A silviculture-oriented spatio-temporal model for germination in Pinus pinea L. in the Spanish Northern Plateau based on a direct seeding experiment

Natural regeneration in Pinus pinea stands commonly fails throughout the Spanish Northern Plateau under current intensive regeneration treatments. As a result, extensive direct seeding is commonly conducted to guarantee regeneration occurrence. In a period of rationalization of the resources devoted to forest management, this kind of techniques may become unaffordable. Given that the climatic and stand factors driving germination remain unknown, tools are required to understand the process and temper the use of direct seeding. In this study, the spatio-temporal pattern of germination of P. pinea was modelled with those purposes. The resulting findings will allow us to (1) determine the main ecological variables involved in germination in the species and (2) infer adequate silvicultural alternatives. The modelling approach focuses on covariates which are readily available to forest managers. A two-step nonlinear mixed model was fitted to predict germination occurrence and abundance in P. pinea under varying climatic, environmental and stand conditions, based on a germination data set covering a 5-year period. The results obtained reveal that the process is primarily driven by climate variables. Favourable conditions for germination commonly occur in fall although the optimum window is often narrow and may not occur at all in some years. At spatial level, it would appear that germination is facilitated by high stand densities, suggesting that current felling intensity should be reduced. In accordance with other studies on P. pinea dispersal, it seems that denser stands during the regeneration period will reduce the present dependence on direct seeding.     

Interactions between a plant growth‐promoting rhizobacterium and smoke‐derived compounds and their effect on okra growth

Plant growth‐promoting rhizobacteria (PGPR) are used in agriculture to improve crop yield. Crude smoke–water (made by bubbling plant‐derived smoke through water) stimulates germination and improves seedling growth. Some active compounds have been isolated from smoke with karrikinolide (KAR₁) stimulating plant growth and trimethylbutenolide (TMB) being inhibitory. These smoke compounds have great potential in agriculture but their interaction with PGPR is unknown. In the present study, a two‐factorial pot trial with three replicates per treatment was designed to investigate the interactions between Bacillus licheniformis and two concentrations each of smoke–water, KAR₁, and TMB on okra (Abelmoschus esculentus). Growth and physiological parameters (chlorophyll, carotenoid, protein, sugar and α‐amylase) of okra as well as bacterial abundance in the rhizosphere were measured after 5 weeks. Application of B. licheniformis and 10^?7 M KAR₁ significantly improved the shoot biomass and 10^?7 M KAR₁ also significantly improved leaf area of okra. However, when 10^?7 M KAR₁ was applied in combination with B. licheniformis, there was an antagonistic effect on plant growth. While TMB had a negative effect on plant growth, a combination treatment of TMB and B. licheniformis overcame the inhibitory effect of TMB resulting in plant growth similar to the control plants. All treatments had no effect on chlorophyll, carotenoid, protein and sugar concentrations, while α‐amylase activity was significantly elevated in okra root treated with 1:500 (v/v) smoke–water. Determining the rhizobacteria populations at harvest showed that all treatments had no significant effect on the rhizosphere microbial abundance. The modes of interaction between PGPR and smoke‐derived compounds need to be further elucidated.     

Sponge-Derived Kocuria and Micrococcus spp. as Sources of the New Thiazolyl Peptide Antibiotic Kocurin

Forty four marine actinomycetes of the family Microccocaceae isolated from sponges collected primarily in Florida Keys (USA) were selected from our strain collection to be studied as new sources for the production of bioactive natural products. A 16S rRNA gene based phylogenetic analysis showed that the strains are members of the genera Kocuria and Micrococcus. To assess their biosynthetic potential, the strains were PCR screened for the presence of secondary metabolite genes encoding nonribosomal synthetase (NRPS) and polyketide synthases (PKS). A small extract collection of 528 crude extracts generated from nutritional microfermentation arrays was tested for the production of bioactive secondary metabolites against clinically relevant strains (Bacillus subtilis, methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter baumannii and Candida albicans). Three independent isolates were shown to produce a new anti-MRSA bioactive compound that was identified as kocurin, a new member of the thiazolyl peptide family of antibiotics emphasizing the role of this family as a prolific resource for novel drugs.     

Leaching of nitrate and phosphorus after autumn and spring application of separated solid animal manures to winter wheat

Animal slurry can be separated into solid and liquid manure fractions to facilitate the transport of nutrients from livestock farms. In Denmark, untreated slurry is normally applied in spring whereas the solid fraction may be applied in autumn, causing increased risk of nitrate and phosphorus (P) leaching. We studied the leaching of nitrate and P in lysimeters with winter wheat crops (Triticum aestivum L.) after autumn incorporation versus spring surface application of solid manure fractions, and we compared also spring applications of mineral N fertilizer and pig slurry. Leaching was compared on a loamy sand and a sandy loam soil. The leaching experiment lasted for 2 yr, and the whole experiment was replicated twice. Nitrate leaching was generally low (19–34 kg N/ha) after spring applications of mineral fertilizer and manures. Nitrate leaching increased significantly after autumn application of the solid manures, and the extra nitrate leached was equivalent to 23–35% of total manure N and corresponded to the ammonium content of the manures. After spring application of solid manures and pig slurry, only a slight rise in N leaching was observed during the following autumn/winter (<5% of total manure N). Total P leaching was 40–165 g P/ha/yr, and the application of solid manure in autumn did not increase P leaching. The nitrogen fertilizer replacement value of solid manure N was similar after autumn and spring application (17–32% of total N). We conclude that from an environmental perspective, solid manure fractions should not be applied to winter wheat on sandy and sandy loam soils under humid North European conditions.     

An overview of fertilizer‐P recommendations in Europe: soil testing,calibration and fertilizer recommendations

The procedure for applying phosphorus (P) fertilizer to soil can be divided into three consecutive steps: (i) Measurement of soil‐P availability, (ii) calibration of the soil‐P fertility level and (iii) estimation of the recommended P dose. Information on each of these steps was obtained for 18 European countries and regions with the aim of comparing P fertilizer recommendation systems at the European scale. We collected information on P fertilizer recommendations through conventional or grey literature, and personal contacts with researchers, laboratories and advisory services. We found much variation between countries for each of the three steps: There are more than 10 soil‐P tests currently in use, apparent contradictions in the interpretation of soil‐P test values and more than 3‐fold differences in the P fertilizer recommendations for similar soil‐crop situations. This last result was confirmed by conducting a simple experimental inter‐laboratory comparison. Moreover, soil properties (pH, clay content) and crop species characteristics (P responsiveness) are used in some countries in the calibration and recommendation steps, but in different ways. However, there are also common characteristics: soil‐P availability is determined in all countries by extraction with chemical reagents and the calibration of the soil‐P test values, and the fertilizer recommendations are based on the results from empirical field trials. Moreover, the fertilizer recommendations are nearly all based on the amount of P exported in the crops. As long as rational scientific and theoretical backgrounds are lacking, there is no point in trying to synchronize the different chemical methods used. We therefore call for a mechanistic approach in which the processes involved in plant P nutrition are truly reproduced by a single standard method or simulated by sorption‐desorption models.     

A Likelihood-Based Model of Fish Growth With Multiple Length Frequency Data

A model for individual growth is an important component in the analysis of fishery resources. Time series of body-length frequency data (LFD) contain information on average individual growth, but age is a latent variable and this makes it difficult to extract growth information objectively. A new method is described here that relaxes some of the assumptions of currently available approaches and that can be used even with large gaps in the time series of LFD. The new method is based on a non-Bayesian hierarchical model where the growth model contains hyper-parameters that depend on parameters of normal mixture models underlying the LFD. Growth hyper-parameters are estimated using a multivariate normal marginal-estimated likelihood function. The method is applied to the squat lobster Pleuroncodes monodon with LFD from six surveys, leading to a precise model of individual growth due to the large sample size in the original LFD sets. ADMB computer code and datasets used in this article are supplied as supplemental material.     

High plant diversity in Eocene South America: evidence from Patagonia

Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude approximately 47 degrees S, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.     

Early plant height: A defining factor for yields of silage maize with contrasting phosphorus supply

Silage maize (Zea mays L.) is an important crop for forage on Northwestern European dairy cattle farms. We examined the effect of readily available soil phosphorus (P) on early maize growth and linked in-season height growth to final harvest yield using field plots with contrasting P supply in a one-year study embedded in a long-term experiment. Water-extractable P (Pw) was used as a proxy for readily available P in soil. Plant height, dry matter (DM) accumulation, P and nitrogen (N) uptakes were determined eight times from the two-leaf stage until final whole-crop harvest and fitted to logistic growth models. The models revealed that the final yield was significantly related to the time required to reach the maximum rate of height growth (occurring from 330 to 485 accumulated growing degree units, GDU), but not the time required to reach the maximum rate of DM accumulation (occurring from 561 to 649 GDU). Furthermore, plant height at the four-leaf stage and onwards was significantly related to the final harvest yield. Soil Pw linked closely to height growth parameters; higher levels of Pw gave earlier peaks in height growth. For this light sandy loam with a wide gradient in P content, we conclude that suboptimal P supply postpones height growth and reduces final yields. A sufficient P supply links to an early rapid increase in plant height and forms the potential for optimum nutrient uptake and high forage yields. Thus, early-season plant height may serve as a simple morphometric indicator for final yields.     

Genetic structure of Lima bean (<Emphasis Type="Italic">Phaseolus lunatus</Emphasis> L.) landraces grown in the Mayan area

Lima bean (Phaseolus lunatus L.) is an important crop in the Mayan culture. The Mayan area, considered as a main center of Mesoamerican diversity, has been divided into two subareas: the Mayan lowlands and the Mayan highlands. The Yucatan Peninsula is part of the Mayan lowlands and holds the highest number of Lima bean landraces of Mexico, but Lima beans are in high risk of genetic erosion due to intensification of the traditional Mayan agriculture. However, information on genetic diversity of Lima beans of the Mayan highlands is lacking. By using 46 landraces collected in the Mayan area (23 from each subarea) and 73 ISSR loci (inter-simple sequence repeats), we analyzed the structure, diversity and genetic relationships of Lima beans of this part of Mesoamerica. High levels of diversity (H _BAY = 0.45) and genetic structure (F _ST = 0.66) were found for the whole Mayan area. Genetic diversity in the Mayan lowlands was apparently higher than the Mayan highlands (H _BAY = 0.44 and 0.36, respectively); but differences were not statistically significant. Genetic structure between the subareas was high (AMOVA = 30% of total variation), most landraces grouping according to their geographic origin. This study shows the importance of the Mayan culture in the diversification and conservation of Lima beans. The results provide important information that should be considered when implementing strategies to collect Lima bean landraces and planning in situ and ex situ programs to conserve these landraces in the Mayan region.