Pine Plantations Research Articles

Modelling branch growth of Korean pine plantations based on stand conditions and climatic factors

To investigate the effects of stand conditions and climatic factors on branch growth and the dynamics of branch growth over time, we constructed a mixed-effects model on branch annual length growth using data from 803 branches of 70 sample trees in Korean pine (Pinus koraiensis Sieb. et al. Zucc.) plantations in Heilongjiang Province, China. The results showed that the introduction of branch age, branch depth into crown, branch diameter with bark, height-diameter ratio of the tree, stand average diameter at breast height, summer mean temperature and summer precipitation significantly improve the model fitting effect. The increase in summer mean temperature promoted branch growth, while the increase in the branch depth into the crown, height-diameter ratio of the tree, stand average diameter at breast height, and summer precipitation negatively impacted branch growth. We found that in the second year, the annual length growth reached a maximum, decreased with increasing branch age and stabilized when the branch age was greater than 20. Younger branches responded more strongly to competitive changes. The influence of summer precipitation on branch growth was greater than that of summer mean temperature. Moreover we found that within the appropriate range, climatic factors will not have a significant impact on branch growth until the summer mean temperature is lower than 16 °C and the summer precipitation exceeds 400 mm, which will have a significant inhibitory effect on branch growth. The introduction of random effects significantly improved the predictive ability of the model, and it was reasonable to select 6 branch annual length growths per branch to estimate random parameters. Our research indicated that branch growth is influenced by the combined effects of climate and competition, which helps to make reasonable forest management decisions under global climate change.

Molecular Characterization and Phylogenetic Analysis of the Pine Tortoise Scale Insect Toumeyella parvicornis (Cockerell) (Hemiptera: Coccidae)

Toumeyella parvicornis (Cockerell) (Hemiptera, Coccidae) is becoming a potential main pest of stone pine plants (Pinus pinea L.), both in urban parks and pinewood forests in Europe. Its recent distribution is a source of concern in several regions of Italy and in France. The early detection of this pest plays a fundamental role to contain its geographical expansion, but its taxonomic identification is still based on laborious observations of the morphological traits. The identification is also complicated by the small size of the pest, which makes the observations possible only through a stereomicroscope. Molecular identification is beneficial for detection, but currently, there is only a single gene sequence available for this pest. This study fills this gap in knowledge by providing the sequences of five different genes (COI, 28S, elongation factor (EF-1α), wingless (wg), and histone H3 (HexA)), together with a phylogenetic analysis carried out among species belonging to Coccidae, one of the most important families of scale insects. The results provide new valuable information about T. parvicornis and may represent useful data for its detection and management practices.

What is the extension of bench terrace construction for forest plantations? The case of North Central Portugal

AbstractOver the last decades, the establishment of new fast‐growing forest plantations has been prospering. Although the European continent has the lowest share worldwide of forest plantations out of its total forest area, the Portuguese reality contrasts this. Since the last century, eucalypt plantations have increased widely in Portugal, and nowadays, it represents 36% of the total country's forests. Consequently, the soils of these plantations are commonly targeted with intensive soil mobilization by heavy machinery before planting, which in the case of sloped areas, frequently results in bench terracing. This study aims to quantify the widespread bench terracing implementation over the last 20 years in the Caramulo Mountains in north central Portugal. To do so, an analysis of satellite imagery was performed with Google Earth Pro, which allowed determining the coverage of forest areas where new terraces have been implemented, and their respective temporal dynamics. These results were then compared with additional spatiotemporal databases on land cover, topography, and bedrock, in order to understand the drivers of terrace implementation. Till date, 15% of the forest area in the mountains of Caramulo is under terraces, and over the last 20 years, the construction rate of new terraced land decreased in time, from 4% between 2000 and 2004 to 2% between 2015 and 2019. Among the two bedrock types existent in the area, terracing was found nearly exclusive over schist bedrock type (97%), while few areas were implemented over granites (3%). Their distribution was found limited above 30° of slope angle while 39% were found implemented below 15° of slope angle, conflicting with literature recommendations. Terracing was also found to be a driver of land cover change in 12% of the newly constructed terraces, whereas 8% were constructed over previous pine plantations and 4% on shrublands. This study allowed identifying several knowledge gaps associated with terracing implementation. Therefore, the authors of this work suggest a multidisciplinary approach when planning new terraces for a better assessment of the benefits and impacts of such land management practices.

Comparisons of PM2.5 mitigation with stand characteristics between evergreen Korean pine plantations and deciduous broad-leaved forests in the Republic of Korea

Owing to industrialization and urbanization in recent decades, fine particulate matter (PM2.5) in the atmosphere has become a major environmental problem worldwide. This environmental issue pushed the use of forests as air filtering tools. However, there is a lack of continuous and long-term forest management to efficiently mitigate PM2.5. In this study, we assessed the potential of different forest types to control air pollution by measuring the seasonal PM2.5 concentrations inside and outside the forest for one year. In addition, the PM2.5 reduction efficiencies (PMREs) of two forest types were compared, and their relationship with stand characteristics was analyzed. The results showed that the average PMRE inside the forests was approximately 18.2%; the seasonal PMRE was highest in winter (approximately 28.1%) and lowest in summer (approximately 9.6%). The average PMRE of the Taehwa deciduous broad-leaved forest (TDF) (approximately 18.8%) was significantly higher than that of the Taehwa coniferous forest (TCF) (approximately 17.5%) (P < 0.001); differences were also observed seasonally. The PMRE in the TCF was higher in spring and summer (P < 0.001), while that in the TDF was higher in autumn and winter (P < 0.001). Furthermore, the PMRE in the TDF was negatively correlated with stand density (P = 0.003) and positively correlated with the average diameter at breast height (DBH) (P = 0.028). However, the PMRE in the TCF did not significantly correlate with stand characteristics. As such, the results of this study revealed the differences in PM2.5 mitigation according to stand characteristics, which should be considered in urban forest management.

Decadienal afforestation and risks to montane grassland amphibians in the Udzungwa Plateau, Tanzania

AbstractHuman modification of the environment has drastically changed ecosystems around the globe. While forest‐loss (deforestation) has been well studied for its effects on ecosystems, afforestation also has major impacts. The Udzungwa Plateau in Tanzania is naturally a mix of forests and grasslands. However, non‐native pine plantations have recently increased in the area displacing the native grasslands of the montane plateau. In this study, we explored the effects of land use change on amphibian communities by comparing amphibian surveys before non‐native plantations were introduced (~2000) and after (2017–2019). To put these amphibian surveys into wider context across the plateau and to distinguish local population loss compared to plateau‐wide extinctions, we sample diversity at new sampling locations and locations with multiple surveys through time. We then assessed landscape change through remotely sensed data and ground surveys. Amphibian encounter surveys found approximately the same species diversity across all sampling locations, but local extinctions appear likely. Remaining amphibians appear to be limited to small refugia in non‐pine wetlands. Approximately half (45%) of the species found have limited distributional ranges (&lt;72,000 km2) and are described as habitat specialists by the IUCN Red List. Monitoring pine plantation growth using remote sensing techniques suggested only limited extensions of plantations between 2000 through to 2013–2016, but ground surveys found small pines (&lt;3 years old) throughout almost all areas identified as grasslands on satellite imagery. Our study highlights the plight of this narrowing biome on the African continent and calls for more research on the impact of non‐native plantations on natural communities.Abstract in Swahili is available with online material.

Phenological Variability of Pinus sylvestris L. Provenances in the International Provenance Test in Kupres, Bosnia and Herzegovina

Scots pine (Pinus sylvestris L.) is an important forest tree species growing on different soils in Bosnia and Herzegovina. Phenological traits are relevant practical indicators of the adaptability and adaptedness of forest tree species. This research aims to determine the dates of the beginning and the end and duration of phases of bud breaking and elongation in P. sylvestris. The results will be used in the selection of best provenances for the areas with late frosts. The materials used were P. sylvestris plants in the international provenance test Kupres. The test was established in 2012 with 15 provenances (three from Austria, one from Bosnia and Herzegovina, two from Germany, three from Italy, one from Poland, one from Romania, one from Slovakia, two from Norway and one from Ukraine). Six phases were observed for bud breaking and elongation. Phase 1 (start of elongation, scales partly disjoined but still covering the young shoot) was recorded on 10 May in all provenances. Phase 5 (2 needles of the same brachyblasts are clearly distinct) first occurred on 6 June on some plants of every provenances except Bugojno (Bosnia and Herzegovina), Delytayn (Ukraine), and Ca Del Lupo (Italy). Understanding phenological phenomena of Scots pine is important since the occurrence of late spring frost can damage the plants of Scots pine in the environmental conditions of Bosnia and Herzegovina. Research should be continued and include an investigation of the influence of seasonal climate and climate changes.

Linking forest management to surrounding lands: a citizen-based approach towards the regional understanding of land-use transitions

The Southeastern United States has high landscape heterogeneity, with heavily managed forestlands, developed agriculture, and multiple metropolitan areas. The spatial pattern of land use is dynamic. Expansion of urban areas convert forested and agricultural land, scrub forests are converted to citrus groves, and some croplands transition to pine plantations. Previous studies have recognized that forest management is the predominant factor in structural and functional changes forests, but little is known about how forest management practices interact with surrounding land uses at the regional scale. The first step in studying the spatial relationships of forest management with surrounding landscapes is to be able to map management practices and describe their proximity to various land uses. There are two major difficulties in generating land use and land management maps at the regional scale by any method: the necessity of large training data sets and expensive computation. The combination of crowdsourced, citizen-science mapping and cloud-based computing may help overcome those difficulties. In this study, OpenStreetMap is incorporated into mapping land use and shows great potential for justifying and monitoring land use at a regional scale. Google Earth Engine enables large-scale spatial analysis and imagery processing by providing a variety of Earth observation datasets and computational resources. By incorporating the OpenStreetMap dataset into Earth observation images to map forest land management practices and determine the distribution of other nearby land uses, we develop a robust regional land-use mapping approach and describe the patterns of how different land uses may affect forest management and vice versa. We find that cropland is more likely to be near ecological forest management patches; few close spatial relationships exist between land uses and preservation forest management, which fulfills the preservation management strategy of sustaining the forests, and production forests have the strongest spatial relationships with croplands. This approach leads to increased understanding of land-use patterns and management practices at local to regional scales.

Tree roots exert greater impacts on phosphorus fractions than aboveground litter in mineral soils under a Pinus sylvestris var. mongolica plantation

Detritus inputs from aboveground litter and belowground roots, as well as roots exudates sustain soil phosphorus (P) supply in forests, but how the aboveground litter and roots differentially and interactively drive soil P transformations and availability is poorly understood. We experimentally removed aboveground litter, and then excluded roots in litter intact/removed plots in a nutrient-poor Mongolian pine (Pinus sylvestris var. mongolica) plantation in northern China. Phosphorus fractions with different bioavailability (labile P, moderately labile P, stable P, and occluded P), P adsorption characteristics and related biochemical properties in mineral soils were examined five years after the establishment of the experiment. Root exclusion significantly reduced labile organic P by 56%, and did not affect other recalcitrant organic P fractions and total organic P in both the litter intact and removed plots. Root exclusion significantly elevated all inorganic P fractions by 21%–26% in the litter removed plots, but not in the litter intact plots. Litter removal alone did not change soil P fractions except that it slightly increased labile organic and stable inorganic P concentrations. Maximum P adsorption capacity was improved by litter removal, but maximum P buffer capacity was neither affected by litter removal nor by root exclusion. Soil organic P fractions were correlated closely with soil microbial biomass, acid phosphatase activities and soil organic carbon, while inorganic P fractions were correlated significantly with exchangeable Ca2+ concentration and pH. The results revealed the predominant role of roots in driving the mobilization of inorganic, as well as mineralization-immobilization of organic P in this Mongolian pine plantation, and highlighted the facilitation of aboveground litter on root driving mobilization of soil inorganic P.

Individual-tree growth system for even-aged Aleppo pine plantations in Aragón, Spain

Aim of study: An individual-tree growth system was developed for Aleppo pine (Pinus halepensis Mill.) plantations.&#x0D; Area of study: Aragón region (Northeast Spain).&#x0D; Material and methods: Two datasets were used: Second and Third Spanish National Forest Inventories (104 plots with 1,678 trees), and ad hoc permanent plots (58 plots with 1720 trees, including 36 dead trees). Individual tree growth system was based on nine models. Different combinations of yield classes, initial stocking rates, thinning parameters, rotation periods, and age at first thinning were evaluated through the three most representative scenarios: timber production; soil conservation and biodiversity enhancement.&#x0D; Main results: The nine models demonstrated a significant explanatory power for the data, with R2 values ranging from 0.71 to 0.99. These findings are consistent with previous research, indicating a strong goodness of fit. Additionally, yield tables were developed for the three prevalent silvicultural scenarios. To enhance usability, all models within the system were seamlessly integrated into a web-based application SIMANFOR.&#x0D; Research highlights: To date, Aleppo pine forest managers in Aragon could only simulate silvicultural scenarios in natural stands. This study provides a new tool for plantations.

Thinning effectively mitigates the decline of aging Mongolian pine plantations by alleviating drought stress and enhancing plant carbon balance

Intensifying drought around the globe poses strong challenges to the growth and survival of trees, emphasizing the urgency of understanding the physiological mechanisms of drought-induced tree decline and mortality and the necessity of using silvicultural approaches to mitigate drought effects on tree growth. We experimentally explored whether thinning enhances tree growth vigor and drought resilience in early aging Mongolian pine (Pinus sylvestris var. mongolica Litv.) plantations in a water-limited area of Northeast China using dendrochronological methods. Meanwhile, we compared plant hydraulic traits, water relations, and non-structural carbohydrate concentrations between trees growing in the thinned and un-thinned stands with the aim of unraveling the physiological mechanisms underlying the density effects on tree growth performance. The results showed that basal area increments of Mongolian pine trees in the high-density plantations started to decline continuously at tree cambium age of around 15 years over about a decade, while thinning effectively reversed their growth decline. Trees in thinned stands exhibited significantly higher predawn leaf water potentials, higher stem hydraulic conductivities, and larger carbon reserves than trees in un-thinned stands. Although trees growing in high-density stands maintained as low risks of xylem hydraulic dysfunction as trees growing in low-density stands, that was at the cost of substantially reducing tree crown size through branch mortality that unavoidably undermined their carbon balance at the whole-plant level. Consistently, trees growing in the thinned low-density stands showed significantly higher levels of non-structural carbohydrate reserve in stems and enhanced growth resilience to extreme drought than trees growing in the high-density reference stands. Our results suggest that thinning can effectively enhance xylem hydraulic transport efficiency and reduce the risk of carbon imbalance by increasing soil water availability and hence mitigates the early aging of Mongolian pine plantations in water-limited environments.

Quantifying carbon additionality for uneven-aged forests

Forests can be managed to sequester atmospheric carbon in addition to producing timber. Forest carbon represents a nature-based solution to climate change and global warming. To internalize the positive externality (social benefit) of forest carbon, additionality must be defined and quantified. In this study, the discounted cash flow approach is applied to an uneven-aged sugar maple forest at a steady state to measure carbon additionality. Carbon credits are generated from the marginal forest growth, while a carbon release penalty is incurred by a harvest. The business-as-usual scenario is defined by a shorter harvest cycle, while an alternative carbon scenario is defined by a longer one. Then, additionality is defined by the difference in the net present value of carbon sequestration on a perpetual basis between the two scenarios. Compared with previous analysis on even-aged southern pine plantations, there is some evidence that the uneven-aged sugar maple forest is less economically effective in carbon offset as indicated by the benefit-cost ratio.

Plantation clear‐fell patches benefit heathland arthropods

Abstract Plantation forests constitute a significant amount of the wooded area in many parts of the globe. However, the extent of biological provision conferred by plantation forest depends on regional conservation priorities and biogeographical context. Here, we evaluate the arthropod biodiversity in a chronosequence of pine plantation (clear‐felled, 1, 3, 5, 7, 9, 13, 21‐years) in the largest lowland conifer forest in the UK. We compare the assemblage within 37 plantation stands and eight important open habitat remnants in a formerly heathland dominated region. We also assess the configuration and potential isolation of ephemeral open early growth stage habitat across a 60‐year plantation rotation. Carabid and spider assemblages changed throughout the sampled chronosequence. In the early growth stages (1–7 years) before canopy closure, arthropod assemblages contained many individuals and species associated with dry‐open habitats, greater numbers of rare species than closed canopy plantation and had similar composition (non‐metric multidimensional scaling) to heathland samples. Early growth stages and heathlands primarily differed in the additional presence of generalist species in the plantation. Species associated with woodland increased in abundance as the plantation aged, but remained far less numerous than dry‐open or generalist species. The spatial distribution of young growth stages across the rotation cycle was significantly clustered in the early and late rotation phases. Plantation landscapes often support high species richness but we highlight their value for vulnerable heathland biodiversity early in the rotation cycle. To increase plantation value regional conservation priorities should be supported with appropriate consideration of growth stage configuration across the full rotation.

Response of C:N:P Stoichiometry to Phosphorus Addition and Homeostasis of Plant Tissues in a Subtropical Slash Pine Plantation

Phosphorus (P) fertilizer is commonly used in subtropical plantations to augment nutrients including carbon (C), nitrogen (N), and P to maintain plants engaged in metabolism. Stoichiometric homeostasis reflects the adaptation of plants to various environments (including P fertilizer supply rates). It is thus of great significance to understand C:N:P stoichiometry in the plant–litter–soil system under P addition and the stoichiometric homeostasis of plant tissues for the P fertilization management of slash pine (Pinus elliottii Engelm) plantations. In subtropical China, we measured the C, N, and P contents in root, branch, needle, litter, and soil in slash pine plantations fertilized with four treatments, P1 (25 kg P ha1 yr1), P2 (50 kg P ha1 yr1), P3 (100 kg P ha1 yr1), and a control (CK), and calculated the stoichiometric homeostasis of plant tissues. The results show that P3 treatment increased the C, N, and P contents of the needle. P2 and P3 treatments increased the P content of the litter and the N:P ratio of the root while decreasing the C:N ratio of the root. P addition treatments increased C and P element accumulation in soil but had no effect on soil stoichiometry. The nutrient contents of needle and branch were higher than those of root and litter, indicating that slash pine was more inclined to allocate nutrients to the aboveground tissues. The stoichiometric homeostasis of C, N, and P among plant tissues was graded as follows: root &gt; branch &gt; needle. The needle’s nutritional homeostasis was C &gt; N &gt; P, with 1/H values of 0.08, 0.34, and 0.74, respectively. These findings demonstrate that during P addition, the C, N, and P stoichiometric homeostasis varied among plant tissues and element types. In conclusion, P application altered nutrient distribution in the plant–litter–soil system, alleviating P restriction in slash pine forests in southern China. P addition levels should be finely adjusted in the future for longer-term observation trials, and the trade-off between P addition rates and economic and ecological advantages should be properly examined.

THE IMPACT OF FOREST FIRES ON THE SOIL COVER IN THE CONDITIONS OF THE KUYAR FORESTRY OF THE REPUBLIC OF MARI EL

The influence of forest fires on the physico-chemical properties of sandy soils formed under pine plantations of the southern Taiga subzone in the conditions of the Republic of Mari El is shown. As a result of investigations of 4 soil sections, including 1 control and analysis of about 30 soil samples, soil parameters with the greatest and least variability were revealed. It was found that only the forest floor, which burned completely, with the formation of a specific Opir horizon, was exposed to a low forest fire, the upper mineral horizons have no signs of pyrogenicity. It was found that in the first post-fire year, the acidity in the upper soil horizons slightly increases compared to the control site, along with this, there is an increase in the amount of exchange bases and the degree of saturation with bases, the content of exchangeable potassium and loss indicators during calcination sharply decreases in forest litter. Regression equations are constructed on the basis of the revealed close relationships. It is concluded that, despite the absence of pyrogenic signs in the upper mineral horizons, their properties also change significantly under the influence of the combustion products embedded here together with the soil solution. To detail the data on the functioning of post-pyrogenic ecosystems, a long period of observations and scientific research is necessary.

Ecological Stoichiometry and Stock Distribution of C, N, and P in Three Forest Types in a Karst Region of China.

Ecological stoichiometry plays important roles in understanding the nutrient constraints on tree growth and development, as well in maintaining ecosystem services in forests, yet the characteristics of carbon:nitrogen:phosphorous (C:N:P) stoichiometry in forests under karst environment have not been sufficiently evaluated. In this study, concentration, distribution, stocks of Nitrogen (N) and Phosphorous (P), and ecological stoichiometry were studied in three common forest types: Masson pine natural forests (MPNF), Masson pine plantation forests (MPPF), and Slash pine plantation forests (SPPF) in a karst region of southwestern China. Results showed that N concentrations were higher in overstory than in understory and litter in the studied forests. However, P concentration was relatively low in overstory component of the forested ecosystems. Meanwhile, the N and P concentrations were higher in SPPF in the stem and litter, while these contents were higher in MPPF and MPNP in the overstory and understory. The N and P stocks ranged from 5.7-6.2 t ha-1, and 0.5-0.6 t ha-1 in the examined forests. The ecological stoichiometry of C:N:P in the three forest types was similar in litter (46-49:2:1), and relatively steady in soil (250-320:13-16:1) and tree leaf (100-200:14-20:1). Soil P status was the primary limiting factor in affecting tree growth in MPPF and SPPF (N:P ratio > 16), while both N and P conditions were the main restrictive factors in MPNP (N:P ratio = 15) in the study area. Our study provides scientific references and useful datasets of C:N:P stoichiometry for sustainable management of forest ecosystems in karst regions.

Group selection cutting for regenerating Mediterranean Pinus pinaster plantations: Gap effects on seedling survival

Diversification of forests, both in terms of structure and species, has been identified as one of the main strategies for adapting forests to climate change. Among the different options available for managers to promote diversification, regeneration cuttings are a suitable option to meet these objectives in adult stands close to rotation ages. The regeneration of maritime pine (Pinus pinaster Ait.) stands is a major issue throughout its distribution area, with summer survival being the main bottleneck for seedling establishment and development. Group selection cutting system may be the best option to promote uneven-aged and mixed structures in shade intolerant species, such as maritime pine. Gaps generate different regeneration niches for species of contrasting shade tolerance while creating uneven-aged stands, which are potentially more resilient to the impacts of climate change.In our experiment, gaps of two different sizes (1.5 and 2.5 times the dominant height of the stand, both sizes being smaller than those proposed in literature) were opened up to test the effects on natural regeneration success in a planted 53-year-old maritime pine stand in Central Spain. There were nine gaps of each size, along with nine control plots, containing 1-m radius subplots distributed within them to record natural regeneration of maritime pine and other species, in addition to several ecological factors and seedling characteristics. A survival model was fitted to highlight the main factors driving seedling survival. Gaps were found to have a significant positive effect on seedling survival, as well as mid-shade positions within the gaps and the age of the seedlings. Summer was found to have a negative effect on seedling survival. No effect of inter-species competition (scrub or herbs), litter coverage or geomorphological characteristics (slope, aspect or altitude) was found. Our results indicate, therefore, that group selection system cuttings, even with small gap sizes (1.5 and 2.5 times the dominant height), would provide a suitable method for the regeneration of Mediterranean maritime pine plantations.

Variations of deep water uptake and water use efficiency indicated divergence in tree growth stability

Insights into forest growth stability in response to intensified climate change and disturbances is critical to maintain the continued flow and stability of forest services. However, the underlying drivers for tree growth stability remain poorly understood. In this study, we quantified the spatiotemporal pattern in tree growth stability of Chinese pine (Pinus tabulaeformis) plantations and its relationship to diverse driving factors (climate, stand structure, ecophysiological traits, soil properties, and topography) across a great climatic gradient in northern China in the period of 1979–2018. We calculated the coefficient of variation of tree ring chronology (TRIcv) to characterize tree growth stability and revealed that the TRIcv increased significantly with increasing multiyear mean aridity index (MAI) and vapor pressure deficit (VPD) spatially. Temporally, TRIcv displayed increasing trend in 25 of 40 study sites. Constrained redundancy analysis revealed that TRIcv was strongly mediated by water availability, water uptake from different soil layers, wood density, tree height, leaf stable carbon isotope discrimination (δ13C), and leaf nutrients. The ratio of water uptake from 60 to 80 cm soil layer and leaf δ13C were the two most important ecohydrological-related factors determining TRIcv, highlighting that the water uptake strategy and leaf water use efficiency play critical role in reshaping the tree growth stability of Chinese pine to cope with the intensifying climate change.

Overexpression of the HcPT1.1 transporter in Hebeloma cylindrosporum alters the phosphorus accumulation of Pinus pinaster and the distribution of HcPT2 in ectomycorrhizae.

Ectomycorrhizal (ECM) fungi are associated with the roots of woody plants in temperate and boreal forests and help them to acquire water and nutrients, particularly phosphorus (P). However, the molecular mechanisms responsible for the transfer of P from the fungus to the plant in ectomycorrhizae are still poorly understood. In the model association between the ECM fungus Hebeloma cylindrosporum and its host plant Pinus pinaster, we have shown that the fungus, which possesses three H+:Pi symporters (HcPT1.1, HcPT1.2 and HcPT2), expresses mainly HcPT1.1 and HcPT2 in the extraradical and intraradical hyphae of ectomycorrhizae to transport P from the soil to colonized roots. The present study focuses on the role of the HcPT1.1 protein in plant P nutrition, in function of P availability. We artificially overexpressed this P transporter by fungal Agrotransformation and investigated the effect of the different lines, wild-type and transformed ones, on plant P accumulation, the distribution of HcPT1.1 and HcPT2 proteins in ectomycorrhizae by immunolocalization, and 32P efflux in an experimental system mimicking intraradical hyphae. Surprisingly, we showed that plants interacting with transgenic fungal lines overexpressing HcPT1.1 did not accumulate more P in their shoots than plants colonized with the control ones. Although the overexpression of HcPT1.1 did not affect the expression levels of the other two P transporters in pure cultures, it induced a strong reduction in HcPT2 proteins in ectomycorrhizae, particularly in intraradical hyphae, but still improved the P status of host plant shoots compared with non-mycorrhizal plants. Finally, 32P efflux from hyphae was higher in lines overexpressing HcPT1.1 than in the control ones. These results suggest that a tight regulation and/or a functional redundancy between the H+:Pi symporters of H. cylindrosporum might exist to ensure a sustainable P delivery to P. pinaster roots.

Loblolly Pine Planting Densities for Landowners in Areas with Poor Pulpwood Markets: Some Considerations

Abstract Loblolly pine plantations in the southeastern United States contribute significantly to local and state timber supply and economies. Planting density greatly affects reforestation costs. It also influences when vegetation starts competing inter- (and intra)-specifically for limited site resources, and when thinnings occur. Planting 600 seedlings per acre essentially forces landowners into two thinnings prior to a final clearcut. However, many landowners are finding it difficult to conduct first thinnings; poor pulpwood markets and lack of interest from loggers have become common. Reforestation costs have increased due to inflation. Thus, given better seedlings, a need for reduced reforestation costs, and the inability of landowners to conduct pulpwood-dominated thinnings, most landowners should plant near 450 seedlings per acre. Here, landowners have more flexibility to adjust to market conditions. If pulpwood markets improve they can participate, but a “pulpwood” first thinning is not absolutely needed. Plus, entry into more valuable chip-n-saw and sawlog markets should occur sooner.

Select or Not? Comparing the Impact of Selective and Schematic Thinning on Scots Pine Tree Growth and Stand Structure

The first commercial thinning usually entails a high cost in harvest operations and a low resulting income. From a practical forestry perspective, a schematic spatial selection might be more efficient than a selective approach. Therefore, this study aimed to compare basal area, total and standing volumes, and periodic annual increment (PAI), as well as stand structure, between different thinning designs (selective and schematic thinning) and strategies (thinning once or more than once) over a long-term monitoring period of Scots pine (Pinus sylvestris) plantations in Sweden. We also evaluated the relevancy of distance-dependent competition indices (CIs) in individual tree growth models by comparing growth model predictions with the use of distance-dependent and distance-independent CIs. Despite higher heterogeneity in schematically thinned stands, there were no significant differences in standing and total volumes (m3·ha−1) among treatments in the short or long term. Although the inclusion of a distance-dependent CI improved the model slightly, distance-independent models predicted diameter growth just as effectively. Schematic thinning could be a viable option for a first commercial thinning or one-time thinning if, at least, one more thinning is included in the management plan, or if the motivating interest is mainly volume.