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51.
Monicah Mucheru-Muna Daniel Mugendi James Kung’u Jayne Mugwe Andre Bationo 《Agroforestry Systems》2007,69(3):189-197
Soil nutrient depletion as a result of continuous cultivation of soils without adequate addition of external inputs is a major
challenge in the highlands of Kenya. An experiment was set up in Meru South District, Kenya in 2000 to investigate the effects
of different soil-incorporated organic (manure, Tithonia diversifolia, Calliandra calothyrsus, Leucaena leucocephala) and mineral fertilizer inputs on maize yield, and soil chemical properties over seven seasons. On average, tithonia treatments
(with or without half recommended rate of mineral fertilizer) gave the highest grain yield (5.5 and 5.4 Mg ha−1 respectively) while the control treatment gave the lowest yield (1.5 Mg ha−1). After 2 years of trial implementation, total soil carbon and nitrogen contents were improved with the application of organic
residues, and manure in particular improved soil calcium content. Results of the economic analysis indicated that on average
across the seven seasons, tithonia with half recommended rate of mineral fertilizer treatment recorded the highest net benefit
(USD 787 ha−1) while the control recorded the lowest (USD 272 ha−1). However, returns to labor or benefit-cost ratios were in most cases not significantly improved when organic materials were
used. 相似文献
52.
基于GIS的秦岭火地塘森林景观生物量变化趋势分析 总被引:4,自引:0,他引:4
在GIS技术的支持下,通过格网取样法获得研究区样点基本环境要素数据及样点单位面积生物量数据;以环境要素数据为自变量,样点单位面积生物量为因变量,采用二元四次多项式建立趋势方程并生成立体模型。研究结果表明,海拔、坡度、坡向等环境因素及其组合对森林景观生物现存量影响显著,森林植被本身的生物学特征及其它干扰因素也对其有重要影响。 相似文献
53.
香叶树和杉木人工林生产力的比较研究 总被引:2,自引:0,他引:2
通过对28年生香叶树与杉木人工林生长和生物量测定,进行香叶树和杉木人工林生产力的比较研究,结果表明:香叶树是一种生长迅速的阔叶树种,其人工林蓄积量为421.88m^3/hm^2,比杉木人工林高7.09%;香叶树人工林分生物量为305.43t/hm^2,是杉木人工林的1.59倍,其生物量乔木层是杉木林的1.68倍. 相似文献
54.
油茶林生物量与养分生物循环的研究 总被引:12,自引:0,他引:12
对不同发育期油茶林生物量与养分的生物循环进行了研究。结果表明,从幼龄期至盛果期油茶林生物量逐步积累,盛果期生物量达到16.139t/hm2,其中经济生物量为1.798t/hm2;不同发育期油茶林分的生产力不同,盛果期油茶林太阳能利用率最高,为0.2%;不同发育期油茶林光合产物在各器官的分配比例不同;不同发育期油茶林系统大量元素(N、P、K、Ca、Mg)的吸收量、存留量、归还量及输出量不同。并提出了油茶林系统施肥的监界量。 相似文献
55.
杨树超短轮伐期经营的生产力及材性的研究 总被引:16,自引:0,他引:16
以美洲黑杨2个无性系为供试材料,研究杨树超短轮伐期经营中地上部分生物量生产、分配模式、N、P、K的输出量及材性。结果表明,在3种密度和3种轮伐期的组合中,2个无性系均以造林密度为10000株·ha-1、轮伐期为3年的林分生物生产力最高,I-69杨为10.52t·ha-1·a-1,NL-80351杨约为12.00t·ha-1·a-1;在生物量的分配比率和作为造纸材的经济生物量上也以这种组合模式最为合理,经济生物量最大,I-69杨为7.14t·ha-1·a-1,NL-80351杨为8·47t·ha-1·a-1。养分输出量的多少与林分的生物量生产和分配比率密切相关。轮伐期为3年,密度为10000株·ha-1的林分N、P、K的输出量最高,I-69杨为33.97kg·ha-1·a-1,NL-80351杨为38.50kg·ha-1·a-1,但NL-80351杨每生产1吨经济生物量所输出的N、P、K总量略低于I-69杨。杨树超短轮伐期经营中生产出的木材都可用作中、低档的造纸原料,其中I-69杨的制浆性能优于NL-80351杨。 相似文献
56.
巴山木竹种群生物量结构研究 总被引:14,自引:0,他引:14
研究了陕西镇巴县巴山木竹种群的生物量结构.结果表明:(1)该巴山木竹种群生物量在各构件单位的分配为秆55.56%,叶3.40%,枝9.51%,鞭8.70%,蔸20.77%,根2.06%;地上部生物量在各年龄的分配1~5年生的分别为19.0%,5.2%,5.4%,4.3%,8.9%,6和7年生的14.6%,8和9年生的18.2%,10a及以上的24.4%;地下部生物量在各土层中的分配是0~2cm的12.9%,20~40cm的43.1%,40cm以下的44.0%.(2)3年生及以下幼龄竹和8年生及以上老龄竹的平均秆重低于标准秆重,4~7年生竹的高于标准秆重.(3)随着竹子幼龄-中龄-老龄的年龄变化,单分株叶构件的绝对重量及其与秆重的比值皆有上升-稳定-下降的变化趋势. 相似文献
57.
The objectives of the study were to investigate mineral soil profiles as a living space for microbial decomposers and the relation of microbial properties to soil acidity. We estimated microbial biomass C on concentration (g g–1 DW) as well as on volume basis (g m–2) and the microbial biomass C to soil organic C ratio along a vertical gradient from L horizon to 20 cm in the mineral soil and along a gradient of increasing acidity at five beech forest stands in Germany. Microbial biomass C concentration ranged from 17,000–34,000 g Cmic g–1 DW in the litter layer and decreased dramatically down the profile to 29–264 g Cmic g–1 DW at 15–20 cm depth in the mineral soil. This represents depth gradients of microbial biomass C concentrations ranging from a factor of 65 in slightly acidic and up to 875 in acidic soils. In contrast, microbial biomass C calculated on a volume basis (g Cmic m–2) showed a different pattern since a considerable part of the microbial biomass C was located in the mineral soils. In the soil profile 22–34% of the microbial biomass C was found in the mineral soil at strictly acidic sites and as much as 64–88% in slightly acidic soils. The microbial biomass C to soil organic carbon ratios decreased in general down from the L horizon in the forest floor to 0–5 cm depth in the mineral soils. In strongly acidic mineral soils however, the C to soil organic carbon ratio increased with depth, suggesting a positive relation to increasing pH. We conclude from depth gradients of soil pH and microbial biomass C to soil organic carbon ratio that pH affects this ratio at acidic sites. The inter-site comparison indicates that acidity restricts microbial biomass C in the mineral soils. 相似文献
58.
P.L. Mafongoya R. Chintu T.S. Chirwa J. Matibini S. Chikale 《Agroforestry Systems》2003,59(3):279-288
Seeking an alternative to Sesbania spp. tree fallows, a Tephrosia species and provenance trial was conducted at Msekera Research Station, Chipata (Zambia) to evaluate eleven Tephrosia vogelii and three Tephrosia candida provenances. They were tested for biomass production, quality of biomass, resistance to root-knot nematodes, nitrogen release,
and for their effects on soil nitrogen dynamics. At the end of 1.5 years, the T. candida provenances 02970, 02971 and 02972 from Madagascar produced two times greater amount of aboveground biomass than the T. vogelii provenances. There was little variability among the T. vogelii provenances in terms of litter and biomass production. Weed growth was significantly greater under T. vogelii than T. candida provenances. While Tephrosia vogelii provenance 98/02 from Zambia and T. candida 02972 were highly tolerant to the Meloidogyne incognita nematodes, T. vogelii provenances 02977, 98/03, 02973 from Kenya, Zambia and Malawi, respectively, were highly susceptible to the nematodes. The
Tephrosia species and provenances showed a wide variability in terms of N, lignin and polyphenol concentration in their foliage. Mineralization
of N in the foliage of T. candida provenances 02970 and 02971 and T. vogelii provenances 98/04 and 02974 from Malawi occurred rapidly within 14 weeks of incubation. At the end of the 2-year growth period,
there was significantly greater total inorganic N under T. candida provenance 02972 (12.5 mg kg−1) than T. vogelii (5 mg kg−1) provenance Mungwi 98/02. Maize (Zea mays L.) yields after T. candida provenances were greater than those after T. vogelii provenances. Further testing of the most promising provenances is needed for their effects on subsequent maize yields under
a range of farm conditions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
59.
We examined the carbon stock and rate of carbon sequestration in a tropical deciduous forest dominated by Dipterocarpus tuberculatus in Manipur,North East India.Estimation of aboveground biomass was determined by harvest method and multiplied with density of tree species.The aboveground biomass was between18.27–21.922 t ha-1and the carbon stock ranged from9.13 to 10.96 t C ha-1across forest stands.Aboveground biomass and carbon stock increased with the increase in tree girth.The rate of carbon sequestration varied from1.4722 to 4.64136 t ha-1year-1among the dominant tree species in forest stands in tropical deciduous forest area.The rate of carbon sequestration depends on species composition,the density of large trees in different girth classes,and anthropogenic disturbances in the present forest ecosystem.Further work is required to identify tree species having the highest potential to sequester CO2 from the atmosphere,which could lead to recommendations for tree plantations in a degraded ecosystem. 相似文献
60.