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1.
Lubomír Adamec 《Biologia》2008,63(4):515-520
Basic respiration characteristics were measured in turions of six aquatic plant species differing greatly in their ecological
and overwintering characteristics both before and after overwintering, i.e., in dormant and non-dormant state: non-carnivorous
Hydrocharis morsus-ranae and Caldesia parnassifolia and carnivorous Aldrovanda vesiculosa, Utricularia australis, U. ochroleuca, and U. bremii, and in non-dormant winter apices of three Australian (sub)tropical populations of Aldrovanda and of two temperate North American Utricularia species, U. purpurea and U. radiata. Respiration rate of autumnal (dormant) turions at 20°C ranged from 0.36 to 1.3 μmol O2 kg−1 (FM) s−1 and, except for U. bremii, increased by 11–114% after overwintering. However, this increase was statistically significant only in two species. Respiration
Q10 in dormant turions ranged within 1.8–2.6 and within 2.3–3.4 in spring (non-dormant) turions. Turions of aquatic plants behave
as typical storage, overwintering organs with low respiration rates. No relationship was found between respiration rate of
turions and overwintering strategy. In spite of their low respiration rates, turions can usually survive only from one season
to another, due to their limited reserves of respiratory substrates for long periods. Contrary to true turions, respiration
rates in non-dormant winter apices both in Australian Aldrovanda populations and temperate U. radiata and U. purpurea, in sprouting turions, and growing shoot apices of Aldrovanda were high and ranged from 2.1 to 3.1 μmol kg−1 (FM) s−1, which is comparable to that in aquatic plant leaves or shoots. 相似文献
2.
Seasonal and spatial patterns of light availability were investigated in the understory of a small fragment (approximately
1300 m2) of a riparian deciduous forest of the Kokai River in central Japan dominated byQuercus acutissima Carruth., with the aim to understand the characteristics of microsite light availability forArisaema heterophyllum Blume, a threatened plant species uniquely associated with the riparian habitat. Diffuse site factor, which is the ratio
of PFD (photon flux density, 400–700 nm) at a microsite to the open sky reference under diffuse light condition, was shown
to be a satisfactory index for the evaluation of light availability for the understory plants in the habitat. Diffuse site
factor 1,0 1,000 understory microsites along a 20 m transect from the edge to the interior of the forest, showed conspicuous
seasonal changes in both mean and variation. Light availability decreased with seasonal tree canopy regeneration, with the
highest spatial heterogeneity being recorded during the time of canopy closure. Auto-correlations of microsite light availability
between different seasons were considerably high, suggesting the stability of relative light availability for individual microsites
throughout the growing season ofA. heterophyllum. Fairly high light availability during summer season, which surpassed 20% of the open sky reference in most microsites, would
be important for the growth and persistence of summer herbaceous plants likeA. heterophyllum. 相似文献
3.
Lubomír Adamec 《Folia Geobotanica》1999,34(3):287-297
New potential sites for the critically-endangered, aquatic carnivorous plantAldrovanda vesiculosa L. (Droseraceae) were selected in North and South Bohemia (Czech Republic) and both its seasonal growth dynamics and overwintering rate were investigated. Groups of either 5 or 10 plants were planted in 1×1 m nylon enclosures in selected shallow, dystrophic waters at the end of May. Plant growth characteristics and water chemistry were investigated at 2 to 5 week intervals over the 1994 growing season inside ten enclosures placed at six sites. Within seven enclosures at three sites, the seasonal growth was very fast and 38–141 turions developed from the initial five plants. Water at these sites was mesotrophic with a high concentration of CO2 above 0.1 mmol.l?1 and pH between 6.2 and 7.6. At the other three sites, plant growth was very poor. The fastest plant propagation was found between late June and mid-August and corresponded with the warmest seasonal period. During this period, the doubling time of the total number of shoot apices was 16.4–34.9 days. Turions developed in mid-September and sank to the bottom by mid-October. In some enclosures, the turions overwintered on the wet bottom whereas they were submersed in the other ones. Though the turions were subject to frosts of up to ?20°C, none died due to the frosts. Grazing of turions by ducks or small rodents was found at some sites. The overwintering rate of turions at sites varied from 0 to 70% and was not related to seasonal growth rate. Most turions floated to the surface and germinated during late April-early May. It is suggested that considerable turion losses in stable, naturalAldrovanda stands are compensated for by fast seasonal shoot growth and branching which leads to the recovery of an abundant plant population. 相似文献
4.
L. Adamec 《Biologia Plantarum》2003,47(3):395-402
Two main dormancy states, innate and imposed dormancy, were characterized in turions (winter buds) of the aquatic carnivorous plant Aldrovanda vesiculosa L. (Droseraceae) kept at 3 ± 1 °C in a refrigerator over the winter. As a result of the breaking of imposed dormancy by a temperature increase (at 15 – 20 °C), some of the turions rose to the water surface within 1 – 3 d and germinated. Turion leaves contained large lacunae with a slimy reticulum and were filled by water over winter. As a result of breaking imposed dormancy, the proportion of gas volume in inner turion leaves rose from 10 – 20 % to 100 % of leaf lacunae volume. The aerobic dark respiration rate of the turions [0.74 – 1.5 μmol O2) kg−1(FM) s−1] slightly increased during innate dormancy after 1 – 2 d at 20 °C, while it was almost constant during the breaking of imposed dormancy. The anaerobic fermentation rate of the turions was only 1.5 – 7 % of the oxygen respiration rate and also was constant during the breaking of imposed dormancy. In turions, the content of glucose, fructose, and sucrose was the same for the two states of dormancy, but starch content was greatly reduced for the imposed dormancy (10 – 11 vs. 32 % DM). It may be suggested that a temperature increase causes an increase of fermentation or respiration which is responsible for the evolution of gas in turion lacunae and, thus, for turion rising. 相似文献
5.
Reconstruction of the carbon balance for microsites in a boreal oligotrophic pine fen, Finland 总被引:11,自引:0,他引:11
J. Alm Alexander Talanov Sanna Saarnio Jouko Silvola Elena Ikkonen Heikki Aaltonen Hannu Nykänen Pertti J. Martikainen 《Oecologia》1997,110(3):423-431
Carbon dioxide (CO2) exchange was studied at flark (minerotrophic hollow), lawn and hummock microsites in an oligotrophic boreal pine fen. Statistical
response functions were constructed for the microsites in order to reconstruct the annual CO2 exchange balance from climate data. Carbon accumulation was estimated from the annual net CO2 exchange, methane (CH4) emissions and leaching of carbon. Due to high water tables in the year 1993, the average carbon accumulation at the flark,
Eriophorum lawn, Carex lawn and hummock microsites was high, 2.91, 6.08, 2.83 and 2.66 mol C m–2, respectively, and for the whole peatland it was 5.66 mol m–2 year–1. During the maximum primary production period in midsummer, hummocks with low water tables emitted less methane than predicted
from the average net ecosystem exchange (NEE), while the Carex lawns emitted slightly more. CH4 release during that period corresponded to 16% of the contemporary NEE. Annual C accumulation rate did not correlate with
annual CH4 release in the microsites studied, but the total community CO2 release seemed to be related to CH4 emissions in the wet microsites, again excluding the hummocks. The dependence of CO2 exchange dynamics on weather events suggests that daily balances in C accumulation are labile and can change from net carbon
uptake to net release, primarily in high hummocks on fens under warmer, drier climatic conditions.
Received: 16 August 1996 / Accepted: 30 November 1996 相似文献
6.
Microsite variation in light availability and seedling growth ofQuercus serrata in a temperate pine forest 总被引:1,自引:0,他引:1
Spatial heterogeneity in light availability for tree seedlings under the canopy of a temperate pine forest was studied. Six-day
measurements at 10-s intervals revealed a great variety in the temporal patterns of photosynthetic photon flux density (PPFD)
and histograms among observation days and microsites; mean daily total PPFD relative to full sun varied from 1.5% to 10.4%
depending on the microsites. The occurrence and duration of PPFD above 80 μmol m−2 s−1, which might reflect sunfleck activity, varied greatly among the microsites. However, several simple empirical relationships
were found between some parameters characterizing microsite light availability and sunfleck activity; the diffuse site factor
was correlated well with other parameters, including daily total PPFD, daily totals and daily summed durations of high PPFD
above any examined threshold level, and its contribution to daily total PPFD. Diffuse site factors which were obtained for
700 microsites within an area of 28 m2 on three different occasions during the growing season showed high correlations within the microsite. Based on the regressed
relationship between the relative growth rate of current-year seedlings ofQuercus serrata and the microsite diffuse site factor and the results of area-survey measurement of the diffuse site factor, an estimation
was made of the abundance of potential ‘safe-sites’ for seedling growth of the species; the ‘safe sites’ were estimated to
cover 40% and 0% of the total area of the sunny and shady sites of the forest, respectively. 相似文献
7.
Photosynthetic photon flux density (PPFD) at 15 cm above the ground was measured at 20 microsites in gaps and grass patches
within aMiscanthus sinensis Anderss community at 10 s intervals during 5 days every month from May to September 1989.
Microsite light availability, which was characterized by daily total PPFD, sunfleck PPFD (PPFD above a threshold value of
50 or 400 μmol m−2 s−1) and the diffuse site factor, showed evident seasonal changes, with a marked reduction between June and July due to the rapid
growth of the grass canopy. The monthly median value of daily total PPFD among the microsites decreased from 10.3 mol m−2 day−1 in May to 0.77 mol m−2 day−1 in September, with a reduction in the diffuse site factor from 31 to 4%. During the summer, the median value of the total
time of sunflecks exceeding 50 μmol m−2 s−1 contributed 7–18% of measurement time, but the contribution of these sunflecks to daily total PPFD ranged from 29 to 59%.
There was considerable microsite variation in light availability throughout the measurement period. Rank correlation analysis
revealed that some microsites, such as those in gaps, consistently received more total PPFD, more sunfleck PPFD and had a
higher diffuse site factor than those in grass patches. The diffuse site factor had a linearly positive relationship with
daily total PPFD and total sunfleck PPFD for the 20 microsites during the measurement period, confirming that the diffuse
site factor is a useful index for microsite light availability withinM. sinensis canopies. 相似文献
8.
Izumi Washitani 《Ecological Research》1992,7(2):187-191
Leaf carbon gain simulation was performed forQuercus serrata seedlings with previously reported 6 day photosynthetic photon flux density (PPFD) histograms from 20 understorey microsites
of a pine forest (Washitani & Tang 1991). This simulation was performed with or without an assumption of the acclimatization
of photosynthetic capacity (Pmax) to microsite light availability. A constant ratio of respiration rate to Pmax, within, the range of 0.07–0.1, was assumed as a constraint. In relatively well illuminated microsites with a diffuse site
factor above 0.1, predicted optimal Pmax was about 5 μmol m−2 s−1, with the predicted mean daily net carbon gain being about 50 mmol m−2 day−1. Each of the predicted optimal Pmax and the simulated mean daily net carbon gains with a constant Pmax (5 μmol m−2 s−1) or the predicted optimal Pmax was linearly related to the microsite light availability index, diffuse site factor. Simulated net carbon gain was negative
at diffuse site factors below 0.04, if the constant of Pmax was assumed. The predicted linear relationship between net carbon gain and diffuse site factor could provide an ecophysiological
basis for the observed linear dependency of the relative growth rate of biomass ofQ. serrata seedlings on the microsite diffuse site factor (Washitani & Tang 1991). 相似文献
9.
Woody vegetation can create distinct subcanopy and interspace microsites, which often result in resource islands in subcanopies
compared to interspaces. This heterogeneity in soil resources contributes to herbaceous vegetation heterogeneity in plant
communities. However, information detailing the impact of disturbance, such as fire, that removes the woody vegetation on
microsites and herbaceous vegetation heterogeneity is limited. The purpose of this study was to determine the influence of
burning on microsites and herbaceous vegetation in subcanopies and interspaces. Six study sites (blocks) were located at the
Northern Great Basin Experimental Range in shrub (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh)-bunchgrass plant communities and one half of each block was burned to remove A. tridentata. Herbaceous vegetation and microsite characteristics were measured 2 years post-fire in intact and burned subcanopies and
interspaces. Burning resulted in microsite and herbaceous vegetation differences between intact and burned subcanopies and
intact and burned interspaces. However, burned subcanopies and burned interspaces appeared to be relatively similar. The similarity
in microsite characteristics probably explains the lack of differences in herbaceous vegetation cover and biomass production
between burned subcanopies and burned interspaces (P > 0.05). However, some microsite and herbaceous vegetation characteristics differed between burned subcanopies and burned
interspaces. Our results suggest that disturbances that remove woody vegetation reduced microsite and herbaceous vegetation
heterogeneity within plant communities, but do not completely remove the resource island effect. This suggests soil resource
heterogeneity may influence post-fire community assembly and contribute to diversity maintenance.
The Eastern Oregon Agricultural Research Center is jointly funded by the USDA-Agricultural Research Service and Oregon State
Agricultural Experiment Station.
Mention of a proprietary product does not constitute a guarantee or warranty of the product by USDA, Oregon State University,
or the authors and does not imply its approval to the exclusion of other products. 相似文献
10.
Myriophyllum verticillatum L. is the single most obstructive aquatic plant in Irish canals. Because of the importance of these canals as national amenities,
considerable resource has been directed towards the long-term control of this aggressive plant. A combination of mechanical
harvesting and chemical treatment has traditionally been employed to control Myriophyllum growth but these methods have only provided short-term control. Myriophyllum verticillatum reproduces by producing turions between September and November each year. These over-wintering propagules sink to the canal
bed where they remain dormant until February. At a trial site on the Royal Canal turions were harvested in November 1994 and
1995, significantly reducing the number of propagules present. Biomass and plant cover with M. verticillatum throughout the 1995 and subsequent growing seasons was dramatically reduced. The implications for weed control programmes,
habitat development and amenity usage are discussed. 相似文献
11.
S. Saarnio Jukka Alm Jouko Silvola Annalea Lohila Hannu Nykänen Pertti J. Martikainen 《Oecologia》1997,110(3):414-422
Temporal and spatial variation in CH4 emissions was studied at hummock, Eriophorum lawn, flark and Carex lawn microsites in an oligotrophic pine fen over the growing season using a static chamber method, and CH4 production and oxidation potentials in peat profiles from hummock and flark were determined in laboratory incubation experiments.
Emissions were lowest in the hummocks, and decreased with increasing hummock height, while in the lawns and flarks they increased
with increasing sedge cover. Statistical response functions with water table and peat temperature as independent variables
were calculated in order to reconstruct seasonal CH4 emissions by reference to the time series for peat temperature and water table specific to each microsite type. Mean CH4 emissions in the whole area in the snow-free period of 1993, weighted in terms of the proportions of the microsites, were
1.7 mol CH4 m–2. Potential CH4 production and oxidation rates were very low in the hummocks rising above the groundwater table, but were relatively similar
when expressed per dry weight of peat both in the hummocks and flarks below the water table. The CH4 production potential increased in autumn at both microsites and CH4 oxidation potential seemed to decrease. The decrease in temperature in autumn certainly reduced in situ decomposition processes,
possibly leaving unused substrates in the peat, which would explain the increase in CH4 production potential.
Received: 16 August 1996 / Accepted: 30 November 1996 相似文献
12.
Seed and microsite limitations of recruitment and the impacts of post-dispersal seed predation at the within population level 总被引:1,自引:0,他引:1
María Calviño-Cancela 《Plant Ecology》2007,192(1):35-44
Seed predation may cause important seed losses in plant populations, but its impact on the dynamics of populations will depend
on the degree of seed or microsite limitations for recruitment. Seed losses will only affect recruitment if it is seed limited.
The nature of recruitment limitation (seeds or microsites) is usually ascribed to whole plant populations but it may vary
within populations among microhabitats and habitats. Thus, the potential impact of seed predation will also vary within the
population, being highest where recruitment is seed limited. The impact to the whole population will depend on the spatial
concordance between the intensity of seed predation and that of seed limitation. Recruitment limitations (with seed addition
experiments), seed predation (with seed removal experiments), and the dynamics of seed availability in the soil (with soil
samples taken both after seed dispersal and before the following dispersal event) of the shrub Corema album (Empetraceae) were investigated in dunes in NW Spain, at microhabitats ‘open ground’, ‘underneath C. album ♀’, and ‘underneath C. album ♂’ at two habitats, sparse and dense scrub. The nature of recruitment limitation (seeds vs. microsites) varied within the
population. It was seed limited in the microhabitat ‘open ground’ and microsite limited under shrub cover. The spatial patterns
of seedling recruitment were unrelated to seed availability but strongly affected by germination requirements. The spatial
discordance between seed availability and recruitment implies a crucial constraint for processes affecting seed availability
(seed predation but also e.g., dispersal) to impact recruitment. They will not affect its spatial pattern but only its quantity
as long as they act in those sites selected by seeds to germinate. Seed predation was highest underneath mother plants and lowest in open ground. Thus, its potential
impact is low, as it is centred where recruitment is not seed limited. This study shows that the analysis of seed predation
in relation to recruitment limitations at smaller spatial scales within the population provides more insight to understand
its impact. 相似文献
13.
Our study focuses on the ground vegetation dynamics and its dependence on microsite conditions in declined climax mountain
Norway spruce forests during the recovery period (1995–2006) following upon the considerable decrease of SO2 pollution. We showed that ground vegetation development shifted from prevailing mosses and vegetation-free sites covered
with spruce litter to dominance by Avenella flexuosa during the earlier period of massive decline of the observed ecosystems. The expansion of Vaccinium myrtillus seems to occur mainly under the gradually defoliating tree crowns whereas larger canopy gaps and quickly deforested areas
are more successfully colonized by grasses, especially Calamagrostis villosa. The gradual spruce stand decline, as well as the corresponding ground vegetation dynamics, proceeded until the end of the
twentieth century. Afterwards, the ground vegetation responded to the interruption of trees dying and stopped its expansion
on spruce litter microsites. Retreat of both dominant grasses accompanied by the remarkable increase in cover of mosses occurred. 相似文献
14.
The species composition and structure of plant communities related to the activity of Formica rufa ants were studied in green moss pine forests located in Nerusso-Desnyanskoe Polesye (Bryansk Province). Four types of microsites
were established and examined: (1) the mound of an active ant nest, (2) the soil bank around an active ant nest, (3) the mound
of an abandoned nest, and (4) the soil bank around an abandoned nest. The background plant community was considered as the
fifth type. According to MRPP method, all pairs of microsites except (3–4) were different both in plant species composition
and species abundance. The microsites created by Formica rufa increase the habitat capacity and β diversity of the plant communities due to the appearance of meadow species requiring
richer soils. 相似文献
15.
Primula nutans Georgi is a herbaceous species broadly distributed in wetlands on the Qinghai–Tibetan Plateau. These wetlands are often spatially
highly heterogeneous because of their hummock-and-hollow microtopography. To address how P. nutans can be so broadly distributed on these wetlands, we examined ramet distribution, abundance, and growth performance in environmentally
variable microsites at the centimeter scale. P. nutans showed significantly higher ramet density on the south-orientated microsites than on the north-orientated microsites. With
increasing relative microsite elevation on the hummocks, ramet density increased significantly, but individual leaf area decreased
significantly. Principle component analysis and multiple regression analysis indicated that microsites at higher elevations
tend to have higher light availability and higher ramet density. The study suggests that P. nutans shows high plasticity in the distribution, abundance, and growth performance in response to the microtopography at the centimeter
scale, which may contribute to the broad distribution of the species in the hummock-and-hollow wetlands in harsh alpine environments
on the Tibetan Plateau. 相似文献
16.
Rodent seed predation and seedling recruitment in mesic grassland 总被引:11,自引:0,他引:11
Seedling recruitment of two grasses (Arrhenatherum elatius and Festuca rubra) and two herbs (Centaurea nigra and Rumex acetosa) was measured in areas with and without rodents to which seeds of each species were sown at three seed densities (1000, 10,000
and 50,000 seeds m−2) in two seasons (spring and autumn 1995). Seed removal was measured for 10-day periods and the fate of seedlings was followed
for 15 months after sowing. The proportion of seed removed ranged from 6 to 85% and increased with increasing seed density
for each species. Rodents had no effect on seedling emergence or survival in the spring sowing. In the autumn sowing, rodents
reduced seedling emergence of all four species sown at 1000 and 10,000 seeds m−2 but had no impact at 50,000 seeds m−2, presumably because of microsite limitation. We suggest the difference between spring and autumn arose because emergence
was seed limited in autumn but microsite limited in spring; microsite availability was higher in autumn because a summer drought
killed plants, reduced plant biomass and opened up the sward. Fifteen months after the autumn sowing, fewer A. elatius and C. nigra seedlings survived on plots exposed to rodents. This result reflected not only the reduced seedling emergence but also increased
seedling mortality (seedling herbivory) in sites exposed to rodents. In contrast, F. rubra and R.acteosa showed density-dependent seedling survival which compensated for initial differences in seedling emergence, so that no effect
of rodents remained after 15 months. The results suggest that rodent seed predation and seedling herbivory exert strong effects
on seedling recruitment of A.elatius and C. nigra when recruitment conditions are favourable (conditions that lead to high microsite availability) and may contribute to both
species being maintained at low densities in the grassland. The results also demonstrate that highly significant impacts of
rodent seed predation at the seedling emergence stage can disappear by the time of plant maturation.
Received: 2 March 1998 / Accepted: 28 September 1998 相似文献
17.
David G. Ainley Peter R. Wilson Kerry J. Barton Grant Ballard Nadav Nur Brian Karl 《Polar Biology》1998,20(5):311-319
We investigated the diet and aspects of foraging effort among Adélie penguins (Pygoscelis adeliae) breeding at three colonies on Ross Island, in the southwestern Ross Sea – Capes Royds, Bird and Crozier – during the chick-provisioning
period of three austral summers, 1994–1995, 1995–1996 and 1996–1997. During the study period, pack-ice cover differed in waters
offshore of these colonies, by colony, seasons and year. Diet differed among colonies only slightly. The fish Pleuragramma antarcticum was the most important prey, especially during years or periods within years when little pack ice was present. With respect
to krill, which composed the remainder of diet, juvenile Euphausia crystallorophias were consumed predominantly in a year of heavy pack-ice cover; more adult krill were consumed in 2 years when pack ice was
sparse. Foraging trip duration differed by colony, season and year and was related directly to distance from the colony to
the nearest pack ice. The amount of food brought to chicks increased as trip duration increased, to a point (2 days), but
then decreased as duration increased further (up to 4 days). On the basis of data on mass of parents and of meal sizes to
chicks, it appeared that on the longest trips more of the food gathered by parents was used for self maintenance; on the longest
trips, parents lost body mass. Successful foraging during chick rearing, the period when adult foraging is most intense, appears
to depend on the proximity of pack ice to nesting colonies for this penguin species.
Received: 1 October 1997 / Accepted: 25 April 1998 相似文献
18.
Benthic macroinvertebrates associated with four species of macrophytes (Nymphoides peltata, Ceratophyllum demersum, Polygonum amphibium and Carex sp.) were investigated during two growing seasons (2001 and 2002) in the slow-flowing Čonakut Channel in the Kopački rit
Nature Park in Croatia. A total of 31 macroinvertebrate taxa were found. C. demersum, a submerged plant with dissected leaves, supported the highest macroinvertebrate abundance, almost seven times more than
N. peltata, a floating plant with undissected leaves, which harboured the lowest abundance during the research period. Chironomidae
larvae (50–83%) and Oligochaeta (14–46%) were the most abundant groups recorded on all macrophyte species. Water-level fluctuation,
because of its influence on the appearance and growth of aquatic vegetation, and the trophic state of water within the macrophyte
stands seemed to be the main factors which affected the taxonomic composition and abundance of macroinvertebrates. 相似文献
19.
Root proliferation characteristics of seven perennial arid-land grasses in nutrient-enriched microsites 总被引:2,自引:0,他引:2
We compared root proliferation in fertilized microsites among seven cultivars of five commonly planted cool-desert perennial grass species that differ in productivity and competitive ability. In a greenhouse experiment on nutrient-limited plants, one soil microsite in each pot received distilled water (control) and a second microsite received a rich, complete nutrient solution (fertilized). Roots in and adjacent to the microsites were mapped on Mylar windows for 22 days after the injections to determine the magnitude and timing of response in root length relative growth rates (RGRs). Because we provided adequate water, used a high level of fertilization in the treatment microsites, and conducted the experiments during rapid vegetative growth, the results provide a measure of the relative capacities and maximal rates of the grasses responses to enriched microsites. Root samples were harvested from control and fertilized microsites at the end of the experiment to determine the morphological basis of the proliferation response. In all seven grasses fine roots proliferated in the fertilized microsites faster than in the control microsites. The grasses did not differ in the timing of their response which showed a peak 7–8 days after injection. Although one species, Pseudoroegneria spicata cv. Goldar, had higher maximum root length RGR and higher RGR ratio (RGR in fertilized to RGR in control microsites) 7–8 days after injection, the seven grasses did not differ significantly in the magnitude of root length RGR response to fertilizer integrated over the 22 day experiment. The grasses also did not differ significantly in root morphological changes in fertilized mocrosites. Compared to roots in control microsites, roots in fertilized microsites had greater specific root length, length of secondary roots per length of main axis, number of lateral and sublateral roots per length of main axis, and mean lateral root length. Root proliferation was mainly the result of increased lateral branching and lateral root growth in all seven grasses. The consistency of root proliferation responses among these seven cultivars suggests that differences in the capacity for, maximum rate, or morphological basis of root proliferation are not directly related to ecological characteristics such as productivity and competitive ability. Other aspects of root response to nutrient enrichment, such as differential responses as a function of microsite nutrient concentration, plant phenology, plant nutrient status, or specific nutrient element(s), may still be important, but further experiments are required to determine whether different responses to enriched soil microsites among species correspond with know species differences in ecological characteristics. 相似文献
20.
Effects of microsite light availability on the growth and survival of transplantedQuercus serrata Thunb. seedlings in aMiscanthus sinensis Anderss. grass canopy were investigated by a “plant's eye view” approach. Diffuse site factors, i.e., the fractional transmissions
of diffuse photosynthetic photon flux density, were estimated at 15 cm aboveground in 108 microsites where the seedlings grew.
Microsite diffuse site factors were significantly different between surviving and dead seedlings during the experiment period
from April to October (F[1,14]=10.9, P<0.01). Relative growth rate of dry weight for individual seedlings positively depended on the diffuse site factors
(r2=0.482, P<0.001 in May; r2=0.312, P<0.001 in October). Only 16 seedlings produced their second stem flush within the grass canopy. The ratio of height
to dry weight of the second stem flush was significantly higher for the seedlings grew in shady microsites than for those
in less shady microsites (r2=0,471, P<0.01 in May). This study suggests that the microsite heterogeneity of light availability is one of the important
factors affecting the establishment of tree seedlings in patchy grasslands. 相似文献