Annual production of Sphagnum on three perched and three raised forested bogs was determined and ... more Annual production of Sphagnum on three perched and three raised forested bogs was determined and compared. Perched bogs occupy small depressions in glacial moraines and raised bogs occur on broad, flat plains. Data from both cranked rods and threads were used with regression techniques to determine rates of growth on hummocks and hollows of bog microrelief. Hummocks and hollows were operationally defined by the characteristic moss species that dominated each position. Over a 3-year sampling period, average rate of moss growth in perched bogs was 3.9 (± 4%) on hummocks and 13.1 cm year−1 (± 13%) in hollows. In raised bogs, the growth was 3.6 (± 4%) and 9.1 cm year−1 (± 14%), respectively. About half the lineal growth occurred early in the growing season, and slightly more of the remaining growth occurred in midseason compared with late season. Conversion to ovendry mass per unit surface area of bog indicates production of 320 on hummocks and 520 in hollows on perched bogs; 300 on hum...
Relationships of quaking aspen (Populus tremuloides Michx.) site index and stand basal area to co... more Relationships of quaking aspen (Populus tremuloides Michx.) site index and stand basal area to conventional soil mapping units and soil mapping units regrouped into great group units in northern Minnesota were examined. Soil survey data from three counties mapped at different scales were used; Carlton County at 1:20,000, Itasca County at 1:24,000, and Crow Wing County at 1:31,680. The vegetation data were collected from 0.4 ha, 10-point cluster forest survey plots. Plots marked on aerial photographs were matched with soil mapping units. Site index for quaking aspen, and for a number of other species, was poorly related to soil mapping units. Stand basal area, however, was related both to mapping units within counties and to the overall great group units. The relationship between forest productivity and soil mapping units needs further evaluation; decisions are necessary regarding the indices appropriate for measurement, and whether the measurement should be of actual or potential productivity.
Mean stem weight and regression of weight on length were used to estimate available browse for sn... more Mean stem weight and regression of weight on length were used to estimate available browse for snowshoe hare (Lepus americanus), and mean stem weight was used to estimate browse use. An initial set of stem weight data, followed by periodic field surveys, supplied estimates of the browse resource by species and by size classes within species. Field time of 30-45 minutes per stand, sampling 30 0.6-m2 plots with a 2-person crew, yielded mean estimates with standard errors of about 15% of the mean. Of the common browse species, roses (Rosa spp.) were most used by hares (12% of that available), and beaked hazel (Corylus cornuta) was least used (3%). The latter, however, produced 30 times more available browse than the rose species. J. WILDL. MANAGE. 44(1):34-40 Determination of the amount of woody browse available to animals and its use can be imprecise, time-consuming, or both. Methods vary from trained estimation (Pechanec and Pickford 1937) to clip-and-weigh. Modifications use average twig weight distal to point of browsing (Shafer 1963) or relate twig weight to diameter at point of browsing (Telfer 1969) to determine availability and/or
Organic carbon (C> storage in complex landscapes and its temporal change can be important in the ... more Organic carbon (C> storage in complex landscapes and its temporal change can be important in the global C budget. Change in C storage between 1938 and 1977 was estimated for a 2224 ha old-field/forest landscape in east-central Minnesota by coupling change in area of seven vegetation types (five forest and two non-forest) with vegetation-specific C densities (mg ha-'). Carbon densities were based on sampling carried out between 1974 and 1990. Areas of vegetation types in 1938 and 1977 were determined from aerial photographs. Carbon density was greatest in forest overstory (60-100 Mg ha-'> and organic and mineral soil (30-100 Mg ha-' to 25 cm depth). Ecosystem C storage was approximately 212 000 Mg in 1938 and 225000 Mg in 1977, an increase of ca. 13000 Mg across the study area. This was due largely to an increase in upland forest at the expense of non-forest area. The largest proportional increase in C storage was in trees (a 13% gain), while mineral soil gained 4% and herbs gained 6%. C storage in 0 horizon and shrubs remained constant. For the 20% of the landscape originally occupied by cultivated fields, an empirical mode1 based on chronosequence studies indicated a 40% increase in C storage over 40 years; C increased in mineral soil, 0 horizon and trees as both herbaceous succession and forest encroachment occurred. Uncertainties of the estimates, based on propagation of standard errors, were 5% to 19% for C storage and 6% to 1000% for change in C storage. Uncertainty was due primarily to sample variability, but included uncertainty in biomass equations and GIS processing. This uncertainty demonstrates the difficulties associated with expanding from point sample data to landscape-scale estimates of C storage.
Forest productivity arises from photosynthetic activity leading to the accumulation of dry matter... more Forest productivity arises from photosynthetic activity leading to the accumulation of dry matter in plants, notably trees of economic size and utility. Photosynthetic processes are in turn dependent on the availability of light, water, nutrients, and temperature as provided by site conditions and including certain aboveground and belowground processes. Thus, when improving productivity, we are working with an ecosystem that
CONCENTRATIONS of mercury in the environment are increasing as a result of human activities, nota... more CONCENTRATIONS of mercury in the environment are increasing as a result of human activities, notably fossil-fuel burning and incineration of municipal wastes. Increasing levels of mercury in aquatic environments and consequently in fish populations are recognized as a public-health problem1,2. Enhanced mercury concentrations in lake sediments relative to pre-industrial values have also been attributed to anthropogenic pollution. It is generally
Organic carbon (C> storage in complex landscapes and its temporal change can be important in the ... more Organic carbon (C> storage in complex landscapes and its temporal change can be important in the global C budget. Change in C storage between 1938 and 1977 was estimated for a 2224 ha old-field/forest landscape in east-central Minnesota by coupling change in area of seven vegetation types (five forest and two non-forest) with vegetation-specific C densities (mg ha-'). Carbon densities were based on sampling carried out between 1974 and 1990. Areas of vegetation types in 1938 and 1977 were determined from aerial photographs. Carbon density was greatest in forest overstory (60-100 Mg ha-'> and organic and mineral soil (30-100 Mg ha-' to 25 cm depth). Ecosystem C storage was approximately 212 000 Mg in 1938 and 225000 Mg in 1977, an increase of ca. 13000 Mg across the study area. This was due largely to an increase in upland forest at the expense of non-forest area. The largest proportional increase in C storage was in trees (a 13% gain), while mineral soil gained 4% and herbs gained 6%. C storage in 0 horizon and shrubs remained constant. For the 20% of the landscape originally occupied by cultivated fields, an empirical mode1 based on chronosequence studies indicated a 40% increase in C storage over 40 years; C increased in mineral soil, 0 horizon and trees as both herbaceous succession and forest encroachment occurred. Uncertainties of the estimates, based on propagation of standard errors, were 5% to 19% for C storage and 6% to 1000% for change in C storage. Uncertainty was due primarily to sample variability, but included uncertainty in biomass equations and GIS processing. This uncertainty demonstrates the difficulties associated with expanding from point sample data to landscape-scale estimates of C storage.
The importance of microrelief in relation to mass loss was studied in a Minnesota ombrotrophic fo... more The importance of microrelief in relation to mass loss was studied in a Minnesota ombrotrophic forested peatland. Litter and paper strips placed in hummocks for 1 yr lost significantly more mass (two and three times, respectively) than similar material placed in hollows. Less favorable environmental conditions for decomposition, especially lower temperature, reduced decomposition in the hollows. Key words: Peatlands, ombrotrophic, decomposition, Histosols
The nitrogen (N) dynamics within short-rotation intensive-culture forest plantations are poorly u... more The nitrogen (N) dynamics within short-rotation intensive-culture forest plantations are poorly understood. We developed a N budget for a 3-year-old hybrid poplar plantation under short-rotation intensive-culture management in northwestern Minnesota. Measured pools and fluxes of N included plant content, atmospheric input, litter fall, microbial biomass, mineralization, nitrification, and denitrification. Total aboveground tree biomass represented only 1.6% of the total N capital. Stable soil organic N was the largest pool, 5670 kg N•ha−1, and constituted 93% of all N within the site. Labile soil organic N and microbial N represented 5.6 and 1.6% of stable soil organic N, respectively. Nitrogen mineralization averaged 56 kg N•ha−1•year−1, and 66% of that production was oxidized to NO3−. Losses of N by denitrification and leaching were small compared with the magnitude of the other fluxes. Results suggest that a relatively high rate of plant uptake and production maintained NH4+ and ...
Inputs, outputs, and pool sizes of total mercury (Hg) were measured in a forested 10 ha,watershed... more Inputs, outputs, and pool sizes of total mercury (Hg) were measured in a forested 10 ha,watershedconsisting of a 7 ha hardwood-dominatedupland surrounding a 3 ha conifer.... dominated peatland, Hydrologic inputs via throughfall and stemflow,134-0.4/zg m-2 yr-1 over the entire watershed, were about double precipitation inputs in the open and were significantly higher in the peatland than in the upland (19.6 vs. 9.8/zg m-2 yr-1). Inputs of Hg via litterfall were 12.34-0.7/zg m-2 yr-1 , not different in the peatland and upland (11.7 vs.
AbstractÐThe eect of all land management practices on carbon (C) balances are under scrutiny, inc... more AbstractÐThe eect of all land management practices on carbon (C) balances are under scrutiny, including the management of short-rotation woody biomass crops. Studies of invasion of old ®elds by forests, and limited information from short-rotation plantations, lead to a hypothesis that such plantations will increase soil C by 10±25 Mg ha À1 over a 10-to 15-year rotation. Soil C under other land uses, such as row crops or pasture, has usually been reduced from native, undisturbed levels. Highly productive woody crops will add substantial C to soil, both above-and below-ground. In addition, within 2±3 years after plantation establishment, mulching by leaf litter and lack of cultivation will slow decomposition and further help retain C. We collected data from ®ve hybrid poplar plantations in Minnesota, from 6 to 15 years old, and found no dierences in soil C compared to adjacent row crops or hayland. A simple analysis of C balance indicated an initial decline and then an increase in soil C, consistent with literature reports. The analysis also indicated that structural roots are very important in plantation soil-C balance. Before de®nitive statements can be made about the C balance of shortrotation plantations, selected plantations must be followed through one or more rotations using standard protocols to facilitate intercomparisons. #
Annual production of Sphagnum on three perched and three raised forested bogs was determined and ... more Annual production of Sphagnum on three perched and three raised forested bogs was determined and compared. Perched bogs occupy small depressions in glacial moraines and raised bogs occur on broad, flat plains. Data from both cranked rods and threads were used with regression techniques to determine rates of growth on hummocks and hollows of bog microrelief. Hummocks and hollows were operationally defined by the characteristic moss species that dominated each position. Over a 3-year sampling period, average rate of moss growth in perched bogs was 3.9 (± 4%) on hummocks and 13.1 cm year−1 (± 13%) in hollows. In raised bogs, the growth was 3.6 (± 4%) and 9.1 cm year−1 (± 14%), respectively. About half the lineal growth occurred early in the growing season, and slightly more of the remaining growth occurred in midseason compared with late season. Conversion to ovendry mass per unit surface area of bog indicates production of 320 on hummocks and 520 in hollows on perched bogs; 300 on hum...
Relationships of quaking aspen (Populus tremuloides Michx.) site index and stand basal area to co... more Relationships of quaking aspen (Populus tremuloides Michx.) site index and stand basal area to conventional soil mapping units and soil mapping units regrouped into great group units in northern Minnesota were examined. Soil survey data from three counties mapped at different scales were used; Carlton County at 1:20,000, Itasca County at 1:24,000, and Crow Wing County at 1:31,680. The vegetation data were collected from 0.4 ha, 10-point cluster forest survey plots. Plots marked on aerial photographs were matched with soil mapping units. Site index for quaking aspen, and for a number of other species, was poorly related to soil mapping units. Stand basal area, however, was related both to mapping units within counties and to the overall great group units. The relationship between forest productivity and soil mapping units needs further evaluation; decisions are necessary regarding the indices appropriate for measurement, and whether the measurement should be of actual or potential productivity.
Mean stem weight and regression of weight on length were used to estimate available browse for sn... more Mean stem weight and regression of weight on length were used to estimate available browse for snowshoe hare (Lepus americanus), and mean stem weight was used to estimate browse use. An initial set of stem weight data, followed by periodic field surveys, supplied estimates of the browse resource by species and by size classes within species. Field time of 30-45 minutes per stand, sampling 30 0.6-m2 plots with a 2-person crew, yielded mean estimates with standard errors of about 15% of the mean. Of the common browse species, roses (Rosa spp.) were most used by hares (12% of that available), and beaked hazel (Corylus cornuta) was least used (3%). The latter, however, produced 30 times more available browse than the rose species. J. WILDL. MANAGE. 44(1):34-40 Determination of the amount of woody browse available to animals and its use can be imprecise, time-consuming, or both. Methods vary from trained estimation (Pechanec and Pickford 1937) to clip-and-weigh. Modifications use average twig weight distal to point of browsing (Shafer 1963) or relate twig weight to diameter at point of browsing (Telfer 1969) to determine availability and/or
Organic carbon (C> storage in complex landscapes and its temporal change can be important in the ... more Organic carbon (C> storage in complex landscapes and its temporal change can be important in the global C budget. Change in C storage between 1938 and 1977 was estimated for a 2224 ha old-field/forest landscape in east-central Minnesota by coupling change in area of seven vegetation types (five forest and two non-forest) with vegetation-specific C densities (mg ha-'). Carbon densities were based on sampling carried out between 1974 and 1990. Areas of vegetation types in 1938 and 1977 were determined from aerial photographs. Carbon density was greatest in forest overstory (60-100 Mg ha-'> and organic and mineral soil (30-100 Mg ha-' to 25 cm depth). Ecosystem C storage was approximately 212 000 Mg in 1938 and 225000 Mg in 1977, an increase of ca. 13000 Mg across the study area. This was due largely to an increase in upland forest at the expense of non-forest area. The largest proportional increase in C storage was in trees (a 13% gain), while mineral soil gained 4% and herbs gained 6%. C storage in 0 horizon and shrubs remained constant. For the 20% of the landscape originally occupied by cultivated fields, an empirical mode1 based on chronosequence studies indicated a 40% increase in C storage over 40 years; C increased in mineral soil, 0 horizon and trees as both herbaceous succession and forest encroachment occurred. Uncertainties of the estimates, based on propagation of standard errors, were 5% to 19% for C storage and 6% to 1000% for change in C storage. Uncertainty was due primarily to sample variability, but included uncertainty in biomass equations and GIS processing. This uncertainty demonstrates the difficulties associated with expanding from point sample data to landscape-scale estimates of C storage.
Forest productivity arises from photosynthetic activity leading to the accumulation of dry matter... more Forest productivity arises from photosynthetic activity leading to the accumulation of dry matter in plants, notably trees of economic size and utility. Photosynthetic processes are in turn dependent on the availability of light, water, nutrients, and temperature as provided by site conditions and including certain aboveground and belowground processes. Thus, when improving productivity, we are working with an ecosystem that
CONCENTRATIONS of mercury in the environment are increasing as a result of human activities, nota... more CONCENTRATIONS of mercury in the environment are increasing as a result of human activities, notably fossil-fuel burning and incineration of municipal wastes. Increasing levels of mercury in aquatic environments and consequently in fish populations are recognized as a public-health problem1,2. Enhanced mercury concentrations in lake sediments relative to pre-industrial values have also been attributed to anthropogenic pollution. It is generally
Organic carbon (C> storage in complex landscapes and its temporal change can be important in the ... more Organic carbon (C> storage in complex landscapes and its temporal change can be important in the global C budget. Change in C storage between 1938 and 1977 was estimated for a 2224 ha old-field/forest landscape in east-central Minnesota by coupling change in area of seven vegetation types (five forest and two non-forest) with vegetation-specific C densities (mg ha-'). Carbon densities were based on sampling carried out between 1974 and 1990. Areas of vegetation types in 1938 and 1977 were determined from aerial photographs. Carbon density was greatest in forest overstory (60-100 Mg ha-'> and organic and mineral soil (30-100 Mg ha-' to 25 cm depth). Ecosystem C storage was approximately 212 000 Mg in 1938 and 225000 Mg in 1977, an increase of ca. 13000 Mg across the study area. This was due largely to an increase in upland forest at the expense of non-forest area. The largest proportional increase in C storage was in trees (a 13% gain), while mineral soil gained 4% and herbs gained 6%. C storage in 0 horizon and shrubs remained constant. For the 20% of the landscape originally occupied by cultivated fields, an empirical mode1 based on chronosequence studies indicated a 40% increase in C storage over 40 years; C increased in mineral soil, 0 horizon and trees as both herbaceous succession and forest encroachment occurred. Uncertainties of the estimates, based on propagation of standard errors, were 5% to 19% for C storage and 6% to 1000% for change in C storage. Uncertainty was due primarily to sample variability, but included uncertainty in biomass equations and GIS processing. This uncertainty demonstrates the difficulties associated with expanding from point sample data to landscape-scale estimates of C storage.
The importance of microrelief in relation to mass loss was studied in a Minnesota ombrotrophic fo... more The importance of microrelief in relation to mass loss was studied in a Minnesota ombrotrophic forested peatland. Litter and paper strips placed in hummocks for 1 yr lost significantly more mass (two and three times, respectively) than similar material placed in hollows. Less favorable environmental conditions for decomposition, especially lower temperature, reduced decomposition in the hollows. Key words: Peatlands, ombrotrophic, decomposition, Histosols
The nitrogen (N) dynamics within short-rotation intensive-culture forest plantations are poorly u... more The nitrogen (N) dynamics within short-rotation intensive-culture forest plantations are poorly understood. We developed a N budget for a 3-year-old hybrid poplar plantation under short-rotation intensive-culture management in northwestern Minnesota. Measured pools and fluxes of N included plant content, atmospheric input, litter fall, microbial biomass, mineralization, nitrification, and denitrification. Total aboveground tree biomass represented only 1.6% of the total N capital. Stable soil organic N was the largest pool, 5670 kg N•ha−1, and constituted 93% of all N within the site. Labile soil organic N and microbial N represented 5.6 and 1.6% of stable soil organic N, respectively. Nitrogen mineralization averaged 56 kg N•ha−1•year−1, and 66% of that production was oxidized to NO3−. Losses of N by denitrification and leaching were small compared with the magnitude of the other fluxes. Results suggest that a relatively high rate of plant uptake and production maintained NH4+ and ...
Inputs, outputs, and pool sizes of total mercury (Hg) were measured in a forested 10 ha,watershed... more Inputs, outputs, and pool sizes of total mercury (Hg) were measured in a forested 10 ha,watershedconsisting of a 7 ha hardwood-dominatedupland surrounding a 3 ha conifer.... dominated peatland, Hydrologic inputs via throughfall and stemflow,134-0.4/zg m-2 yr-1 over the entire watershed, were about double precipitation inputs in the open and were significantly higher in the peatland than in the upland (19.6 vs. 9.8/zg m-2 yr-1). Inputs of Hg via litterfall were 12.34-0.7/zg m-2 yr-1 , not different in the peatland and upland (11.7 vs.
AbstractÐThe eect of all land management practices on carbon (C) balances are under scrutiny, inc... more AbstractÐThe eect of all land management practices on carbon (C) balances are under scrutiny, including the management of short-rotation woody biomass crops. Studies of invasion of old ®elds by forests, and limited information from short-rotation plantations, lead to a hypothesis that such plantations will increase soil C by 10±25 Mg ha À1 over a 10-to 15-year rotation. Soil C under other land uses, such as row crops or pasture, has usually been reduced from native, undisturbed levels. Highly productive woody crops will add substantial C to soil, both above-and below-ground. In addition, within 2±3 years after plantation establishment, mulching by leaf litter and lack of cultivation will slow decomposition and further help retain C. We collected data from ®ve hybrid poplar plantations in Minnesota, from 6 to 15 years old, and found no dierences in soil C compared to adjacent row crops or hayland. A simple analysis of C balance indicated an initial decline and then an increase in soil C, consistent with literature reports. The analysis also indicated that structural roots are very important in plantation soil-C balance. Before de®nitive statements can be made about the C balance of shortrotation plantations, selected plantations must be followed through one or more rotations using standard protocols to facilitate intercomparisons. #
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