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排序方式: 共有107条查询结果,搜索用时 24 毫秒
21.
Elevational and age gradients in hawaiian montane rainforest: foliar and soil nutrients 总被引:2,自引:0,他引:2
Summary Soils and plants were sampled along an elevational gradient from 265–1675 m on a 133-and a 3100-year-old lava flow on Mauna Loa, Hawai'i. Soil organic matter and nutrients accumulated more rapidly at low elevation on the young flow, but reached higher levels at higher elevation on the old flow. Foliar nitrogen and phosphorus concentrations were less and specific leaf weight greater for Metrosideros polymorpha leaves collected at high versus low elevations and on the young versus the old flow. Foliar 13C was strongly correlated with specific leaf weight across the range of sites sampled.Published as a contribution to the Tropical Mountain Ecosystem Program of the IUBS Decade of the Tropics 相似文献
22.
Invasive plant species can substantially alter the soil fertility of the ecosystems they invade, and in doing so have the potential to reduce the suitability of the soil for native species. Even after removal of the invader these alterations can inhibit the reestablishment of native species. We evaluated the impact of invasion by the leguminous shrub Ulex europaeus on soil properties on Mauna Kea, HI. We also investigated the effect of efforts to remove U. europaeus and restore native ecosystems in the study area; where the efforts included bulldozing the U. europaeus and planting introduced Cryptomeria japonica to compete with regenerating U. europaeus. Mauna Kea supports a strong rainfall gradient and substantial associated variation in soil properties. We use statistical models to extract the effect of invasion and restoration from the influence of rainfall. We found U. europaeus decreases soil pH, calcium content, base saturation, and labile phosphorus. Restoration efforts over an 11-year period restored the soil’s calcium and phosphorus content to levels comparable to those found in uninvaded soils on Mauna Kea, demonstrating that the effects of U. europaeus on soils are reversible. 相似文献
23.
Hugh A. L. Henry John D. Juarez† Christopher B. Field † Peter M. Vitousek 《Global Change Biology》2005,11(10):1808-1815
Elevated CO2, N deposition and climate change can alter ecosystem‐level nutrient cycling both directly and indirectly. We explored the interactive effects of these environmental changes on extracellular enzyme activity and organic matter fractionation in soils of a California annual grassland. The activities of hydrolases (polysaccharide‐degrading enzymes and phosphatase) increased significantly in response to nitrate addition, which coincided with an increase in soluble C concentrations under ambient CO2. Water addition and elevated CO2 had negative but nonadditive effects on the activities of these enzymes. In contrast, water addition resulted in an increase in the activities of lignin‐degrading enzymes (phenol oxidase and peroxidase), and a decrease in the free light fraction (FLF) of soil organic matter. Independent of treatment effects, lignin content in the FLF was negatively correlated with the quantity of FLF across all samples. Lignin concentrations were lower in the aggregate‐occluded light fraction (OLF) than the FLF, and there was no correlation between percent lignin and OLF quantity, which was consistent with the protection of soil organic matter in aggregates. Elevated CO2 decreased the quantity of OLF and increased the OLF lignin concentration, however, which is consistent with increased degradation resulting from increased turnover of soil aggregates. Overall, these results suggest that the effects of N addition on hydrolase activity are offset by the interactive effects of water addition and elevated CO2, whereas water and elevated CO2 may cause an increase in the breakdown of soil organic matter as a result of their effects on lignin‐degrading enzymes and soil aggregation, respectively. 相似文献
24.
Element interactions in forest ecosystems: succession,allometry and input-output budgets 总被引:3,自引:3,他引:0
Element interactions within forests differ from those in other major ecosystems for three major reasons: — a greater allocation of carbon to structural material; — a greater element storage within biomass; and — the diversity of carbon- and nutrient-containing metabolites produced. The most important of these differences is structural material, which can lead to C: element ratios in biomass (as a whole) 100 × greater than those in unicellular organisms. Stand allometry causes the amount of carbon stored and C:element ratios in biomass to change in predictable ways in the course of secondary succession. Such changes affect microbial dynamics and C: element interactions within soils. Bicarbonate, organic acids, nitrate, phosphate, and sulfate are major anions within forest soils: they control leaching of both anions and cations. Biotic interactions of C, N, P, and S during both uptake and mineralization control the potential for production of these anions within forests, and geochemical interactions regulate their mobility and loss. 相似文献
25.
A long term study of warblers in the Himalayas reveals a surprising contrast in the effects of warm springs as opposed to warm summers on a signaling trait, emphasizing the need to consider year-round influences of the environment on morphological variation. 相似文献
26.
N : P stoichiometry and protein : RNA ratios in vascular plants: an evaluation of the growth-rate hypothesis 总被引:5,自引:0,他引:5
The growth-rate hypothesis states that fast-growing organisms need relatively more phosphorus-rich RNA to support rapid rates of protein synthesis, and therefore predicts, within and among taxa, increases in RNA and phosphorus content (relative to protein and nitrogen content) with increased growth rate. Here, we present a test of this hypothesis in vascular plants. We determined nitrogen : phosphorus ratios and protein : RNA ratios in pines growing at different rates due to nutrient conditions. In general, when comparing leaves of the same species at low and high growth rates, the faster-growing plants had higher RNA content, higher %N and %P, and lower protein : RNA ratios, but not consistently lower N : P ratios. We found no link between growth rate and foliar N : P or protein : RNA when comparing multiple species of different inherent growth rates. We conclude that plants adjust the balance of protein and RNA to favour either speed or efficiency of protein synthesis, but this balance does not alone dictate leaf stoichiometry. 相似文献
27.
Hugh A. L. Henry Nona R. Chiariello Peter M. Vitousek Harold A. Mooney Christopher B. Field 《Ecosystems》2006,9(7):1066-1075
Although it is widely accepted that elevated atmospheric carbon dioxide (CO2), nitrogen (N) deposition, and climate change will alter ecosystem productivity and function in the coming decades, the combined
effects of these environmental changes may be nonadditive, and their interactions may be altered by disturbances, such as
fire. We examined the influence of a summer wildfire on the interactive effects of elevated CO2, N deposition, and increased precipitation in a full-factorial experiment conducted in a California annual grassland. In
unburned plots, primary production was suppressed under elevated CO2. Burning alone did not significantly affect production, but it increased total production in combination with nitrate additions
and removed the suppressive effect of elevated CO2. Increased production in response to nitrate in burned plots occurred as a result of the enhanced aboveground production
of annual grasses and forbs, whereas the removal of the suppressive effect of elevated CO2 occurred as a result of increased aboveground forb production in burned, CO2-treated plots and decreased root production in burned plots under ambient CO2.The tissue nitrogen–phosphorus ratio, which was assessed for annual grass shoots, decreased with burning and increased with
nitrate addition. Burning removed surface litter from plots, resulting in an increase in maximum daily soil temperatures and
a decrease in soil moisture both early and late in the growing season. Measures of vegetation greenness, based on canopy spectral
reflectance, showed that plants in burned plots grew rapidly early in the season but senesced early. Overall, these results
indicate that fire can alter the effects of elevated CO2 and N addition on productivity in the short term, possibly by promoting increased phosphorus availability. 相似文献
28.
Gregory P. Asner Roberta E. Martin Kimberly M. Carlson Uwe Rascher Peter M. Vitousek 《Ecosystems》2006,9(7):1106-1117
We compiled a time series of Earth Observing-1 Hyperion satellite observations with field measurements to compare the structural,
biochemical, and physiological characteristics of an invasive nitrogen-fixing tree Myrica faya and native Metrosideros polymorpha in montane rainforests in Hawai’i. Satellite-based canopy water measurements closely tracked variations in leaf area index,
and the remotely sensed photochemical and carotenoid reflectance indices (PRI, CRI) indicated variations in upper-canopy leaf
chlorophyll and carotenoid content during a climatological transition. The PRI and CRI were related to differences in light-use
efficiency of each species, as indicated by field measurements of leaf electron transport rate. The suite of hyperspectral
metrics indicated maximum differences in the structure, biochemistry, and physiology of Myrica and Metrosideros when canopy vapor pressure deficit was high during hotter and drier periods. These satellite data, combined with the Carnegue-Ames-Stanford
Approach (CASA) carbon cycle model, suggested that Myrica growth rates were 16–44% higher than Metrosideros, with relative differences between species closely linked to climate conditions. The satellite hyperspectral data identified
the basic biological mechanisms favoring the spread of an introduced tree, and provided a more detailed understanding of how
vegetation–climate interactions affect the time course of plant growth with respect to the invasion process. 相似文献
29.
Foliar and Litter Nutrients, Nutrient Resorption, and Decomposition in Hawaiian Me
t
rosideros polymorpha 总被引:1,自引:0,他引:1
Peter M. Vitousek 《Ecosystems》1998,1(4):401-407
The native tree Metrosideros polymorpha dominates Hawaiian forests across a very wide range of soil fertility, including both sites where forest production is limited
by nitrogen (N) and others where it is limited by phosphorus (P). Five long-term fertilization experiments have further broadened
the range of nutrient availabilities experienced by Metrosideros. Adding P to P-limited sites increased foliar P concentrations threefold and litter P concentrations up to 10-fold; lignin
concentrations decreased, and the decomposability of leaf litter increased from 32%–35% to 36%–46% mass loss in the first
year. Adding N to N-limited sites increased leaf and litter N concentrations by only 15%–20%, with little or no effect on
the decomposability of tissue.
Received 22 January 1998; accepted 4 May 1998. 相似文献
30.
Nutrient limitations to plant growth during primary succession in Hawaii Volcanoes National Park 总被引:11,自引:2,他引:9
Peter M. Vitousek Lawrence R. Walker Louis D. Whiteaker Pamela A. Matson 《Biogeochemistry》1993,23(3):197-215
We determined the effects of nutrient amendments on plant growth in three tropical montane rainforest sites representing a sequence of soil ages (< 30, 200, and 2000 y). Factorial fertilization with nitrogen, phosphorus, and all other essential nutrients (combined) was applied to the two younger sites; only nitrogen was applied to the oldest one. Nitrogen supply represented the most important limitation to plant growth in the two younger sites; additions of nitrogen caused significant increases in tree diameter increment, height growth, litterfall, and most other growth-related parameters. In contrast, nitrogen additions had no significant effect on plant growth in the oldest site. Phosphorus additions increased extractable soil phosphorus and plant tissue phosphorus, but did not increase plant growth at the young sites. The results are consistent with Walker & Syers' (1976) model for the control of nutrient limitation during soil development. 相似文献