Exploring the invasion of rangelands by Acacia mearnsii (black wattle): biophysical characteristics and management implications

Australian acacias have spread to many parts of the world. In South Africa, species such as A. mearnsii and dealbata are invasive. Consequently, more effort has focused on their clearing. In a context of increasing clearing costs, it is crucial to develop innovative ways of managing invasions. Our aim was to understand the biophysical properties of A. mearnsii in grasslands as they relate to grass production and to explore management implications. Aboveground biomass (AGB) of A. mearnsii was determined using a published allometric equation in invaded grasslands of the northern Eastern Cape, South Africa. The relationships among the A. mearnsii leaf area index (LAI), normalised difference vegetation index (NDVI) and AGB were investigated. The influence of A. mearnsii LAI and terrain slope on grass cover was also investigated. Strong linear relationships between NDVI, LAI and AGB were developed. Acacia mearnsii canopy adversely impacted grass production more than terrain slope (p < 0.05) and when LAI approached 2.1, grass cover dropped to below 10% in infested areas. Reducing A. mearnsii canopy could promote grass production while encouraging carbon sequestration. Given the high AGB and clearing costs, it may be prudent to adopt the ‘novel ecosystems’ approach in managing infested landscapes.     

Effects of Acacia nilotica and Acacia karoo diets on Haemonchus contortus infection in goats

This study was carried out to determine the effects of Acacia karoo and Acacia nilotica diets on Haemonchus contortus infections in goats. Twenty-four Boer goats of mixed sex (live weight 17-22 kg) were randomly assigned to four treatment groups, namely: A. nilotica (AN) group, A. karoo (AK) group, control infected with H. contortus (HC) group and the non-infected control (NHC) group. Animals in the AN, AK and HC groups were orally infected with a single dose of 3000 HC third stage larvae. The AN and AK groups had dried leaves of AN and AK, respectively, included in their basal diet at a rate of 40% dry matter (DM) while the HC and NHC groups had the basal diet throughout the experiment. All animals received a total feed allowance of 500 g DM per day and Katambora Rhodes grass hay ad libitum for roughage. Parameters measured included faecal egg counts and live weight. At the end of the experiment, three animals from each group were slaughtered and abomasal worm burdens were determined. A significant decrease in the faecal egg counts was recorded in animals in the AK group (P<0.05) relative to those in the AN and HC groups. The worm burdens were reduced by 34% in the AK group (P<0.05) and by 10% in the AN group (non-significant) relative to the infected control group. The study indicates that the difference in the effects of the two forages on HC infections may be related to type and concentration of tannins.     

Huizache (<Emphasis Type="Italic">Acacia farnesiana</Emphasis>) whole pods (flesh and seeds) as an alternative feed for sheep in Mexico

Two experiments were undertaken to evaluate the use of pods from Huizache (Acacia farnesiana), common in the arid and semiarid regions of Mexico, on the perfromance and apparent digestibility in Pelibuey Mexican hair growing ewe lambs. Twenty-four Pelibuey ewe lambs were used in the animal performance experiment, with a mean live weight of 14.91 ± 1.48 kg, randomnly allocated to three groups which received ad libitum for 77 days (11 weeks) experimental whole rations T0 with 0%, T12 with 12% or T24 with 24% inclusión of dried and ground Huizache pods. Dry matter intakes (g/kg ^0.75 daily) were 83, 95, 90 for T0, T12, and T24 respectively (P > 0.05). Mean daily live-weight gain was 90, 75, and 63 g/day for T0, T12, and T24 (P < 0.001). Nine Pelibuey ewe lambs were used to determine apparent digestibility in vivo of the experimental diets using a 3 × 3 latin square design repeated three times. There were differences in the digestibility of dry matter (P < 0.001), organic matter (P < 0.001), nitrogen (P < 0.031), neutral detergent fibre (P < 0.002), and acid detergent fibre (P < 0.001) being lower in T24. Huizache pods may be an alternative feed when included up to 12% of dry matter in the diets for sheep growing moderately.     

Response of Acacia Sieberiana to Repeated Experimental Burning

We conducted a study on how Acacia sieberiana respond to repeated burning in the Kidepo National Park in northeastern Uganda. The study was conducted to understand effects of common burning regimes (early dry season, late dry season, and no burn [control]) in the area on Acacia sieberiana. The three treatments were applied for three consecutive years to 14 replicate blocks in a randomized block design. All A. sieberiana trees were number tagged and monitored for height and girth (diameter at breast height) growth. All fires were set as head-fires and attained intensity ranging between 422 and 5693 kW · m⁻¹. Both early and late dry season burning increased the number of small (< 49 cm) A. sieberiana trees after 2 yr. Burning did not affect the growth rates. Although the number of trees < 49 cm increased after 2 yr, the mortality in this height class was also increased by the late dry season burning, and after 3 yr of consecutive burning there were no statistical treatment differences in the height class < 49 cm. Late dry season burning also led to high mortality among trees > 250 cm in the third year. Mortality attributed to elephant browsing was important in all treatments but a substantial portion of mortality could not be attributed to any particular cause. In the late burn, fire was the most important mortality factor. Thus, 2 yr of burning may be used as a tool to stimulate recruitment of A. sieberiana, but additional years of late dry season burning will increase the mortality of older trees.     

Characterizing Temporal Ecophysiology for Herbicide Management of Huisache (Acacia farnesiana [L.] Willd.)

Huisache (Vachellia farnesiana [L.] Wight & Arn.) is a woody species native to the western hemisphere that can invade a variety of native rangeland habitats around the world. In South Texas, it is native yet increasing in density and range while displacing more desirable forage plants, and because it resprouts prolifically it has been difficult to control. We therefore attempted to characterize optimal timing and environmental conditions for herbicide control. We collected weather data in four huisache-invaded pastures along the Texas Coastal Bend and recorded the average huisache phenological stage at those pastures each month. We also analyzed root crown total nonstructural carbohydrate (TNC) and huisache mortality resulting from herbicide treatment each month between April 2012 and November 2014. Huisache mortality and TNC data were analyzed using a randomized complete block analysis of variance, with post hoc tests to separate means; Akaike's information criterion determined best-fit models for mortality data. Root crown TNC increased during May, August, and December, indicating downward translocation and the potential for increased mortality of treated plants. Actual mortality was greatest during the months of May, September, October, and November. The best fit model for mortality was a sixth-order polynomial function of mortality versus month; when month was removed as a model factor, the best fit model was a quadratic function of soil temperature (peaking at ≈24.5°C), combined with a quadratic function of phenology (highest at full canopy stage). These results indicate that huisache is best treated with chemicals when soil temperature is near 24.5°C and during the full canopy stage. In the coastal plains of South Texas these variables coincide with two windows of optimal mortality for huisache treatment: May and September−November.     

沿海防护林树种木麻黄和相思生长和抗风性状比较研究

对沿海防护林4,6-8年生中的2个木麻黄无性系和2个8年生相思树种进行林分生长量及其与抗风相关的形态性状和立木材性等方面进行了研究。结果表明,不同林龄的林分生长量差异显著,生长情况表现为随着林龄的增长呈增大的趋势;不同树种/品系立木在胸径、树高、干形、树皮厚度等方面也存在着差异。各性状之间表型相关分析结果表明,除了分枝角度与胸径无相关性外,其他性状与林分立木大小密切相关,均达到显著水平以上。以主成分方法对性状指标进行因子分析结果也表明各性状可分为3类;采取类间平均链锁法对不同林分进行系统聚类结果也表明各林分之间在各性状之间存在着显著的差异,两相思林分区别于木麻黄林分,但木麻黄5和6号样地林分受立地条件影响,明显区别于其他林分而归为一类。“北冕”和“黑格比”强台风对样地风害的综合结果发现:4,6-8年生大部分木麻黄林分只存在断枝/梢等等级较低风害,而相思林分风折严重,马占相思风害等级为6级;台湾相思风害等级为5级;而木麻黄5和6号样地林分受林带前沿的立地条件影响,出现等级较高的风害情况。风害等级与其林分生长、抗风性状之间的回归方程表明,对抗风性影响最大的是应力波速、基本密度和Pilodyn值,其中影响最小的是分枝角度、树高和干形通直度,其中树高、应力波速、冠幅和生长应变值对风害等级呈正向效应,从调查数据和回归模型分析结果看,最不抗风的树种是马占相思,其次是台湾相思,而木麻黄两无性系抗风性强,其中木麻黄粤701略强于麻黄粤601。     

刺槐在生态畜牧业发展中的作用

本语文从节粮畜牧业,生态环境保护和草山草坡改良等方面论述了开发刺槐生产在畜牧业发展中的地位和作用。并针对槐叶开发存在的问题提出了对策建议。     

Diet Quality Modifies Germination of Dichrostachys cinerea and Acacia nilotica Seeds Fed to Ruminants

The pods of many woody plants form an important part of the diet of livestock during the dry season due to their high nutritive value. However, the dispersal of seeds that remain intact and can potentially germinate after excretion is of particular concern when animals consume seeds of encroaching or invasive woody plants. The objectives of this study were to determine the effects of animal species in two experiments (experiment 1: goats, sheep; experiment 2: goats, cattle), diet quality (Medicago sativa hay, Digitaria eriantha hay) and seed characteristics (size, hardness) on the effectiveness of animal seed dispersal and germination of Dichrostachys cinerea and Acacia nilotica seeds. Owing to a limitation on the availability of seeds, the two experiments were done separately at different times. Each animal in both experiments received 1 000 A. nilotica seeds and 1 000 D. cinerea seeds mixed with either a low-quality diet (D. eriantha hay) or a high-quality diet (M. sativa hay). In experiment 1, we found a significant interaction effect of animal species (goats, sheep), diet (high-quality hay, low-quality hay), and seed species (A. nilotica seeds, D. cinerea seeds) on germination (P < 0.0001). There was also a higher seed recovery (P < 0.009) when animals were offered high-quality hay (47.4% ± 4.65) compared to low-quality hay (30.2% ± 3.24). In experiment 2, animal species affected seed recovery (P < 0.0325; goats 32.0% ± 6.44; cattle 50.3% ± 4.27) and germination percentage (P < 0.055; goats 14.1% ± 1.48; cattle 9.3% ± 0.94). The diet quality fed to the animals may affect dispersal and germination. However, animal species and seed characteristics also had important effects on germination of D. cinerea and A. nilotica seeds. Thus, all three of these factors play a major role in dissemination of viable seeds.     

Growth patterns and annual growth cycle of Acacia karroo hayne in relation to water stress

Abstract

The use and replenishment of carbohydrate reserves in Acacia karroo is closely related to the successive events of the annual growth cycle. Acacia karroo displayed the rapid and substantial decline in non‐structural carbohydrates typical of deciduous woody species. In addition, each time shoot, leaf or reproductive organs grew rapidly, reserves declined.

Replenishment begins soon thereafter when the recently emerged leaves are still very small. Water stress does not change the pattern of use and replenishment. However, increasing water stress does slow replenishment down. This probably delays the beginning of the next growth event as well as the growth of organs already initiated.     

The Birds of the Alien Acacia Thickets of the South Western Cape

The plough shell, Bullia rhodostoma (Mollusca: Gastropoda), has been studied on an open sandy beach where it is a common scavenger. Samples taken over a year indicate hatching of young individuals from December to February. They reach a length of about 10 mm after 1 year and 40 mm after 10 years. The von Bertalanffy growth equation is L_t = 47 (1 - e^{-0,19(t+0,23)}) and the annual mortality rate is 0,79. Mean decalcified dry biomass is 209 mg m^-2 and production by growth 189 mg m^-2 y^-1 giving a P/B of 0,9. Most production by adults (>15 mm shell length) goes into reproduction, particularly In the females which grow larger than the males. Production by reproduction is estimated to be about 135 mg m^-2 y^-1. Average calorific values are 19,04 kJ g^-1 dry tissue     

Effects of fire,bruchid beetles and soil type on germination and seedling establishment of Acacia drepanolobium

The effects of fire, bruchid seed beetles and soil type on the germination and seedling establishment of Acacia drepanolobium were experimentally investigated. Seeds subjected to three seed treatments (bruchid damaged, bruchid-free burnt, and bruchid-free unburned) were germinated in three different soil types (black cotton, red sandy, and clay loam soils). Undamaged seeds had significantly higher germination (85.3%) than either beetle damaged (20.6%), or burnt seeds (3.4%). Soil type did not influence germination or seedling survival. Burnt seeds had an average germination of 2% in clay loams and 5.4% in red sandy soils, while beetle damaged seeds had an average germination of 15.6% in clay loams and 28.7% in black cotton soils. Treatment effects on seedling mortality or survival were not significant but seedlings from undamaged seeds had higher survival rates than those damaged by bruchid beetles.     

刺槐蜜中3种酚酸的高效液相色谱法测定

本文采用Folin—Cioealteu法和高效液相色谱-电化学检测法（HPLC-ECD）分析了我国西北地区8种刺槐蜜中总酚含量及咖啡酸、绿原酸和p-香豆酸的含量。结果表明,8种刺槐蜜中均含有3种酚酸,其中咖啡酸和绿原酸含量较高,p-香豆酸含量较低。陕西宜川和洛川两地的刺槐蜜总酚含量最高,甘肃泾川刺槐蜜总酚含量最低,其余地区样品总酚含量差异不明显。     

Serum lipid,enzyme, and hematological responses of broilers fed Acacia angustissima leaf meal-based diets

Tropical Animal Health and Production - The objective of the study was to determine serum lipid, enzyme, and hematological responses of broilers to Acacia angustissima leaf meal. Acacia...     

The influence of an Acacia karroo tree on grass production in its vicinity

Abstract

The investigation was concerned with the impact of an Acacia karroo tree on the productivity of the surrounding herbaceous layer.

It was established that a consistent pattern of grass production occurs around isolated A. karroo trees. This is characterized by high yields under and immediately south of the tree canopy, and low yields immediately to the north of the canopy. The former is attributed to favourable influences by the tree (e.g. shade and tree leaf litter), whereas the latter is probably a result of reduced water input associated with physical redistribution of rainfall by the tree and competition from the tree for soil water.

It is argued that the net effect of the favourable or unfavourable influences of A. karroo on grass production is dependent on tree density. This explains why grass production is greater where there are a few A. karoo trees than where there are no trees and why grass production declines as tree density increases beyond a critical level.     

Effect of intensity and frequency of defoliation on aerial growth and carbohydrate reserve levels in Acacia karroo plants

Acacia karroo trees were defoliated by goats at two intensities and four frequencies; 2, 4, 8 and 12‐weekly. Leaf accumulation and carbohydrate reserve levels were compared to a non‐defoliated control, and to plants (defoliation controls) which were defoliated for the first time that season each time a frequency treatment was defoliated. These plants are activated by defoliation in such a manner that successive defoliations can result in this activation being additive. There is clearly a defoliation level below which they are not activated. Activation appears to be negated to a degree by defoliations at 2 and 4‐weekly frequencies, relative to the 8‐weekly defoliation frequency. The 12‐weekly frequency at heavy defoliation produced less than the same defoliation at 8‐weekly frequency. The 2‐weekly frequency treatments produced as much leaf as the 4 and 12‐weekly defoliations at the same defoliation intensity. The more frequently plants were defoliated, the more carbohydrate reserves dropped. However, plants adjusted to cope with very frequent defoliations. There was no connection between leaf accumulation and carbohydrate reserve levels following the different frequencies and intensities of defoliation.     

The response of Acacia karroo plants to defoliation of the upper or lower canopy

The response of Acacia karroo trees to defoliation of either the upper or lower canopy only, was compared experimentally with that of plants whose whole canopies had been defoliated at a range of defoliation levels. These plants were very sensitive to defoliation of the upper canopy. A 100% defoliation of the upper canopy only, resulted in the same amount of growth as 100% defoliation of the whole canopy. This was considerably less than the growth of plants defoliated overall, at 25% and 50% leaf removal. In contrast, defoliating the bottom half of the canopy only, stimulated growth in the whole canopy to the same degree as defoliation of the whole canopy at 25–50%. The increases of growth were due largely to increased growth in the top half of the canopy. Plants were very sensitive to defoliation in the early‐flush phenophase. This probably masked the positive effects of the partial defoliations applied at this phenophase.     

Effects of condensed tannin from Acacia mearnsii on sheep infected naturally with gastrointestinal helminthes

The effect of tannins on endoparasite control in hair sheep was investigated using 20 entire lambs of the Santa Inês breed. At the beginning of the experiment these animals were 6-months old and weighed 22.5kg+/-4.7. The treatments used were (10 animals each): GT (animals receiving 18g of Acácia negra containing 18% of condensed tannin/animal/week) and GC (animals not receiving tannin). The experiment lasted 84 days, with animals kept on an Andropogon gayanus pasture. Faeces were collected weekly, with weighing and blood collection carried out fortnightly. At slaughter, the adult worms were harvested for identification and counting. Although the GT animals weighed more than the GC lambs at slaughter, these differences were not significant (P>0.05). In general, the values for haemoglobin, hematocrit, total protein, urea, phosphorus and calcium in the serum were within normal levels and no significant differences between groups were observed. For faecal egg count (FEC), lower values were observed throughout the experiment in the group receiving tannin, but these differences were only significant in the eighth week. There was a lower output of eggs by regression for GT compared with GC (P<0.05). The species identified, in decreasing order of worm count, were: Trichostrongylus colubriformis, Haemonchus contortus, Oesophagostomum columbianum, Cooperia sp., Strongyloides papillosus, Trichuris globulosa and Moniezia expansa. The total worm count and number of each species of worm were lower for GT compared with GC for T. colubriformis and Cooperia sp. (P<0.05). Condensed tannin (CT) from A. negra had an antiparasitic effect, thereby representing an alternative for worm control in sheep.