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1.
 通过稀释平板法和常规化学分析法, 对伊犁河谷地区3种龄级(5年、10年、15年)的速生杨欧美黑杨(Populus × euramericana)人工林的土壤微生物数量、组成和土壤养分变化进行了研究。结果表明, 3种不同林龄林地土壤微生物集中分布在10–40 cm土层, 数量和种类组成随季节变化有明显差异。随着林龄的增长, 土壤微生物总数、细菌数量减少, 真菌和放线菌数量在10年生人工林最高, 这一规律随季节变化。三大类土壤微生物的组成比例相对稳定, 不随季节变化而变化。土壤有机碳、氮含量主要集中在0–20 cm土层, 随土壤深度的增加逐渐减少, 其含量及分布受季节和土壤深度不同程度的影响。土壤有机碳含量随林龄的增长而逐渐增高, 有机氮则先减后增。相关分析表明, 土壤微生物总数与土壤有机碳呈负相关, 真菌数量与土壤有机氮呈正相关。3种林地土壤有机C/N比与土壤细菌数量/真菌数量比例一致, 说明速生杨人工林在一定生长年龄内能提高土壤的固碳能力, 改善土壤肥力。  相似文献   
2.
洞庭湖洲滩速生杨树林变化信息提取方法   总被引:1,自引:1,他引:0  
胡砚霞  黄进良  杜耘  韩鹏鹏  王久玲  黄维 《生态学报》2014,34(24):7243-7250
洞庭湖是我国第二大淡水湖,其湿地资源具有重要的生态功能和经济价值。近20年来,洞庭湖洲滩速生杨树林发展迅速,其中西洞庭湖杨树林的扩张最为明显,极大改变了湖区湿地植被分布格局,隐含极大的生态风险。以Landsat ETM+和HJ-1A/1B CCD影像为数据源,提出了洞庭湖速生杨树林变化信息提取的两种方法,并对这两种方法进行了比较研究。一种是分类的方法,即采用面向对象分层信息提取的方法先提取出树林滩地信息,再将距离大堤一定范围内的树林滩地归为防护林,速生杨树林变化的面积即为两个时相提取结果的差值。另一种是变化检测的方法,它是基于像元进行变化检测,先确定出总的变化区域,再从中筛选速生杨树林的变化信息。结果表明:(1)两种提取方法都是可行的,不同方法提取的速生林变化信息存在一定差异,但空间分布大体一致;(2)基于分类的方法总体精度和Kappa系数均略高于基于变化检测的方法:其中基于分类的方法总体精度达84.00%,Kappa系数为0.67,基于变化检测的方法总体精度达83.00%,Kappa系数为0.65;(3)基于分类的方法图斑较大、图斑数较少,基于变化检测的方法图斑较小且较破碎、图斑数多;(4)基于分类的方法漏分较少、错分较多,基于变化检测的方法漏分较多、错分较少。为洞庭湖洲滩杨树林的动态监测提供了研究方法,也为杨树林扩张原因及其生态效应分析提供研究基础。  相似文献   
3.
利用林木边行优势营造杨树速生丰产林的试验研究──林农复合生态经济系统的新模式许鸿儒,刘金声(辽宁省黑山县林业局,121400)(辽宁省林业厅造林处,沈阳110001)范学文(辽宁省锦西市林业局,121500)PlantingofFast-Growin...  相似文献   
4.
《植物生态学报》2021,44(12):1215
Aims Due to fast-growing and high drought stress tolerance, Leucaena leucocephala has been widely used for afforestation in degraded tropical forests worldwide, but it is also a global invasive exotic species. Studies have shown that fast-growing can help L. leucocephala successfully invade subtropical forests. In this study, we aimed to investigate whether fast-growing and high drought stress tolerance can help L. leucocephala invade tropical rain forests.Methods The pioneer community of tropical rain forest which had been invaded by L. leucocephala in the Baopoling Mountain, Sanya, China was the research object. Through the t-test, we compared the differences in key functional traits that were related to growth rate (photosynthesis rate, stomatal conductance and transpiration rate) and drought stress tolerance (leaf turgor loss point) in both wet and dry seasons between L. leucocephala and eight dominant native species of pioneer community of tropical rain forest. And the principal component analysis (PCA) was used to investigate whether these functional traits can best discriminate between Leucaena leucocephala and the eight dominant native species.Important findings Leucaena leucocephala could be invariably growing fast (photosynthesis rate, stomatal conductance and transpiration rate much higher than native species) from wet to dry seasons and had higher drought stress tolerance (leaf turgor loss point much lower than native species) in the dry season. The results of PCA showed that these functional traits could significantly discriminate between L. leucocephala and the eight dominant native species. Therefore, invariable fast-growing from wet to dry season and high drought stress tolerance in the dry season make L. leucocephala successfully invade pioneer communities of tropical rain forests. In the future, these functional traits can be used to select many native species to perform biological control of L. leucocephala in other tropical forests.  相似文献   
5.
6.
C. Fu  §  D. Li  §  W. Hu  §  Y. Wang  § Z. Zhu  §† 《Journal of fish biology》2007,71(SB):174-185
Compensatory growth is a phase of accelerated growth apparent when favourable conditions are restored after a period of growth depression. To investigate if F2 common 'all-fish' growth hormone gene transgenic common carp ( Cyprinus carpio ) could mount compensatory growth, a 9 week study at 29° C was performed. The control group was fed to satiation twice a day throughout the experiment. The other two groups were deprived of feed for 1 or 2 weeks, respectively, and then fed to satiation during the re-feeding period. At the end of the experiment, the live masses of fish in the deprived groups were still significantly lower than those of the controls. During the re-feeding period, size-adjusted mean specific growth rates and mean feed intakes were significantly higher in the deprived fish than in the controls, indicating a partial compensatory growth response in these fish. No significant differences were found in food conversion efficiency between the deprived and control fish during re-feeding, suggesting that hyperphagia was the mechanism responsible for increased growth rates. The proximate composition of the deprived fish at the end of the experiment was similar to that of the control fish. This study is, to our knowledge, the first to report that fast-growing transgenic fish can achieve partial compensation of growth following starvation.  相似文献   
7.
由于生长速率高, 耐旱性强, 银合欢(Leucaena leucocephala)被广泛应用于世界各地退化热带亚热带森林的修复, 但它也是一种全球性的外来入侵植物。已经有研究发现高生长速率可以帮助银合欢成功入侵亚热带森林, 但是目前还不清楚高生长速率和强耐旱性是否能帮助银合欢成功入侵热带森林。该研究以位于中国三亚抱坡岭被银合欢入侵的热带雨林先锋群落为研究对象, 通过t检验比较干季和湿季银合欢和8个热带雨林先锋群落的本地优势种与快速生长(光合速率、气孔导度和蒸腾速率)和耐旱性(叶片膨压丧失点)紧密相关的功能性状的差异, 并利用主成分分析(PCA)研究这些功能性状是否能很好地区分银合欢和其他8个本地优势种。结果表明: 银合欢在干湿季均能快速地生长(比本地物种显著更高的光合速率、气孔导度和蒸腾速率), 且在干季拥有更强的耐旱性(比本地物种显著更低的叶片膨压丧失点)。PCA结果表明这些功能性状能够显著区分银合欢和其他8个本地优势种。因此干湿季的稳定的快速生长和干季的强耐旱性使银合欢成功入侵热带雨林先锋群落。未来可利用这些功能性状筛选合适的本地物种对入侵其他热带森林的银合欢进行有效的生物防治。  相似文献   
8.
Biological nitrogen fixation (BNF) technology with special reference to Rhizobium-legume symbiosis is growing very rapidly with the hope of combatting world hunger by producing cheaper protein for animal and human consumption in the Third World. One can see rapid progress made in the biochemistry and molecular biology of symbiotic nitrogen fixation in general; however, less progress has been made on the ecological aspects despite the fact that an enormous amount of literature is available on inoculation problems and on agronomic aspects of symbiotic nitrogen fixation. So far most information on Rhizobium concerns fast-growing rhizobia and their host legume. Although it is essential that food production using BNF technology should be maximized in the Third World, the least work has been done on slow-growing rhizobia, which are generally found in tropical and sub-tropical soils. The majority of the developing countries are in tropical and sub-tropical regions. Except for R. japonicum, a microsymbiont partner of soybean (Glycine max), the majority of the slow-growing rhizobia belong to the cowpea group, and we refer to cowpea rhizobia as tropical rhizobia species. In this review we have tried to consolidate the recent progress made on ecology and genetics of tropical rhizobia. By using recombinant DNA technology techniques it is expected that super strains of rhizobia with desirable characteristics can be produced. One must evaluate the efficiency and effectiveness of these genetically manipulated laboratory strains under field conditions. In conclusion, if one aims at combatting hunger in the Third World using BNF technology, an intensive research programme on fundamental and applied aspects of tropical rhizobia species is suggested. This involves close cooperation between molecular biologists and microbial ecologists.  相似文献   
9.
To rehabilitate degraded forestlands and conserve the remaining forests in Kalimantan, effective measures are needed that accommodate various land uses in the landscape. We present a pragmatic model for prioritizing target areas for rehabilitation and discuss a potential approach, combining traditional reforestation and the forest management methods of local Dayak tribes with the operations of a commercial tree plantation venture, to promote the rehabilitation of elements of the tropical lowland rainforest. We characterized the vegetation and land use in the study area and assume that rehabilitation and conservation value will be maximized by concentrating rehabilitation efforts around forest patches with high cultural and economic value to the local Dayaks. We simulated potential enlargement of these culturally important forests and built a model to calculate a rehabilitation value for each forest fragment and fragment group with easily measurable criteria of vegetation and area. The model gives priority to areas where large continuous areas of culturally important forests already exist and/or will be created. The individual culturally important forest patches and their total area in the landscape are small, but even a small potential enlargement may be enough to establish relatively large concentrations. The potential matrix area for rehabilitation is dominated by young successional woody vegetation. Forested areas, although heavily degraded, connect several culturally important forest concentrations and are the most desirable target for rehabilitation. A well‐managed commercial tree plantation can enhance conditions for the protection and rehabilitation of degraded forestlands through traditional reforestation and forest management methods.  相似文献   
10.
乔雪涛  何俊  范秀华  孙兆军 《生态学报》2019,39(15):5573-5583
在宁夏引黄灌区次生盐碱地,设置了填埋秸秆层(B)、覆盖秸秆层(M)、填埋配合覆盖秸秆层(B+M)和无任何处理(空白对照,CK)共4种处理,通过随机区组试验,在土壤水盐变化的基础上,通过分析速生杨光谱及光合特性对秸秆层响应,探究不同秸秆层的植物光合速率、色素含量、营养状况以及受胁迫等情况,以期更准确的反应出各处理的改良效果及植被恢复情况。研究结果表明:(1)秸秆层有助于提升灌区次生盐碱地速生杨的光谱与光合等生理状况。B、M和B+M均能显著提升速生杨叶片的最大净光合速率与饱和光强,其中,B和B+M还能够明显降低速生杨叶片的光补偿点和暗呼吸速率,M则不能。B和B+M均显著提高速生杨叶片的净光合速率、蒸腾速率、气孔导度等光合参数。另外,B+M的速生杨叶片光合色素含量最高,营养状况最好,其他光谱参数结果与CK相比都有显著提高。处理B和M也可以显著提高速生杨叶片光合色素含量和营养状况,但效果均不如B+M。(2)B与B+M均能降低不同时期的土壤盐分含量,但B+M在不同时期提高土壤含水量的效果均高于B。M也能降低土壤盐分和提升土壤含水量,但不同时期的效果均不如处理B+M。综合试验结果,在引黄灌区次生盐碱地,不同秸秆层均能不同程度的调节土壤水盐变化,缓解水盐胁迫,提升速生杨光合与光谱特性,其中B+M作为秸秆层效果最佳。  相似文献   
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