The influence of management and nutrient availability on the vegetation dynamics of heathlands characterised by Calluna vulgaris and Erica tetralix were studied in three mountain sites in Northern Spain. A total of 90 plots (1 m 2 each) received different combinations of cutting and twice the estimated background atmospheric deposition of nitrogen (56 kg ha À1 yr À1 ). One of the two dominant ericaceous species was selectively cut by hand at ground level and their regeneration compared in the presence or absence of the other. The results after 2 years showed significant effects of the fertiliser on the vegetation cover, mainly by favouring perennial herbaceous species. There were less noteworthy effects on the number of flowers and on the annual growth of the ericaceous species. It is concluded that, in the short term, increased nutrients alone, at twice the estimated current atmospheric deposition for the area, will not alter significantly the composition of the mountain heathlands. However, once the stands reach the mature phase, the capacity of the community to regenerate after a severe disturbance diminishes. A drastic impact, such as cutting may not result in re-growth of the same shrub species but in replacement by herbaceous species, which will also benefit from the increased nutrients.

We tested how the conditions resulting from alternative management strategies addressed to mitigate abiotic and biotic limitations to plant establishment affect the performance of planted Quercus coccifera seedlings. This species is a xerophytic and heliophillous Mediterranean shrub, of interest for the restoration of abandoned farmland. We hypothesised that release from herb competition by clipping would allow Q. coccifera seedlings to cope more efficiently with water shortage by adjusting their mass allocation pattern. We established three environments of herb competition: absence of competition (AC), reduced competition by clipping (RC), and total competition (TC); and applied two irrigation treatments: low and high irrigation. We measured soil moisture at different depths, above- and below-ground herb biomass, and evaluated seedling responses, such as mortality, growth, biomass allocation, and morphological and physiological features. The TC treatment reduced water availability more than the RC treatment, in agreement with the highest water stress of seedlings under TC conditions. Irrigation increased above- and below-ground herb biomass, whereas clipping reduced herb production. Release of herb competition by clipping increased seedling survivorship by one order of magnitude and resulted in a growth rate comparable to the absence of competition. This growth was mostly related to carbon gain allocated to roots. The competition intensity imposed by treatments was related to a parallel reduction in total plant leaf area, biomass allocated to leaves and shoot:root ratio, and an increase in biomass allocated to roots and leaf mass area. The negative effects of herbs on Q. coccifera seedlings seem the result of competition for both water and light, in contrast with previous research with more mesic Quercus species, for which competition is primarily for water. Clipping of herbs is a feasible technique that greatly improved seedling performance, and thus a valuable alternative to herbicide application, common in native plantations aimed at restoring Mediterranean farmland

No abstract

Equilibrium binding curves were biphasic in control and ethanol‐treated rats. [3H]Muscimol binds to sites of high (KDA of ∼10 nM) and low (KDB of ∼0.3–0.4 µM) affinity. Chronic ethanol treatment produced a decrease in BmaxA value, and the hyperbolic binding profiles were progressively affected by the chronic and in vitro ethanol treatments, with most of this effect corresponding to the high‐affinity site. IC50 and Ki values were calculated for several competing ligands, using membranes from both control and ethanol‐treated animals. The association and dissociation curves were also biphasic, using a radioligand concentration precluding a significant occupancy of the low‐affinity sites, which suggests the existence of two forms or affinity states of the monoliganded receptor. Chronic ethanol treatment did not produce changes in the values of the dissociation rate constants (fast and slow phases). By contrast, we report for the first time a decrease in the values of the association rate constants, with this decrease being higher for the slow phase. Consequently, the dissociation equilibrium constants are two times higher in chronically ethanol‐treated animals for both phases.

Ethanol alters almost all membrane functions, but it behaves essentially like a benzodiazepine-type GABAergic agonist. The mechanism by which ethanol affects the GABA/benzodiazepine complex is not clear. We studied the possible changes in [3H]flunitrazepam binding induced by chronic ethanol treatment, using light microscopic autoradiography, to try to elucidate the controversy underlying this topic. This technique allows us to measure densities of benzodiazepine receptors in different anatomical brain areas--visual cortex and hippocampus--which seem to constitute the anatomical support for the behavioral and physiological responses affected by ethanol. Autoradiographic studies on the visual cortex and hippocampus from rats chronically treated with ethanol do not show statistically significant differences in the binding of [3H]flunitrazepam with respect to control animals. Furthermore, we did not find either rostro-caudal or medio-lateral differences in benzodiazepine receptor densities in each layer of the visual cortex.