Mean Annual Diameter Increment Research Articles

Genotype x environment interaction and climate sensitivity in growth and wood density of European larch

European larch is an ecologically and economically important tree species planted across a wide range of environments. Understanding its response to the rapidly changing climate is essential to developing efficient gene resource management strategies in line with the assisted migration methodology. In this study, we quantified the genotype x environment interaction (GxE) of a larch provenance in a multi-environmental trial analysis using factor analytic (FA) modeling. We analyzed the mean annual height increment (MAI-H), the mean annual diameter increment (MAI-DBH), and wood density (PP). Additionally, we evaluated the effect of several environmental variables on these traits. The genetic correlations between sites varied from −0.53 to 0.99, −0.87 to 0.99, and −0.17 to 0.99 for MAI-H, MAI-DBH, and PP, respectively. This indicates the presence of low to high GxE. The growth traits showed more GxE signal than wood density. Narrow-sense heritability estimates were 0.41, 0.16, and 0.35 for MAI-H, MAI-DBH, and PP, respectively. The FA modeling of order 2 explained 77.4%, 67.9%, and 77.3% of the genetic variance for MAI-H, MAI-DBH, and PP, respectively. For MAI-H, the latent regression plots for the predicted site means indicate a significant positive correlation with the first factor loading. At the individual genotype level, the latent regression plots indicated high levels of GxE, especially for growth traits. Significant and relatively high correlations were found between several EVs and the factor loadings of the FA models, suggesting their possible influence on the genotypic performance across environments. Regarding MAI-H, elevation, averaged monthly mean temperature, precipitation seasonality, and stand age were correlated with the first factor loading. Annual temperature range with both the first and second factor loadings. For MAI-DBH, the mean diurnal range was correlated with the first factor loading. In the case of PP, we found that elevation was correlated with the second factor loading. Overall, this approach successfully modeled the GxE and identified environmental variables likely affecting it. Therefore, we conclude that this methodology is a valuable tool for selecting suitable genotypes adapted to specific environmental conditions.

Soil fertility and drought interact to determine large variations in wood production for a hyperdominant Amazonian tree species

IntroductionThe productivity of the Amazon Rainforest is related to climate and soil fertility. However, the degrees to which these interactions influence multiannual to decadal variations in tree diameter growth are still poorly explored.MethodsTo fill this gap, we used radiocarbon measurements to evaluate the variation in tree growth rates over the past decades in an important hyperdominant species, Eschweilera coriacea (Lecythidaceae), from six sites in the Brazilian Amazon that span a range of soil properties and climate.ResultsUsing linear mixed-effects models, we show that temporal variations in mean annual diameter increment evaluated over a specific time period reflect interactions between soil fertility and the drought index (SPEI-Standardized Precipitation and Evapotranspiration Index).DiscussionOur results indicate that the growth response of trees to drought is strongly dependent on soil conditions, a facet of forest productivity that is still underexplored, and which has great potential for improving predictions of future tropical tree growth in the face of projected climate change.

Analysis of growth and vitality class of Ulin (Eusideroxylon zwageri T. et B.) on Sempaja Arboretum East Kalimantan

The purpose of this study was to determine the growth and vitality class of Ulin stands after the age of 17 years at Sempaja Arboretum, Samarinda East Kalimantan. Collecting data by measuring all species of Ulin which were planted in the arboretum area of 2.5 ha covering diameter/circumference, tree height, and trunk condition in 2020. The growth analysis approach used individual tree increment calculations, while the vitality class and social dynamic assessment were based on the IUFRO classification. The results showed that in the arboretum Sempaja found 82 stems of Ulin which planted as a result of ex-situ conservation activities. The tree’s growth distribution after 17 years was wide both based on the diameter, namely 1.5-11.72 cm, and height, namely 2.4-16.21 m. Based on the mean annual diameter increment (MAId) is 0.09-0.69 cm. yr-1, the height increment (MAIh) is 0.14-0.95 m. yr-1 and volume increment (MAIvol) is 0.00002-0.006 m3.yr-1. The vitality value of Ulin was classified into three classes, meanwhile, the dynamic social was divided into two classes. Based on this assessment, the stand is dominated by trees with average growth and trees requiring maintenance in their development. These results provide input for the need for silvicultural maintenance for the Ulin stand, especially in the management of Sempaja arboretum.

Growth performance of Santalum album its income potentiality: A study from Pyuthan District, Nepal

The Santalum album is becoming a popular income generating tree species in Nepal but its growth performance has not been assessed so far yet. Thus, this study was objectively conducted to assess mean annual increment, income from Santalum album and value chain analysis. The Private plantation of Pyuthan district was selected for the study site. The diameter and height of 450 plants were measured and their age was recorded. Total fifteen key informant interviews, forty five farmers’ interviews and one focused group discussion were conducted to collect primary data. The collected data were analyzed using descriptive and inferential statistics .Mean annual increment, price of Santalum album and contribution of Santalum album in total income were analyzed. The result showed that the highest mean annual diameter increment was 51.94 cm and lowest mean annual increment was 28.25cm, the highest mean height increment was 6.39 m and the lowest mean annual height increment was4.47m and the highest mean volume increment was 0.678 m3but the lowest mean annual volume increment was 0.134 m3. The estimated maximum range of annual income from Santalum album was US$ 221-530 which was 10-15% contribution in farmers annual income while minimum range of this was US$ 194-265 and it contributes<10%.The difference of the price of Santalum album between the farmers and users in Kathmandu was2200 times more.

Impact of thinning and pruning on tree growth, stress wave velocity, and pilodyn penetration response of clonal teak (Tectona grandis) plantation

The objective of this research was to examine the impact of different thinning and pruning intensities on the growth characteristics and wood properties of clonal teak. A 14-year-old clonal teak plantation was used in the study. The first thinning and pruning were established 5 years after planting. Three different levels of thinning (un-thinned, moderate, and heavy) and pruning (low, medium, high) were tested. Growth characteristics, pilodyn penetration, and stress wave velocity were examined. Results showed that different thinning intensities significantly affected the mean annual diameter increment (F = 37.67; p < 0.01). The standing stock estimations of the thinning intensity regimes also significantly differed between different thinning intensities (F = 4.16; p = 0.035). Moreover, pilodyn penetration significantly varied with the thinning treatment (F = 23.53; p < 0.01). The stress wave velocity, however, did not significantly vary with the thinning treatment (F = 2.54; p = 0.11). Meanwhile, the effect of pruning treatment was not observed under all parameters. Heavy thinning treatment promoted all parameters except height and stress wave velocity. A strong positive correlation was observed between pilodyn penetration and DBH. This result suggested that thinning and pruning promoted positive DBH growth and an increase in the economic value of the stand, but it did not affect the wood properties of clonal teak wood.

Selection of dipterocarp species for enrichment planting in a secondary tropical rainforest

The selection of species for enrichment planting that involves native species in a secondary lowland dipterocarps forest as one of the tropical rainforest types should be conducted to maintain the sustainable management of tropical rainforests. The research of species trial of dipterocarp species was planted under a randomized complete block design with four replications. The following parameters were examined: survival rate, diameter breast height (DBH), pilodyn penetration (PP), and stress wave velocity (SWV). The survival rate (F = 1.72; p = 0.047), DBH (F = 6.67, p < 0.0001), and pilodyn penetration (F = 14.19; p < 0.001) significantly differed at 12.5 years after planting. The survival rate of Shorea leprosula was the highest (85%) of all the species, and the survival rate of other species, namely, S. macrophylla, S. ovalis, S. johorensis, S. scaberima, and S. parvifolia, was more than 70%. The best growth of DBH parameter was observed in S. platyclados. The DBH growth of S. platyclados 12.5 years after planting were 27.62 cm (mean annual diameter increment [MADI] = 2.2 cm/year). The species whose growth in DBH was similar to those of S. platyclados were S. leprosula, S. parvivolia, and S. ovalis. However, stress wave velocity (SWV) was not significantly different among dipterocarp species (F = 1.26; p = 0.234). Pilodyn penetration (PP) was significantly correlated with DBH (Pearson’s correlations = 0.306; p < 0.001), whereas stress wave velocity was not significantly correlated with DBH and PP (p > 0.05), and their Pearson’s correlations were 0.043 and −0.012, respectively. These results suggested that each dipterocarp species varied in terms of their growth and wood properties. Thus, choosing the species for enrichment planting in secondary tropical rainforests depends on the characteristics of each species and the desired final product of forest management.

Growth and stem quality of hardwood trees planted 18–29 years ago on abandoned farmland following recommended silvicultural practices

The objective of this study is to provide an account of the growth results of valuable hardwood plantations several decades old which have received silvicultural treatments recommended for planting hardwoods on abandoned farmland. Diameter growth and stem quality of sugar maple (Acer saccharum Marsh.), black walnut (Juglans nigra L.), bur oak (Quercus macrocarpa Michx.) and red oak (Quercus rubra L.) are analysed. Data were from 15 plantations located in south-western Quebec. The mean annual diameter increments were highest for red oak (0.83 cm yr-1) and black walnut (0.75 cm yr-1), and lowest for bur oak (0.55 cm yr-1) and sugar maple (0.51 cm yr-1). These values are comparable to, or exceed, the best rates in the literature. A mean proportion of 78% to 95% of the first log without defects were produced, depending on the species. Tree mean densities (640 trees/ha) will allow a selection of better stems by thinning. Elite trees have diameters that are 17% to 23% above the average. These results lead us to believe in the potential for the production of quality hardwood timber in plantations in Québec.

Dendroecology of Macrolobium acaciifolium (Fabaceae) in Central Amazonian floodplain forests

ABSTRACT The forest dynamics in the Amazonian floodplains is strongly triggered by the flood pulse. Trees respond to unfavorable growth conditions during the flood period by cambial dormancy, which results in the formation of annual growth rings. We determined tree age and compared the mean annual rates of increase in the diameter of Macrolobium acaciifolium with hydrological and climatic factors in three regions of central Amazonian floodplain forest. A wood sample was obtained from each tree using an increment borer. Ring growth was assessed by marginal parenchyma bands to determine tree age and the mean diameter increment. Ring widths were indexed to construct cross-dating chronologies and correlated with climatic and hydrological variables. The analyses demonstrate that the mean annual diameter increment did not differ between the three study sites. The chronologies correlated significantly with the terrestrial phase. There was no significant difference in the ring-width index between El Niño years and other years, and between La Niña and other years. These results show that the hydrological variables can be considered crucial to the rates of tree growth and diameter increment in floodplains, and El Niño signals were not detected in the tree-ring chronologies.

Impacts of climate change on annual diameter increment of natural Calabrian pine (Pinus brutia Ten.) forests in Kahramanmaras

The effects of global warming on climate change have been recognized in global scale and it is expected that these effects will become even more obvious in near future. The climate change, especially in arid, semi-arid, and semi-humid regions, may result in detrimental effects on forests and water resources. Turkey is among the most affected countries from climate change due to located in Mediterranean region. With the global climate change, dams and ponds also influence on tree growth. This study was carried out in Menzelet watershed dam located in Kahramanmaras, Turkey. Menzelet dam was established during 1980-1989 and water deposition started in 1990. The climate of research area is semi-arid and characterized by extreme summer drought. The purpose of this study was to investigate the local climate effects on diameter increments resulted by Menzelet Dam Lake on the naturally distributed Calabrian pine (Pinus brutia Ten.) forests. Therefore, sampling areas were chosen from two different places namely as dam site and control site. Sample plots in dam site and control site were selected from the same stand structure and have the same properties such as site index, altitude, age distribution classes and aspect. Increment cores were taken from 20 Pinus brutia trees using increment borer at breast height (1.30 m) in each sample plots and two increment cores were taken from each tree. WinDENDRO software package was used on the measurement and determination of annual diameter increment. Annual diameter increment of trees in dam site and control site were compared with independent t test using SPSS 20.0 statistical program. The relationships between annual diameter increment and climatic factors such as temperature and precipitation were evaluated using Pearson correlation analysis. According to results, there is a statistically significant difference between average annual diameter increment in dam site and control site and dam influenced forest areas positively with respect to annual diameter increment. The values of the mean annual diameter increment of the trees in dam site are greatly higher than trees in control site. According to correlation analysis, temperature increase negatively affects annual diameter increment in control site. Important increase or decrease of annual total rainfall cause more significant changes in annual diameter increment in control site compare to dam site.

Intra- and interannual variability in diameter increment of Fagus sylvatica L. and Picea abies L. Karst. in relation to weather variables

We examined the effect of weather variables on radial growth of Norway spruce and European beech at the intra- and interannual level. We used database of regular growth measurements at 9 forest sites distributed along an altitudinal and spatial gradient within the Slovakia and Czech Republic. In the period of 2010–2017, we analysed data from 213 dendrometers with manual reading in monthly or biweekly interval. The mean daily and annual diameter increments were analysed in relation to air temperatures and precipitation observed during the respective growing seasons. The general intra-annual diameter increment was modelled using a log-normal function. Results of modelling suggest that precipitation was a better predicting factor of the increment in spruce, while air temperature enhanced predictions of increments in beech. The highest, eight-year-cumulative increment of spruce (31.1 mm) and beech (22.8 mm) was found in the mixed mountainous forest at Poľana site, where both species occur in their growth optimum. The interspecific comparison of radial growth at this site revealed earlier culmination of increment in spruce compared to beech. The growth-limiting weather conditions for spruce occurred especially during the dry season 2015, while in beech sites the slight decrease of annual increment was observed in 2016. In the lowest altitudes of studied forest sites (beech 350 m a.s.l., spruce 440 m a.s.l.) the radial growth was reduced due to high summer temperatures. In the context of further predicted increase of air temperatures, these altitudinal limits for tree growth should be considered in the future forest management in Central Europe.

Predicting site productivity of the timber tree Pterocarpus angolensis

Pterocarpus angolensis is an important timber tree of the miombo woodlands of sub-Saharan Africa. The species only grows in natural mixed forests and little is known about is productivity potential. This study aimed at investigating productivity of P. angolensis on a local scale in Namibia and Angola and on a regional scale in southern Africa. The most commonly accepted productivity indicator is stem diameter increment and this was used to study productivity at a regional scale. Indicators of productivity used at the local scale were basal area, proportional basal area and site form, which were derived from 217 forest inventory plots in Namibia and Angola. The productivity measures were modelled with abiotic site factors; biotic factors were added for the local scale. Results indicated that the most consistent site factors at local and regional scale were not related to climate but to forest cover, with the species having a competitive advantage in more open forests. Mean annual diameter increment in the open forests of Namibia was 0.51 cm after 50 years. Boosted regression tree models at a local scale showed that species presence can be modelled more successfully than species basal area, proportional basal area (correlation of 0.72 vs 0.56 and 0.45, respectively) and site form. The sites with the highest productivity of P. angolensis at the local scale had a temperature seasonality below 34.5 °C, a slope of less than 1.5°, tree cover less than 20% and stand basal area higher than 9 m2 ha−1. The results can assist in establishing a site-dependent growth model for the species and direct forest and fire management towards the most productive areas.

Growth of native tree species planted in montane reforestation projects in the Colombian and Ecuadorian Andes differs among site and species

The tropical Andes in Ecuador and Colombia are a biodiversity hotspot that has endured centuries of forest clearance and degradation. Forest restoration has been identified as a regional conservation priority; in recent decades, native species reforestation projects have proliferated, but little information exists on growth performance of commonly planted tree species in relation to site and soil nutrient status. This study analyzed growth of seven common native species (Alnus acuminata, Baccharis bogotensis, Cedrela montana, Myrica pubesens, Quercus humboltii, Sambucus nigra, Smallanthus pyramidalis) on 12 montane forest sites across the northern region of the tropical Andes. Andean alder (A. acuminata) was the most commonly planted species, and grows at a mean annual diameter increment (MAI-d) of 1.81 cm y−1 and a mean annual height increment (MAI-h) of 0.95 m y−1. S. pyramidalis, a short lived pioneer of the Asteraceae family, also exhibited fast growth rates of 1.64 cm MAI-d and 1.21 m MAI-h. Andean oak (Q. humboltii) was the second-most commonly planted species, growing with an MAI-d of 0.99 cm and MAI-h of 0.56 m. Soil magnesium and potassium were significant predictors of MAI-d and MAI-h for A. acuminata, while soil nitrogen, phosphorous, sodium, and calcium were negatively associated with growth (p < .001). We speculate that A. acuminata did not grow as well on soils richer in calcium and phosphorus because they were less conducive to nitrogen symbiosis common to this species. Soil magnesium and calcium were significant predictors (p < .05) of diameter growth for Q. humboltii. For both species, we attribute growth responses to soil nutrients as a result of the variable nature of fertility in the complex and variable soils that make up the volcanic and surficial geological landscape of the northern Andes. Results indicate that native species can grow in a variety of soil conditions, and exhibit growth rates comparable to non-native species. However, our results suggest native species are site restricted for best growth and should be planted on particular soils. We make recommendations for reforestation for the species in this study.

Growth performance of Avicennia officinalis L. and the effect of spacing on growth and yield of trees planted in the Western coastal belt of Bangladesh

A trial of Avicennia officinalis L. with five different spacings was conducted in the newly accreted lands along the western coastline (Patuakhali district) of Bangladesh since 1993 to assess growth performance and the effect of spacing on tree growth. Data on tree density, height, diameter, bole height, crown diameter were recorded and analyzed when the stand was 19 years old. Mean height ranged from 12.89–13.52 m and diameter at breast height (dbh) from 26.57–32.16 cm in plots of different spacings. The mean annual height increment ranged from 0.67–0.71 m, mean annual diameter increment from 1.40–1.69 cm and wood volume from 6.02–10.04 m3·ha−1·a−1 in different treatments. Significantly greater diameter (32.16 cm) and wood volume (10.04 m3·ha−1·a−1) were obtained with wider (2.13 m × 2.13 m) spacing than with closer spacings. But tree growth was unaffected by other spacings. Growth data were also recorded from other A. officinalis plantations raised by Forest Department (FD) on different islands in Patuakhali and Bhola districts of Bangladesh. At these sites, mean annual height increment ranged from 0.33–0.62 m, mean annual diameter increment from 0.72–1.37 cm and wood volume from 1.55–5.73 m3·ha−1·a−1. The growth performance of A. officinalis indicated that the newly accreted lands along the western shoreline may be suitable for raising Avicennia plantations for the enrichment of coastal vegetation.

Decreases in standing tree-based carbon stocks associated with repeated prescribed fires in a temperate mixed-species eucalypt forest

Prescribed fire is a common management practice in fire-tolerant forests, and one that has potential carbon costs. Previous assessments of the carbon costs of prescribed fire regimes in temperate Australia have been based on little empirical data, and have focused on direct fire effects (area burnt, fuel consumed) but have largely ignored potentially substantive indirect effects on tree mortality and growth. This study measures effects of four prescribed fire treatments on standing tree-based carbon stocks, and on individual tree growth and mortality, in a fire-tolerant eucalypt forest of south-eastern Australia. Prescribed fire treatments were as a factorial combination of two seasons (autumn or spring) and two frequencies (3-yearly ‘High’, or 10-yearly ‘Low’), were replicated over five study areas, and involved 2–7 low-intensity fires over 27years.Total standing tree-based carbon stocks (live and dead) were significantly less in prescribed fire than control treatments. However, the mean carbon difference (25Mgha−1) had a wide 95% confidence interval (2–48Mgha−1), indicating a high degree of uncertainty about the magnitude of prescribed fire effects in these native forests. Overall decreases were consistent with detection of both direct and indirect effects of prescribed fire treatments. Direct combustion effects on bark were minimal (c. 0.2–0.4Mgha−1), but were also indicated by significantly less carbon in dead large stems in fire than control treatments despite evidence of marginally increased mortality of individual large stems in the former. Indirect effects of repeated prescribed fires were also detected as significantly decreased mean annual diameter increment of individual large Eucalyptus obliqua over 27years (particularly of stems 20–50cm diameter). With respect to prescribed fire type, small live stem densities and associated carbon stocks were greater in autumn than spring, and in Low than High frequency treatments, and carbon stocks in large dead stems were greater in High than Low frequency treatments. This suggested that c. 10-yearly fires in autumn provided the most scope for maintaining future capacity to fix carbon. Nonetheless, decreases in total standing tree-based carbon stocks were not significantly different among prescribed fire treatments, suggesting tree-based carbon stocks were more influenced by prescribed fire per se than by fire season or frequency.

Comparison of growth and wood production of Populus deltoides and Paulownia fortunei in Guilan province (Iran)

An area about 3000 m2 located in Shanderman nursary (Guilan province, North Iran) was selected in order to compare increment and wood production of Paulownia fortunei and Populus deltoides (collected from clone no. 69.77), These species were planted at a 4 m by 4 m spacing in the form of complete randomize block design. After planting, they were measured in terms of diameter of the bright height (dbh) and total height. The given parameters were also measured in the second, third and fourth years for determining increment of whole species. The obtained results revealed that after four years, the increment condition of Paulownia fortunei was better than Populus deltoids. The mean annual increment of the both species has increased in comparison with last year and this increment was significant at the 0.01 confidence interval. Mean annual diameter and height increment for Populus deltoides were 2.65 and 201.84 cm, respectively and for Paulownia fortune, it was obtained 5.23 and 298.03 cm, respectively. Mean annual basal area increment of Paulownia fortunei and Populus deltoides was 7.66 and 27 cm2 and there were significant differences between mean dbh, height and basal area increment of Paulownia fortunei and Populus deltoides at the 0.01 confidence interval in this area. Plantation of both Paulownia fortunei and Populus deltoides as pure plantation or mix plantation together did not show a significant difference on mean dbh and height increment of these species at this study area. Keywords: Fast-growing, Increment, Guilan province, Populus deltoids, Paulownia fortunei

Comparison of Growth and Wood Production of Populus deltoides and Paulownia fortunei in Guilan Province (Iran)

An area about 3000 m 2 located in Shanderman nursary (Guilan province, North Iran) was selected in order to compare increment and wood production of Paulownia fortunei and Populus deltoides (collected from clone no. 69.77), These species were planted at a 4 m by 4 m spacing in the form of complete randomize block design. After planting, they were measured in terms of diameter of the bright height (dbh) and total height. The given parameters were also measured in the second, third and fourth years for determining increment of whole species. The obtained results revealed that after four years, the increment condition of Paulownia fortunei was better than Populus deltoides . The mean annual increment of the both species has increased in comparison with last year and this increment was significant at the 0.01 confidence interval. Mean annual diameter and height increment for Populus deltoides were 2.65 and 201.84 cm, respectively and for Paulownia fortunei , it was obtained 5.23 and 298.03 cm, respectively. Mean annual basal area increment of Paulownia fortunei and Populus deltoides was 7.66 and 27 cm 2 and there were significant differences between mean dbh, height and basal area increment of Paulownia fortunei and Populus deltoides at the 0.01 confidence interval in this area. Plantation of both Paulownia fortunei and Populus deltoides as pure plantation or mix plantation together did not show a significant difference on mean dbh and height increment of these species at this study area.

Evaluating the Growth Performance of 4-year-old Neolamarckia cadamba Plantings in Malaysia

The paper highlights the potential of Neolamarckia cadamba and gives the compilation of achieved growth and yield after 4 years of being planted in various sites in Malaysia. The growth and yield performance in Kenangan Manis Bhd, Sandakan showed encouraging results as compared with other sites such as Sabah Softwood Bhd, Tawau; Immense Fleet Bhd, Sibu and Setul Forest Reserve, Mantin. The results generated from this study clearly indicate the ecological requirements of the species for better growth. The short-term observation on the site-species requirements further confirmed the natural habitat of the species as being found in the natural forests. Keywords: Forest plantation, Neolamarckia, mean annual diameter increment.

Ecology of Pericopsis elata (Fabaceae), an Endangered Timber Species in Southeastern Cameroon

AbstractPericopsis elata (Fabaceae) is a tall tree of high commercial value of the moist semi‐deciduous African forests. As a result of decades of logging it is now considered as threatened and listed on the IUCN Red List and CITES Appendix II, even though essential biological parameters controlling its population dynamics remain unknown. This study aims at improving the knowledge of the species' ecological parameters, and at assessing the impact of selective logging on its populations in an 118,052 ha forest in Cameroon. After inventorying the species in 1432 ha, mortality and growth were assessed over continuous 5‐ and 2‐yr periods in unlogged and logged areas, respectively. Phenology was monitored in the unlogged forest during 5 yr. The population structure shows high relative abundance of trees in medium size categories. Mean annual diameter increments in both environments did not differ significantly between unlogged and logged areas. P. elata is a deciduous species that flowers at the end of the main dry season. The minimum reproduction and effective flowering diameters were 32 and 37 cm, respectively. Fruit maturation took place during 7 mo. With a minimum logging diameter of 90 cm, the recovery rate computed over a 30‐yr period was &gt; 100 percent. Selective logging harvested only 12.1 percent of the total number of seed trees and had little influence on the species' biological parameters. Securing sufficient regeneration as a post‐logging action is probably the most important consideration for achieving long‐term sustainability.

Climate–growth relationships of the dominant tree species from semi-arid savanna woodland in Ethiopia

Long-term climate–growth relationships, were examined in tree rings of four co-occurring tree species from semi-arid Acacia savanna woodlands in Ethiopia. The main purpose of the study was to prove the presence of annual tree rings, evaluate the relationship between radial growth and climate parameters, and evaluate the association of El Niño and drought years in Ethiopia. The results showed that all species studied form distinct growth boundaries, though differences in distinctiveness were revealed among the species. Tree rings of the evergreen Balanites aegyptiaca were separated by vessels surrounding a thin parenchyma band and the growth boundary of the deciduous acacias was characterized by thin parenchyma bands. The mean annual diameter increment ranged from 3.6 to 5.0 mm. Acacia senegal and Acacia seyal showed more enhanced growth than Acacia tortilis and B. aegyptiaca. High positive correlations were found between the tree-ring width chronologies and precipitation data, and all species showed similar response to external climate forcing, which supports the formation of one tree-ring per year. Strong declines in tree-ring width correlated remarkably well with past El Niño Southern Oscillation (ENSO) events and drought/famine periods in Ethiopia. Spectral analysis of the master tree-ring chronology indicated occurrences of periodic drought events, which fall within the spectral peak equivalent to 2–8 years. Our results proved the strong linkage between tree-ring chronologies and climate, which sheds light on the potential of dendrochronological studies developing in Ethiopia. The outcome of this study has important implications for paleoclimatic reconstructions and in restoration of degraded lands.

Age, and radial growth dynamics of Pterocarpus angolensis in southern Africa

Pterocarpus angolensis D.C. is a highly valuable and sought after timber species across much of its range in southern Africa. Attempts at plantation cultivation of this species have not been successful, suggesting that sustainable management of natural populations is necessary for the continued utilization of this resource. Such management will require reliable age and long-term growth data. Despite the value of P. angolensis, few long-term studies of the species’ growth rate have been conducted, and some of these studies indicate that current harvest schemes may be inappropriate. This paper presents results of tree-ring analyses of P. angolensis from nine locations across southern Africa. The analyses include estimates of: (1) tree age, (2) diameter increment, (3) the relationship between tree diameter and the percentage of heartwood, and (4) the relationship between mean diameter increment and local rainfall. The mean annual diameter increment averaged over all nine sites was generally lower than other published values, though the range of values was within that of published figures. Cumulative diameter as a function of age indicates that radial growth can be quite variable, both within and among stands. These variable age–diameter relationships within and across the nine sites suggest that diameter may be a reasonable indicator of tree age at the stand level but not across the species’ range. The relationship between stem diameter and percentage heartwood is significantly positive, suggesting that optimal harvesting diameters may be reliably determined. Average annual diameter increment is significantly positively correlated with mean seasonal rainfall, which explains about half of the variance in mean diameter increment. These findings should be helpful for the sustainable management of this important species.