首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Soil nematodes were studied in 39- and 49-year-old “red” dumps mainly composed of Fe2O3 waste pyrite remnants from production of sulphuric and other acids, and in a 84-year-old “white” dump mainly composed of CaCO3 material from soda production. The youngest stage of spontaneous biological succession contained moss–lichen patches which were mainly inhabited by bacterivorous nematodes (Acrobeloides nanus, Panagrolaimus rigidus, Rhabditis terricola, Bursilla monhystera) in very low abundance (about 50×103 ind m−2). Invasion of grass resulted in increase of bacterivorous nematodes up to several millions  ind m−2 but with considerable seasonal fluctuations. Nematode assemblages diversified in sites colonized by various deciduous trees and Paratylenchus straeleni was the dominant plant parasitic nematode. In site with stabilized grass carpet on the “white” dump dominant nematodes were Geocenamus quadrifer and Pungentus engadinensis. Eudorylaimus spp. first appeared in 49-year-old dump but their populations remained very low (1–9×103 ind m−2). Some species found in control deciduous forests on natural soils (e.g. Xenocriconemella macrodora, Cephalenchus hexalineatus, Tylolaimophorus minor, Ogma menzeli, Hoplotylus femina) did not colonize deposits. Natural succession of nematodes on chemical waste materials was very slow and even after about 80 years their communities under deciduous trees showed many differences from those in nearby semi-natural mixed forests.  相似文献   

2.
The population abundance of free-living and plant-parasitic nematodes was investigated in a long-term rotation/tillage/stubble management experiment at Wagga Wagga Agricultural Institute, New South Wales (NSW), Australia. The treatments were a combination of two crop rotations: wheat (Triticum aestivum)–wheat and wheat–lupin (Lupinus angustifolius); two tillage systems: conventional cultivation (CC) and direct drill (DD); and two stubble management practices: stubble retention (SR) and stubble burnt (SB). Plots of one of the wheat–wheat treatments received urea at 100 kg N ha−1 during the cropping season. Soil samples from 0–5 and 5–10 cm depths were collected in September (maximum tillering), October (flowering) and December (after harvest), 2001, to analyse nematode abundance. Soil collected in September was also analysed for concentrations of total and labile C, and pH levels.Three nematode trophic groups, namely bacteria-feeders (primarily Rhabditidae), omnivores (primarily Dorylaimidae excluding plant-parasites and predators) and plant-parasites (Pratylenchus spp. and Paratylenchus spp.) were recorded in each soil sample. Of them, bacteria-feeders (53–99%, population range 933–2750 kg−1 soil) dominated in all soil samples. There was no difference in nematode abundance and community composition between the 0–5 cm and 5–10 cm layers of soil. The mean population of free-living and plant-parasitic nematodes varied significantly between the treatments in all sampling months. In most cases, total free-living nematode densities (Rhabditidae and Dorylaimidae) were significantly (P < 0.001) greater in wheat–lupin rotation than the wheat–wheat rotation irrespective of tillage and stubble management practices. In contrast, a greater population of plant-parasitic nematodes was recorded from plots with wheat–wheat than the wheat–lupin rotation. For treatments with wheat–wheat, total plant-parasitic nematode (Pratylenchus spp. and Paratylenchus spp.) densities were greater in plots without N-fertiliser (295–741 kg−1 soil) than the plots with N-fertiliser (14–158 kg−1 soil).Tillage practices had significant (P < 0.05) effects mostly on the population densities of plant-parasitic nematodes while stubble management had significant effects (P < 0.05) on free-living nematodes. However, interaction effects of tillage and stubble were significant (P < 0.01) for the population densities of free-living nematodes only. Population of Rhabditidae was significantly higher in conventional cultivated plots (7244 kg−1 soil) than the direct drilled (3981 kg−1 soil) plots under stubble retention. In contrast, plots with direct drill and stubble burnt had significantly higher populations of Dorylaimidae than the conventional cultivation with similar stubble management practice. No correlations between abundance of free-living nematodes, and concentration of total C and labile C in soil were observed in this study. These results showed that stubble retention contributed for enormous population density of free-living (beneficial) nematodes while conventional cultivation, irrespective of stubble management, contributed for suppressing plant-parasitic nematodes.  相似文献   

3.
《Applied soil ecology》2001,16(1):23-34
The succession of soil nematodes from initial planting with Pinus sylvestris seedling to about 30-year-old pine plantations on coal mining sands in the Lusatian lignite-mining district near Cottbus (Germany) was studied and compared with the nematode fauna of a 40-year-old semi-natural pine forest on naturally formed sandy soil. The initial stage was primarily characterised by a very low abundance (20×103 individuals/m2), which increased over a period of two years to values common in older pine plantations (500–600×103 individuals/m2). In the semi-natural forest the mean abundance of nematodes was about 1300×103 individuals/m2. Populations of Tardigrada, Rotifera and Enchytraeidae also increased with stand age. Nematode biomass increased from 49 to 543 mg m−2 in pine plantations and slightly decreased in the semi-natural forest to 301 mg m−2 over the period of investigation. The early colonisation of the initial stage was by bacterivorous (Acrobeloides) and fungal feeding (Aphelenchoides) nematodes, but the communities diversified as succession progressed with bacterivorous nematodes of the genera Plectus, Wilsonema and Metateratocephalus, root-fungal feeding Filenchus, omnivorous Aporcelaimellus and Eudorylaimus, and predacious Prionchulus becoming abundant. The abundance of plant-parasitic nematodes was very low. The greatest number of nematode genera was found in the semi-natural forest.  相似文献   

4.
Karin Hohberg   《Pedobiologia》2006,50(3):267-274
In an afforested coal-mining site at Berzdorf, Germany, the soil tardigrade community was investigated. Tardigrade densities ranged from 300 to 33,600 individuals m−2. Tardigrade distribution was very aggregated with standard deviations of up to 220% of mean densities. Fourteen species belonging to five eutardigrade genera were identified. Soils were dominated by the carnivorous tardigrade Macrobiotus richtersi that contributed 60% of overall densities. A comparison between nine soils of different forest ages (4–46 years) and tree species (poplar, alder, pine, mixed deciduous and mixed coniferous) showed no relationship of tardigrade species distribution and abundance to tree species, thickness of organic or litter layer, humus form, pH or soil moisture. Further, no correlation between nematode biomass and Macrobiotus richtersi abundances were detected. The age of afforested soils, however, affected tardigrade densities: younger soils (7–17 years) yielded higher tardigrade numbers compared to 46-year-old sites.Life history investigations on a strain of parthenogenetic Macrobiotus richtersi demonstrated a significant influence of temperature on egg development, survival rate, body growth and generation time. Hatching, first to fourth molts and maturing, on the other hand, were dependent upon body size alone. The simple, new culture method for carnivorous tardigrades described has successfully been utilized for parthenogenetic Macrobiotus richtersi for 6 years.  相似文献   

5.
Understanding how communities of important soil invertebrates vary with land use may lead to the development of more sustainable land-use strategies. We assessed the abundance and species composition of earthworm communities across six replicated long-term experimental ecosystems that span a gradient in agricultural land-use intensity. The experimental systems include a conventional row-crop agricultural system, two lower-intensity row-crop systems (no-till and tilled organic input), an early successional old-field system, a 40–60 years old coniferous forest plantation, and an old-growth deciduous forest system. Earthworm populations varied among systems; they were lowest in the most intensively managed row-crop system (107 m−2) and coniferous forest (160 m−2); intermediate in the old-field (273 m−2), no-till (328 m−2) and tilled organic (344 m−2) cropping systems; and highest in the old-growth deciduous forest system (701 m−2). Juvenile Aporrectodea species were the most common earthworms encountered in intensively managed systems; other species made up a larger proportion of the community in less intensively managed systems. Earthworm community biomass and species richness also varied and were lowest in the conventional row-crop system and greatest in the old-growth forest system. These results suggest that both land-use intensity and land-use type are strong drivers of the abundance and composition of earthworm communities in agricultural ecosystems.  相似文献   

6.
Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) are the two most dominating soil invertebrates in terms of biomass in boreal coniferous forest soils. A microcosm experiment was set up in order to study the influence of pH, moisture and resource addition on D. octaedra and C. sphagnetorum when both species are simultaneously present. Two kinds of coniferous forest humus were used as substrate, pine stand humus (pH 4.2), and spruce stand humus (pH 4.6); in the third treatment the pine stand humus was adjusted with slaked lime (CaOH2) to the same initial pH as the spruce stand humus. Each substrate was adjusted to water contents of 25%, 42.5% and 60% of WHC (referred to as ‘dry’, ‘moist’ and ‘wet’). In the second part of the experiment, spruce needle litter and birch leaf litter were separately added into the pine stand humus (‘moist’, unlimed) and compared with a control without litter. The microcosms were plastic jars with 75 g (d.m.) of humus, into which 4 specimens of D. octaedra and 70 specimens of C. sphagnetorum were added. D. octaedra showed the highest biomass and C. sphagnetorum the lowest biomass in the spruce stand humus with higher pH. Moisture did not affect earthworms, while C. sphagnetorum thrived best at the highest moisture. Addition of both kinds of litter increased the numbers and biomass of D. octaedra, while on C. sphagnetorum resource addition had little effect. The results help to explain the abundance of these two species in coniferous forests differing in soil acidity, moisture and fertility.  相似文献   

7.
Impacts of non-native spruce reforestation on ground beetles were studied. Pitfall catches from recently established (5 years), young (15 years), middle-aged (30 years), old spruce plantation (50 years) and a native beech forest (70 years) were compared. Results indicate that the soil temperature, the pH, the compactness and the CaCO3 content of the soil, the cover of the leaf litter and the herbs and the abundance of the carabids’ preys are the most important factors determining the spatial pattern of ground beetles. Deciduous forest specialist species decreased significantly in abundance in the non-native spruce plantations, and they were abundant only in the native beech forest. Ground beetles that overwinter as larvae and the medium and large beetles were also significantly more abundant in the deciduous forest than in the reforested habitats indicating that the environmental regimes are more even and stable in the deciduous forest than in the plantations. Species typical of open habitats, winged and small beetles increased remarkably in abundance in the recently established plantation. They disappeared or declined in density after closure of the canopy layer suggesting the colonization of new habitats and the process of the secondary succession after reforestation.  相似文献   

8.
pH values and buffering capacity were determined for bark samples of five deciduous trees (oak, alder, hornbeam, ash, linden), one shrub (hazel) and one coniferous tree (scots pine) in the Cracow Industrial Region (Southern Poland) and, for comparison, in the Bia?owieza Forest (North-Eastern Poland). The correlation was found between acidification of tree bark and air pollution by SO2 in these areas. All trees showed the least acidic reaction in the control area (Bia?owieza Forest), more acidic in Niepolomice Forest and the most acidic in the center of Cracow. The buffering capacity of the bark against alkali increased with increasing air pollution. The seasonal fluctuations of pH values and buffering capacity were found. Tree bark is recommended as a sensitive and simple indicator of air pollution.  相似文献   

9.
Samples of strongly acid forest litter and humus from beneath Sitka spruce, heather, Scots pine and larch from two sites in north-east Scotland were incubated aerobically at 20°C in the laboratory. At the Glen Tanar site, spruce litter and larch humus showed significant nitrification and ammonification whereas spruce humus and Scots pine humus produced only NH4+-N. Heather humus showed no net mineralization. At the Fetteresso site, application of fertilizer N, P and K to Sitka spruce up to 3 yr previously, significantly stimulated the production of NO3−-N in both litter and humus.Amendment of the samples with organic N as peptone caused significant increases in NO3−-N production in those samples that already showed nitrification. The increases in NO3−-N generally represented a low proportion of the added peptone-N. Amendment with NH4+-N as (NH4)2SO4 either had no effect or significantly reduced NO3−-N production (in larch humus). The results suggest the occurrence of heterotrophic nitrification in some of these forest samples.Net immobilization of NH4+-N was typically greater in NH4+-N amended than in peptone amended samples, except for heather humus which showed complete immobilization of both N sources.Total mineral N produced at the end of the aerobic incubation was correlated (P < 0.01) with NH4+-N produced during a 30-day anaerobic incubation at 30°C. Net NO3−-N production was greater in litter than in the corresponding humus samples and was correlated (P < 0.001) with initial organic N soluble in 1 m KCl.  相似文献   

10.
In boreal forests ericaceous shrubs often dominate the forest floor vegetation. Nitrogen enrichment has been shown to decrease shrub abundance and in this study we explored whether it also affects the root associated fungal communities. Fine roots of Vaccinium myrtillus were collected in a Norway spruce dominated forest and of Vaccinium vitis-idaea in a Scots pine dominated forest. In both forests, nitrogen enrichment was experimentally induced by adding 12.5 and 50 kg N ha−1 yr−1 for 12 (spruce forest) and four (pine forest) years. Based on terminal restriction fragment length polymorphisms, subcloning and sequencing analyses, the root associated fungal communities were examined. We found 93 fungal species including Asco-, Basidio- and Zygo-mycota. In general, the Rhizoscyphus ericae aggregate was the most dominant and this was followed by Herpotrichiellaceae and Sebacina. Ordination analysis revealed that nitrogen enrichment did not change species composition of the fungal communities in neither the spruce nor the pine forest, while fungal community structures were clearly discriminated between the dominant shrub species in each forest. Similarly, no fungal species showed a significant response to nitrogen enrichment. Therefore, nitrogen enrichment appears to have no effect on root associated fungi of understorey dwarf shrubs in boreal forests, while it is clear that spruce and pine forests harbor distinctive communities of these fungi.  相似文献   

11.
ABSTRACT

To investigate fine root dynamics after thinning (50% of standing tree) and liming calcium magnesium carbonate[CaMg(CO3)2] 2 Mg ha? 1, a 2-year study was performed in 40-year-old pitch pine (Pinus rigida Mill.) and 44-year-old Japanese larch (Larix leptolepis Gord.) plantations in central Korea. Mean total fine root mass (kg ha? 1± SE) in the control, thinned, and limed plots were 1234 ± 32, 1346 ± 67, and 1134 ± 40 for the pitch pine plantation and 1655 ± 48, 1953 ± 58, and 1868 ± 70 for the Japanese larch plantation, respectively. Live fine root mass of pitch pine at 0-10 cm soil depth decreased after thinning and liming. In addition, liming significantly increased dead fine root mass of Japanese larch. Fine root production (kg ha? 1 yr? 1± SE) in the control, thinned and limed plots was 1108 ± 148, 2077 ± 262, and 1686 ± 103 for the pitch pine plantation and 1762 ± 103, 1886 ± 277, and 2176 ± 271 for the Japanese larch plantation, respectively. Fine root turnover rates increased after liming for both plantations. Fine root nitrogen (N) and phosphorus (P) concentrations of Japanese larch (1.012% of N and 0.073% of P) were higher than those of pitch pine (0.809% of N and 0.046% of P) in the control. Also N and P inputs into soil through fine root turnover increased after treatments. Results indicated that comparing fine root dynamics among forest types and after forest management practices might influence differences in soil fertility and underground nutrient cycling.  相似文献   

12.
《Applied soil ecology》2007,35(1):174-183
An increasing amount of evidence shows the context dependent nature of various biotic interactions across terrestrial and aquatic ecosystems. We established a laboratory experiment to study whether the effects of Cognettia sphagnetorum (Enchytraeidae) and ectomycorrhizal fungi on Scots pine (Pinus sylvestris) seedling growth are influenced by wood ash application. Acidic coniferous forest soil was treated with wood ash at 5000 kg ha−1 or left as ash-free control and inoculated with soil saprotrophic microbes and nematodes. The microcosms were destructively sampled 26 and 51 weeks after initiation of the experiment. We measured enchytraeid and pine seedling biomass, abundance of nematodes and leaching of NH4+-N and NO3−-N at both samplings, and root length and N concentration of pine needles at the end of the experiment. On average enchytraeids and mycorrhizal fungi enhanced pine biomass production in the ash-free control soils, however, their impact was most pronounced when these organisms were alone in the systems. In fact, mycorrhizas tended to have a negative impact on the seedlings in the presence of enchytraeids. Wood ash had a clear negative impact on enchytraeid populations. Wood ash decreased pine growth when enchytraeids and EM-fungi were alone in the systems, but when together they apparently compensated for the negative effects of wood ash on the seedlings. It is concluded that interactions between soil fauna, mycorrhizal fungi and plants are context dependent, thereby rendering predictions of the outcome of species interactions in soil food webs a demanding task.  相似文献   

13.
基于不同林分类型下土壤碳氮储量垂直分布   总被引：4，自引：1，他引：3  
以辽东大伙房水库周边防护林典型林分针阔混交林(落叶松-油松-刺槐混交林)、油松林、落叶松林、刺槐林为研究对象,对其土壤养分含量进行测定,研究了不同林分土壤剖面上有机碳、全氮、有机碳储量的分布规律。结果表明:随着土层深度的增大,4种林分的土壤有机碳、全氮含量均逐渐降低;4种林分土壤剖面有机碳含量大小顺序为落叶松林(24.16g/kg)刺槐林(23.07g/kg)针阔混交林(16.06g/kg)油松林(15.76g/kg);全氮含量大小顺序为刺槐林(5.23g/kg)落叶松林(4.57g/kg)油松林(3.45g/kg)针阔混交林(2.42g/kg);C/N平均值大小顺序为落叶松林(7.36)针阔混交林(6.51)油松林(4.67)刺槐林(4.57);4个林分0-40cm土层的有机碳储量大小为落叶松林(112.94t/hm~2)刺槐林(107.40t/hm~2)针阔混交林(105.42t/hm~2)油松林(89.89t/hm~2);4种林分土壤pH无明显差别,各土层土壤pH随土层深度增加而增大;4种林分土壤容重由高到低顺序依次为针阔混交林(1.73g/cm~3)油松(1.65g/cm~3)落叶松(1.64g/cm~3)刺槐(1.56g/cm~3)。4个林分土壤有机碳含量与土壤全氮含量互相间均存在极显著正相关关系,土壤有机碳、全氮含量与C/N之间则没有明显相关关系;在针阔混交林中,土壤容重、土壤全氮含量和土壤pH与土壤有机碳之间存在线性数量关系,而其他纯林则没有这种关系。  相似文献   

14.
Background, Aims, and Scope  An improved understanding of important soil carbon (C) and nutrient pools as well as microbial activities in forest ecosystems is required for developing effective forest management regimes underpinning forest productivity and sustainability. Forest types and management practices can have significant impacts on soil C and nutrient pools as well as biological properties in forest ecosystems. Soil C and nutrient pools were assessed for adjacent natural forest (NF), first rotation (1R) (50-year-old), and second rotation (2R) (1-year-old) hoop pine (Araucaria cunninghamii Ait. ex D. Don) plantations in southeast Queensland of subtropical Australia. Materials and Methods  Five transects spaced 3 m apart with 9 sampling points along each transect were selected (9.6 m × 12.0 m each site), with 45 soil cores (7.5 cm in diameter) collected and separated into 0–10 and 10–20 cm depths. These soils were analysed for total C, total nitrogen (N), C (δ13C) and N (δ15N) isotope composition. The 0–10 cm soils were analysed for pH, CEC, exchangeable cations, total P and total K, and assayed for microbial biomass C and N, respiration, metabolic quotient, potential mineralizable N (PMN), gross N mineralization (M) and immobilization (I). Results  Total C and N in 0–10 cm soils were higher under NF and 1R plantation than under 2R plantation, while they were highest in 10–20 cm soils under NF, followed by the 1R and then 2R plantation. δ13C was lower under NF than under the plantations, while δ15N was higher under NF than under the plantations. Total P was the highest under NF, followed by the 1R and then 2R plantation, while total K was higher under the 2R plantation. No significant differences were detected for pH, CEC, exchangeable cations, microbial C and N, respiration and metabolic quotient among the 3 sites. PMN and M were higher under NF, while I was the highest under the 2R plantation, followed by the NF and then 1R plantation. Discussion  Soil total C and N in 0–10 cm depth were significantly lower under 2R hoop pine plantation than those under NF and 1R hoop pine plantation. There were significant reductions in soil total C and N from NF to 1R and from 1R to 2R hoop pine plantations in 10–20 cm depth. This highlights potential N deficiency in the 2R hoop pine plantations, and application of N fertilizers may be required to improve the productivity of 2R hoop pine plantations. There were no significant differences in other soil chemical and physical properties in 0–10 cm depth among the 3 sites under NF, 1R and 2R hoop pine plantations, except for soil total P and K. Soil microbial biomass C, CO2 respiration and metabolic quotient did not differ among the 3 sites assessed, perhaps mainly due to these biological variables being too sensitive to variations in soil chemical and physical properties and thereby being associated with a larger variability in the soil biological properties. However, soil potential mineralizable N, gross N mineralization and immobilization were rather sensitive to the conversion of NF to hoop pine plantation and forest management practices. Conclusions  Total C and N in the top 20 cm soil were highest under NF, followed by 1R and then 2R hoop pine plantations, indicating that N deficiency may become a growth-limiting factor in the 2R hoop pine plantations and subsequent rotations of hoop pine plantation. The sample size for soil δ13C seems to be much smaller than those for soil total C and N as well as δ15N. The significant reductions in soil total P from NF to 1R and then from 1R to 2R hoop pine plantations highlight that P deficiency might become another growth-limiting factor in the second and subsequent rotations of hoop pine plantations. Soil microbial properties may be associated with large spatial variations due to these biological properties being too sensitive to the variations in soil chemical and physical properties in these forest ecosystems. Recommendations and Perspectives  Soil potential mineralizable N, gross N mineralization and immobilization were useful indices of soil N availability in response to forest types and management practices. The sampling size for soil δ13C was much smaller than the other soil chemical and biological properties due to the different patterns of spatial variation in these soil properties.  相似文献   

15.
Vegetation type and ecosystem structure affect major aspects of the mercury (Hg) cycle in terrestrial ecosystems which serve as important storage pools for a long‐term legacy of natural and anthropogenic Hg release to the environment. The goal of this study was to evaluate the integrated effects of 80 y of different vegetative type on Hg accumulation and partitioning in terrestrial ecosystems by comparing Hg concentrations and pools of two adjacent forests: a coniferous Douglas fir (Pseudotsuga menziesii) and a deciduous red alder (Alnus rubra) stand. These stands grew for > 80 y in close proximity (200 m) with identical site histories, soil parent materials, and atmospheric exposure. Results showed that the Douglas fir stand was characterized by significantly higher Hg concentrations and Hg : C ratios in aboveground biomass compared to the deciduous red alder forest. For foliage, higher Hg concentrations (plus 43 μg kg–1) were expected due to foliage age, but Hg concentrations also were higher in woody tissues (by 2 to 18 μg kg–1) indicating increased uptake of atmospheric Hg by coniferous tissues. These differences were reflected—and further increased—in litter horizons where Hg‐concentration differences increased in highly decomposed litter to > 200 μg kg–1. In soils, no difference in concentrations of Hg was observed, but Hg : C ratios were consistently higher in the coniferous Douglas fir. Estimation of pool sizes of C and Hg in soils and at the whole ecosystem level showed that considerably smaller C pools in the coniferous stand as a result of faster C turnover and lower productivity did not lead to corresponding declines in Hg‐pool sizes. The partitioning of Hg among ecosystem components—including distribution between aboveground and belowground components and distribution through the soil profile—was largely unaffected by forest type. Methyl‐Hg concentrations observed in litter layers were also significantly higher in litter of Douglas fir, along with a higher proportion of methylated Hg of total Hg. In soils, methyl‐Hg concentrations were similar in both stands. Comparison of these adjacent forest stands highlights that vegetation type affects concentrations of total Hg in otherwise equivalent sites and that differences also exist in respect to methylated Hg.  相似文献   

16.
[目的]比较冀北山地天然次生杨桦林(13,18和28a)和人工落叶松林(9,13,15和30a)地上植被层(林冠层、凋落物)的水文调控功能,为评估两种森林类型的转化对该地区水文过程的影响提供科学依据。[方法]采用标准样地和测定分析法对林分的生物量、凋落物及其持水量的进行测算。[结果](1)不同林龄的人工落叶松林地上植被层的降水截留量均大于天然次生杨桦林,且差异显著。(2)两种林分类型不同地上植被层的截留量均表现为:凋落物林冠层灌木层。(3)幼、中龄人工落叶松林的林冠截流量明显大于同龄的天然次生杨桦林,而近熟林,由抚育间伐导致的林分密度下降使得人工落叶松林低于天然次生杨桦林。(4)在各个林龄上,人工落叶松林的凋落物持水量均显著大于天然次生杨桦林,其中13a落叶松为35.36±6.50t/hm2,13a杨桦林为15.79±4.85t/hm2。[结论]冀北山地大面积的人工落叶松林地上植被层具有良好的水文调控功能,其水文调控功能不低于甚至高于当地的天然次生杨桦林,对人工林的抚育间伐在一定程度上会使地上植被层的水文调控功能出现一定程度的下降。  相似文献   

17.
Temporal and spatial variability of soil respiration (Rs) was measured and analyzed in a 74-year-old, mixedwood, boreal forest in Ontario, Canada, over a period of 2 years (August 2003–July 2005). The ranges of Rs measured during the two study years were 0.5–6.9 μmol CO2 m−2 s−1 for 2003–2004 (Year 1) and 0.4–6.8 μmol CO2 m−2 s−1 for 2004–2005 (Year 2). Mean annual Rs for the stand was the same for both years, 2.7 μmol CO2 m−2 s−1. Temporal variability of Rs was controlled mainly by soil temperature (Ts), but soil moisture had a confounding effect on Ts. Annual estimates of total soil CO2 emissions at the site, calculated using a simple empirical Rs–Ts relationship, showed that Rs can account for about 88 ± 27% of total annual ecosystem respiration at the site. The majority of soil CO2 emissions came from the upper 12 to 20 cm organic LFH (litter–fibric–humic) soil layer. The degree of spatial variability in Rs, along the measured transect, was seasonal and followed the seasonal trend of mean Rs: increasing through the growing season and converging to a minimum in winter (coefficient of variation (CV) ranged from 4 to 74% in Year 1 and 4 to 62% in Year 2). Spatial variability in Rs was found to be negatively related to spatial variability in the C:N ratio of the LHF layer at the site. Spatial variability in Rs was also found to depend on forest tree species composition within the stand. Rs was about 15% higher in a broadleaf deciduous tree patch compared to evergreen coniferous area. However, the difference was not always significant (at 95% CI). In general, Rs in the mixedwood patch, having both deciduous and coniferous species, was dominated by broadleaf trees, reflecting changing physiological controls on Rs with seasons. Our results highlight the importance of discerning soil CO2 emissions at a variety of spatial and temporal scales. They also suggest including the LFH soil layer and allowing for seasonal variability in CO2 production within that layer, when modeling soil respiration in forest ecosystems.  相似文献   

18.
《Applied soil ecology》2006,32(3):186-198
Comparisons of organic and inorganic fertilizer effects on nematode communities depend on the specific organic fertilizer used. Field experiments were conducted during 2001 and 2002 in a squash (Cucurbita pepo) agroecosystem to determine if applying sunn hemp (Crotalaria juncea) hay as an organic fertilizer improved nematode communities involved in soil nutrient cycling compared to an equivalent N rate (100 kg N/ha) of ammonium nitrate. Fertilizer source had minimal effect on nematode communities in 2001 when treatments were applied after a winter cover crop of oats (Avena sativa), but differences (P ≤ 0.05) between the fertilizer sources occurred in 2002 when no winter cover cropping preceded squash. Fertilization with sunn hemp hay increased abundance of the bacterivore guilds Ba1 and Ba2, and increased fungivores at the end of the experiment. Compared to ammonium nitrate, fertilization with sunn hemp hay resulted in a community with lower maturity index, higher enrichment index, and lower channel index, consistent with a disturbed and nutrient-enriched soil food web undergoing bacterial decomposition. Sunn hemp hay occasionally stimulated omnivorous nematodes, but suppressed plant-parasitic nematodes relative to ammonium nitrate fertilizer. Increasing the sunn hemp hay rate to 200 kg N/ha increased the abundance of bacterivores, fungivores, and predatory nematodes, and total nematode abundance compared to hay at 100 kg N/ha. Fertilization with ammonium nitrate increased the percentage of herbivores, but reduced percentage and abundance of omnivores. In conclusion, sunn hemp fertilizer maintained greater numbers of nematodes involved in nutrient cycling as compared to ammonium nitrate.  相似文献   

19.
A field trial was conducted during the kharif (rainy) seasons of 2002 and 2003 at the Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India. The trial was carried out to study the effect of planting methods, sources and levels of nitrogen on soil properties, yield and NPK uptake by rice (Oryza sativa L.) under direct seeded condition. Planting methods significantly influenced the physical, chemical and biological properties of soil. Bulk density (1.385 g cm−3), organic carbon (0.43%) and soil moisture content (15.46%) were higher in zero till seeding plots than rotavator and conventional seeding. However, infiltration rate, soil temperature, pH and electrical conductivity showed a declining trend under this treatment and were found maximum (11.54 mm h−1, 36.21 °C at 55 DAS, 30.65 °C at harvest, 7.59 and 0.47 ds m−1) with conventional seeding. The maximum population of bacteria (25.60 × 105), fungi (14.26 × 104) and azotobactor (10.19 × 103) were found in the plot with zero till seeding while in case of actinomycetes the highest population (25.61 × 105) was found in conventional seeding. Nitrogen sources as well as levels failed to bring about any significant change in the soil properties. The highest grain (3825 kg ha−1) and straw yields (5446 kg ha−1) and N, P, K uptake were recorded in conventional seeding and were found significantly superior to zero till seeding (3144 kg ha−1) but it remained at par with rotavator seeding (3585 kg ha−1). Among the nitrogen sources, neem (Azadirachta indica) coated urea produced significantly higher grain (3761 kg ha−1) and straw yields (5396 kg ha−1) with greater NPK uptake than prilled urea and prilled urea + spent mentha. (The distillation waste of mint (Mentha arvensis) herbage is known as spent mentha.) Application of 150 kg N ha−1 produced maximum grain (3828 kg ha−1) and straw yields (5460 kg ha−1) although it remained at par with 100 kg N ha−1 (3738 and 5393 kg ha−1).  相似文献   

20.
Amynthas agrestis is an exotic, invasive earthworm in North America that has been associated with horticulture settings as well as damage to forest soil. An experiment was conducted to find out whether A. agrestis, an earthworm commonly found in mulches in Vermont, stimulates ligninolytic enzymes in the presence of commercial wood mulches. Mesocosms filled with a sandy loam soil were topped with either spruce, cedar or pine mulch. Half of the mesocosms received juvenile A. agrestis, the other half did not. After 7 weeks soils were analyzed for phenoloxidase and peroxidase activity. Most A. agrestis survived and developed into adults during the incubation period. Significantly greater phenoloxidase activity was detected in soils with A. agrestis than without earthworms. Mean (standard deviation) phenoloxidase activities in the presence of A. agrestis were 0.15 (±0.10), 1.14 (±0.46), 2.71 (±0.98) μmol g−1 h−1 for pine, spruce and cedar respectively, and 0.012 (±0.023), 0.25 (±0.25), 0.78 (±0.45) μmol g−1 h−1 in the absence of A. agrestis. There was significantly greater peroxidase activity for the pine and spruce treatment when earthworms were present. Mean peroxidase activities were 0.47 (±0.21), 0.94 (±0.29), 1.20 (±0.77) μmol h−1 g−1 soil for pine, spruce and cedar, respectively for soils with A. agrestis and 0.15 (±0.10), 0.37 (±0.10), 0.63 (±0.30) μmol h−1 g−1 soil in the absence of earthworms. The increased ligninolytic activity in combination with successful maturation of juveniles into adult A. agrestis suggests that mulch can be habitat for these invasive earthworms. This finding is supported by a survey of master gardeners in Vermont and New Hampshire 20% of whom reported to have seen these earthworms mainly in their gardens and mulched beds.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号