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41.
Summary Two alternative estimators of individual tree leaf area (A1) area are used to derive estimates of leaf-area index (L) for 40 plots in Pinus contorta Dougl. stands. One estimator of A1 is based on the common assumption of a constant ratio between A1 and sapwood cross-sectional area at breast height (As). The second estimator of A1 accounts for tree-to-tree variation in the relation between A1 and As. The apparent relationship between stand growth and leaf-area index is strongly dependent on the way leaf area is estimated. When L is derived from a constant A1As ratio, stand growth appears to be strongly correlated with L. However, when L is based on estmates of A1 that account for tree-to-tree variation in the A1 — As relation, stand growth is seen to be only weakly related to L. Stand structure, quantified as percent live-crown, accounts for a great deal of the observed variation in leaf-area efficiency. These contrasting relationships illustrate the importance of unbiased estimates of L in interpreting the link between stand-level processes and leaf area.Utah Aggriculural Experiment Station Journal Paper No. 3333 相似文献
42.
Masayuki Nishida Hirotaka Nishijima Kazuya Yonezawa Isao Sato Teisuke Anzai Kohichi Okita Hisakazu Yasuda 《European journal of applied physiology and occupational physiology》1992,64(6):528-533
To assess exercise energy metabolism of forearm flexor muscles in rowers, six male student rowers and six control subjects matched for age and sex were studied using phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Firstly, to adjust for the effect of differences in cross-sectional muscle area, the maximal cross-sectional area (CSAmax) of the forearm flexor muscles was estimated in each individual using magnetic resonance imaging. Multistage exercise was then carried out with an initial energy production of 1 J.cm-2 CSAmax for 1 min and an increment of 1 J.cm-2 CSAmax every minute to the point of muscle exhaustion. A series of measurements of 31P-MRS were performed every minute. The CSAmax was significantly greater in the student rowers than in the control subjects [19.8 (SD 2.2) vs 17.1 (SD 1.2) cm2, P less than 0.05]. The absolute maximal exercise intensity (J.min-1) was greater in the rowers than in the control subjects. However, the maximal exercise intensity per unit of muscle cross sectional area (J.min-1.cm-2) was not significantly different between the two groups. During mild to moderate exercise intensities, a decrease in phosphocreatine and an increase in inorganic phosphate before the onset of acidosis were significantly less in the rowers, indicating a requirement of less adenosine 5'-diphosphate to drive adenosine 5'-triphosphate production. The onset of acidosis was also significantly delayed in the rowers. No difference was observed in forearm blood flow between the two groups at the same exercise intensity (J.min-1.cm-2).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
43.
Toshiyuki Sato 《Ecological Research》1992,7(1):1-7
Gametophyte populations inAthyrium brevifrons were analysed with respect to population size and surviving area (%) of individual thalli in a transplant garden at Sapporo
during 5–26 April 1983, to study the safe-microsite for gametophyte establishment in nature. Spores dispersed in August 1982
germinated and grew into thalli of various widths (<10 mm); 10.3% of the thalli matured by early October 1982. Maturation
was attained by gametophytes of width 4–7 mm. The number of gametophytes gradually decreased with increasing width. By April
1983, 20.5% of total gametophytes were mature with a mode of 5–6 mm in width. The relative number of gametophytes with surviving
area of 2–20% increased and that of 85–100% decreased in accordance with collection days delayed until after snow-melt. Surviving
area (%) on gametophyte of all widths decreased with decreasing soil moisture contents. In particular, immature gametophytes
of 2–4 mm width showed a significant correlation (P<0.01) between soil moisture content and relative number of gametophytes with 0–20% surviving area and mean surviving area
(%) of every width of thalli. The spring desiccation might be a factor that reduces or limits gametophyte populations in nature. 相似文献
44.
Leaf lifespan as a determinant of leaf structure and function among 23 amazonian tree species 总被引:26,自引:0,他引:26
Summary The relationships between resource availability, plant succession, and species' life history traits are often considered key to understanding variation among species and communities. Leaf lifespan is one trait important in this regard. We observed that leaf lifespan varies 30-fold among 23 species from natural and disturbed communities within a 1-km radius in the northern Amazon basin, near San Carlos de Rio Negro, Venezuela. Moreover, leaf lifespan was highly correlated with a number of important leaf structural and functional characterisues. Stomatal conductance to water vapor (g) and both mass and area-based net photosynthesis decreased with increasing leaf lifespan (r2=0.74, 0.91 and 0.75, respectively). Specific leaf area (SLA) also decreased with increasing leaf lifespan (r2=0.78), while leaf toughness increased (r2=0.62). Correlations between leaf lifespan and leaf nitrogen and phosphorus concentrations were moderate on a weight basis and not significant on an area basis. On an absolute basis, changes in SLA, net photosynthesis and leaf chemistry were large as leaf lifespan varied from 1.5 to 12 months, but such changes were small as leaf lifespan increased from 1 to 5 years. Mass-based net photosynthesis (A/mass) was highly correlated with SLA (r2=0.90) and mass-based leaf nitrogen (N/mass) (r2=0.85), but area-based net photosynthesis (A/area) was not well correlated with any index of leaf structure or chemistry including N/area. Overall, these results indicate that species allocate resources towards a high photosynthetic assimilation rate for a brief time, or provide resistant physical structure that results in a lower rate of carbon assimilation over a longer time, but not both. 相似文献
45.
阔叶树的叶形曲线方程:—适于叶面积计算的数学模型 总被引:3,自引:0,他引:3
树木的叶形可以看作一个平面几何图形。这种几何图形可用解析方程给予表达,我们把这种解析方程称为叶形曲线方程。由于叶形是一个左右对称,而上下不对称的图形,也就是说叶的最宽处绝大多数不在叶的中部,少数在 相似文献
46.
电刺激乌拉坦麻醉的大鼠下丘脑外侧区(LH)可使缰核(Hb)内51.0%的单位兴奋,15.7%的单位抑制,其中发生兴奋反应的单位有15.4%可被逆行激活。双侧Hb内微量注射利多卡因,电刺激LH引起的升压反应可被阻断42.0±28.0%;反之,双侧LH内微量注射利多卡固,电刺激Hb引起的升压反应可被阻断62.0±26.4%。结果表明,LH与Hb在血压调节中相互依赖,具有协同作用。 相似文献
47.
黄淮海平原高产田作物群体结构特征 总被引:9,自引:5,他引:4
本文利用实测资料分析了高产田作物群体结构特征。精播高产栽培麦田春季最大蘖数12×10~6/ha,群体最大叶面积指数5.5—6.0,成穗4.5—5.25×10~6/ha。传统高产栽培麦田春季最大蘖数15—18×10~6/ha,群体最大叶面积指数6.0—6.5,成穗6.0—7.5×10~6/ha。小麦营养生长与生殖生长期叶日积比,精播高产栽培麦田是1∶0.89,传统高产栽培麦田为1∶0.73。夏玉米种植密度主要受叶倾角的影响。紧凑型玉米品种的叶倾角大于65°,种植密度7.5—8.25×10~4/ha;平展型玉米品种的叶倾角小于50°,种植密度5.25—6.0×10~4/ha。 相似文献
48.
A survey of oligotrophic Lake Rara, the biggest lake in Nepal, was carried out from 1982 till 1984. Mean depth is 100 m, and
maximum depth is 167 m. The surface area covers 9.8 km2, and the lake contains 0.98 km3 volume of water.
Transparency was about 16 m, photoquantum yield decreased exponentially with depth below 5 m, and the extinction coefficient
was 8.3 × 10−2. The concentration of Chl.-a was in the range of 0.06–0.46 mg m−3, and total nitrogen was 18–30 μg 1−1. The whole water column was well oxygenated. Primary productivity was extremely low. It has more than 30 inflowing brooks
and one outlet. The water quality of the brooks changes drastically with their location. The pH, electrical conductivity,
and EDTA hardness in the waters from a landslide area were high. In the waters from a rich pine forest they were extremely
low.
The zooplankton consisted of two species of protozoa, five species of rotifers, two species of Cladocera, and two species
of Copepoda. The zooplankton density range was 6200–16200 individuals m−3. The minimum was on November 11th, 1983 and the maximum on August 19th, 1983. 相似文献
49.
50.
Haruki Ochi 《Environmental Biology of Fishes》1985,12(2):155-160
Synopsis Reproductive behavior of the temperate damselfish, Chromis notata, was investigated on the island of Mukaishima, Japan, almost daily during the breeding season in 1982. Both males and females
repeated reproductive cycles many times during the breeding season. Females had a strong tendency to spawn a whole clutch
on one nest during a few hours. The average number of eggs which a male gained per reproductive cycle was estimated at 38560
(480–131100 eggs). Males ordinarily cared for eggs until just prior to hatching, but abandoned more than half of the nests
with the eggs numbering less than 11568.
Contribution 207 from the Mukaishima Marine Biological Station. 相似文献