Middle-aged Stands Research Articles

The stoichiometric characteristics of carbon, nitrogen, and phosphorus in soil aggregates of Cryptomeria japonica plantation with stand ages in the Rainy Area of Western China.

Understanding the variations in soil aggregate composition, as well as the contents and stoichiometry of organic carbon (C), total nitrogen (N) and total phosphorus (P), in the surface layer of Cryptomeria japonica plantations with different stand ages can provide a theoretical basis for the optimized management of plantations and the improvement of soil fertility in the Rainy Area of West China. With the dry-sieving method, we measured the contents of soil aggregates with different sizes in the 0-15 and 15-30 cm soil layers across C. japonica plantations with five distinct developmental stages at Hongya Forestry Farm, Sichuan Province, including young stands (7 years old), middle-aged stands (13 years old), nearly mature stands (24 years old), mature stands (33 years old), and over-mature stands (53 years old). We further analyzed the C, N and P contents and ecological stoichiometric characteristics of soil aggregates. The results showed that the particle size composition of soil aggregates in C. japonica plantations varied among stand ages. The nearly mature and mature stands had higher proportion of large aggregates (0.5-1 and 1-2 mm), whereas the nearly mature stand had a lower proportion of micro-aggregates (0.053-0.25 mm) and the silt-plus-clay fraction (<0.053 mm). Moreover, the C, N and P contents and stoichiometric ratios in soil aggregate showed a unimodal pattern, which increased initially and then decreased with stand age, with peak values in the nearly mature and mature plantations. Furthermore, the C, N and P contents in aggregates in 0-15 cm soil layer were higher than that in the 15-30 cm soil layer. The highest C and N contents were found in the aggregates with particle sizes of 0.5-1 and 0.25-0.5 mm. In conclusion, the near-mature and mature stands of C. japonica plantations have higher nutrient content in soil aggregate, underscoring these stages was critical for maintaining soil fertility and advancing sustainable management practices.

Temporal Variations in Aboveground Biomass, Nutrient Content, and Ecological Stoichiometry in Young and Middle-Aged Stands of Chinese Fir Forests.

Understanding the ecological dynamics of forest ecosystems, particularly the influence of forest age structure on soil carbon (C), nitrogen (N), and phosphorus (P) content, is crucial for effective forest management and conservation. This study aimed to investigate the nutrient storage and ecological stoichiometry across different-aged stands of Chinese fir forests. Soil samples were collected from various depths (0-15 cm, 15-30 cm, and 30-45 cm) across four age groups of Chinese fir forests (8-year-old, 12-year-old, 20-year-old, and 25-year-old) in the Forest Farm, Pingjiang County, China. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured, and their stoichiometries were calculated. The results showed that both individual tree biomass and stand biomass, along with SOC, TN, and TP content, increased with stand age, highlighting the significant importance of stand age on biomass production and nutrient accumulation in forests. Specifically, soil C and P contents significantly increased as the forest aged, while variation in N content was relatively minor. Soil C/N and C/P ratios exhibited variation corresponding to forest age, suggesting alterations in the ecological stoichiometry characteristics of the forests over time. These findings are crucial for understanding the dynamics of ecosystem functioning and nutrient cycling within Chinese fir forests and provide a solid scientific basis for the effective management and conservation of these vital forest ecosystems.

Composition, structure and dynamics of poplar forests in the Lena Pillars National Park

This article presents the findings from research conducted on poplar forests within the Lena Pillars National Park. Prior to this study, there had been no detailed research on the poplar forests in the park; only general characteristicsand brief descriptions of forest types were available. The article provides a comprehensive description of tree stands, analyzes the ecological structure of the flora in poplar forests, examines the dynamics of floodplain vegetation, and traces the succession series in the floodplains of the Buotama, Kuranakh, and Labyya rivers within the National Park. At different stages of development, the forests formed by the poplar tree stand are serial (temporary) types, naturally progressing from rare-herb association, mix herb + Equisetum pretense + Calamagrostis langsdorffii (in young poplar stands) → mix herb + shrubs (middle-aged stands, ripening stands) → tall herb + shrub associations with spruce and larch (in ripening, and overmature forests). As the floodplain emerges, the development of poplar forests inevitably transitions to being replaced by coniferous forests. When the overmature poplar tree stand collapses, spruce and larchspruce and birch forests form in its place. Poplar forests in the Lena Pillars National Park are characterized by high productivity; forest stands develop according to Bonitat classes 3-4. Research on the taxation of poplar forests has allowed for the evaluation of the interdependence of different morphometric traits of poplar trees. The correlation has verified the existence of consistent relationships between specific tax indicators. The findings from the study will contribute to understanding the plant life and vegetation in Lena Pillars National Park and the poplar forests of Yakutia. This data can be used to evaluate how the vegetation in the park’s poplar forests may change in the future.

Changes and influence factors of soil matrix infiltration in Chinese fir plantations with different stand ages in northern Guangxi

Soil matrix infiltration is an important pathway for plantations to obtain water, which affects ecological benefits and water conservation function of plantations. The changes of soil matrix infiltration and its influencing factors in different growth stages of Chinese fir plantations remain unclear. We measured soil matrix infiltration process using a tension infiltrometer in Chinese fir plantations (5, 8, 11, and 15 years old) of Beijiang River Forest Farm in Rongshui, Guangxi, and analyzed soil basic physicochemical properties to identify the dominant factors influencing soil matrix infiltration. The results showed that initial infiltration rate, stable infiltration rate, and cumulative infiltration increased with stand ages. The ranges of different stand ages were 141-180 mm·h-1, 109-150 mm·h-1, and 188-251 mm, respectively. The initial infiltration rate, stable infiltration rate, and cumulative infiltration were significantly positively correlated with soil capillary porosity, soil organic matter, soil water stable macroaggregate, sand content, and clay content, while negatively correlated with soil bulk density and silt content. Early thinning had a positive effect on soil matrix infiltration, but thinning measures after 11 years did not enhance soil matrix infiltration further. Philip model was optimal for describing soil matrix infiltration process in this region. In conclusion, soil matrix infiltration capacity of Chinese fir plantations gradually increased from young to middle-aged stands, but matrix infiltration capacity tended to stabilize after 11 years old. Silt content and water stable macroaggregate were the dominant factors influencing matrix infiltration.

Average weighted estimate of health of forest trees as a criterion for the sanitary condition of a stand

The issue of using a weighted average assessment of the health of trees condition Kср as a criterion for the sanitary condition of a stand on the example of spruce and birch forests. Based on the growth tables, Kср developed for five categories of tree health status with differentiation of results by age groups and assessment methods (by stock volume or by number of trees). It showed that exceeding Kср of 1.5 is not a sufficient criterion for the unsatisfactory sanitary condition of the stand. For a stand with natural thinning by age the estimations Kср are increase from Ia to V quality of locality and are decrease with age groups. The estimates Kср by number of trees may exceed similar estimates by stock volume by 0.1-0.3 points. For a young and middle age of healthy stands with natural thinning, the evaluations Kср usually exceed 1.5 points. Proposed the criteria Kср with the differentiation on age groups and assessment methods. As rough criterion of unsatisfactory sanitary state it is possible to accept excess of average weighted of estimations (on a stock volume/on number of trees): Kср :in middle-aged stands - 1,7/2,0, in ripening stand - 1,5/1,7, in ripe and maturity and old-growth stand 1,2/1,4. Keywords: CONDITION OF FOREST STAND, WEIGHTED AVERAGE ESTIMATE

Forestry and mensuration characteristics of pine stands in the recreation and health-improving forests in the Left Bank Steppe

The study of forestry and stand mensuration characteristics of pine stands in recreational and health-improving forests of the Left Bank Steppe was conducted based on forest management materials. The distribution of pine stands in the recreational and health-improving forests of the region by location, origin, forest types, age groups and classes, site classes, and relative density of stocking was analyzed. For pine stands within the forest areas of green belt) (sites where forest activities are permitted), indicators of the use of forest potential by modal pines were calculated to compare reference stands. It was found that the pine plantations in the recreational and health-improving forests of the region grow in an area of more than 83 thousand hectares. In terms of area, man-made pine stands significantly dominate, the share of which is 93.6 % of the total area, the rest of the area (6.4%) is occupied by pine forests of natural origin. The predominance of pine stands within green belt was revealed. Their proportion is 76.1 % of the total area, including the forestry zone - 59.7 % and the forest park zone – 16.4 %. The significant area of the investigated pine plantations (37% of the total area) is located in the conditions of a fresh oak-pine (mixed) forest on transitional, relatively poor soils (subor in Ukrainian). The most part of forest is middle-aged stands (59.3 % of the total forest area and 70.5 % of the total stock of wood). Moreover, pine forest of I (39,2 %) and II (31,1 %) site classes and 0.7–0.8 density dominated (73.5 %). The rate of utilization of the forest potential by modal pines within forest areas of green belt compared reference stands is relatively low and reaches 63 %.

Anatomical structure and physiological characteristics of Robinia pseudoacacia of different stand ages

Drought intensity and frequency have been increased as a result of global warming. Exploring the drought resistance mechanism of Robinia pseudoacacia plantations of different stand ages on the Loess Plateau is crucial for understanding the stability of forest productivity in the region. We investigated anatomical traits, hydraulic function, and non-structural carbohydrate content of the xylem, as well as their association, in R. pseudoacacia plantations of different stand ages in a semi-arid region. The results showed that the vessel diameter, total pit membrane area, pit membrane area, vesture area, and vestured overlap of young and middle-aged stands were larger than those of mature stands, and the pit density was significantly lower in mature stands. Hydraulic conductivity was significantly related to vessel diameter, pit membrane area, and vesture area. Hydraulic conductivities of branches in young, middle-aged, and mature stands were 2.30, 2.12, and 0.76 kg·m-1·s-1·MPa-1, respectively, with embolism values of 54.5%, 53.8%, and 45.1%. Hydraulic conductivity was significantly related to soluble sugar and starch contents. The soluble sugar contents of branches in young, middle-aged and mature stands were 4.9%, 4.2%, and 3.8%, respectively. Xylem growth capacity of R. pseudoacacia in mature stand declined, resulting in the formation of small vessels with many small pits, which reduced hydraulic conductivity while maintaining hydraulic safety, resulting in a decrease of non-structural carbohydrates content. This study revealed the drought response mechanism of R. pseudoacacia plantations with different ages, providing a scientific foundation for the management and nurturing of R. pseudoacacia plantations on the Loess Plateau.

Response of radial growth of Pinus sylvestris var. mongolica of different stand ages to climate and extreme drought events in the semi-arid region of western Liaoning, Northeast China

The frequency and severity of drought events are increasing under a changing climate, trees of different stand ages respond differently to drought events, which has a great impact on the stability of forest ecosystems. In this study, we measured radial growth (RG) in cored trees from 49 forests including young stands (20–30a) and middle-aged stands (31–50a) of Pinus sylvestris var. mongolica plantations in a semi-arid area of western Liaoning, China. We evaluated the response of RG of P. sylvestris to long-term climate, and calculate three response indicators: resistance (Rt), recovery (Rc) and resilience (Rs), so as to measure the growth response of trees to drought events. Results showed that a negative correlation was detected between RG of young stands and the monthly highest temperature (MHT) in April and May. Positive correlations were found between RG of young stands and the monthly lowest temperature (MLT) across periods from September to November, when RG of young stands was also positively correlated with Palmer Drought Severity Index (PDSI) across whole-years. There was a positive correlation between RG of middle-aged stands and MLT in September, and PDSI from June to December. After the first drought event, most pine trees recovered their RG (Rc &amp;gt; 1, Rs &amp;gt; 1). However, after three consecutive drought events, Rt, Rc, and Rs of pine trees decreased significantly (p &amp;lt; 0.05), and Rt and Rs were less than 1. In summary, younger pine trees are more sensitive to climate change, and spring drought is more inhibitory to growth of pine trees than high summer temperatures. Pine trees have a compensation effect after experiencing drought events, but the cumulative effect of multiple drought events will gradually offset the compensation effect of trees and eventually decline in pine tree growth, while the resistance and resilience of young stands after continuous drought events were significantly lower than those of middle-aged stands, and have a higher risk of death.

Does stand density affect understory vegetation and soil properties of differently aged Robinia pseudoacacia plantations?

Robinia pseudoacacia is the most important tree species used for afforestation on the Chinese Loess Plateau. However, most R. pseudoacacia plantations face environmental problems due to inappropriate initial densities. The sustainable development of R. pseudoacacia plantations is challenging due to significant knowledge gaps regarding the appropriate stand densities for maximizing ecological benefits. Herein, R. pseudoacacia plantations of three age classes—young, middle-aged, and mature—were sampled in the loess hilly-gully region of northern Shaanxi Province, China. Based on stand density, R. pseudoacacia plantations in each age class were categorized as low (<1000 trees ha−1), medium (1000–1500 trees ha−1), and high (>1500 trees ha−1) density. We analyzed the effects of stand density on soil physicochemical properties, understory vegetation community structure, and ecosystem multifunctionality. In young stands, a medium stand density significantly increased the Shannon-Wiener index, species richness, and above-ground biomass of herbaceous communities. In middle-aged stands, stand density had no significant effects on understory diversity, whereas medium-density stands showed increased understory above-ground biomass. In mature stands, low-density stands significantly increased understory above-ground biomass and species richness of herbaceous communities. In all age classes, stand density did not significantly affect shrubby community composition, but herbaceous communities shifted compositionally towards shade-tolerant and drought-tolerant species as stand density increased. In the soils of young and middle-aged stands, organic carbon, ammonium nitrogen, nitrate nitrogen, available phosphorus, and water content were highest in medium-density stands, whereas in mature stands, these variables were highest in low-density plantations. In young, middle-aged, and mature stands, the ecosystem multifunctionality indices were highest at densities of 1000–1500, 1000–1500, and < 1000 trees ha−1, respectively. We concluded that the effects of stand density on ecosystem functions in R. pseudoacacia plantations varied with stand age. Our findings highlight a need to implement age-based stand density management strategies for R. pseudoacacia plantations to improve their ecological benefits.

China’s current forest age structure will lead to weakened carbon sinks in the near future

Forests are chiefly responsible for the terrestrial carbon sink that greatly reduces the buildup of CO2 concentrations in the atmosphere and alleviates climate change. Current predictions of terrestrial carbon sinks in the future have so far ignored the variation of forest carbon uptake with forest age. Here, we predict the role of China's current forest age in future carbon sink capacity by generating a high-resolution (30 m) forest age map in 2019 over China's landmass using satellite and forest inventory data and deriving forest growth curves using measurements of forest biomass and age in 3,121 plots. As China's forests currently have large proportions of young and middle-age stands, we project that China's forests will maintain high growth rates for about 15 years. However, as the forests grow older, their net primary productivity will decline by 5.0%± 1.4% in 2050, 8.4%± 1.6% in 2060, and 16.6%± 2.8% in 2100, indicating weakened carbon sinks in the near future. The weakening of forest carbon sinks can be potentially mitigated by optimizing forest age structure through selective logging and implementing new or improved afforestation. This finding is important not only for the global carbon cycle and climate projections but also for developing forest management strategies to enhance land sinks by alleviating the age effect.

Hydraulic Traits in Populus simonii Carr. at Stands of Categorized Ages in a Semi-Arid Area of Western Liaoning, Northeast China

Poplar plantations can acclimate to drought stress in semi-arid areas, where the variation of stand age may result in varied water adaptation strategies presented as hydrodynamic performance. In this study, nine mature Populus simonii Carr. individuals were targeted as sampling objects in plantations characterized to three stand ages: young (9 yr), middle-aged (17 yr), and near-mature (29 yr) stages in a semi-arid area of western Liaoning, Northeast China. Hydraulic traits were investigated as parameters of leaf pressure-volume curves, xylem embolism vulnerability curves, hydraulic structure, and wood density (WD). Results showed that osmotic potential (Ψtlp) and relative water content at the turgor loss point and cell-wall bulk elastic modulus were lowest in middle-aged stands (−2.19 MPa; 86.71%; 13.75 MPa). Stem and leaf-specific hydraulic conductivity (Ks and LSC) were all the highest in middle-aged stands. Xylem embolism vulnerability (P50) and lethal water potential of trees (P88) increased with the growth of stand age. Young stands faced minimal risk of hydraulic failure according to the stomatal safety margin (SSMtlp, Ψtlp minus P50), which was consistent with the comprehensive evaluation results of the principal component analysis. WD was related to P88 (R2= 0.51; p &lt; 0.05). P50 was related to drought avoidance traits Ψtlp (r = 0.76; p &lt; 0.05) but not to xylem efficiency (Ks). Overall, WD can be an excellent proxy for hydraulic safety monitoring. Young and middle-aged Populus simonii populations are more adaptable to drought conditions than near-mature populations, and near-mature stands should receive intermediate cuttings to avoid exposure to drought stress.

Seasonal variations in carbon, nitrogen, and phosphorus of Pinus yunnanenis at different stand ages.

The seasonal variations in carbon (C), nitrogen (N), and phosphorus (P) at the organ level of Pinus yunnanenis during different season are poorly understood. In this study, the C, N, P, and their stoichiometric ratios in various organs of P. yunnanensis during the four seasons are discussed. The middle and young aged P. yunnanensis forests in central Yunnan province, China were chosen, and the contents of C, N, and P in fine roots (<2mm), stems, needles, and branches were analyzed. The results showed that the C, N, P contents and their ratios in P. yunnanensis were significantly influenced by season and organ, less affected by age. The C content of the middle-aged and young forests decreased continuously from spring to winter, whereas N and P first decreased and then increased. No significant allometric growth relationships were observed between P-C of the branches or stems in the young and middle-aged forests, whereas a significant allometric growth relationship existed for N-P of needles in the young stands, indicating that the P-C and N-P nutrient distribution patterns shows different trends in the organ level in different age stands. The pattern of P allocation between organs shows differences in stand age, with more allocation to needles in middle-aged stands and more allocation to fine roots in young stands. The N:P ratio in needles was less than 14, indicating that P. yunnanensis was mainly limited by N and increasing the application of N fertilizer would be beneficial for the productivity of this stand. The results will be helpful to nutrient management in P. yunnanensis plantation.

Feeding Area and Growth of Trees in the Middle-Aged Pine Plantations

Pine plantations of class 1B were studied, with a density of 0,95 on an area of 0,64 ha, created in a cleared area following the 1.82 × 1.10 m plan. Alive and dead trees and their feeding areas were plotted on the plan in the ArcMap-ArcView programme. The territory was divided into 9 sections, with a density of 76–122% of the average for the plantation. The feeding area the trees had at the age of 30 years affected the trunk diameter at 55 years in sparse areas of the stand on average by 13.3%, and in denser areas by 5.0%. That confirmed the hypothesis that the influence of the tree feeding area on the trunk diameter can also be weak in the middle-aged stands, and the magnitude of its influence depends on the density of the stand. Tree mortality by the age of 55 correlated with the frequency in feeding area classes (r = 0.96 ± 0.03), thus the feeding area being less than the average value increased the probability of a tree falling off by the age of 55 by only 7%. It has been suggested that the decrease in the affect the feeding area has at high density is due to the increased cooperation of trees. With simulated thinning of the stands, with an increase in the feeding area of the remaining trees by 2 times, a corresponding increase in diameter was obtained only in 11% of the trees. The remaining 89% of the trees did not take advantage of the larger feeding area and did not increase in size, despite 25 years of development with a sparser standing. This indicates that in plantations of the second age class, an increase in the feeding area no longer leads to an improvement in their development in the vast majority of cases. Therefore, the density should be reduced at a much earlier age, for example, at 10–15 years.

A new strategy for improving the accuracy of forest aboveground biomass estimates in an alpine region based on multi-source remote sensing

ABSTRACT Spatially explicit information on the distribution of dominant tree species groups and aboveground biomass (AGB) in forested areas is essential for developing targeted forest management and biodiversity conservation measures, as well as assessing forest carbon sequestration capacity. There is a shortage of continuously updated 30-m spatial resolution products for mapping dominant tree species groups. The vast majority of remote sensing-based AGB estimation approaches have relatively low accuracy for dominant tree species groups or forest types and are unsuitable for AGB modeling. Therefore, this study aims to develop an integrated framework that considers the phenological characteristics of different tree species to improve the mapping accuracies of forest dominant tree groups and corresponding AGB estimates. Thirty-meter resolution maps of dominant tree species groups were created using machine learning algorithms and phenological parameters. Features extracted from optical and radar images and phenological characteristics were used to construct AGB estimation models in a temporally consistent manner to improve the AGB estimation accuracy and perform dynamic AGB monitoring. The proposed method accurately characterized the dynamic distribution of the dominant tree species groups in the study area. The traditional AGB model that does not consider different forest types or species had an R2 value of 0.52, whereas the proposed model that considers phenology and forest types had an R2 value of 0.67. This result indicates that incorporating information on phenology and dominant species improves the accuracy of AGB estimations. The AGB in most regions was 30–55 t/ha, showing that the majority of the forests were young or middle-aged stands, and the areal percentage of AGB greater than 30 t/ha increased during the study period, suggesting an improvement in forest quality. Furthermore, the oak AGB was the highest, indicating that oak afforestation should be encouraged to enhance the carbon sequestration capacity of future forest ecosystems. The results provide new insights for researchers and managers to understand the trends of forest development and forest health, as well as technical information and a database for formulating more rational forest management strategies.

Fuel characterization and crown fuel load prediction in non-treated Calabrian pine (Pinus brutia Ten.) plantation areas

Successful management of young, fire-prone Calabrian pine forests requires an accurate characterization of surface and canopy fuel loads at stand level. This study characterizes the surface and canopy fuel characteristics in unthinned Calabrian pine plantations in Turkey. Fifteen sample plots were measured to determine the surface and crown fuel characteristics of very young, young and middle aged Calabrian pine stands (10 to 28 years old). Thirty-six trees were destructively sampled to quantify the crown fuel loads and canopy fuel characteristics of the stands. Surface fuel load ranged from 11.38 t ha-1 in the young stands to 35.27 t ha-1 in the middle aged stands. Dead fuel load as ladder fuels on the trees ranged from 0.77 kg in very young stands to 13.56 kg in the young stands. Live fuel loads on the trees ranged from 0.77 kg to 23.29 kg in the young aged stands. Total active crown fuel load was 58.7%, 52.1% and 49.5% of total crown fuel load in very young, young and middle aged stands, respectively. Our results improve the current crown fuel model predictions and showed the importance of dead fuel load in fire management studies both for the determination of crown fuel loads and the calculation of carbon stocks.

Features of the Territorial Distribution, Composition and Structure of Phytocenoses with the Participation of Fraxinus excelsior, Their Resource Qualities, Ecological and Economic Importance (Southeastern Part of the East European Plain).

At present, the distribution area of Fraxinus excelsior L. in the forest ecosystems of the Volga Region is rather low and ranges from 0.01% to 2.5%. In the Middle Volga Region, using the example of the Penza region, five types of deciduous forests were identified in the composition with Fraxinus excelsior L.: oak forest aegopodium, oak forest nettle, oak forest hazel-linden, oak forest aegopodium-motley grass, oak forest carex-motley grass. In the forest phytocenoses of the Moksha River basin, the quality of Fraxinus excelsior L. is 1.5-1.7. In the forest phytocenoses of the Khoper River basin, the average quality value reaches 2.4-2.8, and in the forest tracts of the Sura river basin it is 2.8-3.2. In the western part of the study area, individuals of age class II-III (21-40, 41-60 years) predominate, in the central part-age class I (1-20 years), in the eastern part-age class V (81-100 years). This circumstance allows us to conclude that its populations in the western regions are represented by stands of different ages; the presence of young stands and middle-aged stands indicates the presence of conditions for reproduction and distribution. At the border of its range, Fraxinus excelsior L. grows in a stable population; in the western part of the Middle Volga Region, the number of species in forest stands with a predominance of Fraxinus excelsior L. is 26-30% higher than this indicator in more eastern regions. In the direction from east to west, the number of species in the composition of forest stands increases (up to 8.4), with a predominance of Fraxinus excelsior L. The number of plant associations increases in the direction from east to west. If in the east of the Penza region Fraxinus excelsior L. occurs in 6-7 plant associations, then in the west of the region-in 18-25 associations. The maximum timber stock for 100 years of Fraxinus excelsior L. stands reaches 380 m3/ha. Such a natural bioresource potential is of importance for the conduct of the national economy. Forest management in phytocenoses with the participation of this tree species is a strategic branch direction. It is expedient to restore populations of Fraxinus excelsior L. everywhere and to cultivate them in the territory of the East European Plain and especially in its south-eastern part. This is fully consistent with the principles of sustainable ecological and economic development against the background of local natural, climatic and geographical conditions. This type is necessary when solving environmental, resource-saving and economic problems in the territory under consideration.

Integrating UAV-SfM and Airborne Lidar Point Cloud Data to Plantation Forest Feature Extraction

A low-cost but accurate remote-sensing-based forest-monitoring tool is necessary for regularly inventorying tree-level parameters and stand-level attributes to achieve sustainable management of timber production forests. Lidar technology is precise for multi-temporal data collection but expensive. A low-cost UAV-based optical sensing method is an economical and flexible alternative for collecting high-resolution images for generating point cloud data and orthophotos for mapping but lacks height accuracy. This study proposes a protocol of integrating a UAV equipped without an RTK instrument and airborne lidar sensors (ALS) for characterizing tree parameters and stand attributes for use in plantation forest management. The proposed method primarily relies on the ALS-based digital elevation model data (ALS-DEM), UAV-based structure-from-motion technique generated digital surface model data (UAV-SfM-DSM), and their derivative canopy height model data (UAV-SfM-CHM). Following traditional forest inventory approaches, a few middle-aged and mature stands of Hinoki cypress (Chamaecyparis obtusa) plantation forests were used to investigate the performance of characterizing forest parameters via the canopy height model. Results show that the proposed method can improve UAV-SfM point cloud referencing transformation accuracy. With the derived CHM data, this method can estimate tree height with an RMSE ranging from 0.43 m to 1.65 m, equivalent to a PRMSE of 2.40–7.84%. The tree height estimates between UAV-based and ALS-based approaches are highly correlated (R2 = 0.98, p &lt; 0.0001), similarly, the height annual growth rate (HAGR) is also significantly correlated (R2 = 0.78, p &lt; 0.0001). The percentage HAGR of Hinoki trees behaves as an exponential decay function of the tree height over an 8-year management period. The stand-level parameters stand density, stand volume stocks, stand basal area, and relative spacing are with an error rate of less than 20% for both UAV-based and ALS-based approaches. Intensive management with regular thinning helps the plantation forests retain a clear crown shape feature, therefore, benefitting tree segmentation for deriving tree parameters and stand attributes.

The dynamics of the carbon storage and fluxes in Scots pine (Pinus sylvestris) chronosequence

To evaluate the impact of stand age on the ecosystem's C budget, as well as the post-harvest recovery of the C storages and fluxes, a chronosequence of Scots pine stands from the clear-cut stage up to the age of 110 years was studied. An age-related trend of net primary production (NPP) demonstrated effective C accumulation in the young and middle-aged stands and their levelling out thereafter.The understorey vegetation contributed 8–46% to total NPP, being lower in the pole and middle-aged stands, but without a clear age related trend. Annual cumulative soil heterotrophic respiration (Rh) demonstrated stable values along the chronosequence, varying between 3.8 and 5.4 t C ha−1 yr−1. The Rh flux of 2.9 t C ha−1 yr−1 at the clear–cut site did not exceed the corresponding value for stands. The NEP along the chronosequence followed the dynamics of the annual biomass production of the trees, peaking at the middle-aged stage and decreasing in the older stands; the NPP of the trees was the main driver directing the dynamics of NEP.There was no significant correlation between Rh and dynamics of aboveground litter or fine root production, which can partly explain why no relationship was established between annual Rh and stand age.The total ecosystem C stocks followed the same trend as cumulative tree biomass, peaking in the older stands, however, the soil C stocks varied along the chronosequence irrespective of stand age.The post-harvest C compensation point was reached at the age of 7-years and C payback occurred at a stand age of 11–12 years. Stands acted as C accumulating ecosystems and average annual C accumulation was around 2.5 t C ha−1 yr−1, except for the youngest stand and the clear-cut area which acted as C sources. In the oldest stand C budget was almost balanced, with a modest annual accumulation of 0.12 t C ha−1 yr−1.

Estimation of litter input in hemi-boreal forests with drained organic soils for improvement of GHG inventories

Assessments of net greenhouse gas (GHG) emissions in forest land with drained organic soils conducted within the scope of National GHG inventories requires reliable data on litter production and carbon (C) input to soil information. To estimate C input through tree above-ground litter, sampling of above-ground litter was done in 36 research sites in Latvia representing typical forests with drained organic soils in hemiboreal region. To estimate C input through tree below-ground litter and litter from ground vegetation, modelling approach based on literature review and data on characteristics of forest stands with drained organic soils in Latvia provided by National Forest Inventory (NFI) was used. The study highlighted dependence of C input to soil through litter production from the stand characteristics and thus significant differences in the C input with litter between young and middle age stands. The study also proves that drained organic soils in middle age forests dominated by Silver birch, Scots pine and Norway spruce may not be the source of net GHG emissions due to offset by C input through litter production. However, there is still high uncertainty of C input with tree below-ground litter and ground vegetation, particularly, mosses, herbs and grasses which may have crucial role in C balance in forests with drained organic soils. Key words: forests, drained organic soils, litter production, carbon input, National GHG inventory

The structure in diameter and sanitary condition of geographical cultures of Scots pine

The study of geographical forest cultures is the scientific basis for forest-seed zoning and selection of tree species. This research identifies the structural features of the diameter of middle-aged stands of different ecotypes of Scots pine (Pinus sylvestris L.) in geographic cultures, as an assessment of its current sanitary state. We studied the stands of 18 forest-steppe and 14 steppe ecotypes. We laid test areas with measuring the diameters of trees with a measuring fork at a height of 1.3 m. Trees with a continuous count were divided into six categories of sanitary status: no signs of weakening, weakened, strongly weakened, shrinking, fresh dead wood and dead wood of past years. Based on the results of continuous recounts, the distribution rows of trees were constructed according to 2- and 4-cm thickness steps. In forest-steppe ecotypes, the distribution of trees along 2-and 4-centimeter-thick steps is single-vertex, but with right asymmetry. The distribution of trees of steppe ecotypes over 2-cm steps of thickness is asymmetric and two-peaked. The distribution of trees of steppe ecotypes by 2-cm thickness steps is asymmetric and two-vertex. The average score of the sanitary state of stands of forest-steppe ecotypes is 1.5 (healthy), in steppe – 1.7 (weakened).