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1.
Dryland salinity is caused by rising saline water tables, the result of relatively recent landscape-scale clearance of deep-rooted
vegetation. One obvious solution to this problem is the reintroduction of deep-rooted vegetation into these landscapes, most
likely non-deciduous trees. Ideally, continually-transpiring deep-rooted trees would remove moisture from throughout the soil
profile, increasing the capacity of the soil to store water, thus lowering water tables by effectively reducing the number
of rainfall events that contribute to groundwater recharge. In this study, we examined how water use by a Eucalyptus sideroxylon A. Cunn. ex Woolls plantation, growing in a salinity-prone landscape, varied in response to rainfall events across four years
of sap flux monitoring. Responses of the plantation were observed across multiple seasons, from above average to well below
average rainfall. We observed that the plantation forest, while capable of continuous water use during drought, was also quite
responsive to rainfall events. During the driest periods, during which shallow soil moisture was reduced to a stable minimum,
the forest continued using water at around 1 mm/day. Generally we observed increases in forest water use following only 5
mm of rainfall, in contrast to 20 mm for neighbouring native vegetation. We compared a range of plausible empirical models
for describing forest water use responses to rainfall. The best model demonstrated that rainfall size, post-rainfall PET and
the interaction between rainfall size and antecedent soil moisture made significant contributions to variation in forest water
use across rainfall events. Interestingly, the model showed that all else equal, higher antecedent soil moisture tended to
reduce potential increases in forest water use in response to rainfall. 相似文献
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Influence of paternally imprinted genes on development. 总被引:4,自引:0,他引:4
S C Barton A C Ferguson-Smith R Fundele M A Surani 《Development (Cambridge, England)》1991,113(2):679-687
The parental origin of chromosomes is critical for normal development in the mouse because some genes are imprinted resulting in a predetermined preferential expression of one of the alleles. Duplication of the paternal (AG: androgenones) or maternal (GG/PG: gynogenones/parthenogenones) genomes will result in an excess or deficiency of gene dosage with corresponding phenotypic effects. Here, we report on the effects of paternally imprinted genes on development following introduction of the AG inner cell mass into normal blastocysts. There was a striking increase in embryonic growth by up to 50%, and a characteristic change in embryonic shape, partly because of the corresponding increase in length of the anterior-posterior axis. These changes, between e12-e15, were proportional to the contribution from AG cells to the embryo. However, a contribution of AG cells in excess of 50% was invariably lethal as development progressed to e15. A limited number of chimeras were capable of full-term development provided there was a relatively low contribution from AG cells. The distribution of AG cells in chimeras was not uniform, especially later in development when there was a disproportionate presence of AG cells in the mesodermally derived tissues. Their contribution was consistently greater in the heart and skeletal muscle, but was considerably lower in the brain. Chimeras detected after birth were either dead or developed severe abnormalities of the skeletal elements, particularly of the ribs which were enlarged, distorted and fused, with greatly increased cartilaginous material with an absence of normal ossification. These phenotypic effects in chimeras are reciprocal to those observed in the presence of GG/PG cells, which resulted in a substantial size reduction approaching 50%.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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David B. Lindenmayer P. W. Lane P. S. Barton Mason Crane Karen Ikin Damian Michael Sachiko Okada 《Biodiversity and Conservation》2016,25(8):1587-1603
The long-term effectiveness of restored areas for biodiversity is poorly known for the majority of restored ecosystems worldwide. We quantified temporal changes in bird occurrence in restoration plantings of different ages and geometries, and compared observed patterns with a reference dataset from woodland remnants on the same farms as our plantings. Over time, bird species richness remained unchanged in spring but exhibited modest increases in winter. We found that wider plantings supported significantly greater bird species richness in spring and winter than narrow plantings. There was no evidence of a significant interaction between planting width and time. We recorded major temporal changes in the occurrence of a range of individual species that indicated a clear turnover of species as plantings matured. Our results further revealed marked differences in individual species occurrence between plantings and woodland remnants. Life-history attributes associated with temporal changes in the bird assemblage were most apparent in winter survey data, and included diet, foraging and nesting patterns, movement behaviour (e.g. migratory vs. dispersive), and body size. Differences in bird assemblages between plantings of different ages suggest that it is important that farms support a range of age classes of planted woodland, if the aim is to maximize the number of native bird species in restored areas. Our data also suggest that changes in the bird species occupying plantings of different ages can be anticipated in a broadly predictable way based on planting geometry (especially width) and key life-history attributes, particularly movement patterns and habitat and diet specialisation. 相似文献
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Background
Amino acids responsible for structure, core function or specificity may be inferred from multiple protein sequence alignments where a limited set of residue types are tolerated. The rise in available protein sequences continues to increase the power of techniques based on this principle. 相似文献8.
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The effects of irrigation and fertiliser regimes on N leaching from the production of couch grass (Cynodon dactylon L.) sod, on a free-draining sandy soil, were evaluated in a 22-month field study. The experimental design used a randomised-block,
split-plot design with three replicates. Main plots consisted of two irrigation treatments: 70 and 140% daily replacement
of pan evaporation; four subplot fertiliser types (water-soluble (predominately NH4NO3), control-release, pelletised poultry manure and pelletised biosolids); and three N application rates (100, 200 and 300 kg
N ha−1 per crop). Nitrogen leaching was assessed by measuring the leachate volumes and concentrations of N species leached from
soil lysimeters (250 mm in diameter by 950 mm in length) installed in 10 m2 turfgrass plots. Nitrogen leaching ranged from 33 to 167 kg N ha−1 over 22 months, depending upon the irrigation and fertiliser treatment. Irrigation treatment affected N leaching more than
fertiliser treatment, and increasing the irrigation from 70 to 140% replacement of daily pan evaporation increased N leaching
for all fertiliser types, and by up to four times. Forty six to 76% of losses occurred from the high irrigation treatments
during the first 16 weeks after the turfgrass was planted as rhizomes. By contrast, N leaching did not appear to increase
following harvest of sod. At the high irrigation treatment, N leaching was greater for the pelletised biosolids than the control-release;
while at the low irrigation treatment, N leaching did not vary between fertiliser types. A significant proportion of the N
leached was in the organic form. Therefore, we recommend total N and mineral N be measured when assessing N leaching from
turfgrass. Nitrogen leaching from turfgrass production is low from all fertiliser types when the irrigation matches turfgrass
water use and N is applied at a rate and frequency that approximates turfgrass requirements.
Section Editor: P. J. Randall 相似文献
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