柞蚕林光合生产力冠层结构特点及其组成树种光合生理特性研究

柞蚕林生态系统是以饲养柞蚕为主要经营目的的柞树林分。冠层结构人工造型，以叶作为系统的主要输出途径。本文主要研究柞蚕林叶生产力、冠层结构特点、林内光分布特性及其组成树种的光合生理特性。比较柞蚕林与天然栎林林冠结构特点及其组成种光合生理特性差异分析影响柞蚕林叶生产力水平的主要因子。测定表明：在一定范围内叶生物量、冠层覆盖度与株数密度呈相关变化。林分株数密度从109株/亩增加到438株/亩，覆盖度和叶生物量分别由20%和51.67kg/亩增大到85%和220kg/亩。柞蚕林冠层结构与天然栎林有较大差异不同树型林冠结构特点不同，通过影响林内光合有效辐射量而影响柞蚕林叶生产力水平。阶梯树型叶生物量最大，中干、无干树型叶生物量差异不显著。林内光照强度随累积叶面积系数呈指数递减。柞蚕林三个主要组成种光合作用特性具有一定差异且受生长时期、温度、叶片生理特性等因子的影响。黑暗预处理使三个树种均产生一个光合诱导期。气孔对光合速率以及光合作用妄动过程均有较大影响。柞蚕林林冠结构特点和光合作用特性对合理安排冠型结构、提高叶生产力水平具有重要作用。

Influência da biomassa inicial sobre o crescimento e a produtividade de peixes em sistema de policultivo

Analisou–se o crescimento dos peixes, a composição das espécies e a produtividade de quatro policultivos (P75, P78, P87 e P207), visando melhorar o manejo e a produtividade pesqueira dos pequenos açudes (0,1–5,0ha) do Semi–Árido brasileiro. Simulou–se as condições desses açudes em viveiros com 120 e 5.000 m² de área, sem renovação de água, utilizando moderada quantidade de adubo e fertilizante. A biomassa inicial variou de 75 a 207kg há^–1, sendo formada por: tilápia do Nilo (Oreochromis niloticus), curimatã pacu (Prochilodus argenteus), carpa comum (Cyprinus carpio), tambaqui (Colossoma macropomum) e tucunaré (Cichla ocellaris). Os peixes apresentaram baixo crescimento (< 0,01g g^–1d^–1) após 75 dias de criação (P78 e 87). O crescimento do tambaqui, da tilápia e da curimatã foi reduzido após 53 dias (P75). Em moderada biomassa, o crescimento do tambaqui foi inferior ao da carpa e da curimatã (P207). A produtividade da tilápia atingiu 720 kg ha^–1ano^–1 (P78), sendo reduzida para 220 kg ha^–1ano^–1 devido ao processo reprodutivo (P75 e P207). A produtividade da carpa de 1.600 kg ha^–1ano^–1 foi superior a dos outros peixes (P87). A biomassa inicial de 75 kg ha^–1 (60:30:4:3:3% de tilápia, tambaqui, carpa, curimatã e tucunaré, respectivamente) otimizou o crescimento e a produtividade dos peixes. A utilização de tilápias monossexadas e o fornecimento da alimentação suplementar ao tambaqui tornam–se imprescindíveis ao policultivo.

Physics, geochemistry and bulk sedimentology on cores from the Peru Basin

Empirical relationships between physical properties determined non-destructively by core logging devices and calibrated by carbonate and opal measurements determined on discrete samples allow extraction of carbonate and opal records from the non-destructive measurements in biogenic settings. Contents of detrital material can be calculated as a residual. For carbonate and opal the correlation coefficients (r) are 0.954 and ?0.916 for sediment density, ?0.816 and 0.845 for compressional-wave velocity, 0.908 and ?0.942 for acoustic impedance, and 0.886 and ?0.865 for sediment color (lightness). Carbonate contents increase in concert with increasing density and acoustic impedance, decreasing velocity and lighter sediment color. The opposite is true for opal. The advantages of deriving the sediment composition quantitatively from core logging are: (i) sampling resolution is increased significantly, (ii) non-destructive data can be gathered rapidly, and (iii) laboratory work on discrete samples can be reduced. Applied to paleoceanographic problems, this method offers the opportunity of precise stratigraphic correlations and of studying processes related to biogenic sedimentation in more detail. Density is most promising because it is most strongly affected by changes in composition.

Sedimentology on cores from the Peru Basin

We investigated surficial sediments for physico-chemical composition from numerous sites of seven study areas in the manganese nodule field of the northern Peru Basin as part of a deep-sea environmental study. Major results from this study are strong variability with respect to water depth, productivity in surface waters, locality, bottom water flow, and seafloor topography. Sediment sites are located mostly in 3900 to 4300 m water depth between the lysocline and the carbonate compensation depth (CCD). Large fluctuations in carbonate content (0% to 80%) determine sediment density and compressional-wave velocity, and, by dilution, contents of opal and non-biogenic material. Mass accumulation rates of biogenic components as well as geochemical proxies (barium and phosphorus) distinguish areas of higher productivity in the northwest near equatorial upwelling and in the northeast close to coastal upwelling, from areas of lower productivity in the west and south. Comparisons between the central Peru Basin area (Discol) and western Peru Basin area (Sediperu) reveals, for the Sediperu area, a shallower CCD, more carbonate but less opal, organic carbon, and non-biogenic material in sediments at the same water depth as well as larger down-core fluctuations of organic carbon and MnO2. Bottom water flow in the abyssal hill topography causes winnowing of material from summits of seamounts and ridges, where organic carbon preservation is poor, to basins where organic carbon preservation is better. Down-core measurements in box cores indicate a three-fold division in the upper 50 cm of the sediment column. An uppermost semi-liquid top layer is dark brown, 5-15 cm thick and contains most of the ferro-manganese nodules. A 5-15 cm thick transition zone of light sediment color has increasing shear strength, lowest opal contents and compressional-wave velocities, but highest carbonate contents and sediment densities. The lowermost layer contains stiffer light gray sediments.