ABSTRACT
Lignin is an abundant and recalcitrant biopolymer of major relevance as soil organic matter (SOM) component playing a significant role in its stabilization. In this work, a factorial field experiment was established, where three climatic treatments (W, warming; D, drought; W + D, warming + drought), mimicking future climate change scenarios were installed over five years in a Mediterranean savannah "dehesa", accounting for its landscape diversity (under the tree canopy and in open grassland). A combination of analytical pyrolysis (Py-GC/MS) and the study of biogeochemical proxies based on lignin monomers is used for the direct detection of lignin-derived phenols and to infer possible shifts in lignin dynamics in soil. A total of 27 main lignin-derived methoxyphenols were identified, exhibiting different patterns and proportions, mainly driven by the effect of habitat, hence biomass inputs to SOM. An accelerated decomposition of lignin moieties -(exhibited by higher LG/LS and Al/K + Ac ratios)- is particularly exacerbated by the effect of all climatic treatments. There is also an overall effect on increasing lignin oxidation of side chain in syringyl units, especially under the tree canopy due to the alteration in biomass degradation and potential stimulation of enzyme activities. Conversely, in open grassland these effects are slower since the microbial community is expected to be already adapted to harsher conditions. Our findings suggests that climate change-related temperature and soil moisture deviations impact soil lignin decomposition in dehesas threatening this productive Mediterranean agroecosystem and affecting the mechanism of soil carbon storage.
Subject(s)
Empyema , Nocardia Infections , Nocardia , Pneumonia , Humans , Aged , Empyema/drug therapy , Nocardia Infections/drug therapyABSTRACT
Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the total trait variation among communities on average. The relative extent of ITV tended to be greater for whole-plant (e.g. plant height) vs. organ-level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait-based community and ecosystem studies.
Subject(s)
Biodiversity , Phenotype , Plant Physiological Phenomena , Species SpecificityABSTRACT
Mast seeding, the synchronous, highly variable seed production among years, is very common in tree species, but there is no consensus about its main causes and the main environmental factors affecting it. In this study, we first analyze a long-term data set on reproductive and vegetative growth of Quercus ilex in a mediterranean woodland in order to identify the main environmental drivers of interannual variation in flower and seed production and contrast the impact of climate vs. adaptive factors as main causes of masting. Second, we conducted an experiment of rainfall exclusion to evaluate the effects of an increasing drought (simulating predictions of global change models) on both reproductive processes. The annual seed crop was always affected by environmental factors related to the precipitation pattern, these abiotic factors disrupting the fruiting process at different periods of time. Seed production was strongly dependent upon water availability for the plant at initial (spring) and advanced (summer) stages of the acorn maturation cycle, whereas the final step of seed development was negatively affected by the frequency of torrential-rain events. We also found clear evidence that seed masting in the study species is not only regulated by selective endogenous rhythms, but is mainly a physiological response to the variable environment. Our results from the rainfall exclusion experiment corroborated the conclusions obtained from the 26-year fruiting record and demonstrated that the high interannual variation in seed crop was mainly determined by the success in seed development rather than by the flowering effort. Under a global change scenario, it could be expected that the drier conditions predicted by climate models reinforce the negative effects of summer drought on seed production, leading to negative consequences for tree recruitment and forest dynamics.
Subject(s)
Droughts , Quercus/physiology , Rain , Seeds/physiology , Ecosystem , Mediterranean Region , Time FactorsABSTRACT
Se realizó una investigación descriptiva, transversal, con el objetivo de analizar el impacto de los defectos congénitos en la tasa de mortalidad infantil en el primer año de vida, en el municipio Arroyo Naranjo durante el período 2000-2006. Se incluyeron 26 niños fallecidos con defectos congénitos, lo que representó el 23 % del total de los fallecidos en este período. Dentro de los defectos congénitos hallados los de etiología multifactorial fueron los más frecuentes, predominaron los del sistema cardiovascular y el sistema nervioso central. Este estudio sienta las bases para trazar estrategias encaminadas a disminuir la frecuencia de defectos congénitos y mejorar la supervivencia de los niños portadores de los mismos en nuestra comunidad(AU)
This paper deals with analyzing the impact of congenital defects on infant mortality, the assessment of the variables associated to congenital defects which caused children to die during their first year of life and the proposal of strategies that allow minimizing the incidence of congenital defects representing a risk for childrens quality of life. An observation cross descriptive inquire, including twenty-six children, who died due to congenital defects in Arroyo Naranjo municipality during the period 2000-2006, representing 23% of all deaths was carried out. The most frequent congenital defects analyzed were of multivariate etiology, the most affected organs or system were the cardiovascular and the central nervous system, while the most common complication was sepsis. Based on these results, strategies intended to reduce the frequency of congenital defects and to improve childrens survival in spite of those problems are proposed(AU)