Improvement of direct tree seeding with cover crops in afforestation: Microclimate and resource availability induced by vegetation composition

The low cost of direct tree seeding makes it increasingly useful for afforestation. However, the success of the technique is often unpredictable due to a series of different adverse biotic and abiotic factors. A plant cover with low competitive ability towards resources could offer a natural alternative to the herbicides currently used to control weeds. The effects of cover plants on availability of resources and microclimate were studied in a field experiment in the central France during three years. An experiment design crossing three mixtures of tree seeds with four vegetation compositions (a bare soil, flora of the meadow, and two mixtures of cover plants) was established and repeated randomly in three blocks in a meadow. Vegetation composition, tree seedling emergence, light availability, soil water content, and temperatures under each treatment were measured. The vegetation composition of the meadow stayed stable, with grass species dominating. The cover plants sown disappeared rapidly after one or two years. Outcome of direct seeding of trees depended on the vegetation treatment. Bare soil gave the highest emergence rate while meadow vegetation gave the lowest, with the mixture of cover plants being intermediate. Light availability and soil water content were very low under the meadow vegetation but were very high on the bare soil, again with cover plant mixtures being intermediate. This study confirms that a bare soil obtained by herbicide is a secure way to ensure tree seedling establishment in afforestation by direct seeding. However, with the onus currently on reducing herbicide use, the results suggest that sowing a mixture of cover plants could be an acceptable alternative to herbicides. The cover plants could offer protection against frost, scorching temperatures, or the water run-off encountered on bare soil. However, there are also a number of unresolved issues that need be addressed before the cover plants technique can be recommended.     

Modelling the influence of site and weed competition on juvenile modulus of elasticity in Pinus radiata across broad environmental gradients

Data from a nationwide set of Pinus radiata D. Don plots established at a range of conventional stand densities were analysed at age 6 to (i) determine how environment and competition from weeds influence dynamic modulus of elasticity (E) of the lower stem base, (ii) develop a predictive multiple regression model of E for basal stemwood and (iii) identify significant direct and indirect environmental influences (through stem slenderness) on E using path analysis.Site had a highly significant (P < 0.001) influence on E, which exhibited a 3-fold range from 1.6 to 5.3 GPa, across 30 sites. When compared to the weed-free controls, weed competition had a significant (P < 0.0001) and substantial effect on E, increasing values by on average 16% (2.76 GPa vs. 2.38 GPa).The positive linear relationship between stem slenderness (determined as tree height/ground-line tree diameter) and E was by far the strongest relationship (R² = 0.71; P < 0.001) among the 20 variables that were significantly related to E. A multiple regression model that included stem slenderness, mean minimum air temperature in mid-autumn, T_min, as positive linear relationships and net nitrogen (N) mineralisation in a negative linear form accounted for 86% of the variance in E. A cross-validation indicated that this model was stable and unbiased, with the validation accounting for 82% of the variance in E. The final path analysis model included T_min, net N mineralisation, below canopy solar radiation and stem slenderness as significant (P < 0.05) direct influences on E. Below canopy radiation, maximum air temperature during mid-summer, soil total phosphorus and carbon:nitrogen ratio were indirectly associated with E through their significant (P < 0.05) direct relationship with stem slenderness.These results provide considerable insight into how environment regulates E of juvenile P. radiata. Low fertility sites that have warm air temperatures and either a high canopy leaf area index, or high levels of woody weed competition, are most likely to produce trees with high stem slenderness and high E. Conversely, sites that are cool over summer and autumn and high in fertility, with low levels of intra- or inter-specific competition for light are likely to produce trees with low stem slenderness and low E.     

芍药资源在园林中的应用

芍药作为一种重要的花卉资源,在园林应用中有着非常广阔的前景。本文在讨论了芍药文化、生态习性及种质资源的基础上,提出了芍药专类园、芍药花台、芍药花带、芍药花境和庭院栽植五种园林造景应用形式,并进一步分析了芍药生态性景观、文化艺术性景观、多样性景观和季相景观的4种营建手法。     

福建省林业与社会经济发展关系分析

在对福建省林业和社会经济情况进行分析的基础上,利用Matlab统计工具,根据林业和社会经济指标,将福建省9个地级市分别进行聚类,探讨了林业与社会经济之间的相关性,并提出了各地区根据自身特点发展林业的建议。     

城市居住区铺装艺术调查与研究

居住区铺装除了要满足基本的使用功能外,还应重视其文化和艺术性。作者通过对昆明市不同年代不同层次居住区的抽样调查,从文化艺术的角度,结合有关铺装的设计理论,系统总结了居住区地面铺装之美。     

Spatio-temporal variation of environmental signals inducing seed germination in temperate conifer plantations and natural hardwood forests in northern Japan

To document the spatial and temporal variation of environmental signals inducing seed germination in temperate forests, we measured temporal patterns of environmental signals and seed germination of six pioneer tree species in unthinned and thinned stands of conifer forests (Cryptomeria japonica plantations) and in the understory and gaps of hardwood forests in Japan. We also conducted germination experiment in laboratory for the six pioneer species to test the effects of red:far-red (R:FR) light ratio and temperature fluctuations on the seed germination. In conifer forests, the photosynthetic photon flux density (PPFD), the R:FR ratio, and the amplitude of temperature fluctuations in thinned stands were 2, 1.5, and 3 times higher, respectively, than those of unthinned stands. The PPFD and R:FR ratios just above forest floor also increased after the removal of thick litter accumulation. As a result, higher seed germination was observed in thinned compared to unthinned stands for three photoblastic species, whereas little differences were observed for three non-photoblastic species. These findings suggest that thinning, which frequently reduces litter accumulation, can substantially affect the regeneration of pioneer species and the resultant species diversity in conifer plantations. None of the measured environmental signals changed seasonally in unthinned stands of conifer forests, but they all changed remarkably in the understory of the hardwood forests. In this system, all signals were high and nearly identical to those in the gaps in early spring prior to canopy closure. Thus, the percent germination of the three photoblastic species was enhanced by high R:FR ratios and/or large temperature fluctuations even beneath the canopy and was nearly equal to that in the thinned conifer stands where the environmental conditions were nearly identical to those in the gaps. However, all of the environmental signals decreased with the expansion of canopy leaves and reached minimums at canopy closure. Even in the thinned stands and the gaps, the PPFD and magnitude of temperature fluctuations decreased over time due to shading by growing herbs and/or emerging canopy leaves. In these temporally changing environments, the germination of all photoblastic species ceased simultaneously. This study clearly demonstrated that the environmental signals inducing seed germination of photoblastic pioneer species spatially and temporally change in temperate forests, particularly in deciduous hardwood forests. Furthermore, these signals, PPFD, R:FR ratio, and the amplitude of temperature fluctuations, appear to play a very important role in tree regeneration and subsequent species diversity.     

关于农业循环经济若干理念与模式的探讨

针对人们对农业循环经济的认识误区,阐述了农业循环经济与循环型农业、生态农业、持续农业等现代农业理念的异同,认为在农业领域发展循环经济应称为农业循环经济,相应的农业形态则称为循环型农业,其与生态农业、持续农业有着显著的差别.同时,根据循环经济的理论内涵,分析了区域农业、高优农业、生物质能源开发等与农业循环经济的关系,提出除了节约型农业、废弃物综合利用、生态农业外,区域农业、高优农业、生物质能源开发是农业循环经济发展的重要模式与内容,并分析了其对农业循环经济的重要作用.     

我国能源作物研究与应用进展

通过回顾我国生物能源与能源作物的研究与应用进展,表明我国生物能源以及能源作物方面与发达国家相比较,在技术储备、产业规模和应用等方面还存在一定差距。我国发展能源作物应充分考虑能源作物的经济效益问题、环境安全问题和社会问题等,以促进能源作物产业的健康有序发展。     

温度和盐浓度对棉籽发芽的影响

以新棉33B为试验材料,研究了不同温度和盐浓度条件对棉籽发芽势及发芽率的影响。结果表明：棉籽发芽受温度和盐度共同影响。温度和盐度对棉籽发芽率存在互作关系。在重度盐碱地种植棉花,采取推迟播期和覆膜等提高地温的办法,可以解决棉田出苗敏感问题,     

鸡IL-2全基因和去信号肽基因的酵母表达研究

根据已发表的鸡白介素-2（ChIL-2）cDNA编码基因序列设计三条引物,利用RT-PCR技术从经诱导的卢氏鸡胚脾淋巴细胞中扩增出429bp的ChIL-2全长基因cDNA和363bp去除信号肽的ChIL-2基因cDNA。分别克隆到酵母表达载体pPICZαA中,并分别转化巴斯德毕赤酵母X-33中,经甲醇诱导,SDS-PAGE检测,在28kD和24kD处有两条清晰的蛋白带,相同条件下pPICZαA-△SIL-2表达量较高。RNAstructure软件分析表明,pPICZαA-IL-2的序列形成了较为稳定的二级结构,不利于翻译,证明信号肽序列的存在对ChIL-2基因在酵母细胞中的表达有一定的影响。