Thinning Intensity Research Articles

Restoration thinning accelerates small tree growth but may slow large tree growth in a multi‐age flood‐dependent forest

Abstract Large tree decline is occurring globally with critical implications for biodiversity and carbon sequestration. Restoration thinning is a potential management action to accelerate tree growth and promote large tree development in forests, yet trials have been limited and results have been mixed. We conducted a large‐scale trial to determine whether restoration thinning could accelerate the development of large trees in river red gum forests in Australia that had experienced widespread woody thickening and a decline of large trees due to long‐term commercial timber harvesting and river regulation. Thinning was conducted on 44 9‐ha plots by removing trees <40 cm diameter from around retained trees at a range of spacings. Initial tree densities ranged from ~260 to ~1860 trees per ha and 8%–86% of trees were removed by thinning. We monitored 1980 trees prior to thinning, and annually for 5 years post‐thinning. We tested the effects of thinning intensity on diameter growth of different sized trees and explored whether long‐ and short‐term water availability affected outcomes. Thinning promoted the growth of small trees <56 cm diameter, especially in drier sites during wet years. Higher thinning intensities reduced the growth rates of large trees (no smaller than 79.5 cm diameter) in wetter sites. For medium‐ and large‐sized trees, long‐ and short‐term water availability were stronger drivers of tree growth than competition due to tree density. Synthesis and applications. Restoration thinning may accelerate tree growth in young river red gum forests where all trees are small. But restoration thinning may be ineffective or detrimental in multi‐aged forests where the goal is to promote the growth rates of trees that are already medium to large in size.

Impact of thinning on leaf economics, plant hydraulics, and growth dynamics

Integrating climate change concerns into forest management strategies remains challenging. Among management strategies, thinning has been proven to alter major components underlying the carbon and water cycles over the short term. However, the functional adaptability of managed forests to cope with long-term drought remains unclear. This study aims to quantify the influence of thinning on key plant functional traits for two pine species, and their impacts on the fundamental processes of tree growth and transpiration. We conducted an experimental silvicultural trial with varying thinning intensities in two Pinus sylvestris and Pinus nigra plantations with the following specific objectives: i) to assess the impact of thinning on major traits involved in the leaf economic spectrum (LES), and hydraulic relations, and ii) to understand which of these traits reflect fundamental aspects of plant growth and transpiration, and their relations with environment. We used a combination of dendrochronological (basal area increment, BAI), sapflow (Fd), and tree ring isotope (δ13C) data, along with key functional and physiological traits including photosynthesis (A), leaf mass area (LMA), Huber value (Hv), sapwood density (Wd), and predawn to midday water potential (Ψpd, Ψmd).Our results revealed species-specific responses, with P. nigra exhibiting a conservative growth strategy, whereas P. sylvestris displayed increased growth after thinning. Despite thinning influenced both BAI and wood δ13C with notable species-dependent variations, we evidenced a general convergence in the relationships between LES traits and Hv across species, treatments and seasons (p < 0.01). BAI responses to thinning translated into predictable changes in key hydraulic traits and adaptive changes in physiological performance. For instance, BAI was inversely related to LMA and Hv. Consistent with LES, variations in LMA influenced A. In turn, seasonal variations in LMA scaled negatively with Ψpd, and Ψmd (p < 0.01). Such a functional adaptation suggests that thinning promotes growth while favouring forest resilience in the long term. This study provides practical implications for the implementation of a trait-based approach into silvicultural frameworks and anticipating the consequences of climate change for managed forest ecosystems.

The economic evaluation of timber obtained from Norway spruce and scots pine grown under different thinning regimes in Lithuania

ABSTRACT In Lithuania, no studies have determined the relationship between the quality and economic benefits of Norway spruce and Scots pine wood based on age, stand density, and various forest management technologies. This study aims to assess and compare the economic benefits of Norway spruce and Scots pine in stands of different initial densities, depending on different forest management measures. This study calculated different pre-commercial thinning intensities 4 times, 3 times, and 2 times and final thinning profitability by stand volume and wood quality parameters modulus of elasticity and bending strength. Moreover, thinning intensities included three initial stand densities of 3000–3100, 2000–2100, and 1000–1100 trees per hectare, and different thinning regimes when the stand was thinned from below at the age of 8–9, 15, 21, and 35 years. The results showed higher profitability in the pre-commercial thinning of low-intensity with higher frequency − 4 thinning operations over the 40 years. However, the high-thinning intensity − 2 thinning operations over 40 years – applied in young Norway spruce and Scots pine stands will reduce wood quality and profitability in the future. The study found that stand thinning of low intensity tends to improve wood quality and the profitability that depends on it. After assessing the wood quality, it turned out that the 40-year-old Scots pine trees were too young to harvest because of low wood quality. However, the timber from Norway spruce trees could be used profitably if there is a market demand.

Effects of Different Thinning Intensities on Carbon Storage in Pinus koraiensis Middle-Aged Plantations in Northeast China

Forest ecosystems are essential to the global carbon cycle because they are the biggest terrestrial carbon reserves. In the management of forests, thinning is a commonly employed strategy, impacting the respiration and biomass loss of trees, thereby modifying forest carbon dynamics. However, there is a lack of scientific research to confirm the impacts of thinning intensities on carbon storage in trees, soil layers, shrubs, and ground vegetation layers as well as its impact on wood production and growth rate. The goal of this study was to find the optimal thinning levels for increasing carbon sequestration during the growth stage of the Korean pine (Pinus koraiensis) middle-aged plantations in Northeast China. In this study, thinning intensity (0, 10, 11, 16, 18, and 22%) affected the carbon storage of trees, tree growth, volume, and, we suspected, soil layer, shrubs, and vegetation (herbs, litter, and grass) also. Specifically, after four years of thinning, the 18% treatment significantly increased total carbon storage, individual organ storage, growth, and tree volume (p &lt; 0.05). These results give us abundant information about how thinning affects the dynamics of carbon storage, wood production, and the interactions between soil and plants in P. koraiensis plantations, contributing to multi-objective management strategies for optimizing carbon sequestration, wood production, and ecosystem health.

Application of silvicultural treatments to improve local Gigantochloa apus (Schult. & Schult.f.) Kurz ex Munro stands for supporting handicraft industries in Gunungkidul region, Indonesia

There is a growing demand within the Gunungkidul region of Indonesia for bamboo, particularly Gigantochloa apus (Schult.f.) Kurz ex Munro, which is used in handicrafts. This study examined ways to enhance the productivity of bamboo to meet the specific requirements of the craft industry in the region. It assessed the impact of three levels of thinning intensity and three types of fertilizer application on the productivity and quality of G. apus. The type of fertilizer application significantly influenced the diameter of the sixth internode and the overall height of the bamboo while having an insignificant effect on the number of bamboo shoots, internode diameter at one meter or internode length. Thinning intensity significantly affected several aspects, including the number of shoots, the diameter of the sixth internode and the overall height of the bamboo. Clump thinning intensity increased the diameter of the remaining bamboo clump but reduced the number of shoots, as well as internode length and overall height. The interaction between thinning intensity and fertilizer application significantly impacted the diameter of bamboo, the diameter of the sixth internode, and the overall height of bamboo, without significant effects on the number of shoots or the internode length.

Формирование морфологии деревьев культивируемых сосновых древостоев

The aim of this study is to assess the qualitative characteristics of the crowns, stems and growth of Scots pine (Pinus sylvestris L.) trees in cultivated stands of a dry forest on gently sloping hills thinned in a regular-uniform manner, as well as to develop proposals for production based on the data obtained. The stands under study grow in the southwestern part of the ribbon forests of the Altai Territory in the territory of the Klyuchevskoye forestry. The thinning was carried out in 2016 as part of the planned forest maintenance activities. The field stage of the research was completed in 2022. The sample plots laid had a rectangular shape and a square of at least 0.25 ha. The assessment of the qualitative characteristics of the trees has been carried out in accordance with the classification proposed by G.A. Chibisov et al. The significance of differences (or their absence) in the tree distribution by quality categories in the plots has been established using the χ2 test for comparing two distributions. The article presents the taxation characteristics of the main forest element of the stands under study, the quality indices for the assessed tree indicators, and the graphs of tree distribution by diameter and quality classes. It has been found that most of the trees have poor crowns (27–45 %) and growth (14–41 %). Such indicators are a consequence of an excessively high density of the stands and the lack of timely thinning. Regular-uniform thinning of moderate and moderately high intensity has contributed to an increase in the quality class of the trees. The impact of high and very high intensity thinning on the stands has been negative. Based on the conducted research, it is recommended to carry out thinning at an earlier age of the stand, abandon the regular-uniform thinning in favor of selective thinning using the grassroots method (if possible) and carry out thinning along the largest exploitable diameter of 10 cm in the studied forest stands and similar ones. The study can be continued by establishing the optimal exploitable diameter in younger plantations and in other types of forests, as well as determining the intervals of optimal density of pine stands of different ages and different types of forest. The results obtained can be useful in designing economic activities in the study area.

Effects of Thinning on Carbon Storage in a Mixed Broadleaved Plantation in a Subtropical Area of China

Forest thinning is a widely used silvicultural method in forest management and has complex effects on carbon sequestration in different types of forest ecosystems. The present study examined the short-term effects of different thinning intensities on carbon storage in an 11-year-old mixed broadleaved plantation. The results partially supported that different thinning intensities have varying impacts on carbon storage in different parts of forest ecosystems. The main results were as follows: (1) The effect of thinning on promoting the growth of fast-growing tree species (Michelia macclurei Dandy and Schima superba Gardn. et Champ.) was earlier than that of slow-growing tree species (Castanopsis hystrix Miq.). (2) A greater thinning intensity conferred greater effects on promoting the tree biomass carbon growth, litter carbon storage, and understory plant diversity, in the order of 41%~50% &gt; 31%~40% &gt; 20%~30%, but these values were lower than those for the unthinned plots. (3) The soil carbon storage declined most in the 41%~50% thinned plots, due to the reduced carbon storage in the humus layer. (4) The 20%~30% thinning intensity promoted carbon sequestration in the short term in the mixed broadleaved plantation. The results suggested that a lower thinning intensity promoted carbon sequestration in the short term, a greater thinning intensity reduced carbon storage at first, but the negative effect on carbon storage exhibited trade-offs later by the growth of tree and understory plant biomass carbon and the accumulation of litter layer carbon.

Thinning enhances forest soil C storage by shifting the soil toward an oligotrophic condition

Forests are significant carbon reservoirs, with approximately one-third of this carbon stored in the soil. Forest thinning, a prevalent management technique, is designed to enhance timber production, preserve biodiversity, and maintain ecosystem functions. Through its influence on biotic and abiotic factors, thinning can profoundly alter soil carbon storage. Yet, the full implications of thinning on forest soil carbon reservoirs and the mechanisms underpinning these changes remain elusive. In this study, we undertook a two-year monitoring initiative, tracking changes in soil extracellular enzyme activities (EEAs), microbial communities, and other abiotic parameters across four thinning intensities within a temperate pine forest. Our results show a marked increase in soil carbon stock following thinning. However, thinning also led to decreased dissolved organic carbon (DOC) content and a reduced DOC to soil organic carbon (SOC) ratio, pointing toward a decline in soil carbon lability. Additionally, fourier transform infrared spectroscopy (FTIR) analysis revealed an augmented relative abundance of aromatic compounds after thinning. There was also a pronounced increase in absolute EEAs (per gram of dry soil) post-thinning, implying nutrient limitations for soil microbes. Concurrently, the composition of bacterial and fungal communities shifted toward oligotrophic dominance post thinning. Specific EEAs (per gram of soil organic matter) exhibit a significant reduction following thinning, indicating a deceleration in organic matter decomposition rates. In essence, our findings reveal that thinning transitions soil toward an oligotrophic state, dampening organic matter decomposition, and thus bolstering the soil carbon storage potential of forest. This study provides enhanced insights into the nuanced relationship between thinning practices and forest soil carbon dynamics, serving as a robust foundation for enlightened forest management strategies.

Impact of Forest Management on Wood Production under Climate Change in the Bonis Catchment

The concept of integrated forest management offers a framework for understanding how forest ecosystem services interact with efforts to conserve natural resources. Forests face various disturbances stemming from human activities, management approaches, and shifts in climate patterns. This study aims to explore how forested watersheds respond to diverse silvicultural practices amidst changing climate conditions. The research is centered in the Bonis catchment, situated in the mountainous region of Sila Greca (latitude 39°25′15″ N, longitude 16°12′38″ W) within Southern Italy’s Calabria region. Nearly 93% of the catchment area is cloaked in a forest dominated by approximately 50-year-old Pinus laricio Poiret stands. To model the catchment’s response to various climate and management scenarios, the FEST-FOREST eco-hydrological model, which is distributed and based on physical principles, has been employed. This model accounts for the dynamic interactions between vegetation and the watershed’s hydrological processes. The monitoring of the basin has been ongoing since 1986, with runoff measurements collected at the catchment outlet using dedicated gauging structures. These data have been utilized to calibrate and validate the model, ensuring its accuracy in simulating future scenarios. These simulation results offer stakeholders some qualitative and scientifically based recommendations for the sustainable management of the catchment. In fact, thinning intensity affects hydrological processes, with a 50% stand density reduction identified as a threshold for significant impact on processes like rainfall partitioning and evapotranspiration. Under heavy thinning scenarios, runoff can change by over 60%, and the impact decreases with larger thinning intervals. Furthermore, different climate scenarios influence stem yield levels, with higher production under RCP 4.5 and RCP 8.5 compared to the base climate scenario. In particular, the RCP 8.5 scenario produces the highest yield due to better forest growth under different climate scenarios. This implies the idea that in regions with a Mediterranean climate and coniferous forests, amidst climate change, meticulous forest management involving precisely calibrated thinning schedules and intensities, tailored to unique biotic and abiotic factors, could potentially enhance carbon sequestration while positively influencing runoff rates.

Thinning vs. Pruning: Impacts on Sap Flow Density and Water Use Efficiency in Young Populus tomentosa Plantations in Northern China

Water is a vital resource for tree growth, and changes in plantation and canopy structure can affect stand transpiration (Ec), consequently influencing water use efficiency (WUE). Populus tomentosa is a fast-growing and productive timber species in China. In recent years, thinning combined with pruning has become a widely used silvicultural practice for timber management. However, its effect on water utilization has been less well studied. To address this gap, we designed experiments with two thinning intensities and three pruning treatments. Thermal dissipation probes were employed to monitor tree sap flow density (Js), and estimated Ec and canopy conductance (gc). We established a relationship between the canopy transpiration per unit leaf area (EL) and gc and climatic factors. Finally, we compared basal area increment (BAI) and WUE among treatments under different rainfall conditions. The results indicated that: (1) The pattern of transpiration changes was consistent at both the individual tree and stand level. (2) The combined effect of T1 (thinning intensity of 833 trees per hectare) and pruning reduced Ec, decreasing the sensitivity of tree transpiration to the climate, with no discernible impact on EL and gc. Conversely, T2 (thinning intensity of 416 trees per hectare) and pruning increased EL and gc but had no effect on Ec, enhancing the sensitivity of tree transpiration to the climate. The sensitivity of gc to VPD suggested a flexible stomatal regulation of transpiration under different combined thinning and pruning treatments. (3) Under T1, only P2 (4 m pruning from ground) promoted WUE, while pruning effects significantly reduced WUE under T2. Overall, the WUE of T2P0 (thinning intensity of 416 trees per hectare combined with no pruning) was significantly higher than that of the other treatments, and that of T1P0 (thinning intensity of 833 trees per hectare combined with no pruning) was significantly lower than that of the other treatments. Additionally, significant differences in Ec and BAI were observed among treatments under different rainfall conditions, with the promotion effect of Ec on BAI being more pronounced in the dry season.

Responses of Fine Root Morphological and Chemical Traits among Branch Orders to Forest Thinning in Pinus massoniana Plantations

Fine roots play an essential role in biogeochemical cycling in forest ecosystems; however, little is known about the response of fine root morphology and chemistry in different root orders to forest management activities such as forest thinning. We investigated the fine root morphological and chemical traits in different root orders of Pinus massoniana under different thinning intensities, namely no thinning, low-intensity thinning (LIT), middle-intensity thinning (MIT), and high-intensity thinning (HIT) (0%, 25%, 45%, and 65% of individual trees eliminated, respectively). We found that forest thinning increased the root diameter (RD) of absorptive roots and decreased that of transport roots, while the trend for the specific root length (SRL) was the opposite. LIT and MIT could increase specific surface area (SSA), especially the SSA of absorptive roots in the MIT treatment. The root tissue density (RTD) of all root sequences in the LIT treatment decreased but increased in the HIT treatment. For the fine root chemical traits, thinning increased the root carbon concentration (RCC) of absorptive roots. The root nitrogen concentration (RNC) and root phosphorus concentration (RPC) of first- to fourth-order roots increased in the LIT and MIT treatments after thinning. Meanwhile, thinning increased root lignin, cellulose, and non-structural carbohydrate (NSC) concentrations. Soil temperature, nitrate, and microbial biomass carbon were factors affecting variations in fine root morphology and chemistry. Forest thinning was likely to shift the absorptive roots’ foraging strategy into a resource-conserving one. Thinning increased fine root chemical traits in most root orders. These findings contributed to our ability to predict how belowground ecological processes are mediated by fine roots under forest management activities.

Integrating Dendrochronological and LiDAR Data to Improve Management of Pinus canariensis Forests under Different Thinning and Climatic Scenarios

Thinning focused on achieving growth and diameter management objectives has typically led to stands with reduced climate sensitivity compared to unthinned stands. We integrated dendrochronological with Airborne Laser Scanner (LiDAR) data and growth models to assess the long-term impact of thinning intensity on Canary pine (Pinus canariensis) radial growth. In 1988, 18 permanent treatment units were established in 73-year-old Canary pine plantations and three thinning treatments were applied (C–control-unthinned; 0% basal area removal; MT–moderate thinning: 10% and 15% basal area removal, and HT–heavy thinning: 46% and 45% basal area removal on the windward and leeward slopes, respectively). Dendrochronological data were measured in 2022 and expressed as basal area increment (BAI). The impact of climate on growth was examined by fitting linear regression models considering two different Representative Concentration Pathway (RCP) climate scenarios, RCP 2.6 and RCP 4.5. Finally, LiDAR data were used for standing segmentation to evaluate changes in overall growth under different climatic scenarios. The LiDAR–stand attributes differed between aspects. The BAI of the most recent 20 years (BAI20) after thinning was significantly higher for the moderate and heavy treatments on the leeward plots (F = 47.31, p &lt; 0.001). On the windward plots, BAI decreased after moderate thinning. Considerable thinning treatments resulted in stronger changes in growth when compared to RCP climatic scenarios. From a silviculture perspective, the mapping of canopy structure and growth response to thinning under different climatic scenarios provides managers with opportunities to conduct thinning strategies for forest adaptation. Combining dendrochronological and LiDAR data at a landscape scale substantially improves the value of the separate datasets as forecasted growth response maps allow improving thinning management plans.

The Seasonal Impact of Thinning Intensities on Soil Carbon Cycling in the Lesser Xing’an Range, Northeast China

Forest degradation, driven by human and natural factors, diminishes ecological functions and carbon storage. Understanding the complex dynamics of soil carbon pools is crucial for the global carbon cycle, although these dynamics are poorly understood. This study examines how different thinning intensities influence seasonal soil carbon cycling in degraded forests. ANOVA revealed significant differences in soil properties across treatments (p &lt; 0.05). Redundancy analysis and random forest analyses were used to explore relationships among thinning intensities, soil properties, and carbon sequestration. Thinning significantly altered soil attributes, as revealed by field experiments and data analysis. Moderate thinning (20% intensity) significantly enhanced litter retention and soil nutrient levels year-round (p &lt; 0.05). Seasonal variations affected soil carbon dynamics and lower thinning intensities improved carbon sequestration in spring and summer. Conversely, higher thinning intensities led to carbon loss in autumn and winter. Litter carbon, fine root carbon, and correction factor significantly respond to thinning intensities year-round as examined through redundancy analysis and random forest analyses. Findings indicate moderate thinning effectively enhances soil carbon sequestration in degraded forests. Strategically planned thinning could aid climate change mitigation by boosting forest soil carbon storage, influencing forest management and conservation.

Mitigating drought mortality by incorporating topography into variable forest thinning strategies

Abstract Drought-induced productivity reductions and tree mortality have been increasing in recent decades in forests around the globe. Developing adaptation strategies hinges on an adequate understanding of the mechanisms governing the drought vulnerability of forest stands. Prescribed reduction in stand density has been used as a management tool to reduce water stress and wildfire risk, but the processes that modulate fine-scale variations in plant water supply and water demand are largely missing in ecosystem models. We used an ecohydrological model that couples plant hydraulics with groundwater hydrology to examine how within-stand variations in tree spatial arrangements and topography might mitigate forest vulnerability to drought at individual-tree and stand scales. Our results demonstrated thinning generally ameliorated plant hydraulic stress and improved carbon and water fluxes of the remaining trees, although the effectiveness varied by climate and topography. Variable thinning that adjusted thinning intensity based on topography-mediated water availability achieved higher stand productivity and lower mortality risk, compared to evenly-spaced thinning at comparable intensities. The results from numerical experiments provided mechanistic evidence that topography mediates the effectiveness of thinning and highlighted the need for an explicit consideration of within-stand heterogeneity in trees and abiotic environments when designing forest thinning to mitigate drought impacts.

Responses of Soil Phosphorus Cycling-Related Microbial Genes to Thinning Intensity in Cunninghamia lanceolata Plantations

Background: Microorganisms are important regulators of soil phosphorus cycling and phosphorus availability in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations. However, the effects of thinning on soil phosphorus cycling by microbes in C. lanceolata plantations remain unclear. Methods: We performed a metagenomic sequencing analysis to investigate how thinning intensities (weak, moderate, and heavy) alter phosphorus cycling related microbial genes and their regulatory effects on soil phosphorus availability in C. lanceolata plantations. Results: Following heavy thinning, the contents of available and labile phosphorus increased by 13.8% and 36.9%, respectively, compared to moderate and weak thinning. Moreover, the relative abundance of genes associated with inorganic phosphorus solubilization increased significantly with the increase in thinning intensity, whereas genes associated with phosphorus uptake and transport significantly decreased. The metagenomic analysis results indicate that Acidobacteria (47.6%–53.5%), Proteobacteria (17.9%–19.1%), and Actinobacteria (11.7%–12.8%) are the major contributors to the functional phosphorus cycling genes in the soil. The random forest analysis results suggested that gcd, plc, phoN, ugpA, and phoR were the critical genes involved in the transformation and use of phosphorus, which in turn increased soil phosphorus availability. Structural equation modeling revealed that soil pH was the primary factor influencing changes in functional genes associated with phosphorus cycling in C. lanceolata plantations. Specifically, soil pH (ranging from 4.3 to 4.9) were positively correlated with genes involved in inorganic phosphate solubilization and organic phosphate mineralization, while negatively correlated with genes related to phosphorus uptake and transport. Conclusions: Taken together, our results demonstrate that the enhanced microbe-mediated mineralization of organic phosphorus and solubilization of inorganic phosphorus are suppressed when uptake and transportation are the mechanisms responsible for the increased soil phosphorus availability under appropriate thinning intensities. Changes in the soil microbial community and phosphorus cycling genes in response to different thinning intensities may maintain soil functionality and nutrient balance in C. lanceolata plantations. These findings contribute to a better understanding of the mechanisms underlying the microbial mediation of phosphorus cycling in the soil of C. lanceolata plantations.

Teak (Tectona grandis Linn. f) and Edaphic Factors Affecting the Regeneration of Woody Species and Their Functional Traits in Economic Forest Plantation, Northern Thailand

Improved understanding of relationships among plant traits, stand characteristics, and soil properties can provide insights into the regenerating tree communities of commercial teak plantations. We investigated whether plant traits could be used to predict the natural regeneration of woody species in teak plantations with different soil and stand conditions. Data were collected in fifty 20 m × 20 m plots that were established in teak plantations of varying ages in northern Thailand. We analyzed differences in stand characteristics, soil properties, and community-level functional traits among sites. The RLQ analysis was performed to explore the associations among species abundances, plant traits, and a combined set of soil variables and stand characteristics. Our results showed that tree species with high leaf dry matter contents and high wood density dominated communities in an older teak plantation and were associated with high OM and N concentrations. Trees with larger leaves are increased in plantations that had experienced their first teak thinning, and were rich in organic matter. Species with high specific leaf areas increased in sites with high teak basal areas and which had experienced more intense thinning on fertile soils. Thick-leaved species had high importance values on sites with high densities of teak and infertile soils. Our results indicated that tree communities with similar conspecific traits were associated with specific soil and stand conditions in teak plantations. A knowledge of these regeneration dynamics may allow forest managers to encourage increased natural regeneration and enhanced diversity in commercial teak plantations.

Productivity of Clonal Teak Plantation Under Different Spacing and Thinning Intensity in Java Monsoon Forest

Intensive silviculture plays a crucial role in selecting superior clones with high productivity. The use of superior clones needs to be accompanied by appropriate environmental conditions. The arrangement of growing space is one way for teak clones to grow optimally and produce quality wood products. It can choose initial spacing in the early growth phase and thinning intensity in the later growth phase. This study aims to assess and determine the growth of superior teak clones with different thinning intensities at different planting distances to optimize the growing space. Optimizing growth space also has the potential for intercropping under the stand to produce more diverse products. The research design was a Split-plot design with three blocks as replications. The main plots had four spacings, including 3 m x 3 m, 6 m x 2 m, 8 m x 2 m, and 10 m x 2 m. Subplots were thinning intensity, including 0% thinning (control), 25% thinning (moderate thinning), and 50% thinning (heavy thinning). The results showed that spacing could significantly affect diameter growth. Silvicultural thinning showed significant differences in diameter growth, CADI, height, and volume per hectare. The diameter growth showed higher growth at larger spacing and higher thinning intensity, while the volume per hectare was low. The tree height parameter increased with the thinning intensity. The CADI after two years of thinning increased by 14–42% at 25% thinning intensity and increased by about 35–48% at 50% thinning intensity compared to no thinning at each spacing. Meanwhile, the volume per hectare was lower at wider spacing and decreased at a high thinning intensity. These results indicate an increase in spacing, and thinning accelerates diameter growth and provides better-growing space for intercrops.

Thinning increases forest ecosystem carbon stocks

Thinning, a major measure of forest management, is known to alter carbon sequestration by affecting the forest microclimate and soil environmental conditions. However, how thinning effect on forest ecosystem carbon stocks have presented inconsistent results. Therefore, we conducted 1776 pairs of thinning experiment observations worldwide to explore how thinning affects forest vegetation and soil carbon stocks. The results showed that overall thinning significantly increased total tree aboveground biomass carbon stocks (AGCtotal, +23.9%, +1.3 Mg ha-1 yr-1), understory vegetation carbon stocks (UVC, +68.3%, 0.12 Mg ha-1 yr-1), and soil organic carbon stocks (SOCstocks, +4.8%, 1.0 Mg ha-1 yr-1) at the global, but exhibited significantly decreased carbon stocks of litterfall (LBC, –9.6%, –0.03 Mg ha-1 yr-1). Belowground biomass carbon stocks remained unchanged under thinning. The sensitivity of carbon sequestration to thinning gradually disappeared after 6 years, except for AGCtotal, as they were jointly subject to stand density and thinning intensity and not just recovery ages. The response to UVC was more positive in medium-density (1500 – 3000 trees ha-1) and moderately thinned (30 – 50%) stands, and the thinning effects on UVC and SOCstocks were more noticeable in the subtropical and temperate zones. In summary, thinning enhanced forest ecosystem carbon sinks (+2.4 Mg ha-1 yr-1) but reduced carbon stocks in low-density stands (≤ 1500 trees ha-1). Soil moisture content (SMC, +6.6%) and bulk density (BD, –1.5%) dynamics after thinning were important factors regulating vegetation growth and soil carbon cycling processes.

Drivers of spatial structure in thinned forests

BackgroundAs is widely known, an increasing number of forest areas were managed to preserve and enhance the health of forest ecosystems. However, previous research on forest management has often overlooked the importance of structure-based. AimsOur objectives were to define the direction of structure-based forest management. Subsequently, we investigated the relationships between forest structure and the regeneration, growth, and mortality of trees under different thinning treatments. Ultimately, the drivers of forest structural change were explored. MethodsOn the basis of 92 sites selected from northeastern China, with different recovery time (from 1 to 15 years) and different thinning intensities (0–59.9%) since the last thinning. Principal component analysis (PCA) identified relationships among factors determining forest spatial structure. The structural equation model (SEM) was used to analyze the driving factors behind the changes in forest spatial structure after thinning. ResultsLight thinning (0–20% trees removed) promoted forest regeneration, and heavy thinning (over 35% of trees removed) facilitated forest growth. However, only moderate thinning (20%–35% trees removed) created a reasonable spatial structure. While dead trees were clustered, and they were hardly affected by thinning intensity. Additionally, thinning intensity, recovery time, and altitude indirectly improve the spatial structure of the forest by influencing diameter at breast height (DBH) and canopy area. ConclusionCreating larger DBH and canopy area through thinning will promote the formation of complex forest structures, which cultivates healthy and stable forests.

State and debris of trees of afforestation belts in arid conditions of the Southern part of Central Siberia

It would be beneficial to consider ways to preserve afforestation belts in arid conditions due to climate change. It was observed that the most favorable conditions for growth were present in the extreme rows (windward and lee) in forest protection belts of Siberian larch, squat elm, and black poplar. This is reflected in the maximum tree size and density. The intensity of thinning along the rows may vary depending on the age of the plantation and the tree species.