Productivity, pest tolerance and carbon sequestration of Khaya grandifoliola in the dry semi-deciduous forest of Ghana: a comparison in pure stands and mixed stands

In order to restore biodiversity in the degraded forest landscape and to use forest plantations for climate change mitigation, experimental plantations of indigenous trees (including mahogany species) and important exotic trees species like Tectona grandis have been established in pure and in mixed stands in the degraded Tain Tributaries Block II Forest Reserve in the dry semi-deciduous forest zone of Ghana. This study assessed the performance of an important indigenous species, Khaya grandifoliola, in pure and in mixed stands, and compared its performance to the exotic tree species, T. grandis. The results from the study indicated that after 4 years, there was a significant difference in the diameter of K. grandifoliola (P = 0.001) between pure and mixed stands with the pure stands having an average diameter of 9.15 ± 0.19 cm compared with 7.81 ± 0.33 cm for mixed stands. Pure stands had a correspondingly higher basal area at breast height for individual trees in pure stands compared with mixed stands. K. grandifoliola also recorded average total height of 5.50 ± 0.13 m and merchantable height 3.63 ± 0.09 m in pure stands, compared to total height of 5.04 ± 0.24 m and merchantable height of 3.52 ± 0.18 m in mixed stands. However, these values were not significantly different between the stands (P > 0.05). Basal area at breast height for K. grandifoliola grown in pure stands was 5.5 ± 0.3 m²/ha at age four, which was significantly higher than the basal area of 1.1 ± 0.4 m²/ha at breast height for K. grandifoliola in mixed stands. Also total volume per hectare was higher in pure stands (17.8 ± 0.9 m³/ha) than in mixed stands (3.4 ± 0.6 m³/ha). Consequently, K. grandifoliola accumulated more carbon in pure stands (10,126 ± 557.2 kg/ha) than in mixed stands (1,976 ± 335.1 kg/ha), but the mixture of the tree species, including K. grandifoliola, accumulated more carbon (11,929 ± 401.3 kg/ha) than the K. grandifoliola in pure stands though not statistically different. Overall, K. grandifoliola performed better in pure stands than in mixed stands. With regards to the tolerance to pest attacks on K. grandifoliola, it was more tolerant to pests’ attacks in mixed stands than in pure stands. There was no statistical difference in diameter growth between K. grandifoliola (9.15 ± 0.19 cm) and T. grandis (9.61 ± 0.26 cm) in pure stands. The values of total height, merchantable height and total volume for T. grandis were 8.22 ± 0.20 m, 5.38 ± 0.18 m and 22.5 ± 1.7 m³/ha respectively which differed significantly from 5.50 ± 0.13 m, 3.63 ± 0.09 m and 17.8 ± 0.9 m³/ha for K. grandifoliola for the same parameters (P < 0.05). However, there was no significant difference between the two species with respect to basal area per hectare (P = 0.189); K. grandifoliola grew to 5.5 ± 0.3 m²/ha and T. grandis grew to 4.8 ± 0.3 m²/ha. T. grandis in pure stands accumulated slightly more aboveground biomass than K. grandifoliola in pure stands after 4 years though not statistically different.     

Aboveground biomass increment and stand dynamics in tropical evergreen broadleaved forest

Forest ecosystems can modify the atmospheric CO₂ through biomass accumulation mostly in tree stems with diameter at breast height (DBH) ≥ 10 cm. Aboveground biomass increment (ΔAGB), and changes in stand AGB, no. stems and basal area (BA) were calculated from mortality, recruitment, and growth data of tree stems in tropical evergreen broadleaved forest, Central Highland Vietnam. Data were derived from ten 1-ha permanent plots established in 2004, where all stems with DBH ≥ 10 cm were tagged, identified to species, and measured for DBH in 2004 and 2012. In an 8-year duration, the increment was 53 ± 10 stems ha^–1, 7.8 ± 0.3 m² ha^–1 for BA and 86.0 ± 4.6 Mg ha^–1 for AGB. The stem mortality rate was 0.9% year^–1 and the stem recruitment rate was 2.2% year^–1. Annual ΔAGB was 10.8 Mg ha^–1 year^–1, equaling to 5.4 Mg C ha^–1 year^–1. Of which, tree stems of 35–80 cm DBH classes accounted for 65%. The results indicated that the forest is in stage of carbon sequestration. Any disturbances causing death of 35–80 cm DBH tree stems will much reduce carbon sequestration capacity and it will take a long time for AGB to return to pre-disturbance stage.     

Structural development and productivity of replanted mangrove plantations in Kenya

Forest structure and productivity was investigated in a 12-year-old Rhizophora mucronata Lam. plantation at Gazi Bay, Kenya. Sampling was carried out in 22, 10 m × 10 m quadrats laid along belt transects perpendicular to the waterline. Within each quadrat all trees with stem diameter greater than 2.5 cm were identified, position marked and counted. Vegetation measurements included tree height (m), canopy cover (%) and stem diameter measured at 1.3 m above the ground (D₁₃₀); from which were derived basal area (m²/ha); stand density (stems/ha) and biomass (t/ha). Information regarding composition and distribution of juveniles was derived using linear regeneration sampling (LRS). The replanted forest had a stand density of 5132 stems/ha; with a mean canopy height and stem diameter of 8.4 ± 1.1 m (range: 3.0–11.0 m) and 6.2 ± 1.87 cm (range: 2.5–12.4 cm), respectively. The total juvenile density was 4886 saplings per hectare; 78.6% of which constituted the parental canopy. The standing biomass for the 12-year-old R. mucronata plantation was 106.7 ± 24.0 t/ha, giving a biomass accumulation rate of 8.9 t/(ha year).     

Growing stock variation in different teak （Tectona grandis） forest stands of Mizoram,India

The growing stock assessment of three different teak forest stands （Tuirial： 500 m asl, Sairang： 200 m asl and Phunchawng： 550 m asl） was done in 2006 in Mizoram, India. Five diameter classes were arbitrarily established for knowing the volume attribute data and population structure, viz. a （10-20 cm）, b （20-30 cm）, c （30-40 cm）, d （40-50 cm）, and e （50-60 cm）. Results revealed that the density of the individuals among the studied stands varied from 280 stems/ha to 620 stems/ha. The average diameter of all the individuals ranged between 27.48 cm and 35.43 cm. Similarly, the average height was oscillated between 17.87 m and 22.24 m. The total basal area was recorded between 24.28 m2.ha-1 and 45.80 m2.ha＂l. The maximum and minimum values of total growing stock under all the diameter classes were 669.01 m3.ha-1 and 284.7 m3.ha-1, respectively. The representation of population structure of different stands explained that the perpetuation of this species was ensured for a quite long time.     

Variation in vegetation composition,biomass production,and carbon storage in ridge top forests of high mountains of Garhwal Himalaya

Abstract

The present study was aimed to anticipate how forest composition, regeneration, biomass production, and carbon storage vary in the ridge top forests of the high mountains of Garhwal Himalaya. For this purpose five major forest types—(a) Pinus wallichiana, (b) Quercus semecarpifolia, (c) Cedrus deodara, (d) Abies spectabilis, and (e) Betula utilis mixed forests—were selected on different ridge tops in the Bhagirathi Catchment Area of the Uttarkashi District of Garhwal Himalaya. The highest species richness (10 species) and stand density (804 ± 184.5 stems ha^?1) were recorded in Abies spectabilis forests, whereas lowest species richness (4 species) and species density (428 ± 144.7 stems ha^?1) were found in Quercus semecarpifolia forests. The total basal cover (TBC) values were maximum (91.1 ± 24.4 m² ha^?1) in Cedrus deodara forests and minimum (26.5 ± 11.7 m² ha^?1) in Pinus wallichiana forests. The highest total biomass density (TBD) (464.2 ± 152.5 Mg ha^?1) and total carbon density (TCD; 208.9 ± 68.6 Mg C ha^?1) values were recorded for Cedrus deodara forests; however, lowest TBD (283.4 ± 74.8 Mg ha^?1) and TCD (127.5 ± 33.7 Mg C ha^?1) values for Quercus semecarpifolia forests. Our study suggests that Abies spectabilis-dominated forests should be encouraged for biodiversity enrichment and reducing carbon emissions on ridge top forests of high mountains.     

Floristic diversity,carbon storage and ecological services of eucalyptus agrosystems in Cameroon

Although agrosystems are recognized for their socio-economic value, few works have been conducted to assign its sequestration potential and ecological services. Accordingly, this study aimed to evaluate the ecological services of the eucalyptus stands in order to permit to small producers the access in carbon credit market. Three stands were selected according to age. Data were compared to that of a savannah (control). In total, 12,817 individuals belonging to 30 families, 53 genera and 70 species were identified in the plantations against 7107 individuals belonging to 24 families, 36 genera and 42 species in the savannah. Gmelina, Annona, Hymenocardia, Allophyllus, Daniellia, Terminalia and Piliostigma were the most represented genera. There was no significant difference between Savannah and plantations in terms of diversity (p > 0.05). The largest stock of carbon was found in oldest stands (108.51 ± 26.46 t C/ha) against 13.62 ± 3.03 t C/ha in Savannah. Eucalyptus saligna stored 39.66 t C/ha (4 t C ha^?1year^?1) in young stands; 57.28 t C/ha (6 t C ha^?1year^?1) in medium stands and 85.46 t C/ha (9 t C ha^?1year^?1) in old stands. The sequestration potential was higher in eucalyptus stands (398.25 t CO_2eq/ha) than savannah (50.05 t CO_2eq/ha). In total 956.82 t CO_2eq/ha were sequestered for an economic value of $9568.45/ha against 50.05 t CO_2eq/ha corresponding to $500.56/ha in Savannah. Eucalyptus stands are carbon sinks and could be an opportunity for financial benefits in the event of payment for environmental services in the context of the CDM process.     

Tree species diversity of a 20-ha plot in a tropical seasonal rainforest in Xishuangbanna, southwest China

We censused all free-standing trees ≥1?cm diameter at breast height (dbh) in a 20-ha plot established in a tropical seasonal rainforest in Xishuangbanna National Nature Reserve, southwest China. A total of 95,834 free-standing trees ≥1?cm dbh were recorded, and 95,498 individuals (accounting for 99.65% of the total), including 468 morphospecies in 213 genera and 70 families, were identified. Thirteen of 468 species (2.78%) had more than 1,000 individual ≥1?cm dbh, which represented 56.36% individuals of the total. On the other hand, 230 of 468 species (49.14%) had a mean density of ≤1 tree per ha, and 69 of 468 species (14.74%) were singletons in the 20-ha plot. The mean species richness, density and basal area per ha were 216.50 species, 4,791.70 stems and 42.34?m², respectively. Pittosporopsis kerrii (20,918 stems, ≥1?cm dbh) of Icacinaceae and Parashorea chinensis (7,919 stems, ≥1?cm dbh) of Dipterocarpaceae were the two most abundant species dominating the emergent layer and treelet layer, respectively. Compared with other 50-ha plots established in other equatorial regions, tree species richness per ha and tree abundance per ha of the plot were at the moderate level.     

Soil-site preferences for mahogany (Swietenia macrophylla King) in the Yucatan Peninsula

Although bigleaf mahogany (Swietenia macrophylla King) is one of the most important commercial timber species in the neotropics, little is known about its site preferences in the Yucatan Peninsula. We evaluated the association of mahogany with soil characteristics using the easily observed characteristics of soil color, stoniness, and relief position. The study was conducted in a commercially managed, medium-height, semi-evergreen, dry tropical forest. A total of 609 mahogany were located along 119 km of transects established in the forest. Forest site conditions were classified in 2,464, 0.78 m² circular plots located systematically along transects, and site conditions of mahogany along the transects were recorded for the area within 1 m radius of each tree. Mahogany preferred level sites with 93% occurring on level conditions compared to 75% for forest site plots (P < 0.001). There was also a preference for black soils (76% of mahogany versus 68% of forest site plots) and a negative preference for red soils (17% versus 27%, P < 0.001). Observed soil site preferences can improve management decisions, including where to plant mahogany and where to apply silvicultural treatments, such as liberation thinning.     

Distribution patterns of tree,understorey, and detritus biomass in coniferous and broad-leaved forests of Western Himalaya,India

Forest biomass pools are the major reservoirs of atmospheric carbon in both coniferous and broad-leaved forest ecosystems and thus play an important role in regulating the regional and global carbon cycle. In this study, we measured the biomass of trees, understorey, and detritus in temperate (coniferous and broad-leaved) forests of Kashmir Himalaya. Total ecosystem dry biomass averaged 234.2 t/ha (ranging from 99.5 to 305.2 t/ha) across all the forest stands, of which 223 t/ha (91.9–283.2 t/ha) were stored in above- and below-ground biomass of trees, 1.3 t/ha (0.18–3.3 t/ha) in understorey vegetation (shrubs and herbaceous), and 9.9 t/ha (4.8–20.9 t/ha) in detritus (including standing and fallen dead trees, and forest floor litter). Among all the forests, the highest tree, understorey, and detritus biomass were observed in mid-altitude Abies pindrow and Pinus wallichiana coniferous forests, whereas the lowest were observed in high-altitude Betula utilis broad-leaved forests. Basal area has showed significant positive relationship with biomass (R² = 0.84–0.97, P < 0.001) and density (R² = 0.49–0.87). The present study will improve our understanding of distribution of biomass (trees, understorey, and detritus) in coniferous and broad-leaved forests and can be used in forest management activities to enhance C sequestration.     

The effects of different types of management,functions, and characteristics of stands in Polish forests on the amount of coarse woody debris

In the modern forestry paradigm, many factors influence the amount of coarse woody debris (CWD). The present paper analyzes the effects of both local (national) programs (special functions of forests) and European programs (Natura 2000 sites), as well as the individual characteristics of forest stands. The study was conducted on 2,752 sampling plots distributed over an area of about 17,500 ha and located in lowland stands having a species composition typical of large areas in central Europe. Natura 2000 areas contained significantly more CWD (8.4 m³/ha) than areas not covered by the program (4.8 m³/ha). However, this is due to the fact that Natura 2000 sites involve well-preserved forest areas, such as nature reserves (26.6 m³/ha). In the managed forests that have been covered by the Natura 2000 program over the past several years, the volume of CWD has not increased. Forests with ecological and social functions differed slightly in the amount of CWD. More CWD occurred in protected animal areas (8.7 m³/ha) than in stands damaged by industry (3.9 m³/ha). Intermediate CWD levels were found in water-protection forests and in forests located around cities and military facilities. In managed forests, the lowest CWD volume was observed in middle-aged stands. The species composition of the stand had little effect on the volume of CWD. Only stands with a predominance of ash and alder had higher CWD levels (13.5 m³/ha). More CWD was found in stands whose species composition did not represent the potential site quality (6.4 m³/ha) than in habitats with the optimum species composition (3.8 m³/ha). CWD volume should be systematically increased taking into consideration local natural conditions. Such efforts should be focused on particularly valuable regions, and especially on Natura 2000 sites, where the threshold values reported from other European forests should be reached. Leaving some trees to die naturally and retaining reasonable amounts of such trees ought to be incorporated into CWD management practice in Poland.     

Should unthinned oak stands of advanced age (≥ 60 yr) be thinned?

ABSTRACT

Oaks (Quercus sp.) account for nearly one-third of the sawtimber harvest in Wisconsin. As trees age, their ability to respond to thinning is reduced; therefore, the objective of this study was to determine whether thinning previously unthinned oak stands of advanced age (≥ 60 yr) would achieve biological, financial, and operational objectives. During 2014, we conducted an inventory of 25 oak stands in northern Wisconsin. Fifteen received their first thinning 8–14 yr ago at ages 60–78 yr and 10 had never been thinned. Stand-level volume growth, logging costs, and net present values were estimated for each site. The age and site index of the thinned and unthinned sites were not significantly different (p > .10). Thinned and unthinned sites grew comparable net volumes per ha (5.09 and 5.90 m³, respectively); however, because this growth was concentrated on fewer trees, the trees on the thinned sites responded vigorously to thinning. As age at first thinning increased, growth response was reduced (p = .067); however, thinning still increased the growth of residual trees. Thinned sites had higher net present values compared to unthinned sites (p < .01) and logging costs were 10.6% lower (p = 0.06). Overall, for stands between 60 and 78 years old, thinning was beneficial financially, operationally, and biologically.     

A comparative assessment on regeneration status of indigenous woody plants in Eucalyptus grandis plantation and adjacent natural forest

Diversity, density and species composition of naturally regenerated woody plants under Eucalyptus grandis plantation and the adjacent natural forest were investigated and compared. Twenty plots, with an area of 20 m × 20 m for each, were established in both of E. grandis plantation and adjacent natural forest, independently. In each plot, species name, abundance, diameter and height were recorded. Numbers of seedling were collected in five sub-plots (4 m²) within each major plot. A total of 46 species in the plantation, and 52 species in the natural forest, which belongs to 36 families were recorded. The diversity of species (H′) is 2.19 in the plantation and 2.74 in the natural forest. The density of understory woody plant was 3842 stems/ha in the plantation and 4122 stems/ha in the natural forest. The densities of seedlings in the natural forest and the plantation were 8101 stems/ha and 4151 stems/ha, respectively. High similarity of woody species composition was found between the natural forest and the plantation. The E. grandis plantation was found favoring the regeneration and growth of Millitia ferruginia and Coffea arabica in a much better way than other underneath woody species.     

Allometric models for estimating aboveground biomass of shade trees and coffee bushes grown together

Allometric models for dominant shade tree species and coffee plants (Coffea arabica) were developed for coffee agroforestry systems in Matagalpa, Nicaragua. The studied shade tree species were Cordia alliodora, Juglans olanchana, Inga tonduzzi and I. punctata. The models predict aboveground biomass based on diameter at breast height (for trees), and the stem diameter at a height of 15 cm and plant height (for coffee plants). In addition, the specific gravity of the studied species was determined.The total aboveground biomass of the shade trees varied between 3.5 and 386 kg per tree, and between 0.005 and 2.8 kg per plant for coffee. The aboveground biomass components (foliage, branch, and stem) are closely related with diameter at breast height (r > 0.75). The best-fit models for aboveground biomass of the shade trees were logarithmic, with adjusted R ² between 0.71 and 0.97. In coffee plants, a high correlation was found (r = 0.84) with the stem diameter at 15 cm height, and the best-fit model was logarithmic, as well. The mean specific gravity was 0.52 (± 0.11) for trees and 0.82 (± 0.06) for coffee plants.     

Carbon accumulation in aboveground and belowground biomass and soil of different age native forest plantations in the humid tropical lowlands of Costa Rica

Generic or default values to account for biomass and carbon accumulation in tropical forest ecosystems are generally recognized as a major source of errors, making site and species specific data the best way to achieve precise and reliable estimates. The objective of our study was to determine carbon in various components (leaves, branches, stems, structural roots and soil) of single-species plantations of Vochysia guatemalensis and Hieronyma alchorneoides from 0 to 16 years of age. Carbon fraction in the biomass, mean (±standard deviation), for the different pools varied between 38.5 and 49.7% (±3 and 3.8). Accumulated carbon in the biomass increased with the plantation age, with mean annual increments of 7.1 and 5.3 Mg ha⁻¹ year⁻¹ for forest plantations of V. guatemalensis and H. alchorneoides, respectively. At all ages, 66.3% (±10.6) of total biomass was found within the aboveground tree components, while 18.6% (±20.9) was found in structural roots. The soil (0–30 cm) contained 62.2 (±13) and 71.5% (±17.1) of the total carbon (biomass plus soil) under V. guatemalensis and H. alchorneoides, respectively. Mean annual increment for carbon in the soil was 1.7 and 1.3 Mg ha⁻¹ year⁻¹ in V. guatemalensis and H. alchorneoides. Allometric equations were constructed to estimate total biomass and carbon in the biomass which had an R ²aj (adjusted R square) greater than 94.5%. Finally, we compare our results to those that could have resulted from the use of default values, showing how site and species specific data contribute to the overall goal of improving carbon estimates and providing a more reliable account of the mitigation potential of forestry activities on climate change.     

Volume equations for poplars growing on farmland in Sweden

Abstract

Volume equations for poplars growing on farmland in Sweden. The aim of the study was to construct a simple volume equation for poplar and to evaluate the equation together with seven published equations. Data from 72 poplars were collected from 37 stands in central and southern Sweden (lat. 55–60°N). The stands’ mean age and density was 21 years and 940 stems ha^?1, respectively and the trees’ mean diameter at breast height (DBH) was 25 cm. One simple volume equation with three parameters to be estimated for poplar was constructed with DBH and total height (H) as independent variables. This equation was analyzed and compared to seven published simple equations. The best performance, in terms of low values of Root Mean Square Error (RMSE) and Absolute Bias, was achieved by the equations developed by Eriksson and by Scott. However, due to these equations high level of multicollinearity an alternative recommendation was made where the constructed equation is recommended.     

Survival and development of Liaodong oak stump sprouts in the Huanglong Mountains of China six years after three partial harvests

The survival and development of Liaodong oak (Quercus liaotungensis Koidz) stump sprouts were studied for 6 years under leave-tree, as well as 60 and 75% crown closure uniform shelterwood in the Huanglong Mountains of China. Stump sprout survival rate, number of sprouts, and sprout height under the three partial harvests during the first year post-harvest did not differ. Six years post-harvest, 78.32% of the stumps had living sprouts. No variation in sprout survival was found among the treatments throughout the study period. The number of living sprouts per stump was 13.77 ± 0.50 in the first growing season after harvest, and dropped to 6.49 ± 0.22 after 6 years. This result indicated the occurrence of self-thinning within the sprout clumps. Moreover, the height of dominant sprout increased from 52.88 ± 1.62 cm (in the first year) to 132.82 ± 2.35 cm (in the sixth year) post-harvest. Sprout height in the leave-tree harvest type was higher than those in the two shelterwoods in the fifth and sixth years after logging. Annual height growth was approximately 8–96 cm during the first growing season, and then decreased at a rate of 1–44 cm per year in the following years. A negative relationship was found between sprout height and the number of sprouts per stump. This result indicated a trade-off between the number of sprouts and height growth. The number of sprouts per stump decreased by about 0.2 stem for each 1 m²/ha increased in residual basal area. Therefore, sprouting may play an important role in the restoration of the secondary forest after harvesting.     

Influence of agroforestry practices on the structure and spatiality of shea trees (Vitellaria paradoxa C.F. Gaertn.) in central-west Burkina Faso

This article examines the role of humans in shaping a shea tree (Vitellaria paradoxa C.F. Gaertn.) population in Prata, central-west Burkina Faso. Four management regimes or land uses were considered: fields cultivated by indigenous Gurunsi farmers, fields cultivated by migrant Moose farmers, fallows, and bush lands. The structure of the shea population differed between Gurunsi and Moose fields and between these fields and fallow and bush lands. The size class distribution of V. paradoxa in fallows and bush lands was skewed towards the lower classes and the slope of the distributions was negative and significant, indicating the occurrence of recruitment. In comparison, Gurunsi fields carried young and mature trees with 95 % of individuals in the 15.5–90 cm range, whereas Moose fields carried no specimen with dbh <16.5 cm. The slope of the size class distribution was slightly negative for Gurunsi fields and slightly positive for Moose fields, but non significant in both cases. Vitellaria paradoxa densities did not significantly differ between Gurunsi (35 stems/ha) and Moose (26 stems/ha) fields, but were higher in fallows (172 stems/ha) and in the bush (161 stems/ha) than in cultivated fields. Nearest neighbour distances were progressively greater from uncultivated fields to Gurunsi and finally Moose fields, whereas shea trees were increasingly aggregated from Moose to Gurunsi fields to fallows and bush lands. In Prata, shea tree management is thus associated with ethnicity and/or with a host/migrant status that confers different farm sizes and levels of tenure security to farming households. Gurunsi and Moose farmers cited productivity, spacing and shading effects as the main factors influencing their decision to conserve specific shea trees in their fields. Results signal favorable prospects for V. paradoxa regeneration in Prata’s fallows and bush lands and to a lesser extent in Gurunsi fields.     

Wound occlusion and decay in Picea abies stems

In forest stands, Picea abies is commonly subjected to logging and bark stripping injuries. Most mechanical wounds do not exceed 300 cm², but their pathological consequences are unclear. The aim of the study was to estimate the rate of wound occlusion and the probability of decay in P. abies stems in relation to initial wound size and wounding season. The study included forty-five stems with 1-, 2-, 3-, 4- and 5-cm-wide by 15-cm-long wounds (15–75 cm²), and eighty-three stems with 15-cm-wide by 20-cm-long wounds (300 cm²), made either in January or in August. After 19–21 years, each wound was assessed for occlusion rate and the presence of decay. All 1- to 2-cm-wide wounds were occluded, compared to 58–70% of the 3- to 4-cm-wide wounds, 25% of the 5-cm-wide wounds, and 0% of the 15-cm-wide wounds. On average, it took 3.6, 5.5, 10.4, 12.7 and 14.7 years to occlude wounds ranging in size from 1- to 5-cm-wide, respectively. After 21 years, the observed size of wounds comprising an initial area of 300 cm² ranged between 14 and 481 cm². Wounding season and stem DBH had no impact on wound healing. Wound decay incidence correlated positively with the initial width of injury (r = 0.925; P < 0.05). All 1- to 2-cm-wide wounds lacked any decay, while the proportions of decay among 3-, 4-, 5- and 15-cm-wide wounds were 58.3, 50.0, 83.3 and 100%, respectively. Length of decay comprised 35–225 cm. Consequently, wounds on P. abies stems greater than 5 cm width are unlikely to be occluded and more prone to decay development.     

Floristic structure and sequestration potential of cashew agroecosystems in Africa: A case study from Cameroon

Agroecosystems are not only recognized by their high capacity of carbon storage and sequestration, they could also offer an opportunity of financial benefits in the event of payment for environmental services. The present study aimed to evaluate the carbon storage and describe the structure of cashew nut plantation. Three types of cashew stand were selected according to the age of plantations; we also used savannah as a treatment witness. Carbon stocks varied according to the age of plantations; 14.51 ± 0.306 t C/ha for plantations aged 0–10 yr; 34.78 ± 0.331 t C/ha for plantations aged 10–20 yr, and 40.02 ± 0.381 t C/ha for plantations aged over 20 yr. In the witness, we found 13.05 ± 0.177 t C/ha. These values were significantly different between the studied sites (p < 0.05). The mean values of the service of carbon sequestration also varied with the age of stands; $53.5/ha/yr (0–10 yr); $63.35/ha/yr (10–20 yr); $73.95/ha/yr (over 20 yr). In regard to carbon storage, $3279 are stored in these stands. These agroecosystems are also true carbon sinks. A development plan of such agroecosystems should be considered for the conservation of the species already endangered by anthropogenic activities on natural ecosystems.     

Free amino acid content in trunk,branches and branchlets of <Emphasis Type="Italic">Araucaria angustifolia</Emphasis> (Araucariaceae)

Araucaria angustifolia (Bertol.) O. Kuntze exhibits dimorphism in its stem structure, where the trunk is orthotropic and branches and branchlets (primary and secondary branches) are plagiotropic. These stems exhibit different behavior when used for vegetative propagation, and only segments of trunk can form a complete plant. The physiological and biochemical mechanisms that characterize these stems are still little known. The aim of this study was to describe the free amino acid profiles in trunks, branches, and branchlets of A. angustifolia. Segments of 5 cm in length were excised from young individuals below the stem apex. The needles were removed and samples were frozen and lyophilized. The determinations were made by high-performance liquid chromatography, and the results were expressed as µg/g fresh weight (FW). The trunks and branches had the highest content of total amino acids, which were 112.23 ± 20.57 µg/g FW and 111.97 ± 27.78 µg/g FW, respectively. The amino acids—glutamine, aspartate and γ-aminobutyric acid and tyrosine—were noticeably higher in the three types of stems. In the trunk, a higher amount of asparagine and tryptophan, was also detected. Glutamic acid and glutamine were found in higher quantities in the branches. The branchlets had very low total amino acid content (30.79 ± 4.19 µg/g FW), wherein asparagine is the only amino acid not detected. Thus, it was observed that the profile of the free amino acid differs among trunks, branches, and branchlets in A. angustifolia, indicating that they perform different functions.