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991.
Effects of continuous cucumber cropping and alternative rotations under protected cultivation on soil microbial community diversity 总被引:16,自引:1,他引:15
The diversity of soil microbial communities as affected by continuous cucumber cropping and alternative rotations under protected
cultivation were evaluated using community level physiological profiles (CLPP) and random amplified polymorphic DNA (RAPD)
analysis. The soils were selected from six cucumber cropping systems, which cover two cropping practices (rotation and continuous
cropping) and a wide spectrum for cucumber cropping history under protected cultivation. Shannon–Weaver index and multivariate
analysis were performed to characterize variations in soil microbial communities. Both CLPP and RAPD techniques demonstrated
that cropping systems and plastic-greenhouse cultivation could considerably affect soil microbial functional diversity and
DNA sequence diversity. The open-field soil had the highest Shannon–Weaver index (3.27 for CLPP and 1.50 for RAPD), whereas
the lowest value occurred in the 7-year continuous protected cultivation soil (3.27 for CLPP and 1.50 for RAPD). The results
demonstrated that continuous plastic-greenhouse cultivation and management can cause the reduction in the species diversity
of the biota. Higher Shannon–Weaver index and coefficients of DNA sequence similarity were found in soils under rotation than
those under continuous cropping. Cluster analysis also indicated that microbial community profiles of continuous cultivation
soils were different from profiles of rotation soils. The reduction in diversity of microbial communities found in continuous
cultivation soils as compared with rotation soils might be due to the differences in the quantity, quality and distribution
of soil organic matter.
Section Editor: D. E. Crowley 相似文献
992.
Resource-Ratio Theory and the Control of Invasive Plants 总被引:1,自引:0,他引:1
W. Stanley Harpole 《Plant and Soil》2006,280(1-2):23-27
There have been relatively few tests of resource-ratio theory in terrestrial systems. Additionally, resources are known to
be an important factor determining the success of invasive species. Here I discuss how the study by Newingham and Belnap (pp.
29–40, this issue) tests predictions of resource-ratio theory and how they apply it to questions of invasion by Bromus tectorum in a terrestrial grassland. 相似文献
993.
Soil Carbon, Nitrogen and Phosphorus Dynamics as Affected by Solarization Alone or Combined with Organic Amendment 总被引:1,自引:0,他引:1
Antonio Gelsomino Luigi Badalucco Loretta Landi Giovanni Cacco 《Plant and Soil》2006,279(1-2):307-325
Soil solarization, alone or combined with organic amendment, is an increasingly attractive approach for managing soil-borne
plant pathogens in agricultural soils. Even though it consists in a relatively mild heating treatment, the increased soil
temperature may strongly affect soil microbial processes and nutrients dynamics. This study aimed to investigate the impact
of solarization, either with or without addition of farmyard manure, in soil dynamics of various C, N and P pools. Changes
in total C, N and P contents and in some functionally-related labile pools (soil microbial biomass C and N, K2SO4-extractable C and N, basal respiration, KCl-exchangeable ammonium and nitrate, and water-soluble P) were followed across
a 72-day field soil solarization experiment carried out during a summer period on a clay loam soil in Southern Italy. Soil
physico-chemical properties (temperature, moisture content and pH) were also monitored. The average soil temperature at 8-cm
depth in solarized soils approached 55 °C as compared to 35 °C found in nonsolarized soil. Two-way ANOVA (solarization×organic
amendment) showed that both factors significantly affected most of the above variables, being the highest influence exerted
by the organic amendment. With no manure addition, solarization did not significantly affect soil total C, N and P pools.
Whereas soil pH, microbial biomass and, at a greater extent, K2SO4-extractable N and KCl-exchangeable ammonium were greatly affected. An increased release of water-soluble P was also found
in solarized soils. Yet, solarization altered the quality of soluble organic residues released in soil as it lowered the C-to-N
ratio of both soil microbial biomass and K2SO4-extractable organic substrates. Additionally, in solarized soils the metabolic quotient (qCO2) significantly increased while the microbial biomass C-to-total organic C ratio (microbial quotient) decreased over the whole
time course. We argued that soil solarization promoted the mineralization of readily decomposable pools of the native soil
organic matter (e.g. the microbial biomass) thus rendering larger, at least over a short-term, the available fraction of some
soil mineral nutrients, namely N and P forms. However, over a longer prospective solarization may lead to an over-exploitation
of labile organic resources in agricultural soils. Manure addition greatly increased the levels of both total and labile C,
N and P pools. Thus, addition of organic amendments could represent an important strategy to protect agricultural lands from
excessive soil resources exploitation and to maintain soil fertility while enhancing pest control. 相似文献
994.
Tree island ecosystems are important and distinct features of Florida Everglades wetlands. We described the inter-relationships
among abiotic factors describing seasonally flooded tree islands and characterized plant–soil relationships in tree islands
occurring in a relatively unimpacted area of the Everglades. We used Principal Components Analysis (PCA) to reduce our multi-factor
dataset, quantified forest structure and vegetation nutrient dynamics, and related these vegetation parameters to PCA summary
variables using linear regression analyses. We found that, of the 21 abiotic parameters used to characterize the ecosystem
structure of seasonally flooded tree islands, 13 parameters were significantly correlated with four principal components,
and they described 78% of the variance among the study islands. Most variation was described by factors related to soil oxidation
and hydrology, exemplifying the sensitivity of tree island structure to hydrologic conditions. PCA summary variables describing
tree island structure were related to variability in Chrysobalanus icaco (L.) canopy cover, Ilex cassine (L.) and Salix caroliniana (Michx.) canopy cover, Myrica cerifera (L.) plot frequency, litter turnover, % phosphorus resorption of co-dominant species, and nitrogen nutrient-use efficiency.
This study supported findings that vegetation characteristics can be sensitive indicators of variability in tree island ecosystem
structure. This study produced valuable, information which was used to recommend ecological targets (i.e. restoration performance
measures) for seasonally flooded tree islands in more impacted regions of the Everglades landscape. 相似文献
995.
平板式光生物反应器中紫球藻培养条件的优化 总被引:1,自引:0,他引:1
研究了平板式光生物反应器中紫球藻(Porphyridium cruentumNaegeli)的培养条件,运用均匀设计法对光照强度、通气速率、装液量、接种密度以及pH等影响紫球藻生长的因素进行优化,获得了在平板式光生物反应器中培养紫球藻的最佳条件:光照强度10 000 lx、通气速率350 L.h-1、装液量6 L、藻细胞接种密度1.1×106mL-1、pH9.0。在最佳条件下藻体的生物量产率和生物量产量分别达到0.431 g.L-1.d-1和3.240 g.L-1,最大生长速率达0.652 g.L-1.d-1,胞外多糖含量高达0.665 g.L-1。另外,在培养过程中隔天补充培养液有利于紫球藻生物量的增加和胞外多糖的产生。 相似文献
996.
997.
Experiments addressing the role of plant species diversity for ecosystem functioning have recently proliferated. Most studies
have focused on plant biomass responses. However, microbial processes involved in the production of N2O and the oxidation of atmospheric CH4 could potentially be affected via effects on N cycling, on soil diffusive properties (due to changes in water relations and
root architecture) and by more direct interactions of plants with soil microbes. We studied ecosystem-level CH4 and N2O fluxes in experimental communities assembled from two pasture soils and from combinations of 1, 3, 6, 8 or 9 species typical
for these pastures. The soils contrasted with respect to texture and fertility. N2O emissions decreased with diversity and increased in the presence of legumes. Soils were sinks for CH4 at all times; legume monocultures were a smaller sink for atmospheric CH4 than non-legume monocultures, but no effect of species richness per se was detected. However, both the exchange of CH4 and N2O strongly depended on plant community composition, and on the interaction of composition with soil type, indicating that
the functional role of species and their interactions differed between soils. N2O fluxes were mainly driven by effects on soil nitrate and on nitrification while soil moisture had less of an effect. Soil
microbial C and N and N mineralisation rates were not altered. The driver of the interactive soil type×plant community composition-effects
was less clear. Because soil methanotrophs may take longer to respond to alterations of N cycling than the 1/2 year treatment
in this study, we also tested species richness-effects in two separate 5-year field studies, but results were ambiguous, indicating
complex interactions with soil disturbance. In conclusion, our study demonstrates that plant community composition can affect
the soil trace gas balance, whereas plant species richness per se was less important; it also indicates a potential link between the botanical composition of plant communities and global
warming. 相似文献
998.
Hao Zhang Gen-Xuan Wang Zhu-Xia Shen Xing-Zheng Zhao Mu-Qing Qiu 《Acta Physiologiae Plantarum》2006,28(4):373-379
The allometric relationships for plant daily biomass production rates, different measures of body size (dry weight and length)
and photosynthetic biomass per plant are reported for two mutants of Arabidopsis thaliana (abi1-1, insensitive to ABA; era1-2, hypersensitive to ABA). Scaling relationships, such as daily rate of growth (G) vs body mass (M), plant body length or plant height (L) vs body mass (M), photosynthetic biomass (M
p
) vs non-photosynthetic biomass (M
n
), and daily rate of growth (G) vs. photosynthetic biomass (M
p
) were significantly different in abi1-1 and era1-2. It is implied that the sensitivity to abscisic acid may change the scaling relationships for plant biomass production rate
and body size in Arabidopsis thaliana. Because these scaling relationships are closely related to sensitivity to abscisic acid, they are of importance for phytohormonal
ecology. 相似文献
999.
Lessons in conservation are often seen as resulting from cycles of overexploitation and subsequent depletion of resources, followed by catastrophic consequences of shortage and starvation, and finally, development of various strategies, including privatization of the commons, to conserve remaining resource stocks. While such scenarios have undoubtedly occurred on many occasions, we suggest that they are not the only means by which people develop conservation practices and concepts. There are other pathways leading to ecological understanding and conservation, which act at a range of scales and levels of complexity. These include: lessons from the past and from other places, perpetuated and strengthened through oral history and discourse; lessons from animals, learned through observation of migration and population cycles, predator effects, and social dynamics; monitoring resources and human effects on resources (positive and negative), building on experiences and expectations; observing changes in ecosystem cycles and natural disturbance events; trial and error experimentation and incremental modification of habitats and populations. Humans, we believe, are capable of building a sophisticated conservation ethic that transcends individual species and resources. A combination of conservation knowledge, practices, and beliefs can lead to increasingly greater sophistication of ecological understanding and the continued encoding of such knowledge in social institutions and worldview. 相似文献
1000.
民勤绿洲生态需水与生态恢复对策 总被引:16,自引:1,他引:15
生态需水是当前水问题的一个研究热点,对于生态环境急剧恶化的内陆干旱区,这一研究尤为紧迫。以民勤绿洲作为研究区,采用阿维里扬诺夫估算方法,对其生态需水量进行了计算。结果表明,民勤绿洲现有植被最低生态需水量为1.4927×108m3,而目前的生态用水量只有0.3525×108m3,远没有达到维持极限抗性面积下的生态需水量。民勤绿洲生态用水的严重不足,主要是受到农田灌溉用水的严重挤占,从而加快了生态环境的日益恶化。通过分析,提出了生态恢复的对策与建议。 相似文献