Deciduous Sites Research Articles

Throughfall and stemflow chemistry under deciduous and coniferous forest canopies in south-central Ontario

By measuring incident precipitation, throughfall, and stemflow chemistry, the roles of coniferous- and deciduous-dominated forest canopies as a source of and sink for ions in precipitation were examined. A regression technique for distinguishing between external (dry deposition) and internal (canopy leaching) sources of ions in the throughfall flux was evaluated. The effect of seasonal changes in the forest canopy on throughfall and stemflow chemistry was also examined. Throughfall comprised 74 and 84%, respectively, of the hydrologic flux at the coniferous and deciduous sites. Sulphate fluxes were highest at the coniferous site during both growing and dormant seasons, suggesting either a higher scavenging efficiency of the needles for atmospheric SO42−, or higher SO42− leaching from the foliage. The deciduous site neutralized acidic inputs, as demonstrated by its net negative H+ flux year round. The buffering capacity of the coniferous forest was exceeded by the higher amount of acid interception by the canopy. Nitrate behaved conservatively and base ions were exported from the canopy. Stemflow contributions of ions, although low, were generally higher than the contribution of stemflow to the hydrologic flux (2–3%). Independent dry deposition measurements for the growing season, when compared with net SO42− flux, overestimated dry deposition collected by the deciduous canopy, but were comparable to the flux at the coniferous site. These data suggest that dry SO2−SO42− deposition may be responsible for all SO42− enrichment seen in throughfall at these sites. A regression technique for separating internal and external ion sources in throughfall yielded inconsistent results, and attributed virtually all ion enrichment to internal sources. Problems with false assumptions and spurious correlations are discussed. We conclude that this method is not satisfactory for separating ion sources. Seasonal patterns in throughfall chemistry are present. During the growing seasons bases exchange for H+ and are exported similarly with SO42−. Hydrogen retention mirrors SO42− export. Base cations (particularly K+) are leached from the canopy primarily during senescence, but from the stem of the tree primarily during the dormant period. This was most evident at the deciduous site. Chloride behaved in a similar manner, while NH4+ and H+ were retained during the senescent period.

Wood Decomposition: Nitrogen and Phosphorus Dynamics in Relation to Extracellular Enzyme Activity

Because plant litter decomposition is directly mediated by extracellular enzymes (ectoenzymes), analyses of the dynamics of their activity may clarify the mechanisms that link decomposition rates to substrate quality and nutrient availability. We investigated this possibility by placing arrays of white birch sticks at eight upland, riparian, and lotic sites on a forested watershed in northern New York. For 3 yr, samples were analyzed for mass loss, protein, total Kjeldahl nitrogen (TKN), and total phosphorus (TP) accumulation, and the activity of 11 classes of extracellular enzymes involved in C, N, and P cycling. The relationship between lignocellulase activity and mass loss did not differ among sites. TKN and TP immobilization exhibited some spatial variation; rates of accumulation per 1% loss of initial mass, estimated from linear regressions, ranged from 2.2 to 4.4 mg/g OM for TP and from 43 to 139 mg/g OM for TKN, with maximum concentrations reached at °80% mass loss. The relationship between the activities of acid phosphatase (AcPase) and N—acetylglucosaminidase (NAGase), enzymes involved in the acquisition of P and N from organic sources, and mass loss displayed even greater variation among sites; the slopes of linear regressions relating mass loss and temporally integrated activity ranged from 0.019 to 0.135 activity—months per mass loss point and 0.107 to 0.775 activity—months per mass loss point, respectively, suggesting that edaphic rather than substrate quality factors were regulating activity. The extent of N limitation at each site was inferred by plotting TKN accumulation, defined as the slope of the linear regression TKN concentration vs. mass loss, in relation to NAGase activity accumulation, defined as the slope of the linear regression cumulative NAGase activity—months vs. mass loss. P limitation at each site was similarly assessed from an analogous plot of TP accumulation in relation to AcPase activity accumulation. Low N or P accumulation in conjunction with high acquisition activity was taken as an indication of nutrient limitation while the converse indicated surfeit. The diagrams suggested that decomposition at the upland hemlock and lotic sites, which displayed intermediate rates of OM loss (zero order k = 0.29 g/mo and 0.23 g/mo, respectively), was primarily N limited, while the riparian sites, which had the lowest rates of OM loss (k = 0.14 g/mo), appeared to be P limited. Relative to the others, OM loss at the upland deciduous sites (k = 0.38 g/mo) was not limited by either N or P. The concordance of field observations with predictions based on ectoenzyme regulation mechanisms suggest that enzyme activity assays in conjunction with nutrient concentration measurements may be a useful indicator of nutrient limitation. An economic model is proposed that directly links N and P availability to litter decomposition rates on the basis of microbial allocation of resources of extracellular enzyme production.

Glucose causes lengthening of the microvilli of the neural plate of the rat embryo and produces a helical pattern on their surface.

Prominent microvilli have been observed on the surface of neural plates in the embryos of many species. Since glucose is the main source of energy for embryos before neural tube closure and the onset of vascular circulation, it was of interest to study the relationship between these microvilli and glucose utilization in the neural plate. By applying microdrops of amniotic fluid to chemstrips, which colorimetrically measure glucose by glucose oxidase reaction, we determined that day 10 rat amniotic fluid glucose level was 31.6 +/- 1.6 mg/dl. On day 10 and within about 20 min from removal of the decidual sites, no glucose was found in the amniotic fluid. By use of a scanning electron microscope, the microvilli of the day 10 neural plate were found to have a 10-fold increase in length during a 40-min exposure to Hanks' solution at 21-23 degrees C. Similarly exposed embryos in Hanks' without glucose did not have microvillus elongation. However, under whole embryo culture conditions at 38 degrees C no extension of the microvilli was found. In the closed neural tube of the day 10 embryo, the microvilli were stubby and did not elongate with glucose exposure. Similarly, day 11 and 14 embryos had short microvilli which did not elongate with direct exposure to glucose at 21-23 degrees C. The short microvilli on the surface of the closed neural tube on day 11, 14, and 16 were associated with low glucose concentrations in the neural tube fluids. By use of a field emission scanning electron microscope, the surfaces of the microvilli in the extended position were seen to be covered by a right-handed helical array of globular objects the size of large molecules. The findings support the hypothesis that microvillar length may modulate glucose uptake. Shortening is associated with low concentrations of glucose in closed neural tubes, and lengthening occurs at glucose exposures of 100 mg/dl.

Nitrate production in nitrogen-saturated acid forest soils: Vertical distribution and characteristics

In order to study the vertical distribution, nature and pH-dependence of nitrate production in nitrogen-saturated acid forest soils, an incubation experiment was carried out using soil cores from five Dutch forests. Soil cores were left intact during incubation and divided into L, F, H horizons and top 5 cm of the mineral soil before analysis. One of the five forest soils revealed no significant NO 3 production during incubation, while in the other four sites different patterns with respect to vertical distribution of NO 3 production were found. The two coniferous sites snowed a dominance of NO 3 production in the ectorganic horizon (L + F + H), while in the two deciduous forests the production of NO 3 in the ectorganic horizon and in the top 5 cm of the mineral soil contributed about equally to total nitrification. At one of the deciduous sites, nitrification in the 5 cm top layer of the mineral soil was higher than the separate NO 3 productions in the L, F and H layer. Experiments with acetylene as a selective inhibitor indicated that the measured NO 3 production in the F layer of all four nitrifying forest sites was mainly carried out by chemolithotrophic bacteria. In the dominant nitrifying compartments, nitrification was mainly found to be acid-tolerant, which underlines the importance of this type of nitrification in N-saturated forest soils.

4830012 High speed nmr imaging method and apparatus : Stephen J Riederer assigned to Duke University

Deriving individual tree information from discrete return, small footprint LiDAR data may improve forest aboveground biomass estimates, and provide tree-level information that is important in many ecological studies. Several crown delineation algorithms have been developed to extract individual tree information from LiDAR point clouds or rasterized canopy height models (CHM), but many of these algorithms have difficulty discriminating between overlapping crowns, and also may fail to detect understory trees. Our approach uses a watershed-based delineation of a CHM, which is subsequently refined using the LiDAR point cloud. Individual tree detection was validated with stem mapped field data from the Smithsonian Environmental Research Center (SERC), Maryland, and on a plot and stand level through comparisons of stem density and basal area to delineated metrics at both SERC and a study area in the Sierra Nevada, California. For individual tree detection, the algorithm correctly identified 70% of dominant trees, 58% of codominant trees, 35% of intermediate trees and 21% of suppressed trees at SERC. The algorithm had difficulty distinguishing between crowns of small, dense understory trees of approximately the same height. Delineated crown volume alone explained 53% and 84% of the variability in basal area at the SERC and Sierra Nevada sites, respectively. The algorithm produced crown area distributions comparable to diameter at breast height (DBH) size class distributions observed in the field in both study sites. The algorithm detected understory crowns better in the conifer-dominated Sierra Nevada site than in the closed-canopy deciduous site in Maryland. The ability for the algorithm to reproduce both accurate tree size distributions and individual crown geometries in two dissimilar and complex forests suggests great promise for applicability to a wide range of forest systems.

Intrapopulation variation in the diet of the wood mouse Apodemus sylvaticus

Variation in the diet of wood mice, Apodemus sylvaticus, was investigated in two contrasting habitats, deciduous and coniferous woodland, over 26 months and in 10 additional sites trapped during winter. Stomach contents were categorized as seed, fruit, green plant, root and animal material. Diet was evaluated using the percentage occurrence of each food type. Age and sex differences in diet occurred infrequently. Seed predominated throughout but was especially prevalent in autumn and winter. There was a peak in the incidence of animal material in the spring and early summer. Animal food was generally more frequent in mice caught in conifer plantations than in deciduous woodland during the longer‐term study. Further, mice from the additional coniferous habitats had greater percentage occurrence of animal food than those from the additional deciduous sites. There was a negative, non‐linear association between relative population size and diet in these winter samples. This suggests that spatial variation in numbers of A. sylvaticus is dictated by food availability and density is locally food limited.

The fate of early fungal colonizers in beech branches decomposing on the forest floor

The dynamics of fungal colonization and species composition of freshly felled lengths of beech branches was monitored at nine deciduous woodland sites in south-west Britain, over a period of 70 weeks. Overall colonization rate was similar on most sites. On two sites which were studied in more detail, colonization data were partitioned between species which are latently present and those which are not. Fungi which were present latently developed rapidly and then began to decline after 32 to 64 weeks, whereas other colonizers developed more slowly and did not decline during the experiment. Cumulative species number data indicated a continuous recruitment of species for at least 70 weeks. Floristic composition of branches on all time sites was generally similar, although some species were found on only one or a few sites and then usually their frequency and abundance were low. Differences were detected in decay rate at different sites, which were presumably attributable to both site factors and decay organisms. Significant differences (P < 0.05) in decay rate were detected between branches which were and those which were not colonized by basidiomycetes.

The Effects of Leaching and Whole‐tree Harvesting on Cation Budgets of Several Forests

AbstractThe effects of acid deposition, natural leaching, and harvesting on base cation export from forests in Maine, Tennessee, South Carolina, North Carolina, and Washington were compared. Based on previous literature, we hypothesized that base cation export via whole‐tree harvesting (WTH) would be nearly independent of soil exchangeable base cation supplies; base cation export via leaching would be strongly dependent on the exchangeable cation supplies as well as the input, production, and mobility of anions. This hypothesis was supported by the data: mixed deciduous sites in Tennessee had among the highest base cation (principally Ca) exports via WTH (1.2 kmolc ha−1 yr−1), yet the lowest soil exchangeable supplies (35 kmolc ha−1), whereas the Washington sites had by far the highest base cation leaching (5–41 kmolc ha−1 yr−1, due to very high levels of naturally produced HCO−3) and soil exchangeable supplies, yet only relatively moderate base cation exports via WTH (0.4 kmolc ha−1 yr−1). Sulfate was either the dominant or a major anion in soil solutions from the eastern sites, suggesting that atmospheric deposition was a major factor in soil leaching from these sites (0.2–2.1 kmolc ha−1 yr−1), but total leaching rates from these sites were much lower than at the Washington sites. Indeed, some of the eastern sites showed a net annual accumulation of one or more base cations from atmospheric deposition. Some of the southeastern sites with Ultisols showed the expected net retention of SO2−4, but the sites in the Tennessee Valley near Oak Ridge showed surprisingly little ecosystem SO2−4 retention, perhaps due to lower soil SO2−4 adsorption in these soils than in other Ultisols.

Local Distribution and Coexistence of two Species of Peromyscus in Vermont

In New England, the woodland deer mouse (Peromyscus maniculatus gracilis) and whitelooted mouse (P. leucopus noveboracensis) are forest-dwelling species that may be found on the same site. Choate (1975) reported that P. maniculatus preferred habitats associated with coniferous forests or northern hardwoods and that P. leucopus was found in slightly more xeric habitats dominated by white pine (Pinus strobus), hemlock (Tsuga canadensis), and oaks (Quercus spp.), with populations occasionally extending into adjacent, more mesic northern hardwood forests. Several other authors also have reported that P. maniculatus is found in moist, cool, or coniferous habitats and that P. leucopus is found in dry, warm, or deciduous sites (Klein, 1960; Smith and Speller, 1970; Wrigley, 1969), although Lovejoy (1970) found P. maniculatus generally using dry habitats in the absence of P. leucopus. Sympatric species coexisting in a stable environment may select different foods, differ in temporal or spatial activity, and/or utilize different habitats, thus presumably reducing competition for niches. Hamilton (1941) noted no differences in food habits of P. mantculatus and P. leucopus. Temporal activity has been found to differ between these species in response to weather parameters (Drickamer and Capone, 1977), but neither seasonal nor circadian differences have been reported in New England. Both species are semi-arboreal and may partition niches spatially, but results of studies of arboreal habits of Peromyscus species do not permit a conclusion for P.m. gracilis and P. 1. noveboracensis (see Tadlock and Klein, 1979; Stahl, 1980; Wolff and Hurlbutt, 1982). Peromyscus maniculatus and P. leucopus appear to occupy similar ecological niches in the Northeast (Klein, 1960; Smith and Speller, 1970). The association of microhabitat structure with the distribution of rodents has received increasing attention in recent years (e.g., Carey et al., 1980; Dueser and Shugart, 1978; Holbrook, 1978; M'Closkey, 1976; M'Closkey and Fieldwick, 1975). Discriminant function analysis (DFA) has been used commonly in small mammal studies to describe microhabitats, demonstrate niche separation, or explain coexistence of sympatric species (Cavallaro et al., 1981). Our study was designed to determine how the distribution of coexisting Peromyscus species is related to microhabitat components of a northern hardwoods forest in southern Vermont. METHODS This study was conducted in a northern hardwoods forest in the Grafton Forest Resources Project area, Grafton, Vermont (45'10'N, in the eastern foothills of the 'Green Mountains. Elevations ranged from 250 to 400 m. Sherman live traps (7.6 by 8.9 by 22.9 cm) were set from 21 May through 20 August 1980 on 88, 0.08-ha plots for a total of 6,600 trap nights. Traps were set 15 through 19 July 1981 on 20 new plots, for 500 trap nights. To sample systematically, each plot contained five live traps, one at plot center and the others equidistant from plot corners and center, along diagonals of the plot (Fig. 1) Plots were at least 100 m apart to reduce the frequency of capturing an individual on adjacent plots. By using many plots widely dispersed throughout the study area, we incorporated much of the variability of forest types and structure. If a standard trap grid (e.g., traps spaced 10-15 m) had been used, the capture of an individual at an adjacent grid location would have been less independent of previous captures. The

Contributions of Acid Deposition and Natural Processes to Cation Leaching from Forest Soils: A Review

Methods of quantifying the roles of atmospheric acid inputs and internal acid generation by carbonic, organic, and nitric acids are illustrated by reviewing data sets from several intensively studied sites in North America. Some of the sites (tropical, temperate deciduous, and temperate coniferous) received acid precipitation whereas others (northern and subalpine) did not. Natural leaching by carbonic acid dominated soil leaching in the tropical and temperate coniferous sites, nitric acid (caused by nitrification) dominated leaching In an N-fixing temperate deciduous site, and organic acids dominated surface soil leaching in the subalpine site and contributed to leaching of surface soils in several other sites. Only at the temperate deciduous sites did atmospheric acid input play a major role in soil leaching. In no case, however, are the annual net losses of cations regarded as alarming as compared to soil exchangeable cation capital. These results were used to illustrate the methods of quantifying the ...

The glycogen content of the early pregnant female hamster genital tract, the fertile conceptus and artificially-induced deciduomata.

SUMMARY The quantitative changes in glycogen content of the hamster uterus, cervix, upper and lower vagina during the first 8 days of pregnancy were measured. The amount of glycogen in the conceptual sites on days 6, 7 and 8 was determined and compared with that of artificially induced deciduomata. The greatest concentration of glycogen was demonstrated in the tissue of the upper portion of the vagina. While no significant differences were found in the uterus, cervix and lower vagina during the time-interval investigated, significant increases in glycogen in upper vaginal tissue occurred on the 6th, 7th and 8th day of pregnancy. Uterine glycogen during the first 5 days, or the interdecidual sites on days 6, 7 and 8, did not differ significantly in their glycogen content. On day 6, when the conceptual site becomes discernible, the glycogen values were increased by 370% over the uterine levels of day 5 followed by a 28- and 31-fold increase on days 7 and 8. The glycogen content of deciduomata induced non-mechanically (saline, oil, air) or by trauma (scratching) did not differ significantly from that of the conceptual sites of normal pregnancy. These findings demonstrate that on day 6 a glycogenic stimulus is evoked which results in local stimulation of glycogen production in the decidual sites and the upper vagina. Induction of deciduomata by different procedures results in quantitatively similar amounts of the polysaccharide. The glycogenic factor, therefore (a) stimulates localized glycogen synthesis and (b) can be evoked by either natural or artificial means.