Effect of elevated temperatures on carbon dioxide exchange in Picea rubens

We examined some of the physiological reasons that may underlie past and expected future migrations of red spruce (Picea rubens Sarg.) by evaluating the effects of high temperatures on photosynthesis and respiration of trees growing on Whiteface Mountain, NY. At temperatures of 35-40 degrees C, the trees exhibited a zero or negative carbon balance. Higher temperatures resulted in cellular disorganization and death. Temperatures around 30 degrees C resulted in reduced CO(2) uptake, a condition that could decrease future reproductive output and competitive stature. We conclude that thermal intolerance explains, at least in part, the absence of red spruce at low elevations and latitudes where temperatures of >/= 30 degrees C occur. We suggest that the thermosensitivity of this species is important with respect to global climate trends and migration patterns.     

Tissue fluoroacetate residues in prairie dogs dosed with low-level sodium monofluoroacetate

A total of 83 black-tailed prairie dogs (Cynomys ludovicianus) from South Dakota were subjected to low-level treatment with sodium monofluoroacetate (Compound 1080) in the laboratory (0.01-0.30 mg 1080/kg). The acute oral median lethal dose (LD50) of 1080 administered by oral gavage was established at 0.173 mg/kg. To assay fluoroacetate residues, 8 kinds of tissue from each of 10 prairie dogs dead of low-level 1080 poisoning were analyzed by capillary gas chromatography-mass spectrometry. Of the total of 79 tissues analyzed, 73 contained less than 100 ppb fluoroacetate, and 67 contained less than 50 ppb fluoroacetate. To test the effect of secondary poisoning on non-target species, 8 European ferrets (Mustela furo) were fed ground whole carcasses of prairie dogs dead of low-level 1080 poisoning, with no observable ill effects on the ferrets.     

Implementing the precautionary approach into fisheries management: Biomass reference points and uncertainty buffers

The precautionary approach to fisheries management advocates for risk-averse management strategies that include biological reference points and account for scientific uncertainty (i.e. process, model and observation uncertainty). In this regard, two approaches have been recommended: (a) biomass reference points to safeguard against low stock biomass, and (b) uncertainty buffers that reduce the catch limit as a function of the scientific uncertainty. This study compares the effectiveness of these two precautionary approaches in recovering over-exploited fish stocks. We evaluate the performance of more than 80 harvest control rules (HCRs) within a stochastic management strategy evaluation (MSE) framework for three stocks with contrasting life-history parameters and under various levels of scientific uncertainty. The results show that both approaches reduce the risk of overfishing at the expense of expected yield. This risk-yield trade-off strongly depends on the HCRs, life-history parameters of the species, as well as the level of the scientific uncertainty. Nevertheless, some combinations of biomass threshold and limit reference points as well as uncertainty buffers lead to a more favourable risk-yield trade-off than other rules. This study elucidates the multiple factors affecting the effectiveness of management strategies and highlights key features of HCRs for precautionary fisheries management.     

Creating wetland islands to enhance shoreline habitat for fish recruitment in a modified shallow lake

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Progress check of yielding ability and stability of selected pre-release bread-wheat cultivars in Zimbabwe

Journal of Crop Science and Biotechnology - The Crop Breeding Institute (CBI) develops new bread-wheat varieties as part of its research mandate. These are tested every year in multi-environmental...     

Dietary fatty acids modulate hormone repsonses in lactating cows: Mechanistic role for 5′-deiodinase activity in tissue

Supplemental dietary fat provides excess fatty acids (FA), which can alter circulating concentrations of several hormones. To test the effects of fatty acid isomer type and possible sites of regulation, we abomasally infused fat mixtures high in cis-C_18:1 FA (iTRS) or no infusion (NI) and performed intravenous arginine (ARG) and intramuscular thyrotropin-releasing hormone (TRH) challenges. The experimental design was a replicated 3 × 3 Latin square. Challenges were conducted on Days 10 (ARG) and 12 (TRH) after initiation of fat infusion on each of three 4-wk experimental periods. Plasma concentrations of IGF-I were lower (P < 0.01) when cows received iCIS or iTRS compared with NI. Plasma insulin concentrations increased with ARG but responses were not affected by FA. Plasma growth hormone (GH) was unchanged after ARG. Peak plasma GH and thyroid-stimulating hormone (TSH) responses to TRH were blunted (P < 0.05 and P < 0.1, respectively), whereas thyroxine (T₄) and triiodothyronine (T3) responses were augmented post-TRH (P < 0.01) when cows received either FA isomer. Prolactin responses to TRH were not different between infusion treatments, although basal plasma concentrations before TRH were higher in cows infused with iTRS (P < 0.05). To focus on fat regulation of the thyroid axis, we tested directly in vitro the ability of fatty acids dissolved with sodium taurocholate to affect Type-I 5'-deiodinase (5'D) activity in bovine liver homogenates. Homogenate 5'D was not affected by C_2:0---C10:0 fatty acids, but decreased linearly (P < 0.01) with increasing concentrations of C_12:0---C_16:0 and C_18:1 isomers. CisC_18:1 decreased 5′D more than the trans-isomer (P < 0.01), the difference was only apparent at concentrations greater than 0.25 mM. The data suggest that various aspects of pituitary hormone regulation are differentially affected by FA composition. Fatty acid infusion may accentuate end organ responses in the thyroid axis and decrease IGF-I in the somatotropic axis. The data also suggest that FA isomer may alter patterns of extrathyroidal generation of thyroid hormones via direct influences on 5′D.