Quantification of the effect of forest harvesting versus climate on streamflow cycles and trends in an evergreen broadleaf catchment

ABSTRACT

A new method known as Unobserved Components–Dynamic Harmonic Regression (UC-DHR) was applied to a 39-year record of rainfall and streamflow for three sub-catchments of the Sarukawa Experimental Watershed in southwestern Japan. Some 25% of the timber was harvested from one of the sub-catchments in May–July 1982 and the objective was to quantify the magnitude of this effect relative to the effects of climate cycles (e.g. Southern Oscillation Index). The observed effects of inter-annual climate cycles (i.e. 0.89–1.36 mm/d) were seen to be comparable (i.e. 0.70–1.17 mm/d) to the effects of harvesting 25% of the standing timber. This result underlines the importance of always quantifying the effect of climate on streamflow response when harvesting impacts are studied.

Editor D. Koutsoyiannis; Associate editor T. Okruszko     

Experimental determination of F and Cl partitioning between lherzolite and basaltic melt

We experimentally determined F and Cl partition coefficients together with that of 19 trace elements (including REE, U-Th, HFSE and LILE) between basaltic melt and lherzolite minerals: olivine, orthopyroxene, clinopyroxene, plagioclase and garnet. Under conditions from 8 to 25 kbars and from 1,265 to 1,430°C, compatibilities of F and Cl are globally ordered as D ^Cpx/melt > D ^Opx/melt > D ^Grt/melt > D ^Ol/melt > D ^Plag/melt, and D _F ^mineral/melt is larger than D _Cl^mineral/melt. Four other major results were brought to light. (1) Chlorine partition coefficients positively correlate with the jadeite component in orthopyroxene, and increase of the CaTs component promotes Cl incorporation in clinopyroxene. (2) Variations of fluorine partition coefficients correlate strongly with melt viscosity. (3) F and Cl partition coefficients correlate with the Young’s modulus (E ₀) of pyroxene octahedral sites (M sites) and with Raman vibrational modes of pyroxenes. This demonstrates a fundamental interaction between the M site of pyroxenes and the incorporation of F and Cl. (4) We also determined the parameters of the lattice-strain model applied to 3+ cation trace elements for the two M sites in orthopyroxene and clinopyroxene: D ₀^M1, D ₀^M2, r ₀^M1, r ₀^M2, E ₀^M1 and E ₀^M2.     

The role of pore water in the mechanical behavior of unsaturated soils

Deformation and failure of soils are governed by the stresses acting on the soil skeleton. The isotropic stress acting on the soil skeleton can be divided into two components. One is the stress component which is transmitted through the soil skeleton. This skeleton stress is influenced by the pore water (bulk water) in the soil. The other is the internal stress component which does not contribute to equilibrium with a given external force. The internal stress is induced by the capillary tension of meniscus water clinging to the contact point of soil particles and acts so as to connect the soil particles tightly. Therefore, in modeling the stress and strain relations for unsaturated soils, it is of much importance to quantitatively evaluate how the pore water exists in the soil. This paper discusses the role of pore water on the mechanical behaviour of the soil. In particular, the significance of the water retention curve is emphasized from a mechanical viewpoint. Essential features required in modeling of the constitutive relations for unsaturated soils are discussed and presented.     

Instability of a highly reducing atmosphere on the primitive Earth

The eddy diffusion coefficient in the primitive upper atmosphere of highly reducing type (CH₄H₂) is estimated to be of the order of 10⁸ cm²sec^?1 or a little less, by solving the dissipation equation of internal gravity waves. Such a strong atmospheric mixing is clearly inconsistent with the previous assumption by McGovern that photochemical equilibrium was established in the upper atmosphere. By taking into account the mixing effect, the exospheric temperature of the highly reducing atmosphere has been computed to be higher than 1300°K. The result indicates that the hypothetical reducing atmosphere might have disappeared, if it existed, in a short time due to the gravitational escape of hydrogen and, consequently, that an anoxygenous but non-reducing atmosphere might be a more plausible environment for the origin of life.     

Flare event statistics on UV Ceti-type stars

A statistical study of 228 flares on the three UV Ceti-type stars, i.e., YZ CMi, AD Leo, and EV Lac, is presented. Observations were gathered by Ichimura and Shimizu over a total monitoring time of 907 hours distributed over 18 years (1971 to 1988). Period analysis of flare activity was performed, and no periodicity was detected on the three stars for either the flare number rate or the energy rate in time-scales ranging from a year up to 14 years. Average colour of flares at peak was (U-B)=–0.98±0.17 and (B-V)=0.05±0.13. Cumulative number distributions of flare event time-integrated energies were solved by a least-squares method on a log-log plot for a power-law function to get both the constant of and the gradient , which were found to be similar among the three stars. The gradient showed that rare large flare events radiate most of the energy released by all the flare events in the monitoring time. The flare number rate and energy rate are similar if the power-law distributions are extended up to a specific maximum energy. In reality, the Kolmogorov-Smirnov test showed that the observed cumulative number distributions of flare event energy were not necessarily a power-law function. The monte-Carlo simulation, however, indicates that the monitoring time and/or the patrol observation time interval may not be long enough to get the average flare number rate and energy rate, especially at the upper energy limits which are statistically unreliable.     

Coronal structure observed at the total solar eclipse of 11 June, 1983 in Indonesia

From the photographs taken at the total solar eclipse of 11 June 1983, we derived the electron density for the north polar rays and for the thread-like fine structures above the active region, which are 10⁸ at 1.4 solar radii and 3×10⁹ at 1.15 solar radii, respectively. The brightness distributions of the corona at the polar region and above the active region, and the flattening index were also derived.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

On the importance of accurately ray-traced troposphere corrections for Interferometric SAR data

Numerical weather models offer the possibility to compute corrections for a variety of space geodetic applications, including remote sensing techniques like interferometric SAR. Due to the computational complexity, exact ray-tracing is avoided in many cases and mapping approaches are applied to transform vertically integrated delay corrections into slant direction. Such an approach works well as long as lateral atmospheric gradients are small enough to be neglected. But since such an approximation holds only for very rare cases it is investigated how horizontal gradients of different atmospheric constituents can evoke errors caused by the mapping strategy. Moreover, it is discussed how sudden changes of wet refractivity can easily lead to millimeter order biases when simplified methods are applied instead of ray-tracing. By an example, based on real InSAR data, the differences of the various troposphere correction schemes are evaluated and it is shown how the interpretation of the geophysical signals can be affected. In addition, it is studied to which extend troposphere noise can be reduced by applying the exact ray-tracing solution.     

Infiltration of refractory melts into the lowermost oceanic crust: evidence from dunite- and gabbro-hosted clinopyroxenes in the Bay of Islands Ophiolite

Up to 3 km of dunitic rocks occur below crustal gabbro in the Blow Me Down massif (Bay of Islands Ophiolite, Newfoundland). Analyses of dunite- and gabbro-hosted clinopyroxene grains (cpx) for rare earth elements (REE), Zr, and Ti reveal three types of chondrite-normalized patterns: N-group patterns are similar to cpx grains as they would form by fractionation from a range of mid ocean ridge basalts (MORB). They are typical for a few higher level dunitic samples as well as mafic cumulates. F-group patterns show light REE depletion, very strong middle REE fractionation and a positive Zr anomaly and occur in dunites only. R-group patterns are severely depleted in both light and heavy REEs relative to MORB-like cpx and two samples of the group display a positive Ti anomaly. They are also restricted to dunitic rocks. The patterns are explained in a two stage model in which an established dunite sequence, dominated by MORB-type cumulate signatures (N-group), was infiltrated by extremely refractory melts. During infiltration of the refractory melt chromatographic fractionation occurred, transforming N-group dunites into F-group and R-group dunites. The F-group patterns are composite patterns: heavy REE, Ti ± Zr reflect the original MORB-like cumulate dunite host, light REEs indicate equilibrium with the infiltrating, refractory melts. Steep slopes in the middle REEs reflect the position of the chromatographic front. For more intense percolation of refractory melts, R-group patterns with a positive Ti anomaly will form by the same process. The rest of the R-group patterns displaying no positive Ti anomaly may represent either the most intensely reacted host rocks or these dunites derive directly as cumulates from refractory melts. Only small volumes of refractory melt (a 5 m column) are required to imprint the observed trace element pattern on the thick original dunite sequence. One of several possible origins for the refractory melts is transformation of original MORB-type melts by way of chromatographic fractionation within the highly depleted, residual uppermost mantle. In the framework of an oceanic spreading centre, the migrating, refractory liquids are considered a late event following the main constructive stage dominated by aggregated melts. The study demonstrates that highly refractory melts can exist under oceanic spreading centres dominated by a MORB-like cumulate and volcanic sequence. Received: 2 September 1996 / Accepted: 20 November 1997     

Distribution of trace elements during breakdown of mantle garnet: an example from Zabargad

Ion probe investigations on mineral phases forming the Al-Di pyroxenites from the Zabargad peridotite body indicate that porphyroclastic pyroxenes in composite mafic layers record an unusual HREE, Zr, Sc enrichment not registered by pyroxenes in spinel websterites. Orthopyroxene in the opx+sp clusters forming the inner, cpx-free zone of layered pyroxenites shows strongly fractionated REE patterns (HREE_N/LREE_N>1000; Yb>100xch) and very high Zr, Sc and Y abundances (up to 30,672 and 60ppm, respectively). In the outer, cpx-rich zone porphyroclastic clinopyroxene is strongly HREE enriched (HREE_N/LREE_N29; Yb 269xch) and displays very high Sc and Zr abundances (up to 819 and 164 ppm, respectively). It is suggested that the unusual trace element abundances are inherited from a precursor garnet. Composite pyroxenite layers are interpreted as former garnet clinopyroxenites characterized by gnt/cpx modal zoning. The sp+opx(cpx-free) assemblage in the inner part is a product of the break-down reaction of garnet upon decompression, with Ca of the original garnet completely entering the enstatite solid solution. The temperature at which the breakdown reaction occurred is estimated to be higher than 1000°C (P in the range 20–30 kbar). In the outer part, decompression caused the garnet to form a sp+opx assemblage; however, the grossularite component participated in the formation of new clinopyroxene which reacted with the clinopyroxene present in the original mode before the decompression reaction, thus forming a cpx₂+sp+opx assemblage. As a result of garnet breakdown, pyroxenes have peculiar HFSE anomalies. Progressive upwelling during the Red Sea rifting produced incomplete reaction under pl-facies conditions. The geochemical signatures of precursor garnet in pyroxenes were partially crased during the recrystallization from granular spincl-bearing to granoblastic plagioclase-bearing assemblages, being preserved only in a few porphyroclast relies. The finding of pyroxenes with trace element characteristics of precursor garnet has important geodynamic and geochemical implications. Al-Di pyroxenite layers had a long history within the mantle, before the continental lithosphere rifting and thinning took place in the region. It is suggested that Al-Di pyroxenites were formed by deep-seated tholeiitic magmatism unrelated to the Red Sea evolution, thus representing the earliest event in the Zabargad upper mantle. Garnet breakdown significantly preceded the metasomatism induced by hydrous fluids (crystallization of Ti-rich pargasite) and the later intrusion of hydrous (Cr-Di) pyroxenite dykes. During the stages of mantle evolution, the HFSE anomalies in pyroxenes varied significantly. We note that the study of HFSE anomalies in mineral phases reveals complex geochemical histories which are not recorded by the whole-rock system.