Grass species composition,yield and quality under and outside tree crowns in a semi‐arid rangeland in south‐western Zimbabwe

Abstract

A two‐year study was conducted in lightly grazed areas of Matopos Research Station, Zimbabwe, to evaluate the impact of widely spaced trees on understorey grass composition, yield and quality. The study trees were Terminalia sericea and Acacia karroo. Ordination techniques using grass density and biomass as indices separated quadrats according to soil type but not grass species according to understorey or open areas or according to tree species. Grass yield under tree crowns was similar to open areas, in contrast with most reports where understorey areas had higher yields. The high understorey grass quality that has been reported from savanna areas exhibiting grass composition differences was not expressed. Selective grazing of palatable perennial grasses growing in association with tree crowns and their eventual replacement by low‐yielding and less‐palatable grasses that normally grow in open areas is proposed as an explanation of the unique tree‐grass interaction scenario of this study. In areas where this replacement has occurred, recovery may require management interventions.     

Picking a tree: habitat use by the tree agama,Acanthocercus atricollis atricollis,in South Africa

We studied tree agama (Acanthocercus a. atricollis) habitat use in the Magaliesberg mountain range in northern South Africa using sightings of marked individuals, and in a few cases, radio-telemetry. Acanthocercus a. atricollis preferentially selected thorn trees (46%; Acacia karroo), followed by common sugarbush (10%; Protea caffra) and dead trees (9%). The type of tree selected was unrelated to lizard age class or sex. Multivariate analysis failed to show any age class or sex effects for specific tree physical characteristics, but did reveal a preference for trees with greater diameter, canopy cover and incidence of parasitic plants. We suggest that more ‘complex’ trees may enhance crypsis, facilitate escape from predation, or provide a foraging advantage. Acanthocercus a. atricollis selected night-time perches higher than those used during the day, possibly further offsetting predation risk.     

Regeneration of tree species in the sub-tropical forest of Alaknanda Valley, Garhwal Himalaya, India

We studied the regeneration of tree species in the sub-tropical forest of Alaknanda Valley in Garhwal Himalaya, India. The overall regeneration status was fairly good in the study area. Seedling density ranged between 520 and 1,240 seedlings per ha while the density of saplings varied between 400 and 800 saplings per ha. Out of eight sites studied, five sites, viz., A1 , A2 , B1 , B2and C2contained the highest number of seedlings (280-480 per ha) and saplings (200-440 per ha) for Pinus roxburghii and remaining three sites viz., C1, D1and D2represented the highest number of seedlings (240-400 per ha) and saplings (200-240 per ha) for Anogeissus latifolius. The DBH class distribution of the tree species revealed that the highest number of individuals was concentrated in the lower diameter classes while smallest numbers were found in the higher diameter classes. Species such as Acacia catechu, Anogeissus latifolius, Dalbergia sissoo, Engelhardtia spicata, Lannea coromandelica, Mallotus philippensis and Pinus roxburghii have the largest number of saplings and seedlings in the lower DBH classes, suggesting that they have good regeneration potential. Other species such as Aegle marmelos, Bauhinia variegata, Bombax ceiba, Cassia fistula, Erythrina variegata, Haldinia cordifolia, Mangifera indica, Ougeinia oojeinensis, Phyllanthus emblica, Syzygium cumini, Terminalia alata and Toona hexandra have either no or very small number of saplings in the lower DBH classes, which indicates that the status of these species implies poor regeneration.     

Response of Three Young Douglas-Fir Plantations to Forest Fertilization with Low Rates of Municipal Biosolids

Abstract

The growth of three young (5-6 years since planting) Douglas-fir plantations fertilized with a single low-rate application of municipal biosolids, ranging from 17-19 dry Mg ha^-1, was studied. Stand measurements showed increases in DBH, height, average and total basal area, average and total volume and average and total dry-weight differences in the biosolids-fertilized vs. control. For instance, average per tree DBH was 14.7% greater than the controls, height by 2.7%, per stem basal area by 27%, per stem average volume by 33%, per stem average dry weight by 38%, basal area per hectare by 28%, volume per hectare by 32% and dry weight per hectare by 36% compared to untreated controls. Comparing differences in volume increases from initial growth periods with the latest growth period indicates that volume increases due to the biosolids treatment are continuing and apparently increasing over time. However, none of these observed differences were statistically significant (0.05 level) due to high variation within and between stands.     

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.     

Lasiodiplodia species associated with dying Euphorbia ingens in South Africa

Various species of Euphorbia occur in South Africa, including herbaceous, succulent and woody types. The largest of the succulent Euphorbia spp. in South Africa is Euphorbia ingens. These trees have been dying at an alarming rate in the Limpopo province during the course of the last 15 years. Investigations into the possible causes of the death have included the possible role of fungal pathogens. Amongst the fungi isolated from diseased trees were species in the Botryosphaeriaceae. The aim of this study was to identify these fungi using morphology and DNA sequence data of two gene regions (TEF 1-α and ITS). Results showed that Lasiodiplodia theobromae and L. mahajangana were present, representing the first report of Lasiodiplodia species on a succulent Euphorbia species. Pathogenicity studies showed that these Lasiodiplodia species can cause infections on healthy E. ingens trees, implicating them as contributors to the decline of E. ingens.     

Varietal Differences of Flood Tolerance during Germination and Selection of the Tolerant Lines in Common Buckwheat

Abstract

We evaluated the varietal difference in the flood tolerance of germinated seed in 17 Japanese varieties of common buckwheat (Fagopyrum esculentum Moench), including both local varieties and bred varieties or lines of different agroecotypes. Germinated seeds were flooded for 1 day in a growth chamber in June, July and August. The mean rate of seedling emergence from the seeds sown on different dates varied with the variety ranging from 20.4 to 57.4%. The mean emergence rate of summer agroecotypes (29.9%) was significantly lower than that of intermediate and late-summer agroecotypes (42.8 and 40.1%, respectively), and that of local varieties (44.2%) was significantly higher than that of bred varieties or lines (31.2%). These results suggest that inherent variation in flood tolerance was decreased by breeding as a result of a bottleneck effect. The local variety ‘Kitou zairai’, which exhibited a high and stable seedling emergence rate, may be a suitable choice in breeding for flood tolerance during germination. We also attempted to select for flood tolerance under mild selection pressure. Mass selection after four generations increased seedling emergence rate in five of six selected lines (with the exception of ‘Kitawasesoba’) compared with those of unselected populations, although the results varied with the line. These results indicate the possibility of breeding for flood tolerance during the germination period.     

Variation in Seed Shape and Husk Color in Japanese Native Cultivars of Common Buckwheat (Fagopyrum esculentum Moench)

Abstract

The variation in seed shape and husk color was investigated in 56 Japanese native cultivars of common buckwheat. Analysis of variance revealed highly significant differences among the cultivars in seed shape characteristics and husk colors. The 1000-seed weight (1000-SW) ranged widely, from 20.4 to 39.0 g, among the cultivars. The cultivars collected from the Kanto region of the mainland had a large length and width of seed and heavy 1000-SW. On the other hand, the cultivars from the Chugoku and Shikoku regions of Japan had a small length and width of seed. The length and width of seeds showed a high positive correlation. The cultivars with a high 1000-SW showed a slight difference between length and width of seed and were typically the triangular type in seed shape. The length/width ratio (L/W) depended on the width rather than the length of seed, though both were negatively correlated with the L/W. Highly positive correlations were found among the L*, a* and b* husk color value. The L* showed a highly positive correlation with growth duration, and the husk color of the cultivars became more deep black as growth duration decreased. The husk color of the cultivars from the Kyushu region (long growth duration) was grayish brown, but that of the cultivars from Nagano Pref. (the shortest growth duration) was characterized as typically deep black. The cultivars collected at lower latitude regions tended to have a lighter color of husk than those from higher latitude regions. The cultivars from the Tohoku region showed a smaller variation for seed size characteristics and 1000-SW, and the cultivars from the Kyushu region showed a smaller variation for husk color.     

高海拔地区百合栽培的花期调控技术初探

该文介绍了百合的生物学特征、对光照、温度及其他环境条件的要求以及这些因素对百合开花的影响,提出在高海拔地区对百合开花期的主要调控技术,为百合的进一步开发利用提供依据。     

野生黄蝉兰无菌快繁技术的研究

[目的]建立野生黄蝉兰的无菌快繁技术体系。[方法]以云南野生黄蝉兰为试材,以自交果实为外植体,通过在1／2MS基本培养基中,添加不同浓度的BA和NAA以及附加物质香蕉泥和活性碳进行培养,构建野生黄蝉兰的非共生萌发和快繁技术体系。[结果]野生黄蝉兰在2．0～2．5mg／LBA与0．5～1．0mg／LNAA的激素组合处理下,40d后种子萌发率可达93％;1／2MS＋2．5mg／LBA＋0．1mg／LNAA＋浓度8％香蕉泥培养的野生黄蝉兰丛芽增殖率为320％;1／2MS＋0．3mg／LNAA＋0．3％活性炭诱导生根率达100％,且植株长势正常。[结论]通过植物组织培养技术,成功构建了野生黄蝉兰的非共生萌发和快繁技术体系。