Pasture production under densely planted young willow and poplar in a silvopastoral system

New Zealand is subject to summer and autumn droughts that limit pasture growth. The planting of willow and poplar trees is one option used to provide green fodder during drought. However, there is a wide concern that such an option can reduce the overall understorey pasture growth. This study evaluated the comparative establishment and growth of densely planted young willow and poplar and their effects on understorey pasture growth. Two experiments were established for 2 years in Palmerston North and Masterton, North Island, New Zealand. In the first experiment, densely planted willow and poplar significantly reduced understorey pasture growth by 24 and 9%, respectively, mainly due to shade, but coupled with soil moisture deficit in summer. In the second experiment, pasture growth in a willow browse block was 52% of that in open pasture as a result of shade and differences in pasture species composition and management. Willow and poplar survival rates were similar (P > 0.05) after 2 years of establishment (100 vs. 90.5%, respectively). However, willow grew faster than poplar in height (1.90 vs. 1.35 m), stem diameter (43.5 vs. 32.6 mm), canopy diameter (69 vs. 34 cm) and number of shoots (8.7 vs. 2.3) at the age of 2 years.     

Pasture production in a silvopastoral system in relation with microclimate variables in the atlantic coast of Spain

Grasses and legumes of high productivity and nutritional quality are a good alternative as pasture supplements in rangelands of low quality forage. Orchardgrass (Dactylis glomerata L. cv. `Artabro') and white clover (Trifolium repens L. cv. `Huia') are known as shade tolerant and low flammability species that have been successfully used in agroforestry systems in Galicia, both diminishing fire hazard compared with natural shrublands. In this study, annual and seasonal production of a grass mixture of both species was quantified during 3 years in a pinewood under different tree canopy covers. Regardless of cover, pasture production increased in summer, and decreased from fall to spring. We obtained a significant correlation between annual pasture production and light transmission through the tree canopy (R² = 0.96, P<0.05). Light transmittance through a maritime pine canopy (Pinus pinaster Ait.) was higher than through a Scots pine canopy (P. sylvestris L.), corresponding to 36–57% and 16–21% of full sunlight respectively. The highest herbage production was obtained in no tree stands and the lowest under a P. sylvestris canopy. Fluctuations inlight transmission, temperature and PAR (Photosynthetically Active Radiation) under tree canopy were less apparent compared with no tree stands. Variation in seasonal production was more pronounced in stands without trees, and appeared more uniform when percentage of light intercepted by tree canopy increased.This revised version was published online in November 2005 with corrections to the Cover Date.     

黄土高原区不同密度刺槐林冠层结构特征及月动态变化

为合理经营黄土高原区刺槐人工林,利用LAI-2200植物冠层分析仪,研究了不同密度刺槐人工林冠层结构特征及月变化。结果表明:密度对LAI(叶面积指数)有影响,随着密度的增加,林分叶面积指数趋于一致;在生长月份上,LAI为先增后降趋势,最大值出现在6月底。密度与冠层开度呈显著负相关,随着密度的增加,刺槐林DIFN明显降低,925～1 125株/hm2与其他3个密度林分有显著性差异;DIFN(无截取散射)随月份的变化均呈"V"字型变化,在6月底至8月初DIFN最低。密度与MTA(平均叶倾角)呈显著正相关,密度在925～1 125株/hm2范围的刺槐林分,叶片几乎处于水平状态,其他3种密度林分MTA均在40°～50°之间有最大分布频率,而月份对MTA影响不显著。对叶面积指数与冠层开度进行回归分析,发现两者之间呈指数回归关系(R2=0.998)。     

Evaluation of leaf display of evergreen broadleaved tree species and deciduous tree species in warm temperate conifer plantations

We investigated the sapling leaf display in the shade among trees of various leaf lifespans co-occurring under the canopy of a warm-temperate conifer plantation. We measured leaf-area ratio (aLAR) and morphological traits of saplings of evergreen broadleaved tree species and a deciduous tree species. Although we found large interspecific and intraspecific differences in aLAR even among saplings of similar size in the homogeneous light environment, we did not find a consistent trend in aLAR with leaf lifespan among the species. While deciduous trees annually produced a large leaf area, some evergreen broadleaved trees retained their leaves across years and had aLAR values as high as those of deciduous trees. Among leaf-level, shoot-level, and individual-level morphological traits, aLAR was positively correlated with current-year shoots mass per aboveground biomass in deciduous trees, and with the area of old leaves per aboveground mass in evergreen broadleaved trees. Thus, tree-to-tree variation in the degrees of annual shoot production and the accumulation of old leaves were responsible for the interspecific and intraspecific variations in aLAR.     

Tree and livestock productivity in relation to tree planting configuration in a silvopastoral system in North Wales, UK

Silvopastoral systems in Europe offer the potential of introducing environmental benefits while at the same time increasing the diversity of farm outputs. The establishment of new silvopastoral systems by planting young trees into existing pasture was investigated at a site in North Wales, UK. Two tree species, sycamore (Acer pseudo-platanus L.) and red alder(Alnus rubra Bong.), were planted into pasture at a range of densities and planting arrangements. Growth of trees planted in farm woodland blocks (2500 stems ha^–1) was compared with the growth of trees planted at 400 stems ha^–1 in clumps and dispersed throughout the plot and at 100 stems ha^–1 (dispersed). Over the first six years after planting, alder trees were significantly taller and larger in diameter than sycamore. Sycamore trees planted at close spacing in farm woodland or clumped arrangements were significantly larger in diameter than widely spaced sycamore at 100 and 400 stems ha^–1. Livestock productivity was unaffected by the presence of trees during the six-year establishment phase of the system. The planting of trees in a clumped pattern appears to combine silvicultural benefits to tree growth with agricultural benefits of maintaining livestock production while trees are established.This revised version was published online in November 2005 with corrections to the Cover Date.     

Ailanthus triphysa at different densities and fertiliser regimes in Kerala, India: growth, yield, nutrient use efficiency and nutrient export through harvest

A split plot trial involving Ailanthus triphysa (ailanthus) at four spacings (3 m×1 m, 2 m×2 m, 3 m×2 m and 3 m×3 m) and four fertiliser regimes (0:0:0, 50:25:25, 100:50:50 and 150:75:75 kg ha⁻¹ per year N, P₂O₅, K₂O) was initiated in June 1991. Objectives included evaluating the growth and yield potential of ailanthus grown under differing density and fertiliser regimes and to estimate the nutrient export through harvest. Ninety-six randomly selected average-sized trees were felled at 8.8 years of age for assessment. Results show that height, diameter, stand leaf area index, biomass production and volume yield were greater in the 2 m×2 m spacing. Repeated application of fertilisers at 1.2, 2.25 and 5.25 years after planting had little effect on biomass and volume yields, presumably because of weed competition (despite periodic weed control), higher pest incidence (in the heavily fertilised plots) and/or moderately adequate soil nutrient levels. Regarding partitioning of tree biomass, stem wood represented the principal component (>70%), while foliage contributed the least (<7%). Conversely, foliar N, P and K concentrations were the highest, followed by branch wood, coarse roots and stem wood. Denser stands showed greater accumulation of N, P and K with higher potential for nutrient export through harvest. However, as the bole fraction accounted for only about 56–64% of the total nutrients removed, leaving other biomass components (foliage and branches) at the site will reduce the associated nutrient export. Wider spacings (3 m×2 m and 3 m×3 m) were more efficient in N and K use, but P use efficiency was higher in 2 m×2 m. Likewise, trees in the no fertiliser plots exhibited greatest N, P and K use efficiencies. Available soil P, K and organic C levels declined with increasing tree density, while repeated fertilisation increased nutrient concentrations. Soil pH and available P levels declined in comparison to the pre-treatment values.     

Validation of a canopy photosynthesis model for cocksfoot pastures grown under different light regimes

Daily net canopy photosynthesis (P _n) was predicted for cocksfoot (Dactylis glomerata L.) canopies grown under different light regimes by integration of a leaf photosynthesis model developed for the light-saturated photosynthetic rate (P _max), photosynthetic efficiency (α) and the degree of curvature (θ) of the leaf light–response curve. When shade was the only limiting factor, the maximum P _n (P _nmax) was predicted to decrease approximately linearly from 33.4 g CO₂ m⁻² d⁻¹ to zero as photosynthetic photon flux density (PPFD) fell from full sunlight (1800 μmol m⁻² s⁻¹ PPFD) to 10% of this in a fluctuating light regime. It was also predicted that at 50% transmissivity P _nmax was higher for a continuous light regime (10.4 g CO₂ m⁻² d⁻¹) than for a fluctuating light regime with the same intensity (8.4 g CO₂ m⁻² d⁻¹). The canopy photosynthesis model was then used to predict dry matter (DM) production for cocksfoot field grown pastures under a diverse range of temperature, herbage nitrogen content and water status conditions in fluctuating light regimes. This prediction required inclusion of leaf area index and leaf canopy angle from field measurements. The model explained about 85% of the variation in observed cocksfoot DM production for a range from 6 to 118 kg DM ha⁻¹ d⁻¹. The proposed model improves understanding of pasture growth prediction through integration of relationships between shade limitations in fluctuating light regimes and other environmental factors that affect the canopy photosynthetic rate of cocksfoot pastures in silvopastoral systems.     

Relationship between tree canopy height and the production of pasture species in a silvopastoral system based on alder trees

Silvopastoral systems in New Zealand that incorporate trees planted to control soil erosion on hills largely rely on the productivity of the pastoral system for financial returns. The effect on pasture productivity of increasing the tree canopy height by pruning Italian gray alder (Alnus cordata) was investigated by measuring the response of light, soil moisture, soil temperature, pasture production of major pasture species, and grazing behaviour of sheep. A split-plot design with four replicates was used. The main plot treatments were three levels of shade (81, 23, and 12% of available photosynthetic photon flux (PPF)), created by pruning 11 year old alder grown at the same density. The sub-plot treatments were four pasture mixes: perennial ryegrass (Lolium perenne), Yorkshire fog (Holcus lanatus), and cocksfoot (Dactylis glomerata), each sown with white clover (Trifolium repens), and cocksfoot sown with lotus (Lotus pedunculatus). Soil temperature was highest under light shade. Total herbage yield at 50 mm stubble height from October to May under heavy and medium shade was 60 and 80%, respectively, of the total herbage harvested under light shade. Cocksfoot had the greatest herbage yield, either with lotus or white clover. The tillering of perennial ryegrass was suppressed by shade more than for the other grass species making ryegrass unsuitable for use in this silvopastoral system. More sheep grazed in the light shade than in the heavy shade, but there was no difference in sheep preference for cocksfoot or Yorkshire fog. Lotus was grazed more frequently than white clover. Pruning of alder to increase canopy height has the potential to improve the productivity of the understorey pasture and its acceptability to sheep.     

Lime,sewage sludge and mineral fertilization in a silvopastoral system developed in very acid soils

In recent years, in the European Union, sewage sludge production has been increased as a result of EU policy (European directive 91/271/EEC). Organic matter and nutrient sewage sludge contents, principally nitrogen, indicate it can be used as fertilizer. The objective of the experiment was to compare the effect of no fertilization, three doses of sewage sludge, with or without liming, and the fertilization usually used in the region applied over a period of 3 years on pasture production and tree growth in a silvopastoral system. The experiment was conducted in the northwest of Spain. The soil was very acid (soil pH = 4.5) and had very low nutrient levels, especially P, that is related to site index. It was sown with a grass mixture (25 kg ha⁻¹ of Lolium perenne L. 10 kg ha⁻¹ of Dactylis glomerata L. and 4 kg ha⁻¹ of Trifolium repens L.) in Autumn 1997 under a plantation of 5-year-old Pinus radiata D. Don at a density of 1,667 trees ha⁻¹. Liming and sewage sludge fertilization increased soil pH and reduced saturated aluminium percentage in the interchange complex (Al/IC) in the soil, coming up the effect before with liming. Medium and high sewage sludge doses increased pasture production in the two first years. In a silvopastoral system, positive tree growth response to different fertilization treatments depended on tree age, initial soil fertility, soil pH, the relationship of competition with pasture production and previous liming application.     

Modeling cotton production response to shading in a pecan alleycropping system using CROPGRO

Light optimization assessment in alleycropping systems through model application is becoming an integral part of agroforestry research. The objective of this study was to use CROPGRO-cotton, a process-based model, to simulate cotton (Gossypium hirsutum L.) production under different levels of light in a pecan (Carya illinoensis K. Koch) alleycropping system in Jay, Florida, USA. Soil classification in the area was Red Bay sandy loam soil (Rhodic Paleudult). To separate roots of cotton and pecan, polyethylene-lined trenches were installed parallel to tree rows, thus competition for water and nutrients was assumed to be non-existent. Four treatments were set up in the CROPGRO-cotton model, as follows: (1) control (full amount of light transmittance), (2) Row 1 (50% light transmittance), (3) Row 4 (55% light transmittance), and (4) Row 8 (70% light transmittance). Cotton model parameters affecting specific leaf area (SLA), leaf area index (LAI), maximum leaf photosynthetic rate (FLMAX) and carbon partitioning were calibrated using the full sun treatment. Measurements of SLA, LAI, and aboveground biomass were made on the different shaded treatments and compared with simulated values. Simulation results showed that aboveground mechanisms affecting production in shaded environment (i.e., SLA, LAI, LFMAX, and carbon partitioning) influence model behavior. After calibration, the model predicted SLA of cotton in all treatments with reasonable precision. However, LAI was underestimated in the more shaded treatment rows 4 and 8. Generally, the model provided a close agreement between measured and simulated biomass both in 2001 and 2002 (R ² = 0.95 and R ² = 0.92, respectively). In 2001, predicted biomass for the control was 5,401 kg ha⁻¹ compared to the measured value of 5,393 kg ha⁻¹. A similar trend was also observed in 2002. The CROPGRO-Cotton model was able to describe variations in growth among the shaded treatments well across both growing seasons. However, it was found that additional research is needed to improve the model’s ability to simulate LAI under shading conditions. Parameters associated with photosynthesis and dry matter partitioning were reasonably stable across shading treatments and years but those associated with leaf area growth varied.     

Managing productivity and drought risk in Eucalyptus globulus plantations in south-western Australia

More than 2.5 million ha of Eucalyptus globulus are now planted across the globe including approximately 500 000 ha in southern Australia. In this region average annual rainfall has declined since 1960 and this trend is predicted to continue in the coming decades. E. globulus is a premium species for paper manufacture and grows well under moderate seasonal water stress. The traits that underpin this rapid early growth also make the species vulnerable to prolonged water stress. We established nitrogen rate and nitrogen-by-stocking experiments in five 2-year-old E. globulus plantations along a climatic gradient in south-western Australia. We measured volume growth, predawn leaf water potential and leaf area index over 7 years or until the plantations were 9 years old. These data were used to explore the relationship between growth and water stress, to understand the mechanistic basis for the relationship and to identify best-bet management strategies for E. globulus plantations in southern Australia.     

Forage production of woody fodder species and herbaceous vegetation in a silvopastoral system in northern Greece

Introduction of woody plants in silvopastoral systems could be an appropriate land-use for the poor sandy soils of the Mediterranean semiarid zone. Forage production of four woody fodder species and herbaceous vegetation in relation to plant spacing and animal (sheep) grazing was studied in a silvopastoral system on such a site in Macedonia, northern Greece. The woody fodder species tested were Robinia pseudoacacia L., Gleditsia triacanthos L., Amorpha fruticosa L. and Morus alba L. They were planted at the spacings 1.5 × 1.5 m,2.5 × 2.5 m and 3.5 × 3.5 m and kept in a shrubby form by topping. They were grazed by sheep (stocking rate of 1.1 sheep/ha/year) in early July and late August of 1992, 1993 and 1994. Among the species Robinia yielded the highest forage production (394 kg/ha). The spacing 1.5 × 1.5 m had the highest (P ≥ 0.05) forage production per area unit (280 kg/ha) while the spacing 3.5 × 3.5 m had the highest forage production per plant (91.8 g/plant). No competition was observed between the woody and the herbaceous plants in the various spacings probably due to topping of the woody species every winter. Percent utilisation of the native herbage dropped as forage of the woody species increased. This revised version was published online in June 2006 with corrections to the Cover Date.     

Wood net primary production resilience in an unmanaged forest transitioning from early to middle succession

The mixed deciduous forests of the upper Midwest, USA are approaching an ecological threshold in which early successional canopy trees are reaching maturity and beginning to senesce, giving way to a more diverse canopy of middle and late successional species. The net primary production (NPP) of these forests is generally considered past peak and in decline, but recent studies show a striking resilience in the NPP trajectories of some middle and late successional forests; yet, the mechanisms controlling such temporal changes in NPP are largely unknown. At the University of Michigan Biological Station in northern Michigan, we used a ≥9-year continuous record of wood net primary production (NPP), leaf area index (LAI), canopy composition, and stem mortality in 30 forested plots to identify the constraints on wood NPP as a mixed forest transitions from early to middle succession. Although wood NPP decreased over time in most stands, the rate of decline was attenuated when the canopy comprised a more diverse assemblage of early and middle/late successional species. The mechanism for sustained NPP in stands with more species diverse canopies was the proliferation of LAI by intact later successional tree species, even as stem mortality rates of early successional trees increased. We conclude that projections of carbon sequestration for the aging mixed forests of the upper Midwest should account for species composition shifts that affect the resilience wood NPP.     

Dry matter production,morphology and nutritive value of <Emphasis Type="Italic">Dactylis glomerata</Emphasis> growing under different light regimes

Plant growth, morphology and nutritive value under shade can differ between temperate grasses. Therefore, the aim of this study was to quantify the dry matter (DM) production, sward morphology, crude protein (CP%), organic matter digestibility (OMD) and macro-nutrient concentrations (P, K, Mg, Ca and S) in a grazed cocksfoot (Dactylis glomerata L.) pasture under 10-year-old Pinus radiata D. Don forest. Four levels of light intensity were compared: full sunlight (100% photosynthetic photon flux density-PPFD), open + wooden slats (∼43% PPFD), trees (∼58% PPFD) and tree + slats (∼24% PPFD). The mean total DM production was 8.2 t DM ha⁻¹ yr⁻¹ in the open and 3.8 t DM ha⁻¹ yr⁻¹ in the trees + slats treatment. The changes in cocksfoot leaf area index (LAI) were related to variations in morphological aspects of the sward such as canopy height and tiller population. CP% increased as PPFD declined with mean values of 18.6% in open and 22.5% in the trees + slats treatment. In contrast, the intensity of fluctuating shade had little effect on OMD with a mean value of 79 ± 3.2%. The mean annual macro-nutrient concentrations in leaves increased as the PPFD level declined mainly between the open and the trees + slats treatments. It therefore appears that heavily shaded dominant temperate pastures in silvopastoral systems limit animal production per hectare through lower DM production rates and per animal through reduced pre-grazing pasture mass of lower bulk density from the etiolated pasture.     

Expansion potential of invasive tree plants in ecoregions under climate change scenarios: an assessment of 54 species at a global scale

Climate change may increase expansion risk of invasive tree plants (ITPs) worldwide. Ecoregions are the power conservation tool for the management of ITPs. However, few studies have investigated the relationship between ITP expansion and ecoregions at the global scale under climate change scenarios. Here, we provided a method to evaluate the expansion potential of 54 representative ITPs in ecoregions specifically under influences of the changing climate at the global scale. We found that climate change due to increasing greenhouse gas (GHG) concentration plays a positive role on the expansion of ITPs. We determined two of the most important ecoregion hotspots of ITP expansion potential, such as New Zealand and South Africa. In addition, ITPs were likely to have a large potential to expand in ecoregions of five different biomes, like temperate broadleaf and mixed forests. The potential expansion of ITPs would increase obviously in ecoregions of Boreal Forests/Taiga and Tundra. More importantly, the ecoregions of high elevation belonging to Tropical and Subtropical Coniferous Forests were expected to experience the higher expansion risk in the low GHG concentration scenario. Given our estimates of ITP expansion for ecoregions, management for the prevention and control for ITPs is urgent at the global scale.     

Carbon and nitrogen in forest floor and mineral soil under six common European tree species

The knowledge of tree species effects on soil C and N pools is scarce, particularly for European deciduous tree species. We studied forest floor and mineral soil carbon and nitrogen under six common European tree species in a common garden design replicated at six sites in Denmark. Three decades after planting the six tree species had different profiles in terms of litterfall, forest floor and mineral soil C and N attributes. Three groups were identified: (1) ash, maple and lime, (2) beech and oak, and (3) spruce. There were significant differences in forest floor and soil C and N contents and C/N ratios, also among the five deciduous tree species. The influence of tree species was most pronounced in the forest floor, where C and N contents increased in the order ash = lime = maple < oak = beech ? spruce. Tree species influenced mineral soil only in some of the sampled soil layers within 30 cm depth. Species with low forest floor C and N content had more C and N in the mineral soil. This opposite trend probably offset the differences in forest floor C and N with no significant difference between tree species in C and N contents of the whole soil profile. The effect of tree species on forest floor C and N content was primarily attributed to large differences in turnover rates as indicated by fractional annual loss of forest floor C and N. The C/N ratio of foliar litterfall was a good indicator of forest floor C and N contents, fractional annual loss of forest floor C and N, and mineral soil N status. Forest floor and litterfall C/N ratios were not related, whereas the C/N ratio of mineral soil (0–30 cm) better indicated N status under deciduous species on rich soil. The results suggest that European deciduous tree species differ in C and N sequestration rates within forest floor and mineral soil, respectively, but there is little evidence of major differences in the combined forest floor and mineral soil after three decades.     

Biomass production by two-year-old poplar clones on floodplain sites in the Lower Midwest, USA

Four Populus clones were grown for two years at 1×1 m spacing for study of total biomass production and carbon sequestration capacity on floodplain sites previously in forage grasses under climatic conditions of the lower Midwest, U.S.A. Total biomass (above-and below-ground) in the first year ranged from 3.9 Mg ha^–1 in a Populus deltoides x P. nigra clone (I45/51) to 1.9 Mg ha^–1 for a local-source Populus deltoides clone (2059). Second year total biomass production was substantially higher, ranging from 13.9 Mg ha^–1 in I45/51 to 7.4 Mg ha^–1 in P. deltoides clone 26C6R51. Second-year leaf area index (LAI) values for I45/51 plants reached 4 during mid-season, indicating essentially complete canopy closure in this clone by the second year after planting. In contrast, maximum mid-season, second-year LAI was significantly lower in P. deltoides clones ( 2.4). There was some evidence for differential allocation to roots and shoots among Populus clones, with 26C6R51 showing relatively more allocation to root biomass than other clones. Second-year growth in Populus deltoides clone 2059 accelerated substantially, and this genotype exhibited two-year biomass accumulation nearly equal to that of I45/51 despite having less leaf area. This result suggested a higher photosynthetic capacity or assimilation efficiency in the former. This revised version was published online in August 2006 with corrections to the Cover Date.     

Soil organic carbon and aggregation under poplar based agroforestry system in relation to tree age and soil type

The poplar based agroforestry system improves aggregation of soil through huge amounts of organic matter in the form of leaf biomass. The extent of improvement may be affected by the age of the poplar trees and the soil type. The surface and subsurface soil samples from agroforestry and adjoining non-agroforestry sites with different years of poplar plantation (1, 3 and 6 years) and varying soil textures (loamy sand and sandy clay) were analyzed for soil organic carbon, its sequestration and aggregate size distribution. The average soil organic carbon increased from 0.36 in sole crop to 0.66% in agroforestry soils. The increase was higher in loamy sand than sandy clay. The soil organic carbon increased with increase in tree age. The soils under agroforestry had 2.9–4.8 Mg ha⁻¹ higher soil organic carbon than in sole crop. The poplar trees could sequester higher soil organic carbon in 0–30 cm profile during the first year of their plantation (6.07 Mg ha⁻¹ year⁻¹) than the subsequent years (1.95–2.63 Mg ha⁻¹ year⁻¹). The sandy clay could sequester higher carbon (2.85 Mg ha⁻¹ year⁻¹) than in loamy sand (2.32 Mg ha⁻¹ year⁻¹). The mean weight diameter (MWD) of soil aggregates increased by 3.2, 7.3 and 13.3 times in soils with 1, 3 and 6 years plantation, respectively from that in sole crop. The increase in MWD with agroforestry was higher in loamy sand than sandy clay soil. The water stable aggregates (WSA >0.25 mm) increased by 14.4, 32.6 and 56.9 times in soils with 1, 3 and 6 years plantation, respectively, from that in sole crop. The WSA >0.25 mm were 6.02 times higher in loamy sand and 2.2 times in sandy clay than in sole crop soils.     

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.     

Variation in seed production among years and among individuals in 11 broadleaf tree species in northern Japan

Seed production is the most problematic part of tree regeneration and is the least amenable to control by silvicultural management. Understanding variability in seed production among years and among trees will allow better planning of seed collection for seedling production and natural regeneration. We estimated the extent of variability in seed production among years and within years among individual trees. Specifically, we measured individual annual seed production in 11 woody species in Hokkaido, northern Japan. We analyzed the coefficient of variation (CV) of seed production among years and among individual trees. We used population- and individual-based CVs (CV_pt and ) to estimate the variability in seed production among individual trees. Alnus hirsuta, in which these CVs among trees were maximal, will require further analyses of the spatial patterns of seed production among individual trees. Additionally, we used population- and individual-based CVs (CV_py and ) to estimate the variability in seed production among years. The was statistically higher than in 2 of the 11 species: Betula maximowicziana and Sorbus alnifolia. Activities for the regeneration of these species should regard the annual variation in seed production as more important than individual variation. For the nine species in which was similar to even if seed production by specific trees was not sufficient for regeneration in a particular year, other trees or stands often had high seed production in that year. We discuss the relative importance of annual and individual variability in determining efficient methods for artificial and natural regeneration of these woody plant species.