MCPB-ethyl疏花对富士苹果授粉受精及胚珠发育的影响

通过在花期用MCPB-ethyl处理,对富士苹果花粉的发芽、花粉管的伸长以及胚珠的发育等进行了形态方面的观察和探讨,以阐明MCPB-ethyl的疏花机制。结果表明,MCPB-ethyl对花粉的发芽及花粉管的伸长没有影响,整个受精过程与对照相同,没有发现异常。但受精后胚乳核只进行了数次分裂便停止生长,此后珠皮、珠心细胞迅速解体。根据以上结果,认为MCPB-ethyl的疏花效果不是通过影响花粉的发芽或花粉管的伸长阻碍受精所致,而是使胚和胚珠的发育停止,形成离层导致了落花。     

不同副梢处理对赤霞珠葡萄生长和结果的影响

试验以3～5年生赤霞珠葡萄(CabernetSauvignon)为试材,对其进行了不同的副梢处理:只留顶端1个副梢、副梢绝后处理、花序以上反复摘心、副梢全留。2年的结果表明:副梢全留(所有副梢全留2～3片叶反复摘心)处理的叶面积指数高,果实的产量和品质高。因此,相对多留副梢叶片,改善了叶幕叶龄结构,提高了果实品质,有利于枝梢成熟。     

Water spray as a potential thinning agent for date palm flowers (Phoenix dactylifera L.) c.v. ‘Lulu’

Flower or fruit thinning is a critical cultural practice in the date palm production chain that affects fruit development, quality and yield and regulates tree yearly bearing. Development of a save and economic thinning agent for date palm is critically required especially under harsh conditions. During 2004 and 2005 seasons, water spray for 3 min was applied at different times following mechanical pollination on ‘Lulu’ date palm cultivar growing under Al-Ain oasis conditions. The results showed that water spray following pollination generally decreased fruit set percentage to different extent depending of the time of application. In this respect, the most effective treatment was water spray after 4 h following pollination. This treatment significantly decreased fruit set percentage (48%) compared to the control (79%), as the mean of both seasons. However, the other treatments including water spray 1 h before pollination also decreased fruit set percentage but to a lesser extent. Fruit quality characteristics especially fruit and flesh weight, length and diameter were significantly increased by water spray treatments during the 2004 season, in contrast to the 2005 season. Thinning with water significantly decreased both bunch weight and total yield per tree at the Tamr stage especially when applied after 4 h following pollination. To the best of our knowledge, this is a pioneer study investigating the role of water as a potential thinning agent for date palm flowers. The use of water spray as a save and economic thinner needs, however, more research work to justify the time following pollination and duration of application which may vary upon cultivar, method of pollination and district.     

水杉人工林抚育间伐的效果比较

在１５ａ生水杉人工林内设立标准地，定量机械间伐，定期测定生长量，对抚育间伐７ａ后的效果及经济效益进行分析，结果表明：（１）不同初植密度的林分采用较小的强度ｐｎ＝２５％，３３％进行间伐，与对照林分相比，平均每公顷生长量分别提高５．９７，９．２７ｍ３，增加９．５７％，１４．８７％；采用较大强度ｐｎ＝５０％进行间伐，与对照林分相比，平均每公顷生长量下降９．７ｍ３，减少１５．５７％。（２）抚育间伐过的林分（间伐强度ｐｎ＝２５％，３３％，５０％）与对照林分相比，单位面积保留木平均生长率分别提高１．３４％，２．００％，１．９７％。（３）抚育间伐的林分与对照林分相比，平均每公顷总产值和利润分别增加６２７８，５７８４元，增长７．７％，９．５％。     

Long-term growth analyses of Japanese cedar trees in a plantation: neighborhood competition and persistence of initial growth deviations

The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37–0.46) of the variation in dbh growth during a 5–11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09–0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50–0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.     

间伐小径木指接技术研究

间伐材指接胶合加工，变短材为长材，弯材为直材，为合理，有效利用间伐材开辟了新路。对间伐材木材含水率，指接端压的大小和时间，指接后养护时间，涂胶量，指榫规格等对指接材抗弯强度的影响进行了研究，并测定了苯酚，间苯二酚，甲醛树脂胶胶合的指接材快速老化性能。     

Growth and structure development of semi-natural larch-spruce-fir (Larix olgensis–Picea jezoensis–Abies nephrolepis) forests in northeast China: 12-year results after thinning

Analyzing and understanding the structure and growth dynamics of semi-natural plantations is useful for their management. Since 1987, 16 plots with 4 treatments (CT: control; LT: light thinning; MT: medium thinning; and HT: heavy thinning) by 0, 20, 30 and 40% of basal area removal, respectively, and four replications were established in semi-natural larch-spruce-fir forests in northeast China. The structure and growth dynamics of semi-natural larch-spruce-fir stands and the effects of thinning on the growth, structure and diversity were examined. A mixed model repeated measures analysis of variance (RMANOVA) was used to test the effects of treatment and time.

Results showed that differences in periodic annual increment (PAI) of stand basal area and volume and the individual diameter and volume among treatments changed over time in a complex statistical interaction. Thinning, however, had a significant effect on growth at tree and stand levels 12 years after thinning while the PAI of the diameter, basal area and volume was positively correlated with thinning intensity. No significant differences were found in the total stand yield among treatments. Composition of tree species group (larch, other conifers and deciduous trees) during monitoring years did not change significantly. Moreover, no significant differences were observed in tree species and size diversity among treatments in the years following thinning. Both thinning and control plots had similar understory plant diversity after the 12 year period. Univariate point pattern analysis revealed that clumped and random distributions were dominant for tree species groups in this study. The current species composition and regeneration dynamics within these semi-natural plantations suggested a development towards mixed coniferous and broad-leaved forests. Management implications for the transformation from larch plantations towards mixed broad-leaved Korean forests with a more diverse structure, the climax vegetation in this region, were discussed.     

Stand density and growth of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> (L.) Karst.) and European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.): evidence from long-term experimental plots

On the basis of nine Norway spruce (Picea abies (L.) Karst.) and ten European beech (Fagus sylvatica L.) thinning experiments in Germany, for which both residual and removed stock had been registered first during 1870, I scrutinize how moderate and heavy thinning from below (B-, C-grade) affects the production of merchantable volume compared with light thinning (A-grade). In relation to A-grade, cumulative merchantable volume (CV) of B- and C-grade amounts in average to 103–107% in juvenile and to 97–102% in mature Norway spruce stands. The corresponding findings for European beech are 101–106% and 94–102%. CV of individual stands varies between 89% and 130% for Norway spruce and 73% and 155% for European beech (CV of A-grade = 100%). These findings are substantiated by the relation between stand density (SDI) and periodic annual increment (PAI). On the B- and C-grade plots of spruce and beech, respectively, SDI was reduced down to 41–91% and 31–83% of the A-grade. When SDI is reduced in young stands, PAI follows a unimodal curve. Norway spruce’s PAI culminates in 109% if SDI is reduced to 59%; European beech’s PAI culminates in 123% when density is reduced to 50%. Whereas Norway spruce’s growth reacts most positively on thinning under poor site conditions and with increment reduction on favourable sites, European beech behaves oppositely. With stand development the culmination point of the unimodal relation moves towards maximum density, so that in older stands PAI follows the increasing pattern, which is the left portion of a unimodal curve. A model is presented which apparently unifies contradictory patterns of stand density–growth reactions by integrating relative stand density, average tree size and site fertility effects, and makes the findings operable for forest management.