Variação do valor cultural da semente Koelreuteria paniculata L. em função do local de colheita e do tratamento pré-germinativo

A Koelreutéria (Koelreuteria paniculata L., Sapindaceae) é uma árvore do Leste da Ásia, introduzida na Península Ibérica como ornamental. Para a sua propagação por semente são geralmente necessários tratamentos de quebra da dormência do tegumento e do embrião. Contudo, alguma bibliografia refere a inexistência de dormência do embrião em ecótipos de regiões mediterrâneas. O objectivo deste estudo consistiu em averiguar o comportamento germinativo da semente de Koelreutérias cultivadas em Portugal. Foram testadas sementes recolhidas em Lisboa e Évora, respectivamente em alinhamento urbano e árvore isolada. Cada proveniência foi dividida em três partes, uma das quais não tratada. As outras foram escarificada com água quente e uma foi estratificada em frio, em areia húmida, durante 31 dias. Foram todas semeadas na estufa do Viveiro do Instituto Superior de Agronomia em tabuleiros com 28 contentores, num delineamento bifactorial com 5 repetições (2 lotes × 3 tratamentos × 5 tabuleiros). A proveniência de Lisboa apresentou germinação significativamente mais elevada do que a de Évora. A escarificação seguida de estratificação deu melhores resultados do que a testemunha e, no caso de Lisboa, do que a estratificação apenas. Estes resultados comprovam a conveniência de quebrar a dormência do embrião na propagação com semente nacional

Influence of mother plant and scarification agents on seed germination rate and vigor in Retama sphaerocarpa L. (Boissier)

Research ArticleThe aim of this study was to optimize nursery production of Retama sphaerocarpa (Fabaceae), an important shrub species characterized by a seed coat dormancy hindering germination, and used in the restoration of degraded arid and semi-arid areas. To assess the influence of scarification agents and mother plant effect on germination rate and seedling vigor, a germination test with fresh seed was performed in a germination chamber using a factorial design with two fixed factors (mother plant effect and scarification agent). Fresh seeds were scarified by sulphuric acid (96% concentration, 60 min) and hot water (80 °C, 30 sec) and their germination compared with untreated control seeds. Scarification of seeds using sulphuric acid has proven the best method to enhance germination of this species, achieving the highest germination rate (>79%) and the best vigor index. Differences between seed lots from different mother plants were statistically significant and could influence seed germination success. We suggest that effectiveness of hot water scarification method may be improved by additional time of seed immersion. Owing to its potential for use in land restoration, bioenergy production and ornamental purposes, increment of commercial demand of this species is expected in the near futureinfo:eu-repo/semantics/publishedVersio

As podas em árvores ornamentais: como e porquê

Ouve-se muitas vezes dizer que as árvores precisam de ser podadas para se desenvolverem bem, mas esta afirmação carece de fundamento. As árvores apareceram na Natureza muito antes de haver homens que as podassem. Apesar disso, sobreviveram e evoluíram assim, sós, durante muitíssimos milénios. As razões para se podar uma árvore podem ser variadas, mas estão todas mais relacionadas com a necessidade que temos de condicionar o desenvolvimento destas plantas, por motivos nossos, do que com necessidades da árvore, que pode perfeitamente sobreviver, crescer e reproduzir-se sem intervenção humana. É daqueles motivos que trata o presente texto, que procurará descrever sumariamente como se formam as copas das árvores e como podemos intervir na sua conformação sem pôr em causa a sua sobrevivência e sanidade

Os mitos urbanos da floresta: a floresta natural

O homem começou a utilizar as árvores e as florestas para os mais diversos fins desde cedo no desenvolvimento das suas sociedades, sendo essa, aliás, uma das razões porque o termo “natural” aplicado às árvores e às florestas deve ser entendido dentro dos limites dessa relação há muito estabelecida, tanto em Portugal, como noutras partes do Mundo. Não é que a floresta deixe por isso de ser um ecossistema natural, no sentido de apresentar o funcionamento organísmico que atribuímos aos ecossistemas e de ser um resultado da acção de forças da Natureza. Contudo, a floresta actual reflecte também, na velha Europa em geral e, em particular,em Portugal, uma influência muito antiga do homem, que nela buscou desde épocas remotas alimento, abrigo, combustível e matérias- primas, condicionando, deste modo, a sua fisionomia e composição específica

Seedling production of woody riparian species from seeds: techniques and results

Rehabilitation of woody riparian galleries largely depends on the availability of seedlings or seeds of autochthonous species, which are usually difficult to obtain in Portugal. The cultural value of autochthonous seeds of several riparian woody species in nursery conditions was evaluated in order to assess seedling production feasibility. The choice of species was based on their occurrence in riparian habitats, even if not exclusive to such environments, and their suitability to establishment studies currently under way. The results indicate that seeds of Celtis australis, Fraxinus angustifolia, Quercus robur, Q. faginea and Platanus × hybrida obtained in Portugal were highly suited to seedling production. Germination of seeds of Acer pseudoplatanus and A. campestre was much more irregular and seeds from Alnus glutinosaand Crataegus monogyna exhibited a very low germination rate. We conclude that seedling production of European hackberry, oaks, narrow-leaved ash, and plane tree and, less clearly, maples, can be successfully carried out in nursery conditions using simple and unsophisticated sowing techniques. For common alder and whitethorn it is preferable to produce seedlings via vegetative propagation as an alternative to more sophisticated nursery pre-germination treatments

The Lambert function on the solution of a delay differential equation

Recently, a new method for computing the analytical solution of a delay differential equation was developed considering a constant initial function. It is based on the existence of a specific class of polynomials in the delay. In this article, we extend this new method to the case of a continuous initial function. We also show the relationship between the new solution’s method and the solution expressed in terms of the Lambert function.info:eu-repo/semantics/publishedVersio

A variant of the method of step algorithm for a delay differential equation

In this paper we develop a new method to obtain explicit solutions for a first order linear delay differential equation based upon the generating function concept. The advantage of this new method as regards the traditional Method of Step Algorithm (MSA) is also showed through an exemple.info:eu-repo/semantics/publishedVersio

Patos e o risco de influenza aviária em Portugal

The outbreak of highly pathogenic avian influenza of the H5N1 virus subtype in Western European countries induced the fear that it could reach Portugal through wild bird migration. Ducks, geese and swans are some of the bird groups with higher prevalence of influenza virus that might be vectors of virus dissemination, considering the existing studies on low pathogenic subtypes that are common in nature (Olsen et al. 2006), and also occur in Portugal (D. Rodrigues et al., unpublished data). Although swans do not occur frequently in Portugal and geese are mostly restricted to Tagus River Estuary Nature Reserve (e.g. Farinha & Costa 1999), ducks are common in Portugal and mostly concentrated on wetlands near the coast (Costa & Guedes 1997), and wintering Aythya duck species are much less numerous than wintering Anas species (e.g. Costa & Guedes 1997). The Portuguese total wintering duck population (Costa & Guedes 1997) is relatively small when compared to the total European population (Scott & Rose 1996), probably due to the location of the country on the South-West limit of the distribution for most of the species (Scott & Rose 1996). However, given the recent occurrence of outbreaks of highly pathogenic avian influenza of the H5N1 subtype in France, Germany, Scotland, Denmark, Sweden and Poland (OIE 2006), there is a risk that outbreaks may also occur in Portugal. In this paper, we aim to discuss the possibility of avian influenza occurrence in Portugal, under the assumptions that outbreaks will persist, will occur new ones or the virus will become endemic on the above mentioned countries and that ducks will be vectors of the viru

Effects of harrowing and fertilisation on understory vegetation and timber production of Eucalyptus globulus Labill. plantation in central Portugal

Harrowing and fertilisation are common practices at middle rotation in Eucalyptus globulus Labill. plantations in Central Portugal. In order to clarify the effects of such practices on understory vegetation and timber production, a field trial was installed in a 5-year-old first rotation eucalyptus plantation, in a region with mixed oceanic and Mediterranean climatic influences. Four treatments that involved harrowing (H), fertilisation (F), harrowing and fertilisation (HF), and control (C) were tested in the study. The treatments were replicated four times and arranged in a simple completely randomised design. Vegetation surveys were performed by the quadrat method in the 3 years following treatments and by the line interception method in the 7th and 8th years. Samples of understory biomass were collected, oven dried and weighed. In treatments with harrowing, the understory vegetation consistently had lower number of species, less plant cover, species diversity, and biomass than the other treatments. The mean total number of species only once reached 10 in H or HF plots, and was always greater than 12 in C and F plots in the first 3 years, but decreased in the 7th and 8th years. In the first 3 years, the understory biomass averaged 30–60 g m 2 in the F and C plots, and never exceeded 13 g m 2 in treatments with harrowing, which corresponded with the proportion of soil coverage by understory vegetation (4–12% in H and HF, and 38–62% in F and C plots). In the 7th and 8th years, differences in the understory biomass were less important, but the control plots consistently had the largest understory biomass. The influence of treatments in timber production was not statistically significant at the end of rotation

Changes in carbon stocks in Eucalyptus globulus Labill. plantations induced by different water and nutrient availability

Changes in the carbon stocks under different soil water and nutrient conditions were studied in Eucalyptus globulus Labill. stands in a field experiment, at O ´ bidos (central Portugal). The treatments were irrigation plus a complete fertiliser solution to simulate ‘near optimal’ nutrition (IF), irrigation only (I), and fertilisers added to rain-fed plots (F). The control (C) received neither water nor fertilisers (except a small amount at planting). The production of biomass (aboveground), the litterfall and the soil chemical composition were evaluated regularly during the experiment. Root biomass was estimated at the end of the experiment. Carbon in biomass, litterfall and soil, increased significantly when water and/or nutrients were supplied, in comparison to the control. The amount of carbon accumulated in the system, 6 years after planting, was 8.22, 10.22, 11.23 and 13.76 kg C m 2 in the control, F, I and IF treatments, respectively. The increase of carbon in the system during the same period was 5.86, 7.86, 8.87 and 11.40 kg C m 2 in the control, F, I and IF treatments, respectively. This rise in carbon resulted from the accumulation of long-lived woody biomass, which represented between 77.7 (in IF) and 82.9% (in the control) of the total rise in carbon. Although water was the main limiting factor for biomass accumulation, the allocation of carbon to the soil was mainly related to nutrient supply, irrespective of water availability. The amount of carbon stored belowground, i.e. soil and forest floor, plus stumps and roots, reached 4.2, 4.7, 4.8 and 6.3 kg C m 2 in the control, F, I and IF treatments, respectively. The increase in C in the mineral soil regarding the initial state was, in the same order as above, 0.21, 0.75, 0.58 and 1.21 kg C m 2. These values were 3.6, 9.6, 6.6 and 10.6% of the C accumulated in the whole system, during the experimental period