Paleogene transgression process and environmental evolution in the deepwater area of the Baiyun Depression in the northern South China Sea

Multiple borehole samples are collected from the Baiyun Depression in deep-water area of the northern South China Sea(SCS)in an effort to reconstruct transgression processes during the Paleogene based on palynalgal analysis.This study indicates that the Baiyun Depression generated a large group of palynopore assemblages and fluvial/lacustrine-related algae during the early and middle Eocene when the Wenchang Formation was deposited.The entire depression was dominated by fluvial and lacustrine facies before transgression.Its eastern and southeastern sags transitioned to shallow marine environment by generating a large abundance of marine dinoflagellates during the Enping deposition of the late Eocene.Meanwhile,the southern uplift zone simply yielded fluvial/lacustrine-related palynopores and algae,and was dominated by the fluvial and lacustrine environment during the early stage of the Enping Formation,prior to shifting into transitional setting in the later period.Northwestern sags remained extensive fluvial and delta facies without existence of marine dinoflagellates.It was until the depositional stage of the Zhuhai Formation(Oligocene)that the overall depression was strongly impacted from transgression process.Both eastern and southeastern sags were mainly under deep marine setting on a continental slope while northwestern and southern areas developed transitional facies.Although distribution and accumulation patterns varied greatly among sub-sags,the overall Baiyun Depression was characterized by widespread development of marine dinoflagellates.It should be noted that the northwestern sag also partly generated large-scale river delta deposits.Due to the eustatic rise and change of SCS spreading axis,the overall Baiyun Depression was mostly influenced by the deep marine environment on a continental slope during the early Miocene.Both northwestern sag and southern uplift zone were found plentiful marine dinoflagellates.In summary,transgression initiated from the eastern and southeastern Baiyun Depression before subsequently progressing into the farther west.Evolution of transgression process is also greatly consistent with the gradual westward expansion of the SCS.

Problems, challenges and future of plant disease management: from an ecological point of view

Plant disease management faces ever-growing challenges due to： （i） increasing demands for total, safe and diverse foods to support the booming global population and its improving living standards; （ii） reducing production potential in agriculture due to competition for land in fertile areas and exhaustion of marginal arable lands; （iii） deteriorating ecology of agro-ecosystems and depletion of natural resources; and （iv） increased risk of disease epidemics resulting from agricultural intensification and monocultures. Future plant disease management should aim to strengthen food security for a stable society while simultaneously safeguarding the health of associated ecosystems and reducing dependency on natural resources. To achieve these multiple functionalities, sustainable plant disease management should place emphases on rational adaptation of resistance, avoidance, elimination and remediation strategies individually and collectively, guided by traits of specific host-pathogen associations using evolutionary ecology principles to create environmental （biotic and abiotic） conditions favorable for host growth and development while adverse to pathogen reproduction and evolution.

Brazilian savanna re-establishment in a monoculture forest:diversity and environmental relations of native regenerating understory in Pinus caribaea Morelet. stands

In this paper we analyze and compare natural regeneration in shrub-tree community in three areas below Pinus caribaea stands and a natural area （cerrado sensu stricto）. We also analyze the influence of biophysical and environmental variables on the distribution of regenerating shrub-tree species. The areas were analyzed and compared in relation to dispersal syndromes as well, being zoochory and anemochory the prevailing syndroms in the four areas. The sites below P. caribaea show a heterogeneous regen- eration with the number of species ranging from 18 to 42. We analyzed the influence of the biophysical and envi- ronmental variables performing a canonical correspon- dence analyses, being found significant values for variables distance from remnant and basal area. The species Si- paruna guianensis, Miconia albicans, Xylopia aromatica, Sclerolobium paniculatum, Casearia sylvestris and P. caribaea were the most importante ones in the four areas,

Effects of 17β-Estradiol on Growth, Primary Metabolism, Phenylpropanoid-Flavonoid Pathways and Pathogen Resistance in Arabidopsis thaliana

Mammalian sex hormones are spread in the environment from natural and anthropogenic sources. In the present study, the effect of estradiol on Arabidopsis thaliana growth primary metabolism, phenylpropanoid and flavonoid pathways and pathogen resistance were investigated. Treatments of Arabidopsis plants with 10 and 100 nM 17β-estradiol resulted in enhanced root growth and shoot biomass. In addition, treated plants had an increased rate of photosynthesis with a concomitant increase in carbohydrate and protein accumulation. Plants exposed to higher concentrations of 17β-estradiol (10 μM) had significantly lower root growth, biomass, photosynthesis rate, primary metabolite and phenylpropanoid and flavonoid contents indicating a toxic effect of estradiol. Treatments with increasing estradiol concentrations (10 nM, 100 nM and 10 μM) resulted in the downregulation of phenylpropanoid-flavonoid pathway genes (PAL1, PAL4, CHI and ANS) and subsequent decreased accumulation of phenolics, flavonoids and anthocyanins. Estradiol-treated plants were inoculated with Pseudomonas syringae pv. Tomato DC3000 and basal resistance was determined. Estradiol treatments rendered plants susceptible to the pathogen, thus compromising the plant defense mechanisms. These results indicate that at low concentrations, estradiol functions as a biostimulant of growth, yield and primary metabolism of Arabidopsis. However, estradiol functions as a potential transcriptional regulator of the phenylpropanoid pathway genes in Arabidopsis, having a negative effect on the phenylpropanoid and flavonoid biosynthetic pathways.

Seasonal change mediates the shift between resource and pollen limitation in Hedysarum scoparium(Fabaceae)

Theory suggests that with sufficient environmental variation, pollen limitation might be observed at some places or times, and resource limitation at others, but there are no empirical data about the effect of seasonal change on the variation of pollen limitation and resource limitation within a flowering season. In this study, we examined pollen and resource limi- tation by comparing fruit set and seed production in natural- and hand-pollinated Hedysarum scoparium flowers in the middle reaches of the Hexi Corridor region, China, in 2010. We also described a role for the first substantial autumn rainfall in mediating a shift between pollen and resource limitation in H. scoparium, but did not analyze this experimentally Our results indicated that H. scoparium was resource limited at peak flowering during the summer, and was pollen limited at peak flowering during the autumn. The seasonal change （summer to autumn） mediated the shift between pollen and resource limitations in H. scoparium. The shift timing depended on the date of the first autumn rainfall in 2010. Changes in the first substantial rainfall in autumn may affect fruiting of H. scoparium, thus affecting population persistence of this species and development/structure of the local ecosystem if such conditions persist.

Spatial distribution patterns of wetland plants in relation to environmental gradient in the Honghe National Nature Reserve, Northeast China

Quantifying correlation between the spatial patterns of natural wetland plants and environmental gradient gives better understanding of wetland habitats, which is the fundamental for the strategy making on the protection and restoration of natural wetlands. In this study, the spatial patterns of wetland plants and the environmental gradient of wetland habitats were assessed in the Honghe National Nature Reserve （HNNR） in Northeast China, a wetland of international importance on the Ramsar list. Biophysical parameters’ values of wetland plants were obtained by field sampling methods, and wetland mapping at the community scale was completed using remote sensing techniques. Digital delineation of the surface water system, hydrological zoning and wetness index were produced by spatial analysis methods in Geographic Information System. An ecological ordination method and two clustering methods were used to quantify the relationship between the spatial distribution patterns of wetland plants and the corresponding environmental gradients. Such quantitative analyses also present the specific diversity of different types of wetland plants based on the environmental attributes of their habitats. With the support from modern geo-information techniques, the experimental results indicate how four ecotypes of wetland plants spatially transit from forest swamp, shrub wetland and meadow into marsh wetland with increasing wetness index and water table. And they also show how wetland spatial distribution patterns are controlled by an environmental gradient of wetness. Another key finding of this research work is that our results present the exact fundamental differences between marsh and non-marsh plants of 11 wetland plant communities within the core study area. Hence, this case study gives a good sample for better understanding of the complex correlation between the spatial patterns of wetland plants and their environmental attributes using advanced digital analysis methods. It is also useful to show how to integrate geoinformatic techniques with statistical analysis methods based on the field data base.

Transition along gradient from warm to mesic temperate forests evaluated by GAMM

Aims The aim of the study was to discover what set of variables best explains the transition from warm to mesic forest vegetation.Based on various variables grouped into sets(geomorphological,ecological,structural,soil characteristics and chorological),six models were built and tested by generalized additive mixed models(GAMMs).We assumed that each set of variables has different explanatory power.Our aim was to compare the six different models(sets of variables),to test which model best explains the species turnover in forest communities along the transition between warm and mesic temperate forests and to try to find reasons for the different explanatory power of the models.Methods The research took place in the southern part of the Balkan Peninsula.Field sampling was done according to standard methods.The gradient from warm to mesic forests was defined as the turnover of species and evaluated by projection of samples on the first unconstrained DCA axis.Geomorphological,ecological,structural and soil characteristics,together with chorological sets of variables,were regressed on the turnover of species composition.Based on the five sets of variables,six models were constructed and tested by generalized additive mixed models.Important Findings Ecological conditions best explain the change of forest communities along the gradient;evolution and the development of vegetation reflected in chorotypes are also of high importance;geomorphology and structure seem not to change so dramatically and soil shows the least significant differences of all.Ecological variables are the most important set of variables in the transition between warm and mesic temperate forests but eco-evolutionary dynamics after the Pleistocene should also be taken into consideration.

Effects of drought and slope aspect on canopy facilitation in a mountainous rangeland

Aims Species composition and diversity of the mountainous rangelands are results of interactions between environmental severities,het-erogeneous topography and facilitative effects by nurse plants.This research was aimed to compare relative effects of these three envi-ronmental variables on the natural vegetation of a mountainous rangeland.For a more detailed understanding,effects of four dif-ferent nurse species were separately compared on the various plant growth forms and on two community plant responses(diversity and abundance).Methods A mountainous semiarid rangeland was selected in Baharkish,Quchan,Northeast of Iran.Density and canopy cover of all plant species were recorded under the canopy of four different shrubs and in open areas,in north and south-facing aspects,and in a normal and a drought year.Shannon diversity,total abundance(%cover)and the abundance of different growth forms were used as crite-ria for assessing effects of the environmental variables.Data were arranged in a factorial combination and analyzed by three-way analysis of variance using a GLM analysis.Important Findings(i)Drought,aspect and canopy created niche differentiation:annual forbs and shrubs were more affected by drought,whereas geophytes and grasses were more responsive to slope aspects.Effects of drought and slope aspect were more profound on species diversity,whereas that of canopy facilitation was stronger on plant abundance.(ii)Canopy facili-tation was dependent on severity of the abiotic factors and life history of interacting species.Canopy facilitation allowed for the persistence of only annual forbs,but it was disadvantaged during the drought year.Plant community responses to abiotic factors(slope and drought)were more dependent on the plant growth form,while responses to canopy facilitation were more dependent on the morphology and/or ecology of nurse shrubs.(iii)Effect of shrubs was dependent on their morphology and ecology:shrubs with larger canopy area and nitrogen fixation capa-bility increased,but those with allelopathic effects or a dense canopy structure decreased the diversity of the understory species.

Effects of nectar-robbing on plant reproduction and evolution

The relationship between plant and pollinator is considered as the mutualism because plant benefits from the pollinator’s transport of male gametes and pollinator benefits from plant’s reward.Nectar robbers are frequently described as cheaters in the plant-pollinator mutualism,because it is assumed that they obtain a reward(nectar)without providing a service(pollination).Nectar robbers are birds,insects,or other flower visitors that remove nectar from flowers through a hole pierced or bitten in the corolla.Nectar robbing repre-sents a complex relationship between animals and plants.Whether plants benefit from the relationship is always a con-troversial issue in earlier studies.This paper is a review of the recent literatures on nectar robbing and attempts to acquire an expanded understanding of the ecological and evolutionary roles that robbers play.Understanding the effects of nectar robbers on the plants that they visited and other flower visi-tors is especially important when one considers the high rates of robbing that a plant population may experience and the high percentage of all flower visitors that nectar robbers make to some species.There are two standpoints in explaining why animals forage on flowers and steal nectar in an illegitimate behavior.One is that animals can only get food in illegitimate way because of the mismatch of the morphologies of animals’mouthparts and floral structure.The other point of view argues that nectar robbing is a relatively more efficient,thus more energy-saving way for animals to get nectar from flowers.This is probably associated with the difficulty of changing attitudes that have been held for a long time.In the case of positive effect,the bodies of nectar robbers frequently touch the sex organs of plants during their visiting to the flowers and causing pollination.The neutral effect,nectar robbers’behavior may destruct the corollas of flowers,but they neither touch the sex organs nor destroy the ovules.Their behavior does not affect the fruit sets or seed sets of the hosting plant.Besides the direct impacts on plants,nectar robbers may also have an indirect effect on the behavior of the legitimate pollinators.Under some circumstances,the change in pollinator behavior could result in improved repro-ductive fitness of plants through increased pollen flow and out-crossing.