Effect of tapping tools and date of tapping on <Emphasis Type="Italic">Acacia polyacantha</Emphasis> gum yield in South Kordofan State,Sudan

A study was conducted in South Kordofan, Sudan to determine the effect of tapping, tapping tools and date of tapping on the gum yield of Acacia polyacantha. A two-factor experiment was conducted for two seasons in 2008-2009. One location was used for two seasons and two locations for one season. The first factor (4 levels) was the tools of tapping: Makmak, Farrar, and Sonki, and the control which was not tapped. The second factor (2 levels) was the date of tapping that comprises mid October and mid November. These treatments were arranged in Randomaized Complete Block Design and replicated three times. Gum yield (g/tree and g/ picking) was recorded for five pickings. Economic analysis was done using the partial budget technique. The results showed highly significant (p < 0.01) differences on gum yield (g/picking and g/tree). The results indicated that the process of tapping increases gum production by 88.4% and 79.8% compared with un-tapped trees, respectively. The date of tapping has no significant effect on gum yield (g/tree and g/picking) of A. polyacantha. Tapping of the tree with Makmak in mid- November was found to be economically beneficial compared to using the other tools and the control. These results could identify a new source of income for the poor farmers in South Kordofan mainly because of the wild occurrence of Kakamut as a potential gum producing tree species grown naturally in the area.     

Effect of grass density and date of tapping on Acacia senegal gum yield in north kordofan state, Sudan

We conducted a two-factor experiment in randomized com- plete block design with four replications during 2004 in El Demokeya Forest Reserve and El Himaira Natural Forest, North Kordofan State, Sudan. The objective was to develop an understanding of the ecological effects of under-story vegetation and tapping date on the productivity of gum arabic from Acacia senegal as over story cover. The first factor was grass cover which was tested in four levels (100% and 50% grass cover in addition to bare and burnt). The second factor, date of tapping was tested in three levels namely (1st Oct, 15th Oct and 1st Nov). The first picking was done after 45 days from tapping and the gum yield up to seven pickings was collected at intervals of 15 days. Gum yield from each picking was collected and weighed using sensitive balance. Analysis of variance was carried out using MSTAT-C statistical package, and the Tukey test was applied for mean comparisons. The results showed highly significant differences (p<0.01) of grass cover on gum arabic yield in the two sites for most of the first consecutive pickings (1st-4th out of seven) in addition to total yield (kg/ha). With exception to the 4th pickings, the interaction effect between the grass densities and tapping date was not significantly different. The total gum yield was significantly (p<0.05) increased in only two pickings (third and fourth) in El Demokeya Forest Reserve and two pickings (1st and 2nd) at El Himaira Natural Forest. The density of grass cover significantly (p<0.05) affected the number of pickings at both sites; the number of gum pickings was directly proportional to grass density. The number of gum pickings was found to be significantly (p < 0.05) increased at the early date of tapping.     

Gum arabic yield in differently managed <Emphasis Type="Italic">Acacia senegal</Emphasis> stands in western Sudan

A comparative study of gum arabic yield trends per tree and picking in relation to stand management (by farmers and by researchers) and type (natural and planted) was conducted at two locations in North Kordofan, Sudan, for a three-year period. In addition, eight-year yield trends in relation to rainfall were compared based on the 1993–2000 gum yield data from 1440 trees. Although the gum arabic yield followed the same trend over time in all stands at both locations, the gum yield from farm stands, whether planted or natural, was 47% to 60% lower than that from research stands. Late tapping reduced the gum yield by 40% and 50% at the two different locations, respectively. Yield was highly affected by rainfall, correlating positively with annual rainfall in six of the eight years of the study. These findings can be used for improving gum arabic yield through management interventions and for predicting yield in relation to stand type, management regime and rainfall.     

Growth performance and gum arabic production of Acacia senegal in northwest lowlands of Ethiopia

Despite the wide distribution of natural stands of Acacia senegal in Ethiopia, commercial exploitation of gum arabic is constrained by lack of tapping and development techniques. We evaluated the gum arabic yield from natural stands of A. senegal and the growth of 6 provenances in different parts of the country. For the gum yield evaluation from natural stands, four tapping positions and three tapping seasons were tested in a factorial RCB design. The second experiment in Metema evaluated survival and growth of six provenances. A. senegal trees in natural stands respond well to tapping if tapped during the appropriate season and at the correct position on the tree. The mean gum yield did not vary significantly by tapping season (p=0.63). Higher mean yield was, however, collected from trees tapped in October (96 g·tree^?1 per two harvests). The mean yield differed significantly (p=0.009) between the tapping positions. Mean separation (α=0.05) shows that trees tapped at mid stem gave higher yield (160 g·tree^?1 per two harvests). The interaction effect of tapping season and position was not significant. Higher mean yield ((70 ± 112) g·tree^?1) was recorded in mid October-mid stem in two harvests. The second experiment indicated statistically significant difference in mean survival (p=0.0298), height (p=0.000) and root collar diameter (RCD), (p=0.012) between the six provenances. Highest survival, height and root collar diameter growth was observed from Abderafi provenance (100%, (148±11) cm, (38±11) mm, respectively). We recommend October and mid-stem and branches as appropriate tapping season and position. We recommend planting of the Abderafi provenance for the study area due to its superior growth and survival. Our study contributes to the proper selection of provenances for plantation development and improved tapping technology for better production of gum arabic in the country.     

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.     

Deterioration of a sustainable agro-silvo-pastoral system in the Sudan: the gum gardens of Kordofan

The development and establishment of agroforestry systems is often suggested as a way to stabilize rural economies in developing countries [King, 1979]. At the same time, some traditional systems are being lost, due to an inability to protect the perennial or tree crop components of the system. These traditional systems and the forces that reinforce or destroy them should be carefully studied by those in the process of encouraging adoption of agroforestry systems in the developing world. The gum gardens of Western Sudan are a case in point.Acacia senegal (hashab) andAcacia seyal (talh) are the two major marketable gum-producing trees found in the western region of Sudan. TheAcacias are grown as part of an agro-silvo-pastoral system that has persisted for more than a hundred years in Kordofan Province, where 70% of Sudan's gum Arabic was once produced, as well as most of its grain and livestock products. After a lengthy drought lasting from 1979 to 1985 gum production in Sudan drastically decreased. It was reported that pest attacks and drought were major causal agents in the decline of gum production [Awouda, 1989; Sungar, 1986]. A survey executed in Northern Kordofan Province, starting in August of 1986, did uncover a great number of deadAcacias due to drought and pest attack, but from interviews with gum farmers we conclude that the decline in gum production is largely due to unfavorable socioeconomic relationships exacerbated by the drought, leading to the deterioration of the agroforestry system of production. An inability to get a fair price for gum at the local level and increasing emphasis on a cash economy led to the neglect of the tree components of the system. The gum gardens have long flourished with the intensive husbandry of small-scale farmers. Once these farmers were no longer able to care for them, the gum trees disappeared from the system, indicating that a lack of community stability can be fatal to even a well-developed agroforestry system.     

Quantitative variation among Kenyan populations of Acacia senegal (L.) Willd. for gum production, seed and growth traits

Acacia senegal (L.) Willd. is an African leguminous multipurpose tree species belonging to subfamily Mimosoideae and subgenus Aculeiferum, highly valued for gum arabic production. This study estimated the genetic diversity within and among Kenyan populations of the species in the Bulla Sambul, Kutulo, Wamba and Meisori populations based on 12 quantitative traits, which included; tree height, diameter at breast height (DBH), number of branches, bark thickness, gum weight and various pod and seed traits on 20 randomly selected trees in every population. Duncan’s multiple range test (DMRT) and the dendrogram distinctively divided the populations into two groups; Wamba and Meisori in one group while Bulla Sambul and Kutulo in the other, indicating geographical structuring of the genetic variability. The trees were larger, taller with greater pod and seed traits in the Wamba and Meisori than the Bulla Sambul and Kutulo populations. Contrarily, trees had lighter seeds, more branches with higher gum weight in the Kutulo and Bulla Sambul than the Wamba and Meisori populations. The Shannon–Weaver diversity index (H), depicted 1,000-seed weight as the most varied trait across the populations. These findings provide essential information on the genetic diversity of the species, necessary for delineation of particular zones for seed sources for germplasm conservation, selection for domestication and improved gum arabic production.     

Standardized gum tapping techniques to maximize yield from high-value Indian tree, <Emphasis Type="Italic">Sterculia urens</Emphasis>

Industrial applications of natural gums have been expanding tremendously, so gum collection from trees provides an important livelihood for local dwellers in drought-prone Rajasthan and its surroundings states. Traditional gum tapping is crude and unscientific; deep incision, untimely extraction and high concentration of chemicals in gum have affected Sterculia urens species in its natural habitat. In studies 2 years on trees having diameter at breast height >40 cm from natural stands to maximize gum collection and standardize the tapping method (bore holes vs. V blazes), tapping season, chemical and concentration, different tapping techniques were tested. For tapping maximum gum was collected using bore hole. Ethephon was better as extraction chemical than sulphuric acid. Bore-hole tapping with a 5-cm hole and ethephon at 300 mg/mL yielded the most gum (135.20 g/tree). Ethephon at 300 mg/mL yielded the most gum. Ethephon induced gummosis without affecting the health of tree. Tapping seasons also significantly affected the gum yield; the most gum was obtained in April–June.     

Ethephon: a tool to boost gum arabic production from Acacia senegal and to enhance gummosis processes

Gum arabic production from Acacia senegal is lower in sub-humid areas than arid areas. Water stress is thought to be the reason for higher yields in arid areas. The application of ethephon is thought to mimic the effect of water stress in other plants. The objective of this study was to determine if the application of ethephon would increase the gum yields of Acacia senegal under sub-humid conditions in Cameroon. Trees receiving 40 or 120 mg ethephon were compared to controls in field experiments at a semi-arid and a sub-humid location in Northern Cameroon, over two seasons. Two provenances from drier areas (Sudan) were compared to the local one. In the first season, gum yield of the local provenance treated with ethephon was increased by 400–600 % compared to the untreated trees. Gum yield at the semi-arid location was 77, 313 and 214 g/tree with 0, 40 and 120 mg ethephon/tree, respectively, while at the sub-humid location, it was 30, 186 and 114 g/tree with 0, 40 and 120 mg ethephon/tree. However, in the second season, the effect of ethephon was not significant in the semi-arid area, whereas it was evident in the sub-humid area (up to 478 g/tree). Moreover, ethephon did not affect gum yield of provenances from drier areas (Sudan). This showed that the water-stress hypothesis has to be refined. The development of ethephon-based tapping systems is promising, but requires further studies with a wider range of environmental conditions and A. senegal provenances.     

Optimizing Tapping-Tree Density of Rubber (<Emphasis Type="Italic">Hevea brasiliensis</Emphasis>) Plantations in South China

Tapping-tree density in rubber plantations affects the production of dry rubber. Farmers can estimate rubber productivity when they know with certainty the number of tapping trees within a plantation and can therefore increase productivity through optimized planting schematics. Historical data on planting distance between trees and between rows, planting density (trees/ha) and tapping-tree density (number of trees under tapping for latex harvest per hectare) from 1952 to 2014 have been collected for plantations in the Hainan, Yunnan and Guangdong provinces of South China. A plantation survey was conducted to collect more detailed data on current tapping tree and planting densities in various plantations in the three provinces. Planting density and row spacing are found to have increased with rubber tree planting time and plant spacing to have declined from 1952 to 2014. Tapping-tree density of rubber plantations from 1955 to 1995 in South China ranges from 270 to 345 tree/ha, averaging 300 trees/ha. Strong typhoons and cold snaps are important drivers of fluctuations in tapping-tree density. The factors driving tapping-tree density are similar across the three provinces but the degree of change differs between provinces. Tapping panel dryness (due to tapping beyond the natural limit of the rubber tree productivity), severe wind damage and cold damage are the major factors resulting in loss of tapping trees in plantations in South China. These results suggest that a combination of environmental management for extreme weather and targeted breeding could improve tapping-tree density in rubber plantation and therefore dry rubber yield per unit area.     

Field-scale influence of karité (Vitellaria paradoxa) on sorghum production in the Sudan zone of Burkina Faso

Sorghum (Sorghum bicolor L. Moench) production in 15 transect blocks, each with a karité (Vitellaria paradoxa C. F. Gaertn.) tree at each end, was evaluated on-farm in a village of southern Burkina Faso in a season of below-average rainfall. Under tree crowns, plant height and grain yield were significantly lower, by a factor of 16% for grain yield, than elsewhere in transects. In addition, mean plant height, and mean biomass and grain production per area as well as per plant were higher at the outside edge of tree crowns than in the middle of the field. Soil moisture content decreased significantly with increasing distance from the tree in the 0–20 cm soil layer. Top soils were also richer in organic carbon and potassium around tree crowns than in the middle of blocks. Sorghum performance in the zone under and around canopies was projected at field scale and compared to central transect controls. Grain production in karité parklands was higher with trees of mean crown radii of 225 to 275 cm, average densities of 12 and 31 trees/ha than in areas without trees. Therefore, farmers do not improve cereal production by reducing parkland tree densities below these levels. When nut production is included in the analysis, maintaining trees in fields can be economically advantageous at all densities.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of <Emphasis Type="Italic">Acacia senegal</Emphasis> on growth and yield of groundnut,sesame and roselle in an agroforestry system in North Kordofan state,Sudan

Two field trials were conducted under rainfed conditions at El-Obeid Research Farm and Eldemokeya Forest Reserve, North Kordofan State during the growing seasons 2004/2005 and 2005/2006. The objective was to investigate the effect of Acacia senegal on the performance and yield of groundnut (Arachis hypogea), sesame (Sesamum indicum) and roselle (Hibiscus sabdariffa) in an agroforestry system. The two trials consisted of seven treatments: three represented the intercropping of groundnut, sesame and roselle with A. senegal, three without trees and one represented A. senegal alone. Data were recorded on soil physical and chemical properties, soil moisture content, crops fresh weight (kg/ha), dry weight (kg/ha), gum yield (g/picking) and crop yield (kg/ha). The trees at El-Obeid yielded no gum, whereas those at Eldemokeya were 15 years old and were tapped as part of the total harvest in the agroforestry plots. Land equivalent ratios (LER) and simple financial analyses of gross surpluses were used to evaluate the productivity of the different treatments. Fresh weight of groundnut, sesame and roselle was significantly different (P < .0.05) at both sites. Higher fresh weights were found under the intercropping system than the sole cropping system. This could be attributed to a shading effect that limits fruit production of the field crops more than vegetative growth. Dry weights were significantly greater for sesame and roselle in both sites, while that of groundnuts was not significantly different. In both sites, intercropping reduced the yield of sesame by 6 and 11% in the first season and 37 and 39% in the second season. The reduction in roselle yield was 19 and 28% in the first season and 15 and 8% in the second season. Yield reduction in groundnut was 35 and 17% in the first season and 35 and 11% in the second season. The combined analysis indicated that intercropping reduced groundnut yield by 26%, sesame by 21% and roselle by 20%. All the treatments gave LER of more than one—indicating the superiority of growing the field crops in intercropping over the sole cropping systems. The highest LER of (1.71) was obtained when roselle was intercropped with A. senegal, while the lowest LER (1.48) was obtained when groundnuts were intercropped with A. senegal. All the treatments gave positive net revenues, the highest being for intercropped roselle (438 SDG/ha). The intercropping of sesame gave the second highest net revenue (387 SDG/ha), while the sole roselle gave the lowest net revenue (97 SDG/ha).     

Arthropod diversity in alley cropped black walnut (Juglans nigra L.) stands in eastern Missouri, USA

Knowledge of the complex interactions among trees, crops and their associated fauna is necessary to determine the viability of a particular agroforestry practice. Information is lacking concerning these interactions, particularly in temperate agroforestry practices. We examined the effects of two forages on the growth, nut production, and arthropod communities of alley cropped eastern black walnut, Juglans nigra L. Experimental plots of eastern black walnut, intercropped with alfalfa, Medicago sativa L., smooth bromegrass, Bromis inermis Leyss., or no vegetation were sampled with sweep nets prior to each cutting date for the forages. Comparisons were made between treatments and sampling dates. Tree growth measurements, nut yield and other nut quality measurements were taken at the end of each growing season. There were no differences in tree growth among alleyway treatments. The first season's nut yield was greater from trees with vegetation-free alleyways; otherwise nut production did not differ among the treatments. Arthropods were more numerous and diverse in alley cropped alfalfa than in alley cropped bromegrass or in the vegetation-free controls. Alley cropped bromegrass supported a more diverse population of arthropods than did the vegetation-free control. Arthropod diversity in the tree canopies did not differ among treatments. Alley cropped forages supported a more diverse and even arthropod fauna than did adjacent monocropped forages. We conclude that alley cropped forages had a relatively minor impact on the growth and nut yield of walnut trees.This revised version was published online in November 2005 with corrections to the Cover Date.     

史密斯桉树母树林营建技术研究

在云南省保山市隆阳区国营林场长岭岗营林区开展了史密斯桉母树林营建技术研究,结果表明:建立史密斯桉母树林要以优良种源选择为基础,并在立地条件较好、交通便利的地块组织实施;依次按50％、40％、40％的疏伐强度进行3次疏伐管理,母树林合理保留密度约270株·hm-2.7年生史密斯桉母树开始开花,花期10-12月,预计种子将于11月一翌年1-2月趋于成熟;母树平均胸径23.1 cm,平均树高17.4m,平均冠幅7.9m,长势十分理想.可为史密斯桉的大面积推广种植提供借鉴和参考.     

Productivity and nutrient cycling in young Acacia senegal farming systems on Vertisol in the Blue Nile region, Sudan

Acacia senegal, the gum arabic-producing tree, is the most important component of traditional dryland agroforestry systems in the␣Sudan. The spatial arrangement of trees and the type of agricultural crop used influence the interaction between trees and crops. Tree and crop growth, gum and crop yields and nutrient cycling were investigated over a period of 4 years. Trees were grown at 5 × 5 m and 10 × 10 m spacing alone or in mixtures with sorghum or sesame. No statistically significant differences in sorghum or sesame yields between the intercropping and control treatments were observed (mean values were 1.54 and 1.54 t ha⁻¹ for sorghum grain and 0.36 and 0.42 t ha⁻¹ for sesame seed in the mixed and mono-crop plots, respectively). At an early stage of agroforestry system management, A. senegal had no detrimental effect on crop yield; however, the pattern of resource capture by trees and crops may change as the system matures. A significant positive relationship existed between the second gum picking and the total gum yield. The second gum picking seems to be a decisive factor in gum production and could be used as an indicator for the prediction of the total gum yield. Soil organic carbon, N, P and K contents were not increased by agroforestry as compared to the initial levels. Soil OC was not increased by agroforestry as compared to sole cropping. There was no evidence that P increased in the topsoil as the agroforestry plantations aged. At a stocking density of 400 trees ha⁻¹ (5 × 5 m spacing), A. senegal accumulated in its biomass a total of 18.0, 1.21, 7.8 and 972 kg ha⁻¹ of N, P, K and OC, respectively. Agroforestry contributed ca. 217 and 1500 kg ha⁻¹ of K and OC, respectively, to the top 25-cm of soil during the first four years of intercropping.     

东风橡胶分公司橡胶芽接树新割制生产情况调查

通过对橡胶树割胶树位调查,低于20割龄胶树实施新割制,一般表现干胶产量增产和年度间产量变化平稳,累计死皮病率低,而高于20割龄胶树实行新割制、老龄割制和强割制,虽然提高刺激剂使用浓度,仍不能表现干胶增产,同时4～5级死皮率明显增高;品系GT1表现比RRIM更耐刺激,增产幅度大,死皮率更低。     

鸟类对南方红豆杉种子的取食与搬运

种子植物天然更新过程大致包括种子生产、种子扩散和种子萌发生长等3个阶段,各阶段所涉及的生物和非生物因子很多(Nathan et al.,2000).Chambers(1994)就种子扩散的动态过程提出了种子命运(seed fate)模型,将种子命运划分为2个阶段:第1扩散阶段,即可萌发的种子从植株(母树)到靠近母树的地面;第2扩散阶段,即种子在地面水平或地面到土层间垂直运动过程.     

高产脂马尾松优树自由授粉家系及其单株选择

根据《福建省地方标准(推荐)FDBT/LY1486脂松香综合标准》的要求,通过建瓯、龙岩两地的高产脂马尾松优树自由授粉子代林产脂力测定结果,发现在19~20年生的子代林中有5个单株的产脂力达到Ⅰ级特高产脂力(10 cm割沟单刀产脂量大于26 g),有11个单株的产脂力达到Ⅱ级特高产脂力(10 cm割沟单刀产脂量20~25 g),还有22个单株达到Ⅲ级普通高产脂力(10 cm割沟单刀产脂量15~20 g)。通过产脂力一般配合力测算结果,在24个家系135个单株的子代林中有11个家系38个单株的一般配合力呈正向效应。选用这些产脂力高的优株作亲本,建立无性系种子园或把子代林分改建成实生种子园,可以提高育种效益。