An oak forest and three wet meadows/fens were reinvestigated after 50 years concerning tree vitality, biomass and productivity, and soil chemistry. Sulphur and nitrogen deposition has changed dramatically during these...An oak forest and three wet meadows/fens were reinvestigated after 50 years concerning tree vitality, biomass and productivity, and soil chemistry. Sulphur and nitrogen deposition has changed dramatically during these years, and the aim was to analyse the differences in both the oak forest and the open field ecosystems. Trees were re-measured and soil profiles were resampled. Important visible changes in the oak forest were stated concerning the vitality of oaks. Aboveground there was a decrease in tree biomass, production and litter fall, but a huge increase in standing dead logs. During the years, the deposition of sulphur had decreased drastically, but nitrogen deposition was still high. Soil acidification in the forest had decreased, reflected in an increased base saturation in the forest, in spite of slightly lowered pH-values. Strongly increased amounts of exchangeable Ca and Mg now appeared in the forest soil, and a substantial transport of calcium and magnesium had obviously taken place from the forest soil to the meadow and fens during the years. However, the most important soil change was the accumulation of organic matter. The increased accumulation of organic matter in turn meant increased amounts of colloid particles and microsites for ion exchange in the soil. This favoured 2-valence base cations, and especially Ca and Mg that increased very much in all the studied ecosystems. Carbon as well as nitrogen had strongly increased in the forest, meadow and fen soils. This was interpreted as a natural result of increased vegetation growth due to high nitrogen deposition, increased global annual temperature and increased carbon dioxide concentration in air. It was concluded that the decreased deposition of sulphur had had a positive effect on soil chemistry, and that the deposition of nitrogen probably had stimulated vegetation growth in general, and contributed to increased amount of organic matter in the soils. However, in this studied oak forest, the decreased vitality and many killed trees were also suspected to be a result of high nitrogen deposition. Obviously increased tree growth was counteracted by decreased stress resistance, and increased appearance of pathogens in the oak trees.展开更多
Plant biomass, primary production and mineral cycling in the beech forest (Fagus sylvatica L.), Hestehave in Jutland, Denmark were studied over a 50-year period. The role of the forest as a carbon sink was also assess...Plant biomass, primary production and mineral cycling in the beech forest (Fagus sylvatica L.), Hestehave in Jutland, Denmark were studied over a 50-year period. The role of the forest as a carbon sink was also assessed. Aboveground tree biomass was 226 t·ha-1 in 1970 and after a 50-year 539 t·ha-1 in 2014, an unexpected increase with 313 t·ha-1. Annual production at those two points in time was 13.4 and 20.5 t·ha-1, respectively. It was apparent that the tree biomass was still acting as a sink for carbon, which was the dominant element in the aboveground parts. The concentration of other elements (N > K > Mg > P > S > Na > Mn > Zn > Fe > Cu) ranged from 495 to 0.4 kg·ha-1. Annual litterfall restored 3.2 t·ha-1 to the soil as organic matter or 1.6 t·ha-1 as carbon. Over the year 53% of the litterfall was decomposed. A pH decrease of 0.95 units in the soil was observed between 1968 and 1993. This was attributed to fallout from a neighbouring thermal heating station affecting sulfur deposition and increasing soil acidification. After 1993, when filters were fitted in the heating station, the pH decrease in the soil was smaller, only 0.09 pH-units up to 2011. The increased tree growth is an additional, likely explanation for the observed soil acidification. Deposition of the growth-limiting element nitrogen increased during later years and is now, most likely around 20 kg·ha-1 per annum, which may partly contribute to the increased production.展开更多
Plant biomass, primary production and mineral cycling were studied in a mixed deciduous forest (Quercus robur L., Tilia cordata L. and Corylus avellana L.) in southern Sweden. Plant biomass amount above and below grou...Plant biomass, primary production and mineral cycling were studied in a mixed deciduous forest (Quercus robur L., Tilia cordata L. and Corylus avellana L.) in southern Sweden. Plant biomass amount above and below ground was 201 and 37 t·ha-1, respectively. Primary production above and below ground was an estimated 13.3 and 2.3 t·ha-1, respectively. Carbon was the dominant element in the forest ecosystem, comprising 133 t·ha-1. Other major elements were: N > Ca > K > Si > Mg > S > Mn > P > Fe and Na (range 1123 to 18 kg·ha-1), followed by some trace elements. Yearly litterfall restored 6.0 t·ha-1 organic matter or 2.3 t·ha-1 carbon. Approximately 45% decomposed and returned to the soil during the year. Monitoring of other elements revealed that the ecosystem received inputs through dry and wet deposition, in particular 34.4 kg·ha-1 S and 9.4 kg·ha-1 of N yearly as throughfall. Determination of yearly biomass increase showed that the oak forest ecosystem was still in an aggradation or accumulation phase.展开更多
文摘An oak forest and three wet meadows/fens were reinvestigated after 50 years concerning tree vitality, biomass and productivity, and soil chemistry. Sulphur and nitrogen deposition has changed dramatically during these years, and the aim was to analyse the differences in both the oak forest and the open field ecosystems. Trees were re-measured and soil profiles were resampled. Important visible changes in the oak forest were stated concerning the vitality of oaks. Aboveground there was a decrease in tree biomass, production and litter fall, but a huge increase in standing dead logs. During the years, the deposition of sulphur had decreased drastically, but nitrogen deposition was still high. Soil acidification in the forest had decreased, reflected in an increased base saturation in the forest, in spite of slightly lowered pH-values. Strongly increased amounts of exchangeable Ca and Mg now appeared in the forest soil, and a substantial transport of calcium and magnesium had obviously taken place from the forest soil to the meadow and fens during the years. However, the most important soil change was the accumulation of organic matter. The increased accumulation of organic matter in turn meant increased amounts of colloid particles and microsites for ion exchange in the soil. This favoured 2-valence base cations, and especially Ca and Mg that increased very much in all the studied ecosystems. Carbon as well as nitrogen had strongly increased in the forest, meadow and fen soils. This was interpreted as a natural result of increased vegetation growth due to high nitrogen deposition, increased global annual temperature and increased carbon dioxide concentration in air. It was concluded that the decreased deposition of sulphur had had a positive effect on soil chemistry, and that the deposition of nitrogen probably had stimulated vegetation growth in general, and contributed to increased amount of organic matter in the soils. However, in this studied oak forest, the decreased vitality and many killed trees were also suspected to be a result of high nitrogen deposition. Obviously increased tree growth was counteracted by decreased stress resistance, and increased appearance of pathogens in the oak trees.
文摘Plant biomass, primary production and mineral cycling in the beech forest (Fagus sylvatica L.), Hestehave in Jutland, Denmark were studied over a 50-year period. The role of the forest as a carbon sink was also assessed. Aboveground tree biomass was 226 t·ha-1 in 1970 and after a 50-year 539 t·ha-1 in 2014, an unexpected increase with 313 t·ha-1. Annual production at those two points in time was 13.4 and 20.5 t·ha-1, respectively. It was apparent that the tree biomass was still acting as a sink for carbon, which was the dominant element in the aboveground parts. The concentration of other elements (N > K > Mg > P > S > Na > Mn > Zn > Fe > Cu) ranged from 495 to 0.4 kg·ha-1. Annual litterfall restored 3.2 t·ha-1 to the soil as organic matter or 1.6 t·ha-1 as carbon. Over the year 53% of the litterfall was decomposed. A pH decrease of 0.95 units in the soil was observed between 1968 and 1993. This was attributed to fallout from a neighbouring thermal heating station affecting sulfur deposition and increasing soil acidification. After 1993, when filters were fitted in the heating station, the pH decrease in the soil was smaller, only 0.09 pH-units up to 2011. The increased tree growth is an additional, likely explanation for the observed soil acidification. Deposition of the growth-limiting element nitrogen increased during later years and is now, most likely around 20 kg·ha-1 per annum, which may partly contribute to the increased production.
文摘Plant biomass, primary production and mineral cycling were studied in a mixed deciduous forest (Quercus robur L., Tilia cordata L. and Corylus avellana L.) in southern Sweden. Plant biomass amount above and below ground was 201 and 37 t·ha-1, respectively. Primary production above and below ground was an estimated 13.3 and 2.3 t·ha-1, respectively. Carbon was the dominant element in the forest ecosystem, comprising 133 t·ha-1. Other major elements were: N > Ca > K > Si > Mg > S > Mn > P > Fe and Na (range 1123 to 18 kg·ha-1), followed by some trace elements. Yearly litterfall restored 6.0 t·ha-1 organic matter or 2.3 t·ha-1 carbon. Approximately 45% decomposed and returned to the soil during the year. Monitoring of other elements revealed that the ecosystem received inputs through dry and wet deposition, in particular 34.4 kg·ha-1 S and 9.4 kg·ha-1 of N yearly as throughfall. Determination of yearly biomass increase showed that the oak forest ecosystem was still in an aggradation or accumulation phase.
