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1.
Defining plant adaptation to soil conditions is critical for the successful introduction of grain legume species into farming
systems. This nutrient solution study examined the effects of pH (4, 5, 6, 7 and 8) and bicarbonate (5 mM KHCO3) on the growth and nodulation of 14 grain legume species supplied with N or reliant on N2-fixation. Species includedPisum sativum L.,Cicer arietinum L.,Lens culinaris Med., and a range ofLupinus, Vicia andLathyrus species.
Species differed greatly in response to solution pH. For both N-fertilized and N2-fixing plants, shoot growth ofL. culinaris was very sensitive to low pH (pH < 7), whereas shoot growth ofLupinus angustifolius L. andLupinus albus L. was sensitive to higher pH (pH ≥ 6). Other species had a broader optimal pH range for growth when supplied with N, but
were generally sensitive to low pH (pH < 7 forC. arietinum andVicia sativa L., pH < 6 forP. sativum, Vicia faba L.,Lathyrus sativus L. andLathyrus cicera L., and pH < 5 forVicia benghalensis L. andVicia narbonensis L.) when reliant on N2-fixation. For these other species, symbiotic N2-fixation appeared to be more sensitive than host plant growth to low pH. This finding was supported by lower nodule numbers
and mass, and lower N concentrations in shoots of sensitive species at low pH relative to higher pH. ForL. culinaris, nodule numbers and mass were relatively unaffected by pH 5–8, N concentrations in shoots were high at low pH and plants
developed symptoms relating to H+ toxicity at pH as high as 7. These results indicate that host plant growth ofL. culinaris is more sensitive to low pH than theRhizobium symbiosis. ForL. albus andL. angustifolius, both host plant growth and symbiotic N2-fixation appeared to be equally sensitive to pH ≥ 6.Lupinus pilosus Murr. was more tolerant of high pH than the otherLupinus species. At pH 4, two genotypes ofC. arietinum had better early nodulation than other species.Vicia ervilia L. nodulated poorly at all levels of solution pH, indicating that the commercial Group E inoculum (Rhizobium leguminosurum bv.viceae SU303) may not be effective for this species in solution culture.
Addition of bicarbonate decreased shoot growth, nodulation and N concentrations in shoots of most species. Early nodulation
(nodule number) ofLathyrus ochrus (L.) DC was not affected by the bicarbonate treatment. 相似文献
2.
By the assumption that both soil moisture and soil air affect plant growth as linear factor, the relationship between mean
plant dry weight and soil moisture content was newly formulated. Its applicability to actual growth data was tested by growing
three species ofBidens under different levels of soil moisture content. The growth data ofBidens well satisfied the new formula. The optimum soil moisture content giving a maximum mean plant dry weight was the largest
inB. frondosa and the smallest inB. biternata. This result well agreed with field observations. The growth factor represented by the new formula was referred to as “repulsive
factor”, and the difference between the repulsive factor and optimum factor was discussed. 相似文献
3.
Factors affecting the establishment of Alnus/Frankia symbioses were studied partly by following the survival ofFrankia strains exposed to different soil conditions, and partly by investigating the effect of pH on nodulation. TwoFrankia strains were used, both of the Sp− type (sporangia not formed in nodules). One of the strains sporulated heavily, while the other formed mainly hyphae. The
strains originated fromAlnus incana root nodules growing in soils of pH 3.5 and 5.0. The optimum pH for their growth in pure culture was found to be 6.7 and
6.2, respectively.
The strains were introduced into twoFrankia-free soils, peat and fine sand. Their survival, measured as the persistance of nodulation capacity using the plant infection
technique, was followed for 14 months. The survival curves of the strains were similar despite the morphological differences
between the strains in pure culture. The nodulation capacities declined over time both at 14 and 22°C. Survival was better
in soils limed to a pH above 6 than in soils at their original pH (peat 2.9, fine sand 4.2).
The effect of pH on nodule formation in Alnus seedlings by theFrankia strains was studied in liquid culture. The number of nodules increased linearly within the pH range studied (3.5–5.8). No
nodules were formed at pH 3.5. 相似文献
4.
This study examined the effects of soil moisture on soil K mobility, dynamics of soil K, soil K fixation, plant growth and
K uptake. A pot experiment, with and without corn (Zea maysL.), was conducted over a 16-d duration using a Yolo silt loam treated with two soil moisture regimes, i.e. constant moisture
vs. wetting–drying (W–D) cycles. Soil K dynamics were determined using both ion exchange resin and direct extraction of soil
solution. Soil K mobility increased significantly with soil moisture content (θv) and there was a positive curvilinear relationship between θv and effective diffusion coefficient (De), suggesting that more K+ can diffuse to the plant roots at sufficient soil moistures. Increase in De could be attributed to the decrease of impedance factor. During W–D cycles, soil solution K concentration increased as soil
solution volume decreased, but soil solution K and NH4
+-extractable K pools decreased. In the constant moisture regime, available K pools decreased over the 16-d duration, but to
a lesser extent than in W–D regime. The W–D cycles significantly enhanced K fixation and reduced available K pools in the
soil in contrast to the constant moisture regime. Potassium fixation by the soil showed a biphasic pattern under the W–D regime,
with a rapid fixation within the first 2 d after re-wetting, followed by a slower fixation. In the soil with constant moisture,
K fixation was rapid during the first 8 h after wetting the soil, and then proceeded so slowly that no significant K fixation
was observed after 4 d. The W–D cycles decreased root and shoot growth and K uptake by corn compared to constant moisture
condition. Our results support the hypothesis that W–D cycles enhance soil K fixation, reduce soil K mobility and plant growth,
and therefore reduce plant K+ uptake.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
How much seed remains in the soil after a fire? 总被引:2,自引:0,他引:2
Soil seed banks that persist after a fire are important in fire-prone habitats as they minimise the risk of decline or local extinction in plants, should the fire-free interval be less than the primary juvenile periods of the species. In two common woody plant genera (Acacia and Grevillea) in southeastern Australia, we examined the size and location of the residual seed bank after fire across areas of varying seedling densities at three locations in comparison to the distribution of seeds in the soil at an unburnt site. We found viable dormant seeds remaining in the soil after fire (evidence of residual soil seed bank). A significantly lower proportion of seeds remained in the top 5 cm of soil than at 5–10 cm or 10–15 cm soil depths, independent of seedling density or plant genus. This was due to greater germination, and possibly some seed mortality, near the soil surface. Reduced germination below 5 cm was probably due to the reduced efficacy of the fire cues that break seed dormancy, a declining ability of seeds to emerge successfully from such depths, and the lower abundance of seeds in the soil at such depths. The magnitude of the residual seed bank was similar across 0–5, 5–10 and 10–15 cm soil depths in Acacia suaveolens. For two Grevillea species, most residual seeds were at 0–5 and 5–10 cm. The residual soil seed bank in the top 10 cm of soil after fire varied across sites with estimates of 0, 19 and 27% in G. speciosa and 23, 35, and 55% in A. suaveolens. At two sites, both species had similar residual seed bank sizes, while at a third, there were large differences between the species (0–55%). The observed patterns imply that the fire-related cues that break seed dormancy generally declined with soil depth. For Acacia, seed dormancy is broken by heat shock, a fire-cue that declines with soil depth. Some 250 species (approx 15% of the fire-prone flora) in the region are thought to have dormancy broken by heat shock. For Grevillea, where seed dormancy is broken by the interaction of smoke and heat shock, at two sites, we suggest three possibilities: (i) the smoke cue declined with soil depth; (ii) both heat and smoke are obligatory for breaking seed dormancy; or (iii) the cues may be independent and additive and below the zone of soil heating, only a proportion of available seeds had dormancy broken by smoke alone. At a third site (no residual seed bank detected) the smoke cue was predicted not to have declined with soil depth. Up to 900 species (just under half the fire-prone flora) in the study region are thought to have seed dormancy broken by the interaction of heat and smoke during the passage of a fire. 相似文献
6.
Summary Ten alfalfa cultivars were used to study the effects of nodulation and variations in resistance to alfalfa sickness. The alfalfa
seedlings were planted in sick soil with three treatment,,i.e.: pasteurized sick soil inoculated with Rhizobium ‘Nitragin’ which served as the control, the inoculated non-pasteurized sick
soil and the non-inoculated non-pasteurized sick soil. None of the alfalfa cultivars were immune from the sickness. Cultivar
‘Anik’ fromMedicago falcata was among the most resistant cultivars. Three Phytophthora root rot resistant cultivars including ‘Agate’, ‘Apollo’ and ‘Ramsey’
were not resistant to the disease. Alfalfa inoculated with Rhizobium showed greatly improved seedling growth. Correlation
coefficients showed that those alfalfa cultivars more resistant to alfalfa sickness produced more dry weight. Dry weight increase
due to nodulation (82%) had more than compensated for the loss of dry weight due to alfalfa sickness (33%). The present study
suggested that the poor growth of alfalfa on sick soil was attributed to both the soil borne pathogens and the poor nodulation
of alfalfa, probably due to the absence of effective Rhizobium in sick soil. Highly significant differences were also obtained
among olfalfa cultivars for plant dry weight in the inoculation treatment. Selection for effective Rhizobium strains and for
alfalfa genotypes which are resistant to alfalfa sickness and are high in nitrogen fixation rates could improve alfalfa yield
in sick soil. 相似文献
7.
Total Al concentration or pH in 1∶5 10 mM CaCl2 extracts and exchangeable Al in 100 mM BaCl2 extracts cannot always distinguish between Al-toxic and Al-nontoxic topsoils. Our objectives were to compare the abilities
of different measures of Al and pH in various extracts to predict the effects of acidity on growth and nodulation of subterranean
clover. In a glasshouse experiment,Trifolium subterraneum L. cv. Mt Barker was grown in acidic soils from 3 sites in the Western Australian wheatbelt with different histories of phosphate
fertilizer application. The pH was adjusted to give a range of 3.8–7 in the centrifuged soil solution (SS). Total (Al-tot),
reactive Al (8-hydroxyquinoline-extractable, Al-HQ) and pH were measured in SS and 1∶5 extracts of KCl, CaCl2 and LaCl3. Another method of estimating reactive Al (Al which reacts with Chelex-100) was also measured in SS only. Other measurements
included exchangeable Al and H, Ca in SS, and P in SS and the CaCl2 extracts. Both plant growth and early nodulation decreased with increasing acidity. Plant growth in the acidified and unlimed
treatments of all soils was best described by Al-HQ in SS, KCl or CaCl2 (r2=0.68–0.70). Multiple regression of relative yield against Al or pH with the concentration of P in SS increased the percentage
variation explained by 10% and 30%, respectively. Early nodulation was well correlated (r2=0.67–0.91) with pH or exch. H, Al-tot or exch. Al and Al-HQ. No improvement in the correlation was gained by including P
using multiple regression. At constant ionic strength, increasing the valence of the extracting cation decreased the ability
of soil tests to distinguish phytotoxic Al. 相似文献
8.
M. R. Carter 《Plant and Soil》1986,94(3):341-348
Summary Field studies were conducted to assess the mineral nutrition and growth of Colorado spruce (Picea pungens Engln) seedlings (2–4 yr) from provenances selected for superior growth on calcareous prairie soils. Tissue nutrient concentrations
and response to nitrogen were determined by use of foliar analysis and growth pattern studies. Soil conditions ranged from
7.6–7.8 for pH, 12–23% for total CaCO3, and 5–6% for active CaCO3. Foliage mineral composition showed relatively low phosphorus (0.09–0.15%) and high calcium (0.45–1.52%) assimilation. Seasonal
growth and seedling response to added nitrogen was not adversely affected by the calcareous soil condition. Levels of nitrogen
in the foliage required for optimum growth ranged from 1.5–2.0% and were similar to that of other conifer species. 相似文献
9.
Seedling growth strategies and seed size effects in fourteen oak species native to different soil moisture habitats 总被引:12,自引:0,他引:12
Seedling growth and morphology are thought to reflect evolutionary responses to habitat or influences of seed size. To test
these hypotheses, we selected fourteen species of North American oaks differing in soil moisture habitat preference and seed
size. Seedlings were grown for 1 – 2 years with abundant soil water and moderate soil nutrition in pots placed outdoors and
in a common garden. Oak species native to xeric environments produced the smallest seedlings. Oaks from hydric soils had more
shoot weight per unit of root weight and more height per unit of total plant weight than did mesic or xeric oaks. Essentially
no differences in leaf area per unit of total plant weight were detected. Species with thinner and larger individual leaves
tended to produce larger seedlings. Within species, seed size was generally unrelated to seedling growth, although results
may have been complicated by uncontrolled genotypic variability. However, when species were compared, those with larger mean
seed size produced larger seedlings. Root/shoot allometry, height growth and leaf thickness in the tested species may reflect
evolutionary responses to soil moisture and flooding. Although seed size influenced seedling growth, no clear relationship
between seed size and soil moisture habitat was found.
Received: 26 March 1995 / Accepted: 30 November 1995 相似文献
10.
A study was conducted to assess the dynamics of vesicular-arbuscular mycorrhizal (VAM) fungi associated with Acacia farnesiana and A. planifrons in moderately fertile alkaline soils. The intensity of root colonization by VAM fungi and the distribution of VAM fungal
structures varied with host species over a period of time. The occurrence of vesicles with varied morphology in the mycorrhizal
roots indicates infection by different VAM fungal species. This was further confirmed from the presence of spores belonging
to different VAM fungal species in the rhizosphere soils. Root colonization and spore number ranged from 56% – 72% and 5 – 14
g –
1soil in A. farnesiana and from 60% – 73% and 5 – 15 g –
1 soil in A. planifrons. Per cent root colonization and VAM spore number in the rhizosphere soil were inversely related to each other in both the
Acacia species. However, patterns of the occurrence of VAM fungal structures were erratic. Spores of Acaulospora foveata, Gigaspora albida, Glomus fasciculatum, G. geosporum and Sclerocystis sinuosa were isolated from the rhizosphere of A. farnesiana whereas A. scrobiculata,
G. pustulatum, G. fasciculatum,
G. geosporum and G. microcarpum were isolated from that of A. planifrons. The response of VAM status to fluctuating edaphic factors varied with host species. In A. farnesiana though soil nitrogen (N) was positively correlated with root colonization, soil moisture, potassium and air temperature were
negatively correlated to both root colonization and spore number. Per cent root colonization and spore number in A. planifrons were negatively related to each other. Further, in A. planifrons as the soil phosphorus and N were negatively correlated with the density of VAM fungal spores, the same edaphic factors along
with soil moisture negatively influenced root colonization.
Received: 16 May 1995 / Accepted: 7 February 1996 相似文献
11.
Mark Bourne Adrienne B. Nicotra Matthew J. Colloff Saul A. Cunningham 《Plant and Soil》2008,305(1-2):145-156
We examined growth of Eucalyptus microcarpa seedlings in soil collected from four sites in southeastern Australia, in which retired pasture land has been revegetated
with mixed plantings of Eucalyptus and Acacia species. Revegetation of farm land in southeastern Australia is an area of major investment. The focus of the study was to
examine the influence of soil biota on seedling growth and its possible interaction with soil enrichment from a legume (Acacia) and decomposition rates. We used a soil freezing treatment (−80°C for 3 days) to retard the soil biota, with the expectation
that invertebrates in particular would be killed. Soil freezing did not cause a nutrient pulse, but did reduce the level of
ammonium in soil. Nitrate levels increased with time in pots, regardless of the soil treatment. Decomposition rates measured
using cellulose substrate were significantly reduced by the freeze treatment, but only for approximately 90 days. Eucalyptus microcarpa seedlings grown in freeze-treated soil were approximately 40% smaller (total biomass), had marginally lower LAR (leaf area
ratio), and significantly lower LMA (leaf mass per area). Low LMA indicates that leaves are either thinner in cross-section
or less dense. We hypothesise that both the poor growth of seedlings and production of less robust leaves are consequences
of reduced availability of soil nutrients due to the diminished soil biota after freeze treatment. Litter under Acacia was richer in nitrogen than litter under Eucalyptus but there was no difference in nitrogen content of soil, and consequently no soil source effects on plant growth or decomposition.
We suggest that variation in the soil biota has the potential to greatly enhance or hinder the success of revegetation on
retired agricultural land, but enrichment of soil by decomposition of nitrogen rich litter in these sites requires longer
than the 8–15 years since they were revegetated. 相似文献
12.
Yu. A. Nikolaev I. A. Borzenkov A. L. Tarasov N. G. Loiko A. N. Kozlova V. F. Gal’chenko G. I. El’-Registan 《Microbiology》2010,79(6):747-752
The adaptogenic effect of the chemical analogues of alkylhydroxybenzenes (AHBs), bacterial extracellular autoregulators (the
individual compound C7-AHB and its technical preparation Sidovit), was demonstrated for two pseudomonad species, Pseudomonas aeruginosa and P. fluorescens. The protective effect of AHBs resulted in increased growth rate and biomass accumulation in bacteria grown under suboptimal
conditions within the species tolerance range. The adaptogenic effect of AHBs (10–50 μmg/l) was more pronounced under more
unfavorable growth conditions. In the case of P. fluorescens, the individual compound C7-AHB increased the biomass yield by 30% under alkaline conditions (pH 9.5), when the growth rate
decreased by 80–90% compared to the optimum (pH 5.5–7.5). The Sidovit preparation, containing a mixture of natural AHBs with
C7-AHB as the main component, increased the growth rate of P. aeruginosa by 40–60% at nonoptimal temperatures (45 and 10°C) or under enhanced salinity (1% NaCl). The action of AHBs as regulators
of the rpoS and SOS response stress regulons was demonstrated to be among the mechanisms of their adaptogenic effect, as was demonstrated
with the relevant reporter genes in the model strains E. coli C600 thi, thr, leuΔ(pro-lac) with the osmE-lacZ and umuD-lacZ hybrid operons, respectively. AHBs are technologically and economically acceptable as adaptogenic supplements for bacterial
preparations used in soil bioremediation and oil spillage removal under conditions unfavorable for microbial growth, including
increased salinity, extreme pH, and fluctuating sub- or supraoptimal temperatures. 相似文献
13.
Rhizobium meliloti proved to be sensitive to low concentrations of the herbicide phosphinothricintripeptide (PTT) and its active ingredient
phosphinothricin (PT), which was formerly assumed to be non-toxic for most of the bacteria analysed. Growth was more strongly
reduced in sterile synthetic media and less reduced in sterile soil; in unsterile soil only a transient growth reduction was
detectable. Sensitivity was also observed in five out of eight other species analysed. In all sensitive species tested, spontaneous
resistances to PT occurred. Under sterile conditions, PTT and PT reduced rhizobial nodulation rates of PT-resistant alfalfa
plants drastically; however, nitrogen fixation in the few nodules that arose was unaffected. Because of the small number of
nodules, the overall fixation rate was strongly diminished. In unsterile soil, nodulation and nitrogen fixation rates were
not changed, possibly because of the rapid degradation of PTT and PT in the soil. Using a herbicide as model substance it
could be demonstrated that the sensitivity of R. meliloti to chemical additives in the soil can be detected by analysing its growth rate, and that even a weak impact can influence
its nodulation capacity. R. meliloti has proven to be a fast, easy and sensitive detection system for bacteriostatic components present in the soil.
Received: 12 April 1996 / Received revision: 15 July 1996 / Accepted: 18 July 1996 相似文献
14.
Poor crop stand is a common problem in saline areas. Germination and seedling emergence may be depressed as a result of impeded
aeration, saline or dry conditions. In this study, we examined the effects of salinity and moisture stress and their interactions
on seed germination and seedling growth of carrots. Variable soil matric and osmotic potentials were either obtained by equilibrating
soil salinized to different degrees on a 0.5 MPa ceramic plate soil moisture extractor or by adding different amounts of salt
solutions to the same mass of air-dried soil, based on a previously determined soil moisture release curve, and allowing to
equilibrate for 1 week.
Germination decreased significantly in the investigated silty soil (Aquic Ustifluvent) at soil moisture potentials higher
than −0.01 MPa, whereas osmotic potentials as low as −0.5 MPa did not influence germination. Matric potentials of −0.3 and
−0.4 MPa, respectively, resulted in a strong decrease (35–95%) of germination and delayed germination by 2 to 5 days in the
silty soil to which different amounts (18 and 36%, respectively) and sizes (0.8–1.2 mm and 1.5–2.2 mm, respectively) of sand
particles had been added. No effect of sand and grain diameter was detected. Germination was not affected by comparable osmotic
potentials.
Seedling growth showed a much higher sensitivity than germination to decreasing matric potentials, but was not affected by
osmotic potentials ranging from −0.05 to −0.5 MPa. Optimum shoot growth occurred at matric potentials between −0.025 and −0.1
MPa. Shoot and root growth decreased markedly at matric potentials higher than −0.01 MPa. Fresh weight of shoots decreased
gradually at matric potentials lower than −0.2 MPa. Root growth was significantly increased at matric potentials of −0.1 to
−0.3 MPa, whereas comparable osmotic potentials did not have equivalent effects.
It is concluded that germination and seedling growth are differently affected by comparable matric and osmotic stresses and
that water stress exerts a more negative effect than salt stress. 相似文献
15.
The rhizobial populations and nodulation status of both indigenous (mainly Acacia species) and some introduced woody legume species were assessed under glasshouse conditions in soils collected from 12 sites located in different ecological zones of Kenya. The populations among the sites, as estimated by the MPN technique, varied from <3.6 to>2.3×105 cells g-1 of soil. There were some intrasite variations in population estimates depending on the trap host species, date of soil collection and the method used in sampling the soils. Nodulation in whole soil also varied across the sites with test species frequently showing higher nodulation ability in native soils. Sesbania sesban (L.) Merr. was the most prolific nodulating species while Acacia tortilis (Forsskal) Hayne was very erratic in nodulation. Nodulation of most species showed interplant and intraspecific variability within a single soil source. 相似文献
16.
Plant needles ofCasuarina equisetifolia were collected and analyzed in parallel with soil analysis. In three strains ofFrankia—symbionts ofCasuarina—their infectivity and plant performance was determinedin vitro after soil amendment with different leaf litter concentrations. Only one strain was able to nodulate the plant at all litter
concentrations (0.5, 3 and 5%) although the nodules were very small. However, all treated plants grew poorly; their growth
was reduced by approximately 90% (for 5% litter concentration) compared to plants grown on untreated soil, on the basis of
total dry mass. Inhibition of nodulation can be attributed to high concentrations of some elements and compounds that were
either found inC. equisetifolia litter or originally found in soil (i.e. chloride, cyanide, copper, manganese and phenols). In general, plant growth decreased as more litter was added. Plant total
nitrogen content was also reduced after increasing the litter concentration. The inhibitory effect of high litter concentrations
was mainly on plant growth and to a lesser extent on plant nodulation byFrankia strains. 相似文献
17.
Anna-Maj Balsberg-Påhlsson 《Plant and Soil》1995,175(1):125-132
Deschampsia flexuosa (L.) Trin. is an abundant grass species in the ground flora of acidic beech forests in southern Sweden. Generally, the species
is restricted to a limited soil pH range (pH 4–5). The main objective was to study the influence of different soil acidities
on germination, initial root development and on the growth of the species. The experiments were carried out under controlled
conditions and designed to simulate the physico-chemical conditions present in the field. By using forest soils within the
pH range 4.0 to 8.3 and artificial variation in pH (3.2 to 7.6) of soil-water extracts, it was possible to evaluate the influence
of soil reaction and the H+ per se. In all experiments seeds have been used. Germination was significantly delayed in the very acid soil (pH 4.0) in
comparison to the germination in soils within the pH range (4.4 to 6.4). Soil substances, other than the H+, might be responsible for this delay in germination, whereas development of the radicle was markedly affected by increasing
H+ concentrations. Especially the development of root hairs was sensitive to H+ and was significantly reduced at a pH<-3.8. By increasing soil acidity the injury symptoms, including curling and discolouring,
became more intense and at the highest acidity (pH 3.2) the radicles appeared brown, stunted and the root hairs were lacking.
Most favourable growth was obtained at pH 4.4 and 5.0. Soil pH levels above and below this range limited both shoot and root
growth. The results showed very good correspondence with observations made in Beech forest soils in southern Sweden, where
the species was growing in soils within the pH range 3.9 to 5.1 with a peak growth at pH 4.3. This study shows that in soils
at pH≤3.8, the poor development of the radicle may be crucial in the establishment ofDeschampsia flexuosa. Root hair development was more sensitive to soil acidity than radicle elongation. Germination was delayed in very acid Beech
forest soils but other factors than the H-ion per se may be responsible for this delay. 相似文献
18.
Exclusion effects on vegetation characteristics and their correlation to soil factors in the semi-arid rangeland of Mu Us Sandland, China 总被引:1,自引:0,他引:1
Exclusion has been applied as a main measure for re-vegetation all over the world. This paper, by comparing the results of
year-round exclusion, seasonal exclusion, and non-exclusion, quantified the vegetation variations under three different exclusion
measures and their correlation to soil factors. The analysis results for community species component and plant diversity using
multi-response permutation procedures (MRPPs) showed that exclusion did change the species component and increase plant diversity
remarkably, while the period of exclusion had no significant influence on these two community features. The indicator species
analysis and calculation of similarity indices indicated that community for year-round exclusion were becoming xerophytization
and unpalatability, and showed highly spatial heterogeneity of plant species distribution, whereas community for seasonal
exclusion was under stable non-equilibrium condition. Detrended correspondence analysis (DCA) and detrend canonical correspondence
analysis (DCCA) results of relationship between plant species and soil variables demonstrated that soil moisture was a controlling
factor for plant species component, microbiotic soil crust cover, soil organic matter, and soil bulk density had significant
effects on soil moisture, among which microbiotic soil crust was a leading factor owing to its limitation to rainfall infiltration
on the one hand, and its constraints to entrance of herbaceous seeds into soil or to germination of soil seeds on the other
hand. As a result of long-term removal of animal grazing, crust kept intact in year-round exclusion community, which was a
main reason of community xerophytization. It was also obvious from ordination results that some important environmental factors,
such as tempo-spatial change of rainfall and corresponding tempo-spatial change of soil moisture, were neglected during direct
gradient analysis. In addition, biodiversity was close related to soil nutrients as well as to soil moisture condition (soil
water content and crust cover), and it had positive relation to available N, and negative relation to available P. Higher
soil N had advantage to non-leguminous plants growth on nutrition-poor sand land definitely. The impact of P to community
component was unclear and should be studied from plant physiology. Further researches on non-equilibrium theory in semi-arid
rangeland will provide a scientific and flexible animal development paradigm for being implementing livestock fen-raising
and grazing-forbidden policies in China.
__________
Translated from Acta Ecologica Sinica, 2005, 25(12): 3212–3219 [译自: 生态学报] 相似文献
19.
While invasive species may be visible indicators of plant community degradation, they may not constitute the only, or even the primary, limitation to stand regeneration. We used seed-augmentation and grass-removal experiments under different canopy conditions to assess the relative importance of dispersal limitation, resource availability, and competition on seedling establishment in the understory shrubs Sophora chrysophilla, Dodonea viscosa, and Pipturus albidus in a montane mesic forest in Hawaii. The study location was an Acacia koa-Metrosideros polymorpha forest at 1000–1500 m elevation on the leeward side of Hawaii Island; it is a closed-canopy forest historically subject to logging and grazing by cattle and sheep and currently dominated by the exotic grass, Ehrharta stipoides, in the herb layer. Seedling establishment after 1 and 2 years was strongly dispersal limited in Sophora and Dodonea, but not in Acacia, a non-augmented species in which abundant seedlings established, nor in Pipterus, in which only one seedling established in 2 years. Grass cover reduced seedling establishment in Acacia, Sophora, and Dodonea and, for the latter two species, seedling establishment was substantially greater in the warmer, more moist forest at the lowest elevation. Light, moisture, and resin-captured N and P were more strongly affected by elevation and canopy composition than by grass cover, but in most cases seedling establishment was not positively correlated with resource availability. Limitations to the establishment of woody seedlings in this forest-grassland mixture vary among species; however, both dispersal limitation and competition from a shade-tolerant grass are important deterrents to regeneration in these forests. 相似文献
20.
We surveyed plant community development at the abandoned Ogushi sulfur mine. We found seven communities dominated by the following
respective species: Deschampsia flexuosa, Miscanthus sinensis, shrub willow, Gaultheria miqueliana–Betula ermanii, Sasa senanensis–Betula ermanii, willow–Betula ermanii, and Sasa kurilensis–Abies veitchii. We examined the succession of these communities, in which younger communities of low height and ground cover contained seedlings
of the successive communities that were taller and had higher ground cover. To understand the development of these different
communities, we surveyed damage from mining pollution and effects of immature soils formed by landslides. The average pH (H2O) was 4.12, and aluminum concentrations were not sufficiently high to damage plant growth, except in areas where sulfur had
been mined. The organic carbon and nitrogen content in soil samples were very low because of a delay in soil development caused
by a large landslide in 1937. Hence, succession was positively correlated with the soil development stage. The delay in soil
development after a large landslide influenced the seven successional steps of the plant communities, but mineral poisons
at the abandoned Ogushi sulfur mine had no effect on succession. 相似文献