Forest Floor Properties Research Articles

Temporal variations of forest floor properties in the Coastal Western Hemlock zone of southern British Columbia

We examined temporal changes in the forest floor across a zonal chronosequence represented by four stages of stand development: stand initiation ( <= 7 years after disturbance), stem exclusion ( ±40-year-old stands), understory reinitiation ( ±60-year-old stands), and old-growth (>350-year-old) stands. All stages, except the old-growth, had a similar history of disturbance: clear-cutting without subsequent burning and silvicultural treatments. Considering thickness and chemical and biotic properties of the LF and H horizons, the most dissimilar stages were the stand initiation and old-growth, and the most similar stages were the stem exclusion and understory reinitiation. Compared with the old-growth stage, the stand initiation stage had about the same thickness of LF and H horizons and bacterial biomass but lower acidity, C:N ratio, fungal biomass, and soil fauna density and higher N mineralization. The stem exclusion and understory reinitiation stages had, in general, properties intermediate between the stand initiation and old-growth stage, with a gradual increase in acidity, C:N ratio, and fungal and faunal populations. After clear-cutting, the forest floor showed inevitable qualitative and quantitative alterations in response to the open-area climate. At the same time, it showed resilience, as most faunal groups of the old-growth stage were present in the stand initiation stage.

Effects of intensive harvesting on forest floor properties in Betula papyrifera stands in Newfoundland

Abstract. Betula papyrifera (White birch) is a common tree throughout the boreal forest of Canada; makes up 12% of the total tree volume in insular Newfoundland. It forms pure stands after harvesting and wildfire disturbance and it is a common component in most softwood stands. Little is known regarding the environmental impact of whole‐tree or conventional harvesting of this species and variation in impact related to variation in soil and site conditions.This study investigates litter and organic matter production and related site ecology in nine medium to high quality Betula papyrifera stands in three locations in central Newfoundland on a variety of land form and drainage conditions. Three sites, Badger West (BW), Moose Pond (MP) and Middleton Lake (ML) were selected. The ML site has the highest quality (with the best height/age ratio, 18 m/60 yr, and height/DBH ratio, 18 m/30 cm, followed by MP and BW. Litter depth on well developed moders or mulls was usually 2 ‐ 3 cm and varied from 1 ‐ 15 cm. Forest floor depths (measured in 324 profiles) rarely reached 20 cm and was commonly 5 ‐ 10 cm; it varied with position and site. Total and available nutrients indicate that B. papyrifera produces one of the highest ‐quality organic matter types of the local forest types and is important in improving site quality. The mean N‐concentration in green foliage (2.21%) and trapped litter (1.03%) was highest at the best quality site ML, followed by MP and BW. The concentration of calcium, 0.85%, was highest at the poorest quality site. Four years after harvesting, litter depth significantly decreased in all sites and treatments with the exception of the BW whole‐tree harvest treatment. Total forest floor depth significantly decreased at all sites in the stem‐only harvest treatment as well as the MP whole‐tree harvest treatment.There was a significant decrease in available nitrogen following harvesting in both treatments at both the MP and BW sites. Change in available phosphorus was insignificant, with the exception of an increase in the MP stem‐only harvest treatment. There was a significant decrease in available potassium at both the ML and BW whole‐tree harvest treatments, but a significant increase in the stem‐only harvest treatments at ML and MP. There was a significant decrease in available calcium in both treatments at both the MP and BW sites.

Temporal variations of forest floor properties in the Coastal Western Hemlock zone of southern British Columbia

Temporal variations of forest floor properties in the Coastal Western Hemlock zone of southern British Columbia

THERMAL CONDUCTIVITY AND WATER RETENTION OF A BLACK SPRUCE FOREST FLOOR

The forest floor of black spruce (Picea mariana (Mill.) B.S.P.) stands is typified by a thick layer of moss and organic material overlying the soil. This layer is an important source of nutrients and water for spruce and provides thermal insulation of permafrost. However, little is known about the water retention characteristics and thermal conductivity of black spruce forest floors. Near Fairbanks, Alaska, in situ thermal conductivity and water content ofa black spruce forest floor (0-0.05 m depth) were assessed during the 1992 growing season. In addition, core samples were taken for laboratory estimates of bulk density, water retention, and thermal conductivity. Bulk density was about 0.035 Mg m -3 at the 0 to 0.10-m depth and 0.050 Mg m -3 at the 0.10 to 0.20-m depth. In situ thermal conductivity of moss was generally smaller than previously estimated and ranged from 0.03 to 0.09 W m- 1 K- 1 over the growing season. Thermal conductivity varied linearly with water content at the 0 to 0.10-m depth and exponentially with water content below 0.10 m. Water retention differed within the forest floor profile, with an apparently smaller air-entry matric suction and pore size distribution index below the 0.1-m depth. This study suggests that variations in bulk density within a forest floor profile, which result from changes in organic material composition, affect both the thermal and hydrologic properties of black spruce forest floors.

Vegetative and edaphic characteristics on relic charcoal hearths in the Appalachian mountains

Relic charcoal hearths are prevalent throughout the Appalachian Mountains as reminders of the wood charcoal era and are evident today by the characteristics of forest stand structure, composition and understory vegetation. The importance of the soil resource to the stability and recovery of these anomalies in the plant community is not well understood. This study was conducted to compare forest floor and soil chemical properties, and vegetative characteristics on relic charcoal hearths to adjacent, non-hearth areas. Overstory tree cover and density was significantly lower on hearths than for adjacent areas. Overstory richness and diversity were consistently, but not significantly, lower on hearths, as were density and species richness of understory and ground vegetation. Little difference between hearth and adjacent forest floor properties was observed; however, soil calcium concentrations, pH. and percent carbon were higher on hearths, and phosphorus concentrations were generally lower. We discuss the effects of releasing large amounts of base-forming cations through repeated use of the hearths and the subsequent long-term effects on soil fertility and vegetative development.

Changes in nutrient availability and forest floor characteristics in relation to stand age and forest composition in the southern part of the boreal forest of northwestern Quebec

Changes in forest floor properties and nutrient availability along a boreal post-fire sere succession covering a time span of 231 years were assessed using soil analysis and exchange resins. A decline in pH (from 5.5 to 3.65), effective cation exchange capacity (CEC) (from 72.5 to 39.6 cmol(+)kg −1), exchangeable cation concentrations, as well as in Ca, Mg, K and PO 4 concentrations on resin was observed. Contrary to what has been reported so far for boreal forests, NO 3 and NH 4 concentrations did not decrease in the course of succession. Ammonium concentrations remained constant while those of NO 3 reached their highest values at age 27, decreased abruptly between ages 27 and 47, and started to increase in older stands. No correlation was found between NO 3 availability and pH, P concentrations or C/N ratio. Interactive effects of stand age and stand composition on nutrient concentrations on resins were evaluated using path analysis. While it is not possible to fully disentangle the contribution of single factors, the results showed a positive effect of aspen on Ca concentrations. These results stressed the need to evaluate the long term impacts of successive rotations of softwood species coupled with the elimination of hardwood competition on the soil base status of plantations.

Wildfire Effects on Forest Floor and Surface Soil in a Table Mountain Pine-Pitch Pine Forest

Wildfire plays a dominant role in creating die environmental and biological conditions necessary for the natural regeneration of mixed Pinus pungens Lamb. (Table Mountain pine)-Pinus rigida Mill. (pitch pine) forests. This study of forest floor and surface soil properties following a mid-July wildfire in these forests in the Shenandoah National Park revealed significant reductions in nutrient contents. Prolific regeneration of the pines occurred following the fire, with over 9,000 seedling/ha tallied in high severity areas, compared with less than 800 seedlings/ha in unburned areas. It is hypothesized that fire degrades site quality and sets back the site succession process so that the pines are better able to compete with invasive, xeric-site deciduous species like oaks and maples. Adjacent, unburned xeric-site oak forests dominate on more moist and fertile sites.

Trace metals in the forest floor at saddleback mountain, maine in relation to aspect, elevation, and cover type

The objectives of this study were to obtain information about trace metal levels in a montane ecosystem in western Maine, and to compare these results to levels of trace metals reported in the literature for other areas of New England. Forest floor samples were collected at Saddleback Mountain, Maine from sites along two elevational transects on the western and eastern slopes. Five sites were located on the western slope, each in a different vegetation zone, and three sites were selected on the eastern slope, each corresponding in elevation and vegetation type as closely as possible to three of the western sites. Forest floor samples were collected as 15 x 15 cm blocks to the surface of the underlying mineral soil and sectioned into 2 cm depth increments. Zinc and Cr concentrations in the forest floor were significantly greater on the western slope (118 and 3.7 mg kg−1, respectively), whereas Pb concentration was greater on the eastern slope (80 mg kg−1) Cadmium, Cr, Cu, Ni, V, and Zn contents were significantly greater on the western slope (45, 83, 79, 143, and 1432 mg in −2, respectively). Copper, Ni, Cd, and Zn concentrations and contents in the forest floor decreased with increasing elevation, and no trends of increasing trace metal contents with increasing elevation were evident. Trace metal concentrations and contents were always lower in the deepest increment of the forest floor as compared to the surface increment (except for Cr), but concentration and content trends with depth varied. Chromium tended to increase with depth where a depth trend was evident. Overall, forest floor trace metal levels were strongly related to forest stand type and forest floor properties.

Decomposition of boreal forest litters from central Alberta under laboratory conditions

Decomposition of foliage litter from jack pine (Pinusbanksiana Lamb.), white spruce (Piceaglauca (Moench) Voss), balsam fir (Abiesbalsamea (L.) Mill.), green alder (Alnuscrispa (Ait.) Pursh.), two feathermosses (Hylocomiumsplendens (Hedw.) B.S.G., Pleuroziumschreberi (Brid.) Mitt.), and a lichen (Cladinamitis (Sandst.) Hale & W. Culb.) was examined by measuring weight loss at 5-week intervals during a 35-week laboratory incubation (constant moisture, 23 °C). Weight loss by most litter types was more precisely described by a two-component than a one-component exponential decay model. Decomposition of lichen was best described by a one-component model as is consistent with the chemical and structural homogeneity of this litter. Decay rate was not correlated with concentration of C, N, soluble tannin or lignin, C:N ratio, or lignin:N ratio, although weight loss and lignin:N ratio were correlated in a combined data set that included data from published literature. Cutting pine needles into 1-cm lengths doubled initial decomposition rates, indicating that physical constraints associated with litter structure exert a strong influence on decomposition. Such structural controls limit the use of litter chemistry to predict decomposition rates. Relative differences in decomposition rates among litter types appeared to be reflected in forest floor properties, suggesting that plant species play different roles in the control of decomposition-related ecosystem processes.

Lateral variability of forest floor properties under second-growth Douglas-fir stands and the usefulness of composite sampling techniques

Lateral variability of forest floor physical and chemical properties is examined in LF and H horizons under six naturally regenerated, second-growth Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands in coastal southwestern British Columbia. The number of samples required to predict a mean value at two confidence levels (P = 0.01 and 0.05) and two allowable errors (10 and 20%) are given for each variable. Total C, N, P, S, Zn, pH, and lipids were the least variable, requiring 2–13 samples to estimate a plot mean with a 10% allowable error at the 95% confidence level in LF horizons and 3–51 samples per lot in H horizons. Total K, Cu, and Mn were found to have moderately high lateral variability, while total Ca, Mn, Al, and Fe all required large numbers of samples to estimate the plot mean. In the second part of the paper, composite samples weighted by field depth and bulk density are compared with the depth and bulk density–weighted arithmetic mean of subsamples analyzed individually. Values from analysis of composite samples were within one standard deviation of the mean, with the exception of P and Cu in the LF horizons and lipids in both horizons. Composite values and mean values were significantly correlated across the six sites for all variables except lipids in LF horizons and total C and Mn in both horizons. Composite samples are suggested to provide an adequate estimate of the mean value of subsamples analyzed individually for most purposes and, for some variables (i.e., Ca, Fe, Al, and Mn), the only feasible method of obtaining an estimate of the mean.

THE FOREST FLOOR: LATERAL VARIABILITY AS REVEALED BY SYSTEMATIC SAMPLING

The forest floor of a mature, naturally regenerated conifer stand on a well-drained podzolic soil in the Central Uplands of New Brunswick was sampled systematically. The forest-floor properties measured were: oven-dried mass per unit area, depth, moisture content, pH, potassium-chloride-extractable NH4-N and NO3-N, water-soluble phosphate, and ammonium-acetate-extractable K, Mg, and Ca. Total elemental C, N, P, K, Mg, Ca, Al, Fe concentrations were also determined. Coefficients of variation varied from 0.066 (total C) to 1.78 (2 N KCl-extractable NO3-N). Concentrations (measured in ppm or percent) were in each case less variable than absolute amounts (measured in kilograms per hectare). Frequency distributions were positively skewed (except for total C and N) and appeared to follow a gamma or Weibull distribution pattern. Key words: Ferro-Humic-Podzol, forest floor, lateral variability, spruce-fir forest, systematic sampling

Comparison of the chemical properties of forest floors, decaying wood, and fine roots in three ecosystems on Vancouver Island

Elemental concentrations were measured and compared for LF horizons, H horizons, decaying wood, and fine (< 2 mm) roots of three ecosystems on northern Vancouver Island. The principal tree species of these ecosystems were western hemlock (Tsugaheterophylla (Raf.) Sarg.), amabilis fir (Abiesamabilis (Dougl.) Forbes), and western red cedar (Thujaplicata Donn.). The H horizons had greater Mg and Na values than the LF horizons, while the opposite result was found for K and loss on ignition (LOI). The decaying wood represents a significant accumulation of nutrient-deficient biomass that could immobilize N. The decomposing fine roots will temporarily immobilize N while possibly increasing the concentration of elements such as Fe, Al, and Mn. These materials should be separated from forest floor samples in order to represent more accurately the nutrient status of forest floor horizons.

Distinguishing the Forest Floors of Three Ecosystems

AbstractForest floor classifications have been based on morphological properties which were perceived to reflect genesis. These classification systems have not been compatible with soil or ecological classifications, which may have limited their application to forest management. Three biogeocoenoses or ecosystem types near Port Hardy, British Columbia were selected for studying forest floor properties. The sites chosen represent xeric, mesic, and hygric positions along a hygrotopic gradient. The forest floor of each site was stratified into LF(01) and H(02) horizons. A stratified random sampling procedure was used to collect 15 samples within the horizon units of each site. Forty variables were measured or calculated for each sample.A two‐way analysis of variance in conjunction with the Student‐Newman‐Keuls Range Test was used to determine which variables, on an individual basis, would distinguish the forest floors of each site, the LF and H horizons overall, and the individual forest floor horizons of each site. The forest floors of the three sites could be differentiated on the basis of total K, exchangeable Na displaced by 1N NH4OAc, and the ratio of loss on ignition to total C (LOI/C). The LF and H horizons overall could be separated by total K, total Zn, exchangeable Ca and K displaced by 1N NH4OAc, exchangeable K displaced by 1N NaCl, base saturation at pH 7.0, pH measured in water and 0.01M CaCl2, LOI, the ratio of total Ca to total Mg, and the ratio of total Ca to total K. The forest floor horizons of all three sites could not be distinguished by use of single variables. Three stepwise discriminant analyses using nine, five, and two variables yielded classification accuracies of 94.4, 81.1, and 71.1%, respectively, for differentiating the forest floor horizons of all three sites. The multivariate analysis showed that the best combination of measurements for distinguishing the forest floor horizons of the individual sites are total N, total K, total P, LOI/C, and cation exchange capacity (CEC) estimated with 1N NaCl.

NUTRIENT VARIABILITY OF FOREST FLOORS NEAR PORT HARDY, BRITISH COLUMBIA, CANADA

The variability of forest floor properties over short distances and the number of samples required to achieve desired levels of precision for estimation of property means have received little attention. The importance of the forest floor for forest management is well known and increasingly forest floor characteristics are being used to classify forest sites. Highly variable forest floor properties require more intensive sampling and often have less predictive value for characterization and classification purposes. A study site at Port Hardy was used to characterize forest floors for selected physical and chemical properties. The three sites chosen represented xeric, mesic and hygric positions along a hygrotopic gradient. A stratified random sampling procedure was used to obtain 15 samples at each site. Fifteen samples were adequate to characterize the means at 10% allowable error with a 95% confidence level for total nitrogen, organic carbon, pH and cation exchange capacity. Greater than 15 samples were required for exchangeable bases and forest floor thickness for the same level of accuracy and confidence. Even at 25% allowable error and 90% confidence, 40 samples and 16 samples, respectively, were required for exchangeable Ca and Mg.

Vegetation–soil relationships along a spruce forest transect in interior Alaska

Five distinct forest communities were recognized along a 3-km transect. These are, listed in order of decreasing elevation: (i) open black spruce/feathermoss - Cladonia, (ii) closed black spruce/feathermoss, (iii) open black spruce/Sphagnum, (iv) black spruce woodland/Eriophorum, and (v) white spruce/alder/Calamagrostis (restricted to a narrow band adjacent to a stream). Several techniques of ordination were used to recognize these five forest communities plus two intergrades: (open black spruce/feathermoss - Cladonia) - (Sphagnum) and open black spruce/Sphagnum - woodland/Eriophorum.The distribution of two-thirds of the plant species was highly correlated with vegetation–slope zones. Results of the fit of Gaussian curves also suggest that vegetation boundaries were well placed. The distribution of the four soil series in the area was well correlated with vegetation–slope zones: three were limited to one zone each. Permafrost, absent from the soil on the ridgetop and upper slope, was generally within 40 to 50 cm of the surface elsewhere and tended to be at shallower depths as elevation decreased. The most striking differences in forest floor properties were found in the white spruce zone compared with the six black spruce dominated zones. The white spruce forest floor was markedly thinner and had higher levels of nutrients. In the six black spruce dominated zones, forest floor thickness and concentrations of N and Mg tended to increase with distance downslope, and P and K decreased.

Effect of Thinning on the Foliage and Forest Floor Properties of Ponderosa Pine Stands

AbstractThe longest and heaviest needle fascicles were associated with greater thinning intensities of ponderosa pine (Pinus ponderosa Laws.) stands 8 years after treatment. The foliar nutrient concentrations did not change significantly between the various thinning regimes. In addition the total forest floor in thinned and unthinned ponderosa pine stands ranged from 17.7 to 34.4 metric tons/ha. On a dry weight basis the F2 horizon constituted 74–88% of the total forest floor. However, nutrient concentrations increased from the foliage to the L to the F1 to the F2 which had the greatest concentrations of nutrients but were not affected by thinning intensity. The greater concentrations in the F2 were probably indicative of the more advanced degree of decomposition. Total nutrients in the forest floor were inversely proportional to the degree of thinning. In the stands at the growing stock level of 6.9 and 48.2 m2/ha (unthinned) total nitrogen was 213 and 301 kg N/ha, respectively. Other nutrient values were 17 and 27 kg P/ha, 18 and 32 kg S/ha, 56 and 75 kg K/ha, 119 and 154 kg Ca/ha, 75 and 126 kg Mg/ha, 26 and 34 kg Zn/ha, and 88 and 156 kg Mn/ha in the stands with growing stock levels of 6.9 and 48.2 m2/ha, respectively.