Tree Growth Rates Research Articles

Second-growth redwood forest responses to restoration treatments

Following 20th century logging, much of the natural coast redwood (Sequoia sempervirens [D.Don.] Endl.) range consists of dense second-growth stands with slow tree growth and low biodiversity. There is a landscape-scale effort in much of coastal northern California to increase tree growth rates and ecosystem biodiversity via thinning treatments, thereby hopefully accelerating the development of old-growth forest characteristics. Redwood National Park has been experimenting with thinning in these forest types since the 1970s. This study investigated short- (1 year post-thinning) and long-term (40 years post-thinning) responses of redwood physiology (water potential and stomatal conductance), redwood growth (via tree-rings), and forest biodiversity (understory plants, birds, and mammals) to restoration thinning treatments. We found that thinning second-growth redwood forests with 40% basal area reduction treatments 1) did not meaningfully influence tree water potential, 2) increased tree stomatal conductance in the short-term, 3) increased tree growth in the long-term, 4) increased understory plant diversity, and 5) did not affect bird or mammal diversity. Collectively, these findings demonstrate that thinning second-growth redwood forests has the potential to accelerate the development of old-growth characteristics. This verification of the efficacy of restoration treatments is important information for land managers, as plans are currently underway to apply these treatments at the landscape-scale. This study can provide useful baseline data to aid future assessments of long-term forest responses to contemporary restoration efforts.

Large tree species composition, not growth rates, is affected by topography in a Bornean tropical forest

AbstractLarge trees (diameter at breast height ≥50 cm) play a vital role in providing ecological services in tropical forests and can store up to 50% of aboveground biomass. We expected that topography (as a nutrient and drought proxy) would affect large tree dynamics, biomass, diversity, and composition patterns. To test this, we established a 15‐ha permanent plot at Andulau Forest Reserve (Brunei Darussalam, Borneo) with an elevation ranging from 42 m (swamp) to 92 m (ridge tops). All 559 large trees (131 species) were labeled, identified, and fitted with dendrometers. Stem density, basal area (BA), soil and litter properties, absolute diameter growth rate (AGR), and recruitment and mortality rates of large trees were determined for five elevational zones for the period 2016–2019. Stem density and BA of large trees were significantly higher in the upslope and ridge areas of the plot, and a clear shift in large tree species composition was found across the elevational zones, with the swampy area differing most from all others. However, AGR did not differ between elevational zones. Large tree mortality was balanced by recruitment, but sample size was too low to detect topographical patterns. Our findings suggest that the large tree community retained similar growth rates across soil water and nutrient gradient via a shift in species composition. If so, predicted declines in large tree productivity with climate change may, over time, also be offset by changes in species composition.

Выращивание культур ели с применением современных гербицидов, не требующее проведения агротехнических уходов

Uncontrolled development of unfavorable vegetation during artificial reforestation reduces survival and growth rates of planted trees, and in some cases causes their death. The use of reforestation equipment is often extremely difficult, therefore the most promising solutions are those involving creation of spruce plantations using seedlings with closed roots and manual planting tools without preliminary mechanical tillage. Long-term protection of plantations from undesirable vegetation is ensured by the use of modern herbicides registered for use in the forest sector in the Russian Federation. The article presents the results of 3-year field experiments on the use of herbicides and their mixtures to supress undesirable vegetation in the first years after planting European spruce (Picea abies (L.) Karst.) in the Leningrad region. High efficiency of herbicides for long-term suppression of shrubs, and herbaceous and woody plants was found. A mixture of herbicides Roundup, WS (360 g/L glyphosate acid), Anchor-85, WDG (750 g/kg sulfometuron-methyl potassium salt) and Arsenal, WC (250 g/L imazapyr) inhibited the development of herbaceous weeds for at least two growing seasons. The processes of undesirable vegetation development after spraying plantations with herbicides, the reaction of seedlings to the use of chemicals, indicators of conditions and growth of conifers were also studied. Analysis of the obtained data proved the possibility of combining a protective chemical pretreatment with herbicides and planting seedlings in a single technological procedure or planting seedlings within a few months after chemical treatment, which significantly reduces the risk of damage to seedlings by herbicides. The survival rate of plantations created by planting one- or two-year-old seedlings with closed roots was 93–98 %; and the biometric indicators were such that spruce plants could successfully compete with undesirable vegetation. The application of the developed method ensures a substantial reduction in labor and other reforestation costs compared to traditional technologies involving preliminary mechanical tillage and subsequent agrotechnical weeding of plantations. For citation: Egorov A.B., Postnikov A.M., Bubnov A.A., Pavluchenkova L.N., Partolina A.N. Cultivation of Spruce Plantations Using Modern Herbicides without Agrotechnical Weeding. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 3, pp. 9–23. DOI: 10.37482/0536-1036-2021-3-9-23

Composition And Diversity Of Plant Species In The Two Types Of Land Cover Of Natural Laboratory Of Hampangen Educational Forest

Forests are natural resources that contribute to sustaining life support systems. The purpose of this study was to determine the composition and diversity of plant species in the Hampangen Educational Forest Nature Laboratory with the object of research on plant species diversity at growth rates of seedlings, poles, saplings, and trees in the observation plots of secondary swamp forest and swamp scrub. The research was conducted using a combination technique of paths and checkered lines in each of the 30 measurement plots in the two types of observation land. The results showed 52 types of plants found in all types of research land—a total of 42 species in secondary swamp forest and 26 species in scrublands. The types of plants that occupy the highest IVI at all growth levels are Akasia, Jambu-jambu, and Meranti. The Diversity Index of plant species in the study area on both land types was classified as moderate, namely in the range 1,871 - 2,968. The evenness index value (E) of plants in the land cover type of secondary swamp forest and swamp scrub was classified as high in the range of 0.753 - 0.849. The Species Richness Index (R) value of the secondary swamp forest land cover type is classified as high, whereas the swamp scrub land cover type is classified as low, while the average species similarity index in the two land cover types is low.

Effects of growth rate of eastern poplar trees on the chemical and morphological characteristics of wood fibers

Attempts are underway to speed up timber production using genetic improvement and enhanced management practices. However, the impacts of possible morphological and chemical changes on the properties of secondary wood products are less studied. This research thus studied the relationship of tree-ring widths of eastern poplar trees (Populus deltoides Bartr.) and the morphological and chemical characteristics of the wood fibers. Cellulose, lignin, ash, and extractives contents were determined according to the Technical Association of Pulp and Paper Industry standards. Accordingly, the mean values of the various parameters measured, such as the fiber length and diameter, the diameter of the cell cavity, and the cell wall thickness along with functionality parameters such as Runkel, slenderness, and flexibility ratio, and the amounts of cellulose, lignin, extractives, and ash contents were determined. As a result, statistical analysis indicated significant correlations between tree-ring width and length and diameter of the fiber, cell cavity, Runkel ratio, cell wall thickness, cellulose content and wood density. On the contrary, there were no significant correlations between tree-ring width and slenderness and flexibility ratios, lignin, ash, and extractives contents. The investigation on the radial variation of wood properties showed from the pith to the bark, fiber length and diameter, cell wall thickness, cellulose, and density increased, and cell cavity, Runkel ratio, ash, extractives, and lignin contents decreased. Overall, increases in tree-ring width of eastern poplar improved wood quality, as raw material, for manufacturing of the most common secondary products in the wood industry, including paper and fiberboard with wide-ranging wood applications.

Trees at a Moderately Arid Site Were More Sensitive to Long-Term Drought

Climate change has dramatically altered the frequency and intensity of droughts, thereby altering tree growth. Understanding whether tree growth in semiarid areas in response to long-term drought and the post-drought recovery rate of tree growth vary along moisture gradients is crucial for predicting future forest change. Here, we assessed the spatial variation in both the growth resistance of Qinghai spruce (Picea crassifolia Kom.) to long-term drought and its post-drought recovery using a stand-total sampling strategy along a moisture gradient that covered three sites (with an annual precipitation of 330.4, 394.2, and 515.9 mm for the western, middle, and eastern sites, respectively) with six plots. Resistance and recovery were evaluated by analyzing the tree growth trends during a long-term drought period (1980–2001) and the subsequent post-drought period (2001–2013), respectively. Our results indicate that the trees with the highest temporal stability were those at the wetter eastern site; specifically, during the long-term drought period, the trees at the wetter eastern site showed the highest resistance (−0.015) and the lowest recovery (0.002). The trees in moderately arid conditions were much more sensitive to climate change than those at the relatively arid western site, showing the lowest resistance (−0.050) and highest recovery (0.020). Climate change had the strongest impact on tree growth at the moderately arid site, contributing 60.6% to the tree growth decreasing trend during the long-term drought period and 65.4% to the tree recovery during the post-drought period, respectively. Climate change had a lower impact on tree growth at the wet and dry sites, contributing less than 50% to the tree growth trends at these sites. The results indicate that a trade-off relationship exists between resistance and recovery at the different sites; that is, the highly resistant trees at the wetter eastern site tend to have lower recovery, whereas the weakly resistant trees at the moderately arid site tend to have higher recovery. These results have implications for predicting tree growth in response to future climate change.

Contrasting Growth Response of Jack Pine and Trembling Aspen to Climate Warming in Quebec Mixedwoods Forests of Eastern Canada Since the Early Twentieth Century

AbstractForest monitoring studies show contrasting trends in tree growth rates since the mid‐twentieth century. However, due to their focus on annual and decadal dynamics, they provide limited insight into the effects of long‐term climatic variability on tree growth. Here, we relied on a large tree‐ring dataset (∼2,700 trees) of two common North American shade‐intolerant tree species, trembling aspen (Populus tremuloides Michx.) and jack pine (Pinus banksiana Lambert), to assess their lifespan‐long growth dynamics in the mixedwood forests of Québec. We also determined how the environmental conditions of the stands influenced tree growth. We observed a significant increase in the radial growth rate of trembling aspen during the study period, while the jack pine decline was not significant. Over the whole study region, the trees growing in sites with lower competition, and those at the lower sections of the terrain slope experienced more of the positive effects of temperature on growth rates. Our study suggests that the tree growth response to climate warming may be species‐specific and will vary across the boreal mixedwoods.

Linking functional traits with tree growth and forest productivity in Quercus ilex forests along a climatic gradient

Plant functional traits are highly plastic to changes in climatic factors and nutrient availability. However, the intraspecific plant response to abiotic factors and the overall effect on tree growth and productivity is still under debate. We studied forest productivity for 30 Quercus ilex subsp. ballota forests in Spain along a broad climatic gradient of aridity (mean annual precipitation from 321 to 858 mm). We used linear mixed models to quantify the effect of climatic and edaphic (soil nutrients, topography, and texture) factors on tree functional traits (leaf and branch traits), and subsequently, the effect of such functional traits and abiotic factors on the relative growth rate (RGR) of adult trees. We used piecewise structural equation models (SEMs) to determine the causal effect of intrinsic and extrinsic factors on forest productivity. Our results showed that tree functional traits were mainly explained by climatic and edaphic factors. Functional traits and tree biomass explained forest biomass and RGR, respectively, which ultimately explained forest productivity. In conclusion, intraspecific variability of functional traits has a significant effect on plant biomass and growth, which ultimately may explain forest productivity in Quercus ilex forests.

Biodiversity index of fruit trees cultivated by communities around marginal land in Jombang Regency, East Java Province, Indonesia

Marginal land conditions are a major problem in reducing the level of diversity of species due to decreased soil, climate, and water quality and topography. This study aims to analyze the diversity index and the dominance of fruit tree species cultivated by surrounding communities. The research method uses nested sampling in 4 (four) sub-districts, each of which is taken three sample villages and each of them is made of three transect plots measuring sample plots 20 × 20 m 2 (trees), 10 × 10 m 2 (poles), and 5×5m 2 (sapling). Data analysis using the Biodiversity R application program with version R 3.6.1. The results of the analysis of the growth rates of the best tree species were found in Ploso Regency because they had the highest growth rates of trees, poles, and saplings. The diversity of fruit tree species is based on the distribution of the highest H index value of 1.47 and the lowest of 0.58 and includes areas that have an abundance of moderate species. Fruit tree species that have the highest importance value index are Mangifera indica (mango) 70.26% with a tree density of 139 individuals per hectare, then Dimocarpus longan (longan) 40.24% with a tree density of 153 individuals per hectare. The results of this study indicate that the community structure of fruit trees in degraded lands is more dominated by plants from the Sapindaceae and Anacardiaceae families which generally grow spread in the 4 sub-districts studied.

Effects of local neighbourhood diversity on crown structure and productivity of individual trees in mature mixed-species forests

BackgroundSpecies-specific genotypic features, local neighbourhood interactions and resource supply strongly influence the tree stature and growth rate. In mixed-species forests, diversity-mediated biomass allocation has been suggested to be a fundamental mechanism underlying the positive biodiversity-productivity relationships. Empirical evidence, however, is rare about the impact of local neighbourhood diversity on tree characteristics analysed at a very high level of detail. To address this issue we analysed these effects on the individual-tree crown architecture and tree productivity in a mature mixed forest in northern Germany.MethodsOur analysis considers multiple target tree species across a local neighbourhood species richness gradient ranging from 1 to 4. We applied terrestrial laser scanning to quantify a large number of individual mature trees (N = 920) at very high accuracy. We evaluated two different neighbour inclusion approaches by analysing both a fixed radius selection procedure and a selection based on overlapping crowns.Results and conclusionsWe show that local neighbourhood species diversity significantly increases crown dimension and wood volume of target trees. Moreover, we found a size-dependency of diversity effects on tree productivity (basal area and wood volume increment) with positive effects for large-sized trees (diameter at breast height (DBH) > 40 cm) and negative effects for small-sized (DBH < 40 cm) trees. In our analysis, the neighbour inclusion approach has a significant impact on the outcome. For scientific studies and the validation of growth models we recommend a neighbour selection by overlapping crowns, because this seems to be the relevant scale at which local neighbourhood interactions occur. Because local neighbourhood diversity promotes individual-tree productivity in mature European mixed-species forests, we conclude that a small-scale species mixture should be considered in management plans.

A strain of Phoma species improves drought tolerance of Pinus tabulaeformis

Global warming has led to frequent droughts, posing challenges for afforestation in arid and semiarid regions. In search of labor-saving and money-saving methods to improve the survival and growth rates of trees in these regions, we isolated and identified fungal endophytes that can potentially enhance the drought-resistance abilities of seedlings. We isolated 93 endophytic strains from the roots of Pinus tabulaeformis trees grown on an arid cliff. Three isolates increased the drought resistance of the tree seedlings. Using morphological, molecular, and physiological-biochemical methods, we identified three isolates as different clones of a strain of Phoma spp. and studied the strain’s effect on stress resistance-related substances in the seedlings. The results showed that the strain improved drought tolerance and increased the seedlings’ proline levels and antioxidant enzyme activities. The strain also secreted abundant extracellular abscisic acid, which likely triggered the seedlings’ protective mechanisms. This endophytic strain may provide a cheaper labor-saving, sustainable alternative to traditional methods of enhancing drought resistance.

Interspecific variation in post‐disturbance growth responses of a savanna tree community and its implications for escaping the fire trap

AbstractVegetation states in savannas are highly sensitive to tree growth rates, which determine whether individual trees can “escape” periodic disturbances. Resprouting trees have lopsided shoot:root ratios and are often multi‐stemmed, and these variables can modify post‐disturbance growth rates and therefore the probability of escape. To date, few studies have systematically examined the implications of interspecific variation in these factors for escape. We conducted a two‐year field experiment across 16 tree species in a South African lowveld savanna to quantify growth metrics following topkill. We examined the dependence of growth on pre‐disturbance stem size and the relationship between growth rate and the tendency of trees to produce a few large vs. many small resprouts following disturbance. We found that resprout growth was strongly influenced by pre‐disturbance size, but the strength of this relationship did not vary across species. In contrast, our results showed that fast‐growing species tended to allocate resources toward a few dominant stems, while slow‐growing species allocated new biomass towards many smaller stems. Tree species that produced a few large stems also tended to produce individual stems that were tall and thin, further suggesting that the “few large vs. many small” axis is linked to intrinsic species attributes. These findings have implications for understanding how interspecific variation in savanna tree communities may influence their ability to escape disturbance traps.

Using terrestrial laser scanning for characterizing tree structural parameters and their changes under different management in a Mediterranean open woodland

Analyzing tree structural features and capturing their temporal dynamic is challenging but crucial for determining key state variables related to plant function, management practices, and aboveground vegetation stocks. Terrestrial laser scanning (TLS) provides a mean for representing those key variables in three-dimensional space and through time.Here we further developed and tested two point cloud slice-based methods for estimating diameter at breast height (DBH) based on how the delineation of the slices of the tree stem point cloud was performed: the first method was based on the circumference of a slice (CM), and the second method was based on the average diameter of a slice (PM). Further, we focused on the characterization of three tree structural properties from TLS: maximum tree height (hmax), crown projected area (CA), and DBH, and then on the evaluation of their biometric relationships. Finally, we tested the potential of multitemporal TLS for evaluating the impact of tree management on tree structural properties and growth in a Mediterranean open woodland. In particular, we evaluated the effect of tree pruning and fertilization on hmax and CA.The study was conducted in three plots exposed to different fertilization treatments in a Mediterranean open woodland with ≃20% of fractional cover of evergreen holm oak (Quercus ilex L.): a control treatment without fertilization, a Nitrogen addition treatment, and a Nitrogen plus Phosphorus addition treatment. Pruning effects on tree growth were assessed in two plots within the control: an unpruned area and an area pruned in 2005.Estimation of the DBH showed a good agreement with field measurements (R2 = 0.93 for PM and R2 = 0.94 for CM). Despite Quercus ilex L. being characterized as a slow-growing species, a temporal difference of three years among TLS was sufficient to quantify the influence of different management strategies on tree structural properties and growth rates. Our results showed: (i) CA increased relatively more than hmax, independent of the respective management strategy, suggesting a preferential lateral growth in holm oak tree canopies in this open woodland, (ii) pruned trees showed larger changes in CA than control trees (Wilcoxon test p < 0.01), whereas fertilized trees grew more in height compared with control trees (Wilcoxon test p < 0.01), and (iii) biometric relationships among plant properties were affected by nutrient fertilization and pruning. These results show that multitemporal TLS shows promise for monitoring even small changes in crown dimensions, and it is a valuable tool for conducting vegetation dynamics studies and quantifying management effects.

The contribution of wildland fire emissions to deposition in the U S: implications for tree growth and survival in the Northwest

Ecosystems require access to key nutrients like nitrogen (N) and sulfur (S) to sustain growth and healthy function. However, excessive deposition can also damage ecosystems through nutrient imbalances, leading to changes in productivity and shifts in ecosystem structure. While wildland fires are a known source of atmospheric N and S, little has been done to examine the implications of wildland fire deposition for vulnerable ecosystems. We combine wildland fire emission estimates, atmospheric chemistry modeling, and forest inventory data to (a) quantify the contribution of wildland fire emissions to N and S deposition across the U S, and (b) assess the subsequent impacts on tree growth and survival rates in areas where impacts are likely meaningful based on the relative contribution of fire to total deposition. We estimate that wildland fires contributed 0.2 kg N ha−1 yr−1 and 0.04 kg S ha−1 yr−1 on average across the U S during 2008–2012, with maxima up to 1.4 kg N ha−1 yr−1 and 0.6 kg S ha−1 yr−1 in the Northwest representing over ∼30% of total deposition in some areas. Based on these fluxes, exceedances of S critical loads as a result of wildland fires are minimal, but exceedances for N may affect the survival and growth rates of 16 tree species across 4.2 million hectares, with the most concentrated impacts occurring in Oregon, northern California, and Idaho. Understanding the broader environmental impacts of wildland fires in the U S will inform future decision making related to both fire management and ecosystem services conservation.

Effects of the Application of Biochar to Plant Growth and Net Primary Production in an Oak Forest

Few studies have evaluated the application of biochar to forest ecosystems and their responses under field conditions. We manually spread grounded biochar on the forest floor, at rates of 0 (control), 5, and 10 Mg ha−1 (C0, C5 and C10, respectively), of an oak forest in central Japan to test the effects of biochar on tree growth and productivity. The relative growth rate of the diameter at breast height (dbh) of canopy oak trees (dbh &gt; 20 cm) significantly increased in C10 compared with that of the control (C0), but not in C5, in the second to third years after application. Despite the increasing growth rate of canopy trees, foliage production (NPPF) and woody production (NPPW) did not respond to biochar application. Conversely, the production of reproductive organs (NPPR, mainly oak acorns) increased in line with the biochar application rate gradients (1.04 ± 0.09 Mg ha−1 yr−1 in C0, 1.30 ± 0.08 Mg ha−1 yr−1 in C5, and 1.47 ± 0.13 Mg ha−1 yr−1 in C10). Since the contribution of NPPR to total NPP was fairly small, there were no significant differences in total NPP (=NPPW + NPPF + NPPR) for C5 (14.57 ± 0.20 Mg ha−1 yr−1) or C10 (16.11 ± 0.73 Mg ha−1 yr−1) compared with the control (15.07 ± 0.48 Mg ha−1 yr−1).

Disentangling the role of competition, light interception, and functional traits in tree growth rate variation in South Asian tropical moist forests

Tropical forests have been focused for mitigating climate change impact through carbon sequestration in plant biomass under clean development mechanism (CDM). Since trees represent more than 98% of the above ground plant biomass, variation in tree growth rate drives carbon dynamics in tropical forests. By using tree-ring analysis, trait-based measurements, and field observations, we aimed at understanding the drivers of growth rate variation in four South Asian tropical moist forest tree species varying in plant functional types. Principal component analysis (PCA) revealed that mainly demographic and wood traits represented the first axis explaining 37% of the variance, whereas the second axis was represented by the leaf traits. Stem growth rate (DI) showed a nonlinear negative relation with competition index (CI) and the ratio of crown surface area to basal area (CBR) in three out of four tree species (p < 0.001) except Lagerstroemia speciosa which showed no significant relationship with any of the studied variables. DI was linearly positively related with light interception index (LI) and the ratio of sapwood area to heartwood area (SHR) in the shade intolerant Magnolia champaca and Toona ciliata (p < 0.001). Sap wood area (SA) had a strong positive effect on DI in the three species (p < 0.001). Taking tree size as a random factor and thus accounting for ontogenetic effects on tree growth, linear mixed effect modelling revealed that CI, SA and SHR are the best predictors of DI in M. champaca (AIC = 25.81, R2m = 0.81) and T. ciliata (AIC = 62.95, R2m = 0.61). In C. tabularis, CI, SA and CBR included in the best model predicting DI (AIC = 94.62, R2m = 0.55). Variance partitioning analysis showed that the highest pure effect was observed in C. tabularis contributed by CI (12%), while the highest joint effect was found in M. champaca contributed by CI, SA and SHR (40%). Our analyses suggest that competition by neighbouring trees especially for soil moisture and the amount of active xylem portion are the main drivers of tree growth in moist tropical forests. Since tree growth rates regulate forest carbon dynamics, the insights into the growth drivers of the four selected species revealed by the study have important implications for forest/plantation management with a focus on carbon storage under CDM.

Wood Products for Cultural Uses: Sustaining Native Resilience and Vital Lifeways in Southeast Alaska, USA

Ongoing revitalization of the &gt;5000-year-old tradition of using trees for vital culture and heritage activities including carving and weaving affirms Alaska Native resilience. However, support for these sustained cultural practices is complicated by environmental and political factors. Carving projects typically require western redcedar (Thuja plicata) or yellow cedar (Callitropsis nootkatensis) trees more than 450 years of age—a tree life stage and growth rate inconsistent with current even-aged forest management strategies. Herein, we qualitatively assess the significance of wood products to rural communities and Indigenous cultures with implications for natural heritage sustainability. In partnership with Alaska Native Tribes, we engaged local youth programs to lead community discussions throughout southeast Alaska to provide specificity to the suite of cultural activities linked to regional forest lands. Results from 58 discussions across 11 southeast Alaska communities (primarily Alaska Native participants) highlighted the cultural importance of forest products including totem poles, dugout canoes, longhouses, woven hats, and woven baskets. Findings indicated spiritual well-being, health, education, tourism, and livelihood significance attributed to these products. Participant-suggested management strategies for increasing supply and expanding access to trees on public lands included: engaging local artisans in forest planning, selecting and delivering specific trees to roads as part of ongoing timber sales, allowing bark removal prior to forest-timber sales, simplifying the tree-acquisition permit process, and setting aside cultural forest groves to sustain trees seven generations into the future. By facilitating discussions, this study fostered relevant place-based youth and community engagement, benefiting youth and enhancing community knowledge transfer while simultaneously summarizing the significance of forest products for resilient culture and heritage activities. Forest management plans aiming to support Alaska Native lifeways may benefit from improved understanding of Indigenous perspectives and worldviews; designation of “culture market values” and “culture targets” can help deliver a broad array of ecosystem services.

Does Juvenile Stand Management Matter? Regional Scenarios of the Long-Term Effects on Wood Production

We analysed the regional level effects of juvenile stand management (early cleaning and precommercial thinning), shortly termed tending on wood production and the profitability of forest management. Altogether ca. 0.4 million hectares of juvenile stands from two significant forestry regions of Finland, South and North Savo, were examined. We used plot-level data of the 11th National Forest Inventory to represent the current status of juvenile stands in the study area, and the Motti stand simulator to predict the future developments of those stands for the next 100 years. We applied three scenarios: (i) Timely tending, (ii) delayed tending, and (iii) no tending, to examine differences between these alternative levels of juvenile stand management. The results showed the benefits of tending at a regional level. Timely tending was the most profitable option when low or modest interest rates (2–3%) were applied in the assessment. Even a short delay in tending clearly increased the tending costs. Delaying and neglecting tending resulted in significant losses, especially in sawlog removals and stumpage earnings. The financial gain from tending was the highest on fertile sites. Due to the high growth rate of trees, the situation may change very quickly on such sites. For the operational forestry, this means that fertile sites should have a high priority when conducting timely tendings.

Global tree-ring analysis reveals rapid decrease in tropical tree longevity with temperature

Forests are the largest terrestrial biomass pool, with over half of this biomass stored in the highly productive tropical lowland forests. The future evolution of forest biomass depends critically on the response of tree longevity and growth rates to future climate. We present an analysis of the variation in tree longevity and growth rate using tree-ring data of 3,343 populations and 438 tree species and assess how climate controls growth and tree longevity across world biomes. Tropical trees grow, on average, two times faster compared to trees from temperate and boreal biomes and live significantly shorter, on average (186 ± 138 y compared to 322 ± 201 y outside the tropics). At the global scale, growth rates and longevity covary strongly with temperature. Within the warm tropical lowlands, where broadleaf species dominate the vegetation, we find consistent decreases in tree longevity with increasing aridity, as well as a pronounced reduction in longevity above mean annual temperatures of 25.4 °C. These independent effects of temperature and water availability on tree longevity in the tropics are consistent with theoretical predictions of increases in evaporative demands at the leaf level under a warmer and drier climate and could explain observed increases in tree mortality in tropical forests, including the Amazon, and shifts in forest composition in western Africa. Our results suggest that conditions supporting only lower tree longevity in the tropical lowlands are likely to expand under future drier and especially warmer climates.

Predawn leaf conductance depends on previous day irradiance but is not related to growth in aspen saplings grown under artificially manipulated air humidity.

Recent studies have suggested that predawn stomatal opening may enhance early-morning photosynthesis (A) and improve the relative growth rate of trees. However, the causality between night-time stomatal conductance, A, and tree growth is disputable because stomatal opening in darkness can be mediated by previous day photosynthate loads and might be a consequence of growth-related processes like dark respiration (R). To identify linkages between night-time leaf conductance (gl_night), A, R, and tree growth, we conducted an experiment in hybrid aspen saplings grown under different air relative humidity (RH) conditions and previous day irradiance level (IR_pday). Predawn leaf conductance (gl_predawn) depended on RH, IR_pday and R (P < 0.05), whereas early-morning gross A (Agross_PAR500) depended on IR_pday and gl_predawn (P < 0.001). Daytime net A was positively related to Agross_PAR500 and leaf [N] (P < 0.05). Tree diameter and height increment correlated positively with gl at the beginning and middle of the night (P < 0.05) but not before dawn. Although our results demonstrate that gl_night was related to tree growth, the relationship was not determined by R. The linkage between gl_predawn and Agross_PAR500 was modified by IR_pday, indicating that daily CO2 assimilation probably provides feedback for stomatal opening before dawn.