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991.
小陇山林区主要林分对降水的再分配 总被引:1,自引:0,他引:1
选择锐齿栎、油松、华山松和落叶松林分为对象,系统同步观测了大气一次性降水过程中,不同郁闭度梯度林分群体的林冠透过降水、树干流量、林冠层截留量与大气降水历时、降水强度变化的基本数据。用数量级化理论(I)和线性方程,动态地描绘出各分量随大气降水变化而变化的趋势。揭示出林分对降水的再分配以及求算1年内不同时段林地补给水量的可靠方程。 相似文献
992.
Zane Kalvīte Zane Lībiete Ivars Kļaviņš Arta Bārdule Kārlis Bičkovskis 《Scandinavian Journal of Forest Research》2021,36(1):1-14
ABSTRACT Despite near-extinction in the nineteenth century, after efficient restoration measures the population of Eurasian beaver (Castor fiber L.) in Latvia currently is viable and growing. While the ecological effect of the species on water quality and biodiversity is generally positive, the high number of animals in production forests often creates challenges for management. Drainage ditches are among the most favoured habitats of beavers resulting in flooded stands, reduced tree growth and economical losses. The aim of the study was to evaluate the chemical properties of water in forest drainage ditches, affected by beaver activity, and their changes after the dam removal. Chemical composition of surface water in ditches was analysed in sampling points above dam, below dam and in the ditch itself after removal of the dam; results compared to pristine beaver site nearby on a small stream. Results did not show significant differences between concentrations above and below dams. After removal of the dams, significant increase in DOC, N-NO3 -, N-NH4 + and TSS concentrations and significant decrease in TP concentrations were observed in some of the sites. Observed concentrations of all measured parameters were significantly lower in pristine beaver site than in beaver sites on drainage ditches. 相似文献
993.
994.
Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone which is distributed in the Dongling Mountain area of Beijing,
was exposed to ambient and enhanced ultraviolet-B (UV-B, 280–320 nm) radiation by artificially supplying a daily dose of 9.4
kJ/m2 for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was
to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ
13C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency
(WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf
total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular
CO2 concentration/ air CO2 concentration (C
i
/C
a) (4.0%), and an increase in leaf tissue δ
13C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%) and WUE (4.1%). The effects of UV-B on the plant were
greatly affected by the water content of the deep soil (30–40 cm). During the dry season, differences in the stomatal conductance,
δ
13C, and WUE between the control and UV-B treated shrubs were very small; whereas, differences became much greater when soil
water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed
over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation
between soil water content and leaf water content, δ
13C, C
i/C
a, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content.
These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment,
it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics.
__________
Translated from Journal of Plant Ecology, 2006, 30(1): 47–56 [译自: 植物生态学报] 相似文献
995.
Four different kinds of water treatments were applied to study the photosynthetic eco-physiological characteristics of Taxodium ascendens seedlings in the environment of the Three Gorges hydro-fluctuation belt. The four kinds of water treatments were: normal
growth water condition (CK), light drought stress (T1), soil water saturation (T2), and soil submersion (T3). The results
showed that different water treatments could effectively influence the content of the photosynthetic pigment, leaf gas exchange
and apparent resources use efficiency of T. ascendens seedlings. It was also demonstrated that the T. ascendens seedlings could not only tolerate water submersion and wet conditions but also endure a certain degree of drought. To establish
a protection forest system in the hydro-fluctuation belt in the Three Gorges Reservoir Area, the species T. ascendens is suitable for planting in conditions of root submersion or water-saturated soil. In case it is planted in drought conditions,
this tree species should be watered appropriately in order to keep its normal net photosynthetic rate.
Translated from Forest Research, 2006, 19(1): 54–60 [译自: 林业科学研究] 相似文献
996.
997.
Sugi (Cryptomeria japonica D. Don) wood was treated with supercritical water (374°C, 22.1MPa), and fractionated into the water-soluble portion, the methanol-soluble portion, and the methanol-insoluble residue. The methanol-soluble portion mainly consisted of the lignin-derived products. To characterize the compounds in the methanol-soluble portion, gel permeation chromatographic (GPC) and gas chromatographic-mass spectrometric (GC-MS) analyses were performed. The GPC analysis indicated that the methanol-soluble portion contained lignin-derived monomeric and dimeric products. GC-MS analysis detected 31 products which were expected to be monomeric compounds, and 18 of these were identified to be guaiacol, methylguaiacol, ethylguaiacol, vinylguaiacol, eugenol, propylguaiacol, vanillin, cis-isoeugenol, homovanillin, trans-isoeugenol, acetoguaiacone, propioguaiacone, guaiacylacetone, 2-methoxy-4-(1-hydroxypropyl)phenol, homovanillic acid, 2-methoxy-4-(prop-1-en-3-one)phenol, coniferyl aldehyde, and ferulic acid. In addition, 22 dimeric products were detected, and 4 of these were believed to be compounds with biphenyl type (5-5), diphenylethane type (-1), stilbene type (-1), and phenylcoumaran type (-5) structures. These results clearly indicated that the methanol-soluble portion included various monomeric and dimeric compounds produced as a result of the cleavage of ether linkages and propyl chains of lignin. 相似文献
998.
Naoko?MikiEmail author Kosei?Otsuki Keiji?Sakamoto Takashi?Nishimoto Ken?Yoshikawa 《Journal of Forest Research》2003,8(3):153-161
To elucidate the differences in the leaf water relations of Pinus densiflora Sieb. et Zucc. growing in different soil moisture conditions, we examined the pressure-volume curve and the diurnal changes in the stomatal conductance, the transpiration rate, and the leaf water potential. The leaf water relations were compared using field-grown 40-year-old pine trees growing on the upper and lower parts of a slope. We also compared the leaf water relations of potted 4-year-old saplings growing at pF 4.2 and pF 1.8 soil moisture levels for almost 1 year. The values of the ratio of symplasmic water at turgor loss point to symplasmic water at saturated point (Vp/Vo) and bulk modulus of elasticity () of both the adult trees on the upper part of the slope and the potted saplings growing on pF 4.2 soil moisture were higher than those values of both the adult trees on the lower part of the slope and the potted saplings growing on pF 1.8 soil moisture, respectively. The field-grown adult tree and the potted saplings growing under long-term water stress tended to reduce their stomatal conductance in response to the acute soil drying. It is suggested that P. densiflora growing under long-term water stress rapidly closed its stomata in response to soil drying and avoided losing water, and could also rapidly absorb water with reducing water loss because of the decrease in the leaf pressure potential derived from the high values. 相似文献
999.
Sesbania [Sesbania sesban (L.) Merr.] fallows are being promoted as a means for replenishing soil fertility in N-depleted soils of small-scale, resource-poor
farmers in southern Africa. Knowledge of soil water distribution in the soil profile and water balance under proposed systems
is important for knowing the long-term implications of the systems at plot, field and watershed levels. Soil water balance
was quantified for maize (Zea mays L.) following 2-year sesbania fallow and in continuous maize with and without fertilizer during 1998–1999 and 1999–2000 at
Chipata in eastern Zambia. Sesbania fallow increased grain yield and dry matter production of subsequent maize per unit amount
of water used. Average maize grain yields following sesbania fallow, and in continuous maize with and without fertilizer were
3, 6 and 1 Mg ha−1 with corresponding water use efficiencies of 4.3, 8.8 and 1.7 kg mm−1 ha−1, respectively. Sesbania fallow increased the soil-water storage in the soil profile and drainage below the maximum crop root
zone compared with the conventionally tilled non-fertilized maize. However, sesbania fallow did not significantly affect the
seasonal crop water use, mainly because rainfall during both the years of the study was above the normal seasonal water requirements
of maize (400 to 600 mm). Besides improving grain yields of maize in rotation, sesbania fallows have the potential to recharge
the subsoil water through increased subsurface drainage and increase nitrate leaching below the crop root zone in excess rainfall
seasons.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
1000.