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Tidal marsh wetlands in the Yellow River Delta provide valuable eco-services to the local population and global ecology. However, this area is suffering from serious degradation under the stresses of social development and climate change. Hydrological connectivity, a new framework in hydrology and ecology, has been proposed as the main factor affecting the ecological processes in coastal wetlands; however, its role in hydrology–soil–vegetation interactions remains unclear. In this study, the researchers parametrically quantified the hydrological connectivity in the tidal marsh wetlands and analyzed its relationship with Phragmites australis, one of the dominant species in this area. Our results showed threshold-like effects on the interaction between hydrological connectivity and P. australis on the plot scale. When biomass is lower than 2.2 kg/m2, the population density and structure size were found to increase with hydrological connectivity. When the biomass is higher than the threshold, the plots disconnected hydrologically because of high water consumption. Compared with soil chemistry, salinity, and water soil content, hydrological connectivity in the surface soil layer is more strongly linked to the plant traits and spatial structure in the tidal marsh wetlands due to the narrow ranges of other variables. Based on the authors’ analysis, the researchers do not recommend dense plantation of P. australis, especially near the freshwater sources in the tidal marsh, because of its high reproduction ability and competitive nature, which may cut the freshwater connectivity off, lowering the richness of plant species and habitat diversity.

Lodging in maize results in grain yield reduction. This experiment investigated the effects of different application rates of the growth retardant, uniconazole (UCZ), and nitrogen (N) on medium and high maize population densities on lodging resistance and yield. UCZ was applied to maize seeds at concentrations of 0 (U0 ) and 25 (U25 ) mg kg-1 , and three different N application rates, 0 (N0 ), 150 (N150 ) and 225 (N225 ) kg ha-1 , at plant densities of 75,000 (D1 ) and 105,000 plants ha-1 (D2 ). UCZ application, different N rates and plant population density affected the lodging resistance and yield attributes of maize. The diameter, plumpness, cortex penetration and bending strengths of the internodes were enhanced with UCZ and N application at medium and high plant density, where maximum values were obtained with U25 N150 D1 . Internode length increased in the high-density population and higher N rate, whereas UCZ reduced internode length, where maximum internode length was obtained with U0 N225 D2 . Plant height, centre of gravity height, ear and height above ear-bearing node were higher with the high N rate, while UCZ reduced it significantly. UCZ, N rate and plant density enhanced lignin accumulation in the third internode and ear-bearing internode, where maximum values were obtained with U25 N150 D1 . Yield and yield attributes were also improved by UCZ, N rate and population density. Treatment with U25 N150 D2 significantly improved grain yield of maize compared with the other treatments.

CITATION: Haarhoff, S. J. & Swanepoel, P. A. 2019. Narrow rows and high maize plant population improve water use and grain yield under conservation agriculture. Agronomy Journal, 112 2):921-931, doi:10.1002/agj2.20085.

Recovery of Mediterranean forests after field abandonment is a slow process, even without propagule limitations. This is mainly due to stressful conditions for seedling establishment. In this context, shrubs play a critical role in facilitating tree recruitment, but how this process unfolds after field abandonment is not entirely known. We evaluated the long-term dynamics of facilitation by the nurse shrub Retama sphaerocarpa in the recruitment of two ecologically contrasting oaks, the evergreen Quercus ilex and the deciduous Quercus faginea. Thirty years after field abandonment, we dated shrubs and oak established in an old field to estimate the annual recruitment rates and investigate temporal recruitment patterns. For oaks, we differentiated recruitment at each microsite (i.e., open or under shrub). To assess how nurse shrubs modulated environmental stressors, we modelled oak recruitment as a function of climatic variables. For the evergreen oak, we assessed these effects within each microsite. Finally, we estimated the annual interaction index between shrubs and oak juveniles as a function of climatic conditions.

International audience; In climate change ecology, simplistic research approaches may yield unrealistically simplistic answers to often more complicated problems. In particular, the complexity of vegetation responses to global climate change begs a better understanding of the impacts of concomitant changes in several climatic drivers, how these impacts vary across different climatic contexts, and of the demographic processes underlying population changes. Using a replicated, factorial, whole‐community transplant experiment, we investigated regional variation in demographic responses of plant populations to increased temperature and/or precipitation. Across four perennial forb species and 12 sites, we found strong responses to both temperature and precipitation change. Changes in population growth rates were mainly due to changes in survival and clonality. In three of the four study species, the combined increase in temperature and precipitation reflected nonadditive, antagonistic interactions of the single climatic changes for population growth rate and survival, while the interactions were additive and synergistic for clonality. This disparity affects the persistence of genotypes, but also suggests that the mechanisms behind the responses of the vital rates differ. In addition, survival effects varied systematically with climatic context, with wetter and warmer + wetter transplants showing less positive or more negative responses at warmer sites. The detailed demographic approach yields important mechanistic insights into how concomitant changes in temperature and precipitation affect plants, which makes our results generalizable beyond the four study species. Our comprehensive study design illustrates the power of replicated field experiments in disentangling the complex relationships and patterns that govern climate change impacts across real‐world species and landscapes.

Masting is defined as the intermittent highly variable production of seed in a plant population. According to reproductive modes, that is, sexual and asexual reproduction, masting species can be separated into three groups, that is, (1) species, for example, bamboo, flower only once before they die; (2) species, for example, Fagus, reproduce sexually; and (3) species, for example, Stipa tenacissima, reproduce both sexually and asexually. Several theories have been proposed to explore the underlying mechanisms of masting. However, to our knowledge, no theory has been found to explain the mechanism of masting species that reproduce both sexually and asexually. Here we refine the Resource Budget Model by considering a trade-off between sexual and asexual reproduction. Besides the depletion efficient (i.e., the ratio of the cost of seed setting and the cost of flowering), other factors, such as the annual remaining resource (i.e., the rest of the resource from the photosynthetic activity after allocating to growth and maintenance), the trade-off between sexual and asexual reproduction, and the reproductive thresholds, also affect masting. Moreover, two potential reproductive strategies are found to explain the mechanisms: (1) When the annual remaining resource is relatively low, plants reproduce asexually and a part of the resource is accumulated as the cost of asexual reproduction is less than the annual remaining resource. Plants flower and set fruits once the accumulated resource exceeds the threshold of sexual reproduction; (2) when the annual remaining resource is relatively high, and the accumulated resource surpasses the threshold of sexual reproduction, masting occurs. Remarkably, under certain depletion efficient, more investigation in sexual reproduction will lead plants to reproduce periodically. Additionally, plants investigate less resource to reproduce periodically when depletion efficient keeps increasing as plants can reproduce efficiently. Overall, our study provides new insights into the interpretation of masting, especially for species that reproduce both sexually and asexually.

Analysis of yield components to address inconsistent maize (Zea mays L.) grain yields across plant populations is limited in Europe and the United States. The research objectives were to compare maize yield components at low and high plant populations in eastern Nebraska and central Croatia using path analysis to better understand maize grain yield determination with changing plant population and determine relative importance among maize primary and secondary yield components. Research was conducted by planting three maize hybrids at 65, 000 plants ha(-1) to 105, 000 plants ha(-1) in 2012 and 2013 at Zagreb, Croatia, and Mead, NE. Grain yield, ears per square meter, rows per ear, ear circumference, kernels per ear, kernels per row, ear length, and kernel weight were determined. Average grain yield was 10.7 Mg ha(-1) and plant population influence on yield was inconsistent and

Summary Classic theories of resource harvest assume logistic growth and incorporate harvest through an additional loss term. This methodology has been applied successfully in forest products harvesting such as timber logging. However, modelling harvest through a loss term is not appropriate for non-timber forest products (NTFP) since harvesting in this case does not always require the complete removal of individual plants. Empirical evidence suggest that NTFP harvest affects plant population growth rates. Additionally, timber and NTFP harvest can have synergistic effects on population dynamics. We develop and analyse a simple model that incorporates non-lethal harvest implicitly through the population growth rate of plants and lethal harvest explicitly through permanent removal of whole plants, with additional synergistic effects on population growth rate. To capture transient dynamics, we model the growth rate of plants explicitly as a dynamic variable affected by harvesting. Transient dynamics results indicate that populations have delayed response to discrete harvesting. We demonstrate exactly how the sustainability of lethal harvest, non-lethal harvest or both types of harvests depends on the demographic effect of each type of harvest on the population growth rate. Finally, we identify a threshold parameter , such that combined lethal and non-lethal harvest results in plant population sustainability when 1 and extinction when 1.

Seed dispersal studies have primarily examined dispersal as a function of distance from the parent tree and/or heterogeneity in dispersal due to animal use of nesting, roosting and sleeping sites. However, non-random heterogeneity in seed dispersal is also likely to result from the post-foraging behavior and movement of frugivores which prefer certain trees. To characterize variation in seed rain at fine scales, we studied the dispersal curve of Prunus ceylanica, a primarily bird-dispersed species. We compared seed rain at conspecifics, heterospecific fruiting trees with similar frugivore assemblages, emergent trees, and the landscape surrounding these trees. Seed rain of P. ceylanica was found to peak globally under the canopy of conspecifics but to peak locally under the canopy and immediate neighborhood of heterospecific fruiting trees. Our results demonstrate that seed rain is highly clumped even at fine spatial scales. A large proportion of seeds are dispersed in specific, localized regions. This variation can have important implications for plant population dynamics and might significantly alter the impact of post-dispersal processes. Seed dispersal models may need to incorporate this heterogeneity to explain manifestations of spatially explicit dynamics like mixed species ‘orchards’.

Anhydrous ammonia (AA) is an important N fertilizer in the United States, and with large farming operations rapid application is needed. This study evaluated the impact of AA application timing and N rates when applied with a high speed low draft (HSLD) or aconventional till knife injection (CTKI) on corn (Zea mays L.) production in no-tillage fields. The study was conducted at sites located in Illinois, Iowa, and Kansas from 2007 to 2009. The experimental design was a split-plot factorial arrangement of application method, timing (fall; spring pre-plant, SP; and sidedress, SD), and five N rates. Fall AA application was least efficient (mean 55 kg N ha–¹ higher optimum N and 2% lower grain yield, GY), with SP and SD equivalent. The HSLD was comparable to the CTKI with most applications, except when high N rates (180 and 225 kg N ha–¹) were applied SP. For these treatments AA injury reduced plant population (PP), early season growth, canopy normalized difference vegetative index (NDVI), and GY. Seedling injury did not occur with any N rate or timing with the CTKI. Shallow AA placement at high speed with the HSLD can provide a viable alternative to traditional deeper knife injection when conditions are suitable for AA application and positioning avoids corn seedling injury. Anhydrous ammonia application with the HSLD, however, should be avoided where high SP AA rates may be placed directly under future corn rows.

Published in Agron. J. 106:1051–1059 (2014) doi:10.2134/agronj13.0435 Copyright © 2014 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. ABSTRACT The agronomic responses of three contrasting soybean [Glycine max (L.) Merr.] varieties to plant populations were examined in two distinct agro-ecological locations (at Samaru Zaria and Samaru-Kataf), both in the Guinea savanna of northern Nigeria in 2009, 2010, and in 2011 growing seasons. Three soybean varieties: TGx1835-10E, TGx1904-6F, and TGx1448-2E differing in maturity duration (early, medium, and late maturing, respectively), were evaluated at four plant populations (266,700, 333,300, 533,300, and 666,700 plants ha–1) using a split plot arrangement in randomized complete block design with three replications. The plant populations were the main plots, whereas varieties were subplots. The proportion of intercepted photosynthetically active radiation (IPAR) and leaf area index (LAI) increased with increasing plant population at both locations, indicating that high leaf area indices and high degree of canopy closure at higher plant population intercepted more light than the canopy at lower population and subsequently resulted in relatively high grain and fodder yields. At both locations, optimum plant populations ranged from 533,300 to 666,700 plants ha-1 across the years. The northern Guinea savanna location (Samaru Zaria) produced more pods m-2, grain yield, and fodder at higher plant populations than that at the southern Guinea savanna (Samaru-Kataf). Varieties TGx1448-2E and TGx1904-6F intercepted higher proportion of IPAR had higher LAI and produced a greater number of pods m-2, seeds m-2, grain yield, and fodder than TGx1835-10E at both locations in years of good rainfall. These data suggest that soybean yields in the Guinea savanna of northern Nigeria can be increased using higher plant populations than those currently recommended.

Allelopathy has traditionally been viewed as a phytotoxic disruption of recipient plant metabolism, and allelopathic effects are generally strongest on species lacking historic exposure to particular phytotoxins (Novel Weapons Hypothesis). However, mounting evidence suggests phytochemical-induced germination inhibition can be an adaptive response to competitive conditions, not the consequence of toxin exposure. That is, selective advantages can exist for seeds to chemically recognize potential competitor presence and defer germination until better establishment conditions occur. This Biochemical Recognition Hypothesis (BRH) contrasts the allelopathy paradigm by predicting greater germination inhibition following phytochemical exposure of sympatric compared to allopatric species. In a glasshouse, we grew 12 species native to Argentinean and North American grasslands and tested whether phytochemical leachates from co-occurring species reduced seedling emergence more than those having no historic association. Two species had 13% and 27% emergence reductions following leachate exposure of sympatric relative to allopatric species, supporting species-specific BR. Intraspecific leachates reduced emergence more than those from heterospecifics, suggesting within-species BR may be common. Only the four smallest seeded species exhibited heterospecific BR responses, suggesting that selection for assessing local competition potential may intensify as seed reserves decline. Importantly, leachate origin did not affect seedling biomass nor accelerate germination, indicating a non-toxic biochemical effect on germination reduction but not growth. Synthesis. Coupling ample theoretical support with empirical evidence here and elsewhere, an ‘eavesdrop-and-wait' competition avoidance strategy could be a common phenomenon. Our findings suggest sympatric association may contribute to evolution of species-specific BR and that seed traits are important in its development. The underlying mechanism affecting these germination decisions may be simple phytochemical-induced hormonal regulation. Factors preclude BR from being ubiquitous but nonetheless, BR provides a potentially powerful mechanism by which some plant populations and the spatiotemporal diversity of some communities are structured. Lastly, allelopathy may be erroneously invoked when phytochemical-induced germination reduction occurs but a toxicity mechanism has not been elucidated. In many cases, this fits more with the BRH than classic allelopathy. Fil: Renne, Ian J.. Youngstown State University; Estados Unidos Fil: Sinn, Brandon T.. Youngstown State University; Estados Unidos Fil: Shook, Gregory W.. Youngstown State University; Estados Unidos Fil: Sedlacko, David M.. Youngstown State University; Estados Unidos Fil: Dull, Jessica R.. Youngstown State University; Argentina Fil: Villarreal, Diego. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Aim Our aims were to determine the pattern of genetic variation in the endemic shrub Nolina parviflora, and to evaluate the influence of the geological history of the Trans-Mexican Volcanic Belt (TMVB) and nearby mountainous regions on plant population divergence.

Cities annex wilderness and alter the interactions between the plant and animal assemblages embedded in the remaining nature fragments. Here, we explore consequences of habitat fragmentation for dispersal of cactus by fruit‐eating mammals in the Sonoran Desert landscape. We use the barrel cactus, Ferocactus wislizeni, as a model system to diagnose (1) how fruit utilization by a mammal assemblage changes with fragment area and isolation, (2) what characteristics make individual plants particularly susceptible to frugivore failure, and (3) how inter‐fragment differences in plant–frugivore interactions influence the seedlings’ susceptibility to other stressors (granivores and drought). We described the type and phenology of plant–animal interactions in 20 fragments along a 0.05–500 ha size continuum within a large city (Tucson, Arizona, USA), and combined allometric scaling models of mammalian home ranges and descriptions of plant size distributions to predict the fraction of the fruit crops accessible to resident mammalian frugivores in each fragment. Fruit removal rates generally increased along a continuum of fragment sizes, and older, taller plants were particularly susceptible to frugivore failure and more likely to have fruits attacked by granivorous rodents. As a result, thresholds where the nature and/or phenology of a plant's interactions with animals changes can be accurately predicted by integrating descriptions of fragment size, fragment isolation, and plant population structure. Last, we found support for the hypothesis that fragmentation‐induced changes in the phenology of fruit removal compromise the seedlings’ ability to exploit precipitation delivered in winter and spring. Specifically, as a result of slower fruit removal, the seed crops in small fragments forfeit access to an increasing proportion of the rains between October and March, which determine whether cactus seedlings can survive the following dry season (April, May, June). We expect these inter‐site differences in the type and phenology of interactions to compromise the integrity of plant populations in smaller fragments, to become increasingly influential in ecological settings in the Sonoran Desert where access to precipitation is essential, and to become increasingly prevalent as the plants in newly fragmented plant populations age (grow) to sizes that are more susceptible to frugivore failure in the defaunated landscapes.

International audience; 1. Grime’s CSR and Tilman’s resource-ratio theories are two major contributions to our understanding of plant community dynamics. They have both been corroborated empirically, whilst providing several contradictory predictions. Notably, contrary to Tilman, Grime predicts that competition for soil resources is unimportant on poor soils. 2. We show that Grime’s CSR theory can be modelled with the same type of differential equations for resource and plant biomass dynamics used by Tilman in his resource-ratio theory. 3. Using this unified modelling framework, we demonstrate that both models predict intense competition for soil resources on poor soils, as long as biomass loss per unit mass is modelled as a size-independent process. When considering biomass loss per unit mass as a size-dependent process mimicking farming activities, both models predict a unimodal relationship between soil fertility and the intensity of soil resource competition, and a decreasing relationship between disturbance rate and resource competition. 4. Synthesis. Our modelling analysis reveals that the resource-ratio and CSR theories make different predictions regarding competition on poor soils, not because of their differing schemes of plant strategies, but because of the different disturbance types that they are considering. Tilman’s predictions apply to little disturbed natural habitats, whilst Grime’s predictions apply to disturbed ones.

In humid savannas, the transition from juvenile to mature tree sizes is thought to be a major demographic bottleneck because smaller plants are topkilled by frequent fires. Species with the highest net rates of sapling growth should dominate the tree component of savannas by reaching fire-proof sizes, ‘escape size’, more rapidly than competitors. However, tests of this prediction have failed to explain eucalypt dominance in Australian savannas as eucalypt mean growth rates are low. We tested the escape hypothesis directly by recording the number and identity of tagged individuals reaching escape size in a long-term study. Results were consistent with the escape hypothesis with greater than six times more eucalypts reaching escape height than non-eucalypts in frequently burnt savannas. The pattern was reversed where fires were excluded for 5 years, with more non-eucalypts emerging than eucalypts. We conclude that mean growth rates alone are a poor predictor of the rates at which juvenile savanna trees transition to mature tree size. Only the fastest growing individuals make the transition to mature trees whereas mean values include many suppressed individuals. Measures of maximum growth rates will provide more robust estimators of demographically important effects on mature tree cover. The mechanistic basis for the remarkable ability of juvenile eucalypts to escape frequent fires is not yet understood.

Earlier soybean [Glycine max (L.) Merr.] planting coupled with increasing seed cost and commodity prices has led to an increase in the number of hectares treated with seed treatments. Ultimately, growers would like to know if applying such treatment is cost effective. Therefore, the objectives of this experiment were to quantify the effects of seed treatment on early season plant population and seed yield and investigate the probability that yield response covered the cost of the seed treatment. Trials were conducted in Wisconsin from 2008 to 2010 at nine locations each year to compare no seed treatment, mefenoxam + fludioxonil (ApronMaxx), and mefenoxam + fludioxonil + thiamethoxam (CruiserMaxx). Results indicated differences in early-season plant population due to cultivar and seed treatment and that seed yield was affected by a cultivar × seed treatment interaction. At a low seed treatment price, the percentage of environments where the probability of breaking even was >50% and ranged from 56 to 67%, while it ranged from 22 to 56% at a higher price. Both ApronMaxx and CruiserMaxx had positive response ratios of 1.5 (p = 0.030) and 2.9% (p < 0.0001), respectively, but responses were cultivar dependent. Given annual environmental variability, a general lack of field information regarding field history of pathogens or insects, and the high turnover rate of soybean cultivars, soybean seed treatments can be a cost-effective component to integrate into soybean production systems.

Summary1. Plant–plant interactions are known to vary with changing environmental conditions; however,we have little empirical knowledge of the impact of abrupt environmental changes on millennialscale plant–plant interaction outcomes for long-lived plant species. Here, we used palaeoecologicaldata(13–7.6 k yearsbp)andanovelstatisticalmodellingapproachtodeterminetheimpactofmul-tipleenvironmentaldriversonpredictedtree–grasspopulationinteractionoutcomesfromourstudysiteineasternEngland.2. Changes from high to low herbivore density shortly preceded changes to low fire levels and ashift to warmer summers. These transitions occurred during a period of increasing nitrogen (N)availability. Shortly thereafter, there was a shift in landscape dominance from grasses to oaks andthenachangetodecreasingNavailability.3. Model predictions of tree–grass interaction outcomes varied over time with respect to all envi-ronmentalchanges.Duringthetimeofhighdisturbancesandcoolsummers,grasseswerepredictedtoout-competeoaks.Afterclimatewarmingandthelossofregulardisturbances,thepredictedout-comewasstablecoexistence.However,changesintheNcyclecorrespondedwithdifferentpredictedoutcomes: unstable competition under increasing N availability and facilitation of oaks by grasseswhenNavailabilitywasdeclining.4. AkaikeInformationCriterionweightsindicatethatclimatewarmingandfewerfireswereconsis-tent with the best-fitting model of oak–grass interactions for the entire time series (i.e. competitiveexclusion to stable coexistence). However, reconciling the conflicting model predictions with theobserved population dynamics suggests that a temporary period of unstable competition precededthepredicted shift tostablecoexistence. Thisdynamic behaviour is consistentwithknown patternsofshiftsbetweenalternativestablestates.5. Synthesis. Weshowthatabruptchanges in environmental conditionsover timeleadtosimilarlyabrupt changes in tree–grass interaction outcomes, which were shown to vary in contrasting direc-tions with respect to resource versus non-resource variables. The approach described here allowsplantecologiststotesthypothesesofplant–plantinteractionsoversuccessionaltimescalesforlong-lived species and thus can lead to new knowledge about the structural role of these interactions incommunitydynamics.Key-words: abrupt climate change, alternative stable states, community dynamics, competi-tion, facilitation, fire, herbivore density, nitrogen availability, plant population, tree–grasscoexistenceIntroduction

Field studies were conducted from 2006 through 2008 to evaluate the effects of twin-row spacings, plant populations, and irrigation on cotton (Gossypium hirsutum L.) lint yields. Twin-row systems, consisting of twin 18-, 25- and 38-cm rows spaced equidistant from the top center on a 1-m bed at populations of 111,000 and 148,000 plants/ha, were compared to conventional single-row systems at equivalent populations. The experiments were performed under irrigated and non-irrigated conditions. Under irrigated conditions, there were no differences in lint yields between single- and twin-row systems regardless of plant population in 2007 and 2008. In 2006, lint yields of 25-cm and 38-cm cotton exceeded that of single rows. Under non-irrigated conditions, lint yield of 18-cm twin-row cotton was greater than other row spacings in 2008, and greater than 38-cm twin-row cotton in 2006 (P > F 0.08 Yr*Rs), regardless of population. The results indicated that 18-cm twin-row systems at populations typically used in single-row systems could increase lint yields under non-irrigated conditions depending on the year and rainfall.

The stemfly, Melanagromyza phaseoli (Tryon) infests stems of over 95% plants of soybean and damages them from the base up to 30 cm height, although the intensity of damage is confined to 25 cm in a majority of the attacked plants. Various levels of stem damage in stemfly infested plant failed to reveal any significant differences among them. However, infestation by the stemfly in a plant tended to reduce its pod bearing and grain weight in comparison to a healthy plant. Considering significant differences in the mean yield of a healthy and infested plant a net loss of 1.1 g/plant is inevitable even in insecticidal treatments. This loss worked out to 2.33 Qn/ha in 53% plants yielding significantly in an optimum plant population of 400 000/ha. Zusammenfassung Uber den Verlust am Ertrag von Schoten und Samen der Sojabohnen durch die Stengelfliege Melanagromyza phaseoli (Tryon) Melanagromyza phaseoli befallt in Indien mehr als 95% der Sojabohnenpflanzen und beschadigt sie vom Grund bis zu maximal 30 cm, meist 25 cm Hohe. Verschiedene Schadensstufen lassen sich an den Stengeln der Pflanzen nicht sicher unterscheiden, jedoch bieten die Verluste an Schoten und Samen eine gute Bewertungsgrundlage. Insgesamt trat selbst an mit Insektiziden behandelten Pflanzen ein mittlerer Nettoernteverlust von 1,1 g/Pflanze auf, das sind bei einem 53% igen Befall und 400 000 Pflanzen/ha 233 kg/ha.

On the strength of different olfactory and gustatory mechanisms of influencing phytophagous insects by food plants it is possible to use the Scotch Pine (Pinus sylvestris) as a diversionary plant within cultures of Crimea Pine (Pinus pallasiana). The essential lower resistance of the Scotch Pine to Aradus cinnamomeus (Heteropt.), Blastophagus piniperda (Coleopt.), Rhyacionia buoliana and Dendrolimus pini (Lepidopt.) prevents these insects from attacking the Crimea Pine. Referring the latter the named insect species under this method are not pests but are indifferent members of the fauna. Zusammenfassung uber Bestandesresistenz gegen forstschadliche Insekten Verschiedenartige olfaktorische und trophische Mechanismen der Einwirkung der Nahrungspflanze auf den Schadling ermoglichen es, die Gemeine Kiefer (Pinus sylvestris) als Ablenkungsbaume innerhalb von Anpflanzungen der Krimkiefer (Pinus pallasiana) zu verwenden. Die Mischung beider — gegen Schadinsekten unterschiedlich resistenter — Kiefernarten schliest eine Anpassung der Schadlinge an die Krimkiefer aus. Bei diesem Verfahren treten Aradus cinnamomeus (Heteropt.), Blastophagus piniperda (Coleopt.), Rhyacionia buoliana sowie Dendrolimus pini (Lepidopt.) nicht als Schadlinge, sondern als indifferente Glieder der Fauna auf.

Although there is a quantitative method that is commonly used for identifying mast-seeding behaviour of a plant population based on the coefficient of variation (i.e. CV is standard deviation/mean>1), there is no general quantitative method for delineating “mast” as opposed to “non-mast” years. Mast years are, however, described qualitatively as years when “large”, “unusually large” and “high” seed production occurs. The use of a consistent and generally applicable method for delineating mast years across species and plant populations is important for synthesizing knowledge of the causes and consequences of mast seeding, which could be confounded by using different methods among studies. We examine six quantitative methods for identifying mast years: four methods from the literature and two methods developed here. We use 36 seed production datasets covering a variety of species with ≥10 years of data to test the performance of these six methods. For each method, we quantify the percentage of the datasets to which the method could be successfully applied, the magnitude of the mast year relative to the mean, the frequency of mast years and the occurrence of consecutive mast years. The majority of the methods failed to meet the criteria for a suitable method. The best method used the number of standard deviates (standardized deviate method) of the annual mean seed production from the long-term mean of the dataset to identify mast-seeding years. General results from the standardized deviate method include that the occurrence of mast-seeding years is largely unrelated to plant population CV, but similar across species and data collection methods.

Triticale (X Triticosecale Wittmack) was evaluated as a complementary pasture to buffer those periods when herbage production from mixed perennial pasture is marginal in the central Appalachian Highlands of the United States. Triticale was sown every month from May to October for five consecutive years from 1999 to 2003. Plant population structure and herbage production were evaluated at intervals until May of the year following establishment. Triticale established quickly at all times of sowing except late October. Wet summers resulted in foliar disease and a rapid decline in plant density when triticale was sown in May and June. In contrast, during the relatively dry summer of 1999, triticale stands exhibited minimal decline. Triticale sown in August had a herbage yield of 1580 kg DM ha )1 when harvested in October which was over twice the herbage yield of triticale sown in May, June and July. Average herbage yield in the following April of triticale sown in September was higher (1750 kg DM ha )1 ) and less variable than herbage yields from other sowing dates. Plant and tiller populations declined throughout the following April but herbage yields in May were high due to stem and seed head development associated with reproductive growth. Incorporating areas of triticale into mixed-species perennial pasture systems could buffer herbage production during hot and dry summer periods as well as during cool periods of late autumn and early spring.