Effect of shade on biomass accumulation and partitioning for Eucalyptus camaldulensis sprouts

ABSTRACT

Eucalyptus is widely cultivated in homogeneous monocultures throughout the world alongside plants of the same age. Furthermore, the productivity of forest stands is highly dependent on how solar radiation is intercepted and used. Meanwhile, it is possible to consider cultivating trees of different ages in the same area, and thus under different regimes of available solar radiation, creating a sequence of plantings and harvestings and to develop Eucalyptus-based agroforestry systems. We have examined biomass accumulation of Eucalyptus camaldulensis along a shade gradient. Eucalyptus trees presented power-law responses to increasing irradiance for biomass, indicating it has low plasticity and is unable to maintain growth under lower irradiance levels. Biomass partitioning showed no dependence on available irradiation. Leaf density presented very little increase toward sunnier places meaning that an increment in Eucalyptus biomass would be mostly due to its increase in size and thus higher radiation interception. Careful management of shade will be a key consideration for the integration of Eucalyptus into agroforestry. With knowledge of the growth habits of different species, we will have the potential to propose more perennial ways in which to manage land and reduce anthropogenic disturbances by avoiding clear-cuts of areas that removes all plant structures.     

招鹰控鼠对高原鼠兔的防效试验

天祝县位于河西走廊东部,草原分布有高寒草甸、灌丛草甸等草甸草原,高原鼠兔是南部草甸草场的优势鼠类,危害严重,有效洞口密度达458个/hm2。为了进行有效防治,制作鹰架,招鹰控鼠。观测结果表明,招鹰控鼠方法控制高原鼠兔效果明显,第3年有效洞口密度平均降低37.5%,植被破坏率平均减少11.4个百分点,有效抑制了高原鼠兔种群数量的恢复,减少了牧草损失。     

Variation in selected solid wood properties of young Pinus patula from diverse sites in the Mpumalanga escarpment area in South Africa

Regression analyses identified ‘Growth Days’ (an index expressing site moisture availability) as the only site variable contributing significantly to the prediction to wood density (R² = 0.57), whereas the model predicting grain angle included only ‘Altitude’ (R² = 0.60). These results surfaced during an investigative study to quantify various sources of variation in wood properties and to quantify the effect of a number of site factors on wood properties of Pinus patula grown in the Mpumalanga escarpment area of South Africa. For this purpose, 10 trees were sampled from each of 17 diverse sites for wood property analyses. The effects of site, distance from the pith and differences between trees within site on wood density, transverse shrinkage, grain angle and dynamic modulus of elasticity were investigated. The site factors considered included a wide variety of soil and climatic factors. The effect of radial distance from the pith and differences between individual trees within sites were highly significant, accounting for most of the variation in wood properties. Although the effects of a number of site factors were statistically significant, they generally explained relatively small but important variation in wood properties among sites. The study not only quantified the effects of important sources of variation on a few key wood properties, but it also revealed that the extent of differences between sites can be explained in terms of some specific site factors. It is envisaged that the results will contribute significantly towards the refinement of current forest site classification systems for improved decision-making with respect to wood quality in intensively managed plantation systems.     

Tree Planting in an Urbanizing South Africa / BOOMAANPLANTING IN VERSTEDELIKENDE SUID-AFRIKA

The title of this paper might well read “Tree planting in an urbanizing and industrializing South Africa”, because in modern South Africa industry is prominent in the urban scene. The importance of trees in the urban landscape is stressed. Purposes for which trees are used in commercial, industrial and residential areas are listed. An account is given of tree planting in boulevards and avenues, state and civic centres, car parks, bus termini, recreational parks, botanical gardens and arboreta, zoological gardens, sports enclosures and children's playgrounds. The role of trees in industrial areas is discussed and the vegetating of mine dumps described. Passing reference is made to the uses of trees on the sea front. Tree planting for economic purposes by civic authorities is briefly touched upon. The value of trees in private gardens is underlined.     

Initial Moisture Content and Density and Drying Rate of Three Pine Species Growing in the Natal Midlands

In this the first of a two-part report, results are given of investigations into the vertical distribution of the moisture content and density of wood and bark, as well as into bark thickness, bark mass and bark volume of two age groups of Pinus elliottii and P. patula trees and one of P. taeda. Variation in wood and bark properties was affected more by position in the stem than by species and age. This precludes the determination of reliable mass/volume conversion figures if stem position is not taken into consideration. The mass loss of logs of the above species after various periods of drying and the development of mass/volume conversion figures will form part of a further report.     

Effects of Nitrogen Fertilizer and Planting Density on the Lignin Synthesis in the Culm in Relation to Lodging Resistance of Buckwheat

Abstract

Lodging is an important constraint limiting buckwheat yield and quality by bending or breaking culm on buckwheat production worldwide. This study was conducted with Ningqiao 01, a moderate lodging resistance cultivar of buckwheat, to determine whether lignin synthesis and lodging resistance of buckwheat are affected by nitrogen fertilizer and planting density. The results showed that the lignin content at the bottom of the 2nd internode was significantly and negatively correlated with lodging index and lodging percentage, but significantly and positively correlated with snapping resistance. The snapping resistance rose and then fell with the increase of nitrogen fertilizer. The snapping resistance decreased with the increase of planting density. The lodging index increased with the increase of nitrogen fertilizer and planting density. The lignin content and its related enzymes activities decreased with the increase of nitrogen fertilizer and planting density. These results suggested that the lignin content is closely related to the lodging resistance of buckwheat, and a higher lignin content could strengthen the lodging resistance of buckwheat. The increase of nitrogen fertilizer and planting density significantly increased the risk of lodging by decreasing the lignin content and its related enzymes activities at the bottom of the 2nd internode.     

A serial cross-sectional study of the prevalence of rabbit haemorrhagic disease on three farms in the lower North Island of New Zealand

AIM: To estimate over a 3-year period following the first release of rabbit haemorrhagic disease virus (RHDV) the prevalence of rabbit haemorrhagic disease (RHD) and the abundance of rabbits (Oryctolagus cuniculus) in an area that historically had low rabbit densities.

METHODS: Three farms grazing predominantly sheep and beef cattle, located close together and with low initial rabbit densities, were selected for study. RHDV had been deliberately released on all farms in December 1997. Farms were visited 2–3 times per year between June 1998 and April 2001. At each visit, rabbits were shot with the aid of spotlights at night and blood samples were collected for detection of RHDV antibodies. Rabbit carcasses were necropsied and the age of the animals was determined. Rabbit abundance on each property was measured throughout the study using spotlight night counts. Logistic regression was used to identify factors associated with the risk of carcasses being seropositive for RHDV.

RESULTS: Rabbit density differed initially between farms (8.2, 9.9, 2.3 rabbits per spotlight km in June 1998), and declined on all three properties over time (1.2, 2.4, 1.1 rabbits per spotlight km in November 2000). Highest antibody titres to RHDV were initially evident on the farm on which rabbits were most abundant. The average prevalence of seropositive rabbits overall was 21% (95% CI=15–28%). Female rabbits tended to be less likely to be seropositive for RHDV than males (OR=0.47; 95% CI=0.21–1.02). The odds of becoming seropositive were reduced for rabbits born in the breeding season of 1999–2000 (OR=0.17; 95% CI=0.05–0.64).

CONCLUSIONS: The temporal pattern of outbreaks measured by peaks of seroprevalence differed between closely-spaced farms when they had different rabbit densities, but were similar when rabbit densities were similar. Microclimate and vegetation influencing abundance of insect vectors for RHDV and intrinsic population-related factors like rabbit breeding behaviour are also likely to be involved in local patterns of spread.     

不同密度麦后直播棉生育特性与经济效益分析

通过麦后直播棉不同密度试验及其与麦套棉经济效益的对比分析,初步探明麦后直播棉的生长发育规律,筛选出麦后直播棉适宜的种植密度为9.0万株/hm2,此密度下产量可达3 738.0 kg/hm2;麦后直播棉经济效益优于传统麦套棉.     

不同基因型鲜食玉米品种适宜种植密度研究

[目的]探讨3种不同基因型鲜食玉米（Zea mays L．）品种在不同地区的适宜种植密度。[方法]3个玉米品种分别为高秆大穗型品种京科糯2000（北京市农林科学院玉米研究中心）、矮秆型品种都市丽人（海南绿川种苗有限公司）、半紧凑或紧凑型品种玉美头601（广西壮邦种业有限公司）。种植密度分别为4．2万、4．8万、5．4万、6．0万、6．62;iq-／hm。。[结果]京科糯2000、都市丽人、玉美头601这3种类型玉米品种在不同地区的最佳种植密度不尽相同。对于高秆大穗型品种京科糯2000,在合浦栽培时最佳种植密度为6．0万株／hm。,在玉林栽培时最佳种植密度为4．8万株／hm。,在崇左栽培时最佳种植密度为6．0万株／hm2。对于矮秆型品种都市丽人,在合浦栽培时最佳种植密度为4．8万株／hm。,在玉林栽培时最佳种植密度为6．0万株／hm。,在崇左栽培时最佳种植密度为6．6万株／hm。对于半紧凑或紧凑型品种玉美头601,在合浦栽培时最佳种植密度为6．6万株／hm。,在玉林栽培时最佳种植密度为5．47万株/hm。,在崇左栽培时最佳种植密度为6．07万株~hm。【结论】该研究可为鲜食糯玉米的高产优质栽培提供参考。     

2003-2018年龙南县地闪时空分布特征分析

利用江西省雷电监测系统获取的2003—2018年赣州地区范围内的地闪定位资料,对闪电的基本特性、日变化、月变化以及闪电密度的分布等方面进行了分析。结果表明,闪电强度平均值为8.27 k A;负地闪数占总闪电数的95.4%,平均闪电强度为-9.94 k A;正负闪电比为4.6%,正闪平均强度为26.38 kA;闪电的月变化表现为单峰型,主要出现在4—9月,其中6—8月最为频繁;一天中闪电活跃期为13:00—19:00;闪电密度分布由北往南依次减少。