菱角萤叶甲种群空间格局研究     

郑福山  杜予州  卢艳阳  强承魁  丁建清 《中国生态农业学报》2006,14(4):171-175

运用2种回归方法和9个聚集度指标对菱角萤叶甲(Galerucella birmanica Jacoby)各虫态的空间格局进行了研究。结果表明,菱角萤叶甲在菱塘基本呈聚集分布,低密度趋向均匀分布,分布的基本成分是个体群;此外,利用空间分布型参数估计个体群的大小(L*)和平均密度(-x)的关系为L*=17.7117 1.5701x-;应用x-=kc(P0-1/kc-1)模型探讨了无虫株率与平均密度的关系,表明实际生产中可应用此模型仿测田间种群密度。同时运用λ参数对聚集原因进行了分析,发现种群的生物学特性和菱角植株的生长状况是影响种群聚集的两个主要原因。  相似文献   

Effects of aggregate structure and organic C on wettability of Ustolls     

A. Eynard  T.E. Schumacher  M.J. Lindstrom  D.D. Malo  R.A. Kohl 《Soil & Tillage Research》2006,88(1-2):205-216

Soil wettability is especially important for rainfed agriculture in climates with a dry period during the growing season. The effect of aggregate structure and soil organic C content on wettability of soil aggregates was determined for grassland (grass) and tilled fields (tillage). Soil organic C, plastic limit, aggregate total porosity, and wettability at 100 mm (rapid wetting) and 300 mm (slow wetting) water tension were measured on soil at 0–0.2 m depth. Natural aggregates from tillage and grass were compared to soil pellets formed by remolding aggregates. At both tensions, wettability of grass aggregates was significantly greater than that of tillage aggregates (P ≤ 0.001). Pellets were significantly less wettable than natural aggregates at 300 mm tension and during the initial wetting at 100 mm tension, but became significantly more wettable with time at 100 mm tension. Cumulative water uptake during 60 min exceeded the initial total porosity of pellets and natural tillage aggregates, suggesting incipient failure (formation of microcracks) during fast wetting. Grass aggregates contained twice as much organic C as tillage aggregates (26 g kg⁻¹ versus 13 g kg⁻¹). Organic C was linearly and positively related to plastic limit, total porosity, and the wettability of natural aggregates at 300 mm tension. At 100 mm tension, organic C was negatively related to wettability of natural aggregates under grass, but unrelated to wettability under tillage. Aggregate wettability was positively related to organic carbon content, except when the arrangement of soil constituents reduced or prevented incipient failure and soil dispersion during rapid wetting resulted in cumulative water uptake (60 min) similar to initial aggregate total porosity. Organic C increased wettability of grass aggregates when compared to tillage aggregates and also stabilized natural aggregates during fast wetting (100 mm tension). Both soil organic C content and aggregate structure were key factors controlling aggregate stability and wettability.  相似文献   

Small grains stubble burning and tillage effects on soil organic C and N, and aggregation in northeastern Saskatchewan     

S.S. Malhi  H.R. Kutcher 《Soil & Tillage Research》2007,94(2):353-361

Field experiments were conducted over 5 years (2000–2004) at two sites (Star City and Birch Hills) in the Saskatchewan Parkland region to determine the effects of tillage and crop residue burning on soil total organic C (TOC), total organic N (TON), light fraction organic matter (LFOM), light fraction organic C (LFOC), light fraction organic N (LFON) and dry aggregation. Two tillage (ZT, zero tillage; CT, conventional tillage, with one tillage in autumn and another in spring) and two burning (B, residue burnt in autumn; NB, residue not burnt and returned to the soil) treatments were combined in a barley (Hordeum vulgare L.)–canola (Brassica napus L.) rotation. After five crop seasons, the mass of TOC and TON in the 0–15 cm soil tended to be greater, whereas mass of LFOM, LFOC and LFON was significantly greater in NB than B treatments at both sites. Zero tillage resulted in greater TOC, TON, LFOM, LFOC and LFON in soil than CT, in both B and NB treatments. The mass of TOC, TON, LFOM, LFOC and LFON in soil was the highest in the ZT–NB treatment, and lowest in the CT–B treatment. Zero tillage had a lower proportion of fine aggregates (<0.83 mm diameter) and a greater proportion of large aggregates (>6.4 mm diameter) at both sites, but the mean weight diameter (MWD) was greater under ZT than CT only at Birch Hills. Although the tillage × burning interaction was not significant in most cases, the ZT–NB treatment usually had the lowest proportion (22.6%) of fine aggregates and the greatest proportion (47.1%) of large aggregates, compared to the highest (34.9%) and the lowest proportion (35.6%) of these aggregates, respectively, in CT–B treatment. This indicated reduced potential for wind erosion when tillage was omitted (ZT) and crop residues were returned to the soil (NB). Returning crop residue to soil rather than burning usually increased soil organic C and N, and aggregation, but the differences between treatments were of greater magnitude between tillage treatments (ZT versus CT) than between burning treatments (B versus NB). Overall, returning crop residues along with ZT improved soil organic C and N, and aggregation, while burning in combination with CT resulted in the deterioration of these soil properties.  相似文献   

The behaviour of the measure of surround in relation to the diameter and spatial structure of a forest stand     

F. Patrick Graz 《European Journal of Forest Research》2008,127(2):165-171

Forestry inventory practices have, in the past, concentrated on obtaining information primarily required for timber management. To assess the ecological impact of exploitation, particularly under continuous cover forest management, diversity measures are required that consider the structural diversity in a forest stand. The measure of surround that was initially developed in Germany may be used to quantify the spatial interspersion of different tree size classes as a measure of spatial diversity. While the measure of surround has been applied to practical problems in the past, little is known about its actual performance in relation to stand compositions. This study investigate the behaviour of the index using a number of simulated age class distributions under various degrees of interspersion to provide a norm against which it may be compared. The measure of surround applied to diameter distributions is closely related to the diameter structure of a stand. When diameter classes are interspersed completely randomly within a stand the relative cumulative frequency of the diameter class provides an estimator of the size specific measure of surround. This provides a baseline from which the index may be interpreted.  相似文献   

Sensitivity of fractal parameters of soil aggregates to different management practices in a Phaeozem in central Argentina   总被引：1，自引：0，他引：1  

R. R. Filgueira  L. L. Fournier  G. O. Sarli  A. Arag  n  W. J. Rawls 《Soil & Tillage Research》1999,52(3-4):217-222

Changes in soil structure often accompany changes in management practices and may affect the effectiveness of these practices. Parameters are needed to quantify these changes. Our objective was to see if fractal dimensions derived from ‘aggregate bulk density–aggregate size’ and ‘aggregate number–aggregate size’ relationships could be applied to quantify such changes. The study was conducted at the Experimental Farm of the School of Agronomy and Forestry Engineering, National University of La Plata, Argentina. A Vertic Phaeozem soil was sampled at seven locations differing in long-term management practices. The ‘aggregate bulk density–aggregate size’ and ‘number of aggregates–aggregate size’ data were obtained for seven ranges of aggregate sizes. Differences in treatments were reflected by the fragmentation fractal dimension but not the mass fractal dimension. The lowest fragmentation fractal dimensions corresponded to plots under long-term no-tillage and the highest to plots with a history of cultivation of rice (Oryza sativa L.) under water. The fragmentation fractal dimension reflected the differences in soil management whereas the mass fractal dimension appeared to be insensitive to those differences.  相似文献   

Iron oxidation in different types of groundwater of Western Siberia     

Leonid V. Serikov  Elena A. Tropina  Liudmila N. Shiyan  Fritz H. Frimmel  George Metreveli  Markus Delay 《Journal of Soils and Sediments》2009,9(2):103-110

Background, aim, and scope  The groundwaters of Western Siberia contain high concentrations of iron, manganese, silicon, ammonium, and, in several cases, hydrogen sulfide, carbonic acids, and dissolved organic substances. Generally, the groundwaters of Western Siberia can be divided into two major types: one type with a relatively low concentration of humic substances and high hardness (water of A type) and a second type with a relatively low hardness and high concentration of humic substances (water of B type). For drinking water production, the waters of A type are mostly treated in the classical way by aeration followed by sand bed filtration. The waters of B type often show problems when treated for iron removal. A part of iron practically does not form the flocs or particles suitable for filtration or sedimentation. The aim of this work was to determine the oxidizability of Fe(II), to characterize the iron colloids, and to investigate the complexation of the iron ions with humic substances and the coagulation of the iron colloids in the presence of dissolved organic matter. Materials and methods  Water samples of the A and B types were taken from bore holes in Western Siberia (A type: in Tomsk and Tomsk region, B type: in Beliy Yar and Kargasok). Depth of sampling was about 200 m below surface. The oxidation of the groundwater samples by air oxygen and ozone was done in a bubble reactor consisting of a glass cylinder with a gas-inlet tube. To produce ozone, a compact ozone generator developed by Tomsk Polytechnic University was used. For the characterization of the colloids in the water of B type, the particle size distribution and the zeta potential were measured. To investigate the formation of complexes between iron and humic substances in the water of B type, size exclusion chromatography was used. The coagulation behavior of iron in the presence of dissolved organic substances was investigated at different pH values. The agglomerates were detected by measuring the optical density using a UV-Vis spectrometer. Results  Ozone showed, as expected, a faster oxidation of Fe(II) than air oxygen. The rate constants for Fe(II) oxidation were not much different for the waters of A and B types when the same oxidation process was used. However, the removal of iron after oxidation and filtration was higher in the water of A type than in the water of B type. No evidence for the formation of soluble complexes between iron and humic substances were found. In the water of A type, the coagulation process started at pH = 4.5 and accelerated with increasing pH value. In the water of B type, the coagulation of colloids occurred only at pH = 11 and higher. Discussion  The oxidation experiments indicated no major effect of dissolved organic carbon concentration on the kinetics of Fe(II) oxidation. In contrast to this, the humic substances showed a significant influence on the aggregation behavior of the iron hydroxide colloids. Due to the sorption of humic substances on the iron hydroxide colloids, they were highly stable in the pH range between 4.5 and 10. The particle size measurements confirmed the presence of small colloids in the water of B type. In contrast to this, the iron hydroxide colloids aggregated rapidly at pH = 11. Conclusions  The results showed a great influence of humic substances on the iron removal from groundwaters of Western Siberia with high organic content. The sorption of humic substances on the iron colloids does not obviously allow their coagulation and formation of flocs suitable for filtration or sedimentation. Recommendations and perspectives  By treatment of groundwaters containing high amounts of humic substances, some problems with the removal of iron are likely to occur. To increase the effectiveness of iron removal, the surface coating and pH-dependent charge effects should be taken into account by the selection and optimization of water treatment processes. The iron colloids coated by humic substances should be separated from the water phase by membrane filtration or by flocculation followed by filtration through different solid materials.  相似文献   

Competition between invasive earthworms (Amynthas corticis, Megascolecidae) and native North American millipedes (Pseudopolydesmus erasus, Polydesmidae): Effects on carbon cycling and soil structure     

Bruce A. Snyder  Bas Boots  Paul F. Hendrix 《Soil biology & biochemistry》2009,41(7):1442-1449

Invasive earthworms can have significant impacts on C dynamics through their feeding, burrowing, and casting activities, including the protection of C in microaggregates and alteration of soil respiration. European earthworm invasion is known to affect soil micro- and mesofauna, but little is known about impacts of invasive earthworms on other soil macrofauna. Asian earthworms (Amynthas spp.) are increasingly being reported in the southern Appalachian Mountains in southeastern North America. This region is home to a diverse assemblage of native millipedes, many of which share niches with earthworm species. This situation indicates potential for earthworm-millipede competition in areas subject to Amynthas invasion.In a laboratory microcosm experiment, we used two ¹³C enriched food sources (red oak, Quercus rubra, and eastern hemlock, Tsuga canadensis) to assess food preferences of millipedes (Pseudopolydesmus erasus), to determine the effects of millipedes and earthworms (Amynthas corticis) on soil structure, and to ascertain the nature and extent of the interactions between earthworms and millipedes. Millipedes consumed both litter species and preferred red oak litter over eastern hemlock litter. Mortality and growth of millipedes were not affected by earthworm presence during the course of the experiment, but millipedes assimilated much less litter-derived C when earthworms were present.Fauna and litter treatments had significant effects on soil respiration. Millipedes alone reduced CO₂ efflux from microcosms relative to no fauna controls, whereas earthworms alone and together with millipedes increased respiration, relative to the no fauna treatment. CO₂ derived from fresh litter was repressed by the presence of macrofauna. The presence of red oak litter increased CO₂ efflux considerably, compared to hemlock litter treatments.Millipedes, earthworms, and both together reduced particulate organic matter. Additionally, earthworms created significant shifts in soil aggregates from the 2000-250 and 250-53 μm fractions to the >2000 μm size class. Earthworm-induced soil aggregation was lessened in the 0-2 cm layer in the presence of millipedes. Earthworms translocated litter-derived C to soil throughout the microcosm.Our results suggest that invasion of ecosystems by A. corticis in the southern Appalachian Mountains is unlikely to be limited by litter species and these earthworms are likely to compete directly for food resources with native millipedes. Widespread invasion could cause a net loss of C due to increased respiration rates, but this may be offset by C protected in water-stable soil aggregates.  相似文献   

Aggregation behavior in the European earwig: Response to impregnated shelters     

《Crop Protection》2014

The European earwig Forficula auricularia Linnaeus (Dermaptera: Forficulidae) is a key predator of pests in pip fruit orchards; however, this insect can also cause economic damage in stone fruit crops. Pheromone-impregnated shelters may be useful to promote earwigs in orchards devoted to pip fruit and also to capture them in those used for stone fruit production. By using corrugated cardboard traps in four orchards during two years, we observed the aggregation behavior of European earwig in canopies. Under laboratory conditions, corrugated cardboard shelters impregnated by 0.2 individuals/cm² over one week attracted earwigs for 5 weeks within a range of 50 cm. Future field work should examine the potential of impregnated shelters to promote earwigs in pip fruit orchards and to remove them from stone fruit ones.  相似文献   

Spatial and temporal uncertainty of crop yield aggregations     

《European Journal of Agronomy》2017

The aggregation of simulated gridded crop yields to national or regional scale requires information on temporal and spatial patterns of crop-specific harvested areas. This analysis estimates the uncertainty of simulated gridded yield time series related to the aggregation with four different harvested area data sets. We compare aggregated yield time series from the Global Gridded Crop Model Intercomparison project for four crop types from 14 models at global, national, and regional scale to determine aggregation-driven differences in mean yields and temporal patterns as measures of uncertainty.The quantity and spatial patterns of harvested areas differ for individual crops among the four data sets applied for the aggregation. Also simulated spatial yield patterns differ among the 14 models. These differences in harvested areas and simulated yield patterns lead to differences in aggregated productivity estimates, both in mean yield and in the temporal dynamics.Among the four investigated crops, wheat yield (17% relative difference) is most affected by the uncertainty introduced by the aggregation at the global scale. The correlation of temporal patterns of global aggregated yield time series can be as low as for soybean (r = 0.28).For the majority of countries, mean relative differences of nationally aggregated yields account for 10% or less. The spatial and temporal difference can be substantial higher for individual countries. Of the top-10 crop producers, aggregated national multi-annual mean relative difference of yields can be up to 67% (maize, South Africa), 43% (wheat, Pakistan), 51% (rice, Japan), and 427% (soybean, Bolivia). Correlations of differently aggregated yield time series can be as low as r = 0.56 (maize, India), r = 0.05 (wheat, Russia), r = 0.13 (rice, Vietnam), and r = −0.01 (soybean, Uruguay). The aggregation to sub-national scale in comparison to country scale shows that spatial uncertainties can cancel out in countries with large harvested areas per crop type. We conclude that the aggregation uncertainty can be substantial for crop productivity and production estimations in the context of food security, impact assessment, and model evaluation exercises.  相似文献   

A comparison of soil and microbial carbon,nitrogen, and phosphorus contents,and macro-aggregate stability of a soil under native forest and after clearance for pastures and plantation forest   总被引：6，自引：0，他引：6  

G. P. Sparling  P. B. S. Hart  J. A. August  D. M. Leslie 《Biology and Fertility of Soils》1994,17(2):91-100

Total, extractable, and microbial C, N, and P, soil respiration, and the water stability of soil aggregates in the F-H layer and top 20 cm of soil of a New Zealand yellow-brown earth (Typic Dystrochrept) were compared under long-term indigenous native forest (Nothofagus truncata), exotic forest (Pinus radiata), unfertilized and fertilized grass/clover pastures, and gorse scrub (Ulex europaeus). Microbial biomass C ranged from 1100 kg ha^-1 (exotic forest) to 1310kg ha^-1 (gorse scrub), and comprised 1–2% of the organic C. Microbial N and P comprised 138–282 and 69–119 kg ha^-1 respectively, with the highest values found under pasture. Microbial N and P comprised 1.8–7.0 and 4.9–18% of total N and P in the topsoils, and 1.8–4.4 and 23–32%, respectively, in the F-H material. Organic C and N were higher under gorse scrub than other vegetation. Total and extractable P were highest under fertilized pasture. Annual fluxes through the soil microbial biomass were estimated to be 36–85 kg N ha^-1 and 18–36 kg P ha^-1, sufficiently large to make a substantial contribution to plant requirements. Differences in macro-aggregate stability were generally small. The current status of this soil several years after the establishment of exotic forestry, pastoral farming, or subsequent reversion to scrubland is that, compared to levels under native forest, there has been no decline in soil and microbial C, N, and P contents or macro-aggregate stability.  相似文献