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181.
182.
Päivi Saari Sanna Saarnio Jussi V. K. Kukkonen Jarkko Akkanen Jaakko Heinonen Veli Saari Jukka Alm 《Biogeochemistry》2009,94(3):217-231
Forest clear-cutting followed by soil preparation means disturbance for soil microorganisms and disruption of N and C cycles.
We measured fluxes of N2O and dissolved organic carbon (DOC) in upland soil (podzol) and adjacent peat within a clear-cut forest catchment. Both soil
types behaved in a similar way, showing net uptake of N2O in the first year after the clear-cutting, and turning to net release in the second. The N2O flux dynamics were similar to those of N content in logging residues, as reported from a nearby site. As organic matter
is used in the food web of the decomposers, we attempted to explain the dynamics of N2O uptake and release by measuring the concurrent dynamics of the low molecular weight (LMW) fraction and the aromaticity of
DOC in a soil solution. The labile and most readily available LMW fractions of DOC were nearly absent in the year following
the clear-cutting, but rose after two years. The more refractory high molecular weight (HMW) fraction of DOC decreased two
years after the clear-cutting. The first year’s net uptake of N2O could be accounted for by the growth of decomposer biomass in the logging residues and detritus from the degenerating ground
vegetation, resulting in immobilization of nitrogen. Simultaneously, the labile, LMW fraction of DOC became almost completely
exhausted. The low availability of the LMW fraction could retard the growth and cause the accumulated decomposer biomass to
collapse. During the following winter and summer the fraction of LMW clearly increased, followed by increased N2O emissions. The presence of LMW DOC fractions, not the concentration of DOC, seems to be an important controller for N2O liberation after a major disturbance such as clear-cutting and site preparation. The complex connection between DOC characteristics,
nitrification or denitrification merits further studies. 相似文献
183.
Natunen Jari; Seppo Antti; Helin Jari; Reinhold Bruce B.; Rabina Jarkko; Costello Catherine E.; Renkonen Ossi 《Glycobiology》1997,7(5):711-718
A novel saccharide was synthesized by incubating globo-N-tetraose,GalNAcß13Gal 相似文献
184.
Cristian M. Aurori AlexandruIoan Giurgiu Benjamin H. Conlon Chedly Kastally Daniel S. Dezmirean Jarkko Routtu Adriana Aurori 《Ecology and evolution》2021,11(2):1057
The parasitic mite Varroa destructor devastates honey bee (Apis mellifera) colonies around the world. Entering a brood cell shortly before capping, the Varroa mother feeds on the honey bee larvae. The hormones 20‐hydroxyecdysone (20E) and juvenile hormone (JH), acquired from the host, have been considered to play a key role in initiating Varroa''s reproductive cycle. This study focuses on differential expression of the genes involved in the biosynthesis of JH and ecdysone at six time points during the first 30 hr after cell capping in both drone and worker larvae of A. mellifera. This time frame, covering the conclusion of the honey bee brood cell invasion and the start of Varroa''s ovogenesis, is critical to the successful initiation of a reproductive cycle. Our findings support a later activation of the ecdysteroid cascade in honey bee drones compared to worker larvae, which could account for the increased egg production of Varroa in A. mellifera drone cells. The JH pathway was generally downregulated confirming its activity is antagonistic to the ecdysteroid pathway during the larva development. Nevertheless, the genes involved in JH synthesis revealed an increased expression in drones. The upregulation of jhamt gene involved in methyl farnesoate (MF) synthesis came into attention since the MF is not only a precursor of JH but it is also an insect pheromone in its own right as well as JH‐like hormone in Acari. This could indicate a possible kairomone effect of MF for attracting the mites into the drone brood cells, along with its potential involvement in ovogenesis after the cell capping, stimulating Varroa''s initiation of egg laying. 相似文献
185.
Anna Poimala Päivi Parikka Jarkko Hantula Eeva J. Vainio 《Environmental microbiology》2021,23(9):5200-5221
Eighty-eight Phytophthora cactorum strains isolated from crown or leather rot of strawberry in 1971–2019 were screened for viruses using RNA-seq and RT-PCR. Remarkably, all but one isolate were virus-infected, most of them harbouring more than one virus of different genera or species. The most common virus occurring in 94% of the isolates was the Phytophthora cactorum RNA virus 1 (PcRV1) resembling members of Totiviridae. Novel viruses related to members of Endornaviridae, named Phytophthora cactorum alphaendornaviruses 1-3 (PcAEV1-3), were found in 57% of the isolates. Four isolates hosted viruses with affinities to Bunyaviridae, named Phytophthora cactorum bunyaviruses 1-3 (PcBV1-3), and a virus resembling members of the proposed genus ‘Ustivirus’, named Phytophthora cactorum usti-like virus (PcUV1), was found in a single isolate. Most of the virus species were represented by several distinct strains sharing ≥81.4% aa sequence identity. We found no evidence of spatial differentiation but some temporal changes in the P. cactorum virus community were observed. Some isolates harboured two or more closely related strains of the same virus (PcAEV1 or PcRV1) sharing 86.6%–96.4% nt identity in their polymerase sequence. This was surprising as viruses with such a high similarity are typically mutually exclusive. 相似文献
186.
Rafiqul Hyder Taina Pennanen Leena Hamberg Eeva J. Vainio Tuula Piri Jarkko Hantula 《Fungal Ecology》2013,6(5):387-396
We investigated the effects of two recently described dsRNA mycoviruses, HetRV3-ec1 and HetRV6-ab6, on Heterobasidion wood decay fungi. The viruses originally inhabited Heterobasidion ecrustosum and Heterobasidion abietinum, and were transferred in the laboratory into other Heterobasidion species. Isogenic virus-free and virus-infected Heterobasidion isolates were used to test the effects of these viruses on their hosts' growth rate and competitive ability against mycorrhizal and decay fungi (Paxillus involutus, Meliniomyces bicolor and Phlebiopsis gigantea). This study shows that: (i) a single virus strain confers different effects on different Heterobasidion host strains; and (ii) a single virus strain may have contrasting effects on the fitness of a single host isolate (ranging from no effect to harmful or beneficial) depending on environmental and ecological conditions. We also report for the first time on the antagonism of Helotiales belonging to the sub-group Rhizocyphus–Meliniomyces against Heterobasidion species. 相似文献
187.
Tomá Grim Jarkko Rutila† Phillip Cassey‡ & Mark E. Hauber§¶ 《Ethology : formerly Zeitschrift fur Tierpsychologie》2009,115(1):14-22
Chicks of some avian brood parasites show high virulence by eliminating all host progeny in the nest whereas others develop in the presence of host nestmates. Common cuckoo ( Cuculus canorus ) chicks are typically highly virulent parasites as they attempt to evict all host eggs and chicks soon after hatching. However, several features of nest design, including steep walls and/or cavity nests, may effectively prevent cuckoo hatchlings from evicting nestmates. A previous observational study showed low success of cuckoo chicks in evicting progeny of a cavity nester host, the redstart ( Phoenicurus phoenicurus ) but cuckoo chicks showed low survival both when reared alone or in mixed broods with host nestmates. Whether poor cuckoo performance was caused by eviction costs and/or by the effect of presence of host chicks per se remains unclear. We experimentally cancelled any potential eviction costs by removing host eggs immediately after the cuckoo hatched and creating mixed broods 5 days later when the eviction instinct of the cuckoo already ceased. Cuckoos that were forced to compete with host nestlings experienced lower provisioning rates, poorer growth, and lower fledging success than control lone cuckoos. Cuckoos in mixed broods that survived until fledging fledged later, and at lower masses, than those in the sole cuckoo group. Thus, the cuckoo gens specializing on redstarts is similar to other cuckoo gentes, whose chicks are more successful in evicting host nestmates, and it does not benefit from the presence of host brood. Cohabitation with host nestlings then should be viewed as a maladaptive by-product of host cavity nest design. 相似文献