共查询到20条相似文献，搜索用时 93 毫秒
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针对天水早春气温波动大,寒潮、大风天气多,低温冷害重而育苗成活率低的气候背景,１９９６～１９９８年对烤烟育苗期间,进行适宜气象条件及最佳育苗设施手对比试验研究,得出当地烤烟幼苗健壮生长的最适环境气象条件,同时,也得出了当地烤烟育苗的最佳设计是双膜纸钵大畦与弓棚大畦,以双膜钵大畦最佳。 相似文献
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普宗朝 《沙漠与绿洲气象(新疆气象)》1993,(3)
计算分析了我国日光温室主要分布地区(30°N以北)温室采光面的最佳倾斜角及其对应的最大平均日总辐射量.结果表明,温室采光面的最佳倾斜角不仅与地理纬度有关,还与辐射状况有关.在此基础上绘出了我国日光温室采光面最佳倾斜角的等值线分布图,并给出了最佳倾斜角的简单确定公式. 相似文献
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１９９５年通过鉴定登记的全省气象科研成果１温室温床育苗微气象调控试验及其开发应用完成单位：西峰农业气象试验站主要研究人员：杨孝儒、段金省、李跃邦内容提要：采用设点观测、对比试验、实际栽培、示范推广和资料分析的综合试验研究方法，准确得出温室、温床、塑料... 相似文献
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温室在国内外已经很普遍,多数温室都是使用较廉价的结构,用聚乙烯(PE)薄膜覆盖而成,多为平顶和低顶角温室,因有限的通风和缺少加热装置,这些塑料温室内部的气候条件与最佳气候条件相差甚远,而且温室内 CO_2浓度明显减少,因而降低光合作用,造成减产。有关这方面的研究国内还很少,本文介绍西班牙的 P.Lorenzo、C.Maroto 和 N.Castilla 在 Almeria 进行的有关这方面的试验研究,以期能对我国今后温室生产起借鉴作用。 相似文献
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日光温室蔬菜最佳生产模式 总被引：1，自引：1，他引：1
通过对1996－2000年天水市日光温室蔬菜生产状况调查资料分析，构造了评价该地温室蔬菜生产中气候资源的利用程度及各种经济行为的模式，计算了几种主要温室蔬菜的经济系数及各种组合的效益系数，得出最佳种植模式的效益矩阵，并线性规划出主要蔬菜品种组合的最优种植比例，为当地合理安排温室蔬菜生产提供了客观的依据。 相似文献
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日光温室加温是改善冬季日光温室作物生长温度环境的主要措施之一。选择典型节能型日光温室,利用暖风机加温试验研究加温方式作用下温室内温度时间、空间变化以及在极端天气条件下和不同外界温度条件下的加温效果,并进行经济投入分析。结果表明：电暖风机加温后温室内温度明显提高且温度分布较均匀,平均温度较对照温室高4.23 ℃,其中平均最低温度提升效果最明显;低温天气时,平均温度比对照温室温度高4.24 ℃;寡照天气时,平均温度比对照温室温度高4.48 ℃。暖风机在外界温度-12 ~-4 ℃时对温室进行加温的效果最佳。通过对几种传统的温室加温方式经济投入的分析表明,电暖风机是一种投资小,耗能低,经济效益相对较高的加温方式。 相似文献
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针对恭城月柿育苗中成活率较低的问题，经过试验分析，选择适合本地气候条件，表现嫁接优势的柿苗砧木，并提出了最佳嫁接时期。 相似文献
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Adaptive management to climate change for Norway spruce forests along a regional gradient in Finland
Zhen-Ming Ge Seppo Kellomäki Heli Peltola Xiao Zhou Hannu Väisänen 《Climatic change》2013,118(2):275-289
We hypothesized that the responses of boreal Norway spruce (Picea abies) forests to climate change would be region-specific due to regional differences in temperature and water availability. In this context, we analyzed the adaptive effects of varied thinning intensities on the gross primary production (GPP), total stem wood growth, and timber yield over a 100-year period using a process-based ecosystem model. Our simulations represented Norway spruce forests for five different bioclimatic zones spanning southern to northern Finland (61–67oN). Ten thinning regimes with thinning intensities ranging from 5 to 50 %, as well as an unthinned regime, were included in the calculations. The results showed that at the southern sites without thinning, the cumulative GPP and total stem wood growth were lower under the changing climate than in the current climate over the simulation period due to greater water depletion via evapotranspiration and reduced soil water availability. At the central and the northern sites, the climate changes increasingly enhanced the GPP and total stem wood growth due to the mitigation of low-temperature limitation and the improved soil water availability. Thinning generally mitigated the soil water deficit by reducing water evaporation and led to a reduction of the natural mortality. At the southern sites, light and moderate thinning intensities increased the GPP and total stem wood growth relative to sites with a changing climate that experienced no thinning. Moreover, moderate thinning resulted in the greatest timber yield. Heavy thinning, in which a large proportion of standing trees were removed, reduced the GPP and total stem wood growth despite allowing increased soil water availability. At the northern sites, all levels of thinning, including light thinning, decreased the GPP and stem wood growth, indicating that soil water availability was not a limiting factor for growth prior to thinning. 相似文献
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近30多年来,由于农田灌溉条件的迅速改善,得到的土壤墒情资料已不能反映自然状态下的土壤墒情变化规律。利用土壤水分平衡方程和Penman公式等计算各旬土壤水分相对盈亏程度并对照2001~2003年在不浇水条件下得到的各旬土壤墒情资料,建立拟和方程,确定了干旱指标,恢复了1970~2003年的逐旬实际干旱序列。结果表明,模拟的逐旬干旱序列较好地滤出了灌溉因素,与实际自然土壤自然干旱程度接近。 相似文献
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Data on carbon and biomass budgets under different land use in tropical savannas and some dry forests are reviewed. Global data show wide ranges of biomass carbon stocks (20-150 Mg C ha-1), net primary production (2-15 Mg C ha-1y-1) and litter production (2-10 Mg C ha-1y-1) for the semiarid tropics. Although ranges for soil carbon are also wide, an average figure for the top 20 cm is probably 10 g C kg-1, or about 25 Mg C ha-1. In order to arrive at a better understanding of C budgets and their controls, two regional reviews are presented for NE Brazil and W. Africa.In NE Brazil approximately 40% of the lands have "near-climax" native vegetation. Less than 10% of the area is planted annually, but about 3-4 times that area is affected by shifting cultivation which has an average cycle of 5 y arable use followed by 20 y or more recovery. Standing biomass of native caatinga shows nearly the full global range with 2-50 Mg C ha-1. Litter fall around 1-2 Mg C ha-1y-1 is partly decomposed and partly consumed by animals, resulting in low average soil C levels near 8 g kg-1, or 20 Mg C ha-1. Under cultivation, C sequestration is decreased, and soils lose approximately half their C stocks before being abandoned.In W. Africa between 50-70% of the land is under a management regime with minimal C returns to the soils. Overgrazing and over-exploitation for fuel wood has resulted in land degradation. Short fallow periods on cultivated lands have caused serious declines in soil C stocks. Both C sequestration and stocks are therefore lower in W. Africa than in NE Brazil.Improvements in the C sequestration in these semi arid regions depend on an increase in crop production under suitable rotations, improved fallow and animal husbandry, and a limitation on biomnass burning. Use of fertilizer is required for improved productivities but socioeconomic constraints largely prevent such improvements, resulting in a very limited scope for changes in soil C management. 相似文献
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Z. A. Shostak 《Russian Meteorology and Hydrology》2011,36(12):837-842
The methods are presented of agrometeorological forecasting of winter and spring grain crops for the district, all types of
farm units, and field taking account of the regional crop forecast, weather conditions, cereal cropping technologies, and
soil cultivation level. The additional yields of winter and spring wheat and spring barley and oat are developed depending
on the soil cultivation level, summertime soil moistening, and doses of mineral fertilizers. The method tested on the basis
of independent data demonstrated that the accuracy of such forecasts is 83–99% for the fields with intensive cultivation technology
and 80% for the farm units. 相似文献
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玉林冬季免耕马铃薯分期播种试验及优质高产气候分析 总被引：1，自引：0，他引：1
对玉林市主栽的马铃薯品种黑龙江K 3紫花,采用稻草免耕、地膜覆盖和常耕栽培三种栽培措施分五次播种进行试验,表明,稻草免耕技术不但对地面温度、土壤湿度有很好调节功能,而且与地膜覆盖和常耕栽培产量差异达极显著水平。以播期为11月30日的产量最高,播期为12月10日产量最低。 相似文献
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The dynamics of terrestrial ecosystems depends on interactions between carbon, nutrient and hydrological cycles. Terrestrial ecosystems retain carbon in live biomass (aboveground and belowground), decomposing organic matter, and soil. Carbon is exchanged naturally between these systems and the atmosphere through photosynthesis, respiration, decomposition, and combustion. Human activities change carbon stock in these pools and exchanges between them and the atmosphere through land-use, land-use change, and forestry.In the present study we estimated the wood (stem) biomass, growing stock (GS) and carbon stock of Indian forests for 1984 and 1994. The forest area, wood biomass, GS, and carbon stock were 63.86 Mha, 4327.99 Mm3, 2398.19 Mt and 1085.06 Mt respectively in 1984 and with the reduction in forest area, 63.34 Mha, in 1994, wood biomass (2395.12 Mt) and carbon stock (1083.69 Mt) also reduced subsequently. The Conifers, of temperate region, stocked maximum carbon in their woods, 28.88 to 65.21 t C ha−1, followed by Mangrove forests, 28.24 t C ha−1, Dipterocarp forests, 28.00 t C ha−1, and Shorea robusta forests, 24.07 t C ha−1. Boswellia serrata, with 0.22 Mha forest area, stocked only 3.91 t C ha−1. To have an idea of rate of carbon loss the negative changes (loss of forest area) in forest area occurred during 1984–1994 (10yrs) and 1991–1994 (4yrs) were also estimated. In India, land-use changes and fuelwood requirements are the main cause of negative change. Total 24.75 Mt C was lost during 1984–1994 and 21.35 Mt C during 1991–94 at a rate of 2.48 Mt C yr−1 and 5.35 Mt C yr−1 respectively. While in other parts of India negative change is due to multiple reasons like fuelwood, extraction of non-wood forest products (NWFPs), illicit felling etc., but in the northeastern region of the country shifting cultivation is the only reason for deforestation. Decrease in forest area due to shifting cultivation accounts for 23.0% of the total deforestation in India, with an annual loss of 0.93 Mt C yr−1. 相似文献
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河西走廊农灌区耕作土壤次生盐渍化成因与防治对策 总被引：1，自引：0，他引：1
产生河西走廊耕作土壤次生盐渍化的主要成因。概括起来为大水漫灌、串灌；大块田土地不平整，灌水不均匀；化肥施用量过高；作物耕作制度不合理；土地弃耕和渠道渗漏等。防治对策是平整土地、合理密植、增大有机肥施用量、节水灌溉防止弃耕。 相似文献
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江苏省梅雨的长期预报和成因分析 总被引：7，自引：3，他引：4
本文提出了江苏省中南部两区梅雨量的一种季度预报方法,发现应用２０年左右前期气候要素场找因子组建的预报方程对随后两年两区梅雨量有明显预报能力。分析表明每隔２－３年,预报因子即有相当的变化,显示出前期气候系统与地区梅雨量的隔季联系有不断调整的现象,但仍然存在一些稳定出现的前期因子群,例如前期当地区域的降水量可能通过调节深层土壤水份仍会隔季影响当地的梅雨量。 相似文献
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Development trends of Russian forests and their impact on the global carbon budget were assessed at the national level on the basis of long-term forest inventory data (1961–1998). Over this period, vegetation of Russian forest lands are estimated as a carbon sink, with an annual average level of carbon sequestration in vegetational organic matter of 210 ± 30 Tg C · yr–1 (soil carbon is not considered in this study), of which 153 Tg C · yr–1 were accumulated in live biomass and 57 Tg C · yr–1 in dead wood. The temporal variability of the sink is very large; for the five-year averages used in the analysis, the C sequestration varies from about 60 to above 300 Tg C· yr–1. It is shown that long-term forest inventory data could serve as an important information base for assessing crucial indicators of full carbon accounting of forests. 相似文献