Morten Ingerslev

Tree mineral nutrition is deteriorating in Europe

The response of forest ecosystems to increased atmospheric CO2 is constrained by nutrient availability. It is thus crucial to account for nutrient limitation when studying the forest response to climate change. The objectives of this study were to describe the nutritional status of the main European tree species, to identify growth-limiting nutrients and to assess changes in tree nutrition during the past two decades. We analysed the foliar nutrition data collected during 1992-2009 on the intensive forest monitoring plots of the ICP Forests programme. Of the 22 significant temporal trends that were observed in foliar nutrient concentrations, 20 were decreasing and two were increasing. Some of these trends were alarming, among which the foliar P concentration in F. sylvatica, Q. Petraea and P. sylvestris that significantly deteriorated during 1992-2009. In Q. Petraea and P. sylvestris, the decrease in foliar P concentration was more pronounced on plots with low foliar P status, meaning that trees with latent P deficiency could become deficient in the near future. Increased tree productivity, possibly resulting from high N deposition and from the global increase in atmospheric CO2, has led to higher nutrient demand by trees. As the soil nutrient supply was not always sufficient to meet the demands of faster growing trees, this could partly explain the deterioration of tree mineral nutrition. The results suggest that when evaluating forest carbon storage capacity and when planning to reduce CO2 emissions by increasing use of wood biomass for bioenergy, it is crucial that nutrient limitations for forest growth are considered.

Main Findings and Future Challenges in Forest Nutritional Research and Management in the Nordic Countries

Previous research has documented that nitrogen fertilization can lead to a significant tree growth increase in large parts of Scandinavia. Nutrient management of Nordic forests is currently under debate, mainly because environmental values are believed to be unnecessarily endangered by these actions. Nutrient management including fertilization, liming, recycling of wood ash or application of alternative nutrient sources can counteract nutrient deficiencies and imbalances, and be used for compensating the nutrients removed through harvesting. For successful implementation of nutritional management measures, several questions should still be studied. These questions mainly concern diagnosis of the need for applications, nutritional sustainability and treatment effects on the forest ecosystem and the surrounding environment.

Effects of liming and fertilization on growth, soil chemistry and soil water chemistry in a Norway spruce plantation on a nutrient-poor soil in Denmark

Abstract During recent years indications of nutritional imbalances in coniferous forest ecosystems have become more common in southern Scandinavia and central Europe. Deposition of acidifying substances, and relative deficiencies of nutrients, and soil acidification are supposed to be important contributing factors in the picture of forest damage. The need for counteractions such as liming and fertilization is thus pressing. A combined liming and fertilization trial was performed in a 59-year-old Norway spruce stand on a nutrient-poor soil at Klosterhede, Denmark. Two types of lime (calcite and dolomite combined with additional kieserite and phosphorus) were applied alone and in combination with conventional NPK fertilizer to form five different treatments. The treatments were carried out in 1986 and in 1994. All the treatments led to significantly increased leaching of ions from the soil within the first 8 months after treatment. Combined calcite and kieserite applications induced acidification pushes in the first period after the treatments. The magnitude of these changes varied strongly according to the different treatments. The alteration of the chemical composition of the soil water seemed to peak within 8 months following the treatments and it was largely eradicated 8 years after establishment of the trial, and 3 years following the last NPK fertilization. The desired geochemical changes of the soil solid phase regarding the counteraction of acidification were achieved in the upper horizons of limed plots (decreased exchangeable acidity (AC) and concentration of exchangeable Al3+, and increased concentration of exchangeable Ca2+ and Mg2+, base saturation (BS), cation exchange capacity (CEC) and pHH2O). Results from the O horizons (N and C concentration, C N ratio and horizon thickness) indicate that mobilization of nitrogen did not increase notably within the first 8 years of treatment in the limed plots, even though the pHH2O in the O horizon of the limed plots was increased and the C N ratio was below 30. The various treatments caused no significant differences in growth increment. The strongest effect observed was a growth rate reduction caused by application of kieserite and calcite. This reduction can presumably be ascribed to stress or even toxicity caused by the increased concentrations of Al3+ and SO42−, and decreased levels of pH in the soil water in the first period after the treatment.

The nutrient status of Norway spruce in pure and in mixed-species stands

Atmospheric deposition of N and S appears to have caused nutrient imbalance in Norway spruce stands in southern Sweden. This calls for a change of forest management to procedures that promote nutrient balance. Studies have shown lower soil acidity in Norway spruce/deciduous mixed stands than in spruce monocultures, but the tree nutrient status in such mixtures has not been much investigated so far. The nutrient status of Norway spruce foliage and top mineral soil chemistry in monocultures and in stands mixed with beech, birch, or oak was investigated through paired comparisons on 30 sites in southern Sweden (27 sites) and eastern Denmark (three sites). In total, 45 mixed stands and 34 pure stands were included in the study. Spruce needles from mixed stands had higher concentrations and ratios to N of K, P, and Zn than needles from pure spruce stands. Among the mixed stands, the K status appeared to be positively correlated with the percentage of deciduous tree basal area. Soil samples from mixed stands had a higher Mg concentration, base saturation, and BC/Al ratio than soil samples from pure stands. The spruce needle nutrient status was comparable in pure stands on fertile sites and in mixed stands on poor sites. We did not detect any differences in spruce tree growth between pure and mixed stands. This paper discusses possible reasons for a positive effect on the tree nutrient status in mixed-species stands and the possibility of using mixed-species stands as a forest management procedure to avoid nutrient imbalance

Above ground biomass and nutrient distribution in a limed and fertilized norway spruce (picea abies) plantation: Part I. Nutrient concentrations

Abstract The spatial variation in the concentrations of various plant nutrients in the above ground biomass was examined in a fertilized and limed 59-year-old Norway spruce stand on a nutrient poor soil at Klosterhede, western Denmark. Two types of lime (calcite and dolomite combined with additional kieserite and phosphate) were applied alone and in combination with conventional NPK fertilizer to form five different treatments. Sample trees of different size classes were felled and the nutrient concentrations of N, P, K, Ca, Mg and S were analysed at various heights from ground level, dividing the biomass into seven compartments (stem wood, stem bark, living branches, dead branches, current year needles, older needles and cones). The nutrient concentrations were generally highest in the actively growing parts of the trees (e.g. needles and stem bark). The concentrations of N, P, K and S were generally higher in current year needles than in older needles, whereas the opposite pattern was observed for the concentrations of Mg and Ca. The concentrations of N, P, S and Ca were increased by the treatments, most pronounced in the actively growing parts of the trees. However, the concentrations of K and Mg seemed unaffected by the treatments. When N and P were applied, the concentrations in the current year needles were elevated to levels that could be considered above deficiency in all parts of the canopy. Nutrient concentrations did not vary with tree size.

Fertilization of Danish Forests: A Review of Experiments

Fertilization experiments in Norway spruce stands on nutrient-poor sites have been practised in Denmark since the eighteenth century. Until 1950, the main aim was to find a nitrogen (N) source that improved the survival of plants in the early growth phase. The N supply could be improved by intercropping with N 2 -fixing plants, and fertilization with phosphorus (P) and potassium (K) improved the growth of the N 2 fixers, thereby improving tree growth and survival. Positive responses of P and K in spruce cultures were seen in the 1960s, and in most cases the N response was dependent on the supply of P and K. Fertilization experiments in mature spruce stands began in the 1960s. Despite 20 yrs of experimentation, no trends can be deduced. The results discouraged fertilization aimed at increasing growth in mature stands, and fertilization stopped in 1989. After 1980, fertilizers were used in experiments aimed at clarifying the causes and effects of forest decline. Fertilization and liming counteracted soil acidification and increased needle nutrient concentrations when they were below deficiency levels. However, positive growth responses have only been recorded in some of the experiments where nutrient deficiencies were overcome. The experiments have not resulted in practical revitalization programmes. Future fertilization of Danish forests may be limited to systems where nutrient extraction is in excess of the carrying capacity of the ecosystem, and presumably where spruce plantations are converted to broadleaved forests. Finally, future events of deposition of acidifying compounds may necessitate counteractive measures.

Fertilization in northern forests - biological, economic and environmental constraints and possibilities

Forests of northern ecosystems respond slowly to management activities and the possibilities to increase the growth in a short-term perspective and meet swift increases in societys demand for biomass are small. An exception among the silvicultural measures is fertilization which can be applied in combination with present management systems and, almost instantly, enhances forest productivity. There may, however, be both economic and environmental constraints to large-scale applications of fertilizers in forest. Here we review the literature concerning biomass production of forests under different fertilization regimens, environmental constraints and possibilities in northern forests on mineral soils. Further on we discuss the implications of both extensive and more intensive fertilization in relation to the developing bioeconomy, which encompasses the production and conversion of renewable biological resources into food, health and industrial products and energy. Fertilization in Sweden and Finland is currently practiced by extensive fertilization regimens where nitrogen fertilizers are applied once, or up to three times, during a rotation period, mainly in mature forest. This type of fertilization gives, in most cases, a small and transient effect on the environment as well as a high rate of return to the forest owner with low-economic risk. The increase in biomass production, however, is relatively small and consequently the impact on the processing industry and the bioeconomy is limited. More intensive fertilization regimens implying intensive fertilization starting in young forests may, on the other hand, considerably increase the biomass supply and value for the industry. The economic and environmental risks of this type of fertilization may, however, be larger and more research is needed on the effects on the stand level, and especially on the landscape level, including late rotation management of the forest.

Exceedance of critical loads and of critical limits impacts tree nutrition across Europe

Key messageExceedance of critical limits in soil solution samples was more frequent in intensively monitored forest plots across Europe with critical loads for acidity and eutrophication exceeded compared to other plots from the same network. Elevated inorganic nitrogen concentrations in soil solution tended to be related to less favourable nutritional status.ContextForests have been exposed to elevated atmospheric deposition of acidifying and eutrophying sulphur and nitrogen compounds for decades. Critical loads have been identified, below which damage due to acidification and eutrophication are not expected to occur.AimsWe explored the relationship between the exceedance of critical loads and inorganic nitrogen concentration, the base cation to aluminium ratio in soil solutions, as well as the nutritional status of trees.MethodsWe used recent data describing deposition, elemental concentrations in soil solution and foliage, as well as the level of damage to foliage recorded at forest plots of the ICP Forests intensive monitoring network across Europe.ResultsCritical loads for inorganic nitrogen deposition were exceeded on about a third to half of the forest plots. Elevated inorganic nitrogen concentrations in soil solution occurred more frequently among these plots. Indications of nutrient imbalances, such as low magnesium concentration in foliage or discolouration of needles and leaves, were seldom but appeared more frequently on plots where the critical limits for soil solution were exceeded.ConclusionThe findings support the hypothesis that elevated nitrogen and sulphur deposition can lead to imbalances in tree nutrition.

Bioenergy in the Nordic-Baltic-NW Russian Region : Status, barriers and future

The status of use of bioenergy, the current barriers for increased use and the future use of bioenergy in the Nordic-Baltic-NW Russian region is described in this report. In this region, forests ar ...

Leaching versus input of nitrogen, potassium and magnesium in different fertilizer regimens in Christmas tree stands of Abies nordmanniana in Denmark

Abstract The effects of nitrogen (N), potassium (K) and magnesium (Mg) fertilization and deposition on nutrient leaching were assessed in four Danish Nordmann fir Christmas tree stands on former arable land. NPK 23-3-7 fertilizer type was applied in doses between 0 and 1200 kg ha−1 year−1. Deposition of N, K and Mg varied between 16 and 21 kg N ha−1 year−1, 2 and 10 kg K ha−1 year−1, and 2 and 3 kg Mg ha−1 year−1. The concentration of NO3–N in the soil water on the sandy sites was characterized by notable pulses contrasting the mitigated peaks on the clayey site. In general, the soil water concentrations and leaching reflected the fertilization, except for K at one clayey site. Mean annual leaching of NO3–N ranged from approximately 6 kg ha−1 year−1 in the control treatment to 235 kg ha−1 year−1 in the 1200 kg ha−1 year−1 fertilizer treatment. In the treatment with the commonly used 300 kg NPK 23-3-7 fertilizer NO3–N leaching was estimated to be approximately 46 kg ha−1 year−1. Annual leaching of N was described in a general model based on the fertilizer input. K and Mg leaching were distinctly more site specific than was N leaching. The magnitude of NO3–N leaching caused by application of 300 kg NPK 23-3-7 fertilizer was between the leaching amounts observed in traditional Danish forestry and Danish agriculture.