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1.
Natural abundance of <Superscript>15</Superscript>N in two cacao plantations with legume and non-legume shade trees 总被引:1,自引:0,他引:1
Natural abundance of 15N was sampled in young and mature leaves, branches, stem, and coarse roots of trees in a cacao (Theobroma cacao) plantation shaded by legume tree Inga edulis and scattered non-legumes, in a cacao plantation with mixed-species shade (legume Gliricidia sepium and several non-legumes), and in a tree hedgerow bordering the plantations in Guácimo, in the humid Caribbean lowlands of
Costa Rica. The deviation of the sample 15N proportion from that of atmosphere (δ15N) was similar in non-legumes Cordia alliodora, Posoqueria latifolia, Rollinia pittieri, and T. cacao. Deep-rooted Hieronyma alchorneoides had lower δ15N than other non-N2-fixers, which probably reflected uptake from a partially different soil N pool. Gliricidia sepium had low δ15N. Inga edulis had high δ15N in leaves and branches but low in stem and coarse roots. The percentage of N fixed from atmosphere out of total tree N (%Nf) in G. sepium varied 56–74%; N2 fixation was more active in July (the rainiest season) than in March (the relatively dry season). The variation of δ15N between organs in I. edulis was probably associated to 15N fractionation in leaves. Stem and coarse root δ15N was assumed to reflect the actual ratio of N2 fixation to soil N uptake; stem-based estimates of %Nf in I. edulis were 48–63%. Theobroma cacao below I. edulis had lower δ15N than T. cacao below mixed-species shade, which may indicate direct N transfer from I. edulis to T. cacao but results so far were inconclusive. Further research should address the 15N fractionation in the studied species for improving the accuracy of the N transfer estimates. The δ15N appeared to vary according to ecophysiological characteristics of the trees. 相似文献
2.
Do multipurpose companion trees affect high value timber trees in a silvopastoral plantation system?
Establishment of native timber trees on deforested land may contribute to the livelihood of farmers, to improved ecosystem
services and to increased greenhouse gas uptake. Here, we present a new silvopastoral planting design to assess species performance
and interspecific competition or facilitation effects among native timber and multipurpose trees in Central America. Two timber
species, Tabebuia rosea and Cedrela odorata, were established in three low-density planting regimes allowing combined tree and future livestock production: (1) solitary
planting, (2) companion planting with Guazuma ulmifolia, and (3) companion planting with the nitrogen-fixing Gliricidia sepium. We quantified survival, growth and reforestation potential of the two timber species subjected to the different planting
regimes for the first 2 years after establishment. Nitrogen concentration as well as stable nitrogen and carbon isotope composition
(δ15N, δ13C) of leaves of the timber saplings were determined. T. rosea showed higher survival and better growth than C. odorata under varying environmental conditions (soil, concomitant vegetation). Performance of the timber saplings was unaffected
by either companion species. Planting regimes had no effect on foliar nitrogen concentration and δ15N of the two timber species, although δ15N values indicated nitrogen fixation activity in G. sepium trees. Planting regimes affected foliar δ13C values in T. rosea. δ13C values were significantly higher in solitarily growing individuals, suggesting lower exposition to water stress conditions
in saplings surrounded by companion species. As we found positively correlated growth traits among timber and multipurpose
trees, a combined planting may benefit farmers by providing additional goods and services. 相似文献
3.
Nitrogen inputs from biological nitrogen fixation contribute to productivity and sustainability of agroforestry systems but
they need to be able to offset export of N when trees are harvested. This study assessed magnitudes of biological nitrogen
fixation (natural 15N abundance) and N balance of Acacia mangium woodlots grown in farmer’s fields, and determined if N2 fixation capacity was affected by tree age. Tree biomass, standing litter, understory vegetation and soil samplings were
conducted in 15 farmer’s fields growing A. mangium as a form of sequential agroforestry in Claveria, Misamis Oriental, Philippines. The trees corresponded to ages of 4, 6,
8, 10 and 12 years, and were replicated three times. Samples from different plant parts and soils (0–100 cm) were collected
and analyzed for δ15N and nutrients. The B-value, needed as a reference of isotopic discrimination when fully reliant on atmospheric N, was generated by growing A. mangium in an N2-free sand culture in the glasshouse. Isotopic discrimination occurring during N2 fixation and metabolic processes indicated variation of δ15N values in the order of nodules > old leaves > young leaves > stems > litterfall and roots of the trees grown in the field,
with values ranging from −0.8 to 3.5‰ except nodules which were enriched and significantly different from other plant parts
(P < 0.0001). Isotopic discrimination was not affected by tree age (P > 0.05). Plants grown in N free sand culture exhibited the same pattern of isotopic discrimination as plants grown in the
field. The estimated B-value for the whole plant of A. mangium was −0.86‰. Mature tree stands of 12 years accumulated up to 1994 kg N ha−1 in aboveground biomass. Average proportion of N derived from N2 fixation of A. mangium was 54% (±22) and was not affected by age (P > 0.05). Average yearly quantities of N2 fixed were 128 kg N ha−1 in above-ground biomass amounting to 1208 kg N fixed ha−1 over 12 years. Harvest of 12-year old trees removed approximately 91% of standing aboveground biomass from the site as timber
and fuel wood. The resulting net N balance was +151 kg N ha−1 derived from remaining leaves, twigs, standing litter, and +562 kg N ha−1 when tree roots were included in the calculation. The fast growing A. mangium appears to be a viable fallow option for managing N in these systems. However, other nutrients have to be replaced by using
part of the timber and fuel wood sales to compensate for large amounts of nutrient removed in order for the system to be sustainable. 相似文献
4.
A long-term (20 months) bulk litter decomposition experiment was conducted in a subtropical plantation in southern China in
order to test the hypothesis that stable isotope discrimination occurs during litter decomposition and that litter decomposition
increases concentrations of nutrients and organic matter in soil. This was achieved by a litter bag technique. Carbon (C),
nitrogen (N) and phosphorus (P) concentrations in the remaining litter as well as δ13C and δ15N during the experimental period were measured. Meanwhile, organic C, alkali-soluble N and available P concentrations were
determined in the soils beneath litter bags and in the soils at the control plots. The dry mass remaining (as % of the initial
mass) during litter decomposition exponentially declined (y = 0.9362 e−0.0365x
, R
2 = 0.93, P < 0.0001), but total C in the remaining litter did not decrease significantly with decomposition process during a 20-month
period. By comparison, total N in the remaining litter significantly increased from 5.8 ± 1.7 g kg−1 dw litter in the first month to 10.1 ± 1.4 g kg−1 dw litter in the 20th month. During the decomposition, δ13C values of the remaining litter showed an insignificant enrichment, while δ15N signatures exhibited a different pattern. It significantly depleted 15N (y = −0.66x + 0.82, R
2 = 0.57, P < 0.0001) during the initial 7 months while showing 15N enrichments in the remaining 13 months (y = 0.10x − 4.23, R
2 = 0.32, P < 0.0001). Statistically, litter decomposition has little impact on concentrations of soil organic C and alkali-soluble N
and available P in the top soil. This indicates that nutrient return to the topsoil through litter decomposition is limited
and that C cycling decoupled from N cycling during decomposition in this subtropical plantation in southern China. 相似文献
5.
Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The wetland zone covered with Picea glehnii pure stand. The riparian zone was deciduous broad-leaved stand dominated by Alnus hirsuta and Salix spp., while the mixture of deciduous broadleaf and evergreen conifer dominated by Betula platyphylla, Quercus crispula and Abies sachalinensis distributed on the upland zone. Annual litterfall averaged 1444, 5122, and 4123 kg.hm^-2·a^-1 in the wetland, riparian and upland zones, respectively. Litterfall production peaked in September-October, and foliage litter contributed the greatest amount (73.4%-87.6 %) of the annual total litterfall. Concentrations of nutrients analyzed in foliage litter of the dominant species showed a similar seasonal variation over the year except for N in P glehnii and A. hirsuta. The nutrient fluxes for all elements analyzed were greatest on riparian zone and lowest in wetland zone. Nutrient fluxes via litterfall followed the decreasing sequence: N (11-129 kg.hm-2.aq) 〉 Ca (9-69) 〉 K (5-20) 〉 Mg (3-15) 〉 P (0.4-4.7) for all stands. Significant differences were found in litterfall production and nutrient fluxes among the different landscape components. There existed significant differences in soil chemistry between the different landscape zones. The consistently low soil C:N ratios at the riparian zone might be due to the higher-quality litter inputs (largely N-fixing alder). 相似文献
6.
Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone which is distributed in the Dongling Mountain area of Beijing,
was exposed to ambient and enhanced ultraviolet-B (UV-B, 280–320 nm) radiation by artificially supplying a daily dose of 9.4
kJ/m2 for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was
to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ
13C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency
(WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf
total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular
CO2 concentration/ air CO2 concentration (C
i
/C
a) (4.0%), and an increase in leaf tissue δ
13C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%) and WUE (4.1%). The effects of UV-B on the plant were
greatly affected by the water content of the deep soil (30–40 cm). During the dry season, differences in the stomatal conductance,
δ
13C, and WUE between the control and UV-B treated shrubs were very small; whereas, differences became much greater when soil
water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed
over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation
between soil water content and leaf water content, δ
13C, C
i/C
a, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content.
These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment,
it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics.
__________
Translated from Journal of Plant Ecology, 2006, 30(1): 47–56 [译自: 植物生态学报] 相似文献
7.
Lvliu Zou Guchou Sun Ping Zhao Xi’an Cai Xiaoping Zeng Xiaojing Liu 《Frontiers of Forestry in China》2009,4(2):201-207
Using the PMS pressure chamber and isotope mass spectrometer (MAT-252), the leaf juice of Acacia mangium was obtained, and the carbon isotope discrimination (D) representing the most recently fixed carbon in the juice was determined.
At the same time, the water-use efficiency of A. mangium was estimated. The results indicated that the carbon isotope ratio in the air of forest canopy (δ
a), 10 m high a bove ground averaged − 7.57 ± 1.41 ‰ in cloudy days, and − 8.54±0.67‰ in sunny days, respectively. The diurnal
change of the carbon isotope ratio in the photosynthetic products of the leaf juice (δ
p) was of saddle type in cloudy days, but dropped down from morning to later afternoon in sunny days. A strong negative correlation
between δ
p and leaf-to-air vapor pressure deficit (D) was observed in sunny days, but a slight change in δ
p was found in cloudy days. The δ
p also decreased with decreasing leaf water potential (Ψ), reflecting that water stress could cause the decrease of δ
p. The carbon isotope discrimination of the leaf juice was positively correlated with the ratio between intercellular (P
i) and atmospheric (P
a) partial pressure of CO2. For A. mangium, the isotope effect on diffusion of atmospheric CO2 via stomata was denoted by a = 4.6‰, and that in net C3 diffusion with respect to P
i was indicated by b = 28.2‰. The results were in reasonable accord with the theoretically diffusive and biochemical fractionation of carbon isotope.
It was defined that carbon isotope discrimination of photosynthetic products in A. mangium leaf juice was in proportion to that from photosynthetic products in dry material. The water-use efficiency estimated by
the carbon isotope discrimination in leaf juice, fit well with that measured by gas exchange system (R
2 = 0.86, p < 0.0001). The application of leaf juice in measuring the stable carbon isotope discrimination would reduce the effects of
fluctuating environmental factors during the synthesis of dry matter, and improve the ecophysiological studies on carbon and
water balance when scaling from the plant to canopy in the fields.
__________
Translated from Chinese Journal of Ecology, 2008, 27(4): 497–503 [译自: 生态学杂志] 相似文献
8.
Fengjun Zhao Rongfu Gao Yingbai Shen Xiaohua Su Bingyu Zhang 《Frontiers of Forestry in China》2006,1(1):89-94
Foliar carbon isotope composition (δ
13C), total dry biomass, and long-term water use efficiency (WUEL) of 12 Populus deltoids clones were studied under water stress in a greenhouse. Total dry biomass of clones decreased greatly, while δ
13C increased. Single-element variance analysis in the same water treatment indicated that WUEL difference among clones was significant. Clones J2, J6, J7, J8, and J9 were excellent with high WUEL. Extremely significant δ
13C differences among water treatments and clones were revealed by two-element variance analysis. Water proved to be the primary
factor affecting δ
13C under water stress. It showed that there was a good positive correlation between δ
13C and WUEL in the same water treatment, and that a high WUEL always coincided with a high δ
13C. δ
13C might be a reliable indirect index to estimate WUEL among P. deltoids clones.
Translated from Scientia Silvae Sinicae, 2005, 41(1) (in Chinese) 相似文献
9.
Mireia Llorente Bruno Glaser María-Belén Turrión 《European Journal of Forest Research》2010,129(6):1143-1153
In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transformed from natural Quercus ilex forest to cropped land. Reforestation with Pinus halepensis has been taking place during the past 40 years. In order to obtain a better understanding of how these disturbances affect
ecosystem functioning, we studied the quantity and quality of soil organic matter (SOM) in natural forest ecosystems, cropland
and Pinus plantations. Density fractionation combined with ultrasonic dispersion enables separation and study of SOM fractions:
free organic matter (OM), OM occluded into aggregates and OM stabilized in organo-mineral complexes, considered on the basis
of the type of physical protection provided. We separated SOM density fractions and determined the concentrations of C and
N, C/N ratios and the natural isotopic abundance (δ13C and δ15N values). Transformation of Quercus forest to cropland resulted in major losses of SOC and N, as expected. However, subsequent
reforestation with Pinus resulted in good recovery of the original SOC and soil N pools. This indicates the potential for
enhanced C storage in agricultural soils by their reversion to a forested state. Study of the density fractions and their
13C and 15N signatures enabled better understanding of the high stability of OM in calcareous soils, and analysis of δ13C variations throughout the profile also enabled identification of past C3/C4 vegetation change. Despite the different OC
contents of soils under different land use, OM stabilization mechanisms were not significantly different. In calcareous soils,
accumulation of SOC and N is mainly due to organo-mineral associations, resulting in physicochemical stabilization against
further decomposition. 相似文献
10.
A field experiment was performed in eastern Kenya to estimate N2 fixation by Sesbania sesban over an 18-month period using the 15N dilution method. The influence of three reference species, Senna spectabilis, Eucalyptus saligna and Grevillea robusta, on the estimates of N2 fixation was also assessed. Percentage Ndfa (nitrogen derived from the atmosphere) was calculated based on foliar atom excess
(FAE), above-ground atom excess (AAE) or whole tree atom excess (WAE) data. The differences in atom% 15N excess values between species and plant parts are presented and discussed. We recommend the use of several reference species
for estimating %Ndfa and that the different results obtained should be carefully considered in relation to the issues being
addressed. In this study, Senna was the most suitable of the three reference species because its N uptake pattern and phenology were very similar to those
of Sesbania. When well established, the amount of N fixed by Sesbania accounts for more than 80% of its total N content, according to FAE-based estimates. We estimated the Ndfa by Sesbania after 18 months to between 500 and 600 kg ha−1 , depending on whether FAE, AAE or WAE data were used and on the choice of reference species. The substantial accumulation
of N in planted Sesbania highlighted its potential to increase the sustainability of crop production on N-limited soils. We consider the 15N dilution method to be appropriate for quantifying N2 fixation in improved fallows in studies, similar to this one, of young trees with high N2-fixing ability. 相似文献
11.
Seedling growth response of two tropical tree species to nitrogen deposition in southern China 总被引:2,自引:0,他引:2
Seedling growth response of two tropical tree species (Schima superba and Cryptocarya concinna) to simulated N deposition was studied during a period of 11 months. One-year-old seedlings were grown in forest soil treated
with N as NH4NO3 at Control–no N addition, N5–5, N10–10, N15–15, and N30–30 g N m−2 year−1. The objective was to examine the effects of N addition on seedling growth and compare this effect between the two tropical
tree species of different species-N-requirement. Results showed that both species responded significantly to N addition and
exhibited positive effect to lower rate of N addition and negative effect to higher rate of N addition on growth parameters
(height and stem base diameter, biomass production, and net photosynthetic rate). The highest values were observed in the
N10 plots for S. superba and in the N15 plots for C. concinna, but the lowest values were observed in the N30 plots for both species. However, the reduction in the N30 plots was more
pronounced for S. superba than for C. concinna relative to the control plots. Our findings suggest that response of seedling growth of tropical tree species to atmospheric
N deposition may vary depending on rate of N deposition and species-N-requirement. 相似文献
12.
This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system
to increase soil fertility and insure sustainability. We analyzed the N2 fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted
in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning
residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied.
Dinitrogen fixation, as estimated by the 15N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average,
76% of the N exports from the plot in tree pruning (194 kg [N] ha–1 yr–1) originated from N2 fixation. Grass production averaged 13 Mg ha–1 yr–1 and N export in cut grass was 195 kg [N] ha–1 yr–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha–1 yr–1. Carbon sequestration averaged 1.9 Mg [C] ha–1 yr–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha–1 yr–1, corresponding to 30% of N2 fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha–1 yr–1) and litter decomposition (40 kg [N] ha–1 yr–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground
tree biomass than nodules.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Photosynthetic induction responses of Pinus koraiensis seedlings grown in different light environments 总被引:2,自引:0,他引:2
The time processes of photosynthetic induction responses to various irradiances in Korean pine (Pinus koraiensis) seedlings grown in open-light environments and in understory of forest were studied in an area near the Research Station
of Changbai Mountain Forest Ecosystems, Jilin Province, China from July 15 to August 5, 1997. The results showed that at 200
μmol·m−2·s−1 photosynthetic photon flux density (PPFD) and 500 μmol·m−2·s−1 PPFD, the induction time for the photosynthetic rates of understory-grown seedlings to reach 50% and 90% steady-state net
photosynthetic rates was longer than that of the open-grown seedlings. The induction responses of open-growth seedlings at
500 μmol·m−2·s−1 PPFD were slower than those at 200 μmol·m−2·s−1 PPFD, but it was the very reverse for understory-growth seedlings, which indicates that the photosynthetic induction times
of Korean pine seedlings grown in the understory depended on the sunfleck intensity.
Biograph: ZHOU Yong-bin (1970-), female, associate professor of Shenyang Agricultural University, Shenyang 110161, P.R. China.
Responsible editor: Song Funan 相似文献
14.
Two-year-old seedlings ofPinus koraiensis, Pinus sylvestriformis andFraxinus mandshurica were treated in open-top chambers with elevated CO2 concentrations (700 μL·L−1, 500 μL·L−1) and ambient CO2 concentrations (350 μL·L−1) in Changbai Mountain from June to Sept. in 1999 and 2001. The net photosynthetic rate, dark respiration rate, ribulose-1,5-bisphosphate
carboxlase (RuBPcase) activity, and chlorophyll content were analyzed. The results indicated the RuBPcase activity of the
three species seedlings increased at elevated CO2 concentrations. The elevated CO2 concentrations stimulated the net photosynthetic rates of three tree species exceptP. sylvestriformis grown under 500 μL·L−1 CO2 concentration. The dark respiration rates ofP. koraiensis andP. sylvestriformis increased under concentration of 700 μL·L−1 CO2, out that ofF. mandshurica decreased under both concentrations 700 μL·L−1 and 500 μL·L−1 CO2. The seedlings ofF. mandshurica decreased in chlorophyll contents at elevated CO2 concentrations.
Foundation item: This paper was supported by the National Natural Science Foundation of China (No. 30070158). Knowledge Innovation Item of
Chinese Academy of Sciences (KZCX2-406) and “Hundred Scientists” Project of Chinese Academy of Sciences.
Biography: Zhou Yu-mei (1973-) Ph. Doctor, Assistant Research fellow Institute of Applied Ecology. Chinese Academy of Sciences. Shenyang
110016. P.R. China.
Responsible editor: Song Funan 相似文献
15.
Eduardo S. Matos Dirk Freese Eduardo S. Mendonça Anna Slazak Reinhard F. Hüttl 《Agroforestry Systems》2011,81(3):203-211
The conversion of silvopasture to different land use systems cause effective changes in soil carbon distribution, due to disturbances
in soil aggregation promoted by soil management and changes in crop residues inputs and decomposability. We evaluate the C
and N stocks, and organic C fractions in soils under continuous arable land (AR) and silvopasture with apple trees and grass
(SP); and after 4 years of conversion from silvopasture to arable land (SP-AR) and grassland (SP-GL). Total N (TN) and organic
C (TOC), as well as microbial biomass carbon (CMB), light fraction (CLF) and heavy fraction (CHF) were evaluated at two different depths (0–10 and 10–20 cm). After 4 years of conversion, SP-AR and SP-GL presented C and
N stocks similar to the observed for SP when the 0–20 cm depth was considered. However, AR presented TOC and TN stocks around
21 and 10% lower than SP, respectively. SP-AR tended to present the lowest CMB stocks and was positively correlated with salt extractable organic C (r
2 = 0.60, P < 0.001). CLF values declined by 62% from 0–10 to the 10–20 cm at SP and SP-GL, however there was no variation with increasing depth for
AR and SP-AR. CHF represented the highest C fraction in soil, corresponding to 82% of TOC. Except for AR, δ13C values of the light fraction increased with increasing depth. In general, heavy fraction tended to be more enriched in δ13C than light fraction. In a long-term, conventional tillage can significantly contribute to reduce TOC and TN stocks when
compared to the silvopastoral system. 相似文献
16.
J.P. Bouillet J.P. Laclau J.L.M. Gonalves M.Z. Moreira P.C.O. Trivelin C. Jourdan E.V. Silva M.C. Piccolo S.M. Tsai A. Galiana 《Forest Ecology and Management》2008,255(12):3918-3930
The sustainability of plantation forests is closely dependent on soil nitrogen availability in short-rotation forests established on low-fertility soils. Planting an understorey of nitrogen-fixing trees might be an attractive option for maintaining the N fertility of soils. The development of mono-specific stands of Acacia mangium (100A:0E) and Eucalyptus grandis (0A:100E) was compared with mixed-species plantations, where A. mangium was planted in a mixture at a density of 50% of that of E. grandis (50A:100E). N2 fixation by A. mangium was quantified in 100A:0E and 50A:100E at age 18 and 30 months by the 15N natural abundance method and in 50A:100E at age 30 months by the 15N dilution method. The consistency of results obtained by isotopic methods was checked against observations of nodulation, Specific Acetylene Reduction Activity (SARA), as well as the dynamics of N accumulation within both species. The different tree components (leaves, branches, stems, stumps, coarse roots, medium-sized roots and fine roots) were sampled on 5–10 trees per species for each age. Litter fall was assessed up to 30 months after planting and used to estimate fine root mortality. Higher N concentrations in A. mangium tree components than in E. grandis might be a result of N2 fixation. However, no evidence of N transfer from A. mangium to E. grandis was found. SARA values were not significantly different in 100A:0E and 50A:100E but the biomass of nodules was 20–30 times higher in 100A:0E than in 50A:100E. At age 18 months, higher δ15N values found in A. mangium tree components than in E. grandis components prevented reliable estimations of the percentage of N derived from atmospheric fixation (%Ndfa). At age 30 months, %Ndfa estimated by natural abundance and by 15N dilution amounted to 10–20 and 60%, respectively. The amount of N derived from N2 fixation in the standing biomass was estimated at 62 kg N ha−1 in 100A:0E and 3 kg N ha−1 in 50A:100E by the 15N natural abundance method, and 16 kg N ha−1 in 50A:100E by the 15N dilution method. The total amount of atmospheric N2 fixed since planting (including fine root mortality and litter fall) was estimated at 66 kg N ha−1 in 100A:0E and 7 kg N ha−1 in 50A:100E by the 15N natural abundance method, and 31 kg N ha−1 in 50A:100E by the 15N dilution method. The most reliable estimation of N2 fixation was likely to be achieved using the 15N dilution method and sampling the whole plant. 相似文献
17.
Fertilizing plantations of fast-growing tree crops, in manners which supply nutrients at rates that match plant demand and
maintain stable internal plant nutrient ratios, can maximize biomass production and carbon sequestration while reducing fertilizer
wastage and pollution. Our objectives were to determine nutrient ratios of common hybrid poplar (Populus trichocarpa Torr. and Gray × Populus deltoides Marsh.) (T × D) clones under steady-state nutrition, and to determine if incremental additions of fertilizer were more successful
than conventional (evenly-split) fertilizer additions in maximizing biomass production and inducing stable nutrient ratios.
Un-rooted cuttings of three T × D clones (49–177, DTAC-7, 15–29) were grown under a conventional regime and a modified-exponential
fertilization regime at three application rates (1.8, 3.7 or 7.4 g N plant−1). Above- and below-ground biomass and nutrient concentrations were measured after one growing season. There were few differences
in total plant biomass between conventional and modified-exponential fertilization regimes, but for one clone, biomass accumulation
equivalent to the highest rate under the conventional regime was achieved with the medium rate of the modified-exponential
regime. Stable nutrient ratios (at conditions consistent with steady-state nutrition) were: 100N:14P:50K (49–177), 100N:13P:49K
(DTAC-7) and 100N:12P:60K (15–29). 相似文献
18.
Rainwater, throughfall, stream water during a non-storm runoff period, and soil water were sampled about every 10 days at six nested basins within the Hitachi Ohta Experimental Watershed in Japan from 1998 to 2001. Basins HA and HB are covered with an 80-year-old artificial forest of Japanese cypress and Japanese cedar. HC and HV are covered with 12-year-old forest of the same species. HO and HX are covered with various aged stands of the same species. The samples were analyzed for the isotopic compositions of 18O and deuterium (D). The weighted means of 18O (D) in HA and HB were –7.35 (–46.7) and –7.38 (–46.8), while they were –7.51 (–48.1) and –7.57 (n/a) in HC and HV, respectively. They were –7.50 (–47.6) and –7.41 (–47.1) in HO and HX, respectively. There was a relative difference of 0.2 (1.4) in 18O (D) between 80-year-old and 12-year-old forest. The stream water during a non-storm runoff period is considered to reflect the effect of evaporation from the forest floor. The evaporation rates from the forest floor were estimated using values in throughfall and stream water using the Rayleigh distillation equation under equilibrium conditions. They were estimated to be 5.5 (9.1), 5.2 (9.0), and 4.9 (8.7)% of annual throughfall in HA, HB, and HX (mature forests), respectively, using 18O (D), and 4.0 (7.6), 4.1 (8.1), and 3.5 (n/a)% of annual throughfall in HC, HO, and HV (young forests), respectively. 相似文献
19.
Camptothecine (CPT) and hydroxycamptothecin (HCPT), two kinds of anti-cancer alkaloids, were extracted from Camptotheca acuminata leaves using homogenate extraction technology under different conditions such as the ratio of material to liquid, ethanol
concentration, and homogenate time. The optimum technology parameters for homogenate extraction of CPT and HCPT from C. acuminata leaves were determined as homogenate time at 8 min, ethanol concentration at 55% and the ratio of material to liquid at 1:15
(g:mL). By using the optimized parameters, we obtained 0.639‰ extraction rate for CPT and 0.437‰ for HCPT. The extraction
yields of CPT and HCPT extracted by homogenating technology were higher than those by other extractive methods, such as ultrasonic,
reflux, shaking in water bath. It is concluded that the homogenate extraction technology was an efficient method for extracting
CPT and HCPT from C. acuminata leaves, with characteristics of less extraction time and high yield.
Foundation project: This research was supported by National Key Technology R & D Program (grant no. 2006BAD18B04).
Biography: SHI Wei-guo (1970–), male, Ph. D. candidate in Northeast Forestry University, Harbin 150040, P. R. China.) 相似文献
20.
Iris Brémaud Nadine Amusant Kazuya Minato Joseph Gril Bernard Thibaut 《Wood Science and Technology》2011,45(3):461-472
Extractives can affect the vibrational properties tanδ (damping coefficient) and E′/ρ (specific Young’s modulus), but this
is highly dependent on species, compounds, and cellular locations. This paper investigates such effects for African Padauk
(Pterocarpus soyauxii Taub.), a tropical hardwood with high extractives content and a preferred material for xylophones. Five groups of 26 heartwood
specimens with large, yet comparable, ranges in vibrational properties were extracted in different solvents. Changes in vibrational
properties were set against yields of extracts and evaluation of their cellular location. Methanol (ME) reached most of the
compounds (13%), located about half in lumen and half in cell-wall. Water solubility was extremely low. tanδ and E′/ρ were
very strongly related (R
2 ≥ 0.93), but native wood had abnormally low values of tanδ, while extraction shifted this relation towards higher tanδ values.
ME extracted heartwood became in agreement with the average of many species, and close to sapwood. Extractions increased tanδ
as much as 60%, irrespective of minute moisture changes or initial properties. Apparent E′/ρ was barely changed (+2% to −4%)
but, after correcting the mass contribution of extracts, it was in fact slightly reduced (down to −10% for high E′/ρ), and
increasingly so for specimens with low initial values of E′/ρ. 相似文献