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根据长白落叶松人工林单木生长模型,运用HookeJeeves求解算法确定了林分初植密度为3 300株/hm~2时,以不同立地的林分木材价值和碳储量同时最大为经营目标的最优经营模式,并分析经营目标对优化结果的影响以及经济参数的敏感性。结果表明:林分初植密度为3 300株/hm~2时,各立地条件下林分最优间伐次数为3次。地位指数16、18、20 m的林分多目标优化的轮伐期分别为50、46、43 a;木材平均产量分别为7.897、9.429、11.070 m~3·hm~(-2)·a~(-1)。随着碳储量权重的增大,碳储量对经营目标最为敏感。在相同立地条件下,随着贴现率的增大,轮伐期延长,净收入、净现值和碳储量减少,木材产量增加。对于相同贴现率,立地质量越好,木材产量、净现值、年均净收入和碳储量越大,轮伐期越短。年均净收入和净现值受木材价格的影响较大,且与木材价格呈现正相关关系,而木材产量和碳储量受木材价格的影响不大。碳储量、净现值、木材产量和年均净收入对营林成本不敏感,木材价格提高或者营林成本降低均能缩短轮伐期。 相似文献
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马尾松人工林森林经营模式评价 总被引:2,自引:0,他引:2
根据不同经营模式(轮伐期经营、近自然经营、无经营)下中龄马尾松人工林样地2期调查数据,利用One-way ANOVA分析森林经营对林分以及单木生长量的影响;比较分析不同森林经营模式对森林结构及树种组成的影响。结果表明,近自然经营相对于轮伐期经营主要是对林分上层木和下层木生长促进效果明显,对中层木生长影响与轮伐期经营效果差异不明显,轮伐期经营与无经营相比较,能有效促进中层林生长,但对上层木及下层木的促进效果不明显;近自然经营能够有效增加林分单位面积蓄积生长量,而轮伐期经营则不然;2种经营模式均能有效增加林分树种多样性与均匀度,但近自然经营明显优于轮伐期经营(两者树种多样性指数差异显著);总的来说,近自然经营优于轮伐期经营,后者虽然一定程度上改变了林分结构,但并没有根本上改善林木生长状况。最后,根据不同经营模式下当前的林分结构提出相应的后续经营建议。 相似文献
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以中亚热带(湖南和江西)杉木林分为研究对象,应用FORECAST模型,探讨了连续4个轮伐期的好中差3种立地杉木林分生长和生态系统过程对N、P、N+P混合施肥的响应.结果表明:与N肥相比,使用P肥对杉木林分生长(如树高、胸经)和生态系统过程(土壤腐殖质、林分凋落物、土壤N和P储量等)具有更好的促进作用;与较好立地相比,在较差立地林分施肥具有更好的效果;在4个轮伐期中,前一个轮伐期施肥后一个轮伐期林分仍具有明显影响,显示了施肥效果的累积性.这些结果对杉木人工林经营、低效林改造具有指导作用. 相似文献
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【目的】探讨采用模拟计算法确定合理年采伐量后的实施效果,为实现森林资源的可持续经营提供支持。【方法】以福建某林业企业经营的杉木、马尾松人工用材林为研究对象,通过模拟计算法模拟林分的采伐和生长,以轮伐期期末成熟林和过熟林的面积占42.8%为控制目标,不断设定年采伐量使一个轮伐期期末的成熟林和过熟林的面积达到设定目标。在此基础上,利用重置成本法、收获现值法、市场价倒算法测算各龄组价值,并通过对比模拟前后的价值分析模拟计算法对价值量的影响。【结果】在一定控制目标下,采用模拟计算得到杉木、马尾松的合理年采伐面积分别为18.7和21.6hm2,根据单位面积蓄积量得到合理采伐量分别为351.5和989.3m3,在此采伐量下林分各龄组分布结构较为均匀、稳定、合理。利用各评估方法测算林分价值量,对比分析各年份的林分价值量,显示模拟计算法在确定合理采伐量的同时,有效提高了林分的价值量。【结论】以轮伐期末成熟林和过熟林面积占42.8%为控制目标,轮伐期期末林分各龄组结构分布均匀,林分价值量提高,有利于森林资源的可持续经营。 相似文献
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福建武平帽布米槠林择伐经营策略初探:II.林分测树因子,物种… 总被引:2,自引:1,他引:1
通过林分测树因子分析,该林分胸径大于42cm以上的材积比例最大;米槠株数最多、材积百分比也最大,马尾松株数虽少,但材积百分比居第二位。择伐对林分多样性指数的影响不大,伐前、伐后近相等。采用皆伐,轮伐期为42年以上,而采用择伐,轮伐期为18年。 相似文献
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本文以使得未来林分永续生产周期的净现值最大为准则,应用变分法建立同龄林分木材收获时间问题的优化控制模型。以东北林区的人工落叶松林资料(260块标准地和62株解析木)为例,说明模型中参数的确定及模型的应用,同时,确定人工落叶松林的最优间伐计划和轮伐期。 相似文献
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王群超 《东北林业大学学报》2011,39(6):98-100
简述了国外基于固碳效益的最优轮伐期的研究.大量研究表明,当考虑人工林的固碳效益时,轮伐期长短会受影响,并会随碳价、贴现率变化而变化,并且这种变化通常很灵敏.通过总结国内关于森林固碳效益方面的研究,推导出固碳效益的一般模型,并将其引入到Faustmann最优轮伐期模型中,从而整理出基于固碳效益的最优轮伐期模型. 相似文献
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用模糊关系方程预估林分蓄积量的研究 总被引:1,自引:0,他引:1
以林分的年龄、胸高断面积、优势木平均高为预估因子,用模糊关系方程预估林分蓄积量。经检验:系统误差为0.274%,精度为96.79%。表明该法预估效果良好,简单易行,有较大的实用价值。 相似文献
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于波涛 《东北林业大学学报》2008,36(6):26-29
从森林资源生长规律的特点出发,根据森林资源的最佳利用理论——最佳轮伐期理论,保证有限林地产生更多的经济价值,即以林地的立地价值最大化为目的,确定具体林地种植的树种和轮伐周期,提出相应的最佳造林采伐方案。以工农林场为例计算分析,结果表明,在充分调查工作的基础上,该方案可实施性很强,并且方案能够保证林地的立地价值最大化,同时将调整期内的经济损失降到最小,对我国森林资源的结构调整具有参考意义。 相似文献
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不同作物种植方式产出效果的定量评价 总被引:8,自引:1,他引:8
应用土地当量比、产量当量、产值当量等不同量化指标,对复种、间作、轮作等不同种植方式的产出效果进行了比较研究。结果表明,与单作一熟农田相比,复种、间作及轮作农田土地利用效率分别提高62%、38%和21%;单位面积产量分别为单作一熟农田的1.63、1.29和1.16倍;复种、间作农田单位面积产值分别为单作一熟农田的1.76和1.35倍。通过综合分析,进一步明确了评价不同种植方式产出效果的客观方法,为今后农作制度中不同种植方式农田产出效果的比较研究提供理论依据。 相似文献
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Estimation of USLE crop and management factor values for crop rotation systems in China 总被引:1,自引:0,他引:1
Soil erosion on cropland is a major source of environmental problems in China ranging from the losses of a non-renewable resource and of nutrients at the source to contamination of downstream areas. Regional soil loss assessments using the Universal Soil Loss Equation(USLE) would supply a scientific basis for soil conservation planning. However, a lack of information on the cover and management(C) factor for cropland, one of the most important factors in the USLE, has limited accurate regional assessments in China due to the large number of crops grown and their complicated rotation systems. In this study, single crop soil loss ratios(SLRs) were collected and quantified for 10 primary crops from past studies or reports. The mean annual C values for 88 crop rotation systems in 12 cropping system regions were estimated based on the combined effects of single crop SLRs and the percentage of annual rainfall erosivity(R) during the corresponding periods for each system. The C values in different cropping system regions were compared and discussed. The results indicated that the SLRs of the 10 primary crops ranged from 0.15 to 0.74. The mean annual C value for all 88 crop rotation systems was 0.34, with a standard deviation of 0.12. The mean C values in the single, double and triple cropping zones were 0.37, 0.36 and 0.28, respectively, and the C value in the triple zone was significantly different from those in single and double zones. The C values of dryland crop systems exhibited significant differences in the single and triple cropping system regions but the differences in the double regions were not significant. This study is the first report of the C values of crop rotation systems in China at the national scale. It will provide necessary and practical parameters for accurately assessing regional soil losses from cropland to guide soil conservation plans and to optimize crop rotation systems. 相似文献
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泉盈 《西南大学学报(自然科学版)》1989,(1)
蔷薇三节叶蜂幼虫为害月季的叶片从而影响花的数量和质量。叶、花的损失量随虫量的增加而加重。当虫量为2、4、6、8、10头/株时,花的美观度分别降低0.32%、2.36%、12.47%、53.1%、88.57%。其观赏阈值为5.5头/株。防治指标为5头/株。 相似文献
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应用“林分结构复原法”评价经营措施及更新效果研究 总被引:1,自引:1,他引:0
介绍了林分调查的一种方法:“林分结构复原法”,即根据林分的现时直径分布和直径生长量,应用林分表法进行径阶转移的原理,推算n年前的直径分布,并根据直径与其他林分因子的关系,再现林分在前n年时的林分结构,从而为评价采伐的合理性以及鉴定超采、盗伐提供可靠数据。 相似文献
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Agriculture and biodiversity: Finding our place in this world 总被引:1,自引:0,他引:1
Jeffrey A. Lockwood 《Agriculture and Human Values》1999,16(4):365-379
Agriculture has been recently viewed as the primary destructive force of biodiversity, but the places that produce our food and fiber may also hold the key to saving the richness of life on earth. This argument is based on three fundamental positions. First, it is argued that to value and thereby preserve and restore biodiversity we must begin by employing anthropocentric ethics. While changing our understanding of intrinsic values (i.e., the unconditional values of biodiversity as a state and process in-and-of-itself, without reference to human interests) is often advocated as the means by which our behavior will reflect the importance of biodiversity, a change in how we perceive and conditionally value biodiversity is proposed as a more effective and compelling approach. Second, I suggest that anthropocentric values can be linked to a sense of Place, with agriculture playing a vital role in this context. Agriculture forms a powerful basis for personal, experiential development of a profound meaning and connection to a setting or landscape. The agricultural setting has tremendous potential for arational (emotional, aesthetic, and spiritual) values that ultimately compel our actions. The constancy of relationship and mutuality of dependency between humans and agricultural lands, particularly extensive agroecosystems, fosters an intensity of association that transcends our recent affinity to wildlands. Third, a mature understanding of places and their biodiversity must include those organisms that account for many of the ecological processes and the majority of the species richness -- the insects. The importance of these insects in structuring the landscape and the effects of habitat destruction on these organisms both suggest a vital, intimate, and reciprocal link between insects and Places. Finally, it is argued that the most important avenue for future efforts to protect and restore biodiversity on the part of agricultural and other scientists is educational -- the presentation of our research to the public in terms that provoke emotional, aesthetic, and spiritual meaning which lies at the core of human values and actions. 相似文献
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为研究不同种植模式稻田生态系统的服务功能价值,通过田间试验,设置Y-OL(70%化肥+30%牛粪-水稻-黑麦草)、Y-OV(70%化肥+30%牛粪-水稻-紫花苕)、Y-ON(70%化肥+30%牛粪-水稻-冬闲)3种优化施肥轮作处理,以常规施肥单作处理C-ON(100%化肥-水稻-冬闲)为对照,结合功能价值评价法和当量因子法对稻田生态系统的服务功能价值进行估算。结果表明,Y-OL和Y-OV处理稻田生态系统服务功能价值分别为169 669元·hm-2和168 405元·hm-2,Y-ON处理为99 247元·hm-2,C-ON处理为72 717元·hm-2;Y-OL和Y-OV处理服务功能总价值均显著高于Y-ON和C-ON处理,且Y-ON处理服务功能总价值显著高于C-ON处理(P<0.05)。其中,优化施肥轮作处理的农产品经济价值、气体调节价值、消纳废弃物价值、水质净化价值、土壤有机质积累价值、营养物质循环价值、生物多样性价值和美学景观价值均显著高于常规施肥单作处理(P<0.05)。优化施肥轮作处理中,水稻-紫花苕轮作的水质净化价值和营养物质循环价值显著高于水稻-黑麦草轮作(P<0.05)。综上所述,70%化肥+30%牛粪-水稻-黑麦草轮作和70%化肥+30%牛粪-水稻-紫花苕轮作的种植模式能有效提高稻田生态系统的服务功能价值,并且70%化肥+30%牛粪-水稻-紫花苕轮作模式效果更佳。 相似文献