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1.
Picea mongolica W. D. Xu. is an endemic species in China. The spruce forest is only found in semi-arid habitat in Inner Mongolia Autonomous Region of China. Based on the simulative defoliation experiment, it was proved that Picea mongolica seedlings had the compensatory and overcompensatory effects under the certain defoliation rate. The results of variance analysis on growth indexes showed that in PM I (natural regeneration seedlings under Picea mongolica forest), the differences of H1 (height in June 23 ) and H2 (height in September 3) were extremely significant, and the difference of D(diameter at the breast height) were not significant. In PM Ⅱ (artificial regeneration seedlings under Betula platyphylla Suk. forest), the difference of H1 was significant, the difference of H2 was not significant, and the difference of D was extremely significant. The regression equations were established and the compensatory and overcompensatory points were obtained. In PM I, the compensatory points of H1, H2, and D were 0.7628, 0.7436, 0.5725, and the overcompensatory points were 0.6056, 0.5802 and 0.2909 respectively. In PM Ⅱ, the compensatory points of H1, H2, and D are 0.5012, 0.3421, 0.2488, and the overcompensatory points are 0.4137, 0.2633 and 0.0747 respectively. These results suggested that the induction of compensatory growth mechanisms in spruce seedlings required a threshold level of defoliation, and the insects in Picea mongolica forest could be controlled in a certain de clree. 相似文献
2.
Baranchikov Yu. N. Perevoznikova V. D. Vishnyakova Z. V. 《Russian Journal of Ecology》2002,33(6):398-401
In the southern-taiga low grass–green moss fir forest completely defoliated by the Siberian moth, the rate of soil respiration in the third year after the pest population outbreak was 1.5 times higher than in an undisturbed tree stand. This was explained by a significant increase in the abundance and activity of soil microorganisms in the pest-defoliated forest, which occurred due to the qualitative changes in the litter composition and the increased temperature and moisture in the upper soil layers. The rate of carbon emission from the soil in the defoliated forest was 41.7 kg/ha per day, compared to 28.3 kg/ha per day in the undisturbed fir forest. 相似文献
3.
The sensitivity of the United States Forest Health Monitoring network to outbreaks of defoliating insects was examined by means of a simulation study. A model constructed specifically for the study was used to generate a wide variety of defoliation patterns in forested landscapes. Forest configuration was that of Minnesota, USA, as expressed by the GAP land cover classification. Combinations of model parameters were based on a Latin Hypercube sample. The relationship between the average number of plots defoliated and outbreak characteristics was then examined via multiple regression. Both theoretical and model results pointed to a strong, linear relationship between the average number of plots defoliated and outbreak size. Model results provided additional insight, suggesting a significant relationship between the average number of plots defoliated and other outbreak characteristics after outbreak size was taken into account. 相似文献
4.
Since 1987 tree crown condition is surveyed annually in large parts of Europe mainly in terms of defoliation. The plot-wise means of defoliation from 1994 to 2000 were evaluated by General Linear Models (GLM) in order to describe country-specific levels of defoliation and age-trends. Additional runs with estimates for influences of insects and fungi were performed. The amount of variance of defoliation explained by country, age and its interaction was between 35% and 59% for the main tree species, except for Quercus ilex. Additionally, up to 10% could be explained by the inclusion of estimates for infestations by insects and fungi. Residuals of the GLMs were taken as a measure of forest condition not biased by country or age effects and interpreted as preliminarily adjusted defoliation (PAD). PAD values were analysed using geostatistical methods. The modelled spatial autocorrelations were used for kriging. The resulting maps give an overview on regions with elevated defoliation, which may pinpoint regional causes of defoliation. The elimination of methodologically caused variance is a precondition of any cause–effect oriented analyses. The combination of explorative modelling and geostatistics will promote the choice of further promising predictors. 相似文献
5.
We tested whether the semi-automatic program CROCO can replace visual assessments of slides to detect changes in defoliation assessment methods. We randomly selected a series of slides of 24 Norway spruce trees with 220 field assessments made between 1986 and 1995. The slides had been randomly arranged and assessed by three experts without knowledge of the tree number or the year when the slide was taken. Defoliation scores were computed with CROCO. Each tree had thus three different defoliation scores, field assessments, photo assessments and CROCO scores.CROCO scores were less correlated with the field assessments (Spearmans rank correlation: 0.67) than were the slide assessments with the field assessments (0.79–0.83). However, CROCO was not biased against the field scores, while slide assessments systematically underestimated defoliation.In a multi-variate mixed effect model none of the variables tree overlap, tree visibility and light conditions was significant in explaining differences between slide assessors and CROCO scores. The same model applied for the differences from the field scores yielded significant effects for poor light conditions (CROCO and all assessors), for crown overlap (CROCO and one assessor) and for visibility (one assessor). We conclude, therefore, that CROCO can be used to detect past and future changes in assessment methods without bias if poor quality photographs are avoided. 相似文献
6.
S. I. Fedorenko 《Russian Journal of Ecology》2001,32(6):432-436
It is shown that both diffuse and complete drying of birch stands is due to the additive effects of meteorological factors (hydrothermal parameters of the first and second halves of the growing period) and tree defoliation by phyllophagous insects, with the former being of primary importance. 相似文献
7.
Summary. Increased abundance of several aliphatic benzyl
and phenylethyl alkanoates were previously associated with
reduced defoliation of
Eucalyptus globulus Labill. by the
autumn gum moth (Mnesampela privata Guenée) in two
clonally replicated F2 families. We examine the robustness
of this association by comparing the abundance of the
implicated foliar wax compounds with defoliation levels in
three plantation sites and a genetics trial in northern
Tasmania. At all locations, the aliphatic alkanoate, benzyl
n-tetracosanoate (C24), was found in significantly higher
abundance in the foliar wax of E. globulus trees that had displayed low M. privata damage (designated resistant) compared to trees that had displayed high damage (designated
susceptible). Further, when sites were combined, benzyl
n-tetracosanoate (C24) accounted for 16 % of variation in
field defoliation. Field defoliation was also positively correlated
to M. privata oviposition both in the field and on
foliage sprigs in a cage. In the cage bioassay, oviposition
accounted for 20 % of variation in field defoliation
making it a better predictor of tree defoliation in the field
than either field oviposition, which accounted for 9 % of
variation, or screening foliage for the abundance of benzyl
n-tetracosanoate (C24). Despite both benzyl n-tetracosanoate
(C24) and oviposition being related to field defoliation, there
was no statistically significant relationship between the
abundance of benzyl n-tetracosanoate (C24) and oviposition
in the field or cage bioassay. Further work is therefore
required to determine if increased levels of this compound in
the foliar wax operates as a direct deterrent to M. privataoviposition. 相似文献
8.
Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988
to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20–30 cm
of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N
ratio). Trees growing on soils with a high pH (≥4.00, in BaCl2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH
<4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with
respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency.
Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation
and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than
trees on more basic soils between 1988 and 1999. Trees ≥100 years old had significantly higher defoliation on more acidic
than on more basic soils, however defoliation dynamics of these trees over 1988–99 was not related to soil acidity. Two biotic
agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics. 相似文献
9.
氟害大豆超氧化物歧化酶活性与叶绿素含量及叶片脱落的关系 总被引:1,自引:0,他引:1
采用人工HF熏气的方法研究了盆栽大豆 (Glycinemax )超氧化物歧化酶 (SOD)活性与叶绿素含量、乙烯产生量、纤维素酶活性之间的关系。结果表明 :(1)HF通过抑制SOD活性降低了叶绿素的含量 ;(2 )HF对参与叶片脱落的纤维素酶的活性诱导是通过抑制SOD活性进而合成大量乙烯实现的。 相似文献
10.
Romualdas Juknys Jone Vencloviene Nerijus Jurkonis Edmundas Bartkevicius Janina Sepetiene 《Environmental monitoring and assessment》2006,121(1-3):517-540
Data on individual tree mortality in relatively healthy (Berezinskiy biosphere reserve) and damaged (surroundings of the mineral fertilizer plant ‘Achema’) even-aged Scots pine (Pinus sylvestris L.) stands are presented. Tree size and competition intensity were found to be the most significant predictors of individual tree mortality in all age groups of the relatively healthy Scots pine stands, however, an essential reduction in the closeness of relations between the tree mortality rate and these variables was determined with the aging of stands. An exponential decrease in tree mortality probability with an increase of tree size is characteristic for trees suffering different competition intensity, however, this decrease becomes much more pronounced as the competition pressure increases. The relations of different tree and stand variables with tree mortality probability have been found to become much weaker in the polluted environment. An exponential increase in tree mortality probability with an increase of crown defoliation was characteristic of damaged Scots pine stands, however, the rate of the increase was different in different age and diameter classes. The impact of crown defoliation on tree mortality rate increased with the aging of stands. At the same defoliation level, individual tree mortality probability was much higher for smaller suppressed trees, however, a relative increase in tree mortality probability along with an increase of crown defoliation was more pronounced for dominant trees. Conclusion: a higher mortality of damaged (defoliated) trees should be considered while assessing losses in forest productivity in a polluted environment. 相似文献