Organic Matter Loading Affects Lodgepole Pine Seedling Growth

Organic matter plays important roles in returning nutrients to the soil, maintaining forest productivity and creating habitats in forest ecosystems. Forest biomass is in increasing demand for energy production, and organic matter has been considered as a potential supply. Thus, an important management question is how much organic matter should be retained after forest harvesting to maintain forest productivity. To address this question, an experimental trial was established in 1996 to evaluate the responses of lodgepole pine seedling growth to organic matter loading treatments. Four organic matter loading treatments were randomly assigned to each of four homogeneous pine sites: removal of all organic matter on the forest floor, organic matter loading quantity similar to whole-tree-harvesting residuals left on site, organic matter loading quantity similar to stem-only-harvesting residuals, and organic matter loading quantity more similar to what would be found in disease- or insect-killed stands. Our 10-year data showed that height and diameter had 29 and 35 % increase, respectively, comparing the treatment with the most organic matter loading to the treatment with the least organic matter loading. The positive response of seedling growth to organic matter loading may be associated with nutrients and/or microclimate change caused by organic matter, and requires further study. The dynamic response of seedling growth to organic matter loading treatments highlights the importance of long-term studies. Implications of those results on organic matter management are discussed in the context of forest productivity sustainability.     

Influence of Woody Debris on Channel Structure in Old Growth and Managed Forest Streams in Central Sweden

Anecdotal information suggests that woody debris have had an important channel-forming role in Swedish streams and rivers, but there are few data to support this view. We identified 10 streams within near-natural and 10 streams within managed forest landscapes in central Sweden, and quantified their channel characteristics and content of woody debris. All pieces of woody debris greater than 0.5 m in length and greater than 0.05 m in base diameter were included. The near-natural forests were situated in reserves protected from forest cutting, whereas the managed forests had previously faced intensive logging in the area adjacent to the stream. The two sets of streams did not differ in general abiotic characteristics such as width, slope, or boulder cover, but the number of wood pieces was twice as high and the wood volume almost four times as high in the near-natural streams. This difference resulted in a higher frequency of debris dams in the near-natural streams. Although the total pool area did not differ between the two sets of streams, the wood-formed pools were larger and deeper, and potentially ecologically more important than other pools. In contrast to what has been believed so far, woody debris can be a channel-forming agent also in steeper streams with boulder beds. In a stepwise multiple regression analysis, pool area was positively and most strongly related to the quantity of woody debris, whereas channel gradient and wood volume were negatively related. The frequency of debris dams increased with the number of pieces of woody debris, but was not affected by other variables. The management implications of this study are that the wood quantity in streams in managed forests would need to be increased if management of streams will target more pristine conditions.     

ATMOSPHERIC CONTRIBUTIONS TO FOREST NUTRIENT CYCLING1

The atmosphere is a significant source of plant nutrients that partially replenishes losses due to timber harvesting. The relative importance of wet and dry deposition depends upon the specific nutrient and site. Nitrogen in bulk precipitation (wetfall and dryfall) is equivalent to at least 70 percent of the nitrogen incorporated annually in above-ground woody tissues of some temperate hardwood forests. Atmospheric sources of calcium and potassium supply between 20 and 40 percent of the nutrients sequestered in woody increments. Annual nutrient inputs in bulk precipitation can exceed removals associated with sawiog harvest over a rotation period. Atmospheric inputs of nitrogen are only slightly less than hydrologic losses immediately after timber harvesting. The deposition of nutrients is highly variable in both time and space; interpretations of nutrient inputs and forest management impacts require quantification of inputs for a variety of ecosystems over long periods of time.     

Influence of Catchment-Scale Military Land Use on Stream Physical and Organic Matter Variables in Small Southeastern Plains Catchments (USA)

We conducted a 3-year study designed to examine the relationship between disturbance from military land use and stream physical and organic matter variables within 12 small (<5.5 km2) Southeastern Plains catchments at the Fort Benning Military Installation, Georgia, USA. Primary land-use categories were based on percentages of bare ground and road cover and nonforested land (grasslands, sparse vegetation, shrublands, fields) in catchments and natural catchments features, including soils (% sandy soils) and catchment size (area). We quantified stream flashiness (determined by slope of recession limbs of storm hydrographs), streambed instability (measured by relative changes in bed height over time), organic matter storage [coarse wood debris (CWD) relative abundance, benthic particulate organic matter (BPOM)] and stream-water dissolved organic carbon concentration (DOC). Stream flashiness was positively correlated with average storm magnitude and percent of the catchment with sandy soil, whereas streambed instability was related to percent of the catchment containing nonforested (disturbed) land. The proportions of in-stream CWD and sediment BPOM, and stream-water DOC were negatively related to the percent of bare ground and road cover in catchments. Collectively, our results suggest that the amount of catchment disturbance causing denuded vegetation and exposed, mobile soil is (1) a key terrestrial influence on stream geomorphology and hydrology and (2) a greater determinant of in-stream organic matter conditions than is natural geomorphic or topographic variation (catchment size, soil type) in these systems.     

Greenhouse gas mitigation options in the Forest sector of Russia: National and project level assessments

Greenhouse gas (GHG) mitigation options in the Russian forest sector include: afforestation and reforestation of unforested/degraded land area; enhanced forest productivity; incorporation of nondestructive methods of wood harvesting in the forest industry; establishment of land protective forest stands; increase in stand age of final harvest in the European part of Russia; increased fire control; increased disease and pest control; and preservation of old growth forests in the Russian Far-East, which are presently threatened. Considering the implementation of all of the options presented, the GHG mitigation potential within the forest and agroforestry sectors of Russia is approximately 0.6–0.7 Pg C/yr or one half of the industrial carbon emissions of the United States. The difference between the GHG mitigation potential and the actual level of GHGs mitigated in the Russian forest sector will depend to a great degree on external financing that may be available. One possibility for external financing is through joint implementation (JI). However, under the JI process, each project will be evaluated by considering a number of criteria including also the difference between the carbon emissions or sequestration for the baseline (or reference) and the project case, the permanence of the project, and leakage. Consequently, a project level assessment must appreciate the near-term constraints that will face practitioners who attempt to realize the GHG mitigation potential in the forest and agroforestry sectors of their countries.     

Greenhouse gas mitigation options in the Forest sector of Russia: National and project level assessments

Greenhouse gas (GHG) mitigation options in the Russian forest sector include: afforestation and reforestation of unforested/degraded land area; enhanced forest productivity; incorporation of nondestructive methods of wood harvesting in the forest industry; establishment of land protective forest stands; increase in stand age of final harvest in the European part of Russia; increased fire control; increased disease and pest control; and preservation of old growth forests in the Russian Far-East, which are presently threatened. Considering the implementation of all of the options presented, the GHG mitigation potential within the forest and agroforestry sectors of Russia is approximately 0.6–0.7 Pg C/yr or one half of the industrial carbon emissions of the United States. The difference between the GHG mitigation potential and the actual level of GHGs mitigated in the Russian forest sector will depend to a great degree on external financing that may be available. One possibility for external financing is through joint implementation (JI). However, under the JI process, each project will be evaluated by considering a number of criteria including also the difference between the carbon emissions or sequestration for the baseline (or reference) and the project case, the permanence of the project, and leakage. Consequently, a project level assessment must appreciate the near-term constraints that will face practitioners who attempt to realize the GHG mitigation potential in the forest and agroforestry sectors of their countries.

     

Chemical and carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance characterization of logyard fines from British Columbia

Phasing out beehive burners and rising costs for landfilling have increased the need to widen options for utilization of the smaller size fractions of woody wastes generated during log handling and sawmilling in British Columbia. We characterized several size classes of logyard fines up to 16 mm sampled from coastal and interior operations. Total C, total N, ash, and condensed tannin concentrations were consistent with properties derived largely from wood, with varying proportions of bark and mixing with mineral soil. Especially for < 3-mm fractions, the latter resulted in high ash contents that would make them unsuitable for fuel. Solid-state 13C cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra were consistent with the chemical data, with high O-alkyl intensity and similarity to naturally occurring woody forest floor; no samples were high in aromatic or phenolic C. Aqueous extracts of two < 16-mm fines, which accounted for only a small proportion of the total C, were enriched in alkyl C and had low or undetectable tannins. Application to forest sites might cause short-term immobilization of N, but also might include possible longer-term benefits from reduction of N loss after harvesting and restoration of soil organic matter in degraded sites.     

Capturing Old-Growth Values for Use in Forest Decision-Making

Old-growth forests have declined significantly across the world. Decisions related to old growth are often mired in challenges of value diversity, conflict, data gaps, and resource pressures. This article describes old-growth values of citizens and groups in Nova Scotia, Canada, for integration in sustainable forest management (SFM) decision-making. The study is based on data from 76 research subjects who participated in nine field trips to forest stands. Research subjects were drawn from Aboriginal groups, environmental organizations, forestry professionals, and rural and urban publics. Diaries, group discussions, and rating sheets were used to elicit information during the field trips. Findings show that different elicitation techniques can influence the articulation of intensity with which some values are held. In addition, certain values are more often associated with old-growth than with other forest-age classes. Some values associated with old-growth are considered more important than others, and some silvicultural treatments are perceived to compromise old-growth values more than others. Demographic characteristics, such as constituency group, gender, and age, are shown to influence value priorities. Ideas on how to incorporate old-growth values into SFM decision-making are highlighted.     

Nitrogen mineralization and microbial activity in oil sands reclaimed boreal forest soils

Organic materials including a peat-mineral mix (PM), a forest floor-mineral mix (L/S), and a combination of the two (L/PM) were used to cap mineral soil materials at surface mine reclamation sites in the Athabasca oil sands region of northeastern Alberta, Canada. The objective of this study was to test whether LFH provided an advantage over peat by stimulating microbial activity and providing more available nitrogen for plant growth. Net nitrification, ammonification, and N mineralization rates were estimated from field incubations using buried bags. In situ gross nitrification and ammonification rates were determined using the 15N isotope pool dilution technique, and microbial biomass C (MBC) and N (MBN) were measured by the chloroform fumigation-extraction method. All reclaimed sites had lower MBC and MBN, and lower net ammonification and net mineralization rates than a natural forest site (NLFH) used as a control, but the reclamation treatment using LFH material by itself had higher gross and net nitrification rates. A positive correlation between in situ moisture content, dissolved organic N, MBC, and MBN was observed, which led us to conduct a moisture manipulation experiment in the laboratory. With the exception of the MBN for the L/S treatment, none of the reclamation treatments ever reached the levels of the natural site during this experiment. However, materials from reclamation treatments that incorporated LFH showed higher respiration rates, MBC, and MBN than the PM treatment, indicating that the addition of LFH as an organic amendment may stimulate microbial activity as compared to the use of peat alone.     

Large Woody Debris Input and Its Influence on Channel Structure in Agricultural Lands of Southeast Brazil

Riparian forests are important for the structure and functioning of stream ecosystems, providing structural components such as large woody debris (LWD). Changes in these forests will cause modifications in the LWD input to streams, affecting their structure. In order to assess the influence of riparian forests changes in LWD supply, 15 catchments (third and fourth order) with riparian forests at different conservation levels were selected for sampling. In each catchment we quantified the abundance, volume and diameter of LWD in stream channels; the number, area and volume of pools formed by LWD and basal area and tree diameter of riparian forest. We found that riparian forests were at a secondary successional stage with predominantly young trees (diameter at breast height <10 cm) in all studied streams. Results showed that basal area and diameter of riparian forest differed between the stream groups (forested and non-forested), but tree density did not differ between groups. Differences were also observed in LWD abundance, volume, frequency of LWD pools with subunits and area and volume of LWD pools. LWD diameter, LWD that form pools diameter and frequency of LWD pools without subunits did not differ between stream groups. Regression analyses showed that LWD abundance and volume, and frequency of LWD pools (with and without subunits) were positively related with the proportion of riparian forest. LWD diameter was not correlated to riparian tree diameter. The frequency of LWD pools was correlated to the abundance and volume of LWD, but characteristics of these pools (area and volume) were not correlated to the diameter of LWD that formed the pools. These results show that alterations in riparian forest cause modifications in the LWD abundance and volume in the stream channel, affecting mainly the structural complexity of these ecosystems (reduction in the number and structural characteristics of LWD pools). Our results also demonstrate that riparian forest conservation actions must consider not only its extension, but also successional stage to guarantee the quantity and quality of LWD necessary to enable the structuring of stream channels.     

Ion cycling in hemlock-northern hardwood forests of the southern Lake Superior region: a preliminary study

Upland forests of the southern Lake Superior region are diverse and contain a shifting mosaic of eastern hemlock [Tsuga canadensis (L.) Carr.] and northern hardwood forests dominated by sugar maple (Acer saccharum Marsh.). In this study, we survey the relative effects of management practice (old growth vs. managed), forest cover type (hemlock vs. northern hardwood), and soil great group (Entic Haplorthod vs. Alfic Oxyaquic Fragiorthod) on ion cycling as a precursor to a longer-term, more detailed study. Bulk precipitation, throughfall, and soil leachates at three depths were collected for two growing seasons in eight stands on the Ottawa National Forest in the Upper Peninsula of Michigan. A total of 1210 solutions were analyzed for pH, Na, K, Mg, Ca, Cl, NO3, and SO4. Losses of base cations (Ca, Mg, K) and SO4 from the bottom of the rooting zone generally were greater in old-growth than in managed northern hardwoods on both fragic and nonfragic soils. Leaching losses of base cations and NO3 usually were greater beneath old-growth northern hardwoods than beneath old-growth hemlock on both soil types and for both forest cover types and management practices on fragic than nonfragic soils. Management practice, forest cover type, and soil type all appear to affect ion cycling within these forests. All of the stands featured striking losses of base cations that probably are influenced strongly by NO3 and SO4 in atmospheric deposition.     

Timber harvest planning—A combined optimization/simulation model

A special cascading fixed charge structure can be used to characterize a forest management planning problem in which the objectives are to identify the optimal shape of forest harvest cutting units and simultaneously to assign facilities for logging those units. We describe a four-part methodology that has been developed to assist forest managers in analyzing areas proposed for harvesting. This methodology performs an analysis of harvesting feasibility, computes the optimal solution to the cascading fixed charge problem, undertakes a GASP IV simulation to provide additional information about the proposed harvesting operation, and permits the forest manager to perform a time-cost analysis that may lead to a more realistic, and thus improved, solution.     

Riparian Zone Management in the Pacific Northwest: Who's Cutting What?

Oncorhynchus sp.), regional governments now restrict timber harvest in riparian forests. I summarize and assess the riparian zone management guidelines of the states of California, Oregon, and Washington (USA) and the province of British Columbia (Canada). Only Oregon and British Columbia protect fish-bearing streams with “no-harvest” zones, and only the wider (20–50 m) no-harvest zones for larger fish-bearing streams in British Columbia are likely to maintain near-natural linkages between riparian and stream ecosystems. All four jurisdictions protect most streams with “management zones” of variable width, in which timber harvest activities are restricted. All the management zone guidelines permit the harvest of the largest conifers from riparian forests and will, if applied over a series of timber harvest rotations (60–80 years), result in the continued removal of potential sources of large woody debris from the region's watersheds. All four jurisdictions require additional protection for streams and watersheds that are severely degraded or (in the United States) contain threatened or endangered species. The governments of the PNW have taken a “manage until degraded, then protect” approach to riparian forest management that is unlikely to maintain or restore the full suite of riparian-stream linkages necessary for lotic ecosystems to function naturally at the stream, watershed, basin, or regional scale.     

Simulating secondary succession of elk forage values in a managed forest landscape,western Washington

Modern timber management practices often influence forage production for elk (Cervus elaphus) on broad temporal and spatial scales in forested landscapes. We incorporated site-specific information on postharvesting forest succession and forage characteristics in a simulation model to evaluate past and future influences of forest management practices on forage values for elk in a commercially managed Douglas fir (Pseudotsuga menziesii, PSME)-western hemlock (Tsuga heterophylla, TSHE) forest in western Washington. We evaluated future effects of: (1) clear-cut logging 0, 20, and 40% of harvestable stands every five years; (2) thinning 20-year-old Douglas fir forests; and (3) reducing the harvesting cycle from 60 to 45 years. Reconstruction of historical patterns of vegetation succession indicated that forage values peaked in the 1960s and declined from the 1970s to the present, but recent values still were higher than may have existed in the unmanaged landscape in 1945. Increased forest harvesting rates had little short-term influence on forage trends because harvestable stands were scarce. Simulations of forest thinning also produced negligible benefits because thinning did not improve forage productivity appreciably at the stand level. Simulations of reduced harvesting cycles shortened the duration of declining forage values from approximately 30 to 15 years. We concluded that simulation models are useful tools for examining landscape responses of forage production to forest management strategies, but the options examined provided little potential for improving elk forages in the immediate future.     

Soil organic carbon decomposition and carbon pools in temperate and sub-tropical forests in China

Decomposition of soil organic carbon (SOC) is a critical component of the global carbon cycle, and accurate estimates of SOC decomposition are important for forest carbon modeling and ultimately for decision making relative to carbon sequestration and mitigation of global climate change. We determined the major pools of SOC in four sites representing major forest types in China: temperate forests at Changbai Mountain (CBM) and Qilian Mountain (QLM), and sub-tropical forests at Yujiang (YJ) and Liping (LP) counties. A 90-day laboratory incubation was conducted to measure CO(2) evolution from forest soils from each site, and data from the incubation study were fitted to a three-pool first-order model that separated mineralizable soil organic carbon into active (C(a)), slow (C(s)) and resistant (C(r)) carbon pools. Results indicate that: (1) the rate of SOC decomposition in the sub-tropical zone was faster than that in the temperature zone, (2) The C(a) pool comprised approximately 1-3% of SOC with an average mean residence time (MRT) of 219 days. The C(s) pool comprised approximately 25-65% with an average MRT of 78 yr. The C(r) pool accounted for approximately 35-80% of SOC, (3) The YJ site in the sub-tropical zone had the greatest C(a) pool and the lowest MRT, while the QLM in the temperature zone had the greatest MRT for both the C(a) and C(s) pools. The results suggest a higher capacity for long-term C sequestration as SOC in temperature forests than in sub-tropical forests.     

Leaching of dissolved organic carbon and carbon dioxide emission after compost application to six nutrient-depleted forest soils

The objective of this study was to assess the effect of compost application on soil respiration and dissolved organic carbon (DOC) output of nutrient-depleted forest soils. An amount of 6.3 kg m(-2) mature compost was applied to the forest floor of European beech (Fagus sylvatica L.), Norway spruce (Picea abies Karst.), and Scots pine (Pinus sylvestris L.) stands at Soiling and Unterlüss, Germany. Cumulative soil respiration significantly increased by 499 g C m(-2) in the spruce stand at Unterlüss and by 274 g C m(-2) in the beech stand at Soiling following compost application whereas soil respiration of the other four stands was not affected. The increases in soil respiration of the two stands were explained by improved microbial decomposition of soil organic matter. The DOC concentrations and fluxes in throughfall and seepage water at 10- and 100-cm depths were determined from August 1997 to March 2000. In the control plots, cumulative DOC outputs at 10 cm ranged between 57 and 95 g C m(-2), with the highest rates in the pine stands. Compost treatment significantly increased cumulative DOC outputs by 31 to 69 g C m(-2) at 10 cm and by 0.3 to 6.6 g C m(-2) at 100 cm. The mineral soils between the 10- and 100-cm depths acted as significant sinks for DOC, as shown by much lower cumulative outputs at 100 cm of 3 to 11 g C m(-2) in the control and 6 to 16 g C m(-2) in the compost plots. Our results suggest that a single, moderate application of mature compost to nutrient-depleted forest soils has little effect on C losses to the atmosphere and ground water.     

Source identification and characterization of the accumulating non-biodegradable organics in Korean reservoirs

An increase in the chemical oxygen demand (COD) has been noticed in most Korean reservoirs. Therefore, this research systematically investigated the causes of organic accumulation. Samples of soil affecting the quality of water of reservoirs were collected at various sources and analyzed for their organic characteristics. The COD to biochemical oxygen demand (BOD) ratio was used as the key parameter in the evaluation of non-biodegradable (NBD) organic accumulation in the reservoirs. Soil samples containing plant roots were agitated, with the supernatant showing COD/BOD ratios of less than 2.8, while those of the composted tree leaves were greater than 5.0, suggesting that humic substances produced in forest areas are a major cause of NBD organic accumulation in reservoirs. In addition, the organic fractionation of the leachate from leaching tests showed that of the various types of hydrophobic natural organic matter (NOM), the larger molecular weight humic acid makes a greater contribution than fulvic acid to the increase in the NBD COD in Korean reservoirs.     

Ground‐Water Response to Forest Harvest: Implications for Hillslope Stability1

Abstract: Timber harvest may contribute to increased landsliding frequency through increased soil saturation or loss of soil strength as roots decay. This study assessed the effects of forest harvest on hillslope hydrology and linked hydrologic change before and after harvest with a simple model of hillslope stability. Observations of peak water table heights in 56 ground‐water monitoring wells showed that soil saturation levels on hillslopes differed significantly with harvest intensity at one of the two study locations following 25%, 75%, and 100% harvest. Before the forest was cut 100%, the average rainfall needed for 50% saturation of the soil was 54 mm, but after clearcutting soils reached an equivalent saturation with 61% less rainfall (21 mm). Hillslope stability model results indicate that shallow soils at both study locations, with slopes generally < 30° (58%), were not steep enough to be affected significantly by observed increases in saturation. The stability model indicates that with 100% harvest, there is a 7% reduction in the factor of safety for slope gradients of 35° (70%) with soil depths of 1.25 m. Forest managers may be aided by an understanding that variable hydrologic effects may result from similar forest harvests having different landscape position, land contributing area, and soil depths.     

PRECISION OF CHANNEL WIDTH AND POOL AREA MEASUREMENTS1

ABSTRACT: The precision of width and pool area measurements has rarely been considered in relation to downstream or at section hydraulic geometry, fisheries studies, long-term or along a continuum research studies, or agency monitoring techniques. We assessed this precision and related it to other stream morphologic characteristics. Confidence limits (95 percent) around mean estimates with four transects (cross-sections perpendicular to the channel center-line) ranged from ± 0.4 to 1.8 m on streams with a width of only 2.2 m. To avoid autocorrelation, transects should be spaced about three channel widths apart. To avoid stochastic inhomogeneity, reach length should be about 30 channel widths or ten transects to optimize sampling efficiency. Precision of width measurements decreased with decreased depth and increased with stream size. Both observations reflect variability caused by features such as boulders or coarse woody debris. Pool area precision increased with pool area reflecting increased precision for flat, wide streams with regular pool-rime sequences. The least precision occurred on small, steep streams with random, boulder or coarse woody debris formed pools.     

Chemistry and long-term decomposition of roots of Douglas-fir grown under elevated atmospheric carbon dioxide and warming conditions

Elevated atmospheric CO(2) concentrations and warming may affect the quality of litters of forest plants and their subsequent decomposition in ecosystems, thereby potentially affecting the global carbon cycle. However, few data on root tissues are available to test this feedback to the atmosphere. In this study, we used fine (diameter < or = 2 mm) and small (2-10 mm) roots of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings that were grown for 4 yr in a 2 x 2 factorial experiment: ambient or elevated (+ 180 ppm) atmospheric CO(2) concentrations, and ambient or elevated (+3.8 degrees C) atmospheric temperature. Exposure to elevated CO(2) significantly increased water-soluble extractives concentration (%WSE), but had little effect on the concentration of N, cellulose, and lignin of roots. Elevated temperature had no effect on substrate quality except for increasing %WSE and decreasing the %lignin content of fine roots. No significant interaction was found between CO(2) and temperature treatments on substrate quality, except for %WSE of the fine roots. Short-term (< or = 9 mo) root decomposition in the field indicated that the roots from the ambient CO(2) and ambient temperature treatment had the slowest rate. However, over a longer period of incubation (9-36 mo) the influence of initial substrate quality on root decomposition diminished. Instead, the location of the field incubation sites exhibited significant control on decomposition. Roots at the warmer, low elevation site decomposed significantly faster than the ones at the cooler, high elevation site. This study indicates that short-term decomposition and long-term responses are not similar. It also suggests that increasing atmospheric CO(2) had little effect on the carbon storage of Douglas-fir old-growth forests of the Pacific Northwest.