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1.
Background: Nitrogen deposition can cause an ecosystem‐level shift in available N (nitrogen) to P (phosphorus) availability. However, most plant N nutrition is from edaphic sources rather than deposition and in seasonally dry grassland systems, root litter is the predominant nutrient source. Aims: We were interested how litter turnover and altered nutrient recycling from dead biomass can compensate for these shifts in ecosystem stoichiometry. Methods: We studied a Mediterranean savanna amended with N or NP treatments three years prior. We measured root and plant‐available soil N:P stoichiometry in two micro‐habitats: open pasture and beneath oak canopies. 15N‐labelled root litter incubated in topsoils without litterbags was used to trace uptake of litter N by herbaceous strata roots. Results: Since fertilization, NP added sites have become relatively P enriched, resulting in lower N:P ratios in living roots than either when N was added alone or control sites. Total litter‐derived 15N uptake by roots was proportional to root ingrowth response but higher in the NP than N treatment, indicating a higher N demand when N and P were added together. We observed more 15N uptake by plants under tree canopies, indicating a tighter nutrient recycling loop in these micro‐habitats in contrast to treatment level ‘fertility' trends. Conclusions: Root stoichiometry responded to manipulated soil nutrient availability and N uptake was altered as plants attempted to compensate for nutrient availability imbalances, indicating that these ecosystem perturbations have long term effects on nutrient cycling which can propagate to whole system function. This was also related to functional community‐level adaptions between micro‐habitats with under canopy communities more able to take advantage of the litter nutrient source.  相似文献   

2.
Alternative use of poultry litter (PL) for forest rather than pasture fertilization would improve forest soil fertility and reduce nutrient build-up in pasture. Yield and nutrient uptake of Alamo switchgrass (Panicum virgatum L.) in a loblolly pine (Pinus taeda L.) silvopasture annually fertilized with PL or urea at 80 and 160 kg N ha?1 for four years, and without fertilization were compared. Treatment effects on soil fertility and effect of PL on runoff water quality were also determined. Fertilization with N increased yields 120% to an average of 3.8 Mg ha?1 yr?1. Since nutrient removal was small, P, base cations and pH increased in the ≤30 cm depth soil with PL. Total P in edge-of-plot runoff was increased by 0.31 kg ha?1 y?1 at the higher PL rate. Two applications at this rate per tree rotation might be justified based on increased soil fertility and infrequently increased P load.  相似文献   

3.
Abstract

Good and balanced citrus nutrition is important for high fruit yields and improved tree performance. A study was conducted for 2?years to investigate the effect of soil application of boron (B) on leaf nutrient content, canopy size, and root length density (RLD). The study was conducted on 10-year-old Candidatus Liberibacter asiaticus (CLas)-infected Vernia sweet orange on Rough Lemon rootstock in a commercial grove east of St. Cloud, FL planted at 375 trees ha?1 on a traditional soluble dry nutrition and spray programs. Treatments were supplied with various ground-applied controlled-release fertilizer treatments containing B. Boron was applied at 0×, 2×, and 4× current University of Florida recommendation where 1×?=?1.12?kg ha?1. Data collected included leaf B nutrient content, soil B concentration, trunk diameters, canopy volumes, soil electrical conductivity, and soil pH. The 0×, 2×, and 4× application rates corresponded with leaf nutrient contents ranging from 56?mg kg?1 and 88?mg kg?1 in March 2017, 162?mg kg?1 and 288?mg kg?1 in September 2017, and 122?mg kg?1 and 320?mg kg?1 in May 2018. Temporary, RLD decreased with time from March to September 2017 by 13, 30, and 37% at the 0, 2.24, and 4.48?kg B ha?1 and increased by 309, 258, and 306% at the 0, 2.24, and 4.48?kg B ha?1, respectively, from September 2017 to May 2018. No consistent pattern was established between soil B application with canopy size.  相似文献   

4.
Afforestation of grasslands can increase C sequestration and provide additional economic and environmental benefits. Pine plantations, however, have often been found to deplete soil organic C and trigger detrimental effects on soils. We examined soil characteristics under a 45-year-old Pinus radiata stand and under adjacent grassland on maritime dunes in temperate Argentina. Soil under the pine plantation had greater soil organic C (+93%), total N (+55%) and available P (+100%) concentrations than under grassland. Carbon was stored under the pinestand at an estimated mean accretion rate of 0.64 Mg ha?1 y?1. At 0- to 25-cm depth, soil C amounted to 61 Mg ha?1 under pine and 27 Mg ha?1 under grassland. Soil C accumulated more on dune slopes (35 Mg ha?1 y?1) than on ridges(29 Mg ha?1 y?1) and bottoms (12 Mg ha?1 y?1). Compared with the grassland, soil acidity, cation-exchange capacity, base losses (K > Ca = Mg) and C/N ratio increased under pine. Spatial heterogeneity in soil characteristics was greater under pine than under grassland. Such variability was non-systematic and did not support the ‘single-tree influence circle’ concept. Afforestation increased C in soil, forest floor and tree biomass in dunes with ustic climate regime.  相似文献   

5.
Surface (0–15 cm) and subsurface (30–45 cm) soil samples from under canopy, edge of canopy and away from canopy of isolated Cordia africana Lam. and Croton macrostachyus Del. trees and their leaves were examined to investigate leaf nutrient content, root biomass and the contribution of trees on farms to soil fertility parameters in Badessa area, eastern Ethiopia. Leaves of C. macrostachyus had 20% higher P and 25% lower K contents than those of C. africana. The studied species had comparable leaf N content. Both species produced shallow lateral roots that extended beyond the canopy zone. Typically, higher fine root biomass was observed in the surface soils than the subsurface soils. Both species did not affect soil organic C, pH and cation exchange capacity. Surface and subsurface soils under tree canopies had 22–26 and 12–17% higher N, respectively, than the corresponding soils away from tree canopies. Surface soil available P under tree canopies was 34–50% higher than the corresponding soil away from canopies. Available P content of subsurface soil was improved only under C. africana canopy. The available P of surface soil under C. macrostachyus canopy was more than double that for C. africana. Trees of both species increased underneath surface and subsurface exchangeable K by 18–46% compared with the corresponding controls. In conclusion, C. macrostachyus and C. africana trees on farms keep soil nutrient high via protection against leaching, translocation of nutrients from deeper to the surface layer and accumulation of litter, which create a temporary nutrient pool in the surface soils under their canopies.  相似文献   

6.
《Journal of plant nutrition》2013,36(4-5):639-650
The aim of the study was to examine the effect of calcium chloride sprays at different water volumes on ‘Szampion’ apple calcium (Ca) concentration. Apple trees were sprayed with CaCl2at a rate of 7 kg ha?1 using 250, 500, 1000, and 1500 L of water which represents: 2.8, 1.4, 0.7 and 0.5% CaCl2 solution, respectively. Sprays with CaCl2 were applied 6, 4, and 2 weeks before fruit harvest by a directed air-jet sprayer with radial fan. Fruit Ca concentrations were determined from the bottom (to 1.5 m height), middle (from 1.6 to 2.3 m height) and top (from 2.4 to 3.0 m height) of tree. The trees unsprayed with Ca served as a control. The study showed that such treatments did not injure leaves and fruit. Efficacy of CaCl2 sprays at studied water rates in increasing fruit Ca concentration was similar. Apples sprayed with Ca from the middle and bottom of tree canopy had higher Ca concentrations than control fruit. Leaf Ca applications at all water volumes had no effect on fruit Ca concentration from tree canopy top, however, laboratory study indicated that apples from this zone had ability to take up exogenous Ca. It was also found that young ‘Szampion’ fruitlets took up clearly less exogenous Ca as compared to mature fruit, which suggests that Ca sprays of this cultivar should be performed mainly at late apple development stages.  相似文献   

7.
ABSTRACT

The endemic tree Acacia koa is used to reforest abandoned agricultural lands in Hawaii. Growth may be constrained by soil infertility and toxic concentrations of aluminum (Al) and manganese (Mn) in acidic Oxisols and Ultisols. The effects of phosphorus (P) fertilization at time of planting, soil type, and seed source on koa growth were studied for three years. Phosphorus, applied as triple superphosphate and at rates of at least 300 kg P ha?1, significantly increased height, basal stem diameter, crown volume, and aboveground wood biomass of trees from the local (Oahu) seed source, but not those from off island (Hawaii). Manganese toxicity in the Oxisol probably slowed growth of the off-site trees. The local seed source grew similarly in both soil types, but the survival rate was lower in the Ultisol, possibly due to its lower water-holding capacity. Increased growth due to fertilization suggested improved P status, but such improvement was not detected by foliar analysis.  相似文献   

8.
The removal or burning of the biomass which frequently includes main roots results in significant nutrient losses from the Brazilian savanna, the Cerrado. To estimate these losses, we quantified above‐ and belowground plant biomass and total nutrient storage in biomass and soil of a typical Cerrado. Dominant tree species in the layer > 2 m were Pouteria torta (MART. ) RADLK ., Ouratea spectabilis (MART .) ENGL ., Roupala montana AUBL ., Byrsonima coccolobifolia H.B. et K., Dalbergia miscolobium BENTH ., Kielmeyera coriacea MART ., and Caryocar brasiliense CAMBESS . which together represented 70 % of the biomass of the > 2 m layer. In the 0.5—2 m tree layer, many different species were found of which Ouratea hexasperma (ST .‐HIL .) BAILL . representing 33 % of the biomass in the 0.5—2 m layer was most abundant. The dominant shrub species were Miconia holosericea DC., Hortia brasiliana VAND . ex DC., Myrcia rostrata DC., Parinari obtusifolia HOOK . f., and Campomanesia velutina BLUME , contributing 93 % to the total shrub biomass. Total aboveground plant biomass was 22.7 Mg ha—1, total belowground plant biomass was 30.4 Mg ha—1. The tree layer > 2 m comprised the largest proportion of the aboveground biomass (64.6 %) > grass/herb (13.0 %) > shrub layer (11.6 %) > tree layer 0.5—2 m (10.8 %). Three quarters of the fine root biomass (17.6 Mg ha—1) were located in the upper 0.3 m of the soil. The element storages (in kg ha—1) were C: 10900, N: 173 N, P: 20, K: 51, Ca: 66, Mg: 20, S: 25, Fe: 10, Mn: 4.2, Zn: 0.35, and Al: 27 in the aboveground biomass, C: 12900, N: 214 N, P: 14, K: 41, Ca: 52, Mg: 10, S: 33, Fe: 2060, Mn: 2.9, Zn: 0.60, and Al: 648 in the belowground biomass, and C: 55400, N: 3510 N, P: 631, K: 366, Ca: 86, Mg: 75, S: 529, Fe: 159000, Mn: 124, Zn: 49, and Al: 434000 in the soil (0—0.3 m). If the above‐ and belowground biomass was completely removed from the Cerrado ecosystem losses would range from 5 % of the total nutrient storage for P to 58 % for Ca referred to a lower ecosystem boundary at 0.3 m mineral soil depth.  相似文献   

9.
A field plot experiment on fertilization with N, Mg and P in Scots pine forest was established. The experiment had a factorial design with three levels of N (0, 30 and 90 kg ha?1), two levels of Mg (0 and 1.5 kg ha?1) and two levels of P (0 and 5.3 kg ha?1). The application was done annually. There was a significant growth increase for the two N treatments. During a period of 5-years the mean increase in volume increment was 2.3 and 4.5 m3 ha?1 for the 30 N and 90 N kg ha?1 yr?1 treatments, respectively. This represents a percentage increase in volume increment of 53 and 102% compared to the untreated control plots. No significant growth effect of P and Mg application was detected, either alone or in combination with N. The needle nutrient concentrations have been followed along with the annual measurements. An increase in N-concentration was detected after the first growing season in the N treated trees. After five years the Mg concentrations in the needles are lower in these treatments. The one year old needles have concentrations as low as 0.05% Mg. No visible deficiency symptoms have been observed. The field experiment effects demonstrates that N is still the most limiting nutrient under these conditions and that there is a relative large potential for N accumulation in these forest types without negative effects.  相似文献   

10.
Sloping and mountainous olive production systems are widespread, occupying large parts of the Mediterranean landscape prone to water erosion. Soil erosion, runoff, and soil water content patterns over a three-year period were monitored in erosion plots on a mountainside with rainfed olive (Olea europaea cv. Picual) trees under: 1) non-tillage with barley strips of 4 m width (BS); 2) non-tillage with native vegetation strips of 4 m width (NVS); and 3) non-tillage without plant strips (NT). The erosion plots, located in Lanjaron (Granada, south-eastern Spain), on a 30% slope, were 192 m2 in area. For assessing soil water dynamics in real-time and near-continuous soil water content measurements, multisensor capacitance probes were installed in the middle of plant strips and beneath the olive tree at five soil depths (10, 20, 30, 50, and 100 cm). The highest erosion and runoff rates were measured under NT, with a mean of 17.3 Mg ha-1 year-1 and 140.0 mm year-1, respectively, over the entire study period. The BS and NVS with respect to the NT reduced erosion by 71% and 59% and runoff by 95% and 94%, respectively. In general, greater available soil water content was found under BS than NVS and NT, especially beneath the olive tree canopies. These results supported the recommendation of non-tillage with barley strips in order to reduce erosion and to preserve soil water for trees in traditional mountainous olive-producing areas, where orchards cover vast tracts of land.  相似文献   

11.
In the natural forest communities of Central Europe, beech (Fagus sylvatica L.) predominates in the tree layer over a wide range of soil conditions. An exception with respect to the dominance of beech are skeleton‐rich soils such as screes where up to 10 broad‐leaved trees co‐exist. In such a Tilia‐Fagus‐Fraxinus‐Acer‐Ulmus forest and an adjacent mono‐specific beech forest we compared (1) soil nutrient pools and net nitrogen mineralization rates, (2) leaf nutrient levels, and (3) leaf litter production and stem increment rates in order to evaluate the relationship between soil conditions and tree species composition. In the mixed forest only a small quantity of fine earth was present (35 g l—1) which was distributed in patches between basalt stones; whereas a significantly higher (P < 0.05) soil quantity (182 g l—1) was found in the beech forest. In the soil patches of the mixed forest C and N concentrations and also concentrations of exchangeable nutrients (K, Ca, Mg) were significantly higher than in the beech forest. Net N mineralization rates on soil dry weight basis in the mixed forest exceeded those in the beech forest by a factor of 2.6. Due to differences in fine earth and stone contents, the volume related soil K pool and the N mineralization rate were lower in the mixed forest (52 kg N ha—1 yr—1, 0—10 cm depth) than in the beech forest (105 kg N ha—1 yr—1). The leaf N and K concentrations of the beech trees did not differ significantly between the stands, which suggests that plant nutrition was not impaired. In the mixed forest leaf litter fall (11 %) and the increment rate of stem basal area (52 %) were lower than in the beech forest. Thus, compared with the adjacent beech forest, the mixed forest stand was characterized by a low volume of patchy distributed nutrient‐rich soil, a lower volume related K pool and N mineralization rate, and low rates of stem increment. Together with other factors such as water availability these patterns may contribute to an explanation of the diverse tree species composition on Central European screes.  相似文献   

12.
Maintaining orchards with trees at optimal leaf nutrient concentrations is one of the key issues for maximizing yield. Experiments for evaluating and updating guidelines are very rare since they require several years of field experiments with mature fruit‐bearing trees. In the present paper, we first evaluated the Israeli guidelines for citrus by comparing them to the Israeli orchard leaf mineral status using a 10‐year leaf‐mineral database (results of 20 244 leaf analyses from commercial orchards all over Israel). Then, we created an updated guideline using a second database (the Israeli National Wastewater Effluent Irrigation Surveys database; INWEIS). This database summarizes yield and leaf mineral concentrations of commercial orchards from all over Israel. The data were collected from 122 orchards: 39 orchards of “Oroblanco” Pomelit (Citrus grandis), 33 orchards of “Michal” mandarin (C. reticulata), 30 orchards of “Star Ruby” grapefruit (C. paradise), and 20 orchards of “Shamouti” oranges (C. sinensis) over a 7‐year period. Based on the first database, there was a disagreement between recommendations and the leaf nutrient status (e.g., the Israeli Ministry of Agriculture recommendations were higher than orchard median values), which indicated that the growers and/or the recommendations need to be corrected. Based on the INWEIS database, a new guideline was set. It was found that the optimal leaf nutrient concentrations for grapefruit trees are 1.7% to 2.1% dry weight (DW) for N, 0.08% to 0.010% DW for P, 0.37% to 0.48% DW for K, and 0.33% to 0.45% DW for Mg. For orange trees, the optimal leaf nutrient concentrations are 1.9% to 2.3% DW for N, 0.11% to 0.14% DW for P, 0.80% to 1.00% DW for K, and 0.19% to 0.26% DW for Mg. For mandarin trees, the optimal leaf nutrient concentrations are 2.0% to 2.4% DW for N, 0.09% to 0.12% DW for P, 0.55% to 0.69% DW for K, and 0.19% to 0.26% DW for Mg. Maintaining leaf nutrient concentrations within these ranges will support maximal yields of 110 to 120 t ha–1 for grapefruit, 65 to 70 t ha–1 for orange, and 60 to 70 t ha–1 for mandarin cultivars.  相似文献   

13.
Abstract

Efficient nutrient and water use are two important considerations to obtain good harvests of wheat. This necessitates the development of an effective nutrient management technique that not only increases yield, but simultaneously can save nutrient and water use. In this context, a field experiment was conducted at Indian Agricultural Research Institute, New Delhi, India to evaluate the residual effect of sesbania and rice bean (in-situ), subabul (ex-situ) green manuring and Zinc (Zn) fertilization, using chelated Zn-ethylenediaminetetraacetic acid (Zn-EDTA) on nutrient use, yields and water productivity of wheat under rice–wheat cropping system. Among residual effects of green manure crops and Zn fertilization, sesbania and foliar spray of 0.5% chelated Zn-EDTA at 20, 40, 60 and 80 days after sowing (DAS) recorded significantly higher nutrient content and uptake and yields than other green manure crops and Zn treatments. Residual effect of sesbania saved about 46.5?×?103 and 30.5?×?103 L irrigation water per tonne of wheat over subabul and rice bean, respectively. Foliar spray of 0.5% chelated Zn-EDTA at 20, 40, 60 and 80 DAS saved about 55.5?×?103, 47?×?103 and 13?×?103 L irrigation water per tonne wheat over residual effect of 5?kg Zn ha?1 through chelated Zn-EDTA as soil application, 2.5?kg Zn ha?1 through chelated Zn-EDTA as soil application + 1 foliar spray of 0.5% chelated Zn-EDTA at flowering and foliar spray of 0.5% chelated Zn-EDTA at active tillering?+?flowering?+?grain filling, respectively. Correlation analysis showed positive correlation between Zn uptake and grain yield.  相似文献   

14.
ABSTRACT

The objective of the experiment was to examine the effects of soil and foliar applications of boron (B) on tart cherry (Prunus cerasus L.) tree vigor, yield, and fruit quality. The study was conducted during 2003–2004 on mature ‘Schattenmorelle’ tart cherry trees grown at a commercial orchard in central Poland on coarse-textured soil with low B content. Trees were supplied with B as foliar sprays or via soil application. Foliar B sprays were performed: (1) in the spring, at the white bud stage, when 5%–10% of flowers were at full bloom, and 5 d after petal fall, at a rate of 0.2 kg B ha?1 per each spray treatment; and (2) in the fall, approximately six weeks before the natural leaf fall, at a rate of 0.8 kg B ha?1. Soil B application was made at the bud-break stage at a rate of 2 kg ha?1. Trees untreated with B served as a control. Spring and fall B sprays increased flower B concentrations, but had no effect on summer leaf B status. Leaf B concentrations of trees with B supplied to the soil were higher than those of the control trees. However, soil B application had no influence on flower B level. Vigor and yield of tart cherry trees were not influenced by B fertilization. Also, mean fruit weight and titratable acidity of fruit did not differ among treatments. Fruit of trees with B supplied to the soil had higher soluble solids concentration (SSC) than those of the control plants. In conclusion, high yield of tart cherry can be obtained on soils with water-soluble B concentrations as low as 0.32 mg kg?1. It is also postulated that at low soil-B availability, under conditions of low-light intensity during fruit ripening, soil-B application increases SSC in tart cherry fruit.  相似文献   

15.
The study assessed the impact of continuous application of vermicompost and chemical fertilizers nitrogen, phosphorus and potassium (NPK) on arecanut in India. Key parameters examined were biomass production, nutrient uptake, yield, soil fertility and net benefit. Pooled analysis of 8-year data revealed that nutrient application registered significantly higher yield (2585–3331 kg ha?1) than no nutrition (1827 kg ha?1). Yields in organic nutrition were around 85% of the yields obtained in inorganic NPK. The concentrations of leaf N and K were significantly higher with NPK than with vermicompost. Vermicompost significantly increased soil organic carbon and the availability of calcium (Ca), magnesium (Mg), manganese (Mn) and copper (Cu), but reduced exchangeable K in soil. The total uptake of K and Ca together contributed positively to 75% variability in total biomass production. Nutrient removal of iron (Fe), P, K and Cu positively influenced the yield with about 81% variability. Biomass partitioning and nutrient uptake pattern are important for fertilization program of arecanut.  相似文献   

16.
The purpose of this study was to determine the nitrogen (N) deposition in a mire of the German National Park Hochharz Mountains in regard to different input pathways of open area and forest stand deposition. High N deposition rates strongly affect the development and growth of mires in general. For determination of the open area N deposition two methods were applied: the bulk deposition method and the Integral Total Nitrogen Input (ITNI) method. This method is based on the 15N isotope dilution technique and was adapted at this study to evaluate its applicability for natural ecosystems as well as to compare with the traditional bulk method. The forest stand deposition included canopy throughfall, stemflow and fog was measured by means of bulk collectors. On the test site, bulk deposition measurements showed an input of 27 kg N ha? 1 yr? 1 in the open area and 47 kg N ha? 1 yr? 1 in the forest stand. The higher N input in the forest stand is caused by interception of fog by the canopy. N concentrations in fog were up to more than six times higher than in rain. The ITNI system yielded a total N deposition of 30 kg N ha? 1 yr? 1 on average in the open area. The small differences between the two simultaneously applied measuring techniques were caused by a minimum biomass development of the autochthonous plant Calamagrostis villosa in the ITNI system. With increasing biomass production the influence of plants on the atmospheric N input also increased. It can be concluded that the ITNI system is beneficial for the application in a natural ecosystem when using more robust and biomass producing plants. The measured atmospheric N deposition exceeds the critical load for nutrient poor mires and represents therefore a potential risk for the continuity of this ecosystem.  相似文献   

17.
The nitrogen (N) and phosphorus (P) nutrient input and output balance and utilization efficiency in the pear tree (Pyrus pyrifolia Nakai) and upland rice (Oryza Sativa L.) inter-cropping system and pear mono-cropping system were analyzed in this paper. Results indicated that nutrient retention in the pear tree and upland rice intercropping system was 188.93 kg ha?1a?1, of which 169.02 kg ha?1a?1 was N, accounting for 89.45%; P was 19. 93kg ha?1a?1, or 10.55% of the total. The annual nutrient absorption of N and P in the pear tree and upland rice intercropping system were 196.46 and 25.27 kg ha?1a?1, respectively. The nutrient absorption amount from rice was 61.32% for N and 69.97% for P, while the pear tree accounted for 6.01% and 8.99% of total N and P absorption, respectively, in the intercropping system. Upland rice intercropped in the pear tree system increased the N and P nutrient-utilization efficiency from 24.31% and 4.06% in the pear tree mono-cropping system to 56.24% and 11.97% in the pear tree and upland rice system.  相似文献   

18.
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19.
ABSTRACT

The aim of this study was to examine response of apple (Malus domestica Borkh.) trees to zinc (Zn) fertilization under conditions of acid coarse-textured soil with low 1M hydrochloric acid (HCl)-soluble Zn level. The experiment was carried out during 2004-2005 at a commercial orchard in Central Poland on mature ‘Jonagold’ apple trees/M.26 EMLA, planted at a spacing of 4 × 2.5 m. The trees were sprayed with Zn: (i) prebloom, at the stage of silver tip, and tight cluster at a rate of 140 and 100 g ha? 1, respectively, (ii) postbloom, at the stage of petal fall, and 2 weeks later at a rate of 80 g ha? 1 in each spray treatment, and (iii) postharvest, 4–5 weeks before the natural leaf fall at a rate of 500 g ha? 1. Other trees were supplied with Zn to soil at a rate of 3 kg ha? 1. In all the studied treatments, Zn was used as ethylenediaminetetraacetic acid (EDTA). Trees unsupplied with Zn served as the control. Tree vigor, fruit set, yield and fruit quality at harvest (mean fruit weight, firmness, color, russeting, soluble solids concentration, and acidity) were not influenced by Zn fertilization. Postharvest Zn sprays slightly damaged leaf tissues but did not cause defoliation. Soil Zn application raised Zn concentrations in flowers, and leaves 28, 56, and 84 days after petal fall. Pre- and postbloom Zn sprays increased Zn status in flowers and leaves 28 days after flowering, respectively. The obtained results indicate that Zn fertilization of ‘Jonagold’ apple trees with Zn status in mid-summer leaves and flowers of 17 mg kg? 1 and 27 mg kg? 1, respectively, is not successful in improving vigor and tree yield.  相似文献   

20.
Long-term eddy covariance measurements over a montado oak woodland in southern Portugal have documented a vulnerability to predicted decreases in springtime rainfall, since water availability during spring limits annual CO2 gain, the growth of fodder for animals, and the production of cork by Quercus suber. The current study examined CO2 exchange of three different herbaceous vegetation components distributed over montado landscapes and within the footprint of long-term landscape eddy covariance monitoring studies. Simultaneous measurements with eddy covariance at two sites and with manually operated chambers at multiple locations revealed that slow drainage of shallow basins, the onset of drying at higher sites and a high release of CO2 below tree canopies significantly influenced the overall course of montado ecosystem gas exchange during the spring.Hyperbolic light response models were employed to up-scale and compare herbaceous gas exchange with landscape net ecosystem CO2 flux. The up-scaling demonstrates the importance of the herbaceous understory in determining annual carbon balance of the montado and suggests a relatively small additional CO2 uptake by the tree canopies and boles, i.e., by the aboveground tree compartment, during springtime. Annual flux totals obtained during the extremely dry year 2005 and a normal precipitation year 2006 for the oak woodland and a nearby grassland were essentially the same, indicating that both ecosystems similarly exploit available resources. Based on comparisons with additional temperate grasslands, we can visualize the montado herbaceous cover as a typical European grassland canopy, but where temperature fluctuations in winter control uptake, and where total production depends on springtime rainfall as it controls phenological events and eventually dieback of the vegetation. On the other hand, tree canopies remain active longer during late spring and early summer, modifying the montado response from that of grassland. Uncertainties in flux estimates via both chamber and eddy covariance methodologies currently prevent a full understanding of vegetation/atmosphere coupling, of the recycling of CO2 between the understory communities and trees, and of relationships between exchange rates of individual components of the vegetation mosaic and overall carbon and water balances in montado landscapes.  相似文献   

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