Artificially regenerating longleaf pine in canopy gaps: initial survival and growth during a year of drought

Nitrogen fertilization in the nursery, along with altering the configuration of forest gaps, may improve the reforestation success of longleaf pine seedlings. During the very droughty 1998 growing season in Florida and Georgia, survival was higher under the forest canopy than in small (0.10 ha, 36 m diameter) and large (1.6 ha, 144 m diameter) canopy gaps. In the large gaps, survival of containerized seedlings was higher along the edges, particularly the SW edge. Shade from adult trees and the nurse effect of shrubs increased survival, while grass competition reduced survival. During dry years part of the “exclusionary zone” along the edge of canopy gaps (SW sector) may serve as a “survival zone”, at least in the short term. A model using oval-shaped gaps oriented from NW to SE, with an area of 0.25 ha is proposed to maximize the survival and growth of artificially regenerated longleaf pine seedlings.     

Clonal and seasonal differences in leaf osmotic potential and organic solutes of five hybrid poplar clones grown under field conditions

Leaf osmotic potential at full turgor (Psi(pio)) and the major solutes that contribute to osmotic potential were characterized in five hybrid poplar clones of Populus trichocarpa Torr. & Gray x P. deltoides Bartr. (TD) and P. deltoides x P. nigra L. (DN), growing under field conditions at two sites in eastern Washington and Oregon, USA. Trees were drip irrigated with 46, 76 or 137 cm of supplemental irrigation during each growing season. Trees at Wallula, WA, which were in their third growing season in 1994, were sampled twice a year for two years (1994 and 1995), and trees at Boardman, OR, which were in their second growing season in 1994, were sampled once a year for three years (1994-1996). At Wallula, the TD and DN clones exhibited lower predawn leaf water potentials in the 46-cm treatment than in the 137-cm treatment (-1.2 versus -0.7 MPa) during a hot, dry period in July 1994. Clone TD had a lower Psi(pio) than Clone DN (-1.67 versus -1.56 MPa) during the same period and the difference was also evident in 1995 (-1.81 versus -1.72 MPa) when trees were in their fourth growing season. There was also a significant treatment effect on Psi(pio) in Clone TD, with trees in the 46-cm treatment having lower Psi(pio) than trees in the 137-cm treatment in July 1994. At Boardman, Psi(pio) was generally high with no treatment differences during the 1994-96 samplings. The TD clones had significantly lower Psi(pio) than the DN clones in 1994 (-1.44 versus -1.36 MPa) and 1996 (-1.72 versus -1.54 MPa), but there was no difference between clones in 1995 (-1.40 versus -1.43 MPa). In 1995, at Wallula, osmotic adjustment in Clone TD was largely accounted for by an increase in sucrose, which constituted 70% of total organic solutes. Although the total concentration of free primary amino acids in this clone was 28% higher in trees in the 46-cm treatment than in trees in the 137-cm treatment, amino acids constituted only a small fraction of the total solute pool. Sixty-two percent of total solutes were inorganic ions in Clone TD compared to 52% in Clone DN, and potassium was the main ion constituting about 30% of total solutes and 50% of total ions. However, the clonal difference in Psi(pio) was not fully accounted for by the difference in solute concentration. Osmotic potential at full turgor declined over the growing season and with age. We conclude that, because the extent of osmotic adjustment exhibited by these clones was small, other drought resistance mechanisms contributed to the clonal differences in field performance.     

Predicting spring phenology and frost damage risk of Betula spp. under climatic warming: a comparison of two models

Timing of bud burst and frost damage risk for leaves of Betula spp. in response to climatic warming in Finland was examined with two models. In the first model, ontogenetic development in spring was triggered by an accumulation of chilling temperatures. The second model assumed an additional signal from the light climate. The two models gave radically different estimates of frost damage risk in response to climate warming. The chilling-triggered model forecast a significant and increasing risk with increased warming, whereas the light-climate-triggered model predicted little or no risk. The chilling-triggered model is widely applied in phenological research; however, there is increasing experimental evidence that light conditions play a role in the timing of spring phenology. Although it is not clear if the light response mechanisms are appropriately represented in our model, the results imply that reliance on a light signal for spring development would afford a degree of protection against possible frost damage under climate warming that would not be present if chilling were the sole determinant. Further experimental tests are required to ascertain the light-related mechanisms controlling phenological timing, so that credible model extrapolations can be undertaken.     

Osmotic potential of several hardwood species as affected by manipulation of throughfall precipitation in an upland oak forest during a dry year

Components of dehydration tolerance, including osmotic potential at full turgor (Psi(pio)) and osmotic adjustment (lowering of Psi(pio)), of several deciduous species were investigated in a mature, upland oak forest in eastern Tennessee. Beginning July 1993, the trees were subjected to one of three throughfall precipitation treatments: ambient, ambient minus 33% (dry treatment), and ambient plus 33% (wet treatment). During the dry 1995 growing season, leaf water potentials of all species declined to between -2.5 and -3.1 MPa in the dry treatment. There was considerable variation in Psi(pio) among species (-1.0 to -2.0 MPa). Based on Psi(pio) values, American beech (Fagus grandifolia Ehrh.), dogwood (Cornus florida L.), and sugar maple (Acer saccharum Marsh.) were least dehydration tolerant, red maple (A. rubrum L.) was intermediate in tolerance, and white oak (Quercus alba L.) and chestnut oak (Quercus prinus L.) were most tolerant. During severe drought, overstory chestnut oak and understory dogwood, red maple and chestnut oak displayed osmotic adjustment (-0.12 to -0.20 MPa) in the dry treatment relative to the wet treatment. (No osmotic adjustment was evident in understory red maple and chestnut oak during the previous wet year.) Osmotic potential at full turgor was generally correlated with leaf water potential, with both declining over the growing season, especially in species that displayed osmotic adjustment. However, osmotic adjustment was not restricted to species considered dehydration tolerant; for example, dogwood typically maintained high Psi(pio) and displayed osmotic adjustment to drought, but had the highest mortality rates of the species studied. Understory saplings tended to have higher Psi(pio) than overstory trees when water availability was high, but Psi(pio) of understory trees declined to values observed for overstory trees during severe drought. We conclude that Psi(pio) varies among deciduous hardwood species and is dependent on canopy position and soil water potential in the rooting zone.     

Tissue distribution of lignans in rats in response to diet, dose-response, and competition with isoflavones

This paper investigates the occurrence and distribution of the lignan metabolites enterodiol (END) and enterolactone (ENL) and the isoflavone daidzein (DAID) in rat tissues by use of liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MSn) following a variety of dietary regimes. Furthermore, we examined the dose-response and distribution of END and ENL in liver, testes, prostate, and lung, and we investigated the effects of competition between lignans and isoflavones on metabolite distribution. In liver, testes, prostate, and lung tissue, dose-related increases in END concentration were observed. In the testes, coadministration of 60 mg/kg secoisolariciresinol diglycoside (SDG) with 60 mg/kg isoflavones produced alterations in the resulting metabolite profile, causing increased END concentration and decreased DAID concentration. Results indicate lignan accumulation in tissues occurs, and coadministration of lignans with isoflavones affects the metabolite profile, with effects dependent on tissue type.     

Breast cancer prevention by green tea catechins and black tea theaflavins in the C3(1) SV40 T,t antigen transgenic mouse model is accompanied by increased apoptosis and a decrease in oxidative DNA adducts

Tea consumption is associated with a reduced risk of mammary cancer as reflected by epidemiological studies and experiments in carcinogen-induced rodent models of mammary carcinogenesis. We tested the hypothesis that green tea catechins (GTC) or theaflavins from black tea (BTT) interfere with mammary carcinogenesis in C3(1) SV40 T,t antigen transgenic multiple mammary adenocarcinoma (TAg) mice and that GTC/BTT affect tumor survival or oxidation status. TAg mice received GTC/BTT (0.05%) in drinking water for their lifetime. As compared to control mice, they survived longer and had smaller tumors. On microscopic inspection, the size of the largest tumor per mouse was decreased by 40-42% (p<0.01). GTC (0.01%) and BTT (0.05%) increased levels of cleaved caspase 3 in tumor tissue by 67 and 38%, respectively (p<0.05), intimating increased apoptosis. Tumor levels of the malondialdehyde-DNA adduct M1dG in mice receiving GTC or BTT (0.05%) were reduced by 78 (p<0.001) or 63% (p<0.05), respectively, as compared to controls. The results render the exploration of the breast cancer chemopreventive properties of tea preparations in humans worthwhile.     

Calcium, diet and fracture risk: a prospective study of 1898 incident fractures among 34 696 British women and men

OBJECTIVE: The risk factors for fractures are incompletely understood. An outstanding question concerns the optimal amount of dietary calcium needed to minimise the risk of fracture. DESIGN: We examined the associations of dietary calcium and other nutrients with self-reported fracture risk in a prospective cohort study. Nutrient intakes were estimated using a semi-quantitative food-frequency questionnaire administered at recruitment. SETTING: The UK. Participants: A total of 26 749 women and 7947 men aged 20-89 years. RESULTS: Over an average of 5.2 years of follow-up, 1555 women and 343 men reported one or more fractures, 72% of these resulting from a fall. Among women, fracture risk was higher at lower calcium intakes, with a relative risk of 1.75 (95% confidence interval (CI) 1.33-2.29) among women with a calcium intake of < 525 mg day- 1 compared with women with a calcium intake of at least 1200 mg day- 1 (test for linear trend, P < 0.001). The association of dietary calcium with fracture risk was stronger among women aged under 50 years at recruitment than among women aged 50 and above. Dietary calcium intake was not associated with fracture risk in men. Fracture risk was not related to the dietary intake of any other nutrient examined. CONCLUSION: In this population, women with a low dietary calcium intake had an increased risk of bone fracture, and this association was more marked among younger women than among older women.     

Mechanisms and management of acaricide resistance for Tetranychus urticae in agroecosystems

Journal of Pest Science - The two-spotted spider mite, Tetranychus urticae Koch, is a constant threat to sustainable production of numerous economically important crops globally. Management of T....     

A spatial risk assessment of bighorn sheep extirpation by grazing domestic sheep on public lands

Bighorn sheep currently occupy just 30% of their historic distribution, and persist in populations less than 5% as abundant overall as their early 19th century counterparts. Present-day recovery of bighorn sheep populations is in large part limited by periodic outbreaks of respiratory disease, which can be transmitted to bighorn sheep via contact with domestic sheep grazing in their vicinity. In order to assess the viability of bighorn sheep populations on the Payette National Forest (PNF) under several alternative proposals for domestic sheep grazing, we developed a series of interlinked models. Using telemetry and habitat data, we characterized herd home ranges and foray movements of bighorn sheep from their home ranges. Combining foray model movement estimates with known domestic sheep grazing areas (allotments), a Risk of Contact Model estimated bighorn sheep contact rates with domestic sheep allotments. Finally, we used demographic and epidemiologic data to construct population and disease transmission models (Disease Model), which we used to estimate bighorn sheep persistence under each alternative grazing scenario. Depending on the probability of disease transmission following interspecies contact, extirpation probabilities for the seven bighorn sheep herds examined here ranged from 20% to 100%. The Disease Model allowed us to assess the probabilities that varied domestic sheep management scenarios would support persistent populations of free-ranging bighorn sheep.