Thick Litter Layer Research Articles

Herb-layer diversity in deciduous forests: Raised by tree richness or beaten by beech?

Where natural production capacity permits, modern silvicultural management in Central Europe frequently aims at the development of mixed broadleaved stands, instead of pure European beech ( Fagus sylvatica) stands. It is crucial to study the effects of these tree-layer diversity variations on herb-layer vegetation, since herb-layer vegetation contributes significantly to ecosystem functioning in forests. In Hainich National Park (Thuringia, Germany), we conducted observational research in deciduous stands to investigate whether herb-layer diversity was related to canopy-layer diversity, and to ascertain possible causal mechanisms. We found that herb-layer vegetation of deciduous forest stands rich in canopy species appeared to be more diverse than herb-layer vegetation of beech-dominated stands. We surmise that herbaceous understorey diversity was indirectly influenced by canopy tree species through the medium of the altered environmental factors soil pH and litter layer thickness. Apparently, lower beech proportion had a more profound effect than the number of secondary tree species. There were no correlations between herb-layer diversity and light transmissibility of the canopy layer, indicating that the light factor was not crucial for herb-layer diversity. At least for the Hainich research sites, our results indicated that small-scale light and soil heterogeneity is insignificant for herb-layer diversity. We found several herb-layer species whose occurrence was particularly correlated with tree-layer diversity and environmental factors. Remarkably, all species positively correlated with soil pH were important for the phytosociological classification of the research sites. Beech-dominated research sites showed high tree-layer volumes, whereas research sites with high tree-layer diversity tended to feature lower tree-layer volumes. These findings could be the result of differing former silvicultural systems and varying soil clay contents affecting tree species composition. In contrast, herb-layer biomass was positively correlated with tree-layer diversity. Herb-layer productivity might be promoted in more diverse research sites by increased nutrient supply and base saturation. It is also possible that greater beech proportion interfered with herb-layer productivity. However, herb-layer biomass was also positively correlated with herb-layer diversity. Hence, our study hints that positive diversity-functioning relationships might occur in the herb-layer of the deciduous forest under investigation.

Litter Decomposition in a California Annual Grassland: Interactions Between Photodegradation and Litter Layer Thickness

In annual grasslands that experience a mediterranean-type climate, the synchrony between plant senescence and peak solar radiation over summer results in high litter sun exposure. We examined the decomposition of both shaded and sun-exposed litter over summer and inferred the effects of photodegradation from changes in mass loss and litter chemistry. The carry-over effects of summer litter exposure on wet season decomposition were also assessed, and the attenuation of photodegradation with litter layer thickness was used to estimate the proportion of grass litter lignin susceptible to photodegradation under different treatments of a factorial global change experiment. Over summer, mass loss from grass and forb litter exposed to ambient sunlight ranged from 8% to 10%, whereas lignin decreased in grass litter by approximately 20%. After one year of decomposition, mass losses from grass leaves exposed to sunlight over summer were more than double the mass losses from summer-shaded leaves. When shade litter layer thickness was varied, mass losses over summer for all treatments were also approximately 8%; however, lignin decreased significantly only in the low shade treatments (0–64 g m−2 of shade litter). Aboveground production of annual grasses nearly quadrupled in response to the combined effects of N addition, elevated atmospheric CO2, increased precipitation and warming. The estimated proportion of grass litter lignin experiencing full photodegradation ranged from 100% under ambient conditions to 31–62% in plots receiving the combined global change treatments. These results reveal an important role of sun exposure over summer in accelerating litter decomposition in these grasslands and provide evidence that future changes in the quantity of litter deposition may modulate the influence of photodegradation integrated across the litter layer.

Beargrass (Xerophyllum tenax) on the Olympic Peninsula, Washington: Autecology and Population Status

We studied the autecology and population status of beargrass (Xerophyllum tenax (Pursh) Nutt.) on the Olympic Peninsula of Washington State, focusing in the Olympic National Forest (ONF). Objectives were to: (1) define and describe beargrass habitat types in the ONF through an exploratory field study, and (2) determine whether beargrass populations in the ONF have declined where the species was historically present. We found three distinct beargrass habitat types in on the ONF: western low elevation, eastern low elevation, and high elevation habitats. These habitat types significantly differ in elevation, slope, topographic moisture, vegetation cover, successional stage, and litter layer thickness. We suggest environmental conditions of these habitat types may be attributed to the glacial and cultural history of the Olympic Peninsula. Beargrass cover in previously established plots on the southeastern Olympic Peninsula declined over the past 17 years, perhaps due to harvesting for the floral industry and ...

Integrated Management of Perennial Pepperweed (Lepidium latifolium)

AbstractPerennial pepperweed is invasive throughout California. It thrives in a wide range of environments and is a common weed in floodplains, pastures, wetlands, and roadsides. In disturbed areas, perennial pepperweed rapidly forms monotypic stands with a thick litter layer. These infestations not only out-compete other vegetation, but prevent re-establishment of desirable species even after perennial pepperweed control. This experiment examined integrated management strategies with the goal of maximizing perennial pepperweed control and establishment of desirable native vegetation. The experiment was conducted at two sites in Lassen County, CA. Both sites were heavily infested with perennial pepperweed and lacked competing vegetation. The experimental design was a split-split-randomized block with four replications. Site preparation treatments included winter burning, summer and fall mowing, winter grazing, and fall disking. These treatments were designed to remove thatch to facilitate herbicide application and reseeding of desirable perennial grasses. Herbicide treatments included chlorsulfuron, 2,4-D, or glyphosate applied at the flower bud stage. Revegetation treatments included no seeding and no-till seeding of native perennial grasses. Most site preparation plus herbicide combinations reduced perennial pepperweed cover > 85% compared to the untreated control, although treatment efficacy was variable between sites and years. Burning, grazing, mowing, or disking in combination with herbicide treatment and no-till seeding was necessary for successful native perennial grass establishment. Burning or mowing with yearly 2,4-D applications for 3 yr gave the best combination of perennial pepperweed control and native grass establishment. Chlorsulfuron caused chlorosis and stunting to western wheatgrass, basin wildrye, and beardless wildrye at both sites when applied the spring before seeding. No treatment offered complete weed control, suggesting follow-up spot herbicide applications are needed for long-term perennial pepperweed suppression. These results provide several successful integrated strategies for control of perennial pepperweed and revegetation to a desired native perennial grass community.

Relationships between permafrost distribution and surface organic layers near Esso, central Kamchatka, Russian Far East

AbstractUnique boreal forest, consisting mainly of sparse larch (Larix cajanderii), creeping pine (Pinus pumila) and birch forest (Betula ermanii), occurs above the lower elevational limit of discontinuous permafrost of about 500 m above sea level in the area around Esso, central Kamchatka (∼56°N). Permafrost is present beneath surfaces covered by Sphagnum or creeping pine, but is absent beneath birch forest. Thermal conductivities in mid‐September are low in Sphagnum (0.07–0.19 W/(m·K)) and in the thick (13–20 cm) litter layer beneath creeping pine‐covered areas (0.06–0.09 W/(m·K)). Seasonal changes in the subsurface ground temperatures beneath creeping pine show that the surface litter prevents ground temperature increases at depth in summer, resulting in a thin active layer (several decimetres). The surface organic layer appears to be the most important factor controlling the presence or absence of permafrost in this area. Copyright © 2008 John Wiley & Sons, Ltd.

Is the age of forest habitats affecting the reproductive rate of generalist predatory ground beetle species?

This study aimed at the effects of habitat age on the reproductive rate of three ground beetle species that are common and widely distributed in forest ecosystems of Europe ( Abax parallelepipedus (Pill. & Mitt.), Pterostichus oblongopunctatus (F.), Pterostichus burmeisteri (Heer.)). The study sites comprised comparable age classes, i.e., young stands, mature stands, and mature forests with upcoming and established natural regeneration of four different forest types, namely pure stands of spruce and Douglas fir, and mixed stands of spruce-beech and oak-beech. As an indicator for the reproductive rate of female beetles, the number of ripe eggs in the ovaries and the duration of the reproduction period were investigated from captures of pitfall trapping (n = 8 per site). The dissection of a total of 1236 females uncovered 1704 eggs. A broad spectrum of environmental factors including microclimate (temperature, humidity, precipitation), soil parameters (moisture, pH, thickness and coverage of litter layer) a...

Terrestrial gastropod responses to an ecosystem-level calcium manipulation in a northern hardwood forest

The effects of acid deposition on soil calcium (Ca), and in turn on land snail populations, have been of heightened concern for several decades. We compiled a 10 year record (1997–2006) of gastropod abundance on two small watersheds at the Hubbard Brook Experimental Forest, one of which was treated with a Ca addition in 1999. In years 3–7 post Ca addition, snail abundance in the treated watershed was 73% higher than in the reference area (p < 0.001); there was no significant difference in the 3 years prior to treatment, and no significant difference in slug abundance in any year. We analyzed relationships between snail density and microsite spatial variation in leaf-litter Ca concentration, litter-layer thickness, tree species composition, slope, dead wood, and forest-floor light level. We found that snail abundance was significantly correlated with litter Ca concentration (p < 0.001) and negatively correlated with the importance value of American beech (p = 0.05). Isotopic-tracer analysis indicated that, on average, 76% of Ca in snail shells 5 years post treatment was derived from the added Ca. However, interannual variation in snail numbers indicates that other factors beyond available Ca have a strong influence on snail abundance.

Effects of understory removal, N fertilization, and litter layer removal on soil N cycling in a 13-year-old white spruce plantation infested with Canada bluejoint grass

Canada bluejoint grass [Calamagrostis canadensis (Michx.) Beauv., referred to as bluejoint below] is a competitive understory species widely distributed in the boreal region in North America and builds up a thick litter layer that alters the soil surface microclimate in heavily infested sites. This study examined the effects of understory removal, N fertilization, and litter layer removal on litter decomposition, soil microbial biomass N (MBN), and net N mineralization and nitrification rates in LFH (the sum of organic horizons of litter, partially decomposed litter and humus on the soil surface) and mineral soil (0–10 cm) in a 13-year-old white spruce [Picea glauca (Moench.) Voss] plantation infested with bluejoint in Alberta, Canada. Removal of the understory vegetation and the litter layer together significantly increased soil temperature at 10 cm below the mineral soil surface by 1.7 and 1.3°C in summer 2003 and 2004, respectively, resulting in increased net N mineralization (by 1.09 and 0.14 mg N kg−1 day−1 in LFH and mineral soil, respectively, in 2004) and net nitrification rates (by 0.10 and 0.20 mg N kg−1 day−1 in LFH and mineral soil, respectively, in 2004). When the understory vegetation was intact, nitrification might have been limited by NH4+ availability due to competition for N from bluejoint and other understory species. Litter layer removal increased litter decomposition rate (percentage mass loss per month) from 2.6 to 3.0% after 15 months of incubation. Nitrogen fertilization did not show consistent effects on soil MBN, but increased net N mineralization and nitrification rates as well as available N concentrations in the soil. Clearly, understory removal combined with N fertilization was most effective in increasing rates of litter decomposition, net N mineralization and nitrification, and soil N availability. The management of understory vegetation dominated by bluejoint in the boreal region should consider the strong effects of understory competition and the accumulated litter layer on soil N cycling and the implications for forest management.

Vector analysis of understory competition, N fertilization, and litter layer removal effects on white spruce growth and nutrition in a 13-year-old plantation

Canada bluejoint grass ( Calamagrostis canadensis (Michx.) Beauv.) is a very competitive understory species and can create a thick litter layer that may decrease tree growth in white spruce ( Picea glauca (Moench.) Voss) stands in the boreal region. We examined the effects of Canada bluejoint grass dominated understory competition, N fertilization, and litter layer removal on the nutrition and growth of white spruce, in relation to soil N availability in a 13-year-old plantation near Whitecourt, Alberta, Canada, in 2003 and 2004. We hypothesized that: (1) understory competition reduces white spruce growth as a result of competition for available N; (2) litter layer removal increases white spruce growth by increasing soil temperature and N availability; (3) N fertilization improves white spruce growth by increasing N availability. Soil gravimetric moisture content in LFH was reduced by understory competition and litter layer removal in 2003, which had a very dry summer. Understory removal increased white spruce diameter growth, 100-needle biomass, and needle N concentration and content. In 2003, N fertilization consistently increased 100-needle weight and needle N content when litter layer was removed, but decreased or did not affect those values without litter layer removal. Nitrogen fertilization increased needle N concentration in 2004. The inconsistent effects of N fertilization may be due to the short-term nature of fertilization effects and immobilization of N by organic matter. Rates of white spruce diameter growth and soil mineral N supply in 2004 were related ( R 2 = 0.65, P < 0.001). Vector analysis showed that N fertilization or litter layer removal with intact understory vegetation either increased or did not affect needle N concentration but decreased tree biomass. We conclude that understory control will benefit tree growth in young white spruce stands in the boreal region that have passed the free-to-grow stage. However, N fertilization or litter layer removal alone in bluejoint infested sites may not benefit the trees.

Tardigrade species composition in young soils and some aspects on life history of Macrobiotus richtersi J. Murray, 1911

Summary In an afforested coal-mining site at Berzdorf, Germany, the soil tardigrade community was investigated. Tardigrade densities ranged from 300 to 33,600 individuals m −2 . Tardigrade distribution was very aggregated with standard deviations of up to 220% of mean densities. Fourteen species belonging to five eutardigrade genera were identified. Soils were dominated by the carnivorous tardigrade Macrobiotus richtersi that contributed 60% of overall densities. A comparison between nine soils of different forest ages (4–46 years) and tree species (poplar, alder, pine, mixed deciduous and mixed coniferous) showed no relationship of tardigrade species distribution and abundance to tree species, thickness of organic or litter layer, humus form, pH or soil moisture. Further, no correlation between nematode biomass and Macrobiotus richtersi abundances were detected. The age of afforested soils, however, affected tardigrade densities: younger soils (7–17 years) yielded higher tardigrade numbers compared to 46-year-old sites. Life history investigations on a strain of parthenogenetic Macrobiotus richtersi demonstrated a significant influence of temperature on egg development, survival rate, body growth and generation time. Hatching, first to fourth molts and maturing, on the other hand, were dependent upon body size alone. The simple, new culture method for carnivorous tardigrades described has successfully been utilized for parthenogenetic Macrobiotus richtersi for 6 years.

Microclimate and Pedogenic Implications in a 50‐Year‐Old Chaparral and Pine Biosequence

Vegetation, which is generally considered a co‐variable controlled by climate in studies of pedogenesis, can itself alter the balance of soil‐forming processes by modifying the microclimate. The chaparral and pine biosequence at the San Dimas Experimental Forest (SDEF) in southern California offers an opportunity to determine the effect of individual species on soil microclimate and related soil properties. Soil temperature and moisture were monitored under pure stands of Coulter pine (Pinus coulteri B. Don), chamise (Adenostoma fasciculatum Hook. and Arn.), and scrub oak (Quercus dumosa Nutt.). Despite the appreciable differences in soil morphology that have evolved under pine compared with oak, the microclimates created by the dense canopies and thick litter layers (7–10 cm) of these two vegetation types were similar. Average monthly soil temperatures within the top 65 cm ranged from about 8 to 20°C under pine and 7 to 18°C under oak. Average monthly water contents ranged from 8 to 32% (by volume) under pine and 6 to 32% under oak. In contrast, average monthly soil temperatures within the top 65 cm under chamise ranged from 6 to 23°C and average monthly water contents were 6 to 36%. Diurnal variation in soil surface temperature under chamise was much more pronounced than under oak and pine because of the relatively open canopy and thin litter layer. Microclimate created by chamise may play an important role in the decomposition rate of litter, but appears to have little influence on soil processes occurring within the mineral soil. Soil macrofaunal communities appear to have a greater effect than microclimate in causing the divergent soil morphologies under oak and pine.

Microclimate and Pedogenic Implications in a 50-Year-Old Chaparral and Pine Biosequence

Vegetation, which is generally considered a co-variable controlled by climate in studies of pedogenesis, can itself alter the balance of soil-forming processes by modifying the microclimate. The chaparral and pine biosequence at the San Dimas Experimental Forest (SDEF) in southern California offers an opportunity to determine the effect of individual species on soil microclimate and related soil properties. Soil temperature and moisture were monitored under pure stands of Coulter pine (Pinus coulteri B. Don), chamise (Adenostoma fasciculatum Hook. and Arn.), and scrub oak (Quercus dumosa Nutt.). Despite the appreciable differences in soil morphology that have evolved under pine compared with oak, the microclimates created by the dense canopies and thick litter layers (7–10 cm) of these two vegetation types were similar. Average monthly soil temperatures within the top 65 cm ranged from about 8 to 20°C under pine and 7 to 18°C under oak. Average monthly water contents ranged from 8 to 32% (by volume) under pine and 6 to 32% under oak. In contrast, average monthly soil temperatures within the top 65 cm under chamise ranged from 6 to 23°C and average monthly water contents were 6 to 36%. Diurnal variation in soil surface temperature under chamise was much more pronounced than under oak and pine because of the relatively open canopy and thin litter layer. Microclimate created by chamise may play an important role in the decomposition rate of litter, but appears to have little influence on soil processes occurring within the mineral soil. Soil macrofaunal communities appear to have a greater effect than microclimate in causing the divergent soil morphologies under oak and pine.

Cumulative effects of fire on a tussock pampa grassland

Abstract In order to test for cumulative effects of fire on Paspalum quadrifarium-dominated grasslands (‘pajonal’), we analysed the impact of single and repeated fires on the community structure and post-fire recovery of canopy after a final, simultaneous fire event. Nine plots were defined within a homogeneous pajonal stand, and treatments of low (LF), medium (MF) and high frequency (HF) of fire were defined by the application of one, two or four cold-season burns, respectively, along a 6-yr period. Both burned and unburned plots were exposed to grazing by cattle during the summer following the first and the third years of that period. High cattle preference for burned sites conditioned fire temperature and vegetation responses to the following burning events. Cumulative effects between successive burning events were observed for the cover of basal area of the dominant and other sprouting species, the cover and thickness of the litter layer, the seed bank size of the principal recruiter species, and the ...

Contents of Cu, Ni and Zn in smelter-polluted soil–plant systems

Intact soil profiles including litter layer and ground vegetation were taken at five distances (0.5, 2, 4, 8 and 60 km) from a Cu–Ni smelter in Harjavalta, SW Finland. The soil cores were placed in 10 l pots and a 4 year-old, bare-rooted pine seedling ( Pinus sylvestris L.) was planted in each. The containers were incubated for17 months in controlled greenhouse conditions. At the end of the experiment the seedlings were harvested and soil samples were taken from each pot and analysed for Cu, Ni and Zn. The absence of atmospheric metal deposition had no reducing effect on the exchangeable heavy-metal contents of the soil pots. Metal uptake by the plant seedlings during the experiment had a negligible effect on the exchangeable heavy-metal content of the soil cores from the most polluted sites. The increase in both the exchangeable and the total humus Cu, Ni and Zn concentrations in the 0.5 km soil cores during the experiment suggested that there were pools of accumulated metals in the thick litter layer on top of the humus.

Effect of litter removal on species richness and acidification of a mixed oak-pine woodland

Eutrophication of woodland ecosystems and disappearance of acidophilous species have often been observed in central and western Europe over recent decades. Considerable increase in air-borne nitrogen and sulphur has been invoked as responsible for these processes in most studies. Historic data indicate that for hundreds of years man removed litter and fodder from many woodlands in these areas. As a result, woodland soils became poorer and more acid than they were originally. Cessation of the removal of materials may resulted in soil enrichment and eutrophication of many woods. This hypothesis was tested in a 16-year litter removal experiment in an acidophilous mixed oak–pine wood in southern Poland. It was found that litter removal resulted in substantial impoverishment of soil. After 16 years soil of the litter removal plots contained significantly less P, Mg and Ca, and had a lower cation exchange capacity (CEC) in the epihumus subhorizon, and less Ca and a lower CEC in the humus and lessivage horizons than soil in the control plots. Vascular plant species and bryophytes colonized the litter removal plots much more frequently. Within 16 years species richness increased in the field layer of these plots, but abundance of dominant species and character of vegetation remained unchanged, while vegetation of the control plots changed from acidophilous to neutrophilous. Disappearance in the control plots of vascular plants species and mosses common in mixed woodlands was caused by thick litter layer which impeded seed germination and seedling development, and by competition of dominant species. The results obtained suggest that acidophilous vegetation in the field layer of the study wood was associated with material removal by man over a long time, and its eutrophication largely resulted from the cessation of traditional methods of management.

The influence of leaf litter layer thickness and seedlings size to spring and establishment of seedlings

The influence of leaf litter layer thickness and seedlings size to spring and establishment of seedlings

Forest floor water dynamics and root water uptake in four forest ecosystems in northwest Amazonia

A common feature in the undisturbed forest ecosystems in the Middle Caquetá (Colombian Amazonia) is the presence of a thick litter layer with abundant fine roots over mineral soils which are highly weathered and very low in available nutrients. In these situations, the litter layer or the forest floor (FF) may play an important role in the forest water balance, controlling water fluxes and nutrient cycling. We investigated the forest floor water dynamics in four representative forest ecosystems in the Middle Caquetá, Colombian Amazonia (tertiary sedimentary plain, high terrace, low terrace and the rarely inundated flood plain). Meteorological conditions were measured on hourly basis, FF water storage capacity, TDR water content in the FF and litterflow or FF drainage were measured daily over a two year period. A dynamic model was developed to simulate FF water storage, root water uptake and drainage to the mineral soil. The four-parameter model was calibrated applying a step-wise procedure. Analysis of collected data showed that FF water content was generally lower in the sedimentary plain than in the other ecosystems, whereas FF water storage was the highest due to a high FF mass. The average storage capacity per unit FF thickness was 1.23 mm cm −1. The sensitivity analysis and calibration of model parameters highlighted the relevance of storage capacity as the most sensitive parameter for the FF water dynamics. For the validation period, there is a good agreement between predicted and measured FF water storage and especially between predicted total drainage from the forest floor and measured litterflow. Model predictions indicate that water uptake from the FF’s during the validation period (190 days) differed between ecosystems, ranging from 15 to about 28% of the reference transpiration. This seems to be related to the fraction of fine roots in the FF in each ecosystem and to the water availability. On the other hand, total drainage to the mineral soil was very similar among ecosystems, except for the sedimentary plain, where total drainage was the lowest with about 87% of incoming throughfall.

Growth and development of ash (Fraxinus excelsior L.) seedlings on different humus types under a closed forest canopy

In Sep. 1995, in stands with ash and oak - beech, 116 two to four-year-old ash (Fraxinus excelsior L.) seedlings were selected in 12 plots in order to assess collar diameter growth, number of leaves, branches and growth flushes (episodes) per seedling, produced during the next two years. At the same time, 30 seedlings were selected to measure the root length and the root: shoot ratio. Seedlings were growing on different levels of soil fertility (humus types of typical mull, acid mull and mull moder), under a dense canopy (2.5% light intensity). The investigation reveals that, under the high shade of the stands, the length of roots as well as root: shoot ratio is greater on more fertile sites (typical mull and acid mull), than on less fertile site (mull moder). However, the mean root length of the seedlings in this deciduous forest never reaches 9 cm, presenting a limited growth on the various humus types and a rather low stability in the thick litter layer on the mull moder humus type. There are no significant differences (P &amp;lt; 0.05) in growth and foliage development of the seedlings produced on the different humus types. After 2 growing seasons, the mean diameter increment does not exceed 0.6 mm. The mean number of branches and leaves increases respectively with 1 and 4-5 units per seedling and that of the growth flushes varies from 2 to 3 units per seedling. As a whole under the full canopy, ash seedlings prove a very poor response to the humus types. The study suggests a proper felling in the closed canopy of the stand in order to encourage the growth and foliage development of the ash seedlings growing on the different humus types.

Soil organic matter accumulation and its implications for nitrogen mineralization and plant species composition during succession in coastal dune slacks

Vegetation and soil development during succession in coastal dune slacks on Terschelling island, the Netherlands, was investigated, by comparing neighbouring ecosystems on similar substrates that had been developing for 1, 5, 35 and 76 years since the vegetation and organic soil layer had been removed. In this successional sequence, soil organic matter accumulated rapidly due to the production of litter and dead roots. N mineralization was extremely low, increasing from 0.2 g m-2 yr-1 after 5 years to 0.8 g m-2 yr-1 after 76 years. It was accompanied by a decline in the pH (KCl) in the upper 10 cm of the soil from 6.8 to 4.4. Most of the above-ground biomass accumulated in the shrub species Oxycoccus macrocarpos and Salix repens. The 5- year-old plots harboured many plant species (18 species per 0.25 m2), but plant species diversity was much lower in the older plots. It is concluded that most changes in species composition and the decline in diversity occurred because early successional plant species were gradually outshaded by the thick litter layer and the accumulated shrub biomass.

The ectomycorrhizal flora of primary and secondary stands of Pinus sylvestris in relation to soil conditions and ectomycorrhizal succession

Abstract. Ectomycorrhizal species composition and sporocarp abundance in two 15–20‐yr old primary stands of Pinus sylvestris in the central part of the Netherlands was compared with those in two 16‐ and 27‐yr old secondary stands of P. sylvestris in the Northeast of the country. The trees of the primary stands were spontaneously seeded in a drifting sand area. Only thin litter and humus layers were present. The trees of the 16‐yr old secondary stand were planted on podzolic sandy soil and those of the 27‐yr old stand on non‐podzolic sandy soil. In both secondary stands thick litter and humus layers had developed. The litter and humus partly originated from former stands at the same sites and partly from the present stands. In the secondary stands the thick litter and humus layers and herb vegetation were removed (‘sod‐cutting’) in order to simulate the thin litter and humus layers in the primary stands. Control treatments were present. Surveys in 1991, 1992 and 1993 showed that sod‐cutting enhanced both abundance and diversity of ectomycorrhizal fungi. However, species richness and diversity were higher in the primary stands than in the secondary ones, also even in the sod‐cut plots. High species richness and diversity were associated with low concentrations of nitrogen and relatively high pH in the litter and humus layers, and in the mineral soil.