375 research outputs found

    New Jewish Specialty Camps: From Idea to realIty

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    Informing Change's evaluation of the Incubator and its camps from 2009 to 2013 addressed five questions, which examined whether and how:1. The new camps had expanded available opportunities for Jewish youth to attend camp 2. The new camps had positively influenced camper attitudes and behaviors about living a Jewish life and broadened their networks of Jewish peers 3. The new camps had developed into sustainable and effective nonprofit camp organizations 4. The Incubator method was an effective strategy for developing and supporting new nonprofit Jewish camps 5. The different specialty camp models met the Jim Joseph Foundation's goals for the IncubatorThe evaluation focused on the cohort of camps as a whole and their aggregate results, rather than evaluating each camp individually. Informing Change provided annual results on camp growth and development to the individual camps as well as support to the camps when interpreting their results and comparing against the aggregate. Each year, the evaluation applied a mixedmethods approach to data collection, which included interviews, surveys, secondary data, observations and organizational capacity assessments. Evaluators surveyed campers both before and after camp; parent surveys were administered after campers had been home from camp for 9 to 11 months

    Plasticity of Chasmogamous and Cleistogamous Reproductive Allocation in Grasses

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    Cleistogamy is more common in grasses than in any other angiosperm family. Both self-fertilized cleistogamous (CL) spikelets and open-pollinated chasmogamous (CH) spikelets are typically produced. Relative allocation to CL and CH varies among species and populations, and is inïŹ‚uenced by ontogeny and environment. The balance between reproductive modes can be expressed as a CH/CL ratio. This ratio is very plastic, and stressful conditions can result in values Amphicarpum purshii, an annual with subterranean CL spikelets, CH/CL declined as density increased because CH decreased more than CL as size was reduced by intraspeciïŹc competition. In the shade-tolerant annual Microstegium vimineum, CH/CL was lowest in large greenhouse-grown plants in an unlimited, sunny environment, but was highest in small plants from a shady forest interior; tiller vegetative mass often showed a negative allometric relation to CH and CL allocation. In the perennial Dichanthelium clandestinum, CH and CL allocation varied among populations, but there was no consistent effect of light on CH/CL. The phenology of reproduction strongly affects CH/CL. In Danthonia spicata, CH/CL was high early in the season as CH ïŹ‚owering commenced, but dropped quickly as axillary CL spikelets matured; A. purshii showed the opposite pattern because CL reproduction occurred ïŹrst. The assumption that cleistogamy simply provides reproductive assurance should be reevaluated in light of new information on phenology and allometry. Changes in the balance between CH and CL caused by environmental factors may be indirect effects of size. Evolutionary models that do not explore the plasticity and allometry of CH and CL reproduction may not be useful in predicting the myriad patterns in nature

    Sources and modes of action of invasive knotweed allelopathy : the effects of leaf litter and trained soil on the germination and growth of native plants

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    Invasive knotweeds, native to Eastern Asia, are among the most dominant plant invaders of European and North American temperate ecosystems. Recent studies indicate that one cause of this dominance might be allelopathy, but the possible sources and modes of action of this allelopathy are insufficiently understood. Here, we asked whether the invasive knotweed Fallopia × bohemica can exert allelopathic effects on native plants also through its leaf litter, or through persistent soil contaminants, and whether these affect the germination or growth of native plants. In a germination experiment with nine native species neither litter leachate, an aqueous extract of knotweed leaves added to the soil, nor trained soil with a history of Fallopia pre-cultivation suppressed the germination or early growth of natives. A mesocosm study with experimental native communities showed that the presence of F. × bohemica, although not a dominant in these communities, caused significant shifts of life-history strategy in two dominant natives, and that similar effects could be elicited through litter leachates or trained soil alone. However, there were hardly any effects on the biomass of natives. Our study indicates that knotweed allelopathy acts on the growth rather than germination of natives, and that soil contamination through persistent allelochemicals may not be a significant problem in habitat restoration. It also shows that allelopathic effects can sometimes be subtle changes in life-history and allocation patterns of the affected species

    Infection by a foliar endophyte elicits novel arabidopside-based plant defence reactions in its host, Cirsium arvense

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    Endophytic fungi live asymptomatically within plants. They are usually regarded as non-pathogenic or even mutualistic, but whether plants respond antagonistically to their presence remains unclear, particularly in the little-studied associations between endophytes and nong-raminoid herbaceous plants. We investigated the effects of the endophyte Chaetomium cochlioides on leaf chemistry in Cirsium arvense. Plants were sprayed with spores; leaf material from both subsequent new growth and the sprayed leaves was analysed 2 wk later. Infection frequency was 91% and63% for sprayed and new growth, respectively, indicating that C. cochlioides rapidly infects new foliage. Metabolomic analyses revealed marked changes in leaf chemistry with infection, especially in new growth. Changes in several novel oxylipin metabolites were detected, including arabi-dopsides reported here for the first time in a plant species other than Arabidopsis thaliana,and a jasmonate-containing galactolipid. The production of these metabolites in response to endophyte presence, particularly in newly infected foliage, suggests that endophytes elicit similar chemical responses in plants to those usually produced following wounding, herbivory and pathogen invasion. Whether en-dophytes benefit their hosts may depend on a complex series of chemically mediated interactions between the plant, the endophyte, other microbial colonists and natural enemies

    The interplay between the effectiveness of the grass-endophyte mutualism and the genetic variability of the host plant

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    Neotyphodium endophytic fungi, the asexual state of EpichloĂ« species, protect cool-season grasses against stresses. The outcomes of Neotyphodium-grass symbioses are agronomically relevant as they may affect the productivity of pastures. It has been suggested that the mutualism is characteristic of agronomic grasses and that differential rates of gene flow between both partners’ populations are expected to disrupt the specificity of the association and, thus, the mutualism in wild grasses. We propose that compatibility is necessary but not sufficient to explain the outcomes of Neotyphodium-grass symbiosis, and advance a model that links genetic compatibility, mutualism effectiveness, and endophyte transmission efficiency. For endophytes that reproduce clonally and depend on allogamous hosts for reproduction and dissemination, we propose that this symbiosis works as an integrated entity where gene flow promotes its fitness and evolution. Compatibility between the host plant and the fungal endophyte would be high in genetically close parents; however, mutualism effectiveness and transmission efficiency would be low in fitness depressed host plants. Increasing the genetic distance of mating parents would increase mutualism effectiveness and transmission efficiency. This tendency would be broken when the genetic distance between parents is high (out-breeding depression). Our model allows for testable hypotheses that would contribute to understand the coevolutionary origin and future of the endophyte-grass mutualism

    Growth dynamics of deciduous species during their life period: A case study of urban green space in India

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    It is evident that grass density (GD) and shoot growth rate (SGR) governs the differential settlement of substructure, groundwater recharge, and stability of green infrastructure. GD and SGR are usually assumed to be constant during the entire life period of vegetation. However, spatial and temporal dynamics of GD and SGR in urban green space were rarely explored previously. The main objective of this study is to explore the spatial and temporal dynamics of GD and SGR in urban space vegetated with deciduous species (mix grass i.e., Poaceae and Bauhinia purpurea). Field monitoring was conducted in the urban green space for one year (i.e., life period of selected species). The monitoring period includes the growth period and gradual wilting period. Substantial spatial variation of GD was found during the first six months. GD away from the tree trunk was found to be 1.02–56.3 times higher than that near the tree trunk during the first six months. Thereafter, any spatial variation of GD was not found in the next six months. Unlike the GD, SGR was found to vary during the entire life period of mix grass. In addition, SGR away from the tree trunk was found to be 1.1–4.6 times higher than that near the tree trunk. Any relationship between GD and rainfall depth was not found. Whereas, SGR mainly depends on rainfall depth. The hypothesis of uniformity in GD and SGR during the life period of deciduous species was not found to be true

    Relationship between Reproductive Allocation and Relative Abundance among 32 Species of a Tibetan Alpine Meadow: Effects of Fertilization and Grazing

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    Background: Understanding the relationship between species traits and species abundance is an important goal in ecology and biodiversity science. Although theoretical studies predict that traits related to performance (e.g. reproductive allocation) are most directly linked to species abundance within a community, empirical investigations have rarely been done. It also remains unclear how environmental factors such as grazing or fertilizer application affect the predicted relationship. Methodology: We conducted a 3-year field experiment in a Tibetan alpine meadow to assess the relationship between plant reproductive allocation (RA) and species relative abundance (SRA) on control, grazed and fertilized plots. Overall, the studied plant community contained 32 common species. Principal Findings: At the treatment level, (i) RA was negatively correlated with SRA on control plots and during the first year on fertilized plots. (ii) No negative RA–SRA correlations were observed on grazed plots and during the second and third year on fertilized plots. (iii) Seed size was positively correlated with SRA on control plots. At the plot level, the correlation between SRA and RA were not affected by treatment, year or species composition. Conclusions/Significance: Our study shows that the performance-related trait RA can negatively affect SRA within communities, which is possibly due to the tradeoffs between clonal growth (for space occupancy) and sexual reproduction. We propose that if different species occupy different positions along these tradeoffs it will contribute to biodiversity maintenance in local communities or even at lager scale
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