Clear-cutting reduces nitrate leaching in a pine plantation of high natural N status     

R. L. Parfitt  G. J. Salt  L. F. Hill 《Forest Ecology and Management》2002,170(1-3):43-53

Following the tree harvest, the biogeochemistry of a catchment is modified by changes in soil temperature and moisture, and nutrient cycling. We monitored soil-solution and stream-water chemistry, and soil properties in a Pinus radiata D. Don plantation in New Zealand before and after clear-cutting and replanting in 1997. The annual rainfall during the study was 1440–1860 mm. The soil was a 1800-year-old pumice soil of high natural N status; the catchment had received large inputs of volcanic N in rain, probably over the 1800 years since the pumice had been deposited. The leaching loss of nitrate-N was 28 kg ha⁻¹ yr⁻¹ in 1996, and then decreased sharply after clear-cutting to 3 kg ha⁻¹ yr⁻¹ in 1998 and <1 kg ha⁻¹ yr⁻¹ in 1999. Weed growth and soil microbial biomass increased during this time, and would have removed much of the N from soil solution in the upper soil layers. Although the catchment was small (8.7 ha), there was a 2-year lag until N decreased in stream-water; the losses of dissolved organic N to stream-water were low. There was no change in soil pH over the 4 years, but spring-water pH appeared to increase, which was consistent with the increase in bicarbonate that accompanied grass/weed growth. The export of cations (mmol_c l⁻¹) in the spring-water was Na>Ca>Mg=K as expected for rhyolitic pumice, and the total concentration was probably controlled by the accompanying anions. The export of anions was NO₃=Cl>SO₄=HCO₃ before harvest and HCO₃=Cl>SO₄=NO₃ after harvest.  相似文献   

Deposition of atmospheric constituents and its impact on nutrient budgets of oak forests (Quercus petraea and Quercus robur) in Lower Austria     

T.W. Berger  G. Glatzel 《Forest Ecology and Management》1994,70(1-3):183-193

Geochemical processes in central European oak ecosystems (Quercus petraea and Quercus robur) suffering stand decline were studied in two oak stands of the Weinviertel, Lower Austria, about 30 km north of Vienna. Stores of chemical elements were determined by soil and biomass inventories. Deposition input was monitored over a 2 year period by bulk sampling of throughfall. Soil solution chemistry was studied by tension lysimetry over a 1 year period. Mineral nutrition of oak was judged by foliar analysis. Bulk deposition rates were 10–12 kg N ha⁻¹ year⁻¹, and 15–20 kg S ha⁻¹ year⁻¹. Total annual nitrogen gain is high. Both systems lose calcium and magnesium. Foliar nutrient levels indicate sufficient nutrition with main mineral nutrients, except for magnesium, which is in moderately low supply. Based on these findings, the hypothesis that pollutant deposition has been the cause of a sudden and severe appearance of decline symptoms in the second half of the 1980s must be dismissed. The data on deposition rates and ecosystem nutrient status, however, indicate that the soil of both systems is acidifying, nitrogen stores are increasing, and magnesium pools are depleted. If deposition of pollutants continues at current rates, a slow but steady degradation of many oak ecosystems in the Austrian Weinviertel is inevitable.  相似文献   

Effect of clear-cutting and site preparation on the level and quality of groundwater in some headwater catchments in eastern Finland     

Hannu Mannerkoski  Leena Finr  Sirpa Piirainen  Michael Starr 《Forest Ecology and Management》2005,220(1-3):107-117

The impact of forest management (clear-cutting and site preparation) on stream hydrology has been studied in five small catchments in eastern Finland from 1991 and on groundwater levels and quality from 1994. The period 1992–1996 was a calibration period and in the autumn of 1996, 10% and 30% of the area of two of these catchments were clear-cut according to the forest management plan. Regeneration was carried out by disc-plowing in the autumn of 1998 and planting with Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings in the spring of 1999. The depth and quality of groundwater was monitored with four to nine groundwater wells installed in each catchment. There were 32 wells in all, 16 on upland mineral soils and 16 on peatlands (the perforated part of the pipe was totally put into the underlying mineral soil at eight sites). Sampling was made monthly during spring (March–May) and autumn (November–December) and bimonthly during summer (June–October). The samples were chemically analyzed for pH, electrical conductivity, and concentrations of total P and Fe (before filtration), and total N, NO₃⁻-N, NH₄⁺-N, total P, PO₄³⁻-P, SO₄²⁻-S, Ca²⁺, Mg²⁺, K⁺, Na⁺, Mn, Zn, Fe, Al³⁺, Cl⁻ (after filtration through 0.45 μm membrane filter). Data collected until the end of 2001 are reported. Groundwater was found in the down-slope wells in lower-lying areas, but not in those installed on the slopes with a thin (1–2 m) soil layer. Clear-cutting did not significantly affect groundwater levels in the wells. Nitrate N concentrations increased from 0.03 mg L⁻¹ level after clear-cutting and again after site preparation in the wells on upland soils and peatlands receiving water from the managed parts of the catchment. In one well at the lower edge of the managed area NO₃⁻-N concentrations reached 1–1.4 mg L⁻¹ in 2001 (fifth year after clear-cutting, third after disc-plowing), but mean concentrations remained <0.3 mg L⁻¹. Chloride concentrations also increased (50–100%) after treatments but the concentrations of other solutes showed no significant effect of treatment. It was concluded that changes in groundwater quality and quantity related to the clear-cutting were small and did not represent a danger to water quality or quantity.  相似文献   

Effects of nitrogen on the growth of jack pine competing with Canada blue-joint grass and large-leaved aster     

D. E. Robinson  R. G. Wagner  C. J. Swanton 《Forest Ecology and Management》2002,160(1-3):233-242

Biomass, leaf area, canopy photosynthesis, photosynthetic nitrogen-use efficiency (PNUE), nitrogen-partitioning ratio (NPR: ratio of nitrogen taken up by jack pine relative to two different competitor species), and nitrogen uptake (NU) of jack pine (Pinus banksiana Lamb.) competing with large-leaved aster (Aster macrophyllus L.) and Canada blue-joint grass (Calamagrostis canadensis (Michx.) Beauv.) were examined at three nitrogen levels in a controlled-environment growth chamber. When grown with large-leaved aster, jack pine biomass, photosynthesis and PNUE (p<0.001) increased as nitrogen level increased. Jack pine biomass, photosynthesis and NPR (p<0.001) decreased as nitrogen level increased when grown with Canada blue-joint grass. At the lowest nitrogen supply level, jack pine photosynthesis decreased as competitor PNUE increased (r²=0.84, p<0.001). Jack pine photosynthesis decreased as NU of large-leaved aster (37.5 mg N l⁻¹: r²=0.75, p<0.001; 100 mg N l⁻¹: r²=0.86, p<0.001) and Canada blue-joint grass (37.5 mg N l⁻¹: r²=0.96, p<0.001; 100 mg N l⁻¹: r²=0.84, p<0.001) increased. NU and PNUE may play an important role in the outcome of interactions between jack pine seedlings and competing forest vegetation in newly planted stands.  相似文献   

Nutrient accumulation and role of atmospheric deposition in coniferous stands   总被引：1，自引：0，他引：1  

Finn H. Braekke 《Forest Ecology and Management》1990,30(1-4):351-359

Three stand types on drained wetlands, all 31 years old, were studied. The stands were: (1) Scots pine, unfertilized; (2) Scots pine, fertilized; and (3) Norway spruce, fertilized. Amounts of nutrients (N, K, Ca, Mg, P, S, B, Fe, Mn, Zn, Cu) in above-ground biomass for all three stand types could be simulated precisely by a curvilinear regression model, with stand volume on bark as regressor. Net H⁺ production of the fertilized pine was estimated to be 661 mol H⁺ ha⁻¹ year⁻¹ from establishment to 31 years of age. The corresponding value for spruce was 1232 mol H⁺ ha⁻¹ year⁻¹. Atmospheric inputs to the pine and spruce sites were 695 and 516 mol H⁺ ha⁻¹ year⁻¹, respectively. Atmospheric input of N was 2.3 and 1.3 times the accumulation in the biomass of unfertilized and fertilized pine, whereas the value for spruce was 0.7. The corresponding ratios for S were 43, 19, and 11.  相似文献   

Water use in thinned loblolly pine plantations     

W.R. Stogsdili  Jr.  R.F. Wittwer  T.C. Hennessey  P.M. Dougherty 《Forest Ecology and Management》1992,50(3-4):233-245

Soil moisture and throughfall were monitored for two growing seasons under three thinning intensities: basal areas of 7.8 m²ha⁻¹, 12.6 m²ha⁻¹ and 26.6 m²ha⁻¹ (unthinned control) in an 11- to 12-year-old loblolly pine (Pinus taeda L.) plantation. The first year after thinning soil water decreased at a rate of 0.8 mm day⁻¹, 1.0 mm day⁻¹ and 1.4 mm day⁻¹, respectively, in the 7.8 m²ha⁻¹, 12.6 m²ha⁻¹, and 26.6 m²ha⁻¹ basal area plots between May and late August. The more rapid development of soil moisture deficits in the unthinned stand was owing to both greater soil moisture use and reduced throughfall. For the same time period in the second year, with below-normal rainfall, soil moisture deficits developed at a rate of 1.5, 1.5 and 1.7 mm day⁻¹ for the two heavily thinned and the unthinned treatments. Estimated growing season soil water use rates were 4.4 mm day⁻¹, 4.2 mm day⁻¹, and 4.0 mm day⁻¹, respectively for the 7.8 m²ha⁻¹, 12.6 m²ha⁻¹ and 26.6 m²ha⁻¹ basal area levels in Year 1. The second year after thinning water use rates for the same period were 2.7 mm day⁻¹, 2.6 mm day⁻¹, and 2.5 mm day⁻¹, respectively. The results of this study suggest that the capacity to manage available water in loblolly pine stands by thinning is more a function of reduced interception loss and increased throughfall than reduced water use and is also weather dependent. Growing seasons with low rainfall or only one or two large rainfall events will not permit much opportunity to manage soil moisture.  相似文献   

Biomass and carbon sequestration of ponderosa pine plantations and native cypress forests in northwest Patagonia   总被引：18，自引：0，他引：18  

Pablo Laclau   《Forest Ecology and Management》2003,180(1-3):317-333

Fast growth tree plantations and secondary forests are considered highly efficient carbon sinks. In northwest Patagonia, more than 2 million ha of rangelands are suitable for forestry, and tree plantation or native forest restoration could largely contribute to climate change mitigation. The commonest baseline is the heavily grazed gramineous steppe of Festuca pallescens (St. Yves) Parodi. To assess the carbon sequestration potential of ponderosa pine (Pinus ponderosa (Dougl.) Laws) plantations and native cypress (Austrocedrus chilensis (Don) Flor. et Boutl.), individual above and below ground biomass models were developed, and scaled to stand level in forests between 600 and 1500 annual rainfall. To calculate the carbon sequestration baseline, the pasture biomass was simulated. Also, soil carbon at two depths was assessed in paired pine-cypress-pasture sample plots, the same as the litter carbon content of both forest types. Individual stem, foliage, branch and root log linear equations adjusted for pine and cypress trees presented similar slopes (P>0.05), although some differed in the elevations. Biomass carbon was 52.3 Mg ha⁻¹ (S.D.=30.6) for pine stands and 73.2 Mg ha⁻¹ (S.D.=95.4) for cypress forests, given stand volumes of 148.1 and 168.4 m³ ha⁻¹, respectively. Soil carbon (litter included) was 86.3 Mg ha⁻¹ (S.D.=46.5) for pine stands and 116.5 Mg ha⁻¹ (S.D.=38.5) for cypress. Root/shoot ratio was 19.5 and 11.4%, respectively. The low r/s value for cypress may account for differences in nutrient cycling and water uptake potential. At stand level, differences in foliage, taproot and soil carbon compartments were highly significative (P<0.01) between both forest types. In pine stands, both biomass and soil carbon were highly explained by the rainfall gradient (r²=0.94). Nevertheless, such a relationship was not found for cypress, possibly due to stand and soil disturbances in sample plots. The carbon baseline estimated in pasture biomass, including litter, was 2.6 Mg ha⁻¹ (S.D.=0.8). Since no differences in soil carbon were found between pasture and both forest types, additionality should be accounted only by biomass. However, the replacement of pasture by pine plantations may decrease the soil carbon storage, at least during the first years. On the other hand, the soil may be a more relevant compartment of sequestered carbon in cypress forests, and if pine plantation replaces cypress forests, soil carbon losses could cause a negative balance.  相似文献   

The effects of limestone and of limestone plus NPK fertilization on the soil and mass balance of a spruce stand (Picea abies (L.) Karst.) in the Vosges mountains     

A.D Mohamed  J Ranger  E Dambrine  M Bonneau  D Gelhaye  A Granier   《Forest Ecology and Management》1993,60(3-4):291-310

Calcareous amendment and/or fertilization trials were carried out in a declining 66-year-old Norway spruce (Picea abies (L.) Karst.) stand in the Vosges mountains (northeast France, altitude 1100 m) in 1985. The aim was to test tree response to nutritional deficiencies (Ca + Mg) and to alleviate soil acidity. In 1988, experimental equipment was set up to collect atmospheric input (bulk precipitation, throughfall) and soil seepage water. The soils are podzolic (‘ocre-podzolique’), derived from an acid-poor granitic bedrock (‘granite du Valtin’). The soils are coarsely textured, hence very porous. They are very acid (pH 3.4 in the A₁ horizon, and pH 4.1 in the Bs horizon). The cation exchange capacity (CEC) is highly saturated in exchangeable acidity: 86% in the A₁ horizon. Ca²⁺ + Mg²⁺ saturation is very low (<10% in A¹ and <1% in the subsoil). Liming and fertilization significantly increase soil pH, base cation saturation and decrease soil acidity, especially in the surface horizons.

Bulk precipitation is dilute and acidic (pH 4.5); ion concentration of the precipitation greatly increases after passing through the tree canopy. Dry deposition is moderate and has values in the lower range reported for Europe.

Nitrification produced large amounts of NO₃⁻-N and H⁺ ions in the O layer and organo-mineral horizons. Nitrate and aluminium dominate the chemical composition of the soil see-page water.

Liming induces a considerable rise in the soil solution pH and the base cations (Ca²⁺ + Mg²⁺) and decreases nitrate and aluminium substantially. Liming alone seems to lower the rate of nitrification. Addition of fertilizers increases the deep drainage of base cations which could reduce the long term efficiency of liming.

Improvement of tree health-status accords with the positive effects of liming and/or fertilization on the soil's solid phase and solution.  相似文献   

Some nutrient dynamics associated with litterfall and litter decomposition in hoop pine plantations of southeast Queensland, Australia     

K. A. Bubb  Z. H. Xu  J. A. Simpson  P. G. Saffigna 《Forest Ecology and Management》1998,110(1-3):343-352

Litterfall was collected over a 12-month period with littertraps in hoop pine (Araucaria cunninghamii) plantations aged 10, 14 and 62 years in southeast Queensland, Australia. The bulk of litterfall occurred during spring, mainly as hoop pine foliage with the annual litterfall ranging between 6.0 and 10.9 t ha⁻¹, respectively, for the younger stands (10 and 14 years) and the mature 62-year old stand. The amount of nitrogen (N) and phosphorous (P) recycled annually through litterfall was lower in the younger stands (28–37 kg N ha⁻¹ and 4.4–5.3 kg P ha⁻¹) compared with that of the mature stand (85 N ha⁻¹ and 6.2 kg P ha⁻¹). The N and P retranslocated during senescence varied across the three stands studied with a trend for N and P retranslocation to increase as availability of soil mineral-N decreased.

Decomposition of the hoop pine foliage component of litter was also studied in the same stands using a litterbag technique and mass-balance analysis. The estimated half-life of hoop pine foliage mass ranged between 1.5 and 1.8 years. Litter-mass loss was strongly correlated with litter substrate quality indicators of N, C, P, C/N ratio, lignin, lignin/N ratio and polyphenols. During the course of the study, there was no difference in litter-mass loss between the stands of different ages. During the 15-month period, the order of element release from the hoop pine litter was K>Na>C>Mg>P, with N, Ca and Mn generally demonstrating varying degrees of net accumulation. During the course of the study, the lignin/C ratio of the hoop pine litter increased from 0.61 to 0.96. This suggested that the litter-C was predominantly in a recalcitrant form and, therefore, the associated N was unlikely to be rapidly released in the hoop pine litter layer.  相似文献   

Biomass distribution and productivity ofPinus edulis—Juniperus monosperma woodlands of north-central Arizona     

Charles C. Grier  Katherine J. Elliott  Deborah G. McCullough 《Forest Ecology and Management》1992,50(3-4):331-350

Above-ground biomass distribution, leaf area, above-ground net primary productivity and foliage characteristics were determined for 90- and 350-year-oldPinus edulis-Juniperus monosperma ecosystems on the Colorado Plateau of northern Arizona. These ecosystems have low biomass, leaf area and primary productivity compared with forests in wetter environments. Biomass of the 350-year-old pinyon-juniper stand examined in this study was 54.1 mg ha⁻¹; that of the 90-year-old stand was 23.7 mg ha⁻¹. Above-ground net primary production averaged 2.12 mg ha⁻¹ year⁻¹ for the young and 2.88 mg ha⁻¹ year⁻¹ for the mature stand; tree production was about 80% of these values for both stands. Projected ecosystem leaf area (LAI) of the stands was 1.72 m² m⁻² and 1.85 m² m⁻², respectively. Production efficiency (dry matter production per unit leaf area) was 0.129 kg m⁻² year⁻¹ for the young, and 0.160 kg m⁻² year⁻¹ for the mature stand. Production efficiency of the study sites was below the 0.188 kg m⁻² year⁻¹ reported for xeric, pure juniper stands in the northern Great Basin. Biomass of pinyon-juniper ecosystems of northern Arizona is generally below the 60–121 mg ha⁻¹ reported for pinyon-juniper stands of the western Great Basin in Nevada. A climatic gradient with summer precipitation decreasing between southeast Arizona and northwest Nevada occurs in the pinyon-juniper region. Great Basin pinyon-juniper ecosystems lie at the dry-summer end of this gradient while pinyon-juniper ecosystems of the Colorado Plateau lie at about the middle of this gradient. In spite of wetter summers, pinyon-juniper ecosystems of northern Arizona are less productive than those of the Great Basin.  相似文献   

Nitrogen mineralization in irrigated plantations of shisham and mulberry     

Z. Javid  R.F. Fisher   《Forest Ecology and Management》1991,40(3-4):209-219

Ammonification and nitrification rates and nitrogen uptake were measured using the buried-bag technique in irrigated mixed plantations of shisham (Dalbergia sissoo Roxb. ex DC.) and mulberry (Morus alba L.). Nitrogen transformations were rapid in these stands, particularly following thinning to reduce stand density. In young stands, net N mineralization was 26.72 mg N kg⁻¹ soil month⁻¹ (approximately 480 kg ha⁻¹ month⁻¹), but, as the end of the 22-year rotation approached, nitrification slowed to 13.41 mg N kg⁻¹ soil month⁻¹ (approximately 241 kg ha⁻¹ month⁻¹). N₂-fixing shisham appeared to respond after thinning only to the increased space and temporarily reduced competition for light and moisture, but mulberry appeared to benefit greatly from the nitrogen released through mineralization following thinning.  相似文献   

Influence of harvesting on biogeochemical exchange in sheetflow and soil processes in a eutrophic floodplain forest     

B. G. Lockaby  R. G. Clawson  K. Flynn  R. Rummer  S. Meadows  B. Stokes  J. Stanturf 《Forest Ecology and Management》1997,90(2-3):187-194

Floodplain forests contribute to the maintenance of water quality as a result of various biogeochemical transformations which occur within them. In particular, they can serve as sinks for nutrient run-off from adjacent uplands or as nutrient transformers as water moves downstream. However, little is known about the potential that land management activities may have for alteration of these biogeochemical functions. This paper examines the effects of three harvesting regimes (unharvested control, clearcut, and partial cut) on the physical and chemical parameters within the Flint River floodplain located in southwestern Georgia, USA. Data presented in this paper were collected during the year following initiation of the harvesting treatments which occurred in September of 1993. Sheetflow water chemistry (total suspended solids (TSS), total dissolved solids (TDS), nitrate (NO₃⁻), phosphate (PO₄³⁻), sulfate (SO₄²⁻), calcium (Ca²⁺), potassium (K⁺), magnesium (Mg²⁺), ammonium (NH₄⁺), total phosphorous (P), total nitrogen (N), total carbon (C), dissolved organic carbon (DOC)), sedimentation rates, depth of soil oxidation after flooding, saturated hydraulic conductivity, and bulk density were measured. During the year immediately after treatment installation, alterations in some of the physical and chemical properties (TDS, NO₃⁻, total P, and K⁺) of floodwaters crossing harvest plots were detected. Soil oxidation depths, saturated hydraulic conductivity and bulk density also changed with treatment. The meaning of the changes detected is uncertain but they suggest the nature of potential changes in nutrient spiralling and non-point source cumulative effects that may occur within a managed watershed. Second-year data may offer an interesting comparison of sheetflow chemistry and sedimentation changes between vegetated and non-vegetated conditions.  相似文献   

Nitrogen deposition in Casuarina equisetifolia (Forst.) plantation stands in the dry tropics of Sonbhadra, India     

Alok K. Srivastava  R.S. Ambasht   《Forest Ecology and Management》1994,70(1-3):341-348

Periodic variations in the concentration, deposition and canopy impact of different forms of N on annual N deposition through rainfall, throughfall and stemflow in 5 and 8 year old stands of Casuarina equisetifolia were studied. Throughfall and stemflow ranged from 70 to 76% and 5–6% of annual precipitation respectively. The total N deposition by rainfall was 11.1 kg ha⁻¹ year⁻¹, and by throughfall was 13.6 kg ha⁻¹ year⁻¹ and 16.5 kg ha⁻¹ year⁻¹ in 5-year-old and 8-year old plantations, respectively. The quantities of N deposited through stemflow in the two plantations were nearly identical, accounting for 1.6 kg ha⁻¹ year⁻¹. Observations of the monthly deposition of NH₄,N, NO₃-N, Kjeldahl-N and organic-N revealed that maximum deposition occurred in July and the minimum in September. Organic-N deposition was 17% less (5-year) than the rainwater content. Net deposition of N, as an effect of canopy, was 7–8.7 kg ha⁻¹ year⁻¹, which was added directly to the available nutrient pool of soil.  相似文献   

Nitrate dynamics after clear felling monitored by in vivo nitrate reductase activity (NRA) and natural N abundance of Deschampsia flexuosa (L.) Trin.     

Lars Hgbom  Urban Nilsson  Gran rlander 《Forest Ecology and Management》2002,160(1-3):273-280

The N dynamics following clear felling, focusing on NO₃⁻ turnover, were studied at four forested sites in southern Sweden. Two different methods were used to study N availability: (i) an in vivo nitrate reductase activity (NRA) bioassay and (ii) measurements of natural abundance of stable N isotopes in leaves of the grass species Deschampsia flexuosa, and in organic soil horizons. At each of the four sites, six plots were established and each year, for 5 consecutive years (1989–1993), one plot per site was felled. Thus, in 1993 there were five plots with different ages since clear felling and one control (closed forest) plot at each site. NRA was analyzed three times annually during the years 1989–1993. Samples for grass and soil analysis of δ¹⁵N, total N and soil pH were taken in 1993 only. NRA rapidly increased after the felling and remained high throughout the studied period. This suggests that there was an increased pool of plant-available soil NO₃⁻ more than 5 years after clear felling. Despite differences in site productivity and N deposition between the four sites, no significant differences in NRA were found between the sites. There were also rapid changes in δ¹⁵N in leaves of D. flexuosa, coinciding with the increases in NRA, during the first 3 years after felling. In contrast to NRA, shoot δ¹⁵N decreased 3–4 years after the felling at three out of four sites. Variations in the δ¹⁵N figures between sites may have been largely due to between-site differences in field-layer retention of N. At two of the sites, where NO₃⁻ leaching was also measured, a correlation was found between the NO₃⁻ concentration in the water and the difference in δ¹⁵N between D. flexuosa leaves from felled and closed forest plots. The data presented here suggest that NO₃⁻ leakage after clear felling is a rapid process, which is influenced by the development of field-layer biomass after the felling. Furthermore, losses of NO₃⁻ through leaching rapidly change the natural abundance of the plant available N pools in the soil.  相似文献   

Thinning, burning, and thin-burn fuel treatment effects on soil properties in a Sierra Nevada mixed-conifer forest   总被引：1，自引：0，他引：1  

Emily E.Y. Moghaddas  Scott L. Stephens 《Forest Ecology and Management》2007,250(3):156-166

More than a century of fire exclusion and past timber management practices in many Sierra Nevada mixed-conifer forests have led to increased stand densities and fuel accumulation, with a corresponding risk of large, high severity wildfires. To reduce hazardous fuel accumulations and restore the health and natural processes of forest ecosystems, fuel management programs often employ thinning and prescribed fire treatments, both alone and in combination. We evaluated forest floor and mineral soil chemical and physical characteristics following these treatments in a managed Sierra Nevada mixed-conifer forest using a fully replicated study design with four separate treatments: THIN, BURN, THIN + BURN, and an untreated CONTROL. Compared to the CONTROL, the BURN and THIN + BURN treatments consumed a large amount of the forest floor, reducing the mass and depth by more than 80%. These treatments reduced the forest floor C and N pools by more than 85%, resulting in reductions of 25 Mg C ha⁻¹ and more than 700 kg N ha⁻¹ from the forest floor. Despite these large losses from the organic horizons, no significant differences in mineral soil total C and N pools were detected among treatments. Compared with the CONTROL and THIN treatments, the BURN and THIN + BURN significantly increased the mineral soil NO₃-N concentration, pool of inorganic N, pH, and exposed bare soil. The THIN + BURN treatment significantly increased the concentrations of NH₄-N and exchangeable Ca relative to the CONTROL. No significant differences in the net rates of nitrification, N mineralization, or bulk density were detected among the four treatments. The BURN treatment reduced mineral soil C concentration and CEC, while the THIN + BURN treatment had the greatest increase in inorganic N. Fire effects on soil pH and inorganic N were moderated in skid trails due to reduced fuel continuity and consumption. In light of the current management emphasis on hazardous fuels reduction, we recommend that researchers investigating fire effects in harvested stands include skid trail influences in their study design.  相似文献   

Biogeochemical impacts of clearfelling and reforestation on blanket peatland streams I. phosphorus     

T. Cummins  Edward P. Farrell 《Forest Ecology and Management》2003,180(1-3):545-555

Forest drains and streams on blanket peatland in western Ireland were sampled weekly, 1996–2000, using continuous, depth-proportional passive sampling, and analysed for molybdate-reactive phosphorus (MRP) by the acid–antimony-molybdate method. The study area was largely clearfelled and partly reforested with wind-rowing, drainage, planting, and aerially applied rock phosphate equivalent to 70 kg P/ha. Further felled areas were not wind-rowed, drained or fertilised for reforestation. Catchment areas were of the following orders: 1 ha (two forest drains); 10–20 ha (two semi-permanent drains, one permanent stream); 1–3 km² (three permanent streams). Streamwater from three undisturbed closed-canopy-forest catchments had pre-felling median concentrations of MRP (all values are μg MRP l⁻¹) of 9 (catchment approximately 1 km²), 13 (1 ha) and 93 (1 ha). Clearfelling was associated with large increases (maxima 305, 4164 and 3530 μg MRP l⁻¹) in MRP concentrations in each case. Following protracted mechanical operations in four other catchments of ca. 1 km², 20, 10 and 10 ha, with apparently existing elevated MRP concentrations (medians 41, 328, 102, 214 μg MRP l⁻¹) fertilising gave major rises (maxima 218, 2723, 806, 2323 μg MRP l⁻¹). The three smaller catchments showed subsequent exponential-type declines, while the 1 km² catchment had sustained high values (median 74 μg MRP l⁻¹) over the remaining study period. The higher values in this one larger stream were seasonally cyclical, with a late summer maximum. Annual median MRP values above 70 μg l⁻¹ represent a seriously polluted state for these streams, which qualify as waterways under relevant statutes, but it is not clear what implications these results have for downstream river-water quality in larger channels.  相似文献   

Variation in the amount and quality of litterfall in a Pinus sylvestris L. stand growing on a bog     

Leena Finr 《Forest Ecology and Management》1996,80(1-3):1-11

The amount and nutrient content of the above-ground litterfall was followed for 9 years in an unfertilized, PKMgB and NPKMgB fertilized Scots pine stand growing on a drained ombrotrophic bog in eastern Finland. The annual litterfall on unfertilized plots was 1995 kg ha⁻¹, of which needles accounted for 74%. The effective temperature sum (threshold value + 5°C) explained 99% of the annual variation in the amount of needle litterfall when the data from one atypical year were excluded from the analysis. Nutrient concentrations were, except for Fe, higher in needle litter than in the other litterfall fractions. Nitrogen, P and K concentrations were low in autumn, and those of Ca and Mn high, possibly owing to variation in the mobility of elements during senescence. The annual litterfall input of N to the soil was 12.4 kg ha⁻¹, and the corresponding values for P and K were 0.08 kg ha⁻¹ and 1.81 kg ha⁻¹, respectively. Fertilization reduced needle litterfall in the first year after treatment, but had no effect thereafter. The amount of other litterfall fractions was not affected by fertilization in any of the 9 years of the study. Nitrogen, P, K and B concentrations increased in the needle litter after both fertilization treatments. The results indicate long-term cycling of fertilizer nutrients on the site.  相似文献   

Water/nutrient interactions affecting the productivity of stands of Pinus radiata     

R.E. McMurtrie  M.L. Benson  S. Linder  S.W. Running  T. Talsma  W.J.B. Crane  B.J. Myers 《Forest Ecology and Management》1990,30(1-4):415-423

The accumulation of above-ground biomass and the seasonal patterns of leaf-area development, foliar nutrient concentrations and tree and soil water-status have been measured for fertilised, irrigated, and control stands of Pinus radiata D. Don growing on a low-productivity site, average annual precipitation of 790 mm, near Canberra in southeastern Australia. In the second growing-season after treatments commenced, projected leaf-area index reached peak values of 7 on the irrigated/fertilised stands compared with approximately 5 on the other stands. Average canopy nitrogen concentration (dry-weight basis) varied across the treatments from 9 to 17 mg g⁻¹. Measurements of soil and tree water-status over a 2-year period indicated that stands which were not irrigated experienced summer droughts of up to 4 months duration.

Annual volume production measured over the 2-year period ranged from 17 to 45 m³ ha⁻¹. The extent to which this variation could be attributed to differences in leaf area, rats of photosynthesis, duration of the period of positive net photosynthesis, and hence growth, was analysed in terms of a process-based model of stand growth dependent on climate and soil water-balance.

Annual canopy net photosynthesis simulated by the model ranged from 18 t carbon ha⁻¹ for the control stand to 38 t ha⁻¹ for the irrigated/fertilised stands. Simulations indicated that 67% of this difference could be attributed to the role of irrigation in extending the period of active growth. The additional leaf area carried by the irrigated/fertilised stands contributed a further 23%, while differences in rates of photosynthesis, related to nitrogen nutrition, explained the remaining 10%.  相似文献   

山西太岳山典型森林群落土壤有机质及氮素研究   总被引：2，自引：0，他引：2  

朱建奎  韩海荣  伊力塔  刘利 《林业资源管理》2009,(2)

分析了太岳山7种典型森林群落土壤有机质和氮素的基本状况,结果表明:不同林型,土壤腐殖质层和淀积层有机质含量均是油松辽东栎混交林最高,分别为4.908g/kg和3.528g/kg;土壤腐殖质层有机质含量油松林最低,为3.959g/kg,淀积层有机质含量山杨林最低,为1.779g/kg;土壤腐殖质层全氮含量,白桦林最高,为0.368%,辽东栎林最低,为0.176%。;土壤腐殖质层速效氮含量华北落叶松林最高,为292.191mg/kg,油松林最低,为167.725mg/kg;土壤淀积层全氮含量油松林最高,为0.277%,油松辽东栎混交林最低,为0.094%;土壤淀积层速效氮含量山杨林最高为200.183mg/kg,油松辽东栎混交林最低,为49.151mg/kg;土壤有机质、全氮及速效氮含量均是上层土壤高于下层。腐殖质层和淀积层土壤有机质含量在各林型间差异均不显著(P>0.05),而全氮和速效氮含量在各林型间的差异均达到极显著水平(P<0.01)。  相似文献   

Dynamics and potentials of carbon sequestration in managed stands and wood products in Finland under changing climatic conditions   总被引：1，自引：0，他引：1  

Timo Karjalainen 《Forest Ecology and Management》1996,80(1-3):113-132

Carbon (C) sequestration was studied in managed boreal forest stands and in wood products under current and changing climate in Finland. The C flows were simulated with a gap-type forest model interfaced with a wood product model. Sites in the simulations represented medium fertile southern and northern Finland sites, and stands were pure Scots pine and Norway spruce stands or mixtures of silver and pubescent birch.

Changing climate increased C sequestration clearly in northern Finland, but in southern Finland sequestration even decreased. Temperature is currently the major factor limiting tree growth in northern Finland. In southern Finland, the total average C balance over the 150 year period increased slightly in Scots pine stands and wood products, from 0.78 Mg C ha⁻¹ per year to 0.84 Mg C ha⁻¹ per year, while in birch stands and wood products the increase was larger, from 0.64 Mg C ha⁻¹ per year to 0.92 Mg C ha⁻¹ per year. In Norway spruce stands and wood products, the total average balance decreased substantially, from 0.96 Mg C ha⁻¹ per year to 0.32 Mg C ha⁻¹ per year. In northern Finland, the total average C balance of the 150 year period increased under changing climate, regardless of tree species: in Scots pine stands and wood products from 1.10 Mg C ha⁻¹ per year to 1.42 Mg C ha⁻¹ per year, in Norway spruce stands and wood products from 0.69 Mg C ha⁻¹ per year to 0.99 Mg C ha⁻¹ per year, and in birch stands and wood products from 0.43 Mg C ha⁻¹ per year to 0.60 Mg C ha⁻¹ per year.

C sequestration in unmanaged stands was larger than in managed systems, regardless of climate. However, wood products should be included in C sequestration assessments since 12–55% of the total 45–214 Mg C ha⁻¹ after 150 years' simulation was in products, depending on tree species, climate and location. The largest C flow from managed system back into the atmosphere was from litter, 36–47% of the total flow, from vegetation 22–32%, from soil organic matter 25–30%. Emissions from the production process and burning of discarded products were 1–6% of the total flow, and emissions from landfills less than 1%.  相似文献