Published online 29 September 2005
Published in Soil Sci Soc Am J 69:1799-1805 (2005)
DOI: 10.2136/sssaj2003.0341
© 2005 Soil Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
Forest, Range & Wildland Soils
Growth Responses of Pinus radiata and Soil Changes following Periodic Fertilization
C. Ringrosea,b,* and
W. A. Neilsena
a Forestry Tasmania, 79 Melville St., Hobart, Tasmania, 7000, Australia
b Cooperative Research Centre for Sustainable Production Forestry, GPO Box 252-12, Hobart 7001 Australia
* Corresponding author (carolyn.ringrose{at}forestrytas.com.au)
 |
ABSTRACT
|
|---|
Low growth rates of Pinus radiata D. Don plantations on soils of low nutrient status in Tasmania require the development of nutrient management systems involving fertilization throughout the life of the stand. Periodic fertilization through 15 yr, in a Pinus radiata D. Don plantation in northeastern Tasmania was evaluated for effects on stand growth and soil. Substantial stem volume increases due to N and P fertilizer, applied as ammonium sulfate and single superphosphate were observed. Two applications of P fertilizer totaling 144 kg P ha–1 produced substantial increases in stem volume growth from 67 to 192 m3 ha–1. With P plus 13 annual applications of N fertilizer at 100 kg N ha–1 yr–1, stem volume growth increased from 192 to 344 m3 ha–1 over the 15-yr period. Although fertilizing every second and fourth year produced less response, these treatments had better fertilizer-use efficiency. Long-term fertilization resulted in increases in concentrations of nutrients in the forest floor and the surface soil. The highest rates of fertilization were accompanied by significant reductions in soil pH throughout the soil profile, from 4.1 to 3.4 units. Reduction in pH occurred with both nitrogenous and phosphatic fertilizers. Substantial reductions in exchangeable Mg concentrations, from 235 to 88 µg g–1, were also measured throughout the soil profile. The highest rate of N application significantly increased the total O2 horizon biomass, with N mass doubling within the O2 horizon.
Abbreviations: AAS, atomic absorption spectrometry • BA, basal area • CAI, current annual increment • DBHOB, diameter at breast height over bark • LSD, least significant difference • MAI, mean annual increment • MDH, mean dominant height • PAI, periodic annual increment • NIL, Nil treatment • (P), superphosphate only applied twice • P2YN2Y, superphosphate and ammonium sulfate applied every second year • (P)N1Y, superphosphate twice and ammonium sulfate applied annually • (P)N2Y, superphosphate twice and ammonium sulfate applied ever second year • (P)N4Y, superphosphate twice and ammonium sulfate applied every fourth year • SPH, stems ha–1
|
INTRODUCTION
|
|---|
ESTABLISHMENT OF P. radiata plantations on soils of low nutrient status require the development of nutrient management systems involving fertilization at establishment followed by further applications through the life of the stand. Prescription N and P fertilization at planting, and in early stages of tree establishment are needed at many sites to achieve rapid early growth and high survival rates (Gentle et al., 1965). Later-age application of P at P-deficient sites can increase P. radiata plantation growth by an average of 10 m3 ha–1 yr–1, through 10 yr or more (Gentle et al., 1965; Neilsen et al., 1984). The magnitude and longevity of the response to P application depend on soil properties such as inherent P concentration, P sorption capacity, and soil pH (Pritchett and Comerford, 1982).
Although applications of large quantities of N fertilizer have produced growth responses, declines in such responses are associated with decreasing fertilizer-elevated soil N concentrations within the year following its application (Johnson et al., 1980; Adams and Attiwill, 1983; Khanna et al., 1992; Fisher and Binkley, 2000). Therefore repeated applications are required to obtain lasting growth responses (Neilsen et al., 1992; Neilsen and Lynch, 1998). The frequency of repeated applications depends on the period of elevated availability and cycling of applied nutrients in the soil system and the efficiency of internal recycling of nutrients (Switzer and Nelson, 1972). Following canopy development, internal redistribution, nutrient return and decomposition become critical processes in supplying nutrients for new growth (Miller, 1981).
In a stand of P. radiata in Tasmania, annually fertilized for 12 yr (100 kg N ha–1 yr–1), needle N concentration began to decline within 2 yr of cessation of fertilization (Neilsen and Lynch, 1998). Needle mass remained constant for 5 yr following fertilizer cessation. Growth rates decreased marginally for a period of 4 yr, from a peak of 34 m3 ha–1 yr–1 current annual increment (CAI), before falling dramatically in the fifth year to 17 m3 ha–1 yr–1 CAI. It was concluded that periodic applications, at least every fourth year, would be required to maintain vitality of this plantation (Neilsen and Lynch, 1998). Less frequent applications might not provide sufficient continuity of nutrient supply to maintain economic growth rates. Conversely, periods between applications need to be as long as possible to minimize costs associated with fertilization.
Although fertilizers may be used to increase forest growth there is concern that long-term N application may impact on forest sustainability through changes in soil chemistry. Nitrogen fertilization has been found to increase soil acidity across a range of sites (Adams and Martin, 1984; Tamm and Popovic, 1995; Homann et al., 2001). Low soil pH can decrease the rate at which organic N is mineralized (Adams and Martin, 1984), and can reduce the availability of cations such as Ca and Mg. The forest floor also plays a major role in mineral cycling in many forest ecosystems. Tamm and Popovic (1995) noted the importance of the litter in the retention of base cations within northern hemisphere forest systems, and its importance when planning management systems for fertilization. The mass and nutrient content of the forest floor is variable between species, stand age, site, and fertilizer treatment (Baker et al., 1986; Crane and Banks, 1992; Neilsen and Lynch, 1998).
A large proportion of the P. radiata estate in Australia is planted on soils formed on siliceous sediments, much of which is of low-nutrient-status (Khanna et al., 1992). The majority of the Tasmanian estate is on similar parent materials but the climate is cooler. The site selected for this research was representative of the Tasmanian estate.
The objectives of this study were to examine possible options for improving plantation growth on low-nutrient-status soils in Tasmania through various periodic applications of later age fertilization, to determine the effects of those periodic fertilizations on soil chemical properties, and to investigate the role of the forest floor as a nutrient pool. Investigation of foliar nutrient levels was also undertaken periodically during the experiment.
|
MATERIALS AND METHODS
|
|---|
A field fertilization experiment was established in a 20-yr-old P. radiata plantation in the northeast of Tasmania (41°28' S lat., 148°00' E Long.). This older stand was selected for this experiment to determine the resilience of P. radiata when fertilized at a later age with N, applied periodically, and in combination with P.
At plantation establishment (1967) spacing was 3 by 2.2 m. The plantation area was thinned, at establishment of the fertilization experiment, from 1520 stems per hectare (SPH) to 870 SPH, approximately 58% of initial stocking (from 23.6 to 18.3 m2 ha–1 mean basal area [BA]). The thinning was mainly aimed at removing small diameter, poorly formed, and forked trees.
The vegetation on the site before conversion to P. radiata plantation was mature Eucalyptus sieberi (L.A.S. Johnson) of 20- to 29-m height. The site has an easterly aspect, about 10% slope, and an altitude of 350 m. The understory consisted of moderately dense bracken fern [Pteridium esculentum (Forst. f.)]. The soil was a Typic Haplohumult with loam over clay, formed on metamorphosed shales of Devonian–Silurian age. Total soil depth was about 0.8 m. The 24-yr average annual rainfall (1962–1986) was 938 mm, spread fairly evenly through the year. However, annual rainfall is highly variable.
There were two replicates (blocks) of six treatments (Table 1). The 12 rectangular plots each had a total area of 668 m2. The two blocks were determined on the basis of initial stand mean BA, with one block containing the six highest BA plots (BA 20.3 to 20.5 m2 ha–1), the other the six lowest BA plots (BA 16.2 to 16.3 m2 ha–1). Within each plot, a subplot of 25 trees (288 m2) was selected for measurement, allowing for a buffer zone between treatments.
Phosphorus was applied at establishment of the fertilizer experiment (June 1987) and when needed as indicated by foliar analysis, to maintain foliar P concentrations close to 0.12%, the concentration considered adequate for good growth. Reapplication was performed 6 yr after initial fertilizer application, when analysis showed low foliar P concentration, with 144 kg P ha–1 applied. The periodic N application experiment was designed with four levels of regular N applications; no N [(P)], N applied at every fourth year [(P)N4Y], every second year [(P)N2Y], and annually [(P)N1Y]. Based on previous experiments 100 kg N ha–1 was applied each application (Neilsen and Lynch, 1998). In addition, two other treatments were included, a treatment without P (NIL), and a treatment of N plus P applied every second year (P2YN2Y) (Table 1). Fertilizers used were single superphosphate, ammonium sulfate, or mixtures of the two, resulting in large quantities of S and Ca also being applied (Table 1). Fertilizers were broadcast by hand.
All 25 trees on the subplots were measured for diameter at breast height (1.3 m) over bark (DBHOB) annually from establishment for 15 yr. The two tallest trees on each whole plot were measured for height as mean dominant height (MDH), based on the tallest 50 SPH evenly distributed over the area. Stand volume was calculated from volume tables.
Sampling and Analysis
Foliar sampling was performed before fertilization at age 17, and at ages 22, 23, and 34 yr. One-year-old foliage was sampled from the upper third of tree crowns. Three selected trees per plot were sampled by climbing and sampling, or using a shotgun to collect twigs. Needles from the three trees were stripped from each branch and combined, on the basis of equal mass, for each plot. Samples were prepared and analyzed as described by Neilsen et al. (1992). Drying was performed at 70°C before the sample was ground in a Wiley mill before analysis.
The impact of long-term nutrient inputs on forest soils was considered by examining soil profile differences at the end of the experiment. Pits were dug in the center of each of the NIL and (P)N1Y plots, between tree rows. Pits were dug to the depth of the decomposing bedrock, at approximately 0.8 m, and soil horizons were described and sampled for analysis. Physical and chemical parameters for each horizon were measured and analyzed. Additionally, soils on all plots were sampled by soil auger to a depth of 50 cm, in 10-cm increments. Each 10-cm increment sample was bulked from each of four auger holes per plot. Soils were air dried and sieved to <2 mm for chemical analysis. Bulk density for soils was calculated from intact cores sampled from soil pits, in 10-cm increments, to a depth of 50 cm.
Forest floor was collected in autumn using a 25 by 20 cm frame. Samples were separated into two horizons, the undecomposed organic matter (O1 horizon) and the decomposed organic matter (O2 horizon) (McDonald et al., 1990). Five-litter samples were collected per plot and the O1 and O2 horizon samples were bulked by plot separately for biomass determination. Only the O2 horizon was analyzed. Total nutrient content in the O2 horizon and soil profile were estimated from these measurements.
Foliar and litter samples were digested by acid hydrogen peroxide (Lowther, 1980). The digest was analyzed for N based on the indophenol blue method (Reardon et al., 1966), P by the molybdate blue method (Murphy and Riley, 1962) and Ca, K, and Mg by atomic absorption spectrometry (AAS). For soils, total N and P were analyzed by semimicro-Kjeldahl automated color, method 7A2 (Rayment and Higginson, 1992). Total soil Mg, Ca, and K were analyzed by AAS following nitric acid digestion (Rayment and Higginson, 1992). Exchangeable Ca, Mg, and K were extracted using 1 M ammonium chloride at pH 7.0 (Rayment and Higginson, 1992). Organic C in soil was determined by the Walkley–Black method (Rayment and Higginson, 1992). Soil pH was measured in a 1:5 soil/distilled water ratio using soils, which had not been dried. Mineral N (ammonium plus nitrate) was extracted from <2-mm soils maintained at field moisture using cold 2 M KCl, Method 7C1 (Rayment and Higginson, 1992). Mineral N within the extracts was measured using a flow injection analyzer, QuikChem 8000 Methods 13-107-06-2D (ammonium) and 12-07-04-1-F (nitrate) (Lachat Instruments, Milwaukee, WI).
Data Analysis
Total nutrient content in the biomass of P. radiata trees was estimated using an equation derived from Neilsen and Lynch (1998) (Table 2). Mean tree total content of N, P, Ca, and Mg was regressed against mean tree volume and this was applied to the mean tree total volume for the plots. Estimates based on mean tree volume are unbiased but may have an error of up to 10% (Crow, 1971).
Analysis of variance and least significant difference (LSD) tests were used to test the significance of treatment and soil profile depths on nutrient content and the effect of treatment on foliar nutrient content. Group regression analysis was used to evaluate growth responses (Genstat 5 Committee, 1988). Significance is reported at the p < 0.05 level.
|
RESULTS
|
|---|
Growth and Health of Plantations
Total stem volume increment in the 15 yr following the commencement of fertilizer treatments showed increasing growth from applied P and with more frequent N applications (Fig. 1)
. The greatest response was from (P)N1Y resulting in six times the growth of NIL and double the growth of (P). Phosphorus reapplied at age 26 yr resulted in an increasing growth of (P) over NIL. During the last 6 yr in measurement there was virtually no stem volume increment increase of the NIL plots (Fig. 1).
View larger version (23K):
[in this window]
[in a new window]
|
Fig. 1. Growth of P. radiata NIL and plots with various fertilizer treatments following initial application at age 20 years. Arrows indicate four yearly applications. Bars indicate least significant difference between treatments (LSD).
|
|
During the term of the experiment, the periodic annual increment (PAI) was 4 m3 ha–1yr–1 for the NIL, 13 m3 ha–1yr–1 for (P), and 27 m3 ha–1yr–1 for (P)N1Y. For up to 7 yr after initial treatment, (P)N1Y had a significant advantage over (P)N4Y. The total growth obtained during the 15 yr as a response to the quantity of N applied (fertilizer-use efficiency) showed a decrease in efficiency with annual application compared with application every second or every fourth year (Fig. 1).
Foliar N and P concentration varied among sampling times. Before treatment the P concentration was below 0.08%, and NIL trees remained at concentrations between 0.08 and 0.09% in all samples (Table 3). Even with fertilizer treatment the foliar concentration of N and P remained marginal in all samples (N < 1.2% and P < 0.12%). Only in the samples taken at age 34 yr were the foliar N concentrations of the four treatments receiving N, (P)N1Y, (P)N2Y, (P)N4Y, and P2YN2Y, significantly higher than those of NIL. During the period of research the foliar N concentration within NIL trees declined substantially from 1.11 to 0.85%, concomitant with a decline in the canopy mass. In samples taken at Ages 22 and 34 yr, the (P) trees had higher foliar P concentration than the NIL trees (Table 3). After the second application of P, foliar P concentrations were still significantly higher 8 yr later.
View this table:
[in this window]
[in a new window]
|
Table 3. Foliar nutrient concentrations (in 1-yr-old needles) for N and P for various treatments following initial treatment at age 20 yr in P. radiata. Letters indicate significant difference between treatments (p < 0.05).
|
|
Fertilizer Effects on the Soil Profile, Soil pH, and Soil Chemistry
There were significant differences in nutrient distribution within the soil profiles at tree age 34 yr. The heaviest fertilizer treatments resulted in a significant increase in the mass of the O2 horizon, with over 70 Mg ha–1 for the annually fertilized treatments, compared with 40 Mg ha–1 for NIL (Table 4). There was significantly more N in the litter and surface soil, 0 to 20 cm, in the (P)N1Y compared with (P). The greater mass of the O2 horizon and higher N concentration in that horizon combined to form a substantial nutrient pool.
View this table:
[in this window]
[in a new window]
|
Table 4. Mass of forest floor, O1 and O2 horizons, under P. radiata at tree age 34 yr. Letters indicate significant difference between treatments (p < 0.05).
|
|
Based on regressions developed for P. radiata on a similar site (Table 2), it was estimated that there was double the P and almost three times the N in (P)N1Y trees compared with NIL. However, substantial variations in nutrient loads at the experimental site resulted in no significant differences in total N content in the soils. Soil mineral N was dominated by ammonium 
, with nitrate commonly below detectable limits. Ammonium increased significantly with the rate of N application within the surface 0 to 10 cm of soil (Table 5). The remaining soil to a depth of 50 cm was generally lower in NH4+, in fertilized treatments, than NIL suggesting little downward movement of mineral N.
View this table:
[in this window]
[in a new window]
|
Table 5. O2 horizon and soil pH and exchangeable Mg, Ca, and K and total NH4+ for various treatments under P. radiata. Letters indicate significant difference between treatments (p < 0.05).
|
|
There was significant accumulation of P within the O2 horizon in (P)N1Y compared with (P). Phosphorus application alone resulted in no significant increase in total P in the top 50 cm of soil (Table 6). Increased S contents were observed in the O2 horizon and throughout the 50-cm depth, but were only significantly higher in the top 50 cm of soil receiving the highest amounts of S added in fertilizers (Table 6). Application of N significantly increased the total soil C content of the top 50 cm of the soil profile. The soil C was concentrated in the surface 0 to 10 cm. At the highest N application rate soil C content in this horizon doubled from 21 Mg ha–1 in NIL to 41 Mg ha–1 in (P)N1Y (Table 6).
View this table:
[in this window]
[in a new window]
|
Table 6. Nutrient contents within the tree, O2 horizon and soil for various treatments under P. radiata. Letters indicate significant difference between treatments (p < 0.05).
|
|
Fertilizer application significantly reduced pH by up to 0.7 of a unit in the 0- to 50-cm soil depth and by 0.3 of a unit in the O2 horizon (Table 5). Increasing rates of N application resulted in increasing reductions in pH, with (P)N4Y, (P)N2Y, and (P)N1Y reductions being significant compared with (P). Treatment P2YN2Y caused a significantly greater drop in pH than (P)N2Y (Table 5). At the highest rate, annual fertilizer application resulted in pH reduction from 3.8 to 3.4 units within the surface 0 to 10 cm. The reduction in pH resulting from annual application of fertilizer was greatest in the 20- to 50-cm layer, where the reduction averaged 0.9 units (Table 5). Declines in pH in the soil profile were linear with quantity of fertilizer applied.
Exchangeable Mg was significantly lower in the top 50 cm for all fertilizer treatments (Table 5). Higher rates of N application resulted in greater reductions in exchangeable Mg. Significant reductions were measured throughout the soil profile (Table 5). Nitrogen fertilization significantly reduced exchangeable Ca in the top 50 cm of soil by 50% compared with NIL and by 75% when compared with (P). The higher rate of N application resulted in a significant reduction of exchangeable Ca. Base saturation was also significantly reduced from fertilizing, by about 60% throughout the profile. No significant differences in total Ca, total Mg, or exchangeable K were found (Tables 5 and 6).
|
DISCUSSION
|
|---|
Growth Responses
The soil type on which the experiment was established has been defined as P deficient, and large growth increases have been obtained on this soil type from applications of P fertilizer (Neilsen et al., 1984). The constraint on growth from P deficiency, measured as low P concentration in the foliage before fertilizing at this site, was relieved with two single applications of P resulting in a three-fold increase in stem volume increment, compared with unfertilized trees. Single applications of P fertilizer have produced continued responses for many years in a number of forest crops (Ballard, 1978; Turner and Lambert, 1986).
Rates of N mineralization depend greatly on climate, and in cool-temperate forests these are low, sometimes <10 kg N ha–1 yr–1. Low rates of N mineralization mean that high growth rates could be achieved only through fertilization (Binkley and Hart, 1989; Jacobson and Pettersson, 2001). The site used for this research is not uncommon with low native soil nutrients. Such problems will become more common as soil organic matter declines with production above sustainable levels. Economic plantation growth cannot be sustained from native soil N alone. Large growth responses resulting from applied N fertilizer could be sustained by further fertilizer additions, recycling of N within the trees, or supply from mineralization of accumulated soil N (Neilsen et al., 1992). In this study, N application to a P. radiata plantation yearly, every second and every fourth year through 15 yr, resulted in improved growth increases that depended on the amount of N applied. Nitrogen application at the highest rate almost doubled the plantation production from 192 m3 ha–1 with P only to 344 m3 ha–1 on this site during the 15 yr of the research. This was in agreement with the large volume increase in P. radiata from annual and periodic N application observed in a number of field experiments (Raison et al., 1990; Neilsen and Lynch, 1998). The total growth showed lower fertilizer response efficiency with annual application compared with applications every second or fourth year. Once the P. radiata stand was carrying full canopy, applications every fourth year were sufficient to maintain growth. This 4-yr period has provided the opportunity to develop a viable fertilizing program. For economic return on investment in Tasmania, plantation growth in excess of 20 m3 ha–1 mean annual increment (MAI), and probably 25 m3 ha–1 MAI, are required. Many soils have low organic matter levels and meeting these growth rates requires fertilizer additions.
Changes in Nutrient Distribution within Soil and Litter Horizons
With fertilization the forest floor constitutes a large and significant source of mineralizable nutrients. The highest rate of N application significantly increased the total O2 horizon biomass, with N mass doubling within the O2 horizon. This was in agreement with work in a range of forest stands that have shown increased forest floor organic matter production and N mass due to N fertilization (Nohrstedt, 1990; Neilsen and Lynch, 1998). In P. radiata, Baker et al. (1986) reported a stand fertilized with a total of 960 kg N ha–1 over 10 yr, which had 15 Mg litter ha–1 (containing 210 kg N ha–1 and 18 kg P ha–1) compared with unfertilized plots with 6 Mg litter ha–1 (containing 57 kg N ha–1 and 12 kg P ha–1).
Soil Acidification
Large decreases in soil pH occurred after long-term N additions (as ammonium sulfate) with greater changes with increased applications. Results from studies on the effects of various types and rates of N fertilizers on soil pH have varied. Minor or no changes in pH have been observed in some long-term experiments, using multiple applications of either ammonium nitrate or urea at rates totaling over 1000 kg N ha–1 (Nohrstedt, 1990; Homann et al., 2001). Other studies, using the same fertilizers, have determined substantial reductions in pH, but only at rates of 74 kg N ha–1 yr–1 or more, or at lower rates if combined with P and K fertilizers (Tamm and Popovic, 1995). On similar soils to the P. radiata site, fertilizing with a total of 1346 kg N ha–1 through 12 yr, mainly as urea, did not significantly reduce pH (Neilsen et al., 1992).
Because of the fertilizers used here, single-superphosphate and ammonium sulfate, large amounts of S, up to 1.7 Mg ha–1, were applied to the plots and this was also likely to have contributed to acidification of the soils. Sulfur in acid rain is implicated in reducing soil pH and S has been used as a means of reducing pH in experiments in Europe, either as sulfuric acid or as elemental S (Tamm and Popovic, 1995). Soils differ in their ability to buffer added S (Binkley et al., 1988).
Changes in Magnesium and Calcium
Reductions in exchangeable Mg were significant and the decline was associated with pH changes within these soils. High rates of N application significantly reduced exchangeable Mg by about 50% throughout the profile. Deficiency of Mg has been identified for a range of Tasmanian soils (W.A. Neilsen, Forestry Tasmania, personal communication, 1999), and this needs to be addressed in conjunction with any proposals of increased production through fertilizer use or any regime maximizing volume production.
Many studies in Europe and Northern America have observed decreases in exchangeable Ca and Mg within the soil profile. Such losses in base cations associated with acid deposition and harvesting have been linked to declines in forest health and productivity (Watmough and Dillon, 2003). In this research, annual N applications decreased base saturation by one third throughout the entire profile.
|
CONCLUSIONS
|
|---|
On soils where available nutrients are limited Pinus radiata plantation productivity can be increased substantially through periodic fertilization. Nutritional management of plantations requires information on soil and site characteristics, and clear guidelines on where fertilizers are needed, when to apply them, what products to apply, and at what rates. The proposition to use fertilizers to lift the performance of plantations on soils of low productivity, as well as the productivity of many satisfactorily performing plantations, needs to be carefully monitored. Increased N retention within the tree, forest floor, and surface soils is important when considering the management of sites for further plantation establishment. Removal of the forest floor organic matter and any surface soil from clearing or burning could result in substantial reductions in the available nutrient pool.
The effects of fertilizers on soil pH are site-specific and varied but can be substantial and progressive. We observed a decline in pH that was linear with quantity of fertilizer applied. Substantial pH changes, of up to 0.7 units, within the soil profile pose serious long-term consequences for productivity. Further evaluation of types of fertilizer and rates of application used in forestry will be needed to select those that will have no impact or at least minimize change. Urea should have a lower impact on pH than ammonium sulfate or ammonium nitrate. Some forest soils are particularly vulnerable to change with initially low pH and low buffering capacity. The reasons for pH change also need to be better understood. Changes in soil organic matter and accumulation of organic material in the forest floor are likely to be involved in pH changes.
|
ACKNOWLEDGMENTS
|
|---|
The establishment, measurement, and analysis of the research experiment was funded by Forestry Tasmania. Wally Pataczek managed the research for many years with assistance from a number of field and research staff. The final analyses were supported by the Cooperative Research Centre for Sustainable Production Forestry CRCSPF and Rayonier Tasmania.
Received for publication December 19, 2003.
|
REFERENCES
|
|---|
- Adams, M.A., and P.M. Attiwill. 1983. Patterns of nitrogen mineralisation in 23-year old pine forests following N fertilising. For. Ecol. Manage. 7:241–248.
- Adams, M.A., and J.B. Martin. 1984. Liming effects on nitrogen use and efficiency. p. 417–426. In R.D. Hauck (ed.) Nitrogen in Crop Production. ASA, CSSA, and SSSA, Madison, WI.
- Baker, T.G., G.R. Oliver, and P.D. Hodgkiss. 1986. Distribution and cycling of nutrients in Pinus radiata as affected by past lupin growth and fertilizer. For. Ecol. Manage. 17:169–187.[CrossRef]
- Ballard, R. 1978. Effect of first rotation phosphorus applications on fertilizer requirements of second rotation radiata pine. N.Z. J. For. Sci. 8:135–145.
- Binkley, D., C.T. Driscoll, H.L. Allen, P. Schoeneberger, and D. McAvoy. 1988. Acidic deposition and forest soils. Springer-Verlag, New York.
- Binkley, D., and S.C. Hart. 1989. The components of nitrogen availability assessments in forest soils. Adv. Soil Sci. 10:55–112.
- Crane, W.J.B., and J.C.G. Banks. 1992. Accumulation and retranslocation of foliar nitrogen in fertilised and irrigated Pinus radiata. For. Ecol. Manage. 52:201–223.[CrossRef]
- Crow, T.R. 1971. Estimation of biomass in an even-aged stand-regression and ‘mean tree’ techniques. p. 35–48. In Working Group on Forest Biomass Studies. Section 25, Growth and Yield. International Union of Forest Research Organizations. XVth IUFRO Congress, 15–20 Mar. 1971. University of Florida, Gainesville, FL.
- Fisher, R.F., and D. Binkley. 2000. Ecology and management of forest soils. 3rd ed. John Wiley & Sons, New York.
- Genstat 5 Committee. 1988. Reference manual. Oxford Science Publication, Oxford.
- Gentle, S.W., F.R. Humphreys, and M.J. Lambert. 1965. An examination of a Pinus radiata phosphate fertilizer trial fifteen years after treatment. For. Sci. 11:315–324.
- Homann, P.S., B.A. Caldwell, H.N. Chappell, P. Sollins, and C.W. Swanston. 2001. Douglas-fir soil C and N properties a decade after termination of urea fertilization. Can. J. For. Res. 31:2225–2236.[CrossRef]
- Jacobson, S., and F. Pettersson. 2001. Growth responses following nitrogen and N-P-K-Mg additions to previously N-fertilized Scots pine and Norway spruce stands on mineral soils in Sweden. Can. J. For. Res. 31:899–909.[CrossRef]
- Johnson, D.W., N.T. Edwards, and D.E. Todd. 1980. Nitrogen mineralization, immobilization and nitrification following Urea fertilization of a forest soil under field and laboratory conditions. Soil Sci. Soc. Am. J. 44:610–616.[Abstract/Free Full Text]
- Khanna, P.K., R.J. Raison, R.A. Falkiner, I.R. Willett, and M.J. Connell. 1992. Effects of N P K fertilisation on the chemistry of a yellow podzolic soil under Pinus radiata. For. Ecol. Manage. 52:65–85.[CrossRef]
- Lowther, J.R. 1980. Use of single acid-hydrogen peroxide digest for analysis of Pinus radiata needles. Commun. Soil Sci. Plant Anal. 11:175–188.
- McDonald, R.C., R.F. Isbell, J.G. Speight, J. Walker, and M.S. Hopkins. 1990. Australian soil and land survey field handbook. Second ed. Inkata Press, Melbourne.
- Miller, H.G. 1981. Forest fertilization: Some guiding concepts. Forestry 54:157–168.[Abstract/Free Full Text]
- Murphy, J., and J.P. Riley. 1962. A modified single solution method for the determination of phosphate in natural waters. Anal. Chim. Acta 27:31–36.[CrossRef]
- Neilsen, W.A., G.R. Davis, J.G. McDavitt, and W. Pataczek. 1984. Growth and nutrient uptake of Pinus radiata seedlings over the first 3 years following treatment with nitrogen and phosphorus fertilizers. Aust. For. Res. 14:1–10.
- Neilsen, W.A., and T. Lynch. 1998. Implications of pre- and post-fertilizing changes in growth and nitrogen pools following multiple applications of nitrogen fertilizer to Pinus radiata stand over 12 years. Plant Soil 202:295–307.[CrossRef]
- Neilsen, W.A., W. Pataczek, T. Lynch, and R. Pyke. 1992. Growth response of Pinus radiata to multiple applications of nitrogen fertilizer and evaluation of the quality of added nitrogen remaining in the forest system. Plant Soil 144:207–217.[CrossRef]
- Nohrstedt, H.-O. 1990. Effects of repeated nitrogen fertilization with different doses on soil properties in a Pinus sylvesteris stand. Scand. J. For. Res. 5:3–15.
- Pritchett, W.L., and N.B. Comerford. 1982. Long-term response to phosphorus fertilization on selected southeastern coastal plain soils. Soil Sci. Soc. Am. J. 46:640–644.[Abstract/Free Full Text]
- Raison, R.J., P.K. Khanna, M.J. Connell, and R.A. Falkiner. 1990. Effects of water availability and fertilization on nitrogen cycling in a stand of Pinus radiata. For. Ecol. Manage. 30:31–43.
- Rayment, G.E., and F.R. Higginson. 1992. Australian Laboratory Handbook of soil and water chemical methods. Inkata Press, Melbourne.
- Reardon, J., J.A. Foreman, and R.L. Searcy. 1966. New reactants for the colorimetric determination of ammonia. Clin. Chim. Acta 14:403–405.[CrossRef]
- Switzer, G.L., and L.E. Nelson. 1972. Nutrient accumulation and cycling in lobby pine (pinus taeda L.) Plantation ecosystems: The first 20 years. Soil Sci. Soc. Am. Proc. 36:143–147.
- Tamm, C.O., and B. Popovic. 1995. Long-term field experiments simulating increased decomposition of sulfur and nitrogen to forest plots. Ecol. Bull. 44:301–321.
- Turner, J., and M.J. Lambert. 1986. Fate of applied nutrients in a long-term superphosphate trial in Pinus radiata. Plant Soil 93:373–382.[CrossRef]
- Watmough, S.A., and P.J. Dillon. 2003. Base cation and nitrogen budgets for seven forested catchments in central Ontario, 1983–1999. For. Ecol. Manage. 177:155–177.[CrossRef]
TOP
ABSTRACT
INTRODUCTION
