林下经济的主要模式及优劣分析

从生态结构、资源利用特点、操作便利性、副效应等方面分析了近年国内几种主要林下经济模式的优劣。林药模式基本上没有种间矛盾,但不适合大规模经营;林菌模式适应种类多且地域广,但对栽培区水源条件、交通条件要求较高;林禽模式宜根据不同禽种生态习性择地饲养和轮养,应特别注意解决污染和疫病问题;林草、畜模式宜将林下种草和动物圈养结合起来,防患面源污染和疫病,防止对林地土壤扰动太大;林虫（蜂）模式中适合发展的经济昆虫较多,应根据各地传统习惯和加工能力,分项发展;林花模式中,适合林下种植的花卉和荫生植物较多,这一模式相对而言,对林地的干扰较少,是自然界中自然存在的一类群落结构,合理性较好。以上各种经济模式各有特点,各见其长,均可供林权主发展林下经济时甄别选择。林下经济发展应遵循生态优先原则,注意群落种问关系的协调。林下经济物种不可生硬拼凑,本木倒置。各模式的推广应充分考虑气候、市场等地域特点。文章还介绍了一种菌根性食用菌模式。菌根性食用菌与多种树木有天然的共生关系,且多是市场俏销的种类。利用已经发展成熟的栽培技术提高林下菌根性食用菌栽培集约化程度,可实现多年持续高产、高效益,且对林地的人为干预最少,能很好地保护林地生物多样性。这是其它模式所不具备的优势。因此,认为菌根性食用菌模式是目前最能兼顾生态与经济效益,前景良好的林下经济模式。     

Effects of trees on the yield of irrigated wheat crop in semi-arid regions

A study was conducted in the semi-arid regions of Haryana, in Northern India, to see the effect of Azadirachta indica, Prosopis cineraria, Dalbergia sissoo and Acacia nilotica on the yield of irrigated wheat crop. Data on crop yield for each tree species at different distances (1, 3, 5 and 7 m) and four directions (east, west, north and south) from the tree bases and control (no trees) were collected. Results indicate that A. indica and P. cineraria did not show any significant difference in the wheat yield while the other two species (D. sissoo and A. nilotica) showed a reduction in wheat yield. A. nilotica had the most significant and prominent effect, and a reduction of nearly 40 to 60% wheat yield was observed. The effect of this tree species was observed even beyond the spread of the crown. D. sissoo reduced yield by 4 to 30% but the reduction was only up to a distance of 3 m. In general, the impact of trees on wheat yield was observed up to 3 m distance and there is little, if any, impact up to 5 m distance and almost no impact at 7 m distance. In all the tree species, the wheat yield was reduced to a maximum on the north side of the trees and had almost no effect in the southern direction. Crop maturity was observed to be delayed by three weeks under A. nilotica, by 9–10 days under D. sissoo, and only by 6–7 days under P. cineraria and A. indica.     

Traditional agroforestry,parcel management,and social forestry development in a pioneer agricultural community: the case of Jala-jala,Rizal, Philippines

This paper overviews a variety of traditional agroforestry systems found in a small community of Filipino migrant farmers. Background information provides context, and then case studies of seven farmers are offered to illustrate the functions which their agroforestries fulfill in a situation of parcellization of farm-holdings into both level and sloping fields. The implications of the brief portraits presented for further research and development and for the acceptability of a social forestry program now going on in the community are suggested.     

Revival of an ancient starch crop: a review of the agronomy of the sago palm

Since 1971 there has been a revival of interest in the possibilities for cultivation of the true sago palm, Metroxylon spp. Agronomic and economic research shows that the palm can become an important starch producing crop. Many queries concerning the agronomy of the crop have been solved. The palm is especially suited to humid tropical lowlands. It is fairly salinity tolerant, but less tolerant to swampy conditions than generally thought. Research programmes to solve the remaining problems have been started in Sarawak on peat soils and will be started in Indonesia on mineral soils, both regarding the cultivated crop and exploitation of natural stands. Yields of 5 tons of dry starch per ha and year in the first year, increasing to 15 tons in the tenth, are to be expected in good quality natural stands under cultivation and on mineral soils. In new plantings there will be no yield in the first eight years; after that yields will increase rapidly to 25 tons per ha and year, tapering off slowly to 15 tons. Yields on peat soils under cultivation are expected to remain 25% lower. In both natural stands and plantings an extensive drainage system is to be provided, which also allows the trunks, the raw material, to be floated out to the factory. Both systems of cultivation are expected to be economically viable with an internal rate of return estimated at 10%.     

Benefit-cost analysis of raising Pinus wallichiana seedlings in different capacities/sizes of root trainers in the nursery

Modern nursery methods of seedling production in different sized root trainers,were compared by raising seedlings of Pinus wallichiana involving costs incurred and benefits received. In order to provide a common basis for the comparisons,the study involved the raising of 1000 seedlings annually on a continuous basis for seven years. A relative economic analysis of raising P. wallichiana seedlings in 300,150 and 100 cm3 root trainers was carried out and we estimated that the root trainers of 300 cm3 capacity...     

Benefit-cost analysis of raising Pinus wallichiana seedlings in different capacities/sizes of root trainers in the nursery

Modern nursery methods of seedling production in different sized root trainers, were compared by raising seedlings of Pinus wallichiana involving costs incurred and benefits received. In order to provide a common basis for the comparisons, the study involved the raising of 1000 seedlings annually on a continuous basis for seven years. A relative economic analysis of raising P. wallichiana seedlings in 300, 150 and 100 cm³ root trainers was carried out and we estimated that the root trainers of 300 cm³ capacity recorded the highest total input cost of Rs. 35571 and Rs. 40018 for 1000 seedlings produced annually at discount rates of 12% and 6%. Seedlings raised in 100 cm³ root trainers recorded the lowest total input cost of Rs. 23390 and Rs. 27737 per 1000 seedlings annually at discount rates of 12% and 6%. Hence, returns per rupee invested in raising seedlings in the 100 cm³ root trainers accounted for the maximum benefit-cost ratio (i.e., 1.56 and 1.61) at discount rates of 12% and 6%. Thus seedlings raised in 100 cm³ and 150 cm³ root trainers were found to be most cost effective when compared with seedlings grown in 300 cm³ root trainers. The results can be attributed to the larger number of cells per tray (higher growth density) in the 100 and 150 cm³ root trainers, compared to the number of seedlings in the 300 cm³ root trainers.     

Application of the stock change and the production approach to Harvested Wood Products in the EU-15 countries: a comparative analysis

With the analytical tool: Frankfurt Harvested Wood Products (HWP) Model, carbon stocks and carbon stock changes of HWP, either in USE or in LANDFILLS, have been evaluated from the readily available statistical data base of the FAO, FAOSTAT, on the wood commodities: “Sawnwood and Wood-based Panels” and the paper commodities: “Paper and Paperboard”. Essential differences have been found between the individual 15 EU countries in the comparison of the Stock Change Approach and the Production Approach, as well as in the comparison of the stock changes of HWP with the National Greenhouse Gas (GHG) budgets. The stock changes for the HWP in USE within the EU-15 Community have been calculated to be 10.83 Mt C/a (39.71 Mt CO₂/a) based on the Stock Change Approach and 9.81 Mt C/a (35.97 Mt CO₂/a) for the Production Approach, respectively. These numbers can be compared to the total GHG Inventory of the EU-15 of 4,095 Mt CO₂ equivalents, including all six Kyoto gases, which shows that the carbon sequestration of HWP in USE is of the order of 1% relative to GHG Inventory. The GHG balance for the carbon stock changes of HWP in LANDFILLS is of similar magnitude as for the HWP in USE, and therefore a sink when methane outgasing is disregarded. However, when methane outgasing is considered, which is formed as a 1:1 mixture with CO₂ under the prevailing anaerobic conditions the GHG balance results in minus 10.0 Mt C equivalent/a and minus 10.6 Mt C equivalent/a for the Stock Change Approach and the Production Approach under the parameters chosen in this study. Presented in Dublin, October 6–9, 2004, COST-21 Plenary Session.     

Mapping the effect of spatial and temporal variation in climate and soils on Eucalyptus plantation production with 3-PG,a process-based growth model

In the wet tropics, near the Atlantic Coast of Brazil, drought may reduce plantation yields by as much one-third over a six-to-seven-year rotation. For land owners, annual variation in production cannot be estimated with empirical models. In this paper, we examine whether the process-based growth model, 3-PG is sufficiently sensitive to climatic variation to provide a virtual record of changes in growing stock across 180,000 ha eucalypt plantation estate. We first mapped variation in climate and soil properties, and then ran simulations for the current planted forest with ages varying from one to seven years. Model predictions of stand volume and mean tree diameter agreed closely with measurements acquired on 60 reference plots monitored over the test period; the prediction of mean annual increment (MAI) was less reliable. Available soil water (ASW) and leaf area index (LAI) were also measured and compared with the model estimations. Vapour pressure deficit (VPD) and ASW accounted for most of the variation in yields. We conclude that this spatial modelling approach offers a reasonable alternative to extensive ground surveys, particularly when climatic variation extends beyond the historical average for a region.     

High levels of pollen dispersal detected through paternity analysis from a continuous Symphonia globulifera population in the Brazilian Amazon

In this study, six highly polymorphic microsatellite loci and a categorical paternity analysis approach were used to investigate the contemporary pollen gene flow in the neotropical tree species Symphonia globulifera. Data for this study were taken from a 500 ha experimental plot in a dense terra firme forest in the Eastern Brazilian Amazon and included the mapping and genotyping of 161 reproductive trees, representing more than 90% of all adult trees, and the collection of 748 open-pollinated seeds from 56 seed-trees over two field seasons (2002 and 2003). High levels of pollen immigration from outside of the study plot were detected in both sampled seed-years (≥49%) suggesting long distance pollen gene flow. Low levels of self-fertilization were also detected (≤2%). The analysis showed long distance pollen dispersal occurred within the study area in both 2002 (δ = 907 ± 652 m SD) and 2003 (δ = 963 ± 542 m SD). Patterns of pollen dispersal distance within the plot were also found to be shorter than the distances between potential male parents and seed-trees. This result indicates that the distance between trees does not explain the identified pollen dispersal pattern. Our results support the hypothesis that animal pollinated species occurring in low-density populations can disperse pollen in long distances, despite the very dense nature of the forest.