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81.
试验对免炼山与炼山造林对当年生桉树生长的影响进行实地调查。结果表明:免炼山造林不影响桉树当年的生长量,具有操作方法简单,成本较低,符合可持续发展经营的要求。 相似文献
82.
秸秆捆烧清洁供暖技术评价 总被引:2,自引:2,他引:0
中国北方地区秸秆资源丰富,将秸秆打捆转化为能源实现清洁取暖,既能解决秸秆过剩问题,又能有效替代煤炭,对改善大气质量和人居环境具有重要意义。为探究秸秆捆烧清洁供暖技术的能源效率、经济效益和温室气体排放,采用3E(Economic,Energy and Environment)评价模型,从作物种植收获到秸秆捆烧供暖应用全过程开展系统评价。结果表明,秸秆捆烧供暖技术的能源和经济效益较好、温室气体排放少,适于居住较集中的村镇地区冬季供暖,也可用于农业、工业园区等区域供热。供暖面积0.5×104~10×104m2范围内,供暖面积越高,能源和经济环境效益越好,秸秆捆烧供暖的净能量10 512~10 774.8 MJ/t,能量产出投入比8.4~8.5,能源转化率较高,温室气体CO2当量排放量为9.67~11.21 g/MJ;经济成本391.1~560.5元/t(折合16.2~23.8元/m2),按基准收益率8%计算,供暖规模应不小于2×104 m2,若不考虑折旧只考虑运行成本,则供暖面积应不小于1×104 m2。与秸秆成型燃料和秸秆炭气联产供暖技术比较,均具有较好的经济效益,秸秆捆烧供暖技术的能量效益最优,温室气体排放量最少。与煤炭供暖技术相比,3种秸秆供暖技术的净能量产出不如煤炭,但温室气体排放仅为煤炭的1/10~1/7,秸秆清洁供暖技术的环境效益显著。 相似文献
83.
[目的]利用燃烧概率模型模拟计划火烧前后两种情景下的森林燃烧概率,在景观尺度上定量评估计划火烧在林火预防中的作用。[方法]利用SPOT6卫星数据提取大兴安岭部分区域在2016年火险期前进行计划火烧处理的可燃物状况,基于研究区附近地面气象观测数据利用R软件计算2016年火险期每日的火险指数,通过BURN-P3模型分别模拟计划火烧前后的森林燃烧性,评估计划火烧对森林燃烧概率和火行为的影响。[结果]2016年火险期前该区域进行计划火烧的面积为44 931 hm2,占区域总面积的20.8%。计划火烧后,研究区平均燃烧概率从0.016 4降到0.012 4,落叶针叶林、常绿针叶林、针阔混交林、草地和落叶阔叶林平均燃烧概率分别降低4.2%、3.5%、5.9%、2.3%和0.6%。计划火烧前研究区的平均火烧强度和平均蔓延速度分别为548.9 kW·m-2和2.2 m·min-1,通过计划火烧处理,火烧强度和蔓延速度分别降低17.9%和24.3%。落叶针叶林和针阔混交林是发生树冠火的主要类型,火强度高、火蔓延速度快。计划火烧处理后研究区... 相似文献
84.
等养分条件下稻草还田替代双季早稻氮钾肥比例的研究 总被引:7,自引:4,他引:7
85.
86.
The seasonal distribution of fires is one fire regime variable which has received little attention with regard to its effects on plants. For species with a short life-span that recruits after fire, the seasonal timing of a fire can be expected to be important due to effects on potential growth period and reproduction. We observed phenology and reproductive output in two annual and fire-dependent Geranium spp. in the southern part of the European boreal forest. In a garden experiment with the two species under two levels of nutrition, we established cohorts of seedlings at several dates over three summers. Time from germination to flowering and first mature seed differed little between the two species and levels of nutrition; i.e. plant size or level of nutrition had almost no effect on phenology. However, emergence time controlled the timing of reproduction. Most plants emerging before the second week of July in the garden experiment bolted the same year. Plants emerging later behaved as winter-annuals and started to flower in June the following year. A similar dichotomy was observed for populations of Geranium spp. at a number of burnt forest sites that differed in date of fire. This response is likely controlled by photoperiod. Nevertheless, at sites that burnt early some plants did not bolt in the same season; probably an effect of variable seedling emergence dates in the populations. In both the field and garden experiment, there were plants entering reproduction too late to produce mature seeds. Our results indicate that management fires should be conducted either very early, or during July and August to achieve a high seed production in these rare forest plants. 相似文献
87.
Over a period of 16 years, unburned longleaf pine (Pinus palustris Mill.) pole stands grew an average of 27% more volume than similar stands regularly burned. Treatments included biennial burns in winter, spring, and summer plus an unburned check, each of which was combined with three supplemental treatments, namely, initial herbicide injection of all hardwoods, repeated handclearing of all woody stems, and no treatment. All unburned and winter-burned plots were paired to study this growth reduction relative to treatments. The status of nitrogen, phosphorus, available moisture holding capacity, bulk density, and macropore space was determined in both surface and subsurface soils. Foliage from pines on sampled plots was analyzed for N, P, K, Ca, Mg, Mn, Cu, Fe, and Zn. Burning did not significantly affect either soil N and P or foliar nutrients. However, burning reduced available moisture holding capacity and macropore space and increased the bulk density of surface soils, and also reduced the moisture-holding capacity of subsurface soils. The results from this and other studies suggest that growth losses are due, at least in part, to increased moisture stress associated with changes in soil physical properties. 相似文献
88.
Johann G. Goldammer 《Agroforestry Systems》1988,6(1):235-252
Tropical forest land is increasingly influenced by man-caused wildfires. The vast majority of the forested area burnt and cleared annually is in the tropics. The use of fire in rural land-use systems is the major cause of the wildfires. Five broad causative agencies of wildfires are presented, shifting cultivation, grazing, non-wood forest products, migration programs and the wildland/residential interface. Integrated concepts of prescribed burning and prescribed grazing may offer solutions to the tropical wildland fire problems. 相似文献
89.
浅谈阻燃中密度纤维板 总被引:2,自引:1,他引:2
介绍了中密度纤维板的生产现状和前景,阻燃中纤板所用阻燃剂的种类。阻燃的机理和处理方法。同时,论述了中纤板阻燃的必要性和紧迫性。并讨论了阻燃中纤板的发展方向。 相似文献
90.
Alex Fajardo Jonathan M. Graham John M. Goodburn Carl E. Fiedler 《Forest Ecology and Management》2007
Little is known about ponderosa pine forest ecosystem responses to restoration practices in the Northern Rocky Mountains, USA. In this study, restoration treatments aimed at approximating historical forest structure and disturbances included modified single-tree selection cutting, with and without prescribed burning. We compared the effectiveness of restoration treatments on growth, vigor, and composition of recruitment responses with untreated controls. We used a randomized block design to detect treatment differences in mean individual tree basal area increment (BAInc10), growth efficiency (GE), and recruitment abundance between two restoration treatments (Cut-only and Cut-burn) and a Control. We further examined treatment effects by tree age-class (Young, Mature, Presettlement) using a spatial ANOVA model that incorporates the spatial autocorrelation among trees within experimental units. Ten years after implementing restoration treatments, mean individual tree BAInc10 and GE were significantly higher for treated units relative to Control units; all three age-classes benefited similarly from restoration treatments relative to the Control, with the greatest response in the Cut-only and moderate response in the Cut-burn. When treated units were compared, Cut-burn negatively affected BAInc10 and GE relative to Cut-only. Presettlement trees responded positively to treatment relative to the Control, particularly for BAInc10, demonstrating the potential of these old trees to respond to reduced competition. The Cut-burn treatment, in contrast, negatively affected the BAInc10 and GE response of postsettlement trees when compared to Cut-only. Restoration treatments did not reduce the amount of Douglas-fir recruits. In addition, the recruitment of both ponderosa pine and Douglas-fir species was associated with the proximate cover of woody debris in Cut-only and Control treatments. Finally, special consideration needs to be taken for spring Cut-burn treatments, which appeared to dampen growth and vigor, relative to Cut-only, particularly for Young and Mature trees, and increased recruitment of ponderosa pine and particularly Douglas-fir. 相似文献