The afforestation of sites disturbed after coal mining has shown to be a favorite technique to restore all ecosystem functions. Leaf traits of trees used in restoration may substantially affect ...nutrient return decomposition rates in soil and thus, ecosystem development. The aim of the study was to compare seasonal changes between the individual tree species at two different sites focussing on seasonal changes of leaf biochemistry, elemental composition, and their role in nutrient return to the forest floor and nutrient cycling. Foliage and litterfall characteristics (specific leaf area (SLA), nutrients, phenolics, lignin, chlorophylls, and cellulose contents) were studied at two sites of the same age (25 years) with different tree species at post-mining sites at the Sokolov area around 50° 14′ 09 N and 12° 39′ 05 E (Czech Republic). The first two sites (unreclaimed) were left to spontaneous succession with a dominance of Betula pendula, Salix caprea, and Populus tremula. The second two sites (reclaimed) was land levelled and afforested by Alders (Alnus glutinosa, Alnus incana). The study showed that foliage quality and composition differed between individual tree species and between sites, especially in the contents of nitrogen (N), calcium (Ca), magnesium (Mg), potassium (K), and lignin concentration. Alder reclamation was most influenced by a symbiotic relationship with bacteria Frankia which support a high concentration of N in foliage and litterfall. However, the highest concentration of basic elements (Ca, Mg, K) was in foliage and litter of unreclaimed sites. A. incana had the highest content of lignin in foliage which increased steeply from August to September. Also, the content of lignin increased slightly in litterfall of unreclaimed sites during the vegetation season thought could have lead to slowing decomposition of litterfall and nutrient cycling in comparison to reclaimed sites.
•Foliage and litter of spontaneous regrowth and restored alder plantation differed.•Both types vegetation had similar content of chlorophyll and seasonal dynamics.•Alder foliage and litter have a higher N content.•Spontaneous regrowth foliage and litter has higher Ca, Mg, K.•Regrowth had a higher lignin content than Alder plantation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Rate of photosynthesis and related plant carbohydrate status are crucial factors affecting plant vigor. Sugars providing carbon and energy sources serve also as important signaling molecules ...governing plant growth and development through a complex regulatory network. These facts are often neglected when mixotrophic cultivation of plants in vitro is used, where artificial exogenous sugar supply hinders studies of metabolism as well as sugar‐driven developmental processes. We compared the growth, selected gas‐exchange parameters and sugar metabolism characteristics in four model plants, potato (Solanum tuberosum ‘Lada’), tobacco (Nicotiana tabacum ‘Samsun’), rapeseed (Brassica napus ‘Asgard’) and strawberry (Fragaria vesca), under both photomixotrophic (PM) and photoautotrophic (PA) conditions. To ensure PA conditions, we used our improved sun caps that serve as gas and light permeable covers for cultivation vessels. We found bigger biomass accumulation, larger leaf areas, higher stomatal conductance and higher instantaneous water use efficiency and lower root sugar contents in PA plants compared to PM ones. However, for other characteristics (root biomass, root/shoot ratio, pigment contents, leaf sugar and starch levels and transpiration rates), a strong species‐dependent reactions to the exogenous sugar supply was noted, which does not allow to create a general view on the overall impact of PM nutrition under in vitro conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Earthworms are important drivers for the formation of soil structure and play a key role in soil organic matter (SOM) dynamics. Our previous long-term (126weeks) laboratory experiment showed that ...carbon (C) loss declined through time in soil when litter was mixed and consumed by earthworms (Lumbricus rubellus). Eventually, the C loss was lower than in treatments where litter was mechanically mixed into soil with exclusion of earthworms. However, it is not clear if the solely physical manipulation of soil or biological activity of earthworms lead to different SOM quality, which would result in a distinction in C loss and consequently C sequestration. Thus, we differentiated between physical (mechanical mixing) and earthworm effects on SOM composition. Two types of soil were used in the experiment: clay and sand, and these were incubated with alder (Alnus glutinosa) and willow (Salix caprea) litter, respectively. The combination of soils and litter types corresponds to the natural combinations at the sampling sites.
To explain underlying mechanisms of a lower C loss in the earthworm vs. mechanically mixed treatment, we separated SOM fractions in order to gain pools defined in the Rothamsted model. Chemical differences between initial litter and the active and slow pool of SOM obtained by fractionation were studied. No significant differences between the earthworm and mechanically mixed treatment were found in C, nitrogen (N), and phenol contents, composition of major chemical groups of litter studied by solid-state 13C NMR spectroscopy, and composition of aromatic components of SOM studied by analytical pyrolysis (Py GC/MS). This lack of differences in chemical composition suggests that greater SOM sequestration in the earthworm treatment is likely to be connected with physical protection of SOM inside cast aggregates rather than with chemical changes in SOM mediated by earthworms.
•Earthworms supported a higher C stock in treatments with clay.•Earthworm and mechanically mixed treatments did not differ in chemical composition.•Stabilization of SOM in earthworm treatments is connected with physical protection.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Remote sensing is one of the modern methods that have significantly developed over the last two decades and, nowadays, it provides a new means for forest monitoring. High spatial and temporal ...resolutions are demanded for the accurate and timely monitoring of forests. In this study, multi-spectral Unmanned Aerial Vehicle (UAV) images were used to estimate canopy parameters (definition of crown extent, top, and height, as well as photosynthetic pigment contents). The UAV images in Green, Red, Red-Edge, and Near infrared (NIR) bands were acquired by Parrot Sequoia camera over selected sites in two small catchments (Czech Republic) covered dominantly by Norway spruce monocultures. Individual tree extents, together with tree tops and heights, were derived from the Canopy Height Model (CHM). In addition, the following were tested: (i) to what extent can the linear relationship be established between selected vegetation indexes (Normalized Difference Vegetation Index (NDVI) and NDVIred edge) derived for individual trees and the corresponding ground truth (e.g., biochemically assessed needle photosynthetic pigment contents) and (ii) whether needle age selection as a ground truth and crown light conditions affect the validity of linear models. The results of the conducted statistical analysis show that the two vegetation indexes (NDVI and NDVIred edge) tested here have the potential to assess photosynthetic pigments in Norway spruce forests at a semi-quantitative level; however, the needle-age selection as a ground truth was revealed to be a very important factor. The only usable results were obtained for linear models when using the second year needle pigment contents as a ground truth. On the other hand, the illumination conditions of the crown proved to have very little effect on the model’s validity. No study was found to directly compare these results conducted on coniferous forest stands. This shows that there is a further need for studies dealing with a quantitative estimation of the biochemical variables of nature coniferous forests when employing spectral data that were acquired by the UAV platform at a very high spatial resolution.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Forest top-of-canopy (TOC) reflectance observed by remote sensing instruments is driven by a wide range of parameters, including optical properties of leaves being the major driver, understory and ...bark together with structural properties of the forest - spatial distribution of leaves and branches in the canopy contributing also to variable extent. In addition, the instantaneous observation geometry (e.g. the sun and sensor zenith and azimuth angles) largely influences the observed TOC reflectance due to the changes in shadow fraction in the canopies. As a result, forest TOC reflectance is highly dynamic, following the seasonal patterns of optical and structural properties of vegetation.
From the above-mentioned factors, the leaf optical properties are the most important. They hold an information on leaf biochemical (e.g. chlorophyll and carotenoid contents), water content and structural (e.g., leaf thickness, distribution of pigments within a leaf) properties at the leaf-level. Whereas biochemical effects on leaf reflectance are well understood, the role of dorsiventral asymmetry leaf internal structure on two-sided leaf optical properties has not been paid much attention, assuming equal optical properties on both leaf sides. However, the internal structure of a dorsiventral leaf is highly asymmetric often having different surface structure, tissue density and pigment distribution. Moreover, leaf optical properties are rarely measured during phenological development with high time resolution. Typically, studies focus on peak growing season neglecting the dynamic seasonal change of optical properties for broadleaved vegetation of temperate forests.
In this study, we measured the seasonal course of leaf-level two-sided optical properties, biochemical and structural traits of five common broadleaved tree species of Central Europe (Betula pendula, Fagus sylvatica, Acer pseudoplatanus, Acer platanoides, and Sorbus aucuparia) with a typical dorsiventral, leaf anatomy without heliotropism. We link their leaf optical properties (e.g. reflectance difference of adaxial and abaxial sides, reflectance to transmittance ratio, fraction of specular component of leaf reflectance) with the laboratory analyses of inner leaf structure for contrasting leaf phenological stages from spring to fall. This allowed us to quantify both, species and seasonal differences of leaf dorsiventral optical properties and the role of inner leaf structure on leaf dorsiventral optical properties. Next, we up-scaled measured leaf-level dorsiventral optical properties to canopy level using Discrete Anisotropic Radiative Transfer model (DART) for three contrasting seasonal phenological stages - early spring (day of the year; DOY 115), summer (DOY 212) and fall (DOY 285). The aim was to quantify the impact of leaf optical properties parametrization (i.e. assuming equal optical properties on both sides, or dorsiventral leaf optical properties asymmetry) for forest of different species composition, vegetation phenological stage and observation geometries. The biggest differences between simulations were observed in VIS and NIR regions, where the neglecting differences in abaxial side leaf reflectance may introduce relative difference up to 20%, causing the underestimation of “one-sided” scenario compared to “two-sided” one, especially for off-nadir backscattering viewing directions. This may lead to increase in uncertainty when interpreting remote sensing observations, namely the chlorophyll content retrievals from back-scattering observation geometries and canopy structural retrievals (e.g. leaf area index) for all viewing geometries. We, thus, suggest to account for leaf reflectance dorsiventral differences in the next generation of radiative transfer models.
•Trends in dorsiventral leaf reflectance are driven by leaf structure.•Biggest differences in studied leaf traits were observed in early spring and autumn.•Seasonal leaf reflectance asymmetry upscaled in complex radiative transfer model.•Neglecting lower side reflectance may underestimate relative reflectance by 20%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, we examine leaf reflectance as the main optical property used in remote sensing of vegetation. The total leaf reflectance consists of two main components: a diffuse component, ...originating from the leaf interior, and a component reflected directly from the leaf surface. The latter contains specular (mirror-like) reflectance (SR) and surface particle scattering, driven by the surface roughness. Our study aimed to (1) reveal the effects of key leaf structural traits on SR in 400–2500 nm, and (2) compare the performance of PLSR models of leaf biophysical properties based on the total reflectance and SR removal reflectance. Four Arabidopsis thaliana structural surface mutants and six Hieracium species differing in trichome properties were studied. PCA did not reveal any systematic effect of trichome density, length, and morphology on SR. Therefore, the results do not support the hypothesis that leaves with denser and longer trichomes have lower SR and higher total reflectance than the smooth leaves. SR removal did not remarkably improve PLSR models of biophysical traits (up to 2% of RMSE). Thus, in herbaceous dorsiventral leaves with relatively sparse trichomes of various morphology and without apparent waxy surface, we cannot confirm that SR removal significantly improves biophysical trait prediction.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ericaceae (the heath family) are widely distributed calcifuges inhabiting soils with inherently poor nutrient status. Ericaceae overcome nutrient limitation through symbiosis with ericoid mycorrhizal ...(ErM) fungi that mobilize nutrients complexed in recalcitrant organic matter. At present, recognized ErM fungi include a narrow taxonomic range within the Ascomycota, and the Sebacinales, basal Hymenomycetes with unclamped hyphae and imperforate parenthesomes. Here we describe a novel type of basidiomycetous ErM symbiosis, termed 'sheathed ericoid mycorrhiza', discovered in two habitats in mid-Norway as a co-dominant mycorrhizal symbiosis in Vaccinium spp. The basidiomycete forming sheathed ErM possesses clamped hyphae with perforate parenthesomes, produces 1- to 3-layer sheaths around terminal parts of hair roots and colonizes their rhizodermis intracellularly forming hyphal coils typical for ErM symbiosis. Two basidiomycetous isolates were obtained from sheathed ErM and molecular and phylogenetic tools were used to determine their identity; they were also examined for the ability to form sheathed ErM and lignocellulolytic potential. Surprisingly, ITS rDNA of both conspecific isolates failed to amplify with the most commonly used primer pairs, including ITS1 and ITS1F + ITS4. Phylogenetic analysis of nuclear LSU, SSU and 5.8S rDNA indicates that the basidiomycete occupies a long branch residing in the proximity of Trechisporales and Hymenochaetales, but lacks a clear sequence relationship (>90% similarity) to fungi currently placed in these orders. The basidiomycete formed the characteristic sheathed ErM symbiosis and enhanced growth of Vaccinium spp. in vitro, and degraded a recalcitrant aromatic substrate that was left unaltered by common ErM ascomycetes. Our findings provide coherent evidence that this hitherto undescribed basidiomycete forms a morphologically distinct ErM symbiosis that may occur at significant levels under natural conditions, yet remain undetected when subject to amplification by 'universal' primers. The lignocellulolytic assay suggests the basidiomycete may confer host adaptations distinct from those provisioned by the so far investigated ascomycetous ErM fungi.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
ABSTRACTLeaf traits can be used to elucidate vegetation functional responses to global climate change. Pigments, water and leaf mass per area are the most used traits. However, detailed anatomical ...traits such as leaf thickness, the thickness of palisade and spongy parenchyma are often neglected, although they affect leaf physiological function and optical properties. Our aim was to produce partial least squares regression (PLSR) models for estimating leaf traits using biconical reflectance factor (BCRF). We established that estimation of leaf anatomical properties differs when using BCRF obtained from the upper and lower surface of the leaf. PLSR explained that 90% of the variability was based on total chlorophyll content (R2 = 0.95), spongy parenchyma to leaf thickness ratio (R2 = 0.94), equivalent water thickness (R2 = 0.93) and leaf mass per area (R2 = 0.91) or leaf thickness (R2 = 0.90). We conclude that internal asymmetry in leaf structure affects significantly leaf optical properties and should not be neglected in radiative transfer modelling at the leaf level and when upscaling leaf properties to the canopy.
We examined the seasonal changes in biophysical, anatomical, and optical traits of young leaves, formed throughout the vegetative season due to sylleptic growth, and mature leaves formed by proleptic ...growth in spring. Leaf developmental categories contribute to the top-of-canopy reflectance and should be considered when taking ground truth for remote sensing studies (RS). Deciduous tree species, Betula pendula, Populus tremula, and Alnus incana, were sampled from May to October 2018 in an Estonian hemiboreal forest. Chlorophyll and carotenoid content were detected biochemically; leaf anatomical traits (leaf, palisade, and spongy mesophyll thickness) were measured on leaf cross-sections; leaf reflectance was measured by a spectroradiometer with an integrating sphere (350–2500 nm). Biophysical and anatomical leaf traits were related to 64 vegetation indices (VIs). Linear models based on VIs for all tested leaf traits were more robust if both juvenile and mature leaves were included. This study provides information on which VIs are interchangeable or independent. Pigment and leaf thickness sensitive indices formed PC1; water and structural trait related VIs formed an independent group associated with PC3. Type of growth and leaf age could affect the validation of biophysical and anatomical leaf trait retrieval from the optical signal. It is, therefore, necessary to sample both leaf developmental categories—young and mature—in RS, especially if sampling is only once within the vegetation season.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
To understand why excrements of soil macrofauna often decompose more slowly than leaf litter, we fed Bibio marci larvae the litter of tree species differing in litter quality (Alnus glutinosa, Salix ...caprea, and Quercus robur) and then measured respiration induced by litter and excrements. We also measured respiration induced by the same litter artificially modified to mimic faunal effects; the litter was modified by grinding, grinding with alkalinization to pH = 11, grinding with coating by kaolinite, and grinding with both alkalinization and coating. Decomposition of excrements tended to be slower for willow and was significantly slower for oak and alder than for the corresponding litter. With oak, decomposition was slower for all artificially modified litter than for non-modified litter. The reduction in the decomposition was similar for excrements and for alder and willow litter that was ground, coated, and alkalinized. In alder, a similar reduction was found in ground and alkalinized litter. 13C NMR indicated that gut passage increases aliphatic components and decreases polysaccharides. Pyrolysis indicated that gut passage increases the ratio of guaiacyl to hydroxymethyl derivatives in lignin. Our findings indicate that the decreased decomposition rate of excrements might result from the removal of easily available polysaccharides, the increase in aliphatic components, an increase in the resistant components of lignin, the accumulation of microbial cell walls, and the binding of nitrogen into complexes with aromatic components. Several of these mechanisms are supported or determined by litter alkalinization during gut passage.
•Respiration of litter and excrements of Bibio marci was measured.•Decomposition of excrements was slower than decomposition of the corresponding litter.•This slower decomposition corresponds with litter alkalization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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