mycorrhizal symbiosis in P-sensitive Eucalyptus marginata but not in P-tolerant Acacia celastrifolia

Many plant species from regions with ancient, highly-weathered nutrient-depleted soils have specialised adaptations for acquiring P and are sensitive to excess P-supply. Mycorrhizal associations may regulate P-uptake at high external P-concentrations, potentially reducing P-toxicity. We predicted that excess P-application will negatively impact species from the nutrient-depleted jarrah forest of Western Australia and that mycorrhizal inoculation will reduce P-toxicity by regulating P-uptake. For seedlings of the N2-fixing legume Acacia celastrifolia and the tree species Eucalyptus marginata, we measured growth at P-concentrations of 0 to 90 mg kg-1 soil and in relation to inoculation with the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis. Non-inoculated A. celastrifolia maintained leaf P-concentrations at <2 mg g-1 dry mass (DM) across the range of external P-concentrations. However, for non-inoculated E. marginata, as external P-concentrations increased leaf P also increased, reaching >9 mg g-1 DM at 30 mg P kg-1 soil. A. celastrifolia DM increased with increasing external P-concentrations, while E. marginata DM was maximal at 15 mg P kg-1 soil, declining at higher external P concentrations. Neither DM nor leaf P of A. celastrifolia were affected by inoculation with AMF. For E. marginata, even at 90 mg P kg-1 soil, inoculation with AMF resulted in leaf P remaining <1 mg g-1 DM, and DM being maintained. These data strengthen the evidence base that AMF may not only facilitate P-uptake at low external P-concentrations, but are also important for moderating P-uptake at elevated external P-concentrations and maintaining plant P concentrations within a relatively narrow concentration range.

Climatic rather than edaphic variables determine leaf C, N, P stoichiometry of deciduous Quercus species

Purpose Leaf stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) is indicative of plant nutrient limitation, community composition, ecosystem function. Understanding leaf stoichiometry patterns of C, N, P of eurytopic species at genus-level across large-scale geographic regions and identifying their driven factors are of great importance to assess and to predict species’ distribution range shifts affected by climate change. Methods Here, we determined the patterns of leaf C, N, P stoichiometry of five deciduous oaks species (Quercus) across China covering ~ 20 latitude (~ 21–41˚ N) and longitude (~ 99–119˚ E) degrees, and detected their relationships with climatic, edaphic variables. Results We found that the concentrations ([ ]) of leaf C, N and the ratios ( / ) of N: P, C: P significantly increased, while leaf [P] and C/N decreased with the increasing latitude. However, leaf stoichiometry had no significant trends along the longitudinal gradient with an exception of leaf [C] which decreased with increasing longitude. The climatic variables, i.e. mean annual temperature precipitation (MAP), the max temperature of the warmest month (Tmax), temperature seasonality (TS), aridity index (AI) were the determinants on the geographic patterns of leaf C, N, P stoichiometry. The studied deciduous Quercus species growing in warm and wet environments tended to increase leaf [C], [N], C/P, and N/P, but to decrease leaf [P] and C/N, which maybe their nutritional strategies to improve adaptability. Conclusion The adaptative mechanisms of leaf stoichiometry should be further studied to assess the fate of deciduous Quercus species affected by climate change.

Leaf Elemental Stoichiometry of Stellera Chamaejasme L. in Response to Environmental Factors in Degraded Grasslands Across Northern China

Plant leaf stoichiometry reflect its adaptations to environments. Leaf stoichiometry variations across different environments have been extensively studied among grassland plants, but little is known about intraspecific leaf stoichiometry, especially for widely distributed species, such as Stellera chamaejasme L. In order to evaluate the biogeographical drivers for leaf elemental stoichiometry in S. chamaejasme, leaf and soil samples were collected from 29 invaded sites in the two plateaus of distinct environments [the Inner Mongolian Plateau (IM) and Qinghai-Tibet Plateau (QT)] in Northern China. Leaf C, N, P, and K and their stoichiometric ratios, and soil physicochemical properties were determined. Results showed that mean leaf C, N, P, and K concentrations were 498.60, 19.95, 2.15, and 6.57 g kg-1, respectively; the C/N, C/P, and N/P ratios were 25.46, 246.22, and 9.84, respectively. Only leaf K was significantly different between the two environments studied. Soil physicochemical properties of S. chamaejasme invaded area varied wildly, suggesting this wide ranging species tend to be insensitive to variation in soil nutrient availability. C and N content of S. chamaejasme leaves were unaffected by any environmental factors. However, the stoichiometric homeostasis of P and K was observed. The correlation between leaf P and climate factors was significant only in IM, while leaf K was significantly related to climate factors only in QT. Partial least squares path modeling suggested that soil exerted a significant effect on LP and climate affected leaf P and K both directly and indirectly in QT, while LP appeared to be limited mainly by climatic factors via direct ways and LK was not affected significantly by any environmental factors in IM. This study evaluated the S. chamaejasme leaf elemental stoichiometry and their relationships with environmental variables, which can help understand the plant biogeographic patterns and adaption strategy in degraded grasslands in China.