The effect of scalping on seedling establishment after seed tree cutting of Scots pine stands in drained peatlands in northern Finland

We studied the establishment of natural seedlings after seed tree cutting and scalping in two drained Scots pine peatland stands in northern Finland (Simo and Sievi). Approximately, 50?ha^?1 of Scots pine stems were retained on both sites. During the six subsequent years, five seedling surveys were conducted. The effect of site preparation was analysed using generalized linear mixed models (GLMM). The mean density of pine seedlings increased more quickly in the scalped plots and was ca. 1.1?m^?2 after six years compared to 0.87?m^?2 in the non-scalped plots, on average. Scalping increased the number of pine seedlings 2-fold compared to that in non-treated plots in Simo, however, in Sievi non-treated plots had 30% higher pine seedling density after six years. Downy birch seedling density was 9–10-fold compared to that of non-treated plots in both sites. In terms of seedling density, seed tree cutting led to satisfactory pine regeneration after just two growing seasons in drained pine peatlands, even without scalping. Scalping significantly increased the number of pine seedlings, but it also enhanced the germination of birch seedlings strongly.     

Impact of indigenous aphids on development of the invasive common ragweed (<Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis> L.) in Hungary

The common ragweed, Ambrosia artemisiifolia is a widespread invasive weed species in Europe. In order to estimate the deteriorative effect of native arthropods on the invasive ragweed the effect of three indigenous aphid species on plant development and pollen production was studied. Common ragweed plants grown in a greenhouse were artificially infested with five apterous individuals of either Aphis fabae, Brachycaudus helichrysi or Myzus persicae at the 4-leaf stage. Feeding by all three aphid species over a 5-week period significantly reduced plant height, the number of male inflorescences, the length of racemes, pollen emission and plant dry mass. Brachycaudus helichrysi produced the largest colonies, followed by A. fabae and M. persicae. In a host plant choice test, B. helichrysi showed significant preference for ragweed over sunflower, whereas A. fabae preferred sunflower and M. persicae did not show any preference. In a field experiment, the growth rate of A. fabae on caged ragweed plants was similar to that in the greenhouse, but the final numbers of B. helichrysi and M. persicae after 30 days was ten and seven times lower than under greenhouse conditions, respectively. On exposed field plants, B. helichrysi was more abundant than other species. However, no aphid species affected the height or dry mass of either caged or exposed plants during a 30-day period. Under controlled conditions aphids effectively hampered development and pollen production of ragweed, however, under Hungarian field conditions the development of ragweed was much more dynamic, therefore no deleterious effect of aphid feeding occurred.     

Improving the estimation of landscape scale seed dispersal by integrating seedling recruitment

? Context

Dispersal and recruitment play a critical role in determining the abundance and the spatial structure of regeneration.

? Aim

In this study, we estimated landscape scale seed dispersal using the inverse modeling method by fitting seedling counts to seed tree location and fertility in the European silver fir Abies alba Miller.

? Methods

Seed trees and seedlings from three age cohorts were counted in 30 plots on Mont Ventoux (southeastern France) at elevations from 995 to 1,605?m, where the following ecological variables were measured: elevation, slope, aspect, light availability, and tree density. We developed and fitted a dispersal model, including a new parameter, recruitment rate, which depended both on the ecological characteristics of the plots and on seed production.

? Results

Elevation was the factor that affected seedling recruitment the most, with an optimum value at around 1,200?m. Estimated A. alba seed dispersal distances were short (median values for the three cohorts, respectively, 16.4?C13.2?C19.6?m).

? Discussion

We demonstrated that including the ecological characteristics of plots and post-dispersal recruitment processes realistically reduced estimates of seed dispersal distances which are otherwise grossly over-estimated using inverse modeling procedures.     

Is nitrogen fertilization in the nursery a suitable tool for enhancing the performance of Mediterranean oak plantations?

Mediterranean oaks frequently have poor performance in forest restoration projects. We analyzed if nitrogen (N) fertilization during nursery cultivation enhances the outplanting performance of two ecologically distinct oaks, Quercus coccifera L. an evergreen shrub, and Quercus faginea L., a deciduous tree. Additionally, we compared the sufficiency N levels of both oaks and if root growth capacity (RGC) and photosynthesis testing at low air temperature better discriminated among fertilization treatments than testing at mild temperature. Plants were cultivated under five N fertilization rates (0, 30, 75, 150 and 200 mg N plant^?1) for one growing season. At the end of the cultivation period several plant material and performance attributes were measured. RGC and photosynthesis were assessed at mild temperature and cool conditions in Q. coccifera, while in Q. faginea these attributes were only analyzed at mild temperature conditions. Q. coccifera seedlings were transplanted into four terraces that imposed increasing drought stress, while Q. faginea seedlings were transplanted into an abandoned wheat cropland. Sufficiency level was higher for the tree (150 mg N plant^?1) than for the shrub (75 mg N plant^?1) Nitrogen-deprived Q. coccifera plants had higher frost damage than remaining treatments, which did not differ among them. Fertilization in Q. faginea did not affect photosynthesis rate but it delayed leaf senescence and abscission. RGC increased with fertilization in both species. Testing temperature did not change the effect of fertilization on RGC in Q. coccifera. Photosynthesis in cool conditions discriminated N-deprived seedlings from the remaining treatments, but treatments did not differ in photosynthesis at mild temperature. Fertilization enhanced outplanting survival in Q. coccifera, primarily in the terraces imposing stronger drought stress, while fertilization only increased growth in the terraces imposing mild drought stress. Overall, survival and growth was positively related to seedling size at planting in both oaks. Additionally, Q. coccifera survival was also positively related to RGC in the harsh planting conditions. Field growth was positively related to RGC and plant N concentration in both oaks but the relation was weak or nonexistent under harsh conditions in Q. coccifera. We conclude that fertilization in the nursery is an important tool for improving the success of oak plantations in Mediterranean continental sites, and that large and N-rich seedling have greater field performance than small and low tissue N concentration seedlings, especially in harsh field sites.     

Variation in seed rain from Widdringtonia whytei growing in different conditions on Mulanje Mountain in Malawi

Mulanje Mountain is one of the examples of tropical montane landscapes with plant populations varying in size from small fragments of less than 1 ha to riverine strips and stands of more than 100 ha. Seed availability is a potential limiting factor in vegetation recovery in such landscapes. Field observation on seed rain and seed limitation was conducted in 2008 and 2009 in three sizes of forest fragments at three sites on the mountain to investigate: (1) whether size of Widdringtonia whytei forest patches influences seed-rain density; (2) whether W. whytei seed rain occurs in a specific season; and (3) if seed limitation differs from within forest patches to the adjacent non-forest patch habitats. The results showed that there was a distinct difference in seed-rain density among fragments where large fragments (>20 trees) collected higher seed-rain density (10.4 ± 0.9 seeds m^?2 y^?1) than small fragments (1.1 ± 0.4 seeds m^?2 y^?1). The seed-rain density differed significantly between 2008 (2.1 ± 0.6 seeds m^?2 y^?1)and 2009 (6.1 ± 1.1 seeds m^?2 y^?1). Seed rain was recorded every month of the year but the densities were not significantly different among months. Seed-rain density was highest inside the forest fragments (12.04 ± 2.3 seeds m^?2 y^?1) and decreased drastically and very significantly at the edges (1.0 ± 0.8 seed m^?2 y^?1) and outside the forest fragments (0.11 ±0.1 seed m^?2 y^?1). Seed limitation was strong (0.98) on all sites; 0.95 in large fragments and 0.99 in medium and small fragments, respectively. Therefore, it can be concluded from this study that the presence and retention of more seed trees ensures the continued availability of W. whytei seed on the forest floor within the context of limited seed dispersal.     

Practical large-scale forest stand inventory using a small-footprint airborne scanning laser

Mean tree height, dominant height, mean diameter, stem number, basal area and timber volume of 116 georeferenced field sample plots were estimated from various canopy height and canopy density metrics derived by means of a small-footprint laser scanner over young and mature forest stands using regression analysis. The sample plots were distributed systematically throughout a 6500 ha study area, and the size of each plot was 232.9 m². Regressions for coniferous forest explained 60–97% of the variability in ground reference values of the six studied characteristics. A proposed practical two-phase procedure for prediction of corresponding characteristics of entire forest stands was tested. Fifty-seven test plots within the study area with a size of approximately 3740 m² each were divided into 232.9 m² regular grid cells. The six examined characteristics were predicted for each grid cell from the corresponding laser data using the estimated regression equations. Average values for each test plot were computed and compared with ground-based estimates measured over the entire plot. The bias and standard deviations of the differences between predicted and ground reference values (in parentheses) of mean height, dominant height, mean diameter, stem number, basal area and volume were ?0.58 to ?0.85 m (0.64–1.01 m), ?0.60 to ?0.99 m (0.67–0.84 m), 0.15–0.74 cm (1.33–2.42 cm), 34–108 ha^?1 (97–466 ha^?1), 0.43–2.51 m² ha^?1 (1.83–3.94 m² ha^?1) and 5.9–16.1 m³ ha^?1 (15.1–35.1 m³ ha^?1), respectively.     

Can the shrub Chromolaena odorata (Asteraceae) be considered as improving soil biology and plant nutrient availability?

This paper attempts to provide a new perception of the weed Chromolaena odorata (Asteraceae) which is considered as a plague in agriculture or as a soil fertility indicator. The study was conducted in the forest-savanna transition zone of C?te d??Ivoire and aimed to compare soil biological activity and plant nutrient availability under three well-represented vegetation features, including C. odorata lands (ChrO), shrub savannas (ShrS), and grass savannas (GraS). Each of these vegetation features included five plot replicates (50?m?×?50?m size) distributed in the landscape. Soil chemical parameters such as pH, organic matter, soluble phosphorus, exchangeable bases, and biological parameters such as abundance and diversity of earthworms, and soil enzymatic activities were investigated. Composite soil samples were collected and analyzed for chemical and microbial parameters while earthworms were sampled using the Tropical Soil Biology and Fertility 25?×?25?×?30?cm soil monolith method. A principal component analysis showed a clear demarcation between C. odorata plots and the savanna ones. Soluble P and exchangeable bases were significantly higher under ChrO than under both savannas. Earthworm density was twice higher under ChrO (433.3?±?90.8?ind?m^?2) than under ShrS (173.9?±?61.5?ind?m^?2) and GraS (176.0?±?40.6?ind?m^?2) and this was accounted for by the abundance of detritivores and polyhumics. Acid and alkaline phosphatase activities under ChrO (2.9?±?0.2 and 2.5?±?0.3???mol pNP?g^?1 soil?h^?1, respectively) were twice higher than under both savannas. Based on the fact that ChrO and ShrS were located on similar soil types and had the same topographic position, we concluded that the establishment of C. odorata in a savanna land and its subsequent high biomass and quality-litter production were mostly the reasons of the improvement in soil biology and plant nutrient availability. Between-savanna comparison showed that ShrS, with higher CEC and exchangeable bases, was somewhat more fertile than GraS, probably because of a better soil physical status. In view of the agronomic potentials of the shrub C. odorata, it may be taken as a basis for improved fallow in Africa.     

Recovery of understory vegetation biomass and biodiversity in burned larch boreal forests in Northeastern China

Recovery of biomass and biodiversity of forest understory vegetation after fire disturbance has been widely studied; however, how this relationship changes and what are the determinants at different post-fire stages in larch boreal forests are still unclear. We investigated a chronosequence of 81 understory plots in larch boreal forests that were disturbed by fires in 1987 (S5), 1992 (S4), 1996 (S3), 2002 (S2), or 2007 (S1). Analysis of variance was conducted to test the differences of biodiversity and biomass among various post-fire stages. Different regression models were used to fit the relationship between biomass and biodiversity, while factors influencing this relationship were identified by boosted regression tree analysis. Results showed that total understory biomass increased from 2.51?t?ha^?1 in S1 to 8.47?t?ha^?1 in S3 and declined to 5?t?ha^?1 in S5. Similar dynamics were also found between species richness and species diversity. Positive linear correlations linked biomass and biodiversity throughout most of the post-fire periods. Slope and stand density were the two most important factors influencing the secondary succession of understory vegetation after fire. Geographical factors and overstory competition determine the orientation of vegetation recovery, and the impacts of climate on vegetation are muted after fire disturbances.     

Modeling nitrogen uptake for hybrid poplar with and without weed competition

Quantitative understanding of nutrient uptake by competing plants with different root systems can be a beneficial tool in designing the nutrient management strategies for competing plant environments. A field study was conducted at two sites (Alfalfa and Pasture site) near Meadow Lake, Saskatchewan, Canada to investigate the effect of weed competition on the growth and nitrogen (N) uptake by hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) using the Soil Supply and Nutrient Demand (SSAND) model. Hybrid poplar was grown with and without weeds (mainly dandelion (Taraxacum officinale F.H. Wigg.) and quackgrass (Elymus repens (L.) Gould) for 50, 79 and 100 days. Above-ground and below-ground growth of hybrid poplar was adversely affected by the presence of weeds at both sites. At the end of the experimental period, hybrid poplar in the control treatment took up 15.8 and 15.7 mmol N plant⁻¹ while seedlings in the weed treatments accumulated only 1.7 and 2.1 mmol N plant⁻¹ at the Pasture and Alfalfa sites, respectively. The SSAND model predictions for hybrid poplar N uptake at the Pasture site were in close agreement with measured N uptake in the control treatment (slope = 0.95-0.98). Model predictions for the Alfalfa site underestimated N uptake in the control treatment compared to measured values (slope = 0.75-0.77). The SSAND model greatly underestimated N uptake by both hybrid poplar and weeds grown in the weed treatment. Including N mineralization as a model input also did not improve the N uptake predictions; however, including changing soil water content greatly improved the prediction of N uptake by both hybrid poplar and weeds. Results from this study suggest that weed control is an essential practice to successful establishment of hybrid poplar plantations. Furthermore, the SSAND model can be a potentially useful tool for enhancing our understanding of plant nutrient uptake under field conditions where the dynamic nature of soil moisture and mineralization processes influence plant growth.     

Absorption and partitioning of applied 15N in a black pepper + erythrina system in Kerala, India

The fate of applied N in soil and its relative uptake by black pepper vine and erythrina tree on which the vine was trailed, were determined using ¹⁵N-labelled urea. Rapid depletion of ¹⁵N from 0-50 cm root zone was noticed due to heavy leaching during rains. The isotope content of the soil fell below the detection limit within one month of urea application. Both the vine and support tree absorbed N from the labelled fertilizer applied to the soil basin of the vine. Fertilizer use efficiency in black pepper vine was very low, in the range of 6 to 12%. On the other hand, the contribution of applied urea towards N uptake by erythrina support tree was 24 to 40%. Poor utilization of the applied N by the vine was, besides leaching of the nutrient, due to the severe root competition from the support tree. The overall utilization of the applied N was 51.4% by the vine and tree put together when N was applied at the rate of 25 g plant^–1 and 31.0% for the dose of 50 g N plant^–1.     

Gross nitrification rates in four Japanese forest soils: heterotrophic versus autotrophic and the regulation factors for the nitrification

Measurements of gross NH ₄ ⁺ and NO ₃ ^? production in forest soils were conducted using the ¹⁵N pool dilution method. Mineral topsoils (0?C10?cm depth) were collected from four forests from northern to southern Japan with a natural climate gradient to elucidate the mechanisms regulating gross nitrification rates in forest soils. Additionally, we attempted to evaluate the relative importance of heterotrophic nitrification in gross total nitrification using acetylene as a specific inhibitor of autotrophic nitrification. Distinct differences were found among sites in the gross rates of NH ₄ ⁺ production (3.1?C11.4?mg?N?kg^?1?day^?1) and gross total nitrification (0.0?C6.1?mg?N?kg^?1?day^?1). The rates of gross heterotrophic nitrification were low in this study, indicating that heterotrophic nitrification is of minor importance in most forest mineral topsoils in Japan. Significant relations were found between gross autotrophic nitrification and gross NH ₄ ⁺ production, soil N, and soil C concentrations, but none was found between gross autotrophic nitrification and soil pH. We determined the critical value of the gross NH ₄ ⁺ production rates for gross autotrophic nitrification under which no gross autotrophic nitrification occurred, as well as the critical soil C/N ratio above which gross autotrophic nitrification ceased. Results show that tight coupling of production and consumption of NH ₄ ⁺ prevents autotrophic nitrifiers from utilizing NH ₄ ⁺ as long as NH ₄ ⁺ availability is low.     

Nitrogen cycling in Pinus sylvestris stands exposed to different nitrogen inputs

The objective of this study was to quantify the effects of high nitrogen (N) inputs on N cycling in a 35–45-yr-old Scots pine (Pinus sylvestris L.) forest. Nitrogen was added annually (single doses) as NH₄NO₃ in doses of 0 (N0), 30 (N1) and 90 (N2) kg N ha^?1 yr^?1. The only N input to the N0 plots was atmospheric deposition of 10 kg N ha^?1 yr^?1. The N cycle in these plots was tight, with almost complete retention of the incoming N. In the N1 plots the N retention was 83% after 9 yrs of N addition. The trees were the major sink, but the soil also contributed to the N retention. In the N2 plots the N retention was 63%, being mainly accounted for by accumulation in the soil. The leaching of N from the N2 stands was as high as 35 kg N ha^?1 yr^?1. The N2 system was N saturated.     

Economics of intercropping loblolly pine and switchgrass for bioenergy markets in the southeastern United States

The main objective of this study was to assess the economics of alley cropping of loblolly pine (Pinus taeda L.) and switchgrass (Panicum virgatum) in the southern United States. Assuming a price range of switchgrass between $15 and $50?Mg^?1 and yield of 12?Mg?ha^?1 year^?1, we investigated the effect of switchgrass production on the optimal forest management for loblolly pine stands under different stumpage prices. We considered the following potential scenarios: no competition between species for resources; reduced loblolly pine productivity due to competition with switchgrass; and reduced productivity of both species due to competition for nutrients, water and light. Findings also suggested that the optimal system would depend on the competitive interactions between switchgrass and loblolly pine crops, and the expected prices for each crop. Loblolly pine monoculture would be the most profitable option for landowners compared to intercropping systems with switchgrass below $30?Mg^?1. However, when switchgrass prices are ??$30?Mg^?1, landowners would be financially better off adopting intercropping if competitive interaction between crops were minimal. In order to realize higher economic returns for intercropping system, forest landowners must make some efforts in order to diminish the decline of productivity.     

Effects of nurse trees,spacing, and tree species on biomass production in mixed forest plantations

Growing concern about increasing concentrations of greenhouse gases in the atmosphere, and resulting global climate change, has spurred a growing demand for renewable energy. In this study, we hypothesized that a nurse tree crop may provide additional early yields of biomass for fuel, while in the longterm leading to deciduous stands that are believed to better meet the demands for other ecosystem services. Ten different species combinations were planted, with two different stocking densities, at three different sites in Denmark. Significant differences, with regard to biomass production, were observed among the different sites (P?P??1?yr^?1 more biomass. The additional biomass production was similar to what was obtained in stands with conifers only (Sitka spruce, Douglas-fir and Japanese larch), which produced 4.9–6.1?t ha^?1yr^?1 more biomass than the pure beech stands. No effects of initial planting density (P?=?.19), or of initial weeding (P?=?.81), on biomass production were observed. Biomass production of the broadleaved crop was in most cases reduced due to competition. However, provided timely thinning of nurse trees, the qualitative development of the trees will allow for long-term timber production.     

Evaluation of Irrigation Practices for Growth,Biomass Production,and Nutrient Partitioning in Eucalyptus camaldulensis Plants in Indian Dry Zone

Supplemental irrigation is essential to increase tree productivity in dry areas to fulfill the local needs. One-year-old Eucalyptus camaldulensis Dehnh plants were planted in July 1998 and supplemental irrigation was provided at 36.2 mm (I₁), 26.5 mm (I₂), 20.2 mm (I₃), 18.1 mm (I₄), and live saving (I₅). Frequency and quantity of irrigation increased with an increase in irrigation level enhancing plant height, collar diameter, and biomass. These variables were highest at I₁, but water use efficiency (WUE) was highest at I₂. Dry biomass production increased from 1.18 kg plant^?1 at I₅ to 13.75 kg plant^?1 at I₁ at 24-month age. Biomass allocation to root increased from I₁ to I₅ but it was at the expense of leaf and branches. Height, collar diameter, dry biomass, and nutrient uptake indicated a non-linear increase with total quantity of water. Partitioning of N, Mg, Fe, Mn, Cu, and Zn was greater to stem; and those of P, K, and Ca was greater to leaf than to the other parts. Conclusively, I₃ and I₄ levels supported establishment whereas I₂ level was best for growth and productivity of E. camaldulensis plants in dry areas. The I₁ level could be tried to increase water use and reduce salinity buildup.     

Pre-commercial thinning,birch admixture and sprout management in planted Norway spruce stands in South Sweden

Early management of the regenerated seedlings shapes the future stand properties. To address these issues, pre-commercial thinning (PCT) and control treatments were applied to planted Norway spruce (Picea abies L. Karst) and naturally regenerated birch (Betula pendula Roth., Betula pubescens Ehrh.) stands in forest experiments in southern Sweden (lat. 56–57?N) containing 1.1–5.5?m tall saplings. The treatments were retention of 1000 or 2000?stems?ha^?1 of Norway spruce, with no birch or birch at 1000?stems?ha^?1. Treatments were replicated with and without annual removal of birch sprouts from stumps. The periodic annual increment (PAI) over five years was calculated for total stand volume and individual trees. The mean PAI of dominant trees was significantly higher both following all PCT treatments than controls, and following low rather than high-density PCT. Birch retention did not affect growth of the dominant trees but PAI was lower in plots with uncontrolled sprouting. The PAI of birch was significantly higher in low-density Norway spruce plots than in control plots and the high-density plots. The treatment response was significant even in stands with initial heights of only 1–2?m.     

Changes in soil properties and plant biodiversity after 12 years of rehabilitating livestock farms in the Hyrcanian Forests

Livestock presence in forest ecosystems is considered a factor in forest destruction in developing countries; therefore, rehabilitation practices following livestock exclusion could be a good way to restore forests. The main purpose of this study was to investigate the changes in the soil properties and plant biodiversity 12 years after applying fencing and planting in the livestock farms in the Hyrcanian Forests of Iran. First, three regions close to each other were selected and then four areas (treatments) were considered in each region: 1. An area under livestock use (L), 2. an enclosed area (E; with fences, established in 2007), 3. a planted area (P; established with Acer velutinum seedlings in 2007), and 4. a control area (C; natural forest); therefore, a total of 12 areas were considered. In each of the 12 areas, three plots (20?×?20 m) were randomly established (a total of 36 plots), and all the vascular plants in the herbaceous layer and woody species seedlings were recorded in order to study the biodiversity of the vegetation cover. One soil sample was taken from each plot to examine the physical and chemical properties of the soil. The results showed that bulk density, pH, electrical conductivity (EC), and available potassium were not significantly different between the C, E, and P treatments. Rehabilitation practices improved the soil pH (P: 6.36?±?0.06, E: 6.59?±?0.08), EC (P: 0.86?±?0.05, E: 0.82?±?0.04 ds cm^?1), total nitrogen (P: 0.31?±?0.001, E: 0.31?±?0.005), available phosphorus (P: 10.13?±?2.22, E: 19.29?±?2.43 mg kg^?1), and available potassium (P: 1369.60?±?31.06, E: 1898.80?±?448.60 mg kg^?1). The Margalef index was lower in the L area and no significant difference was observed between the E and P areas. Since the multivariate analysis (based on the vegetation and soil data) showed that P and E had more similarity to C, these treatments could accelerate the forest restoration process.

     

Light-mediated influence of three understorey species (Calluna vulgaris, Pteridium aquilinum, Molinia caerulea) on the growth of Pinus sylvestris seedlings

Depending on its developmental and morphological characteristics, shrubby or herbaceous understorey vegetation interacts differently with tree seedlings during the regeneration process. In acidic temperate forests, three common understorey plant species??Calluna vulgaris (L.) Hull, Pteridium aquilinum (L.) Kuhn in Kersten, Molinia caerulea (L.) Moench??are known to rapidly colonize forest gaps. Therefore, they often develop at the expense of light-demanding Scots pine (Pinus sylvestris L.) seedlings. An experiment was set up in a nursery in central France to mimic early competition occurring in a newly created gap between Scots pine seedlings and these three common understorey species (young forest-harvested individuals planted at 5 densities from 0 to 57 plants m^?2). Pine seedling survival and growth (height, diameter, shoot and root biomass) and a functional trait (leaf mass on an area basis, LMA) were measured for 2 years, and cross-analysed against plant density, plant cover and available light. When understorey plant density increased, pine seedling diameter growth and biomass were negatively affected by all three plant species; height growth only slowed beneath Pteridium. These negative effects were closely linked to competition for light beneath Pteridium and Molinia. The application of the Beer?CLambert law gave an extinction coefficient k that was high for Pteridium, intermediate for Molinia and much lower for Calluna. LMA was confirmed as an effective foliar trait to reflect the degree of stress undergone by pine seedlings.     

Optimal management of Korean pine plantations in multifunctional forestry

Korean pine is one of the most important plantation species in northeast China.Besides timber,it produces edible nuts and plantations sequester carbon dioxide from the atmosphere.This study optimized the management of Korean pine plantations for timber production,seed production,carbon sequestration and for the joint production of multiple benefits.As the first step,models were developed for stand dynamics and seed production.These models were used in a simulation–optimization system to find optimal timing and type of thinning treatments and optimal rotation lengths.It was found that three thinnings during the rotation period were optimal.When the amount or profitability of timber production is maximized,suitable rotation lengths are 65–70 years and wood production is 5.5–6.0 m~3 ha~(-1) a~(-1).The optimal thinning regime is thinning from above.In seed production,optimal rotation lengths are over 100 years.When carbon sequestration in living biomass is maximized,stands should not be clear-cut until trees start to die due to senescence.In the joint production of multiple benefits,the optimal rotation length is 86 years if all benefits(wood,economic profits,seed,carbon sequestration) are equally important.In this management schedule,mean annual wood production is 5.5 m~2 ha~(-1) and mean annual seed yield 141 kg ha~(-1).It was concluded that it is better to produce timber and seeds in the same stands rather than assign stands to either timber production or seed production.     

Changes in topsoil, standing litter and tree nutrient content of a Pinus patula plantation after phosphorus and potassium fertilization

A major goal for sustainable forestry management is to prevent a decline in soil fertility over time. The impact of phosphorus (P) and potassium (K) fertilization on the nutrients in the foliage, standing litter and topsoil (0 to ?10?cm) at the end of the third crop rotation (at age 15?years) was determined. Three quantities (20/20, 40/40 and 80/80?kg?ha^?1) of both P and K fertilizer was applied at different stages of stand development (all at planting, all post-pruning at age 5?years, or applying 20/20 at planting and the rest post-pruning). The results showed that the effect of P fertilizer was more pronounced than the effect of K fertilizer. Compared to the control, the application of 80/80 PK fertilizer increased the concentration of plant available P (Bray II) in the first ?10?cm of the topsoil from 3 to 12?mg P kg^?1 and increased the foliar P level to 0.13%. The foliar P as well as the concentration of plant available P in the topsoil increased when the fertilizer was applied post-pruning. The split application of either 40/40 or 80/80 PK fertilizer increased the stemwood P concentration by 50%, compared to the 23?mg P kg^?1 on the control plots. Application of the 40/40 and 80/80 quantities of fertilizer increased the dry mass (DM) of the standing litter layer by 27?Mg DM ha^?1 (35%), which also affected the P and K content per hectare. A larger proportion of the applied fertilizer-K than fertilizer-P was removed from the site in stemwood and stembark, indicating that the re-application of K in the subsequent rotations will be important for sustainable production.