Fertilization

Some forests grow where important nutrients limit tree growth. Fertilizing forests with those nutrients is a proven method to increase tree growth, resulting in greater stand volume, greater carbon storage and reduced harvest ages. Understanding where nutrient deficiencies occur and how trees respond is an important focus of fertilization research.

Responses of Western Hemlock, Western Redcedar, and Amabilis Fir to Fertilization - TR123

In British Columbia, three tree species—western hemlock (Tsuga heterophylla (Raf.) Sarg.), western redcedar (Thuja plicata Donn ex D. Don), and amabilis fir (Abies amabilis Dougl. ex Forbes)—dominate coastal forests. With concerns about the long-term supply of timber from coastal forests, attention has been focussed on management and productivity of regenerating natural stands and plantations. The British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development (FLNRORD) has been investing in fertilization as a strategy for increasing rates of growth and stand development in regenerating forests. This report synthesizes published data and analyzes responses by western hemlock, western redcedar, and amabilis fir to various fertilization applications in coastal British Columbia and northern Washington State. The results improve understanding of growth response to fertilizer applications and identify key information needs for current and future forest fertilization investments under two FLNRORD programs: Forests for Tomorrow (FFT) and Forest Carbon Initiative (FCI).  

Tree Damage after Fertilization of Thinned Lodgepole Pine, Douglas-fir, and Spruce Stands in the British Columbia Interior - TR120

As a silvicultural practice, forest fertilization has emerged to mitigate risks and reduce the effect of damage agents on timber supply due to climate change and on subsequent extensive landscape-scale natural disturbances in British Columbia. In total, 61 installations were established in the central and southern interior of British Columbia to quantify fertilization responses of major commercial tree species. One-time fertilization with two to five kinds of fertilizer blends was applied, and the stand ages at fertilization ranged from 9 to 58 years. Plots were repeatedly measured at 3-year intervals, although a few plots were measured 2–4 years after fertilization. The repeated measurements (up to 18 years after fertilization) indicated that trees were damaged by various damage agents in the experimental sites, and that the fertilization may have been associated with the damage agents’ activities. This report provides a descriptive overview of the damage that occurred after fertilization in the EP886 installations.

A Systematic Review of Forest Fertilization Research in Interior British Columbia - TR111

The Forests for Tomorrow (FFT) Program is investing in fertilization as a mitigation strategy to address mid-term timber supply disruptions in the interior of British Columbia due to the mountain pine beetle outbreak. Forest fertilization has been shown to increase tree growth, accelerate stand development, and shorten rotation ages, but the response to fertilization varies with species, and site and stand conditions. The FFT Program relies on the results of fertilization research conducted over 30 years by the B.C. Ministry of Forests, Lands and Natural Resource Operations for decision-making regarding operational fertilization. As FFT considers the expansion of the fertilization program, a review of research results to date was needed to identify knowledge gaps and information needs. As a result, a systematic review of existing published information was conducted on the growth response of interior tree species—lodgepole pine (Pinus contorta var. latifolia Engelm), interior spruce (Picea glauca [Moench] Voss, Picea engelmannii Parry ex Engelm, and their hybrids), and Douglas-fir (Pseudotsuga menziesii)—to fertilization in relation to fertilization type and amount, damaging agents, stand density, site quality, and stand age at fertilization.

Conifer and Vegetation Responses to Pre-planting Applications of Glyphosate and Hexazinone on a Boreal Backlog Site - TR87

We examined conifer and vegetation responses to pre-planting applications of glyphosate and hexazinone 30 years after establishment on a boreal site with a history of logging and wildfire. The chemical treatments were effective in assisting the establishment of white spruce as a dominant tree in the mixed-species stands that have developed. Only 100 stems per hectare of spruce were present in the aspen-dominated stand where no spruce planting or other treatment had been conducted post-wildfire. Broadleaf trees were 19%, 24%, and 99% of the stand basal area in the glyphosate treated, hexazinone treated, and untreated areas, respectively. The untreated area was following a successional development trajectory typical of shade-intolerant tree species.

Assessing the Fertilization Response Potential of Subalpine Fir (Abies lasiocarpa): A Retrospective Study - EN93

Pre- and post-fertilization tree growth in unfertilized and fertilized thinned stands was used to estimate the 7-year radial growth response of operationally fertilized subalpine fir (Abies lasiocarpa). Despite large stem growth variability in thinned, and thinned and fertilized stands, the 7-year growth increment of fertilized trees was apparently 51–57% larger than the estimated growth that would have occurred had the stand not been fertilized. These results are consistent with the favourable fertilization responses reported for other Abies species. Reliable growth and yield data from well-designed fertilizer experiments are needed to provide a stronger basis for statistical inference of fertilization response and to provide area-based growth response estimates for subalpine fir. In the interim, however, some operational fertilization of subalpine fir may be justified, especially in vigorous, well-spaced (i.e., not overly dense) immature stands with a moderate component of nutrient-deficient interior spruce.

Effects of Intensive Fertilization on the Foliar Nutrition and Growth of Young Lodgepole Pine Forests in the British Columbia Interior - TR58

The effects of different regimes and frequencies of repeated fertilization on the foliar nutrition and growth of young lodgepole pine were investigated at five locations in central British Columbia. When applied at 6-year intervals to 9- to 15-year-old stands, two applications of nitrogen (totalling 400 kg N/ha), with and without other added nutrients, produced 12-year relative stand volume increments that were 7-36% higher than control values. In absolute terms, fertilized stand volume gains ranged from 8.5 to 17.2 m³/ha over 12 years. Yearly applications of N and other nutrients produced variable results, with 12-year relative stand volume increments ranging from 16% lower (-19.5 m³/ha) to 60% higher (22.8 m³/ha) than control values. Poor radial and height increment in some intensively fertilized treatment plots was typically associated with foliar nutrient imbalances (e.g., N/Cu, N/Mg) and lower growth efficiency (i.e., wood production per unit of leaf area). Overall, the 12-year results indicate that yearly nutrient additions are relatively ineffective and inefficient in stimulating the growth of young lodgepole pine. However, periodic application of balanced fertilizers to healthy, nutrient-deficient stands may be a viable strategy for increasing fibre yield, reducing rotation length, and sequestering carbon in managed lodgepole pine forests.

Effects of Repeated Fertilization on Forest Floor and Mineral Soil Properties in Young Lodgepole Pine and Spruce Forests in Central British Columbia - TR52

The 12-year effects of different regimes and frequencies of repeated fertilization (applied periodically and yearly) on forest floor and mineral soil properties were evaluated at two study sites in central British Columbia. When applied at 6-year intervals to 10- to 12-year-old lodgepole pine and spruce plantations, two applications of urea (totalling 400 kg N/ha), with and without other added nutrients, had few measurable effects on forest floor or mineral soil properties 12 years after initial fertilization. Conversely, 12 years of annual nutrient additions (775-1600 kg N/ha in total) had significant effects on several forest floor and mineral soil properties, but the effects were different at the two study sites. At Crow Creek, yearly fertilization of spruce resulted in larger forest floor mass, lower carbon/nitrogen ratio, lower ph, higher mineralizable nitrogen (N), and larger pools of total N, carbon (C), and sulphur (S) in the forest floor and mineral soil. Pools of forest floor total phosphorus (P) and potassium (K) were larger in annually fertilized plots than in control plots after 12 years. Extractable P, N, and S, and exchangeable K and magnesium (Mg) levels were also higher in intensively fertilized forest floors and mineral soils at Crow Creek. These results indicate that large and frequent nutrient additions may increase the rate of N cycling and site quality and may also promote above- and below-ground C sequestration.

Effects of Repeated Fertilization on Fine Roots, Mycorrhizae, and Soil Mesofauna in Young Lodgepole Pine and Spruce Forests in Central British Columbia - EN84

The 10-year effects of different regimes of repeated fertilization on fine roots, mycorrhizae, and soil mesofauna were evaluated in young stands of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) and interior spruce (Picea glauca [Moench] Voss, Picea engelmannii Parry, and their naturally occurring hybrids) in central British Columbia. Fine root attributes and mesofauna responded differently to repeated fertilization regimes at the pine and spruce study sites. The length and vigour of lodgepole pine fine roots, the abundance of active roots, and the percent mycorrhizal colonization decreased with fertilization, especially in the most intensive fertilization regime. In contrast, the fine roots of fertilized interior spruce increased in length and the relative abundance of active and mycorrhizal roots was unaffected by treatment. Repeated fertilization of lodgepole pine altered mycorrhizal community structure and reduced species richness (number of species) and diversity (evenness). 

Assessing the Effects of Fertilization on Understorey Vegetation in Young Lodgepole Pine and Spruce Forests in Central British Columbia - EN81

The 6-year effects of different regimes of single and repeated nutrient additions on the amount, richness, and diversity of understorey vegetation were evaluated in young stands of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) and interior spruce (Picea glauca [Moench] Voss, Picea engelmannii Parry, and their naturally occurring hybrids) in central British Columbia. At both sites, a single, multi-nutrient fertilization had relatively small effects on total understorey biomass after 6 years, whereas the effects of repeated fertilization on total biomass were much larger and statistically significant. The amount and relative abundance of shrubs and herbs commonly associated with nitrogen-rich soils (fireweed, aster, prickly rose, currant, raspberry) increased following fertilization, especially when nutrients were applied repeatedly. Conversely, indicators of nitrogen-poor soils (bunchberry, huckleberry, kinnikinnick) generally declined in abundance following single and repeated fertilization.

Comparing the Effects of Urea and Ammonium Nitrate Fertilizers on the Growth and Foliar Nutrition of Lodgepole Pine: 6-year Results - EN78

The 6-year effects of urea (46-0-0) and ammonium nitrate (AN; 34-0-0) fertilizers, applied alone and in combination with other nutrients, on tree growth and foliar nutrition were evaluated in a 22-year-old, thinned lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stand in central British Columbia. Results indicate that lodgepole pine has no clear preference for a particular nitrogen (N) source, when applied alone or combined with other potential growth-limiting nutrients. Results also indicate that N-deficient lodgepole pine may not respond favourably to N fertilization unless other nutrients are combined with N in the fertilizer prescription. When applied alone, fall-applied AN and urea were relatively ineffective in stimulating tree growth at this site, apparently due to induced deficiencies of other nutrients (especially sulfur). Foliar nutrient status and growth were significantly improved by including a complete fertilizer with both N sources. 

Sulphur Fertilization of Lodgepole Pine: A Stable Isotope Tracer Study - TR20

Widespread sulphur (S) deficiencies have been detected in lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stands in the Sub-Boreal Spruce biogeoclimatic zone of central interior British Columbia. Field experiments in this region have shown that addition of sulphate-S to nitrogen (N) fertilization treatments rapidly increases foliar S concentrations, and usually improves tree growth responses relative to N-only treatments. However, there is an insufficient scientific basis for choosing this S form over more slowly available elemental S-based fertilizers.

To address this knowledge gap, this study was begun in 200? to compare the behaviour of sulphate-S and elemental-S fertilizers in an area-based fertilizer trial, using stable isotope tracer methods to examine the fate and transformations of fertilizer S. Fertilizer treatments were applied to two lodgepole pine stands, near Fraser Lake (Holy Cross site) and in the Bowron River valley (Kenneth Creek site), in fall 2002. This establishment report reviews background literature relevant to this study, details the experimental design and methods used, and documents the initial soil and stand conditions at the time the experimental treatments were installed.

Sulphur Deficiencies in Lodgepole Pine: Occurrence, Diagnosis, and Treatment - EN71

Sulphur (S) deficiencies are widespread in lodgepole pine stands in the British Columbia central interior. Low soil S availability can limit tree growth responses to nitrogen (N) fertilization. Refined diagnostic criteria and decision-making tools enable more reliable identification of stands that will respond to inclusion of S in fertilizer prescriptions. Most research and large-scale aerial fertilizer operations have used soluble sulphate-S sources, but evidence is accumulating that elemental-S provides equally satisfactory long-term amelioration of S deficiencies. New research is using stable isotope tracer methods to improve understanding of the fate and transformations of S fertilizers. For sites where fertilization may not be feasible, soil conservation is particularly important for preventing further losses of limited S.

Effects of Intensive Fertilization on the Foliar Nutrition and Growth of Young Lodgepole Pine and Spruce Forests in the Interior of British Columbia - TR18

The preliminary effects of different regimes and frequencies of repeated fertilization on foliar nutrition and growth of eight young lodgepole pine and interior spruce forests in north-central British Columbia are reported. At least 6 years of growth measurements have been obtained from seven of the eight "maximum productivity" installations. These results indicate that the repeated fertilization of young managed forests may be a potentially viable strategy for addressing timber supply challenges in the interior of British Columbia. Young spruce plantations are apparently particularly well suited to intensive forest management. Although four of the five lodgepole pine installations have produced significant growth gains following periodic (every 6 years) and yearly fertilization, the responses to date have been more variable and consistently smaller than those obtained at the spruce study sites.

Influences of Clearcut Harvesting and Fertilization on Structure and Function of the Soil Food Web in ICH Forests in Southern B.C. - EN59

This Extension Note is intended for foresters and managers interested in the potential effects of fertilization and clearcutting on soil ecosystem processes in ICH forests. It may also be of interest to researchers interested in links between N cycling and the composition of the soil biota, forest certifiers interested in sustainability indicators for forest practices, and the general public interested in the biology of ICH forests. The information gained in this study should be helpful for management of wet-belt forests in a manner that sustains both soil and forest productivity.

Ten-year Responses of White Spruce and Associated Vegetation after Glyphosate Treatment at Tsilcoh River - EN55

To establish a stand of desirable trees successfully, vegetation management is usually needed as part of site preparation or during the first few years after regeneration, especially when the vegetation competition is very intense. In 1988, an operational trial was established in a one-year-old white spruce (Picea glauca) plantation in the SBSdw3 biogeoclimatic zone to examine the effectiveness of glyphosate herbicide on a vegetation community. The study consists of two 1 ha treatment plots, one of which was treated with aerially applied glyphosate at a rate of 2.14 kg a.i./ha. Ten years after treatment, glyphosate had significantly increased height, basal diameter and crown radius, and reduced height-to-basal diameter ratio. The herbicide treatment did not result in more free-growing spruce trees per hectare 11 years after planting because aspen patch was present in portion of the treated plot and further assessment may be needed as the trees are still in free growing window. Glyphosate had no significant affect on plant species diversity.

Douglas-fir Fertilization with Biosolids: Five-year Results at Whistler, B.C. - EN50

Biosolids at 750, 1000 and 1500kgn/ha and conventional fertilizer at 225 kg-n/ha were applied in each of three seasons (spring, summer, and fall) to a 15-year-old coastal Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plantation that had recently been pre-commercially thinned and pruned. Five-year results showed that rate and timing effects were independent. No height-growth response was evident, but annual diameter growth for all biosolids treatments averaged three times higher than for conventional fertilizer. Seasonal application differences were small but statistically significant. All plots, including the controls, experienced extensive top damage from snow and ice. Similar to growth, damage was greatest with biosolids fertilization. The study shows promise for biosolids fertilization as a viable alternative to conventional fertilization, but application in locations prone to snow and ice damage should be avoided.

Ten-year Conifer and Vegetation Responses to Glyphosate Treatment in the SBSdw3 - EN48

In forestry, vegetation management treatments are widely used to enhance establishment of young stands and achieve free growing requirements. In 1988, an operational herbicide monitoring trial was established in a 1-year-old white spruce (Picea glauca) plantation in the SBSdw3 biogeoclimatic zone to examine the effectiveness of glyphosate herbicide on a vegetation community. The study consists of two 1 ha treatment plots, one of which was treated with aerially applied glyphosate at a rate of 2.14 kg a.i./ha. Ten years after treatment, glyphosate had increased height and basal diameter, reduced height-to-diameter ratio, and improved vigour of white spruce. Eleven years after planting, the glyphosate treated plot had significantly greater number of free growing spruce per ha, and significantly less percent cover and density of broadleaves than the untreated control plot. However, the treatment did not affect the plant species richness. Yield projections for white spruce an trembling aspen based on MGM suggest that treatment applied to control broadleaves and shrubs has the potential to increase conifer yield and reduce conifer rotation age.

Using Foliar Nutrient Levels to Predict Lodgepole Pine Fertilization Response - EN44

ix-year basal area responses to nitrogen fertilizer, either alone or in combination with sulphur, were compared with pre-treatment measures of foliar nitrogen and sulphur in 31 lodgepole pine stands in the Interior of British Columbia. Results from this analysis indicate that pre-fertilization levels of foliar nitrogen, sulphur, and inorganic sulphate-sulphur are useful for predicting whether lodgepole pine will respond significantly to fertilization with either nitrogen alone or a combination of nitrogen and sulphur, and for estimating the magnitude of the expected responses. By using these tools, the chances of making the appropriate fertilizer prescription may be significantly improved.

First-year Growth Responses of Young Red Alder Stands to Fertilization - EN36

Red alder (Alnus rubra Bong.) is the most abundant deciduous broad-leaved tree species in coastal British Columbia. It is a source of products ranging from firewood to furniture, cabinets, and turned-wood novelties (Plank and Willits 1994). In addition, red alder seedlings are planted to restore roads and landings, to stabilize slides, and to reduce laminated root rot (Phellinus weirii) on infected sites. Understanding how to maximize the growth and quality of red alder is important, because more is being planted and harvested in British Columbia. Historically, red alder was unwanted in the Pacific Northwest. In recent years, however, increasing demand for red alder has led to localized shortages in Oregon and Washington (Raettig et al. 1995). In British Columbia, volumes harvested on Crown land have averaged 228 000 m 3 per year from 1994 through 1998. Meanwhile, the number of red alder seedlings produced for planting on Crown and private land increased from a yearly average of about 14 000 from 1994 to 1996 to a yearly average of 251 000 from 1997 to 1999. Silvical characteristics that make alder an appealing species to grow include (1) juvenile growth rates that greatly exceed those of associated conifers on optimal sites, (2) immunity to laminated root rot, and (3) the ability to fix atmospheric nitrogen, in symbiotic association with the soil actinomycete Frankia sp. The ability to fix nitrogen is unique among native trees in British Columbia.