Diversity of ectomycorrhizal fungi in Britain: a test of the species–area relationship, and the role of host specificity

The host range of ectomycorrhizal (ECM) fungi in Britain was examined by compilation of a data matrix from published literature sources, based primarily on accounts of sporocarp associations with particular host genera. Information was gathered for 577 species of ECM fungi belonging to 51 genera, and 25 genera of host trees, representing the majority of ECM fungal species and host genera recorded in Britain.
Pronounced variation was recorded in the number of ECM fungal species associated with different host genera, with over 200 species recorded with Betula , Fagus , Pinus and Quercus . There was a positive linear relationship ( r ²=0·47, P =0·007) between the number of species of ECM fungi associated with different host genera and the total area occupied by each tree genus in Britain (both values log-transformed). There was also variation in the number of species of ECM fungi which were apparently specific to particular host genera, values ranging from zero (in 15 genera) to >40 in the case of Betula and Fagus . In total, 233 fungal species appeared to be specific to a single host genus (i.e. 40% of those surveyed). Comparison of the ECM mycota associated with different host genera by PCA accounted for 17% of the total variation, with genera belonging to the Fagaceae ( Quercus , Fagus and Castanea ) tending to cluster together, indicating a degree of overlap in their ECM associates. Exotic conifer species, which displayed a lower ECM diversity than would be expected from their distributional areas, were characterized by a high degree of overlap with the ECM associates of Pinus and Betula .
These results indicate that the abundance of different genera of host trees and variation in host specificity could provide a basis for understanding patterns of diversity in ECM fungi within Britain.     

POSTDISPERSAL SELECTION FOLLOWING MIXED MATING IN EUCALYPTUS REGNANS

Eucalyptus regnans is a mass flowering, tall forest tree of southeastern Australia with a mixed mating system. A field trial containing randomized single tree plots of self, outcross, and naturally open-pollinated (OP) progenies of 13 parents from two natural populations was surveyed over 15 yr. Inbreeding depression in survival at 15 years was 67% for selfs, one of the highest levels reported for a tree species, and differed little between populations. OP progenies were intermediate and the difference in fitness among the three cross types indicated that at planting, 59% were derived from outcrossing. However, with selection against the inbred progenies, this increased to 83% by 15 yr of age. Most selection against selfs occurred after four years, coincident with canopy closure and the apparent onset of intense competition.     

托里桉混交林小气候特点初探

1982年8月份,我们对3年生已经郁闭的托里桉(Eucalyptus torelliana)+大叶相思(Acaciaauriculiformis)混交林与托里桉纯林,进行了全月小气候观测,前者与后者比较:地面日平均温度低1.7℃;日平均最高温度低6.7℃;5、10、15、20厘米土深日平均温分别低1.6℃、1.5℃、1.4℃,1.4℃;地面与1.5米高的平均光照强度分别减少3.7倍与6.7倍。表现出混交林良好的生态效应。由于观测时期为广东的台风雨季,常有间歇性降雨,故相对湿度与蒸发量差异不显著。     

GRAFT UNION FORMATION IN DOUGLAS-FIR

Greenhouse-grown Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) graft unions were examined between 2 and 84 days after grafting. Room temperature was maintained at 60-70 F throughout the growing season. In most respects grafts of Douglas-fir followed development patterns previously reported for spruce and pine grafts, but specific differences were noted in contributing cell types, time of formation, and mode of healing. The time interval from first occurrence to occurrence in 80% of the grafts is as follows: contact layers, 2 days; callus bridges, 10-14 days; periderm, 10-17 days; cambia, 17-23 days. Callus bridges were generally of secondary phloem or cortex origin. Callus lignification began along cut edges of the union at 14 days and was completed across the entire length of the union by 17 days. Lignified tracheids were continuous across union zones at 35 days. When proper grafting techniques were used, all tissue systems necessary for a successful union were present 35 days after grafting. Poor grafting techniques at times retarded cambium formation for 3 months or more.     

桉叶油的化学成分

云南产蓝桉叶油,即桉叶油(eucalyptus oil)经GC/MS/DS分析,鉴定了其中的17个已知化合物,主要化学成分是桉叶油素(66.42％)和α-蒎烯(27.18％),但不含有黄樟油素,是云南的一大骨干香料油产品。