武夷山低海拔和高海拔森林土壤有机碳的矿化特征

研究不同海拔土壤有机碳矿化对深入认识不同海拔森林土壤有机碳动态变化具有重要意义.本文以武夷山低海拔和高海拔森林土壤为研究对象,通过室内模拟其在各自年平均气温(17、9℃)条件下的矿化培养试验,探讨土壤有机碳矿化特征的差异.结果表明:培养126 d后,尽管高海拔森林土壤的有机碳含量显著高于低海拔森林土壤,但低海拔和高海拔森林土壤在各自环境温度背景下的有机碳累积矿化量并无显著差异.一级动力学方程均能较好地模拟高低海拔森林土壤有机碳矿化特征,高海拔和低海拔森林土壤有机碳潜在矿化量(CP)和矿化速率常数均无显著差异,但低海拔土壤C_P/SOC值和矿化率显著高于高海拔土壤,表明在环境温度背景下,低海拔土壤固碳能力低于高海拔土壤.随着培养时间增加,高海拔土壤微生物生物量碳和微生物熵显著高于低海拔土壤,表明高海拔土壤微生物的碳同化量高于低海拔土壤微生物,有利于有机碳的积累.高海拔森林土壤中的β-葡萄糖甘酶和纤维素水解酶高于低海拔森林土壤,说明高海拔土壤微生物可能更多地分解活性碳.未来气候变暖可能暗示着会降低高海拔土壤有机碳固碳能力和微生物碳利用效率,从而导致土壤有机碳储量下降.     

Growth response of Afzelia africana Sm. seedlings to ectomycorrhizal inoculation in a nutrient-deficient soil

 The growth and mineral nutrition responses of seedlings of two provenances of Afzelia africana Sm. from Senegal and Burkina Faso, inoculated with four ectomycorrhizal (ECM) fungi (Scleroderma spp. and an unidentified isolate) from the same regions were assessed in a pot experiment in a savanna ECM-propagule-free soil deficient in NPK. There was little variation in the ability of the different fungal species to colonize roots of either provenance of A. africana or to produce external hyphal in soil. Root colonization by ECM fungi and their hyphal development were not related to mineral nutrition or ECM dependency. Differences in P, N, Mg and Ca concentrations in the leaves of inoculated and non-inoculated Afzelia seedlings were not always associated with production of biomass. Only leaf K concentration increased in both provenances after ECM inoculation. However, the Burkina Faso provenance responded better to inoculation with the two fungal isolates than the Senegal provenance in terms of biomass production. This was due to stimulation of root dry weight of the Burkina Faso provenance. Therefore, the hypothesis arises that non-nutritional rather than nutritional effects explain the contribution of ECM inoculation to the growth of A. africana seedlings. Accepted: 27 April 1999     

Monitoring of bacterial community in a coniferous forest soil after a wildfire

Changes in the soil bacterial community of a coniferous forest were analyzed to assess microbial responses to wildfire. Soil samples were collected from three different depths in lightly and severely burned areas, as well as a nearby unburned control area. Direct bacterial counts ranged from 3.3-22.6 x 10(8) cells/(g.soil). In surface soil, direct bacterial counts of unburned soil exhibited a great degree of fluctuation. Those in lightly burned soil changed less, but no significant variation was observed in the severely burned soil. The fluctuations of direct bacterial count were less in the middle and deep soil layers. The structure of the bacterial community was analyzed via the fluorescent in situ hybridization method. The number of bacteria detected with the eubacteria-targeted probe out of the direct bacterial count varied from 30.3 to 84.7%, and these ratios were generally higher in the burned soils than in the unburned control soils. In the surface unburned soil, the ratios of alpha-, beta- and gamma-proteobacteria, Cytophaga-Flavobacterium group, and other eubacteria groups to total eubacteria were 9.9, 10.6, 15.5, 9.0, and 55.0%, respectively, and these ratios were relatively stable. The ratios of alpha-, beta- and gamma-proteobacteria, and Cytophaga-Flavobacterium group to total eubacteria increased immediately after the wildfire, and the other eubacterial proportions decreased in the surface and middle layer soils. By way of contrast, the composition of the 5 groups of eubacteria in the subsurface soil exhibited no significant fluctuations during the entire period. The total bacterial population and bacterial community structure disturbed by wildfire soon began to recover, and original levels seemed to be restored 3 months after the wildfire.     

The Restoration of Degraded Mountain Woodlands: Effects of Seed Provenance and Microsite Characteristics on Polylepis australis Seedling Survival and Growth in Central Argentina

South American high‐mountain ecosystems are greatly influenced by human disturbance. In the mountains of Córdoba, Argentina, Polylepis australis (Rosaceae) woodlands are currently highly fragmented and subject to extensive burning and livestock grazing, resulting in severe changes of habitat characteristics, which hamper natural regeneration. In order to find out how to achieve successful reforestation, we compared P. australis seedling survival and growth and the development of a shrubby habit for two seed provenances and different planting microsites. Survival of planted seedlings after 5 years was 70%, with most deaths (19%) in the first year and declining mortality with ongoing establishment. Survival did not show any relationship with seed provenance or microsite characteristics. Height growth averaged 34.6 ± 1.2 cm in 5 years. Seedlings produced from seeds collected in a well‐preserved woodland grew taller and showed a higher tendency for development of shrubby habit than those produced from seeds collected in a degraded woodland. Seedlings planted in more degraded microsites with exposed soil or rock due to past grazing pressure grew less and developed a more shrubby habit than those planted in better preserved microsites. Our results show that restoration of degraded areas with P. australis is possible and that there is potential to improve restoration success with a careful selection of seed provenance and planting microsites.     

Bioreduction of Cr(VI) by Bacillus sp. QH-1 isolated from soil under chromium-containing slag heap in high altitude area

A chromium-reducing strain QH-1, identified as Bacillus sp., was isolated from soil under chromium-containing slag heap in Qinghai high altitude area, China. The strain was found to resist 200 mg/L Cr(VI), and Cr(VI) negatively affects the metabolic activity of the cells, as well as the cell morphology of Bacillus sp. QH-1. The reduction efficiency of Cr(VI) at concentrations of Cr(VI) 25 mg/L, 50 mg/L, 100 mg/L and 200 mg/L were 99.48 %, 65.99 %, 23.22 % and 6.99 %, respectively, decreasing with increasing initial Cr(VI) concentration. This indicates that the toxicity of Cr(VI) increased with concentration. Energy dispersive X-ray analysis revealed that there was insoluble Cr(III) generated during Cr(VI) reduction. In order to apply strain QH-1 to remove Cr(VI) from groundwater, factors of concentration of electron donors (glucose) and temperature were investigated in a synthetic medium. The results demonstrated that glucose could promote the reduction of Cr(VI) by this strain, and the general trend of Cr(VI) reduction increased with temperature within the range of 4 to 37 °C. Cr(VI) was reduced effectively at 25 °C and 37 °C, and all of Cr(VI) was reduced after 96 h at 37 °C, while the reduction was slow at 4 °C and 15 °C, and it almost ceased after about 120 h. These results could be potentially useful for the bioremediation of Cr(VI) in groundwater.     

Rapid atrazine mineralisation in soil slurry and moist soil by inoculation of an atrazine-degrading Pseudomonas sp. strain

The evaluation of pesticide-mineralising microorganisms to clean-up contaminated soils was studied with the widely applied and easily detectable compound atrazine, which is rapidly mineralised by several microorganisms including the Pseudomonas sp. strain Yaya 6. The rate of atrazine removal was proportional to the water content of the soil and the amount of bacteria added to the soil. In soil slurry, 6 mg atrazine kg soil⁻¹ was eliminated within 1 day after application of 0.3 g dry weight inoculant biomass kg soil⁻¹ and within 5 days when 0.003 g kg soil⁻¹ was used. In partially saturated soil (60% of the maximal water-holding capacity) 15 mg atrazine kg soil⁻¹ was eliminated within 2 days by 1 g biomass kg soil⁻¹ and within 25 days when 0.01 g biomass kg soil⁻¹ was used. In unsaturated soil, about 60% [U-ring-¹⁴C]atrazine was converted to ¹⁴CO₂ within 14 days. Atrazine was very efficiently removed by the inoculant biomass, not only in soil that was freshly contaminated but also in soil aged with atrazine for up to 260 days. The bacteria exposed to atrazine in unsaturated sterile soil were still active after a starvation period of 240 days: 15 mg newly added atrazine kg soil⁻¹ was eliminated within 5 days. Received: 31 October 1997 / Received revision: 16 January 1998 / Accepted: 18 January 1998     

Generation of negative air ions by wheat seedlings in a high voltage electrization of soil

It was shown that plantlets of wheat (Triticum vulgare) are capable of generating negative aeroions during the electrization of soil by high-voltage impulses. Soil electrization was carried out either from the moment of planting of seeds or from the appearance of the first seedlings. The concentration of negative ions was measured in the air at a distance of 50 cm from plants. In both variants, similar growth-related changes in the concentration of negative ions were observed. The generation of negative ions began on day 6 after the planting of seeds and reached a concentration of 380 x 10(3) ion/cm3. During the next three days, this level remained unchanged. On day 10, the generation of negative aeroions increased abruptly; on days 10-14, it was twofold as high as on days 7-9. The level of generation of negative aeroions by plants stimulated from the moment of appearance of plantlets was 5-8% higher than by plants stimulated from the moment of planting. The intensity of generation of negative aeroions upon additional illumination and in full darkness remained unchanged.     

干旱区湿地芦苇各器官生态化学计量对土壤因子的响应

了解植物养分浓度及其化学计量对土壤因子的响应,对预测脆弱而敏感生态系统对环境变化的响应至关重要.以敦煌阳关湿地优势种芦苇(Phragmites australis)为对象,通过野外调查与实验分析,研究芦苇不同器官生态化学计量特征及其影响因素.结果 表明:芦苇各器官C、P含量为叶＞根＞茎,N含量及N∶P为叶＞茎＞根,C∶...     

Growth and survival of seedlings of native plants in an impoverished and highly disturbed soil following inoculation with arbuscular mycorrhizal fungi

We investigated whether arbuscular mycorrhizas influenced growth and survival of seedlings in an extremely impoverished and highly disturbed soil. Seedlings of four plants species native to the site were either inoculated with native sporocarpic arbuscular mycorrhizal (AM) fungi or fertilised prior to transplanting, and followed over 86 weeks at the site. One treatment was also irrigated with N-rich leachate from the site. In a laboratory experiment, seedlings were fertilised with excess P for 6 weeks, and location of the P store determined. Growth and survival of AM and fertilised seedlings were similar at the site. Inoculated mycorrhizal fungi and roots appeared to extend into the surrounding soil together. P concentration in leaves of all plants was extremely low. Irrigation with leachate increased growth of seedlings. In the laboratory experiment, significantly more P was stored in roots than shoots. We suggest that successful revegetation of extremely disturbed and impoverished sites requires selection of mycorrhizal fungi and plants to suit the edaphic conditions and methods of out-planting.     

神农架不同海拔典型森林凋落物的分解特征

采用凋落物分解袋法,研究了神农架不同海拔3种典型森林凋落物的分解动态.结果表明: 依据分解速率,常绿阔叶林、常绿落叶阔叶混交林和落叶阔叶林3种典型森林凋落物的分解过程明显分为两个阶段,前期(0～360 d)凋落物的质量损失率为后期(361～720 d)的2.62～4.08倍,前期的分解速率分别为后期的2.71、1.72和2.69倍.凋落物分解95%所需的时间分别为3.84、4.54和4.16 a.分解后期凋落物的分解速率与C/N及N、半纤维素、纤维素、木质素含量均呈显著相关关系.
     

The recovery of damaged pine forests in an area formerly polluted by nitrogen

An area in Lithuania containing coniferous stands of Scots pine and Norway spruce that were dead or damaged due to nitrogen pollution by a nitrogen fertilizer plant (JV Achema) was found to have expanded between 1974 and 1989 to a distance of 20 to 25 km northeast of the plant in the direction of prevailing winds. Over the last 10 years, when nitrogen pollution by the plant had decreased, a clear process of recovery of the damaged ecosystems could be observed. The following features of this process as it occurred in damaged Scots pine stands are discussed: (1) refoliation (or decreased defoliation) of damaged trees, where a clear positive trend could be observed; (2) changes in the species composition and in the covering by ground vegetation, where small changes and indication of less-nitrophilous species coverage could be detected; and (3) chemical and acidity changes in Luvisols and Arenosols, where a significant decrease could be seen especially concerning nitrate concentrations.     

The establishment patterns of tree seedlings are determined immediately after wildfire in a black spruce (Picea mariana) forest

Fire severity is predicted to increase in boreal regions due to global warming. We hypothesized that these extreme events will alter regeneration patterns of black spruce (Picea mariana). To test this hypothesis, we monitored seed dispersal and seedling emergence, survival and growth for 6 years from 2005 to 2010 after the 2004 wildfire on Poker Flat, interior Alaska, using 96 1 × 1 m plots. A total of 1,300 seedlings of black spruce and three broad-leaved deciduous trees (Populus tremuloides, Betula papyrifera, and Salix spp.) were recorded. Black spruce seedlings colonized burned and unburned ground surfaces for the first 2 years after the wildfire and established on any topographical surface, while the broad-leaved trees emerged less in areas of lower elevation, slope gradient and canopy openness and only on burned surfaces. Vascular plant cover on the ground floor increased the seedling establishment of black spruce and broad-leaved trees, most likely because of seed-trap effects. Black spruce grew faster on burned surface than on unburned surfaces. However, broad-leaved trees grew faster than black spruce on burned surfaces. Black spruce regenerates even after severe wildfire when the microtopography restricts the colonization of broad-leaved trees. The regeneration trajectories are determined soon after wildfire by a combination of seed limitation for black spruce and habitat preference for broad-leaved trees.     

Adaptive transgenerational plasticity in an annual plant: grandparental and parental drought stress enhance performance of seedlings in dry soil

Stressful parental (usually maternal) environments can dramatically influence expression of traits in offspring, in some cases resulting in phenotypes that are adaptive to the inducing stress. The ecological and evolutionary impact of such transgenerational plasticity depends on both its persistence across generations and its adaptive value. Few studies have examined both aspects of transgenerational plasticity within a given system. Here we report the results of a growth-chamber study of adaptive transgenerational plasticity across two generations, using the widespread annual plant Polygonum persicaria as a naturally evolved model system. We grew five inbred Polygonum genetic lines in controlled dry vs. moist soil environments for two generations in a fully factorial design, producing replicate individuals of each genetic line with all permutations of grandparental and parental environment. We then measured the effects of these two-generational stress histories on traits critical for functioning in dry soil, in a third (grandchild) generation of seedling offspring raised in the dry treatment. Both grandparental and parental moisture environment significantly influenced seedling development: seedlings of drought-stressed grandparents or parents produced longer root systems that extended deeper and faster into dry soil compared with seedlings of the same genetic lines whose grandparents and/or parents had been amply watered. Offspring of stressed individuals also grew to a greater biomass than offspring of nonstressed parents and grandparents. Importantly, the effects of drought were cumulative over the course of two generations: when both grandparents and parents were drought-stressed, offspring had the greatest provisioning, germinated earliest, and developed into the largest seedlings with the most extensive root systems. Along with these functionally appropriate developmental effects, seedlings produced after two previous drought-stressed generations had significantly greater survivorship in very dry soil than did seedlings with no history of drought. These findings show that plastic responses to naturalistic resource stresses experienced by grandparents and parents can "preadapt" offspring for functioning under the same stresses in ways that measurably influence realized fitness. Possible implications of these environmentally-induced, inherited adaptations are discussed with respect to ecological distribution, persistence under novel stresses, and evolution in natural populations.     

武夷山不同海拔高度土壤活性有机碳变化

采用连续熏蒸 培养法,测定了福建武夷山自然保护区不同海拔高度具有代表性的中亚热带常绿阔叶林、针叶林、亚高山矮林以及高山草甸土壤中有效碳含量,分析了土壤有效碳（LOC）与微生物量碳（MBC）、土壤总有机碳（TOC）、细根生物量（FRB）和土壤全氮（TN）之间的关系.结果表明：土壤有效碳占总有机碳的3.40%～7.46%;微生物量碳只是土壤有效碳中的一部分,占土壤有效碳26.87%～80.38%; 不同林分土壤有效碳含量随海拔增高而显著增大,随土层深度的增加而降低;土壤有效碳与微生物量碳、土壤总有机碳、细根生物量、土壤全氮之间呈极显著的相关关系.高海拔土壤有效碳含量显著高于低海拔土壤.     

Field microplot performance of the peach-almond hybrid GF-677 after inoculation with arbuscular mycorrhizal fungi in a replant soil infested with root-knot nematodes

The effects of arbuscular mycorrhizae (AM) on the development and nutrition of the peach almond hybrid GF-677 rootstock in a replant soil heavily infested with Meloidogyne javanica were evaluated in field microplot conditions for two growing seasons. There was a significant beneficial effect of mycorrhizal inoculation on plant growth and nutrition in previously pasteurized replant soil. In natural replant soil, early inoculation with a mixed AM inoculum of Glomus intraradices, Glomus mosseae and Glomus etunicatum did not affect growth parameters. Whilst inoculation with these AM fungi led to suppression of root-knot nematode reproduction, natural mycorrhizal colonization of the replant soil with native AM fungi did not. Accepted: 6 December 2000     

Bicarbonate concentration as affected by soil water content controls iron nutrition of peanut plants in a calcareous soil.

Strategy I peanut plants are frequently subjected to iron deficiency when growing in calcareous soils, which contain high concentrations of bicarbonate. In calcareous soils under field conditions, it has been noted that chlorosis increases in severity after excessive rainfall or irrigation, but the chlorosis symptoms of peanuts are alleviated after waterlogged soils dry. A pot experiment was conducted simulating the chlorosis symptom observed in the field when peanut plants are exposed to fluctuating soil water content induced from rainfall or irrigation. We investigated the bicarbonate fluctuations resulting from adjustable soil water content (SWC) that could lead to bicarbonate-induced iron chlorosis of peanuts growing in calcareous soil. The experiments included three treatments of SWC (50% of water holding capacity (WHC), 80% of WHC, and 100% of WHC) under two levels of CaCO(3) concentrations (at 8.67% and 18.67%.) The results showed that the iron nutrition of peanuts could be regulated by different SWC at both CaCO(3) levels. Our observations indicate that iron deficiency chlorosis symptoms in peanuts grown in high soil water content were more severe, compared to those of peanuts in lower soil water content. A shift from high soil water content to lower soil water content could improve or eliminate the iron deficiency chlorosis symptom of peanuts. The HCO(3)(-) concentration in the peanut rhizosphere increased with increasing SWC and CaCO(3) content and it correlated with the level of soil water content. We suggest that variations in the soil water content could induce HCO(3)(-) concentration variation in the rhizosphere of peanuts. Consequently, the high HCO(3)(-) concentration, which is induced by a high water content in calcareous soil and a high CaCO(3) level, could inhibit the physiological response to iron deficiency of peanuts, resulting in iron deficiency chlorosis. The study indicates that a reasonable agricultural practice of irrigation and drainage should be considered to improve and prevent iron deficiency chlorosis of strategy I plants in calcareous soil.     

Myanmarorchestia victoria sp.nov.(Crustacea,Amphipoda, Talitridae), a new species of landhopper from the high altitude forests in Myanmar

Myanmarorchestia victoria sp.nov.is described from high altitude habitats in Myanmar.The new species differs morphologically from its congeners by palp of maxilliped narrow;sexually dimorphic gnathopod Ⅱ,propodus of male chelate and propodus of female mitten-shaped;and dimorphic uropod Ⅱ,outer ramus of male with small teeth distally,outer ramus of female with three distal spines.Analysis of DNA barcode sequences and niche distinctiveness support recognition of the new species.     

Dehydration tolerance in apple seedlings is affected by an inhibitor of ABA 8'-hydroxylase CYP707A

The effects of an abscisic acid (ABA) 8′-hydroxylase inhibitor (Abz-F1) on ABA catabolism, stomatal aperture, and water potential were examined in apple seedlings under dehydration and rehydration conditions. In this study, 9-cis-epoxycarotenoid dioxigenase (MdNCED) and ABA 8′-hydroxylase (MdCYP707A) genes were isolated and their expressions were investigated under dehydration and rehydration conditions. The stomatal aperture decreased up to 4 h after spraying with Abz-F1 and the stomatal aperture in the Abz-F1-treated leaves was generally lower than that in the untreated control-leaves during the dehydration condition. Although the water potential in untreated control-leaves decreased with the progress of dehydration, it was maintained at a higher level in the Abz-F1 treated-leaves than in the untreated control-leaves during dehydration. Endogenous ABA concentrations increased with dehydration in both the Abz-F1 treated- and untreated-control-leaves, but the ABA levels in the Abz-F1 treated-leaves were higher than those in the untreated control-leaves throughout dehydration. In contrast, the phaseic acid (PA) concentrations in the Abz-F1 treated-leaves were lower than those in the untreated control-leaves during dehydration. The expressions of MdNCEDs in the Abz-F1 treated-leaves were lower than those in the untreated control-leaves regardless of the higher endogenous ABA concentrations. Moreover, the expressions of MdCYP707As in the Abz-F1 treated-leaves were also lower than those in the untreated control-leaves. Higher 50% effective concentrations (EC₅₀) and ascorbic acid concentrations were observed in the Abz-F1 treated-leaves, which show that the oxidative damage under dehydration may be reduced by Abz-F1 application.These results suggest that prompt stomata closure is required for survival under dehydration, and Abz-F1 application may therefore be of practical use. The increase of endogenous ABA, which induced prompt stomata closure in Abz-F1 treated-leaves may depend on inhibition of the expression of MdCYP707As. Furthermore, the results showed the close relationship between MdNCEDs and MdCYP707As on ABA catabolism.     

Dynamics of soil organic carbon and soil fertility affected by alfalfa productivity in a semiarid agro-ecosystem

We explore the dynamics of soil organic carbon of various forms and its relation with soil fertility in seeded alfalfa grassland established using a field micro-catchment technique to harvest water on the semiarid Loess Plateau in China. Five regimes were set up: (1) conventional flat cultivation without mulch (CK), (2) ridges and furrows were set up alternately on flat land, with 15 cm between each so that the distance between successive ridges (or successive furrows) was 30 cm, and the ridges were mulched with plastic film (M30), (3) similar to M30, but with twice the distance between furrows and ridges (M60), (4) similar to M30, but the ridges were not mulched (B30), (5) similar to M60, but the ridges were not mulched (B60). The increase in alfalfa forage yield in the mulch regimes promotes soil organic carbon (SOC) content, the light fraction of organic carbon (LFOC), the heavy fraction of organic carbon (HFOC) and microbial biomass carbon (MBC). MBC was significantly higher in M30 and M60 than in the other regimes. Significant positive correlation is found between MBC and LFOC (R=0.89; P<0.0001), and MBC and HFOC (R=0.82; P=0.00016). At the end of our three-year experiment, the C/N ratio of 10.09 in M60 was significantly (P<0.005) higher than the other regimes. Since a lower C/N ratio accelerates SOC decomposition in this region, the higher C/N ratio in M60 could limit mineralization of soil nitrogen, conserving soil nitrogen and SOC. The lower ratio of nitrate and nitrite nitrogen to total nitrogen, of 10.74, in M60 at the end of this experiment than in the other regimes and before sowing supports this point. The correlations of SOC with available P and with the ratio of available P to total P are positive in the dry year of 2001, but negative in the wet year of 2002. This can be explained on the basis that a high forage yield of alfalfa requires more soil available P in the wet years than in the dry years.