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1.
Detailed studies have been undertaken to define pruning regimes for Eucalyptus nitens, but little is known of E. globulus responses to pruning although this is a more commonly planted species. This paper describes experiments that aimed to identify (a) levels of pruning that reduce E. globulus growth, (b) physiological processes contributing to those growth responses, (c) the incidence of decay and factors influencing decay incidence following pruning of E. globulus, and (d) comparative responses of E. nitens and E. globulus to live branch pruning. Results of a field experiment indicated that removal of between 30 and 50% of the crown length was appropriate for E. globulus plantations verging on canopy closure. The significant reduction in height growth associated with removal of 50 or 70% of crown length suggested pruning should remain below 50% of crown length if reduced stem growth of pruned trees was to be avoided. Stem volume was only significantly reduced over the period of the experiment by 70% pruning, but it was estimated that standing volume following removal of 50% of crown length would be reduced by 82 m 3 ha −1 over a 20-year rotation if there were no other silvicultural interventions. The growth responses observed were probably related to large reductions in leaf area following 50 or 70% removal of crown length. Trees responded to pruning by changing patterns of biomass partitioning to favour stem growth at the expense of branch growth. A glasshouse study determined that light-saturated net CO 2 uptake ( Amax) increased following pruning. E. nitens seedlings had both a higher baseline Amax and higher Amax following pruning than did E. globulus, which could partially explain the greater effect of pruning on E. globulus growth than has been observed for E. nitens in other studies. This result, as well as apparently different patterns of foliage distribution through the crowns of E. globulus and E. nitens, suggested that models of pruning responses need to be parameterised for both species. In addition, a more conservative pruning regime may be appropriate for E. globulus than E. nitens. Pruning increased the frequency of branch traces with decay infection, and there was a trend towards increasing decay outbreaks with increasing pruning severity. Decay outbreaks were more likely to occur following pruning of high angle or larger diameter branches. 相似文献
2.
The competition–density (C–D) effect for Chinese fir ( Cunninghamia lanceolata (Lamb.) Hook.) and Masson pine ( Pinus massoniana Lamb.) stands was analyzed using the reciprocal equation of the C–D effect, i.e. 1/ w= Aρ+ B, where w and ρ, respectively, represent mean stem volume and stand density. The C–D curve, which is given by the reciprocal equation on logarithmic coordinates, shifted upward with the progress of time. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. The biological time τ defined as the integral of λ( t), the coefficient of growth in the general logistic growth curve, with respect to physical time t, tended to increase to an asymptote with increasing t. With increasing τ, the coefficient A, the reciprocal of which means the asymptote of yield (= wρ), increased abruptly up to a maximum value and then tended to decrease gradually to a constant level. On the other hand, the coefficient B, the reciprocal of which means the asymptote of mean stem volume, decreased exponentially and tended to close to zero with increasing τ. The λ( t) decreased with increasing stand age, whereas the final yield Y( t) defined as W( t) ρ, where W( t) is the asymptote of w in the general logistic growth curve, tended to increase gradually with increasing stand age. 相似文献
3.
We examined how white pine ( Pinus strobus L.) seedlings planted under a mature cover of white and red ( Pinus resinosa Ait.) pine in eastern Ontario (Canada) responded to treatments aimed at improving light and soil conditions for seedling growth. The treatments were: (a) three levels of partial cutting (no cut or CS0, cut to one-crown spacing between residual trees or CS1, cut to two-crown spacing or CS2); (b) two levels of vegetation control (without herbicide or H0, with herbicide or H1); and (c) two levels of soil scarification (S0 and S1). On the third growing season after planting, total growth of seedlings was lowest in CS0 treatment and similar in CS1 and CS2 treatments. The CS2 created better growing light conditions than the CS1, with and average of 50% of full light at seedling height, which corresponded to the maximum height and diameter growth rates of seedlings. However, CS2 also stimulated the growth of competing woody vegetation (both understory trees and shrubs), and resulted in greater microsite heterogeneity of light availability. Scarification warmed the soil (approximately 1–3 °C in the middle of the growing season), decreased the density of competing trees, but increased the shrub density, with no impact on white pine seedling growth. The treatments had no effect on light-saturated photosynthetic rate ( A) of current-year foliage of seedlings, nor on their midday shoot water potential. Leaf N was higher in partial cuts and with vegetation control, but the relationship between N and A was weak to non-existent for the different foliage classes. Measures of the proportion of aboveground biomass allocated to foliage (leaf-mass ratio) suggest an acclimation response of young white pine that improves growth under moderate light availability and compensates for the lack of leaf-level photosynthetic plasticity. We suggest a combination of soil scarification under a one-crown spacing partial cut (corresponding to 14 m 2 ha −1 of residual basal area, or an average of 32% of available light at seedling height) as an establishment cut. This should provide optimum growth conditions for planted understory white pine, while also favoring natural regeneration and providing some protection against damage from insects and disease. 相似文献
4.
The objectives of this study were: (1) to quantify the genetic variation in foliar nutrient concentration in relation to foliar carbon isotope composition ( δ13C) and tree growth of 122 clones of ca. 4-year-old F 1 hybrids between slash pine ( Pinus elliottii Engelm var. elliottii) and Caribbean pine ( P. caribaea var. hondurensis Barr. et Golf.) grown at two experimental sites with different water and nutrient availability in southeast Queensland, Australia and (2) to examine the potential of using foliar nutrient concentration of the 4-year-old tree canopies for selecting elite F 1 hybrid pine clones with improved nutrient-use efficiency (NUE) and water-use efficiency (WUE), and ultimately enhanced tree growth under ambient growing conditions. There were significant differences in foliar nutrient concentrations between two canopy positions (upper outer and lower outer canopy) sampled, between summer and winter, and between the two sites. This highlights that foliar nutrient concentrations are influenced by sampling and environment. Significant genetic variations in foliar nutrient concentrations were detected between the clones, between the female parents, and between the male parents of the clones in both sampling seasons at both sites. Depending on the nutrient concerned, canopy position, season, and site sampled, the clones accounted for 4.7–33.9% of the total variation in foliar nutrient concentrations, the clone female parents for 0–25.1% and the clone male parents for 0–28.6%. The site-by-clone interactions were statistically significant for foliar N, P, Mg, Cu, Zn, Mn, Fe and mineral concentrations at the upper outer canopy in summer, and for foliar N concentration in winter. There were significant, positive correlations between clone means of foliar δ13C and N concentration at the upper outer canopy in summer for the wet site, while clone foliar δ13C was also positively related to clone foliar N concentration at both canopy positions in summer for the dry site. This suggests that clone WUE as reflected in foliar δ13C may be improved by selecting elite clones with higher foliar N concentration and increased photosynthesis, leading to enhanced tree growth when both water and N are the major growth-limiting factors. This is supported by the positive correlation detected between clone tree height and foliar N concentration at the upper outer canopy for both sites. Thus, foliar nutrient (particularly N) concentration, together with foliar δ13C, may be useful for assisting in selection of exotic pine clones with improved NUE and WUE, and enhanced tree growth under the nutrient- and water-limiting environments. 相似文献
5.
Early growth and physiology of longleaf pine ( Pinus palustris Mill.) seedlings were studied in response to light, water and nitrogen under greenhouse conditions. The experiment was conducted with 1-year-old seedlings grown in 11.3 l pots. The experimental design was a split-plot factorial with two levels (low and high) of each of the factors, replicated in three blocks. The four factorial combinations of water and nitrogen were randomly applied to 15 pots (sub-plots) in each of the light treatment (main plot). Data were collected on survival, root collar diameter (RCD), and height on a monthly basis. Biomass (shoot, root and needle), leaf area index, specific needle area, and needle nutrient (N, P, K, Ca, and Mg) concentrations were determined following final harvest after 16 months. Physiological data (net photosynthesis and transpiration) were collected monthly from March to July during the second growing season. Height and RCD were significantly influenced by nitrogen and water and by the interaction between them with no apparent effect of light. Seedlings grew 93% taller in the high nitrogen and well watered (HNWW) treatment compared to the low nitrogen and water stressed (LNWS) treatment. Similarly, a significant increase (78%) in RCD was observed for seedlings in the HNWW treatment over the LNWS treatment. Light, along with water and nitrogen, played an important role in seedling biomass growth, especially when water was not limiting. Biomass partitioning (as measured by root:shoot ratio) was affected only by nitrogen and water. Nutrient stress had a greater influence on carbon allocation (69% increase in root:shoot ratio) than water stress (19% increase). Net photosynthesis (Pnet) was significantly higher for seedlings in the high resource than in the low resource treatments with significant light×water and nitrogen×water interactions. Transpiration rate was higher (75%) under the WW treatment compared to the WS treatment. Longleaf pine seedlings grown under the LNWW treatment had the lowest foliar nitrogen (0.71%) whereas seedlings in the HNWS treatment had the highest (1.46%). Increasing the availability of light (through larger canopy openings or controlling midstory density) and soil nitrogen (through fertilization) may not result in greater Pnet and improved seedling growth unless soil water is not limiting. 相似文献
6.
The N dynamics following clear felling, focusing on NO 3− turnover, were studied at four forested sites in southern Sweden. Two different methods were used to study N availability: (i) an in vivo nitrate reductase activity (NRA) bioassay and (ii) measurements of natural abundance of stable N isotopes in leaves of the grass species Deschampsia flexuosa, and in organic soil horizons. At each of the four sites, six plots were established and each year, for 5 consecutive years (1989–1993), one plot per site was felled. Thus, in 1993 there were five plots with different ages since clear felling and one control (closed forest) plot at each site. NRA was analyzed three times annually during the years 1989–1993. Samples for grass and soil analysis of δ15N, total N and soil pH were taken in 1993 only. NRA rapidly increased after the felling and remained high throughout the studied period. This suggests that there was an increased pool of plant-available soil NO 3− more than 5 years after clear felling. Despite differences in site productivity and N deposition between the four sites, no significant differences in NRA were found between the sites. There were also rapid changes in δ15N in leaves of D. flexuosa, coinciding with the increases in NRA, during the first 3 years after felling. In contrast to NRA, shoot δ15N decreased 3–4 years after the felling at three out of four sites. Variations in the δ15N figures between sites may have been largely due to between-site differences in field-layer retention of N. At two of the sites, where NO 3− leaching was also measured, a correlation was found between the NO 3− concentration in the water and the difference in δ15N between D. flexuosa leaves from felled and closed forest plots. The data presented here suggest that NO 3− leakage after clear felling is a rapid process, which is influenced by the development of field-layer biomass after the felling. Furthermore, losses of NO 3− through leaching rapidly change the natural abundance of the plant available N pools in the soil. 相似文献
7.
Four half-sib families of Pinus radiata (D. Don) (20080, 20010, 20022 and 20062) were grown in pots under conditions where P was either deficient or adequate and water was supplied daily. Seedlings of all four families were exposed to 340 (ambient levels) or 660 μl CO 2l −1 in controlled-environment chambers for 16 weeks. Families 20010 and 20062 were grown at the same CO 2 concentrations for 22 weeks. A subset of plants grown in the chambers were subject to drought and their water potentials and relative water contents measured. In the glasshouse experiment, photosynthesis, conductance and elongation of needles were measured. The fresh and dry-weights of the tops of the plants were measured in both experiments. Elevated CO2 concentrations increased shoot growth in all families, apparently through increases in photosynthesis. At 340 μl CO2l−1, family 20062 accumulated the most dry-weight and 20010 the least. However, family 20010 responded so strongly to 660 μl CO2l−1 that it produced as much dry-matter as 20062. Phosphorus deficiency generally diminished the response to high CO2. Again, 20010 was outstanding in that its CO2 response was least reduced by P deficiency. Carbon-dioxide enrichment did not increase the drought-tolerance of any of the four families, either by reducing conductance or by facilitating osmotic adjustment. These results provide strong indications that the higher levels of atmospheric CO2 expected in the next century will increase the growth of P. radiata where P availability is adequate, but may reduce growth in areas where rainfall is low. Finally, the capacity to respond to CO2 enrichment appears to be widely distributed among superior P. radiata genotypes selected by the Forestry Commission of New South Wales. However the magnitude of response varies considerably, particularly where P is deficient. 相似文献
8.
Three different stock sizes of containerized black spruce ( Picea mariana [Mill.] B.S.P.) seedlings were planted in an abandoned agricultural field. The small planting stock was of a conventional type produced in 110 cm 3 containers. The experimental medium and large stock types were produced in 340 and 700 cm 3 containers, respectively. Gas exchange, xylem water potential and dry masses were measured six times during each of the first two growing seasons in field plots with and without vegetation control. During the first growing season, the effect of planting shock masked most physiological and growth differences among seedling types. During the second growing season, in plots with vegetation control, small and medium seedlings had similar values of physiological variables and of growth as measured by relative growth rates (RGR), but the large seedlings showed lower values of both net photosynthesis and of RGR, a difference attributed to low initial quality of the root system in the larger seedlings. In plots without vegetation control, the trend was identical, but differences were not significant; the greater height of the larger seedlings, and the resulting greater access to light, compensated for their lower initial quality. The similarity in response between the medium and the small seedlings shows that a fourfold increase in shoot size (1.68–6.82 g) in the initial size and a doubling of the shoot : root ratio (2.17–4.54) of the planting stock did not result in increased planting shock or reduced growth in these containerized conifer stock types. The results also show the importance of the interaction between stock height and the vertical light profile created by the competing vegetation in the final assessment of stock performance. 相似文献
10.
For 3 years following a severe, November 1992 tornado, abundance and growth of tree regeneration in intact forest-floor and windthrow-pit microsites were studied in three mixed pine and hardwood stands in the Georgia Piedmont, USA. The research had two objectives: (1) determine if performance of tree regeneration differed between microsite types and between pre- and post-tornado cohorts on intact forest-floor microsites, and (2) determine if variation in light and soil water availability from the disturbance affected performance of eight species artificially seeded into intact forest-floor microsites. Near each of the 42 sample points (12–20 per site) spaced on 15 m grids, species and height of tree seedlings were recorded within a 1 m radius plot of intact forest floor and the nearest windthrow pit. Intact forest-floor microsites were dominated by two late-successional species, Acer rubrum (3.5 pre-tornado stems per m 2 and 1.8 post-tornado stems per m 2) and Ostrya virginiana (2.6 post-tornado stems per m 2), while windthrow pits were dominated by an early successional species, Liriodendron tulipifera (1.7 stems per m 2). Although seedling survival did not vary significantly among species or microsite types, first-year height of seedlings in intact forest-floor microsites (24 cm) was significantly greater than those in windthrow-pit microsites (19 cm). Second-year height growth of new seedlings of Cornus florida in intact forest-floor microsites (52 cm) significantly exceeded that of many other combinations of species and microsite type. Species artificially-seeded into intact forest-floor microsites in 1994 and 1995 varied considerably in emergence (<1–24%), survival (<1–16%), and height (5–15 cm), and those with the heaviest seed survived best. From 1994 to 1995, average gap fraction, an index of light availability, decreased 17% from 0.23 to 0.19. Soil water content in 1995 under gap fractions of greater than 0.3 (21%) averaged significantly less than under gap fractions of either 0.1–0.3 (24%) or less than 0.1 (26%). Significant positive correlations were detected for relationships of emergence and survival of several species to soil water content. Overall rankings of seedling performance between microsites (intact forest floor>windthrow pits), between cohorts (pre-tornado>post-tornado origin), and among species (mid- to late->early-successional species) indicate that advanced regeneration and new seedlings of A. rubrum, O. virginiana, and C. florida will be long-term dominants of the understory because of their high abundance, initial growth responses, and shade tolerance. 相似文献
11.
Both incoming shortwave radiation ( Rg) and photosynthetically active radiation (PAR) in percentage of full daylight were measured at the same time by point and strip sampling in four plots (0.1 ha) of Picea abies (L.) Karst. The standard deviations (%) of Rg and PAR were, respectively, 11.1 and 9.8 at 64 points, 15.7 and 13.9 at 32 points, and 24.7 and 23.8 at 16 points per plot. A period of at least 40 s per strip (30 m min−1) gives a CV (coefficient of variation) of 30%. There is no significant difference between relative irradiance (RI) estimated by the point method (64 points) and by the strip method (8 strips). Curves of RI (Rg and PAR) and basal area (m2 ha−1), diameter sum (m ha−1) and density (stems ha−1) of fifteen trials with different thinning programmes are presented. Irradiance (Rg) in heavily thinned stands was 3–14% of irradiance on an open place. The irradiance, Rg, in extra-heavily thinned stands is 12–27%, and in unthinned stands, 1–3% that of an open place. The Rg curve lies above the PAR curve in all cases. Some practical implications of the study are presented. Heavy thinning of Norway spruce stands gives RI (Rg) values 10% at basal area of 25m2 ha−1 which is necessary to minimize development of suckers of broadleaved trees. 相似文献
12.
通过对5个月生4种不同炼苗密度的尾巨桉优良无性系 DH 32-29幼苗树高、地径及各器官生物量进行调查分析，结果表明：4种不同炼苗密度间苗高无显著差异；而地径差异达到极显著水平，并呈极显著负相关；不同炼苗密度单株间及各器官生物量均差异显著，单株生物量、叶片、茎干与根系的生物量均随炼苗密度增加而降低；考虑到空间利用率、通风保水性及疾病易感程度综合分析，炼苗密度以45株·盘 -1效果最佳。 相似文献
13.
The impact of forest management (clear-cutting and site preparation) on stream hydrology has been studied in five small catchments in eastern Finland from 1991 and on groundwater levels and quality from 1994. The period 1992–1996 was a calibration period and in the autumn of 1996, 10% and 30% of the area of two of these catchments were clear-cut according to the forest management plan. Regeneration was carried out by disc-plowing in the autumn of 1998 and planting with Scots pine ( Pinus sylvestris) and Norway spruce ( Picea abies) seedlings in the spring of 1999. The depth and quality of groundwater was monitored with four to nine groundwater wells installed in each catchment. There were 32 wells in all, 16 on upland mineral soils and 16 on peatlands (the perforated part of the pipe was totally put into the underlying mineral soil at eight sites). Sampling was made monthly during spring (March–May) and autumn (November–December) and bimonthly during summer (June–October). The samples were chemically analyzed for pH, electrical conductivity, and concentrations of total P and Fe (before filtration), and total N, NO 3−-N, NH 4+-N, total P, PO 43−-P, SO 42−-S, Ca 2+, Mg 2+, K +, Na +, Mn, Zn, Fe, Al 3+, Cl − (after filtration through 0.45 μm membrane filter). Data collected until the end of 2001 are reported. Groundwater was found in the down-slope wells in lower-lying areas, but not in those installed on the slopes with a thin (1–2 m) soil layer. Clear-cutting did not significantly affect groundwater levels in the wells. Nitrate N concentrations increased from 0.03 mg L −1 level after clear-cutting and again after site preparation in the wells on upland soils and peatlands receiving water from the managed parts of the catchment. In one well at the lower edge of the managed area NO 3−-N concentrations reached 1–1.4 mg L −1 in 2001 (fifth year after clear-cutting, third after disc-plowing), but mean concentrations remained <0.3 mg L −1. Chloride concentrations also increased (50–100%) after treatments but the concentrations of other solutes showed no significant effect of treatment. It was concluded that changes in groundwater quality and quantity related to the clear-cutting were small and did not represent a danger to water quality or quantity. 相似文献
14.
植物生长延缓剂能够抑制植物细胞生长,使植株长得粗壮,根系发达,从而增强植物的抗逆性。试验研究了不同浓度的植物生长延缓剂矮壮素(CCC)和多效唑(PP 333)对越冬期辣韭矢竹组培苗生长的影响。结果表明:经CCC和PP 333处理后的苗木,植株高生长明显降低,而分枝率和分蘖率显著增加;对植株叶绿素荧光参数的影响表现为,PSⅡ最大光化学效率( Fv/Fm)、非光化学猝灭系数( NPQ)和电子传递速率(ETR)均显著上升,光化学量子效率( ΦPSⅡ)和光化学猝灭系数( qP)均显著下降,表明竹苗接受和传递光电子的能力增强,光合潜力上升,光机构得到保护,受低温伤害减轻,植株抗寒性增强。比较不同浓度CCC和PP 333的处理效果显示,800 mg/L的PP 333和3 000 mg/L的CCC处理的植株均有较好的抗寒能力。综合来看,3 000 mg/L的CCC对辣韭矢竹苗在寒冷条件下的保护最全面。 相似文献
15.
A 3 year field and pot study was conducted to determine the effects of several biotic and abiotic factors on the early growth of western hemlock ( Tsuga heterophylla (Raf.) Sarg.), western redcedar ( Thuja plicata, Donn) and Sitka spruce ( Picea sitchensis, Bong. Carr.) seedlings established on 2- and 8-year-old clearcut sites previously occupied by old-growth western hemlock and western redcedar forests (referred to as younger and older CH, respectively), and on adjacent 2-year-old clearcut sites previously occupied by second-growth western hemlock and amabilis fir ( Amabilis amabilis (Dougl.) Forbes) forests (referred to as younger HA) in coastal British Columbia. The objective of the study was to determine which factors are associated with the poor growth characteristic of the salal ( Gaultheria shallon, Pursh) dominated CH clearcut sites. No soil moisture deficits were measured on any of the three types of clearcut sites at any time of year. The best seeding growth was on the younger HA sites followed by the younger CH sites and then the older CH sites. The better growth on the younger HA sites was associated with a higher availability of N and P in the first 20 cm depth of the forest floor. No differences in matric soil water potential and pH, and only small differences in soil temperature were measured between the three types of clearcut sites. Complete removal of the competing vegetation on the younger and older CH sites resulted in an increase in conifer seedling growth and in the availability of N (22–40%) and P (15–32%); however, it did not affect cellulose decomposition and matric soil water potential, and increased soil temperature only slightly. Both western hemlock and Sitka spruce seedlings were very responsive to differences in nutrient availability measured between types of clearcut sites and planting treatments. In contrast, western redcedar was not responsive. All three conifer species had very high mycorrhizal colonization on the younger CH sites, and this was not altered by the removal of the competing vegetation (mainly salal). These results suggest that the nutritional stress and poor growth of conifers on salal-dominated CH clearcut sites in coastal British Columbia can be explained by:(1) inherently low forest floor nutrient availability; (2) competition between salal and conifer seedlings for scarce nutrients and nutrient immobilization in salal; (3) declining nutrient availability a few years after clearcutting and slashburning. 相似文献
16.
The response of Caribbean pine ( Pinus caribaea Morelet. var. hondurensis Barr. and Golf.), slash pine ( Pinus elliottii Englem. var. elliottii) and their F 1 hybrid to soil waterlogging was studied under glasshouse conditions. Plants were grown in either a lateritic or gleyed podzolic soil and pots were flooded in both autumn and summer treatments. Plant responses were influenced by both season and duration of flooding, and by soil type. All the Caribbean pine seedlings survived the autumn flooding, but showed very slow growth and had very low needle conductances. Summer-flooded plants exhibited rapid stomatal closure and low needle water-potentials accompanied by needle dehydration. All of the summer-flooded Caribbean pine seedlings died. Slash pine was much more flood-tolerant than was Caribbean pine, whilst the F1 hybrid was intermediate between the two parents. All slash pine and F1 hybrid seedlings survived autumn flooding and continued to grow, but survival was reduced with summer flooding, particularly in the short-term flooding treatment. Slash pine and F1 hybrid seedlings showed morphological features of flood tolerance with production of adventitious roots and formation of lenticels in association with stem hypertrophy. Although stomatal opening was evident during autumn flooding, needle conductance was very much reduced in summer-flooded plants of these two taxa. Needle water-potential and relative water content were maintained near the control value in flooded slash pine grown in both soil types, but only for the F1 hybrid in the flooded lateritic podzolic soil. 相似文献
17.
Calcareous amendment and/or fertilization trials were carried out in a declining 66-year-old Norway spruce ( Picea abies (L.) Karst.) stand in the Vosges mountains (northeast France, altitude 1100 m) in 1985. The aim was to test tree response to nutritional deficiencies (Ca + Mg) and to alleviate soil acidity. In 1988, experimental equipment was set up to collect atmospheric input (bulk precipitation, throughfall) and soil seepage water. The soils are podzolic (‘ocre-podzolique’), derived from an acid-poor granitic bedrock (‘granite du Valtin’). The soils are coarsely textured, hence very porous. They are very acid (pH 3.4 in the A 1 horizon, and pH 4.1 in the Bs horizon). The cation exchange capacity (CEC) is highly saturated in exchangeable acidity: 86% in the A 1 horizon. Ca 2+ + Mg 2+ saturation is very low (<10% in A 1 and <1% in the subsoil). Liming and fertilization significantly increase soil pH, base cation saturation and decrease soil acidity, especially in the surface horizons. Bulk precipitation is dilute and acidic (pH 4.5); ion concentration of the precipitation greatly increases after passing through the tree canopy. Dry deposition is moderate and has values in the lower range reported for Europe. Nitrification produced large amounts of NO3−-N and H+ ions in the O layer and organo-mineral horizons. Nitrate and aluminium dominate the chemical composition of the soil see-page water. Liming induces a considerable rise in the soil solution pH and the base cations (Ca2+ + Mg2+) and decreases nitrate and aluminium substantially. Liming alone seems to lower the rate of nitrification. Addition of fertilizers increases the deep drainage of base cations which could reduce the long term efficiency of liming. Improvement of tree health-status accords with the positive effects of liming and/or fertilization on the soil's solid phase and solution. 相似文献
18.
以2年生晚松盆栽苗为供试材料,从抗大气环境中SO 2污染方面对晚松的抗逆能力进行了定量评价,为晚松的园林应用提供理论依据。研究表明,晚松叶绿素a、b对模拟SO 2污染反应敏感,叶绿素b所受伤害大于叶绿素a,类胡萝卜素较不敏感。过氧化物酶活性的提高有助于减轻膜脂过氧化造成的伤害,从而使其在SO 2污染胁迫较轻(10 mmol/L)时免受伤害。 相似文献
19.
采用L 9(3 4)正交设计对造林11和15个月的盈江省藤分别开展施肥试验,施肥后1个月测定苗木的生长指标,包括地径、冠幅、叶片数、叶片长及新叶数,研究不同肥料种类(N:P:K为11:8:6的复合肥、N:P:K为20:5:20的复合肥、过磷酸钙)、施肥量(25 g/株、50 g/株、75 g/株)以及是否施用尿素对苗木生长的影响。结果表明:肥料施用量、是否施尿素以及两者的组合是影响苗木生长的主导因子;不同肥料种类及不同的施用量对苗木各生长指标的影响不同;不同肥料种类对冠幅、叶片长和新叶数具有极显著或显著的影响( P冠幅=0.017<0.05, P叶片长=0.004<0.01, P新叶数=0.038<0.05),不同肥料施肥量则极显著影响地径、冠幅和叶片长( P=0.000<0.01),尿素不同施用量显著影响叶的生长。总体而言,过磷酸钙有利于盈江省藤叶的生长,N:P:K配比为11:8:6的复合肥可增加苗木叶片数和新叶数,尿素对苗木生长具有负效应,不宜施尿素。 相似文献
20.
Research reported here has evaluated interactions of factors limiting the biological potential of slash pine ( Pinus elliottii var. elliottii Engelm.) and loblolly pine ( P. Taeda L.). Water and nutrients were manipulated by irrigation, weed control, and intensive fertilization. Genetic factors were incorporated as (1) improved loblolly seedlings from a commercial clonal seed orchard and (2) slash seedlings from four fast-growing, open-pollinated seed-orchard clones. Three replications of a 2 × 2 × 2 factorial experiment were established on a Typic Haplaquod soil in northern Florida using four cultural treatments: no treatment (F0H0); weed control (F0H1); fertilizer (F1F0); and combination of weed control and fertilizer (F1H1) for each species. During the first year there were large, sustained responses to all cultural practices. Loblolly and slash pine showed similar growth responses and had a lengthened growing season (60–100 days). Slash pine growth was superior to that of loblolly. Growth responses observed during the first year continued. After 4 years, irrigation had no measurable effect on tree growth. Both pine species responded equally to F1H0 and F0H1, but slash retained a slight edge. Extra nutrients]available via fertilizer, reduced competition, or additional rooting space, increased slash-pine volume index from an average of 2.0 m 3 ha −1 (F0H0) to 11.90 and 13.59 m 3 ha −1 (F0H1 and F1H0, respectively). The F1H1 treatment produced the largest slash-pine response, diameter at breast height ( Dbh) averaged 9.84 cm, height reached 5.02 m, and volume index rose to about 22.94 m 3 ha −1. With teh F1H1 treatment, average loblolly-pine height and volume exceeded that of the average slash pine. At age 4, the growth response due to increased nutrient supply was 13–29 times that of the best genetic response within F0H0 trees of the four slash-pine progenies. The best-growing slash-pine family (6–56) exceeded loblolly-pine growth under all four treatments and approximated the vigor shown by slash pine in the southern hemisphere. 相似文献
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