Heartwood and Sapwood Variation and Development in Chenshan Red-Heart Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook)

Chenshan red-heart Chinese fir is a provenance of Cunninghamia lanceolata, with high-value red heartwood, which is widely used in high-quality furniture and construction. Yet, there is still little information on heartwood development of this tree for high-value decorative timber, which is essential to improve one's plantation management strategy. Here, we investigated the horizontal and vertical variation of heartwood and sapwood and simulated heartwood formation process using stem analysis method. We selected 15 sample trees from five plots of 20 m × 30 m in Chenshan red-heart Chinese fir plantations (9, 15, 26, 29, and 34 years old, respectively). The results showed that Chenshan red-heart Chinese fir stems began to form heartwood when the xylem diameter reached 4 to 8 cm. The heartwood diameter and area, as well as the sapwood area, all increased in the different-aged Chenshan red-heart Chinese firs with increasing xylem diameter and decreased with increasing tree height. As tree height increased, the red heartwood formation rate declined at all ages. Relationship analysis showed that xylem diameter was the most important factor influencing heartwood formation. Red heartwood rate at breast height could be modeled by logistic models. We concluded that heartwood formation began at about 7 years old, and the formation rate increased until peaking at 60 percent at 40 years old. In conclusion, it will be imperative to prolong the Chenshan red-heart Chinese fir rotation period from the currently common 25 years to about 40 years to achieve the maximum sustainable yield of high-value decorative timber.

Radial variations in xylem sap flux in a temperate red pine plantation forest

Background Scaling sap flux measurements to whole-tree water use or stand-level transpiration is often done using measurements conducted at a single point in the sapwood of the tree and has the potential to cause significant errors. Previous studies have shown that much of this uncertainty is related to (i) measurement of sapwood area and (ii) variations in sap flow at different depths within the tree sapwood. Results This study measured sap flux density at three depth intervals in the sapwood of 88-year-old red pine (Pinus resinosa) trees to more accurately estimate water-use at the tree- and stand-level in a plantation forest near Lake Erie in Southern Ontario, Canada. Results showed that most of the water transport (65%) occurred in the outermost sapwood, while only 26% and 9% of water was transported in the middle and innermost depths of sapwood, respectively. Conclusions These results suggest that failing to consider radial variations in sap flux density within trees can lead to an overestimation of transpiration by as much as 81%, which may cause large uncertainties in water budgets at the ecosystem and catchment scale. This study will help to improve our understanding of water use dynamics and reduce uncertainties in sap flow measurements in the temperate pine forest ecosystems in the Great Lakes region and help in protecting these forests in the face of climate change.

Seasonal variation in foliar properties in Mediterranean Pine forests of different post-fire age

<p>Foliar properties play a crucial role in local and global biochemical cycles. Systematic variation in key leaf traits has been reported both between and within species. Intraspecific variation in leaf traits is controlled by micro-environmental conditions and follows seasonal patterns. In this study we examine the seasonal patterns of six foliar traits including leaf area (LA), leaf thickness (Lth), leaf mass per area (LMA), leaf dry matter content (LDMC), leaf area to sapwood area ratio (LA/SA) and branch wood density (WD) in addition to the associated parameters of the Michaelis-Menten light response curve (i.e. light saturated net photosynthetic rate (Asat), half saturation coefficient (Km) and dark respiration rate (Rd)). We measured on a monthly basis the foliar traits and developed light response curves in four Pinus brutia dominated stands along a post-fire chronosequence (15, 40, 70 and 90 years) from sunlit branches. Significant differences in the interannual trait variability were found between stands for LDMC, WD and Asat, with the highest variability identified in the younger plot. LA/SA, Rd and Km also showed strong interannual variability although not statistically different between plots. A mixed effect model analysis revealed high intraclass correlation coefficients for Km and Asat suggesting that net photosynthesis is following systematic seasonal patterns. Overall LA was higher and LDMC was lower in the oldest plot and WD was higher in the denser (40 years) plot. Interestingly gas exchange parameters did not show differences in their overall mean values. Across plots, Asat was strongly positively related to Km, and LMA was positively related to LDMC and Lth. LDMC was also positively related with Asat and negatively with Lth. A principal component analysis (PCA) revealed two major dimensions of intraspecific trait variability within our plots. The first PCA axis was positively related to Asat, Km, LDMC and LMA suggesting that regardless of the stand age needles are placed along a fast-slow carbon gain dimension with denser needles illustrating faster area-based photosynthesis. The second PCA axis was positively related to LA and Lth suggesting that bigger needles are also thicker. A subsequent permutational multivariate analysis of variance revealed that the centroids and the dispersion of the trait syndromes differed between stands, with the youngest plot illustrating higher trait dispersion and the oldest plot characterized by bigger and thicker needles. Thus, in older stands were competition for light is higher, needles are deployed to be bigger and thicker to optimize light capture, while in younger stands they are optimized along a leaf density - photosynthetic capacity spectrum depending on (more heterogeneous) microenvironmental conditions. Our findings illustrate that intraspecific variation can be attributed to either seasonal (abiotic) light availability or to (biotic) heterogeneity related to stand structure, and have important implications for local scale forest dynamics models.</p><p>«This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning 2014-2020» in the context of the project “Carbon fluxes across a post-fire chronosequence in Pinus brutia Ten forests.” (MIS 5049513)».</p>

Allometric models for the estimation of leaf area and dry weight from sapwood and heartwood area in black locust (R. pseudacacia)

<p>Allometric equations relating a tree’s vascular system with its leaf area and dry weight are developed for numerous forest species, in order to link their hydraulic architecture to carbon and biomass allocation. In 1964, Shinozaki <em>et al.</em> published the Pipe Model Theory (PMT) according to which, a given amount of leaves is supported by and is directly proportional to the area of the conductive tissue of the trunk. The present study aimed at testing whether PMT applies for <em>R. pseudacacia</em> plantations established for restoration and carbon sequestration purposes. A total of 25 trees of black locust grown at the restored former open-cast mining areas of the lignite center of the Hellenic Public Power Corporation (HPPC) in Ptolemaida and Aminteo, NW Greece, were destructively sampled. For each tree we determined its leaf area, foliage dry weight, diameter at breast height, as well as the cross-sectional areas of the trunk, the sapwood and the current sapwood at the stump height (0.30m), the breast height (1.3m), in the middle of the stem, at the base of live crown, at 1/3 and 2/3 of the length of the crown. The relationships of leaf area and foliage dry weight with the different cross-sectional areas at the selected stem heights were tested with simple and multiple linear regression models at p<0.001.</p><p>Among all tested relationships, PMT was more strongly verified by the linear relationship estimating both leaf area and foliage dry weight by the total cross-sectional area at the middle of the stem (R<sup>2</sup>=0.81). Sapwood area was found to be a less strong estimator of leaf area and foliage dry weight. The best relationships between sapwood area and leaf area / foliage were established when measured at the 1/3 of the length of the crown (R<sup>2</sup>=0.70 and 0.77, for leaf area and dry weight, respectively). The widely used relationship of sapwood at breast height to both leaf area and weight was less strong in our study (R<sup>2</sup>=0.66 and 0.68, for leaf area and dry weight, respectively). Furthermore, our results were not consistent with the theory of Shinozaki et al. (1964) that the ratio of leaf area to sapwood area increases from the top of the tree to the base of crown, where it is stabilized until breast height. These deviations may be due to the age of the studied plantations which does not exceed 30 years and the properties of the growth substrate consisting mainly of depositions from the extraction of lignite. The strongest allometric models for the estimation of leaf area and weight by tree diameter were built at breast height (R<sup>2</sup>=0.72) and at the base of live crown (R<sup>2</sup>=0.73), respectively. In addition, the trees’ diameter at the base of live crown could be reliably estimated by their diameter at breast height (R<sup>2</sup>=0.78). Our results were only partly consistent with the PMT. However, the established relationships may be useful for modelling and assessment of carbon allocation, water balance and growth of black locust plantations in restoration sites.</p>

Comparative models disentangle drivers of fruit production variability of an economically and ecologically important long-lived Amazonian tree

Trees in the upper canopy contribute disproportionately to forest ecosystem productivity. The large, canopy-emergent Bertholletia excelsa also supports a multimillion-dollar commodity crop (Brazil nut), harvested almost exclusively from Amazonian forests. B. excelsa fruit production, however is extremely variable within populations and years, destabilizing local harvester livelihoods and the extractive economy. To understand this variability, data were collected in Acre, Brazil over 10 years at two sites with similar climate and forest types, but different fruit production levels, despite their proximity (~ 30 km). One site consistently produced more fruit, showed less individual- and population-level variability, and had significantly higher soil P and K levels. The strongest predictor of fruit production was crown area. Elevation and sapwood area also significantly impacted fruit production, but effects differed by site. While number of wet days and dry season vapor pressure prior to flowering were significant production predictors, no climatic variables completely captured annual observed variation. Trees on the site with higher available P and K produced nearly three times more fruits, and appeared more resilient to prolonged drought and drier atmospheric conditions. Management activities, such as targeted fertilization, may shield income-dependent harvesters from expected climate changes and production swings, ultimately contributing to conservation of old growth forests where this species thrives.

Wood Permeability Assessment of Young Teak (Tectona grandis L.f.)

Wood properties of young teak (Tectona grandis L.f.) is inferior, and then preservative treatment is one possible solution to enhance its service life. The uptake and movement of preservatives through wood cell structure is directly connected to the wood permeability. There are two simple methods to identify wood permeability: water soaking and bubble test methods. This paper assesses the young teak permeability by water soaking and bubble test methods. The assessment was conducted into five cm thick young-teak discs by soaking in the red-dye water and blowing air into the discs which had been coated with soap. Results show that the heartwood is less permeable than sapwood. Red-dye penetrates almost 100% of the sapwood area, and the red-dye did not penetrate in the heartwood. Red-dye only penetrates in the cracked heartwood through the void volume in the cracking heartwood. There is a transition zone between sapwood and heartwood, and it is refractory. Bubble test with air pressure from compressor could open the air-pathway in the heartwood and sapwood of young-teak discs taken from Bogor. The bubble test result of young-teak discs from Madiun showed air-pathway only in the sapwood, but heartwood. The air pressure is not capable of moving the vapour through the wood cell. It indicates that the heartwood of young-teak from Madiun is less permeable and less possibility for pressure treatment.

Phenotypic Plasticity of Drought Tolerance Traits in a Widespread Eucalypt (Eucalyptus obliqua)

Long-term studies of tree responses to drought stress help us to understand the capacity of species to adapt to their environment. In this study, we investigated how Eucalyptus obliqua adjusts physiological and morphological traits in response to seasonal and multi-year droughts. We monitored physiological and morphological traits over multiple years in undisturbed control and throughfall reduction plots in a eucalypt forest in south-eastern Australia. The throughfall reduction treatment did not induce significantly lower soil moisture in the throughfall reduction plots compared with the control plots. However, natural variability in precipitation and evaporative demand induced drought stress of varying intensity each summer in all plots. We observed a significant relationship between seasonal precipitation and leaf pre-dawn water potential (ΨPD), with less precipitation over summer, resulting in a decline in ΨPD and drought stress when ΨPD fell below −0.75 MPa. Eucalyptus obliqua responded to short-term summer drought through rapid leaf osmotic adjustment which lowered the leaf water potential at the turgor loss point beyond the minimum leaf water potential. Morphological adjustments, such as the reduction of leaf area to sapwood area (higher Huber Value) were moderate during the measurement period and only occurred under severe drought stress (pre-dawn water potential < −1.2 MPa). Overall, E. obliqua responded to short-term mild drought stress through physiological trait plasticity, while morphological adjustment only occurred under a more severe water deficit.

Leaf area – sapwood area relationship in Scots pine (Pinus sylvestris L.) under mistletoe (Viscum album ssp. austriacum) infection

Leaf area is linearly correlated with sapwood area in trees. The linearity of this relationship can be affected by some biotic and abiotic factors. Mistletoes are hemi parasitic plants that take up water and mineral nutrients from their hosts and affect host physiological responses. There is no conclusive evidence to show the effect of pine mistletoe (Viscum album ssp. austriacum) on leaf area and sapwood area relationship in Scots pine trees (Pinus sylvestris L.) at tree level. The aim of this study is to determine and quantify the effect of pine mistletoe on the structural variation of leaf area and sapwood area relationship at tree level in Scots pine. A total of 18 mistletoe infected and 12 uninfected Scots pine trees were destructively sampled. All needles and mistletoes were completely removed from sampled trees to determine needle and mistletoe characteristics, biomass and leaf area. Sapwood areas at breast height (BH) and at crown base height (CBH) were determined from wood discs taken from BH (1.3m) and CBH. Sapwood area was delineated by benzidine staining method. Pearson correlation, t-test and regression analyses were conducted to determine the relationship between sapwood area and needle-mistletoe leaf area relationships. The results indicated that both the relationships between sapwood area and leaf area in uninfected, and sapwood area and total leaf area (needle plus mistletoe leaf only) in infected trees were linear. However, the slope of regression equation for mistletoe infected trees was considerably lower when compared to the uninfected trees. As for the variation of the sapwood area along the stem below live crown, there was a slight difference between sapwood area at BH and CBH. The study showed also that mistletoe infection led to a significant reduction in needle size (length, width, area and weight) in Scots pine trees. Significant relationships were found between the sapwood area and leaf area in this study. The results of this study may help fill the gap in the knowledge concerning the impacts of pine mistletoe on the dynamics of Scots pine trees.

Modelling Canopy Actual Transpiration in the Boreal Forest with Reduced Error Propagation

The authors have developed a scaling approach to aggregate tree sap flux with reduced error propagation in modeled estimates of actual transpiration () of three boreal species. The approach covers three scales: tree point, single tree trunk, and plot scale. Throughout the development of this approach the error propagated from one scale to the next was reduced by analyzing the main sources of error and exploring how some field and lab techniques, and mathematical modeling can potentially reduce the error on measured or estimated parameters. Field measurements of tree sap flux at the tree point scale are used to obtain canopy transpiration estimates at the plot scale in combination with allometric correlations of sapwood depth (measured microscopically and scaled to plots), sapwood area, and leaf area index. We compared the final estimates to actual evapotranspiration and actual transpiration calculated with the Penman–Monteith equation, and the modified Penman–Monteith equation, respectively, at the plot scale. The scaled canopy transpiration represented a significant fraction of the forest evapotranspiration, which was always greater than 70%. To understand climate change impacts in forested areas, more accurate actual transpiration estimates are necessary. We suggest our model as a suitable approach to obtain reliable estimates in forested areas with low tree diversity.