The biology, ecology and agroforestry potential of the raintree, Samanea saman (Jacq.) Merr.

Samanea saman (Jacq.) Merr. (syn. Albizia saman (Jacq.) F. v. Muell.) is a large tree, native to tropical America, which has now become widespread throughout the humid and subhumid tropics. Although noted as a promising agroforestry species, there is little specific research that substantiates this potential. On the basis of a review of its biology, ecology and recorded uses, it is concluded that the most appropriate use for S. saman would be in an extensive silvopastoral system for cattle production. The tree provides excellent protective shade, and produces highly palatable pods that are suitable as a dry season feed supplement. Additionally, there are reports of enhanced grass production beneath its canopy indicating a potential role in maintaining or improving the productivity of tropical grasslands. It is concluded that the tree should receive more research attention, focusing particularly on its interaction with the herbaceous understorey and the identification of provenances adapted to a variety of environmental conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Micronutrient, magnesium and phosphorus effects on biomass and leaf tissue nutrient concentrations of field grown Leucaena leucocephala

To optimize biomass and crude protein (CP) production for leucaena (Leucaena leucocephala) in southern Texas, field trials were conducted with treatment combinations of three levels of phosphorus (P) , two levels of Mg and two levels of soluble trace element mixture (STEM). The P was banded in the soil while the Mg and micronutrient blend were applied to the foliage. A combination of P (22 kg ha^-1), Mg and STEM fertilizers significantly increased biomass from 2555 kg ha^-1 to 3028 kg ha^-1. This treatment was associated with an increase in leaf CP from 27.9% to 31.0%. P fertilizer had no significant effect on leaf P, but significantly increased leaf nitrogen (N) and leaf copper (Cu). A foliar spray of Mg significantly increased leaf N, P, and Cu. A foliar spray of a complete micronutrient blend increased leaf Cu. Biomass production was correlated positively (decreasing order) with leaf Cu, N, and Mg and negatively with Zn. Leaf N was positively correlated with leaf P and calcium. The critical tissue concentrations (CTC) (where 90% of predicted maximum leaf protein was obtained) were 0.18% and 4.49 mg kg^-1 for leaf P and Cu, respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

Traditional agroforestry practices in Zimbabwe

Traditional agroforestry systems in the communal areas of Zimbabwe are described. There are systems centered on main fields, on home gardens, on homesites and on grazing areas. In the main fields, the major tree-related management practice is the conservation of preferred indigenous fruit trees. Fruit trees are also the focus of forestry activities around the gardens and the homesite; but here it is the planting of exotic species. In a localized area of Zimbabwe Acacia albida is important in fields. There is almost no use of tree fallows in Zimbabwe. Trees in grazing areas have numerous roles, but at present there is little knowledge about traditional management practices in these areas. In the development of agroforestry systems in Zimbabwe it is suggested that those systems designed to improve fodder production will make a significant contribution to farm productivity because of the importance of cattle in the farming system and the present fodder shortage. Interventions involving the planting of fruit trees are likely to be very successful, as there is much interest in such planting. Another area that needs to be developed is that of tree plantings to improve soil fertility.     

Variation in the chemical composition of green leaves and leaf litters from three deciduous tree species growing on different soil types

The chemical composition of green leaves and leaf litters of sweet chestnut (Castanea sativa), oak (Quercus robur) and beech (Fagus sylvatica) were determined for 26 sites grouped into high fertility (HF) and low fertility (LF) soils according to base saturation and N-mineralization potentials. Measurements were made of total carbon, acid detergent fibre (ADF), Klason lignin, holo-cellulose, sugar constituents of hemicellulose and phenylpropanoid derivatives of lignin, and nutrient concentrations (N, Ca, P, Mg, K and Mn). Leaf and litter constituents varied within and between species according to soil groups, but beech showed contrasting responses to oak and chestnut. Beech leaves had lower ADF, lignin and cellulose on HF soils than LF soils, whereas oak and chestnut leaves had higher ADF, lignin and cellulose on HF than the LF soils. Conversely, the same constituents in beech leaf litter were higher on HF soils than LF soils, but lower in oak and chestnut leaf litter on HF soils than LF soils. The phenylpropanoid derivatives of lignin and sugar constituents of hemicellulose also showed similar variations in relation to soil groups with contrasting patterns for in leaves and litters. Re-absorption of N from leaves before litter fall was negatively correlated with soil N mineralization potential for beech (highest on LF soils) but showed an unexpected, positive relationship for oak and chestnut (highest on HF soils). These intra-specific differences of leaf and litter chemistry in relation to soil fertility status are unprecedented and largely unexplained. The observed patterns reflect phenotypic responses to soil type that result in continuum of litter quality, within and between tree species, that have been shown in related studies to significantly influence litter decomposition rates.     

桑天牛羧酸酯酶和谷胱甘肽S—转移酶与杨树次生代谢物质相关性研究

对取食8种杨树的桑天牛幼虫羧酯酯酶和谷胱甘肽S－转移酶活力进行了测定，证实取食不同杨树的桑天牛幼虫羧酸酯酶和谷胱甘肽S－转移酶活力存在显著差异。采用高效液相色谱法对8种杨树的14种次生代谢物质含量进行了测定，经聚类分析将8种杨树分为2类：加拿大杨、I－214杨、北京杨、J－2杨、J－1杨、山海关杨为一类，毛白杨、新疆杨为另一类。对羧酸酯酶和谷胱甘肽S－转移酶活力与杨树次生代谢物质进行了逐步回归分析，逐步回归方程表明，杨树丁香酸、绿原酸含量高，苯酚、对羟基苯甲酸含量降低，则羧酸酯酶活力会较高；杨树苯酚含量增高，阿魏酸含量降低，则谷胱甘肽S－转移酶活力会较高。     

Effect of drought on diameter increment of Quercus ilex, Phillyrea latifolia, and Arbutus unedo in a holm oak forest of NE Spain

The present study was carried out to elucidate the drought growth responses of Quercus ilex L., Phillyrea latifolia L., Arbutus unedo L., and other accompanying woody species of the Mediterranean holm oak forest. We submitted holm oak forest stands in Prades mountains (NE Spain) to a 2-year experimental drought. We reduced soil water availability about 15% by plastic strips and funnels that partially excluded rain throughfall and by ditch interception of water runoff. Mean stem diameter increment showed a great variation depending on the species. A. unedo had larger growth rates than Q. ilex and P. latifolia, but it was also the species that experimented the highest growth reduction in the drought plots (77%), suggesting a higher drought sensitivity than Q. ilex (55%) and P. latifolia (no drought effect). The growth reduction was specially marked in the larger trees. Aboveground stand biomass increment, estimated from stem diameter by allometric relationships, was 1.9 Mg ha⁻¹ per year in the control plots. The 15% reduction in the upper soil moisture produced 42% reduction in this biomass increment. In the drier conditions predicted in this Mediterranean area in the frame of climate change, an important reduction of growth rates can be hence expected, accompanied by a gain of dominance of drought-tolerant species such as P. latifolia in detriment of more mesic species such as Q. ilex.     

泰山岱庙古树名木的现状与保护

为掌握泰山岱庙古村名木的生长状况，在进行调查的基础上分析了古树名木生长不利的因素，提出了泰山岱庙古树名木保护中存在的问题，并阐述了古树名木的保护措施。     

4种饲用树木在河北坝上地区的引种初报

报道了蒙古岩黄芪、细枝岩黄芪、紫穗槐和刺槐等４个优良饲用树种在河北坝上地区引种后的生长表现及物候特征。引种研究表明，蒙古岩黄芪和细枝岩黄芪均能顺利越冬并能完成整个生长发育过程，而刺槐和紫穗槐地上部分冬季遭冻害，且不能完成整个生长发育过程。除刺槐外，其他３个树种均可在坝上进行大规模育苗。     

湿地松纯林补植阔叶树实验初报

对泰和湿地松纯林补植阔叶树实验地进行调查，结果表明：山杜英、木荷为当地适合的补阔树种。补植阔叶树能减少林地水土流失，改善林分小气候，具有较好的生态效益。     

北美浆果树种在中国西部地区引种效果及应用前景

中国西部地区水资源贫乏，生态环境极其脆弱，适合生长的造林树种十分稀少，为此近10a来引进了许多北美生态经济型灌木类浆果树种，以满足生态环境恢复和建设的需要。引种试验结果表明，多数树种适合在中国西部地区栽培，发展前景十分广阔，应尽快大面积推广。同时也指出了易出现的问题、解决方法及发展建议。