Microsite Types Research Articles

Changes in the understory during 14 years following catastrophic windthrow in two Minnesota forests

Abstract. We studied the effects of windthrow on the understory plant species composition of a pine forest (dominated by Pinus strobus) and an oak forest (dominated by Quercus ellipsoidalis). We recorded the presence of vascular plant species in randomly located quadrats in the two forests, and in three microsite types associated with tipup mounds (pit, old soil and new soil) in the pine forest at irregular intervals over the course of 14 years. The understories of the two forests remained distinct throughout the study. The frequency of occurrence of a number of forest floor species considerably increased; few species decreased. The disturbance specialists Rubus idaeus and Polygonum cilinode increased in frequency throughout the study in the pine forest, but are beginning to decline in the less disturbed oak forest. Annuals and biennials preferentially colonized the disturbed soil of microsites on tipups, and declined in frequency after about 7 yr. Both forests have increased in understory species richness, but have not changed substantially in the distribution of growth forms. Despite early differences in species composition, microsite types associated with tipup mounds became more similar through time. Although small in magnitude, there was a directional change in understory composition at both forests, with no apparent sign of a return to pre‐disturbance conditions.

Seedling emergence and survival in contrasting soil microsites in Patagonian Monte shrubland

Abstract. The potential of two perennial species (Larrea divaricata and Stipa tenuis) to colonize different soil microsites was analyzed in the Patagonian Monte shrubland. We hypothesize that the short‐lived grass S. tenuis is more able to colonize the soil of microsites beneath vegetation patches where N‐fertility is higher than those in bare soil, while the long‐lived shrub L. divaricata colonizes different soil microsites irrespective of their N fertility. A greenhouse experiment was carried out to evaluate the emergence and survival of both species in different soil microsites at different water, inorganic N and seed densities. In all cases soil microsites were seed limited since the addition of viable seeds increased seedling emergence. Both species showed, however, different abilities to emerge and survive in different soil microsites. Microsites of bare soil were more favourable for seedling emergence and survival of L. divaricata than those beneath vegetation patches, independent of their water status. This ability of L. divaricata can not be explained on the basis of increased water or N availability, but probably because of lower salt content of bare soil. The addition of inorganic N reduced the survival of L. divaricata in both microsites but increased individual plant performance. The emergence and survival of S. tenuis was not different in both types of soil microsites but the addition of inorganic N increased seedling emergence and plant biomass. According to these results, emergence and plant performance of S. tenuis may be promoted during humid years by increased concentration of inorganic N. Since N mineralization occurs at a higher rate in soil microsites beneath vegetation patches than in those of bare soil, higher plant performance and probably establishment of S. tenuis is to be expected. These results are consistent with an existing conceptual model of plant dynamics under various grazing intensities in the Patagonian Monte shrubland based on previous field observations.

Effects of clonal integration on plant plasticity in Fragaria chiloensis

The ability of clonal plants to transport substances between ramets located in different microsites also allows them to modify the plastic responses of individual ramets to local environmental conditions. By equalising concentrations of substances between ramets, physiological integration might decrease responses to local conditions. However, integration has also been observed to increase plasticity and induce novel plastic responses in ramets. To ask how integration modifies plant plasticity in the clonal herb, Fragaria chiloensis, ramets were given either low light and high nitrogen or high light and low nitrogen, simulating a pattern of resource patchiness in their native habitat. Ramets in contrasting light/nitrogen treatments were either connected or single. Effects of light/nitrogen and connection were measured at three levels of morphological organisation, the organ, the ramet, and the clonal fragment. Connection between ramets reduced or had no effect on plastic responses in leaf size at the level of the plant organ. This suggested that integration dampened certain plastic responses. Connection induced a new plastic response at the level of the clonal fragment, an increase in allocation to vegetative reproduction in patches of low light and high nitrogen. It is concluded that clonal integration can have different effects on plant plasticity at different levels of plant organisation. It appears that, at least in this species, integration can increase plasticity at the level of the clonal fragment and concentrate vegetative reproduction in particular microsite types.

Effects of Ant Species Composition on Seed Removal in Deciduous Forest in Eastern Europe

Ant species contribute differently to the removal of elaiosome-bearing seeds. Microhabitats on the deciduous forest floor differ in the composition of ant species; these differences may influence the dispersal of myrmecochorous plants. This study examined removal rates of Viola odorata seeds which were dispersed by foragers of four ant species Formica polyctena (FP), Lasius fuliginosus (LF), Myrmica rubra (MR). and Leptothorax nylanderi (LN). We observed (I) the visit rates of ants and removal rates of seeds at three microhabitats with different ant species composition: FP territory with MR and LN. LF territory with AIR and LN, AIR territory with LN; (2) the contribution of different ant species to the seed removal rates; (3) effects of microsite type on the duration of seed manipulation by ant workers; (4) number of seeds handled by workers of different ant species: (5) effects of learning and recruitment on seed removal rates in three ant species FP. LF, and MR. At each territory the main contribution to visit rates and to seed removal rates was made by the most dominant ant species. The duration of seed manipulation by AIR ants at both FP and LF territories was significantly shorter than that by FP and LF ants. Under the pressure of large LF and FP, the AIR workers left the seed depot twice as quickly as in the absence of other ant species. Thus, duration of seed manipulation by MR was significantly shorter at FP, and especially, at LF territories than at MR territory. In all territories the duration of seed manipulation by LN was significantly longer than by other ant species. Learning (MR) or recruitment (FP) took place during seed removal. There were no differences in the duration of seed manipulation between experienced and inexperienced ants of both LF and FP. Inexperienced individuals of MR manipulated seeds twice as long as experienced ones. Experienced ants removed seeds with higher frequency than inexperienced ones regardless of ant species. It is concluded that ant species composition strongly influences the removal rates of seeds and potentially the fate of seeds of a myrmecochore. FP territory, providing the fastest removal of the fruit content, is presumably the most advantageous for the myrmecochore.

RESOURCE CONGRUENCE AND FOREST REGENERATION FOLLOWING AN EXPERIMENTAL HURRICANE BLOWDOWN

Catastrophic uprooting of forest canopy trees creates mounds, pits, and other microsites that provide opportunities for regeneration of particular species. We measured environmental factors on five types of microsites created by simulated blowdown of a mixed deciduous forest in central New England, United States. We then estimated spatial variation in resource levels and quantified congruence among different resources at each site. Effects of simulated blowdown on light levels and CO2 concentrations were more pronounced after three years than effects on nitrogen availability and other soil resources. Spatial heterogeneity in light levels and net nitrification rates was greater in the blowdown, but heterogeneities of soil organic matter concentration and net mineralization rates were greater in the undisturbed forest. Availability of nitrate, a limiting resource in most New England forests, was low on mounds and in pits, but high on the vertical portion of forest floor resulting from uprooting of canopy trees. At a spatial scale relevant to seedlings, resource congruence was greater in the undisturbed forest than in the experimental blowdown, primarily because of the effects of blowdown on light levels. Congruence in the blowdown increased with an increase in spatial scale, but congruence in the undisturbed forest was similar at both spatial scales. Seedling growth of two birch species was correlated with light levels and with congruence among soil resources. This study shows that immediate disturbance effects on microtopography and light levels determine recruitment patterns of colonizing species, with changes in soil resource levels influencing later community development. Furthermore, some species appear to respond to resource congruence, which may provide an additional dimension to the regeneration niche.

REGENERATION OF THREE SYMPATRIC BIRCH SPECIES ON EXPERIMENTAL HURRICANE BLOWDOWN MICROSITES

Tip-up mounds, pits, and other microsites created by hurricanes may promote diversity in many forests by providing opportunities for different species to regenerate. To see if we could detect differences in microsite preference among closely related species, we studied the regeneration of three sympatric Betula species on five types of microsites on experimental mound–pit complexes. Microsites were created by pulling down canopy trees to simulate damage from past hurricanes in southern New England. Seeds were collected in litter traps and experimentally released over mounds and pits to determine effects of microtopography on fine-scale dispersal patterns. The fate of naturally germinating seedlings was monitored on the disturbed site, and seedlings were also transplanted onto microsites to examine growth patterns, causes of mortality, and leaf-level physiology. Seed rain onto the disturbed site was abundant and spatially heterogeneous because of scattered residual canopy trees and surviving uprooted trees. Seeds tended to disperse away from vertically oriented surfaces of mounds and to accumulate in pits. Most seedlings germinated on scarified level areas rather than on mounds or in pits, but mounds became more favorable for germination the second year following disturbance. Two fundamentally different types of mortality were observed in transplanted seedlings. Extrinsic factors such as frost heaving, burial by soil and litter, and browsing were dominant on some microsites. Mortality due to these factors occurred primarily during the winter and was unrelated to seedling size. On other microsites, resource limitation (low light levels and lack of water or nutrients) was the major cause of death. Small seedlings were most susceptible to mortality on these microsites, and most deaths occurred during the growing season. White birch (Betula papyrifera Marsh.) exhibited the fastest growth and most flexible photosynthetic response to changing light levels but suffered greatest mortality on shaded microsites. Black birch (B. lenta L.) showed increased leaf area ratio in shaded conditions. Yellow birch (B. alleghaniensis Britt.) was least flexible and grew more slowly than the other species but was best able to survive on shaded microsites. All species attained maximum growth on tip-up mounds. After three growing seasons, the tallest seedlings reached nearly 3 m above the forest floor, enabling us to predict which individuals would ultimately reach the canopy to complete the regeneration process.

Seedling establishment in different microsites on Mount St. Helens, Washington, USA

On the volcanically devastated Pumice Plain of Mount St. Helens, plant species colonized microsites differentially. Peak colonization did not occur in the same microsites as peak establishment and growth. In addition, observed microsite colonization patterns differed between years. Two studies were conducted. The first assessed seedling establishment and growth from seeds sown at different microsites. The second assessed colonization into four microsite types that were constructed on the Pumice Plain. Hypochaeris radicata was the most common species to survive when the same number of seeds of four species were planted; however, Anaphalis margaritacea was the most common colonizer of microsites. Microsites with the largest biomass plants in the first study generally had the highest colonization in the second study. Sites that do not possess features to trap seeds, such as flats and ridges, are not opportune places for a plant to grow since there is little microclimatic or substrate amelioration. Thus, flat microsites had low biomass in the establishment experiment due to the lack of amelioration and contained few plants in the colonization experiment due to a lack of seed trapping mechanisms. These results show that in the primary successional landscape of Mount St. Helens microsites are critical to revegetation dynamics. Changes in the pattern of microsite colonization between years emphasizes the dynamic nature of the landscape and the important influences of climate, substrate amelioration and seed rain to plant establishment.

Stand Structure and the Regeneration of Chamaecyparis pisifera (Sieb. et Zucc.) Endl. on Sites with Different Soil Development in an Old-growth Coniferous Forest, Central Japan

Stand structure and the regeneration of Chamaecyparis pisifera on sites with and without well-developed soil in an old-growth coniferous forest, Akasawa Forest Reserve, central Japan, were investigated, along with their relationships to other important coniferous species. Of stems of C. pisifera ≥5 cm diameter at breast height, stems with intermediate size were absent in stands on the developed-soil site, while those with smaller size increased in stands on the undeveloped-soil site, which supported a higher density of C. pisifera. In the stands without recent tree-fall of canopy stems on the developed-soil site, canopy stems of C. pisifera were distributed uniformly and the understory stems, patchily. On the other hand, both canopy and understory stems of C. pisifera in stands on the undeveloped-soil site were distributed patchily. In the understory, C. pisifera occurred as clonal patches formed by vegetative reproduction on various types of microsites including bare rocks. However, the clonal patches did not occur in a stand on the developed-soil site with dense saplings of an evergreen conifer, Thujopsis dolabrata, which can expand vegetatively with a well developed soil layer. Gap formation may induce C. pisifera to develop tree-form stems from shrubby clonal patches. On developed-soil sites, C. pisifera stands that survive a long disturbance-free period on this site need catastrophic disturbance for their regeneration, which will eliminate T. dolabrata in the understory and create bare soil for colonization of C. pisifera from seeds. On undeveloped-soil sites, C. pisifera replaces itself continuously by effective vegetative reproduction. Ground instability and the wet condition of this site may promote the replacement.

Seasonal variation in CH 4 emissions and production and oxidation potentials at microsites on an oligotrophic pine fen

Temporal and spatial variation in CH4 emissions was studied at hummock, Eriophorum lawn, flark and Carex lawn microsites in an oligotrophic pine fen over the growing season using a static chamber method, and CH4 production and oxidation potentials in peat profiles from hummock and flark were determined in laboratory incubation experiments. Emissions were lowest in the hummocks, and decreased with increasing hummock height, while in the lawns and flarks they increased with increasing sedge cover. Statistical response functions with water table and peat temperature as independent variables were calculated in order to reconstruct seasonal CH4 emissions by reference to the time series for peat temperature and water table specific to each microsite type. Mean CH4 emissions in the whole area in the snow-free period of 1993, weighted in terms of the proportions of the microsites, were 1.7 mol CH4 m-2. Potential CH4 production and oxidation rates were very low in the hummocks rising above the groundwater table, but were relatively similar when expressed per dry weight of peat both in the hummocks and flarks below the water table. The CH4 production potential increased in autumn at both microsites and CH4 oxidation potential seemed to decrease. The decrease in temperature in autumn certainly reduced in situ decomposition processes, possibly leaving unused substrates in the peat, which would explain the increase in CH4 production potential.

Effects of Microtopography and Disturbance on Fine-Root Dynamics in Wetland Forests of Low-Order Stream Floodplains

-Fine-root mass and net primary productivity (NPP) were assessed in two forested wedlands located in floodplains of low-order streams in southern Alabama. In one experiment, live and dead fine-root (<5 mm diam) mass in the upper 20 cm of soil were estimated by periodic soil coring for 7 mo. Cores were collected from P-fertilized and unfertilized portions of three microsite types: hummock, flat and hollow. In a second experiment, cores to 50 cm deep were collected from clear-cut and adjacent unharvested (reference) zones for 19 mo. In the first experiment, fine-root mass was significandly affected by microsite but not fertilizer. Roots were least abundant but temporally most variable in hollows, and fine-root NPP (estimated by summing root mass differences between sample dates) was greatest in hollows followed by flats and hummocks. In the clear-cut experiment, total fine-root mass was highly variable in clear-cut and reference sites. The ratio of liveto totalroot mass was significandly lower on clear-cut sites on four of nine sample dates. NPP in the upper 50 cm of soil ranged between 1.90 and 4.55 megagrams per ha per year and was consistendly, but not significantly, greater on reference than on clear-cut sites. This study suggests that fine-root dynamics in forested wetlands are affected by microtopography and possibly by disturbance to the overstory.

Influence of Gap Disturbances and Type of Microsites on Seedling Establishment in Bouteloua Gracilis

1 We examined the effects of patch disturbance leading to removal of conspecific neighbours, and of microsite type on the emergence, survival, and performance of seedlings of Bouteloua gracilis at a shortgrass steppe site. Our hypothesis was that the death and/or removal of a full-size B. gracilis plant, would result in increased availability of below-ground resources and thus promote the establishment of conspecific seedlings. 2 In 1990 and 1991, experimental plots were treated to mimic the effects of some common patch disturbance types. Caryopses were then planted into both plant microsites (i.e. located in the hummock formed by adult plants of B. gracilis) and bare soil. Seedlings were watered until they were past the stage of adventitious root development. Soil water contents were recorded during and after the cessation of watering. 3 In 1991, results clearly showed that the effect of removal of established neighbours was significant in favouring seedling establishment. Differences among disturbance types were of lesser magnitude. Seedling responses were associated with soil water relations. Following cessation of watering, control plots with intact canopies showed more rapid depletion of soil water than disturbed plots. 4 The positive effect of bare soil microsites during emergence and early survival was associated with changes in superficial (0-5 cm) soil-water relations. Type of microsite was important for plant responses only during the early stages of seedling development, although soil water differences remained significant after the cessation of watering. 5 These results support the idea that gap-disturbances must occur to achieve the regeneration of the dominant species. The detrimental effect of microsites associated with the plant hummock may affect the pattern of emergence, resulting in a tendency for seedlings to establish in areas that were not occupied by their predecessors. Interference of established plants via below-ground competition and microsite favourability plays a key role in the regeneration of B. gracilis in this shortgrass community.

Ecology of Testaceans (Protozoa: Rhizopoda) in Mires in Southern Finland: II. Multivariate Analysis

The distribution of 41 testacean species (Protozoa: Rhizopoda) and a rotifer, Habrotrocha angusticollis (Rotifera: Bdelloidea) was analyzed in relation to 12 environmental variables by multivariate numerical techniques. Statistical analyses were performed using absolute numbers of testaceans estimated from 90 representative microsite types in six mires in the raised bog region of southern Finland. Two-way indicator species analysis (TWINSPAN) and both indirect (DCA) and direct (CCA) gradient analysis indicated that individual testaceans and certain assemblages of testaceans were dependent upon more than a single environmental factor, with soil moisture content being the most important. In microsite types where soil moisture content was not strongly affecting testaceans, the trophic status and DOC of the water proved to be important. The 12 environmental variables included in our survey accounted for 69.1% of the total variance according to the CCA-ordination. In decreasing order of importance were depth of water table, soil moisture content, trophic status of the site, C/N ratio of the peat, water pH, depth of testacean sample, and DOC of water. The agglomerative cluster analysis by means of Van Der Maarel's similarity index recognized nine testacean groups, which are comparable to groups identified by TWINSPAN along ecological gradients from dry to wet and from oligotrophic to eutrophic microsites.

Flood Disturbance and the Coexistence of Species in a Lowland Podocarp Forest, South Westland, New Zealand

The structure and composition of four forest stands affected by catastrophic floods on a lowland floodplain, south Westland, New Zealand, was investigated using stand history reconstruction. Age and size structures, and tree locations were used to identify cohorts of trees that were initiated by flood events. This, along with information on species microsite preferences and spatial patterning, was used to reconstruct the patterns of establishment of the four dominant canopy trees (Dacrycarpus dacrydioides, Dacrydium cupressinum, Prumnopitys ferruginea and Weinmannia racemosa) in response to flood disturbance. The four species coexisted by partitioning establishment sites with respect to the amount of overhead cover and the type of forest floor microsite (...)

Buried propagule bank of a high subalpine site: microsite variation and comparisons with aboveground vegetation

We assessed the composition and spatial pattern of the persistent buried propagule bank (seeds and vegetative structures) of a treeline site in the Oregon Cascade Mountains. We monitored emergence from soil cores removed from four microsite types and recorded vegetation cover and seedling abundance on the site. Over 3100 seedlings/m2 emerged from the greenhouse soil cores; the seed bank was dominated by Juncus species. Few vegetative sprouts emerged. Vegetated microsites produced significantly more emergents than did bare soils, but even bare soils contained abundant seeds. Overall site cover was low and few seedlings occurred on the site. Discrepancies between aboveground and belowground abundance were common. Phyllodoce empetriformis and Luetkea pectinata were abundant in the vegetation and produced many seeds but were poorly represented in the seed bank and as seedlings on the site. Other species were abundant in the seed bank, but rare in the vegetation. Our results indicate that despite the abundance of seeds in bare soil, colonization is likely to be extremely slow. Key words: seed bank, subalpine, seedlings, microsite, spatial pattern.

Microsite Variability and Safe Site Description for Western Larch Germination and Establishment

OSWALD, B. P. (Department of Plant and Soil Science, Alabama AM shading, moss, and large vegetation were not significantly effected by treatment. Seven western larch (Larix occidentalis) seeds were distributed after burning treatment on each sample point, and the number of germinations, germinants and seedlings were tracked over two growing seasons. Germinations (741) and germinants (656) from 17,500 seeds occurred on a wide variety of burned and unburned microsite types. Microsite types with successful germination, germinants, and seedling establishment are the (seedbed with proper conditions) for these stages of seedling development. Safe site requirements became more specific as the seedling developed, with only 47 seedlings surviving to the end of the first growing season. Seedlings survived on safe sites which represented 1.5% of the -total area. The eight physical characteristics used to describe microsite types were evaluated with discriminant analysis for significance at each seedling stage. Significant variables and interactions were identified for regression. Analysis produced high (R2 = 0.75) predictability at the end of the first growing season for initial seedling establishment. Safe sites are described for seedling establishment, with site, seedbed treatment, shading and moss as significant variables. The safe site concept appears useful in evaluating germination and initial establishment of western larch.

Role of Uprooting in Composition and Dynamics of an Old‐growth Forest in Japan

Seedling, sapling, and tree composition in several types of gap and nongap microsites were examined in an old—growth temperate mixed forest in western Japan. The distribution of species was not related to gap size (10—340 m2). Seedling communities on tip—up mounds and those on fallen boles of coniferous trees were rich and composed of pioneer species. In contrast, understory composition in gaps without uprooting did not differ from undisturbed forest. Dwarf bamboo, which dominates the forest floor and prevents tree regeneration, magnifies the effect of uprooting. Species with small, wind—dispersed seeds were found mainly on disturbed soil, while species with large, animal—dispersed seeds did not have any bias in distribution. Soil disturbance is a more important feature of the disturbance regime of this forest than is gap formation, with regards to maintaining species richness.

Microsite variations in soil chemistry and nitrogen mineralization in a beech-maple forest

Though whole forest stand and ecosystem estimates of soil nitrogen dynamics are common, few studies have included measurements of within-stand variations in N mineralization and nitrification among microsites. We evaluated soil chemical status, net mineralization and nitrification potential during Autumn 1986 in A- and B-horizon soils taken from near the bases of Fagus grandifolia (American beech), Acer saccharum (sugar maple), and Fraxinus americana (white ash) trees and from sites > 2 m from trees using buried bag exposures. Fagus sites had significantly lower pH in both horizons than did other sites. Soils near Acer trees had higher organic C and NH 4 + concentrations and Fraxinus soils had significantly higher PO 4 3− availability. Moisture and NO 3 − concentrations were similar among microsites. Using stepwise discriminant analysis, we constructed functions which differentiated among site types at P < 0.01 on the basis of these chemical measures. A-horizon N mineralization rates were generally 50% greater near Acer trees than away from trees, with Fagus and Fraxinus sites intermediate. B-horizon mineralization rates were highest under Fraxinus, but only 2–36% of A-horizon rates. Relative nitrification was approached 100% in all site types despite soil pH < 4. Calculation of N mineralization on an area basis with and without accounting for the differences among microsite types indicates that whole-ecosystem estimates of N mineralization generated by sampling schemes which do not explicitly include unique microsites around tree bases may be biased low by 8–20%.

Hydrochory and Regeneration in A Bald Cypress‐Water Tupelo Swamp Forest

The importance of hydrochory, or seed dispersal by water, to the regeneration of Taxodium distichum (bald cypress) and Nyssa aquatica (water tupelo) as examined in a forested floodplain of the Savannah River in South Carolina. Seedfall and dispersal by water were quantified for 2 yr using floating seed traps. Water depth, surface velocity, and flow direction were monitored over the same period. Seedfall for bald cypress and water tupelo occurred primarily from early fall throughout the winter, when water levels were rising in the swamp. Extended buoyancy periods for newly released seeds and fruits (bald cypress: 42 ± 37 d; water tupelo: 85 ± 36 d) prolonged dispersal for both species. Flowing water transported experimentally released seeds long distances, but in a uniform direction, and concentrated them nonrandomly against logs, trees, knees, and other emergent substrates. An examination of the soil seed banks in five microsite types supported the results of the seed transport study. Lowest woody seed densities occurred in the open areas, and highest seed densities occurred in sediments adjacent to emergent substrates such as logs. Additionally, elevated water levels of 1—2 m caused by short—term, high—discharge floods scoured seeds of Nyssa sylvatica var. biflora, Quercus spp., Liquidambar styraciflua, Pinus taeda, and other species from adjacent bottomland hardwood communities and transported them into the bald cypress—water tupelo forest. We conclude that elevated water levels, which occur during late fall when seeds are released, influence the distribution of bald cypress and water tupelo seeds and their availability for recruitment. Short—term, deeper floods may also be important for seed transport among bottomland hardwood communities that are spatially separated or differ in species composition.

Seed dispersal, seedling emergence, and early survival of Larixlaricina (DuRoi) K. Koch in the Tanana Valley, Alaska

The seasonal and spatial patterns of seed release, germling emergence, and early survival of Larixlaricina (DuRoi) K. Koch were studied in 1980–1981 near Fairbanks, Alaska. Dispersal was studied on one wetland site. Seedling emergence and 1-year survival were studied on three wetland microsite types (troughs, feathermoss, and tussock tops, located at increasing elevations above permafrost) and in mineral soil and undisturbed feathermoss seedbeds in a mature Piceaglauca stand of alluvial origin. Approximately 95% of the viable Larix seed from the 1980 cone crop fell by November 1980. Spatial distribution of seed away from the stand was erratic because of variable winds and the presence of a single Larix away from the stand edge. Average dispersal distances were less than those reported for other coniferous species. Emergence and early survival in both site types were affected by seedbed type. In the alluvial stand, germination and 1-year survival were greater on mineral seedbeds than on feathermoss. Emergence began in mid-July, well after minimum temperatures required for germination had been reached; timing appeared to be related to differences in volumetric moisture contents of the two seedbed types. Although cumulative totals of emergence and mortality did not differ between microsite types in the wetland, seasonal patterns of each differed with microsite. Emergence in troughs was delayed until early July by cold seedbed temperatures; increased precipitation in mid to late July raised the water table and flooded newly emerged seedlings in trough microsites but moistened feathermoss sufficiently to promote germination. Variation in emergence and mortality was high within a given microsite type.

Evaluation of planting sites common to a southeast Alaska clear-cut. IV. Nutrient levels in ectomycorrhizal Sitka spruce seedlings

Sitka spruce (Piceasitchensis (Bong.) Carr.) seedlings colonized by the ectomycorrhizal fungi Laccarialaccata (Scop. ex Fr.) Berk and Br., Hebelomacrustuliniforme (Bull, ex St. Amans) Quel., or Cenococcumgeophilum Fr. and a noninoculated control were planted on rotten wood, undisturbed duff, undisturbed duff on the north side of large stumps, and exposed mineral soil in an area recently clear-cut on Chichagof Island, southeast Alaska. Uptake and concentrations of N, P, K, Ca, Mg, and several micronutrients in foliage, stems, and roots were determined 2 years after outplanting. There were no significant interactions between fungal treatments and microsite types for uptake or concentration of any nutrient. Uptake and concentrations of N and P in foliage and roots did not differ significantly among fungal treatments. Foliar K and Cu concentrations were significantly higher in control seedlings than in those with L. laccata ectomycorrhizae. Calcium was the only nutrient analyzed that was present in higher concentrations in seedlings inoculated with H. crustuliniforme than in controls. Concentrations of foliar P, Mn, and Zn were significantly greater in seedlings grown on undisturbed duff (protected north side) than in seedlings grown on exposed mineral soil. However, foliar concentrations of all nutrients tested were not significantly different between seedlings grown on undisturbed duff (unprotected sites) and those grown on mineral soil. Seedlings grown on rotten wood had significantly greater concentrations of foliar Ca than seedlings grown on either exposed mineral soil or undisturbed duff. The on-site colonization of control seedlings after outplanting indicates that resident ectomycorrhizal fungi readily establish and appear to provide equal if not improved nutrient benefits compared to inoculated seedlings. Greater nutritional benefits were derived by planting on certain microsite types (duff and protected duff) than by inoculating with specific ectomycorrhizal fungi.