共查询到6条相似文献,搜索用时 3 毫秒
1.
Tiemo Kahl Christian Wirth Martina Mund Gerhard Böhnisch Ernst-Detlef Schulze 《European Journal of Forest Research》2009,128(5):467-473
To evaluate the mass of coarse woody debris (CWD), it is necessary to quantify its density. Drill resistance measurements
are introduced as a approach to estimate the density of CWD in different stages of decay. Dead logs of Norway spruce [Picea abies (L.) Karst.] from a Central European mountainous site were used as a test system to compare the new method with conventional
predictors of wood density such as fast quantitative field estimates (e.g., knife probe) and classification of decay classes
based on a set of qualitative traits and quantitative estimates. The model containing only drill resistance as a predictor
explained 65% of the variation in wood density and was markedly better than models containing one or more of several conventional
predictors. However, we show that the relationship between drill resistance and gravimetric wood density relationship is sensitive
to the decay status. Therefore, the best model combines drill resistance and decay class (adj. R2 = 0.732). An additional experiment showed that drill resistance is also sensitive to the moisture state (fresh vs. oven-dry)
of the sample. The major potential of the method lies in its non-destructive nature which allows repeated sampling in long-term
ecosystem studies or in protected areas where destructive sampling is prohibited. The limitations of the method are discussed
and recommendations for applications are given. 相似文献
2.
《Scandinavian Journal of Forest Research》2012,27(6):496-504
The effect of the timing of precommercial thinning on the productivity of work was examined in young Norway spruce [Picea abies (L.) Karst.] stands in southern Finland. The common problem of large variation between sample plots in time studies was avoided by introducing a new approach based on a combination of stand measurements, tree-ring analysis and existing work productivity functions. The results indicated that a 2 year delay in the precommercial thinning of a stand was enough to cause an increase of 10-42% in the consumption of working time at a mean height of 1.5-3.1 m. At a later thinning, at a mean height 4.1-7.2 m, the increase was 8-24%. The development of the stand up to the first commercial thinning was not significantly influenced by a 2 year delay in the late precommercial thinning. 相似文献
3.
《Scandinavian Journal of Forest Research》2012,27(3):213-222
Forest management practices have led to a reduction in the volume and a change in the composition of coarse woody debris (CWD) in many forest types. This study compared CWD volume and composition in reserves and two types of managed forest in the central boreal zone of Sweden. Ten areas were surveyed, each containing clear-cut, mature managed and old-growth stands, to determine the volume of standing and lying CWD in terms of species composition, decay class and size class. Volumes of CWD on clear-cuts and in mature managed forests were high compared with previous studies. Old-growth forests (72.6 m3 ha?1) contained a greater volume of CWD than mature managed forests (23.3 m3 ha?1) and clear-cuts (13.6 m3 ha?1). Differences were greatest for the larger size classes and intermediate decay stages. Despite stand ages being up to 144 years, CWD volume and composition in managed forests was more similar to clear-cuts than to old-growth forests. 相似文献
4.
《Scandinavian Journal of Forest Research》2012,27(6):498-504
Abstract Abundant flowering occurred in a central Swedish trial with 10-yr-old Picea abies L. (Karst.) cuttings, taken on 4-yr-old seedlings. Large deviations in cone-set between clones were assumed to reflect different stages in transition from juvenile to flowering competent phase. Rooting success and first-yr growth performance (leader length, leader origin and plagiotropic growth) were studied on cuttings originating from the upper and lower parts of the crown in 15 clones with heavy cone-set and 15 clones without cones. Twigs from the lower part of the crown had a significantly higher rooting percentage. Cone-set did not have an effect on any of the variables analysed. The results suggest that flowering ability and rooting capacity are independent age-related processes, implying that selection for high rooting capacity in clonal forestry does not reduce flowering competence. The results will have a great impact on breeding of P. abies, since both early flowering and high rooting ability are important traits for reducing the turnover time of the breeding cycle. 相似文献
5.
When spring frosts occur on recently planted forest sites, severe damage may occur to the seedlings. The aim of the present study was to test how different low levels of nutrient concentrations in Norway spruce (Picea abies (L.) Karst.) seedlings affected spring frost hardiness and time of bud break. Seedlings were grown in a greenhouse for one season and supplied with fertiliser containing 22, 43 and 72 mg N l–1, respectively. The treatments resulted in needle nitrogen concentrations ranging from 0.9 to 1.8% in autumn. After winter storage at 0 °C, bud break was recorded on seedlings growing in the greenhouse, outdoors and in growth chambers at 12 °C and at 17 °C. Freezing tests were performed on seedlings directly removed from winter storage and following one week growth in the greenhouse. Seedlings receiving fertiliser with 43 mg N l–1 had less freezing injury than the two other fertilisation treatments in the present study. The earliest bud break occurred in seedlings receiving 72 mg N l–1. 相似文献
6.
《Scandinavian Journal of Forest Research》2012,27(1-4):341-346
Endogenous gibberellin A1 (GA1), GA3, GA4 and GA9 were quantitated in elongating shoots of Norway spruce [Picea abies (L.) Karst.] grafts with a good or a poor flowering history. The grafts were grown either in a natural environment outdoors, cool and wet (CW) treatment, or in a greenhouse with elevated temperatures and controlled drought stress, hot and dry (HD) treatment. The GAs were quantitated by gas chromatography‐mass spectrometry selected ion monitoring (GC‐MS SIM) using deuterated GA1, GA3, GA4 and GA9 as internal standards. Terminal shoots from the second whorl of branches were harvested at 76%, 86% and 96% shoot elongation for the CW treated grafts and at 90% and 99% shoot elongation for the HD treated grafts. The content of GAs in the CW grafts was highest during most rapid shoot elongation, GA9 being the dominant GA. The levels decreased as shoot elongation ceased. This was also noted for GA‐content in shoots of the HD treated grafts. A comparison of the GA‐amounts at ca. 96% of total shoot elongation for the CW treated grafts and ca. 99% of total shoot elongation for the HD treated grafts revealed that shoots of the good flowering clone had a higher content of GA9 and a lower content of GA, and GA3. When comparing the HD treated and CW treated grafts, the shoots of HD treated grafts contained higher concentrations of GA9 but lower concentrations of GA, and GA3. Calculating the ratios between [GA9] and [GA1] resulted in a ratio of 12.5 and 36.6 for the good flowering clone grown outdoors and in greenhouse, respectively. The same ratios were for the poor flowering clone 1.45 and 3.8 when grown outdoors and in greenhouse, respectively. A higher ratio may indicate a higher capacity of synthezise the importance of flowering GA4 from GA9 and a lower conversion of GA4 to GA1, thereby favouring the diffentiation to reproductive buds. 相似文献