Integrated global assessment of the natural forest carbon potential

Forests are a substantial terrestrial carbon sink, but anthropogenic changes in land use and climate have considerably reduced the scale of this system1. Remote-sensing estimates to quantify carbon losses from global forests2,3,4,5 are characterized by considerable uncertainty and we lack a comprehensive ground-sourced evaluation to benchmark these estimates. Here we combine several ground-sourced6 and satellite-derived approaches2,7,8 to evaluate the scale of the global forest carbon potential outside agricultural and urban lands. Despite regional variation, the predictions demonstrated remarkable consistency at a global scale, with only a 12% difference between the ground-sourced and satellite-derived estimates. At present, global forest carbon storage is markedly under the natural potential, with a total deficit of 226 Gt (model range = 151–363 Gt) in areas with low human footprint. Most (61%, 139 Gt C) of this potential is in areas with existing forests, in which ecosystem protection can allow forests to recover to maturity. The remaining 39% (87 Gt C) of potential lies in regions in which forests have been removed or fragmented. Although forests cannot be a substitute for emissions reductions, our results support the idea2,3,9 that the conservation, restoration and sustainable management of diverse forests offer valuable contributions to meeting global climate and biodiversity targets

Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

Electrodeposition of black chromium from self regulating electrolytes

A strong need islelt by a practical plater for a black chrome bath which can be operated around the ambient temperature (30°C) and at normally employed current densities and preferably not associated with any necessity of controlling the catalyst concentration. In the work now reported, experiments were carried out on the solubility of calcium fluoride gt 30°C in chromic acid solutions with a concentration range of .200- 425 g 1 I. Barium hydroxide was introduced in adequate quantities to desulphate chromic acid and also to counteract any drag-in of sulphate. Hullcell experiments were carried out at 23" and 31°C in order to assess approximately the cunent density range over which black chromium deposition was possible. This was followed by experiments in plating to study the effects of different parameters like chromic acid concentration, current density. temperature and duration of deposition on the nature of finish and deposition

Studies on hydrogen co-deposition during electrode position of metals with particular reference to chromium

The hydrogen embrittlement characteristics of steel during electrode position of chromium, have been evaluated by the electro permeation technique – the first report with special reference to chromium deposition. Electro permeation characteristics of standard, high-sulphate and sulphate-cryolite electrolytes, have been investigated over a polarizing current density (c.d) range of 165 to 1080 mA.cm -2 and temperature range of 30 ° to 50 ° C. The maximum coverage of hydrogen observed was typical of each electrolyte and did not vary systematically with the c.d. or temperature, as in the case of an acid or alkali and limiting c.d. was responsible for such a behavior. High temperature – high ratio and tetra chromate chrome solutions were similarly studied. The permeation rates of widely different deposits – crack free to highly cracked and mirror bright to dull – have been explained in terms of (i) crack nature; (ii) physical appearance and (iii) degree of packing (coarse/fine grained). Further, the difference in the ability of fine and big cracks to ‘block’ or ‘favor’ hydrogen entry respectively has been interpreted in terms of the concepts on ‘mechanism of chromium deposition’ put forward by Gerischer and Kappel and ‘micro throwing power’. A majority (70%) of chromium deposits possess medium or high ‘porosity’ enabling easy de-embrittling by baking the plated specimen, as observed in practice. The diffusion coefficient, D for hydrogen in steel was evaluated by three methods and they agree with the reported values. From the decay curve the hydrogen retained by the chromium deposit is estimated and is found to vary from 2-7 cm 3 per 100 gm of deposit for crack free deposits to 20-54 cm 3 for highly cracked deposits (100 gm. Of chrome deposit considered). A preliminary ‘strike’ in chromium plating confers enhanced embrittlement to the steel. In salvaging work, presence of a previous chromium layer effectively blocks the hydrogen entry during subsequent chromium plating and thus reduces significantly the risk of embrittlement of the substrate. Polarisation of steel in pure chromic acid introduces large quantities of hydrogen into the cathode, compared to the chrome baths and the films formed are highly porous and hence can be degassed by banking. Studies in four types of nickel electrolytes indicate that they confer insignificant embrittlement. The D values are in conformity with the values obtained in chromium electrolytes.Chromium deposition over nickel undercoat shows that thin deposits up to 20 microns enhance the permeation rate and 34 to 58 microns thick deposits lower the hydrogen entry by 25%, compared to chromium plating without an undercoat. Electrode position of copper from cyanide electrolytes is similar to chromium deposition, from hydrogen permeation view point. The D values agree well with the values obtained in chromium and nickel electrolytes. As low as 1.5 micron thick copper undercoat is capable of blocking completely the hydrogen entry during subsequent chromium deposition

Electron microscope observations on electrolytic Ni-Mo-Fe coatings

Selected Ni-Mo-Fe coatings were electrodeposited from ammoniacal citrate baths by varying the plating parameters. Their surfaces were examined by scanning electron microscopy for topography and SE imaging. Observed electrocatalytic, corrosion and optical properties of the coatings were found to be dependent on surface structure. The results were also used to understand the influence of electrodeposition variables. The plating diameters were found to have strong influence on the surface structure. Increases in deposition CD resulted in phase segregation in these materials. Also it was confirmed that increases in molybdenum content of the plating bath introduced heterogeneity in the plated samples with occurrence of more than one phase. Multinucleation in crystal structure was observed in samples electrodeposited at near neutral pH levels, again due to increased molybdenum content. The coatings reveal network formation at 300 deg. C. Inclusion of Mn was helpful in obtaining homogeneous deposit

Influence of plating variables on the electrocatalytic behavior of Ni-Mn electrocoated cathodes for alkaline water electrolysis

The electrocatalytic properties of Ni-Mn codeposits as a function of plating parameters is studied in detail. Higher current densities, moderate temperature and baths of neutral pH yield good electrocatalyst