Forest Fertilization Research Articles

Long‐Term Effects of Forest Fertilization on Site Organic Matter and Nutrients

AbstractThe long‐term effects of time‐of‐planting fertilization on the accumulation and distribution of above‐ and belowground organic matter and nutrients are largely unknown for intensively managed southern pine (Pinus spp.) stands in the U.S. lower Coastal Plain. These effects were investigated using a 25‐yr‐old slash pine (P. elliottii Engelm. var. elliottii) plantation in north Florida. The experiment was conducted on a poorly drained, P‐deficient Rutlege soil (sandy, siliceous, thermic Typic Humaquept) using a randomized complete block design. The experimental treatments included: (i) control, (ii) NPK (112, 39, and 45 kg ha−1 using ordinary superphosphate [OSP] + N and K) and (iii) P (314 kg P ha−1 using ground rock phosphate [GRP]). Fertilization significantly increased total aboveground organic matter accumulation, with levels for the OSP + NK and GRP treatments being 2.5 and 1.8 times greater than the control, respectively. Levels of soil organic matter measured to a depth of 91 cm did not vary, however. Treatment effects were found for P, K, and Ca levels in the fertilized slash pine biomass components and surface soil. Long‐term differences in extractable soil P were most pronounced for the GRP treatment, with concentrations in the surface 15 cm being 2.6 times greater than the control; only the high P treatment sustained foliar P levels within the published critical range for slash pine. While field trials are required to confirm actual fertilizer carryover effects, results from this experiment suggest that sites previously fertilized with operational P rates (40–80 kg ha−1) will again require treatment when establishing the next pine rotation.

Impact of forest fertilizers on winter pastures of semi-domesticated reindeer

The effects of forest fertilizers on Calluna vulgaris, Vaccinium vitis-idaea, Cladina arbusculua, Cladina rangiferina and Cladina stellaris were studied during an eleven-year experimental period in Vasterbotten, Sweden. The study site was situated in the boreal region and was part of a 130 years old Pinus sylvestris stand. The forest type is mainly the dry dwarf-shrub type. Thirty-two demarcated plots (20 m x 20 m) were grouped into eight blocks, each containing four plots. In 1979 and 1985 fertilizations with ammonium nitrate equiavalent to 150 kg N/ha, with ammonium nitrate equiavalent to 250 kg N/ha and with urea equiavalent to 150 kg N/ha were carried out. Field sampling wad done in late July 1979, 1980, 1982, 1984, 1985, 1986, 1988 and 1990. Main parameters studied were coverage, height and standing crop. Effects were visible already after one growing season. All treatments had a positive effect on the growth of C. vulgaris and V. vitis-idaea. Doses around or over 150 kg N/ha, gave a clearly negative effect (range 23% - 73%) on the standing crop of Cladina spp. for a period of time exceeding eleven years compared to the control standing crop.

Microbial biomass P, labile P, and acid phosphatase activity in the humus layer of a spruce forest, after repeated additions of fertilizers

A 20-year-old forest fertilization trial was used to investigate the effects of repeated P additions on P availability in the humus layer of a Norway spruce forest soil. N was supplied annually, and P, K, and micronutrients were supplied every 4th year. The last P application was made 2 years before the investigation started. Microbial P concentrations in the P+NK+micro-amended plots were about half as high as those in the control and the N-only treatment. In plots without P amendments, around 50% of the total P in the humus layer was found in microorganisms, whereas in P-amended plots the figure was around 25%. The block supporting more rapid tree growth, situated on the middle of a slope, showed a significantly higher microbial biomass P concentration than the less productive block at the bottom of the slope. Labile P concentrations did not vary between treatments and thus could not have directly contributed to the treatment-related differences in total microbial biomass P. Acid phosphatase activities were around three times lower in the sites treated with P+NK+micro-nutrients. Two sources are suggested for the acid phosphatases, active excretion by living roots and fungi and passive release from ruptured cells. For all eight plots investigated, there was a positive correlation (R=0.83) between acid phosphatase activity and the microbial P concentration. The P concentration in current-year needles was the lowest in the N-only treatment at 1,13 mg g-1 dry weight, and the highest in the P+NK + micronutrients + lime treatment at 1.92 mg g-1 dry weight. The P:N ratio in needles varied from 0.115 in the P+NK + micronutrients + lime plots to 0.068 in the N-only plots. The latter value is at the level where P is considered to be the growth rate-determining nutrient.

Studies of 13C in the foliage reveal interactions between nutrients and water in forest fertilization experiments

Addition of N to an initially N-limited forest increases foliage biomass, demand for water and the probability of water stress. Effects of water and N on tree growth are thus compounded. The 13C abundance of plant tissues is directly correlated with water use efficiency (WUE), and could be used to disentangle the effect of water alone on carbon fixation. However, the 13C abundance may also be directly influenced by changes in rates of photosynthesis related to variations in N status, and by variations in N metabolism via non-RuBisCo carboxylations, and indirectly by effects of N source on WUE. We studied the 13C abundance of current needles from top whorls in two long-term fertilization experiments, one in Norway spruce (Picea abies Karst.) and one in Scots pine (Pinus sylvestris L.). As predicted, N fertilization increased foliage biomass and δ (‰). In the experiment with spruce this effect on 13C abundance was correlated with volume production and foliage biomass in a dry year, but was not seen in a wet year after 19 years of continuous annual N fertilization, which rules out the possible influences of N metabolism and changes in rates of photosynthesis. In the experiment with pine, which was at a drier site, needles from N-fertilized plots had a higher 13C abundance in three dry years, but not significantly so in a wet year. We suggest that effects of N source (NH4+ or NO3−) on 13C abundance are unlikely to be important under these experimental conditions. The balance between demand and supply of water should thus be the major determinant of the 13C abundance of current needles on top whorls. This opens possibilities to conduct retrospective studies of the role of water supply in fertilization experiments.

Effects on water chemistry, benthic invertebrates and brown trout following forest fertilization in Central Sweden

Two coniferous forest drainage areas in central Sweden were partially fertilized with ammonium nitrate and calcium ammonium nitrate respectively, both at a dose of 150 kg N ha‐1. During the following years observations were made on stream water chemistry, invertebrates and brown trout (Salmo trutta L.). Upstream stations were used as controls. Very high concentrations of inorganic N (up to 45 mg l‐1) were recorded immediately after the fertilization. Thereafter, concentration decreased rapidly but remained elevated during the whole study period. Acidity conditions (pH, alkalinity, aluminium) were unaffected by both treatments. The only registered effect on the benthic fauna was a three‐ to five‐fold increase of drifting invertebrates during the first four‐five days after the treatment. However, this did not reduce the population density at the treated stations. No effects on population of trout were recorded.

Plenary lecture: The use of iron and other trace element fertilizers in mitigating global warming

Abstract If current trends continue, before the end of the next century atmospheric CO2 levels will be about double those of a century ago. Other greenhouse gases, including methane and chlorofluorocarbons, also are increasing at similar or even higher rates. The effects of such global atmospheric changes on climate, and, thus, on agriculture, forestry and natural ecosystems, are uncertain. Only the results of the planetary “experiment”; itself will provide a definitive answer. Current projections range from catastrophic to favorable. Prudence suggests that steps be taken to slow down these rapid atmospheric changes, even in the absence of a definitive estimate of risks. Natural sinks for CO2 already account for the disappearance of as much as 60% of anthropogenic CO2 production due to fossil fuel combustion, deforestation, and soil organic carbon oxidation. Thus, current rates of increases in atmospheric CO2, about 0.4% per year, could be cut in half by reducing anthropogenic CO2 outputs by 20%, or increasing sinks by a similar amount. Such a reduction would significantly reduce the risks of major climatic changes. Programs to reduce greenhouse gas emissions are being instituted in Japan and Europe, but not in the U.S. or most other countries. Reduction of CO2 buildup must focus on the reduction of the major sources ‐fossil fuel usage, deforestation, soil carbon oxidation ‐ and on increasing sinks. The only practical methods for increasing CO2 sinks are based on photosynthesis, primarily through increased C storage in standing tree biomass, the use biomass as substitutes for fossil fuels, and, possibly, through the stimulation of ocean primary productivity by iron fertilization. Fertilizing forests and oceans with iron and other trace elements to increase primary productivity and CO2 sequestration is an attractive concept Application of small quantities of trace elements, could, in principle, result in the sequestration of many tons of CO2. Iron limits primary productivity in some ocean areas. How to practically fertilize the oceans with iron, the environmental impacts of such additions, and their effectiveness in reducing atmospheric CO2 concentrations are controversial issues. Long‐term studies of ocean fertilization will be required, and such schemes can not be included in current global warming mitigation options. Iron and other trace elements are often limiting factors in agriculture, and many reports exist of such limitations in managed forestry. However, it is presently unclear how widespread such deficiencies are in managed forests, and global effects on CO2 balances can not be projected. Fertilization with major nutrients ‐ P, K, and N ‐ is often effective in stimulating forest productivity and could be an economical approach to large‐scale CO2 sequestration. Increased forest fertilization with major nutrients will, in many cases, also require applications of some trace elements. In conclusion, forest fertilization with trace elements and even major nutrients could be an affordable and near‐term method of reducing future global warming.

Forest fertilization: Its potential to increase the CO2 storage capacity and to alleviate the decline of the global forests

Healthy forests are essential for life on earth. Their multiple benefits include sustainable production of wood and other products, soil protection, air and water purification, wildlife habitat, noise control, various types of recreation, but also climate regulation and CO2 storage. Owing to man-made influences, forests have been endangered since a long time. In various parts of the world these adverse impacts are now representing a risk for human life. For example, the still increasing destruction of tropical and subtropical forests leads to detrimental soil erosion problems and great losses of soil fertility including soil C. Furthermore, atmospheric pollution brought about forest declines in Europe, North America and elsewhere. In order to overcome these and related problems a variety of efforts have been established. In commercial forests of the temperate/boreal zones forest management practices including fertilization regimes focusing on sustainably increasing yields have been utilized for several centuries. However, new management strategies are under research and/or have been implemented in these forest ecosystems to mitigate the so called new types of forest damage. As these declines are frequently associated with nutritional disturbances fertilizer applications have proven useful when conducted properly. Agro-forestry is one approach to reduce the further deterioration of tropical/subtropical forests. Also rehabilitation of devastated land its partly concentrated on afforestation. With the ever increasing demands of a fast growing human population and increasing CO2 concentrations in the atmosphere, proper multi-purpose forestry on a permanent or short rotation basis or in the wide realm of agro-forestry is essential for mankind. In many cases adequate forest management will only be possible when soil fertility is restored and/or maintained through fertilization/manuring considering the demand of a specific forest stand/system under specific site conditions.

Nonpoint sources

Nonpoint sources

Variations in 15N abundance in a forest fertilization trial: Critical loads of N, N saturation, contamination and effects of revitalization fertilization

15N abundances of current needles of Norway spruce collected during 23 yrs of a forest fertilization experiment were studied in order to follow ecosystem gains and losses of N. Unlabelled ammonium nitrate at four rates (N0–N3), phosphorus at three rates (P0–P2), and potassium plus other elements including micronutrients at two rates (K0–K1), had been applied to plots in a complete factorial design. Nitrogen had been applied annually at average rates of 0, 34, 68 and 102 kg N ha-1 yr-1. Tree growth had responded positively to additions of N, but the response was remarkably more positive to the N2P2K1 treatment. In N1 treatments, δ15N (‰) declined over time. This was consistent with an earlier study, and should reflect a change in 15N abundance towards that of fertilizer N (minus discrimination during uptake), which in turn means accretion of most of the N added. As in the earlier study, in which N3 plots lost most of the N added, the present N3 plots showed an increasing δ15N (‰). This pattern was not significantly affected by additions of P and K plus other elements, although a weak negative effect of P on N accretion was indicated, i.e. there was a tendency δ15N (‰) to be higher when P was added. This, and another recent result based on an N budget, shows that so-called revitalization fertilization may well increase growth of trees, but also promotes losses of N from the ecosystem. As in the previous study, a decline in δ15N (‰) on control plots provided evidence of contamination. Given a removal of 100 kg N ha-1 at stem harvest and a leaching of 2 kg N ha-1 yr-1, our data on 15N suggest that a load of 9 kg N ha-1 yr-1 would saturate the ecosystem after 100 years. This load is only about twice the annual deposition at the site.

Morphology, Incidence and Fertilization Effects on the Vesicular-Arbuscular Mycorrhizae of Acer Saccharum in a Quebec Hardwood Forest

The condition and incidence of vesicular-arbuscular mycorrhizae of Acer saccharum (sugar maple) in a natural hardwood forest in the Lower Laurentians of Quebec was examined. The effects of forest fertilization on the mycorrhizae were also studied. Microscopic examination revealed VAM structures which included hyphal coils, vesicles, and arbuscules. Vesicles and hyphal coils were the most frequently observed structures, whereas arbuscules were rarely seen. Seasonal differences in the incidence of vesicular-arbuscular mycorrhizae were observed but these differences were not consistent from year to year. Generally, infection rates were lowest in mid-summer. Fertilization of forest soil with a base cation mixture did not appear to affect either the condition or the incidence of VAM.

Effects of fertilizer on bryophytes in Swedish experiments on forest fertilization

Swedish experiments on the optimal fertilization for forests were used to study the effects of ammonium nitrate, urea, and a compound PK fertilizer on bryophytes. The experiments were analysed with ANOVA. The abundance of Brachythecium oedipodium, B. reflexum, and B. starkei was significantly raised by addition of ammonium nitrate or urea. However, at doses larger than 60 kg N/ha/year these species tended to decline. Hylocomium splenders and Pleurozium schreberi declined strongly at nitrogen doses of 30–60 kg N/ha/year. We could not confirm that bryophytes and lichens are more sensitive to urea than to ammonium nitrate. Addition of PK, whether alone or combined with ammonium nitrate or urea, has minor but significant effects upon bryophytes, additional to those of nitrogen. The results support the hypothesis that some recent changes in the composition of the herb and bryophyte layer of W European forests are caused by raised levels of soil N.

Dynamics of soil nitrate after forest fertilization as monitored by the plant nitrate reductase assay

Nitrate reductase activity (NRA) of the grass Deschampsia flexuosa (L.) Trin., was used to monitor avialable soil nitrate after fertilization of coniferous forests in northern Sweden with ammonium nitrate or urea (300 or 150 kg N ha −1). Small plots (9 m 2), at three sites of different quality class, were followed for 2–3 years. The poorest site is a groundwater recharge area, whereas discharges occur temporarily at the intermediate site and frequently at the richest site; these variations in transport of solutes explain the differences in productivity. Applications of ammonium nitrate gave, as expected, rapid and substantial increases in NRA. In the case of urea, slow and small increases in NRA indicated that nitrification took place. Treatment with ammonium chloride at the poorest site (pH 4.0) produced an increase in NRA similar to that given by urea application. On ammonium nitrate treated plots in discharge areas, there was a decline from peak NRA to levels near those of the controls within 2 weeks, in connection with a period of rainfall and high groundwater level. On plots treated with ammonium nitrate in the recharge area, soil nitrate remained at a high level throughout the first growing period. We suggest that leaching of nitrate may be a common phenomenon in discharge areas. We further suggest that 15N fertilizer budgets, which have been conducted only in recharge areas, should also be carried out at sites with discharge.

EFFECTS OF FOREST FERTILIZATION ON STREAM WATER CHEMISTRY IN THE APPALACHIANS1

ABSTRACT: Stream water chemistry was monitored on two watersheds on the Fernow Experimental Forest in north‐central West Virginia to determine the effects of forest fertilization on annual nutrient exports. Ammonium nitrate and triple superphosphate were applied simultaneously at rates of 336 kg ha−1 N and 224 kg ha−1 P2O5, respectively, which are similar to rates used in commercial forest operations. The treatment significantly increased outputs of several ions. Annual outputs of nitrate N increased as much as 18 times over pretreatment levels, and calcium and magnesium increased as much as three times over pretreatment levels the first year after fertilization. Outputs for these nutrients were elevated for all three post‐treatment years. Although nitrate N increased significantly, only about 20 percent of the applied fertilizer was accounted for in stream water exports. Outputs of phosphate P declined following fertilization, probably because the watersheds are phosphorus deficient, but by the third year, they slightly exceeded predicted values. Estimated nutrient losses to deep seepage were substantial, especially on the leakier south‐facing catchmeat, on which some nutrient losses were equal to or greater than those in stream water. When the nutrient exports associated with both stream discharge and ground water recharge were combined, the percentages of applied N that were lost were similar on the two watersheds, averaging 27.5 percent. Less than 1 percent of the applied P was lost from either watershed in the combination of streamflow and deep seepage.

Estimating Annual Increment Response to Forest Fertilization: A Comparison of Methods by Uniformity Trials

Abstract Several estimators of annual basal area increment response to forest fertilization are compared using mean square error. Estimates of mean square error are obtained through uniformity trials. The unadjusted response estimator, that is, the annual basal area increment difference between the treated and the control plots, has an annual root mean square error of approximately 0.1 m²/ha. The other estimators use pretreatment increment difference to improve the response estimate. The easily calculated constant and ratio estimators are satisfactory, with root mean square errors of approximately 0.04 m²/ha initially, rising to about 0.1 m²/ha about 20 years after the pretreatment period. Estimators using time series, covariance, or regression adjustment do not improve upon this. The data has its origin from a broad set of fertilization field trials on Pinus sylvestris L. and Picea abies L. Karst. in the southeast of Norway. For. Sci. 37(1):123-135.

Results and experiences from fertilization experiments in The Netherlands

Forest fertilization in the Netherlands has played an important role in the phase of afforestation of former heathlands. Research started in the early fifties, but results were not applied in practical forestry. A review is presented on forest fertilization in practice, and on the main results of the activities of De Dorschkamp on NPK fertilization, liming and micronutrients application. Attention is paid to problems which have developed during the past ten years.

Forest fertilization research and practice in the Pacific Northwest

Forest managers in the Pacific Northwest (PNW) use fertilization as a means to increase timber yields in managed stands. Information on the biological basis for nutrient amendments and stand growth responses to fertilization is required to effectively use fertilization as a silvicultural tool, and research programs in mineral cycling and forest nutrition have been underway in the region for about four decades. Most PNW Douglas-fir forest sites are nitrogen deficient. Mineral cycling research has shown high C/N ratios and low nitrification rates for soils in the region. Research and development projects in the Pacific Northwest have produced an information base that is used to select sites and stands for fertilization and to forecast growth after treatment. Much of the basis for operational fertilization programs in western Oregon and Washington comes from cooperative research programs; current activities for these programs are directed toward improving site-specific response information. Forest fertilization in the Pacific Northwest has become a silvicultural practice of major significance over the past two decades. Forest industry and government organizations managing forest lands in western Oregon and Washington apply nitrogen fertilizer to Douglas-fir stands over a range of soil and stand types (operational fertilization of other species is minor). About 50,000 to 55,000 ha are fertilized each year, and future programs will likely be of similar magnitude. Most current plans for management regimes including fertilization call for multiple applications.

Forest fertilization ? present state and history with special reference to South German conditions

Until well into the eighteenth century, forestry was largely confined to the poorer soils and sites too difficult for farming properly and ravaged by destructive lumbering, burning and grazing. Up to the mid-20th century there was much extraction of litter. All this resulted in nutrient impoverishment which persists to the present day. There has been some improvement through corrective fertilization. Such treatment over the past 30 years brought about yield improvement of around 3 m3/ha/year compared to untreated areas. This, no doubt, was largely because of the former widespread deficiencies of nitrogen and phosphate and weathering under high rainfall during the course of the experiments. Returns from fertilizer were very variable and such large improvements were not always the rule. Whether such results are still obtainable today when growth performance in many areas is so much improved or under different climatic conditions may be doubtful.

Assessment of the ecological effects of forest fertilization using an experimental watershed approach

In the research project ARINUS, the effects of restabilization measures (fertilization with readily soluble MgSO4) on the element cycling of Norway spruce ecosystems in the Black Forest (SW Germany) are studied. The objective is to quantify the natural and anthropogenic components of element cycling. Interrelations between the terrestrial and aquatic subsystem are assessed using an integrated approach which combines flux measurements in representative plots with input/output balances of small experimental watersheds. The paper discusses the initial effects of a whole-watershed treatment with Kieserite (750 kg ha−1 MgSO4 · H2O) based on the Mg and S cycling in the control watershed. With the fertilizer, 130 kg ha−1 Mg and 170 kg ha−1 S were introduced into the system. Fertilization resulted in increased levels of Mg and S in the needles. Despite high inorganic Al concentrations and extremely low Ca/Al ratios in soil solution, there was no evidence for ‘Al toxicity’. Since fertilizer losses from the system 1 1/2 years (2 growing seasons) after the treatment have been modest, surface water was hardly been affected. More than 75% of the applied Mg has remained in the ecosystem, primarily in the intensively rooted upper soil layer. Also S has been retained to a considerable extent. The mobility of fertilizer sulfate in acidic forest soils is substantially lower than has been hitherto assumed from laboratory experiments. Therefore, fertilization with readily soluble sulfate-based Mg fertilizers is recommended as an efficient and — in comparison to liming — less risky restabilization measure on sites with a high potential for nitrification.

PREDICTING UREA HYDROLYSIS AT LOW TEMPERATURES IN BRITISH COLUMBIA FOREST SOILS

Urease activity in 14 sites, representing a wide range of forest and soil types, was determined by a non-buffer method. Urease activity in L-H horizons ranged from 23–203 μg N hydrolyzed (g soil)−1 h−1 at 40 °C. In all soils, urease activity decreased dramatically with depth. At 0 °C, hydrolysis was estimated at 26.8 and 1.9 μg N g−1 h−1 for L-H and Bf horizons, respectively, for one site. Theoretical estimation of hydrolysis at 0 °C for the site with the lowest activity suggested that an operational application of urea (200 kg N ha−1) applied to snow could be hydrolyzed within 6 days in the rooting zone of all the soils studied. Key words: Urease activity, energy of activation, forest fertilization, Brunisols, Luvisols, Podzols

Optimizing the process of forest fertilization as a control system

We propose a new method for determining optimal fertilization strategies for tree plantations. The method is based on principles of Control Theory and basically consists in evaluating approximately the equations governing the dynamics of the system fertilizer-tree, and then applying optimization techniques adapted to additive cost functions. We describe the procedure as used in a real experiment withEucalyptus rostrata.