Liming in Sweden

Air-borne pollutants have acidified 90,000 km of running water and at least 18,000 of Sweden's 90,000 lakes. In 1977 a national liming program to mitigate the effects of acidification in surface waters started with governmental support. Governmental subsidies usually amount to 85 % of the total liming cost but can in rare cases be extended to 100 % when waters of great national interest are threatened. The main liming agent is limestone of the size 0 to 0,2 mm. In lakes lime is spread by pontoon boats, helicopters and other vehicles. In running waters dosers and diversion wells are used. By 1985, the national liming program has been able to lime approximately 3,000 lakes and 100 streams.     

Effects of Liming and Fertilization (N,PK) on Chemistry and Nitrogen Turnover in Acidic Forest Soils in SW Sweden

SW Sweden has very acidic forest soils because of deposition ofair-borne pollutants. Large-scale liming and fertilization have been proposed as countermeasures against a possible future development of forest decline. To test the effects of suggested treatments, liming (3 or 6 t ha¹) and fertilization with easily soluble PK (25 or 50 kg P, 80 or 160 kg K ha¹) or N(20 kg N ha¹ annually in the form of NH₄ NO₃) were applied in different combinations in four experiments in 30–60 yr-old Picea abies forests in SW Sweden. Four yearsafter the initial application of the fertilizers, samples were taken from the O-horizon and the two uppermost 5 cm thick layersof the mineral soil. Their pH(H₂O) and easily extractable Ca, Mg, K, P and inorganic N contents were analyzed. Samples werealso incubated to estimate net N mineralization and potential nitrification rates. Liming increased the pH by 0.6–1 unit in the O-horizon, and by 0.1 unit in the mineral soil. The Ca + Mg content increased by 15–25 kmol_c ha¹ (4–8 foldincrease) in the O-horizon of the limed plots, while an increaseof 5 kmol_c ha¹ (two-fold increase) was observed in theuppermost 5 cm of the mineral soil. Liming did not affect extractable P, K or inorganic N contents. Net N mineralization and potential nitrification rates in the O-horizon were enhanced 1.5- and 6-fold, respectively, by liming, but it had no apparenteffect in the mineral soil. N fertilization caused a slight increase (1.5 kg ha¹) in the content of inorganic N, buthad no effects on the other variables measured. The amount ofextractable P was raised by 16 kg ha¹ in plots given the high P dose (50 kg ha¹), but no other effects of PK fertilization were detected.     

Changes in soil ph over a 50-year period under different forest canopies in SW Sweden

Reinvestigation of soil profiles, down to 70 cm depth in mineral soil, sampled for measurements in 1927 revealed a general decrease in pH for spruce and hardwood stands with 0.3 to 0.9 units. The pH-changes in the top soil can partly be explained by biological acidification, increasing with stand age. Stand age and species composition have less influence in deeper soil horizons and much of the acidification there is ascribed to acid deposition.     

Evasion of mercury vapor from the surface of a recently limed acid forest lake in Sweden

Mercury is emitted from soil and water surfaces, but few actual direct flux measurements have been reported. During June, 1994 we performed the first micrometeorological measurements of Hg vapor fluxes over a boreal forest lake. Using highly precise methods with multiple replicate samplers, we measured concentration gradients of Hg vapor, CO₂ and H₂O over the lake surface. Mercury was readily emitted from the lake surface, and we found no evidence of Hg dry deposition to the lake. Emission rates over the lake averaged 8.5 ng m² h^?1, and appeared to be weakly influenced by water temperature and solar radiation. These fluxes were somewhat higher than those previously measured using surface chambers at this site.     

Liming the acid lake Hovvatn,Norway: A whole-ecosystem study

Hovvatn, a 1-km² chronically-acidified lake in southernmost Norway, was treated with 200 tonne of powdered limestone in March 1981. An additional 40 tonne were added to a 0.046 km² pond (Pollen) draining into Hovvatn. The lakes were stocked with brown trout in June 1981 and in each subsequent year. At ice-out pH rose from 4.4 to 6.3 (Hovvatn) and 7.5 (Pollen), Ca and alkalinity increased, and total Al decreased by 120 μg L^?1. None of the other major ions exhibited significant changes in concentration. Total organic Cand Pincreased after liming. The phytoplankton community was dominated by chrysophytes and did not change significantly following liming. The zooplankton community was typical of acid lakes prior to liming. There was a clear succession in species dominance following treatment, although no new species immigrated to the lakes. Zoobenthos changed from a community characterized by low abundance and reduced number of species to increased abundances of oligochaetes, mayflies and chironomids. Hovvatn and Pollen were barren of fish prior to stocking. The stocked fish showed remarkably high growth rate during the first years. Liming apparently improved conditions for zoobenthos, enhancing the processing of fine detritus which in turn resulted in elevated levels of TOC and P in the lakewaters during the first year after liming. The “oligotrophication” process typical of acid lakes was temporarily reversed by liming. The interactions between groups of organisms in Hovvatn and Pollen indicates that many years are required before a new steady-state can be attained following liming.     

Liming and fertilization as mitigation tools in declining forest ecosystems

In central Europe the ‘new type’ forest damages have been observed since the mid 1970's. Various investigations indicate that the declines are frequently associated with nutritional disturbances. Good correlations between the site specific substrate chemistry and the actual nutritional status of the trees/stands were found. To explain the sudden and widespread appearance of the forest declines, adverse anthropogenic impacts mainly due to elevated emissions of air pollutants and their atmospheric derivatives are hypothesized in combination with natural stress factors. Causal mechanisms include soil degradation due to accelerated soil acidification and increased nutrient leaching from the canopy of forest stands. Fertilization and liming experiments have demonstrated that a fast and sustained revitalization and restabilization of declining forest ecosystems marked by nutritional disturbances can be achieved. This is demonstrated by chemical and histological foliar analyses generally combined with a visible improvement of the phenotype. Soil analyses reveal a considerable positive change of the chemical soil status due to the site and species specific application of appropriate amounts of fast soluble fertilizers and lime. Considering these recent favorable findings, as well as based on observations from historic fertilization and liming trials nutrient supplementation and liming have become common tools to counteract the new type forest damages in West Germany.     

Net ecosystem exchange, evapotranspiration and canopy conductance in a riparian forest

The ecosystem fluxes of mass and energy were quantified for a riparian cottonwood (Populus fremontii S. Watson) stand, and the daily and seasonal courses of evapotranspiration, CO₂ flux, and canopy conductance were described, using eddy covariance. The ecosystem-level evapotranspiration results are consistent with those of other riparian studies; high vapor pressure deficit and increased groundwater depth resulted in reduced canopy conductance, and the annual cumulative evapotranspiration of 1095 mm was more than double the magnitude of precipitation. In addition, the cottonwood forest was a strong sink of CO₂, absorbing 310 g C m⁻² from the atmosphere in the first 365 days of the study. On weekly to annual time scales, hydrology was strongly linked with the net atmosphere-ecosystem exchange of CO₂, with ecosystem productivity greatest when groundwater depth was ∼2 m below the ground surface. Increases in groundwater depth beyond the depth of 2 m corresponded with decreased CO₂ uptake and evapotranspiration. Saturated soils caused by flooding and shallow groundwater depths also resulted in reduced ecosystem fluxes of CO₂ and water.     

The River Bjerkreim in SW Norway - Successful Chemical and Biological Recovery after Liming

On a large scale, the acidified River Bjerkreim, southwestern Norway, has been treated with lime since the autumn 1996. During the Atlantic salmon (Salmon salar) smolting period pH has been above 6.2 and LAl concentrations below 10 µg L-l. Before 1996, only the western part of the watercourse harboured acid-sensitive species, such as the Atlantic salmon, snails, mayflies, daphnids and Gammarus lacustris. Prior to liming in 1996, Atlantic salmon fry (0+) and parr (≥1+) were found in 4 of 20 sampling sites, contrary to 17 (fry) and 12 (parr) in 1999. Atlantic salmon catches have increased from about 0.8 tons in 1994 to about 10 tons in 1998 and 1999. Acid-sensitive invertebrates have invaded the limed parts of the river.     

Components,drivers and temporal dynamics of ecosystem respiration in a Mediterranean pine forest

To investigate the climate impacts on the different components of ecosystem respiration, we combined soil efflux data from a tree-girdling experiment with eddy covariance CO₂ fluxes in a Mediterranean maritime pine (Pinus pinaster) forest in Central Italy. 73 trees were stem girdled to stop the flux of photosynthates from the canopy to the roots, and weekly soil respiration surveys were carried out for one year. Heterotrophic respiration (R_H) was estimated from the soil CO₂ flux measured in girdled plots, and rhizosphere respiration (R_Ab) was calculated as the difference between respiration from controls (R_S) and girdled plots (R_H).Results show that the R_S dynamics were clearly driven by R_H (average R_H/R_S ratio 0.74). R_H predictably responded to environmental variables, being predominantly controlled by soil water availability during the hot and dry growing season (May–October) and by soil temperature during the wetter and colder months (November–March). High R_S and R_H peaks were recorded after rain pulses greater than 10 mm on dry soil, indicating that large soil carbon emissions were driven by the rapid microbial oxidation of labile carbon compounds. We also observed a time-lag of one week between water pulses and R_Ab peaks, which might be due to the delay in the translocation of recently assimilated photosynthates from the canopy to the root system. At the ecosystem scale, total autotrophic respiration (R_At, i.e. the sum of carbon respired by the rhizosphere and aboveground biomass) amounted to 60% of ecosystem respiration. R_At was predominantly controlled by photosynthesis, and showed high temperature sensitivity (Q₁₀) only during the wet periods. Despite the fact that the study coincided with an anomalous dry year and results might therefore not represent a general pattern, these data highlight the complex climatic control of the respiratory processes responsible for ecosystem CO₂ emissions.     

Fine root decomposition,nutrient mobilization and fungal communities in a pine forest ecosystem

Despite its importance to energy flow and nutrient cycling the process of fine root decomposition has received comparatively little detailed research. Disruption of the fine root-soil interface during preparation of root litterbags for decomposition studies could affect decay rates and nutrient mobilization in part by altering the community of decay organisms. We compared rates of decomposition and nutrient release from fine roots of pine between litterbags and intact cores and characterized the fungal community in the decomposing roots. Fine root decomposition was about twice as fast overall for intact cores than litterbags, and rapid mobilization of N and P was observed for roots in cores whereas nutrients were immobilized in litterbags. Fungal communities characterized using 454 pyrosequencing were considerably different between decaying roots in intact cores and litterbags. Most interesting, taxa from ectomycorrhizal fungal orders such as Boletales, Thelephorales and Cantharellales appeared to be more common in decaying roots from cores than litterbags. Moreover, the rate of N and P mobilization from decaying fine roots was highly correlated with taxa from two orders of ectomycorrhizal fungi (Thelephorales, Cantharellales). Although we caution that DNA identified from the decaying roots cannot be conclusively ascribed to active fungi, the results provide tentative support for a significant role of ectomycorrhizal fungi in decomposition and nutrient mobilization from fine roots of pine.     

Carbon dioxide and energy fluxes from a boreal mixedwood forest ecosystem in Ontario, Canada

A long-term flux measurement station has been established in a 74-year-old mixedwood forest ecosystem, located approximately 80 km west of Timmins in northern Ontario, as part of the Fluxnet-Canada Research Network (FCRN). Measurements of energy, water vapour, and carbon dioxide fluxes have been made continuously since August 2003 using the eddy covariance technique, along with ancillary meteorological variables. The spatial structure of the site was evaluated using a variety of sources and techniques, including remote sensing, showing that this forest is mixed but relatively homogeneous. The canopy top height is remarkably constant at between 30 and 32 m. The basal area varies from 18 to 27 m² ha⁻¹, and the aboveground biomass ranges from 82 to 122 Mg ha⁻¹. In this paper, we summarize the diurnal and seasonal patters of carbon dioxide exchange and water loss from September 1, 2003 to August 31, 2004. Net ecosystem productivity (NEP) is strongly related to temperature. Atmospheric vapour pressure deficit (VPD) in this ecosystem exerted strong biophysical control on the daily gross ecosystem productivity (GEP) and evapotranspiration. Seasonal change in shortwave albedo, as a result of the presence of mixed deciduous and coniferous species, was clearly evident. Albedo changes were comparable to the seasonal pattern of NEP. The dormant season lasts more than 6 months of the year at this station. This forest was a moderate sink of carbon over the measurement period. Annual values of GEP, ecosystem respiration (R), and NEP were 1075, 919, and 156 ± 35 g C m⁻², respectively.     

Potential hazards of lime application in a damaged pine forest ecosystem in Berlin,Germany

Ninety percent of the pines (P. Sylvestris) in the forests of Berlin (West) are classified as damaged. Needle and leaf analyses do not indicate nutrient deficiencies. In site of high S-inputs (55 kg ha^?1 yr^?1 with throughfall) total acid inputs are moderate (2.4 kmol ha^?1 yr^?1) due to their neutralization by carbonatic dusts. Heavy metal depositions have led to accumulations in the forest floor (e.g. Pb 150 mg kg^?1, Cd 0.5 mg kg^?1). The dominating soil type, a cambic arenosol (Ustipsamment) is strongly acidified (pH 3.2 – 4.0) and poor in available nutrients. On an experimental plot, the application of dolomitic lime (6.1 tons ha^?1) and fertilizer (145 kg ha^?1 K₂SO₄) led to a significant increase m pH and base saturation in the top 10 cm of the mineral soil after 2 yr. The data on element fluxes give evidence for increased mineralization rates, enhanced heavy metal accumulation in the forest floor and increased soil solution concentrations of potentially hazardous substances (Al, Cd, NO₃). The lime application is discussed in terms of site specific effects on ecosystem stability and groundwater quality.     

Transport of metal cations through a nutrient-poor forest ecosystem

Metal cations were analyzed in bulk precipitation, soil water, and stream flow in a southeastern U.S. lower Coastal Plain pine flatwoods for 6 yr. Extractable ions in mineral soil and total amounts in herbaceous vegetation were also determined. Concentrations for all ions were higher in soil water than in bulk precipitation, but especially Na⁺ and Mg⁺⁺. There were smaller concentration differences between soil water and stream flow, except for three-fold higher Ca⁺⁺ in stream flow. Base saturation in the mineral soil was less than 10%, with Al dominating cation exchange sites. Of all cations, only K showed a significant relationship between exchangeable amounts in the soil and total amounts in herb layer vegetation. Soils in the watershed-ecosystem are experiencing minimal mineral weathering, although this can be spatially quite variable. We conclude that the chemistry of such soils is susceptible to change over several forest harvest rotations and continued acid deposition.

     

森林生态系统碳蓄积与碳循环

通过系统论述森林生态系统碳蓄积与碳循环的研究方法、森林生态系统碳蓄积与碳循环过程的时空特征以及森林与大气间碳交换的环境响应机制,发现：生物量法是研究碳蓄积的经典方法,而涡度相关法侧重于碳交换的过程与机制研究;森林生态系统在低纬度地区表现为碳源,而在中高纬度地区表现为碳汇,随着演替过程的进展,森林碳蓄积逐渐增大,直到顶级群落表现为相对碳平衡状态;辐射、温度和水分状况等环境因子通过对森林生态系统光合生产力（光合生产力）和生态系统呼吸的影响决定净生态系统碳收支的环境响应。同时指出我国森林生态系统碳蓄积和碳循环研究存在的问题和发展前景。     

Phosphorus loads from peaty polders in the SW Frisian lake District,The Netherlands

The purpose of this study was to quantify discharges and P-loads from peaty polders (total surface area 11560 ha) surrounding lakes in south-western Friesland , and to examine whether processes inside the polders contribute to the P-loads to the lakes. A detailed study in the Echtener Veenpolder (2850 ha), the largest polder in the study area, showed annuall gross P-loads of 1.3 to 1.83 kg P ha^?1 polder area and net P-loads of 0.63 to 1.48 kg P ha^?1 Processes inside this polder, such as leaching, surface runoff, resuspension, spreading manure and fertilizers, can result in high total P concentrations (TP) in discharged polder water (up to 0.9 mg L^?1) and therefore contribute to the P-load from the polder to lake Tjeukemeer. During 1984–1987 the averaged TP concentrations in polder water were higher than in lake Tjeukemeer water: 0.37 mg L^?1 and 0.28 mg L^?1, respectively. The annual gross P-loads from 11 other polders ranged from 1.01 to 4.13 kg P ha^?1 polder area, while TP concentrations reached values up to 3.0 mg L^?1. The P-loads from five polders to lake Tjeukemeer were high compared with the loads to the other lakes in the district. Particularly, during the winter period (October–April) P-loads were highest: up to 3.13 kg P ha^?1. This paper shows that hydrological measures and the reduction of the concentrations are important to combat the eutrophication problem in the lakes. However, for an optimally integrated water management of the polders, further research is needed to develop, for example, dynamical water and P balances in order to gain a better insight into the role of agriculture.     

Liming effects on some chemical and biological parameters of soil (spodosols and histosols) in a hardwood forest watershed

Acidic lakes and streams can be restored with base application (usually limestone) provided that the base does not wash out before the benefits of alkalization can be realized; liming soils of the adjoining watershed may be an alternative approach. This study was conducted to provide a scientific basis for soil liming. Plots (50 m²) with different limestone dosages (e.g. 0, 5, 10 or 15 Mg CaCO₃ ha^–1) were established on each of two different soils (a Spodosol and a Histosol) in the Woods Lake watershed of the Adirondack Park Region of New York, USA. Six months after soil liming much of the added limestone was still present in both the Spodosol and in the Histosol. Ten months after soil liming results indicated that: (1) soil pH increased (> 1 unit) but mostly in the top 1 cm; (2) net N mineralization increased from 9.6 to ca. 15 µg N g^–1 d ^–1 and nitrification increased from 2.8 to ca. 8 µg N g^–1 d^–1; (3) denitrification was not affected (98 µg N g^–1 d^–1);(4) CO₂ production potential decreased in the surface soil and as a function of limestone dosage (60 to 6 µmol g^–1 d^–1); and (5) soluble SO _inf4 ^sup2– concentrations in the Histosol were not affected (105 µmol L^–1). Liming acidic forest soils with > 5 Mg CaCO₃ ha^–1 may increase the soil's acid neutralizing capacity, which could provide long-term benefits for surface water acidification.     

The carbon cycle and global forest ecosystem

Attempts to account for the fluxes by quantifying C sources and sinks have provided evidence of a missing C sink (Detwiler and Hall, 1988), which may be located somewhere in the temperate region of the northern hemisphere (Tanset al., 1990). Until recently, most estimates have concluded that the temperate forest is a small C source. Two recent papers (Sedjo, 1992; Kauppiet al., 1992) provided evidence that the temperate forests are substantial C sinks. This paper combines these earlier findings on temeperate forest carbon sequestration with a new estimate of the annual C releases due to tropical deforestation, 1.7 Gt, which is obtained using the FAO estimates of the rate of deforestation in the tropics over the decade of the 1980s and conservative estimates of C releases associated with this deforestation. Finally, to this is added the crude estimate of C export by the global river system found in Hallet al. (1992). Applying these estimates of the C sink function of both temperate and tropical forests to Detwiler and Hall's alternative C budgets largely eliminates the “missing C” hypothesized by Detwiler and Hall, and Tanset al.     

Liming effects on some chemical and biological parameters of soil (spodosols and histosols) in a hardwood forest watershed

Acidic lakes and streams can be restored with base application (usually limestone) provided that the base does not wash out before the benefits of alkalization can be realized; liming soils of the adjoining watershed may be an alternative approach. This study was conducted to provide a scientific basis for soil liming. Plots (50 m²) with different limestone dosages (e.g. 0, 5, 10 or 15 Mg CaCO₃ ha^?1) were established on each of two different soils (a Spodosol and a Histosol) in the Woods Lake watershed of the Adirondack Park Region of New York, USA. Six months after soil liming much of the added limestone was still present in both the Spodosol and in the Histosol. Ten months after soil liming results indicated that: (1) soil pH increased (>1 unit) but mostly in the top 1 cm; (2) net N mineralization increased from 9.6 to ca. 15 µg N g^?1 d^?1 and nitrification increased from 2.8 to ca. 8 µg N g^?1 d^?1; (3) denitrification was not affected (98 µg N g^?1 d^?1); (4) CO₂ production potential decreased in the surface soil and as a function of limestone dosage (60 to 6 µmol g^?1 d^?1); and (5) soluble SO ₄ ^2? concentrations in the Histosol were not affected (105 µmol L^?1). Liming acidic forest soils with >5 Mg CaCO₃ ha^?1 may increase the soil's acid neutralizing capacity, which could provide long-term benefits for surface water acidification.     

Trace elements in the hydrologic cycle of a tolerant hardwood forest ecosystem

The concentrations and annual fluxes of Fe, Al, Mn, Cu and Pb were measured during 1983 in bulk precipitation, throughfall, stem-flow, forest floor percolate, mineral soil solution below the root zone and streamflow in a maple-birch stand on an acid podzolic soil at the Turkey Lakes Watershed (TLW), Ontario. Inputs of metals to TLW in precipitation were small in comparison with those in the eastern United States and Europe. Considerable loss of Mn and Cu from the vegetation during both the growing and the dormant (leafless) periods was observed and presumed to be due to leaching. The enrichment in soil solution of all metals examined, in relation to throughfall, was greatest for Al (7X) and least for Cu (1.2X). Aluminum was mobilized in both the forest floor and the mineral soil, the latter possibly in association with SO₄ ^2?. Copper was solubilized in the lower forest floor or the mineral soil. Surface soil contents of Al and Cu were reduced by Al and, to a lesser extent, Cu leaching beyond the effective rooting zone. Iron, Mn and Pb were mobilized largely in the F horizon of the forest floor, most likely by organic acids. Leaching of Fe, Mn and Pb was reduced by metal accumulation in vegetation, the lower forest floor, or mineral soil within the effective rooting zone of the vegetation. Most (80 to 99%) of the metals leached from the rooting zone were retained in the watershed and did, not appear in streamwater.     

大岗山森林生态系统服务功能及其价值评估

 通过构建适合大岗山森林生态系统服务功能的评估指标体系,依据大岗山森林生态站长期、连续观测数据及多年科研成果、2次二类森林资源调查资料及社会经济公共数据估算大岗山"九五"和"十五"期间森林生态系统服务功能的总价值。结果表明:"九五"期间大岗山森林生态系统服务功能总价值平均为1亿8495.00万元/a,单位面积价值为7.89万元/(hm2.a),"十五"期间为1亿9180.00万元/a,单位面积价值为8.09万元/(hm2.a),总价值增长3.70%,单位面积价值增长2.63%;在7项森林生态系统服务功能中,"九五"和"十五"期间大小顺序依次均为涵养水源>固碳制氧>保护生物多样性>净化大气环境>保育土壤>林木营养积累>森林游憩与生态文化,"九五"和"十五"期间各森林类型总价值大小顺序均为毛竹林>杉木>硬阔类>软阔类>针阔混交类>灌木>马尾松,单位面积价值大小顺序均为硬阔类>软阔类>毛竹林>灌木>马尾松>针阔混交类>杉木。