Antibody-based assay for galacturonan deesterification on wood pulp fibers during bleaching

Antibodies recognizing galacturonan were used in immunoassays for industrial unbleached and hydrogen peroxide-bleached chemithermomechanical pulp (CTMP). The assays were based on a colorimetric method using specific monoclonal antibody recognition of acidic and methylated homogalacturonan, respectively, on the pulp fiber surfaces. Alkaline phosphatase-conjugated antibodies were linked to the galacturonan specific antibodies, and an alkaline phosphatase substrate (p-nitrophenylphosphate) was used to develop a yellow reaction product that can be followed spectrophotometrically. Together the newly developed immunoassays were able to describe the deesterification, specifically, of surface-localized galacturonan on CTMP, induced by alkaline hydrogen peroxide bleaching. Unbleached CTMP showed relatively more labeling by methylated galacturonan recognizing antibodies, whereas bleached CTMP was relatively more labeled for acidic galacturonan. The increase in negative charge of the bleached pulp was also shown by polyelectrolyte titration; the negative surface charge was 9.3 μeq g⁻¹ in unbleached CTMP and 21.7 μeq g⁻¹ in bleached pulp.     

Studies on interactions between aluminum compounds and cellulosic fibers in water by means of27Al-NMR

Interactions between pulp fibers and aluminum compounds in pulp suspensions were studied using fibrous cellulose (FC) and fibrous carboxymethylcellulose (FCMC) powders as models of pulp fibers by X-ray fluorescence analysis and²⁷Al nuclear magnetic resonance. When deionized water was used at pH 4–5, water-soluble cationic aluminum species (Al³⁺, aluminum oligomer, and polyaluminum species) were adsorbed on the solid FCMC, forming carboxylic acid aluminum salts by cation exchange. The formation of these nondissociated pulp-COOAl type structures in paper sheets may contribute to some decreases in hydrophilic property. On the other hand, the water-soluble cationic aluminum species had nearly no interactions with hydroxyl groups of solid cellulose in the suspensions at pH 4–5. When tap water was used at pH 5–7, some aluminum components were retained on not only FCMC but also the FC sample. Probably, water-insoluble Al(OH)₃ flocs are formed in the suspensions at pH 5–7 and retained on the FC sample by simple filtration effect. Therefore, two mechanisms of the aluminum retention (i.e., electrostatic interactions and a simple filtration effect) may exist between pulp fibers and aluminum components in the practical papermaking process.This research was presented in part at the 5th annual meeting of the Japan Cellulose Society, Kyoto, July 1998     

Fodder production responses to pruning height and fodder quality of some trees and shrubs in a forest-savanna transition zone in southwestern Nigeria

Seasonal fodder production responses of five shrubs (Centrosema arenarium, Desmodium strigillosum, Desmodium velutinum, Phyllodium pulchellum, and Tadehagi triquetrum)and five trees (Albizia gummifera, Berlinia grandiflora, Albizia niopoides, Bauhinia monandra, and Inga edulis) to pruning heights ranging from 15 to 75 cm were evaluated during the main-wet, minor-wet, and dry seasons of 1993 and 1994 in the forest-savanna transition zone of West Africa. Fodder from the main-wet season was analysed for nitrogen (N) and phosphorus (P), and dry matter degradation characteristics after 6, 12, 24, 48, 72 and 96 h of incubation in rumen-fistulated N'Dama steers. In the minor-wet season, fodder production of all species increased in response to increasing pruning height with the exception of P. pulchellum and A. gummifera. Highest fodder production was attained at a pruning height of 45 cm for the Desmodium species, 50 cm for P. pulchellum, and 75 cm for the rest of the species. Concentrations of N and P varied significantly among the species; for N the ranges were 28.7–38.8 g kg^–1 (shrubs) and 25.3–44.5 g kg^–1 (trees), while for P the ranges were 3.26–7.04 g mg^–1 (shrubs) and 3.58–6.76 g mg^–1 (trees). Dry matter degradation characteristics differed significantly among shrubs and trees; ranges for shrubs were: soluble fraction (a), 128–185; degradable fraction (b), 664–703; potential degradability (PD), 793–857, as g kg^–1; rate of degradation (c), 0.0241–0.0308 as % h^–1 while for trees ranges were: (a), 139–160; (b), 651–826; (PD), 824–970, as g kg^–1; (c), 0.0143–0.0227 as % h^–1. Based on fodder production and quality, C. arenarium, D. strigillosum, D. velutinum, B. monandra, I. edulis, and A. niopoides were the most promising species for the development of animal agroforestry technologies in the west African forest-savanna transition zone and similar environments in the tropics.This revised version was published online in November 2005 with corrections to the Cover Date.     

The influence of the ethanol pumping of wheat straw and of the beating of pulp on the resulting paper sheets

This paper reports on the influence of independent variables in the pulping of wheat straw (viz. cooking temperature and time, and ethanol concentration), and of the number of PFI beating revolutions to which the pulp is subjected, on the yield and Shopper-Riegler index of the pulp, and on the breaking length, stretch, burst index and tear index of the resulting paper sheets. By using a central composite factor design and the BMDP software suite, equations that relate each dependent variable to the different independent variables were obtained that reproduce the experimental results for the dependent variables with errors less than 25% at temperatures, times, ethanol concentrations and numbers of PFI beating revolutions in the ranges 140–180°C, 60–120 min, 40–80% and 0–1750, respectively. Ensuring the optimal Shopper-Riegler index for the pulp (73.18°SR), and also the optimal breaking length (6276 m), stretch (2.57%) and burst index (3.72 kN/g) for the papers sheets, entails using a high temperature (180°C), a large number of PFI beating revolutions (1750) and medium-to-high ethanol concentration and time values; these conditions, however, decrease the tear index for the paper sheets below the optimum level (4.60 mNm²/g). A high temperature and a large number of PFI beating revolutions, in conjunction with a low ethanol concentration (60%) and a short time (60 min), can be used to save solvent and increase the production; the values thus obtained for the dependent variables differ by less than 30% from their optimum levels in the worst case.     

亚硫酸盐蔗渣浆的纤维素酶水解及其机理研究

研究了影响纤维素酶水解亚硫酸盐蔗渣浆的一些影响因素,采用离子色谱、X射线衍射(XRD)、傅里叶红外光谱(FT-IR)和原子力显微镜(AFM)对水解液成分、纤维素超分子结构及纤维形态的变化进行了分析。结果表明,在最适条件下,未漂浆和漂白浆的水解得率分别为74.89%和70.67%,漂白浆的水解得率低于未漂浆。水解产生的纤维二糖的质量浓度随反应进行逐渐降低,其中未漂浆的纤维二糖质量浓度由6 h时的7.95 g/L降到了72 h时的2.44 g/L,漂白浆的纤维二糖质量浓度由6 h时的6.59 g/L降到了72 h时的3.11 g/L。酶解使纤维素结晶度升高,但没有改变晶型。     

Biomass, carbon and nitrogen dynamics of multi-species riparian buffers within an agricultural watershed in Iowa, USA

This study was conducted to determine biomass dynamics, carbon sequestration and plant nitrogen immobilization in multispecies riparian buffers, cool-season grass buffers and adjacent crop fields in central Iowa. The seven-year-old multispecies buffers were composed of poplar (Populus×euroamericana Eugenei) and switchgrass (Panicum virgatum L.). The cool-season grass buffers were dominated by non-native forage grasses (Bromus inermis Leysser., Phleum pratense L. and Poa pratensis L). Crop fields were under an annual corn-soybean rotation. Aboveground non-woody live and dead biomass were determined by direct harvests throughout two growing seasons. The dynamics of fine (0–2 mm) and small roots (2–5 mm) were assessed by sequentially collecting 35 cm deep, 5.4 cm diameter cores (125 cm deep cores in the second year) from April through November. Biomass of poplar trees was estimated using allometric equations developed by destructive sampling of trees. Poplar had the greatest aboveground live biomass, N and C pools, while switchgrass had the highest mean aboveground dead biomass, C and N pools. Over the two-year sampling period, live fine root biomass and root C and N in the riparian buffers were significantly greater than in crop fields. Growing-season mean biomass, C and N pools were greater in the multispecies buffer than in either of the crop fields or cool-season grass buffers. Rates of C accumulation in plant and litter biomass in the planted poplar and switchgrass stands averaged 2960 and 820 kg C ha^–1 y^–1, respectively. Nitrogen immobilization rates in the poplar stands and switchgrass sites averaged 37 and 16 kg N ha^–1 y^–1, respectively. Planted riparian buffers containing native perennial species therefore have the potential to sequester C from the atmosphere, and to immobilize N in biomass, therefore slowing or preventing N losses to the atmosphere and to ground and surface waters.This revised version was published online in November 2005 with corrections to the Cover Date.     

Agroforestry systems for soil and water conservation and sustainable production from foothill areas of north India

Some conservation based agroforestry systems (AFS) were developed for possible adoption in place of high risk rainfed farming on land capability classes Ito IV of a typical topo-sequence of foothill north India. The agri-silvi-horticulture system integrating leucaena, lemon, papaya and turmeric on class I irrigated land provided sustainable mean net returns of Rs. 17066 against Rs. 7852 ha.^–1 yr.^–1 from double cropped agricultural system. The intercropping of cluster beans with leucaena gave the highest net returns of Rs. 3540 ha.^–1 yr.^–1 in the agri-silvicultural system adopted on class II land. Eucalyptus terettcornis (Smith) in top and Bhabbar grass (Eulaliopsis binata Retz) in the understorey on a sandy loam class III land gave four years (1985–1988) mean air dry grass yield of 4.2 (used for paper pulp) from October and 1.19 t. ha^–1 yr.^–1 (used for fodder) from June cut. The net returns from grass alone were Rs. 4672 against Rs. 1679 ha.^–1 yr.^–1 from rainfed field crops raised on an adjoining plot. The returns from trees would be additional. Bhabbar grass raised under Acacia species on a 25 to 30% sloping gravelly class IV land provided yield varying from 2.18 to 4.31 from October cut and 0.50 to 1.1 t. ha.^–1 yr.^–1 from June cut with 6 years mean of 3.9 t. ha.^–1 yr.^–1 which at 1988 prices provided net returns of Rs. 2402 ha^–1. These AFS proved superior to traditional farming on each land capability class.     

Nitrogen mineralization and maize yields following application of tree prunings to a sandy soil in Zimbabwe

Despite the promotion of prunings as sources of nitrogen for crops, lack of synchronization between N mineralization from prunings and plant uptake remains a major limitation to the impact of prunings on crop yields. A laboratory and a field experiment were therefore carried out to determine the mineralization patterns of selected prunings and assess the potential that exists to improve synchrony by mixing prunings of different quality. The laboratory incubation experiment was conducted for 84 days to determine the C and N release patterns of prunings of different quality and the manipulation of the C and N mineralization trends by mixing prunings of different quality. High quality prunings were considered to be those with high CO₂ evolution rates and mineralize N rapidly. The % C and % N released in 84 days were highest for the high quality prunings of Tithonia diversifolia (70% and 30% respectively) and least for the low quality prunings of Flemingia macrophylla (25% and –5% respectively). The medium quality prunings of Acacia angustissima and Calliandra calothyrsus had similar proportions of released C and N (about 40% C and 10% N). Different mixtures of T. diversifolia with other species showed contrasting influence on C release and N mineralization. Most mixtures released less C than that predicted, but in contrast most mixtures released N at a rate either matching or above the predicted. The % N released was strongly correlated with the polyphenol protein binding capacity (r² = 0.53) and also with the % C released (r² = 0.62). The field experiment was done for two cropping seasons to determine the effects of the prunings of these species and their mixtures on maize grain yield. The prunings were added at 5 t ha^–1 and incorporated into the top 15 cm by hand hoeing in the first season and their residual effects were monitored in the second season. Medium and low quality prunings produced significantly (p < 0.05) higher maize grain yields in the first season ranging between 2.4 t ha^–1 and 3.4 t ha^–1 compared with T. diversifolia which produced 1.7 t ha^–1. This suggested better synchrony in N release and uptake by maize with medium and low quality prunings compared with high quality prunings. The only mixture that indicated improved synchrony was the mixture of T. diversifolia and C. calothyrsus. This study showed that mixing prunings of different quality produce different patterns of N mineralization, some of which were unexpected and had a potential for improving N synchrony.This revised version was published online in November 2005 with corrections to the Cover Date.     

Species and site selection for timber production on farm boundaries in the humid Atlantic Lowlands of Costa Rica and Panama

In 1987–89 the CATIE-GTZ Agroforestry Project set up experiments with five timber tree species planted in single lines on twelve farm boundaries in cooperation with local farmers. When the trees were five years old, their height, diameter and total stem volume were: Acacia mangium 17 m, 19 cm and 67 m³ km^–1, Cordia alliodora 14 m, 20 cm and 46 m³ km^–1, Eucalyptus deglupta 22 m, 24 cm and 85 m³ km^–1, Tectona grandis 17 m, 20 m and 64 m³ km^–1, Terminalia ivorensis 18 m, 23 cm and 104 m³ km^–1. Considering these excellent growth rates, planting of Cordia alliodora, Eucalyptus deglupta and Tectona grandis in lines on farm boundaries should be promoted. T. ivorensis and A. mangium are not recommendable for sites with impeded drainage because of mortality caused by root rot, mostly due to Rosellinia sp.     

Development of utility and location indices for classifying agroforestry species: the case of Rwanda

In a study of farmer knowledge and experimentation of trees and tree cultivation, two categories of farmer consultants were identified, tree experts (n = 44) and control farmers (n = 70), via a two stage process of knowledge ranking and community interviews conducted in three communes in southern Rwanda in 1992. A detailed inventory of tree species was conducted revealing two key characteristics for on-farm trees: multiple utility and high locational flexibility. In order to logically organize the species inventory, two indices, a utility index (UI) and a locational flexibility index (LFI), were developed. The two indices were calculated for each species and then plotted as the axes on a bivariate grid. While few species had both high utility and flexibility indices, the majority that did were indigenous species long used in agroforestry systems (e.g., Euphorbia tirucalli, Vernonia amygdalina, Erythrina abyssinica, etc.). A few naturalized exotics introduced in the 1930s (e.g., Grevillea robusta, Eucalyptus camaldulensis, E. saligna, E. maideni, Cupressus lusitanica and Persea gratissima) were also appreciated for their multiple utility and locational flexibility. Farm sizes varied, averaging 1.27 ha among tree experts and 0.18 ha in the control group. The mean number of species cultivated was significantly higher on tree expert farms (P < 0.01). However, tree density was much lower on tree expert farms (731 trees · ha^–1) than on control farms (1,689 trees · ha^–1). Competitive species were found primarily on larger farms, whereas smaller farms were associated with species of greater UI and LFI. Farmers demonstrated deliberate and rational choices about which trees to plant in accordance with each species utility and flexibility in relation to land availability.     

Changes in stem taper for birch plants growing in tree shelters

Plantings with pendula (Betula pendula Roth) and pubescent (Betula pubescens Ehrh.) birches were studied on five localities (Lat. 57–60 ° N) in Sweden. Seedlings were planted in 1988 or 1989. The experiment contained 50 plants per parcel and five replications per treatment. Among treatments harrowed area and birches covered with tree shelter were included. In spring 1993 five plants growing on harrowed area, with and without tree shelter, respectively were randomly chosen on each parcel. A total of 25 birches per treatment, species and locality were used. The trial was replicated in 1994 and 1995. The plant height was estimated and diameter at 20 and 60% of tree height was measured each year for 4 yr. The stem taper was calculated by the quotient D₆₀/D₂₀. The stem taper for birches without tree shelter was 0.5 for both species on all localities. The quotients for birches, which have grown in tree shelter, were 0.6–0.75 the first years of the trial. Then the quotients decreased and 2–3 years later they were on the same level as for birches planted without tree shelters. The results of the studies indicate that tree shelters should be removed two to three years after the plant has reached the top of the shelter. The height of the tree shelter might be shortened to 0.8–1.0 m to stabilise the plant earlier than with the conventional shelter height of 1.2 m.     

Comparison of soil nitrogen dynamics under beech,Norway spruce and Scots pine in central Germany

To investigate the effect of tree species on soil N dynamics in temperate forest ecosystems, total N (Nt), microbial N (Nmic), net N mineralization, net nitrification, and other soil chemical properties were comparatively examined in beech (64–68 years old) and Norway spruce (53–55 years old) on sites 1 and 2, and beech and Scots pine (45 years old) on site 3. The initial soil conditions of the two corresponding stands at each site were similar; soil types were dystric Planosol (site 1), stagnic Gleysols (site 2), and Podzols (site 3). In organic layers (LOf₁, Of₂, Oh), Nmic and Nmic/Nt, averaged over three sampling times (Aug., Nov., Apr.), were higher under the beech stands than under the corresponding coniferous ones. However, the Nmic in the organic layers under beech had a greater temporal variation. Incubation (10 weeks, 22 °C, samples from November) results showed that the net N mineralization rates in organic layers were relatively high with values of 8.1 to 24.8 mg N kg^–1 d^–1. Between the two corresponding stands, the differences in net N mineralization rates in most of the organic layers were very small. In contrast, initial net nitrification rates (0.2–17.1 mg N kg^–1 day^–1) were considerably lower in most of the organic layers under the conifer than under the beech. In the mineral soil (0–10 cm), Nmic values ranged from 4.1–72.7 mg kg^–1, following a clear sequence: August>November>April. Nmic values under the beech stands were significantly higher than those under the corresponding coniferous stands for samples from August and April, but not from November. The net N mineralization rates were very low in all the mineral soils studied (0.05–0.33 mg N kg^–1 day^–1), and no significant difference appeared between the two contrasting tree species.     

Species screening for short-term planted fallows in the highlands of western Kenya

Short-term improved fallow technology, which is characterised by deliberate planting of fast growing N₂ fixing legumes species in rotation with crops is currently being promoted for soil fertility replenishment in the small holder farms in the tropics. Recent research and extension efforts on this technology have mainly focused on a narrow range of species. There is a need to evaluate more alternative species in order to diversify the options available to farmers and hence reduce the risks of over dependence on fewer species. We evaluated twenty-two shrubby and herbaceous species for their site adaptability, biomass and nutrient accumulation, biomass quality and maize yield response to soil incorporated plant biomass after the fallow (six and twelve months) in three different field experiments on a Kandiudalfic Eutrudox in western Kenya. Species which yielded large amounts ofthe most biomass N adequate for two to three maize crops were Sesbania sesban, Tephrosia vogelii, Tephrosia candida, Crotalaria grahamiana, Dodonea viscosa, Colopogonium mucunoides, Desmondium uncinatum, Glycine wightii and Macroptilium atropurpureum. Most fallow species tested recycled <22 kg P ha^–1 in plant biomass. Significant amounts of K were recycled through plant biomass of Sesbania sesban, Tithonia diversifolia, Tephrosia candida, Crotalaria grahamiana, Dodonea viscosa, Colopogonium mucunoides, Desmondium uncinatum, Glycine wightii, Macroptilium atropurpureum and natural weed fallows. Recyclable K in plant biomass ranged between 4 and 188 kg ha^–1Two methods of establishing S. sesban and T. vogelii fallows did not result in significant differences in biomass and nutrient yields at the end of the fallow period. Shrubby species gave Hhigh lignin (>10%) and polyphenol (>2%) concentrations. were found only in the shrubby species, and the (Ppolyphenol + lignin ): N ratio varied widely (0.3–5) amongst the species. evaluated. Maize yield increased by two-fold in the first season following the fallow phase compared with continuous maize for most species. Results suggest that there are a wide variety of legumes that could be used for use in improved fallow technologies aimed at ameliorating nutrient degraded soils and subsequently enhancing crop yields.This revised version was published online in November 2005 with corrections to the Cover Date.     

Steam explosion pretreatment used to remove hemicellulose to enhance the production of a eucalyptus organosolv dissolving pulp

The steam explosion (SE) pretreatment associated with the organosolv process was investigated to produce dissolving pulp from eucalyptus. Prehydrolysis Kraft (PHK) pulping was also done to produce viscose and acetate grade pulps as reference. The organosolv pulps were delignified in two steps with sodium chlorite. Viscose and acetate grade PHK pulps were bleached by OD₀(EH)D₁P and OD₀(EP)D₁PCCE sequences, respectively. Dilute acid-catalyzed (with acid addition) SE pretreatment dissolved more xylan than auto-catalyzed (no acid addition) SE pretreatment. Steam-exploded unbleached organosolv pulps showed lower residual lignin content and screened yield than unbleached organosolv pulps without SE pretreatment. Steam explosion pretreatment helped to decrease lignin content and damaged fiber length of unbleached organosolv pulps. The 1.0% H₂SO₄ organosolv pulp (organosolv dissolving pulp at bioconversion conditions) showed the highest reactivity. Even showing low viscosity for some applications, in general, the organosolv dissolving pulps produced in this study can be used for making lyocell fibers.     

Mixed-species plantations of Acacia mangium and Eucalyptus grandis in Brazil: 2: Nitrogen accumulation in the stands and biological N2 fixation

The sustainability of plantation forests is closely dependent on soil nitrogen availability in short-rotation forests established on low-fertility soils. Planting an understorey of nitrogen-fixing trees might be an attractive option for maintaining the N fertility of soils. The development of mono-specific stands of Acacia mangium (100A:0E) and Eucalyptus grandis (0A:100E) was compared with mixed-species plantations, where A. mangium was planted in a mixture at a density of 50% of that of E. grandis (50A:100E). N₂ fixation by A. mangium was quantified in 100A:0E and 50A:100E at age 18 and 30 months by the ¹⁵N natural abundance method and in 50A:100E at age 30 months by the ¹⁵N dilution method. The consistency of results obtained by isotopic methods was checked against observations of nodulation, Specific Acetylene Reduction Activity (SARA), as well as the dynamics of N accumulation within both species. The different tree components (leaves, branches, stems, stumps, coarse roots, medium-sized roots and fine roots) were sampled on 5–10 trees per species for each age. Litter fall was assessed up to 30 months after planting and used to estimate fine root mortality. Higher N concentrations in A. mangium tree components than in E. grandis might be a result of N₂ fixation. However, no evidence of N transfer from A. mangium to E. grandis was found. SARA values were not significantly different in 100A:0E and 50A:100E but the biomass of nodules was 20–30 times higher in 100A:0E than in 50A:100E. At age 18 months, higher δ¹⁵N values found in A. mangium tree components than in E. grandis components prevented reliable estimations of the percentage of N derived from atmospheric fixation (%Ndfa). At age 30 months, %Ndfa estimated by natural abundance and by ¹⁵N dilution amounted to 10–20 and 60%, respectively. The amount of N derived from N₂ fixation in the standing biomass was estimated at 62 kg N ha⁻¹ in 100A:0E and 3 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 16 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The total amount of atmospheric N₂ fixed since planting (including fine root mortality and litter fall) was estimated at 66 kg N ha⁻¹ in 100A:0E and 7 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 31 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The most reliable estimation of N₂ fixation was likely to be achieved using the ¹⁵N dilution method and sampling the whole plant.     

Influence of the chemical composition of kenaf bast and core on the alkaline pulping response

The bast and core of kenaf,Hibiscus cannabinus L., have markedly different chemical components and alkaline cooking responses. The bast had about double the hot-water extractives content and only about half the lignin content of the core. The core contained a large amount of hemicellulose, mostly composed of xylan. The lignin structures of bast and core were also quite different: The former had a significant abundance of syringyl structures. Evidence showed that the bast was much more easily delignified than the core. When the bast and core were cooked together in alkaline condition, the pulp yields at the same kappa number were higher than those of the individual pulpings of bast and core. The bast-core pulping gave a positive effect on the yield of bast pulp in the sodaanthraquinone and kraft pulpings. On the other hand, kenaf was abundant in the hot water extractives. These extractives consumed alkali during cooking to a relatively large extent but acted as a protector of hemicellulose and slightly increased the pulp yields.Part of this paper was presented at the 48th and 49th Annual Meetings of the Japan Wood Research Society, Shizuoka, April 3–5, 1998 and Tokyo, April 3–5, 1999     

Long-term effects of post-harvest stump removal and N-fertilization on understory vegetation in Western USA forests

Intensive forest management practices often disturb understory vegetation, and the recovery of these plant communities may depend on the type and severity of the disturbance. We examined the effects of stump removal and N-fertilization on understory plant communities and functional group (shrubs, graminoids, forbs, and introduced species) cover and diversity at five study areas in the Pacific Northwest of North America 24–28 years after treatment. Treatments at each study area included stumped and non-stumped controls as well as four levels of broadcast ammonium nitrate (0, 336, 672, and 1345 kg N ha⁻¹) in all combinations. Stumping had significant effects on community composition at all sites, and several plant species were associated (p < 0.05) with either controls or stumped plots. Diversity of graminoids, forbs and introduced species increased in stumped areas region wide. Stumping reduced cover and diversity of shrubs at some sites. Cover of graminoids and forbs also increased in stumped plots at some study areas. Forbs like Viola sempervirens were often indicators of stump removal while shrubs such as Acer circinatum tended to be associated with non-stumped plots. N-fertilization affected community composition at only one study area, and had no effects on cover or richness of functional groups. Stump removal has lasting impacts on plant communities and may make them more vulnerable to colonization by introduced species.     

Faidherbia albida and its effects on Ethiopian highland Vertisols

On a Vertisol under 850 mm rainfall, at an altitude of 1850 m, Faidherbia albida trees that occurred at 6.52 trees ha^–1, with a canopy cover that range from 97 m² ha^–1 to 229 m² ha^–1 were recorded. Studies on the lateral and vertical influence of the tree canopy on some physical and chemical properties of the soil, show apparent higher organic matter on the West side of the tree than the East due to accumulated wind blown litter by prevalent wind direction, and organic matter, N, P and K levels were higher under the tree canopy than outside for all directions and depths studied. Soil pH, exchangeable Na, Ca and Mg under the canopy and outside were similar. Available water capacity was 1.5 to 2 times more under than outside the tree. Noticeable increases in the silt fraction under the tree was recorded and discussed in relation to soil condition improvement and plant growth.     

14C-Lignin degradation by three Australian termite species

Summary The termites Nasutitermes exitiosus (Hill), Coptotermes acinaciformis (Froggatt), and Mastotermes darwiniensis Froggatt were examined for their ability to degrade lignin. Several ¹⁴C-(lignin)-lignocelluloses labelled in the 3 side chain position were prepared by infusing plant stems for seven days with the lignin precursor, ¹⁴C-cinnamic acid. Based on acid and alkali solubilites, the lignin precursor was more deeply incorporated into the lignin polymer than usually reported for ¹⁴C-(lignin)-lignocellulose preparations. N. exitiosus was able to degrade a ¹⁴C-(U-ring)-synthetic lignin (5% breakdown) and the lignin component of certain hardwood ¹⁴C-(lignin)-lignocelluloses (about 4–6.5% breakdown), but not the lignin component of softwood ¹⁴C-(lignin)-lignocellulose. Both C. acinaciformis and M. darwiniensis were less able to degrade any of the ¹⁴C-lignins than N. exitiosus. The difference may be due to their possessing different types of gut symbionts. Most of the degradation by N. exitiosus took place during the first week of the 14 day bioassays. Very low amounts (0.03–0.21%) were degraded in the faeces.The author wishes to thank Dr. J. R. J. French and Dr. G. Ettershank for their helpful advice during the work, Dr. T. K. Kirk for his generous gift of synthetic lignin, and J. W. Creffield for collecting the lower termites. E. Longmore and P. J. Pahl provided advice on statistical analysis