Large-scale historical afforestation failure with Pinus cembra in the Swiss Prealps

New Forests - Between the nineteenth and early twentieth centuries, large-scale afforestation projects were undertaken in the Swiss Prealps. The Swiss stone pine (Pinus cembra L.), an emblematic...     

Infection of Norway spruce (Picea abies (L.) Karst.) seedlings with Pythium irregulare Buism. and Pythium ultimum Trow.: histological and biochemical responses

We have studied the reaction of Picea abies seedlings to infection with Pythium. The highly virulent species Pythium ultimum and the less virulent species Pythium irregulare germinated on the root and hypocotyl surface, formed appressoria and penetrated through the stomata as well as through the epidermis. No major differences in the growth of both fungal species were observed during the early events of colonization. The less virulent species formed about 25% more appressoria suggesting that the fungus experienced difficulties with penetration. Differences were observed in the response of the host plant to infection. Autofluorescence, possibly related to deposition of lignin or lignin-like materials increased more in cortical and endodermal tissue colonized with the highly virulent P. ultimum than with the less virulent P. irregulare. Chitinase activity was highest in the tissues most extensively colonized by the fungus. In addition, a systemic increase of chitinase activity was also detected. Interestingly, chitinase activity increased systemically in cotyledons which were never in contact with the pathogen, indicating the translocation of a systemic signal. Salicylic acid was also detected in spruce seedlings; its level increased in roots during infection with the less virulent P. irregulare.     

Effects of 2,3,6-TBA on seed germination,early development,and mortality of Pinus resinosa seedlings1

This study shows extreme phytotoxicity of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) to Pinus resinosa seedlings in the cotyledon stage of development. 2,3,6-TBA caused abnormal seedling development and mortality.     

Effects on seedling development of direct contact of Pinus resinosa seeds or young seedlings with Captan1

Captan, at concentrations up to 2500 ppm did not affect seed germination of Pinus resinosa Ait. However, concentrations of 500 ppm or higher injured roots, stems, and cotyledons within 13 days. Root injury consisted of collapse of root hair cells, epidermal cells, and cortical cells; cotyledon injury of collapse of epidermal and mesophyll cells.     

Thermal and mechanical properties of flax-reinforced polycaprolactone composites

Thermomechanical and mechanical properties of polycaprolactone/flax composites were investigated. The composites were prepared by melt mixing with three different filler loadings. Except from heating (to eliminate the moisture) no other procedures were applied to the raw materials, neither compatibilizer agent was used. The tensile and impact properties were evaluated and dynamic mechanical analysis was performed. Additionally the materials have been characterized by means of DSC technique. The resulting material reveal enhanced mechanical properties due to reinforcement caused by fibers and by high interfacial adhesion.     

Effects of transpiration rate on boron uptake by roots and translocation to shoots of table beets (Beta vulgaris L.) 1

The effects of transpiration rate on B uptake by roots and translocation to shoots of table beet (Beta vulgaris L. cv. Red Ace) plants were studied under conditions of environmental control. Plants grown under high or low relative humidities (RH) had low or high rates of transpiration, respectively. Dry weights and B contents of shoots and roots were higher among plants grown at 80% RH and B concentrations of roots were lower compared to plants grown at 30% RH. Shoot B concentrations were not affected by RH. Rates of growth and B accumulation in shoots were closely correlated for plants grown in 30% or 80% RH. These parameters were not closely correlated in roots.

The rate of B uptake per g root dry weight was greater in plants having higher transpiration rates; whereas the rate of B translocation to shoots per g dry weight was independent of transpiration rate. Thus we propose that B translocation to shoots is controlled mechanistically by rates of dry matter accumulation during stages of rapid growth, i.e. a sink effect.     

Influence of Livestock Grazing Strategies on Riparian Response to Wildfire in Northern Nevada

In 1999–2001 wildfires burned 1.13 million ha across northern Nevada, burning through many grazed riparian areas. With increases in wildfire frequency and extent predicted throughout the Great Basin, an understanding of the interactive effects of wildfire, livestock grazing, and natural hydrologic characteristics is critical. A comparison of pre- and postfire stream surveys provided a unique opportunity to statistically assess changes in stream survey attributes at 43 burned and 38 unburned streams. Livestock grazing variables derived from an extensive federal grazing allotment inventory were used to identify interactive effects of grazing strategies, fire, and natural stressors across 81 independent riparian areas. Differences between baseline and “postfire” stream survey attributes were evaluated for significance using the nonparametric Mann–Whitney test for paired data. Binary logistic regression models evaluated the influence of fire, grazing, and hydrologic characteristics on observed stream survey attribute changes. Grazing attributes contributed most significantly to the bankfull width increase and bank stability rating decrease models. The odds of bankfull width degradation (increase in bankfull width) decreased where there had been rest is some recent years compared to continuous grazing. As the number of days grazed during the growing season increased, the odds of bank stability degradation also increased. The occurrence of fire was not significant in any model. Variation in the riparian width model was attributed primarily to hydrologic characteristics, not grazing. For the models in which grazing variables played a role, stream survey attributes were more likely to improve over time when coupled with a history of rotational grazing and limited duration of use during the growing season. This supports long-term riparian functional recovery through application of riparian complementary grazing strategies.     

Past,present and future suitable areas for the relict tree Pterocarya fraxinifolia (Juglandaceae): Integrating fossil records,niche modeling,and phylogeography for conservation

European Journal of Forest Research - Pterocarya fraxinifolia, native to the southern Caucasus and adjacent areas, has been widely introduced in Europe. In this study, we investigate the following:...