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93.
云南西双版纳基诺巴卡土地利用/土地覆盖时空动态研究 总被引:3,自引:3,他引:3
该研究以地理学为理论依据,以3S技术、PRA访谈、田野社区调查为主要手段,对基诺山土地利用/土地覆盖时空演变进行了35a跨度的分段对比研究和驱动因子分析。研究表明:轮作周期的缩短,将直接影响到植被自然演替的方向和群落的恢复;土地利用的高破碎度加大空间异质性,给地段性生态环境增加压力;森林组分的变化,将直接影响到山地生态系统的稳定性,生物多样性的保护;研究区人口目前未对耕地产生较大压力,人地矛盾主要是在农业耕作的方式上而不是土地对人口的承载能力上;国家政策和市场经济是土地利用/土地覆盖变化的决定因素,基诺族土地价值观是土地利用/土地覆盖变化的内核。 相似文献
94.
W. de Vries E. E. J. M. Leeters C. M. A. Hendriks 《Water, air, and soil pollution》1995,85(3):1063-1068
Effects of elevated S and N deposition on the solution chemistry of Dutch forest soils are mainly manifested by increased concentrations of Al associated with increased concentrations of SO4 and NO4. Presumed critical Al/base cation ratios are often exceeded below 20 cm soil depth. There is also evidence that elevated N deposion during the last decades affected the forest nutrient status and caused large changes in forest vegetation. About half of the Dutch forests have absolute shortage of P and relative Mg deficiencies compared to foliar N contents. Evidence from field studies of a relationship between soil acidification and nutrient imbalances in the soil and the foliage on one hand and the vitality of forests on the other hand is, however, lacking. 相似文献
95.
J. Naranjo de la F. S. Salgado-Garcí a L.C. Lagunes-Espinoza E. Carrillo-Avila D.J. Palma-L pez 《Soil & Tillage Research》2006,88(1-2):160-167
A study to evaluate the changes in the fertility of Fluvisols under continuous cultivation of sugarcane was conducted in the vicinity of the Santa Rosalía sugar refinery. About 4000 ha of Fluvisols have been under sugarcane cultivation for more than 30 years. Three representative plots under monoculture for 5, 10, 20 and 30 years, were selected under on-farm conditions. Several samples were obtained from crop row and inter-row zones, at 0–30 cm soil depth, and composited into four samples for each plot. Soil samples were analyzed for pH, organic matter, total organic C, total nitrogen, available phosphorus, exchangeable potassium, calcium and magnesium, cation exchange capacity, texture and bulk density. There were significant changes in the soil chemical properties due to 30 years of monoculture, except for OM, exchangeable K, Ca, Mg and CEC. Total soil organic C, total N and P declined by 17, 21 and 37%, respectively, by 30 years of monoculture of sugarcane. These losses mainly occurred during the first 20 years of cultivation. However, the adverse effect of decline in soil fertility was not reflected in the sugarcane yields. The 67% increase in yields observed between 5 and 30 years of monoculture may be attributed to the adoption of recommended cultural practices and to farmer's experience. Soil physical properties were not affected by the intensive sugarcane cultivation. A complete adoption of recommended practices by SR among farmers and a revision of the N and P fertilization rate are necessary to maintain the fertility of sugarcane soils. 相似文献
96.
Impact of land-use changes and sedimentation on the Muhammad Nur Reservoir, South Kalimantan, Indonesia 总被引:1,自引:0,他引:1
The Muhammad Nur Reservoir (MNR) is a major multipurpose reservoir located on the Riam Kanan River in the Indonesian Province
of South Kalimantan. The MNR has a high sediment trap efficiency and there is concern that accelerated erosion in the catchment,
resulting from inappropriate land use, poses a significant threat to the storage capacity and effective life span of the reservoir.
Furthermore, on-going deforestation of large parts of the catchment may have changed the inflow pattern to the reservoir.
This paper uses data from fieldwork and published information from different sources to examine the extent of erosion and
sedimentation in the catchment and the sediment delivery to the reservoir. Water level variations in the reservoir over a
22-year period are examined for changes that might indicate an alteration of the hydrologic balance in the catchment. 相似文献
97.
In order to reduce nutrient wastes to the environment the supply should be in accordance to the demand for these. Two experiments were conducted to study and quantify the effect of temperature, irradiance, and plant age on the uptake of nitrate (NO3?), ammonium (NH4+), dihydrogen phosphate ion (H2PO4?), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and sulfate (SO42). In the first experiment, various levels of temperature and irradiance were applied to plants in a growth chamber, while in the second experiment the uptake was studied along the crop season under greenhouse conditions. The uptake rates were calculated at 2-hour intervals through sampling the nutrient solution and analyzing it by inductively coupled plasma atomic emission spectrometry (ICP-AES). Increasing light and temperature enhance the uptake rates, while the rates decrease with plant age. Nitrogen absorption was similar during the day as during the night. No differences were found in the absorption of H2PO4?, K+, Ca2+, Mg2+, and SO42? between day and night. Nitrate absorption was found to have a positive correlation with the absorption of all the ions except for NH4+. 相似文献
98.
美国红枫在成都立地条件下,在园林上有少量的应用。通过处理观察其叶片色彩变化、落叶情况以及和自然变色的对比,试图找到使色彩变化更明显的人工方法,剖析外来秋色叶树种在成都的适应情况,力图使成都的园林色彩更丰富。 相似文献
99.
间作模式下桑树与大豆叶片的光合日变化特点 总被引:5,自引:0,他引:5
为了提高桑树与大豆间作模式下地上部分的光能利用率,优化桑树与大豆复合经营的空间配置,研究了在这一间作模式下生育后期速生桑树和大豆叶片的光合日变化特点.结果表明:无论在单作还是间作模式下大豆叶片在13:00时均表现出明显的光合"午休"现象,其光合性能并未因间作桑树而受到影响;一天之中,桑树叶片分别在9:00时和13:00时出现光抑制现象,并且13:00时光抑制的程度和持续的时间均大于9:00时出现的,不同种植模式下桑树叶片的光合日变化情况存在着明显的差异,一天之中,间作模式下桑树叶片的P_r、_r、和F_v /F_m等光合指标值均优于单作模式的桑树叶片,桑树与大豆间作具有一定程度的种间促进作用,1年生桑树幼苗与大豆间作能明显提高生育后期速生桑树叶片的光合生产能力,从而可实现高产的目的. 相似文献
100.