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1.
The Landesumweltamt North-Rhine Westfalia is operating eight open-top chambers as well as six reference plots at a site on a westerly exposed slope (540 m a.s.) in the Egge mountains, 130 km northeast of the Ruhr area. Since 1991 eighteen 6 yr old beech trees (Fagus sylvatica L.) per plot/chamber were exposed either to ambient air (AA), non-filtered air (NF) or charcoal-filtered air. Ambient air pollutants (O3. SO2, NOx) as well as meteorological parameters were monitored continuously inside chambers as well as in the ambient. Growth parameters (bud development, stem diameter, shoot length, shoot diameter, leaf area, leaf colouration, leaf abscission) were assessed over the years 1992–1994.Even in the first year a marked earlier colouration of the leaves was observed in the NF (AOT 40=16.2 ppm·hr) versus the CF treatment (AOT 40=0.2 ppm·hr) and leaf abscission was two weeks earlier on NF-trees, indicating the common ozone effect of early senescence. Effects became more pronounced with increasing time of exposure. While hardly any effects on growth could be seen during the first and second year, shoot length and shoot diameter were reduced significantly by about 15 % in NF versus CF treatments in 1994. Similar effects were seen for the leaf area. No effects could be shown for bud development or stem diameter. Ozone specific symptoms were observed on individual trees in the NF and AA treatments and especially pronounced in 1994 (AOT 40=24.1 ppm·hr), but also to a much lesser extent in the CF-treatment. AOT40 value of 10 ppm·h, proposed as provisional standard for the protection of trees by UN-ECE seems to be stringent enough according to the results of this exposure study.  相似文献   

2.
Time of mulching can influence the growth environment and performance of white yam (Dioscorea rotundata Poir). An on-farm trial was conducted during the 1988–1989 and 1989–1990 seasons (October–August) in Nigeria to determine the effect of time of mulching (October–February) on the hydrothermal regime and emergence, growth and tuber yield of white yam. Application of 12.5 mg ha−1 of dry Eupatorium odoratum L. (Syn. Chromolaena odorata L.) mulch on top of the mounds significantly improved soil moisture content of the 15 cm surface layer by 50–120 g kg−1 and decreased the maximum soil temperature by 2–7°C at 15 cm depth in the early growing season (March–April). The emergence and development of yam seedlings were significantly lower in unmulched plots than in mulch-treated plots. Mulching significantly increased tuber yield by about 10–15 mg ha−1 season−1. Plots mulched in October–December were more moist by 20–60 g kg−1 and cooler by 1–3°C, and had 27–44% greater emergence than those mulched in January or February. The number of leaves per plant, vine diameter and leaf area index were also significantly greater in plots mulched in October–December than plots mulched in January or February. Consequently, shoot dry weight was about 28–36% greater in yam mulched in October–December than in yam mulched in February. However, the time of mulching had no effect on soil moisture of the surface layer at the beginning of the rainy season (April), on yam emergence in May and on tuber yield and yield components. Although time of mulching did not significantly affect tuber yield, the increase (10–15%) in the tuber yield of yam mulched in December–February compared to the yam mulched in October or November was considerable. It was concluded that yam planted in October, just before the rain stops, can be mulched in January or February without detrimental effect on emergence, growth and tuber yield.  相似文献   

3.
The symbiotic efficiency of coastal sand dune rhizobial isolates on four cultivated legumes, cowpea (Vigna unguiculata), green gram (Vigna radiata), black gram (Vigna mungo) and horse gram (Macrotyloma uniflorum), was assessed. Among the isolates of Someshwara (S1–S5), inoculation of S5 resulted in the highest increase of shoot biomass in cowpea (control vs experimental, 1:6), while inoculation of P1 among the Padubidri isolates (P1–P5) induced the highest shoot biomass in cowpea (1:14.4). Inoculation of the isolate P2 induced higher shoot biomass against uninoculated controls of horse gram (12.6:1), green gram (11.2:1) and black gram (6.1:1). One-way ANOVA revealed significant difference in the shoot biomass between uninoculated and inoculated cowpea plants with ten rhizobial isolates (P <0.05). Cultivation of surface-sterilized green gram seeds on unsterilized dune sand resulted in profuse flowering as well as nodules within 6 weeks indicating possibilities for isolating efficient rhizobial strains through cultivating edible legumes on coastal sand dune soils.  相似文献   

4.
The effects of different soil textures (namely sand, loam, and clay) on peanut growth and development were investigated using the carton planting method. The results showed that sand is conducive to the growth of stems and leaves of peanuts in the early growth period, loam is conducive to the growth of stems and leaves in the middle and late periods, and clay is not conducive to the growth of stems and leaves of peanuts throughout the entire growth period. Soil texture had a significant effect on the number of peanut flowers. This is because the amount of flowering peanuts was insufficient in the clay. Although the amount of flowering peanuts was large in the sand, the peanuts mainly flowered in the late period, and there was a large amount of fruitless flowers. In the loam, the peanuts mainly flowered in the early period, and there was a large amount of fruitful flowers. The difference in the total number of pegs between the sand and loam was not significant, but either had more pegs than when grown in clay. Peanuts accumulated pod dry matter quickly in the sand early in the season, but pod growth slowed later in the season. The pod dry matter in the loam was accumulated mostly in the middle and late periods. Clay was not conducive to pod dry-matter accumulation. The moderate aeration and water and fertility retention of the loam was more suitable for peanut growth and development, as well as yield formation.  相似文献   

5.
In order to assess to what degree the ongoing global warming has affected flowering time of apple trees in the Nordic climate, we studied flowering phenology of trees in an orchard in Southern Norway. Correlation analysis of a 70-year (1946–2016) data series for flowering time of the cultivar ‘Gravenstein’ revealed a close relationship of the flowering phenophase with April–May heat accumulation (r?=??0.98). Over the last 50-year period, flowering was advanced by 16 days in response to the temperature rises. Similarly, on average for 12 cultivars of varying earliness, flowering was advanced by 9 days over the latest 30-year period (1986–2016). Furthermore, the interrelationship between various phenological stages and floral morphogenesis of the same cultivars in the years 2013 and 2014 was studied, and related to flower-bud formation. The different stages of floral morphogenesis were identified, presented and used as a basis for assessment of flower-bud development in serial dissections. Floral initiation in spurs of actively growing trees took place in late July, approx. 8 weeks after full bloom, whereas in extension shoots, initiation took place after growth cessation in August, approximately 2 weeks later. Decreasing temperatures in mid-August coincided with the cessation of growth and floral initiation in extension shoots, suggesting that the processes may be causally related. The results show that, in the Nordic climate, the period between blooming and initiation of new floral primordia is considerably shorter than in warmer climates, suggesting that the period is only marginally long for completion of shoot growth, and hence, timely floral initiation. This may be an important reason for the irregular flowering and frequent incidences of alternate bearing in apple trees in the cool Nordic climate. The presented information can be useful for determination of the correct timing of flower and fruit thinning to counterbalance biennial bearing.  相似文献   

6.
Abstract

Potassium sulfate was applied to established, non‐irrigated, K deficient trees on fine textured soil by banding, placing in augered holes and injecting into the soil. Additional trees received a heavy compost mulch in early fall. Trenches were dug in the fall beside trees to break roots and then were backfilled with K2SO4, dolomite lime or a combination of the two. One percent K solutions of KNO3 or K2SO4 were sprayed on trees four times during the growth season.

Sweet cherry trees only responded to compost mulch applications within two years. August midshoot leaf K, leaf N and fruit size were increased within one year however tree growth and yield were not affected. Fruit size and shoot growth were partially dependent on August leaf K level.

August midshoot leaf K of prune trees was increased within one growing season by all treatments except trench plus lime. Trees receiving compost also had increased levels of leaf N, P, Ca, Mn, Fe, Cu and B. Yield and shoot growth were increased only by compost mulch applications. Fruit size was partially dependent on August leaf K levels.  相似文献   

7.
Christ‘s thorn (Ziziphus spina-christi L. Desf.) is ecologically and economically important in Iran. Since it is a crosspollinated plant with a wide range of genetic variability, an investigation was carried out to determine the best method for mass and clonal propagation. Three vegetative methods were examined, including 1) cutting, where shoots with a 22-25 cm length and three shoot diameters were treated with two culture media; 2) layering, where air layering and trench layering treatments consisted of three growth regulators at three levels of concentration; and 3) tissue culture with nodal segments bearing axillary buds that were removed from shoots of mature trees at different seasons. Several experiments were carried out to determine the best disinfectant chemical, the best culture method, the best season, the appropriate explant characteristics and media type. Rooting was successful only on the sandy beds for cuttings with more than 8.0 mm diameter. For the trench layering method, only one specimen in one replicate rooted a very small root, while for the air layering method, only seedlings with growth regulator treatments rooted successfully. The best season for explant harvesting was determined as mid summer, and among the disinfecting treatments, Ca(OCI)2 at a concentration of 0.5g kg^-1 for 20 minutes was the best. There were no significant differences for shoot weight and length with a Murashige and Skoog (MS) medium with and without a hormone.  相似文献   

8.
Summary Dynamics of barley N, mineral N, and organic N were compared at Ellerslie (Black Chernozem, Typic Cryoboroll) and Breton (Gray Luvisol, Typic Cryoboralf) in central Alberta, using 15N-urea. On average, shoot N and shoot 15N recoveries at Ellerslie (14.1 g m–2, 36%) were greater than at Breton (4.5 g m–2, 17%). Root N (g m–2) did not significantly differ between sites (0–30 cm) but root 15N recovery was greater at Breton (3.4%) than Ellerslie (1.8%). Low levels of shoot N and shoot 15N at Breton were partly due to very wet soil conditions in July, which resulted in premature shoot senescence and low plant N uptake. Although the total 15N recoveries from the system (to 30 cm depth) at Ellerslie (63%) and Breton (56%) were similar, soil 15N was greater at Breton (35%) than at Ellerslie (26%). There were no differences in mineral N between sites but the average 15N recovery in the mineral-N pool was significantly greater at Ellerslie (3.3%) than at Breton (1.6%). There was no difference in 15N recovery in the microbial biomass (3%) between sites, although non-microbial organic 15N was greater at Breton (31 %) than at Ellerslie (20%). The two soils showed differences in the relative size of kinetically active N pools and in relative mineralization rates. Microbial N (0–30 cm) was greater at Ellerslie (13.3 g m–2) than at Breton (9.9 g m–2), but total microbial N made up a larger proportion of total soil N at Breton (1.6%) than at Ellerslie (0.9%). In the 0–10 cm interval, microbial N was 1.7-fold greater and non-microbial active N was 3-fold greater at Breton compared to Ellerslie, when expressed as a proportion of total soil N. Net N mineralization in a 10-day laboratory incubation was 1.4-fold greater in the Black Chernozem (0–10 cm interval) from Ellerslie, compared to the Gray Luvisol from Breton, when expressed per gram of soil. Net N mineralization in the soil from Breton was double that of the soil from Ellerslie, when expressed as a proportion of soil N. Although soil N (g m–2) was 2.5-fold greater at Ellerslie compared to Breton, it was cycled more rapidly at Breton.  相似文献   

9.
The yield of direct-seeded and transplanted upland rice was investigated for seven tillage methods for an ultisol in a high rainfall region of southeastern Nigeria. The tillage methods were: two compaction passes of a 6-t roller with and without residue mulch; six compaction passes with mulch; ploughing with and without mulch and no-till with and without mulch. Soil compaction decreased seedling emergence and shoot and root growth. Residue mulching decreased seedling emergence by 35.6% in direct-seeded rice. There were more leaves, productive tillers and dry matter in the ploughed plots. Root densities at 10–20- and 20–30-cm depths were higher by 157 and 47%, respectively, in ploughed treatments. The highest grain yields of 6.3 and 6.1 Mg ha−1 in ploughed plots for the first and second seasons, respectively, were associated with greater uptake of P, Na, Fe and Zn at flowering and of N, Mg, K, Mn and Cu at both maximum tillering and flowering growth stages. The grain yield in the first season was 2.1 and 2.5 Mg ha−1 for two- and six-compaction pass mulched plots, respectively. In the second season, the yields of no-till and compacted treatments were identical and ranged from 1.5 to 2.4 Mg ha−1. Mulching decreased grain yield by 43, 27 and 12% on compacted, no-till and ploughed plots, respectively, due to transient flooding and mechanical impedance to seedling emergence by the mulch cover. Within the unmulched treatments, ploughing increased rice yield by 71 and 35% over two compaction passes and the no-till treatments, respectively. The least bulk density and penetrometer resistance were also observed in ploughed plots.  相似文献   

10.
Twenty one samples of argan oil of different geographical origin (Tidzi, Tamanar, Benaiznassen, Ait mzal, Ait Baha, Ighrem, Aoulouz) and/or prepared following a different process (traditional, mechanical, or industrial) were collected and their physico-chemical properties analyzed. Sample acidity was found between 0.14 and 1.40%, unsaponifiable matter between 0.34 and 0.79%, saponification value between 180.0 and 199.6, highest peroxide index was 5.72 meq/kg, refractive index (20 degrees C) between 1.4644 and 1.4705, and UV absorption at 270 nm between 0.228 and 0.605. This study, carried out on randomly selected samples, clearly demonstrates that press extraction does not alter either the chemical composition of argan oil or its physico-chemical characteristics. It also demonstrates that press extraction respects the critical factors reported for traditionally prepared oils and necessary to obtain a beneficial effect on human health (a specific fatty acid balance and high tocopherol and sterol levels). In addition, this study should be useful for the establishment of a national quality standard.  相似文献   

11.
A vigorous root system is essential for efficient use of plant nutrients. This paper focuses on root growth and its response to tillage changes in the most fertile soil horizon, 0–40 cm depth. The field experiment was established in 1995 on clay soil, with 45–50% clay and 5.5% organic matter in the topsoil. Three tillage treatments were mouldboard plough to a depth of 20 cm (conventional), field cultivator to a depth of 8 cm, and no primary tillage (conservation). The field had an oat (Avena sativa L.)–barley (Hordeum vulgare L.) crop rotation. In 1997–1998 and 2000, root distribution during the growing season was evaluated by a non-destructive minirhizotron (MR) and video recording method. Root length density and root diameter were also measured once a season (1997 and 1998) by destructive root sampling and image analysis of washed roots. At shoot elongation, root numbers increased more under conventional than conservation tillage, at soil depth of 10–25 cm. The effect was clear for both barley (1997) and oat (2000) with maximum root numbers of 175 and 210 per 100 cm2 by mouldboard ploughing, but 120 and 170 per 100 cm2 under unploughed conditions (in the whole 0–0.4 m region). The suboptimal condition of unploughed soil was also indicated by lower shoot nutrient contents at tillering (studied in 1997) and by higher penetrometer resistance (studied in 1998, 2000) and lower macroporosity (studied in 2000) at 10–25 cm soil depth. Root growth dynamics were similar for both plant species. Root diameter was not significantly affected by the tillage treatments. Discontinuation of mouldboard ploughing reduced root growth (P<0.05) within this clay soil 5 years after the tillage change, although conservation tillage preserved more water for plant use. The data show that a clay soil can be too dense for optimal rooting during the 3rd–6th-years after discontinuation of ploughing.  相似文献   

12.
Summary Root and stem nodulation, nitrogen fixation (acetylene-reducing activity), growth and N accumulation bySesbania rostrata as affected by season and inoculation were studied in a pot experiment. The effects ofS. rostrata as a green manure on succeeding wet-season and dry-season rice yields and total N balance were also studied.S. rostrata grown during the wet season showed better growth, nodulation, and greater acetylene-reducing activity than that grown during the dry season. Inoculation withAzorhizobium caulinodans ORS 571 StrSpc® (resistant to streptomycin and spectinomycin) on the stem alone or on both root and stem significantly increased N2 fixation by the plants. Soil and seed inoculation yielded active root nodules under flooded conditions. Plants that were not inoculated on the stem did not develop stem nodules. The nitrogenase activity of the root nodules was greater than that of the stem nodules in about 50-day-oldS. rostrata. S. rostrata incorporation, irrespective of inoculation, significantly increased the grain yield and N uptake of the succeeding wet season and dry season rice crops. The inoculated treatments produced a significantly greater N gain (873 mg N pot–1) than the noinoculation (712 mg N pot–1) treatment. About 80% of the N gained was transferred to the succeeding rice crops and about 20% remained in the soil. The soil N in the flooded fallow-rice treatment significantly declined (–140 mg N pot–1) but significantly increased in bothS. rostrata-rice treatments (159 and 151 mg N pot–1 in uninoculated and inoculated treatments respectively). The N-balance data gave extrapolated values of N2 fixed per hectare at about 303 kg N ha–1 per two crops forS. rostrata (uninoculated)-rice and 383 forS. rostrata (inoculated)-rice.  相似文献   

13.
Five field experiments were conducted to study the effects of continuous plastic film mulching on rice yield, water use efficiency and soil properties on different soils with great environmental variabilities in Zhejiang Province, China, under non-flooding condition. The experiment started in 2001 at five sites and ended in 2003 with one rice crop annually. Three treatments included plastic film mulching with no flooding (PM), no plastic film mulching and no flooding (UM), and traditional flooding management (TF). Soil samples were collected after the third year of the experimentation and were analyzed for soil properties. PM increased soil temperature, accelerated decomposition of organic carbon and root growth, there was a slight but statistically insignificant trend of decline in soil bulk density. PM produced the similar rice grain yield as TF at two sites, significantly higher grain yield (5.8% and 20.0% higher) at other two sites, but significantly lower (34.3% lower) yield at one site where no irrigation water was applied and rainfall was the sole water source for rice growth. PM increased water use efficiency by 69.6–106.0% and irrigation water use efficiency by 273.7–519.6%. Compared to TF, PM decreased soil organic matter content by 8.3–24.5%, soil total N by 5.2–22.0%, and available K by 9.6–50.4% at all sites. PM treatment also reduced soil available N by 8.5–26.5% at four sites. Soil total P content in PM treatments reduced by 13.5–27.8% at three sites, and increased by 6.6–8.2% at other two sites. However, PM increased soil available P by 20.9–64.7% at all sites. Systematic cluster analysis indicated the PM treatment distinctively clustered from the other treatment. These results suggested PM could gain higher yield under appropriate water condition and PM may change soil nutrient cycle.  相似文献   

14.
A greenhouse experiment was conducted to assess the arbuscular mycorrhizal (AM) fungi inoculum potential for Leucaena leucocephala in a range of nutrient-depleted farm soils in western Kenya. Leucaena was grown in 12 uninoculated farm soils with pH 5.0–6.7, with or without rock P and farmyard manure. Root infection, nodulation, and shoot and root weight were determined 25, 46, and 69 days after planting. Spore concentrations in the farm soils at the start of the experiment ranged from 44 to 126 live spores per 100 g dry soil with 6–10 species per soil, principally Scutellospora spp. and Acaulospora spp. Nodulation was absent or poor in all soils, indicating the need for rhizobial inoculation of species belonging to the leucaena crossinoculation group in this agrosystem. Rock-P alone increased final shoot dry weight by a factor of 1.4, manure alone by 1.8, and rock-P plus manure by 1.9, compared with no ameliorant. Root infection with AM fungi was detected in all soils 25 days after planting and increased linearly in the different farm soils to values of 33–65% 69 days after planting. Soil pH and root infection 25 days after planting accounted for much of the variation in final shoot weight among soils with no amelioront (87%). As early root infection increased from 20 to 40% at soil pH 5.0, the predicted final shoot dry weight was doubled, and the response to ameliorants was reduced by two-thirds. The growth responses to increased infection became smaller as pH increased from 5.0 to 6.5.  相似文献   

15.
Surface (0–15 cm) and subsurface (30–45 cm) soil samples from under canopy, edge of canopy and away from canopy of isolated Cordia africana Lam. and Croton macrostachyus Del. trees and their leaves were examined to investigate leaf nutrient content, root biomass and the contribution of trees on farms to soil fertility parameters in Badessa area, eastern Ethiopia. Leaves of C. macrostachyus had 20% higher P and 25% lower K contents than those of C. africana. The studied species had comparable leaf N content. Both species produced shallow lateral roots that extended beyond the canopy zone. Typically, higher fine root biomass was observed in the surface soils than the subsurface soils. Both species did not affect soil organic C, pH and cation exchange capacity. Surface and subsurface soils under tree canopies had 22–26 and 12–17% higher N, respectively, than the corresponding soils away from tree canopies. Surface soil available P under tree canopies was 34–50% higher than the corresponding soil away from canopies. Available P content of subsurface soil was improved only under C. africana canopy. The available P of surface soil under C. macrostachyus canopy was more than double that for C. africana. Trees of both species increased underneath surface and subsurface exchangeable K by 18–46% compared with the corresponding controls. In conclusion, C. macrostachyus and C. africana trees on farms keep soil nutrient high via protection against leaching, translocation of nutrients from deeper to the surface layer and accumulation of litter, which create a temporary nutrient pool in the surface soils under their canopies.  相似文献   

16.
Pearl millet [Pennisetum glaucum (L). R. Br.] (syn. P. americanum (L.) Leeke) germplasm from Cameroon was collected jointly by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and the National Cereals Research and Extension Project (NCRE)/Institute of Agronomic Research (IAR), Maroua, Cameroon. Of the 1261 samples collected, 888 are pearl millet and 12 wild relatives of Pennisetums. A total of 918 accessions of pearl millet were evaluated during rainy and postrainy seasons at ICRISAT Asia Center (IAC), Patancheru, India, and 748 at Maroua, Cameroon. Considerable variation was observed for all the characters studies. At IAC, Patancheru, time to flower varied from 56 to 146 days with a mean of 114±0.62 days during the rainy and 46 to 128 days with a mean of 67±0.28 days during the postrainy season. At Maroua, the flowering time ranged from 49 to 112 days with a mean of 81±0.34 days. Plant height ranged from 230 to 450 cm with a mean of 353±1.52 cm. Spike and grain characters were more stable compared to flowering and plant height. The expression of spike characters was comparable to evaluation in postrainy season at IAC, Patancheru. In Cameroon, farmers classify pearl millet as Yadiri and Mouri, which vary for plant canopy, spike and grain characters. Mouri matures in about 95–110 days, extensively grown in the low rainfall areas of Extreme North province. Yadiri matures in 120–140 days, generally grown in the high rainfall areas of the North, Adamaoua provinces, and on the hill slopes of Extreme North province. Millet germplasm from Cameroon is a good source for more number of productive tillers, large compact spikes, and larger ivory and cream colored grain besides its potential for forage.Submitted as ICRISAT Journal Article No. 1803.  相似文献   

17.
Increasing and maintaining crop residues in predominantly cereal-based rotations of the US Pacific Northwest is critical to controlling soil erosion. The core collection of lentil (Lens culinaris Medik.) germplasm comprising 287 accessions was evaluated for variation in phenological, morphological and growth parameters including seed yields and residue amounts over a two-year period under conventional tillage and no-till conditions. The objectives of this study were (i) assess lentil genetic variation in germplasm for variation in biomass production and seed yield, (ii) assess the relationship of phenological and morphological traits with biomass and seed yield and (iii) identify high biomass producing germplasm for use as parents in the breeding program. Days to flowering and days to maturity ranged from 31 to 78 and from 71 to 106 days, respectively. Time to flowering in terms of cumulative heat units was a more efficient measurement than days to flowering. Plant height and plant canopy width had a significant association with total biomass, seed yield and residue amounts. Total biomass ranged from 788–6389 kg ha–1 under conventional tillage, while the range under no-till conditions was 1045–6195 kg ha–1. Most of the lines with higher biomass also produced the highest seed yields and residue amounts. Overall, only one accession produced more residue than `Laird'. In the more favorable environment of 1997, six accessions exceeded the control cultivars, `Laird' and `Indianhead', for residue amounts, and seven and twenty-four accessions exceeded control cultivars, `Pardina' and `Brewer', for seed yield. Results indicated that plant height, canopy width at maturity and seed yield explained most of the variation in biomass and residue production. Large seeded germplasm consistently had a longer reproductive growth period than small seeded accessions and had 17%, 7% and 21% more biomass, seed yield and residue, respectively. Our data indicated significant variation in lentil germplasm for biomass, seed yield and residue amounts to warrant their use in the breeding program.  相似文献   

18.
We used the needle trace method to investigate changes in the state of a Scots pine (Pinus sylvestris L.) stand in a bog (Voorepera) in the north-eastern part of Estonia, the most polluted area of the country. Additionally, we chose six sampling sites in other parts of Northeast Estonia (polluted area) and eight sites in southern Estonia (unpolluted area) to compare the state of pine stands in different bogs. During the period of 1964–1997, the radial growth had increased from 0.27 to 2.16 mm yr–1 and the annual shoot length from 0.10 to 0.28 m in Voorepera. Mean values of the period (1.13 mm yr–1 and 0.26 m, respectively) were two and four times higher in Voorepera than the average of the other bogs (0.5 mm yr–1 and 0.06 m, respectively). Maximum needle age fluctuated between three and five growing seasons in Voorepera, the mean (four growing seasons) was similar to that of other bogs (four growing seasons). Except radial growth, which was 0.6 mm yr–1 in the polluted area and 0.4 mm yr–1 in the unpolluted area, other indices of trees' health (shoot growth, needle age, nitrogen concentration in needles) and substrate conditions (water pH and N concentration) did not show clear differences between polluted and unpolluted areas. We conclude that air pollution from oil shale industry (thermal power plant and chemical factories) enhances the growth of pines in bogs, which can induce drastic changes in these ecosystems. However, the effect is currently obvious only in the vicinity of pollution sources.  相似文献   

19.
An endemic dwarf birch, Betula apoiensis, is critically endangered, and two populations of this species are restricted to the ridges of Mt. Apoi in Hokkaido, Japan. We observed the flowering phenology, pollen dispersal, and viable seed production and conducted pollination experiments in order to examine pollen limitation and hybridization with a sympatric congener, B. ermanii. B. apoiensis flowered earlier than B. ermanii but had a more variable flowering time among trees than B. ermanii. The female flowering of B. apoiensis temporally overlapped with the male flowering of B. ermanii as well as with that of B. apoiensis. Pollination experiments demonstrated that seed set and seed germination were higher in female flowers outcrossed than in those that were non-pollinated, selfed, hybridized with B. ermanii pollen, or pollinated naturally. A few selfed or hybrid seeds were filled and germinated, which indicates that self-incompatibility and reproductive barriers are not complete. Logistic regressions of local density of conspecific trees on natural seed set and seed germination were significantly positive. These results suggest that B. apoiensis is pollen-limited.  相似文献   

20.
A field experiment was conducted to study and compare the effectiveness of two arbuscular mycorrhizal fungi (AMF), Glomus macrocarpum (GM) and Glomus fasciculatum (GF) on three accessions of Artemisia annua. The AM inoculation significantly increased the production of herbage, dry weight of shoot, nutrient status (P, Zn and Fe) of shoot, concentration of essential oil and artemisinin in leaves as compared to non-inoculated plants. The extent of growth, nutrient concentration and production of secondary plant metabolites varied with the fungus–plant accession combination. The mycorrhizal dependency of the three accessions was related to the shoot: root ratio. Comparing the two fungal inoculants in regard to increase in essential oil concentration in shoot, the effectiveness of GF was more than that of GM. While in two accessions, GM was more effective in enhancing artemisinin concentration than GF. Increase in concentration of essential oil was found to be positively correlated to P-status of the plant. Conversely, no correlation was found between shoot-P and artemisinin concentration.  相似文献   

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