Growth and Mycorrhizal Community Structure ofPinus sylvestrisSeedlings following the Addition of Forest Litter

Abstract

We report the effects of pine and oak litter on species composition and diversity of mycorrhizal fungi colonizing 2-year-old Pinus sylvestris L. seedlings grown in a bare-root nursery in Lithuania. A layer of pine or oak litter was placed on the surface of the nursery bed soil to mimic natural litter cover. Oak litter amendment appeared to be most favorable for seedling survival, with a 73% survival rate, in contrast to the untreated mineral bed soil (44%). The concentrations of total N, P, K, Ca, and Mg were higher in oak growth medium than in pine growth medium. Relative to the control (pH 6.1), the pH was lower in pine growth medium (5.8) and higher in oak growth medium (6.3). There were also twofold and threefold increases in the C content of growth medium with the addition of pine and oak litter, respectively. Among seven mycorrhizal morphotypes, eight different mycorrhizal taxa were identified: Suillus luteus, Suillus variegatus, Wilcoxina mikolae, a Tuber sp., a Tomentella sp., Cenococcum geophilum, Amphinema byssoides, and one unidentified ectomycorrhizal symbiont. Forest litter addition affected the relative abundance of mycorrhizal symbionts more than their overall representation. This was more pronounced for pine litter than for oak litter, with 40% and 25% increases in the abundance of suilloid mycorrhizae, respectively. Our findings provide preliminary evidence that changes in the supply of organic matter through litter manipulation may have far-reaching effects on the chemistry of soil, thus influencing the growth and survival of Scots pine seedlings and their mycorrhizal communities.In the boreal zone, Scots pine (Pinus sylvestris L.) is widely planted for reforestation and afforestation of marginally economic agricultural land (25,26). For example, in Lithuania 76.4 million seedlings are planted each year; approximately 20% of these are Scots pine (36). An important factor in the performance of outplanted conifers is the association of plant roots with ectomycorrhizal (ECM) fungi (7, 37). ECM fungi are essential for nutrient acquisition and plant protection against root pathogens and drought stress (51). Pinus species are dependent on symbiosis to develop optimally under natural conditions (40).ECM fungi naturally established in nurseries are diverse, and their establishment depends on several factors, including host species relationships, sylvicultural practices, and nursery conditions (11, 35). Early differences in ECM colonization of tree seedlings may affect their performance after outplanting to forest sites (30). The application of forest litter to nurserygrown seedlings can be useful in enhancing ECM colonization and the field performance of outplanted seedlings (8, 47).In forest nurseries, attempts have been made to use various germination media instead of mineral soils. The Dunemann system of nursery practice demonstrated that spruce needles are a good medium for raising conifer seedlings (24). A series of experiments following the Dunemann scheme showed that germination, growth, and sur...

Forest litter as the mulch improving growth and ectomycorrhizal diversity of bare-root Scots pine (Pinus sylvestris) seedlings

“…Similar sampling completeness is noted in many other studies as reported by Dickie (2007). All examined mycorrhizas are ubiquitous and the identity of EM fungi composing these morphotypes was established by molecular methods in bare-root forest nurseries in a previous study (Rudawska et al 2001, Iwanski et al 2006, Aučina et al 2007, Leski et al 2010. Our results indicate that the widespread W. mikolae mycorrhizae at the initial stages of seedling growth is better adapted to nursery conditions than other ECM fungal taxa, such as M. bicolor, C. geophilum, Atheliaceae sp., S. luteus, L. laccata, and unidentified Ascomycetes.…”

“…Forest floor as an appropriate rooting medium for planted tree seedlings has also been noted by other authors (Balisky et al 1995, Hallsby 1995, McMinn 1982, Sutton 1993. Also in our previous study performed on two-years-old Scots pine seedlings, height and survival of seedlings were considerably improved by natural pine and oak litter cover on the surface of the nursery bed soil (Aučina et al 2007). Although the foliar nutrient composition of the pine seedlings in our study was not examined, we presumed that the enhanced seedling growth and higher biomass parameters (in pine litter only) might be (at least partly) related to the nutritional effect of the tested forest litters.…”

“…However, data regarding the effect of litter addition on ECM colonization and community structure are inconsistent. Both positive and negative effects of forest litter amendment have been observed in different experiments (Brearley et al 2003, Cullings et al 2003, Aučina et al 2007). …”

“…Soil samples from growth medium were mixed, dried at 40 °C, and soil carbon content and the nutrient composition (N, P, K, Mg and Ca) were determined in four repetitions. A complete description of the growth medium analysis is presented in our earlier paper (Aučina et al 2007). …”

“…In our previous experiment, natural forest litter cover on the surface of the nursery bed soil considerably improved two years old Scots pine seedling survival and positively affected their ECM communities (Aučina et al 2007). However, in present forestry practice the use of two years old seedlings tends to be rare and the use of one-year-old seedlings, especially on dry sites, is becoming increasingly frequent (Barzdajn 2009).…”