Uses of tropical deciduous forest species by the Yucatecan Maya

We present the uses that the Maya of Tixcacaltuyub and Tixpeual, Yucatán, México, have for the trees and shrubs of their surrounding tropical dry and deciduous forests; we add the uses for trees and shrubs in their homegardens, because they complement their basic needs. A total of 301 shrubs and tree species were present either in the forest or homegardens sampled; 222 species (73.7%) have at least one reported use. The species with more uses are: Bursera simaruba (10), Gliricidia sepium (10), Cordia dodecandra (9), Plumeria rubra (7), Caesalpinia gaumeri (7), Vitex gaumeri (7), Enterolobium cyclocarpum (7), and Piscidia piscipula (7). More species (152/69.7%) are classified for medical purposes, followed by apiculture (87/39.9%), food (66/30.3%), fuel (38/17.4%), building (41/18.8%) and timber (25/11.5%). Despite the lack of important commercial species (timber, fruit) in this type of tropical forest, we discuss the importance of the tropical dry forest of Yucatán as an area where management could lead to sustainable production of honey, deer and building material for houses.

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Resumen Presentamos los usos que los mayas de Tixcacaltuyub y Tixpeual, Yucatán, México, le dan a los árboles y arbustos presentes en los bosques tropicales deciduo y seco que les rodean. Asímismo, agregamos los usos para los árboles y arbustos del huerto familiar, ya que estos complementan sus necesidades básicas. Se encontraron un total de 301 especies de árboles y arbustos en el bosque y los huertos; 222 especies (73·7%) tienen al menos un uso reportado. Las especies con más usos son: Bursera simaruba (10), Gliricidia sepium (10), Cordia dodecandra (9), Plumeria rubra (7), Caesalpinia gaumeri (7), Vitex gaumeri (7), Enterolobium cyclocarpum (7) y Piscidia piscipula (7). Se clasificaron mas especies (152/69.7%) para uso medicinal que para cualquier otro uso, le siguieron en orden decreciente, apicolas (87/39.9%), alimenticias (66/30.3%), combustibles (38/17.4%), para construcción (41/18.8%) y maderables (25/11.5%). A pesar de la ausencia de especies importantes comercialmente (maderables, frutos) en este tipo de bosque, discutimos la importancia del bosque tropical seco de Yucatán como un área en la cual el manejo puede conducir a un aprovechamiento sostenido para apicultura, alimento para venado y material para construir habitaciones.

     

Establishment of two indigenous timber species in dairy pastures in Costa Rica

A silvopastoral model that combines the production of pasture herbage with valuable native timber species has potential to simultaneously address the multiple goals of reforestation, conservation of native species and enterprise intensification. The objective of this study was to design, establish and monitor early growth of a silvopastoral experiment on a dairy farm in the north Atlantic zone of Costa Rica. Two indigenous timber species, Vochysia guatemalensis and Hyeronima alchorneoides were planted with and without the tropical pasture legume, Arachis pintoi in a split plot design, (2 × 2) factorial arrangement of treatments with four replications. After the first two years, V. guatemalensis was significantly taller (3.1 m) than H. alchorneoides (2.5 m). The mean root collar diameter for V. guatemalensis was significantly larger (6.5 cm) than H. alchorneoides (4.5 cm). Two-year establishment was acceptable for the tree component (83 to 85% survival) but poor for A. pintoi (2 to 8% of the sward). The most important pest affecting the establishment of the timber species was the leaf cutter ant, Atta cephalotes. An insect larvae, Cosmopterix sp., severely damaged 39% of the V. guatemalensis trees by repeatedly attacking their apical meristems. The two-year establishment data was insufficient to accurately predict future wood volume. A hypothetical economic analysis concluded that the silvopastoral system must average at least 1.2 m³ wood volume/paddock/year (20 m³/ha/year) throughout the first ten years of growth to assure a positive economic return from timber. The experiment is planned for a ten year period, which corresponds to the estimated rotation length for harvesting the timber species. This revised version was published online in June 2006 with corrections to the Cover Date.     

滇南热区铁刀木生物量的研究

据对滇南热区铁刀木地上部分生物量的调查分析，单株主干及侧枝材约占８３％，干皮及叶约占１７％。不同经级的单株立木，８０％的带皮干材分配于树干中部以下。８６％～９５％的枝、叶集中于树干中部以上。２～３年生实生或萌生林年均每公顷产气干柴１５～６０Ｔ，单位面积产柴量超过其它速生薪材树种。     

Successional patterns and gap phase dynamics of a humid tropical forest of the Western Ghats of Kerala, India: ground vegetation, biomass, productivity and nutrient cycling

The population dynamics of the ground vegetation and its energetics such as biomass accumulation and net primary productivity, and the nutrient cycling patterns in the humid tropical forest of the Western Ghats in India are largely determined by gap age and by whether gaps are formed naturally or through selection felling. Responses of plant categories such as herbs, shrubs, tree seedlings and saplings also vary depending upon gap type and age. An exotic species such as Chromolaena odorata occurred only in selection-felled gaps ((9 ± 3)−(49 ± 4) individuals (100 m)⁻²). Nilgirianthus ciliatus, a dominant shrub, plays a key role in the gaps in determining population dynamics of others. The net primary productivity of the ground vegetation, which is about 31.17 ± 4.26 kg (100 m)⁻² year⁻¹ in an undisturbed site, increased a year after gap formation to 102.82 ± 6.46 kg (100 m)⁻² year⁻¹ in natural gaps and to 71.82 ± 2.36 kg (100 m)⁻² year⁻¹ in selection-felled gaps. Five years after gap formation, net primary productivity of the ground vegetation declined considerably, this being related to decline in fast-growing shrub and secondary tree species in the vegetation and gap closure. A similar trend was also recorded for the rates of nutrient uptake and nutrient accumulation in the vegetation.

In natural gaps the soil nutrient level increased gradually with gap age. This could be attributed to slow release of nutrients from the fallen trunks and nutrient storage in the rapidly recovering vegetation. In contrast, in selection-felled gaps, the quantities of soil nutrients such as nitrogen, phosphorus and magnesium were higher in 1-year-old gaps than in undisturbed sites, owing to the release of these nutrients from leaf litter and wood debris which were deposited in larger quantities within the gap itself, and owing to sparse ground vegetation resulting from the greater disturbance of the soil, in the first 1 or 2 years. The fractional annual turnover rates of elements of the ground vegetation and the soil were higher in 1-year-old gaps and declined with gap age. The significance of these results for forest management is discussed.     

Phosphate sorption curves as a soil testing technique: A simplified approach

Abstract

Single point phosphate sorption curves effectively estimated phosphate fertilizer requirements while requiring less work than multiple point curves. Correlation coefficients of 0.961 and 0.981 were obtained when phosphate rates, estimated using single point curves, were compared with those from multiple point curves. Reducing the ionic strength of the supporting electrolyte solution by using 0.001 M CaCl₂ or water rather than 0.01 M CaCl₂ during equilibration increased dissolved inorganic phosphate 73% and 141% on the average thus improving analytical precision. The relative effects of salt concentration were sufficiently independent of pH and phosphorus concentration to suggest that a simple conversion factor can be used to convert external P requirements from one set of equilibrium conditions (salt concentration) to another.     

热带南亚热带地区优良珍贵阔叶树种选择与发展

分析了优良珍贵阔叶树的用途、适应性、经济效益、生态效益和社会效益等因素，探讨热带、南亚热带地区优良珍贵阔叶树种的选择，并提出发展优良珍贵阔叶树种时存在的问题和应对措施。     

在建设国际旅游岛背景下加快发展海南热带休闲农业的思路与对策

休闲农业是农业和服务业相结合的一种新兴休闲服务产业。海南建设国际旅游岛，加快海南农业现代化步伐，需要加快发展热带休闲农业。本文从海南发展热带休闲农业的必要性与可行性入手，分析制约其发展的诸多因素，提出加快发展海南热带休闲农业的思路与对策。