Variability in Soil Macronutrient Stocks across a Chronosequence of Masson Pine Plantations

Plantations play a vital role in the global nutrient cycle because they have large stocks of soil macronutrients. However, the impacts of plantations on soil macronutrient stocks combined with stand age and soil physicochemical properties have not been well quantified. We compared soil macronutrient stocks at soil depths of 0−20 and 20−40 cm across a 7-, 14-, 25-, and 30-year chronosequence of Masson pine (Pinus massoniana Lamb.) plantations. The results showed that the nitrogen (N), phosphorus (P), and potassium (K) stocks first increased and then decreased with stand age. The highest N and P stocks were observed in the 14-year-old plantation, and the 25-year-old plantation displayed the highest K stock. The C, N, and P stocks declined with increasing soil depth across all sites, whereas the reverse trend was found in the K stock. Carbon stocks were highest for all plantations, followed by the K, N, and P stocks. Plantation soils exhibited a higher C:P ratio and a lower P:K ratio at various soil depths. The dominant controlling factors for the soil macronutrient stocks varied significantly at different stand ages and soil depths according to statistical analysis. For the total soil system, the C stock was affected by the available nutrients, organic matter, and stoichiometry; the available nutrients and organic matter were the determinant factors of the N and P stocks. Aggregate stability could be the primary parameter affecting the K stock. Organic matter explained most of the variation in soil macronutrient stocks, followed by the P:K ratio and available K. Collectively, our results suggest that the response of soil macronutrient stocks to stand age and soil depth will be dependent on different soil physicochemical properties, and P and K may be important limiting factors in Masson pine plantation ecosystems.

Silicon Changes C:N:P Stoichiometry and Favors Pre-Sprouted Seedling Growth, Yield and the Technological Quality of Sugarcane.

The importance of silicon (Si) in sugarcane is well known, but its effects on changing C:N:P stoichiometry enough to increase pre-sprouted seedling (PSS) and sugarcane development in the field remains unknown. To that end, the present study aimed to assess whether Si fertigation favors its absorption enough to change elemental stoichiometry (C:N:P), physiological attributes and PSS growth, as well as the growth, stem yield and juice quality of sugarcane. Two field experiments were conducted in the PSS formation stage and another in the sugarcane plant development phase. Experiment 1 was carried out in a greenhouse with PSSs under two treatments: in the absence and presence of Si (2 mmol L−1) fertigation. Experiment 2 was performed in the field in red-yellow argisol with the sugarcane plant undergoing the following treatments: absence of Si (No Si); Si supplied by fertigation during the PSS formation and sugarcane plant development phases (Si–C); and Si supplied during the PSS formation and sugarcane plant development phases (Si–M+C). The following were assessed in experiment I: growth, leaf green color index (GCI), chlorophyll fluorescence, C, N, P, and Si content, and C:Si, C:N and C:P stoichiometric ratios. In experiment II, the same stoichiometric ratios were assessed, as well as sugarcane growth, stem yield and juice quality. Si reduced the C:Si, C:N and C:P stoichiometric ratios in PSS. The C:Si ratio in the leaves and stems declined with the supply of Si, while the C:N and C:P ratio in the leaves and stem was higher in plants that received Si in the Si-M+C treatment. Applying Si fertigation in PSS formation to promote changes in C:N:P stoichiometry favored photosynthetic efficiency and growth. The Si–M+C treatment stood out, since it also caused enough C:N:P stoichiometric changes to increase sugarcane growth, yield and juice quality.

Stoichiometry of C:N:P in the Roots of Alhagi sparsifolia Is More Sensitive to Soil Nutrients Than Aboveground Organs

The stoichiometry of carbon, nitrogen, and phosphorus (C:N:P) among leaves, stems, and roots reflects trade-offs in plants for acquiring resources and their growth strategy. The widely distributed plant Alhagi sparsifolia is an ideal species to study the ecological stoichiometry in different organs in response to the availability of nutrients and water in the desert ecosystem. However, which response of organs is most sensitive to environmental conditions is still unclear. To answer this question, we collected samples of plants and soils including not only aboveground leaves and stems, but also underground roots and soils from a wide range of arid areas during the growing season. The C, N, P, C:N, C:P, and N:P ratios in leaves, thorns, stems, and roots were derived to explore their relationship as well as their response mechanisms to nutrients and water spanning 1 m deep in the soil. The results showed that the order of N concentration was leaves > thorns > stems > roots, that the concentration of P in the leaves, thorns, and stems was similar, and that their values were higher than those in the roots. First, the C:N ratios in the leaves and stems were significantly positively correlated with the ratio in roots. The C:N ratios in each organ showed a significant relationship with the soil alkali hydrolyzable nitrogen (SAN) above a depth of 60 cm. In addition to SAN, soil available phosphorus (SAP) and soil organic carbon (SOC) affect the C:N ratio in the roots. Second, the C:P and N:P ratios in aboveground organs showed no correlations with the ratios in roots. The C:P and N:P ratios in the leaves and thorns have no relationship with soil nutrients, while the C:P ratio in roots was influenced by SAN and SOC in all soil layers. Finally, the N:P ratios in roots were also affected by nutrients in different soil depths at 0–20 and 60–80 cm. These results illustrate that the roots were more sensitive to soil nutrients than the aboveground parts. Our study of ecological stoichiometry also suggests a novel systematic approach for analyzing the sensitivity of responses of an organ to environmental conditions.

A critical assessment of the stoichiometric knife-edge: no evidence for artifacts caused by the experimental P-supplementation of algae

The stoichiometric knife-edge refers to the reduced performance of consumers encountering food with excess phosphorus (P) relative to carbon (C) or nitrogen (N). Studies that provide evidence for such knife-edge in aquatic systems often apply phosphate supplementation to create P-rich food treatments. However, this method may suffer from artifacts, because after uptake algae may store P in a form different from the P-rich biomolecules typically consumed by zooplankton. Our aim was to test if P supplementation results in potential biases. We experimentally exposed populations of the herbivore rotifer species, Brachionus calyciflorus (Pallas), to four different food quality treatments: algae grown under P-saturating (HPchem, molar C:P ratio = 59.7 ± 2.7) and P-sufficient (MPchem, molar C:P = 116.3 ± 5.2) conditions in chemostats, and algae grown under P-limiting conditions, but with molar C:P ratios equal to HPchem and MPchem treatments, respectively (HPLP+P, molar C:P = 59.8 ± 0.14; MPLP+P, molar C:P = 121.0 ± 4.3). The latter two treatments were achieved through P-supplementation of P-limited algae. Results show that for rotifers fed algae with either excess or intermediate P content, population growth rates were consistently higher on algae grown in chemostats than algae treated with the P supplementation method. Importantly, growth rates were also consistently lower in HP than in MP treatments and the magnitude of this negative impact was independent on algal growth history. The latter result confirms the existence of a stoichiometric knife-edge and indicates that P supplementation is a reliable method to study the relative effect of excess P on zooplankton performance in a standardized way.

Unveiling the Efficiency of Psychrophillic Aporrectodea caliginosa in Deciphering the Nutrients from Dalweed and Cow Manure with Bio-Optimization of Coprolites

There is an immense demand for vermicomposting employing psychrophilic vermiculture (Aporrectodea caliginosa) for management of wastes under the Himalayan ecosystem. Dalweed (weeds from the world-famous urban Dal Lake) and cow manure (CM) are cheaply and abundantly available bio resources in Kashmir valley. Dalweed (DW), disposed of in the heart of the city, ascribes unpleasant effects on tourism and the natural ecosystem. Initial substrate mixtures of DW and CM with different ratios (CM100, DW100, CM80:DW20, CM60:DW40, CM40:DW60 and CM20:DW80) and castings harvested were analyzed for the following parameters: pH, TOC, TN, NO3- P, K, Fe, Zn, C:N, C:P, and C:S ratio. The results of a 56day study revealed in consistency and disparity towards the bio-optimization of coprolites depending upon the type of waste residue and mixture ratio used. Treatments with medium to low dalweed residues (CM60:DW40 followed by CM80:DW20) were found to be optimum and significantly primed chemical properties of castings using A. caligenosa. C:N, C:P, and C:S ratios showed a non-linear response with maximum decrease in C:N ratio by 35%, C:P ratio by 38% in CM100, and C:S ratio by 67% in DW100. Humification ratio, humification index, and percent humic acids were changed across all the treatments with the highest respective values of 21.33 ± 1.05, 11.33 ± 0.76, and 47.83 ± 0.76 for CM60:DW40. Results also showed that the earthworm population and biomass significantly increased with the highest respective increments of 57.53% and 74.88% in CM60:DW40 over initial values. Moreover, the highest number of cocoons (95.67 ± 1.17) were recorded within CM60:DW40 and the lowest in the control (43.33 ± 1.53). Dehydrogenase and fluorescein diacetate activities were inconsistent with the highest in CM40:DW60 (64.64%) and CM20:DW80 (63.54%) respectively over the initial substrates, while highest urease activity (74.40%) was observed from CM100. The results highlight the role of A. caliginosa in sustainable transformation of CM and DW with insightful, beneficial, and priming impacts on castings for its agronomic value.

MODELLING THE TERRESTRIAL NITROGEN AND PHOSPHORUS CYCLE IN THE UVic ESCM

<div> <div> <div> <p>The role of nitrogen and phosphorus in terrestrial ecosystems has been shown to be critical in the regulation of the terrestrial carbon cycle. Therefore, the implementation of nutrient limitation in Earth System Models should be considered in order to have a more accurate representation of carbon fluxes, vegetation distribution and the response of the biosphere to climate change. Previous attempts to introduce the terrestrial nitrogen cycle and nutrient limitation in the UVic ESCM resulted in an incomplete project that was not added to the regular structure of the model. Here, we intend to improve the current state of the terrestrial nitrogen cycle and to develop a new terrestrial phosphorus cycle that will be coupled to the carbon cycle. The most prominent changes in the N cycle are the enforcement of N mass conservation and the merge with a deep land surface and a new wetland model. The N and P cycles estimates the fluxes between three organic pools: litter, soil and vegetation compartments (leaf, root and wood), two N pools (NH<sub>4</sub><sup>+</sup>, NO<sub>3</sub><sup>-</sup>) and one inorganic P pool. The basic structure of the N cycle was left in place, it estimates the inputs via biological nitrogen fixation and outputs via leaching, furthermore, with the merger with the new wetland model denitrification was added to the N loss of the system. The P cycle accounts the inputs from estimations of rock weathering and losses from occlusion and leaching. Both cycles regulate the vegetation system in 2 ways: (1) by controlling vegetation biomass if nutrient is limiting, reducing the amount of carbon in the plant compartments until the C:N or C:P ratio is met and (2) directly regulating the primary productivity by taking into account the relationship between leaf N and P and the maximum carboxylation rate (Vcmax). We aim to improve projections of the future CO<sub>2</sub> fertilization feedback, and thus carbon budgets and ZEC.</p> </div> </div> </div>

Body Size Plasticity of Weevil Larvae (Curculio davidi) (Coleoptera: Curculionidae) and Its Stoichiometric Relationship With Different Hosts

Parasites obtain energy and nutrients from the host, and their body size is also usually limited by host size. However, the regulatory mechanisms that control the plasticity of parasite body sizes and the stoichiometric relationships with their hosts remain unclear. Here we investigated the concentrations of 14 elements (C, H, O, N, P, S, K, Na, Ca, Mg, Al, Fe, Mn, and Zn) in the acorns of three oak species (Quercus spp.), in their endoparasitic weevil (Curculio davidi Fairmaire) (Coleoptera: Curculionidae) larvae and in the larval feces, and the weight of weevil larvae within different hosts in a warm-temperate zone of China. Our results showed that the three acorn species exhibited significant differences in C, H, O, P, K, Mg, and Mn concentrations. However, in the weevil larvae, only P, Mn, and C:P ratio revealed significant differences. Weevil larvae preferentially absorbed and retained N, Zn, Na, and P, whereas Mn, K, Ca, and O were passively absorbed and transported. The weevil larvae weight was associated with acorn stoichiometry, and positively correlated with acorn size. Weevil larvae P decreased, but Mn and C:P increased with their weight, implying highly variable in somatic stoichiometry are coupled with the plasticity of body size. Interestingly, weevil larvae weight was negatively correlated with acorn infection rate, indicating small-size parasitic insects might have higher fitness level in parasite–host systems than larger-size ones. Our results suggest that variation in P, Mn, and C:P in parasites may play critical roles in shaping their body size and in improving their fitness.

Results of posterior lamellar femto-keratoplasty using two different lasers

Purpose. To evaluate the results of treatment of patients with pseudophakic bullous keratopathy (PBK) by the method of posterior lamellar femto-keratoplasty with ultrathin graft (FS-DSEK) harvested using two different lasers. Material and methods. The results of surgical treatment of 82 patients (82 eyes) underwent posterior lamellar femto-keratoplasty for PBK were analyzed. In the 1st group included 43 patients (43 eyes) with PBK underwent FS-DSEK using FS laser Femto-Visum (Optosystems, Russia). In the 2nd group included 39 patients (39 eyes) with PBK underwent FS-DSEK using LDV Z8 (Ziemer, Switzerland). Observation period was 1 year. Before and after surgery following indicators were evaluated: uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), postoperative astigmatism, central corneal thickness (CCT), graft thickness, center-periphery (C:P) ratio, endothelial cell density (ECD), endothelial cell (EC) loss, optical density. Results. Transparent engraftment at 1-year observation period was observed in 88% of cases. In the 1st group UCVA=0.22±0.11, BSCVA=0.32±0.12, in the 2nd group UCVA=0.18±0.08, BSCVA=0.29±0.1 (p>0.05). The maximum BSCVA in both groups was 0.6. Postoperative astigmatism was comparative in 2nd groups – 1.43±1.1 and 1.38±1.0 D, respectively (p>0.05). In the 1st group, CCT=549±31, graft thickness in the central zone – 83±12, C:P ratio – 0.92±0.05; in the 2nd group CCT=546±28, graft thickness – 80±10, C:P ratio – 0.94±0.06 (p>0.05). In the 1st group ECD – 1326±282, EC loss – 55±6%; ECD in the 2nd – 850±230, EC loss – 70±7% (p<0.05). According to the results of densitometry, optical density of the posterior layers of the cornea and «donor–recipient» interface zone was higher in the 2nd group, both in the central and in the paracentral zones: in the 1st group in the posterior layers of the stroma – 16.4±1.2 (0–2 mm) and 15.8±1.0 (2–6 mm), in the interface zone – 14.5±0.9 (0–2) and 13.9±0.8 (2–6), in the 2nd group in the posterior layers – 18.3±1.3 (0–2 mm) and 17.9±1.1 (2–6 mm), and in the interface zone – 17.3±1.2 (0–2 mm) and 17.0±1.0 (2–6 mm, p<0.05). Conclusions. FS-DSEK showed high efficiency for treating patients with PBK. Functional results were comparative in 2nd groups. Statistical analysis showed highest safety of transplanted endothelium in the 1st group at 1-year observation period. Key words: pseudophakic bullous keratopathy, femtosecond laser, posterior lamellar keratoplasty, corneal endotheliumultrathin graft.

Net Primary Production Predicted by the Proportion of C:N:P Stoichiometric Ratio in the Leaf-Stem and Root of Cynodon Dactylon (Linn.) in the Riparian Zone of the Three Gorges Reservoir

Net primary production (NPP) is closely related to the proportion of carbon (C), nitrogen (N) and phosphorus (P) in the leaf-stem and root of perennial herbs. However, the relationship of NPP with the C:N:P stoichiometric ratio in above- and below-ground plant tissues remains unknown under the periodic flooding stresses in the riparian zone ecosystem. In this study, the leaf-stem and root C, N, P content and biomass of Cynodon dactylon (Linn.) Pers. (C. dactylon) were investigated at the riparian zone altitudes of 145–155, 155–165, and 165–175 m above sea level (masl) of in a Three Gorges Reservoir (TGR) tributary–Pengxi River. The results showed that the NPP and biomass of C. dactylon had a similar decreasing trend with a riparian zone altitudes decrease. The root of C. dactylon showed relatively lower N and P content, but much higher N and P use efficiency with higher C:N and C:P ratio than that of a leaf-stem under N limitation conditions. NPP was positively correlated to C:N in the stem-leaf to root ratio (C:Nstem-leaf/root) and C:P ratio in the root (C:Proot ratio). Hydrological and C:N:P stoichiometric variables could predict 68% of the NPP variance, and thus could be regarded as the main predictor of NPP in the riparian zone of the TGR.

Soil carbon, nitrogen and phosphorus ecological stoichiometry shifts with tree species in subalpine plantations

Understanding ecological stoichiometric characteristics of soil nutrient elements, such as carbon (C), nitrogen (N) and phosphorus (P) is crucial to guide ecological restoration of plantations in ecologically vulnerable areas, such as alpine and subalpine regions. However, there has been only a few related studies, and thus whether and how different tree species would affect soil C:N:P ecological stoichiometry remains unclear. We compared soil C:N:P ecological stoichiometry of Pinus tabulaeformis, Larix kaempferi and Cercidiphyllum japonicum to primary shrubland in a subalpine region. We observed strong tree-specific and depth-dependent effects on soil C:N:P stoichiometry in subalpine plantations. In general, the C:N, C:P and N:P of topsoil (0–10 cm) are higher than subsoil (>10 cm) layer at 0–30 cm depth profiles. The differences in C:N, N:P and C:P at the topsoil across target tree species were significantly linked to standing litter stock, tree biomass/total aboveground biomass and Margalef’s index of plant community, respectively, whereas the observed variations of C:N, N:P and C:P ratio among soil profiles are closely related to differences in soil bulk density, soil moisture, the quantity and quality of aboveground litter inputs as well as underground fine root across plantations examined. Our results highlight that soil nutrients in plantation depend on litter quantity and quality of selected tree species as well as soil physical attributes. Therefore, matching site with trees is crucial to enhance ecological functioning in degraded regions resulting from human activity.