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Abstract. Woodland colonization on wetlands is considered to have a detrimental effect on their ecological value, even though detailed analysis of this process is lacking. This paper provides an evaluation of the ecological changes resulting from succession of poor fen (base‐poor mire) to willow wet woodland on Goss Moor NNR in Cornwall, UK. Different ages of willow carr were associated with eight understorey communities. During willow colonization, in the ground flora, there was a progressive decrease in poor fen species and an associated increase in woodland species, which appeared to be related to an increase in canopy cover and therefore shade. The most diverse community was found to be the most recent willow and was dominated by poor fen species. The oldest willow was the second most diverse and was associated with a reduction in poor fen species and an increase in woodland species. Architectural features were used successfully to assess the general condition and structure of willow. Tree height and DBH were identified as useful parameters to accurately assess willow age in the field. The implications of active intervention to remove willow in order to conserve the full range of communities within the hydrosere are discussed. 相似文献
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Annemarie MM Vlaar Angela EP Bouwmans Marinus JPG van Kroonenburgh Werner H Mess Selma C Tromp Piet GWM Wuisman Alfons GH Kessels Ania Winogrodzka Wim EJ Weber 《BMC neurology》2007,7(1):28
Background
Parkinson's disease (PD) is the second most common neurodegenerative disorder. As there is no definitive diagnostic test, its diagnosis is based on clinical criteria. Recently transcranial duplex scanning (TCD) of the substantia nigra in the brainstem has been proposed as an instrument to diagnose PD. We and others have found that TCD scanning of substantia nigra duplex is a relatively accurate diagnostic instrument in patients with parkinsonian symptoms. However, all studies on TCD so far have involved well-defined, later-stage PD patients, which will obviously lead to an overestimate of the diagnostic accuracy of TCD. 相似文献4.
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BŁAŻEJ BERKOWSKI CHRISTIAN KLUG 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2012,45(1):24-33
Berkowski, B & Klug, C. 2011: Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco. Lethaia, Vol. 45, pp. 24–33. In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host‐animals, is rather rare. A host reaction is usually needed to proof the syn vivo‐settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world‐renowned Moroccan mud‐mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small‐scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral‐meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa. 相似文献
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Annemarie MM Vlaar Marinus JPG van Kroonenburgh Alfons GH Kessels Wim EJ Weber 《BMC neurology》2007,7(1):27
Background
Parkinson's disease (PD) is the second most common neurodegenerative disorder. One of the most widely used techniques to diagnose PD is a Single Photon Emission Computer Tomography (SPECT) scan to visualise the integrity of the dopaminergic pathways in the brain. Despite this there remains some discussion on the value of SPECT in the differential diagnosis of PD. We did a meta-analysis of all the existing literature on the diagnostic accuracy of both pre- and post-synaptic SPECT imaging in the differential diagnosis of PD. 相似文献8.
Otero-Lobato MJ Kaats-Richters VE Koper C Vlietstra EJ Havenith RW Jenneskens LW Seinen W 《Mutation research》2005,581(1-2):115-132
The bacterial mutagenic response (Ames-assay, Salmonella typhimurium strain TA98+/-S9-mix) of a series of monocyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs) identified in combustion exhausts, viz. cyclopenta[cd]pyrene (1), acephenanthrylene (2), aceanthrylene (3) and cyclopenta[hi]chrysene (4), is re-evaluated. The mutagenic effects are compared with those exerted by the corresponding partially hydrogenated derivatives, 3,4-dihydrocyclopenta[cd]pyrene (5), 4,5-dihydroacephenanthrylene (6), 1,2-dihydroaceanthrylene (7) and 4,5-dihydrocyclopenta[hi]chrysene (8). It is shown that the olefinic bond of the externally fused five-membered ring of 1, 3 and 4 is of importance for a positive mutagenic response. In contrast, whilst CP-PAH 2 is found inactive, its dihydro analogue (6) shows a weak metabolism-dependent response. The importance of epoxide formation at the external olefinic bond in the five-membered ring is substantiated by the bacterial mutagenic response of independently synthesized cyclopenta[cd]pyrene-3,4-epoxide (9), acephenanthrylene-4,5-epoxide (10), aceanthrylene-1,2-epoxide (11) and cyclopenta[hi]chrysene-4,5-epoxide (12). Their role as ultimate, active mutagenic forms, when CP-PAHs 1, 3 and 4 exhibit a positive mutagenic response, is confirmed. Semi-empirical Austin Model 1 (AM1) calculations on the formation of the CP-arene oxides (9-12) and their conversion into the monohydroxy-carbocations (9a-12a and 9b-12b) via epoxide-ring opening support our results. For 2 and 4, which also possess a bay-region besides an annelated cyclopenta moiety, the calculations rationalize that epoxidation at the olefinic bond of the cyclopenta moiety is favoured. 相似文献
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Vincent EJ Jassey Geneviève Chiapusio Philippe Binet Alexandre Buttler Fatima Laggoun‐Défarge Frédéric Delarue Nadine Bernard Edward AD Mitchell Marie‐Laure Toussaint André‐Jean Francez Daniel Gilbert 《Global Change Biology》2013,19(3):811-823
Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above‐ and belowground linkages that regulate soil organic carbon dynamics and C‐balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and negative impacts of warming on specific microbial functional groups, leading to destabilization of the microbial food web. We observed a strong reduction (70%) in the biomass of top‐predators (testate amoebae) in warmed plots. Such a loss caused a shortening of microbial food chains, which in turn stimulated microbial activity, leading to slight increases in levels of nutrients and labile C in water. We further show that warming altered the regulatory role of Sphagnum‐polyphenols on microbial community structure with a potential inhibition of top predators. In addition, warming caused a decrease in Sphagnum cover and an increase in vascular plant cover. Using structural equation modelling, we show that changes in the microbial food web affected the relationships between plants, soil water chemistry, and microbial communities. These results suggest that warming will destabilize C and nutrient recycling of peatlands via changes in above‐ and belowground linkages, and therefore, the microbial food web associated with mosses will feedback positively to global warming by destabilizing the carbon cycle. This study confirms that microbial food webs thus constitute a key element in the functioning of peatland ecosystems. Their study can help understand how mosses, as ecosystem engineers, tightly regulate biogeochemical cycling and climate feedback in peatlands 相似文献