林农复合生态系统评价指标体系探讨

本文以生态经济学理论和系统工程学原理为基础，建立了林农复合生态系统的结构评价，功能评价，效益评价的评价指标体系，并探讨了林农复合生态系统评价指标体系设置的原则和评价方法。     

Comparative growth performance of some multipurpose trees and shrubs grown at Machakos,Kenya

Growth rates of 29 multipurpose trees grown in an agroforestry arboretum for six years at a sub-humid to semi-arid climatic zone are presented. Exotic species such as Grevillea robusta, Sesbania grandiflora, Leucaena leucocephala, Cassia siamea and Sesbania sesban, some of which were outside their traditional climatic zones, had higher diameters, heights and bole volumes/tree (upto 130% more in certain cases) than of the indigenous species. However, poor performance of several species (both exotic and indigenous) would limit their agroforestry potentials at the evaluation site or other similar areas.     

Plant species in the Kilimanjaro agroforestry system

An inventory of plant species was conducted on farms, farm boundaries and homesteads in the Kilimanjaro agroforestry system. The survey covered 30 farms in 6 villages in Hai District on the slopes of Mount Kilimanjaro, Tanzania. Over 100 plant species spread over 40 families were identified and their uses obtained through interviews with farmers. The species identified include 53 tree species, 29 food crop species, 21 non-woody plants of economic value and 8 weed species. The food crops, trees and other economically useful plants are carefully chosen by the local farmers and intimately intercropped on the same unit of land. In most cases, the plants had two or more uses of which food, fuelwood, medicine, poles, timber and fodder were the most important.     

Iterative increase of economic tree species in managed swidden-fallows of the Amazon

Fallow utilization schemes are becoming increasingly popular in agroforestry designs. However little attention has been given to the fate of valuable fallow plants after the end of the initial fallow cycle, and over successive fallow cycles on a regional or inter-fallow level. Evidence is presented here for the spontaneous long-term community enrichment of an area with valuable plants in a cyclic or iterative fashion, in the context of an existing fallow utilization scheme in the Amazon. Review of the ecological processes which operate at microsite, field and community levels indicate that:

The economic impacts of agroforestry in the Northern Plains of China

In an effort to mitigate severe environmental problems, the Chinese government introduced ecological agriculture as an approach to sustainable grain production. One such method heavily employed in the Northern Plains of China is agroforestry. This region provides a unique case to assess the effect of agroforestry on agricultural output. This paper estimates a production function with a measure for forest cover to test the hypothesis that agroforestry makes a positive and significant contribution to agricultural output. Evidence shows that the effects of agroforestry on agricultural output are positive, though not always significant. This finding is relevant not only to Chinese agriculture, but also in answering the question of how agricultural sustainability can be accomplished in the long term. With increasing populations and decreasing opportunities for land expansion globally, agroforestry is one answer to improving agricultural growth.     

杨农间作田的光强和土壤水分状况及其对农作物的影响

试验选择株行距３ｍ×２８ｍ,１０￣１１ａ的杨农间作田,研究其光强和土壤水分空间分布与农作物生长发育的关系。结果表明,间作田林冠下和林冠外的光强分别为全日照的３６．４％和７４．８％;行中为８０．２％,林冠下和林冠外的土壤含水率分别为行中的６２．６３％￣６７．７１％和８８．８８％￣７３．７３％,由于光照不足和水分胁迫,降低了作物的株高和叶面积,使花生和小麦的平均产量比对照田分别降低２２．３％和１９．９     

豫东黄河故道农林复合生态模式经济效益分析

以商丘市梁园区为例,对豫东黄河故道的农林复合生态模式进行了调查研究。结果表明在黄河故道发展农林复合生态系统可以为当地创造一定的经济与生态效益。根据研究地区的自然与社会环境条件,可以发展以下几种农林复合生态模式:①林农复合生态模式,在幼龄林中种植小麦、油菜等喜光作物;②林药复合生态模式,树龄达到4年以后在林下种植耐阴的药用植物;③林牧复合生态模式,林冠完全郁闭之后在林下养鸡等。     

Effects of shade on arbuscular mycorrhizal colonization and growth of crops and tree seedlings in Central India

The study was conducted to investigate the effects of different light intensities (25, 50, 67, and 100% of full sun [open]) on arbuscular mycorrhizal (AM) colonization and growth of two intercrops (a rainy season crop, Phaseolus mungo Roxb. var. PU-35 and a winter crop, Triticum aestivum L. var. WH-147) and seedlings of two multipurpose tree species (Eucalyptus tereticornis Sm. [Clone C-7, ITC, Bhadrachalam] and Albizia procera Benth.) of Central India. The results showed that various plant growth parameters viz., shoot length, dry weight and phosphorus (P) uptake were adversely affected by low light intensity. Inoculations with AM fungi (Acaulospora scrobiculata Trappe, Glomus intraradix Schenck & Smith and an unidentified Glomus species) increased the plant growth on account of all measured parameters under tested light conditions. Mycorrhizal efficiency of different AM fungi varied in narrow range. AM inoculants were more efficient at higher light intensity in above mentioned plant species, except wheat. Data on colonization of P. mungo, T. aestivum, E. tereticornis and A. procera showed that formation of arbuscules, vesicles and sporocarp was delayed by lower light intensity. Colonization index of host roots and spore counts increased with increase in light intensity during successive months after inoculation. Data on effect of light regimes on microclimate of net house showed that lux meter reading decreased as per grades of shading nets used during both rainy and winter seasons. With increase in light intensity, ambient temperature, soil surface temperature and sub surface temperature at 15 cm depth increased, except that the ambient and soil surface temperature in control (open) were slightly lower than net house observations during January and February. Value of ambient temperature varied in narrow range, with in treatments as compared to soil surface and sub soil surface temperature at 15 cm depth. Soil surface temperature at 25% of full sunlight was less than respective control values by 2–11°C and sub soil temperature at 15 cm depth was less by 4–12°C. The values of different microclimate parameters varied in narrower range during winter season as compared to rainy season. While ranking the importance of two factors studied—light and AM fungi—for their effect on the growth and P uptake by different plant species, inoculations with AM fungi came in the first place (explained 50–82% variation) and light substantially increased the values of R ² in stepwise regression analysis (forward selection). The results suggest that AM inoculation may enhance the growth and P uptake of intercrops under tree shade and the tree canopy management is likely to increase the efficiency of AM inoculants in agroforestry systems. Use of excessive shading (25% of full sun or more) in nurseries may be avoided and PAR (photosynthetically active radiation) lamps may be used to increase growth and colonization index of tree seedlings.     

Soil carbon stock in relation to plant diversity of homegardens in Kerala,India

Conservation of biodiversity and mitigation of global warming are two major environmental challenges today. In this context, the relationship between biodiversity (especially plant diversity) and soil carbon (C) sequestration (as a means of mitigating global warming) has become a subject of considerable scientific interest. This relationship was tested for homegardens (HG), a popular and sustainable agroforestry system in the tropics, in Thrissur district, Kerala, India. The major objectives were to examine how tree density and plant-stand characteristics of homegardens affect soil C sequestration. Soil samples were collected at four depths (0–20, 20–50, 50–80, 80–100 cm) from HG of varying sizes and age classes, and their total C content determined. Tree density and plant-stand characteristics such as species richness (Margalef Index) and diversity (Shannon Index) of the HG were also determined. Results indicated that the soil C stock was directly related to plant diversity of HG. Homegardens with higher, compared to those with lower, number of plant species, as well as higher species richness and tree density had higher soil carbon, especially in the top 50 cm of soil. Overall, within 1 m profile, soil C content ranged from 101.5 to 127.4 Mg ha⁻¹. Smaller-sized HG (<0.4 ha) that had higher tree density and plant-species density had more soil C per unit area (119.3 Mg ha⁻¹) of land than larger-sized ones (>0.4 ha) (108.2 Mg ha⁻¹). Soil C content, especially below 50 cm, was higher in older gardens. The enhanced soil-C storage in species-rich homegardens could have relevance and applications in broader ecological contexts.

Coppicing improved fallows are profitable for maize production in striga infested soils of western Kenya

Striga hermonthica (striga) weed is a major threat to crop production in sub-Saharan Africa, and short duration improved fallow species have recently been found to reduce the effects of this weed because of their ability to replenish soil nitrogen. The objective of this study was to compare the efficacy and profitability of coppicing improved fallow species (Gliricidia sepium [gliricidia], Leucaena trichandra [leucaena] and Calliandra calothyrsus [calliandra]) and non-coppicing species (Sesbania sesban [sesbania], Mucuna pruriens [mucuna], and Tephrosia vogelii [tephrosia]), in controlling striga. Natural fallow and a sole maize crop were included as control treatments. The fallow treatments were split into two and either fertilized with N or unfertilized. The results showed that coppicing fallows produced higher biomass than non-coppicing fallows. For example, Callindra (coppicing fallow species) produced 19.5 and 41.4 Mg ha⁻¹ of leafy and woody biomass, respectively after four cumulative harvests as compared with Sesbania (non-coppicing species), which produced only 2.3 and 5.9 Mg ha⁻¹ leaf and woody biomass, respectively. Improved fallows reduced striga population in proportion to the amount of leafy biomass incorporated into the soil (r = 0.87). N application increased cumulative maize yield by between 15–28% in improved fallow systems and by as much as 51–83% in the control treatments. Added total costs of the coppicing fallows did not differ significantly from those of the non-coppicing fallows and control treatments. However, the added net benefits of the coppicing fallows were significantly higher (US$ 527 for +N and 428 for −N subplots; P < 0.01) than those of the non-coppicing fallows (US$ 374 for +N and 278 for −N), and the least for the control treatments. The most profitable fallow system was Tephrosia with net added benefits of US$ 453.5 ha⁻¹ season⁻¹ without N, and US$ 586.7 ha⁻¹ season⁻¹ with added N.