Agroforestry in Mexico: Can the past be a guarantee for the future?

Some aspects of agroforestry systems in Mexico are reviewed, including the chinampas, a unique type of prehispanic home-garden, still in use today, mainly in the Mexico valley; the Huastec té'lom (in the north of Veracruz State) an agroforestry technique used by the farmers for sustainable exploitation of natural resources; and forest-farming among the Maya (Yucatan), a production strategy which has evolved over a long period. Some other, more recent agroforesting techniques are also reviewed. The discussion emphasizes the biological, ecological and social significance of agroforestry systems. Agroforestry, however, must be considered within its socio-economic context. Assessing the needs and potentialities of a region must be the first step towards integrating agroforestry systems into the socio-economic realities of today.     

The life cycle and natural history of the tropical aphid Cerataphis fransseni (Homoptera: Aphididae: Hormaphidinae), with reference to the evolution of host alternation in aphids

We describe the life cycle and general biology of the tropical cerataphidine aphid Cerataphis fransseni. We demonstrate that this aphid migrates between trees of Styrax benzoin and various species of palms; palm-feeding populations have previously been known as C. variabilis and C. palmae, which now become synonyms of C. fransseni. On S. benzoin the fundatrix induces a relatively simple gall which can contain >6000 aphids at maturity with a large number of reproductively sterile soldiers that protect the gall from predators. These galls are apparently produced throughout the year. Colonies on the secondary host plants, palms, are apparently obligately tended by ants whereas colonies within galls on Styrax are never tended by ants. We discuss the life cycle of this tropical aphid with respect to hypotheses for the evolution and maintenance of host alternation.     

低温处理对6种园林绿化树种幼苗生理生化特性的影响

为选择广东地区耐寒树种,对大花五桠果(Dillenia turbinata)、双翼豆(Peltophorum tonkinense)、海南山竹子(Garcinia oblongifolia)、盆架子(Alstonia scholaris)、非洲桃花心木(Khaya senegalensis)和海南红豆(Ormosia pinnata)6种幼苗进行10℃条件下0.5、3、5和8天的低温处理,研究其生理指标变化。结果显示：随着低温胁迫时间的延长,6树种幼苗叶片的相对电导率均表现出增加的趋势,脯氨酸含量大幅波动,叶绿素含量呈小幅波动,丙二醛含量为先上升后下降;除大花五桠果的SOD活性显著低于对照,其他树种的SOD活性波动后趋于对照水平。随着低温胁迫时间的延长,各树种幼苗叶片的可溶性蛋白质含量经过波动,最后大于或接近对照。经主成分分析得出6个树种的耐寒能力强弱顺序依次为海南红豆、非洲桃花心木、盆架子、海南山竹子、双翼豆、大花五桠果。     

神经细胞营养因子与运动神经元的存活和凋亡

文章就神经营养因子有选择性地保障神经元健康存活,防止凋亡和损伤所引起的神经元退变及促进再生等生物学效应,和神经营养因子效应及神经细胞,运动神经元存活,凋亡及其特征等方面研究进行综述,并对该领域中研究的新进展摘要说明.     

Altitudinal patterns of abundances and parasitism in frugivorous drosophilids in west Java,Indonesia

Abundances and parasitism rates of frugivorous drosophilid flies were studied in three localities at altitudes of 250–1350 m in and near Bogor, Indonesia. The drosophilid and parasitoid species were classified into four groups: low-altitude species, high-altitude species, species abundant at a mid-altitude location and species occurring rather evenly from low to high locations. The ananassae and immigrans species groups were major drosophilids collected. All species of the ananassae species group were more abundant at lower altitudes, and the parasitism rate in this species group decreased with increasing altitude. Thus, the host abundance seems to affect the parasitism rate. On the other hand, the rate of parasitism in the immigrans species group showed no apparent relation with altitude or density, possibly due to the fact that species of this species group varied in altitudinal distribution. It is also suggested that the diversity of drosophilid species affects the composition of parasitoid species.     

热带亚热带森林叶凋落物交互分解的研究

为了检验全球变暖对森林凋落物分解的影响,在跨气候带的大尺度下进行森林凋落物的交互分解实验,在热带的尖峰岭和亚热带的鼎湖山各选样地1个,它们有相似的海拔高度、土壤类型、年均降雨量及干湿季节律,气温为主要差异,年均气温相差3.7℃.各样地分别收集了10种当地的优势树种的凋落叶.其中2个样地各自的优势种青皮和锥栗,2个样地均有的共同种荷木作为单种样.10种凋落叶的等重量混合为混合样,共计6类凋落叶,分别交互置于2个样地分解.结果表明:6类凋落叶在尖峰岭的分解速率显著地大于在鼎湖山的分解速率;凋落叶分解的表观Q10在3.7～7.5范围内.证实在这个温差范围内,凋落物分解加快的程度可达1.36～3.06倍.