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961.
We investigated effects of stem phloem girdles on apical control of branch angle, stem and branch growth and stem air content in six conifer species. A stem girdle 2 cm above a branch caused the branch to bend upward in all six species. Upward bending was associated with increased formation and action of compression wood (CW) in the lower portion of the branch. Compression wood also formed in the main stem below the branch, suggesting increased auxin production in the branch. A stem girdle 2 cm below a branch (the branch remained directly connected to the apex and distal branches) released the branch from apical control in Tsuga canadensis (L.) Carr., Pinus contorta Dougl. ex Loud. and Pseudotsuga menziesii (Mirb.) Franco. The branch bent up, but there was no CW formation in the stem. In Pinus rigida Mill., the branch exhibited increased cambial activity but did not bend up. A stem girdle > 20 cm below a branch did not release the branch from apical control in any of the species. These results support the hypothesis that branches compete with the subjacent stem for branch-produced photosynthate and that when the branch lacks this competitive sink it is released from apical control. A stem girdle 2 cm below a branch did not cause release of apical control in either Juniperus virginiana L. or Picea abies (L.) Karst. In these species, decreased shoot elongation and cambial activity above the girdle probably prevented release. A stem girdle 2 cm below a branch increased air content in the stem below the girdle in four of five species, whereas the other girdle treatments had no significant effect on stem air content. Although growth was inhibited above the girdle in the two species with the largest increase in air content, growth was not inhibited in the other species. High air content in stem segments isolated from distal auxin and carbohydrate sources is consistent with the hypothesis that a carbohydrate supply is required to refill embolized cells. 相似文献
962.
To record photosynthetically active radiation (PAR) simultaneously at a number of points throughout a forest canopy, we developed a simple, inexpensive (< $10 US) current-to-voltage converter that processes the current generated by a photodiode radiation sensor to a voltage range that is recordable with a miniature data logger. The converter, which weighs less than 75 g and has a volume of only 100 cm(3), is built around an ultra-low power OP-90 precision operational amplifier, which consumes less than 0.5 mA at 9 V when converting the output of a Li-Cor LI-190SA quantum sensor exposed to photosynthetically active radiation (PAR) of 2500 &mgr;mol m(-2) s(-1) or only 5 &mgr;A in low light. A small 9-V battery thus powers the amplifier for more than 1000 h of continuous operation. Correlations between photometer readings and voltage output from the current-to-voltage converter were high and linear at both high and low PAR. Sixteen Li-Cor LI-190SA quantum sensors each equipped with current-to-voltage converters and connected to a miniature data logger were deployed in the upper branches of a Panamanian tropical rainforest canopy. Each unit performed reliably during a one- or two-week evaluation. 相似文献
963.
Dipl.-Forstwirt Barbara Luber 《Journal of pest science》1983,56(1):9-10
Old larvae ofN. sertifer treated with SIR Bay 8514, an insect growth regulator similar to Diflubenzuron produced partly (17–24%) abnormal cocoons showing a hole or a broad fissure in their middle region. Such phenomenon was not known hitherto. 相似文献
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Thomas Wutzler Barbara Köstner Christian Bernhofer 《European Journal of Forest Research》2007,126(3):371-383
The Kyoto-protocol permits the accounting of changes in forest carbon stocks due to forestry. Therefore, forest owners are
interested in a reproducible quantification of carbon stocks at the level of forest management units and the impact of management
to these stocks or their changes. We calculated the carbon stocks in tree biomass and the organic layer including their uncertainties
for several forest management units (Tharandt forest, Eastern Germany, 5,500 ha) spatially explicit at the scale of individual
stands by using standard forest data sources. Additionally, soil carbon stocks along a catena were quantified. Finally, carbon
stocks of spruce and beech dominated stands were compared and effects of thinning intensity and site conditions were assessed.
We combined forest inventory and data of site conditions by using the spatial unions of the shapes (i.e., polygons) in the
stand map and the site map. Area weighted means of carbon (C) stocks reached 10.0 kg/m2 in tree biomass, 3.0 kg/m2 in the
organic layer and 7.3 kg/m2 in mineral soil. Spatially explicit error propagation yielded a precision of the relative error
of carbon stocks at the total studied area of 1% for tree biomass, 45% for the organic layer, and 20% for mineral soil. Mature
beech dominated stands at the Tharandt forest had higher tree biomass carbon stocks (13.4 kg/m2) and lower organic layer carbon
stocks (1.8 kg/m2) compared to stands dominated by spruce (11.6, 3.0 kg/m2). The difference of tree biomass stocks was mainly
due to differences in thinning intensity. The additional effect of site conditions on tree carbon stocks was very small. We
conclude that the spatially explicit combination of stand scale inventory data with data on site conditions is suited to quantify
carbon stocks in tree biomass and organic layer at operational scale. 相似文献
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Barbara Glanemann Karen Humm Mariana Abreu Sophie Aspinall David Buckeridge Hope Carveth Hannah Darcy Jessica Florey Polly Frowde Isuru Gajanayake Kate Green Emma Holmes Alenka Hrovat Anne-Katherine Jasensky Bryn A Jones Vasiliki Lantzaki Eve JY Lo Kirsty MacDonald Kevin O'Brien Alejandro Suárez-Bonnet Nele Van den Steen Balazs Szladovits Annelies Willems Helen Wilson 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2023,37(1):126-132