复合农林业系统碳贮量研究进展

CO2作为一种主要温室气体,其固存与排放对全球气候变化有重要影响。本文以复合农林业系统为研究对象,介绍了农林复合类型中林木、农作物、凋落物、土壤碳贮量的估算方法,并指出目前碳贮量研究方面的问题和发展方向,为碳循环研究提供部分基础研究数据和理论支持。     

黑龙江林业的发展应该关注森林碳汇问题

森林生态系统在全球碳循环与平衡中具有极为重要的和不可替代的地位和作用,随着《京都议定书》正式生效,森林碳汇问题已经越来越受到世界各国的重视。黑龙江省森林资源丰富,是我国最主要的林区,巨大的“碳汇”既具有重要的生态功能,也蕴藏着潜在的巨大经济利益,因此,研究我省应对《京都议定书》生效、开展森林碳汇项目的对策研究是极为必要的。     

森林、造林、再造林和毁林的定义与碳计量问题

森林的定义与土地利用，土地利用变化和林业（LULUCF）碳吸收或排放的计量密切相关。同时也是造林，再造林和毁林（ARD）定义的基础；ARD的定义直接关系到《京都议定书》第三条第三款（3.3条款）ARD活动引起的汇清除的计量和大小。本文基于森林有关定义国际研讨会和IPCC有关LULUCF碳计量的方法学指南的研讨和交流。通过大量资料收集和信息查询，对主要国际公约，国际组织和各国森林和ARD的定义进行了调研。并分析讨论了不同定义及其对LULUCF碳计量的影响。提出了碳计量中需要关注的焦点问题。     

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N₂ fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the ¹⁵N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg [N] ha^–1 yr^–1) originated from N₂ fixation. Grass production averaged 13 Mg ha^–1 yr^–1 and N export in cut grass was 195 kg [N] ha^–1 yr^–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha^–1 yr^–1. Carbon sequestration averaged 1.9 Mg [C] ha^–1 yr^–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha^–1 yr^–1, corresponding to 30% of N₂ fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha^–1 yr^–1) and litter decomposition (40 kg [N] ha^–1 yr^–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. This revised version was published online in June 2006 with corrections to the Cover Date.     

温室效应对红桦泡囊丛枝菌根侵染率和侵染强度的影响

本试验以红桦（Betulaalbo-sinensis）为材料，研究不同处理条件下，AMF侵染率和侵染强度的变化规律。结果表明：（1）在自然状态下，AMF的侵染率和侵染强度高；（2）光照强度可提高AMF的侵染率和侵染强度；（3）温度升高和二氧化碳浓度倍增加强AMF的侵染强度；（4）温度差值在4℃～7℃时对AMF侵染率有促进作用；（5）温度差值在2℃～4℃和二氧化碳浓度倍增对AMF侵染率夏季起抑制作用，秋季起促进作用；（6）从夏季到秋季，AMF侵染率下降，而二氧化碳浓度倍数却使AMF侵染率上升。     

Energy and carbon dioxide (CO2) balance of logging residues as alternative energy resources: system analysis based on the method of a life cycle inventory (LCI) analysis

Using the method of a life cycle inventory (LCI) analysis, the energy balance and the carbon dioxide (CO₂) emission of logging residues from Japanese conventional forestry as alternative energy resources were analyzed over the entire life cycle of the residues. The fuel consumption for forestry machines was measured in field experiments for harvesting and transporting logging residues at forestry operating sites in Japan. In addition, a total audit of energy consumption was undertaken. It involved an assessment of materials, construction, and the repair and maintenance of forestry machines as well as the costs associated with an energy-conversion plant. As a result, the ratio of energy output to input was calculated to be 5.69, indicating that the system examined in this study could be feasible as an energy production system. The CO₂ emission per MWh_e (e: electricity) of the biomass-fired power generation plant was calculated to be 61.8kgCO₂/MWh_e, while that of coal-fired power generation plants in Japan is 960kgCO₂/MWh_e. Therefore, the reduction in the amount of CO₂ emission that would result from replacing coal with biomass for power generation by as much as 3.0 million dry-t/year of logging residues in Japan was estimated to be 1.66 million tCO₂/year, corresponding to 0.142% of the national CO₂ emission. This study provides evidence that Japan could reduce its domestic CO₂ emission by using logging residues as alternative energy resources.     

Effects Of Thinning In a Water-Limited Holm Oak Forest

ABSTRACT

A natural holm oak forest was selectively thinned to test thinning as a tool to reduce tree mortality, increase productivity, and reverse the recent regression of the dominant species (Quercus ilex) induced by climate change. Thinning increased aboveground productivity and reduced stem mortality in this Mediterranean forest during four years just after thinning, contributing to the maintenance of forest functioning under changing climatic conditions. Q. ilex was the only species positively affected by the thinning: stem growth increased for all stem sizes, and mortality was significantly lower in thinned plots. On the contrary, mortality rates of Phillyrea latifolia and Arbutus unedo were not significantly lower. Stem growth increased for P. latifolia only in the smallest stem-size class. Our results highlight the suitability of selective thinning for improving the forest productivity and ensuring the conservation of Mediterranean coppices. Other benefits of selective thinning, such as a decrease in the risk of fire dispersion and an increase in the water supply for human populations, are also discussed.     

The North American long-term soil productivity experiment: Findings from the first decade of research

First decade findings on the impacts of organic matter removal and soil compaction are reported for the 26 oldest installations in the nation-wide network of long-term soil productivity sites. Complete removal of surface organic matter led to declines in soil C concentration to 20 cm depth and to reduced nutrient availability. The effect is attributed mainly to the loss of the forest floor. Soil C storage seemed undiminished, but could be explained by bulk density changes following disturbance and to decomposition inputs of organic C from roots remaining from the harvested forest. Biomass removal during harvesting had no influence on forest growth through 10 years. Soil compaction effects depended upon initial bulk density. Soils with densities greater than 1.4 Mg m⁻³ resisted compaction. Density recovery was slow, particularly on soils with frigid temperature regimes. Forest productivity response to soil compaction depended both on soil texture and the degree of understory competition. Production declined on compacted clay soils, increased on sands, and generally was unaffected if an understory was absent.     

The carbon budget of an adult <Emphasis Type="Italic">Pinus cembra</Emphasis> tree at the alpine timberline in the Central Austrian Alps

We investigated carbon (C) uptake and respiratory losses of an adult Pinus cembra tree at the alpine timberline throughout an entire year by means of an automated, multiplexing gas exchange system. These chamber measurements were then combined with biomass data for scaling up the C budget to the tree level. Integrated over an entire year, the cumulative C gain of the tree under study was 23.5 kg of C in 2002. The daily C balance was negative for 5 months and the estimated total wintertime respiratory losses were 9% of the amount of C fixed during the growing season. The total annual C loss of the tree consumed 55% of the annual net C gain and the remaining surplus was stored in new tissues (36%) and used for fine root growth (9%). Thus, the overall C budget of P. cembra at the upper timberline is balanced fairly well, although the C sink strength in fine roots is strongly limited owing to low root zone temperatures when compared to conifers at lower elevation sites.     

Rapid production of high-strength cement-bonded particleboard using gaseous or supercritical carbon dioxide

This study deals with the effects of curing treatment with gaseous and supercritical carbon dioxide on the properties of cement-bonded particleboard (CBP) manufactured by the conventional cold-pressing method. The hydration of cement and the mechanism of improvement were examined using X-ray diffractometry (XRD), thermal gravimetry (TG-DTG), and scanning electron microscopy (SEM) observations. The results are as follows: (1) The curing of cement was accelerated concomitantly with the improvement in mechanical and dimensional properties of CBP significantly by curing with gaseous or supercritical carbon dioxide. (2) Supercritical carbon dioxide curing imparted boards optimal properties at a faster rate than did gaseous curing. (3) Accelerated formation of calcium silicate hydrate and calcium carbonate and the interlocking of those hydration products on the wood surface are potentially the main reasons for the superior strength of carbon dioxide-cured boards.