Weight Of Forest Floor Research Articles

Impacts of whole-tree harvesting and winter windrowing on soil pH and base status of clayey sites of northwestern Quebec

To assess the impact of forest operations on soil nutrient status, modifications to forest floor, to 0–10 and 10–20 cm mineral soil base status, and to pH were evaluated 5–12 years following whole-tree harvesting and winter windrowing on dry to fresh and moist clayey sites in the clay belt region of northwestern Quebec. Whole-tree harvesting had few impacts on base concentrations and soil pH of dry to fresh sites. On moist sites, significant decreases in pH (−0.60 to −0.84 units), exchangeable Ca, total Ca, and, exchangeable Mg concentrations, base saturation, and effective cation exchange capacity were observed following harvesting. On dry to fresh sites, a decrease in the forest floor weight (−55%) accounted for significant reductions in exchangeable Ca (−55%), total Ca (−61%), and exchangeable K (−40%) pools in this layer, while reserves of both mineral layers were not affected. On moist sites, significant decreases in exchangeable Ca (−42 to −65%) and Mg (−35 to −56%) reserves occurred in all soil layers, while forest floor reserves of total Ca, Mg, and K decreased by 67, 48, and 40%, respectively. These reductions were caused by a loss of substrate in the forest floor (−44%) and a decrease in effective cation exchange capacity, exchangeable Ca saturation, and total Ca concentrations. Impacts of windrowing following whole-tree harvesting were limited to a reduction in reserves of exchangeable Ca (−22%), exchangeable Mg (−27%), total Ca (−20%), and total Mg (−29%) pools of the forest floor of moist sites. Values reported here are much greater than values generally predicted by a balance sheet approach and underline the need for more process-oriented studies. Impacts of these losses on long-term site productivity remain to be investigated.

Effects of the amount and composition of the forest floor on emergence and early establishment of loblolly pine seedlings

Five forest floor weights (0, 10, 20, 30, and 40 Mg/ha), three forest floor compositions (pine, pine–hardwood, and hardwood), and two seed placements (forest floor and soil surface) were tested in a three-factorial, split-plot design with four incomplete, randomized blocks. The experiment was conducted in a nursery setting and used wooden frames to define 0.145-m2 subplots. Forest floor composition had no significant effect on emergence or establishment of loblolly pine (Pinustaeda L.) seedlings. Numbers of emerging and established seedlings displayed a negative exponential relationship with forest floor weight (fit indices of 0.62 and 0.62, respectively). Seed placement significantly affected the number of emerging seedlings (forest floor > soil surface) and their survival (forest floor < soil surface). However, seed placement had no overall significant effect on the number of established seedlings because effects on emergence and survival essentially canceled out. Germination of herbaceous seeds in the soil bank also displayed a negative exponential trend with forest floor weight (fit indices of 0.46 and 0.50 for the weight of grasses and forbs, respectively) and was not significantly affected by forest floor composition. Results indicate that forest floor composition is not a factor in the natural regeneration of the pine component of mixed pine–hardwood stands and suggest that when pine seed production is adequate, moderate amounts of forest floor material will improve pine seedling development because of suppression of herbaceous vegetation.

Effects of earthworm invasion on morphology, carbon, and nitrogen of a forest soil

Soil samples were collected over 14 years from a sandy loam forest soil in northern Minnesota. During the study earthworm numbers increased from zero to 592 m −2, the forest floor weight and thickness decreased by about 85%, and the E horizon was completely replaced by an A horizon. Development of the A horizon resulted in a increase of carbon and nitrogen concentrations but no changes in soil pH or C/N ratios in the surface mineral soil. Total soil carbon to a depth of 50 cm decreased at a rate of 0.6 Mg ha −1 year −1 during the study. Soil humus forms were mor at the beginning of the study and mull by the end. Site productivity, as inferred from herb weight or litterfall, was not affected by the increase in earthworm numbers.

Soil mineral nitrogen changes following prescribed burning in ponderosa pine

In a ponderosa pine (Pinus ponderosa Laws.) forest near Flagstaff, AZ, USA, there was a striking pattern in forest characteristics, consisting of substands of old-growth trees (28–120 cm diameter at breast height (dbh) and 200–500 years old) and of saplings (1.5–10 cm dbh and 60–70 years old) in a matrix of pole-sized trees (10–28 cm dbh and 60–100 years old). Tree size and forest floor mass decreased from old-growth to pole to sapling substands, but soluble N (as KCl extractable inorganic N) in the mineral soil did not vary substantially among substands before prescribed burning.Prescribed burning had little immediate impact on the overstory but substantially decreased the forest floor mass, with the greatest absolute and relative decreases being in the old-growth substands. Immediately after burning, ammonium-nitrogen (NH4-N) increased from 2.3 to 45.1 mg kg−1 in the old-growth substands, from 1.3 to 26.7 mg kg−1 in the pole substands, and from 1.3 to 8.3 mg kg−1 in the sapling substands. These differences in NH4-N among the substand types are directly correlated with differences in the initial forest floor weight and the amount of forest floor burned. Nitrate-nitrogen (NO3-N) was not changed immediately after burning.By 1 year after burning, NH4-N had declined substantially with only the old-growth substands being significantly higher than controls (30.0 versus 2.56 mg kg−1). Much of this decline showed up as an increase in NO3-N, particularly for the old-growth substands where NO3-N was 18.6 mg kg−1 on burned plots compared with 0.03 mg kg−1 on controls.These results support the conclusion that while increases in NH4-N are an immediate effect of burning (most likely from NH4-N produced by pyrolysis of forest floor material), nitrate increases, which occur later, are most likely caused by nitrification of the high NH4-N produced immediately after burning.A preliminary budgetary analysis for the mineral soil showed an immediate increase in inorganic N of 34.3 kg ha−1 in old-growth substands, 14.7 kg ha−1 in pole substands, and 4.0 kg ha−1 in sapling substands. Because these increases appear to have been transferred directly to the mineral soil from the forest floor, previous studies which have not accounted for this phenomenon may have somewhat overestimated N volatization losses from burning.

Effects of bigleaf maple on soils in Douglas-fir forests

Soil chemical and physical properties, forest floor weights, nutrient content and turnover rates, and litter fall weights and nutrient content under bigleaf maple (Acermacrophyllum Pursh) and Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii) were compared on five sites on the eastern margin of the Oregon Coast Range. Litter fall weight and nutrient content were significantly greater under maple on every site for every macronutrient and for most micronutrients. Forest floor biomass and nutrient content were extremely variable, much more so than litter fall, and there were no consistent differences between the two species. However, turnover rates for forest floor biomass and nutrients were significantly faster under maple for every nutrient at every site. Bulk density of mineral soil was also highly variable with significant differences at only two sites. Soil under maple was consistently higher in nitrogen, and less consistently, in potassium. There were no consistent trends in amounts of calcium, magnesium, or phosphorus. Soil organic carbon content under maple was significantly greater than under Douglas-fir on four of five sites. These differences may result from the more rapid turnover of forest floors under maple trees.

Nitrogen and Carbon accretion on Ohio coal minesoils: Influence of soil-forming factors

Plantations of white pine ( Pinus strobus L.), tuliptree ( Liriodendron tulipifera L.), white ash ( Fraxinus americana L.) and black locust ( Robinia pseudoacacia L.), established in 1946 on ungraded calcareous, neutral or acid coal spoils, were sampled in 1976 for weight, carbon and nitrogen content of the forest floor, and for total N concentration in 4 depth increments of the underlying mineral soil. Minesoil characteristics were related to the following soil-forming factors: parent material (overburden), organisms (tree species) and relief (aspect and slope position). Forest floor weight was high under white pine on all parent materials and under black locust on acid parent material. Nitrogen content of the forest floor was highest on acid minesoil, as was total weight of N in the forest floor under all species except tuliptree. Although concentration of N in the forest floor was highest under black locust, total weight of forest floor N under pine exceeded that under locust on calcareous and neutral minesoils because of the much greater weight of forest floor under pine. C/N ration of forest floor was lowest under locust and on the acid minesoil. Total N concentration was highest at all depths in soils that formed under black locust: rate of decrease in total N concentration between the 0–5 and 5–15 cm depth increments was also greatest under black locust. Soils formed on calcareous parent material had higher total N concentrations at all depths than those formed on neutral or acid parent materials. We estimate that concentration of total N in the 0–5 cm horizon of calcareous minesoils has increased from 0.04 to 0.23% in the 30 years since tree establishment. The corresponding increase in the acid minesoils has been from 0.03 to 0.18%. Our results show that accretion of carbon and nitrogen on minesoils will be influenced both by overburden strata placed at the surface as parent material of the new soil and by tree species chosen for planting.

Nitrogen dynamics in conifer-dominated forests with and without hardwoods

Nitrogen and carbon in the surface 12 cm of mineral soil, N in leaf litterfall, anaerobic N mineralization rates in the soil and forest floor, and root and N accretion to sand traps placed in surface soil layers were compared in forests with hardwoods either completely or partially removed during a conifer thinning 3 years before. An adjacent unthinned conifer–hardwood stand was also included. Conifer stocking did not differ between thinned stands with and without hardwoods. Stands without hardwoods averaged 520 kg/ha more N in mineral soil (p < 0.001), 20% more N mineralized from soil during 7-day incubations (p < 0.001), and lower soil C:N ratio (p = 0.02) than stands with hardwoods. These variables did not differ between thinned and unthinned mixed stands. Soil N did not correlate with the number of hardwoods removed. Weight of forest floor and rate of N mineralization from the forest floor did not differ between mixed and pure stands. However, stands with hardwoods returned about 10 kg•ha−1•year−1 more N in leaf litter (due to higher N concentration in conifer litter as well as the presence of high-N hardwood litter); stands without hardwoods accreted about 10 kg•ha−1•year−1 more N in sand traps. Soil N mineralization in mixed stands correlated positively with N mineralization in the forest floor but not with N accretion to sand traps, while the opposite was true in pure conifer stands. Although pretreatment variability among stands cannot be ruled out, the replicated treatments within a relatively uniform area make it appear likely that differences were related to the presence or absence of hardwoods. This was not a simple additive effect, however, but a community-level phenomenon, that is, conifers cycled N differently when mixed with hardwoods than when in pure stands.

Selected Parameters of Fire Behavior and Pinus banksiana Lamb. Regeneration in Eastern Ontario

Fire behavior variables were quantified in eastern Ontario jack pine (Pinus banksiana Lamb.) ecosystems and used to interpret observed fire impacts and effects. A series of seven fires, ranging in frontal fire intensity from 70 to 17 000 W/m, were documented. Forest floor moisture content prior to burning was negatively correlated with weight of forest floor consumed per unit area (r2 = 0.97) and per cent mineral soil bared (r2 = 0.95). Frontal fire intensity was positively correlated with per cent tree mortality (r2 = 0.98) and mean height of char (r2 = 0.76). Frontal fire intensities of 17 000 kW/m resulted in seedling numbers of 30 000 to over 50 000 ha−1 considered to be more than adequate for establishing the next generation of crop trees. Jack pine mean seedling height, 13 to 16 years after fire, was also positively correlated with frontal fire intensity (r2 = 0.82), ranging from 0.5 to 3.8 m on lowest and highest intensity burns, respectively. Similar relationships were found when seedling height was regressed against per cent tree mortality (r2 = 0.62) and forest floor consumption (r2 = 0.79).Results are discussed in terms of ecological requirements of the species, particularly during the regeneration phase, and it is concluded that quantification of fire behavior observations is mandatory if burning conditions are to be understood and/or duplicated by the land manager for the attainment of a given forest management objective.

Nutrient dynamics in the litter fall and forest floor of an 18-year-old loblolly pine plantation

Dry weight and N, P, K, Ca, and Mg concentrations were monitored in the litter fall and forest floor of a loblolly pine (Pinustaeda) plantation in north Louisiana for 2 years. Dry weights of both litter fall and forest floor were statistically stable during the sampling period, possibly indicating steady-state conditions. A comparison of litter fall with forest floor weights indicated rapid decomposition (floor turnover = 1.5 years) relative to that of other loblolly pine systems.

Forest floor dynamics in a chronosequence of hardwood stands in central Nova Scotia

A postclear-cutting chronosequence of hardwood stands in Nova Scotia was examined for patterns of forest floor weight, concentration of selected nutrients, rate of potential insitu litter decomposition (litterbags), and potential lab ammonification and nitrification. Some evidence was found that the forest floor experiences weight loss following clear-cutting. However, the large weight losses and clear pattern of recovery described by others for New Hampshire hardwood chronosequences were not observed. The lack of close agreement may have been a result of intra- and inter-stand variation in forest floor weight in our study. This spatial variation was greater than any effect as a result of clear-cutting. There was no significant relationship between insitu weight loss of leaves or twigs with stand age. No clear-cutting effect was observed in the laboratory for potential ammonification, which occurred readily in all stands (three clear-cuttings, three mature stands). Limed materials produced significantly more mineralized N (nitrate N + ammonium N) than did unlimed materials. Concentrations of ammonium N in F and H horizon field material were significantly higher on clear-cuttings than in mature stands. However, since this measurement reflects net rather than total production, it is not evidence that higher rates of ammonification occurred on clear-cuttings. Potential nitrification was not an important process in F and H horizon materials at their natural pH. Nitrification occurred readily in limed materials, but there were no significant differences among different aged stands. Concentrations of nitrate N in field F and H horizon material were low for all stands, with a mean of 9 ± 7 ppm (n = 350). However, in 7% of field samples, nitrate N ≥ 15 ppm was found; in 2%, ≥30 ppm was found.

Soil Nutrient Changes Following Whole Tree Harvesting on Three Northern Hardwood Sites

AbstractThree northern hardwood stands were clearcut to evaluate the effect of whole tree harvesting on sites of varying quality. Stands were growing on sandy, outwash soils and had red maple (Acer rubrum L.) site indices of 15, 19, and 20 and biomass values of 114, 165, and 181 Mg ha−1. Harvesting did not alter extractable soil P levels significantly on any site. Forest floor weights decreased to similar values on all sites 1.5 yr after harvest. Nitrogen losses of over 1.3 Mg ha−1 occurred in the top meter of soil on all sites. This was attributed to the mixing of the forest floor with the surface mineral soil by the full tree skidding and the subsequent leaching of mineralized N. Soil exchangeable K decreased more than 1 Mg ha−1 on all sites. Changes in Ca and Mg were much smaller on the low and medium than on the high site. These losses from surface soil horizons are higher than reported previously for clearcutting northern hardwoods on till soils. The greatest impact of whole tree harvest on soil nutrients occurred on the better sites in this study rather than on the poor quality site.

Changes in lead, zinc, copper, dry weight, and organic matter content of the forest floor of white pine stands in central Massachusetts over 16 years

Lead, zinc, copper, dry weight, and organic matter content of the L, F, and H layers of the forest floor were measured in 10 white pine stands in central Massachusetts in 1962 and again in 1978, thus providing quantitative estimates of these parameters at two points in time 16 years apart. Forest floor material retained from a 1962 quantitative study of forest floor weight was compared with samples from the same plots in the same stands collected in 1978. Total lead content increased significantly. Average lead concentration increased in all layers, but the increases were not statistically significant primarily due to the dilution effect of the concurrent increase in the mass of the forest floor. The observed net increase in lead of 30 mg m/sup -2/ year/sup -1/ is approximately 80% of the estimated total annual input of this element via precipitation in this region during the 16-year period. There were no statistically significant changes in total zinc and copper content of the forest floor. Since the forest floor's total dry weight increased significantly (42%), zinc and copper concentration decreased significantly. The results of this study emphasize the importance of determining both concentration and amount of trace elements in soilmore » studies.« less

Decomposition and nutrient release in Douglas-fir needle litter in relation to stand development

Decomposition rates and changes in the nutrient content of needle litter were examined in an age sequence of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands in western Washington. The stands at the initiation of the study were 11, 24, 44, 75, and 97 years old. Nylon litter bags (1 mm mesh) containing needles from the 44-year-old stand were placed in the stands in February 1975. Bags were collected after 3, 6, 12, and 24 months, weighed, and analyzed for N, P, K, Ca, Mg, Mn, and lignin. Decomposition constants (k values) were determined. After 2 years, maximum decomposition rate occurred in the 24-year-old stand, where temperature and moisture conditions were most favorable. Low litter moisture tended to inhibit decomposition in summer. Values of k determined from 1-year weight loss data and percent needle lignin after 2 years were significantly different between stands. Values of k determined from weight loss were greater than those determined from litter fall weight: forest floor weight ratios. Loss of elements from litter bags after 2 years was in the following sequence in all stands, N < Mn < Ca < Mg < P < K. Annual stand net productivity was strongly correlated to N + K loss from litter bags (r = 0.96).

Forest Floor in the Piedmont Region of South Carolina

AbstractThe annual litter fall, weight of forest floor, and organic matter incorporation in the surface foot of mineral soil are reported for three pine, three pine‐hardwood, and three hardwood stands in the South Carolina Piedmont.The litter fall for the stands averaged 4,400 pounds per acre, of which 3,500 pounds was leaf material. The weight of the forest floor was greatest in the pine stands and least in the hardwoods. The forest floor weight, expressed on a volatile matter basis, ranged from 6,160 pounds per acre in an old hardwood stand to 16,430 pounds in a 40‐year‐old shortleaf pine stand. The organic matter content in the surface foot of mineral soil ranged from 83,550 pounds per acre in the old hardwood stand to 25,780 pounds in a young loblolly pine plantation. The weight of the forest floor and organic matter in the mineral soil show that decomposition is more rapid beneath hardwood stands.The forest floors are classified as to humus type and the discussion presented shows some practical application of the information to forest management work.