Maximum Basal Area Research Articles

The return of tall forests: Reconstructing the canopy resilience of an extensively harvested primary forest in Mediterranean mountains

Understanding recovery times and mechanisms of ecosystem dynamics towards the old-growth stage is crucial for forest restoration, but still poorly delineated in Mediterranean. Through tree-ring methods, we reconstructed the return of a tall canopy after severe human disturbance in a mixed beech (Fagus sylvatica) and silver fir (Abies alba) forest, located at a mountain site in the southern edge of both species' range (Gariglione, south Italy). The primary forest was extensively harvested between 1930 and 1950, removing up to 91 % of the biomass. Growth histories, climate-growth relationships and time-series of growth dominance in Gariglione were compared with a network of protected mature and old-growth beech forests distributed along a wide elevational gradient in the same region. We found that the renewed tall canopy of Gariglione is mainly composed of remnant trees, which include uncut trees and saplings, and the post-harvesting regeneration mostly represented by fir. Canopy beech trees reached maximum basal area increment (BAI) in the 1970s, 40–50 years after cutting. Then, beech BAI shifted towards negative trends in phase with drying climate (PDSI), while fir maintained a sustained growth until 2000. This growth asynchrony between the two species conferred community stability over the last decades. The network comparison highlighted the common negative impact of summer drought on high-frequency growth signals of beech in south Italy. However, analysis of long-term mean growth trends indicates decreasing BAI limited to Gariglione beech, revealing relevant differences due to site ecology and its interactions with legacy effects of past management in driving growth responses to climate change. Indeed, lowland mature beech forests showed increasing BAI in the last decades, while primary high-mountain forests displayed a remarkably stable low oscillating growth. In all the Mediterranean forests we studied, large and old trees showed a marked growth acclimation despite ongoing climate warming, demonstrating the effectiveness of landscape rewilding.

Growth, Biomass and Carbon Sequestration of Populus deltoides Clones

To study the growth performance of twenty clone viz. G - 48, AM - 48, AM - 49, AM - 41, BR - 510, AM - 50, FS - 18, FS - 190, FS - 155, L - 90, L - 87, L - 89, S7 C 1, S7 C15, S7 C20, S7 C4, L - 200 - 84, Bahar, Udai and Kranti of Populus deltoides at Prayagraj, Uttar Pradesh. The experiment was established in year February 2018 and growth performance data were recorded after 4 years in February 2022. The maximum height was found in Udai (11.57 ± 0.23 m) followed by L - 87 (10.22 ± 0.42 m) and minimum in Bahar (6.74 ± 0.19 m) whereas the maximum diameter was found in L - 87 (10.79 ± 0.63 cm) followed by S7 C1, (10.63 ± 0.33 cm) and minimum in Bahar (4.97 ± 0.06 cm). The maximum basal area L 87 (91.39 cm2 tree-1) followed by S7 C1 (88.70 cm2 tree-1) and minimum in Bahar (19.39 cm2 tree-1) whereas maximum volume Udai (1386.66 m3ha-1) followed by L-87 (1303.37 m3ha-1) and minimum in Bahar (182.37 m3ha-1). The biomass, carbon stock and carbon sequestration in poplar was maximum in Udai followed by L- 87 and minimum in Bahar for biomass (1146.59, 1077.22 and 150.79 t ha-1) carbon stock (573.30, 538.86 and 75.40 t ha-1) and carbon sequestration (2104.00, 1977.62 and 276.71 t ha-1) respectively.

Modelling individual tree maximum basal area growth rates of five tall eucalypt species growing in even-aged forests

Inventory plot data were available providing over 87,000 individual tree basal area growth rates from even-aged native forests of three ash eucalypts (Eucalyptus regnans, E. obliqua, and E. delegatensis), from temperate regions, and two other species from more sub-tropical climes (E. grandis and E. pilularis). Models were developed relating maximum observed growth rates for these species in relation to tree size when, presumably, trees were under ideal environmental conditions and without competition from neighbours for site growth resources. These maximum growth rates increased with increasing tree size to a maximum of their own and then declined as tree size (hence age) increased further. The tree sizes, at which these maximum growth rates reached their maxima, were much greater for the ash eucalypts than for the other two species. It is hypothesised that the ash eucalypts may have evolved physiological characteristics that make them more efficient in compensating for the well-known physiological constraints imposed on growth rates as trees grow to great heights and ages.

Unlocking nature's hidden treasure: Unveiling forest status, biomass and carbon wealth in the Binsar Wildlife Sanctuary, Uttarakhand for climate change mitigation

In the context of present climate change concerns, the quantification of forest biomass and the comprehension of carbon stock distribution within protected areas are of paramount importance for exact carbon budgeting and the development of effective forest management strategies. This study conducted comprehensive field assessments with the primary objective of quantifying tree biomass and carbon stocks, as well as assessing structural attributes of forest stands. These assessments involved the meticulous collection of ground-based data encompassing various structural attributes, including circumference at breast height (CBH), stem height, basal area, stem density, frequency, girth class by utilizing a simple random sampling methodology. The results of this study unveiled substantial variations in all tree structural attributes across different forest stands along altitudinal gradients. Notably, species richness, tree density and species diversity exhibited an upward trend with increasing altitude. The maximum tree species richness (25) and tree density (1068 ± 102.2 individuals ha−1) were recorded at stand-IV, situated between 2200 to 2400 m, however, stand-I exhibited the maximum basal area. The highest aboveground, belowground, total biomass, and carbon stock was estimated in the stand-IV, with values of 279.12 ± 17.56 Mg ha−1, 65.58±11.20 Mg ha−1, 344.70 ± 20.66 Mg ha−1, and 163.73 ± 10.33 Mg ha−1, respectively. The study further revealed a positive correlation between elevation and species richness, biomass, and carbon stock. Additionally, it demonstrated positive correlations between total biomass and carbon stock with species richness, total basal area, and tree density. These findings convey immediate significance for the development and implementation of climate change mitigation policies and practices, particularly within the context of protected areas in the Himalayan landscape.

Effects of site productivity on individual tree maximum basal area growth rates of Eucalyptus pilularis in subtropical Australia

Inventory data were available from 96 plots of even-aged, monoculture, tall-open forests of Eucalyptus pilularis Smith, aged 2–63 years, growing in sub-tropical regions along the east coast of Australia. A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal area. For any tree size, this maximum increased as site productivity increased. However, the size at which this maximum occurred decreased as productivity increased. Much research has shown that, at any stand age, trees of a particular stem basal area are taller on more productive sites than on less productive ones. Taller trees incur greater respiratory costs to ensure maintenance of the photosynthetic capacity of their canopies; this reduces their growth rates. It was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site, whilst trees with smaller basal areas will have the maximum possible on a more productive site. The model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.

Species Diversity Assessment along Altitudinal Gradient in Cold Desert Juniperus Forest of North-Western Himalaya

The present study was carried out in the cold desert ecosystem of pure Juniperus forest in Northwestern Himalayan region to assess the species diversity along the altitudinal gradient. The entire study area was divided into eight main plots along altitudinal gradient starting from 3000m up to >4260m amsl with 180m elevational distance between two adjacent main plots. A total of 9 shrub and 19 herb species were reported in the entire study area at different altitudes. The maximum density among shrubs was reported for Ephedra vulgaris (853.33 N ha -1 ) at A 6 and whereas, Juniperus communis has the highest basal area (6642.77 cm 2 ha -1 ) at A 2 elevation. Ephedra vulgaris was the most dominant shrub with an IVI value of 206.19 at A 8, which contributed 33. 11 % of shrub species. Â Artemisia maritima was the most frequently occurring herb species with the highest density (47666. 67 N ha -1 ) at A 1 . The maximum basal area was reported for Waldhemia tomentosa (45373.67 cm 2 ha -1 ) at A 4 elevation. Species richness was found to be markedly declined with an increase in altitude. However, the richness was found to be maximum at mid of the elevation gradient A 4 and A 5 . Shannon-Wiener diversity index (H') and concentration of dominance (Cd) have shown a negative relationship. The study provides necessary information about the distribution and diversity of essential shrubs and herb species at different altitudes for regeneration, sustainable forest management and conservation actions around the mid-altitudes of the cold desert of northwestern Himalayas.

Assessment of Carbon Stock and Carbon Sequestration Potential in three major density-based forest ecosystems of Tripura, North-East India

Forest ecosystems are playing major role in regulating the carbon cycle of the earth. We have investigated the vegetation carbon, below ground soil carbon, soil nutrient properties and carbon sequestration potential of three different density-based forest ecosystems viz ., Open forest (OP), very dense forests (VDF) and moderately dense forests (MDF) of Tripura, Northeast India. The tree biomass was analyzed by the allometric method of Nath et al. (2019) and IPCC (2019) default manual was chosen below-ground measurement. While the total biomass carbon was estimated with the manual of Brown et al. (1989) method. The SOC stock was analyzed by the formula of the Blanco-Canqui and Lal. (2008). It was observed that the three categories of forests have variation in carbon stock and carbon sequestration potential. The stand density recorded higher in OF , while the VDF recorded maximum basal area. The biomass-C and Sequestration potential were recorded higher in VDF and MDF respectively. The rate of the sequestration percentage was recorded highest in VDF and lowest in MDF. The SOC stock was observed maximum in MDF followed by OF and VDF. The Soil Physico-chemical properties have been showing variations along with the forest categories. However, these forests have been facing a greater number of anthropogenic disturbances, which decreases the species number and its richness to the wild day-by-day. We suggest more future studies on these forest types to explore ecosystem level carbon stock, and restored such systems for better understanding their role in carbon management.

Dendrochronological study of Cedrus deodar Grown at Kumrat valley Dir Upper KPK, Pakistan: Evaluation of Tree Age and Increment Based on Increment Core

The present research was conducted for tree-rings study in a mixed stand of Himalayan Species Credur deodar in Kumrat valley Dir Upper KPK, Pakistan. Tree-rings analysis was related to the counting of tree ring. Random sampling method was used, and 70 sample trees were selected, tree heights and diameters were measured, and increment cores were collected from each sample-tree diameter at the height at breast point to be analyzed and studied in the laboratory. The objectives of the study were to determine the exact age of tree and to evaluate total and mean annual increment in the basal area and tree volume based on the increment cores. Regression models revealed the impacts of tree age on the basal area and tree-volume increment. Results showed the minimum basal-area increment was 0.0028 m2 at the age of 10 years, the maximum basal-area increment was 2.658 m2 at the age of 60 years, with mean was 0.95±0.677 m2 at the age of 36 years and R2 was 0.9593. The maximum tree-volume increment was 1.42 m3 at the age of 60 years, the minimum tree-volume increment was 0.010 m3 at the age of 10 years, with mean was 1.35±0.96 m3 at the age of 36 years and R2 was 0.9167. The minimum mean annual-basal area increment was 0.0027 m2, the maximum mean annual-basal area increment was 0.048 m2, and the average increment was 0.022±0.010 m2. The maximum mean-annual increment in tree volume was 0.068 m3 at the age of 60 years, the minimum mean-annual increment was 0.0039 m3 at the age of 10 years, with mean was 0.032±0.014 m3 at the age of 36 years and R2 was 0.8903. Results showed a strong positive relationship of tree age with area and volume increment.
 Keywords: Basal area, increment, tree age, volume

Simulating the effects of thinning and species mixing on stands of oak (Quercus petraea (Matt.) Liebl./Quercus robur L.) and pine (Pinus sylvestris L.) across Europe

Tree species mixing of oak (Quercus petraea (Matt.) Liebl./Quercus robur L.) and pine (Pinus sylvestris L.) has been shown to have positive effects on ecosystem service provision. From a management perspective, however, it is still uncertain which thinning regime provides the highest possible productivity of mixed oak–pine forests in the long term. Because of a lack of empirical studies dealing with thinning and species mixing effects on oak–pine forests, we simulated forest growth in order to test which thinning type and intensity may provide the highest productivity in the long-term. To achieve this, we simulated the growth of pure and mixed stands of oak and pine for 100 years in 23 triplets located on an ecological gradient across Europe. For this purpose, we applied four different growth simulators and compared their results: the distance-independent single-tree simulator PROGNAUS, the distance-dependent single-tree simulator SILVA, the gap model ForCEEPS, and the process-based simulator 3D-CMCC-FEM. We investigated the effects of species mixing and thinning from the upper (thinning from above) and lower tail (thinning from below) of the diameter distribution by reducing the stand basal area to 50 and 80% of the maximum basal area. We compared simulated results of the relative volume productivity of mixed versus pure stands and of thinned versus unthinned stands to empirical results previously obtained on the same set of triplets. Simulated relative volume productivity ranged between 61 and 156%, although extremes of 10% and of 300% could be observed. We found the relative volume productivity to be influenced by stand age, but not by stand density, except for PROGNAUS. Relative volume productivity did not increase with the site water supply of the triplet location. Highest long-term productivity for oak, pine and oak–pine stands can be expected in consequence of thinning from above, but the effect of thinning intensity differed between simulators. Thinning effects were positively affected by stand density, but not by stand age, except for thinning from above predicted by PROGNAUS. Predicted thinning effects showed good approximation of results from thinning experiments for oak, but not for pine stands. We hypothesize the results might be caused by the insufficient simulator representation of climate and its interaction with other site variables and stand structure. Further work is needed to reduce the revealed limitations of the existing growth models, as we currently see no alternative to such kind of studies and simulators.

Assessment of woody species diversity and composition along a disturbance gradient in Behali Reserve Forest of Biswanath district, Assam, India

The present study was carried out in Behali Reserve Forest, a semi-evergreen forest of Assam, India to record and analyze the woody species diversity and community characteristics using random sampling. Altogether, 35 quadrats (20 m × 20 m) were randomly established and studied from August 2018 to April 2019 spreading across nine study sites. A total of 128 (118 identified and 10 unidentified) woody species from 83 genera and 43 families were found in the sampled area of 1.4 ha. Lauraceae with 19 species was the richest family by species followed by Euphorbiaceae and Phyllanthaceae (eight species each). Altogether, 787 individuals were recorded from the sampled plots and the stand density ranged between 250 individuals × ha-1 to 725 individuals × ha-1 with mean stand density of 543 individuals × ha-1. Species-wise density analysis revealed that Magnolia hodgsonii (96.43 individuals × ha-1) has the maximum tree density. Plot wise analysis showed that Dikal (58.32 m2 × ha-1) recorded the maximum basal area as well as the equitability index of 0.95. In Serelia, we recorded the highest Simpson index (0.92), Shannon H index (2.76), Brillouin index (2.11), Menhinick (3.49), Margalef (5.29) and Fisher alpha index (26.59). In Radhasu, we recorded maximum evenness (0.90), dominance (0.58) and Berger-Parker index (0.65). The maximal values of Chao index (38.53) was recorded in Hatimara. Our study also revealed that diversity was maximal for the community under medium level of disturbance in the reserve, while communities under the lowest and highest disturbance pressure had minimal diversity. The Behali Reserve Forest exhibited a great species richness (118 species), mean basal area (44.42 m2 × ha-1) and stand density (in total, 788 individuals per study area of 1.4 ha) compared to the other forests of the northeastern region of India.

The relationship between volume increment and stand density in Norway spruce plantations

AbstractAn understanding of the relationship between volume increment and stand density (basal area, stand density index, etc.) is of utmost importance for properly managing stand density to achieve specific management objectives. There are two main approaches to analyse growth–density relationships. The first relates volume increment to stand density through a basic relationship, which can vary with site productivity, age, and potentially incorporates treatment effects. The second is to relate the volume increment and density of thinned experimental plots relative to that of an unthinned experimental plot on the same site. Using a dataset of 229 thinned and unthinned experimental plots of Norway spruce, a growth model is developed describing the relationship between gross or net volume increment and basal area. The models indicate that gross volume increases with increasing basal area up to 50 m2 and thereafter becomes constant out to the maximum basal area. Alternatively, net volume increment was maximized at a basal area of 43 m2 and decreased with further increases in basal area. However, the models indicated a wide range where net volume increment was essentially constant, varying by less than 1 m3 ha−1 year−1. An analysis of different thinning scenarios indicated that the relative relationship between volume increment and stand density was dynamic and changed over the course of a rotation.

Changes in quantity, morphology and nitrogen content of fine roots with stand development in a subalpine fir-wave forest

ABSTRACTTo determine the change in nutrient absorption capacity with stand development, we aimed to clarify the changes in fine root characteristics with stand development and stand characteristics. Stand characteristics (stand age, maximum tree height, tree density and basal area) and fine root characteristics were examined in three fir-wave stands that aged sequentially along the slope in a subalpine Abies forest in central Japan. The biomass, length, surface area and N content of fine roots did not change, but the specific root length (SRL) decreased with stand development, i.e. distance from the upper side of each transect. On the other hand, we observed an increase in fine root biomass with stand characteristics, i.e. maximum tree height and basal area of the Abies community, while a decrease in SRL was also observed. These changes resulted in an increase in surface area and N content of fine roots. However, the surface area of absorptive roots that were <0.5 mm in diameter did not change with stand characteristics. Thus, we suggest that the nutrient absorption capacity of the subalpine Abies community increased with aboveground biomass from the viewpoint of comprehensive activity of fine roots, but not from the viewpoint of fine root morphology. We further confirmed that the ratios of surface area and N content of fine roots to basal area decreased with stand development. Future research is needed to understand the actual effect of surface area and N content of fine roots on the maintenance of aboveground organs.

Geospatial technology based diversity and above ground biomass assessment of woody species of West Kameng district of Arunachal Pradesh

ABSTRACTComprehending the prominence of forest carbon in climate change, this study was piloted in different land use of West Kameng district, Arunachal Pradesh, India to record the floristic composition, community characteristics, and above ground biomass (AGB) carbon using random sampling and geospatial approach. Preliminary field survey was done in 2016. Altogether 45 quadrats (0.1 ha each) were laid. Total tree richness recorded was 164 species from 49 families. Dominance and frequency distribution pattern of species revealed heterogeneity in composition with majority species showing clumped distribution. Plantations showed highest tree density while mixed dense forest showed maximum basal area (58.89 m2 ha−1). Estimated AGB were 218.21 ton/ha for mixed dense forest, 84.94 ton/ha for abandoned forest, and 105.09 ton/ha for plantations. Total estimated carbon stocks were 120.01, 46.17, and 57.80 ton/ha for mixed dense, abandoned forest, and plantations, respectively. Predicted average AGB using Geographic Information System (GIS) techniques was 163.25 ton/ha. Field-based AGB was slightly greater than the values observed from satellite data. Findings of the study may be useful for calculating total biomass and carbon stored in the major land cover of the district in particular and region in general. It will also support in future studies for calculating the long-term data on biomass carbon sequestration.

Biomass Allocation and Carbon Stock in Elm (Ulmus Wallichiana Planch) Plantation

The present investigation was conducted on a 22- year old Elm plantation established at Wadura campus of SKUAST-Kashmir. Four diameter classes viz., D1 (5-10cm), D2 (10-15cm), D3 (15-20cm) and D4 (&gt;20cm) were stratified from the plantation and 24 trees (6 from each diameter class) were randomly selected and felled in the year 2015. The growth parameters of the trees increased with increase in the diameter class. The maximum height, dbh, basal area and stem volume were 14.98m, 23.77cm, 0.044m2 and 0.400m3, respectively. Biomass per tree of all tree components viz., stem, branches, foliage and roots showed significant increase with increase in the diameter of the trees. The total biomass, carbon stock and carbon dioxide equivalent increased from lower to higher diameter classes. The highest values observed for these parameters were 475.54 kg/tree (fresh), 148.59 kg/tree and 543.82 kg/tree, respectively under D4 diameter class. The biomass allocation coefficient of branch and root (BACb and BACr) attained higher values in lower diameter classes. The maximum and minimum values of these coefficients were 0.158 and 0.085; 0.298 and 0.278, respectively under D1 and D4 diameter classes. The size of trees did not produce significant effect on the biomass allocation coefficient of foliage (BACf). The diameter of the trees produced non-significant difference in the growth efficiency (GE) of different tree components.

Stand Structure, Productivity and Carbon Sequestration Potential of Oak Dominated Forests in Kumaun Himalaya

Present study deals with stand structure, biomass, productivity and carbon sequestration in oak dominated forests mixed with other broad leaved tree species. The sites of studied forests were located in Nainital region between 29058’ N lat. and 79028’ E long at 1500-2150 m elevation. Tree density of forests ranged from 980-1100 ind.ha-1. Of this, oak trees shared 69-97%. The basal area of trees was 31.81 to 63.93 m2 ha-1. R. arboreum and Q. floribunda shared maximum basal area 16.45 and 16.32 m2 ha-1, respectively in forest site-1 and 2 while Quercus leucotrichophora shared maximum (35.69 m2 ha-1) in site-3. The biomass and primary productivity of tree species ranged from 481-569 t ha-1 and 16.9-20.9 t ha-1yr-1, respectively. Of this, biomass and primary productivity of oak tree species accounted for 81 to 95 and 78 to 98%, respectively. Carbon stock and carbon sequestration ranged from 228 to 270 t ha-1 and 8.0 to 9.9 t ha-1yr-1, respectively. The share of oak tree species ranged from 81 to 94.7 and 79 to 97%, respectively. The diversity of tree species ranged from 0.03 to 0.16 in forest sites-1, 2 and 3. The diversity of oak species was 0.08-0.16 in all the forest sites. Thus it is concluded that among the oak tree species, Quercus floribunda and Quercus leucotrichophora were highly dominated in the studied forests. The climax form of oak dominated trees in the studied forest sites depicted slightly lower richness and diversity of tree species compared to the forests in the region and elsewhere. As far as dry matter and carbon of forests is concerned, these estimates are close to the earlier reports of forests in the region. Therefore, studied forests have the potential to increase the diversity, productivity and carbon sequestration of forest tree species by providing the adequate scientific conservation and management inputs.

Diversity and production in an Afromontane Forest

This contribution evaluates the effect of forest structure and tree species diversity on plot productivity and individual tree growth in the unique Knysna forests in Southern Africa using mapped tree data from an observational study that has been re-measured over a period of 40 years. The effects of tree species diversity and forest structure on tree growth and forest production are evaluated on three levels of resolution: a) the forest community (canopy, sub-canopy species), b) the subplots (number of trees per ha, skewness of the diameter distribution, diameter coefficient of variation) and c) the immediate neighborhood of selected reference trees (“Mingling”, “Dominance”, Aggregation” and “Size Variation”). An analysis of the community level identified two distinct clusters, one including dominant/canopy species with the highest growth rates and a greater variation of growth, and another cluster which includes the remaining subcanopy species which have a smaller maximum size and lower rates of growth. The area-based structure variables on plot level have a highly significant effect on total basal area growth. However, the effects of forest density and species richness on productivity were not straight forward. Maximum basal area production of about 0.75 m2/ha/year is achieved at medium levels of richness (around 20 species per ha) and medium levels of density (around 30 m2/ha basal area) using percentile regression estimates. The relative “Dominance” of a selected reference tree had a highly significant effect on individual tree growth on all investigated species. Other neighbourhood structure variables were only occasionally significant or not significant at all. This contribution presents a new theoretical framework for analysing natural forests that includes community, plot and neighborhood variables of forest structure and diversity, and a first specific analysis of the structure and dynamics of the Knysna Afromontane Forest, based on a unique set of longterm observations. The species-area (SAR) model developed in this study, represents a new general approach that can be used to derive a common standard of tree species diversity for different plot sizes, the species richness per hectare.

WIDE-AREA MAPPING OF FOREST WITH NATIONAL AIRBORNE LASER SCANNING AND FIELD INVENTORY DATASETS

Airborne laser scanning (ALS) remote sensing data are now available for entire countries such as Switzerland. Methods for the estimation of forest parameters from ALS have been intensively investigated in the past years. However, the implementation of a forest mapping workflow based on available data at a regional level still remains challenging. A case study was implemented in the Canton of Valais (Switzerland). The national ALS dataset and field data of the Swiss National Forest Inventory were used to calibrate estimation models for mean and maximum height, basal area, stem density, mean diameter and stem volume. When stratification was performed based on ALS acquisition settings and geographical criteria, satisfactory prediction models were obtained for volume (R&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;&amp;thinsp;=&amp;thinsp;0.61 with a root mean square error of 47&amp;thinsp;%) and basal area (respectively 0.51 and 45&amp;thinsp;%) while height variables had an error lower than 19%. This case study shows that the use of nationwide ALS and field datasets for forest resources mapping is cost efficient, but additional investigations are required to handle the limitations of the input data and optimize the accuracy.

Comparing individual-tree growth models using principles of stand growth for Norway spruce, Scots pine, and European beech

We examined the relationship between thinning intensity and volume increment predicted by four commonly used individual-tree growth models in Central Europe (i.e., BWIN, Moses, Prognaus, and Silva). We replicated conditions of older growth and yield experiments by selecting 34 young, dense plots of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and European beech (Fagus sylvatica L.). At these plots, we simulated growth, with mortality only, to obtain the maximum basal area. Maximum basal area was then decreased by 5% or 10% steps using thinning from below. Maximum density varied considerably between simulators; it was mostly in a reasonable range but partly exceeded the maximum basal area observed by the Austrian National Forest Inventory or the self-thinning line. In almost all cases, simulated volume increment was highest at maximum basal area and then decreased with decreasing basal area. Critical basal area, at which 95% of maximum volume increment can be achieved, ranged from 0.46 to 0.96. For all simulators, critical basal area was lower for the more shade-tolerant species. It increased with age, except for Norway spruce, when simulated with the BWIN model. Age, where mean annual increment culminated, compared well with yield tables.

A comparison of different methods to estimate species proportions by area in mixed stands

Aim of the study: This paper presents the most appropriate ways to estimate the species proportions by area in mixed stands of Norway spruce (Picea abies L. Karst.) and European beech (Fagus sylvatica L.) by comparing stand level and individual tree level approaches. It also investigates whether different ways of describing species proportions by area can result in different judgments on the over- or under-yielding of species in mixtures.Area of the study: Three triplets of pure and mixed stands of Norway spruce and European beech in three locations in the northeast of Austria are investigated. The three locations differ considerably in slope, bedrock and soil type as well as in site index.Material and Methods: In all 9 plots the coordinates of all trees, their dbh, height, height to the crown base and five year increment were measured. The potentially available areas of individual trees are calculated by Voronoi- diagrams and potential densities are estimated from the comparable pure stands, yield tables, and published equations for maximum basal area and Reineke’s maximum density line.Main results: The species proportions estimated by the individual tree approach with leaf area as growth characteristic gave the best fit with the stand approach with the most appropriate, regional maximum basal area equations. By using various definitions of species proportions, in the worst case the mixing effects on individual species can be seriously over- or underestimated while the mixing effects on the total increment is only negligibly affected.Research highlightsMeasures of species proportions by area are needed for comparing growth per hectare of a species in a mixed stand with that of the same species in a pure standSpecies proportions at the stand level are based on estimates of the species’ potential densities, either in terms of maximum basal area or of maximum stand density indexSpecies proportions at the tree level are derived from the area potentially available (APA) to the individual trees, based on the coordinates of trees in the stands, and on their growth characteristics, such as crown projection area or leaf areaFor the examples of Norway spruce - European beech stands, the species proportions derived according to the individual tree approach using leaf area as growth characteristics fits best with the stand approach using the most appropriate maximum basal area equationsKeywords: Picea abies; Fagus sylvatica; mixture proportion; growth efficiency; mixing effect.Abbreviations used: APA – area potentially available.

Relação da razão do quociente diâmetro e área basal com o autodesbaste em povoamentos equiâneos de &lt;i&gt;Pinus taeda&lt;/i&gt; L.

http://dx.doi.org/10.5902/1980509814584Este trabalho teve por objetivo estudar a relação do diâmetro médio e da área basal no momento do autodesbaste, o crescimento diamétrico e a ocorrência do autodesbaste, o momento de autodesbaste com base na proporção de diâmetro-área basal, a taxa de autodesbaste comparando-a com a lei da potência -3/2 em povoamentos de Pinus taeda L., em vários espaçamentos, manejado em densidade completa. O modelo de Tang foi empregado relacionando o número de árvores por hectare com o diâmetro médio, a partir de dados de parcelas permanentes, medidas anualmente até os 18 anos em experimento de espaçamento. O modelo de autodesbaste mostrou ótima precisão e elevada eficiência, porém, apresentou coeficiente angular de -1,65 com inclinação diferente da preconizada na lei de autodesbaste de -3/2. No momento da ocorrência do autodesbaste, as árvores atingiram diâmetros 14 e 17 cm, nos espaçamento de 2 x 2 e 3 x 2 m, com áreas basais de 38,8 e 47,5 m2/ha, respectivamente. Em todos os espaçamentos a área basal máxima foi de 78 m2/ha, aos 18 anos de idade, apresentando ainda tendência ascendente. Nesses espaçamentos, o quociente do diâmetro pela área basal no momento de ocorrência do autodesbaste foram 0,36 e 0,37, respectivamente.