Dissolved carbon dioxide gas diffusion in green Nothofagus fusca heartwood

Summary Non-steady state desorption of dissolved carbon dioxide gas from green Nothofagus fusca heartwoood boards saturated with carbon dioxide gas at a pressure of 1.5 MPa was used to measure transverse dissolved carbon dioxide gas diffusivities at 1, 20 and 30 °C. Mean transverse diffusion coefficients were 0.6×10^-11m²s^-1 at 1 °C, 4.2×10^-11m²s^-1 at 20 °C, and 8.4×10^-11m²s^-1 at 30 °C. These are 0.6, 2.5 and 3.8% of the dissolved carbon dioxide gas diffusivities in water at 1, 20 and 30 °C respectively. The activation energy of dissolved carbon dioxide gas diffusion in green N. fusca heartwood is 59. 4 kJ mol^-1. This is three times the activation energy of dissolved carbon dioxide gas diffusion in water. This suggests the presence of a reaction mechanism between the dissolved carbon dioxide molecules and the cell wall constituents.The Forest Research Institute, Ministry of Forestry, New Zealand, supported this work by way of a postgraduate studentship.     

Transverse shape analysis of xylem ground tissues by Fourier transform image analysis II: cell wall directions and reconstruction of cell shapes

Cell wall directions of tracheids in transverse sections of Agathis sp. and Cryptomeria japonica and fiber bodies in Magnolia obovata were quantified by Fourier transform image analysis (FTIA). Three kinds of information about cell shapes were determined from the angular distribution functions of the net map-power spectrum pattern (NM-PSP): (1) the peak angle expresses the most frequent cell wall direction, (2) the area of the peak is indicative of cell wall length, and (3) the dispersion of the peak indicates the fluctuation of cell wall orientation. Fluctuations were expressed as the standard deviation (σ) by the use of statistical analysis. Cell wall directions in Agathis, that is, directions of the tangential and radial walls (three orientations were detected) were 0° (σ = 7°), 59° (12°), 91° (9°), and 122° (12°), respectively. Pentagonal and hexagonal models were reconstructed as cell shape models in a calculated ratio of 60 : 40. On the other hand, directions were 0° (5°), 76° (12°), 89° (5°), and 102° (12°) in a calculated ratio of 45 : 55 in Cryptomeria. Fiber bodies were extracted in Magnolia and their wall directions were 0° (5°), 50° (7°), 90° (6°), and 131° (7°), respectively. The ordinary accumulated image analysis (OAIA) was checked at the same time in Agathis, and indicated that FTIA could be used as a method of reconstruction of cell shape.     

Evaporation over a tropical tidal salt flat

Measurements of temperature, wind speed and humidity within 6 mof the surface of a mangrove-fringed tidal tropical salt flatwere performed. Using the aerodynamic method, this data was usedto infer evaporation rates from the salt flat. For a few daysafter tidal inundation or rain, the salt flats were wet andevaporation rates of about 5×10^-3 m day^-1 prevailed. By 8 daysafter tidal inundation and with no rain, evaporation rates haddropped to less than 2×10^-3 m day^-1. The monthly evaporation ratewas about 7×10^-2 m. This generates high salinity which, togetherwith surface temperatures exceeding 50°C, prevents colonisationof these areas by mangroves.     

Hydrolysis kinetics of hexosanes entering into the composition of white water coming from the fiber board industry

Summary Hydrolysis kinetics of hexosanes entering into the composition of white water coming from the fiber board industry to hexoses, catalyzed by sulphuric acid and hydrochloric acid has been investigated. Constant rates of the reaction, catalyzed by 0.31 m sulphuric acid, determined at the temperatures 353 °K, 363 °K, 373 °K are respectively equal to: 1.40·10^-5s^-1, 5.75·10^-5s^-1, 30.06·10^-5s^-1.Constant rates of the reaction, catalyzed by 1 m hydrochloric acid, determined at the temperatures 343 °K, 353 °K, 363 °K are respectively equal to: 0.2008·10^-5s^-1, 0.82·10^-5s^-1, 3.63·10^-5s^-1.Constant rates of the reaction, catalyzed by 2 m hydrochloric acid, determined at the temperatures 343 °K, 353 °K, 363 °K are equal respectively to: 0.52·10^-5s^-1, 2.25·10^-5s^-1, 8.15·10^-5s^-1. Constant rates of the reaction, catalyzed by 3 m hydrochloric acid, determined at the temperatures 343 °K, 353 °K, 363 °K are respectively equal to: 3.824·10^-5s^-1, 8.596·10^-5s^-1, 13.10·10^-5s^-1.The activation enthalpy of the reaction, catalyzed by 0.31 m sulphuric acid, determined in the range of temperatures 353 °K–373 °K is equal to 168.36 kJmol^-1. The activation entropy of the reaction, catalyzed by 0.31 m sulphuric acid is equal to 136.19 JK^-1mol^-1. The activation enthalpy of the reaction, catalyzed by 1 m, 2 m, 3 m hydrochloric acid, determined in the range of temperatures 343 °K–363 °K is equal to 145.37 kJmol^-1. The activation entropy of the reaction catalyzed by 1 m, 2 m, 3 m hydrochloric acid is respectively equal to: 68.97 J K^-1mol^-1, 75.73 J K^-1mol^-1, 79.68 JK^-1mol^-1.     

Study of the release in water of a chemical used for preservation of wood. Effect of the dimensions of the wood

Summary Various chemicals are used for protecting wood samples against fungi, and some of them are released in water, leading to pollution of the water. The kinetics of release of pentachlorophenol in water has here been studied, by considering the diffusion through the wood along the three principal axes of diffusion. The experiments and the modelling of the process is successfully coupled. The numerical model takes the three principal diffusivities, the partition factor, the volumes of wood and water into account. The effect of the length of the wood sample taken along the longitudinal axis of diffusion is especially studied, as the longitudinal diffusivity is much higher than the other two principal diffusivities. The effect of the relative volumes of wood and water is also of considerable interest not only for the concentration of the chemical in water but also for the rate of release.Symbols C concentration of liquid (g/cm³) - C_s, C_eq,t concentration of liquid on the surface, at equilibrium with the surrounding, respectively - C_i,j,k concentration of liquid in the wood at position (i, j, k) - D diffusivity (cm²/s) - h coefficient of mass transfer on the surface (cm/s) - i, j, k integers characterizing the position in the wood - K partition factor - L, R, T dimensions of the parallelepipedic wood sample - Mini amount of chemical contained in the wood at the beginning of the desorption - M_L, M_R, M_T dimensionless numbers - M_t, M amount of chemical released up to time t, up to infinite time, respectively - N half-number of slices taken in the wood parallelepiped along each dimension - V_water volume of the surrounding water - x, y, z coordinates - L, R, T thickness of the slices taken in the wood for calculation - t increment of time     

Dynamic soil processes on heathland due to changes in vegetation to oak and Sitka spruce

Soil and soil water chemistry under three different vegetation-types on a former heath area were investigated in Jutland, Denmark. An unmanaged heathland left undisturbed since the start of this century is now invaded by the oaks. Together with a small Sitka plantation (age 60 years), soil development due to vegetation changes was investigated. The typical heathland podzol soil had changed within decades under the oak trees towards an acid brown soil. The soil under the Sitka spruce had changed towards a more strongly podzolized soil compared to the former heath soil. Present processes occurring within the soil were investigated by analysis of soil solution chemistry. The leaching of inorganic ions and soluble organic matter had increased manifold under Sitka spruce. Nitrification increased markedly with soil depth probably due to effects of higher pH. The increase of nitrate with soil depth was followed by a similar increase in dissolved aluminium. The equivalence of the dissolved organic carbon varies under oak and heath between 6 and 10 m eqv g⁻¹ TOC and under Sitka the equivalence of the dissolved carbon was between 10 and 15 m eqv g⁻¹. No nitrate and only traces of ammonium were found in soil water from the upper 30 cm of the soil under heath. Soil nitrogen was almost exclusively (more than 90%) connected to the carbon cycle. Under Sitka spruce generally less than 20% of soil water nitrogen was coupled to the carbon cycle, i.e. most of the nitrogen in the soil water leaving the rooting zone under Sitka spruce was nitrate. In the oak forest, nitrate only appeared as traces in the soil water in the winter period and in the summer period in relatively higher amounts. Generally, between 80% and 90% of the nitrogen was coupled to the carbon cycle in the winter and in the summer only 50%.     

Stream size influences stream temperature impacts and recovery rates after clearfell logging

Water temperature has profound effects on stream ecosystems. We studied effects of clear-fell logging Pinus radiata plantations on mid-summer water temperatures and recovery times in streams with 2–12 m wide channels. Post-logging increases were 2–3.8 °C for summer daily means and 4–7.3 °C for summer daily maxima. Rates of recovery of thermal regimes after logging were strongly negatively correlated with stream size, as indexed by catchment area, channel width or baseflow (r² = 0.80–0.93). Summer daily mean and maximum temperatures declined during the riparian vegetation regrowth phase by 0.18 and 0.47 °C year⁻¹, respectively, for the largest stream and 1.4 and 1.9 °C year⁻¹ in the smallest stream. Thermal regimes were restored in small streams (2–4 m wide channels) about 6–8 years after clearfelling. In medium-sized streams (6–12 m wide channels), we predict this recovery will take 12–16 years.     

Moisture diffusion coefficient of reaction woods: compression wood of Picea abies L. and tension wood of Fagus sylvatica L.

The moisture diffusion coefficient of compression wood in spruce (P. abies) and tension wood in beech (F. sylvatica) was examined. The results indicated that the diffusion coefficient measured under steady-state condition (cup method) could well characterize the drying kinetics of the reaction woods. The compression wood offered more resistance to the moisture diffusivity when compared with the corresponding normal wood. The thick cell wall rich in lignin explains the small mass diffusivity in compression wood. In contrast, the mass diffusivity in beech is almost always higher in tension wood than in normal wood, in spite of similar density values. The high moisture diffusion in tension wood can be explained by the ease of bound water diffusion in the gelatinous layers (G-layers).     

Dissolved organic carbon and nitrogen leaching from Scots pine, Norway spruce and silver birch stands in southern Sweden

The effects of three common tree species - Scots pine, Norway spruce and silver birch - on leaching of dissolved organic carbon and dissolved nitrogen were studied in an experimental forest with podzolised soils in southern Sweden. We analyzed soil water collected with lysimeters and modeled water fluxes to estimate dissolved C and N fluxes. Specific UV absorbance (SUVA) was analyzed to get information about the quality of dissolved organic matter leached from the different stands. Under the O horizon, DOC concentrations and fluxes in the birch stands were lower than in the spruce and pine stands; annual fluxes were 21 g m⁻² y⁻¹ for birch and 38 g m⁻² y⁻¹ and 37 g C m⁻² y⁻¹ for spruce and pine, respectively. Under the B horizon, annual fluxes for all tree species ranged between 3 and 5 g C m⁻² y⁻¹, implying greater loss of DOC in the mineral soil in the coniferous stands than in the birch stands. We did not find any effect of tree species on the quality of the dissolved organic matter, as measured by SUVA, indicating that the chemical composition of the organic matter was similar in leachates from all three tree species. Substantial amounts of nitrogen was leached out of the soil profile at the bottom of the B horizon from the pine and birch stands, whereas the spruce stands seemed to retain most of the nitrogen in the soil. These differences in N leaching have implications for soil N budgets.     

The ultrastructure of cellulose from wood

Summary Since in these studies wood is used as basic material for the isolation of cellulose the structure and the composition of this planty substance were considered in greater detail. New measurements of the fiber dimensions and the thickness of the cell wall layers of typical springwood and summerwood tracheids in combination with data obtained from literature led to a model showing the most probable distribution of cellulose, polyoses, and lignin within the cell wall. The ultrastructural composition of the wood cell wall has been deduced from the properties and the behaviour of the cell wall components. The described model will be the basis for subsequent considerations.

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Zusammenfassung Da bei diesen Untersuchungen Holz das Ausgangsmaterial zur Isolierung von Cellulose bildet, wurden die Struktur und die Zusammensetzung dieser pflanzlichen Substanz näher betrachtet. Neue Messungen der Faserdimensionen und der Dicke der einzelnen Wandschichten typischer Früh- und Spätholztracheiden in Verbindung mit Literaturwerten führten zu einem Modell, das die wahrscheinlichste Verteilung von Cellulose, Polyosen und Lignin innerhalb der Zellwand zeigt. Die ultrastrukturelle Zusammensetzung der verholzten Zellwand wurde aus den Eigenschaften und dem Verhalten der Zellwandkomponenten abgeleitet. Das beschriebene Modell wird die Grundlage für nachfolgende Betrachtungen bilden.

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Dedicated in appreciation to my esteemed teacher Prof. Dr.-Ing. Georg Jayme, on the occasion of his 70th birthday.     

The Summerwood: Springwood Ratio in Conifers: How it arises, varies, and affects end use for timber, board, and paper

A theoretical discussion of variation in summerwood and springwoodcontents among conifers. Three methods of measuring these, bycross-sectional area of logs, by dryweight fibre percentage,and by nominal specific gravity, are compared. High-summerwood tissues have a nominal specific gravity of 0?45or over; low-summerwood tissues have a specific gravity below0?45. All conifers have a low summerwood content in their juvenilewood or core wood formed towards their stem-tips. In Pinus,Larix, and Pseudotsuga the summerwood percentage increases markedlywith age, but only in the outer layers towards the butt; inPicea, Abies, and Tsuga similar increases occur, but high-summerwoodtissues are seldom found. Within any species, and for any particulargrowth rate, low-summerwood tissues are characteristic of regionsof high relative humidity where summer water deficits rarelyoccur, such as high altitudes, far northern latitudes, and themaritime climate of western Britain. High-summerwood tissuesdevelop where summer temperatures are high, with associatedstrong sunshine, low relative humidity, and frequent summerwater deficits. High-summerwood tissues have greater strength in compressionand bending, relative to volume; but low-summerwood tissueshave greater strength relative to their weight. Low-summerwoodmaterial has proved satisfactory for most structural purposes,and for the manufacture of several kinds of artificial board.Its technical properties for the making of many types of paperare excellent, provided high resistance to tearing is not required.Likely summerwood content should guide planting programmes andmarketing policies.     

Some considerations in heterogeneous nonisothermal transport models for wood: a numerical study

This study compares a number of coupled heat and mass transfer models and presents numerical comparisons of phenomenological coefficients between the four models (Stanish, Perre, Pang, and Avramidis) that are most frequently used in the literature to describe wood-drying processes. The USDA sorption isotherm, the Hailwood-Horrobin model, was adopted to calculate the relations between moisture content in wood and water vapor pressure at any temperature. Due to different assumptions about the driving forces of heat and mass transfer, coefficients in each model represent different values for moisture content and temperature and are closely related to each other. In the case of isothermal mass transfer, the moisture diffusion coefficient in the transverse directions from the Stanish and Pang models increased with decreasing moisture content. This contradicts the Avramidis and Perre models and numerous experimental results. Thermal diffusion effects on the drying process may not be predominant because the nonisothermal state is relatively short. Therefore, the Perre model, which does not consider the thermal diffusion effect, has been used successfully in the drying simulation. However, it may be erroneous in certain cases when the nonisothermal state prevails over the system, such as building physics. The Pang model cannot explain the phenomena of thermal diffusion and moisture thermodiffusion. It might be reasonable to modify the thermal diffusion of the Avramidis model, which is lower than that of the Stanish model. The apparent heat diffusivity was higher than the true heat diffusivity.     

Determination of the effective water conductivity of red pine sapwood

Summary The instantaneous profile method was used to establish the boundary desorption curve of the effective water conductivity function of red pine (Pinus resinosa Ait.) sapwood in the radial and tangential directions from nearly saturated to dry conditions at 18, 56 and 85 °C. The results obtained demonstrate that the effective water conductivity is a function of moisture content, temperature, and direction of flow. The effective water conductivity increases by several orders of magnitude (10⁴–10⁵) as moisture content increases from dry to nearly saturated conditions at a given temperature. The effective water conductivity also increases by a factor varying between 10 and 50 as temperature rises from 18 to 85 °C in the moisture content range considered. The variation of the moisture content–water potential relationship with temperature can explain part of the temperature effect. The effective water conductivity was generally higher in the radial direction than in the tangential direction in a ratio varying from about 1/1 to 3/1 depending on moisture content and temperature. Finally, the flux–gradient relationships obtained at given moisture contents were found to be linear, confirming the validity of using a moisture flux equation considering the water potential gradient as the driving force for the experimental conditions considered in the present work. The knowledge of the effective water conductivity function and of the moisture content–water potential relationship allows the utilization of a two-dimensional model of moisture movement in wood during drying using the gradient in water potential as the driving force for drying at temperatures up to 85 °C. Received 27 February 1998     

Water quality of Kaptai reservoir in Chittagong Hill Tracts of Bangladesh

A study was conducted in Kaptai reservoir, one of the largest man-made freshwater lakes of South-east Asia, to determine present status of water quality and its suitability for fishing and other uses. Water samplings were from middle part of the reservoir at 0.2 and 0.8 fractional depths at five different locations from upstream to downstream viz. Burburichara, Maichchari, Subolong, Basanthakum, and Rangamati. Water analyses show that concentrations of NO3-N, K+ and total P, and suspended solid at all the sampling stations were beyond the recommended values for fish culture. Concentrations of Na+, Ca2+, Mg2+, SO42-, Cl-, total dissolved solid (TDS), dissolved oxygen (DO) and chemical oxygen demand (COD) were within the standards for aquaculture. Concentrations of NO3-N, SO42-, K+ and total P showed no definite trend with depths, locations as well as rainy and dry seasons. Water pH, conductivity, Na+ and HCO3- contents were lower in rainy season, and DO and COD higher at almost all the locations in both the depths, compared with dry season. Total solids and concentrations of TDS, DO, COD, Ca2+, Mg2+ and Na+ were higher in upstream and decreased gradually towards downstream in the reservoir. Concentrations of DO and Ca2+ and pH were higher and Mg2+ less at 0.2-fractional depth than those at 0.8-fractional depth at almost all the locations. The reservoir is in mesotrophic condition containing high concentration of NO3-N and total P, in alarming status with the presence of excessive suspended solids from urban pollution around the town. It is necessary to adopt measures for protecting water quality in the reservoir due to such deteriorations.     

Comparative study of organic solvent-soluble and water-soluble lipophilic extractives from wheat straw 2: spectroscopic and thermal analysis

As a continuing study of six organic solventsoluble lipophilic extractives and one water-soluble lipophilic extract from wheat straw, seven extracts were further compared using Fourier transform-infrared (FT-IR) analysis,¹H and¹³C nuclear magnetic resonance (NMR) spectroscopy, and thermal analysis. In the FT-IR spectra of two-thirds chloroform/one-third methanol, methyltertbutyl ether (MTBE), hexane, petroleum ether, and dichloromethane extracts, a strong band at 1746cm^–1 is indicative of the ester carbonyl of triglycerides or steryl esters or waxes, whereas the occurrence of carboxylic carbonyl of free fatty acids or resin acids at 1712–1719 cm^–1 is verified in the spectra of two-thirds toluene/one-third ethanol and hot water extracts. Signals at 187.9,178.4, and 173.3 ppm in the¹³C NMR spectrum of MTBE extract correspond to carbonyl groups of resin acids, fatty acids, and fatty acid/steryl esters, respectively. All the extractives were to varying degrees thermally unstable at a temperature of about 200°C, and the melting temperature occurred at about 54°C.     

Effects of chronic nitrogen amendment on dissolved organic matter and inorganic nitrogen in soil solution

Increased atmospheric deposition of N to forests is an issue of global concern, with largely undocumented long-term effects on soil solution chemistry. In contrast to bulk soil properties, which are typically slow to respond to a chronic stress, soil solution chemistry may provide an early indication of the long-term changes in soils associated with a chronic stress. At the Harvard Forest, soil solution was collected beneath the forest floor in zero tension lysimeters for 10 years (1993–2002) as part of an N saturation experiment. The experiment was begun in 1988 with 5 or 15 g N m⁻² per year added to hardwood and pine forest plots, and our samples thus characterize the long-term response to N fertilization. Samples were routinely analyzed for inorganic nitrogen, dissolved organic nitrogen (DON), and dissolved organic carbon (DOC); selected samples were also analyzed to determine qualitative changes in the composition of dissolved organic matter. Fluxes of DOC, DON, and inorganic N were calculated based on modeled water loss from the forest floor and observed concentrations in lysimeter samples. The concentration and flux of inorganic N lost from the forest floor in percolating soil solution are strongly affected by N fertilization and have not shown any consistent trends over time. On average, inorganic N fluxes have reached or exceeded the level of fertilizer application in most plots. Concentrations of DOC were unchanged by N fertilization in both the hardwood and pine stands, with long-term seasonal averages ranging from 31–57 mg l⁻¹ (hardwood) and 36–93 mg l⁻¹ (pine). Annual fluxes of DOC ranged from 30–50 g m⁻² per year. DON concentrations more than doubled, resulting in a shift toward N-rich organic matter in soil solution percolating from the plots, and DON fluxes of 1–3 g m⁻² per year. The DOC:DON ratio of soil solution under high N application (10–20) was about half that of controls. The organic chemistry of soil solution undergoes large qualitative changes in response to N addition. With N saturation, there is proportionally more hydrophilic material in the total DON pool, and a lower C:N ratio in the hydrophobic fraction of the total DOM pool. Overall, our data show that fundamental changes in the chemistry of forest floor solution have occurred in response to N fertilization prior to initiation of our sampling. During the decade of this study (years 5–14 of N application) both inorganic N and dissolved organic matter concentrations have changed little despite the significant biotic changes that have accompanied N saturation.     

Diffusion of chemicals into archaeological waterlogged hardwoods obtained from the Thang Long Imperial Citadel site,Vietnam

This study shows a method to easily develop suitable impregnation procedure of chemicals for preserving the archaeological waterlogged wood (WW) using diffusion constant. The steady-state diffusion coefficients of polyethylene glycol 4000 (PEG4000), trehalose, and keratin through eight archaeological waterlogged wood species were obtained from the total amounts of the chemicals diffused through the wood samples. The diffusion coefficients were strongly affected by the anatomical structures of the wood species and degree of wood deterioration. Within the same species of wood, the highest diffusion rates were measured in the longitudinal direction, followed by those in the radial and tangential directions. The longitudinal diffusion coefficients were 1.5- to 8.1-times higher than the radial diffusion coefficients, which were in turn approximately 1.1- to 5.7-times higher than the tangential diffusion coefficients. The diffusion rates were found to be inversely proportional to the molecular weight of the diffusing chemical. The diffusivity of trehalose through the waterlogged woods was found to be higher than those of keratin and PEG4000. This study provides a potential method to easily estimate chemical diffusion coefficients for dip-diffusion treatments.     

Untersuchungen zur Wirkung von Methylbromid besonders bei niedrigen Temperaturen gegen Khaprakäfer-Larven (Trogoderma granarium Everts (Dermestidae,Coleoptera)

Tests on the efficiency of methyl bromide especially at lower temperatures in controlling Khapra Beetle Larvae (Trogoderma granarium Everts), Dermestidae, Coleoptera In the laboratory, experiments were carried out to investigate the efficiency of methyl bromide in controlling the Khapra Beetle (Trogoderma granarium Everts) in a specially developed fumigation apparatus at 30, 25, 20, 15, 10, 5, 0, –6, and –10 °C as well as 40 – 70% relative humidity. The lethal dosis as c. t. products in mg.h/l were estimated at different temperatures from the dosis-mortality regression lines. The treated larvae were divided after the fumigation into two series (1 and 2). The larvae of serie 1 were held immediately after the fumigation time at 28°C, while the larvae of serie 2 were kept for another 10 days at the same fumigation temperature, then removed to 28°C until final control. Experimental results of both series showed that, for a given mortality the c. t. product required at low temperatures considerably increased and accordingly the tolerance of the larvae decreased with a rise in temperature (in range 0–30°C). A maximum in the tolerance of the larvae to methyl bromide was found at 0°C. At lower trial temperatures –6 and –10°C the required c. t. product subsequently decreased. This result was caused through the combined harmful effect of the low temperatures and the methyl bromide. It is evident from the estimated values that the c. t. products of methyl bromide required for a given mortality in serie 2 especially at lower temperatures (from +10 to –10°C) are lower than that in serie 1. For example in serie 2 the c. t. product required to kill the larvae decreased at 5°C to less than 50%. This effect of the post-treatment temperature was also examined to obtain the shortest holding time for maximum mortality, which was observed after 3–4, 7–8, 7–8 and 8–9 days at 10, 5, 0, and –6°C respectively. From a practical aspect this result is of great importance, because it proves the influence of the factors prevailing after a quarantine fumigation.     

On movement of water through wood — The diffusion coefficient

Summary It is demonstrated that there can be only one driving potential for the movement of water through wood and this will be a function of wood state. On the assumption that the driving potential is the partial pressure of water vapour, a theoretical expression is derived for the diffusion coefficient. Such expression is fitted to diffusion coefficients for Scots pine and a remarkably good fit is obtained.Symbols a reciprocal mean radius of curvature of a capillary meniscus; also taken to be the radius of the corresponding exposed liquid surface, m - b spacing between flow paths in the cell wall, m - D diffusion coefficient for water in wood with vapour pressure as the driving potential, kg/ms Pa - D_a diffusion coefficient for water vapour through air, kg/ms Pa - D diffusion coefficient for water in wood with the driving potential - D diffusion coefficient for water in wood with the driving potential - D₀ diffusion coefficient for water in wood with vapour pressure as the driving potential, which is associated with leakage paths through the wood, kg/ms Pa - D_f diffusion coefficient for water in wood with vapour pressure as the driving potential, corresponding to fibre saturation and with no leakage paths, kg/ms Pa - D_c diffusion coefficient for water in wood with vapour pressure as the driving potential, which is associated with the constriction of the vapour flow as it approaches the cell wall, kg/ms Pa - D diffusion coefficient for water in wood with moisture content as the driving potential, kg/ms - diffusivity for water vapour in air, m²/s - F flux of water, kg/m² s - p partial pressure of water vapour, Pa - R specific gas constant for water, J/kg K - r fractional relative humidity - T temperature, K - x length coordinate in direction of flow, m - the dimensionless ratio D_f/D_c evaluated at r=1/e - arbitrary driving potential for movement of water in wood - cell spacing in the direction of water flux, m - density of liquid water, kg/m³ - coefficient of surface tension, N/m - arbitrary driving potential for movement of water in wood - fractional moisture content     

Assessment of ecosystem services as an opportunity for the conservation and management of native forests in Chile

This paper quantifies two important native forest ecosystem services in southern Chile: water supply and recreational fishing opportunities. We analyzed streamflow in relation to forest cover in six watersheds located in the Valdivian Coastal Range (39°50′–40°05′S), the effect of forest management on streamflow in two watersheds in the Valdivian Andes (600–650 m of elevation; 39°37′S), and fish abundance as a function of forest cover in 17 watersheds located in the Coastal Range and the Central Depression (39°50′–42°30′S). We found that the annual direct runoff coefficient (quickflow/precipitation) and total streamflow/precipitation in the dry summer season were positively correlated with native forest cover in the watershed (R² = 0.67 and 0.76; ^*P = 0.045 and 0.027, respectively) during four years of observations. Conversely, a negative correlation was found between summer runoff coefficients (total streamflow/precipitation) and cover of Eucalyptus spp. and Pinusradiata plantations (R² = 0.84; ^*P = 0.010). We estimated a mean increase of 14.1% in total summer streamflow for every 10% increase in native forest cover in the watershed. The analysis of streamflow changes between two paired watersheds dominated by native secondary Nothofagus stands, one thinned with 35% of basal area removal and a control, showed that the former had a 40% increase during summer (four years of observations). The best correlation between fish abundance and forest cover was found between trout abundance (%) and secondary native forest area in 1000 m × 60 m stream buffers (R² = 0.65, ^***P < 0.0001). We estimated a 14.6% increase in trout abundance for every 10% increase of native forest cover in these buffers. Similar approaches to quantify forest ecosystem services could be used elsewhere and provide useful information for policy and decision-making regarding forest conservation and management.