Twenty-six years of aspen regeneration under varying light conditions in a boreal mixedwood forest

Density, height, and diameter at breast height of trembling aspen (Populus tremuloides Michx.) sucker regeneration were assessed over a 26-year period in openings created by harvesting in a 40-year-old aspen stand in northeastern Ontario (Canada). The opening types were 9- and 18-m diameter circles, 9- and 18- 150-m east-west strips, and a 100- 150-m clearcut, representing a range of light conditions. Density, height, and diameter at breast height of aspen regeneration were significantly affected by opening type, location relative to opening, and time since harvest. By year 26, aspen densities in circular openings declined to 0, despite high initial recruitment, and trembling aspen heights were significantly lower in the 9-m strips than in the 18-m strips or the clearcut. Year 26 aspen density, volume, and basal area increased with increasing initial light intensity, with the highest rate of increase between 80 and 100% light levels. Understory vegetation cover was largely unaffected by opening size; however, substantial understory aspen regeneration occurred in the smaller openings. Results support the traditional view that aspen is best managed under the clearcut silvicultural system, and >80% full light is recommended for adequate long-term aspen regeneration.

Twenty-six years of aspen regeneration under varying light conditions in a boreal mixedwood forest

Density, height, and diameter at breast height of trembling aspen (Populus tremuloides Michx.) sucker regeneration were assessed over a 26-year period in openings created by harvesting in a 40-year-old aspen stand in northeastern Ontario (Canada). The opening types were 9- and 18-m diameter circles, 9- and 18- _ 150-m east-west strips, and a 100- _ 150-m clearcut, representing a range of light conditions. Density, height, and diameter at breast height of aspen regeneration were significantly affected by opening type, location relative to opening, and time since harvest. By year 26, aspen densities in circular openings declined to 0, despite high initial recruitment, and trembling aspen heights were significantly lower in the 9-m strips than in the 18-m strips or the clearcut. Year 26 aspen density, volume, and basal area increased with increasing initial light intensity, with the highest rate of increase between 80 and 100% light levels. Understory vegetation cover was largely unaffected by opening size; however, substantial understory aspen regeneration occurred in the smaller openings. Results support the traditional view that aspen is best managed under the clearcut silvicultural system, and >80% full light is recommended for adequate long-term aspen regeneration.

Nesting near road edges improves nest success and post-fledging survival of White-rumped Shamas (Copsychus malabaricus) in northeastern Thailand

ABSTRACT Road edges in the temperate zone often negatively affect reproductive success, post-fledging survival, and dispersal of forest birds through processes associated with edge habitats. This pattern is less clear in the tropics due to a lack of studies using natural nests and radio-tagged fledglings as well as an almost complete absence of information on nest and fledgling predators. We investigated the influence of road edge on nest success, post-fledging survival, and dispersal of White-rumped Shama (Copsychus malabaricus) in a dry evergreen forest in northeastern Thailand. One hundred nest boxes were placed in forest interior (≥1,000 m from edge of a 5-lane highway) and 100 near forest edge (≤200 m) to assess nesting success. We radio-tracked 50 fledglings from these boxes, 25 each for edge and interior, for 7 weeks after fledging. Nest success and post-fledging survival were 11.6% and 23.6% higher at the edge versus the interior. Predation had the strongest influence on survival, accounting for 100% of nest and 94% of fledgling mortality. Fledglings used locations with denser understory vegetation cover relative to the available habitat, probably to reduce predation risk. Green cat snake (Boiga cyanea) and northern pig-tailed macaque (Macaca leonina), which likely prefer forest interiors over edges, were the primary predators of nests and fledglings in this landscape. There were no significant differences in timing of dispersal and dispersal distance or dispersal direction in relation to proximity to edge. Our results suggest that the impacts of edge effects on the reproductive success of birds appear to be strongly dependent on the habitat preferences of locally dominant predators. Further research will be needed to identify key predators and broadly assess their foraging behaviors in individual landscapes.

Evaluación del uso de LiDAR discreto, full-waveform y TLS en la clasificación por composición de especies en bosques mediterráneos

<p>LiDAR technology –airborne and terrestrial- is becoming more relevant in the development of forest inventories, which are crucial to better understand and manage forest ecosystems. In this study, we assessed a classification of species composition in a Mediterranean forest following the C4.5 decision tree. Different data sets from airborne laser scanner full-waveform (ALS_FW), discrete (ALS_D) and terrestrial laser scanner (TLS) were combined as input data for the classification. Species composition were divided into five classes: pure Quercus ilex plots (QUI); pure Pinus halepensis dense regenerated (HALr); pure P. halepensis (HAL); pure P. pinaster (PIN); and mixed P. pinaster and Q. suber (mPIN). Furthermore, the class HAL was subdivided in low and dense understory vegetation cover. As a result, combination of ALS_FW and TLS reached 85.2% of overall accuracy classifying classes HAL, PIN and mPIN. Combining ALS_FW and ALS_D, the overall accuracy was 77.0% to discriminate among the five classes. Finally, classification of understory vegetation cover using ALS_FW reached an overall accuracy of 90.9%. In general, combination of ALS_FW and TLS improved the overall accuracy of classifying among HAL, PIN and mPIN by 7.4% compared to the use of the data sets separately, and by 33.3% with respect to the use of ALS_D only. ALS_FW metrics, in particular those specifically designed for detection of understory vegetation, increased the overall accuracy 9.1% with respect to ALS_D metrics. These analyses show that classification in forest ecosystems with presence of understory vegetation and intermediate canopy strata is improved when ALS_FW and/or TLS are used instead of ALS_D.</p>

Leaf area index change in ice-storm-damaged sugar maple stands

Changes in Leaf Area Index (LAI) between the summers of 1999 and 2000 were measured using the TRAC optical instrument in sugar maple stands damaged by the 1998 ice storm. Changes were determined to be significant if they were greater than the 95% bounds of the instrument precision. They were evaluated in relation to 1998 canopy damage estimates, 1999 stand treatments (lime, fertilizer, lime + fertilizer, herbicide, none), and 1999 understory vegetation cover. Results show that LAI change is significantly related to overstory damage, and understory abundance in the 0–7-m height range. Plot treatments were not related to these LAI changes, possibly due to the short time interval between application and LAI measurement. Keywords: forest damage, ice storm, leaf area index, optical instruments, TRAC

Early understory succession following catastrophic wind damage in a deciduous forest

Early succession was followed in a 2.5-ha gap created by a severe wind storm in a 5.5-ha fragment of eastern North American deciduous forest. Understory vegetation cover by species, light, soil moisture, and levels of several major nutrients were measured in 1 × 2 m census plots 3 years prior to the disturbance. Coincidentally, the storm felled 50-55% of the trees over a portion of these plots. Vegetation cover by species was again measured in all plots 3 years following the disturbance. Species were grouped by growth form, and group cover values used to examine changes in the composition of the vegetation and to determine whether these changes were correlated with any measured predisturbance environmental variables. Given the size of the gap, shade-intolerant tree species were expected to increase but did not, most likely because of repression by the shrub layer. The main response to the disturbance appeared to occur through reorganization of existing vegetation. The value of predisturbance species cover data and limitations of our sample sizes are discussed.