Tree Growth Rates Research Articles

Response of tree growth to nutrient addition is size dependent in a subtropical forest

Understanding how nutrient addition affects the tree growth is critical for assessing forest ecosystem function and processes, especially in the context of increased nitrogen (N) and phosphorus (P) deposition. Subtropical forests are often considered N-rich and P-poor ecosystems, but few existing studies follow the traditional “P limitation” paradigm, possibly due to differences in nutrient requirements among trees of different size classes. We conducted a three-year fertilization experiment with four treatments (Control, N-treatment, P-treatment, and NP-treatment). We measured soil nutrient availability, leaf stoichiometry, and relative growth rate (RGR) of trees across three size classes (small, medium and large) in 64 plots. We found that N and NP-treatments increased the RGR of large trees. P-treatment increased the RGR of small trees. RGR was mainly affected by N addition, the total effect of P addition was only 10 % of that of N addition. The effect of nutrient addition on RGR was mainly regulated by leaf stoichiometry. This study reveals that nutrient limitation is size dependent, indicating that continuous unbalanced N and P deposition will inhibit the growth of small trees and increase the instability of subtropical forest stand structure, but may improve the carbon sink function of large trees.

Inventory of mangrove species diversity in Ruar village, Biak Numor Regency, Papua Province

Efforts to preserve mangrove forests through species diversity inventory are important input data in mangrove forest management. The purpose of this research is to investigate the potential and diversity of mangrove forest species in Ruar village, Biak Numfor Regency, Papua Province. Inventory of mangrove species using the grid line method which is laid systematically. The distance between the lanes is determined to be 200 meters and plots are placed to the left and right of the lanes, making up as many as six lanes/transects. The results of this study, there are 5 species, namely Sonneratia alba, Rhyzophora stylosa, Rhyzophora apiculata Bl, Bruguiera gymnorhyza (L) Lamk, Ceriops tagal (Perr). C.B.Rob. On tree growth rates were dominated by Rhyzophora apiculate Bl (INP 152.73%), sapling and seedling rates dominated by Bruguiera gymnoriza (L) Lamk (INP 137.85% and INP 128.46%). Species diversity index according to tree growth rate (0.874), sapling rate (0.678) and seedling rate (0.667). According to Shannon-Wienner criterion (H’ <1), the species diversity index in the mangrove forest of Ruar Village, Biak Numfor Regency is low. Species enrichment planting activities are needed in maintaining and increasing the diversity of mangrove species to control environmental disturbances.

Plant Adaptation and Phosphorus Limitation in Tropical Forests: A Theoretical and Empirical Assessment

Ecosystem dynamics are shaped by plant adaptation to environmental stress, yet the conditions under which this occurs remain poorly understood. We developed a theoretical framework to predict how strategies used by tropical trees to cope with low-phosphorus (P) availability (that is, traits related to P uptake, and use) influence growth under P limitation. We then tested this framework against data on tree species in Borneo and a meta-analysis of results from pantropical nutrient addition experiments. Our theoretical framework predicts that plant traits associated with low-P environments, including enhanced P allocation to leaves, efficient P resorption, and root phosphatase activity, alleviate the negative effects of P scarcity more strongly for “inefficiently” growing plants, represented by large trees and old-growth forests, compared with saplings or secondary forests. In agreement with this prediction, changes in traits related to low-P environments increased the potential relative growth rate of large trees more than small trees in Borneo. Finally, theoretical expectation was supported by a meta-analysis which revealed stronger P limitation in saplings and secondary forests than in old-growth forests. Together, these findings provide a novel framework to interpret the relationship between resource constraints and plant performance and reinforce the importance of accounting for plant adaption to predict ecosystem responses to P limitation in tropical forests.

Reduction of the mangosteen tree (Garcinia mangostana L.) production cycle: effect of soil type and fertilisers

BackgroundShortening the vegetative cycle of slow-growing crops is a significant challenge for breeders, agronomists, and growers. This reduction is particularly crucial for the mangosteen (Garcinia mangostana) as it would make it easier for farmers to adopt this crop. The mangosteen tree is notoriously slow-growing, taking between 8 and 15 years to produce its first fruits. The plant's slow growth and late fruiting pose a significant obstacle to its adoption and spread in rural areas. In Côte d'Ivoire, these constraints have limited its cultivation to small farms owned by a few producers. However, it could be an alternative for diversifying agricultural income and contributing to poverty reduction in rural areas. This study aims to evaluate the effects of soil type and fertiliser on the agronomic parameters of mangosteen tree growth. The goal is to contribute to shortening its vegetative phase.ResultsThe study results indicate that soil type and fertiliser have a significant effect on mangosteen growth parameters. Evaluating the agronomic performance of mangosteen, it was found that lowland soil promotes better plant growth. Growth rate and height growth were found to be significantly influenced (p = 0.03). After 36 months of monitoring, the growth rates for mangosteen trees grown on lowland soil were 53.08 ± 7.30%, while those grown on forest soil were 41.51 ± 13.43%. Additionally, the use of foliar and granular N-P-K fertilisers resulted in earlier fruiting, starting from the 5th year of cultivation.ConclusionsThe results showed that fertilisers play a crucial role in managing and shortening the juvenile phase of the mangosteen tree. Foliar and NPK fertilisers performed exceptionally well, resulting in earlier fruiting of mangosteen trees, starting from the 5th year of cultivation.

How Pollution and Climate Change Affect the Future of Mangrove Forest—A Simulation Study on the Mangrove Area in the Thi Vai Catchment, Vietnam

Environmental pollution and climate change have been reported to severely affect the growth and productivity of mangroves. However, it is still unclear how the mangroves will fare if stressed by these adverse conditions, and how the mangroves might fare if these conditions improve. In this study, the trends of mangrove forests in the Thi Vai catchment (Vietnam) were assessed using mathematical models, addressing the polluted environment under climate change conditions. This simulated study was conducted based on the analysis of different types of data. Data on 18 elements’ concentrations accumulated in mangrove tissues in this catchment were analyzed in relation to the states of tree growth rates. Data on the economic productivity and water quality of the Thi Vai River in the five years from 2017 to 2021 were analyzed to detect the main sources of pollution that induced damage to mangrove forests. The results achieved from data analysis are the linear and nonlinear interactions between the concentrations of tissue-accumulated substances and the growth rates of trees. Concentrations of P, Mg, and Sr in mangrove leaves have a linear relationship with plant growth while Cr, Cu, and Ni accumulated in roots have a nonlinear relationship. The mining industry and accommodation and food services are the main contributing sources of Cr and Cu, which affect mangrove health. Information supplied from the data analysis helped in designing the scenarios of different combined environmental conditions for model simulations. Our previously developed mangrove dynamics model was applied to predict the trajectory of the mangrove forest in this area under a total of 16 combined environmental condition scenarios.

Large-scale determinants of street tree growth rates across an urban environment.

Urban street trees offer cities critical environmental and social benefits. In New York City (NYC), a decadal census of every street tree is conducted to help understand and manage the urban forest. However, it has previously been impossible to analyze growth of an individual tree because of uncertainty in tree location. This study overcomes this limitation using a three-step alignment process for identifying individual trees with ZIP Codes, address, and species instead of map coordinates. We estimated individual growth rates for 126,362 street trees (59 species and 19% of 2015 trees) using the difference between diameter at breast height (DBH) from the 2005 and 2015 tree censuses. The tree identification method was verified by locating and measuring the DBH of select trees and measuring a set of trees annually for over 5 years. We examined determinants of tree growth rates and explored their spatial distribution. In our newly created NYC tree growth database, fourteen species have over 1000 unique trees. The three most abundant tree species vary in growth rates; London Planetree (n = 32,056, 0.163 in/yr) grew the slowest compared to Honeylocust (n = 15,967, 0.356 in/yr), and Callery Pear (n = 15,902, 0.334 in/yr). Overall, Silver Linden was the fastest growing species (n = 1,149, 0.510 in/yr). Ordinary least squares regression that incorporated biological factors including size and the local urban form indicated that species was the major factor controlling growth rates, and tree stewardship had only a small effect. Furthermore, tree measurements by volunteer community scientists were as accurate as those made by NYC staff. Examining city wide patterns of tree growth indicates that areas with a higher Social Vulnerability Index have higher than expected growth rates. Continued efforts in street tree planting should utilize known growth rates while incorporating community voices to better provide long-term ecosystem services across NYC.

Atributos das árvores hospedeiras, e não a diversidade da comunidade, conduzem a abundância de epífitas em florestas tropicais sazonais

Abstract Epiphytes are considered indicators of forest ecological integrity, but the factors that explain their abundance are still not well understood. We here evaluated tree colonization by epiphytes in old-growth monospecific reforestation stands of Astronium urundeuva (M.Allemão) Engl. (Anacardiaceae) and Eucalyptus saligna Sm. (Myrtaceae), in comparison to a neighbor seasonal tropical forest fragment under similar environmental conditions. In each forest type, we identified and measured all trees (planted and colonizers) from 5-cm stem diameter in five 200 m² plots and quantified all vascular epiphytes per tree. Tree species were categorized by bark roughness, canopy deciduousness and growth rate. The abundance of epiphytes and the frequency of host trees were higher in the A. urundeuva plantation than in the native forest, with the E. saligna stand in an intermediate position. Also, we found that host traits influenced the abundance of epiphytes in their trunks. Host trees had average stem perimeter and height both higher than non-hosts, which indicates that colonization is more likely to occur in older trees. The average abundance of epiphytes per tree was higher in species with rough bark, but no relationship was found with canopy deciduousness or tree growth rate. We evidenced, therefore, that forest plantations, even if monospecific, can provide habitat for epiphytes. However, at community level, colonization success, either in native or restored forest, depends on the relative abundance of species whose bark type favors epiphytes establishment.

Phenology and radial growth of poplars in wide alley agroforestry systems and the effect on yield of annual intercrops in the first four years of tree age

Silvoarable agroforestry systems have the potential to combat the negative effects of climate change while also enhancing productivity per unit land. Although the growth rate of large-spaced trees remains poorly investigated and the yield of annual intercrops uncertain, silvoarable agroforestry systems with poplar are receiving an ever-growing interest. This study assessed the growth of the new HES (High Environmental Sustainability) poplar clone, Moncalvo, arranged in 40-m spaced parallel alleys with a density of 35 trees ha−1 (SA, silvoarable). Their growth was compared to those cultivated in a specialized poplar plantation (C, control) with 277 trees ha−1, and the agronomic impact on wheat and soybean as intercrops was explored. Measurements took place between 2018 and 2021 during the first 4 years, which represents the midpoint of the expected poplar rotation. Here it was demonstrated that at the end of the investigated period, diameter at breast height was significantly greater (23.8 vs. 20.5 cm, +16%) and the plant height lower (14.3 vs. 15.5 m, −8%) in poplar grown in SA as compared to those in C, likely due to reduced intraspecific competition for environmental resources. In SA, seasonal tree phenology was delayed by approximately two weeks in spring, possibly due to the high sensitivity of poplar to low soil water content and cooler night air temperatures in springtime. The grain yield of wheat was not impaired by tree shading but instead occasionally improved when neighboring the poplar alley (e.g., year 2021: +28% at 12 m from the tree row vs. full sun conditions), while soybean yield was generally reduced (maximum −38% at 6 m from the tree row). This study innovatively studied the growth response of HES poplar clones in silvoarable systems by providing valuable insights into the growth dynamics of trees grown in combination with field crops. It is concluded that poplars in wide spaced alleys of silvoarable systems in temperate climates grow faster than poplars in plantations of high population density due to enhanced access to resources, while future investigations will allow for the identification of clone-specific rotation durations. In the arable tree interrow, winter crops more readily benefit from such agroforestry system than summer crops due to reduced cycle overlap and light competition with the tree canopy.

Evaluation of Tree-Growth Rate in the Laurentides Wildlife Reserve Using GEDI and Airborne-LiDAR Data

Loss of forest cover and derived effects on forest ecosystems services has led to the establishment of land management policies and forest monitoring systems, and consequently to the demand for accurate and multitemporal data on forest extent and structure. In recent years, spaceborne Light Detection and Ranging (LiDAR) missions, such as the Global Ecosystem Dynamics Investigation (GEDI) instrument, have facilitated the repeated acquisition of data on the vertical structure of vegetation. In this study, we designed an approach incorporating GEDI and airborne LiDAR data, in addition to detailed forestry inventory data, for estimating tree-growth dynamics for the Laurentides wildlife reserve in Canada. We estimated an average tree-growth rate of 0.32 ± 0.23 (SD) m/year for the study site and evaluated our results against field data and a time series of NDVI from Landsat images. The results are in agreement with expected patterns in tree-growth rates related to tree species and forest stand age, and the produced dataset is able to track disturbance events resulting in the loss of canopy height. Our study demonstrates the benefits of using spaceborne-LiDAR data for extending the temporal coverage of forestry inventories and highlights the ability of GEDI data for detecting changes in forests’ vertical structure.

Transitional responses of tree growth to climate warming at the southernmost margin of high latitudinal permafrost distribution

The marked increase in temperature warming and permafrost degradation has raised apprehensions about the fate of forests of boreal forests in permafrost regions. However, the impact of climate on tree growth is not limited to direct effects but also involves complex interactions with permafrost. The degradation of permafrost poses a threat to forest growth that has received insufficient attention thus far, after analyzing the impact of permafrost degradation and climate on Dahurican larch (Larix gmelinii) growth from six forest sites with two maximum active layer thickness (ALT) classifications (more and less than tree root length) across the southern margin of the permafrost region. We found that accompanying the continued degradation of permafrost, tree growth was inhibited (slope = −0.67, p < 0.05) by the degradation of permafrost and the growth-climate relationship was shifted from positive to negative at maximum ALT less than tree root length sites. However, the growth rate of trees significantly accelerated (slope = 5.46, p < 0.05) at maximum ALT more than tree root length sites. Path analysis indicated that tree growth did not benefit from temperature warming and more stress could be caused by waterlogging due to permafrost degradation at maximum ALT less than tree root length sites, however, enhanced tree growth primarily by reducing the physical spatial constraints and root layer additional water source with permafrost degradation at maximum ALT more than tree root length sites. It also implies that the matchiness between tree root and maximum active layer depth is critical to the effect of permafrost degradation on tree growth. The transitional response to climate warming and the opposite trend of tree growth at two ALT classification sites suggest that future tree growth responds to the different stages of permafrost degradation differently. Our study provides a new insight on permafrost degradation impact on tree growth.

Determining Allometry and Carbon Sequestration Potential of Breadfruit (Artocarpus altilis) as a Climate-Smart Staple in Hawai‘i

Breadfruit (Artocarpus altilis) is an underutilized Pacific tree crop that has been highlighted as having substantial potential to contribute to global food security and climate-smart agriculture, including adaptation to and mitigation of climate change. To explore the carbon sequestration potential of breadfruit production, we characterize tree volume, wood density, carbon density, foliar biomass, and growth rates of breadfruit in Hawai‘i. Strong relationships to trunk or branch diameter were displayed for wood density (r2 0.81), carbon density (r2 0.87), and foliar biomass (r2 0.91), which were combined to generate an allometric prediction of tree volume (r2 0.98) based on tree diameter at breast height. Growth rates, as measured by diameter at breast height, were well predicted over time when trees were classified by habitat suitability. We extrapolate potential breadfruit growth and carbon sequestration in above-ground biomass to the landscape scale over time. This study shows that breadfruit is on the low end of broadleaf tropical trees in moist and wet environments, but in an orchard can be expected to sequester ~69.1 tons of carbon per hectare in its above-ground biomass over a 20-year period.

PERTUMBUHAN DAN PERKEMBANGAN TANAMAN Gmelina moluccana (RE-NUMERASI KEDELAPAN)

This research aims to determine the annual growth rate, diameter growth, and technical rotation age achievement of Titi trees (Gmelina moluccana) 8 years after planting. The method employed is a quantitative descriptive approach, involving the re-measurement (re-numeration) of Titi trees to calculate growth rates and observe changes in growth stages. The results of the study indicate a current annual increment (CAI) of 2.69 cm/yr for diameter in the eighth year, and a mean annual increment (MAI) of 1.52 cm/yr for diameter. In terms of height, the current annual increment (CAI) is 2.48 cm/yr in the eighth year, with a mean annual increment (MAI) of 1.49 cm/yr. The achievement of the technical rotation age for Titi trees (Gmelina moluccana) based on diameter growth is reached in the seventh year. In the eighth year, the development of Titi trees (Gmelina moluccana) shows that 23 individuals are still at the pole stage, 52 individuals have reached the tree stage, and there are no trees that have flowered or fruited yet.

Growth responses to climate warming and their physiological mechanisms differ between mature and young larch trees in a boreal permafrost region

The effects of tree age-related intrinsic water-use efficiency (iWUE) under climate change such as warming and rising atmospheric CO2 concentrations (Ca) on tree growth are still poorly understood. We measured tree-ring δ13C, δ18O, tree-ring width, and their relationships with climate variables, calculated iWUE for relatively young (90 ± 5 yr) and mature (230 ± 40 yr) Larix dahurica trees in a boreal permafrost region in northeastern China. The period of tree-ring measurements covering 70 years includes a pre-warming period (1951–1984; base period) and a warm period (1985–2018; warm period). The growth rate of both mature and young trees did not change with time over the base period, while the mature trees but not the young ones significantly increased the growth rate with time over the warm period. The iWUE of mature trees consistently increased from 1951 to 2018, whereas that of the young trees increased only with time during the warm period from 1985 to 2018. The tree-ring δ13C and δ18O were not correlated for both young and mature trees over both base and warm periods, except for a significantly positive correlation between tree-ring δ13C and δ18O for mature trees during the warm period. We found that mature trees were more sensitive to Ca than young trees. Our results suggest that mature trees have a more ‘conservative’ (low stomatal conductance (gs), constant assimilation rate (A)) water use strategy than young trees (constant gs, high A) in the permafrost regions in a warming world.

Modeling Above-Ground Carbon Dynamics under Different Silvicultural Treatments on the McDonald–Dunn Research Forest

Forest management decisions affect carbon stock and rates of sequestration. One subject of debate is the rotation age that will optimize sequestration over extended periods. Some argue that shorter rotations facilitate greater sequestration rates due to the accelerated growth rates of younger trees compared to mature or old-growth trees. Others maintain that frequent harvesting will not allow forest carbon to rebound after each subsequent rotation, and thus more extended periods between clearcutting is the superior choice. These contrasting viewpoints are mirrored regarding the impact of thinning treatments, in that either thinning will enhance forest carbon uptake by facilitating improved and sustained r growth of residual trees or removing any above-ground biomass will outweigh the yields. This study aims to compare the different suites of management decisions and identify practical combinations of rotation ages and thinning applications that will optimize carbon sequestration while meeting other objectives over a 240-year projection timeframe. Stand development under different harvest rotations and thinning specifications was modeled using a Forest Vegetation Simulator (FVS). We found that site productivity was the primary determinant in stand-above-ground carbon dynamics under various management scenarios. Thus, the optimal rotation age/thinning treatment combinations differed between site classes. High productivity stands were estimated to sequester the most above-ground live carbon with 60-year rotations with a low-intensity thin at age 40. Moderately productive stands performed the best with 80-year rotations when two low-intensity thinning treatments were applied between harvests. For high and moderate productivity stands, estimates of gross carbon increased when two low or moderate-intensity thinning treatments were applied within 80- or 120-year rotations. High-intensity thinning treatments reduced total carbon sequestered over the 240-year projection timeframe for all productivity levels and rotation ages, except for low productivity stands under 120-year rotations.

Anatomical distribution of starch in the stemwood influences carbon dynamics and suggests storage‐growth trade‐offs in some tropical trees

Abstract Trees balance temporal asynchrony in carbon source and sink activity by accumulating and using non‐structural carbon (NSC). Previous work has demonstrated differences in the amount and distribution of NSC stored in stemwood in tropical tree species and related these patterns in NSC distribution to tree growth and mortality rates. However, we still do not know how changes in the amount and location of starch, a major component of NSC in stemwood, influence the seasonal carbon dynamics of mature trees and how this may reflect storage‐growth trade‐offs. In this work, we hypothesized that combining two life history traits, here leaf habit (evergreen/semi‐deciduous) and the anatomical distribution of starch within the stemwood (parenchyma storage and fibre storage), would allow us to explain differences in the seasonal interplay between carbon sources and sinks and the use and accumulation of starch in the tree stem. We expected semi‐deciduous/fibre‐storing species to have greater seasonal amplitudes of carbon source and sink activity, and therefore greater variation in starch content and stronger storage‐growth trade‐offs than evergreen/parenchyma‐storing species. We measured monthly increments in stem radial growth, soluble sugars and starch every 3 months during 2019 in Dacryodes microcarpa (semi‐deciduous/fibre‐storing species), Ocotea leucoxylon (evergreen/parenchyma‐storing species) and Sacoglottis guianensis (semi‐deciduous/parenchyma‐storing species). We found seasonal changes in starch but not sugars in the semi‐deciduous species, with greater amplitude in the fibre‐storing species that also had greater storage capacity and stem respiration rates. The fibre‐storing species further showed a negative relationship between starch consumption/accumulation and growth during the rainy season, suggesting a trade‐off between growth and storage, with starch accumulating in some cases when growth was low. Synthesis. Our results show the influence of seasonal starch storage on carbon dynamics in three species of tropical trees that differ in leaf phenology and starch storage traits. Semi‐deciduous/fibre‐storing species have greater temporal variation in carbon sink activities and more seasonally dynamic starch content. Since the fibre‐storing species we studied are slower‐growing and longer‐lived trees with lower mortality rates compared to the parenchyma‐storing species, these results may provide clues about how storage traits could influence their survival and life span.

Climatic Warming-Induced Drought Stress Has Resulted in the Transition of Tree Growth Sensitivity from Temperature to Precipitation in the Loess Plateau of China.

Ongoing climate warming poses significant threats to forest ecosystems, particularly in drylands. Here, we assess the intricate responses of tree growth to climate change across two warming phases (1910-1940 and 1970-2000) of the 20th century in the Loess Plateau of China. To achieve this, we analyzed a dataset encompassing 53 ring-width chronologies extracted from 13 diverse tree species, enabling us to discern and characterize the prevailing trends in tree growth over these warming phases. The difference in the primary contributors over two warming phases was compared to investigate the association of tree growth with climatic drivers. We found that the first warming phase exerted a stimulating effect on tree growth, with climate warming correlating to heightened growth rates. However, a contrasting pattern emerged in the second phase as accelerated drought conditions emerged as a predominant limiting factor, dampening tree growth rates. The response of tree growth to climate changed markedly during the two warming phases. Initially, temperature assumed a dominant role in driving the tree growth of growth season during the first warming phase. Instead, precipitation and drought stress became the main factors affecting tree growth in the second phase. This drought stress manifested predominantly during the early and late growing seasons. Our findings confirm the discernible transition of warming-induced tree growth in water-limited regions and highlight the vulnerability of dryland forests to the escalating dual challenges of heightened warming and drying. If the warming trend continues unabated in the Loess Plateau, further deterioration in tree growth and heightened mortality rates are foreseeable outcomes. Some adaptive forest managements should be encouraged to sustain the integrity and resilience of these vital ecosystems in the Loess Plateau and similar regions.

Root vascular anatomy predicts maximum growth rates in savanna trees and grasses

AbstractRoot‐based functional traits are relatively overlooked as drivers of savanna plant community dynamics, an important gap in water‐limited ecosystems. Recent work has shed light on patterns of trait coordination in roots, but less is known about the relationship between root functional traits, water acquisition, and plant demographic rates. Here, we investigated how fine‐root vascular and morphological traits are related in two dominant PFTs (C3 trees and C4 grasses from the savanna biome), whether root traits can predict plant relative growth rate (RGR), and whether root trait multivariate relationships differ in trees and grasses. We used root data from 21 tree and 18 grass species grown under greenhouse conditions, and quantified a suite of vascular and morphological root traits. We used a principal components analysis (PCA) to identify common axes of trait variation, compared trait correlation matrices between the two PFTs, and investigated the relationship between PCA axes and individual traits and RGR. We found that there was no clear single axis integrating vascular and morphological traits, but found that vascular anatomy predicted RGR in both trees and grasses. Trait correlation matrices differed in trees and grasses, suggesting potentially divergent patterns of trait coordination between the two functional types. Our results suggested that, despite differences in trait relationships between trees and grasses, root conductivity may constrain maximum growth rate in both PFTs, highlighting the critical role that water relations play in savanna vegetation dynamics and suggesting that root water transport capacity is an important predictor of plant performance in the savanna biome.

Assessing future climate trends and implications for managed forests across Canadian ecozones

Climate change interacts with ecological processes leading to changes in tree and forest growth rate, biome shifts and species composition, all of which are influenced by disturbances. This study explores future overarching climate trends of eight of Canada's ecozones containing managed forests. For the 2071 to 2100 period, climate projections indicate a warming trend of up to an additional 5.5 °C and an overall increase in annual precipitation. Future trends suggest marked contrast between coastal and interior forests and polarization between western and eastern forests. Warmer temperatures, accumulating degree-days above 5 °C and frost-free days suggest longer and drier growing seasons and greater risk of drought particularly in moisture-limited areas such as montane cordillera, taiga shield and boreal shield ecozones. Warmer temperatures and rising precipitation combined with less snow suggest shorter and wetter future winters. This indicates greater risk of rain-on-snow and freeze-thaw events, flooding and landslides particularly in coastal ecozones. We discuss how these projections are likely to result in shifts in dominant species and abundance, which when coupled with the cumulative effects of future disturbances, is likely to alter future forest dynamics and impact harvestable wood volumes for Canada's forestry industry.

Dynamics of litterfall production in a forest damaged by oak wilt disease: a case study in a warm-temperate secondary forest

ABSTRACT Quantification of litterfall production is crucial for evaluating net primary productivity and nutrient cycling in forest ecosystems. High mortality among trees in the family Fagaceae due to Japanese oak wilt disease (JOW) might affect litterfall production in secondary forests; however, few studies have quantified these effects. We investigated litterfall production and forest structure in warm-temperate secondary forests in the Kaisho Forest over 6 and 12 years, respectively, and compared the dynamics among different phases of a JOW outbreak to assess the impacts of JOW on litterfall production. We found that total annual litterfall and leaf fall showed little change in peak to post-JOW periods and that changes in basal area were unrelated to total litterfall and leaf fall. The observed fluctuation in BA in the Kaisho Forest may not have been large enough to clearly reveal the effect of JOW during these periods. Canopy gaps formed by JOW may enhance the recruitment and growth rates of sub-canopy and understory trees. Our results may only be applicable to warm secondary forests where evergreen trees are replacing deciduous trees. Additional information on litterfall production in JOW-disturbed secondary forests is needed.

Tree growth rate under urban limiting conditions

The benefits of green areas mostly depend on the trees’ dimension, which in the urban environment is not as predictable as it is in woodland. Growth models based on tree height and tree diameter at breast height have been largely employed to predict tree growth also in urbanised contexts. However, city environments differ from natural ones, and in addition to geographical influence, they present high variability in growth conditions within a few metres. Different urban conditions may influence tree vertical and diametral growth. The present study aims to jointly consider the effect of urban environment, maintenance practices and available space on the size growth of some tree species. Dendrometrical, space, management and status parameters of the sampled trees were collected during field surveys 14 years apart. Tree height and diameter at breast height data interpolations were realised and charted by an open-source graphing calculator to build three different growth equations (linear, logarithmic and logistic) for each of the five species considered regardless of tree growth conditions. The comparison between the comprehensive best-fitting models realised within this study and a USA inventory-based study highlighted quite similar tree growth trends, probably due to the consideration of both constrained and unconstrained trees. Furthermore, a study on the curves of same-growth condition trees of the same species was conducted. Generally, heavy pruning techniques such as control and pollard pruning, characterised by the removal of a consistent part of the tree crown, stand out as the main growth-limiting factor for the different species.