Age determination of large live trees with inner cavities: radiocarbon dating of Platland tree,a giant African baobab

• Introduction   

For large trees without a continuous sequence of growth rings in their trunk, such as the African baobab (Adansonia digitata L.), the only accurate method for age determination is radiocarbon dating. As of today, this method was limited to dating samples collected from the remains of dead specimens.     

Changes in protein synthesis during drought conditioning in roots of jack pine seedlings (Pinus banksiana Lamb.)

The impact of drought conditioning on the ability of eight-week-old jack pine (Pinus banksiana Lamb.) seedlings to withstand drought was assessed. Two progressive cycles of drought conditioning significantly increased the survival of seedlings subjected to a subsequent prolonged drought. The in vivo accumulation of several root membrane proteins during drought conditioning was correlated with an increase in seedling survival. A group of root proteins, ranging in molecular mass from 43 to 47 kDa, increased accumulation during one cycle of drought conditioning and to a lesser extent during two cycles of drought conditioning. The accumulation of several low molecular mass membrane and soluble proteins also increased during drought conditioning, suggesting that these proteins may play an important role in the enhancement of drought tolerance. In vitro translation studies showed a general increase in the abundance of protein products encoded by mRNAs from drought-conditioned seedlings. Although the majority of the in vitro translation products appeared in both control and drought-conditioned seedlings, one mRNA encoding a 15 kDA translated protein was more prominent during the second cycle of drought conditioning.     

Setting management limits for the production and utilization of herbage for out-of-season grazing

Three experiments were carried out on perennial ryegrass‐dominant swards to provide a basis for recommendations for the limits to (a) building up and timing of utilization of a herbage ‘bank’ for out‐of‐season grazing and (b) duration and intensity of early spring grazing in the United Kingdom and Ireland. In experiment 1, the effect of regrowth interval (from 7 September, 20 October, 17 November or 15 December) in autumn on herbage accumulation, leaf turnover and on subsequent spring growth was investigated. Swards regrown from early September reached maximum herbage mass (about 3 t ha^–1 DM) and leaf lamina content in mid‐November, by which time senescence rate exceeded rate of production of new leaves. New leaf production and senescence rates were greater in swards remaining uncut until December than in those cut in October or November. Time of defoliation up to December had no effect on spring herbage mass in the subsequent spring. Defoliating in March reduced herbage mass in late May by less than 20%. Experiment 2 investigated the progress in herbage growth and senescence in swards regrowing from different times in late summer and autumn to produce herbage for utilization beyond the normal grazing season. Treatments in a randomized block design with three replicates were regrowths from 19 July, 8 August, 30 August and 20 September. Based on a lower ceiling of leaf and total herbage mass being reached with progressively later regrowths, beyond which leaf senescence generally exceeded leaf production and herbage mass declined, it was concluded that currently recommended rotation lengths for this period should extend from 3 weeks in late July to 8 weeks for swards previously grazed in mid‐September. In both experiments, leaf senescence commenced earlier (by one leaf‐age category) than previously published estimates and so brought forward the time at which senescence rates balanced leaf growth rates. In experiment 3, designed to evaluate the effect of daily grazing period and intensity in early spring on herbage regrowth, dairy cows grazed successive plots (replicates) for 2 or 4 h each day at two intensities (target residual heights of 5 or 7 cm) in March to mid‐April. Regrowth rate was similar in all treatments including the ungrazed control, despite soil moisture content being relatively high on occasions. Tiller density was significantly reduced in May by grazing plots in early or mid‐April. It is concluded that in autumn there are limits to which rotation lengths should be extended to produce herbage for out‐of‐season grazing owing to attainment of ceiling yields. Although utilization in early spring may reduce herbage availability in spring, out‐of‐season utilization need not reduce herbage growth rates in early spring.     

Oceanographic influences on the distribution of Baltic cod, Gadus morhua, during spawning in the Bornholm Basin of the Baltic Sea

The Baltic Sea is a stratified, semienclosed sea typified by a low-salinity surface layer and a deep saline layer of varying volume, salinity, temperature and oxygen concentration. The relationships between these oceanographic factors and the distribution of Baltic cod are presented, utilizing results from a survey carried out during the 1995 spawning period in the Bornholm Basin, at present the main spawning area of this stock. Cod distribution, abundance and population structure were estimated from hydroacoustic and trawl data and related to hydrographic parameters as well as to bottom depth. In the central basin, cod were aggregated in an intermediate layer about 15 m thick. This area of peak abundance was defined at its upper limit by the halocline and at the lower limit by oxygen content. The majority of individuals caught in the basin centre were in spawning or pre-spawning condition with a high proportion of males to females. On the basin slopes, aggregations of cod were found near the bottom. These individuals were mainly immature and maturing stages with an increasing proportion of females to males with size. Salinity and oxygen conditions were found to be the major factors influencing the vertical and horizontal distribution of adult cod. Abundance of immature cod was also positively related to decreasing bottom depths. The effect of temperature was minor. The observed size- and sex-dependent spawning aggregation patterns, in association with habitat volume and stock size, may influence cod catchability and thereby the assessment and exploitation patterns of this stock.     

An evaluation of an inoculant/enzyme preparation as an additive for grass silage for dairy cattle

Herbage from the first regrowth of perennial ryegrass-based swards was directly ensiled after treatment with a bacterial inoculant/enzyme preparation (SIL-ALL, Alltech UK) at 3·0 1 t^?1, formic acid (850 g kg^?1) at 2·59 1 t^?1 or no additive (Control). The mean dry matter (DM) and water-soluble carbohydrate concentrations of the grass were 185 and 24·0 g kg^?1 (fresh basis) respectively. Lactic acid concentrations after ensiling increased at a lower rate in formic acid-treated herbage than with the other treatments. All silages were well preserved and formic acid-treated silage had a lower ultimate concentration of lactic acid and higher concentration of water-soluble carbohydrate. Effluent output was increased on a proportional basis by ?0·06 with formic treatment, whereas the inoculant reduced effluent output by 0·05 in comparison with the mean effluent production of the control silage. The in vivo digestibilities of the silages were determined using sheep. The digestibilities of DM, organic matter and energy were significantly higher with inoculant-treated silage than with formic acid treatment, whereas values for the control silage were intermediate. The three silages were offered ad libitum to forty dairy cows with individual recording of daily intakes for a 10-week period in a randomized block experiment with four treatments. Sixteen animals were offered the control silage with half of these offered 3 kg concentrates per day (C3) and the other half offered 7 kg concentrates per day (C7). Twelve animals were allocated to each of the additive-treated silages, with concentrates offered at 5 kg d^?1. Treatment effects on animal performance were measured in weeks 7–10. To compare animal performance for the treated silages with the control, an estimate of performance at 5 kg concentrates per day was obtained by regression using values obtained at 3 and 7 kg concentrates. In comparison with estimated silage intake for the control silage with 5 kg d^?1 concentrates, inoculant and formic acid treatment of the silages increased dry matter intake by 0·04 (P > 0·05) and 0·13 (P > 0·01) respectively. In comparison with estimated milk production and yield of fat plus protein for the control treatment with 5 kg d^?1 concentrates, neither inoculant treatment nor formic acid treatment produced any significant differences.     

The relationship between level of sward height reduction in a rotationally grazed sward and short-term intake rates of dairy cows

The objective of this study was to investigate the relationship between level of sward height reduction (SHR) and short-term intake of herbage by lactating dairy cows offered swards differing in initial bulk density (BD). Three experiments were carried out in which cows were presented with swards representing different levels of SHR (nominally described as ungrazed, low, moderate and high). Experiments 1 and 2 differed with respect to initial sward BD [ungrazed sward 1·7 vs. 2·5 kg dry matter (DM) m^?3 respectively]. Experiment 3 investigated the interaction between BD and SHR. In each experiment, sixteen Holstein/Friesian cows (fitted with excreta collection bags) grazed for a 1-h period in 200-m² plots that had been grazed on the previous day to predetermined sward surface heights (SSH) (= levels of SHR). Herbage intake rates were assessed from changes in live weight, with a correction for insensible weight loss (IWL). Biting rates were recorded from visual observation. High levels of SHR were associated with a significant reduction in SSH, herbage mass and leaf fraction, and a significant increase in sward BD, stem and dead fraction, and DM concentration. Herbage intake, expressed either as DM intake per bite or DM intake per hour, declined as level of SHR increased from low to high. The level of SHR generally had no effect on biting rate. Intake rates varied from 1·9 to 4·4 kg DM h^?1, whereas DM intake bite^?1 ranged from 0·5 to 1·3 g. Pooled regression analysis identified SSH (P < 0·001; r² = 0·94) as the principal determinant of DM intake bite^?1. The regression equation was not significantly improved by the addition of terms for leaf fraction, BD, or herbage mass. In Experiment 3, a significant interaction between level of SHR and sward BD was observed. It is concluded that the principal factor controlling intake (g DM bite^?1 or kg DM h^?1), as swards are progressively grazed down, is SSH, but at a high level of SHR, sward BD also influences intake bite^?1.