Pinus Sylvestris Seedlings Research Articles

Root architecture might account for contrasting establishment success of Pseudotsuga menziesii var. menziesii and Pinus sylvestris in Central Europe under dry conditions

Pinus sylvestris seedlings quickly expand their roots to deeper soil layers while Pseudotsuga menziesii concentrates its root system in the topsoil, thereby running the risk of desiccation during long dry spells, as indicated by lower survival after simulated summer drought. Pseudotsuga menziesii (Douglas-fir) is regarded as a promising species to maintain the productivity of Central European lowland forests given the projected increase of long dry spells. Will the species be able to regenerate from seed and spread outside plantations in a drier temperate Europe? We measured the relative growth rate, biomass allocation, root architecture, and phenotypic plasticity of Pseudotsuga menziesii seedlings sown in a common garden and grown under current precipitation and prolonged drought, respectively. The species’ competitive ability with respect to Pinus sylvestris L., the most drought-tolerant native conifer in Central Europe, was assessed during three growing seasons. Pinus sylvestris seedlings had higher relative growth rates than did Pseudotsuga menziesii seedlings, first in terms of aboveground biomass and later in terms of shoot height. This resulted in heavier and taller seedlings after three growing seasons under both moist and dry conditions. Shorter vertical roots corresponded with lower survival of Pseudotsuga menziesii seedlings under dry conditions. Fast root proliferation allows Pinus sylvestris seedlings to reach deeper water pools that are less rapidly depleted during transient drought. By contrast, the shallow root system might put Pseudotsuga menziesii seedlings at the risk of desiccation during prolonged dry spells.

Способность грибов естественных микробных сообществ к адаптации в загрязненной пестицидами почве лесного питомника при биоремедиации

Последствиями применения пестицидов для борьбы с сорными растениями в лесных питомниках Уральского региона являются загрязнение почвы и негативное влияние на сеянцы сосны обыкновенной (Pinus sylvestris). Самоочищения почвы лесного питомника, которое функционирует постоянно два-три десятилетия, быстрыми темпами не происходит, поэтому необходимо проведение специальных биоремедиационных мероприятий, ускоряющих процессы разложения остаточных количеств пестицидов. Биоремедиация почвы с использованием естественных микробиоценозов способствует очищению почвы и созданию благоприятных условий для роста сеянцев. В разложении пестицидов большую роль играют грибы-сапрофиты, способные трансформировать сложные пестициды и имеющие широкую специализацию. Кроме того, еще одним аспектом для изучения возможности сохранения грибных микроорганизмов из естественных насаждений в агрокультурной почве, предназначенной для выращивания сеянцев хвойных пород, является то, что условия роста сеянцев в питомнике, где многолетние обработки пестицидами и удобрениями влияют на специализированный грибной фон, будут улучшены при внесении и успешной адаптации грибов, способных образовывать микоризу. Показано, что при отборе природных комплексов микроорганизмов из насаждений разного типа и переносе их в условия лесного питомника грибы, входящие в них, имеют разную степень сохранения в почве. Наблюдение за изменением численности грибов в трех полевых опытах показало, что способностью более успешно приживаться в почве лесного питомника при выращивании сеянцев сосны обыкновенной обладают грибные комплексы лесной подстилки, взятые из березового и смешанного по породному составу насаждений.

High-Throughput Sequencing Shows High Fungal Diversity and Community Segregation in the Rhizospheres of Container-Grown Conifer Seedlings

Forest nurseries in Sweden produce ca. 360 million seedlings of Pinus sylvestris L. and Picea abies (L.) Karst. annually. Fungi represent the largest microbial component in rhizospheres and may significantly affect health and, consequently, quality of the seedlings. The aim of this study was to assess fungi focusing on pathogens in roots and the sphagnum peat growth substrate of healthy-looking P. sylvestris and P. abies seedlings from nine forest nurseries situated in northern, central and southern regions of Sweden. We hypothesized that nursery stock and the growth substrate can provide a venue for dissemination of fungal diseases. In each nursery and for each tree species, 100 seedlings with the growth substrate were collected during the dormant period. DNA was isolated from parts of root systems and from samples of the growth substrate, amplified using internal transcribed spacer of rDNA as a marker and 454-sequenced. Clustering at 98.5% similarity of 169,844 high-quality sequences resulted in 619 non-singleton fungal taxa. Although results showed that management practices in forest nurseries generally give a healthy stock, latent establishment of pathogenic fungi in both roots and the growth substrate supported the hypothesis. Furthermore, seedling roots and the growth substrate were inhabited by distinct communities of fungi, and lifestyles of these fungi largely determined community segregation into particular ecological niche.

毛乌素沙地优势灌丛对两种松树幼苗的保育作用

PDF HTML阅读 XML下载 导出引用 引用提醒 毛乌素沙地优势灌丛对两种松树幼苗的保育作用 DOI: 10.5846/stxb201505271061 作者: 作者单位: 陕西师范大学生命科学学院;榆林学院生命科学学院,陕西师范大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 陕西省教育厅专项科研计划资助项目（09JK839）；榆林市科技计划资助项目（2015CXY-03） Nurse effects of dominant shrubs on the seedlings of two Pinus species in the mu us sandy land in Northwest China Author: Affiliation: College of Life Sciences, Shaanxi Normal University;College of Life Sciences, Yulin University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:选择毛乌素沙地优势灌丛柠条（Caragana intermedia）、紫穗槐（Amorpha fruticosa）和沙柳（Salix psammophila）作为保育植物，选择2年生油松（Pinus tabulaeformis）和樟子松（Pinus sylvestris）幼苗作为目标植物，将其分别种植在开阔地、柠条、紫穗槐和沙柳4种微生境下，连续3a监测油松和樟子松幼苗的存活和生长动态，从而确定毛乌素沙地优势灌丛是否对植物幼苗的定居有促进作用。结果表明：柠条、紫穗槐和沙柳冠层下光照强度、大气温度和土壤温度都显著低于开阔地，致使土壤湿度增高，油松幼苗总存活率均显著高于开阔地，而樟子松幼苗总存活率仅紫穗槐冠层下显著高于开阔地（P < 0.05）。紫穗槐冠层下油松和樟子松幼苗总存活率均最高（P < 0.05），外来种紫穗槐可选为保育植物。保育灌丛下松树幼苗的主枝生长良好，并未受到抑制，但第1年主枝生长长度最小。光照强度和土壤湿度是决定主枝生长长度的重要因素。保育灌丛高度和冠幅面积与油松和樟子松幼苗存活率呈显著正相关（P < 0.05）。固氮灌丛（紫穗槐和柠条）对松树幼苗存活有持续的促进作用，但柠条冠幅结构紧密，可能因为对光的竞争，减弱了促进作用。沙柳灌丛下松树幼苗的存活率较低。油松幼苗具有一定程度的耐阴性，樟子松幼苗喜光性强，保育灌丛下油松幼苗存活率显著高于樟子松幼苗（P < 0.05）。总的来说，保育灌丛对松树幼苗的定居有促进作用，保育植物技术可作为一种有效的恢复措施，应用在毛乌素沙地的植被恢复中来。但是，保育灌丛的选择要考虑是本土种或外来种，以及灌丛的高度、冠幅大小、冠幅结构和化学效应，恢复物种的选择要考虑其自身的生物学特性及其与保育植物的相互作用。 Abstract:Over-grazing, mining, and inappropriate agricultural management practices combined with repeated drought events in the Mu Us sandy land in northern part of Shaanxi, Northwest China, have caused severe desertification. This landscape-scale degradation has significantly declined the possibility of natural ecosystem recovery. These conditions warrant ecological restoration of these areas to allow the re-development of sustainable ecosystems. Seedling establishment is the most crucial stage in a restoration project. In the Mu Us sandy land, restoration efforts might have been largely limited owing to the soil moisture deficiency, temperature fluctuations, high light intensities, low soil fertility, competition, allelopathy, herbivory, and wind. Several restoration techniques have long been used to alleviate these problems; however, their application has been restricted by low seedling and plant survival as well as high cost. Thus, developing novel, low-cost, and efficient restoration techniques is necessary. Plant-plant interaction effects provided by nurse plants can significantly increase or decrease the seed germination rates and establishment of seedlings under their canopies. Therefore, this study primarily aimed to determine the ability of shrubs to be used as a restoration tool in the Mu Us sandy land. Two-year-old seedlings of Pinus tabulaeformis and Pinus sylvestris were planted under the canopies of three shrub species (Caragana intermedia, Amorpha fruticosa, and Salix psammophila) or in open areas with no shrubs as a control; the objective was to determine whether the presence of shrubs facilitated the establishment of pine seedlings, which was assessed three times over three consecutive growing seasons, in the Mu Us sandy land. The height and canopy spatial area of shrubs were measured. The microclimate conditions (light intensity, air and soil temperatures, as well as soil moisture) were recorded in the four microhabitats, that is, under the canopy of each of the three shrubs and in areas without the shrubs (control). The near-surface light intensity as well as air and soil temperatures were lower under the shrubs, which led to higher soil moisture; because of these conditions, the survival rates of P. tabulaeformis seedlings growing under the canopy of the shrub species were higher than those of the seedlings growing in the control area (P < 0.05). However, the survival rates of P. sylvestris seedlings were higher only under the canopy of A. fruticosa (P < 0.05). The survival rates of P. tabulaeformis and P. sylvestris seedlings were the highest under the canopy of A. fruticosa (P < 0.05). Thus, the exotic species, A. fruticosa, could be used successfully as a nurse plant. Increased plant height and canopy area of nurse shrubs might improve the establishment of pine seedlings. The leguminous shrubs (C. intermedia and A. fruticosa) showed continuous facilitation of seedling establishment during moderate drought stress (summers of 2012, 2013, and 2014), but the presence of a dense and small shrub, C. intermedia, reduced the rate of seedling establishment possibly because of the competition for light. In 2012, S. psammophila also facilitated seedling establishment, but an unknown effect led to a high mortality rate for seedlings growing under their canopy. A noteworthy finding was that the growth of the two pine species was not inhibited when they were planted under the three shrubs. Pine seedlings had the shortest leader shoot lengths in 2012, with light intensity and soil moisture as important factors that controlled their length. The shade-tolerant species, P. tabulaeformis, had a higher seedling survival rate than that of P. sylvestris. In conclusion, nurse-shrub facilitation can be used as an effective restoration strategy in the Mu Us sandy land. However, the successful use of shrubs as nurse plants depends on their origin and morphological characteristics and ecological effects; the selection of target species depends on their tolerance of shade and their interaction with nurse plants. 参考文献 相似文献 引证文献

Interactive effects of juvenile defoliation, light conditions, and interspecific competition on growth and ectomycorrhizal colonization of Fagus sylvatica and Pinus sylvestris seedlings.

Seedlings of forest tree species are exposed to a number of abiotic (organ loss or damage, light shortage) and biotic (interspecific competition) stress factors, which may lead to an inhibition of growth and reproduction and, eventually, to plant death. Growth of the host and its mycorrhizal symbiont is often closely linked, and hence, host damage may negatively affect the symbiont. We designed a pot experiment to study the response of light-demanding Pinus sylvestris and shade-tolerant Fagus sylvatica seedlings to a set of abiotic and biotic stresses and subsequent effects on ectomycorrhizal (ECM) root tip colonization, seedling biomass, and leaf nitrogen content. The light regime had a more pronounced effect on ECM colonization than did juvenile damage. The interspecific competition resulted in higher ECM root tip abundance for Pinus, but this effect was insignificant in Fagus. Low light and interspecific competition resulted in lower seedling biomass compared to high light, and the effect of the latter was partially masked by high light. Leaf nitrogen responded differently in Fagus and Pinus when they grew in interspecific competition. Our results indicated that for both light-demanding (Pinus) and shade-tolerant (Fagus) species, the light environment was a major factor affecting seedling growth and ECM root tip abundance. The light conditions favorable for the growth of seedlings may to some extent compensate for the harmful effects of juvenile organ loss or damage and interspecific competition.

Herbivory and seedling establishment in Pyrenean forests: Influence of micro- and meso-habitat factors on browsing pressure

Browsing damage is among the most determinant factors that limit the establishment of tree seedlings in forests. In some areas, this process leads to massive mortalities that can reduce or even completely prevent the regeneration of some tree species. Mediterranean mountain forests have undergone during the last decades important changes in land-uses that have significantly altered the type and abundance of herbivore populations. In this study we assessed the impact of current grazing conditions in forest regeneration using a set of experimental plantations established in the Eastern Pyrenees in areas visited by domestic livestock (cattle and horses) and wild ungulates (mainly roe deer and chamois). We analyzed during 4years the role of seedling species and size, mesohabitat (elevation and type of forest cover) and microhabitat (herbaceous cover, distance to shrub, and light availability) on the browsing-induced mortality of more than 500 seedlings of Pinus sylvestris, Pinus uncinata, Betula pendula and Abies alba, the most common tree species in the study area. Browsing-induced mortality for the three conifer species was much lower (<15%) than the one observed for B. pendula (>40%) and depended on both microhabitat – mainly on the distance to protective elements such as shrubs; and mesohabitat, with an interaction between the elevational belt (site) and the type of forest cover (gaps vs. understory). In the subalpine belt, browsing on A. alba and P. uncinata was higher during summer at plots located in the forest understory whereas, during winter, it was higher at plots located in gaps. The study shows that both mesohabitat and microhabitat can exert an effect on the patterns of plant damage by herbivores, providing useful information to adapt forest management in areas particularly exposed to them.

Positive shrub–tree interactions facilitate woody encroachment in boreal peatlands

Summary Boreal ecosystems are warming roughly twice as fast as the global average, resulting in woody expansion that could further speed up the climate warming. Boreal peatbogs are waterlogged systems that store more than 30% of the global soil carbon. Facilitative effects of shrubs and trees on the establishment of new individuals could increase tree cover with profound consequences for the structure and functioning of boreal peatbogs, carbon sequestration and climate. We conducted two field experiments in boreal peatbogs to assess the mechanisms that explain tree seedling recruitment and to estimate the strength of positive feedbacks between shrubs and trees. We planted seeds and seedlings of Pinus sylvestris in microsites with contrasting water‐tables and woody cover and manipulated both shrub canopy and root competition. We monitored seedling emergence, growth and survival for up to four growing seasons and assessed how seedling responses related to abiotic and biotic conditions. We found that tree recruitment is more successful in drier topographical microsites with deeper water‐tables. On these hummocks, shrubs have both positive and negative effects on tree seedling establishment. Shrub cover improved tree seedling condition, growth and survival during the warmest growing season. In turn, higher tree basal area correlates positively with soil nutrient availability, shrub biomass and abundance of tree juveniles. Synthesis. Our results suggest that shrubs facilitate tree colonization of peatbogs which further increases shrub growth. These facilitative effects seem to be stronger under warmer conditions suggesting that a higher frequency of warmer and dry summers may lead to stronger positive interactions between shrubs and trees that could eventually facilitate a shift from moss to tree‐dominated systems.

Short-Term Influence of Clinker Dust and Wood Ash on Macronutrients and Growth in Norway Spruce (Picea abies) and Scots Pine (Pinus sylvestris) Seedlings

The effects of clinker dust and wood ash on Norway spruce and Scots pine seedlings were compared in buried pots. Clinker dust (0.5 kg m−2) and wood ash (0.5 kg m−2) were applied to the surface of a nutrient-poor mineral soil. In the second year, the increase in soil pH by the dust and ash were larger than in the first year. Both alkaline treatments caused a large increase in the needle potassium (K) concentration. An excess of soil K relative to magnesium (Mg) was observed by decreased Mg concentration in needles shortly after treatment. However, Mg concentration in needles stayed in the sufficiency range. Current results confirmed earlier findings that despite a positive effect on base cation nutrition, wood ash has a low potential for increasing the biomass of forest stands on mineral soils due to the N limitation in these soils.

Ectomycorrhizal fungi in association with Pinus sylvestris seedlings promote soil aggregation and soil water repellency

Research on fungal effects on soil aggregation has been heavily biased towards arbuscular mycorrhiza. Even though ectomycorrhizal fungi are thought to be as important as arbuscular mycorrhizal fungi and saprotrophic fungi in contributing to soil structure, there are few experimental studies on this topic. Here we quantified how nine ectomycorrhizal fungi in association with Pinus sylvestris seedlings affected soil aggregation and soil water repellency (SWR) of a sandy loamy soil. Water-stable aggregates (>0.25 mm diameter) increased by 6–12% when plants were associated with Laccaria bicolor, Laccaria laccata, Lactarius theiogalus, Paxillus involutus and Suillus bovinus. Mean weight diameter (MWD) of soil aggregates also increased, primarily in the 2–4 mm diameter size class. However, Suillus granulatus increased water-stable aggregates but not MWD, conversely Rhizopogon roseolus and Suillus luteus increased MWD but not water-stable aggregates. We also found Lt. theiogalus, R. roseolus and S. luteus promoted SWR. Furthermore, hyphal length was weakly correlated with MWD (R = 0.27, P < 0.05), especially with aggregate mass in the 2–4 mm size class (R = 0.32, P < 0.05). However, we could not identify clear soil effects (soil pH, soil protein content) serving as explanation for either soil aggregation or SWR. Thus, we conclude that interactions between fungi and soil structure are a species-dependent processes based on yet to be characterized fungal traits. Our results have added further evidence from direct experimentation that ectomycorrhizal fungi can contribute to soil aggregation and SWR.

Drought resistance of Pinus sylvestris seedlings conferred by plastic root architecture rather than ectomycorrhizal colonisation

Increased summer drought is considered as a threat to the regeneration of Pinus sylvestris in the Central Alps. To a certain degree, seedlings are able to mitigate negative effects of drought by altering root/shoot ratios. But, seedlings may also enhance access to water and nutrients by cooperation with ectomycorrhizal fungi. We tested the importance of both mechanisms for drought resistance of P. sylvestris seedlings during early establishment and assessed whether differences occur between topsoil and deeper soil layers. Biomass allocation and colonisation of fine roots by ectomycorrhizal fungi were assessed in seedlings grown for 6 months in a common garden under different precipitation scenarios: constant drought (March–September), summer drought (June–September), and wet conditions. Root/shoot ratios increased from 0.6 under wet conditions to 0.8 under drought conditions, irrespective of the onset of the drought (March vs. June). In both drought scenarios, seedlings had shorter roots in the topsoil, increased the number of root tips per root length in both soil layers, but did not alter the colonisation rate of root tips by ectomycorrhizal fungi. We conclude that plasticity in root architecture is an important mechanism for drought resistance of P. sylvestris during early seedling establishment.

Influence of substrate compaction in nursery containers on the growth of Scots pine (Pinus sylvestris L.) seedlings

Abstract The paper presents research on influence of nursery soil compaction, composed of peat (90%) and perlite (10%), on the growth of seedlings of Pinus sylvestris grown in containers. Polyethylene nursery are containers used for the seedling production. These containers were filled with three different densities of the peat and perlite substrate (0.3, 0.5 and 0.7 g·cm-3). During the experiment, nursery containers were initially placed in a plastic tent for a period of two months, and then for three months further months in an open nursery field. Growth measurements for individual plants were the length of shoots and the root system, root collar diameter, root and shoot dry weight and photosynthetic rate. There was a relationship between the extent of compaction of the soil substrate and all analyzed growth parameters of seedlings. A more compact substrate adversely affected on the number of grown seedlings and their length but positively influenced the dry mass of pine seedlings.

Root-associated fungi of healthy-looking Pinus sylvestris and Picea abies seedlings in Swedish forest nurseries

The aim of this study was to assess fungal communities in roots of healthy-looking Pinus sylvestris L. and Picea abies (L.) Karst. seedlings in nine forest nurseries in Sweden using a combination of traditional culturing and direct sequencing of internal transcribed spacer of fungal ribosomal RNA (ITS rRNA) from the roots. Culturing from 1800 surface-sterilised root segments resulted in 2387 fungal cultures representing 42 different taxa. Direct sequencing from 180 root segments resulted in 119 ITS rRNA sequences representing 25 different taxa. In total, 55 different fungal taxa were detected using both methods. Although direct sequencing was more efficient than culturing in detecting different fungal taxa, both methods provided complementary information about fungal communities in roots since each detected rather different groups of fungi. The most dominant taxa detected by culturing were Trichoderma viride Pers. (19.5%), Phoma mucivora Davey & Currah (19.1%), Phialocephala fortinii Wang & Wilcox (17.4%) and Meliniomyces variabilis Hambl. & Sigler (10.2%), while Thelephora terrestris Ehrh. (26.1%), Unidentified sp. NS126 (25.2%) and Heliotales sp. C20 (10.1%) were most commonly detected by direct sequencing. In conclusion, results showed that forest nurseries in Sweden harbour diverse communities of fungi associated with the roots of healthy-looking P. sylvestris and P. abies seedlings. Although fungal communities were often dominated by saprotrophs and endophytes, several facultative pathogens were also detected indicating that under suitable conditions they may be a potential threat to the plants.

Survival and strobili production in topgrafted scions from young Pinus sylvestris seedlings

Reducing the generation turnover increases the genetic gain in a breeding programme. Topgrafting, new genetic material being grafted into the crown of ramets of reproductive mature trees, can deliver this aim since it is able to induce strobili production in young material of conifers. To this end, I studied the effect of scion age (seedlings of 4–6 years from seed) on topgraft vitality/survival, and female and male strobili production in Pinus sylvestris (L.) over 5 years. The seedlings' growing environment prior to topgrafting had a significant impact on topgraft vitality, with more vital topgrafts obtained from potted seedlings than from seedlings grown in raised nursery beds. However, the growth environment had no clear effect on female or male strobili production. In the second year, after grafting up to 76% of the topgrafted seedlings had female strobili. Vitality increased with age of the seedling from which the scions were collected, but differences in both female and male strobili production were only marginal. The position of the topgraft within the interstock crown influenced both vitality and strobili production, with higher vitality and greater male strobili production in low positions and greater female strobili production in high positions. Based on these results, breeders should perform topgrafting as soon as the seedlings have enough scions for planned crossing activities.

The comparisons between Picea abies and Pinus sylvestris in respect of lead phytoremediation potential

Nowadays, heavy metals pollution has made some environmental problems in the biosphere. The technique of phytoremediation is using the plants in removing these environmental pollutants .In this study, Forty five three- year old seedlings of Pinus sylvestris L and Picea abies (L.) Karst were planted in plastic pots that there were put in open area. For each species, fifteen pots were treated with three lead concentrations 0 (control), 800, and 1600 mg Kg-1. At the end of October the amounts of Pb in roots, stems, leaves and soil were measured using ICP. Random data in 15 repetitions were analyzed using one-way analysis of variance. The results indicated that unlike Picea abies, P. sylvestris was suitable as a lead phytoremediation plant. In 800 mg kg-1 the Pb accumulation in both parts of P. sylvestris roots and stems while in high concentration 1600 mg kg-1, maximum Pb accumulation was observed in roots and leaves. In the species Picea abies we didn't observe any significant differences in Pb absorption between treatment and control up to 800 ppm, while in 1600 ppm Pb concentration was transported to stems and leaves. Comparison between the remaining Pb in different treatment levels of each horizontal layer of soil in P.sylvestris seedlings showed there was a significant difference only in first layer of soil. In P.abies there were significantly differences in horizons first and third. In conclusion, Pinus sylvestris is more suitable for Pb phytoremediation than Picea abies. * Corresponding Author: Seyyedeh Mahdokht Maddah  s.m.maddah@iausr.ac.ir

Effects of pre-harvest fertilization and subsequent soil scarification on the growth of planted Pinus sylvestris seedlings and ground vegetation after clear-felling

Fertilization and scarification are both performed to increase tree production at different stages of forest rotation periods. In this study, the effects of previous nitrogen fertilizations and scarification after clear felling on planted Pinus sylvestris L. seedlings and ground vegetation were investigated. Two fertilization experiments established around 1980 were harvested in 2006, after which the plots were scarified by disc trenching and re-planted. The plots had been repeatedly fertilized over a 20-year period before harvesting, with total N doses of 0, 450, 900 or 1800 kg N ha -1. After five growing seasons, the growth, survival and nutrient contents of the seedlings were measured, and ground vegetation was collected to estimate its biomass and nutrient content. Pre-harvest fertilization alone had only minor effects on the results, but scarification increased both the survival and growth of the planted seedlings. However, without scarification, seedling mortality increased with increasing fertilization intensity. The ground vegetation biomass was higher in plots without scarification, but the total biomass of seedlings and ground vegetation was similar in all treatments. Scarification thus favored seedling growth at the expense of ground vegetation. Only a few effects on nutrient content were found, but there were no signs of nutrient imbalance in any of the treatments. At higher levels of fertilization, the K:N ratio in the seedlings decreased while the K content in the ground vegetation increased. Overall, scarification had a greater impact than pre-harvest fertilization on the planted seedlings and the ground vegetation.

Browsing by large herbivores on Scots pine (Pinus sylvestris) seedlings in mixture with ash (Fraxinus excelsior) or silver birch (Betula pendula)

Food selection by large herbivores occurs at a hierarchy of scales, for example landscape, patch or plant. Several hypotheses regarding food plant selection on patch or plant level have been developed. In this cafeteria-type design field experiment, conducted during one winter immediately after planting, we tested the effect of species mixture on browsing by large herbivores (mainly roe deer) on Scots pine seedlings in mixture with seedlings of ash (highly preferred) or silver birch (less preferred). Browsing on Scots pine was not affected by species mixture, neither in terms of the number of browsed pines nor browsing intensity. Instead, browsed biomass was positively and significantly correlated to the total biomass available for browsing. Also, there were differences due to species, with ash being most browsed (44.6%), followed by Scots pine (18.9%) and silver birch (11.6%). Browsed biomass per browsed seedling, however, was largest for Scots pine. In addition, browsed seedlings were initially taller compared to unbrowsed seedlings for all species. The main management implication in this study is that the species mixture did not influence large herbivore browsing on Scots pine seedlings. Hence, removing or discouraging more (or less) attractive browse species in early stages of pine regeneration activities seems unnecessary from the point of large herbivore browsing.

Growth response of drought-stressed Pinus sylvestris seedlings to single- and multi-species inoculation with ectomycorrhizal fungi.

Many trees species form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve nutrient and water acquisition of their host. Until now it is unclear whether the species richness of ECM fungi is beneficial for tree seedling performance, be it during moist conditions or drought. We performed a pot experiment using Pinus sylvestris seedlings inoculated with four selected ECM fungi (Cenococcum geophilum, Paxillus involutus, Rhizopogon roseolus and Suillus granulatus) to investigate (i) whether these four ECM fungi, in monoculture or in species mixtures, affect growth of P. sylvestris seedlings, and (ii) whether this effect can be attributed to species number per se or to species identity. Two different watering regimes (moist vs. dry) were applied to examine the context-dependency of the results. Additionally, we assessed the activity of eight extracellular enzymes in the root tips. Shoot growth was enhanced in the presence of S. granulatus, but not by any other ECM fungal species. The positive effect of S. granulatus on shoot growth was more pronounced under moist (threefold increase) than under dry conditions (twofold increase), indicating that the investigated ECM fungi did not provide additional support during drought stress. The activity of secreted extracellular enzymes was higher in S. granulatus than in any other species. In conclusion, our findings suggest that ECM fungal species composition may affect seedling performance in terms of aboveground biomass.

Effect of raw humus under two adult Scots pine stands on ectomycorrhization, nutritional status, nitrogen uptake, phosphorus uptake and growth of Pinus sylvestris seedlings

Ectomycorrhiza (EM) formation improves tree growth and nutrient acquisition, particularly that of nitrogen (N). Few studies have coupled the effects of naturally occurring EM morphotypes to the nutrition of host trees. To investigate this, pine seedlings were grown on raw humus substrates collected at two forest sites, R2 and R3. Ectomycorrhiza morphotypes were identified, and their respective N uptake rates from organic (2-(13)C, (15)N-glycine) and inorganic ((15)NH(4)Cl, Na(15)NO(3), (15)NH(4)NO(3), NH(4)(15)NO(3)) sources as well as their phosphate uptake rates were determined. Subsequently, the growth and nutritional status of the seedlings were analyzed. Two dominant EM morphotypes displayed significantly different mycorrhization rates in the two substrates. Rhizopogon luteolus Fr. (RL) was dominant in R2 and Suillus bovinus (Pers.) Kuntze (SB) was dominant in R3. (15)N uptake of RL EM was at all times higher than that of SB EM. Phosphate uptake rates by the EM morphotypes did not differ significantly. The number of RL EM correlated negatively and the number of SB EM correlated positively with pine growth rate. Increased arginine concentrations and critical P/N ratios in needles indicated nutrient imbalances of pine seedlings from humus R2, predominantly mycorrhizal with RL. We conclude that different N supply in raw humus under Scots pine stands can induce shifts in the EM frequency of pine seedlings, and this may lead to EM formation by fungal strains with different ability to support tree growth.

High resolution characterization of ectomycorrhizal fungal-mineral interactions in axenic microcosm experiments

Microcosms with Pinus sylvestris seedlings in symbiosis with the fungus mycorrhizal Paxillus involutus were established, and atomic force microscopy (AFM) was used to characterise plant photosynthate-driven fungal interactions with mineral surfaces. Comparison of images of the same area of the minerals before and after mycorrhizal fungal colonization showed extensive growth of hyphae on three different mineral surfaces – hornblende, biotite and chlorite. A layer of biological exudate, or biolayer, covered the entire mineral surface and was composed of globular features of diameter 10–80 nm, and the morphology of the biolayer differed among mineral types. Similar-sized components were found on the fungal hyphae, but with a more elongated profile. Biolayer and hyphae surfaces both appeared to be hydrophobic with the hyphal surfaces yielding higher maximal adhesive interactions and a wider range of values: the mean (± SE) adhesive forces were 2.63 ± 0.03 and 3.46 ± 0.18 nN for biolayer and hypha, respectively. The highest adhesion forces are preferentially localized at the hyphal surface above the Spitzenkorper region and close to the tip, with a mean interaction force in this locality of 5.24 ± 0.49 nN. Biolayer thickness was between 10 and 40 nm. The underlying mineral was easily broken up by the tip, in contrast to the native mineral. These observations of mineral surfaces colonised by mycorrhizal fungus demonstrate how fungal hyphae are able to form a layer of organic exudates, or biolayer, and its role in hyphal attachment and potential weathering of ferromagnesian silicates, which may supply nutrients to the plant.

Phenotypic plasticity facilitates resistance to climate change in a highly variable environment

Increased summer drought will exacerbate the regeneration of many tree species at their lower latitudinal and altitudinal distribution limits. In vulnerable habitats, introduction of more drought-tolerant provenances or species is currently considered to accelerate tree species migration and facilitate forest persistence. Trade-offs between drought adaptation and growth plasticity might, however, limit the effectiveness of assisted migration, especially if introductions focus on provenances or species from different climatic regions. We tested in a common garden experiment the performance of Pinus sylvestris seedlings from the continental Central Alps under increased temperatures and extended spring and/or summer drought, and compared seedling emergence, survival and biomass allocation to that of P. sylvestris and closely related Pinus nigra from a Mediterranean seed source. Soil heating had only minor effects on seedling performance but high spring precipitation doubled the number of continental P. sylvestris seedlings present after the summer drought. At the same time, twice as many seedlings of the Mediterranean than the continental P. sylvestris provenance were present, which was due to both higher emergence and lower mortality under dry conditions. Both P. sylvestris provenances allocated similar amounts of biomass to roots when grown under low summer precipitation. Mediterranean seedlings, however, revealed lower phenotypic plasticity than continental seedlings under high precipitation, which might limit their competitive ability in continental Alpine forests in non-drought years. By contrast, high variability in the response of individual seedlings to summer drought indicates the potential of continental P. sylvestris provenances to adapt to changing environmental conditions.