Wood Specific Gravity Research Articles

Testing a generalized leaf mass estimation method for diverse tree species and climates of the continental United States.

Estimating tree leaf biomass can be challenging in applications where predictions for multiple tree species is required. This is especially evident where there is limited or no data available for some of the species of interest. Here we use an extensive national database of observations (61 species, 3628 trees) and formulate models of varying complexity, ranging from a simple model with diameter at breast height (DBH) as the only predictor to more complex models with up to 8 predictors (DBH, leaf longevity, live crown ratio, wood specific gravity, shade tolerance, mean annual temperature, and mean annual precipitation), to estimate tree leaf biomass for any species across the continental United States. The most complex with all eight predictors was the best and explained 74%-86% of the variation in leaf mass. Consideration was given to the difficulty of measuring all of these predictor variables for model application, but many are easily obtained or already widely collected. Because most of the model variables are independent of species and key species-level variables are available from published values, our results show that leaf biomass can be estimated for new species not included in the data used to fit the model. The latter assertion was evaluated using a novel "leave-one-species-out" cross-validation approach, which showed that our chosen model performs similarly for species used to calibrate the model, as well as those not used to develop it. The models exhibited a strong bias toward overestimation for a relatively small subset of the trees. Despite these limitations, the models presented here can provide leaf biomass estimates for multiple species over large spatial scales and can be applied to new species or species with limited leaf biomass data available.

Allometric equations for biomass and carbon stock estimation of small diameter woody species from tropical dry deciduous forests: Support to REDD+

In order to assess the contribution to the overall carbon stock and generate carbon credits under REDD+, it is essential to have an accurate estimation of biomass of different forest components. Forest cover in India is gradually increasing due to the active restoration of degraded land and plantation on waste and barren lands leading to an increase in the abundance of small diameter woody species. However, these were not included in biomass studies due to the non- availability of adequate allometric equations and low carbon stocks compared to mature individuals. We have harvested 589 individuals belonging to 23 woody species at the seedling and sapling stage from a tropical dry deciduous forest and developed species specific allometric equation and general allometric equation for aboveground biomass estimation. Further, the belowground biomass equation of 9 species were also developed using above ground biomass and root to shoot ratio as predictor variable. In the case of general equation, the combination of diameter with height and diameter, height and wood specific gravity exhibited highest adjusted R2 value. In case of species-specific allometric equations, combination of diameter with height predicts above ground biomass more precisely as compared to the diameter and wood specific gravity. Since the estimation of wood specific gravity requires destruction of lower diameter individuals, usage of diameter and height for biomass estimation would help protecting regeneration as both methods yield same results. All the equations developed in the present study for below ground biomass predicts biomass precisely. We suggest use of species specific allometric model developed with diameter and height for estimation of biomass. Further, general models consisting of height and diameter may be used for biomass estimation in case of non-availability of species specific equations without destroying the regeneration.

Effects of Water Availability on the Relationships Between Hydraulic and Economic Traits in the Quercus wutaishanica Forests.

Water availability is a key environmental factor affecting plant species distribution, and the relationships between hydraulic and economic traits are important for understanding the species’ distribution patterns. However, in the same community type but within different soil water availabilities, the relationships in congeneric species remain ambiguous. In northwest China, Quercus wutaishanica forests in the Qinling Mountains (QM, humid region) and Loess Plateau (LP, drought region) have different species composition owing to contrasting soil water availability, but with common species occurring in two regions. We analyzed eight hydraulic traits [stomatal density (SD), vein density (VD), wood specific gravity (WSGbranch), lower leaf area: sapwood area (Al: As), stomatal length (SL), turgor loss point (ΨTlp), maximum vessel diameter (Vdmax) and height (Height)] and five economic traits [leaf dry matter content (LDMC), leaf tissue density (TD), leaf dry mass per area (LMA), Leaf thickness (LT) and maximum net photosynthetic rate (Pmax)] of congeneric species (including common species and endemic species) in Q. wutaishanica forests of QM and LP. We explored whether the congeneric species have different economic and hydraulic traits across regions. And whether the relationship between hydraulic and economic traits was determined by soil water availability, and whether it was related to species distribution and congeneric endemic species composition of the same community. We found that LP species tended to have higher SD, VD, WSGbranch, Al: As, SL, ΨTlp and Vdmax than QM species. There was a significant trade-off between hydraulic efficiency and safety across congeneric species. Also, the relationships between hydraulic and economic traits were closer in LP than in QM. These results suggested that relationships between hydraulic and economic traits, hydraulic efficiency and safety played the role in constraining species distribution across regions. Interestingly, some relationships between traits changed (from significant correlation to non-correlation) in common species across two regions (from LP to QM), but not in endemic species. The change of these seven pairs of relationships might be a reason for common species’ wide occurrence in the two Q. wutaishanica forests with different soil water availability. In drought or humid conditions, congeneric species developed different types of adaptation mechanisms. The study helps to understand the environmental adaptive strategies of plant species, and the results improve our understanding of the role of both hydraulic and economic traits during community assembly.

Wood-specific gravity and carbon proportion of multifunctional agroforestry trees in foothills of Nilgiris, Western Ghats, India

Wood-specific gravity and carbon proportion of multifunctional agroforestry trees in foothills of Nilgiris, Western Ghats, India

Wood specific gravity in Indian forests: A review.

Wood specific gravity (WSG) is an important attribute for biomass estimation of forest trees. It is an important factor in converting forest volume into biomass. However, a number of factors like climatic condition, geographic location, management practice, age of tree, location of sample collection etc. may affect WSG. In India, forests have been classified into 6 major groups, 16 groups and other sub groups on the basis of climatic, edaphic and successional variations. A number of studies conducted on above ground biomass and carbon stock using non-destructive method used global, regional or reported WSG leading to inaccuracies in biomass estimation. The present paper is a comprehensive review on methodology of wood specific gravity estimation, wood specific gravity values of a number of species reported from different forest groups of India. A total of 88 critical research papers and reports for last 20 years were found meeting the aims, were collected from relevant sources. Methodology for determining WSG is discussed for accurate estimation. Comparative analysis of common species distributed in different forest groups does not show a generalized trend for WSG, as the same forest group does not exhibit similar WSG in tree species. However, it is evident that juvenility effect has greater bearing on wood specific gravity variation than climate. Analysis of data shows a greater bearing of edaphic factor on WSG, than the climatic factor. It is suggested that for estimation of biomass, habitat specific WSG is ideal to attain accuracy.

Ignoring variation in wood density drives substantial bias in biomass estimates across spatial scales

Rapid development of remote sensing and Light Detection and Ranging (LiDAR) technology has refined estimates of tree architecture and extrapolation of biomass across large spatial scales. Yet, current biomass maps show significant discrepancies and mismatch to independent ground data. A potential obstacle to accurate biomass estimation is the loss of information on wood density, which can vary at local and regional scales, in the extrapolation process. Here we investigate if variation in wood specific gravity (WSG) substantially impacts the distribution of above-ground biomass (AGB) across a range of scales from local plots to large regions. We collected wood cores and measured tree volume in 341 forest sites across large altitudinal and climatic gradients in Colombia. At all spatial scales, variation in WSG was substantial compared to variation in volume. Imputing study-wide average values of WSG induced regional biases in AGB estimates of almost 30%, consequently undervaluing the difference between forest areas of low and high average wood density. Further, neither stem size nor climate usefully predicted WSG when accounting for spatial dependencies among our sampling plots. These results suggest that remote sensing- and LiDAR-based projections to biomass estimates can be considerably improved by explicitly accounting for spatial variation in WSG, necessitating further research on the spatial distribution of WSG and potential environmental predictors to advance efficient and accurate large-scale mapping of biomass.

Allometric models to predict the individual aboveground biomass of shrubs of Malagasy xerophytic thickets

Xerophytic thicket (XT) is a shrubby vegetation found in the semi-arid southern and south-western Madagascar. Above ground biomass (AGB) is a key element to understand how this ecosystem is operating and then to design and implement any sustainable management strategy. This study aimed to build AGB allometric models for Malagasy XT shrubs. One hundred and ninety-eight individuals belonging to 20 XT common species were harvested. The models linked AGB to height, diameter at breast height (DBH), basal diameter, stem number and wood specific gravity. Empirical models taking into account the shrub architecture (multistemmed with single basal stem and first branches below a height of 1.3 m, multistemmed with multiple basal stems and shrubs with first branches over a height of 1.3 m) are more efficient to predict XT shrub AGB than the pantropical tree AGB model.

Altitude and community traits explain rain forest stand dynamics over a 2370‐m altitudinal gradient in Costa Rica

AbstractStand dynamic rates in Earth's vitally important tropical mountain rain forests are a central component of the response of these forests to global change, but their relationships to environmental gradients are poorly understood. We worked in mature forests on a 440–2810 m asl altitudinal gradient on Costa Rica's Talamanca Cordillera, making five censuses of 29 0.25‐ha permanent sample plots during 2012–2019. We determined mortality and recruitment rates, as well as basal area (G) increments, for individuals ≥10 cm diameter at breast height. Our main hypothesis was that stand dynamic rates decrease with altitude (therefore temperature); we also tested the hypotheses that rates increase with plot community‐weighted mean specific leaf area (CWM SLA) and decrease with CWM wood specific gravity (WSG). We developed regressions using generalized additive models to test our hypotheses. Mortality and recruitment rates decreased with altitude in line with our main hypothesis, though the strongly non‐linear mortality trend may be driven by extreme weather and temperature. Also, the best model for recruitment rates included plot CWM SLA with a negative relationship. Gross basal area increment ∆Ggross, the annual basal area increment of trees that survived the study period, had a hump‐shaped relationship to altitude, possibly related to the low CWM WSG of mid‐altitude forests. ∆Ggross was indeed negatively related to CWM WSG. However, net basal area growth (∆Gnet, the annualized difference between initial and final plot basal areas) was positively related to altitude due to low mortality in montane forests, in a model with CWM WSG with a negative relationship. ∆Gnet was negative in nine of the 29 plots at <1500 m asl. Patterns of rain forest stand dynamics on this long altitudinal gradient go beyond a direct response to temperature, and further work is required to improve scenarios of forest response to climate change. CWM traits should be measured to improve understanding. The effects of storms and lightning on low‐ and middle‐altitude forest and the potentially high resilience of montane Fagaceae‐dominated forests require attention. Diversity, not generality, should be expected on comparing tropical forest altitudinal transects.

Radial variations in wood functional traits in a rain forest from eastern Amazonia

Key messagePositive radial trends in WSG were common among light-demanding species, and were mainly explained by radial shift in fiber and parenchyma traits.Trees can modify their wood structure in response to changes in mechanical, hydraulic and storage demands during their life-cycles. Thus, examining radial variations in wood traits is important to expand our knowledge of tree functioning and species ecological strategies. Yet, several aspects of radial changes in wood functional traits are still poorly understood, especially in angiosperm trees from tropical humid forests. Here, we examined radial shifts in wood traits in trunks of tropical forest species and explored their potential ecological implications. We first examined radial variations in wood specific gravity (WSG). Then, we asked what anatomical traits drove radial variations in WSG, and whether WSG, vessel fraction and specific hydraulic conductivity vary independently from each other along the radius gradients. We measured WSG and eight wood anatomical traits, at different radial positions along the trunks, in 19 tree species with contrasting shade-tolerance from a lowland tropical forest in eastern Amazonia. Most species had significant radials shifts in WSG. Positive radial gradients in WSG (i.e., increments from pith to bark) were common among shade-intolerant species and were explained by different combinations of fiber and parenchyma traits, while negative radial shifts in WSG (e.g., decreases towards the bark) were present in shade-tolerants, but were generally weakly related to anatomical traits. We also found that, in general, WSG was unrelated to vessel fraction and specific hydraulic conductivity in any radial position. This study illustrates the contrasting radial variations in wood functional traits that occur in tree species from a humid lowland tropical forest. In particular, our results provide valuable insights into the anatomical traits driving WSG variations during tree development. These insights are important to expand our knowledge on tree ecological strategies by providing evidence on how wood allocation varies as trees grow, which in turn can be useful in studying trait-demography associations, and in estimating tree above-ground biomass.

CHARACTERIZATION OF PAULOWNIA TOMENTOSA STEUD TREES GROWN IN A 5-YEAR-OLD PLANTATION IN COSTA RICA

Paulownia tomentosa is utilized in Costa Rica and other countries for wood production and as feedstock for biomass, though the variation of wood properties for this species is scarcely known. In this work, the specific wood properties of a 5-year-old plantation in Costa Rica were studied. The results showed that bark and pith percentage and wood specific gravity (SG) increased with tree trunk height, while the proportion of heartwood, green wood density and green wood moisture content decreased. The average wood SG was 0.26 and tended to increase from pith to bark. Low wood SG values are related to low mechanical properties, with the advantage that wood shrinkage is low as well, which gives this wood species the potential to be utilized for reforestation purposes in Costa Rica. The gross calorific value of this species was 17809 kJ/kg, which, together with its cellulose and extractives contents, recommend P. tomentosa as a biomass source for energy production.

Temporal dynamics of above ground biomass of Kaimoor Wildlife Sanctuary, Uttar Pradesh, India: conjunctive use of field and Landsat data

The present study assesses the temporal dynamics of above ground biomass (AGB) in Kaimoor Wildlife Sanctuary (KWS), Uttar Pradesh, India using series of Landsat data for the years 1989, 2000, 2010 and 2018. The satellite images were preprocessed for surface reflectance, and subsequently we computed Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI), and Enhanced Vegetation Index (EVI). A forest density map was generated by slicing the computed NDVI and this was used as a basis for sampling strategy. A total of 30 sampling locations were randomly identified. Plot size of 30 m × 30 m was established. Tree species were enumerated at each plot and the girth at breast height and tree height measurements were recorded for the year 2018. Tree and plot level AGB (i.e. AGBF, t ha−1) was computed by multiplying the tree volume and specific gravity of wood. AGB (i.e. AGBP) prediction models were developed as linear regression equations for the year 2018 by assessing the vegetation indices and the AGBF. The significant AGBP models (R2 = 0.94; P = 0.0001) were applied for all study years after the data correction among the Landsat sensor series. The AGBP was over estimated (22.67 t ha−1; 7.75%) compared to AGBF (t ha−1). Moreover, EVI (R2 = 0.90) was found to be a better predictor for AGB compared to NDVI (R2 = 0.69) or SAVI (R2 = 0.77). The AGBP of KWS ranged between 289 ± 36 (in 1989) and 292 ± 40 (in 2018) with an average decadal positive change of 1.06%.

Dispersal limitation, soil, and fire affect functional properties of tropical secondary forests on abandoned cattle ranching landscapes

Forest age is a major predictor of secondary forest functional properties and through the chronosequence approach continues to be a principal focus in local, landscape, and regional-scale studies of secondary succession. Recent work has shown that patterns of temporal change in functional properties differ markedly between wet and seasonally dry lowland forests, suggesting that decreasing light and increasing water availability, respectively, are the main drivers of successional change. Meanwhile, however, the potentially marked effects of anthropogenic factors (especially fire), soils, climate, and dispersal limitation on the variation of forest characteristics over landscapes remain poorly understood. We studied the functional properties of seasonally dry secondary forests 5–35 years after pasture abandonment on the Nicoya Peninsula, Costa Rica. We measured 11 functional traits for 63 dominant tree and palm species in 52 plots of 0.12 ha. We used linear regression and variation partitioning to determine the relative importance of soil, climate, site use, fire history, spatial factors, and forest age in the determination of community weighted mean (CWM) trait values. CWM leaf trait and stem trait spectra of the 52 plots were orthogonal in a PCA ordination. Our seasonal forest hypothesis, that forest functional properties become more acquisitive with age as suggested by other authors, was not supported, perhaps because our chronosequence was relatively short. Our fire tolerance hypothesis was that bark thickness, wood specific gravity and resprouting capacity would increase with time of exposure to fires. This hypothesis was not supported for bark thickness. Rather, our results suggest that wood specific gravity and resprouting capacity are better predictors of fire tolerance. Also, our results suggest that >10 years of exposure to fire generates changes in forest fire tolerance strategies from high CWM bark thickness to high wood specific gravity. Finally, we tested our dispersal limitation hypothesis, that spatial variables, expressed as principal coordinates of neighbor matrices (PCNM) eigenfunctions, predict variation in forest functional properties, using variation partitioning analysis with matrices of climate, soil, anthropogenic and spatial variables. The results (overall model R2 = 0.46) indicated that spatial variables, followed by soil (acidity, depth, and extractable Mn), are the best overall predictors of forest functional traits values, supporting this hypothesis. Overall, fire, dispersal limitation and soil characteristics explain the functional properties of these secondary forests, with no effect of age in the 5–35 years range. This indicates a critical need for sampling designs and analytical approaches that take into account all these factors to advance understanding of tropical seasonal forest recovery at the landscape scale.

Models to predict whole-disk specific gravity and moisture content in planted longleaf pine from cutover and old field sites

Efforts to restore longleaf pine across the southeast United States have occurred on two distinct site types: cutover forests and old agricultural fields. We measured wood and bark physical properties of unthinned planted longleaf pine from 16 stands across Georgia, ages 12 to 25, with eight stands sampled from each site type. Three-hundred and twenty trees were felled and 3572 disks collected from within the trees. Wood and bark specific gravity (SG), moisture content (MC), and proportion of bark were measured. Non-linear mixed effects models were developed to predict the variation in wood and bark SG with respect to relative height, age, and site type. Cutover sites had higher whole-tree wood SG (0.504 vs 0.455) and bark SG (0.374 vs 0.347) than old agricultural fields. The models explained 50% and 37% of the variability in wood and bark SG, respectively. Moisture content models were fitted as a function of SG for wood (R2 = 0.87) and bark (R2 = 0.71). Bark thickness, dry mass, and green volume were higher for cutover forest sites. Trees sampled included both defect-free and defect-containing trees; however, no significant differences in the wood physical properties were found. These results provide important information for the utilization of plantation longleaf pine.

Variation in specific gravity and carbon proportion of agroforestry tree species of Himalaya

Country-specific emission factors for the Agriculture, Forestry, and Other Land Use (AFOLU) sector are important for the national greenhouse gas (GHG) inventory. Carbon stocks of trees outside forests (TOF) and agroforestry is lacking due to the unavailability of wood density and carbon fraction of various tree species. The present study is an attempt to provide estimates of wood specific gravity (WSG) and carbon content (CC) in agroforestry tree species being cultivated by farmers in Garhwal Himalaya, India for precise estimation of biomass carbon of TOF and agroforestry. A total of 160 quadrats were laid randomly in agroforestry farms to represent the area of Pauri Garhwal and Rudraprayag districts of Garhwal Himalaya. A minimum of ten matured individuals for all 33 important agroforestry species including fruit trees were randomly selected from the quadrats. Minimum ten wood samples for each species were collected at 1.37 m height from ground for each individual. The samples were wood cores to the pith and were extracted from trees circumference using an increment borer for estimation of WSG and CC. The WSG of Carica papaya was minimum to the tune of 0.16 g cm−3 and maximum for Quercus leucotrichophora with 0.81 g cm−3. The carbon content varied from 36.37% for Carica papaya to 46.52% for Pinus roxburghii. The results of the present study differed from the earlier reports for other locations suggesting the importance of developing data set on WSG and CC for precise estimation of biomass carbon stock. The estimates of WSG and CC of agroforestry tree species would complement and improve the accuracy of national GHG inventory reporting in India for tree cover. Moreover, the accurate evaluation of carbon stock would be the enabling factor for the formulation of suitable policies and programmes for forest conservation, and sustainable rural livelihood through land use based adaptation and mitigation option.

Long-term effects of stand density management and genotype on wood properties of loblolly pine (Pinus taeda L.) in the mid-South USA

Changes in ownership and forest product use patterns have incentivized growing loblolly pine (Pinus taeda L.) for chip-and-saw and sawtimber in shorter rotations in the southeastern United States. These management objectives can be accomplished by relatively low stand densities and moving fast-growing genotypes from the Atlantic Coastal Plain to other regions of the loblolly pine range, but wood quality concerns accompany these silvicultural options. In three trials in the Western Gulf region of the mid-South United States, effects of stand density management options on key wood properties (specific gravity, corewood (juvenile wood) diameter, corewood proportion, latewood proportion, corewood:outerwood (juvenile wood:mature wood) transition age as determined using specific gravity) were tested. At one site, clearwood modulus of elasticity (MOE) and modulus of rupture (MOR) were measured. Genotypes of Atlantic Coastal Plain and Western Gulf origin were also tested at two sites. In a trial in which stand density was managed at diverse levels through sequential thinning, beginning at precommercial size, only a regime that was commercially thinned to half its density two times from 297 TPH at age 7 to 62 TPH by age 41 had significant reductions in MOE, MOR, and specific gravity. Corewood diameter increased with decreasing planting density at two sites at the northwestern edge of the loblolly pine range, but corewood proportion declined with decreasing planting density due to greater diameter growth and earlier transition from corewood to outerwood. Specific gravity differences among planting densities was site-specific, with no differences at the more well-drained site. Latewood proportion, which was greater at higher planting densities, was more strongly correlated with specific gravity differences among planting densities. A planting density between 1075 and 1680 TPH would likely be optimum for these site conditions for balancing tree volume growth with minimizing reductions in specific gravity associated with reduced latewood proportion and larger corewood size. The Atlantic Coastal Plain genotype retained its tendencies to transition to outerwood earlier and have greater latewood proportions relative to a local genotype when planted at these Western Gulf sites, and its specific gravity was similar to that of the local genotype. Together these trials suggest that forest managers have flexibility in managing loblolly pine stand density without altering wood properties. Furthermore, these results provide some evidence that moving genotypes may not carry a risk of reduced wood specific gravity.

The Selection of Environmentally Friendly Wood for Raw Materials in the Creative Industries

The global economic crisis that hit the world turned out to cause a decline in exports. Therefore, in need of creative industries in raw materials production process and marketing. One of the creative efforts is the selection of wood raw materials for the industry is by using environmentally friendly wood species because it can reduce global warming. Still, the selling value of products in the export market is very high. The study design used a complete randomised design with an advanced Tukey test based on one factor, which is the types of wood that are Sengon, Waru Gunung, and Johar wood. The parameters observed are specific gravity, wood colour, adhesive strength, and formaldehyde emissions. The results showed that are Sengon, Waru Gunung, and Johar wood have different specific gravity, wood colour, and formaldehyde emissions. The average density of Sengon wood is 0.236, Waru Gunung wood is 0.570, and Johar wood is 0.654. The adhesive strength of Sengon wood 41.948 kg/cm2, Waru Gunung wood is 45.555 kg/cm2, and Johar wood 54.040 kg/cm2. Besides, the formaldehyde emissions for Sengon wood is 0.575 ppm (0.575 x10-3 ug/ml), Waru Gunung wood 0.462 ppm, and Johar wood 0.473 ppm. The higher the wood specific gravity, it will result in the wood colour and lower formaldehyde emissions. Wood with medium to high density (Waru Gunung and Johar) acknowledged as the environmentally friendly woods, and it can be used as raw material for creative industries.

Heritability and type B genetic correlation estimates for coastal douglas-fir in the US Pacific Northwest: trends and insights from 906 first-generation and second-cycle tests

ABSTRACT Genetic parameters are reported for coastal Douglas-fir, from measurements on 24,000 first-generation open-pollinated families (786 test sites) and 2,400 second-cycle crosses (120 test sites) over a period of 45 years. The following were estimated: across-site narrow-sense individual heritability (h2 A), narrow-sense family mean heritability (h2 F), and type B genetic correlation (rB), and. narrow-sense single-site heritability (h2 w). The main traits were height, diameter at breast height (dbh), volume index (both cycles), and incidence of stem forking and ramicorn branching, upper stem sinuosity, and second flushing in the leader (second cycle). Smaller datasets were available for progression of budburst, straightness, needle retention, wood specific gravity and acoustic velocity. Measurements were between three and 30 years from planting. The dataset contained at least one trait measured for 2.602 million trees . Heritability (h2 A) estimates for height, dbh, volume and sinuosity ranged from 0.15 to 0.30, with a wider range for h2 w estimates. Heritabilities were higher in the second cycle. Forking and ramicorn branching had good h2 F heritabilities. Second flushing had high h2 A and rB values; the same is often true for AV. Budburst was the most strongly inherited trait. h2 w for height, dbh, volume, forking and ramicorns was correlated with means for those traits.

Use of a pin-penetration wood density meter to determine the density of 25 Indonesian species

The pin-penetration device is a minimally destructive instrument that is widely used to estimate the physical properties of wood, e.g., density, with advantages such as reduced testing times, low costs, and fewer defects induced in the wood being tested. In this study, such a device was used on 25 Indonesian hardwood species with a strength class (SC) distribution from SC II to IV (according to the Indonesian classification of wood SCs). Tests were conducted on three different orthogonal planes, i.e., cross-sectional, radial, and tangential planes. The wood density ranged from 0.28 to 0.88 g/cm3, and the specific gravity was 0.25 to 0.76. The cross-sectional plane penetration depth of the wood was significantly greater than that of either the radial or tangential plane, whereas the pin penetration values of the radial and tangential planes were not significantly different. A prediction model for predicting the density and specific gravity of wood via pin penetration showed a significant regression. Thus, the use of a pin-penetration device was found to be suitable for estimating wood density and specific gravity in a range of SCs of tropical wood species regardless of species.

Factors controlling the productivity of tropical Andean forests: climate and soil are more important than tree diversity

Abstract. Theory predicts positive effects of species richness on the productivity of plant communities through complementary resource use and facilitative interactions between species. Results from manipulative experiments with tropical tree species indicate a positive diversity–productivity relationship (DPR), but the existing evidence from natural forests is scarce and contradictory. We studied forest aboveground productivity in more than 80 humid tropical montane old-growth forests in two highly diverse Andean regions with large geological and topographic heterogeneity and related productivity to tree diversity and climatic, edaphic and stand structural factors with a likely influence on productivity. Main determinants of wood production in the perhumid study regions were elevation (as a proxy for temperature), soil nutrient (N, P and base cation) availability and forest structural parameters (wood specific gravity, aboveground biomass). Tree diversity had only a small positive influence on productivity, even though tree species numbers varied largely (6–27 species per 0.04 ha). We conclude that the productivity of highly diverse Neotropical montane forests is primarily controlled by thermal and edaphic factors and stand structural properties, while tree diversity is of minor importance.

Fungal succession in decomposing woody debris across a tropical forest disturbance gradient

Fungi decompose woody debris, an important carbon pool in forests. Fungal community structure is expected to vary according to the wood species, habitats and extent of abiotic disturbance, which have consequences for carbon cycling in tropical forests. Here we examined the effects of fungal diversity and composition on woody debris decomposition rates and sought potential mechanisms to explain an observed lack of difference in decomposition rates across a disturbance gradient in a tropical montane rainforest in Xishuangbanna, SW China. We measured wood specific gravity (WSG) loss from 280 logs of Litsea cubeba and Castanopsis mekongensis over 3 years and monitored fungal communities from 418 samples using next-generation sequencing after 0, 18 and 36 months field exposure. Wood species and termite presence determined changes in fungal diversity through time. Overall there was a peak in fungal diversity at 18 mo, suggesting an initial period of colonization followed by a period of increasingly competitive interactions leading to decreased diversity. Litsea logs, which had relatively low initial WSG and thinner bark, harbored higher fungal diversity. Shared fungal OTUs between wood species peaked at 18 mo (~50%). However, fungal diversity was not a significant predictor of WSG loss. An effect of habitat on fungal community composition suggests that functional replacement explains the similar decay rates across the disturbance gradient. In addition, the proportions of saprotroph and white-rot fungi increased through time regardless of wood species. Termite presence reduced WSG loss, but the effect was mediated via the abundance of soft rot fungi. Our results suggest that changes in functional traits, rather than fungal species diversity, may better explain variation in WSG loss. Future studies should investigate roles of fungal functional traits and rot types, particularly those of Ascomycete fungi, whose roles in wood decay are still poorly characterized.