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1.
A dendrochronological technique was used to investigate canopy recruitment of beech (Fagus engleriana Seem.) trees in western Hubei Province of Central China by identifying growth releases through gap formation. The results
indicated that 83% and 17% of the canopy trees regenerate in gaps and the understory, respectively. Radial growth analyses
demonstrated that there are three modes for beech regeneration and canopy recruitment: (1) gap origin without suppression;
(2) gap origin with period(s) of suppression; and (3) understory origin. Multiple periods of release and suppression imply
that beech regeneration and canopy recruitment are very sensitive to gap formation. 相似文献
2.
M. Panayotov D. KulakowskiL. Laranjeiro Dos Santos P. Bebi 《Forest Ecology and Management》2011,262(3):470-481
Correct knowledge of disturbance ecology is essential for understanding the characteristic behavior of forest ecosystems and for guiding appropriate management strategies. However, the role of natural disturbances in shaping European mountain forest ecosystems has not been adequately studied, possibly because of the perception that the development of most European forests is primarily shaped by human influences and/or fine-scale gap-phase dynamics.In the present study, we investigate the long-term disturbance history of old protected forest dominated by Norway spruce in the Parangalitsa Reserve, Bulgaria. We used aerial photo interpretation and dendroecological methods to reconstruct the history of wind, insect, and fire disturbances across a topographically complex landscape. Over the past 150 years wind has been the most important disturbance agent in this ecosystem and at least 18% of the forested area shows evidence of high-severity blowdowns. Windthrow patches ranged in size from <1 ha to >10 ha (minimum 0.11 ha, mean 0.16 ha, maximum 10 ha). Although small disturbances were much more frequent, few larger blowdowns accounted for most of the disturbed area. Pure coniferous and single-cohort coniferous forest patches were more affected by blowdowns than mixed coniferous-deciduous and multi-cohort coniferous forest patches. Although bark beetle (Ips typhographus) populations were large enough to cause mortality of some live trees, the populations did not grow to epidemic proportions during recent decades. Fire disturbance was of limited importance in the last 200 years and only two patches (4% of the study area) showed evidence of fire.The present research indicates that wind disturbances have been characteristic of these ecosystems at least over the past decades to centuries. Thus, blowdowns appear integral to the normal function and structure of the Picea-dominated mountain forests in the region and such events, in and of themselves, do not represent unhealthy forest conditions or environmental emergencies. Management strategies that aim to maintain these ecosystems within a natural range of variation should incorporate wind disturbances into the management strategy. The frequency and magnitude of future wind disturbances may be considered within the historical framework described in the current study to assess potential effects of climate change on altered disturbance regimes. 相似文献
3.
Potential role of soil calcium in recovery of paper birch following ice storm injury in Vermont, USA
Joshua M. Halman Paul G. SchabergGary J. Hawley Christopher F. Hansen 《Forest Ecology and Management》2011,261(9):1539-1545
In recent years, an increased number of mature paper birch (Betula papyrifera Marsh.) and heart-leafed paper birch (B. papyrifera var. cordifolia (Regel) Fern.) in northeastern United States forests have exhibited decline symptoms including foliar loss, reduced fine branching, and tree mortality. We assessed crown health, radial growth, and available soil cations in 2006 as a preliminary assessment of factors that may be influencing paper birch decline. Tree rings began to decrease in width in 1998—the year of a severe region-wide ice storm. All trees (regardless of their current decline status) experienced reduced growth starting in 1998 and tree growth continued to decrease for two years following the ice storm. After this generalized growth decrease, trees that now have vigorous crowns showed a marked increase in growth, whereas trees that now have low crown vigor did not rebound in growth, but instead exhibited a significantly higher incidence of locally absent annual rings. Extractable soil-aluminum (Al), a phytotoxic element mobilized by acid deposition, was significantly higher in soils associated with declining trees compared to those adjacent to vigorous trees. Higher soil calcium (Ca) availability was associated with both vigorous crowns and increased radial growth following the 1998 ice storm. Furthermore, increased soil Ca availability was negatively correlated to the percentage of declining trees, and positively related to increased radial growth, whereas elevation was not significantly associated with either parameter. Although previously overlooked as a factor influencing paper birch recovery from injury, we found that available soil Ca was linked to crown vigor and rebounds in growth following an inciting event. 相似文献
4.
A long history of human presence in the Alps has made studies of natural forest structure, composition, and disturbance processes difficult. In the Slovenian Alps, we identified a mixed European beech (Fagus sylvatica L.)-silver fir (Abies alba Mill.)-Norway spruce (Picea abies (L.) Karst.) stand with old-growth characteristics that escaped past cutting. We reconstructed the dynamics of the stand using a combination of stand and age structure analyses, dendroecological evidence of past canopy disturbance, and historical evidence of past human activities. The disturbance reconstruction revealed a stand-scale disturbance in the 1850s. Based on the presence of pit-and-mound topography throughout much of the stand and the absence of logging activities found in historical records, we assume this event was caused by strong winds. The current structure and composition of the stand are largely a result of this event. Post-disturbance forest development was dominated by the release of shade tolerant regeneration, especially F. sylvatica. The windthrow also created appropriate conditions (i.e. increased light and exposed mineral soil) for recruitment of less shade tolerant species, including larch (Larix decidua Mill.) and maple (Acer pseudoplatanus L.). The results suggest that periodic, intermediate severity wind disturbances, similar to the event documented here, may have had an important influence on pre-settlement forest dynamics in mixed mountain forests of the Alps, and add to the limited available information regarding the historic range of natural variability of disturbance processes. This information may be useful for forest management that attempts to emulate natural processes. 相似文献
5.
We investigated the temporal dynamics of large woody debris (LWD) in five headwater streams before and after the 2001 Dogrib fire in the foothills of Alberta. The density of LWD varied from 5 to 41 logs per 50 m of stream reach and accounted for 19.4 ± 5.1 m3 ha−1 (mean ± standard error) of wood in the riparian zones and 114.1 ± 30.1 m3 ha−1 of wood in the bankfull margins of the stream channel. Individual logs averaged 18.9 ± 1.15 cm in diameter, 5.5 ± 0.7 m in length, and 0.2 ± 0.02 m3 in volume. Logs became significantly shorter in decay classes II–IV. Bridges were longer than partial bridges, which were longer than loose and buried LWD. Individual log volume was greatest for bridges, but not significantly different among other position classes. Bridges and loose LWD contributed little to stream morphology and function; however, 55% of partial bridges and all buried logs contributed to sediment storage, channel armouring, or riffles and pools in the stream channel. 相似文献
6.
Peter Kirchner Franco Biondi Ross Edwards Joseph R. McConnell 《Journal of Forest Research》2008,13(6):347-356
Trace metal accumulation in tree rings of Jeffrey pines (Pinus jeffreyi) from the Lake Tahoe basin (Sierra Nevada, CA, USA) was determined using high resolution inductively coupled plasma mass
spectrometry (HR-ICP–MS). The objectives of this study were (1) to establish baseline values for aluminium (Al), chromium
(Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), strontium (Sr), cadmium (Cd), barium (Ba),
and lead (Pb); (2) to investigate the intra-tree and inter-tree variability of these trace metals, and (3) to assess differences
in metal concentrations related to automobile traffic. Two field collection sites were selected with similar ecologic attributes,
one proximal to a heavily traveled highway, and the other isolated from any local source of auto emissions. At each site two
trees with similar features were selected, and two increment cores collected from each tree. Cores were cross-dated, cleaned
of contamination, dissected into 5-year increments, ashed, and acid digested, before analysis by HR-ICP–MS. Time series spanning
191–326 years were developed for the 12 trace metals. Variability was high within and between trees, most likely because of
physiologic mechanisms for element sequestration and allocation. The best intra-tree correlation was found for Ba, Sr, Mn,
and Co; of these elements, Co showed an overall increase over time, whereas Sr and Ba displayed an opposite trend, and Mn
fluctuated over time. Mean Co concentration at the near-highway site was higher, whereas mean Sr, Ba, and Mn concentrations
were lower, than at the control site. 相似文献
7.
Christoph Dittmar Wolfgang Fricke Wolfram Elling 《European Journal of Forest Research》2006,125(3):249-259
Phenological, temperature, and tree-ring data were used in order to identify and quantify the impact of late frosts on common beech (Fagus sylvatica L.) at different altitudes in Southern Germany during the last century. For this intention, dendroecological investigations were made upon trees at the Meteorological Observatory Hohenpeißenberg as well as from seven stands in the Bavarian Forest and 17 stands at the northern fringe of the Alps. From these locations, a considerable number of severe growth minima in the tree-ring series could be related to late frost in the days of or immediately after leaf unfolding. The frequency of frost-related growth minima increases with altitude. In individual years, radial growth can be reduced by more than 90% (stand mean) in relation to the average growth of the ten previous years. Hence, late frosts are considered as important ecological events that strongly affect beech vitality and competitiveness especially at high altitudes. Evidence of significant impacts on radial growth by late frosts distinct before leaf unfolding or with temperatures above ?3°C was not found. Also, increasing frequency and intensity of late frosts during recent decades were not ascertained. Hence, the recently observed decreased vitality of common beech accompanied by growth depressions especially at high altitude sites in Central Europe cannot be explained as a consequence of late frost damage. 相似文献
8.
《Scandinavian Journal of Forest Research》2012,27(2):151-160
A particle inflow gun enabled efficient production of transgenic plantlets of Picea abies from embryogenic suspension cultures. In transient assays, the Zea ubiquitin promoter was 12-16 times as active as the 35S promoter. For stable transformation, the plasmid pAHC25 contained the bar gene and the gusA gene, both driven by the Zea ubiquitin promoter. Cells were maintained from 1 to 3 h before bombardment on proliferation medium supplemented with 0.25 M myoinositol and, from day 8, supplemented with Basta as selective agent. Embryogenic colonies resistant to Basta appeared from two months after bombardment. Of over 100 independent Basta-resistant sublines tested, 65% expressed the co-transformed reporter gene, even when it was not linked to the selectable marker. Over 80% of the sublines retained their embryogenic potential. Of 11 transformants analyzed, 4 contained transgenes in low copy number (1-3), the rest contained transgenes in up to 15-20 copies. Over 200 Basta-resistant sublines from four cell lines have been established, of which 138 are confirmed as transformed. Plantlets have been regenerated and grown on in pots. 相似文献
9.
Jesús Julio Camarero Christof BiglerJuan Carlos Linares Eustaquio Gil-Pelegrín 《Forest Ecology and Management》2011,262(5):759-769
The causal factors and effects of forest declines are not well understood in temperate conifer forests. Most studies have focused on climatic and environmental stressors and have obviated the potential role of historical forest management as a predisposing factor of decline. Here, we assess if the recent silver fir (Abies alba) decline observed in the Spanish Pyrenees was predisposed by historical logging and incited by warming-induced drought stress. We analysed a dataset of environmental, structural, and historical variables at the tree and stand level including 32 sites with contrasting degrees of defoliation distributed over 5600 km2. We followed a dendroecological approach to reconstruct historical logging and to infer the effects of warming-induced drought stress on growth. The silver fir decline was more severe and widespread in western low-elevation mixed forests dominated by trees of small size and slow growth. These sites were subject to higher water deficits than eastern sites, where late-summer rainfall as the key climatic variable controlling silver fir growth was higher. Declining sites showed more frequent growth releases induced by historical logging than non-declining sites. Historical logging and warming-induced drought acted as long-term predisposing and short-term inciting factors of silver fir decline in the Pyrenees, respectively. We suggest that biomass increases caused by past intense logging affected the vulnerability of silver fir against late-summer water deficit. Future research in declining temperate conifer forests should consider the interacting role of predisposing historical management and inducing climatic stressors such as droughts. 相似文献
10.
Wolfram Elling Christoph Dittmar Klaus Pfaffelmoser Thomas Rötzer 《Forest Ecology and Management》2009
Causes of decline and silver fir (Abies alba Mill.) mortality in Central Europe have been controversially discussed for a long time. This contribution details a comprehensive dendroecological investigation of two basic and alternative hypotheses that explain the decline by either climatic influences or by SO2 pollution as the primary factors. Growth reduction between the 1960s and 1980s as well as the recovery of growth during recent decades have be seen as a response to complex interactions of multiple factors. Herein, we undertake a multidisciplinary evaluation of a broad database, representing the long-term growth of 1010 firs from 51 sites, long-term climate records as well as data assessing the long-term pollution situation in Southern Germany. The results provide clear evidence that SO2-immissions play a key role in decline and that tree growth corresponds with the regional and temporal pattern of SO2 pollution. Calculations with a new complex growth model indicate that tree-ring widths of fir at many sites were more influenced by SO2 than by any other growth-determining factor during the second half of the last century. Strongest coherence between measured and modelled ring widths are found if – in addition to temperature, available soil water content, heavy frost events and long-term growth trends – the site-specific trend of SO2 pollution is included. Both the immediate response to SO2 pollution and the quick recovery of fir since the beginning of the 1980s after the decrease of SO2 emissions indicate a direct impact of SO2 in gaseous form and not via the soil in terms of soil acidification. Tree-ring widths document that radial growth response occurs at air concentrations above 10 μg SO2 m−3 (annual average), which can be thought of as a critical threshold for silver fir health. Since the beginning of the 1980s, increasing growth trends have been observed which predominantly result from decreased SO2 pollution in most parts of Central Europe, although climate change, fertilization by nitrogen deposition and a reduced tree-to-tree competition are also relevant factors. The drastic reduction of SO2 emission during the recent decades significantly improved the environmental conditions for fir. Consequently, an increased cultivation of silver fir on suitable sites is recommended. 相似文献