Grasses, olive, parietaria and cypress in Athens: Pollen sampling from 1995 to 1999

The airborne pollens can produce asthma andrhinoconjuctivitis (pollinosis). Sincegeographic and climatic factors influence thequality and quantity of pollen counts invarious countries and between seasons, the aimof the study was to record major seasonalallergenic pollens; grasses, olive, parietariaand cypress in Athens during five consecutiveseasons throughout the years 1995–1999. Thedaily pollen count was carried out every yearfrom March to October using a Burcardvolumetric weekly spore trap, which was placedabout 20 m from the ground, in Athens citycentre. Daily values were expressed as numberof pollen grains/m³ of air. The meanmonthly values of pollens/m³ were used tocompare the results of the consecutive years.Recording of the major pollen allergens inAthens area for five consecutive years led tothe assessment of the pollination period foreach of these plants and confirmed thevariations in the amount of pollen per plantper year.     

GIS and Remote Sensing for Detecting Yield Loss in Cranberry Culture

The primary goal of our research is to develop key elements of a precision agriculture program applicable to high-value woody perennial crops, such as cranberries. These crop systems exhibit tremendous variability in crop yields and quality as imposed by variations in soil properties (water availability and nutrient deficiency) that lead to crop stress (disease development and weed competition). Some of the variability present in the growing environment results in persistent yield losses as well as crop-quality reductions. We are using state-of-the-art methodologies (GIS, GPS, remote sensing) to identify and map spatial variations of the crop. Through image-processing methods (NDVI and unsupervised classification), approximately 65% of the variation in yield was described using 4-m multispectral satellite data as a base image.     

Invasive species in China — an overview

China is a vast country with rich biodiversity, which makes China especially vulnerable to invasive species. It has a long history of introduction of non-native species, especially those with perceived beneficial impacts. Its rapid economic development, including an explosive growth in international trade and transportation, has increased the potential for new introductions. Currently, alien species are widespread in the country, occur in many ecosystems, represent most major taxonomic groups, and are introduced unintentionally as well as intentionally for cultivation. The paper lists various cases of invasive species which have caused significant threats or damages to local natural or artificial ecosystems, and indicates that two example industries (fresh water fisheries and lawn grasses) have brought or tend to bring in many invasive species and hence have caused or will cause changes and loss of biodiversity in local ecosystems. Based on these studies, it is suggested that China combat the problem through enhancing awareness, development of a database on invasive species, strengthening international co-operation, preparing case studies and introducing the necessary legislation, regulations and monitoring.     

Accelerated seedling emergence in interspecific competitive neighbourhoods

Seed dormancy models suggest that evaluation of environmental conditions should influence the decision to germinate and that waiting for more favourable conditions may increase potential fitness. However, because rapid emergence is often positively correlated with performance and survival, an alternative strategy to accelerate the rate of emergence may increase the potential for site pre-emption. This response is more likely to be found in seasonal environments with greater potential for rapid resource depletion in which early emergence may confer a competitive advantage. The experiments reported here found more rapid emergence in a perennial grass species when it was planted in potentially highly competitive interspecific neighbourhoods. This response suggests an inherent ability in seeds of this species to sense and respond to the competitive nature of the immediate neighbourhood.     

Biological nitrogen fixation in grass–clover affected by animal excreta

Aiming at estimating the average N2-fixation in a pasture, ap preciating the great variability due to patchy urine and dung deposition, the in fluence of dairy cow excreta on biological N2-fixation in a perennial ryegrass–white clover mixture was studied using natural urine and dung. Application of urine as well as dung affected the N2-fixation by promoting the growth of grass and thereby the proportion of clover was significantly reduced. Also the proportion of clover-N derived from the atmosphere (pNdfa) was significantly reduced. In control plots clover dry matter constituted between 40 and 50% of the total dry matter production and the pNdfa ranged between 0.8 and 0.9. Addition of urine caused a significant increase in the grass growth rates, which was the primary reason for a decrease in proportion of clover. At the same time pNdfa decreased to 0.2–0.4 followed by an increase resulting in a total reduction of 45% in the N2-fixation in urine affected areas over a period of four months. The dung only affected the N2-fixation for a distance of up to 10 cm from the edge of the dung pats. In this border area the pNdfa decreased from 0.85 to 0.75 during one month after application followed by an increase, so that after three months there was no difference between pNdfa at 0–10 and 10–20 cm distance from the dung hill. The proportion of clover was lower in the 0–10 cm than in the 10–20 cm distance, which totally resulted in a total reduction of 20% in the N2-fixation over a period of four months in the 0–10 cm area around the dung pats. Considering the proportion of a pasture which may by affected by excreta at a stocking density of 4–6 cows ha-1, the length of the grazing period, the frequency of excretion and the area covered by individual patches, it was estimated that the N2-fixation in a grass-clover pasture would be reduced by 10–15% compared to the N2-fixation in a grass-clover sward not exposed to animal excreta.     

Development of microsatellite markers in a clonal perennial herb,Convallaria keiskei

We developed eight polymorphic microsatellite simple sequence repeat (SSR) loci from genomic DNA of a clonal perennial herb, Convallaria keiskei, using a dual‐suppression‐polymerase chain reaction (PCR) technique and an improved technique. These markers with four to 10 alleles per locus identified 29 genotypes in 82 samples collected from a population in Hokkaido, Japan. The observed and expected heterozygosities ranged from 0.241 to 0.862 and from 0.639 to 0.825, respectively. These SSR markers will be available to identify genets and evaluate genetic diversity of C. keiskei.