Direct measurements of carbon exchange at forest disturbance sites: a review of results with the eddy covariance method

ABSTRACT

Boreal and temperate forests cover a large part of the Earth. Forest ecosystems are a key focus for research because of their role in the carbon (C) balance and cycle. Increasing atmospheric temperatures, different disturbances (fire, storm and insects) and forest management (clear-cutting) will change considerably the C status of forest ecosystems. Using the eddy covariance (EC) method, we can define interactions among environmental factors that influence the C-balance and whether a forest ecosystem is functioning as a C-sink or C-source or possibly is C-neutral. In our review of published studies of different disturbances, we found that most of the post-disturbance studies based on EC method focused on the effects of forest fire and clear-cutting, only a few studies studies focused on the effects of storms and insects. Generally a forest is a C-source until several years after disturbance and then a forest is able to absorb C and become a C-sink. Recovery to C-sink status required up to 20 years in clear-cut areas. Recovery following wildfire disturbance was much longer, possibly more than 50 years. Recovery to C-sink status required approximately 5 years after storm and insect outbreak, however we can not predict overall recovery period because of the missing data.     

干巴菌菌丝营养生理特性的初步研究

本文报道了不同碳源、氮源、微量元素及维生素培养基对干巴菌菌丝生长的影响。试验表明，干巴菌菌丝利用最好的的碳源是葡萄糖，其次是蔗糖。利用最好的氮源是硝酸钙，其次是硝酸铵和硫酸铵，对蛋白胨和尿素的利用效果差。缺少碳源或氮源时，菌丝生长细弱、稀少，不形成原基。微量元素和维生素均对干巴菌菌丝生长有促进作用，其中以锰、铜和维生素Ｂ２的作用尤为突出。     

Effects of shade,altitude and management on multiple ecosystem services in coffee agroecosystems

Agroforestry systems provide diverse ecosystem services that contribute to farmer livelihoods and the conservation of natural resources. Despite these known benefits, there is still limited understanding on how shade trees affect the provision of multiple ecosystem services at the same time and the potential trade-offs or synergies among them. To fill this knowledge gap, we quantified four major ecosystem services (regulation of pests and diseases; provisioning of agroforestry products; maintenance of soil fertility; and carbon sequestration) in 69 coffee agroecosystems belonging to smallholder farmers under a range of altitudes (as representative of environmental conditions) and management conditions, in the region of Turrialba, Costa Rica. We first analyzed the individual effects of altitude, types of shade and management intensity and their interactions on the provision of ecosystem services. In order to identify potential trade-offs and synergies, we then analyzed bivariate relationships between different ecosystem services, and between individual ecosystem services and plant biodiversity. We also explored which types of shade provided better levels of ecosystem services. The effectiveness of different types of shade in providing ecosystem services depended on their interactions with altitude and coffee management, with different ecosystem services responding differently to these factors. No trade-offs were found among the different ecosystem services studied or between ecosystem services and biodiversity, suggesting that it is possible to increase the provision of multiple ecosystem services at the same time. Overall, both low and highly diversified coffee agroforestry systems had better ability to provide ecosystem services than coffee monocultures in full sun. Based on our findings, we suggest that coffee agroforestry systems should be designed with diversified, productive shade canopies and managed with a medium intensity of cropping practices, with the aim of ensuring the continued provision of multiple ecosystem services.     

Stability of co‐composted hydrochar and biochar under field conditions in a temperate soil

Hydrothermally converted biomass (hydrochar) is evaluated as a carbon‐rich soil amendment in addition to pyrogenic biochar. After assessing the suitability of hydrochar for use in agriculture, its environmental safety and comparing its chemistry with that of biochar, we describe a field trial established at Halle (Germany) under natural conditions for a temperate climate and without further external management practices. The main objective of our study was to analyse the stability and hence the C sequestration potential of composted chars over a period of 2 years. Four treatments (no amendment control, compost, co‐composted hydrochar and co‐composted biochar) in fourfold field replication were chosen to make a direct comparison of biochar and hydrochar under field conditions. The total organic carbon and total N increased in all treatments in comparison with the control but only in biochar‐amended treatments were N concentrations more stable. Composted biochar showed significantly more black carbon content in topsoil, sampled some months after application, compared with all other treatments. We show that hydrochar is less suitable for long‐term C sequestration in comparison with biochar but has potential for soil amelioration because it delivers essential nutrients. On the other hand, biochar is richer in polyaromatic C than hydrochar and therefore is more stable in the long term. We assessed biochar stability using the black carbon analysis of the different soil samples.     

Reliable data on fine-root turnover from sequential soil coring in an old carbon budget for a 14-year-old Scots pine from the late 1970s: Comments on Majdi et al., Scandinavian Journal of Forest Research 22: 299–303

Abstract

Comprehensive data from different research workers were included in the compilation of a carbon budget for a 14-year-old Scots pine (Pinus sylvestris) in the late 1970s, within the SWECON project (the Swedish Coniferous Forest Project). In a recent paper in the Scandinavian Journal of Forest Research, the authors published a surprisingly high turnover rate of fine roots (7.4 year^?1), maintaining that they had used our old SWECON data from our sequential soil coring. However, a close examination of our original data suggests a turnover of fine-root biomass of 2.3 and for fine-root standing crop (biomass+necromass) of 2.0 year^?1. Supporting evidence is available from other forest sites suggesting that our turnover rates were correctly estimated. Certain errors may exist in different parts of our old carbon budget, e.g. some measurements were carried out for different parts of the tree, while others were attributed to the whole stand. The sequential soil coring technique still remains the best technique available for fine-root growth and turnover estimates in forest stands.     

黄瓜单性结实果实发育与碳氮变化的关系

对黄瓜单性结实品系P 116 8和非单性结实品系UP 3315进行授粉和不授粉处理 ,P 116 8在不授粉的情况下 ,仍具有较好的结实性能 ,其单果质量、果长和果实体积均接近于授粉后生长的果实 ,非单性结实品系UP 3315在不授粉的情况下幼果在花后 3d(天 )就停止发育 ,不能形成产量。随着果实的生长发育 ,果实内碳、氮含量迅速增加 ,花后单果可溶性总糖和蛋白质含量与单果质量呈正相关关系     

猴头菌营养生长最佳条件研究

对4个猴头菌菌株的研究表明,猴头菌营养生长阶段最佳碳源为淀粉,最佳氮源为麦麸及蛋白胨,最适碳氮比为20∶1,最适pH为4.0～5.0,最适温度为25～29℃。     

Progress of Study on Oriented Growth of Carbon Nanotubes

Owing to unique structure and characteristics of carbon nanotubes, much more are attracted attentions since they were discovered. In recent years, carbon nanotubes have been successfully synthesized by various methods. Especially, highly aligned carbon nanotubes were grown by chemical vapor deposition (CVD) and the oriented growth of carbon nanotubes became realized, resulting in many applications of carbon nanotubes and researches on them. In the work, the methods and mechanisms of orientation growth of carbon nanotubes were reviewed, and it was analyzed and discussed that different methods influenced on the process of growing carbon nanotubes. Simultaneously, it was emphatically analyzed that catalyst particles affected on orientation growth of carbon nanotubes during their growth.     

Associations between grain yield and carbon isotope discrimination in cowpea

Twenty cowpea (Vigna unguiculata L. Walp.) genotypes, comprising Kenyan cultivars and Kenyan and introduced breedings lines, were grown in 15 replicated field trials carried out at three locations in semi-arid eastern Kenya over four seasons. Grain and straw yields and the carbon isotope discrimination (Δ) of this material were determined, and days to flowering and maturity observed.None of the seasons in which the trials were conducted was appreciably drier than the long term average for the sites, and some trials received excessive rain. Averaging the data for the 15 trials, one genotype yielded much less grain (77 g m⁻²) than the 19 others, whose yield ranged from 125 to 177 g m⁻² (average 148 g m⁻²). Trial mean yield trials had a high straw Δ (r = +0.567) and had received more rain between flowering and maturity (r = +0.428) than lower yielding ones. Among genotypes, averaging over trials, the correlation coefficient (r) between grain yield and grain Δ was +0.394, and between grain yield and straw Δ, +0.460. Early genotypes had the highest grain Δ and straw Δ. The correlation among genotypes between date of flowering and grain Δ was −0.632 and with straw Δ, −0.502. When comparisons were made among trials, there was no clear relationship between the strength of the correlations among genotypes between grain yield and straw Δ or grain Δ and the degree of stress experienced by a trial (as indicated by the rainfall it had received). It appeared that this was because the variances of grain Δ and straw Δ were greater in the most droughted trials, whereas the variance of yield was greatest in the least droughted trials.It is concluded that the genetic correlation between grain yield and either grain Δ or straw Δ is unlikely to be strong enough to make either Δ a useful surrogate or adjunct in selecting for high yield in the segregating generations of a breeding programme for semi-arid eastern Kenya, but that Δ may be of value in the selection of parent genotypes.