Determinants and correlates of above-ground biomass in a secondary hillside rainforest in Central Vietnam     

Roland Cochard  Yen Thi Van  Dung Tri Ngo 《New Forests》2018,49(3):429-455

Despite inception of carbon-conservation forestry programs, information about total above-ground woody biomass (TAGB) in Vietnamese secondary lowland rainforests is still scarce. We elucidated major factors influencing local variation of TAGB within an anthropogenically modified hillside forest in Th?a Thiên-Hu? Province. On forty 400 m² sized plots all tree species were recorded, and their biomass was calculated using allometric equations. In addition, bio-physical parameters relating to terrain and soils were measured. Effects of bio-physical variables on forest TAGB were assessed using multivariate regression methods. Forest TAGB (average 117 Mg ha^?1) was primarily explained by forest structural variables, i.e. tree densities and average heights, in particular presence of large trees. TAGB was largely determined by the biomass of a few species which dominated different forest parts (ridges or hill base); TAGB was hardly influenced by species diversity. Many dominant trees were light-demanding species; these were characterised by scarce rejuvenation and high tree mortality. Bio-physical patterns indicated that previous logging impacts persisted and continued to influence seedling establishment, sapling growth/survival, and—ultimately—species composition. Nutrient patterns were mostly explained by interactions with certain tree species and tree foliage cover, as modulated by terrain and logging impacts. Development trajectories of TAGB over the next 10–20 years could not be predicted easily since (1) many functionally important late-succession species (e.g. dipterocarps) were very scarce; (2) the sizes of initially established light-demanding species appeared to meet limits, including increasing tree mortality; and (3) rejuvenation and species succession differed locally and proceeded along largely unpredictable pathways. Some suggestions for further research are made.  相似文献   

Recovery of fungicide-resistant <Emphasis Type="Italic">Botrytis</Emphasis> isolates from strawberry nursery plants     

Roland W. S. Weber  Alfred-Peter Entrop 《European journal of plant pathology / European Foundation for Plant Pathology》2017,149(3):739-742

In a four-year survey of strawberry nursery plants, 340 Botrytis isolates were collected and examined for fungicide resistance. High percentages of isolates with resistance to members of all fungicide classes registered on strawberries in Germany were found, i.e. trifloxystrobin (90.3%), boscalid (53.8%), cyprodinil (41.5%), fludioxonil (28.2%) and fenhexamid (15.6%). Of these isolates, 10.3% possessed multiple resistance to all compounds. At 5.0%, resistance to the recently registered fungicide fluopyram was low. Dutch nursery material harboured significantly higher proportions of isolates with resistance to any or all fungicides than plants produced in Germany. These data point to nursery plants as a possible route of introducing fungicide-resistant Botrytis strains into commercial strawberry fields.  相似文献   

Winter wheat yield loss in response to Avena fatua competition and effect of reduced herbicide dose rates on seed production of this species     

Jäck  Ortrud  Menegat  Alexander  Gerhards  Roland 《植物病害和植物保护杂志》2017,124(4):371-382

Journal of Plant Diseases and Protection - Avena fatua is one of the most abundant and competitive grass weed species in cereal cropping systems worldwide. Despite its main occurrence in summer...  相似文献   

Multi-scale Modeling of Animal Movement and General Behavior Data Using Hidden Markov Models with Hierarchical Structures     

Vianey Leos-Barajas  Eric J. Gangloff  Timo Adam  Roland Langrock  Floris M. van Beest  Jacob Nabe-Nielsen  Juan M. Morales 《Journal of Agricultural, Biological & Environmental Statistics》2017,22(3):232-248

Hidden Markov models (HMMs) are commonly used to model animal movement data and infer aspects of animal behavior. An HMM assumes that each data point from a time series of observations stems from one of N possible states. The states are loosely connected to behavioral modes that manifest themselves at the temporal resolution at which observations are made. Due to advances in tag technology and tracking with digital video recordings, data can be collected at increasingly fine temporal resolutions. Yet, inferences at time scales cruder than those at which data are collected and, which correspond to larger-scale behavioral processes, are not yet answered via HMMs. We include additional hierarchical structures to the basic HMM framework, incorporating multiple Markov chains at various time scales. The hierarchically structured HMMs allow for behavioral inferences at multiple time scales and can also serve as a means to avoid coarsening data. Our proposed framework is one of the first that models animal behavior simultaneously at multiple time scales, opening new possibilities in the area of animal movement and behavior modeling. We illustrate the application of hierarchically structured HMMs in two real-data examples: (i) vertical movements of harbor porpoises observed in the field, and (ii) garter snake movement data collected as part of an experimental design. Supplementary materials accompanying this paper appear online.  相似文献   

Guest Editor’s Introduction to the Special Issue on “Animal Movement Modeling”     

Mevin B. Hooten  Ruth King  Roland Langrock 《Journal of Agricultural, Biological & Environmental Statistics》2017,22(3):224-231

In this introduction, we provide a brief overview to statistical models for animal trajectories and then summarize the set of invited articles that comprise the issue.  相似文献   

Selecting cotton yield response function to estimate profit-maximizing potassium fertilization rates for cotton production in Tennessee     

Xavier Harmon  Christopher N. Boyer  C. Owen Gwathmey  James A. Larson  Roland K. Roberts 《Journal of plant nutrition》2017,40(11):1547-1556

Recent research has shown that stochastic yield response functions fit data better than deterministic yield response functions; however, little research exists comparing profit-maximizing fertilizer rates for upland cotton (Gossypium hirsutum L.) using stochastic and deterministic yield response functions. The objective of this research was to determine the most appropriate yield response functional form from which to determine the profit-maximizing potassium (K) rate for cotton in Tennessee. Data were used from a nine-year K fertilizer experiment in Jackson, Tennessee. Quadratic, quadratic-plus-plateau, linear response plateau, and linear response stochastic plateau response functions were estimated to determine the yield response function that best fit the data. The linear response stochastic plateau function was the most suitable yield response function for the data. The profit-maximizing K rate ranged from 65.2 to 74.3 kg K ha^?1. Misspecification of the yield response function recommended over-application of K fertilizer and decreased the producer's short-term profits.  相似文献   

Occurrence of aphid vector and genetic tolerance to infection by potyvirus in hot pepper     

Fekadu Marame  Chemeda Fininsa  Harjit Singh  Lemma Dessalegne  Anhild Andersson  Roland Sigvald 《Euphytica》2010,172(1):77-91

The productivity and marketable quality of hot pepper (Capsicum annuum var. annuum L.) are low in tropical regions mainly due to virus infections and lack of effective virus management strategies. The absence of effective virus management strategies could be attributed to lack of information on virus vectors and host resistance. Parental (P₁ and P₂) and progeny (F₁, B₁, B₂ and F₂) generations of five hot pepper crosses were grown in Ethiopia at three sites (Bako, Hawasa and Melkasa) to monitor number and species of potential aphid vectors, disease incidence levels with regards to natural infections by Potato virus Y (PVY) and Ethiopian pepper mottle virus (EPMV) complex, and to determine genetic tolerance of the crop to the viruses. Disease incidence was assessed before the flowering stage of the crop plants using visible disease symptoms due to infections by PVY and EPMV. The serological tests revealed presence of symptomless genotypes of the crop to the virus infections. Aphid species potentially transmitting the viruses, such as Acyrthosiphon pisum (Harris), Aphis fabae (Scopoli), and Myzus persicae (Sulzer), were identified from specimens caught by yellow water traps. The highest number of aphids from yellow water traps was recorded at a dense foliage growth stage of the crop at Melkasa. Highly significant variation was observed among generations of the five crosses in response to infections by PVY and EPMV complex. The most susceptible parents had the levels of disease incidences ranging from 80 to 90%, whereas their progenies had only below 30% incidence levels. The most tolerant parent remained symptomless to the natural infections of PVY- and EPMV-complex. Incidence levels in progenies of a cross from the most susceptible and tolerant parents remained below 20%. Based on serological test, the proportion of PVY-positive plants ranged from 0 to 75% and of EPMV-positive plants from 0 to 25%, with 0 to 17% co-infection by the two viruses. Availability of virus sources in the vicinity, efficiency of aphids in vectoring, weather conditions during the growth period, genetic tolerance and the growth stage of the crop affected natural infection by PVY- and EPMV-complex. Exploitation of the genetic potential of introduced elite genotypes and their progenies along with breeding elite local cultivars for resistance and excluding aphid vectors at young (seedling) stage of the crop plants could be helpful for minimizing losses in yield and quality of hot pepper due to infections by PVY- and EPMV-complex.  相似文献   

Long-term monitoring of the metal accumulation in forests measured by use of the moss technique     

Winfried Schr?der  Roland Pesch 《European Journal of Forest Research》2010,129(3):475-488

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Drivers of bryophyte diversity allow implications for forest management with a focus on climate change     

Stefanie Raabe  Jörg Müller  Michael Manthey  Oliver Dürhammer  Ulrich Teuber  Axel Göttlein  Bernhard Förster  Roland Brandl  Claus Bässler 《Forest Ecology and Management》2010

Understanding the major drivers of diversity in forests is crucial for ecologists, conservationists, and particularly forest managers. In most forested habitats, bryophytes are diverse and important primary producers. Here we report the first study of the relative importance of regional macroclimate as compared to local variables on abundance, species richness, and community composition of bryophytes growing in soil and in dead wood in a mountain temperate forest. Using PCA axes, we built predictor sets for macroclimate, microclimate, soil attributes, and dead wood availability. The explanatory power of each set was tested using variance partitioning. Abundance and species richness of soil bryophytes was best explained by microclimate, whereas the community composition did not distinctively differ between the environmental sets. In contrast, dead wood bryophyte abundance, species richness, and community composition was clearly driven by macroclimate. Among the single axes, the component represented best by soil moisture was the main driver for soil bryophyte abundance. In contrast, dead wood bryophyte abundance was mostly affected by components correlated with minimum global radiation and minimum temperatures as well as by the component represented by dead wood. The component represented by canopy openness was superior in explaining the community composition of both soil and dead wood bryophytes. We conclude that (1) dead wood amounts should be increased in closed stands to act as a buffer during climate changes, and (2) open canopy, which provides important habitats for soil-inhabiting bryophytes, should be provided by management with slow reforestation after natural or logging openings.  相似文献   

Schnelle und einfache Methode zum Nachweis der Fenhexamid-Resistenz bei Botrytis     

Roland W. S. Weber 《Erwerbs-Obstbau》2010,52(1):27-32

Isolates of Botrytis cinerea collected from Northern German strawberry and raspberry farms were grouped into three categories according to their pattern of resistance against the fungicide fenhexamid. Strains with baseline sensitivity showed EC₅₀ values of 0.06–0.10 ppm (conidial germ-tube elongation) and 0.07–0.16 ppm (mycelial growth assay). For partially resistant isolates, the corresponding EC₅₀ values were similar for germ-tube elongation but higher (> 0.39 ppm) for mycelial growth. Highly resistant isolates produced more than 50% growth in both assays even at 200 ppm fenhexamid, the highest concentration tested. These isolates matched the criteria of resistance group Hyd R3. By means of a simple test consisting of the harvesting of conidia from sporulating field samples and their direct assay by germ-tube elongation, Hyd R3 resistance was identified within 24 h of sampling. If this assay is performed on overwintered samples prior to blossom time, site-specific recommendations about the use of fenhexamid can be made to the farmer during the running vegetation period.  相似文献