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1.
Juan Shi Youqing Luo Xiaosu Yan Weiping Chen Ping Jiang 《Frontiers of Forestry in China》2009,4(1):117-122
Pine wood nematode (PWN, Bursaphelenchus xylophilus), originating from North America, causes destructive pine wilt disease. Different pine forest ecosystems have different resistances
to B. xylophilus, and after its invasion, the resilience and restoration direction of different ecosystems also varies. In this study, an
interpretative structural model was applied for analyzing the response of pine forest ecosystem to PWN disturbance. The result
showed that a five-degree multi-stage hierarchical system affected the response of the pine forest ecosystem to PWN disturbance,
in which direct affecting factors are resistance and resilience. Furthermore, the analysis to the 2nd, 3rd and 4th degree
factors showed that not only does distribution pattern of plant species and pine’s ecological features affect the resistance
of pine forests’ ecosystem, but removal of attacked trees and other measures also influence the resistance through indirectly
affecting the damage degree of Monochamus alternatus and distribution pattern of plant species. As for resilience, it is influenced directly by soil factors, hydrology, surrounding
species provenance and biological characteristics of the second and jointly dominant species, and the climate factors can
also have a direct or indirect effect on it by affecting the above factors. Among the fifth elements, the elevation, gradient
and slope direction, topographical factors, diversity of geographical location and improvement of prevention technology all
influence the response of pine forest ecosystem to PWN disturbance.
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Translated from Scientia Silvae Sinicae, 2007, 43(8): 85–90 [译自: 林业科学] 相似文献
2.
The ability of the pine wood nematode,Bursaphelenchus xylophilus, a pathogen that causes pine wilt disease, to kill cortical cells of Japanese black pine,Pinus thunbergii, during early development of the disease was conjectured to be a function of nematode developmental stage. A tangential segment
of bark was removed from a 2-cm-long current-year stem. The cortex-exposed segments with cut cortical resin canals were designated
as + RC-segments and those without them as − RC-segments. When a nematode population containing many older juveniles and adults
(NL) was inoculated onto the cut surface, the − RC-segments were still alive 4 d after inoculation, as were non-inoculated
control segments. When cortex-exposed segments were inoculated with either a nematode population containing many younger nematodes
(NS) or with nematodes isolated from inoculated pine cuttings that also contained many younger juveniles, most tissue cells
in − RC-segments died 4 d after inoculation, suggesting that younger juveniles killed pine cells directly, in contrast with
older juveniles and adults. When nematodes were inoculated onto + RC-segments in which they could easily enter resin canals,
both NL and NS killed the segment tissues. This suggests that NL is pathogenic to pine cells while living in resin canals.
Such differences in the pathogenicity of NL and NS to pine parenchymatous cells were also demonstrated in a pathogenicity
assay system using bark peelings, which allowed an estimate of direct attack on the cambial cells by nematodes. Based on these
results, we hypothesize that younger juveniles are pathogenic to pine parenchymatous cells, while adults and older juveniles
are not pathogenic.
This work was supported in part by Grants-in-Aid for Scientific Research (No.01440012 and 06454088) and for Young Scientists
(to K.I.) from Ministry of Education, Science, Culture, and Sports of Japan, and by a grant from PROBRAIN. 相似文献
3.
研究表明 :在松材线虫病发生区 ,其病害的扩展、流行与马尾松毛虫危害有着密切的关系。当年受马尾松毛虫危害的松林 ,枯死松树数量平均为 77 879株 /hm2 ,比未受松毛虫危害的松林 (对照 ) 17 2 73株 /hm2 ,多 35 1% ;次年 ,前者平均枯死松树达 2 0 4 8株 /hm2 ,为对照 2 89株 /hm2 的 6 0 8%。松毛虫危害加速松材线虫病流行的原因是 ,松毛虫危害松树 ,削弱树势 ;弱势的松树招引松墨天牛侵入并增殖加快松树死亡 ;次年大量天牛从“松毛虫危害松木”上羽化 ,侵染健康松林 ,导致松材线虫病进一步扩散和流行。由此认为松毛虫危害是促使松材线虫病流行的重要因子 ,防治松毛虫是控制松材线虫病流行的重要环节之一 相似文献
4.
Simulated acid rain (SAR) at three pH levels (pH 4, 3, 2) was applied to only the top or both the top and roots of 4-month-old
Japanese black pine seedlings repeatedly for two months. Then the seedlings were inoculated with a virulent isolate (S10)
of pinewood nematode,Bursaphelenchus xylophilus. The exposure to SAR at any level did not kill the seedlings. When inoculated with nematodes, however, the nematode population
build-up was significantly higher in the seedlings pretreated with SAR at any level than in the control at the 7th and 17th
day after inoculation, and subsequent disease symptom development was also significantly accelerated by the exposure to SAR
at pH 2 and 3. This result indicates that even acid rain at pH 4 has the potential for promoting population growth of pinewood
nematodes in 4-month-old Japanese black pine seedlings. 相似文献
5.
When pine trees are invaded by pine wilt diseases, the severely infected pine trees will die and fall down, or they will be
removed when found to be damaged by the disease. It gives rise to the invasion of other species in these empty niches originally
occupied by pine trees, i.e., competing surrounding trees or understory shrubs will invade the empty niches during the following
years. As a result, the spatial distribution and pattern of the main tree species in a pine forest will change, and a niche
variety in the main population will occur. In the end, the direction of the succession and restoration of the pine forest
ecosystem will be affected. In our study, a Pinus massoniana forest with the dominant shrub, Pleioblastus amarus, was invaded by pine wood nematode and was clear cut. Selecting this community as our research object, we studied the effect
of the invasion of the pine wood nematode on the growth of the dominant shrub, P. amarus, in this Pinus massoniana forest. Our results show that, after the attacked pine trees were removed, the niche was occupied by Pleioblastus amarus and other shrubs, which benefited the growth of P. amarus to its climax. Growth of P. amarus at the climax stage was greater compared with the unhealthy pine forest and the control group. 相似文献
6.
7.
为了提高长白落叶松-红松林的生产力和生物多样性,2005年秋对长白落叶松人工林进行疏伐,伐后林冠下栽植4年生红松。2012年秋又对上层长白落叶松进行生长伐,设计轻度、中度和强度3种间伐强度和1组未间伐林分(对照),分析5年后不同间伐强度对林下植物多样性和土壤理化性质的影响。结果表明:①抚育间伐能提高林下植物多样性,林下灌木层植物丰富度随着间伐强度的增加而增加,轻度、中度和强度间伐差异显著(p<0.05)。林下灌木层植物多样性指数随着间伐强度的增加而增加,对照与中度间伐、强度间伐差异显著(p<0.05),但中度间伐和强度间伐差异不显著。林下草本层植物的丰富度和多样性指数随着间伐强度的增加而增加,各间伐强度均与对照差异显著(p<0.05),但轻度间伐和中度间伐差异不显著。②适度抚育间伐能改善土壤的理化性质,随着间伐强度的增加,土壤容重有所降低,土壤孔隙度和持水量有所提高;土壤pH值呈现先升高后略有降低的趋势,全K、速效K、全P、速效P、全N、速效N含量先升高后略有降低,其中中度间伐效果最好。综合考虑,对长白落叶松林分进行中度间伐较为适宜。 相似文献
8.
The bambooPhyllostachys bambusoides has been widely planted on riverbanks in Japan to protect against erosion. Recently, unmanagedP. bambusoides stands with high culm density are spreading along the banks of rivers. In order to study the impact of the bamboo stands
on riparian ecosystems, the relations between bamboo stand structure, light conditions and plant communities under the canopy
were examined. The study sites were set in bamboo stands with various culm densities in the middle of the Yahagi River in
Toyota, Aichi Prefecture. There was a close relationship between canopy coverage and relative photon flux density (RPFD) in
the bamboo stands. RPFD showed a highly negative relationship with total culm density, whereas no significant relation was
observed between the basal area of bamboo and RPFD. The total number of plant species in the bamboo stands increased with
decreasing culm density. Only a small number of tree saplings were observed in the stands with the highest culm densities,
while several species of forest floor herbs were found in the stands with lower culm densities. A number of invasive and annual
plants colonized the thinned stand. We suggest that moderate thinning and clearing of dead culms are needed to maintain biological
diversity in the bamboo stands on riverbanks. 相似文献
9.
Rupert Seidl Werner Rammer Dietmar Jger Manfred J. Lexer 《Forest Ecology and Management》2008,256(3):209-220
The likely environmental changes throughout the next century have the potential to strongly alter forest disturbance regimes which may heavily affect forest functions as well as forest management. Forest stands already poorly adapted to current environmental conditions, such as secondary Norway spruce (Picea abies (L.) Karst.) forests outside their natural range, are expected to be particularly prone to such risks. By means of a simulation study, a secondary Norway spruce forest management unit in Austria was studied under conditions of climatic change with regard to effects of bark beetle disturbance on timber production and carbon sequestration over a time period of 100 years. The modified patch model PICUS v1.41, including a submodule of bark beetle-induced tree mortality, was employed to assess four alternative management strategies: (a) Norway spruce age-class forestry, (b) Norway spruce continuous cover forestry, (c) conversion to mixed species stands, and (d) no management. Two sets of simulations were investigated, one without the consideration of biotic disturbances, the other including possible bark beetle damages. Simulations were conducted for a de-trended baseline climate (1961–1990) as well as for two transient climate change scenarios featuring a distinct increase in temperature. The main objectives were to: (i) estimate the effects of bark beetle damage on timber production and carbon (C) sequestration under climate change; (ii) assess the effects of disregarding bark beetle disturbance in the analysis.Results indicated a strong increase in bark beetle damage under climate change scenarios (up to +219% in terms of timber volume losses) compared to the baseline climate scenario. Furthermore, distinct differences were revealed between the studied management strategies, pointing at considerably lower amounts of salvage in the conversion strategy. In terms of C storage, increased biotic disturbances under climate change reduced C storage in the actively managed strategies (up to −41.0 tC ha−1) over the 100-year simulation period, whereas in the unmanaged control variant some scenarios even resulted in increased C sequestration due to a stand density effect.Comparing the simulation series with and without bark beetle disturbances the main findings were: (i) forest C storage was higher in all actively managed strategies under climate change, when biotic disturbances were disregarded (up to +31.6 tC ha−1 over 100 years); and (ii) in the undisturbed, unmanaged variant C sequestration was lower compared to the simulations with bark beetle disturbance (up to −69.9 tC ha−1 over 100 years). The study highlights the importance of including the full range of ecosystem-specific disturbances by isolating the effect of one important agent on timber production and C sequestration. 相似文献