Propagating framework trees to restore seasonally dry tropical forest in northern Thailand

In northern Thailand, a growing interest in restoring forests for wildlife conservation and environmental protection is increasing demand for high quality planting stock of a wide range of native forest tree species. Since most native tree species have never been grown in nurseries, their production is hindered by a lack of knowledge of basic propagation methods. Basic data on germination and performance of ten indigenous framework tree species, Castanopsis acuminatissima, Dalbergia rimosa, Diospyros glandulosa, Eugenia albiflora, Ficus glaberrima var. glaberrima, Lithocarpus craibianus, Melia toosendan, Prunus cerasoides, Quercus semiserrata and Spondias axillaris were collected during the production process. Different species produce seeds at different times of the year and they have different growth rates, yet saplings must attain a plantable size by the optimum planting time i.e. the start of the wet season. Germination percentages ranged from 38 to 89%, and the time in the nursery to reach a plantable size ranged from 119 days for Prunus cerasoides, when it had reached a mean height of 48.6 cm (SD 7.9), to 609 days for Lithocarpus craibianus, when it had reached mean height of 40.5 cm (SD 10.6). This paper discusses the scheduling of production for these candidate framework species.     

Silvicultural treatments enhance growth rates of future crop trees in a tropical dry forest

Silvicultural treatments are often needed in selectively logged tropical forest to enhance the growth rates of many commercial tree species and, consequently, for recovering a larger proportion of the initial volume harvested over the next cutting cycle. The available data in the literature suggest, however, that the effect of silvicultural treatments on tree growth is smaller in dry forests than in humid forest tree species. In this study, we analyze the effect of logging and application of additional silvicultural treatments (liana cutting and girdling of competing trees) on the growth rates of future crop trees (FCTs; i.e., trees of current and potentially commercial timber species with adequate form and apparent growth potential). The study was carried out in a tropical dry forest in Bolivia where a set of 21.25-ha plots were monitored for 4 years post-logging. Plots received one of four treatments that varied in intensity of both logging and silvicultural treatments as follows: normal (reduced-impact) logging; normal logging and low-intensity silviculture; increased logging intensity and high-intensity silviculture; and, unlogged controls. The silvicultural treatments applied to FCTs involved liberation from lianas and overtopping trees. Results showed that rates of FCT stem diameter growth increased with light availability, logging intensity, and intensity of silvicultural treatments, and decrease with liana infestation degree. Growth rate increment was larger in the light and intensive silvicultural treatment (22–27%). Long-lived pioneer species showed the strongest response to intensive silviculture (50% increase) followed by total shade-tolerant species (24%) and partial shade-tolerant species (10%). While reduced-impact logging is often not sufficient to guarantee the sustainability of timber yields, application of silvicultural treatments that substantially enhanced the growth rates of FCTs will help move the management of these forests closer to the goal of sustained yield.     

The interplay between leaf water potential and osmotic adjustment on photosynthetic and growth parameters of tropical dry forest trees

Mimosa tenuiflora and Piptadenia stipulacea are commonly accepted as drought-tolerant species but little is known about their response to drought followed by rehydration.Therefore,the interplay between leaf water potential and osmotic adjustment on photo synthetic and growth parameters of these species was examined.A greenhouse study was conducted in a split-plot design with two water conditions in the main plots(control;drought followed by rehydration),and eight sampling times in the subplots(1...     

Direct seeding of late-successional trees to restore tropical montane forest

Natural regeneration of large-seeded, late-successional trees in fragmented tropical landscapes can be strongly limited by a lack of seed dispersal resulting in the need for more intensive restoration approaches, such as enrichment planting, to include these species in future forests. Direct seeding may be an alternative low-cost approach to planting nursery-raised tree seedlings, but there is minimal information on its efficacy or when in the successional process this technique will be most successful. We tested directly seeding five native tree species into habitats representing passive and active restoration approaches: (1) recently abandoned pasture; (2) naturally establishing, young secondary forests; and (3) young, mixed-species (fast-growing N-fixers and commercially valuable species) tree plantations established to facilitate montane forest recovery in southern Costa Rica. We monitored germination, survival, growth, and above- and below-ground biomass over a 2-year period. Germination in pastures, secondary forests, and tree plantations was similar (∼43%). Seedling survival after one and two years was significantly higher under tree plantations (91% year 1, 75% year 2) compared to secondary forests (76, 44%) or pastures (74, 41%). Moreover, seedlings had greater total biomass and lower root:shoot ratios in the plantations, suggesting higher nutrient availability in that treatment. Costs for direct seeding were 10- to 30-fold less per 100 seedlings after 2-year compared to nursery-raised seedlings planted at the same sites; however, there are important trade-offs to the two restoration approaches. Planting nursery-raised seedling is a more effective but higher cost approach for rapidly establishing canopy cover and restoring large areas whereas direct seeding is a more efficient way to enrich an existing system. We particularly recommend using direct seeding as a complimentary measure to the more intensive restoration approach of planting fast-growing and N-fixing trees.     

Physiological and phenological responses of oak seedlings to oak forest soil in the absence of trees

Established trees influence the growth and physiology of seedlings by altering above- and belowground conditions; however, tree influences on seedling physiology via belowground interactions are not well understood. We used soil transfers to an open field to examine the belowground influences of a Quercus ellipsoidalis E.J.Hill dominated forest on Q. ellipsoidalis seedling mycorrhizal infection, nutrient uptake, growth and photosynthesis over three years. After two years, seedlings planted with large quantities of forest soil (HF treatment) had greater leaf mass and foliar N concentrations than seedlings receiving smaller quantities of forest soil (LF) and control treatments. Mycorrhizal infection was greater in the HF treatment after one year compared with the LF and control treatments, with a positive correlation of foliar N and mycorrhizal infection in Year 2. There were marked effects of treatments on seedling spring phenology with HF seedlings breaking bud up to 17 days earlier than seedlings in the other treatments. The HF seedlings also had more rapid leaf expansion and larger leaves, and an increase in net photosynthetic rates. These results highlight complex linkages between above- and belowground physiology: forest soil had substantial effects on seedling physiology, including traits such as phenology that have previously been considered to be under aboveground control. Belowground influences of trees on conspecific seedlings may play a critical role in early seedling establishment.     

Foliar temperature tolerance of temperate and tropical evergreen rain forest trees of Australia

Australian rain forests extend from tropical climates in the north to temperate climates in the south, providing an opportunity to investigate physiological responses to temperature of both temperate and tropical species within the same forest type. Eight, rain forest canopy tree species were selected to cover the 33 degrees latitudinal range of rain forests in eastern Australia. Temperature tolerance was measured in 6-year-old plants grown in a common environment, by exposing leaves to a series of high temperatures during late summer and a series of freezing temperatures during midwinter. Damage was evaluated based on chlorophyll fluorescence measurements made 2 h after exposure and by visual assessment of leaf damage made a week after exposure. Leaves of the tropical species were more heat tolerant and less frost tolerant than leaves of the temperate species, which is consistent with their climate distributions. In contrast, the temperature tolerance of the photosynthetic apparatus was unrelated to climate in a species' native habitat. However, the tropical species underwent significant photoinhibition during winter. All species maintained the integrity of the photosynthetic apparatus and avoided tissue damage over a similar span of temperatures (about 60 degrees C), reflecting the similar annual temperature ranges in Australia's temperate and tropical rain forests. Chlorophyll fluorescence measurements and visual assessment of leaf damage provided different estimates of the absolute and relative temperature tolerances of the species, thus emphasizing the importance of a direct assessment of tissue damage for determining a species' temperature tolerance.     

Instant trees: Using giant vegetative stakes in tropical forest restoration

Remnant trees have been widely reported to facilitate tropical forest recovery, however, few restoration strategies can mimic the role such trees play in their absence. This study evaluated the establishment success and growth of planting oversized vegetative ‘stakes’ (>4 m tall) of three species: Ficus pertusa (Moraceae), Bursera simaruba (Burseraceae), and Erythrina poeppigiana (Fabaceae) at three different sites in southern Costa Rica. I found high establishment rates for all species (range 67–100%) with no mortality for Erythrina. This result was coupled with a rapid development of canopy area over 1 yr for Erythrina (7.69 ± 0.86 m²) and Bursera (1.82 ± 0.86 m²), but not Ficus (0.23 ± 0.04 m²). Similar results are reported for height. The study presents an important new addition to the growing body of literature on the use of stakes in tropical restoration, where, oversized stakes may be planted as solitary individuals in restoration sites to mimic the role played by remnant trees in forest recovery.     

Relationships between diameter and height of trees in natural tropical forest in Tanzania

The relationship between tree height (h) and tree diameter at breast height (dbh) is an important element describing forest stands. In addition, h often is a required variable in volume and biomass models. Measurements of h are, however, more time consuming compared to those of dbh, and visual obstructions, rounded crown forms, leaning trees and terrain slopes represent additional error sources for h measurements. The aim of this study was therefore to develop h–dbh relationship models for natural tropical forest in Tanzania. Both general forest type specific models and models for tree species groups were developed. A comprehensive data set with 2 623 trees from 410 different tree species collected from a total of 1 191 plots and 38 sites covering the four main forest types of miombo woodland, acacia savanna, montane forest and lowland forests was applied. Tree species groups were constructed by using a k-means clustering procedure based on the h–dbh allometry, and a number of different non-linear model forms were tested. When considering the complexity of natural tropical forests in general and in particular variations of h–dbh relationships due to high species diversity in such forests, the model fit and performance were considered to be appropriate. Results also indicate that tree species group models perform better than forest type models. Despite the fact that the residual errors level associated with the models were relatively high, the models are still considered to be applicable for large parts of Tanzanian forests with an appropriate level of reliability.     

Growth,survival, carbon rates for some dry tropical forest trees used in enrichment planting in the Cerro Blanco protected forest on the Ecuadorian coast

Deforestation principally to establish cattle pastures has created large expanses of land dominated by exotic grass prior to the establishment of the Cerro Blanco Protected Forest in Ecuador. A dry forest restoration program was carried out from 2008 to 2017. Tree planting sites were cleared in parallel lines through abandoned pasture and secondary vegetation using manual labor. Native tree species were produced in a nursery on site and used in yearly plantings during the rainy season. A total of 637 hectares were planted at an average stocking density of 1,000 trees per hectare. Growth data was collected from trees planted in nine sites from 2008 to 2017. Mortality rates were determined from a sample of 400 trees of twenty-two species. Survival of all species was greater than 50%. Ten species had survival rates greater than 90%. Vitex gigantea, with high survival rates, also had significantly greater growth rates than the other species (p < 0.0001) and showed the greatest yearly accumulation of total carbon (2.07 Kg C yr ^?1 stem^?1). Other species with high growth rates were Cordia alliodora and Centrolobium ochroxylum. This restoration program demonstrates that the dry forest restoration with timely maintenance and protection from fire and grazing is possible with intensive tree planting of native species.     

Regeneration of timber trees in a logged tropical forest in North Bolivia

For sustainable forest management, it is important to know the response of timber species to the change in environment caused by logging. We performed a 2-year study on germination, survival and growth of four timber species, Cedrela odorata, Swietenia macrophylla, Hymenaea courbaril, and Cariniana micrantha, and one non-commercial species Tachigali vasquezii. We sowed seeds of these species in five microenvironments: log landing, gap-crown and gap-trunk, skidder trail and understory, in a tropical lowland moist rain forest in northern Bolivia. We related seed and seedling performance to light availability, soil compaction, and plant competition. Germination did not differ significantly between microenvironments but survival of germinated seeds for most species was significantly higher (P < 0.05) in the log landing (46–100%) than in the understory (0–7%). After 2 years, the tallest plants were always found in the log landing (119–190 cm) and the smallest in the understory (12–26 cm) caused by a higher relative height growth rate (RHGR) in the log landing (0.003–0.004 cm cm⁻¹ per day) compared to the understory (0.000–0.001 cm cm⁻¹ per day). During the first year RHGR was positively related to canopy openness for all species and negatively to the number of overtopping competitors for three species. During the second year also water infiltration explained observed variation to RHGR. These results show that abandoned log landings and logging gaps are suitable environments for the regeneration of timber species studied. This finding suggests that the removal of competitors in log landings and logging gaps combined with leaving seed trees near these microenvironments or sowing seeds, will improve regeneration of timber species in tropical forests.     

Coppice regrowth in a disturbed tropical dry limestone forest in Jamaica

The Hellshire Hills are an extensive area of tropical dry forest over limestone, located on the south coast of Jamaica. Despite being a protected area, they are subject to encroachment and clearance by charcoal burners, leaving a relatively pristine core within more disturbed areas of forest. Future management requires a consideration of the forest’s resilience to such disturbance, and this study reports on coppice regrowth following clearance. The number of coppice shoots and the length and diameter at breast height (DBH) of the leading shoots were measured on tree stumps 14 months after they were cut in an experiment. Coppice regrowth after cutting was measured on a total of 476 stumps, representing 51 species. Coppice production and growth was vigorous as there was an extremely high incidence of coppice regrowth among and within the species in this forest after it had been cut. Initial regrowth was high with the diameter recovered by the leading shoots after 14 months approximating to 29% per year. Of the 51 species sampled three did not coppice at all and the average percent of individuals found with shoots within each species was 81%. The height and diameter of the leading shoots was significantly different among the species and the average height recorded of the leading shoots was 114 cm while the average diameter recorded was 10 mm. Larger sized stems (>10 cm DBH) on average produced more coppice shoots and larger sized shoots than smaller sized stems (<10 cm DBH) while smaller sized stems recovered more biomass than larger sized stems irrespective of species. The average diameter of the leading shoots decreased significantly with increasing shoot densities. At the species level there was a significant relationship between stem diameter and the number of shoots produced in seven of the 27 species analysed and three species returned significant relationships between stem diameter and average height of leading shoots. Coppice regrowth clearly offers considerable resilience to disturbance in this dry forest where successful regeneration by seed is highly susceptible to rainfall seasonality. However, the different abilities of species to produce coppice shoots will likely affect long-term species diversity if the present rate of clearance continues.     

Carbon density and accumulation in woody species of tropical dry forest in India

We studied the carbon density and accumulation in trees at five sites in a tropical dry forest (TDF) to address the questions: how is the TDF structured in terms of tree and carbon density in different DBH (diameter at breast height) classes? What are the levels of carbon density and accumulation in the woody species of TDF? Is the vegetation carbon density evenly distributed across the forest? Does carbon stored in the soil reflect the pattern of aboveground vegetation carbon density? Which species in the forest have a high potential for carbon accumulation? The WSG among species ranged from 0.39 to 0.78 g cm⁻³. Our study indicated that most of the carbon resides in the old-growth (high DBH) trees; 88-97% carbon occurred in individuals ?19.1 cm DBH, and therefore extra care is required to protect such trees in the dry forest. Acacia catechu, Buchanania lanzan, Hardwickia binata, Shorea robusta and Terminalia tomentosa accounted for more than 10 t ha⁻¹ carbon density, warranting extra efforts for their protection. Species also differed in their capacity to accumulate carbon indicating variable suitability for afforestation. Annually, the forest accumulated 5.3 t-C ha⁻¹ yr⁻¹ on the most productive, wettest Hathinala site to 0.05 t-C ha⁻¹ yr⁻¹ on the least productive, driest Kotwa site. This study indicated a marked patchy distribution of carbon density (151 t-C ha⁻¹ on the Hathinala site to 15.6 t-C ha⁻¹ on the Kotwa site); the maximum value was more than nine times the minimum value. These findings suggest that there is a substantial scope to increase the carbon density and accumulation in this forest through management strategies focused on the protection, from deforestation and fire, of the high carbon density sites and the old-growth trees, and increasing the stocking density of the forest by planting species with high potential for carbon accumulation.     

Aboveground biomass estimation of small diameter woody species of tropical dry forest

Estimation of accurate biomass of different forest components is important to estimate their contribution to total carbon stock. There is lack of allometric equations for biomass estimation of woody species at sapling stage in tropical dry forest (TDF), and therefore, the carbon stored in this forest component is ignored. We harvested 46 woody species at sapling stage in a TDF and developed regression models for the biomass estimation of foliage, branch, bole and the total aboveground part. For foliage and branch biomass, the models with only stem diameter as estimator showed greater R ². For bole and aboveground biomass, the models including wood specific gravity or wood density exhibited higher R ² than those without wood density. Also, the model consisting of wood density, stem diameter and height had the lowest standard error of estimate for bole and aboveground biomass. Moreover, the R ² values are very similar among models for each component. The measurement error of height and the use of a standard value of wood density together may introduce more than 2 % error into the models. Therefore, we suggest using diameter-only model, which may be more practical and equally accurate when applied to stands outside our study area.     

Composition,structure and diversity characterization of dry tropical forest of Chhattisgarh using satellite data

The purpose of this study was to characterize the land use, vegetation structure, and diversity in the Barnowpara Sanctuary, Raipur district, Chhattisgarh, India through the use of satellite remote sensing and GIS. Land cover and vegetation were spatially analyzed by digitally classifying IRS 1D LISS III satellite data using a maximum likelihood algorithm. Later, the variations in structure and diversity in different forest types and classes were quantified by adopting quadratic sampling procedures. Nine land-cover types were delineated: teak forest, dense mixed forest, degraded mixed forest, Sal mixed forest, open mixed forest, young teak plantation, grasslands, agriculture, habitation, and water bodies. The classification accuracy for different land-use classes ranged from 71.23% to 100%. The highest accuracy was observed in water bodies and grassland, followed by habitation and agriculture, teak forest, degraded mixed forest, and dense mixed forest. The accuracy was lower in open mixed forest, and sal mixed forest. Results revealed that density of different forest types varied from 324 to 733 trees ha-1, basal area from 8.13 to 28.87 m2·ha-1 and number of species from 20 to 40. Similarly, the diversity ranged from 1.36 to 2.98, concentration of dominance from 0.06 to 0.49, species richness from 3.88 to 6.86, and beta diversity from 1.29 to 2.21. The sal mixed forest type recorded the highest basal area, diversity was highest in the dense mixed forest, and the teak forest recorded maximum density, which was poor in degraded mixed forests. The study also showed that Normalized Difference Vegetation Index(NDVI) was strongly correlated to with the Shannon Index and species richness.     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Assessment of biomass and net primary productivity of a dry tropical forest using geospatial technology

This study quantifies biomass, aboveground and belowground net productivity, along with additional environmental factors over a 2-3 year period in Barnawapara Sanctuary of Chhattisgarh, India through satellite remotesensing and GIS techniques. Ten sampling quadrates20×20, 5×5 and 1×1 m were randomly laid for overstorey (OS), understorey (US) and ground vegetation(GS), respectively. Girth of trees was measured at breast height and collar diameters of shrubs and herbs at 0.1 m height. Biomass was estimated using allometric regression equations and herb biomass by harvesting. Net primary productivity (NPP) was determined by Ssumming biomass increment and litter crop values. Aspect and slope influenced the vegetation types, biomass and NPP in different forests. Standing biomass and NPP varied from 18.6 to101.5 Mg ha^-1 and 5.3 to 12.7 Mg ha^-1 a^-1, respectively,in different forest types. The highest biomass was found in dense mixed forest, while net production recoded in Teak forests. Both were lowest in degraded mixed forests of different forest types. OS, US and GS contributed 90.4, 8.7and 0.7%, respectively, for the total mean standing biomass in different forests. This study developed spectral models for the estimation of biomass and NPP using Normalized Difference Vegetation Index and other vegetation indices.The study demonstrated the potential of geospatial tools for estimation of biomass and net productivity of dry tropical forest ecosystem.     

Dynamics of transpiration, sap flow and use of stored water in tropical forest canopy trees

In large trees, the daily onset of transpiration causes water to be withdrawn from internal storage compartments, resulting in lags between changes in transpiration and sap flow at the base of the tree. We measured time courses of sap flow, hydraulic resistance, plant water potential and stomatal resistance in co-occurring tropical forest canopy trees with trunk diameters ranging from 0.34-0.98 m, to determine how total daily water use and daily reliance on stored water scaled with size. We also examined the effects of scale and tree hydraulic properties on apparent time constants for changes in transpiration and water flow in response to fluctuating environmental variables. Time constants for water movement were estimated from whole-tree hydraulic resistance (R) and capacitance (C) using an electric circuit analogy, and from rates of change in water movement through intact trees. Total daily water use and reliance on stored water were strongly correlated with trunk diameter, independent of species. Although total daily withdrawal of water from internal storage increased with tree size, its relative contribution to the daily water budget (approximately 10%) remained constant. Net withdrawal of water from storage ceased when upper branch water potential corresponded to the sapwood water potential (Psi(sw)) at which further withdrawal of water from sapwood would have caused Psi(sw) to decline precipitously. Stomatal coordination of vapor and liquid phase resistances played a key role in limiting stored water use to a nearly constant fraction of total daily water use. Time constants for changes in transpiration, estimated as the product of whole- tree R and C, were similar among individuals (~0.53 h), indicating that R and C co-varied with tree size in an inverse manner. Similarly, time constants estimated from rates of change in crown and basal sap flux were nearly identical among individuals and therefore independent of tree size and species.     

Constraints on physiological function associated with branch architecture and wood density in tropical forest trees

This study examined how leaf and stem functional traits related to gas exchange and water balance scale with two potential proxies for tree hydraulic architecture: the leaf area:sapwood area ratio (A(L):A(S)) and wood density (rho(w)). We studied the upper crowns of individuals of 15 tropical forest tree species at two sites in Panama with contrasting moisture regimes and forest types. Transpiration and maximum photosynthetic electron transport rate (ETR(max)) per unit leaf area declined sharply with increasing A(L):A(S), as did the ratio of ETR(max) to leaf N content, an index of photosynthetic nitrogen-use efficiency. Midday leaf water potential, bulk leaf osmotic potential at zero turgor, branch xylem specific conductivity, leaf-specific conductivity and stem and leaf capacitance all declined with increasing rho(w). At the branch scale, A(L):A(S) and total leaf N content per unit sapwood area increased with rho(w), resulting in a 30% increase in ETR(max) per unit sapwood area with a doubling of rho(w). These compensatory adjustments in A(L):A(S), N allocation and potential photosynthetic capacity at the branch level were insufficient to completely offset the increased carbon costs of producing denser wood, and exacerbated the negative impact of increasing rho(w) on branch hydraulics and leaf water status. The suite of tree functional and architectural traits studied appeared to be constrained by the hydraulic and mechanical consequences of variation in rho(w).     

Local knowledge helps select species for forest restoration in a tropical dry forest of central Veracruz, Mexico

Species for restoration forestry on degraded lands in the tropics are often restricted to a few well-known exotic timber species. This selection frequently leads to failed projects, as local people expect trees to cover a number of uses, not only timber. We studied local knowledge of the usefulness, scarcity and importance for wildlife of native tree species in central Veracruz, Mexico, a region with mainly secondary vegetation and remnants of tropical dry forest. Data were obtained from several workshops, in depth interviews of 40 key informants, field walks with informants, and botanical collections. Analysis included indices for cultural importance, scarcity and wildlife relevance. We documented 76 species in one or more of the categories, from primary, secondary, agroforestry and riparian habitats. Fabaceae was the most important family. All of the species were useful for humans, mainly for rural construction, food, fence posts and fuel. Two-thirds of the species were considered scarce though they were not necessarily rare??some were highly useful, overexploited species with populations insufficient for demand; this category included five of the ten most important species culturally. Also, two-thirds of the tree taxa were considered important for wildlife, especially species of Moraceae. The study shows that the local population is highly aware of the varying functions of trees in the landscape. However, few of the important species are available from regional nurseries. We propose a number of species for restoration forestry, agroforestry systems and enrichment plantings that would be valued by landowners.     

土著植物产品对印度森林病虫害防治的生物功效：综述

讨论了苦楝树和其他热带树种天然产品在印度森林病虫害防治中的生物功效。这些树木产品可起到拒食素、防护剂、不育诱导剂、毒素等作用,可以调控害虫生长,具有效力高、价格低廉和对环境无公害的特点。将这些树木产品整合到森林虫害管理策略中,会增强森林的可持续性,防止木材质量衰退。表3参61。