Forest Fertilization Research Articles

Spruce and pine utilization of phosphorus in soil amended with 33P‐labelled hydroxylapatite

AbstractMined rock phosphate is expected to become a scarce resource within the next few decades as global phosphorus (P) deposits are declining. As a result, mineral P fertilizer will be less available and more expensive. Therefore, improved knowledge is needed on other P resources, for example, apatite fertilizers derived from the by‐products of iron mining. Forestry is a potential future consumer of apatite‐rich products with the aim of obtaining more wood per hectare. The actual P availability in apatite to plants has so far been barely quantified. We therefore examined tree P uptake using 33P apatite under chamber‐grown and outdoor conditions. We examined the P uptake for the two main conifer species spruce (Picea abies) and pine (Pinus sylvestris) used in Fenno‐Scandinavian forestry. We synthesized 33P‐enriched apatite and applied it to mesocosms with growing seedlings of spruce and pine. The P uptake from 33P‐labelled hydroxylapatite was subsequently traced by (bio)imaging of radioactivity in the plants and by liquid scintillation counting (LSC) upon destructive harvest in all plant fractions (leaves, stem and roots) and rhizosphere soil. Two climatic conditions were compared, one at natural outdoor conditions and one set as 5°C warmer than the climate record from the previous years. Plant P uptake from 33P‐labelled hydroxylapatite was enhanced in chamber‐grown compared with outdoor seedlings for both tree species. This uptake was manifested in the clear radioactive images obtained over ca. 1 month after soil apatite application. Furthermore, all aboveground plant fractions of both spruce and pine seedlings showed a higher P uptake in warmer than colder daytime environments. The observed quantities and rates of P uptake from 33P‐labelled hydroxylapatite by spruce (18 Bq g−1 hour−1) and pine (83 Bq g−1 hour−1; averages in chamber condition) are as to our knowledge unique observations. Natural forest soils in Sweden are often P‐poor. Our research suggests that apatite‐based P fertilization of spruce and pine forests can increase wood production by overcoming any existing P limitation.

Assessing the impacts of experimental mid-rotation forest fertiliser treatments on water quality

Assessing the impacts of experimental mid-rotation forest fertiliser treatments on water quality

Soil-based assessment of site productivity for southern pine plantations in the coastal plain of the southeastern US: (II) slash pine

Non-industrial private forest landowners and foresters often rely on outdated site index models for forest productivity predictions, which hinders accurate assessment. To address this issue, 157 slash pine plots were established in the coastal plain of Georgia, USA, to collect tree and soil data. Using regression tree and linear regression models, we identified modified Cooperative Research in Forest Fertilization soil groups and surface soil extractable phosphorus as significant predictors of site index. The optimal regression tree model (R2 = 0.490, RMSE = 1.72 m) outperformed the linear regression model. Updated site index and simulated mean annual increments for slash pine were compared with long-term experimental study data, as well as with previous findings for loblolly pine in the same region (Zhao et al., 2024a). The new predictive models will help non-industrial private forest landowners evaluate slash pine productivity in the Coastal Plain region, applicable across diverse sites.

Soil-based assessment of site productivity for southern pine plantations in the coastal plain of the southeastern US: (I) loblolly pine

Site productivity and forest management strategies hinge on intrinsic site resources such as soil water and nutrient availability. In this study, regression tree model and linear regression model approaches were employed to quantify the relationship between site index and soil parameters for loblolly pine plantations in the Coastal Plain. Both the optimal regression tree model and the final linear regression model identified modified CRIFF (Cooperative Research in Forest Fertilization) soil groups and surface soil extractable phosphorus (Mehlich 1 P) as significant variables for predicting site index. The final linear regression model, with a R2 of 0.899 and an RMSE of 1.12 m, exhibited superior performance compared to the optimal regression tree model. Additionally, mean annual increments in stand volume and green weight for each soil group were simulated and compared with data from a long-term loblolly pine culture/density experimental study in the same region. These resulting predictive models offer applicability across diverse sites and are particularly well-suited for areas where forest stands are not currently established.

Impact of long-term application of biosolids to surface water nitrogen in a working forest plantation in King County, Washington

Forest fertilization with municipal biosolids has been shown to increase tree growth and enhance forest soils. However, there are concerns that nitrogen from the biosolids could impact surface waters through movement from subsurface flow. Here we analyzed data on soil and surface water nitrogen from a working tree plantation that has used biosolids for over three decades to see if there was evidence of N movement through the soil to surface waters. GIS (Geographic Information System) was used to map application units over time and LiDAR (Light Detection and Ranging) was used to delineate watersheds. The program is located in King County Washington with biosolids provided by the King County Wastewater Treatment program. We assembled records to determine if there is any evidence of movement of NO3− through soils or any enrichment in surface waters. While soils show evidence of NO3− enrichment following biosolids application with cumulative loading rates up to 26 Mg ha−1, this is generally limited to the ’A’ soil horizon and does not increase linearly with increased biosolids loading rates. There was no indication of increased surface water NO3− concentration relative to biosolids application rates, with a small trend of decreasing water NO3− over time. Surface water NO3− concentration was not correlated with the fraction of the watershed area that had been amended with biosolids, and there was no observable increase in surface water NO3− with increased frequency of biosolids applications to the tree plantations. These results suggest that the current biosolids program is sufficiently protective of ground and surface waters. These observations suggest that biosolids application can be conducted on a large scale with multiple benefits and no discernible impact to surface waters.

Diminishing legacy effects from forest fertilization on stand structure, vegetation community, and soil function

While there is consensus that fertilization with nitrogen (N) is a cost-effective way of increasing both forest biomass yield and timber harvest profitability, the strength and longevity of legacy effects are debated. To quantify legacy effects of past fertilization, we analysed 21 mixed Pinus sylvesteris and Picea abies stands. The stands, on average 23 years old at the time of this study, were either unfertilized (n=7), fertilized with 150 kg N ha−1 once 36 years ago (n=7), or twice, 45 and 36 years ago, respectively (n=7), during the previous stand rotation. We performed measurements on soil N mineralisation and N availability, forest growth, ground vegetation community composition, soil and vegetation C/N ratios and soil C and N stocks, many of which responded to legacy N fertilization earlier in stand development. Our results show that the legacy effects of fertilization during the previous stand rotation have diminished through time, indicating an eventual convergence of stand properties. Specifically, all significant effects present in the previous measurement period (over a decade ago), were weaker or completely absent in the current study (i.e. 36 years after fertilization and 23 years after initiation of the new stands). None-the-less, this indicates a longer legacy effect of N fertilization than what is normally considered and suggests that care should be taken to mitigate unwanted, long-term effects when utilizing N addition to promote tree growth in boreal forests.

Pollen indices of Cedrus atlantica Manetti populations vary with geographical localities in the Moroccan Atlas Mountains

North Africa’s forests of Cedrus atlantica Manetti have declined drastically, by more than 58% in the last 130 years, and many stands are likely to disappear entirely in the coming decades. This study on the interactions between C. atlantica pollen characters (production, germination, and pollen tube length) and locality characters in Morocco, using seventy individuals from seven geographically distant populations, showed that pollen indices varied according to station. Pollen production was high in the populations of the Moudemam-1 and Seheb stations, intermediate in the Ait Oufella and Ait Ayach stations, and low in the Zerrouka, Ras Elma and Moudemam-2 stations. Pollen germination was very low for the populations in the Seheb and Moudemam-1 stations but high in the other stations. On the other hand, the longest pollen tubes were recorded in the Moudemam-1 population, while those in the other stations were shorter. These results show an inverse variation between the pollen indices characterizing the populations of the stations studied. The shortest pollen tube length classes [0-100] to [300-400] accounted for 85.98% of all classes and were assessed for the Zerrouka, Ait Oufella and Ait Ayach stations. The other classes were more represented or exclusive to the population of the Moudemam-1 station. These results could have implications not only for assessing pollen variations according to geographical localities but also for optimizing fertilization in cedar forests by selecting the best clones for this species.

Shifts in microbial community composition and metabolism correspond with rapid soil carbon accumulation in response to 20 years of simulated nitrogen deposition

Anthropogenic nitrogen (N) deposition and fertilization in boreal forests frequently reduces decomposition and soil respiration and enhances C storage in the topsoil. This enhancement of the C sink can be as strong as the aboveground biomass response to N additions and has implications for the global C cycle, but the mechanisms remain elusive. We hypothesized that this effect would be associated with a shift in the microbial community and its activity, and particularly by fungal taxa reported to be capable of lignin degradation and organic N acquisition. We sampled the organic layer below the intact litter of a Norway spruce (Picea abies (L.) Karst) forest in northern Sweden after 20 years of annual N additions at low (12.5 kg N ha−1 yr−1) and high (50 kg N ha−1 yr−1) rates. We measured microbial biomass using phospholipid fatty-acid analysis (PLFA) and ergosterol measurements and used ITS metagenomics to profile the fungal community of soil and fine-roots. We probed the metabolic activity of the soil community by measuring the activity of extracellular enzymes and evaluated its relationships with the most N responsive soil fungal species. Nitrogen addition decreased the abundance of fungal PLFA markers and changed the fungal community in humus and fine-roots. Specifically, the humus community changed in part due to a shift from Oidiodendron pilicola, Cenococcum geophilum, and Cortinarius caperatus to Tylospora fibrillosa and Russula griseascens. These microbial community changes were associated with decreased activity of Mn-peroxidase and peptidase, and an increase in the activity of C acquiring enzymes. Our results show that the rapid accumulation of C in the humus layer frequently observed in areas with high N deposition is consistent with a shift in microbial metabolism, where decomposition associated with organic N acquisition is downregulated when inorganic N forms are readily available.

Effects of forest conservation and management on timber, ecosystem carbon, dead wood and habitat suitability area in a boreal forest under climate change

We used forest ecosystem model simulations to study how forest conservation and management intensity affected timber yield, ecosystem carbon stocks, amount of dead wood, and habitat suitability area in a middle boreal forest region of Finland under changing climate over a 90-year simulation period. We used the following forest conservation and management scenarios: baseline forest management (BM), BM with 10 or 20% increase of conservation area with or without intensified forest management (i.e. improved forest regeneration material and forest fertilization). The simulations were done under current climate (reference period of 1981–2010), and Representative Concentration Pathway (RCP) climate change projections under the RCP2.6 and RCP4.5 forcing scenarios. Overall, increasing the forest conservation area decreased timber yield and increased the ecosystem carbon stock, the amount of dead wood and consequently the area of suitable habitat for saproxylic species. The use of intensified forest management reduced the loss of timber yield, increased ecosystem carbon stock, the amount of dead wood and area of suitable habitat for saproxylic species. At the end of simulation period, the use of intensified forest management even overcompensated (4–6% higher) the timber loss from 10% increase of conservation area. Under changing climate, timber yield, the amount of dead wood and the area of suitable habitats for saproxylic species increased. To conclude, with intensified forest management it is possible, in the short term, to decrease the loss of timber yield through increased forest conservation area and in the long term maintain or even increase it compared to baseline forest management.

Microeconomics of Nitrogen Fertilization in Boreal Carbon Forestry

The nitrogen fertilization of boreal forests is investigated in terms of microeconomics as a tool for carbon sequestration. The effects of nitrogen fertilization’s timing on the return rate on capital and the expected value of the timber stock are investigated within a set of semi-fertile, spruce-dominated boreal stands using an inventory-based growth model. Early fertilization tends to shorten rotations, reducing timber stock and carbon storage. The same applies to fertilization after the second thinning. Fertilization applied ten years before stand maturity is profitable and increases the timber stock, but the latter effect is small. The fertilization of mature stands, extending any rotation by ten years, effectively increases the carbon stock. Profitability varies but is increased by fertilization instead of merely extending the rotation.

Monitoring Intertidal Habitats for Effects from Biosolids Applications onto an Adjacent Forestry Plantation

Stabilised organic solids derived from sewage sludge (“biosolids”) are applied to land as an alternative to disposal as landfill. This study evaluated the long-term effects of biosolids applied to forestry plantations on the adjacent intertidal habitats of Rabbit Island (New Zealand). On this island, biosolids are applied to enhance the growth of trees (Pinus radiata). Shoreline topography, macroalgal cover, sediment grain size, the concentrations of nutrients, trace metals, and faecal indicator bacteria, and benthic infaunal communities were studied in 2008, 2014, and 2019 at twelve intertidal transect sites (four “reference” and eight “application”) adjacent to forestry blocks where biosolids have been applied over a period of 24 years. The sediment composition did not differ significantly between the survey years or between the reference and application sites. Total nitrogen concentrations in the sediments increased over time at some transects, but such increases were not consistent among the application transects. No symptoms of excessive algal growth, sediment anoxia, and hydrogen sulphide odours were observed at most sites. Key infaunal taxa were similar between the reference and application transects. Overall, no long-term adverse changes to intertidal habitats attributed to biosolids application were detected between the reference and application sites. This study shows that biosolids application can co-occur without detectable adverse effects on nearby intertidal environments. In a global context of rising concern over climate change, environmental pollution, and resource scarcity, forest fertilisation with biosolids can facilitate biomass production and soil development while protecting valued coastal ecosystems.

Soil Characteristics and Fertility of the Unique Jarrah Forest of Southwestern Australia, with Particular Consideration of Plant Nutrition and Land Rehabilitation

The jarrah forest is a natural ecosystem with significant endemism in the flora and fauna. The forest stands on the western edge of the ancient Great Plateau of Western Australia on the granitic shield of the Yilgarn craton (2.5 Gya). The long-term migration of soluble iron and aluminium led to the formation of bauxite ore. The regolith ore is bound by surficial topsoil and deep pallid zone kaolinite clays, primarily used in land rehabilitation. We investigated the chemical fertility of the substrates, along with key physical properties. We found the capacity of these soils to provide a stable growth medium differed considerably in their ability to retain and supply nutrients. These substrates are deficient in nitrogen, phosphorus, and micronutrients. In the topsoil, 15% of total P is plant-available, while in the pallid zone layer, only 1% of total P is available. 31P-NMR showed no organic P in the pallid zone, whereas the topsoil had significant organic P and, consequently, a supply of phosphate ions. This shows the importance of organic P in the topsoil for ecosystem nutrition when inorganic fertilisers are not applied in state-of-the-art restoration schemes.

Effects of physiological integration on nitrogen use efficiency of moso bamboo in homogeneous and heterogeneous environments.

Moso bamboo is one of the important clonal plants with complex underground rhizome-root system. Ramets connected by rhizome can translocate and share nitrogen (N), which may affect the nitrogen use efficiency (NUE) of moso bamboo. The aims of this study were to investigate the mechanisms of N physiological integration and its relationship with NUE of moso bamboo. A pot experiment was conducted to trace the movement of 15N between the connected ramets of moso bamboo in both homogeneous and heterogeneous N environments. Results showed that N translocation within clonal fragments of moso bamboo was detected in both homogeneous and heterogeneous environments. The intensity of physiological integration (IPI) was significantly lower in homogeneous environments than that in heterogeneous environments. 15N translocation between the connected ramtes of moso bamboo was determined by the source-sink relationship in heterogeneous environments, and the 15N allocation of the fertilized ramet was higher than that of the connected unfertilized ramet. The NUE of connected treatment was significantly higher than that of severed treatment, which suggested that physiological integration significantly improved the NUE of moso bamboo. In addition, the NUE of moso bamboo was significantly higher in heterogeneous environments than that in homogeneous environments. The contribution rate of physiological integration (CPI) on NUE in heterogeneous environments was significantly higher than that in homogenous environments. These results will provide theoretical basis for precision fertilization in moso bamboo forests.

Nitrogen fertilization in bamboo forest accelerates the shoot growth and alters the lignification process in shoots

As one of the key nutrients, nitrogen is a major driving force for plant growth and development, and ultimately contributes to biomass improvement. However, little is known about the common genetic basis of bamboo growth with nitrogen fertilization in forests. Here, the physiological-biochemical characteristics showed that nitrogen fertilization in moso bamboo forest obviously affected the activities of multiple enzymes in bamboo shoots, which led to changes in metabolite content. The lignin content was significantly inhibited in bamboo shoots during the early stages of fast growth (from 1.0 m to 4.0 m), while the content was subsequently promoted at the late stage, which resulted in a lignin content similar to that of the control observed in 8.0 m shoots. By integrating the physiological-biochemical and transcriptome data, we generated a global map of changes in the transcriptomic dynamics during fast growth, which showed that upregulated DEGs in 1.0 m and 4.0 m shoots were significantly enriched in growth- and development-related GO terms, while those DEGs in 8.0 m shoots were enriched in lignin biosynthesis-related GO terms. Using weighted correlation network analysis (WGCNA), two complex regulatory networks were constructed: two key structural genes (KSGs) and 118 transcription factors (TFs) involved in nitrogen metabolism and 17 KSGs and 102 TFs involved in lignin biosynthesis. Furthermore, the regulatory mechanism of KSGs targeted by TFs was validated by yeast one-hybrid assays. Overall, nitrogen fertilization differentially affected moso bamboo shoots at different fast growth stages through the expression of genes involved in multiple metabolic pathways, indicating that moso bamboo has plasticity to environmental factors. These results provide a better understanding of the changing patterns in moso bamboo shoots and lay a foundation for the genetic improvement and sustainable management of bamboo forests via nitrogen fertilization. • Nitrogen fertilization promotes the growth of moso bamboo shoots. • Nitrogen fertilization changes the shoot lignification process through the gene expression in shoots. • Moso bamboo shoots prefer to use ammonium nitrogen at the late stage of fast growth.

Sidestream materials show potential as top-dressed soil improvers for peatland forests.

The effects of top-dressing of several industrial and farming sidestream materials on the growth of downy birch (Betula pubescens Ehrh.) and Scots pine (Pinus sylvestris L.) seedlings in natural sphagnum peat soil were evaluated. Wood fly ash, industrial filter cake waste, mine tailings sand (quartz feldspar from lithium orebody), and digestate and liquid reject of cow manure from a biogas plant were studied for their physical and chemical properties, as well as for their effects as soil ameliorants on seedling growth during one growing period in a greenhouse. Each material was top-dressed on unfertilised peat in pots in quantities that corresponded to the amounts of ash used in Finnish peatland forest fertilisation (2-6tha-1). During growing, the pH of percolate water from the growing pots was below 4, and in the treatments with filter cake even below 3. However, no clear impairment of seedling growth due to acidity was observed. In all treatments, birch and pine seedlings grew at least as well as in the unfertilised peat (control treatment). Growth was strongest in the peat top-dressed with additives originating from cow manure, in which the high N and P contents promoted growth so much that foliar N was found to be diluted with respect to a high P content in the birch seedlings. No harmful concentrations of heavy metal residues were observed from the materials used. Overall, the results suggest that all the used sidestream materials show potential as soil improvers on forested peatlands.

Nutrition diagnosis and fertilization of Pinus armandii forest in the Qinling Mountains, China

We examined the contents of total nitrogen (TN) and total phosphorus (TP) in needle, litter, and soil of Pinus armandii forest on the southern slope of the Qinling Mountains in Shaanxi, China. We conducted nutrition diagnosis of P. armandii forest, analyzed nutrient limitation pattern, the fertilization types and amount to increase growth, to provide support for precision fertilization and scientific cultivation of big timber of P. armandii. The results showed that the proportion of big timber (DBH>26 cm) and individuals with the potential to grow into big timber (18 cm<DBH≤26 cm) was 29.0% and 60.6%, respectively. The needle N and P contents were 12.65 and 1.34 g·kg-1, respectively, and the N:P was 10.24 (<14, unrestricted threshold of forest growth). The N and P resorption efficiency of needle was 33.8% and 48.0%, respectively. In 0-10 cm soil layer, soil N and P contents were significantly negatively correlated with that in the needle, but positively correlated with that in litter. The relationship between the needle N:P and soil N storage was expressed by a quadratic function. The growth of P. armandii was N limited, and an addition rate of 0.42 t N·hm-2 would ensure normal growth of all individual trees. We recommended the rate of 0.16 t N·hm-2 to the trees with the potential to grow into big timber to promote them to be big timber in a short period, allocating nitrogen to individual plants in proportion to the biomass of individual trees in the stand per unit area.

Half-a-century effects of a slow-release nitrogen fertilizer, ureaformaldehyde, on stand growth and soil processes in a Scots pine stand

Slow-release nitrogen fertilizers have received little attention as alternatives to conventional fast-release fertilizers in N-limited boreal forests. Slow-release fertilizers better match the rate at which trees can uptake nutrients from the soil solution and are less likely to be vulnerable to losses to the environment. Ureaformaldehyde is a polymer that is synthesized from formaldehyde and urea and mainly used as a nitrogen fertilizer in lawns and greenhouse cultivations. Our goal was to assess ureaformaldehyde (UF) as a forest fertilizer. We aimed to determine its long-term effects on tree ring widths and stand basal area growth and how the effects differ from those of a conventional fast-release N fertilizer, ammonium nitrate (AN). We also attempted to determine whether the fertilizer additions changed soil organic matter properties in the long term. The study site was an unfertile Scots pine (Pinus sylvestris L.) stand with study plots with both fertilizer treatments that were performed 47 years ago and unfertilized control plots. As expected, AN addition resulted in a sharp increase in tree ring widths and the annual basal area increment that lasted for approximately seven years. UF addition caused a slower increase that lasted much longer, approximately 17 years. In addition, the UF addition showed indications that it slightly enhanced the growth even during the last decade. Our results also suggested that different fertilization treatments resulted in differences in tree size distribution. After almost a half century, some signs of UF-induced effects were still visible in soil organic matter; for instance, the humus layer in the UF treatment had a lower C-to-N ratio by 7 units than that in the humus layer of the AN treatment. In conclusion, slow-release ureaformaldehyde has a considerably longer effect on tree growth than conventional ammonium-nitrate fertilizer and, after almost a half century, there were signs that it still increased nitrogen availability for trees.

Interspecific differences in the responses of root phosphatase activities and morphology to nitrogen and phosphorus fertilization in Bornean tropical rain forests.

Soil organic phosphorus (P) compounds can be the main P source for plants in P‐limited tropical rainforests. Phosphorus occurs in diverse chemical forms, including monoester P, diester P, and phytate, which require enzymatic hydrolysis by phosphatase into inorganic P before assimilation by plants. The interactions between plant interspecific differences in organic P acquisition strategies via phosphatase activities with root morphological traits would lead to P resource partitioning, but they have not been rigorously evaluated. We measured the activities of three classes of phosphatases (phosphomonoesterase, PME; phosphodiesterase, PDE; and phytase, PhT), specific root length (SRL), root diameter, and root tissue density in mature tree species with different mycorrhizal associations (ectomycorrhizal [ECM] or arbuscular mycorrhizal [AM]) and different successional status (climax or pioneer species) in Sabah, Malaysia. We studied nitrogen (N)‐ and P‐fertilized plots to evaluate the acquisition strategies for organic P under P‐limited conditions 7 years after fertilization was initiated. P fertilization reduced the PME activity in all studied species and reduced PhT and PDE activities more in climax species than in the two pioneer species, irrespective of the mycorrhizal type. PDE activity increased in some climax species after N fertilization, suggesting that these species allocate excess N to the synthesis of PDE. Moreover, PME and PhT activities, but not PDE activity, correlated positively with SRL. We suggest that climax species tend to be more strongly dependent on recalcitrant organic P (i.e., phytate and/or diester P) than pioneer species, regardless of the mycorrhizal type. We also suggest that trees in which root PME or PhT activity is enhanced can increase their SRL to acquire P efficiently. Resource partitioning of soil organic P would occur among species through differences in their phosphatase activities, which plays potentially ecologically important role in reducing the competition among coexisting tree species in lowland tropical rainforests.

Response of Pinus tabuliformis saplings to continuous autumn fertilization treatments in the mountains of Eastern Liaoning Province, China.

Autumn fertilization is an important cultivation and management measure used to provide nutrients at the hardening stage during the end of the growing season—bolstering nutrient reserves and promoting additional growth in the following spring. Previous studies mainly focused on short-term or one-time fertilization treatment of container seedlings, and few studies have observed the effects of autumn fertilization of large-area forests over multiple continuous years. The growth dynamics and nutrient changes during autumn in 324 Pinus tabuliformis saplings in the temperate zone of China (in the eastern Liaoning mountains) were studied under field conditions with different fertilizer treatments for three consecutive years. The second year of autumn fertilization promoted the growth of tree height and annual leaf length more significantly than that in the first year, the change in diameter at breast height (DBH) was significant. Tree height (TH) in spring increased at a faster rate than in autumn, while DBH stably increased throughout the year. The increase in TH, DBH, and annual leaf length (ALL) under all fertilization treatments was higher than that of the control group, and the decrease in annual branch length (ABL) was higher than that of the control group. High N significantly increased the concentration of new coniferous N (NLN), soil total N (STN), and soil alkali-hydrolyzable N (SAHN) in P. tabuliformis saplings. High P significantly increased the concentration of P in annual needles and soil total P (STP), and decreased the concentration of N in new needles. In addition, there is a certain correlation between the N and P concentration in the needles and soil, representing the competition and interactions between plant nutrient demand and soil nutrient supply. The most favorable fertilizer treatment consisted of high N and low P (urea 204 g, calcium superphosphate 104 g), which provide support for the formulation of a reasonable fertilization technology for P. tabuliformis in the mountains of Eastern Liaoning Province, China.

The Impact of Forest Fertilization on the Ecological Quality of Two Hemiboreal Streams

The present study aimed to detect any changes in concentrations of nutrients and evaluate the impact on the quality of two hemiboreal streams that collect a discharge from two fertilized Scots pine stands. In 2017, nitrogen-containing mineral fertilizer was spread in pine stands on mineral soil located near the first stream. In 2018, potassium containing wood ash was spread in pine stands on organic soil near the second stream. From 2017 to 2020, surveys of physico-chemical parameters, diatoms, macrophytes, and macroinvertebrates were performed to determine the possible effects of fertilization on the ecological quality of the streams. A control site upstream of the fertilized forest stand and a treatment site downstream of the fertilized forest stand was monitored at each stream. Water quality indices, chemical parameters of surface water, and indicator species analysis showed no short-term impact of forest soil improvement with wood ash and ammonium nitrate. We found no clear patterns before and after the fertilization events in both streams, although we did observe inter- and intra-annual differences in aquatic biota and stream ecological quality mainly caused by local environmental factors.