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•Repeated fertilisation of young Norway spruce supports greater gains than late-rotation fertilisation.•Operationally viable 2-yearly fertilisation more than doubled stem volume yield ...on nutrient-poor soils.•Plot-level responses remained valid at the stand-level.•High NUE implies small N leaching and gaseous losses despite higher N addition.•Early, repeated fertilisation in northern forests may aid biomass demand and mitigate climate change.
Silvicultural techniques aimed at promoting forest biomass production can help meet the growing demand for renewable materials and mitigate climate change. One-time nitrogen (N) addition late in the rotation is a well-established method to stimulate growth in coniferous forests in northern Europe, but the potential gains from earlier and repeated fertiliser application remain uncertain. Here, we tested the impact of repeated fertilisation in juvenile Norway spruce stands across 9 sites covering a wide range of growing conditions over a 700 km stretch from central to southern Sweden. We tested the fertilisation effects using two separate studies: i) an interval trial with a fertilisation frequency of one (F1), two (F2), or three years (F3) performed at plot-level across five sites (2002–2014), and ii) a practice-oriented trial with a two-year fertilisation interval (F2) applied at stand-level and replicated at four sites (2003–2013). The composition of the nutrient mix in each plot was optimised based on foliar nutrient analyses. In the interval trial, all three fertilisation schedules strongly increased periodic annual increment (PAI) (F1: 105 %, F2: 93 %, F3: 79 %) relative to the unfertilised control, resulting in more than a doubling of stem volume yield in the F1 and F2 treatments (120 % and 110 %, respectively) and a significantly smaller but still sizeable yield stimulation of 82 % in the F3 treatment. Nitrogen use efficiency (NUE, stemwood volume increase per unit mass of N added) was similar among fertilisation intervals (on average 130 m3 ha−1 1000 kg N−1), indicating that the extra N provided through yearly fertilisation (F1) is redundant given the similar stemwood yields in the F2 treatment. In the practice-oriented trial, the sole F2 treatment increased PAI by 95 % over the control, translating into a yield stimulation of 114 % and an almost identical NUE to that of the interval trial. NUE greatly exceeded the figures typically observed with traditional late-rotation fertilisation and correlated inversely with baseline site productivity (using site index as a proxy) in the F1 and F2 treatments (the latter pooled across the two trials). Our results clearly indicate that nutrient limitation restricts growth and carbon (C) capture in young Norway spruce plantations in northern Europe to less than half of their potential, highlighting repeated fertilisation at nutrient-poor sites as an effective management tool to support a growing bioeconomy and enhance C sequestration.
•High nitrogen concentrations have a negative effect on radial growth.•Overfertilized trees produce tracheids with thinner cell walls.•Wood structure in over-fertilized trees can affect water ...transport in the trunk.•Overfertilized trees produce wood with inferior wood properties.
Fertilisation is often used to increase plant productivity in agriculture but has also been used in forestry. In our study, Scots pine forest growing in a nitrogen-poor environment was fertilised with NPK post-production wastewater from a potato starch factory. Our research aimed to investigate the dependence of tree growth on different NPK concentrations. Cell characteristics such as cell wall thickness (CWT), lumen diameter (LD) and tree-ring features such as ring width (RW), total number of cells in annual growth (nTotal), earlywood (EW) and latewood (LW) were investigated. Twenty-six years of regular fertilisation of the forest with different doses of wastewater rich in NPK elements have affected the anatomical structure of Scots pine trees. It is presumed that the reduction in CWT and LD on the fertilised site was due to deficiencies in plant water conductivity, which may have occurred due to physiological drought. The influence of nitrogen on unfertilised site from the wastewater area could contribute to the CWT thickening. The results confirm that the use of NPK in excessive doses is detrimental to trees' conductive system.
Climate change has led to a focus on forest management techniques to increase carbon (C) sequestration as a mitigation measure. Fertilisation and increased removal of biomass have been proposed. But ...these and other forest practices may have undesirable effects on surface water quality. In naturally acid-sensitive areas such as much of Fennoscandia a concern is acidification due to acid deposition in combination with forest practices that increase the removal of base cations and leaching of nitrate (NO
3
). Here we apply the biogeochemical model MAGIC to the coniferous-forested catchment at Birkenes, southernmost Norway, to simulate the effects of forest fertilisation and harvest on soil and streamwater. The model was calibrated to the 40-year data for water quality, soil and vegetation and then used to simulate fertilisation and clearcutting of the mature forest by either conventional stem-only harvest (SOH) or whole-tree harvest (WTH). The 5 - 10-year pulse of NO
3
following clearcut was larger with SOH than WTH. WTH causes larger acidification of surface water relative to SOH, due to greater depletion of base cations, N and C from the soil. The use of forestry as a climate mitigation measure should take into consideration the potential effects on soil and surface water quality.
Fertilisation with nutrient optimisation has in Sweden resulted in large increases in volume growth in young stands of Norway spruce. There are, however, environmental concerns about repeated ...fertilisation and one is the risk of nutrient leakage to ground water resources and aquatic ecosystems after clear-cutting of such forests. The present study followed soil-water chemistry in optimised fertilised stands after clear-cutting, as well as effects of harvest of slash on nutrient leakage. Parts of a 30-year-old stand of Norway spruce, which had been subject to a nutrient optimisation experiment for 17 years, were clear-cut. A split-plot design with whole-tree harvesting as the subplot treatment was applied. Lysimeters were installed and soil-water sampled at nine occasions during the following four years. No significant effects of fertilisation on nitrate leaching were found, while harvest of slash affected the concentration of Ca, DOC, DON, K, Mg, ammonium and nitrate, as well as pH in the soil solution. While no effects of fertilisation could be seen on the soil water concentration of N, the results indicate an interaction between fertilisation and harvest of slash on the concentration of nitrate in the soil solution. The results indicate that forest-floor vegetation plays an important role in the retention of N after clear-cutting of fertilised forests.
► We measured N leaching in Pinus radiata plantations after fertilising with urea. ► A water balance model was used to estimate soil water drainage. ► Fertiliser increased nitrate leaching at eight ...sites by 0–15kgha−1 over 2years. ► Greater nitrate leaching occurred on sand and low-productivity high-rainfall sites. ► Fertiliser did not increase leaching of ammonium-N or organic-N.
Although there is an opportunity to increase the productivity of Pinus radiata plantations in New Zealand through nitrogen (N) fertilisation, this treatment may reduce the quality of drainage water through leaching of nitrate-N. To improve our understanding of the effects of N fertilisation on potential N leaching, N concentrations in soil water below the root zone and potential losses were investigated after N fertiliser was applied as urea at 200kgha−1 of N to 7–9year-old operational plantations at 10 sites in New Zealand. A water balance model was used to estimate soil water drainage on a daily basis. Annual drainage ranged from 70 to 1,199mm and was closely correlated with annual rainfall. Nitrate-N, ammonium-N and organic-N concentrations in unfertilised control plots ranged between 0.03–2.26mgL−1, 0.06–0.49mgL−1 and 0.44–0.95mgL−1 respectively. Fertilisation significantly increased nitrate-N concentrations at four sites but did not affect ammonium-N or organic-N concentrations. In the 2years after fertiliser application, fertiliser increased nitrate-N leaching at eight of the 10 sites by 0–15kgha−1 (average 6.4kgha−1 or 3.2% of the N applied). These values underestimate total nitrate-N loss as fertiliser enhanced leaching at two sites had not ceased after 2years. Nitrogen fertilisation caused much greater increases in nitrate-N loss at a low productivity, high rainfall site (28kgha−1of N), and a coastal sand site (90kgha−1of N). To reduce losses at such sites, fertiliser should be applied at reduced rates in multiple applications. Factors that seem to have pre-disposed sites to nitrate-N leaching following N fertilisation include a pasture land-use history, the presence of a high component of the N-fixer Ulex europaeus in the understory, and soil C/N ratios of 15 or lower. Organic-N dominated leaching at 7 of the 10 sites, consistent with the pattern observed in unpolluted old-growth southern hemisphere forests, but mineral-N dominated at three sites, two of which had a recent land-use history of fertilised pasture.
Context A puzzling aspect of microtine population fluctuations is the damping out or collapsing of cycles over the last three decades, particularly in northern Europe. Occasional population ...fluctuations of Microtus may also have been damped out in temperate and boreal forests of the Pacific North-west of North America. One cause might be the presence of cattle (Bos taurus) grazing in forest habitats that offer summer forage. Aims We tested hypotheses (H) that abundance, population fluctuations, and demographic parameters of reproduction, recruitment and survival, of Microtus pennsylvanicus would be driven by understory plant productivity. Two predictions follow from this hypothesis: (H1) enhanced abundance and demography in fertilised stands, and (H2) reduced abundance and demography in stands with cattle grazing. Methods Study areas were located in ‘grazed’ and ‘ungrazed’ young forests in south-central British Columbia, Canada. Each study area had four replicate units of unfertilised and repeatedly fertilised stands. Herbaceous vegetation and meadow vole (M. pennsylvanicus) populations were sampled from 1993 to 2002. Key results Mean abundance of total herbs, grasses, and fireweed (Epilobium angustifolium) increased dramatically (8 to 34 times higher) with fertilisation in the ungrazed stands. Mean abundance of meadow voles was 3.1 to 8.5 times higher in the nutrient-enriched herbaceous vegetation in the ungrazed fertilised than grazed fertilised stands. Demographic variables also followed this pattern of abundance. Except for two years, mean abundance of meadow voles was similar between fertilised and unfertilised stands at the grazed area, with some degree of fluctuations generated in grazed stands. Thus, H1 and H2 were at least partly supported for M. pennsylvanicus in fertilised stands. Conclusions In high-quality habitats where cover and other attributes of vegetation are substantial enough to generate population increases and fluctuations of Microtus, grazing of vegetation by cattle or other livestock may indeed lead to potential collapse of fluctuations. Degree of grazing pressure would be crucial, but considering the widespread nature of grazing in the continuum of post-harvest forested sites in the Pacific North-west of North America, moderate to heavy grazing pressure is common. Implications Reductions in populations of microtines have serious consequences for predator communities and other ecological functions.
Intensive nutrient fertilisation of forests has been suggested as a method to increase production of biofuels as a replacement for fossil fuels. We used a field experiment in a Norway spruce,
Picea ...abies (L.) Karst., stand in northern Sweden to examine possible long-term effects of forest fertilisation on soil fauna (Oribatida, Mesostigmata, Collembola, predatory macroarthropods). Fertilisers had been applied annually for a period of 13 years, both in solid and liquid form, and N was added as ammonium nitrate (75–100
kg
N
ha
−1 per year). For comparison, control plots and plots receiving only irrigation were included. An autumn sampling showed soil fauna decreases in plots receiving fertiliser in solid form, but increases in plots receiving liquid fertiliser. Clear shifts in community composition following both fertilisation methods were seen in Oribatida and Collembola, but species number and diversity were not significantly affected. This was probably due to increases in tolerant species that balanced decreases in other species. Liquid fertilisation had less negative effects on many species than fertilisation in solid form. Irrigation alone did not affect faunal abundances and had no effect on community composition of Oribatida and Collembola. The study indicates that intensive forest fertilisation will cause large shifts in soil microarthropod communities, but that species richness may remain unaffected. The risk of species loss will probably depend upon the size of the areas used for this purpose.
The above-ground accumulation of N, N uptake and litter quality resulting from improved or deteriorated availability of water and nutrients in a 25 year old Norway spruce stand in SW Sweden (as part ...of the Skogaby project) is presented. Treatment include irrigation; artificial drought; ammonium sulphate addition; N-free-fertilisation and irrigation with liquid fertilisers including a complete set of nutrients according to the Ingested principle (fertigation). At start of the experiment the stand contained 86.5 t dry mass and 352 kg N ha⁻¹. The following three years the annual N uptake in untreated trees was 32 kg N ha⁻¹ to be compared with the annual N throughfall of 17 kg ha⁻¹. Simultaneously, the treatment with ammonium sulphate and liquid fertilisation resulted in 48 and 56 kg ha⁻¹ y⁻¹, respectively, in treatment specific N-uptake following an application of 100 kg N ha⁻¹ y⁻¹. Addition of a N-free fertiliser resulted in improved N-uptake by 19 kg N ha⁻¹ y⁻¹ and irrigation by 10 kg N ha⁻¹ y⁻¹, compared to control. A linear relation between total above-ground dry mass production and N-uptake was found for trees growing with similar water availability. Dry mass production increased with increased water availability given the same N-uptake. It is concluded that the studied stand this far is not N saturated', as N fertilisation resulted in both increased N uptake and increased growth. Addition of a N-free-fertiliser resulted in increased uptake of N compared to the control, indicating an increased mineralisation rate or uptake capacity of the root system. The linear relation between N uptake and biomass production shows that at this study site N is a highly limiting factor for growth.
A 22-year-old crop of Pinus contorta on oligotrophic peat was found to contain 85 kg ha⁻¹ more K than adjacent unplanted areas. It is suggested that the forest cover aids in conserving rainfall ...derived K which in the natural (unplanted) state is lost to drainage.
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