The return of an experimentally N-saturated boreal forest to an N-limited state: observations on the soil microbial community structure,biotic N retention capacity and gross N mineralisation

Background and aims

To find out how N-saturated forests can return to an N-limited state, we examined the recovery of biotic N sinks under decreasing N supply.

Methods

. We studied a 40-year-old experiment in Pinus sylvestris forest, with control plots, N0, three N treatments, N1-N3, of which N3 was stopped after 20 years, allowing observation of recovery.

Results

In N3, the N concentration in foliage was still slightly elevated, but the N uptake capacity of ectomycorrhizal (ECM) roots in N3 was no longer lower than in N0. Per area the amount of a biomarker for fungi, here mainly attributed ECM, was higher in N3 and N0 than in N1 and N2. Retention of labeled ¹⁵NH₄ ⁺ by the soil was greater in the control (99 %) and N3 (86 %), than in N1 (45 %) and N2 (29 %); we ascribe these differences to biotic retention because cation exchange capacity did not vary. Gross N mineralisation and retention of N correlated, negatively and positively, respectively, with abundance of ECM fungal biomarker.

Conclusions

. The results suggest a key role for ECM fungi in regulating the N cycle. We propose, in accordance with plant C allocation theory, that recovery is driven by increased tree below-ground C allocation to ECM roots and fungi.     

A review of Turkish saproxylic beetles from the European Red List

The conservation of beetles that depend on dying or dead wood (i.e. saproxylic), has received a great deal of attention in many parts of the world in recent years. Human activities such as urbanization and logging, and their results, e.g. global warming, destroy natural ecosystems and threaten unusual species such as Lucanus cervus (L. 1758), Rosalia alpina (L. 1758), Limoniscus violaceus (Müller 1821) and Osmoderma eremita (Scopoli 1763). Attempts have been made to conserve the habitats upon which these species depend. Although represented by a large number of species, saproxylic beetles in Turkey have not received much attention. Although some Turkish studies have acknowledged their value, comprehensive investigations of these species are very limited. The aim of this study is to make a list, from the literature, of the species that are endangered in Europe and found in Turkey, to highlight the importance of these species. The research includes 151 saproxylic beetle species belonging to the families Bostrichidae, Cerambycidae, Elateridae, Eucnemidae, Scarabaeidae, Euchiridae, Lucanidae and Mycetophagidae. The list of Turkish saproxylic beetles was prepared using the European Red List of Saproxylic Beetles. Information is provided about the IUCN Red List category in Europe, the locations of the species in Turkey, and their global geographic range. We gathered all data about these species from the international literature. Furthermore, we also include in the list certain species whose locations are not specified, but which inhabit Turkey. We obtained their records from some catalogs in Turkey. In addition to the list, we prepared three distribution maps for Turkey. The maps show distribution in Turkey of some species in the Endangered, Vulnerable and Near Threatened categories in the European Red List. It is expected that this study will lead to comprehensive studies on saproxylic beetles from Turkey.     

Nutrients and disturbance history in two Plantago species: maternal effects as a clue for observed dichotomy between resprouting and seeding strategies

We assessed the role of nutrients and disturbance experienced by mothers (maternal effects) in the growth of progeny in a pot experiment using two Plantago species. Photosynthetic capacity, biomass allocation and fecundity were measured. Offspring of plants grown in nutrient poor conditions produced more leaves, spikes and longer leaves and in case of P. lanceolata , they had also higher photosynthetic capacity. The progeny of P. media mothers that had resprouted after disturbance was favored in nutrient poor conditions whereas the progeny of undisturbed plants was favored in nutrient rich conditions.
This study demonstrates that maternal effects may play a role in the success of either a seeding or a resprouting strategy in environments with different nutrient availability. Moreover, we showed that alteration of photosynthetic capacity, even during adult stages, is a mechanism through which maternal plants may impact their progeny.     

Clonal growth and sexual reproduction: tradeoffs and environmental constraints

Clonal growth confers a number of benefits on plants, but involves some costs as well. We examined whether seed reproduction is reduced in clonal plants due to these costs. Further, we investigated whether this relationship differs for species with optima at stressful or low‐productivity sites, as a possible indication that clonality acts as insurance against reduced seed reproduction in such conditions. We evaluated 472 species for which seed production per unit area had been determined, and employed this information together with data on seed mass, height at maturity, clonal traits and optimum habitat conditions (using Ellenberg indicator values). There was a strong hyperbolic relationship between seed output and seed mass, with a scaling coefficient of ?1, indicative of a simple tradeoff relationship. We performed analyses both with and without taking phylogeny into account. Reproductive output (i.e. the product of seed output and seed size) of was lower in clonal than in non‐clonal plants (in both with and without phylogeny incorporated in the analyses); within non‐clonal species, it was high in annuals and monocarpic plants relative to nonclonal perennials. Reproductive output was lower in clonal plants with extensive lateral spread. This may be due to lower mortality of such plants, which should favor reduced reproductive output, but direct resource tradeoff may also be involved. Reproductive output in all clonal and non‐clonal plants increased with the nutrient status and light level of the species’ optimum, and decreased with moisture. Because the proportion of clonal plants in vegetation is known to decrease along the same gradients, we can infer that as sexual reproduction becomes increasingly difficult in terms of these characteristics, clonal plants may capitalize on their capacity to bypass it. However, the relationships with habitat parameters disappeared in the phylogenetically corrected analysis, indicating that habitat preferences and reproductive output evolved together.     

Plastid transformation in greening scales of the onion bulb (Allium cepa,Alliaceae)

The greening of the upper part of the outerAllium cepa L. bulb scales, in particular along the vascular regions, is limited to the hypodermal cells in which typical leucoplasts are transformed to normal and functional chloroplasts. This process is light dependent and cannot afterwards be reversed or modified by darkness. The changes in fine structure are described and briefly discussed.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday and 55 years after the publication of his Grundriß der Cytologie.     

Regression analysis of the spontaneous spike activity of neurons in snail ganglia

Regression analysis of the spontaneous spike activity of neurons in Helix pomatia was carried out with the aim to establish the statistical parameters of this activity under constant experimental conditions and during longer time intervals. The activity of 38 randomly chosen neurons in visceral and parietal ganglia, penetrated by microelectrodes and activated either endogenously by pacemaker potentials or by synaptic inputs, was recorded during time intervals lasting from 20 min to 3 h. The main results of the statistical analyses are presented in the table where the parameters of both cell types are listed. The validity of the regression analysis applied here is discussed from the point of the possibility it offers for carrying on the data processing quickly and without applying complex calculating means. The results are also considered regarding the current interest of our research group.     

Vegetation of the <Emphasis Type="Italic">Hydrochari-Lemnete</Emphasis> and <Emphasis Type="Italic">Potametea</Emphasis> classes in the Danube-Tisza-Danube hydrosystem (Serbia)

Aquatic vegetation of Hydrochari-Lemnetea and Potametea classes in the Danube-Tisza-Danube hydrosystem (Hs DTD) was studied in 2009–2012, by applying the standard Braun-Blanquet method. The canal network vegetation comprises 14 associations, with Trapetum natantis and Ceratophylletum demersi being the most widely distributed. Hs DTD is also a habitat for several important endangered species, which serve as edificators of the following phytocenoses: Nymphaeetum albae, Nymphaeetum albo-luteae, Nymphoidetum peltatae, Trapetum natantis, Lemno-Spirodeletum, Salvinio-Spirodeletum polyrrhizae, Lemno-Utricularietum vulgaris, Potametum nodosi, Myriophyllo-Potametum and Najadetum marinae. In the studied vegetation, we also found an invasive phytocenosis Elodeetum canadensis that did not have an expanding tendency, and Ceratophyllo demersi-Vallisnerietum spiralis that had this tendency, which made monitoring its stands necessary. Physico-chemical analyses of water, conducted at localities in which the studied phytocenoses thrive, revealed that the development and distribution of most phytocenoses is closely linked with specific habitat conditions. Among the studied parameters, the most significant for the phytocenoses differentiation were: pH, alkalinity, COD-MnO₄, BOD₅, NO ₃ ^? , NO ₂ ^? , PO ₄ ^3? and the concentration of total phosphorus.