Small twigs represent a substantial input of organic carbon into forest soils, but potential influencing factors on their decomposition have rarely been investigated. Here, we studied potential ...effects of twig size on decomposition and associated composition and activity of microbial communities during decomposition. Because the surface area for microbial colonization and the volume of accessible substrate increases with decreasing twig size, we hypothesized that twig size affects both microbial community and decomposition rate. Litterbags with twigs (Salix caprea) of two different diameters were placed within the litter layer and consecutively collected over a seven-year period. We determined the mass loss and microbial measures after each sampling event. The observed microbial parameters suggested a faster microbial colonization of thin twigs, where the proportion of bacteria was higher than in thick twigs. The development of the microbial community in thick twigs was more gradual and the proportion of fungi was higher. Despite this differential and successional development of microbial communities (and against our hypothesis), the mass loss among different twig diameters did not differ after our seven-year experiment, indicating that surface-to-volume ratios, though a primary control on microbial succession, may have limited predictive power for twig decomposition rates.
In dioecious, zoophilous plants potential pollinators have to be attracted to both sexes and switch between individuals of both sexes for pollination to occur. It often has been suggested that males ...and females require different numbers of visits for maximum reproductive success because male fertility is more likely limited by access to mates, whereas female fertility is rather limited by resource availability. According to sexual selection theory, males therefore should invest more in pollinator attraction (advertisement, reward) than females. However, our knowledge on the sex specific investment in floral rewards and advertisement, and its effects on pollinator behaviour is limited. Here, we use an approach that includes chemical, spectrophotometric, and behavioural studies i) to elucidate differences in floral nectar reward and advertisement (visual, olfactory cues) in dioecious sallow, Salix caprea, ii) to determine the relative importance of visual and olfactory floral cues in attracting honey bee pollinators, and iii) to test for differential attractiveness of female and male inflorescence cues to honey bees. Nectar amount and sugar concentration are comparable, but sugar composition varies between the sexes. Olfactory sallow cues are more attractive to honey bees than visual cues; however, a combination of both cues elicits the strongest behavioural responses in bees. Male flowers are due to the yellow pollen more colourful and emit a higher amount of scent than females. Honey bees prefer the visual but not the olfactory display of males over those of females. In all, the data of our multifaceted study are consistent with the sexual selection theory and provide novel insights on how the model organism honey bee uses visual and olfactory floral cues for locating host plants.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The aims of the study were: (i) to compare leaf reflectance in visible (VIS) (400-700 nm), near-infrared (NIR) (740-1140 nm) and short-wave infrared (SWIR) (2000-2400 nm) spectral ranges measured ...monthly by a contact probe on a single leaf and a stack of five leaves (measurement setup (MS)) of two broadleaved tree species during the vegetative season; and (ii) to test if and how selected vegetation indices differ under these two MS. In VIS, the pigment-related spectral region, the effect of MS on reflectance was negligible. The major influence of MS on reflectance was detected in NIR (up to 25%), the structure-related spectral range; and weaker effect in SWIR, the water-related spectral range. Vegetation indices involving VIS wavelengths were independent of MS while indices combining wavelengths from both VIS and NIR were MS-affected throughout the season. The effect of leaf stacking contributed to weakening the correlation between the leaf chlorophyll content and selected vegetation indices due to a higher leaf mass per area of the leaf sample. The majority of MS-affected indices were better correlated with chlorophyll content in both species in comparison with MS-unaffected indices. Therefore, in terms of monitoring leaf chlorophyll content using the contact probe reflectance measurement, these MS-affected indices should be used with caution, as discussed in the paper. If the vegetation indices are used for assessment of plant physiological status in various times of the vegetative season, then it is essential to take into consideration their possible changes induced by the particular contact probe measurement setup regarding the leaf stacking.
Prolonged periods without precipitation in spring prevent timely and rapid germination of pioneer tree seeds and could lead to an accelerated loss of germination capacity (reduced lifespan). To get ...knowledge about the shortening of seed lifespan and, thus, the shortening of natural regeneration windows under climate change, an experiment was conducted. Seeds of
Alnus glutinosa
,
Betula pendula
,
Populus tremula
,
Salix caprea
,
Larix decidua
,
Pinus sylvestris,
and
Picea abies
were exposed to temperatures of 15 °C, 25 °C (past or present climate), and 40 °C (future climate) with low or high humidity for a period of 3 months. Regardless of air humidity, the initial germination percentage of
Alnus glutinosa
,
Betula pendula
,
Larix decidua,
and
Pinus sylvestris
seeds decreased only slightly by 5–15% over the 91-day period when stored at 15 °C and 25 °C. For
Populus tremula
and
Salix caprea
, time windows of maximum 14–49 days and 42–91 days were identified, respectively.
However, as climate change progresses with rising temperatures and increasing absolute air humidity values, the window of opportunity for successful germination will shorten for all studied tree species. In the moist air humidity variant of 40 °C, the germination percentage dropped to 0% after 42 days for
Alnus glutinosa
,
Betula pendula,
and
Larix decidua
. The natural regeneration window will be reduced by half from more than three months to about three weeks under climate change. The lifespan of
Populus tremula
and
Salix caprea
seeds will be shortened to 1 week. For
Picea abies
, the time window will shorten to a maximum of 28 days.
A variety of plants growing on metalliferous soils accumulate metals in their harvestable parts and have the potential to be used for phytoremediation of heavy metal polluted land. There is ...increasing evidence that rhizosphere bacteria contribute to the metal extraction process, but the mechanisms of this plant-microbe interaction are not yet understood. In this study ten rhizosphere isolates obtained from heavy metal accumulating willows affiliating with Pseudomonas, Janthinobacterium, Serratia, Flavobacterium, Streptomyces and Agromyces were analysed for their effect on plant growth, Zn and Cd uptake. In plate assays Zn, Cd and Pb resistances and the ability of the bacteria to produce indole-3-acetic acid (IAA), 1-amino-cyclopropane-1-carboxylic acid deaminase (ACC deaminase) and siderophores were determined. The isolates showed resistance to high Zn concentrations, indicating an adaptation to high concentrations of mobile Zn in the rhizosphere of Salix caprea. Four siderophore producers, two IAA producers and one strain producing both siderophores and IAA were identified. None of the analysed strains produced ACC deaminase. Metal mobilization by bacterial metabolites was assessed by extracting Zn and Cd from soil with supernatants of liquid cultures. Strain Agromyces AR33 almost doubled Zn and Cd extractability, probably by the relase of Zn and Cd specific ligands. The remaining strains, immobilized both metals. When Salix caprea plantlets were grown in γ-sterilized, Zn/Cd/Pb contaminated soil and inoculated with the Zn resistant isolates, Streptomyces AR17 enhanced Zn and Cd uptake. Agromyces AR33 tendentiously promoted plant growth and thereby increased the total amount of Zn and Cd extracted from soil. The IAA producing strains did not affect plant growth, and the siderophore producers did not enhance Zn and Cd accumulation. Apparently other mechanisms than the production of IAA, ACC deaminase and siderophores were involved in the observed plant-microbe interactions.
Resistance to anthelmintic drugs in gastrointestinal nematodes (GIN) of sheep is of high concern for livestock production worldwide. In Calabria (southern Italy), many plants have been used in ...ethnoveterinary medicine for parasite control in small ruminants. Here, we present an in vivo evaluation of anthelmintic efficacy of three plant extracts. The first was based on bark and leaves of Salix caprea, the second and the third were based on the whole plant Artemisia campestris and whole fruit (seeds and peel) of Punica granatum, respectively. Anthelmintic efficacy was evaluated according to the fecal egg count reduction test (FECRT) performed with the FLOTAC technique. The results showed a significant anthelmintic effect of Punica granatum macerate (50%), a low effectiveness of the Artemisia campestris macerate (20%), and a complete ineffectiveness of Salix caprea macerate (0.1%). With these outcomes, we report a P. granatum-based remedy reducing 50% GIN egg output. This result was obtained without using any synthetic drug, paving the way for the employment of green veterinary pharmacology (GVP) as a complementary and sustainable method to reduce the use of chemicals and to counteract anthelmintic resistance.
Metal-accumulating woody species have been considered for phytoextraction of metal-contaminated sites. We investigated Zn and Cd accumulation in tissues of adult trees and associated herbaceous ...species collected from contaminated areas in Central Europe. We found considerable Cd and Zn accumulation in various willow, poplar and birch species with up to 116
mg
Cd
kg
−1 and 4680
mg
Zn
kg
−1 in leaves of
Salix caprea. Annual variation of Cd and Zn concentrations in leaves of
Salix caprea were small, indicating that data obtained in different years can be compared. Metal concentrations in leaves were not related to total (
aqua regia) or labile (1
M NH
4NO
3 extract) concentrations in soil but the accumulation factors (leaf concentration: soil concentration) for Cd and Zn followed an inverse log type function. Metal partitioning between tissues showed a minimum in the wood, with increasing concentrations of Cd and Zn towards the leaves and fine roots.
Adult field-grown Salix caprea, Populus tremula and other tree species accumulate up to 4680
mg
Zn
kg
−1 and 116
mg
Cd
kg
−1 in their leaves.
Background
The Mediterranean basin is currently facing major changes in fire regimes as a result of climate and land-use changes. These alterations could affect the ability of forests to recover ...after a fire, hence triggering degradation processes and modifying the provision of fundamental ecosystem services. Examining patterns and drivers of post-fire forest recovery, particularly for obligate seeders without specific fire-adaptive traits, thus becomes a priority for researchers and land managers. We studied the post-fire dynamics of Scots pine (
Pinus sylvestris
L.) stands affected by a mixed-severity fire in North-Western Italy, aiming to understand the impact of fire on soil properties and assess drivers, spatial distribution, and characteristics of short-term post-fire recovery.
Results
We observed that fire did not significantly affect soil organic carbon (OC) content, while we detected significantly lower nitrogen (N) content in severely burnt sites. Regeneration density was particularly abundant in medium-severity areas, while it drastically decreased in high-severity patches. The most abundant tree species in the regeneration layer was Scots pine, followed by goat willow (
Salix caprea
L.), European aspen (
Populus tremula
L.), and, to a lesser extent, European larch (
Larix decidua
Mill.). Slope, fire severity, and distance from seed trees emerged as the most important drivers of post-fire forest regeneration patterns.
Conclusions
Our results highlight the importance of preserving seed trees from salvage logging, even if they are damaged and have a low survival probability. Active post-fire management, such as tree planting, should be limited to large and severely burnt patches, where natural forest regeneration struggles to settle, increasing the risk of ecosystem degradation. These findings could be useful for informing land managers, helping them to enhance potential mitigation strategies in similar ecosystems and plan appropriate restoration approaches.
QUESTIONS: Has the observed decline in the willow Salix caprea L., one of the most common colonizers of post‐mining sites in Central Europe, contributed to changes in the rest of the plant community ...on post‐mining sites? How does S. caprea modify its understorey? How is the understorey vegetation affected by above‐ground and below‐ground competition with S. caprea? LOCATION: Heaps after coal mining near Sokolov, Czech Republic (50°14′21″ N, 12°40′45″ E). METHODS: The effects of above‐ground and below‐ground competition with the willow S. caprea on its understorey plant community were studied in un‐reclaimed post‐mining sites. Below‐ground competition was evaluated by comparing (1) frames inserted into the soil that excluded woody roots (frame treatment), (2) frames that initially excluded woody root growth but then allowed regrowth of the roots (open‐frame treatment), and (3) undisturbed soil (no‐frame treatment). These treatments were combined with S. caprea thinning to assess the effect of above‐ground competition. RESULTS: Three years after the start of the experiment, above‐ground competition from S. caprea (as modified by thinning of the S. caprea canopy) had not affected understorey biomass or species number, but had affected species composition. In contrast, below‐ground competition significantly affected both the above‐ground and below‐ground biomass of the understorey. The above‐ground biomass of the understorey was larger in the frame treatment (which excluded woody roots) than in the other two treatments. The below‐ground biomass of the understorey was larger in the frame than in the open‐frame treatment. Unlike above‐ground competition (light availability), below‐ground competition did not affect understorey species composition. CONCLUSIONS: Our results suggest that S. caprea is an important component during plant succession on post‐mining sites because it considerably modifies its understorey plant community. Below‐ground competition is a major reason for the low cover and biomass of the herbaceous understorey in S. caprea stands on post‐mining sites.
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