Stemwood Production Research Articles

Foliage re-establishment of Pinus palustris Mill. saplings after spring or fall prescribed fire

Repeated fire is key to the viability of longleaf pine (Pinus palustris Mill.) ecosystems, but its acceptance as a management tool may depend on satisfactory longleaf pine growth. This is because longleaf pine establishment often has the dual-purpose of ecosystem restoration and stemwood production. Timely recovery of scorched foliage among longleaf pine seedlings and saplings supports maximum juvenile growth. We identified two means of foliage re-establishment in the growing season after prescribed fire regardless of the season of fire application. New foliage growth after spring or fall fire was correlated with un-scorched foliage biomass and the presence of lateral branches. After prescribed fire in spring, foliage biomass recovery also appeared to benefit from the mobilization of starch. The high carbon demand of foliage recovery after fall prescribed fire was associated with interruption of seasonal starch accumulation in the stem and taproot. The implication of low starch accumulation in stem and taproot tissues during the growing season after fall prescribed fire is unknown and warrants further investigation. Our results demonstrate a positive influence of residual foliage, lateral branches, and stored starch on timely foliage recovery of young longleaf pines after fire. Together with knowledge of longleaf pine development and fuel and climate conditions at the time of prescribed fire, this information will aid prescribed fire practitioners charged with maintaining longleaf pine stands of high vigor.

Genetic Parameters of Growth Traits and Stem Quality of Silver Birch in a Low-Density Clonal Plantation

Silver birch (Betula pendula Roth) is productive on abandoned agriculture land, and thus might be considered as an option for profitable plantation forestry. Application of the most productive genotypes is essential. However, information about genetic gains in low-density plantations is still lacking. A 40-year-old low-density (400 trees ha−1) plantation of 22 grafted silver birch plus-tree clones growing on former agricultural land in the central Latvia was studied. Although grafted plantations are not common in commercial forestry, the trial provided an opportunity to assess genetic parameters of middle-aged birch. The plantation that had reached the target diameter for final harvest (DBH (diameter at breast height) = 27.7 ± 5.5 cm) had an 85% survival rate, and stemwood productivity was 5.25 m3 ha−1year−1. Still, rootstock × scion interaction and cyclophysis might have caused some biases. Broad-sense heritability (H2) ranged from 0.02 for probability of spike knots to 0.40 for branch angle. Estimated H2 for monetary value of stemwood was 0.16. In general, the correlations between growth and stem quality traits were weak, implying independent genetic control, though branchiness strongly correlated with diameter at breast height. The monetary value of stemwood strongly correlated with productivity traits. The observed correlations suggested that productivity and stem quality of birch might be improved simultaneously by genetic selection.

Effect of tree spacing on growth and wood density of 38-year-old Cariniana legalis trees in Brazil

Average wood density of 38-year-old Cariniana legalis (Mart.) Kuntze, a Brazilian native forest species, was found to increase with faster growth and lower stocking, while decreasing from pith to bark. A complete randomised block design was planted with five blocks. Ten trees were harvested in each of three spacing treatments. We hypothesised that the stand stemwood production would not significantly differ depending on tree spacing. However, tree growth would be higher in the wider spacing and wood density would be higher in the narrower spacing. The diameter growth of trees was higher at 3 m × 2.5 m than at 3 m × 2 m and 3 m × 1.5 m. Nevertheless, this higher individual tree growth at 3 m × 2.5 m did not compensate for the greater tree stock density at 3 m × 1.5 m with stand stemwood production at 38 years of 530 m3 ha−1 and 649 m3 ha−1, respectively. These results suggest that C. legalis, which can produce up to 17 m3 ha−1 y−1 of medium-to high-density timber – about 800 kg m−3 – is a promising native species for forest plantations in Brazil.

Soil bacterial community responses to long-term fertilizer treatments in Paulownia plantations in subtropical China

The use of fertilizers to overcome nutrient constraints is standard practice in Paulownia fortunei plantations to increase stem wood production and tree yields. However, little is known about the responses and important role of the soil bacteria involved in the increases of soil fertility and standing volume with different fertilization. The 16S rRNA was used to compare four different fertilizer treatments for soil bacterial communities in three P. fortunei plantations, in Hunan Province, China. The results showed that the soil bacteria richness was significantly higher in plantations fertilized for ten years than for shorter times. The phyla Acidobacteria and Gemmatimonadetes were more prevalent for ten-year old plantations, and Firmicutes significantly increased with organic manure treatment (denoted as OM; p<0.05). OM significantly increased the ratio of Bacilli-like sequences in Firmicutes to 87%, 97% and 78% in seven-, nine- and ten-year-old plantations, respectively (p<0.05), while control and inorganic fertilizer had no effect. Principal coordinate analysis revealed that the soil bacterial communities in OM were different from the control and inorganic fertilizer in the three different plantations. Canonical correspondence analyses showed that available phosphorus and available magnesium were the most strongly related to bacterial community composition. The addition of OM led to soil being more fertile and an increased standing volume compared with the other fertilizer treatments. Bacilli, the most abundant class of Firmicutes may represent the bacterial type that responded most distinctly to organic manure fertilization and could be highly effective bacteria to increase soil fertility and achieve sustainable development of P. fortunei plantations.

The interactions of climate, spacing and genetics on clonal Eucalyptus plantations across Brazil and Uruguay

Abstract Intensively managed plantations account for 1.5% of the world’s forests, but they meet one-third of the demand for wood products. Eucalyptus plantations are among the most productive, with rates of growth depending heavily on genetics, silviculture, and climate. The TECHS Project examines productivity at 36 locations across a 3500 km gradient from Brazil to Uruguay, testing the interacting influences of genetics, temperature and precipitation on stemwood production. Across all sites and genotypes, stemwood production in the middle of the 6-year rotation (the peak period of growth) averaged 22 Mg ha−1 yr−1. Production varied by fivefold across sites, and by about 2-fold among genotypes within each site. The best clones at each location grew 1.5–4 Mg ha−1 yr−1 more than the average for all clones, underscoring the importance of matching genotypes to local site conditions. Contrary to patterns for natural forests across geographic gradients, Eucalyptus production declined with increasing temperature, dropping by 2.5 Mg ha−1 yr−1 for a 1 °C temperature increase. The temperature effect was likely driven in part by the geographic covariance of temperature and rainfall, as rainfall tended to decline by 78 mm yr−1 for each 1 °C increase in temperature. Stemwood production increased an average of 1.5 Mg ha−1 yr−1 for each 100 mm yr−1 increase in precipitation, but when the covariation of temperature and precipitation were included the apparent influence of precipitation declined to 0.4 Mg ha−1 yr−1 for each 100 mm yr−1 increase in precipitation. Future results will determine if within-site reductions in ambient rainfall have the same apparent influences as the rainfall pattern across the geographic gradient, as well as quantifying the importance of insects and pests in affecting growth. The supply of wood from intensively managed plantations will be strongly influenced by both temperature and precipitation at plantation locations, and with changing climates.

Functional response of coniferous trees and stands to commercial thinning in eastern Canada

The overall objectives of commercial thinning are to increase individual stem growth and, arguably, to increase stand yield. Yet few empirical results are available that would confirm the treatment meets such expectations in an industrial context. We studied the response of stands to commercial thinning with a particular focus on variables that were related to processes of stemwood production at the tree and stand levels. We inventoried permanent sample plots established between 1980 and 2000 in naturally regenerated conifer stands of southern Quebec seven to ten years after thinning. We reconstituted tree leaf area and wood production per unit leaf area using field and dendrochronological data for different years following thinning. Mixed linear models showed that tree basal area and leaf area increments following treatment were strongly related to the tree distance from the nearest skid trail. Wood production per unit leaf area was significantly higher for trees located within 5m of a skid trail compared to control trees as soon as one year following thinning application, while significant differences in tree leaf area required five years. Compared to control stands, thinned stands had higher wood production per unit leaf area, but merchantable volume increment did not differ. These results provided insight into growth processes that are involved in tree responses to mechanized thinning and could aid in the development of decision tools that determine the suitability of stands for receiving the treatment.

The Production of Stemwood and Bark of Birch in Chernigiv Polissya

Досліджено продукцію стовбурової деревини та кори дерев берези повислої. Експериментальну базу даних склали тимчасові пробні площі, зібрані за спеціальною методикою. Здійснено статистичний аналіз таксаційних показників та аналіз якісних ознак компонент стовбурів дерев. Опрацьовано нормативи оцінювання продукції стовбурової деревини та кори дерев берези повислої. Встановлено, що березові насадження в умовах Чернігівського Полісся є високопродуктивними, щорічно забезпечують високий річний приріст продукції стовбурів дерев.

Potassium fertilization increases water-use efficiency for stem biomass production without affecting intrinsic water-use efficiency in Eucalyptus grandis plantations

Adaptive strategies to improve tree water-use efficiency (WUE) are required to meet the global demand for wood in a future drier climate. A large-scale throughfall exclusion experiment was set up in Brazil to study the interaction between water status and potassium (K) or sodium (Na) availability on the ecophysiology of Eucalyptus grandis trees. This experiment focused primarily on the changes in aboveground net primary production, stand water use, phloem sap and leaf δ13C, net CO2 assimilation and stomatal conductance. The correlations between these response variables were determined to gain insight into the factors controlling water-use efficiency in tropical eucalypt plantations. The intrinsic WUE in individual leaves (the ratio of net CO2 assimilation to stomatal conductance) was estimated at a very short time scale from the leaf gas exchange. Sap flow measurements were carried out to assess the WUE for stemwood production (the ratio of wood biomass increment to stand water use).Averaged over the two water supply regimes, the stemwood biomass 3years after planting was 173% higher in trees fertilized with K and 79% higher in trees fertilized with Na than in trees with no K and Na addition. Excluding 37% of the throughfall reduced stemwood production only for trees fertilized with K. Total canopy transpiration between 1 and 3years after planting increased from about 750 to 1300mmy−1 in response to K fertilization with a low influence of the water supply regime. K fertilization increased WUE for stemwood production by approx. 60% with or without throughfall exclusion. There was a strong positive correlation between phloem sap δ13C and short-term leaf-level intrinsic WUE. Whatever the water and nutrient supply regime, the gas exchange WUE estimates were not correlated with WUE for stemwood production. Phloem sap δ13C and leaf δ13C were therefore not valuable proxies of WUE for stemwood production. The allocation pattern in response to nutrient and water supply appeared to be a major driver of WUE for stemwood production. In areas with very deep tropical soils and annual rainfall <1500mm, our results suggest that breeding programs selecting the eucalypt clones with the highest growth rates tend to select the genotypes with the highest water-use efficiency for wood production.

Two-year throughfall and fertilization effects on leaf physiology and growth of loblolly pine in the Georgia Piedmont

Loblolly pine is the most extensively planted and productive commercial pine species in the southeastern United States, but future increases in drought frequency and intensity may affect plantation productivity. To better understand the potential impacts of reduced precipitation on loblolly pine productivity, the interactive effects of throughfall (ambient versus an approximate 30% reduction) and fertilization (no fertilization versus one time fertilization with 224kgNha−1, 28kgPha−1, 56kg Kha−1, and micronutrients) on growth, leaf area index (LAI), intercepted photosynthetically radiation (IPAR) and leaf-level physiology in a 7-year-old loblolly pine plantation were studied over two years. During a year with below average annual precipitation (831mm), the throughfall reduction treatment decreased predawn leaf water potential, leaf gas exchange rates, needle elongation, basal area increment and stemwood production, and effects were independent of fertilization treatment. Leaf light-saturated net photosynthesis and stemwood production were on average 12% and 13% lower, respectively, in response to reduced throughfall treatment. During the following year with higher precipitation (1413mm), reduced throughfall treatment decreased only leaf water potential. One-time fertilization had the largest impact on growth through increases in LAI, IPAR and total absorbed photosynthetically active radiation rather than changes in growth efficiency. Enhancement of growth by fertilization was independent of the reduced throughfall treatment in both years.

Soil carbon stocks and forest biomass following conversion of pasture to broadleaf and conifer plantations in southeastern Brazil

Increased soil carbon sequestration can potentially mitigate CO2 emission and can indicate sustainable forest management. This study aims to determine the relative influence of commercial plantation tree species on soil carbon following establishment on former tropical pastures. Soil carbon (organic horizon plus mineral soil from 0 to 45cm) and stemwood productivity were quantified from 6 to 34year-old conifer and broadleaf plantations in a sandy Oxisol (Typic Hapludox) in southeastern Brazil. Study plots consisted of ten pastures paired with broadleaf plantations and ten additional broadleaf plantations paired with conifer plantations. Pastures primarily consisted of Brachiaria decumbens Stapf., while broadleaf plantations were primarily Eucalyptus, but also included one plot each of three other broadleaf species. Conifer stands were made up of Pinus species. Average stemwood productivity (± standard error) was 9.7 (±1.0) MgCha−1yr−1 for broadleaf and 5.7 (±0.5) MgCha−1yr−1 for conifer plantations, but did not correlate to soil C. The soil C in the paired Pasture–Broadleaf plots averaged 36.0±1.7MgCha−1 in pastures and 36.8±1.9MgCha−1 in broadleaf plantations. The Broadleaf–Conifer plots averaged 38.3±1.9MgCha−1 for broadleaf plantations and 36.0±1.6MgCha−1 for conifers. Our results show little difference in soil C across vegetation types, providing evidence that conifer and broadleaf plantations overall maintain similar levels of soil carbon to pasture land-use up to 34years following land conversion. Soil C differences between Pasture–Broadleaf pairs indicated a small decline in soil C accretion early after plantation establishment, followed by recovery to slightly higher accretion rates.

Simulated transformation of even-aged Norway spruce stands to multi-layered forests: an experiment to explore the potential of tree size differentiation

The study investigated the possibility to transform normal young Norway spruce (Picea abies (L.) Karst) forests to develop more heterogeneous stand structures, aiming for multi-layered forest in the long run. On three sites in central and south Sweden, 60 per cent of stand basal area was removed by thinning mainly medium-sized trees and leaving the smallest and the largest trees. Over the next 50 years, future stand development was simulated using a single-tree growth model. Simulations were run with and without ingrowth. An additional ingrowth scenario after soil preparation was tested. Basal area was kept between 10 and 20 m2 ha−1 during simulations. Projected stem wood production for the next 50 years was one-third lower compared with conventional thinning regimes. After 50 years, a multi-layered forest structure was indicated for the boreal sites in central Sweden, but not for the site in south Sweden.

Above-ground tree biomass and allometric relationships of Cinnamomum tamala grown in the western hill regions of Nepal

Biomass regression models are presented describing total above-ground biomass, stem wood, branch wood, foliage and bark production for Tejpat (Cinnamomum tamala), a multipurpose tree which is found abundantly distributed and grown in western hill districts of Nepal. A total of 56 Tejpat trees between 6.2 and 16.5 cm diameter at breast height (DBH) from farmers’ farmland and marginal land in Arghakhanchi, Gulmi and Palpa districts were sampled and harvested. Mean fresh weight of total above-ground biomass, stem wood, branch wood, foliage and bark was 77.03, 36.39, 15.16, 17.53 and 8.2 kg tree -1, respectively. Allocation of biomass was more in stem (47.24% tree-1) than in foliage (22.75% tree-1), branch (19.69% tree-1) and bark (10.31% tree-1). Weight of tree component was estimated as a function of DBH. After removal of the outliers, data were randomly divided into two datasets: 70% for model calibration and another 30% for model validation. Correlation analysis showed positive stronger linear relationship between DBH and biomass. Five regression models (linear, logarithmic, quadratic, power and exponential) were developed. All models were statistically significant, with R2 ranging from 0.64 to 0.83. Model validation was based on root mean square error (RMSE). RMSE percentage for the best-fit equation varied between 16.64% and 44.82%. Linear model resulted in the least error and was selected as the best-fit model for prediction of biomass of bark, foliage, branch, stem and total above ground tree biomass. Biomass models developed could be applied to obtain biomass of different tree components of Tejpat grown in the study area and could even be applied to other areas which have similar conditions; but it should be validated before using them in new sites and conditions. DOI: http://dx.doi.org/10.3126/banko.v21i1.9058 Banko Janakari, Vol. 21, No. 1 2011; 3-12

The relationship between tree species richness, canopy space exploration and productivity in a temperate broad-leaf mixed forest

The relationship between tree species richness and forest productivity is not well understood. We used ground-based laser scanning for analyzing the canopy structure and three-dimensional space filling by foliage and twigs in a species-rich temperate old-growth forest to test the hypotheses that (i) canopy space filling increases with tree species richness, and (ii) a higher degree of canopy space filling in diverse stands is linked to higher aboveground productivity (NPPa). Space filling was quantified in 80 plots with variable species composition (five species) and species richness (1–3 species) and related to stem wood and litter production. Neither space filling nor NPPa were higher in more diverse than monospecific plots, while species identity had a significant effect on the patterns of space occupation in the sun and shade crown. We conclude that increased complementarity in canopy space filling among the species is not an important productivity-determining factor in this temperate mixed forest.

Climate Responses of Aboveground Productivity and Allocation in Fagus sylvatica: A Transect Study in Mature Forests

According to recent climate change scenarios, temperate forests will be increasingly exposed to droughts in the 21st century which are thought to affect productivity. Although decreasing timber yield with reduced precipitation has frequently been reported from temperate forests, the dependence of forest net primary production (NPP) on precipitation is little understood. In a 3-year transect study (2009–2011) carried out in 12 mature beech forests (Fagus sylvatica) along a precipitation gradient (820–540 mm y−1) in Northern Germany, we measured all aboveground NPP components (NPPa; stem wood, leaf mass, flower and fruit production) and analyzed relationships with monthly weather data. Because we measured NPPa under a broad range of precipitation levels, drought lengths and mast fruiting intensities, the climatic controls of aboveground productivity and carbon allocation could be analyzed in detail. Despite a significant decrease in annual (and growing season) precipitation sums along the transect, NPPa remained largely invariant in each of the years, but varied remarkably between the years (means of 981, 702, 955 g DM m−2 y−1, respectively). Variation in NPPa was most closely related to current year’s early summer weather conditions (June–July), whereas the patterns of biomass allocation to wood, leaf, and fruit production responded to the previous summer’s weather. Wood production cannot predict NPPa in beech due to alternative allocation priorities of vegetative and reproductive growth. Our results show that apparent drought-induced reductions in beech timber yield often are the result of allocation shifts toward fruit production triggered by warm and dry weather in the previous summer.

Comparison of stem volume of Eastern white pine (Pinus strobus L.) and Scotch pine (Pinus sylvestris L.)

This study deals with mensurational and volumetric characteristics of introduced Eastern white pine (Pinus strobus) in comparison with native Scotch pine (Pinus sylvestris) of the similar age and habitat. Municipal forests of Hradec Králové city (an area with the natural occurrence of Scotch pine and introduced Eastern white pine; east part of Bohemia, altitude from 250 to 280 m a.s.l.) belong to typological unit – nutrient-very poor, and acidic sites. There comparative analysis of basic stem variables (stem diameter at the breast-height – DBH, total tree height – H and stem volume – V) of dominant trees (10 individuals with the highest DBH of both species) in four suitable forest stands of age from 42 to 102 years was done. Statistical analysis showed similar trends in all forests stands. Eastern white pine compared to Scotch pine reached larger mean DBH (up to 16%). H – values do not have a clear trend across the forest stands and did not show large differences in all cases. Eastern white pine compared to Scotch pine showed also larger mean stem volume (up to 47%). Therefore, introduced Eastern white pine reached higher stem size parameters and wood production compared to native Scotch pine in studied forest district.

Source-driven remobilizations of nutrients within stem wood in Eucalyptus grandis plantations

Nutrient remobilizations in tree ligneous components have been little studied in tropical forests. A complete randomized block design was installed in Brazilian eucalypt plantations to quantify the remobilizations of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) within stem wood. Three treatments were studied: control with neither K nor Na addition (C), 3 kmol ha−1 K applied (+K), and 3 kmol ha−1 Na applied (+Na). Biomass and nutrient contents were measured in the stem wood of eight trees destructively sampled at 1, 2, 3 and 4 years after planting in each treatment and annual rings were localized on discs of wood sampled every 3 m in half of the trees. Chemical analyses and wood density measurements were performed individually for each ring per level and per tree sampled. Nutrient remobilizations in annual rings were calculated through mass balance between two successive ages. Our results show that nutrient remobilizations within stem wood were mainly source-driven. Potassium and Na additions largely increased their concentration in the outer rings as well as the amounts remobilized in the first 2 years after the wood formation. The amount of Na remobilized in annual rings was 15 % higher in +Na than in +K the fourth year after planting despite a 34 % higher production of stem wood in +K leading to a much higher nutrient sink. A partial substitution of K by Na in the remobilizations within stem wood might contribute to enhancing Eucalyptus grandis growth in K-depleted soils.

Productivity differences among loblolly pine genotypes are independent of individual-tree biomass partitioning and growth efficiency

Genetic differences in individual-tree biomass partitioning, growth efficiency, and stem relative growth rate (RGR) could confer intraspecific productivity differences and might strongly influence forest ecosystem carbon storage. We examined the relationship between genotype productivity (stem volume), whole-tree biomass partitioning, growth efficiency (stem wood production per unit leaf area), and stem RGR among nine different loblolly pine (Pinus taeda L.) genotypes from three different genetic groups of contrasting inherent genetic homogeneity: three open-pollinated (half-sib) families, three mass-control pollinated (full-sib) families, and three clonal varieties. We hypothesized that genotype productivity would be positively associated with increased partitioning to stem wood relative to other plant parts, higher stem RGR, and enhanced growth efficiency. After 3 years under plantation conditions, genotypes showed significant differences in stem volume, percent stem wood, percent branch wood, and partitioning to fine roots, yet no differences in stem RGR or growth efficiency. Furthermore, genotypic differences in stem volume were independent of genotypic differences in biomass partitioning, and overall, we found no evidence to support the hypothesized relationships. Even so, the observed variation in biomass partitioning has implications for forest C sequestration as genotypes which partition more biomass to long-lived biomass pools such as stems, may sequester more C. Moreover, the lack of a genetic relationship between stem volume and belowground partitioning suggests that highly productive genotypes may be planted without compromising belowground C storage.

Effects of stump extraction on the carbon sequestration inNorway spruce forest ecosystems under varying thinning regimes with implications for fossil fuel substitution

AbstractThe overall aim of this work was to assess the effects of stump and root extraction on the long‐term carbon sequestration and average carbon storage in the integrated production of energy biomass and stemwood (pulpwood and sawlogs) under different thinning options (unthinned, current thinning and 30% increased thinning thresholds from current thresholds). The growth and development of Norway spruce (Picea abiesL. Karst.) stands on a fertile site (Oxalis‐myrtillus) in central Finland (Joensuu region: 62˚39΄N, 29˚37΄E) was simulated for two consecutive rotation periods (80 + 80 years/160 years). Stemwood and energy biomass production, carbon sequestration, and average storage and emission dynamics related to the entire production process of biomass were assessed. The assessment was done by employing a life cycle assessment tool, which combines simulation outputs from an ecosystem model and the related technosystem emissions. It was found that stump and root harvesting constituted 21–36% of the total biomass production (energy biomass and stemwood) depending on the thinning regimes and rotation period. No considerable effect was found in stemwood production when stump and root extraction was compared to the regime in which stumps and roots were left at the site. Stump and root extraction did not affect carbon sequestration on the following rotation and, in fact, an increase in forest growth was found for the unthinned and 30% increased thresholds compared to the first rotation. The results also showed that if current thinning threshold is increased, win‐win situations are possible, especially when climate change mitigation is the main concern. The substitution of coal with energy biomass is possible without reducing carbon storage in the forest ecosystem. The utilization of energy biomass, including stumps and roots, instead of coal could reduce up to 33% of emissions over two rotation periods depending on the thinning regimes. Even if stumps and roots were excluded, a maximum of 19% carbon emissions could be reduced by using only logging residues.

Tolerance and growth responses of populus hybrids and their genetically modified varieties to simulated leaf damage and harvest

Tolerance is along with resistance the two most basic mechanisms used by trees to mitigate damage by herbivores and together they comprise important traits in plant material used in forestry. Genetic modification of trees has targeted various traits including resistance with promising results. Nevertheless, little is still known of how changes of the plant genome may interact with damage to affect tolerance and productivity of the trees. To address this we tested tolerance and growth responses of two different populus hybrids and their corresponding GM varieties to simulated leaf damage and harvest.Morphological growth responses to leaf damage included a decreased biomass production of the effected shoot (e.g. the main stem) which was partly compensated for increased biomass production in the undamaged branches. This compensation was mainly due to growth responses in already existing branches rather than stimulation of new buds. However, despite growth inductions in branches the net growth response seen over the whole plant was negative, e.g. plants could not fully compensate for lost leaf tissue and thus showed under-compensation for damage.We further show that the ability for post harvest re-growth correlated positively with the biomass of plants at harvest but only for the high damage treatment and not for low to intermediate levels of damage under which this relationship was neutral. Tolerance may thus have intricate influence over the success of short rotation plantation practices under which plants are subjected to repeated harvests while simultaneously being subjected to increased risk of severe leaf damage by herbivores.The ability for tolerance did not differ significantly between the two tested hybrids or among hybrids and their corresponding GM varieties. This was also so for the capacity for re-growth after harvest. The production of stem wood and leaves as well as total biomass was, however, significantly different among lines. These among line differences were both caused by differences between the two Wt hybrids (e.g. Wt-Lignin produced ∼37% more biomass than Wt-Bt) and differences caused by genetic modification (e.g. Wt-Bt produced ∼19% more biomass compared to Bt27).Our results give a strong indication that the growth responses of the GM varieties to leaf damage and harvest were substantially equivalent with their corresponding non-GM varieties. These similarities predict that the effect of damage on production should be alike regardless of if the GM or non-GM products are used.

Stand-level patterns of carbon fluxes and partitioning in a Eucalyptus grandis plantation across a gradient of productivity, in Sao Paulo State, Brazil

Wood production represents a large but variable fraction of gross primary production (GPP) in highly productive Eucalyptus plantations. Assessing patterns of carbon (C) partitioning (C flux as a fraction of GPP) between above- and belowground components is essential to understand mechanisms driving the C budget of these plantations. Better knowledge of fluxes and partitioning to woody and non-woody tissues in response to site characteristics and resource availability could provide opportunities to increase forest productivity. Our study aimed at investigating how C allocation varied within one apparently homogeneous 90 ha stand of Eucalyptus grandis (W. Hill ex Maiden) in Southeastern Brazil. We assessed annual above-ground net primary production (ANPP: stem, leaf, and branch production) and total belowground C flux (TBCF: the sum of root production and respiration and mycorrhizal production and respiration), GPP (computed as the sum of ANPP, TBCF and estimated aboveground respiration) on 12 plots representing the gradient of productivity found within the stand. The spatial heterogeneity of topography and associated soil attributes across the stand likely explained this fertility gradient. Component fluxes of GPP and C partitioning were found to vary among plots. Stem NPP ranged from 554 g C m(-2) year(-1) on the plot with lowest GPP to 923 g C m(-2) year(-1) on the plot with highest GPP. Total belowground carbon flux ranged from 497 to 1235 g C m(-2) year(-1) and showed no relationship with ANPP or GPP. Carbon partitioning to stem NPP increased from 0.19 to 0.23, showing a positive trend of increase with GPP (R(2) = 0.29, P = 0.07). Variations in stem wood production across the gradient of productivity observed at our experimental site were a result of the variability in C partitioning to different forest system components.