异担子菌及其病害防治的研究现状

北半球针叶林最严重的森林病害是由广义的多年异担子菌(Heterobasidion annosum sensu lato)引起的干基白色腐朽病,但近年的研究表明多年异担子菌并不是单一的物种,目前在欧洲已分出3个独立的种,即原始多年异担子菌(Heterobasidion annosum sensu stricto)、小孔异担子菌(Heterobasidion parviporum)和冷杉异担子菌(Heterobasidi-on abietinum),它们生物学习性、形态结构,生态学,寄主范围和发生区域均有差异。应用大伏革菌Phlebiopsisgigantea对该类病害进行生物防治是较好的方法。将中国东北和西南(云南)的异担子菌单孢菌株与欧洲的三种异担子菌进行交配,结果表明中国东北和西南地区的异担子菌与原始多年异担子菌无性亲和反应,而与小孔异担子菌有性融合反应,因此中国东北和西南地区的异担子菌是小孔异担子菌,目前中国并不存在原始多年异担子菌。由于原始多年异担子菌和冷杉异担子菌均为严重的森林病原菌,应将其作为对外检疫对象。     

Estimating “autotrophic” belowground respiration in spruce and beech forests: decreases following girdling

Seasonal fluxes of CO₂ from soil and the contribution of autotrophic (root + mycorrhizal) to total soil respiration (SR) were estimated for a mixed stand of European beech (Fagus sylvatica) and Norway spruce (Picea abies) in Central Europe. Mature trees of each species were girdled in August 2002 to eliminate carbohydrate allocation to roots. SR was measured at distances of 0.5, 1.0, and 1.5/2.0 m from the bole of each tree at 1–2 weeks intervals throughout the fall of 2002 and monthly during the spring and summer of 2003. The contribution of roots and mycorrhizae to total SR was estimated by the decrease in SR compared to ungirdled control trees to account for seasonal patterns evident in controls. SR decreased with soil temperature in the fall 2002 and increased again in 2003 as soil warmed. During most of the study period, SR was strongly related to soil temperature. During the dry summer of 2003, however, SR appeared to be uncoupled from temperature and was strongly related to soil water content (SWC). Mean rates of SR in beech and spruce control plots as well as root densities did not show a clear pattern with distance from the bole. SR decreased to levels below controls in beech within a few days after girdling, whereas spruce did not show a significant decrease until October 2002, 6 weeks after girdling. In both beech and spruce, decreased SR in response to girdling was greatest closest to the bole, possibly reflecting increased mycorrhizal activity close to the bole. Autotrophic respiration was estimated in beech to be as much as 50% of the total SR in the stand. The contribution of autotrophic respiration was less certain for spruce, although close to the bole, the autotrophic fraction may contribute to total SR as much as in beech. The large fraction of autotrophic respiration in total SR requires better understanding of tree level stresses that affect carbon allocation below ground.     

Planted conifer seedling growth under two soil thermal regimes in high-elevation forest openings in interior British Columbia

A field trial was conducted investigating the single season growth response of 1+0 313 PSB Engelmann spruce (Picea engelmannii Parry ex Engelm.) and lodgepole pine (Pinus contorta Dougl. ex Loud.) seedlings planted into two different soil thermal regimes at three high-elevation locations spanning 200 km in the Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone in the Cariboo Mountains of central British Columbia. Temperature treatments represented the extremes of soil temperature commonly found in high-elevation clear-cuts. A warm soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 18 to 25 °C at –10 cm) consisting of a bare mineral soil hummock (average dimensions of 100 cm × 100 cm × 40 cm) was contrasted with a cool soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 10 to 13 °C at –10 cm) comprised of organic forest floor overlying mineral soil. By the end of the growing season, seedlings of both species planted into the warm treatment generally exhibited greater root, stem, foliage, and total seedling biomass than cool treatment seedlings. Measurements of root growth at 30, 60, and 90 days after planting showed that total root number and total root length were consistently greater for warm treatment seedlings than for cool treatment seedlings. Root growth was greater from the bottom rather than from the side of the root plug for all seedlings. These results suggest that the effect of low soil temperatures on outplanted styroblock conifer seedlings is pronounced and may be limiting growth performance in high-elevation plantations in British Columbia. We recommend silvicultural treatments that secure natural regeneration, ensure that warmer microsites are always planted, and utilize seedling stocktypes able to make rapid lateral root growth into warmer surface organic horizons.     

Fine roots refilling process in an artificial gap in a Picea mongolica forest

Picea mongolica is an endemic but endangered species in China. The spruce forest is only found in sandy forest-steppe ecotones. In this study, we examined the initial response of the quantity and refilling process of fine roots in an artificial canopy gap with a diameter of 36 m in a P. mongolica forest. Under the canopy, the fine root length densities of trees, shrubs and herbs were 2,622, 864 and 3,086 m·m–2, respectively. The fine root biomass of trees, shrubs and herbs were 148, 62 and 65 g·m–2, respect...     

Morphological plasticity of cotton roots in response to interspecific competition with pecan in an alleycropping system in the southern United States

A study was conducted in northwest Florida, USA, to investigate root development and morphology of cotton (Gossypium hirsutum L.) under pecan (Carya illinoensis K. Koch) trees in an alleycropping experiment. Root:shoot ratio, root biomass, total root length and root length density were examined under three treatments: (1) barrier (separating belowground interspecific competition by trenching to a depth of 120 cm and installing polyethylene barrier), (2) non-barrier (root systems were free to interact), and (3) monoculture of cotton (without above and belowground interspecific competition with trees). Results indicated that plants in the barrier and non-barrier treatments had lower root:shoot ratios compared to the monoculture treatment. Belowground competition for resources between pecan and cotton in the non-barrier treatment resulted in 25 and 33% reduction of total root length (359 cm) when compared to that of the barrier (477 cm) and monoculture (539 cm) treatments, respectively. The non-barrier plants also exhibited the lowest root length density. Specific root length was highest for the monoculture (179 cm g⁻¹) and lowest for the non-barrier treatment (146 cm g⁻¹) with the barrier treatment being intermediate (165 cm g⁻¹). Interspecific competition with pecan significantly altered root development and morphology of cotton plants. Research in agroforestry should take into account the developmental differences in root systems of the associated crop species so that better models incorporating nutrient and water uptake can be developed.     

Root parameters of forest trees as sensitive indicators of acidifying pollutants: a review of research of Japanese forest trees

The root parameters of forest trees can be indicators of a changing environment. We summarize the results of root studies with regard to the effects of acidifying pollutants, especially soil acidification and aluminum toxicity, on various root parameters of Japanese forest trees under experimentally controlled conditions. All root parameters such as biomass, morphology, nutritional status, and physiology can be regarded as indicators, because, under laboratory conditions, root responses occur prior to the responses in the aboveground parts. However, considering the conditions of forest sites, the nutritional status and physiological changes are better indicators of soil acidification and Al stress than the biomass and morphological response. The currently available data suggest that the most important indicator is the Ca/Al molar ratio in roots of Japanese tree species. In order to predict and detect the initial effects of soil acidification, we postulate that the specific root response to the Ca/Al molar ratio of tree roots should be considered as a parameter for use in long-term forest monitoring sites.     

不定根发生机理的研究进展

不定根的发生是一个复杂的过程,许多因子在这个过程中起调控作用。文章介绍了国内外关于基因表达、内源激素水平、酶的活性以及多胺水平影响不定根发生机理的研究进展。     

Estimating the production and mortality of fine roots in a Japanese cedar (Cryptomeria japonica D. Don) plantation using a minirhizotron technique

Fine roots are a key component of forested ecosystems, but available information is still limited. This study examined the production and mortality of fine roots less than 1 mm in diameter in a Japanese cedar (Cryptomeria japonica D. Don) plantation located on the Kanto Plain in central Japan. We used a minirhizotron technique in combination with soil coring, and collected data for 1 year (May 2002–May 2003). Fine root production and mortality were determined from changes in the lengths of individual fine roots on minirhizotron tubes. Both fine root production and mortality rates were greater in the upper soil than in lower soil levels. Both rates were seasonal, with higher values in summer than in winter; this trend was more pronounced in upper soil levels. These results suggest that environmental conditions, such as temperature or soil properties, affect the production and mortality rates of fine roots. Fine root production and mortality occurred simultaneously, and their rates were similar, which may have led to unclear seasonal changes in fine root standing crop estimates. Soil coring indicated that the fine root biomass of this stand was about 120 g m⁻², of which 40% was from Japanese cedar. The estimated rates of dry matter production and mortality of total fine roots, including understory plants, were both approximately 300 g m⁻² year⁻¹.     

A Study on Water Exchange in Root Zone of ProtectiveForest Ecosystem in Loess Area

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