Environmental and Biotic Controls over Aboveground Biomass Throughout a Tropical Rain Forest

The environmental and biotic factors affecting spatial variation in canopy three-dimensional (3-D) structure and aboveground tree biomass (AGB) are poorly understood in tropical rain forests. We combined field measurements and airborne light detection and ranging (lidar) to quantify 3-D structure and AGB across a 5,016 ha rain forest reserve on the northeastern flank of Mauna Kea volcano, Hawaii Island. We compared AGB among native stands dominated by Metrosideros polymorpha found along a 600–1800 m elevation/climate gradient, and on three substrate-age classes of 5, 20, and 65 kyr. We also analyzed how alien tree invasion, canopy species dominance and topographic relief influence AGB levels. Canopy vertical profiles derived from lidar measurements were strong predictors (r ² = 0.78) of AGB across sites and species. Mean AGB ranged from 48 to 363 Mg ha⁻¹ in native forest stands. Increasing elevation corresponded to a 53–84% decrease in AGB levels, depending upon substrate age. Holding climate constant, changes in substrate age from 5 to 65 kyr corresponded to a 23–53% decline in biomass. Invasion by Psidium cattleianum and Ficus rubiginosa trees resulted in a 19–38% decrease in AGB, with these carbon losses mediated by substrate age. In contrast, the spread of former plantation tree species Fraxinus uhdei corresponded to a 7- to 10-fold increase in biomass. The effects of topographic relief at both local and regional scales were evident in the AGB maps, with poorly drained terrain harboring 76% lower biomass than forests on well-drained relief. Our results quantify the absolute and relative importance of environmental factors controlling spatial variation in tree biomass across a rain forest landscape, and highlight the rapid changes in carbon storage incurred following biological invasion. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author Contributions  GPA and RFH conceived of or designed the study. GPA, RFH, TAV, DEK, and TKB performed research and analyzed data. GPA, RFH, DEK, and TKB contributed new methods or models. GPA wrote the article.     

Phosphate-buffered saline-based nucleofection of primary endothelial cells

Although various nonviral transfection methods are available, cell toxicity, low transfection efficiency, and high cost remain hurdles for in vitro gene delivery in cultured primary endothelial cells. Recently, unprecedented transfection efficiency for primary endothelial cells has been achieved due to the newly developed nucleofection technology that uses a combination of novel electroporation condition and specific buffer components that stabilize the cells in the electrical field. Despite superior transfection efficiency and cell viability, high cost of the technology has discouraged cardiovascular researchers from liberally adopting this new technology. Here we report that a phosphate-buffered saline (PBS)-based nucleofection method can be used for efficient gene delivery into primary endothelial cells and other types of cells. Comparative analyses of transfection efficiency and cell viability for primary arterial, venous, microvascular, and lymphatic endothelial cells were performed using PBS. Compared with the commercial buffers, PBS can support equally remarkable nucleofection efficiency to both primary and nonprimary cells. Moreover, PBS-mediated nucleofection of small interfering RNA (siRNA) showed more than 90% knockdown of the expression of target genes in primary endothelial cells. We demonstrate that PBS can be an unprecedented economical alternative to the high-cost buffers or nucleofection of various primary and nonprimary cells.     

Structural and spectropotentiometric analysis of Blastochloris viridis heterodimer mutant reaction center

Heterodimer mutant reaction centers (RCs) of Blastochloris viridis were crystallized using microfluidic technology. In this mutant, a leucine residue replaced the histidine residue which had acted as a fifth ligand to the bacteriochlorophyll (BChl) of the primary electron donor dimer M site (HisM200). With the loss of the histidine-coordinated Mg, one bacteriochlorophyll of the special pair was converted into a bacteriopheophytin (BPhe), and the primary donor became a heterodimer supermolecule. The crystals had dimensions 400 × 100 × 100 μm, belonged to space group P4₃2₁2, and were isomorphous to the ones reported earlier for the wild type (WT) strain. The structure was solved to a 2.5 Å resolution limit. Electron-density maps confirmed the replacement of the histidine residue and the absence of Mg. Structural changes in the heterodimer mutant RC relative to the WT included the absence of the water molecule that is typically positioned between the M side of the primary donor and the accessory BChl, a slight shift in the position of amino acids surrounding the site of the mutation, and the rotation of the M194 phenylalanine. The cytochrome subunit was anchored similarly as in the WT and had no detectable changes in its overall position. The highly conserved tyrosine L162, located between the primary donor and the highest potential heme C₃₈₀, revealed only a minor deviation of its hydroxyl group. Concomitantly to modification of the BChl molecule, the redox potential of the heterodimer primary donor increased relative to that of the WT organism (772 mV vs. 517 mV). The availability of this heterodimer mutant and its crystal structure provides opportunities for investigating changes in light-induced electron transfer that reflect differences in redox cascades.     

Water balance comparison of two small experimental basins with different vegetation cover

In a river, the flow directly affects the physical and chemical properties of its water, with further consequences for aquatic biota. Land use practices and vegetation cover play a significant role in the water cycle. The wide-spread perception of forest cover, in terms of hydrology is that forests may reduce water runoff: although in rare instances the contrary has been reported. Water runoff varies seasonally and depends on the forest tree species. By no means can it be considered constant over large expanses of area or for various rainfall patterns. In this paper, the results of a long-term hydrological survey conducted in two experimental microbasins (operated by the Institute of Hydrology SAS, IH SAS) with different land use practices are presented. The Rybárik microbasin (0.119 km²) is dominated by row crop production. The basin was 70% cultivated by the state farm and 30% by a private farm. The Lesny microbasin (0.086 km²) is covered by a deciduous hornbeam regrowth forest (Carpinus betulus). The analysis revealed that the difference in the runoff from the forest and the agricultural land increases with increasing precipitation; however, at some point (extreme precipitations with low probability) the runoff from these basins is nearly equal.     

Differential Responses of Postmetamorphic Amphibians to Cattle Grazing in Wetlands

ABSTRACT Global amphibian declines have been linked to various anthropogenic land uses. Recent studies have documented negative impacts of cropland agriculture and deforestation on amphibians; however, few have examined potential impacts of cattle grazing in wetlands on resident amphibians. Therefore, we measured differences in number of captures and body size of postmetamorphic amphibians, egg mass abundance, and shoreline vegetation structure and composition between 4 wetlands with direct cattle access and 4 wetlands from which cattle were excluded on the Cumberland Plateau in Tennessee, USA. We captured amphibians at wetlands from March to August 2005 and 2006 using pitfall traps. Number of green frog (Rana clamitans) metamorphs captured at nonaccess wetlands was 2.5 times and 9.8 times greater than at wetlands with cattle access in 2005 and 2006, respectively. However, number of American toads (Bufo americanus) captured was 68 times and 76 times greater at cattle-access wetlands in 2005 and 2006, respectively. In general, metamorph body size was negatively correlated with species-specific capture rate. We detected no differences in egg mass abundance between cattle land-use types. Height, percent horizontal cover, and percent vertical cover of shoreline vegetation were 74%,25%, and 84% greater, respectively, in nonaccess wetlands in 2005; vegetation trends were similar in 2006. Our results suggest that cattle impact amphibian populations but effects vary by species. Differences in postmetamorphic capture rate may be related to less emergent vegetation at cattle-access wetlands. Although body size differed between land uses for metamorphs, these trends probably were short-lived, because we did not detect differences in juvenile and adult body size between land uses for most species. Based on our findings, we suggest that fencing cattle from wetlands may be a prudent conservation strategy for some amphibian species (e.g., ranids), whereas other species (e.g., bufonids) may benefit from controlled grazing.     

Spatio-temporal variations of functional groups in a Populus nigra L. entomocenosis in the Mitidja plain (Algeria)

This study presents the first data describing the communities of insects and arachnida colonizing 4 aerial compartments of Populus nigra. In terms of temporal variation and total abundance, the analyses show that the communities are structurally and functionally different. It also appears that the taxonomic richness of the communities, and partly their temporal distribution, change according to the gradient of the energy and defense resources under the effect of seasonal variations. The highest species richness recorded on the leaves compartment is due to the amplitude of histo-physiological modifications observed throughout the growing season. To cite this article: Z.-E. Djazouli et al., C. R. Biologies 332 (2009).     

Dendrin在初级感觉神经元内的表达

Dendrin作为一类新的树突蛋白,在脑内的表达随着行为活动的改变而变化。最近本课题组采用免疫组织化学方法对dendrin在小鼠初级感觉神经元内的表达进行了研究,并进一步研究外周神经损伤后dendrin在背根神经节和脊髓背角内的表达变化。本文还就dendrin的生物学特征以及在神经系统内表达情况对其近期研究成果和未来发展趋势进行综述。     

潮间带盐生植物生境微生物药用前景

近海潮间带植物生境的微生物是最富有生物多样性的海洋种群,其生境的独特性决定了该区域微生物较高的药用价值。文中介绍了我国南北方海域近海潮间带植物生境和微生物的特性及药用前景,为该区域微生物的开发利用提供参考。     

Can mobile sandy land be vegetated in the cold and dry Tibetan Plateau in China?

Desertification has taken place in the overgrazed grassland of the Tibetan Plateau,China,and the area of mobile sandy land has increased in recent decades.The challenging problem about desertification control is how to restore the vegetation of mobile sandy lands caused by severe desertification.Sand drifting is now regarded as the limiting factor of vegetation restoration in such lands.The initial phase of vegetation restoration is plant colonization,but it is often aborted due to sand drifting,and then vegetation restoration fails to proceed.For the sake of revegetation,the first step is to stop sand drifting to ensure plant colonization.In the northeastern Tibetan Plateau,China,feasible approaches have been found through long-term experiments,and the vegetation is being restored satisfactorily with these approaches in experimental sandy lands.The approaches comprise three types:enclosure,mechanical barriers and biological barriers.Different sandy lands require dissimilar combinations of these approaches.Enclosures may be adequate to revegetate inter-dunes or degraded grassland even in cold regions like the Tibetan Plateau,China,but it is deficient for revegetation of the shifting sand dunes unless mechanical and biological barriers are established simultaneously.     

Emergence and transmission of visual awareness through optical coding in the brain: A redox molecular hypothesis on visual mental imagery

Does the primary visual cortex mediate consciousness for higher-level stages of information processing by providing an outlet for mental imagery? Evidence based on neural electrical activity is inconclusive as reflected in the “imagery debate” in cognitive science. Neural information and activity, however, also depend on regulated biophoton (optical) signaling. During encoding and retrieval of visual information, regulated electrical (redox) signals of neurons are converted into synchronized biophoton signals by bioluminescent radical processes. That is, visual information may be represented by regulated biophotons of mitochondrial networks in retinotopically organized cytochrome oxidase-rich neural networks within early visual areas. Therefore, we hypothesize that regulated biophotons can generate intrinsic optical representations in the primary visual cortex and then propagate variably degraded versions along cytochrome oxidase pathways during both perception and imagery. Testing this hypothesis requires to establish a methodology for measurement of in vivo and/or in vitro increases of biophoton emission in humans' brain during phosphene inductions by transcranial magnetic stimulation and to compare the decrease in phosphene thresholds during transcranial magnetic stimulation and imagery. Our hypothesis provides a molecular mechanism for the visual buffer and for imagery as the prevalent communication mode (through optical signaling) within the brain. If confirmed empirically, this hypothesis could resolve the imagery debate and the underlying issue of continuity between perception and abstract thought.