Modeling the forest phosphorus nutrition in a southwestern Swedish forest site

In this study, a phosphorus (P) module containing the biogeochemical P cycle has been developed and integrated into the forest ecosystem model ForSAFE. The model was able to adequately reproduce the measured soil water chemistry, tree biomass (wood and foliage), and the biomass nutrient concentrations at a spruce site in southern Sweden. Both model and measurements indicated that the site showed signs of P limitation at the time of the study, but the model predicted that it may return to an N-limited state in the future if N deposition declines strongly. It is implied by the model that at present time, the plant takes up 0.50 g P m−2 y−1, of which 80% comes from mineralization and the remainder comes from net inputs, i.e. deposition and weathering. The sorption/desorption equilibrium of P contributed marginally to the supply of bioavailable P, but acted as a buffer, particularly during disturbances

Att se skogens alla värden – en samhällsekonomisk analys

Det pågår en intensiv debatt om hur vi bäst kan använda skogen som resurs. Att ersätta fossila bränslen med förnybara bränslen från den svenska skogen lyfts fram som ett sätt att bidra till klimatmål. Men ett ökat uttag av biomassa kräver att skogen brukas mer intensivt vilket kan vara negativt för en rad andra samhällsmål som skogen bidrar till. Vad skulle ett intensivare skogsbruk totalt sett betyda för samhället? Resultaten visar att: Skogen bidrar med stora värden till samhället utöver produktionen av biomassa. När hänsyn även tas till sociala och miljömässiga värden kan ett mer intensivt skogsbruk än idag vara negativt för samhället. Ett mer varierat skogsbruk, som exempelvis inkluderar hyggesfritt bruk, kan ge större värden både idag och för framtida generationer

Storm disturbances in a Swedish forest-A case study comparing monitoring and modelling

A Norway spruce (Picea abies Karst) forest site in southwest Sweden was chosen to study the effects of storm disturbances over the period 1997-2009, during which two storms, 'Lothar' (December 1999) and 'Gudrun' (January 2005), affected the area. Monitored deposition data, soil water chemistry data and forest inventory data were compared with the predictions of an integrated ecosystem model, ForSAFE, in an effort to reveal and understand the effects of storms on acidification/recovery in forest soils. Both storms caused windthrow loss leading to increased nitrate and sulphate concentrations in soil water as a result of stimulated mineralization. Lothar led to increased concentrations of Na+, Mg2+, and Cl- in soil water due to sea-salt episode. No general sea-salt episode was seen following Gudrun, but small sea-salt episodes were observed in 2007 and 2008. Each sea-salt episode caused a temporary decrease of pH, and a subsequent recovery, but overall, the soil water pH decreased from 4.54 to 3.86 after Lothar. Modelling suggested that the site was recovering from acidification from 1990s, and would continue to recover in future. Both modelled and monitored data showed that storm caused disturbances in the recovery; monitored data even suggested that soil acidification happened due to storm disturbances. Sea-salt episode does not increase soil acidity in the long term, and will probably decrease the soil acidity by replenishing the base saturation. The modelled data also suggested that storms with only windthrow would not have effects on soil acidification recovery in the long term, but they may influence the soil fertility by losses of base cations. (C) 2015 Elsevier B.V. All rights reserved

Modelling nutrient transport from forest ecosystems to surface waters : The model ForSAFE-2D

Forests provide multiple products and services which are all are linked to water resources. Trees need water to grow and, at the same time, they change the quality and the quantity of runoff by modifying water and nutrient cycling. The understanding of the interactions between forest and water is fundamental to assess the consequences of natural and anthropogenic pressures, such as climate change and forest management, on the provision of forest products and services.Due to the complexity of ecosystems, models are often used to understand the interactions between different system components under a changing environment. ForSAFE is a dynamic, mechanistic ecosystem model simulating the storage and fluxes of chemical elements in forest ecosystems. It was developed to better understand the effects of environmental changes on the chemistry of forest biomass, soil and soil water at the forest plot level.The first two studies in this thesis are examples of the application of ForSAFE in forest stands in Southern Sweden. The model is used to simulate the effects of anthropogenic and natural disturbances on different ecosystem indicators, including indicators of soil water quality. The studies show that nutrient leaching below the rooting zone is positively related to the nutrient availability at the site, soil disturbances and the amount of organic material left in the forest after tree felling or a storm. Both types of disturbance produce a temporary increase of the acidity of the soil solution, but long-term effects where not predicted by the model. Compared to harvesting, a higher nutrient release in the soil solution can occur after storms due to root lifting causing increased mineralisation, a larger amount of biomass left at the site due to technical and economic constraints and larger canopy openings. In addition, sea-salt episodes can increase the acidity of the soil solution in the first years after the storm. When considering other ecosystem services, trade-offs can exist between the reduction of nutrient loads in the soil solution and the accumulation of carbon in the forest.The conclusions drawn from the application of ForSAFE at the forest plot level are valid for the soil water chemistry in the unsaturated zone. In this thesis, an effort has been made to expand the model simulations from the plot to the hillslope scale to understand how forest ecosystems can affect the chemistry of the streams. A new hydrology concept was integrated in ForSAFE-2D that simulates two-dimensional flows of water and chemical elements from the forest to the stream.ForSAFE-2D allows a better representation of the moisture content by simulating an increasing water saturation level in deeper soil layers and towards the stream. The simulated transport of a tracer along a hillslope shows that the model is capable of capturing the average concentrations of the tracer in the stream. This capability is based on a correct representation of the long-term average runoff and of tracer concentrations in the soil solution.The results also highlight some of the issues that should be addressed by follow-up research studies. The partitioning of water between base flow and peak flows suggests that the simulation of flow paths by ForSAFE-2D should be re-evaluated. A correct representation of flow paths will be crucial when simulating the transport of elements or compounds which change concentration with depth or distance from the stream (e.g. dissolved organic matter). In addition, the effects of saturation on weathering, as well as decomposition, show that the regulation of these processes at increasing moisture contents should be updated. Finally, the process regulating the allocation of carbon and nutrients to foliage should be revised to increase the share of foliage in the tree biomass and thereby correct the simulation of evapotranspiration

Water limitation can negate the effect of higher temperatures on forest carbon sequestration

Climate change will bring about a consistent increase in temperatures. Annual precipitation rates are also expected to increase in boreal countries, but the seasonal distribution will be uneven, and several areas in the boreal zone will experience wetter winters and drier summers. This study uses the dynamic forest ecosystem model ForSAFE to estimate the combined effect of changes in temperature and precipitation on forest carbon stocks in Sweden. The model is used to simulate carbon stock changes in 544 productive forest sites from the Swedish National Forest Inventory. Forest carbon stocks under two alternative climate scenarios are compared to stocks under a hypothetical scenario of no climate change (baseline). Results show that lower water availability in the future can cause a significant reduction in tree carbon compared to a baseline scenario, particularly expressed in the southern and eastern parts of Sweden. In contrast, the north-western parts will experience an increase in tree carbon stocks. Results show also that summer precipitation is a better predictor of tree carbon reduction than annual precipitation. Finally, the change in soil carbon stock is less conspicuous than in tree carbon stock, showing no significant change in the north and a relatively small but consistent decline in the south. The study indicates that the prospect of higher water deficit caused by climate change cannot be ignored in future forest management planning

Evaluating the contribution of forest ecosystem services to societal welfare through linking dynamic ecosystem modelling with economic valuation

Trade-offs exist among the multiple ecosystem services (ES) generated by forests. Generally, wood production conflicts with the provisioning of public-good ES such as the storage of carbon, nutrient retention and conservation of biodiversity. Recognizing that forests generate both private- and public-good ES implies that forestry should be optimized to maximize the contribution of forests to societal welfare. Here we develop an integrated approach for evaluating the contribution of forest ES to welfare. Our approach links the results from dynamic ecosystem modelling to economic valuation and benefit-cost analysis to evaluate the impacts of alternative forestry practices on welfare. We apply the approach to a Norway spruce forest in southern Sweden. We show that current practices are not maximizing societal welfare, because of conflicts in the optimal choice of practices from society's and forest owners’ perspectives, and the distribution of welfare between generations. In particular, intensifying biomass production is shown to reduce welfare due to the concomitant degradation of public-good ES, while welfare would improve through expansion of continuous cover forestry. We anticipate that this type of approach will aid the sustainable development of forestry, by informing decision makers of the impacts of alternative forestry practices on societal welfare

Water Limitation in Forest Soils Regulates the Increase in Weathering Rates under Climate Change

Climate change is generally expected to have a positive effect on weathering rates, due to the strong temperature dependence of the weathering process. Important feedback mechanisms such as changes in soil moisture, tree growth and organic matter decomposition can affect the response of weathering rates to climate change. In this study, the dynamic forest ecosystem model ForSAFE, with mechanistic descriptions of tree growth, organic matter decomposition, weathering, hydrology and ion exchange processes, is used to investigate the effects of future climate scenarios on base cation weathering rates. In total, 544 productive coniferous forest sites from the Swedish National Forest Inventory are modelled, and differences in weathering responses to changes in climate from two Global Climate Models are investigated. The study shows that weathering rates at the simulated sites are likely to increase, but not to the extent predicted by a direct response to elevated air temperatures. Besides the result that increases in soil temperatures are less evident than those in air temperature, the study shows that soil moisture availability has a strong potential to limit the expected response to increased temperature. While changes in annual precipitation may not indicate further risk for more severe water deficits, seasonal differences show a clear difference between winters and summers. Taking into account the seasonal variation, the study shows that reduced soil water availability in the summer seasons will strongly limit the expected gain in weathering associated with higher temperatures

Trade-Offs Between Forest Protection and Wood Supply in Europe

Forest protection is one of the main measures to prevent loss of biological and landscape diversity. This study aimed to assess to what extent forests are currently protected and how felling restrictions affect the potential annual wood supply within 27 European Union member states, Norway, and Switzerland and to discuss trade-offs between intensified use of forest biomass and forest protection efforts. Protected forests covered 33 million ha (20 % of total forest area) in 2005, of which 16 million ha was protected for biodiversity and the remaining area for landscape diversity. Within the protected areas, on average 48 % of the volume cannot be harvested in forests protected for biodiversity and 40 % in forests protected for landscapes. Consequently, 73 million m(3) (10 % of the annual theoretical potential supply from the total forest area) of wood cannot be felled from the protected forests in Europe. Protected forests do not necessarily affect wood supply given the current demand for wood in Europe. However, if demand for wood from European forests for material and energy use significantly increases, the impact of existing protected forest networks may become significant after all. On the other hand, wood harvesting is allowed to a fair extent in many protected areas. Hence, the question could be raised whether biodiversity and landscape diversity within designated areas are sufficiently protected. Careful planning is required to accommodate both the protection of biological and landscape diversity and demand for wood, while not forgetting all other services that forests provide