| 1. |
- Daniau, A. -L, et al.
(författare)
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predictability of biomass burning in response to climate changes
- 2012
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 26, s. GB4007-
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Tidskriftsartikel (refereegranskat)abstract
- Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo-fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.
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| 2. |
- Power, M. J., et al.
(författare)
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Changes in fire regimes since the Last Glacial Maximum : an assessment based on a global synthesis and analysis of charcoal data
- 2008
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 30:7-8, s. 887-907
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Tidskriftsartikel (refereegranskat)abstract
- Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to ∼11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from ∼19,000 to ∼17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ∼13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to ∼3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.
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| 3. |
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| 4. |
- Komatsu, Kimberly J., et al.
(författare)
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Global change effects on plant communities are magnified by time and the number of global change factors imposed
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116:36, s. 17867-17873
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Tidskriftsartikel (refereegranskat)abstract
- Accurate prediction of community responses to global change drivers (GCDs) is critical given the effects of biodiversity on ecosystem services. There is consensus that human activities are driving species extinctions at the global scale, but debate remains over whether GCDs are systematically altering local communities worldwide. Across 105 experiments that included over 400 experimental manipulations, we found evidence for a lagged response of herbaceous plant communities to GCDs caused by shifts in the identities and relative abundances of species, often without a corresponding difference in species richness. These results provide evidence that community responses are pervasive across a wide variety of GCDs on long-term temporal scales and that these responses increase in strength when multiple GCDs are simultaneously imposed.Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.
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| 5. |
- Hallett, S. L., et al.
(författare)
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Dissemination of triactinomyxons (Myxozoa) via oligochaetes used as live food for aquarium fishes
- 2005
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Ingår i: Diseases of Aquatic Organisms. - 0177-5103. ; 65:2, s. 137-152
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Tidskriftsartikel (refereegranskat)abstract
- Freshwater 'tubifex' oligochaetes sold as live food for aquarium fishes were purchased from several pet shops in Munich, Germany, over a 1 yr period (March 2001 to February 2002). These samples were screened for parasitic infections of actinosporean myxozoans to gauge the possibility of parasite dispersal via this route. Of 7 samples, 6 contained infected oligochaetes; waterborne spores were present in 5 samples at the time of purchase. In the laboratory, 12 different types of actinosporeans were released by the oligochaetes. These could be assigned to 4 collective groups: triactinomyxon, aurantiactinomyxon, raabeia and hexactinomyxon; 4 novel triactinomyxons are described herein, a fifth triactinomyxon has been described earlier. Phenotypic descriptions of the spores are accompanied by molecular sequence data (18S rDNA). Descriptions of the other actinosporean types appear elsewhere. The worms sold as 'tubifex' originated from eastern European countries and were identified as a mix of Tubifex tubifex, Limnodrilus hoffmeisteri and L. udekemianus. Sale of live worms (and their accompanying parasite load) has clearly the potential to facilitate introduction both of parasites and suitable hosts to new areas.
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| 6. |
- Hallett, S. L., et al.
(författare)
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Molecular methods clarify morphometric variation in triactinomyxon spores (Myxozoa) released from different oligochaete hosts.
- 2004
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Ingår i: Systematic Parasitology. - 0165-5752. ; 57:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Thirty-nine freshwater tubificid oligochaetes were isolated, each of which harboured a triactinomyxon infection. Spore characteristics include the typical triactinomyxon anchor shape, eight germ cells within the sporoplasm and three unequal (two long and one shorter) caudal processes with square tips. Despite morphological similarities between the spores from the different hosts, their morphometrical data varied considerably; significantly, the ranges of dimensions of the smallest and largest exemplars were mutually exclusive. In order to ascertain the true number of spore types present, molecular methods were employed. Samples of waterborne spores, including the smallest and largest representatives, were selected from 11 host oligochaetes (all Tubifex tubifex Müller) and a nested PCR-RFLP `riboprint' analysis performed. The small subunit ribosomal DNA gene (18S rDNA) was targetted and amplified through two rounds of PCR, then digested with the restriction enzymes Dde I and Hha I. The resultant major cleavage patterns produced by both enzymes indicated a single triactinomyxon form; however, the pattern of several less intense bands varied between the samples. From a subset of five samples drawn from across the full spectrum of spore sizes, a 327 bp region near the 5prime was sequenced and was identical for all five samples. Comparison of this 327 bp region with that of 12 other triactinomyxons in GenBank showed 68.7–96.9% similarity (at least 9 base differences). A further 469 bp generated for each of the smallest, largest and mid-range (= reference) spore samples was identical also. The reference sample was sequenced further to yield 1,554 bp of 18S rDNA (GenBank accession number AY162270); comparison with other Myxozoa indicated this sequence was novel. The morphometrics of our triactinomyxon did not correlate with any published description. The morphometrical variation exhibited by spores of the triactinomyxon type in this study raises questions about the validity of using morphometrical data to distinguish spore types and suggests that there could be taxonomic redundancy in the diversity of actinosporeans recorded in the literature. The additional information provided by molecular data in this study was pivotal in the clarification of morphometrical variation exhibited by morphologically similar triactinomyxon spores released from different oligochaete hosts.
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| 7. |
- Hallett, S. L., et al.
(författare)
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Myxozoan parasites disseminated via oligochaete worms as live food for aquarium fishes: descriptions of aurantiactinomyxon and raabeia actinospore types
- 2006
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Ingår i: Diseases of Aquatic Organisms. - 0177-5103. ; 69:2-3, s. 213-225
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Tidskriftsartikel (refereegranskat)abstract
- A total of 7 samples of live freshwater oligochaetes (mixed species), sold as 'tubifex' worms as food for aquarium fishes, were purchased over a 1 yr period from several pet shops in Munich, Germany, and screened for parasitic infections of myxozoans. The water associated with 5 samples contained actinospores at the time of purchase; 6 samples subsequently released spores in the laboratory. In all, 12 types of actinospores (Myxozoa: Myxosporea) from 4 collective groups were released by the oligochaetes. In the current study we provide descriptions of 2 aurantiactinomyxons (Myxobolus intimus Zaika, 1965 and type 1 nov.) and 3 raabeias (type 1 and 2 nov., Raabeia type 1 of Oumouna et al., 2003); descriptions of the 5 triactinomyxon and 2 hexactinomyxon types have been published previously. We include both raabeia and echinactinomyxon types in differential diagnoses of our raabeia forms because a clear distinction between these groups no longer exists in the literature. Comparison of 18S rDNA sequence data revealed that 1 of the novel aurantiactinomyxons was Myxobolus intimus. The sale of worms hundreds of km away from their point of origin is a means of dissemination of myxozoan parasites.
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