Relative Diameter Growth Rate Research Articles

Nursery production, acclimatization, and orchard transplantation of Argania spinosa: Evaluating the impact of costs and plant age

The depletion of the argan area over time underscores the importance of enhancing the quality of argan seedlings to support regeneration. Key factors such as seedling age and nursery techniques including shade, substrate, and container play a crucial role in improving seedling quality and ensuring successful transplantation. Our study assessed the impact of seedling age, shading, substrate composition, and container volume on argan seedling production during the nursery phase and their influence in the transplantation phase. The findings revealed 40% shade covering in 12- and 18-month-old seedlings exhibited the most growth potential, while unshaded compartments were suitable for 6-month-old seedlings. Substrates S1, S3 and S6 respectively, resulted in the highest quality seedlings overall, with S1 being the most effective for 6-month-old seedlings, and S3 and S6 showing more impact for 12- and 18-month-old seedlings. Furthermore, the use of larger containers contributed to the production of high-quality seedlings. Field results showed lower mortality rates across different seedling ages (3.1% to 9.3%) and revealed no significant difference among the combinations, except for seedlings produced under 40% shade, where the S3C3 combination followed by S1C2 in the 6-month nursery production period demonstrated the highest relative growth rate in shoot length. The relative growth rate in diameter reported its highest value in the S1C2 combination of 18-month and 6-month-old seedlings. A cost benefit analysis was carried out, which revealed that the cost-effective combination was S1C2, followed by S3C3 for 6-month-old nursery age under the 40% compartment.

Seedling ecology of Aucoumea klaineana Pierre, the most important timber species in Central Africa

Aucoumea klaineana Pierre is the most exploited timber species in Central Africa. In natural forests, its regeneration is hindered by various factors, including limited light availability and pest attacks. To address these challenges and develop effective forest management practices, a comprehensive understanding of A. klaineana seedling ecology is necessary. This study investigated the light requirements and pest resistance of A. klaineana seedlings under different light conditions through an 18-month experiment conducted in Gabon. Six shade houses with varying light intensities were constructed, ranging from 1 % to 62 % of full irradiance, along with an unshaded platform representing 100 % light. Six-month-old seedlings were planted among shade houses and platform and monitored monthly for growth parameters (relative growth rate in height and diameter), morphological parameters (number of leaves, both total and compound) and mortality. Productivity (total seedling biomass), biomass allocation traits (leaves, roots, and stem mass ratios), number of branches, and symptoms of pests attacks were assessed after 18 months. Resultsreveal that light conditions influence seedling performance, with optimal levels for biomass and relative growth rate in diameter and height identified between 9 % and 62 % of relative irradiance. However, pest infestation, particularly by psyllids and black canker, poses substantial threats to seedling growth, health, and form, regardless of light conditions. Pest attacks had a significant impact on growth but not on survival, which remained high (97.1 %) even under extreme lights conditions (1 % and 100 % of relative irradiance). The findings underscore the importance of integrating pest management strategies and adapting silvicultural practices to meet the species’ ecological requirements. We suggest planting A. klaineana in small groups (to allow root anastomoses), separated by other species (to limit pest contamination), under light canopy cover (around 9–62 % of relative irradiance, to promote sustained growth rates at the seedling stage). This approach should ensure the conservation of A. klaineana populations and the long-term viability of Central Africa's timber industry.

Morpho-Physiological Strategies of Shorea leprosula Miq. and Shorea acuminata Dyer in Response to Light Intensity and Nutrient Amendments

Successfully restoring degraded forest areas depends on seedlings adapting their growth to suit harsh environments. Hence, the requirements for seedlings’ growth need to be addressed before replanting degraded sites. The present study determines the effect of abiotic factors viz. light irradiance (8%, 30%, and 100%), nutrient addition (no fertiliser (NF), NPK, and vermicompost) on the growth performance and photosynthetic capacity of two dipterocarp species seedlings, Shorea leprosula Miq. and Shorea acuminata Dyer. The morphological characteristics assessed for growth performance comprised plant height, stem diameter, leaf count, leaf area, relative chlorophyll concentration, biomass, and root-to-shoot ratio. Li-Cor 6400 and 6800 were used to measure the leaf gas exchange traits, including photosynthetic rate (A), transpiration rate (E), intercellular CO2 concentration (Ci), stomatal conductance (gsw), and water-use efficiency (WUE). Our results demonstrated that different levels of light intensity and nutrient amendment significantly impacted plant-growth performance. Plants grown in 30% irradiance showed better growth performance in terms of relative height growth rate (RHGR), mean number of leaves, and leaf areas 41%, 24%, and 32% higher than the control. The A value was also higher in 30% irradiance, but no significant differences were observed between each level of light irradiance. The addition of vermicompost gave better growth for RHGR, relative diameter growth rate (RDGR), mean number of leaves, biomass, and relative chlorophyll concentrations 47%, 40%, 131%, 19%, and 27% higher than the control, respectively. However, the results obtained for photosynthetic parameters were contrary to growth performance. The photosynthesis rate (A) was higher (14.8%) in NPK compared to the control, and the other photosynthetic parameters did not differ significantly despite different nutrient amendments. In terms of species, S. leprosula has better growth performance and photosynthetic characteristics than S. acuminata in different light irradiance and nutrient amendments, thereby rendering S. leprosula the preferred rehabilitation species. Generally, nutrient addition of either NPK or vermicompost and 30% light irradiance gave better morphological and physiological growth for both species. The outcome of this study could provide a better understanding on the forest rehabilitation strategy to reduce the seedling-mortality rate, particularly for climax tree species.

Effects of Forest Gap and Seed Size on Germination and Early Seedling Growth in Quercus acutissima Plantation in Mount Tai, China

Elucidating the influence mechanisms of seed germination and seedling growth is important for revealing the natural regeneration of forest plantations. We collected the seeds from 58-year-old Quercus acutissima Carruth. forest, and the seeds were further divided into three classes: large, medium, and small, and sown under the forest gaps (I, 197.82 m2; II, 91.85 m2, III, understory) to observe seed germination and early seedling growth. Precipitation in the study area and soil moisture content in the forest gaps were also observed during the trial period. The results showed that the precipitation in 2019 was similar to that in 2020; both were significantly lower than the precipitation in 2021. The difference in soil water content between gaps I and II was not significant, and both were significantly lower than III. The order of seedling emergence rate in gaps was II > III > I, but the minimum was almost close to zero in I. Large and medium seeds showed significantly greater emergence rate than small seeds. The seedlings of II had higher seedling height, ground diameter, ground diameter relative growth rate, seedling biomass, root surface area, and root volume than those of III. Large seeds had the highest ground diameter, ground diameter relative growth rate, biomass, root mass ratio, root shoot ratio, and root surface area. Correlation analysis showed that seedling biomass was significantly and positively correlated with root surface area and root volume, and significantly and negatively correlated with specific root length and specific root surface area. The regulation of soil moisture in the gap and the adaptability related to seed size were two key factors influencing the seed germination and early seedling growth of Q. acutissima.

Linking Plant Functional Traits to Demography in a Fragmented Landscape

Habitat loss in highly deforested landscapes such as the Brazilian Atlantic Forest has been severely affecting the diversity and survival of palm species. As some species are more sensitive than others, trait responses to the environment, as well as environmental effects on fecundity, growth, and mortality rates, may affect species demography. Considering this context, we studied functional and demographic responses of three palm species (Astrocaryum aculeatissimum, Euterpe edulis, and Geonoma schottiana) to habitat loss in the Atlantic Forest in southeastern Brazil by measuring morpho-physiological traits related to plant growth and light acquisition for photosynthesis. We also tested the response of population fitness to fragment size. Plant survival and growth was subsequently monitored in 2006 and 2007, and population dynamics were summarized in pool matrices for large and small forest fragments in the monitoring periods comprehending one full year between 2005–2006 and 2006–2007. The asymptotic growth rate of populations (defined here as population fitness, λ) in five forest fragments was then calculated. Diameter of individuals of the demography plots (from year 2005 to 2007) was used to calculate the relative diameter growth rate. Later, in 2015, we measured a set of morpho-physiological functional traits in palms in the same plots used in the demographic studies. While A. aculeatissimum populations were stable in both monitoring periods in small and large fragments, E. edulis populations were predicted to decline due to intense predation by monkeys in the large fragment, but were stable in the smaller fragments, and G. schottiana populations were stable in the large fragments in both monitoring periods, but populations in the smaller fragments were predicted to decline in the second period, i.e., with lower fitness in these fragments. In addition, the functional traits analyzed showed that G. schottiana is a forest interior species associated with the shade/understory environment response. E. edulis was also affected by the size of the fragment, but due to a disruptive interaction with a predator and showed intermediate functional traits values. On the other hand, A. aculeatissimum thrived in areas with higher and lower incidence of light and was not demographically affected by forest remnant size. This suggests that E. edulis and A. aculeatissimum are habitat generalists. We concluded that differences in the ecophysiological performance of palms due to distinct morpho-physiological functional traits related to leaf economic spectrum, such as LDMC or specific leaf area (SLA) and to photosynthetic responses to light environment as electron transport rate (ETR) and saturation irradiance (Ik) were linked to the demographic variation observed in forest remnants of different size.

Growth responses of light demanding and shade tolerant peat swamp forest saplings to elevated CO2

Aim: To determine the growth responses of two peat swamp forest species, Shorea platycarpa, a shade-tolerant slow-growing species and Macaranga pruinosa, a light-demanding fast-growing species under elevated atmospheric CO2 concentration. Methodology: The saplings of both species were grown in a shade house at ambient (400±50 µmol mol-1) and in an open roof ventilation greenhouse at elevated atmospheric CO2 concentration 800±50 µmol mol-1 for seven months. The temperature in both environments ranged between 25-33°C with 55–60% sunlight transmittance and the saplings were thoroughly watered twice a day. Plants growth measurements were estimated at frequent intervals. Saplings biomass characteristics were examined using destructive methods after seven months of treatment and non-destructive method was used for determination of leaf area. Results: Elevated CO2 enhanced all the growth characteristics in M. pruinosa with a significant increase was observed particularly on both height and diameter relative growth rate and biomass characteristics. The height relative growth rate and leaf area were significantly reduced under elevated CO2 in S. platycarpa but did not affect the shoot or root diameter and biomass significantly. A positive correlation (r =0.77, p>0.05) between stem biomass and basal diameter for plants under elevated CO2 was recorded for M. pruinosa, but not in S. platycarpa. Both species showed negative correlation (S. platycarpa; r = -0.53, M. pruinosa; r = -0.46, p>0.05) between stem growth and stem biomass at elevated CO2. Interpretation: These results unveiled profound effects of elevated CO2 on the growth of light-demanding species M. pruinosa, while shade-tolerant species S. platycarpa was not relatively affected by elevated CO2. This underscored the necessity to analyse different species performance to elevated CO2, thereby improving the ability to predict tropical swamp forest ecosystem responses to rising CO2.

Sewage sludge organic fertilizer as a promoter of initial growth of Euterpe edulis Mart., an endangered palm

Purpose The overharvesting of the endemic palm tree Euterpe edulis Mart. (Arecaceae) from the Brazilian Atlantic Forest hotspot and the destination given to the sludge produced from urban sewage treatment are both serious environmental issues caused by human activities. In order to find solutions or alternatives for both the issues, we aimed to investigate the effect of increasing rates of a sewage sludge organic fertilizer (SSOF), produced by composting sewage sludge and solid waste, on the initial growth of E. edulis. Methods We mixed sand with 0, 62.5, 125, and 250 kg·m−3 of SSOF in 8 L (21 cm height × 24 cm top diameter × 20.5 cm base diameter) pots and then planted a seedling of E. edulis in each pot. We assessed the seedlings’ height and stem diameter relative growth rate (RGR), biomass, root to shoot ratio, and shoot macronutrient (nitrogen, phosphorous, potassium, calcium, magnesium, and sulphur) concentrations in relation to fertilizer levels. We also evaluated the relation between plant height and diameter over time for each fertilization level. Results We found that height and stem diameter RGRs, biomass accumulation, and N and P shoot concentrations of E. edulis were positively related to SSOF levels between 120 and 250 kg·m−3 in the substrate. Conclusions Our study demonstrates that SSOF can be further used as an alternative to sewage sludge disposal and contribute to E. edulis cultivation, and, hence, its conservation.

Shea (<i>Vitellaria paradoxa</i> C.F. Gaertn.) Growth Improvement by Mycorrhizal Inoculation in Controlled Conditions

This study is Shea Park restoration contribution. In this study, Shea butter was cultivated for 12 months on non-sterile culture substrate and then inoculated with arbuscular mycorrhizal fungi (AMF). The mycorrhizal parameters were evaluated at 12 months after sowing and the growth parameters of the plants at 4 and 12 months after sowing. The results showed mycorrhizal infection of all treatments and stimulation of Shea’s growth according to inocula. Yac 2 mix allowed a better improvement Shea growth. This inoculum improved Shea height growth by 10.34% at 4 months and 29.02% at 12 months after sowing compared to the treatment inoculated with Glomus aggregatum, by 46.02% at 4 months and 80.71% at 12 months after sowing compared to controls. Glomus aggregatum improved Shea height by 32.33% at 4 months and 40.06% at 12 months after sowing compared to controls. This inoculum also improved the Shea collar diameter by 12% at 4 months and 28.53% at 12 months after sowing compared to the treatment inoculated with Glomus aggregatum, by 53.86% at 4 months and 75.85% at 12 months after sowing compared to controls. Glomus aggregatum improves the Shea height by 37.38% at 4 months and 36.81% at 12 months after sowing compared to controls. Yac 2 mix also improves the height relative growth rate by 33.33% and the collar diameter relative growth rate by 54.54% compared to the controls. This study has shown promising results for the restoration of the Shea Park and deserves to be deepened by extending it to other mycorrhizal strains.

Mycorrhizal Inoculation Effect on the Forage Cowpea Biomass Production in Burkina Faso

In Burkina Faso, breeding occupies an important place in the country’s economy, but is based essentially on the exploitation of the natural resources (pasture) which remains limited in extent due to the extension of land cultivated by agricultural practices extensive. Food is one of the most important limiting factors in animal production, hence the need to develop mechanisms to improve the production of food resources. This study is a contribution to fodder production improvement. In this study, cowpea was grown in a greenhouse for 60 days and inoculated with two inocula of arbuscular mycorrhizal fungi. The growth parameters were measured at 30 and 60 days after sowing. Shoot, root and total biomass were evaluated 60 days after sowing. The results show Yac 2 mix inoculum improves height growth (95.5%), height relative growth rate (525%), collar diameter (138%), collar diameter relative growth rate (328.57%), shoot biomass (396.3%), root biomass by (205.66%), total biomass by (320%), total nitrogen of aerial parts (92.39%) and total phosphorus of aerial parts (143.48%) compared to control. Yac 2 mix appears the most effective of all inoculum used in this study.

The Diversity and Diameter Growth Rate of Sprouting-Type Tree in Bukit Pinang-Pinang Forest Permanent Plots

The process of forest regeneration can take place within a certain period of time. Sprouting is a form of strategy for in adapting to its environment for success in regenerating. The Research on the diversity and diameter growth rate of sprouting-type tree in Bukit Pinang-pinang forest permanent plots, West Sumatra was carried out from October 2012 to December 2016 in the forest of Bukit Pinang-Pinang, West Sumatra and Herbarium Department of Biology, Universitas Andalas, Padang. This research was conducted using a survey method by census. The parameters analyzed were plant species composition, Morishita Index, Mann-Whitney test, Regression and Correlation test as well as RDGR (Relative Diameter of Growth Rate). The result of experiment was found 40 species of trees sprouting type in forest permanent plot Bukit Pinang-Pinang. The pattern of sprouting type trees distribution in the study locations was found to have a clustered, random and uniform pattern. Relative Diameter Growth Rate (RDGR) of 40 sprouting types of trees in the Bukit Pinang-Pinang forest permanent plots ranged from 0.003 cm/cm/year to 0.0288 cm/cm/year. Altitude did not affect RDGR of an individual tree sprouting type for 31 years

Effects of Initial Soil Properties on Three-Year Performance of Six Tree Species in Tropical Dry Forest Restoration Plantings

Deforestation of tropical dry forest reduces soil fertility, with negative effects on future restoration intervention. To evaluate the effect of initial soil properties on three-year performance of six tree species in restoration settings, we measured C, N, and P contents in topsoils of 48 plots under minimal (exclusions of livestock grazing) and maximal (plantings of six native species) restoration intervention during two years in tropical dry forest in central Mexico. Survival and height and diameter relative growth rates were evaluated by species and by growth rank (three fast- and three slow-growing species). After two years, organic C and the C:N ratio increased early during natural succession; these increases might be related to high density of N2-fixing recruits at both intervention levels. Changes in N availability for plants (i.e., NO3− and NH4+ contents) occurred after cattle exclusion. After 40 months, the fast-growing legume Leucaena esculenta (DC.) Benth. had the highest survival (65.55%) and relative growth rate in both height (3.16%) and diameter (5.67%). Fast-growing species had higher survival and diameter growth rates than slow-growing species. Higher diameter growth rates for fast-growing species may be associated with a higher ability to forage for soil resources, whereas similar height growth rates for slow and fast-growing species suggested low competition for light due to slow natural succession at the site. Planted seedlings had higher survival possibly due to initial high NO3− content in the soil. Also, fast-growing species seem to benefit from initially higher pH in the soil. Both soil properties (i.e., pH and NO3−) may be augmented to favor the performance of fast-growing species in restoration plantings and to further accelerate soil recovery in tropical dry forests.

Influence of Root System Characteristics on Black Spruce Seedling Responses to Limiting Conditions.

Roots directly affect planted seedling adaptation to new growing conditions at reforestation sites. To test the influence of root characteristics on the short-term response of seedlings to limiting resources (water, nutrient, or oxygen), we conducted two experiments. We compared (1) the growth and physiology of three types of four-year-old black spruce (Picea mariana (Mill.) BSP) seedlings (Containerized, highly developed initial roots restricted to a plug; bareroot, less developed but unrestricted initial roots; deeply-planted containerized, restricted initial and adventitious roots) to different combinations of irrigation and fertilization. We also investigated (2) the cellular plasticity of adventitious and initial roots to three irrigation regimes including flooding. Bareroot seedlings had better relative growth rates in height than containerized seedlings, probably due to their larger initial size. On the other hand, containerized seedlings took better advantage of fertilization, as shown by a higher relative growth rate in diameter compared to bareroot seedlings and were less affected by water limitation, possibly due to the root plug acting as an additional water reserve capacity. For containerized seedlings, the presence of adventitious roots was beneficial to height growth and physiological performances compared to seedlings with initial roots only. Adventitious roots showed great cell plasticity, particularly under flooding conditions.

Cost-efficiency analysis of seedling introduction vs. direct seeding of Oreomunnea mexicana for secondary forest enrichment

Abstract Among recovery strategies for secondary and degraded tropical forests, the introduction of tree species is one of the most commonly used. This is achieved particularly through the planting of nursery-grown seedlings (i.e. seedling introduction). Another less common technique, but one that could prove efficient, is sowing seeds (i.e. direct seeding) in the forest floor. However, very few comparisons have been made in the literature in terms of the ecological and economic costs and benefits between these two techniques. This study presents a cost-efficiency analysis of the introduction of seedlings and seeds of Oreomunnea mexicana (a threatened species in Mexico) in a secondary Tropical Montane Cloud Forest in central Veracruz, evaluating (1) the performance of the seedlings derived from each of the two practices, (2) the relationship of their performance with the environmental variables at the microsite level, and (3) the ecological and economic cost-efficiency of each practice. At the end of the experiment, survival was higher in the nursery-grown than in the direct-seeded seedlings (97% vs. 22%, respectively); however, the relative growth rate in height was lower for the planted than the emerged seedlings (0.02 ± 0.002 vs. 0.03 ± 0.002 cm cm−1 month−1). Relative growth rate in diameter was similar in seedlings introduced by either technique. No predation of seeds or seedlings was registered. The cost-efficiency analysis revealed that, considering the costs of production and plantation, introducing seedlings was almost two times more expensive compared to direct seeding. Results suggest that recovery of this species is feasible with combined practices depending upon the life stage of the plant and the conditions of the microsite. Improvements to these techniques, such as protection of the seed plumules, could confer even greater ecological and economic advantages for the introduction of O. mexicana in tropical secondary forests.

Canopy treatment influences growth of replacement tree species inFraxinus nigraforests threatened by the emerald ash borer in Minnesota, USA

Fraxinus nigra Marsh. (black ash), a dominant tree species of wetland forests in northern Minnesota, USA, is imperiled by the invasive insect emerald ash borer (EAB; Agrilus planipennis Fairmaire, 1888). Regeneration of associated tree species is generally low in F. nigra forests and could be impacted further by climate change. Proactive management may be critical to maintaining tree cover and ecosystem function following EAB invasion. We investigated the mean height and diameter relative growth rate (RGR) of seedlings of 10 potential replacement tree species, including two from the next southern climate zone projected to be adapted to the future northern Minnesota climate. Seedlings were planted in F. nigra wetlands under four canopy treatments: unharvested control, clearcut, girdling F. nigra to emulate EAB-induced mortality, and group selection. Mean height and diameter RGR was fastest overall in the clearcut treatment, followed by the girdling, group selection, and control treatments. Depending on species, treatment significantly influenced RGR. Several species projected to be adapted to the future northern Minnesota climate had moderate to rapid mean RGR, including one from the next southern climate zone. Our results suggest that seedling plantings and overstory treatment represent an effective strategy for establishing F. nigra replacement tree species as EAB approaches, while reducing future risk from climate change.

Effects of Long-Term Periodic Submergence on Photosynthesis and Growth of Taxodium distichum and Taxodium ascendens Saplings in the Hydro-Fluctuation Zone of the Three Gorges Reservoir of China.

Responses of bald cypress (Taxodium distichum) and pond cypress (Taxodium ascendens) saplings in photosynthesis and growth to long-term periodic submergence in situ in the hydro-fluctuation zone of the Three Gorges Dam Reservoir (TGDR) were studied. Water treatments of periodic deep submergence (DS) and moderate submergence (MS) in situ were imposed on 2-year-old bald cypress and pond cypress saplings. The effects of periodic submergence on photosynthesis and growth were investigated after 3 years (i.e. 3 cycles) compared to a control (i.e. shallow submergence, abbreviated as SS). Results showed that pond cypress had no significant change in net photosynthetic rate (Pn) in response to periodic moderate and deep submergence in contrast to a significant decrease in Pn of bald cypress under both submergence treatments, when compared to that of SS. Ratios of Chlorophyll a/b and Chlorophylls/Carotenoid of pond cypress were significantly increased in periodic moderate submergence and deep submergence, while bald cypress showed no significant change. Diameter at breast height (DBH) and tree height of both species were significantly reduced along with submergence depth. Relative diameter and height growth rates of the two species were also reduced under deeper submergence. Moreover, bald cypress displayed higher relative diameter growth rate than pond cypress under deep submergence mainly attributed to higher productivity of the larger crown area of bald cypress. When subjected to deep subergence, both species showed significant reduction in primary branch number, while in moderate submergence, bald cypress but not pond cypress showed significant reduction in primary branch number. These results indicate that both bald cypress and pond cypress are suitbale candidates for reforestation in the TGDR region thanks to their submergence tolerance characteristics, but bald cypress can grow better than pond cypress under deep submergence overall.

Growth Performance of Three Indigenous Tree Species (Cratoxylum arborescens Vahl. Blume, Alstonia spathulata Blume, and Stemonurus scorpioides Becc.) Planted at Burned Area in Klias Peat Swamp Forest, Beaufort, Sabah, Malaysia

<p>The aim of the study was to evaluate the growth performance of three indigenous tree species planted under open area planting technique of burned area at Klias Peat Swamp Forest, Beaufort, Sabah. Three indigenous tree species was used in this study, namely are <em>Cratoxylum arborescens</em> (Vahl) Blume (Geronggang), <em>Alstonia spathulata</em> Blume (Pulai), and <em>Stemonurus scorpioides</em> Becc. (Katok). A total of 45 seedlings for each species were examined using Randomized Complete Block Design (RCBD) with spacing of 3mx3m. Data collection for height, diameter, and survivality was recorded every two weeks within 10 weeks period from the seedlings was planted. Results from this study showed, the growth performance of Geronggang species was much better than the Pulai species, while all the Katok seedlings were died after week 6 in this experiment. The Geronggang species had the average mean height increment of 24.17 cm and average mean diameter increment of 2.76 mm, while Pulai species had average mean height increment of 9.36 cm and average mean diameter increment with 1.86 mm. For the survivality results, it showed that the Geronggang species had the highest survivality rate at 93.33% and Pulai species with 86.67%. There was a significant difference in term of relative height growth rate between Geronggang and Pulai species. However, there was no significant difference in term of relative diameter growth rate at significant level of P ≤ 0.05. The findings indicates that Geronggang and Pulai are suitable to be planted at burned area in Klias peat swamp forest for the purpose of reforestation using open area planting technique, while the Katok species is not suitable due to environment consideration. The better growth performance of the Geronggang and Pulai species are because they can easily adapted with the open area planting at the study site.</p>

Ecophysiological responses of two dominant subalpine tree species Betula albo-sinensis and Abies faxoniana to intra- and interspecific competition under elevated temperature

Seedlings of tree species Abies faxoniana and Betula albo-sinensis were grown under different competition regimes (single plant, monoculture or mixture) at ambient temperature (AT) and elevated temperature (ET) to evaluate the impact of inter- and intraspecific competition on photosynthesis capacity, N resorption efficiency, N uptake patterns, water use efficiency (foliar carbon isotope composition, δ13C) and root carbon reserve accumulation. Our results showed that ET did not have significant effects on relative height growth rate (RGRH), relative diameter growth rate (RGRD), chlorophyll fluorescence parameters (Fv/Fm, ΦPSII), light-saturated photosynthetic rate (A1400) and nitrogen uptake in A. faxoniana, but it significantly reduced the values of these parameters in B. albo-sinensis. On the other hand, RGRH of A. faxoniana was not influenced by intraspecific competition irrespective of temperature regimes, while in B. albo-sinensis intraspecific competition was severer under AT than under ET. Decreased photosynthetic capacity and reduced plant size detected in B. albo-sinensis under ET likely contribute to its low intraspecific competitive ability. However, we found positive effects of interspecific competition on A. faxoniana but negative effects on B. albo-sinensis under ET, as A. faxoniana exposed to interspecific competition showed higher RGRH, RGRD, A1400, chlorophyll fluorescence parameters, foliar δ13C, foliar N, and percentages of 15N-ammonium and 15N-nitrate recovery than did A. faxoniana exposed to intraspecific competition or no competition. The results indicate that A. faxoniana is a better competitor than B. albo-sinensis under ET. Further, A. faxoniana altered resource use patterns and had a high plasticity in its ammonium uptake in mixtures compared with monocultures under ET, while B. albo-sinensis did not change its N use pattern. In all, our results showed that high temperature stress tolerance (e.g., higher root carbon accumulation), high ability to keep carbon balance (e.g., higher water use efficiency, lower leaf respiration rate, higher Fv/Fm), as well as a better N acquisition ability make A. faxoniana a better competitor when compared to B. albo-sinensisg under ET.

Spatial Distribution and Growth Characteristics of Gyrinops walla Gaertn. (Thymelaeaceae) in Sri Lanka

Gyrinops walla Gaertn. (Family: Thymelaeaceae), an understory tree species, grows naturallyin moist forests of Sri Lanka, where it is vulnerable and in south-west of India, where it isvery rare. With indiscriminate felling in the wild, for its high-valued resin products, itscurrent threat status may be even higher. The objective of this study is to gain anunderstanding of the spatial distribution and some growth characteristics of Gyrinops wallaimportant for its conservation in the wild and for its domestication. This study is based on (i) botanical surveys/inventories for information on geographicaldistribution, (ii) multiple plot-based research in nine wet lowland and four intermediate zoneforests to understand its population demography, and (iii) a 25 ha forest dynamics plot atSinharaja (Sin-FDP), where the local distribution of G. walla, its growth and survival ofindividuals >1cm dbh have been censused thrice over 10 years. In Sri Lanka, G. walla grows in lowland and lower montane rain forests, and moist seasonalforests, distributed in at least 20 different agro-ecological zones, indicating potential areas forits restoration and domestication. In natural habitats, its populations show a typical reverse-Jpattern, with a higher abundance of juveniles, depicting a stable and self-thinning population.In the ridge-valley catenal landscape of the Sin-FDP, G. walla grows better on the higherwell-drained slopes (490-575 m), compared to the wetter lower slopes (424-490 m). In the25 ha of the Sin-FDP, there were only 338 individuals of G. walla, the largest <50 cm dbhand 67% of the population only between 1-4 cm dbh. The relative diameter growth rate ofindividuals measured in two censuses in the Sin-FDP showed a decreasing trend withincrease in the size of individuals. These results suggest that extensive removal of large reproductively mature individuals mayadversely affect the future population demography of this threatened species. Investigatingits reproductive ecology and low-cost propagation methods are imperative prerequisites touse G. walla in restoration forestry programs and in domestication, thus reducing pressure onthis rapidly dwindling natural resource.

Thinning effect on height and radial growth of Pinus thunbergii Parlat. trees with special reference to trunk slenderness in a matured coastal forest in Hokkaido, Japan

To evaluate the effect of thinning on a mature coastal Pinus thunbergii Parlat. forest in Hokkaido, northern Japan, we established four study plots with different thinning intensities (control and 20, 40, and 60 % thinned at individual base; each 20 m × 20 m) and monitored them for 10 years. Radial growth of individual trees in the 60 % thinned plot was significantly greater than that in the other plots, whereas height growth in the 60 % thinned plot was significantly lower than in the other plots. Applying the height growth contribution index, which represents the trade-off between relative height growth rate and relative diameter growth rate, revealed that individual trees in the control and weakly (20 and 40 %) thinned plots had invested more in height growth compared to trees in the 60 % thinned plot. Though higher trunk slenderness value (>80) indicates higher susceptibility to meteorological disturbance such as wind storm and heavy snow, trunk slenderness in the control and the weakly thinned plots increased significantly compared to that in the 60 % thinned plot. In this study, 44.3 % of trees in the control plot had trunk slenderness values >80 over a period of 10 years. The number of trees with trunk slenderness values >80 also increased in the weakly thinned plots. In contrast, no increase was observed in the 60 % thinned plot. In Japan, the thinning intensity is legally supposed to be <35 % of stand volume, which is not enough to improve tree architecture in terms of trunk slenderness.

Drought Tolerance Of &lt;i&gt;Garcinia kola&lt;/i&gt; And &lt;i&gt;Garcinia afzelii&lt;/i&gt; At The Seedlings Stage

Garcinia kola and Garcinia afzelii are very useful forest tree species for chew stick and medicinal purposes in West Africa. They are currently receiving attention for cultivation due to the dwindling stocks of the species in the natural forest. Soil moisture is one of the most critical environmental factors that affect seedling growth in the field. The study was therefore conducted to test the response of the two species to variability in water availability. The seedlings were subjected to simulated no drought, 15-day drought, 30-day drought and 84-day drought. Seedling response to watering after 60-day simulated drought by withholding of watering was also monitored. Relative growth rate (RGR) in diameter decreased with the prolongation of the simulated drought period, and the difference was significant among all the treatments. For G. afzelii , simulated 84-day drought exhibited negative RGR in diameter, whereas for G. kola both the simulated 30-day and 84-day drought exhibited negative RGR in diameter. The RGR in height and leaf production was similar for the simulated no drought and the 15-day drought but significantly different from the 30-day and the 84-day drought period for G. afzelii. However for G. kola , it was the 15-day and 30-day simulated drought that were similar. Leaf production was highly correlated with height growth than with diameter growth. Release of drought-stress by the resumption of watering triggered leaf shedding up to a minimum value and thereafter increased. The relative rate of leaf production after re-watering increased, however the rate declined with the passage of time for G. afzelii but continued to increase for G. kola. Diameter growth was more affected than height by the dry conditions. The growth performance of G. afzelii was generally better than that of G. kola and both species have mechanisms for overcoming dry periods without experiencing mortality. Garcinia afzelii can be established in any of the forest zones, whereas Garcinia kola should preferably be established in Wet/Moist Forest and moist semi deciduous forest zones. Keywords : Garcinia species, simulated drought, diameter growth, height growth, leaf production