Effect of increasing distance fromAcacia nilotica trees on wheat yield

Planting trees in the cultivated fields of Pakistan is a controversial topic between foresters and agriculturists. Some farmers believe that trees significantly reduce their crop yields; therefore they avoid planting trees in their fields. On the other hand, many foresters claim trees are beneficial for crops. This study was conducted to determine the influence of boundary trees (Acacia nilotica) on the growth and yield of associated wheat crops under irrigated conditions in Punjab, Pakistan. Results indicate that close proximity to trees adversely affected tillers/m², weight/1000 grain and the grain yield of wheat planted up to a distance of 8.5 m from the trees. Plant height and grains/spike were least affected. In general, the growth and yield of wheat improved as distance from the tree increased. Tree size did not affect wheat height, tillers/m², grains/spike or weight/1000 grain. The grain yields were slightly lower near the largest trees (50–54.9 cm DBH trees).     

Farmer’s Perception of and Factors Influencing Agroforestry Practices in the Indus River Basin,Pakistan

Agroforestry practices of farming communities are investigated in southern Punjab province, Pakistan. It is hypothesized that rural people of this areas are more inclined than elsewhere in the province to practice agroforestry due to greater profitability than cropping. A landholder survey revealed that the majority of farmers are inclined to plant trees on their land. Low accessibility of institutional credit is a constraint for both agroforestry farmers (AF) and non-agroforestry farmers. However, among AF respondents only 24% were found to need credit for agroforestry practice, as against nearly 76% for crop production. Mostly farmers were found to have positive perceptions regarding agroforestry practice, because they understand the multiple benefits from growing trees, compared with cropping where farmers face various constraints, including poor access to credit, natural hazards, and little support from local authorities. Further, effort to sensitize farmers that growing trees has multiple benefits compared to only cultivation of field crops can bring about change in farmer’s perceptions and attitudes in the Indus River basin, resulting in motivation for agroforestry adoption.     

Integration of indigenous wild woody perennial edible fruit bearing species in the agricultural landscapes of Amhara region,Ethiopia

The study was undertaken in three districts of Amhara region to assess the extent and purpose of integration of wild indigenous woody perennial fruit bearing species in the agricultural landscapes, appraise their species composition and diversity and identify factors holding back farm integration. Data were gathered through interviews administered to 90 randomly chosen household heads, and fruit trees census in each and every plot of the informants. Species diversity was found to be low and vary by farm, land use type and site. Altogether 17 species were recorded in the agricultural settings. Species retention in the different land use types appears to be governed by species relative importance and compatibility with annual crops, where farm edges recorded a higher ethno-ecological importance score. Nevertheless, as it stands now fruit bearing species are retained primarily for non-fruit utilities. Free availability, land shortage, slope and altitude as well as disgrace feelings are among the major factors holding back farm integration and diversity of indigenous species for fruit production. Should they are additionally exploited for their fruits proper, there is a critical need to raise recognition and awareness at the rural grassroots level and instill knowledge about the food values, and assist in appropriate tree management techniques and inter-cropping regimes as well as accessing markets.     

Exotic tree species displace indigenous ones on farms at intermediate altitudes around Mount Kenya

Agroforestry systems are potentially suitable for conservation of tree genetic resources. Farmers around Mt. Kenya usually integrate trees into their farm. Large parts of these trees seem to be of exotic origin, whereas indigenous species have priority for conservation. This study aimed at determining on-farm richness, composition and frequency of indigenous and exotic woody species around Mount Kenya to assess the suitability of farms for the conservation of indigenous tree species. 265 on-farm plots of 0.5 ha size each were selected in 18 different agro-ecological zones by using a stratified sampling scheme. All woody species within the plot were recorded with their local and scientific names. Total species richness was 424 (including 306 indigenous ones), mean richness per plot 16.5 species (including 8.8 indigenous ones). Eight out of the 10 most frequent species were exotic ones with Grevillea robusta from Australia ranking first (found on almost 76% of the surveyed farms). The proportion of indigenous species increased with increasing aridity and temperature. Dominance of exotic species was found at farms of humid mid- and highlands. Ordination analysis revealed that mostly exotic species contributed to separation of farms in the highlands and upper midlands, whereas indigenous species in the lower midlands and lowlands. As the frequencies of most indigenous trees were low, only parts of the surveyed farms can contribute to conservation of tree genetic resources, particularly the less intensively managed farms of the more arid lands. Farmers’ access to knowledge on valuable indigenous tree species and to quality seedlings of these trees need to be improved to increase indigenous species’ frequencies on farms and possibly to replace some of the exotic species in the future.     

Changes of land tenure and the introduction of tree cash crops by shifting cultivators: The case of the Paluan Muruts in Sabah, Malaysia

Shifting cultivation is one of the main factors that has caused forest degradation in many tropical countries. In Sabah, Malaysia, the government has granted land titles to local farmers outside the Forest reserve, and introduced tree cash crops to reduce farmers’ dependence on shifting cultivation. Granting land titles, however, was not always an incentive for farmers to plant tree cash crops. Farmers often planted tree cash crops on land without secure legal rights. The Land Ordinance and illegal logging had introduced exclusive and (semi-)permanent rights to land into this region, and the Forest reserve also was divided among villagers. The Land Ordinance stipulates that planting trees confers permanent heritable and transferable rights of use and occupancy but not within Forest reserves. Local farmers who were anxious about their land rights believed that they could obtain those rights even within the Forest reserve, and applied for land titles. Farmers planted tree cash crops not only for future income but also to secure their land rights. At present, the policy of Forest reserve has nearly collapsed in this region and it is impossible to neglect or remove local farmers if the government utilizes Forest reserves for any purpose. Lands in the interior regions will be reclassified in the near future out of necessity.     

Tree gardening and taungya on Java: examples of agroforestry techniques in the humid tropics

Agroforestry is a general concept for a land management system combining trees and agricultural crops. For application, various specific techniques can be chosen. Each of these techniques is adjusted to a specific set of environmental as well as socio-economic factors. Agroforestry cultivators or managers belonging to varying social strata and institutional groupings may practice different forms of agroforestry, even within the same general region. This is demonstrated on the basis of two contrasting types of agroforestry which are found on the Indonesian island of Java. Tree gardening or the cultivation of a wide variety of crops in a multiple-storeyed agroforestry system is an indegenous practice on private lands, while taungya or the intercropping of young tree plantations with staple crops is practiced on state forest lands. Both systems are described as to their management characteristics, past development as well as possibilities and constraints for further development. These two practices are then compared as to various attributes, like producer group, production purpose, area of cultivation, land ownership situation, structural organization of crop combinations, possibilities for improved cultivation techniques, and suitability for application in rural development for specific target groups.This paper is a slightly revised version of a contribution to a lecture series on agro-forestry organized by the Departments of Forestry, Wageningen University.     

Plant-soil interactions in multistrata agroforestry in the humid tropicsa

Multistrata agroforestry systems with tree crops comprise a variety of land use systems ranging from plantations of coffee, cacao or tea with shade trees to highly diversified homegardens and multi-storey tree gardens. Research on plant-soil interactions has concentrated on the former. Tree crop-based land use systems are more efficient in maintaining soil fertility than annual cropping systems. Certain tree crop plantations have remained productive for many decades, whereas homegardens have existed in the same place for centuries. However, cases of fertility decline under tree crops, including multistrata agroforestry systems, have also been reported, and research on the causal factors (both socioeconomic and biophysical) is needed. Plantation establishment is a critical phase, during which the tree crops require inputs but do not provide economic outputs. In larger plantations, tree crops are often established together with a leguminous cover crop, whereas in smallholder agriculture, the initial association with food crops and short-lived cash crops can have both socioeconomic and biological advantages. Fertilizers applied to, and financed by, such crops can help to `recapitalize' soil fertility and improve the development conditions of the young tree crops. Favorable effects on soil fertility and crop nutrition have been observed in associations of tree crops with N<sub>2</sub>-fixing legume trees, especially under N-deficient conditions. Depending on site conditions, the substitution of legume `service' trees with fast-growing timber trees may lead to problems of competition for nutrients and water, which may be alleviated through appropriate planting designs. The reduction of nutrient leaching and the recycling of subsoil nutrients are ways to increase the availability of nutrients in multistrata systems, and at the same time, reduce negative environmental impacts. These processes are optimized through fuller occupation of the soil volume by roots, allowing a limited amount of competition between associated species. The analysis of temporal and spatial patterns of water and nutrient availability within a system helps to optimize the use of soil resources, e.g., by showing where more plants can be added or fertilizer rates reduced. Important research topics in multistrata agroforestry include plantation establishment, plant arrangement and management for maximum complementarity of resource use in space and time, and the optimization of soil biological processes, such as soil organic matter build-up and the stabilization and improvement of soil structure by roots, fauna and microflora. This revised version was published online in June 2006 with corrections to the Cover Date.     

A general classification of agroforestry practice

Present classification schemes confuse agroforestry practices, where trees are intimately associated with agricultural components at a field scale, with the whole farm and forest systems of which they form a part. In fact, it is common for farming systems to involve the integration of several reasonably discrete agroforestry practices, on different types of land. The purpose of a general classification is to identify different types of agroforestry and to group those that are similar, thereby facilitating communication and the organized storage of information. A new scheme is proposed that uses the ‘practice’ rather than the ‘system’ as the unit of classification. This allows an efficient grouping of practices that have a similar underlying ecology and prospects for management. A two stage definition of agroforestry is proposed that distinguishes an interdisciplinary approach to land use from a set of integrated land use practices. Four levels of organization are recognized through analysis of the role of trees in agricultural landscapes: the land use system, categories of land use within systems, discrete groups of components (trees, crops, animals) managed together, and functionally connected groups of such discrete practices in time and space. Precedents for this form of analysis are found in the literature and it conforms with generally accepted methods of systems analysis. Classification of major types of agroforestry practice proceeds primarily according to the components involved and the predominant usage of land. A secondary scheme further classifies these in terms of the arrangement, density and diversity of the tree components involved. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agroforestry Systems as Alternative Land-Use Options in the Arid Zone of Thal,Pakistan

Agroforestry offers unique opportunities for increasing biodiversity, preventing land degradation, and alleviating poverty, particularly in developing countries, but factors explaining the adoption by farmers are not well understood. A survey of 524 farm households was conducted in Bhakkar district of Punjab, Pakistan to study factors that determine the adoption of agroforestry on the sand dunes in the resource-deficient region of Thal. Two types of agroforestry systems were studied: intercropping and border cropping (also known as boundary or perimeter planting). Both agroforestry systems included irrigated cultivation of the timber trees Eucalyptus camaldulensis (local name: sufeda) and Tamarix aphylla (local name: sars) with wheat, chickpeas (Cicer arietinum) (local name: chana) or cluster beans (Cyamous tetragocalobe) (local name: guars). The majority of the farmers was in favour of intercropping and border cropping. Most farmers reported the protection of nearby crops from dust storms as the most important positive perception about both agroforestry systems. Age, education, and farm to market distance were significant determinants of agroforestry adoption. Older and less-educated farmers, with farms closer to markets were less likely to adopt tree planting or border cropping in Thal. In general, the agroforestry systems examined were more likely to be adopted by farmers who can wait 3–4 years for harvesting crop outputs, but not by poorer farmers who are totally dependent on subsistence agriculture and cannot afford the high initial cost of agroforestry establishment, nor can they wait for crop output for extended periods. Furthermore, the adoption of both agroforestry systems was more likely in remote marginal areas than in areas close to markets. To increase agroforestry adoption rates, government policies should strengthen farmers’ knowledge of every stage of agroforestry through extension services, focusing particularly among the prime prospects, i.e. farmers who will be most likely to adopt agroforestry. Once the prime prospects have adopted it, the older, less-educated, and poor farmers of the rural population can be also focused on to motivate adoption.     

Socioeconomic factors affecting the adoption potential of improved tree fallows in Africa

In many parts of Africa, farmers periodically fallow their land, which is allowing land to lie idle for one or more seasons primarily to restore its fertility. This paper assesses the feasibility, profitability, and acceptability of improved tree fallows, which are the deliberate planting of trees or shrubs in rotation with crops to improve soil fertility. Improved tree fallows are assessed at different stages of intensification, drawing on farmers' experiences in three different settings. In extensive systems where land is plentiful and existing fallows with natural regeneration of vegetation restore soil fertility (southern Cameroon), farmers have little incentive to invest labor in establishing improved fallows. Where population density is higher and fallow periods are decreasing and farmers perceive a decline in soil fertility (eastern Zambia), improved fallows have great potential. In intensive systems where land is unavailable and cropping is often continuous (western Kenya), many farmers find it difficult to fallow land. Even here, there is scope for introducing improved fallows, especially among farmers who have off-farm income. Labor constraints and institutional support were found to greatly influence the feasibility of improved fallows. In intensive systems, low returns to cropping, low base yields, and a high opportunity cost of labor increase the returns to improved fallows. Principal factors associated with acceptability include past perception of soil fertility problems, past use of measures for improving soil fertility, current fallowing, economic importance of annual cropping, and wealth level. Adoption potential may be increased by reducing fallow periods, intercropping trees and crops during the first season, reducing establishment costs, producing higher value by-products, and by encouraging farmers to test improved fallows on high-value crops.This revised version was published online in November 2005 with corrections to the Cover Date.     

Soil water competition in a temperate hedgerow agroforestry system in South Africa

An on-farm trial was conducted to determine dry matter production of four fodder tree species and their effect on soil water and maize production. The trees were planted in rows intercropped with maize. The four tree species selected were Acacia karroo Hayne (indigenous fodder tree), Leucaena leucocephala (Lam.) De Wit (nitrogen fixing), Morus alba L. (fodder and fruit), and Gleditsia triacanthos L. (fodder and fuel). Volumetric soil water was measured in the upper 0.3 m of soil in each row of the trial using the time domain reflectometry technique. The neutron probe technique was used for monitoring the water content deeper in the soil. Geostatistical methods were used to analyse treatment differences in the upper 0.3 m of soil. The soil water content did not differ significantly between the maize and tree rows indicating that competition for water in the upper horizon was not the reason for lower maize yields. However, at greater soil depths (75–125 cm) trees in the wide spacing used less water than those in the narrow spacing. Light interception was an important factor in reducing maize yields in the row nearest to the trees. High soil water values recorded during summer indicated that in the current cycle of good rainfall the plants in the agroforestry trial were not stressed. Thus the trees do not compete with the crops for soil moisture in good rainfall seasons. However, this study would need further evaluation for the competition for water for the low rainfall years. Since the trees have access to water at greater depths, they are likely to be more productive into the dry season than shallow rooted crops.     

Effects of scattered Acacia tortilis (Forssk) hayne on soil properties in different land uses in Central Rift Valley of Ethiopia

Among several agroforestry practices in the Central Rift Valley (CRV) of Ethiopia, Acacia tortilis-dominated Parkland agroforestry systems are common. Utilizable information regarding the effects of the tree species on soil conditions in Ethiopia is very scarce to be of use for improved agricultural productivity. This study was conducted in three land use types in CRV areas in Oromia National Regional State in Ethiopia. The aim of the study was to determine the effects of A. tortilis on soil fertility variations along a gradient from the tree base to open area in different land use types. Soil samples from surface layers (0–15 cm) were taken at four concentric transects distances from tree base (0.5, 2 and 4 m), compared with soil samples from the adjacent open areas (15 m distance from the tree canopy cover), and then analyzed following the standard procedures. The results of the study indicated that except for Na the amount of soil nutrients under A. tortilis were significantly varied (P < 0.05) in the land use types. Generally, comparisons between under the canopy and outside the canopy of the tree species indicated a highly significant difference on major soil fertility parameters. The effect of the tree species on soil fertility parameters was significantly higher with the distance from the tree base to outside of the canopy. But soil texture was not affected, indicating that it is more related to parent material and land use practices than the tree influence. The study revealed that the indigenous Parkland agroforestry practices of A. tortilis tree improve soil fertility. Hence, the soil patches observed under A. tortilis trees can be important local nutrient reserves, leading to soil heterogeneity in an otherwise uniform agricultural landscape. This may be important for the agricultural landscape health and on farm biodiversity conservation in agricultural landscapes of similar agroecological conditions.     

紫色土流失区造林技术

紫色土流失区造林技术是在划分流失地类型的基础上,采取生物和工程措施相结合的方法,适地适材选择造林树种。流失区适宜造林树种以侧柏为主,辅以建柏、闽粤栲、火力楠等树种。     

Economic opportunities for smallholders to combine pulpwood trees and food crops

Input/output data from tree growing experiments in Southeast Asia were analysed within the framework of a model of a smallholder farm. Data on cropping were obtained from surveys of farmers. Prior to formulating a whole farm model, this input/output data were modified in two ways: (a) a yield penalty was imposed upon a continuous cropping regime to reflect the impact of land degradation; (b) an agroforestry (intercropping) activity was synthesised by reference to an existing agroforestry bioeconomic model. The modelling framework was conventional linear programming. The interplay of land area availability, land and labour productivity, and interest rates lead to a relatively complex picture, even for the simplified farming systems that were examined. Model results showed a clear indication of the potential role of trees, but this potential role decreased with increasing interest rates. The analysis suggested that smaller farms will be less inclined towards tree growing. A mixture of trees and crops appears attractive, on purely economic grounds, over a wide range of interest rates and land areas. Consideration of factors outside the model, such as risk aversion objectives of smallholders, and their limited opportunities to borrow for investments in tree planting, reinforce the tendency to combine trees and crops.     

Indigenous fruit trees of Madagascar: potential components of agroforestry systems to improve human nutrition and restore biological diversity

Biodiversity in Eastern Madagascar is threatened by slash and burn agriculture, which is resulting in species extinction, land and soil degradation and rural impoverishment. An ethnobotanical study was undertaken to determine the domestication potential of indigenous fruit tree species as components of agroforestry systems. Four major selection criteria were used: nutritional and income needs of the population, diversification of the agroecosystem, and protection of plant and animal diversity. At three sites, Andasibe, Masoala and Ranomafana, in the humid primary forest region of Eastern Madagascar, a total of 150 wild fruit species from 82 genera and 42 families, of which 85% were indigenous and 92% of woody habit, were identified. In contrast to most of the deforested areas in Madagascar, the rural population in these areas possess an intimate knowledge of indigenous plant resources. Most of the indigenous fruits are collected from the forest but for a few species, domestication is initiated by managing naturally established species or by planting individual trees in agricultural fields. Wild fruits supplement the daily diet, substitute for exotic fruits, gain importance during periods of food shortage and are most appreciated by children. Commercialization of wild fruits is mainly undertaken by the poorer section of the population. Gender related differences in knowledge and preferences on species were identified and related to the respective household responsibilities. A list of the 26 priority species was established based on the preferences of children, women and men at the three sites. Local, fruit-eating lemur species are also highly dependent on indigenous fruit trees and are crucial for successful regeneration of forest vegetation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Can the ecosystem mimic hypotheses be applied to farms in African savannahs?

The first ecosystem mimic hypothesis suggests clear advantages if man-made land use systems do not deviate greatly in their resource use patterns from natural ecosystems typical of a given climatic zone. The second hypothesis claims that additional advantages will accrue if agroecosystems also maintain a substantial part of the diversity of natural systems. We test these hypotheses for the savannah zone of sub-Saharan Africa, with its low soil fertility and variable rainfall. Where annual food crops replace the natural grass understorey of savannah systems, water use will decrease and stream and groundwater flow change, unless tree density increases relative to the natural situation. Increasing tree density, however, will decrease crop yields, unless the trees meet specific criteria. Food crop production in the parkland systems may benefit from lower temperatures under tree canopies, but water use by trees providing this shade will prevent crops from benefiting. In old parkland trees that farmers have traditionally retained when opening fields for crops, water use per unit shade is less than in most fast growing trees introduced for agroforestry trials. Strong competition between plants adapted to years with different rainfall patterns may stabilise total system productivity -- but this will be appreciated by a farmer only if the components are of comparable value. The best precondition for farmers to maintain diversity in their agroecosystem hinges on the availability of a broad basket of choices, without clear winners or 'best bets'. This revised version was published online in June 2006 with corrections to the Cover Date.     

半干旱黄土丘陵沟壑区人工林对土壤水分的适宜性分析

于2007～2010年生长季节,对侧柏、山杏、油松、柠条和山毛桃等林地土壤水分进行连续监测,并查阅相同树种和立地条件下的林分根系分布资料,以土壤水分对林木耗水满足程度作为评价指标,对半干旱黄土丘陵沟壑区小流域微地形条件下人工林对土壤水分的适宜性进行研究.结果显示:不同林分根系的垂直分布和土壤水分垂直变异相关性显著,水分...     

Improving the Traditional Acacia Senegal-Crop System in Sudan: The Effect of Tree Density on Water Use, Gum Production and Crop Yields

The traditional Acacia senegal bush-fallow in North Kordofan, Sudan, was disrupted and the traditional rotational fallow cultivation cycle has been shortened or completely abandoned, causing decline in soil fertility and crop and gum yields. An agroforestry system may give reasonable crop and gum yields, and be more appealing to farmers. We studied the effect of tree density (266 or 433 trees ha⁻¹) on two traditional crops; sorghum (Sorghum bicolor) early maturing variety and karkadeh (Hibiscus sabdariffa), with regard to physiological interactions, yields and soil water depletion. There was little evidence of complementarity of resource sharing between trees and crops, since both trees and field crops competed for soil water from the same depth. Intercropping significantly affected the soil water status, photosynthesis and stomatal conductance in trees and crops. Gum production per unit area increased when sorghum was intercropped with trees in low or high density. However, karkadeh reduced the gum yield significantly at high tree density. Yields of sorghum and karkadeh planted within trees of high density diminished by 44 and 55% compared to sole crops, respectively. Intercropping increased the rain use efficiency significantly compared to trees and field crops grown solely. Karkadeh appears to be more appropriate for intercropping with A. senegal than sorghum and particularly recommendable in combination with low tree density. Modification of tree density can be used as a management tool to mitigate competitive interaction in the intercropping system.     

Land suitability evaluation for multiple crop agroforestry planning using GIS and multi-criteria decision analysis: A case study in Fiji

We present novel methods that use geographic information systems (GIS) and multi-criteria decision analysis (MCDA) to evaluate land suitability for a set of seven agroforestry crops, with the aim to differentiate relative land suitability and its potential to achieve different benefit goals for the Sigatoka Valley, Fiji. Our first model (Land Suitability) identifies optimal areas for each crop based on readily available edaphic and environmental cultivation criteria and common GIS datasets. The second model (Weighted Maximum) uses objective approaches for weighting the relative importance of target crops to derive a multi-crop suitability map. We use the analytical hierarchy process (AHP) technique (a form of MCDA) to identify the relative importance of five benefit types (i.e. agroforestry initiative goals/AHP Objectives). AHP criterion weights were used to map the most important crops for different agroforestry goals. Our methods are unique among GIS-MCDA applications of land suitability analysis in that our aim was to investigate and spatially evaluate land use suitability for multiple crops on a per-crop basis, whereas the aim of most GIS-MCDA land suitability analyses is to evaluate relative suitability (e.g. low, medium, high), evaluate potential for different land uses (e.g. production, intensive, or multifunctional) or land suitability for a single crop. We conclude that the methods described can be adapted to agroforestry initiatives and other similar land use suitability applications in the Pacific region and other geographical settings.

     

Incorporating indigenous knowledge of fodder trees into small-scale silvopastoral systems in Jamaica

A study was conducted to identify and explore indigenous knowledge relating to fodder trees and silvopastoral management systems of small-scale farmers in seasonally dry areas of Jamaica. The objectives of the study were to: 1) explore farmers indigenous knowledge relating to fodder trees and silvopastoral management systems in a subtropical dry climate; 2) examine pastoral land-use systems and technologies in current use; and 3) seek to integrate this information into silvopastoral tree fodder systems. Data were gathered via observation and semistructured interviewing. A snowball sampling strategy was used to purposively select all small-scale farmers who had cattle in the Green Park valley for interview.Of forty farmers interviewed, 37 males (92.5%) and 3 females (7.5%) were primary caretakers of cattle. Twenty-seven of 40 farmers (68%) raised cattle to generate income. During extended droughts farmers are forced to look for alternatives to desiccated, overgrazed pasture grasses, including: 1) local travel to harvest sugar cane tops and to cut Guinea grass (Panicum maximum); 2) purchase of bag feed; and 3) harvest and use of tree fodder. Preferred fodder trees were identified as Bacedar (Guazama ulmifolia), Guango (Albizia saman), Breadnut (Brosimum alicastrum) and Quickstick (Gliricidia sepium).Recommended silvopastoral management systems include fodder hedgerows, three strata forage systems, and living fences. In addition, production of indigenous fodder tree species, introducing improved tree fodder species, and planting improved pasture grasses concurrent with cash trees is suggested.