The effects of stump size and within-gap position on sprout non-structural carbohydrates concentrations and regeneration in forest gaps vary among species with different shade tolerances

Background To restore secondary forests (major forest resources worldwide), it is essential to accelerate the natural regeneration of dominant trees by altering micro-environments. Forest gaps are products of various disturbances, ranging from natural storms or wildfires to anthropogenic events like logging and slashing-and-burning, and sprouts of most tree species with non-structural carbohydrates (NSCs) storage can regenerate from stumps after gap formation. However, how the stump sprouts with diverse NSCs storages and stump sizes (i.e., diameters) adapt to various micro-environments of within-gap positions remains unclear. Therefore in this study, we monitored the stump sprout regeneration (density, survival, and growth) and NSCs concentrations of three dominant tree species with different shade tolerances and varying stump diameters at five within-gap positions for the first two consecutive years after gap formation. Results Stump diameter was positively correlated with sprout density, growth, and survival of all three tree species, but insignificantly related with sprout NSCs concentrations at the early stage after gap formation. The effect of within-gap position on sprout NSCs concentrations was different among species. After an environmental adaptation of two growing seasons, the north of gap (higher light availability and lower soil moisture habitat) was the least conducive for shade-intolerant Quercus mongolica to accumulate leaf NSCs, and the east of gap (shadier and drier habitat) was conducive to increasing the leaf NSCs concentrations of shade-tolerant Tilia mandshurica. Conclusions Within-gap position significantly affected leaf NSCs concentrations of all three tree species, but most of the sprout growth, survival, and stem NSCs concentrations were independent of the various within-gap positions. Besides stump diameter, the NSCs stored in stump and root systems and the interspecific differences in shade tolerance also contributed more in sprout regeneration at the early stage (2 years) of gap formation. A prolonged monitoring (> 10 years) is needed to further examine the long-term effects of stump diameter and within-gap position on sprout regeneration. All of these findings could be applied to gap-based silviculture by promoting sprout regeneration of dominant tree species with different shade tolerances, which would help accelerate the restoration of temperate secondary forests.

Sprout Regeneration of Shrub Willows after Cutting

Shrub willow (Salix L. spp.) is a promising bioenergy resource crop due to its high growth rates and superb regenerative ability. Sprouting capacity is influenced by many factors, such as parent tree species and size, which are important limiting factors for stump survival or sprout growth. In this study, we aimed to quantify the survival and regeneration performance of sprouts (including sprout height, sprout diameter, sprout number, leaf morphological traits, leaf chlorophyll content, and ground part dry biomass) from the stumps of two Salix species from three diameter classes (10–15, 16–19, and 20–30 mm). An attempt was made to explore why the stump size affects the regeneration of willows by analyzing the carbon and nitrogen proportion of stumps. Stump survival did not differ between the two Salix species. However, the sprout regeneration of S. triandra was much better than that of S. suchowensis. An increase in stump diameter caused increases in the number of sprouts produced per stump, the mean height and basal diameter of sprouts per stump, the leaf chlorophyll content, and the biomass of sprouts per stump. By contrast, stump diameter did not significantly affect stump survival. The results indicate that the larger stumps store more carbon and nitrogen than small-sized stumps, which may be one of the reasons why the larger willow stumps have a stronger resprouting ability. This study provides essential information regarding the sprout regeneration of short-rotation coppice willow plantations after harvest.

Stump Sprout Characteristics of Three Commercial Tree Species in Suriname

We compared stump sprouting by three common timber species in Suriname on the basis of sprout origins on stumps, sprout densities, and sprout height:diameter ratios. We then compared some leaf and stem functional traits of 15–18-month-old resprouts and nearby conspecific saplings of the same height (0.5–3.5 m) but unknown age. Stumps of Dicorynia guianensis Amsh. (29–103 cm in diameter) produced the most sprouts (x = 9.2/stump), followed by the 50–71 cm diameter stumps of Eperua falcata Amsh. (10.6/stump), and the 30–78 cm diameter Qualea rosea Amsh. (5.9/stump); sprout density did not vary with stump diameter. Sprouts emerged from the lower, middle, and upper thirds of the stumps of all three species, but not from the vicinity of the exposed vascular cambium in Qualea. With increased resprout density, heights of the tallest sprout per stump tended to increase but height:diameter ratios increased only in Dicorynia. Compared to conspecific saplings, sprouts displayed higher height-diameter ratios, higher leaf-to-wood mass ratios (LWR), and lower wood densities, but did not differ in leaf mass per unit area (LMA) or leaf water contents. These acquisitive functional traits may reflect increased resprout access to water and nutrients via the extensive root system of the stump. That we did not encounter live stump sprouts from the previous round of selective logging, approximately 25 years before our study, suggests that stump sprouts in our study area grow rapidly but do not live long.

Assessment of Eucalyptus Globulus Coppice Yield in the Highland Areas of North Shewa, Ethiopia

One of the old traditional methods of silvicultural management is coppicing. Many woody species produce new shoots successfully after coppicing. Regeneration of forest through coppice can be used for short rotation of tree to produce wood biomass for construction and fuel purposes. There are different levels of coppice practiced in Eucalyptus globulus plantation in the highland areas of North Shewa. However, there was no evidence or study which coppice levels can give high yield. Therefore, the objective of this study was to compare yield of E. globulus at different coppice level in the highland areas of North Shewa, Ethiopia. Fifty sampled plots were purposively selected for this study. Volume, mean annual increment, stump height and diameter, stem number and harvesting age were determined from sampled plots. The results revealed that there was no yield difference (p> 0.05) between zero, first, second and third coppice levels. However, stump diameter and number of shoots per stump, stump height were significantly different among 1, 2, 3 coppice levels (p<0.05). Number of shoots were positively correlated with stump diameter and height (r = 0.77, r = 0.72) respectively. Farmers mostly coppice E.globulus from November to December and from April to June. Although statistically there was no yield difference between coppice levels, as farmers described the first coppice has higher yield than other coppice levels. The numbers of shoots per stump were higher in the second and third coppice and this could affect stem quality especially at early stage. Altogether the mean number of stems per hectare was 10812 which is higher than previous studies. Therefore, early silvicultural activities like thinning, early coppice management and pruning has to be done to increase wood stem quality and to promote growth as well.

Comparison of Volumes Estimated from Breast Height and Stump Diameters: Application to Tectona grandis Data

Models estimating tree volume from stump diameter are important forest-management tools when volume estimation is needed postharvest, and dbh values are unavailable, for example the incidence of timber trespass. However, the use of stump diameter as the only independent variable for predicting tree volume has been limited. Therefore, in this article, stump diameter was used to estimate stem volume of Tectona grandis Linn. f, and this was compared with volume estimated from diameter at breast height. Five functions were considered each for the two stem diameters: simple linear, semilogarithmic, zero-intercept, power, and growth. Model assessment was based on least values of the root mean square error and Akaike information criterion. The results showed that the growth model had the best overall performance for both sets of volume models. A paired-sample t-test was used to compare volume estimated by stump diameter and volume estimated by diameter at breast height at 5 percent significance level. The results showed that there were no significant differences (P = .087) between timber volumes estimated from both stem diameters. Therefore, both diameters can be used interchangeably for modeling tree volume.

Assessment of Eucalyptus Globulus Coppice Yield in the Highland Areas of North Shewa, Ethiopia

One of the old traditional methods of silvicultural management is coppicing. Many woody species produce new shoots successfully after coppicing. Regeneration of forest through coppice can be used for short rotation of tree to produce wood biomass for construction and fuel purposes. There are different levels of coppice practiced in Eucalyptus globulus plantation in the highland areas of North Shewa. However, there was no evidence or study which coppice levels can give high yield. Therefore, the objective of this study was to compare yield of E. globulus at different coppice level in the highland areas of North Shewa, Ethiopia. Fifty sampled plots were purposively selected for this study. Volume, mean annual increment, stump height and diameter, stem number and harvesting age were determined from sampled plots. The results revealed that there was no yield difference (p> 0.05) between zero, first, second and third coppice levels. However, stump diameter and number of shoots per stump, stump height were significantly different among 1, 2, 3 coppice levels (p<0.05). Number of shoots were positively correlated with stump diameter and height (r = 0.77, r = 0.72) respectively. Farmers mostly coppice E.globulus from November to December and from April to June. Although statistically there was no yield difference between coppice levels, as farmers described the first coppice has higher yield than other coppice levels. The numbers of shoots per stump were higher in the second and third coppice and this could affect stem quality especially at early stage. Altogether the mean number of stems per hectare was 10812 which is higher than previous studies. Therefore, early silvicultural activities like thinning, early coppice management and pruning has to be done to increase wood stem quality and to promote growth as well.