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H. González-Rodríguez T. G. Domínguez-Gómez I. Cantú-Silva M. V. Gómez-Meza R. G. Ramírez-Lozano M. Pando-Moreno C. J. Fernández 《Plant Ecology》2011,212(10):1747-1757
The aim of this study was to determine the litterfall production and macronutrient (Ca, K, Mg, N, and P) deposition through
leaf litter in four sites with different types of vegetation. Site one (Bosque Escuela) was located at 1600 m a.s.l. in a
pine forest mixed with deciduous trees, second site (Crucitas at 550 m a.s.l.) in the ecotone of a Quercus spp. forest and the Tamaulipan thornscrub and third and fourth sites (Campus at 350 m a.s.l. and Cascajoso at 300 m a.s.l.,
respectively) were in the Tamaulipan thornscrub. Litter constituents (leaves, reproductive structures, twigs, and miscellaneous
residues) were collected at 15-day intervals from December 21, 2006, throughout December 20, 2007. Collections were carried
out in ten litter traps (1.0 × 1.0 m) randomly situated at each site of approximately 2,500 m2. Total annual litterfall deposition was 4407, 7397, 6304, and 6527 kg ha−1 y−1 for Bosque Escuela, Crucitas, Campus and Cascajoso, respectively. Of total annual litter production, leaves were higher varying
from 74 (Bosque Escuela) to 86% (Cascajoso) followed by twigs from 4 (Cascajoso) to 14% (Crucitas), reproductive structures
from 6 (Bosque Escuela) to 10% (Crucitas), and miscellaneous litterfall from <1 (Campus) to 12% (Bosque Escuela). The Ca annual
deposition was significantly higher in Cascajoso (232.7 kg ha−1 y−1), followed by Campus (182.3), Crucitas (130.5) and Bosque Escuela (30.3). The K (37.5, 32.5, 24.8, 7.2, respectively), Mg
(22.6, 17.7, 13.7, 4.5, respectively) followed the same pattern as Ca. However, N was higher in Campus (85.8) followed by
Crucitas (85.1), Cascajoso (68.3), and Bosque Escuela (18.3). The P was higher in Campus and Crucitas (4.0) followed by Cascajoso
(3.4) and Bosque Escuela (1.4). On an annual basis for all sites, the order of nutrient deposition through leaf litter was
Ca > N> K > Mg > P, whereas on site basis of total nutrient deposition (Ca + N + K + Mg + P), the order was Cascajoso > Campus > Crucitas > Bosque
Escuela. Ca, K, Mg, N, and P nutrient use efficiency values in leaf litter were higher in Bosque Escuela, while lower figures
were acquired in Cascajoso and Crucitas sites. It seems that the highest litterfall deposition was found in the ecotone of
a Quercus spp. forest and the Tamaulipan thornscrub; however, the Tamaulipan thornscrub vegetation alone had better leaf litter nutrient
return. 相似文献
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V. F. Gallucci † R. J. Foy ‡§ S. M. O'Brien A. Aires-da -Silva H. Nesse B. Langseth N. Vega I. Taylor K. J. Goldman ¶ 《Journal of fish biology》2008,73(3):732-739
A pregnant salmon shark Lamna ditropis, captured in Alaska in December 2006, held two male and two female oophagous embryos (two per uterus) nourished by a single large 7·5 kg ovary. This discovery provides new data and insights into reproduction of the species and new perspective on the genus Lamna . 相似文献
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C Tefé-Silva CT Beneli MR Celes ER Machado MT Ueta CA Sorgi EM Floriano LH Faccioli SG Ramos 《Parasitology international》2012,61(3):425-430
Strongyloidiasis is an intestinal parasitosis with an obligatory pulmonary cycle. A Th2-type immune response is induced and amplifies the cellular response through the secretion of inflammatory mediators. Although this response has been described as being similar to asthma, airway remodeling during pulmonary migration of larvae has not yet been established. The aim of this study was to identify the occurrence of airway remodeling during Strongyloides venezuelensis (S. v.) infection and to determine the ability of dexamethasone treatment to interfere with the mechanisms involved in this process. Rats were inoculated with 9,000 S. v. larvae, treated with dexamethasone (2 mg/kg) and killed at 1, 3, 5, 7, 14 and 21 days. Morphological and morphometric analyzes with routine stains and immunohistochemistry were conducted, and some inflammatory mediators were evaluated using ELISA. Goblet cell hyperplasia and increased bronchiolar thickness, characterized by edema, neovascularization, inflammatory infiltrate, collagen deposition and enlargement of the smooth muscle cell layer were observed. VEGF, IL1-β and IL-4 levels were elevated throughout the course of the infection. The morphological findings and the immunomodulatory response to the infection were drastically reduced in dexamethasone-treated rats. The pulmonary migration of S. venezuelensis larvae produced a transitory, but significant amount of airway remodeling with a slight residual bronchiolar fibrosis. The exact mechanisms involved in this process require further study. 相似文献
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