Tropisternus lateralis (Say) (Coleoptera: Hydrophilidae) as a potential stand reducer in water-seeded rice under a continuous flood     

《Crop Protection》2013

Water-seeded rice under a continuous flood is susceptible to stand reduction by aquatic invertebrates. Field observations in water-seeded rice with reduced stand revealed the possibility that Tropisternus lateralis may be responsible for dramatically reducing rice stands. Greenhouse experiments were performed with aerated, covered bins that were water-seeded and infested with varying densities of T. lateralis. Uprooted seedlings (floaters) were counted and removed, and stands were recorded. Results showed significantly increased numbers of floaters in bins with higher densities of T. lateralis. Stands were also significantly reduced in the higher density bins. The results of these experiments strongly suggest that T. lateralis is responsible for dislodging rice seedlings in a water-seeded regime with a continuous flood. Foraging activity appeared to be associated with this damage. Observations also suggest female T. lateralis may be more likely to dislodge seedlings than males because of their egg laying activities.  相似文献   

Environmental effects on linseed (Linum usitatissimum L.) yield and growth of flax at different stand densities     

R. Casa  G. Russell  B. Lo Cascio  F. Rossini 《European Journal of Agronomy》1999,11(3-4):267-278

The effect of environmental factors and stand density on linseed (Linum usitatissimum L.) yield was investigated by examining yield components and development rates from 4 years of field experiments carried out at Viterbo, Central Italy, in which different seed rates were tested. Spring sowings were carried out using the linseed cultivar ‘Mikael’. Growth analysis using the functional approach and modelling using the SUCROS model for potential production parameterized for linseed were used to carry out a more detailed analysis of environmental effects.

Linseed yields varied greatly in response to weather and soil type but showed very little effect of plant density. The crop was able to compensate for reduced stand densities mainly by increasing the number of capsules per plant. All yield components were significantly influenced by weather as represented by the year of sowing. Growth analysis showed that the unit leaf rate had higher values at lower stand densities, suggesting that self-shading at higher densities decreased the efficiency of the foliage. The environmental factors most likely to affect yields were high temperature, due to its effect on development rate, and the consequent shortening of the growing cycle and perhaps water shortage. The foliage duration was more important than the maximum leaf area index.  相似文献   

秦巴山区油松飞播林林分密度控制图的编制     

王锁民 《陕西林业科技》1993,(1):28-32

通过对207块油松飞播标准地材料整理分析,编制了我省秦巴山区油松飞播林林分密度控制图。编图的理论精度,等直径线为95.58%,等树高线为95.42%。适用性检验结果也表明该图可应用于生产。  相似文献   

长白落叶松人工林建筑材林分经营模型微机系统     

李梦  李元 《东北林业大学学报》1997,25(3):26-29

在全林分生长模型析基础上，用ＶｉｓｕａｌＢａｓｉｃ（ＶＢ）语言建立了长白落叶松建筑材料分经营模型微机系统。由参数设置、生长模拟，图形显示，打印数表和模式报告５部分构成。根据功能设计。每一部分被划分若干模块。系统优化采用动态规划方法。经济分析随生长模拟同时完成。  相似文献   

Composition and structure of natural mixed-oak stands in northern and central Portugal     

João P.F. Carvalho 《Forest Ecology and Management》2011,262(10):1928-1937

Stand composition and structure of natural mixed-oak stands of common-oak (Quercus robur L.) and pyrenean-oak (Quercus pyrenaica Willd.) were studied. Diverse compositional and structural elements in early and late successional stand stages were analysed. The study was conducted in north and central Portugal where different natural mixed oak forests types are located. The following mixed-oak forest types involving common-oak and pyrenean-oak were studied: common-oak & other hardwoods; common-oak & cork-oak (Quercus suber L.); ash (Fraxinus angustifolia Vahl) & pyrenean-oak; and pyrenean-oak & madrone (Arbutus unedo L.). Measurements were made in early and late successional stand stages on the different mixed oak forest types. Different stand characteristics and indices were used to describe and compare stand structure and composition. The study showed changes in species diversity and stand structure. Most tree species in mature stands are present in early stages but with higher abundance. Shannon diversity index may change between 0.798 and 1.915. Significant differences on species diversity and abundance were found depending on the forest type and successional stage. Mature mixed-oak forests have high species diversity with an abundance of small to medium tree size species. Species distribution and diameter differentiation indices range from 0.30 to 0.70 and 0.52 to 0.82, respectively, revealing significant structural complexity. The average number of standing and downed dead trees was 265 and 83 trees ha⁻¹ for early and late stage, respectively, with 6.9 and 65.4 m³ ha⁻¹. Higher values of stand diversity index were 41 and 53 in more complex and developed forests. Later stand stages have complex structure, with a wider range of tree diameter distribution and higher degree of irregularity.  相似文献   

The conservation value of oil palm plantation estates, smallholdings and logged peat swamp forest for birds     

Badrul Azhar  David B. LindenmayerJeff Wood  Joern FischerAdrian Manning  Chris McElhinnyMohamed Zakaria 《Forest Ecology and Management》2011,262(12):2306-2315

The expansion of industrial oil palm cultivation threatens tropical biodiversity globally, especially in developing countries. Driven by plans to generate economic revenue, large-scale plantations are emerging in Southeast Asia, Africa and Brazilian Amazon. However, the ecological impacts of the sector are poorly studied with respect to oil palm management system, and recommended conservation measures are based on limited data. We studied avifauna in oil palm landscapes in Peninsular Malaysia under different management systems (large plantation estates versus smallholdings) and age classes (uniform age versus mixed-age stands). We sampled 41 large plantation estates and 14 smallholdings, as well as 20 sites in an extensively logged peat swamp forest, the type of natural forest prior to conversion to oil palms. Compared with logged peat swamp forest, our results showed that forest conversion to oil palm cultivation may have eliminated 48-60% of bird species. We also found: (i) plantation estates and smallholdings supported similar bird assemblages but the latter supported significantly more species (P = 0.007); and (ii) despite reduced species richness in oil palm landscapes, we found high abundance of some individual bird species in specific types of stands including some forest, migratory, and wetland species. Conversion of natural forest to oil palm landscapes should not occur in the future through clearing of primary or secondary native forests. To complement conventional conservation approaches (e.g. the establishment of protected areas) in palm oil-producing countries, existing plantation estates and smallholdings should be managed in ways to promote improved conservation outcomes, although oil palm landscapes maintained a fraction of the original forest biodiversity. Managing habitat heterogeneity at both a local and a landscape-level is highly recommended in oil palm landscapes to maintain and/or enhance avian biodiversity.  相似文献   

Snow disturbances in secondary Norway spruce forests in Central Europe: Regression modeling and its implications for forest management     

Tomáš Hlásny  Štěpán K?ístek  Ji?í Trombik 《Forest Ecology and Management》2011,262(12):2151-2161

Snow is an important ecological factor limiting vegetation distribution, growth, and regeneration, and the importance of snow in the latitudes of Central Europe is expected to increase in the future. We assessed snow damage to secondary spruce stands (not of native provenance therefore not adapted to local conditions) in a mountainous region of 14500 ha in Central Europe (Moravian-Silesian Beskids, Czech Republic). We used neural networks-based regression modeling to study the relationship between stand and environmental parameters and four types of snow damage (top tree, crown, and stem breakage, and uprooting) that occurred during heavy snowfalls in winter 2005/2006 and 2009. Almost 40000 trees were sampled in 345 plots after each of these two events.The results suggest that parameters that can be controlled by forest management (mainly stand density and taper) were not closely associated with spruce forest resistance to snow damage. Investigated snow damage types were primarily related to the developmental stage of the stand, as indicated by stand volume, age, height, and diameter. Damage in 2009, which was caused by shorter-lasting and lower snow loads than the damage in 2005/2006, was also associated with elevation and snow depth. The response of snow damage to all stand development-related variables was clearly unimodal.We infer that forest management can reduce snow damage to secondary spruce forests in Central Europe only to a limited extent, especially under heavy snow loads. This conclusion is supported by the heavy snows that have frequently fallen on forests in Central Europe in the past and the projected increase in winter precipitation in mid- and northern latitudes; thereby increasing snow damage to forest in the future. Therefore, managers of such spruce forests should not specifically consider forest resistance to snow damage but should apply general practices that maintain forest health and productivity.  相似文献   

天然红松树木生长特征与林分结构的研究   总被引：3，自引：0，他引：3  

葛剑平  李景文 《东北林业大学学报》1992,20(2):9-16

通过对树木生长规律和群落结构、动态过程的研究,提出了应用树木生长模型研究林分垂直结构与树木生长动态之间相互关系的新方法。预测了红松树木生长和形态的时空模式以及树木不同发育阶段影响生长主要因子的差异性。结果表明,天然红松生长和形态特征的形成是与其林隙更新途径密切相关的。在树龄160a以前主要为高生长时期,受林隙形成的垂直层次上的生境控制;树龄在160a以后为径生长时期,林木达到上层林冠,从营养生长转变为生殖生长,顶端开始结实,主干开始分叉,叶面积增大,形态呈平顶状。此阶段林木生长主要依赖于立地条件。  相似文献   

两种杨树矮林地上生物量及树皮比例早期测算     

戴丽莉  贾黎明  高媛  戴腾飞 《东北林业大学学报》2015,(7):102-109

通过建立茎干离地22 cm的直径(D22)与单枝地上生物量的关系,估算林分地上生物量,并对三倍体毛白杨B301和欧美杨107在3种栽植密度下林分地上生物量及收获物质量进行早期测算。结果表明:三倍体毛白杨B301林分各栽植密度的单枝地上生物量和单枝树皮地上生物量差异均不显著;欧美杨107在20 000株/hm2栽植密度下,单枝地上生物量和单枝树皮地上生物量均显著小于栽植密度为5 000株/hm2;2种杨树林分地上生物量和林分树皮地上生物量均随着栽植密度的增大而增大,且各栽植密度间的差异达到了极显著水平。  相似文献   

Intensive,site-specific silviculture: Manipulating resource availability at establishment for improved stand productivity. A review of South African research     

Ben du Toit  Colin W. Smith  Keith M. Little  Grant Boreham  Robert N. Pallett 《Forest Ecology and Management》2010

An important window of opportunity to increase and sustain productivity in short-rotation plantations is the period from felling through re-establishment to canopy closure. This paper explores the effects, interactions and response mechanisms of intensive silvicultural practices on plantation productivity and sustainability, using five South African case studies (a–e). (a) Land preparation trials showed that complete surface cultivation by ploughing had a significant beneficial effect when afforestation is done for the first time in grasslands, improving basal area growth by 11–52% over pitting only. However, similar treatments have not resulted in significant growth responses under re-establishment conditions. (b) Stand growth suppression resulting chiefly from soil compaction during mechanised harvesting operations is strongly related to soil type, soil textural class and residue management options. Volume growth reduction in short-rotation eucalypt crops ranged from 25% on compaction sensitive loamy soils to less than 2% in resistant sandy soils. (c) The response mechanism whereby vegetation management improves stand productivity is a reduction in both inter-specific and intra-genotypic competition for resources, as well as a decrease in stand variability. Operationally, the most important criteria in a vegetation management programme relate to the timing of control operations across diverse site conditions. In local trials, the primary factors controlling the time taken for competition-induced tree growth suppression to occur were related to altitude, slash burning and the interaction between these factors, which facilitated the development of regional vegetation management strategies. (d) Empirical fertilizer trials in short-rotation hardwood stands have shown significant improvements in final productivity (commonly 20–90 m³ ha⁻¹ in eucalypts and 30–50 m³ ha⁻¹ in Acacia), as well as wood density (15–30 kg m⁻³ for eucalypts) following improvements in early nutrition. Improved nutrition was achieved through fertilization at planting or indirectly through residue management. The response mechanism is primarily due to early canopy development and associated increases in light capture, coupled with a more modest increase in canopy quantum efficiency and above-ground carbon allocation on a dry site. On sites with abundant water supply, increased quantum efficiency is likely to be the dominant response mechanism. (e) A series of operational gains trials tested the interactive effect of genetic tree improvement, site–genotype interaction, stand density and vegetation management + fertilization on eucalypt stand growth across five sites. There were no significant interactions between factors, but importantly, the results were additive, emphasizing the need to optimise each practice in the value chain to achieve maximum productivity.  相似文献