Current Annual Increment Research Articles

EVALUATION OF MLR AND GWR REGRESSION MODELS OF CURRENT ANNUAL INCREMENT PREDICTED BY GROWING STOCK, TOPOGRAPHICAL AND LANDSAT 8 SPECTRAL DATA IN THE NORTHEAST BOSNIAN MIXED FOREST

UDK: 630*52/*56:519.8(497.6)
 The aim of this research was to evaluate estimates of the current annual increment of volume (CAIv) variability considering growing stock (V) as structural variable and topographic conditions and Landsat 8 spectral response as environmental variables on hilly and mountainous mixed forests in the northeast Bosnia using multiple linear regressions based on ordinary least squares (MLR) and geographically weighted regression (GWR).
 Sample data contains geo-referenced forest inventory data, CAIv (m3/ha/year) and V (m3/ha), extracted values from digital terrain model (altitude, slope and aspect) and derived principal components values from Landsat 8 satellite image for forest stands of the management unit located on hilly and mountain positions in protected area Konjuh, Kladanj. Here are applied MLR and GWR using stepwise procedure. MLR and GWR analyses resulted with global coefficients of significant predictors on hilly position. This was expected due to homogenous vegetation and environmental conditions on hilly position. It was found that growing stock affected CAIv the most. Significant improvement of regression modeling is achieved by GWR appliance on sample from mountainous position. There were obtained local influence of growing stock and the first principle component related to green biomass on CAIv. The highest improvement is found for broadleaves CAIv where quantification of local variability of growing stock increased adjusted coefficient of determination about 11% and reduced relative root mean square error for 6%. Local character of green biomass related to conifers CAIv did not improve regression estimation significantly. The broadleaves root mean square error based on GWR was 1.60 m3/ha/year (coefficient of variation more than 30%) which is still high so further modeling including other structural characteristics (stems number, basal area, mixture) as predictors is required.

Almacenamiento de carbono en un bosque de Pinus pseudostrobus en Nuevo San Juan, Michoacán

En el presente trabajo se utilizó el modelo dinámico CO2Fix para Windows Ver. 1.2., para obtener la captura potencial de carbono en la comunidad de Nuevo San Juan (NSJ). El carbono total estimado en el largo plazo (250 años) fue de 217 tC/ha; la biomasa (aérea y subterránea) con 74 tC/ha, los productos con 49 tC/ha y el suelo con 94 tC/ha. Se estimó que en el mismo plazo se tiene un potencial de captura de carbono en el bosque de la comunidad de 1.9 MtC en sus 8,870 ha. Así mismo se realizaron análisis de sensibilidad de tres parámetros, para identificar la diferencia potencial en la captura de carbono (tiempo de vida de los productos, tasas de humificación y descomposición ±30% del valor original). Por último, se describe la importancia del uso del modelo CO2Fix como una herramienta en el manejo forestal, especialmente para las plantaciones forestales. La simulación se basó, en lo posible, en datos disponibles localmente: (a) superficie del área de estudio; (b) manejo forestal: ciclos de aclareos, corta de regeneración y corta de liberación; existencias reales (E.R.), y volumen de madera extraído; (c) crecimiento del árbol: incremento corriente anual (ICA), diámetro, altura, edad e incremento medio anual (IMA); y (d) productos derivados como: papel, cajas de empaque, madera para construcción, madera para muebles, madera para energía y madera muerta.

Mapping the accumulation of woody biomass in Mediterranean beech forests by the combination of BIOME-BGC and ancillary data

A modelling strategy is proposed to obtain spatially explicit estimates of net carbon accumulation in Italian beech forests. This approach is based on the use of a biogeochemical model, BIOME-BGC, which is capable of simulating all main processes of ecosystems in quasi-equilibrium conditions. The model predictions are then corrected for actual forest biomass (growing stock volume) and stand age. The method is applied to predict the current annual increment (CAI) of 30 beech forest stands in Molise, Central Italy, which have been sampled during several measurement campaigns. A preliminary test is conducted to assess the model’s ability to reproduce the interannual production variations of these stands. Trials are then carried out driving the modelling strategy with both growing stock measurements collected in the field and a recently produced growing stock map. The final CAI estimates are validated through comparison with conventionally collected dendrochronological measurements. The results obtained indicate that the modelling approach is capable of reproducing interannual variations of net primary production and estimating the ground CAIs with an acceptable accuracy and when driven by the mapped growing stock. Additionally, the CAI estimates are not affected by the silvicultural system and development stage of the observed stands.

Effect of thinning on above-ground biomass accumulation in a Douglas-fir plantation in southern Italy

We investigated the effects of a long-term thinning experiment on the distribution of above-ground biomass of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) in a plantation in southern Italy. Allometric equations were used to estimate biomass and partitioning to stem and crown compartments. Variation in biomass stock estimated with allometric equations were evaluated according to seven thinning treatments: geometric-systematic (1 row every 3), selective (light-moderate-heavy), mixed systematic-selective (1 row every 4, 1 row every 5), unthinned (control). Over the experimental period of 13 years, current annual increments of carbon were lower (3.4 Mg ha−1 year−1) in control plots than in treated plots. At age 30, plots subjected to light selective thinning showed higher values of above-ground biomass (249.7 Mg ha−1). The biomass harvested with this treatment was 29.3 Mg ha−1, and the mean annual increment of carbon over 13 years was 4.8 Mg ha−1. Our results showed that light thinning stimulated increase in carbon stock, with a minimal loss of carbon during the treatment and a current annual increment of carbon higher than in control sub-plots and sub-plots thinned using systematic methods. This treatment yielded least carbon emissions and we affirm it has discrete global warming mitigation potential.

Growth dynamics of rubber tree clones in northwestern Minas Gerais, Brazil

ABSTRACT: This study aimed to evaluate the growth of rubber tree clones ( Hevea brasiliensis (Willd.exA.Juss.) Müll. Arg.) in the Northwest region of Minas Gerais, Brazil. Randomized blocks, constituted of three treatments (rubber tree clones) and four repetitions were used, and evaluated as plots subdivided in time. Subplots represent the evaluations carried out at the ages 62, 77, 87, 99, 113 and 128 months after planting. It was evaluated survival, stem circumference and total plant height. Current annual increment and average annual increment of circumference and also the number of trees fit for rubber tapping were calculated. Results obtained indicate that clones GT 1, IAN 2880, IAC 15, RRIM 600, PB 235 and IAN 3156 have potential to establish under local edaphoclimatic conditions. Increase in plant height and stem circumference throughout the evaluation period makes it evident that the clones have different growing paces in the studied region. Clones GT 1, IAN 3087, IAN 3156 and PR 255 had larger stalk circumference at 128 months, and PR 255 was the only one fit for rubber tapping at the age of 128 months after planting.

Degree of Hybridization in Seed Stands of Pinus engelmannii Carr. In the Sierra Madre Occidental, Durango, Mexico.

Hybridization is an important evolutionary force, because interspecific gene transfer can introduce more new genetic material than is directly generated by mutations. Pinus engelmannii Carr. is one of the nine most common pine species in the pine-oak forest ecoregion in the state of Durango, Mexico. This species is widely harvested for lumber and is also used in reforestation programmes. Interspecific hybrids between P.engelmannii and Pinus arizonica Engelm. have been detected by morphological analysis. The presence of hybrids in P. engelmannii seed stands may affect seed quality and reforestation success. Therefore, the goals of this research were to identify introgressive hybridization between P. engelmannii and other pine species in eight seed stands of this species in Durango, Mexico, and to examine how hybrid proportion is related to mean genetic dissimilarity between trees in these stands, using Amplified Fragment Length Polymorphism (AFLP) markers and morphological traits. Differences in the average current annual increment of putative hybrids and pure trees were also tested for statistical significance. Morphological and genetic analyses of 280 adult trees were carried out. Putative hybrids were found in all the seed stands studied. The hybrids did not differ from the pure trees in vigour or robustness. All stands with putative P. engelmannii hybrids detected by both AFLPs and morphological traits showed the highest average values of the Tanimoto distance, which indicates: i) more heterogeneous genetic material, ii) higher genetic variation and therefore iii) the higher evolutionary potential of these stands, and iv) that the morphological differentiation (hybrid/not hybrid) is strongly associated with the Tanimoto distance per stand. We conclude that natural pairwise hybrids are very common in the studied stands. Both morphological and molecular approaches are necessary to confirm the genetic identity of forest reproductive material.

Effect of local stand structure on leaf area, growth, and growth efficiency following thinning of white spruce

We examined the influence of stand structure surrounding individual dominant and codominant trees on leaf area, tree growth, and growth efficiency (stem growth per unit leaf area) in young white spruce (Picea glauca (Moench) Voss) plantations. Objectives were to (i) test the hypothesis that individual tree volume increment and growth efficiency increase with increasing growing space, and (ii) determine the relative importance of growth efficiency and leaf area to stem volume increment in young spruce following thinning. Growing space was expressed as area potentially available (APA) to each tree. Relative current annual volume increment (annual increment divided by the mean increment for the 3years immediately preceding thinning) increased linearly with increasing APA 2 and 3years after thinning, supporting our hypothesis that tree volume increment increases with APA. Growth efficiency however, was not related to APA. Leaf area was positively related to APA 3years after thinning, and current annual volume increment was related to leaf area. Leaf area per tree increased from 17.8m2 to 29.8m2 over the 3years (2011–2013) following thinning and was 16.5–18.7m2 for unthinned trees over the same period. Growth efficiency decreased from 1.35 to 0.64dm3m−2 for thinned trees and from 0.74 to 0.55dm3m−2 for unthinned trees from 2010 to 2013. Growth efficiency did not differ between thinned and unthinned trees, but it was significantly lower in year 3 than year 1 after thinning (p=0.0178) and significantly lower than the prethinning growth efficiency (p=0.0034). Our results show that thinning increased individual tree volume increment by increasing leaf area of remaining trees and not by increasing their growth efficiency.

Effect of gases and particulate matter from electricity generation process on the radial growth of teak plantations surrounding Mae Moh power plant, Lampang province

The objectives of this study were to investigate radial growth patterns and influences of polluting gases and particulate matter on the radial growth of teak plantations surrounding the Mae Moh Power Plant. Twenty-four 32-year-old teak trees were selected from Mae Jang and Mae Moh plantations, which were 5 km and 15 km from the Mae Moe power plant, respectively. Forty-eight sample cores were collected from the 24 trees (two cores per tree). The growth patterns of all the cores were analyzed following the standard methods of dendrochronology. The relationships between the growth pattern and the amounts of sulfur dioxide, nitrogen dioxide, carbon monoxide and particulate matter were measured as average daily rates and then analyzed. The study showed that the best-fit model for the relationship between the radial current annual increment at breast height (CAIdbh) and time (Y) was an exponential equation. The fitted equations were: CAIdbh = 10.657e(−0.031Y) for Mae Moh plantation and CAIdbh = 12.518e(−0.032Y) for Mae Jang plantation. The coefficient of determination for the fitted equations was 0.410 and 0.423 for the Mae Moh and Mae Jang plantations, respectively. Moreover, carbon monoxide (CO) and sulfur dioxide (SO2) had a statistically significant effect on radial teak growth (RT) in the Mae Jang plantation, with a coefficient of determination of 0.69 (RTmj = 0.571 + 0.429(CO) − 0.023(SO2)).

Biomass production and nitrogen balance of naturally afforested silver birch (<i>Betula pendula</i> Roth.) stand in Estonia

Silver birch ( Roth.) is one of the main pioneer tree species occupying large areas of abandoned agricultural lands under natural succession in Estonia. We estimated aboveground biomass (AGB) dynamics during 17 growing seasons, and analysed soil nitrogen (N) and carbon (C) dynamics for 10 year period in a silver birch stand growing on former arable land. Main N fluxes were estimated and nitrogen budget for 10-year-old stand was compiled. The leafless AGB and stem mass of the stand at the age of 17-years were 94 and 76 Mg ha respectively. The current annual increment (CAI) of stemwood fluctuated, peaking at 10 Mg ha yr at the age of 15 years; the mean annual increment (MAI) fluctuated at around 4–5 Mg ha. The annual leaf mass of the stand stabilised at around 3 Mg ha yr. The stand density decreased from 11600 to 2700 trees ha in the 8- and 17-year-old stand, respectively. The largest fluxes in N budget were net nitrogen mineralization and gaseous N-N emission. The estimated fluxes of NO and N were 0.12 and 83 kg ha yr, respectively; N leaching was negligible. Nitrogen retranslocation from senescing leaves was approximately 45 kg ha, N was mainly retranslocated into stembark. The N content in the upper 0–10 cm soil layer increased significantly (145 kg ha) from 2004 to 2014; soil C content remained stable. Both the woody biomass dynamics and the N cycling of the stand witness the potential for bioenergetics of such ecosystems.Betula pendula–1–1–1–1–1–1–1222–1–1–1–1

Biomass Accumulation and Carbon Stocks in 13 Different Clones of Teak (Tectona Grandis Linn. F.) in Odisha, India

The rate of biomass accumulation and carbon stocks of 13 different clones of Teak in Odisha were studied to identify the promising genotypes suitable for massive clonal plantations in Odisha. ORANP2 produced highest biomass among the 13 clones of teak i.e. 223.72m3/ha, while ORANP1 registered lowest value of 64.05m3/ha in regards to biomass accumulation. The total carbon stock values were found in the range of 32.02-111.86t/ha for 13 different clones of teak. The Mean Annual Increment (MAI) value for total tree biomass lies between 1.91t/ha to 4.76t/ha in different clones of teak studied. Similarly the total CO2 content was evinced to be varied from 128.77 to 440.21t/ha among the clones studied. The Current Annual Increment (CAI) values for total carbon stock and carbon content varied from 0.95-2.38t/ha and 3.50-8.73t/ha with the net annual carbon storage was found to be within 2.91-8.16t/ha. ORANP2 was found to be superior one in terms of net biomass and carbon content. It was ascertained that selection of suitable teak clone is highly required to meet both economic and environmental obligations.

EVOLUÇÃO DAS VARIÁVEIS DENDROMÉTRICAS DA BRACATINGA POR CLASSE DE SÍTIO

A identificação do ritmo de crescimento das variáveis dendrométricas de espécies florestais com o uso da análise de tronco é rápida, eficiente e de grande importância na tomada de decisões para o manejador florestal. Sendo assim, objetivou-se neste trabalho analisar a evolução das curvas de produção, Incremento Médio Anual (IMA) e Incremento Corrente Anual (ICA) da altura, diâmetro, área transversal e volume individual da Bracatinga (Mimosa scabrella), em diferentes classes de sítio, bem como, ajustar modelos matemáticos para expressar a evolução dessas variáveis, ao longo dos anos. A base de dados proveio da análise completa de tronco de 29 árvores, coletadas na região metropolitana de Curitiba, com idades variando de sete a 18 anos, distribuídas em três classes de sítio. Após as medições e processamento básico dos dados, ajustaram-se seis modelos matemáticos conhecidos na literatura, para cada uma das quatro variáveis dendrométricas em análise, independentemente para cada sítio. O melhor modelo foi escolhido com base no coeficiente de determinação ajustado (R²aj), erro padrão de estimativa em percentagem (Syx%) e análise gráfica de resíduos. Os resultados mostraram que o modelo de Chapman-Richards foi o de melhor ajuste para quase todas as variáveis em análise dentro dos três sítios. Verificou-se, também, que a ordem de culminação do incremento corrente anual seguiu a ordem cronológica esperada, isto é, primeiro a altura, seguida pelo diâmetro, área transversal e, por último, o volume, em todos os sítios.

Prediction of forest NPP in Italy by the combination of ground and remote sensing data

Our research group has recently proposed a strategy to simulate net forest carbon fluxes based on the coupling of a NDVI-driven parametric model, Modified C-Fix, and of a biogeochemical model, BIOME-BGC. The outputs of the two models are combined through the use of a proxy of ecosystem distance from equilibrium condition which accounts for the occurred disturbances. This modeling strategy is currently applied to all Italian forest areas using an available set of NDVI images and ancillary data descriptive of an 8-year period (1999–2006). The obtained estimates of forest net primary production (NPP) are first analyzed in order to assess the importance of the main model drivers on relevant spatial variability. This analysis indicates that growing stock is the most influential model driver, followed by forest type and meteorological variables. In particular, the positive influence of growing stock on NPP can be constrained by thermal and water limitations, which are most evident in the upper mountain and most southern zones, respectively. Next, the NPP estimates, aggregated over seven main forest types and twenty administrative regions in Italy, are converted into current annual increment of standing volume (CAI) by specific coefficients. The accuracy of these CAI estimates is finally assessed by comparison with the ground data collected during a recent national forest inventory. The results obtained indicate that the modeling approach tends to overestimate the ground CAI for most forest types. In particular, the overestimation is notable for forest types which are mostly managed as coppice, while it is negligible for high forests. The possible origins of these phenomena are investigated by examining the main model drivers together with the results of previous studies and of older forest inventories. The implications of using different NPP estimation methods are finally discussed in view of assessing the forest carbon budget on a national basis.

Limiting factors for lodgepole pine (Pinus contorta) and white spruce (Picea glauca) growth differ in some reconstructed sites in the Athabasca oil sands region

Peat-mineral soil mix (PMM) over tailings sand (TS) or overburden (OB) is a commonly used prescription for oil sands reclamation. The TS and OB (the substrates) often have unfavorable conditions such as high salinity, soil compaction, low nutrient availability in OB, and low nutrient and water availabilities in TS, which may limit tree growth. The objective of this study was to identify limiting factors for growth of lodgepole pine (Pinus contorta) on PMM over TS and white spruce (Picea glauca) on PMM over OB in the Athabasca oil sands region, Alberta, Canada. In the pine sites, mean annual growth of height (HG), diameter at breast height (DBHG) and aboveground biomass (ABG) were significantly correlated with volumetric water content (VWC) in PMM and foliar δ13C in current-year needles. Sites with high productivities had the lowest foliar δ13C relative to sites with low and medium productivities. The VWC and dissolved organic carbon (DOC) together explained 80% of the variation in both the current annual increment of height (HI) (p=0.007) and aboveground biomass (ABI) (p=0.008). In the spruce sites, foliar potassium (K) and foliar and soil nitrogen (N) concentrations were positively correlated with HG, DBHG and ABG, consistent with patterns in K and inorganic N (the sum of NH4+-N and NO3−-N) concentrations in PMM in those sites. Soil electrical conductivity (EC) and bulk density (Db) were greater in low than in medium and high productivity sites. The Db and inorganic N concentration together explained 67% of the variation in HI (p=0.037), while Db and EC together explained 79% of the variation in ABI (p=0.009). In conclusion, lodgepole pine trees planted on PMM over TS sites were limited by low water availability, while low soil N availability and high salinity limited the growth of white spruce trees planted on PMM over OB sites. Reclamation practices need to address water and nutrient limitations to ensure the success of reclaiming disturbed areas in the oil sands region.

Invasive Tree Species Robinia pseudoacacia: A Potential Biomass Resource in Nagano Prefecture, Japan

The introduced tree species, Robinia pseudoacacia (black locust), has spread extensively in many countries. Because of its active regeneration and rapid initial growth, R. pseudoacacia has not been successfully eradicated despite many efforts. To manage this species, developing information on the growth of R. pseudoacacia as a biomass resource is desirable, and this will motivate logging and could contribute to the extermination or sustainable use of this species. In the present study, the stand volume and growth of R. pseudoacacia forests in riverbeds along the Chikumagawa River in Nagano Prefecture in Japan were examined by tree ring and stem analyses. Seven plots were established in R. pseudoacacia riparian forests of varying ages, and 611 measurements of diameter at breast height and 386 measurements of tree height were made. Stand volumes, which were estimated using equations of stem volume curve based on the results of stem analysis of 47 sample trees, were almost the same as or higher than those of native broadleaf forests in Japan. Stand volumes continued to increase for more than 20 years. Current annual increments of four plots (aged 13–22 years) indicated that it could take <5 years after regeneration for the annual increment of R. pseudoacacia forests to reach a maximum level. Growth of R. pseudoacacia was comparable to or faster than native broadleaved species in Japan, showing the possibility of short rotation harvesting.

Assessing most relevant factors to simulate current annual increments of beech forests in Italy

Recent work of our research group demonstrated the applicability of a calibrated bio-geochemical model, BIOME-BGC, for estimating current annual increments (CAIs) of Mediterranean forests. In the current case, the model is applied to assess the gross primary production (GPP) of nine beech forest sites in Italy using a previously produced data set of meteorological data descriptive of a ten-year period (1999-2008). The obtained GPP estimates are integrated with relevant autotrophic respirations and allocations to derive forest net primary production (NPP) averages for the same forests. The simulations are performed assuming different levels of ecosystem disequilibrium, i.e. progressively taking into account the effects of specific site history in terms of woody biomass removal and stand aging.The NPP estimates, converted into CAIs by means of specific coefficients, are validated through comparison with data derived from tree growth measurements. Results indicate that the modelling of quasi-equilibrium conditions tends to produce overestimated CAI values, particularly for not fully stocked, old stands. The inclusion of information on existing biomass introduces a partial improvement, while optimal results are obtained when information on ecosystem development phase is considered. The implications of using different NPP estimation methods are finally discussed in the perspective of assessing the forest carbon budget on a national basis.

Relação entre alongamento anual da copa e o incremento diamétrico de árvores singulares de &lt;i&gt;Cedrela fissilis&lt;/i&gt; (Vell)

http://dx.doi.org/10.5902/1980509812354O crescimento da copa é uma variável pouco conhecida no campo florestal. Esta estrutura fotossintética tão importante para o crescimento da árvore encontra-se em um nível de difícil acesso para o manejador florestal e, portanto, pouco se conhece sobre seu desenvolvimento. Assim, o objetivo dessa pesquisa foi modelar o alongamento anual da copa utilizando como variável independente o incremento corrente anual em diâmetro do tronco de Cedrela fissilis. Utilizando 22 árvores singulares determinou-se o alongamento anual da copa e o incremento corrente anual em diâmetro no período de oito anos. Demonstrou-se que o desenvolvimento da copa esta relacionado com o incremento diamétrico (r=0,53; p&lt;0,0001), entretanto, para estimar o alongamento anual da copa com maior precisão, o modelo linear misto também incluiu o diâmetro a altura do peito e a altura comercial, que explicou 70% da variação total do alongamento do galho por classe de altura total.

Production of Douglas-Fir in the Czech Republic based on national forest inventory data

This article summarizes basic estimates of productivity and trend analysis of one of the principal introduced forest tree species in the Czech Republic, i.e. Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco). As a comparison, we also examine grand fir (Abies grandis [D. Don] Lindl), northern red oak (Quercus rubra L. syn. Quercus borealis Michx.) and black locust (Robinia pseudoacacia L). This paper presents estimates of forest land area, standing volume, annual and total increments, distribution of age classes, average ages and site indexes for the period 1979&amp;ndash;2010. All data were obtained from the national forest inventory of the Czech Republic. Korf&amp;rsquo;s growth function was used for the assessment of current and mean annual increments (CAI, MAI) of Douglas-fir compared to other tree species. Our results suggest a decline in the annual area afforested by Douglas-fir, as influenced by the State administration management choices, a low rate of an increase in the forest land area, increasing average age of the forests. On the other hand, we observed a dramatic increase in the standing volume as well as high annual increments in volume. Douglas-fir is the most productive major tree species in the Czech Republic and there is a great potential to expand its use throughout the country.

Application of a single-tree identification algorithm to LiDAR data for the simulation of stem volume current annual increment

A single-tree identification method has been applied to light detection and ranging (LiDAR) data acquired over a protected coastal area in Tuscany (San Rossore Regional Park, Central Italy). The method, which is based on the computation of the convergence index from the LiDAR tree-height image, is capable of identifying individual pine trees in densely populated stands. The main features of each pine tree (height and crown size) are also estimated, which allows the final prediction of stem volume. The accuracy of the stem volume estimates is first assessed through a comparison with the ground measurements of a recent forest inventory of the park [San Rossore Forest Inventory (SRFI)]. This test indicates that stem volume is predicted with moderate accuracy at stand level ( r around 0.65). The stem volume estimates are then used to drive a modeling strategy which, on the basis of remotely sensed and ancillary data, is capable of predicting stem volume current annual increment (CAI). A final accuracy assessment indicates that the use of LiDAR stem volumes in place of the SRFI measurements only slightly deteriorates the quality of the obtained stand CAI estimates.

Effects of planting density and cultural intensity on stand and crown attributes of mid-rotation loblolly pine plantations

Loblolly pine (Pinus taeda) is an important timber species in the southeastern US and abroad. A better understanding of loblolly pine crown relationships with growth has implications for improving productivity estimates using process-based models or remote sensing techniques. Four study installations in the Upper Coastal Plain and Piedmont of Georgia were used to examine the effects of planting density and cultural intensity on loblolly pine stand growth and crown attributes. Treatments included six planting densities, ranging from 740 to 4440 trees ha−1, in a split-plot design with two different levels of fertilization and competition control. The “low intensity (LI)” cultural treatment included relatively high nutrient inputs and early competition control. The “high intensity (HI)” cultural treatment included even greater nutrient inputs and complete sustained competition control. Treatment effects on stand and crown attributes were examined at age 13. Fertilization and competition control did not have a major influence on stand and crown attributes. Stands planted at lower densities resulted in significantly greater DBH and height but less standing volume per hectare, basal area per hectare, and current annual increment (CAI) volume growth compared to stands planted at higher densities. Stand-level foliar biomass, peak projected leaf area index (LAI), foliar nitrogen (N) content, specific leaf area (SLA), and intercepted photosynthetically active radiation (IPAR) were significantly greater for stands planted at higher densities, while live crown length and crown ratio were significantly greater for stands planted at the lower densities. IPAR efficiency (CAI per IPAR) was significantly affected by planting density, with values of 0.32–0.42m3 %IPAR−1 for 740 and 4440 trees ha−1, respectively. At this stage of stand development, light limitations due to high stocking have a greater influence on growth than soil resource limitations for the loblolly pine plantations analyzed in this study. Higher density stands resulted in increased SLA and IPAR efficiency, supporting the idea that higher density stands utilize light more efficiently than lower density stands.

Application of the CBM-CFS3 model to estimate Italy's forest carbon budget, 1995–2020

The estimation of past and future forest carbon (C) dynamics in European countries is a challenging task due to complex and varying silvicultural systems, including uneven-aged forest management, and incomplete inventory data time series. In this study, we tested the use of the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) in Italy, a country exemplifying most of these challenges. Our objective was to develop estimates of forest carbon budgets of the Forest Management area (including all forests existing in 1990) for the period 1995–2009, and to simulate alternative scenarios of natural disturbance (fire) and harvest rates to 2020. A number of methodological challenges required modifications to the default model implementation. Based on National Forest Inventory (NFI) data, we (i) developed a historic library of yield curves derived from standing volume and age data, reflecting the effect of past silvicultural activities and natural disturbances, and a current library of yield curves derived from the current net annual increment; (ii) reconstructed the age structure for a period antecedent to the reference NFI year (2005), to compare the model results with data from other sources; and (iii) developed a novel approach for the simulation of uneven-aged forests. For the period 2000–2009, the model estimated an average annual sink of −23.7Mt CO2yr−1 excluding fires in Italy's managed forests. Adding fires to the simulation reduced the sink to −20.5Mt CO2yr−1. The projected sink (excluding all fires) for the year 2020 was −23.4Mt CO2yr−1 assuming average (2000–2009) harvest rates. A 36% increase in harvest rates by 2020 reduced the sink to −17.3Mt CO2yr−1. By comparing the model results with NFI data and other independent studies, we demonstrate the utility of the CBM-CFS3 both for estimating the current forest sink in even-aged and more complex uneven-aged silvicultural systems in Italy, and for exploring the impact of different harvest and natural disturbances scenarios in managed forests. This study demonstrates the utility of the CBM-CFS3 to national-scale estimation of past and future greenhouse gas emissions and provides the foundation for the model's future implementation to other European countries.