The establishment and early growth of three leguminous tree species for use in silvopastoral systems of the southeastern USA

Demand for goat meat in the eastern USA is growing as a result of preference by ethnic communities. Meat goat production systems in the southeastern USA should be designed to take advantage of the goats' natural preference for browse. Trees could contribute to system productivity by supplying required nutrients when demand by growing animals is critical and the quality of forage is limited. A field study was established in Wake County, NC to evaluate the establishment and early growth characteristics of three leguminous tree species, Robinia pseudoacacia, Gleditsia triacanthos, and Albizia julibrissin. The three tree species were planted in single-row plots following a randomized complete block design (3 × 2 × 2, replicated six times) with two planting densities (intra-row spacing of 50 or 100 cm) and two coppice heights (25 or 50 cm). Bare-root seedlings were planted in March 1995, evaluated for browse quality (composited samples) in August 1995, coppiced in February 1996, evaluated for herbage mass and quality in July 1996, and evaluated for goat preference in August 1996. Herbage mass produced during the second season ranged from about 200 (G. tricanthos) to 3,200 kg/ha (R. pseudoacacia). Estimates of herbage quality were high for all species. Crude protein and acid detergent fiber of leaflets ranged from 23 to 28% and 12 to 22%, respectively. Robinia pseudoacacia has a high potential as a browse species for goats due to high herbage production (mean of 2,390 kg/ha) and goat preference. Gleditsia triacanthos was judged to be a low value browse species. Albizia julibrissin, although not highly preferred by goats in the trial holds sufficient potential to warrant further investigation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Establishment and early growth characteristics of six Paulownia genotypes for goat browse in Raleigh, NC, USA

Meat goat production in the eastern USA is increasing as a result of growing demand from various ethnic groups. Because goats naturally prefer a high proportion of browse in their diets, research was initiated to investigate various silvopastoral production systems. The genus Paulownia contains several species which exhibit rapid juvenile growth and other characteristics that justify research into their potential use in meat goat feeding systems. In May 1997, six Paulownia genotypes were planted in a randomized complete block experiment with six replications. Trees were between 6 and 12 cm in height at planting. Genotypes included: P. fortunei seedlings, P. tomentosa seedlings, P. elongata seedlings and three P. elongata clones. Each 4-m wide plot contained a single row of 12 trees with an intra-row spacing of 1 m. Plant measurements included height, root collar diameter (RCD) at 3 cm above soil surface, and the number of main branches. Leaf samples were collected from all six replications for estimates of herbage quality. During 1998, trees were browsed with goats on two occasions to assess palatability of the herbage and to determine any preference for specific genotypes by the animals. Compared with seedling trees of all three species, the three P. elongata clones were taller (clones: 79.7 cm, seedlings: 55.9 cm; P < 0.01), had larger RCDs (clones: 18.4 mm, seedlings: 13.9 mm; P < 0.01) and had a higher branching frequency (clones: 4.9, seedlings: 1.5; P < 0.01) by the end of the first growing season. Mortality averaged 4.8% across all treatments and ranged between 0 and 8%. Early in the 1998 growing season before trees were browsed, P. elongata clones grew more rapidly than seedlings (clones: 116.4 cm, seedlings: 84.1 cm; P < 0.01). Estimates of herbage quality indicated favorable concentrations of energy and protein for lamina. In vitro true dry matter disappearance ranged from 85.4 (blades) to 71.5% (petioles) and crude protein from 25.1 (blades) to 4.9% (petioles). Animals readily browsed the lamina during two separate sessions, but no clear preference trends were observed among the different Paulownia genotypes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Vertical root distribution characters of<Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> on the Loess Plateau in China

On the Loess Plateau, water is the main limiting factors for vegetation growth. Root distribution characters have special ecological meaning as it reflected the utilizations of trees to the environments. Even-aged stands ofRobinia pseudoacacia on slope lands facing south and north were selected as sampling plots for root distribution investigation. Investigatiing results showed that indicated that on all sites, root biomass decreased with depth, and the distribution depth of fine root was deeper than that of coarser root. The results of variance analysis indicated that there were great differences in root biomass among different diameter classes, and coarser root was the main sources of variance, and the root biomass, especially fine root (ϕ<3mm) biomass on northern exposition sites was bigger than that on southern exposition sites. Analysis of the vertical root distribution parameters, root extinction coefficient, β indicated that the value of β on northern exposition was more than 0.982, while the value of β on southern exposition was less than 0.982, which indicated that the vertical root distribution depth ofRobinia pseudoacacia on southern exposition was deeper than that on southern exposition. And the distribution depth of fine roots (Φ<1mm) was deeper than that of thicker roots(Φ<3mm), which was in favor of the uptake of water and nutrients from deeper layers, helped the trees to adapt the arid environment, and promoted the growth of the upper parts of the tree. Foundation Item: This research was supported by National Natural Science Foundation of China (30371150 and 40371075). Biography: LI Peng (1974-) male, post: Ph. D. in Northwest Scientific & Technological University of Agriculture and Forestry, Yangling 712100, Shaanxi Province, P. R. China. Tel: 029-82312651. Responsible editor: Chai Ruihal     

Management Effects on Biomass and Foliar Nutritive Value of <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> and <Emphasis Type="Italic">Gleditsia triacanthos</Emphasis> f. <Emphasis Type="Italic">inermis</Emphasis> in Arkansas,USA

The browse potential of black locust (Robinia pseudoacacia L.) and thornless honey locust [Gleditsia triacanthos f. inermis (L.) Zabel] has not been adequately tested. Our objective was to determine effects of fertilization and pollarding on biomass and foliar nutritive value in separate studies of black locust and thornless honey locust in Arkansas, USA. Shoots were sampled monthly for two consecutive growing seasons in 2002 and 2003 to determine foliar, shoot, and total aboveground biomass, shoot basal diameter, and foliar nutritive value (crude protein and in vitro digestibility). Black locust yielded more foliar biomass when pollarded at 50 or 100 cm and fertilized with 600 kg P ha⁻¹, than at 5 cm with or without P, averaging 3.5 Mg dry matter ha⁻¹. Black locust foliar crude protein and in vitro dry matter digestibility ( ≤ 170 and 534 g kg⁻¹, respectively) decreased as leaves aged, but still met maintenance needs for beef cattle (Bos taurus L.). Thornless honey locust had little agronomic potential because of slow establishment, low foliar yield (330 kg ha⁻¹), and a 2% reversion to undesirable thorny phenotype. Black locust should be considered for livestock browse when drought induces semi-dormancy of herbaceous forages.     

Soil physical factors affecting the growth of sycamore (Acer pseudoplatanus L.) in a silvopastoral system on a stony upland soil in North-East Scotland

Tree growth and soil physical properties were compared on two grazed plots planted with sycamore at 5 and 10 m square spacing on an upland Scottish site. Both plots received fertilizer and stocking density of ewes and lambs was adjusted to maintain a constant sward height.Mean tree height in 1990 and height increment (1988–90) were significantly greater in the 5 m spaced plot (P<0.05). Although matric potential under the trees was generally greater than in the grassed rows between trees, mean penetration resistance (37–107 mm depth) was significantly greater (P<0.01) under the trees. Even when the soil was close to field capacity, less than 10% of penetrometer readings were < 1 MPa under the trees, in comparison to 44% in grassed areas between trees. This demonstrates that surface compaction due to preferential treading by sheep near the base of trees was sufficient to have seriously reduced tree root growth. Penetration resistance under the 5 m spaced trees was significantly less (P<0.05) than under the 10 m spaced trees. A technique for estimating the probability of root deflections by stones (in 35 mm depth intervals), Ps, from penetrometer readings was used. A significant relationship (P<0.1) was found between tree height increment and depth to Ps0.4 in the 10 m plot.     

Biomass production and root distribution of Gmelina arborea under an agrisilviculture system in subhumid tropics of Central India

A study of an agrisilviculture system comprising Gmelina arborea and soybean (Glycine max) was conducted in the subhumid region of Central India. Above- and below-ground biomass production and distribution of coarse and fine roots were studied in 4-year-old G. arborea, planted at a spacing of 2 × 2 m, 2 × 3 m, 2 × 4 m and 2 × 5 m. The total biomass varied from 10.89 Mg ha^–1 to 3.65 Mg ha^–1 depending on the tree density. Among the different tree components, stemwood contributed maximum biomass (54.3–79.4%), followed by branches and leaves. Root distribution pattern showed that most of the coarse roots were distributed in the top 40 cm of soil, whereas fine roots were concentrated in the top 20 cm. Coarse root biomass decreased with an increase in spacing. The spread of roots was asymmetrical in trees planted at 2 × 2 m and 2 × 3 m spacings, while it was symmetrical in trees planted at wide spacings. No significant difference was observed in the fine root biomass in different stands. The root:shoot ratio increased with an increase in spacing. Crop (soybean) growth and productivity varied significantly and it increased with a decrease in tree density. Soybean yield varied between 1.5 Mg ha^–1 to 2.1 Mg ha^–1. The role of root architecture of G. arborea trees on productivity of crops under agri-silviculture system is discussed.     

Invasive Tree Species <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis>: A Potential Biomass Resource in Nagano Prefecture,Japan

The introduced tree species, Robinia pseudoacacia (black locust), has spread extensively in many countries. Because of its active regeneration and rapid initial growth, R. pseudoacacia has not been successfully eradicated despite many efforts. To manage this species, developing information on the growth of R. pseudoacacia as a biomass resource is desirable, and this will motivate logging and could contribute to the extermination or sustainable use of this species. In the present study, the stand volume and growth of R. pseudoacacia forests in riverbeds along the Chikumagawa River in Nagano Prefecture in Japan were examined by tree ring and stem analyses. Seven plots were established in R. pseudoacacia riparian forests of varying ages, and 611 measurements of diameter at breast height and 386 measurements of tree height were made. Stand volumes, which were estimated using equations of stem volume curve based on the results of stem analysis of 47 sample trees, were almost the same as or higher than those of native broadleaf forests in Japan. Stand volumes continued to increase for more than 20 years. Current annual increments of four plots (aged 13–22 years) indicated that it could take <5 years after regeneration for the annual increment of R. pseudoacacia forests to reach a maximum level. Growth of R. pseudoacacia was comparable to or faster than native broadleaved species in Japan, showing the possibility of short rotation harvesting.     

A comparison between excavator-based harvester productivity in coppiced and planted Eucalyptus grandis compartments in KwaZulu-Natal,South Africa

Due to the labour challenges in South Africa, mechanised forestry equipment has increasingly been required to operate in complex forest conditions – such as coppiced Eucalyptus compartments – where they have not operated before. For this reason, harvesters are either used in certain coppiced compartments with uncertain productivity expectations, or harvesters are not used in these compartments due to a lack of productivity knowledge. This research aimed to determine the influence of tree volume and tree form on the productivity of an excavator-based harvester in coppiced regrowth – with either double or single stems, or planted single stems – in Eucalyptus grandis pulpwood compartments. In addition, the stem felled first and the distance between stems were investigated for coppiced double stems. The stem felled first is whichever stem between the two coppiced double stems the harvester grabbed, felled and processed first. The tree volume was determined; thereafter the trees were classified into different form classes. The tree volume and the cycle time were used to determine productivity. The research results showed that planted trees had the highest productivity across all tree sizes, followed by coppiced single stems and then coppiced double stems. When harvesting a 0.2 m³ tree, the mean harvester productivity was 8.7 m³ per productive machine hour (PMH₀) in coppiced double stems, 13.8 m³ per PMH₀ in coppiced single stems and 16.1 m³ per PMH₀ in planted trees. In coppiced double stems the productivity was significantly influenced by the size of the stem felled first. In coppiced double stems the productivity was not significantly influenced by the distance between stems. The productivity for both coppiced single stems and coppiced double stems was significantly influenced by stem form. The poorly formed trees had lower productivity compared to the trees with good form.     

Propagation ofRobinia pseudoacacia Linn. and Grewiaoptiva Drummond from rooted stem cuttings

Rapid vegetative propagation of promising multipurpose trees is an important need in agroforestry development. Grewia optiva andRobinia pseudoacacia are two such species, about the propagation of which very little is known. The rooting ability of stem cuttings harvested from juvenile (2 year-old) and mature hardwood(15 year-old) trees of Robinia pseudoacacia andGrewia optiva was significantly influenced by the period or season of harvesting cutting. Juvenile cuttings of both species rooted significantly better (42.9% in R. pseudoacacia and 46.6% in G. optiva) than mature hardwood cuttings (34.7% in R.pseudoacacia and 41.4% in G. optiva). The effect was more pronounced in auxin treated cuttings. InR. pseudoacacia, the highest rooting in juvenile(83.3%) and mature (66.6%) cuttings prepared in spring season was observed with the NAA (500 mg/l) treatment. InG. optiva, IBA (250 mg/l) in the monsoon season was most effective and recorded a maximum of 80% and 70%rooting in juvenile and mature cuttings, respectively. The auxin treatments also significantly enhanced the number of roots (23.8 inR. pseudoacacia and 17.6 in G.optiva) and their mean length (14.3 cm inR. pseudoacacia and 16.1 cm inG. optiva). Interactions between age, season and treatments were significant at P < 0.05 level for rooting percent in R. pseudoacacia and non-significant for G. optiva. The results of this study suggest that it is possible to develop clones of genetically superior trees of R. pseudoacacia and G.optiva for use in agroforestry or afforestation programmes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Herbage response to spacing of loblolly pine trees in a minimal management silvopasture in southeastern USA

Loblolly pine (Pinus taeda L.) silvopastures often are established and maintained on sites of poor soil fertility and minimal fertilizer input. Our objective was to determine whether row spacing affected yield, quality, and botanical composition of minimally managed herbage in loblolly pine early in the tree rotation. Plots were randomly located equidistant from bordering tree rows in each of eight alley width treatments that were 2.4, 3.6, 4.9, 7.3, 9.7, 12.2, 14.6 m wide, and no trees. Row spacing affected the yield, quality, and botanical composition of pasture five to six years in the rotation especially at densities exceeding 840 trees ha^–1. Botanical composition shifted from predominantly cool-season to warm-season grasses between annual first- and second-harvests, respectively, which caused seasonal differences in several yield and quality traits. Tall fescue (Festuca arundinacea Schreb.) production appeared to be unsustainable under minimal management. Herbage yield generally increased, but quality and minerals (crude protein, IVDMD, Ca, and P) tended to decrease with spacing. The 4.9 m row spacing was minimally acceptable for herbage yield and quality. System design should seek to balance tree-crop yield and quality within the context of management constraints and site productivity.This revised version was published online in November 2005 with corrections to the Cover Date.     

Incidence and Severity of Bean Rust (Uromyces appendiculatus) in Alleys between Leucaena Hedgerows in Kenya

The effects of inter-row spacing of Leucaena leucocephala (Lam.) de Wit in an alley cropping system on the incidence and severity of rust (Uromyces appendiculatus (Pers.) Unger) on intercropped beans (Phaseolus vulgaris L.) and their yield were examined over 2 years (1993 and 1994) at Chepkoilel Campus in Kenya. Each experiment consisted of three randomized blocks with treatments of three alley widths (2 m, 4 m and 8 m) and a treeless control with two intra-row spacings of Leucaena (0.5 m and 1.0 m). Hedgerows were coppiced at 1.0 m height and pruned subsequently at 2–3 months intervals. No fertilizer was applied but Leucaena loppings were incorporated as green leaf manure. Rust on beans was assessed at three growth stages in each season, using the Centro International de Agricultura Tropical (CIAT) scales. Microclimate was monitored in treatments, in 1994. Bean growth and yield were also measured. Rust increased with increasing alley width and was less severe in bean rows adjacent to hedgerows. Bean yield was highest in the treeless control plots and declined with decreasing alley width. Beans in 2 m alleys had significantly lower (p < 0.05) yields than 8 m alleys and treeless control plots. Bean growth was greatly modified in 2 m alleys and close to hedgerows. Light availability and diurnal temperature increased with alley width but relative humidity and leaf wetness duration decreased. Proximity to hedgerows also had marked effect on microclimate. The changes in yield, rust incidence and severity were examined in relation to microclimate, inoculum survival and dispersal.     

To prune or not to prune Faidherbia albida: competing needs for water,wheat and tree products in semi-arid Ethiopia

Faidherbia albida is one of the scattered trees commonly intercropped with most cereals in Ethiopia due to its positive impacts. The tree is pruned for various purposes including for fencing and fuelwood. In this study, the impact of pruning on water relations of F. albida and on understorey wheat productivity was investigated. The on-farm study was conducted in Ejerssa Joro, semi-arid Ethiopia. Six mature trees were selected; three were fully pruned and three were left unpruned. Sap flow and leaf water potential were measured on these trees. Crop gas exchange, aboveground biomass and grain yield were measured under and outside tree canopies. The highest and the lowest sap volumes, recorded from unpruned F. albida, during the dry period, were 153 L day^?1 and 20 L day^?1, respectively. The highest and the lowest sap volumes were 13.4 L day^?1 and 0.04 L day^?1 recorded during the wet period. Wheat CO₂ assimilation was highest (7.8 µmolm^?2 s^?1) at 1 m distance and declined away from the tree trunk under unpruned trees. Aboveground biomass and grain yield under unpruned treatments were significantly (P?<?0.05) higher than outside of canopy of same tree and outside canopies of pruned trees. Pruning reduced aboveground biomass and grain yield by 30% and 27%, respectively; despite the higher water uptake by unpruned trees. We recommend that intensive pruning of F. albida be discouraged and propose further studies on optimal pruning for increased food production and provision of tree products to meet farmers’ needs.

     

Millettia ferruginea from southern Ethiopia: Impacts on soil fertility and growth of maize

Growing agricultural crops under Millettia ferruginea (Hochst.) Baker, a tree that is endemic to Ethiopia, is an age-old practice in the country, but the beneficial effects of the tree on crops have not been scientifically quantified. To achieve this, four isolated and nearly identical Millettia trees growing on similar site conditions were selected and canopy coverage of each tree was divided into four radial transects. Four plots of 0.5 × 0.5 m were established on each radial transect at 0.5 to 1, 2.5 to 3, 4.5 to 5, and 6.5 to 7 m away from the tree bases. The control plot was established at 29.5 to 30 m. Composite soil samples from each of the four plots located at a comparable distance and at two soil depths, 0 to 10 and 20 to 30 cm, were collected and analyzed. The level of surface soil P, organic C, exchangeable base-forming cations and cation exchange capacity were all significantly higher (P < 0.000 to P < 0.015) under the trees than in the open field. Nutrient levels declined with depth and increasing distances from the tree trunk. Soil pH values did not show significant horizontal or vertical variations in all the soil samples analyzed. Maize plants grown on soils collected from underneath Millettia trees resulted in significantly better growth responses and higher dry matter yield as compared to the control (P < 0.001). Socioeconomic studies indicated that Millettia trees have good standing in the region both because of their desirable biological characteristics and because of their economic benefits.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of tree spacing on growth and wood density of 38-year-old Cariniana legalis trees in Brazil

Average wood density of 38-year-old Cariniana legalis (Mart.) Kuntze, a Brazilian native forest species, was found to increase with faster growth and lower stocking, while decreasing from pith to bark. A complete randomised block design was planted with five blocks. Ten trees were harvested in each of three spacing treatments. We hypothesised that the stand stemwood production would not significantly differ depending on tree spacing. However, tree growth would be higher in the wider spacing and wood density would be higher in the narrower spacing. The diameter growth of trees was higher at 3 m × 2.5 m than at 3 m × 2 m and 3 m × 1.5 m. Nevertheless, this higher individual tree growth at 3 m × 2.5 m did not compensate for the greater tree stock density at 3 m × 1.5 m with stand stemwood production at 38 years of 530 m3 ha^?1 and 649 m³ ha^?1, respectively. These results suggest that C. legalis, which can produce up to 17 m³ ha^?1 y^?1 of medium-to high-density timber – about 800 kg m^?3 – is a promising native species for forest plantations in Brazil.     

陕北黄土区坡面微地形对乔木空间分布的影响

[目的]传统造林树木种植点设计忽略了黄土坡面微地形对其生长的影响,研究切沟、塌陷地、缓台等微地形与现有林分乔木空间分布的耦合关系,可为近自然造林及乔灌混交水土保持林结构配置提供参考。[方法]以陕西省吴起县三道川流域内原状坡面及微地形的植被调查数据为基础,采用Arcgis9.3软件的空间分析工具和格局强度指标研究坡面微地形对乔木空间分布的影响。[结果]坡面微地形面积占样地面积的21.03%,微地形上乔木株数占样地总数的51.77%,乔木主要分布在坡面微地形上。乔木在切沟和缓台主要呈聚集分布,在塌陷和陡坎主要呈随机分布。乔木在不同坡面微地形分布差异极显著,榆树、小叶杨、山杏主要聚集分布在切沟,河北杨主要聚集分布在切沟和缓台,刺槐主要聚集分布在缓台。[结论]坡面各类微地形因其土壤水分等微生境差异而对乔木空间分布影响显著,在近自然植被重建中需根据坡面各类微地形生境及空间分布规律长期保持配置树木种植点,切沟以河北杨、小叶杨、榆树等树种为主,缓台以河北杨、刺槐搭配为宜,塌陷以河北杨、小叶杨为宜。     

Pasture production under different tree species and densities in an Atlantic silvopastoral system

We studied the effect of six tree species planted at six different densities on pasture production seven years after establishment. Annual and seasonal pasture production was studied every six months, over three years. Pasture production was lower under conifer trees (Pseudotsuga menziesii (Mirb.) Franco, Pinus pinaster Aiton, Pinus radiata D. Don) than under broadleaved trees (Betula alba L., Quercus rubra L. and Castanea sativa Mill.). Annual pasture production under Pseudotsuga menziesii and Pinus pinaster decreased progressively starting from 952 trees ha⁻¹, while decline in herbage production under Pinus radiata began to occur at 427 trees ha⁻¹. Tree density effect on pasture production was detected at 2,000 trees ha⁻¹ for all of the deciduous species studied. This effect on pasture production was more important in the first six months of the year (June sampling), while from June to December herbage production was less affected by tree density. The tree effect became more noticeable over time, with the last sampling showing the inverse relationship between tree density and herbage production most clearly. Seven years after tree establishment, pasture production was quite consistent under tree densities between 190 trees ha⁻¹ and 556 trees ha⁻¹ and declined remarkably from 556 trees ha⁻¹ to 2,500 trees ha⁻¹. The study also indicated that by the sixth growing season, annual pasture production under different tree species is inversely correlated with tree leaf area index.     

Effect of spacing and water availability on root:shoot ratio in Eucalyptus camaldulensis

Our limited understanding of the processes that control the allocation of biomass in trees is one of the factors that hinders our ability to develop mechanistic models of tree growth. Furthermore, accurate assessment of carbon sequestration by forests is hampered by lack of information regarding below-ground biomass. Below-ground to above-ground biomass ratios (BGB:AGB) are known to vary with a number of environmental factors, tending to increase in drier, harsher conditions. However, there are few, good datasets of BGB:AGB ratios of large trees, especially native Australian species. We aimed to investigate the response of BGB:AGB to water availability and tree spacing in 10-year-old Eucalyptus camaldulensis growing in a plantation in a low rainfall area.We carefully harvested 16 trees, ranging in diameter at breast height (DBH) from 7.6 to 25 cm, from a research trial near Deniliquin, NSW. Four replicates of each treatment from a factorial design with wide (3 m × 6 m) and narrow (3 m × 1.5 m) spaced trees and with natural rainfall (408 mm/year) (control) or irrigated plots (flooded six times per year) were selected. Above-ground tree parts were harvested separating stem, branch and foliage. Soil cores to 1 m depth were taken to sample small roots (<15 mm diameter) within each plot, then all roots >15 mm belonging to each tree were excavated using compressed air and an excavator. Roots were separated into six size classes within the range from <2 to >50 mm.Both water and spacing treatments influenced tree growth with trees being larger in irrigated, wide spaced plots. The BGB:AGB ratio was strongly influenced by irrigation (0.68 control, 0.34 irrigated) but not spacing. Allometric analysis of above- and below-ground biomass as a function of DBH showed that the relationship between DBH and above-ground biomass was conserved across treatments.By contrast, the relationship between DBH and below-ground biomass was influenced by water availability, commensurate with the large differences in BGB:AGB ratio. The BGB:AGB ratio increased with tree size largely due to an increase in small roots.The proportion of total root mass in the small roots (<15 mm) obtained through coring was 25–48% with 18–30% of total root biomass in the <5 mm diameter class.     

Leaf dynamics and protein content of six important fodder trees of the western Himalaya

Leaf production, leaf fall, leaf protein and net primary productivity have been reported for 4-year-old fodder trees in the mid-western Himalaya (altitude 1350 m; rainfall 1100 mm). The species include; Grewia optiva, Robinia pseudoacacia and Celtis australis growing in the open and Quercus glauca, Q. leucotrichophora and Ilex odorata growing in the forest. G. optiva, R. pseudoacacia and C. australis showed two distinct periods of leaf flush, and their leaves were short-lived (180 to 360 days) compared with the remaining three species which retained their leaves for more than two years, and had only one flush period during March–April. The open site species showed much higher leaf production, and the leaves contained a significantly (P < 0.05) higher protein content, compared with the forest group. Net primary productivity of G. optiva, C. australis and R. pseudoacacia was significantly (P < 0.05) higher than the forest species, which may be related to their high leaf production and rapid turnover rate of the leaves. The results are useful for management of these species in agroforestry systems.     

Effect of spacing on growth and biomass production of Gliricidia sepium (jacq) walp in an alley cropping system in Sierra Leone

This paper describes a study into the influences of spacing on the early performance and biomass production of Gliricidia sepium in an alley cropping system in southern Sierra Leone. Four between-row spacings of 2, 4, 6 and 8 m were combined with three within-row spacings (0.25, 0.50 and 1.00m) in a split plot experimental design.Survival, tree height and leaf nitrogen content were not affected by between- or within-row spacings. For the other parameters measured, namely root-collar diameter, branch production, total biomass and nitrogen yields per hectare, it was found that for equivalent tree densities, the lower the rectangularity of planting, the better the performance of the individual trees, and consequently the greater the yields per hectare.Total biomass production per unit area was, expectedly, greatest where the spacings between hedgerows were closest, while production per plant decreased with closer within-row spacings. The total fresh and dry weights of leaves and stems, as well as leaf nitrogen yields per unit area were strongly influenced by between-row spacing and less so by within-row spacing.     

Role of income diversification in protecting natural forests: evidence from rural households in forest margins of Sri Lanka

Ranchers need alternative livestock feeds when herbaceous forages become limiting in summer. Our objectives were to determine: (1) leaf and stem biomass components, (2) nutritive value [in vitro dry matter digestibility (IVDMD), total nonstructural carbohydrate (TNC), N, and N digestibility] of leaves for animal browse, (3) concentration of the secondary metabolites robinin and mimosine, and (4) in vitro leaf and bark toxicity for black locust (Robinia pseudoacacia L.) and mimosa (Albizia julibrissin Durz.), respectively, pollarded at 50 cm in Arkansas, USA. Black locust exceeded mimosa for every yield component (leaf mass tree⁻¹, leaves shoot⁻¹, shoots tree⁻¹, shoot mass tree⁻¹, stem basal area, and biomass tree⁻¹) except mass leaf⁻¹. Projected yields were 1,900 and 1,600 kg leaves ha⁻¹ for black locust and mimosa, respectively, assuming a population of 12,300 trees ha⁻¹. Mimosa leaves had greater IVDMD, TNC, and N digestibility than black locust. Mimosa leaves exceeded the nutritional N requirements of growing cattle (Bos taurus L.) and goats (Capra hircus L.), but protein supplementation would be needed for growing goats grazing black locust leaves. Tissue concentrations of secondary metabolites robinin and mimosine were below detectable limits in black locust and mimosa, respectively. The extract of black locust bark, but not leaves, was toxic to bioassayed African green monkey (Cercopithecus aethiops L.) cells. Either black locust or mimosa could provide moderate quantities of high quality, rotationally grazed forage for goats during summer months when herbaceous forage may in short supply.