热带水果在观光果园的应用

观光果园的发展较快,但是观光果园的果树种类较为单一。通过引种和调查,笔者基于用途和果肉性状,将热带水果划分为八大类,这有助于热带水果在观光果园的应用。研究强调热带水果在观光果园的应用应遵循一定的原则并采用相应的方式。     

海口琼山府城公共园林发展演变初探

在景观全球化的背景之下,城市个性和地域历史越来越受到重视,公共园林发展建设也成为了核心竞争力之一。在结合历史文献和前人研究成果的基础上,通过走访调研、拍照实测和绘图分析等方法,系统梳理出海口琼山府城的公共园林在不同时期的发展情况,从"城市发展——公共园林""公共园林——民众生活"的关系探索其生成原因、公共性质和时代特征,对今后公共空间的整合、地域文化的传承及社会生活质量的提升都有着非凡的价值。     

竹子在中国古典园林中的应用

竹子以其独有的材质魅力和高贵品格吸引着历代帝王和文人墨客的喜爱,成为中国古典园林造景中的重要组成。我国西周时期就有记载竹子在园林中的应用,到了元明清时期已经发展成熟并且取得了较高的世界地位。梳理、学习中国古代造园中竹景观的应用对于打造现代竹景观尤为重要。     

Predator-prey relationships and responses of ungulates and their predators to the establishment of protected areas: A case study of tigers, leopards and their prey in Bardia National Park, Nepal

Interactions among sympatric large predators and their prey and how they respond to conservation measures are poorly known. This study examines predictions concerning the effects of establishing a protected area in Nepal on tigers (Panthera tigris), leopards (Panthera pardus), and their ungulate prey. Within a part of the park, after 22 years the total density of wild ungulates had increased fourfold, to ca. 200 animals/km², almost exclusively due to a remarkable increase in chital deer (Axis axis). Tiger density also increased markedly to nearly 20 animals/100 km², whereas leopard density did not and was ca. 5 animals/100 km². The prediction that grazers should increase more than browsers was only partially supported. The prediction of positive density dependence in prey selection was not supported. Instead, the most abundant species (chital and hog deer, Axis porcinus) were killed less frequently than expected, whereas the lower-density wild boar (Sus scrofa) was preferred. Predictions that (i) initially rare species suffer highest predation was partially supported, that (ii) predation is highest among the most abundant prey was not supported, and that (iii) predation is highest among the most preferred prey independently of their densities was supported. Clearly, the conservation efforts adopted in Bardia were successful, as both tigers and their natural prey base increased. However, the positive numerical response of tigers limited and depressed the abundance of some prey species. Thus, conservation activities aimed at restoring large predators are likely to change in the composition of the overall mammal community, potentially eliminating rare but preferred prey species.     

A variable edge effect on trees of Bwindi Impenetrable National Park, Uganda, and its bearing on measurement parameters

With tropical forests under increased pressure from fragmentation and nascent effects of climate change, it is imperative to reliably predict change for timely reduction of impacts. This depends on measuring the right variables and analyzing them in ways that best detect change. I compared the usefulness of density, species richness, species diversity, and size in detecting edge penetration; and other parameters in revealing edge effect on tree species in Bwindi Impenetrable National Park, Uganda. Trees were sampled in 104 1 km edge-interior transects set around the entire park. Density and species richness were better indicators of edge-width than girth size and diversity measurements, both showing edge penetration as most intense within 300 m, although effect was detectable up to 900-1000 m. This estimate compared closely with an earlier estimate of 300-350 m obtained using incidences of resource harvest. Among other measures, measures of tree species abundance and frequency showed significant response to the edge by both early succession and primary forest species; while analyses of density showed edge response primarily by forest interior species. Parameters of tree size and their derivatives showed edge response by the lowest number of species. These results suggest that to measure edge effects reliably, it is important to select the right parameters.     

Genetic trends in a Holstein × other breeds multibreed dairy population in Central Thailand

Genetic variability and genetic trends for 305-day milk yield (MY), 305-day fat yield (FY), and average 305-day fat percent (FP) were evaluated using monthly test-day records from first-lactation cows collected from 1991 to 2005 in 92 farms located in Central Thailand. Estimates of variance and covariance components and breeding values (EBV) were obtained using a multiple-trait animal model. Fixed effects were contemporary group (herd–year–season), calving age, additive genetic group as a function of Holstein fraction, and non-additive genetic group as function of heterosis effect. Random effects were animal and residual. Program ASREML was used to perform computations. Estimates of heritabilities were 0.38 ± 0.10 for MY, 0.25 ± 0.11 for FY, and 0.22 ± 0.11 for FP. Although the difference between the mean MY for cows in 1991 and 2005 was 324.1 kg, the regression of mean cow EBV for MY on year was 6.5 kg/year. Differences between mean cow EBV for FY and FP in 1991 and 2005 and their corresponding regressions of mean FY and FP on year were all near zero. Similarly, mean EBV for sires and dams of cows also showed near zero trends during these years. A factor contributing to the near complete absence of genetic trends was likely the variety of criteria used by producers to choose sires and to keep dams in addition to EBV (e.g., availability of semen, reproductive ability, adaptation to hot and humid conditions). It also appears that high percent Holstein cows failed to reach their production potential under the management, nutrition, and hot and humid climatic conditions in this tropical region. Changes in nutrition and management would be needed for high percent Holstein cows to show an upward trend in Central Thailand.     

The horizontal barrier effect of stems on the foraging behaviour of cattle grazing five tropical grasses

The rate of nutrient intake (RNI) is a primary determinant of animal performance in grazing cattle and depends on both diet quality and instantaneous intake rate (IIR). In turn, diet quality and IIR are a function of the foraging behaviour of the animal (selectivity, bite mass and bite rate) and the characteristics of the sward. In this study we evaluated the effect of the stem density and the tensile resistance of stems on the foraging behaviour of cattle grazing tropical pasture species. The methodology involved the use of small sown microswards offered to tethered cattle. The experiment consisted of a factorial combination of five tropical grasses [Bothriochloa pertusa (Bp), Chloris barbata (Cb), Chloris gayana (Cg), Cynodon dactylon (Cd) and Heteropogon contortus (Hc)] and three stem densities (0, 400 and 800 stems m^− 2). Bp and Cd had stems of significantly lower tensile resistance (19 and 15 N respectively) (Group 1) than those of Cb, Cg and Hc (110, 211 and 167 N respectively) (Group 2). The steers avoided stems of Group 2 and thus, reduced bite area, bite mass, IIR and RNI as stem density increased. However, the animals did not avoid stems of Group 1 and there was no effect of stem density on any of the foraging behaviour variables when cattle grazed species in Group 1. These results confirm that RNI and plant part selection is closely associated with the tensile resistance of the stem.     

Silvicultural treatments enhance growth rates of future crop trees in a tropical dry forest

Silvicultural treatments are often needed in selectively logged tropical forest to enhance the growth rates of many commercial tree species and, consequently, for recovering a larger proportion of the initial volume harvested over the next cutting cycle. The available data in the literature suggest, however, that the effect of silvicultural treatments on tree growth is smaller in dry forests than in humid forest tree species. In this study, we analyze the effect of logging and application of additional silvicultural treatments (liana cutting and girdling of competing trees) on the growth rates of future crop trees (FCTs; i.e., trees of current and potentially commercial timber species with adequate form and apparent growth potential). The study was carried out in a tropical dry forest in Bolivia where a set of 21.25-ha plots were monitored for 4 years post-logging. Plots received one of four treatments that varied in intensity of both logging and silvicultural treatments as follows: normal (reduced-impact) logging; normal logging and low-intensity silviculture; increased logging intensity and high-intensity silviculture; and, unlogged controls. The silvicultural treatments applied to FCTs involved liberation from lianas and overtopping trees. Results showed that rates of FCT stem diameter growth increased with light availability, logging intensity, and intensity of silvicultural treatments, and decrease with liana infestation degree. Growth rate increment was larger in the light and intensive silvicultural treatment (22–27%). Long-lived pioneer species showed the strongest response to intensive silviculture (50% increase) followed by total shade-tolerant species (24%) and partial shade-tolerant species (10%). While reduced-impact logging is often not sufficient to guarantee the sustainability of timber yields, application of silvicultural treatments that substantially enhanced the growth rates of FCTs will help move the management of these forests closer to the goal of sustained yield.     

Detecting changes in habitat-scale bee foraging in a tropical fragmented landscape using stable isotopes

As the body of research on the ecosystem service of pollination grows, our ability to tackle a range of agricultural, conservation, and land management issues is limited by our understanding of pollinator foraging patterns and requirements. In particular, better knowledge of which habitats bees utilize for foraging over their lifetime would inform a range of applied and theoretical questions. Traditional methods of studying foraging are either impractical for insects (e.g. radio tracking) or else are limited spatially or temporally (e.g. observations by researchers). Here we describe a method for using stable isotopes of carbon and nitrogen from bee tissues to gain an integrated signal of which habitats a bee has foraged in over its lifetime, using three species of social stingless bee (Apidae: Meliponini) in a fragmented tropical forest landscape in southern Costa Rica as a test case.     

Ecology and regeneration of tropical dry forests in the Americas: Implications for management

Dry forests represent the most endangered ecosystem in tropical regions and continue to be one of the most sought after environments for human colonization, development and production. In spite of this, dry forests are one of the least well studied tropical habitats. This special issue is dedicated to reviewing much of the information that exists about tropical dry forest in the Americas. The introduction summarizes the articles presented herein, highlighting management strategies that are suggested throughout the special issue that may be useful for conserving tropical dry forest environments.