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1.
辣木幼林对氮、磷、钾肥效响应及叶片的生理反应   总被引：2，自引：1，他引：2       下载免费PDF全文
[目的]研究辣木幼林时期对大量元素的需求状况。[方法]应用"3414"配方施肥试验设计,探讨N、P、K配方施肥对元阳干热河谷辣木幼龄林的生长量、叶片色素含量(叶绿素a、b及类胡萝卜素)和叶片含水率的影响。[结果]肥力补充对辣木幼林的生长具有非常明显的促进效果,其中N肥各施肥配方对幼林的各项生长量指标和生理指标具有显著或极显著的影响,P肥对除地径增量和叶片含水率之外的其它设定指标也表现出显著效果,而K肥各施肥处理仅对冠高增量、冠高比增量和叶片含水率具有显著影响。[结论]综合方差分析、多重比较、极差分析和相关分析结果,显著促进树高、地径、冠幅生长和叶片色素积累的组合均为本试验设计的中高施肥量配比,其中N3P2K3为最优组合。辣木幼龄阶段对大量元素需求非常旺盛,以维持其快速增长的生物量。  相似文献   

2.
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   

3.
[目的]为明确辣木生长对养分的需求及叶片养分吸收状况。[方法]研究采取田间小区实验,设置N_(80)、N_(80)P_(20)、N_(80)K_(40)、P_(20)K_(40)、N_(80)P_(20)K_(40)、N_(60)P_(20)K_(60)和不施肥对照7个处理,测定分析不同氮、磷、钾配比施肥对辣木生长及叶片养分吸收的影响。[结果]不同氮、磷、钾配比施肥处理下,辣木生长速度先快后缓慢,处理90 d后株高、冠幅和鲜叶生物量的最高值及地径的次高值均出现在N_(80)中,N_(60)P_(20)K_(60)的株高、地径及N_(80)K_(40)的鲜叶生物量仅次于N_(80)处理;不同氮、磷、钾配比施肥均促进了辣木叶片中全氮、全磷含量的累积,但降低了全钾含量;除N_(80)外,其它处理叶片叶绿素含量均低于CK,高氮处理的叶绿素含量均高于P_(20)K_(40)和N_(60)P_(20)K_(60),N_(80)P_(20)高于N_(80)K_(40)。[结论]各元素对辣木生长影响大小为NKP,对叶片中叶绿素含量影响大小为NPK,叶片中营养元素含量大小为NKP。综合试验结果中辣木主要生长指标的生长及叶片养分吸收情况,配比施肥最优处理为N_(80),且该施肥处理主要适用于辣木幼龄及速生生长阶段。  相似文献   

4.
Trees which root below crops may have a beneficial role in simultaneous agroforestry systems by intercepting and recycling nutrients which leach below the crop rooting zone. They may also compete less strongly for nutrients than trees which root mainly within the same zone as crops. To test these hypotheses we placed highly enriched 15N-labelled ammonium sulphate at three depths in the soil between mixed hedgerows of the shallow-rooting Gliricidia sepium and the deep rooting Peltophorum dasyrrhachis. A year after the isotope application most of the residual 15N in the soil remained close to the injection points due to the joint application with a carbon source which promoted 15N immobilization. Temporal 15N uptake patterns (two-weekly leaf sub-sampling) as well as total 15N recovery measurements suggested that Peltophorum obtained more N from the subsoil than Gliricidia. Despite this Gliricidia appeared to compete weakly with the crop for N as it recovered little 15N from any depth but obtained an estimated 44–58% of its N from atmospheric N2-fixation. Gliricidia took up an estimated 21 kg N ha–1 and Peltophorum an estimated 42 kg N ha–1 from beneath the main crop rooting zone. The results demonstrate that direct placement of 15N can be used to identify N sourcing by trees and crops in simultaneous agroforestry systems, although the heterogeneity of tree root distributions needs to be taken into account when designing experiments. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

5.
We used long-term in situ (15)N labeling of the soil to investigate the contribution of the two main nitrogen (N) sources (N uptake versus N reserves) to sun shoot growth from bud burst to full leaf expansion in 50-year-old sessile oaks. Recovery of (15)N by growing compartments (leaves, twigs and buds) and presence of (15)N in phloem sap were checked weekly. During the first 2 weeks following bud burst, remobilized N contributed ~90% of total N in growing leaves and twigs. Nitrogen uptake from the soil started concomitantly with N remobilization but contributed only slightly to bud burst. However, the fraction of total N due to N uptake increased markedly once bud burst had occurred, reaching 27% in fully expanded leaves and 18% in developed twigs. In phloem sap, the (15)N label appeared a few days after the beginning of labeling and increased until the end of bud burst, and then decreased at full leaf expansion in June. Of all the shoot compartments, leaves attracted most of the absorbed N, which accounted for 68% of new N in shoots, whereas twigs and new buds accounted for only 28 and 3%, respectively. New N allocated to leaves increased from unfolding to full expansion as total N concentration in the leaves decreased. Our results underline the crucial role played by stored N in rapid leaf growth and in the sustained growth of oak trees. Any factors that reduce N storage in autumn may therefore impair spring shoot growth.  相似文献   

6.
The effectiveness of spraying foliage with urea to provide nitrogen (N) to augment the seasonal internal cycling of N in young nectarine trees (Prunus persica (L.) Batsch var. nectarina (Ait. f. Maxim.), cv. Stark Red Gold) was studied. One-year-old trees were grown with contrasting N supplies during the summer and foliage was sprayed with a 2% urea solution labeled with (15)N just before leaf senescence started. After leaf abscission had finished, the trees were repotted in sand and given no further N. Remobilization of both labeled and unlabeled N for leaf growth the following spring was quantified. Leaves absorbed between 58 and 69% of the (15)N intercepted by the canopy irrespective of tree N status. During leaf senescence, the majority of (15)N was withdrawn from the leaves into the shoot and roots. Remobilization of (15)N the following spring was also unaffected by tree N status. About 38-46% of (15)N in the trees was recovered in the new growth. More unlabeled N (derived from root uptake) was remobilized for leaf growth in the spring than was withdrawn from leaves during canopy senescence the previous autumn. Therefore, soil-applied N augmented N storage pools directly, and contributed more to N remobilization the following spring than did foliar-absorbed (15)N.  相似文献   

7.
Studies of nitrogen (N) use by plants have confirmed some winter N uptake; however, the mode of regulation of plant N use in winter is unknown. The regulation of N use by plants during winter may differ from that in the growing season, as plant growth strongly affects N use. We investigated the effects of winter buds on winter N use by Japanese red pine (Pinus densiflora), as a previous study demonstrated that N absorbed during winter contributes significantly to leaf growth in the following spring. We conducted a bud pruning experiment during winter to examine the effects of winter buds on winter N uptake and allocation among plant organs using 15N labeling. Over a three-week labeling period, the 15N content in roots increased to 0.20 ± 0.12 mg N g DW?1, which is equivalent to 1.8 ± 1.1 % of the total N content in the roots. However, this absorbed 15N rarely appeared in needles and buds. Bud pruning did not affect 15N uptake and allocation. On the other hand, significant total N retranslocation was found within the crowns of saplings without bud pruning, but N was not retranslocated in bud-pruned plants. The bud pruning experiment indicated that N was retranslocated from needles into winter buds. Since soil N availability changes dramatically and is unstable in many forest ecosystems, N contained in needles would be a more stable source of N than newly absorbed N.  相似文献   

8.
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   

9.
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   

10.
Fast growing trees, in particular nitrogen fixing trees, are essential for the establishment of sustainable agroforestry practices by resource-poor and/or environmentally conscious aarmers. An important selection factor for trees is therefore high N2 fixing capability. This study was conducted to examine biological nitrogen fixation (BNF) in Leucaena leucocephala L., as affected by growth in pots containing 4, 10, 15 and 30 kg soil and when grown together with Eucalyptus camaldulensis. BNF was measured by the 15N isotope dilution technique. Leucaena and Eucalyptus were grown either sole (SL, SE) or in two mixtures (1:1 - L1:E1 and 1:2 - L1:E2) for a period of 6 months. Planting pattern influenced (P < 0.05) dry matter and N content of shoot and roots of Eucalyptus, as the sole planted trees gave the highest yield. Dry matter, N content and total amount of N fixed by Leucaena significantly decreased with decreasing rooting volume. Also, the smaller the rooting volume (or soil weight), the higher was the proportion (%) of N derived from the atmosphere (%Ndfa) by leucaena. For each rooting volume, the sole or mixed planting pattern did not significantly influence either the proportion (%) or amount of N fixed by leucaena. For these trees, therefore, rooting volume rather than cropping pattern influenced the proportion and amount of nitrogen fixed.  相似文献   

11.
Theobroma cacao seedlings were grown alone (TCA) or associated with saplings of N2-fixing shade trees Gliricidia sepium and Inga edulis in 200 l of 15N labelled soil within a physical root barrier for studying direct nitrogen transfer between the trees and cacao. Root:shoot partitioning ratio for sapling total N was lower than biomass root:shoot ratio in all species. Sapling total 15N was partitioned between root and shoot in about the same ratio as total N in cacao and inga but in gliricidia much higher proportion of 15N than total N was found in roots. Thus, whole plant harvesting should be used in 15N studies whenever possible. Average percentage of fixed N out of total tree N was 74 and 81% for inga estimated by a yield-independent and yield-dependent method, respectively, and 85% for gliricidia independently of estimation method. Strong isotopic evidence on direct N transfer from trees to cacao was observed in two cases out of ten with both tree species. Direct N transfer was not correlated with mycorrhizal colonisation of either donor or receiver plant roots. Direct N transfer from inga and gliricidia to cacao is conceivable but its prevalence and the transfer pathway via mycorrhizal connections or via reabsorption of N-rich legume root exudates by cacao require further study. Competition in the restricted soil space may also have limited the apparent transfer in this study because the trees accumulated more soil-derived N than cacao in spite of active N2 fixation.  相似文献   

12.

Context

The reforestation of degraded tropical pastures requires innovative tree planting systems that consider land user needs.

Aim

We established a silvopastoral reforestation system and assessed the effects of companion trees on the native timber tree Tabebuia rosea in Panama. Timber tree individuals were established in (1) solitary plantings (TSol) or in companion plantings with (2) Guazuma ulmifolia (TGua) or (3) the nitrogen-fixing Gliricidia sepium (TGli).

Methods

We quantified growth characteristics and herbivory of T. rosea, and analyzed leaf chemistry (including the stable isotopes ??15N and ??13C) and structure (leaf mass per area).

Results

Companion trees significantly affected stem diameter growth of T. rosea. Stem diameter growth was as high in TGli trees as in TSol trees but was reduced in TGua trees. Furthermore, TGua trees had higher leaf water content, and lower ??13C and lower leaf mass-to-area ratio than TGli trees, suggesting there were effects of shading by G. ulmifolia on T. rosea. Herbivory was high but not affected by planting regimes. Leafing phenology did not differ between planting regimes and G. sepium did not increase nitrogen content in T. rosea leaves.

Conclusion

Companion tree planting can support timber tree growth in silvopastoral reforestations, but adequate species selection is crucial for successful implementation of this planting system. Tree?Ctree interactions seem to be more relevant for timber tree growth than herbivory in the studied system.  相似文献   

13.
To quantify the nitrogen (N) use by Pinus densiflora trees growing on an infertile lava surface, N pools, N requirement and N uptake through fine roots and N deposition from the atmosphere were estimated. The N requirement and the N uptake of fine roots were 55.5kgNha–1year–1 and 39.7kgNha–1, respectively. Thus, the ratio of N uptake to N requirement of the fine roots was 71.5%. Including fine-root contribution, the total N requirement of the P. densiflora trees was 98.6kgNha–1year–1, and the total N uptake was 64.2kgNha–1year–1. Thus, the N uptake of the P. densiflora trees was 64.1% of the N requirement, indicating that P. densiflora trees growing on an infertile lava surface obtain some of their N from below-ground organic material layers every year and the contribution of N storage in trees for their growth is not any higher than indicated in previous reports that excluded fine-roots contribution. The wet N deposition of our research forest was only 5.8% of the N requirement of the P. densiflora trees and only 8.9% of the N uptake. Movement of the below-ground organic material layer N concentrations in the F- and L-layers coincides with needle development and fine-root growth, suggesting the possibility that P. densiflora trees extract N from the organic N of those layers for growth.  相似文献   

14.
[目的]通过对比研究华山松和油松不同叶龄针叶形态、光合速率、叶绿素和叶氮含量对林窗式疏伐的响应,探讨林窗大小、叶龄和树种对林窗式疏伐后叶光合特性响应的影响。[方法]2008年在30年生华山松和油松混交人工林中,设置对照、小林窗(80 m2)和中林窗(110 m2)处理,2013年以对照样地内和林窗边缘华山松和油松为研究对象,测定其当年生、1年生和2年生叶比叶重(LMA)、单位叶面积叶绿素a(Chl a)、叶绿素b含量(Chl b)、氮含量(N)、最大净光合速率(Amax)、光合氮利用效率(PNUE)等指标。[结果]小林窗和中林窗疏伐对叶光合特性影响一致,均对当年生叶影响不显著,但显著改变了1年生和2年生叶绿素含量、N和PNUE,提高了其Amax。华山松叶LMA、叶绿素含量、N、Amax均低于油松,两树种多年生叶对林窗式疏伐的响应也明显不同:林窗边缘华山松1年生和2年生叶LMA和N与对照差异不显著,但叶绿素含量低于对照,PNUE和Amax显著高于对照;林窗边缘油松1年生和2年生叶LMA和PNUE与对照差异不显著,但N和Amax显著高于对照。[结论]80 110 m2林窗疏伐显著改变叶光合特性,提高其光合潜力;林窗疏伐影响1年生和2年生叶光合特性,对当年生叶影响不显著;华山松和油松对林窗式疏伐的响应特征存在差异。  相似文献   

15.
In a 12-year-old Pinus radiata plantation, three dominant and three suppressed trees removed by thinning were randomly selected, and needles, annual rings from basal stem disks and bark were collected and analyzed to study the relationships of climate, tree age, dominance and growth with tree δ15N. The high foliar N concentration (1.35–2.73 % N, dw) suggested that N was not limiting tree growth, therefore allowing plants to fractionate versus δ15N, leading to differences in δ15N among trees. Most wood δ15Nair values were below the δ15Nair natural abundance in the dominant pines (?2.43 to +1.69 ‰) and above it in the suppressed trees (+0.73 to +3.35 ‰), likely due to the access of dominants to exogenous N sources with lower δ15Nair than those of suppressed. However, no dominance effect was detected in δ15Nair of bark and needles that decreased in the order: buds (+1.20 to +2.44 ‰) > needles 1 year (?0.27 to +1.43 ‰) > needles 2 years (?0.97 to +0.41 ‰) > bark (?1.18 to +0.15 ‰). Compared with the soil N in the 0–15 cm layer (δ15Nair = +4.8 ‰), all plant material was 15N-depleted. Results suggest that seedlings and foliar buds have a less efficient system for N conservation and recycling, with higher losses. The linear regression models showed that both biotic (dominance and tree age) and abiotic factors (temperature in spring–summer and annual precipitation) are needed to explain the wood δ15Nair satisfactorily.  相似文献   

16.
We evaluated gas exchange, chlorophyll index (CI) using SPAD-502 chlorophyll meter, and leaf nutritional responses in one-year-old northern red oak (Quercus rubra L.) container seedlings transplanted into control (unfertilized) or fertilized (0.86 g N plant?1) sand culture and grown in a greenhouse for 90 days. We labeled current nitrogen (N) uptake with (15NH4)2SO4 and directly quantified proportional contributions of N derived from fertilizer (NF) compared with retranslocation or N derived from plant (NP) in leaf growth of red oak seedlings. NF met a greater N demand in leaf growth of fertilized plants while unfertilized seedlings relied entirely on NP for their leaf growth. Fertilization increased leaf dry mass by 67% and new stem dry mass by 253% 90 days after transplanting compared to control seedlings. Specific leaf area (SLA) was not significantly altered but CI increased 90 days after transplanting. Higher leaf N concentration and content in fertilized compared with control seedlings was linked to greater chlorophyll concentrations in the former plants. The higher coefficient of determination (r 2 = 0.72) noted between leaf N concentrations and CI suggests that the SPAD meter could be a useful tool for assessing leaf N status in northern red oak seedlings. Fertilized seedlings exhibited higher net assimilation, stomatal conductance, and transpiration rates compared with controls. Increased seedling growth in response to fertilization was related to maintenance of higher gas exchange and greater nutrient uptake, which could improve outplanting success.  相似文献   

17.
Elstar apple trees (Malus domestica Borkh.) on M.9 rootstock received either 5 or 35 g N tree(-1) year(-1) during the first two growing seasons after planting, applied as Ca(NO(3))(2) on a daily basis for nine weeks through a drip irrigation system. During the third growing season (1994), all trees were treated with 20 g N tree(-1) year(-1) as (15)NH(4) (15)NO(3) with applications starting on April 22 and continuing for 10 weeks. Soil solution nitrate-N and ammonium-N were monitored weekly with suction lysimeters located 30 cm beneath the drip emitters. Spur and shoot leaves were sampled intensively from full bloom to the end of rapid shoot growth. During the period of nitrogen application, soil solution nitrate-N and ammonium-N were relatively constant, at about 24 and 1.0 mg l(-1) respectively. Growth of the spur leaves was completed by one week after full bloom (May 12), whereas biomass of the shoot leaves increased until mid-June. Nitrogen for growth of the spur leaves was supplied mainly from remobilization, which was dependent on previous N supply. Accumulation of fertilizer N in spur leaves was independent of previous N treatments and continued until the end of the monitoring period (June 24), but contributed only 13% to total spur leaf N. Nitrogen for shoot leaf growth was independent of previous N treatments and was initially supplied primarily by remobilization, but by the end of extension growth, fertilizer N contributed 48% to total shoot leaf N. Linear increases in leaf N uptake throughout the period of rapid shoot growth and the large contribution of fertilizer N to total shoot leaf N were attributed to the constant supply of N available in the root zone through daily N fertilization.  相似文献   

18.
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19.
In order to quantify the effects of thinning on biochemical photosynthesis parameters and changes in leaf nitrogen contents associated with the process of crown reclosure, the maximum rate of carboxylation (V cmax), the leaf nitrogen concentration per unit area (N a), and the photosynthetic photon flux density (PPFD) were measured at four crown heights in both thinned (1500 trees ha−1) and unthinned control (3000 trees ha−1) stands of ten-year-old Chamaecyparis obtusa (36°3′N, 140°7′E) trees during four consecutive growing seasons after thinning. Thinning increased V cmax in the lower and middle crowns in the first year after thinning, and leaves in the lower crown of the thinned stand maintained high V cmax for four years, whereas they abscised in the second year in the control stand. Significant increases in V cmax were detected even in the upper crowns of trees in the thinned stand in the second year. Thinning did not affect N a at any of the crown positions in the first year, but significantly increased N a in the middle crowns from the second year after thinning. Thus, the redistribution of nitrogen between leaves, driven by increases in light and nutrient availability due to the 50% thinning, appears to have enhanced photosynthetic rates in the thinned stand. Thinning also significantly affected the slope of the linear relationship between N a and V cmax initially after thinning, but its effect on this relationship was negligible after the second year. These quantitative results may be used to simplify the estimation of the likely effects of management practices on carbon fixation in forest canopies.  相似文献   

20.
Allocation of biomass and nutrient elements including Nitrogen to above and belowground compartments of beech seedlings (Fagus sylvatica L.) treated by labeled nitrogen fertilizer in the form of 15NH4 and 15NO3 were investigated at the end of two successive growing seasons. Pot cultured beech seedlings were grown at a green house on intact soil cores sampled from three adjacent stands including beech, Norway spruce and mixed beech-spruce cultures of Solling forest, Germany. Comparing biomass allocation and nutrients concentrations of the seedlings between the control and 15N-fertilized treatments revealed no significant effect of N fertilization on nutrients uptake by seedlings over the experiment. The form of N input influenced its movement into plant pools. It was demonstrated that beech seedlings take up nitrogen mainly in the form of nitrate, which is then reduced in the leaves, although the differences between the retention of NO3 ?-N and NH4 +-N in plants were not statistically significant. Percent recoveries of 15N in trees were typically greater after 15NO3 than after 15NH4 additions. It was indicated that immobilization of 15N tracer in fine roots was a slower process comparing other plant compartments such as stem and coarse roots, but a powerful sink for N during the course of study.  相似文献   

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