2026-02-11
Ferhat Bolat, Alkan Günlü, İlker Ercanlı
Background: Relationship between height (H) and diameter (D) highly depends on site conditions and stand structures. In this regard, this study aimed to build a new site-specific model based on the Chapman-Richards function, for the Crimean pine stands in the Black Sea Backward Region of Türkiye. Methods: The model was developed using the mixed-effects framework and its accuracy and performance were assessed using a validation data set. The model was then compared to two highly predictive models derived from the Chapman-Richards function through fit statistics, curvature and bias measures of nonlinearity, and biological principles. Results: The new model resulted in the most favourable fit statistics and nonlinearity measures, and also exhibited a suitable H-D curve that was compatible with the ecological conditions of the study area. While the alternative models in the current literature showed good fit statistics, they resulted in biased parameter estimates and produced inappropriate H-D curves. The proposed model, however, demonstrated a satisfactory accuracy when validated using the validation data set. Conclusions: (1) It is essential to assess H-D models by considering both fit statistics and curvature and bias measures of nonlinearity; and (2) it is crucial to examine whether H-D models are appropriate for the specific ecological conditions of a particular region.
2025-09-05
Sue Kee Ng, Pascal Sirguey, Todd Redpath
Background: Global canopy height models are becoming prolific yet require evaluation across New Zealand's diverse vegetation types to assess their accuracy and applicability. Accurate measurement of canopy height is crucial for estimating above-ground woody biomass, which is essential for modelling carbon emissions and sequestration in the context of climate change. These models generally rely on remote sensing data and machine learning techniques, with Light Detection and Ranging (LiDAR) technology commonly employed for precise measurement. Methods: This study validated the three latest global canopy height models, each provided at a different resolution: 30-metre, 10-metre, and 1-metre. We assessed the accuracy of the selected models by comparing them against canopy height estimates derived from local Airborne Laser Scanning (ALS) datasets, which served as our reference data. Eleven regions across New Zealand were selected based on ALS data availability, encompassing five vegetation and land cover types. Our methodology involved utilising and automating the processing of large New Zealand ALS datasets. To align resolutions for comparison, the reference canopy height was calculated by aggregating average or maximum heights at 10 and 30 m spatial resolution. Model performances were assessed using statistical metrics, including root-mean-square error (RMSE), bias, and R². Results: Overall, all models exhibited relatively low R² values, indicating limited capture of canopy height variability. The Potapov 30-metre model performed best with average aggregation in shorter vegetation. In contrast, the Lang 10-metre model showed improved accuracy with maximum aggregation, particularly in taller vegetation, but visual boundaries between different vegetation types were not as distinct. The Tolan 1-metre model provided a balanced approach, minimising biases in lower heights but underestimating taller canopies. Results highlight model-specific strengths for varying vegetation structures and the sensitivity of performances to aggregation methods applied to high-resolution reference ALS data. Conclusions: All three global canopy height models exhibit varied performance across New Zealand's vegetation types. The findings highlight the importance of vegetation-specific applications to optimise each global model’s accuracy. Currently, these models are suitable for carbon accounting efforts as supplementary tools rather than replacements for existing methodologies.
2025-09-03
Adam Sean Forbes
Background: The ecological science associated with transitioning exotic forest to native dominance (hereafter transitional forestry, transition forests) is currently limited, yet this form of forest has expanded rapidly. In part, this is related to forest-based carbon credit schemes which have driven large-scale afforestation in exotic trees. In other circumstances (e.g., for soil conservation or values-based reasons such as biodiversity conservation), forest owners wish to transition their exotic forest to native forest without harvest. Knowledge is required to inform management of realistic expectations for regeneration and succession both spatially and temporally. Methods: Mature (>20-year-old) Pinus radiata plantations were surveyed along three elevation-climate gradients in the Waikato region of New Zealand to explore the composition and structure (including native carbon stocks) of plantation understories and whether these parameters vary spatially over several decades. Mammalian browsing was also recorded. Results: Native woody stem densities were variable. Factors indicated as driving variability were stand age, elevation, topographic shelter, soil hydrology, solar radiation, and air temperature. On average, understories comprised five native woody species in the seedling tier, a single native species in the sapling tier, and a single native species in the tree tier. The most common species were the sub-canopy tree species Melicytus ramiflorus , Geniostoma ligustrifolium , and Aristotelia serrata. Tall old-growth species, such as Beilschmiedia tawa , Podocarpus totara , Pectinopitys ferruginea , and Prumnopitys taxifolia , occurred in only particular circumstances and on average at densities too low to form a meaningful part of a future forest canopy. Average species richness was low, although some diversity hotspots occurred. Carbon stocks in native trees and tree ferns in the understories were on average 1.55±0.38 tCha –1 . Heavy browsing by mammalian herbivores was recorded at 60% of plots. Conclusions: These data indicate typical understorey conditions in mature P. radiata plantations for this area of New Zealand in the absence of management to promote a native transition. These data also highlight the importance of browser control, enrichment planting of tall old-growth species, and canopy manipulations to accelerate regeneration and succession in non-harvest P. radiata plantations. The data suggest transitional forestry should only be attempted at scales that can be reasonably managed, and there is a need for caution against large-scale establishment of P. radiata for transitional forestry as at large scales, achieving adequate levels of management are uncertain.
2025-08-07
Stuart Fraser, Emily McLay, Christine Todoroki, Nicolò Camarretta, Ian Hood
Background: Red needle cast (RNC) is a foliar disease of radiata pine ( Pinus radiata D.Don) in New Zealand caused by Phytophthora pluvialis Reeser, W.L.Sutton & E.M.Hansen and, to a lesser extent, Phytophthora kernoviae Brasier, Beales & S.A.Kirk. Incidence and severity of RNC vary substantially between years. To investigate the impact of seasonal weather variables on this variation, RNC was assessed annually for ten years at radiata pine transects. Methods: Fifty-three transects were established in 2015 in the Central North Island and Gisborne Region (east coast North Island) of New Zealand, with twenty-three monitored until 2024 (surviving harvest). The relationship between seasonal weather variables and RNC severity was analysed using two non-parametric statistical approaches: (1) correlation analyses (Spearman correlations, r s , where positive values indicate an increase in RNC severity with an increase in the explanatory variable); and (2) binary recursive partitioning (with models trained on 85% of observations and tested on the remaining 15%). Results: Disease expressed more consistently, and severity was generally greater, at Gisborne sites. Disease severity peaked in 2017 and 2023 in both regions. Autumn (March-May) variables tended to be prevalent amongst predictors of RNC severity. Autumn soil moisture index (calculated from cumulative rainfall and evapotranspiration) was the most strongly correlated variable for the Gisborne dataset (r s = 0.70) and, along with vapour pressure, were the key partitioning variables in the recursive partitioning model. The strongest correlating variable for the Central North Island dataset was autumn potential evapotranspiration (r s = -0.46) while the most important variable and first data partition was autumn vapour pressure. Model evaluation metrics indicated good performance: R 2 values were 0.63 and 0.68 for the Gisborne and Central North Island test datasets respectively, and mean absolute errors were 18.1 % and 7.8 % for the respective datasets. Conclusions: The importance of autumn more than summer weather variables in determining disease expression differs from the findings of previous studies and indicates that conditions during periods of exponential epidemic growth may be as, or more, important than initial inoculum level in determining RNC severity. Proactive control activities may require long-term weather forecasting or frequent monitoring during this season.
2025-06-19
Serajis Salekin, Christian Roschak, Greg Steward
Background: Robust species-specific height-diameter (H-D) equations are necessary for the estimation and prediction of tree volume, yield, biomass or carbon stocks. In addition, information about height growth characteristics allows for the analysis of stand growth dynamics. But there is a general lack of species-specific growth models for most New Zealand native tree species considered for plantation and wood production. Therefore, the aim of this study was to develop a species- and site-specific H-D model for planted lowland tōtara ( Podocarpus totara G. Benn. ex D. Don). Methods: The models were developed using data from 719 individually measured trees aged 11 to 110 years from eight different sites in the North Island of New Zealand. Two different modelling approaches, traditional non-linear and linear mixed effect, were used. The process included selecting, testing, conditioning, and extending a total of 18 different equations by incorporating site-specific tree variables. Results: The most precise model predicting the H-D relationship was reported by linear mixed-effect models that include diameter at breast height (DBH at 1.4 m, cm) and age (years). The final model had a low root mean square error (RMSE, 0.21, m), mean absolute error (MAE, 0.16, m) and high R 2 (0.94), which slightly increased during validation. Conclusions: The study demonstrated a robust process and reported the most plausible and parsimonious model to predict P. totara ’s H-D relationship, which serves as the basis for species-specific growth dynamics. The reported models provide for the first time the opportunity to predict the H-D relationship of planted P. totara in New Zealand. This fills a long existing knowledge gap and provides forest growers and managers important decision-making information.
2025-03-07
Sabrina Dookie, Abdullah Adil Ansari, Sirpaul Jaikishun
Background: Fire plays a key role in the world’s wetland ecosystems, affecting the fundamental aspects of their ecological functioning. The increased frequency of wildfires continues to exert a significant influence on the succession of mangrove ecosystems and the spatial distribution of species. Numerous studies have attempted to highlight the effect of fires on forest ecosystem function and integrity; however, the results are inconclusive. In particular, it remains uncertain whether forest fires have direct impacts and implications on mangrove ecosystems, a forest type known for its distinct characteristics and low ignition rates due to high moisture levels. Methods: We have conducted a comprehensive review of over 120 relevant scholarly articles found through formal searches of literature and citation databases and by surveying relevant publications to identify and examine the interactions, prevalence, and implications of forest fires in mangrove ecosystems globally. We have also synthesised the impacts of recurrent fires on the numerous ecological goods and services offered by mangroves and highlighted the existing literature gaps and directions for future research. Results: Mangrove forest fires are prevalent in many countries across the world with varying distributions of forested areas. While there are numerous causes of wildfires in mangroves, most occurrences are due to a combination of natural dry periods (El Niño events) and anthropogenic activities, which may deliberately or accidentally increase fire regimes. There are many negative effects of mangrove forest fires which can affect the goods and services provided to the environment and society, including habitat loss, pollution, and wildlife destruction. However, our findings have highlighted some cases where wildfires have positive effects on mangrove ecosystems by encouraging nutrient enrichment and habitat expansion. Our review reports numerous literature gaps with high priorities for future research on understanding sustainable forest management with the coexistence of fires through preservation, conservation, and public awareness. Conclusions: Forest fires are prevalent in mangrove ecosystems due to a combination of natural phenomena and human-induced factors. With predominantly negative effects, forest fires result in a loss of ecological integrity, leading to severe economic losses and habitat degradation. Emphasis should therefore be placed on sustainable forestry and public awareness for the mitigation of the dynamic effects of forest fires on mangrove ecosystems.
2025-02-26
Michael Marden, Norman William Herbert Mason, Suzanne Lambie, Donna Rowan
Background: Changes in biomass and carbon stocks of open-spaced plantings are important considerations in the restoration of biodiversity and ecological function of New Zealand’s degraded (non-forested) landscapes and streamside margins. Species- and age-specific allometric relationships of biomass and carbon stocks were developed for a diverse range of indigenous seral shrub and tree species during their juvenile growth period. Methods: Whole plants of Coprosma robusta Raoul (karamu), Plagianthus regius ( Poit.) Hochr. (lowland ribbonwood), Sophora tetraptera J.S.Muell. (eastern kōwhai), Pittosporum eugenoides (Cunn.) (lemonwood), Pittosporum tenuifolium (Gaertner) (kōhūhū), Hoheria populnea A.Cunn. (North Island lacebark), Myrsine australis (A.Rich) Allan (māpou), Pseudopanax arboreus (Murray) Philipson (fivefinger), Cordyline australis (G. Forst.) Endl. (cabbage tree), Knightia excelsa (R.Br.) (rewarewa), Leptospermum scoparium (J.R.Forst. & G.Forst (mānuka), and Coriaria arborea (Linds) (tree tutu) were planted as 2-year-old nursery-raised seedlings in a plot-based field trial. Plants of each species were destructively sampled annually over 5 consecutive years and species-specific allometric equations developed for foliage, branch, stem, total above-ground biomass (AGB), total below-ground biomass (BGB), and whole plant biomass to calculate carbon stocks. Results: In each year and for each of the 12 test species, root-collar diameter over bark (RCD) gave the best fit for plant height, foliage, branch, stem, total AGB, total BGB, and whole plant biomass. At age 5 years, Coriaria arborea and Cordyline australis accumulated significantly more AGB ( P = 0.05) than the remaining species, none of which were not significantly different from one another and each species had allocated more than 20% of their total biomass to BGB, with BGB:AGB ratios of between 0.24 and 0.44. Species-specific mean tree biomass values at this age ranged from 0.5 to 14.0 kg per plant. The planting of equal numbers of the seven best-performing species as 2-year-old seedlings could potentially amass a carbon stock of 13.1 t CO 2 1000 stems ha -1 within 3 years after establishment as open-spaced plantings. Conclusions: RCD proved to be a reliable predictor of plant height, foliage biomass, branch biomass, stem biomass, total ABG, total BGB, and whole plant biomass. Optimisation of the carbon potential amassed by mixed plantings of indigenous seral plants will require the development of allometric equations for a wider range of species best suited to restoring ecological integrity to degraded landscapes and to improve the accuracy of existing biomass and carbon stock inventories.
2024-09-07
Youssef Dallahi, Amal Boujraf, Abdelaziz Smouni, Mouna Fahr, Ahmed El Aboudi, Collins Ashianga Orlando, Kamal Laabou, Abderrahim Ferradous, Mohamed Mahmoud Ould Abidine
Background: Argan ( Argania spinosa ) is an important arid species in Morocco, hence the need to undertake nursery practices that promote its regeneration and sustainability in a vulnerable environment. This study aimed to examine the effect of container size and growing medium on morphological traits, biomass, as well as root morphology of one-year-old argan seedlings in the Marrakech region of Morocco. Methods: Three container sizes of 300, 400, and 500 cm 3 were selected in which seven types of growing media with varying proportions of acacia compost, crushed cypress cones, Barbary thuja, eucalyptus capsule composts, and potting soil were used. Subsequently, measurements of plant growth variables and biomass, as well as identification of root deformations were carried out. Results: Our results show that container size and growth medium strongly influenced (p < 0.001) morphological traits and biomass of argan seedlings. Growth was highest in seedlings grown in the 500 cm 3 container on substrates composed of both 100% acacia compost and 50% potting soil + 50% acacia compost, while it was lowest in seedlings in the 300 cm 3 container with the compost composed of a mixture of equal proportions of cypress and Barbary thuja, and eucalyptus. While the main root deformities were hooked roots (14.1%) and root eccentricity (13.0%), seedlings with multiple deformities were by far the most common (38.4%). The size of the container did not seem to influence their occurrence, whereas about 35% of the deformations were observed in seedlings grown on substrates composed of mixtures of potting soil and acacia compost, cypress cones, and Barbary thuja and eucalyptus composts. Conclusions: This study shows the importance of adopting an adequate protocol to allow the regeneration of forest species with the necessary characteristics to survive the often-challenging environmental conditions prevailing not only in southern Morocco but also across most of the country.
2024-07-21
Brenda R. Baillie, Joane S. Elleouet, Graham W. R. Coker
Background: Planted forests face on-going challenges to increase productivity while remaining within sustainable limits. Forest management activities that potentially impact on water quality are under increasing public scrutiny and regulatory controls. New Zealand’s forest industry is experimenting with aerially applied, mid-rotation fertiliser treatments as a sustainable option to increase productivity from planted forests. However, the effect of such applications on water quality requires investigation. Methods: Field trials were established to assess the effects of two conventional fertiliser applications (either granular di-ammonium phosphate (DAP) or granular urea) and a new-to-forestry liquid foliar fertiliser blend, on nitrogen and phosphorus concentrations in stream water of three planted forest sites representing a range of New Zealand climatic and soil environments. Results: Overall, the liquid foliar fertiliser treatment had the least impact on water quality compared with the two conventional fertiliser treatments. On the day of fertiliser application, when compared with pre-treatment in-stream concentrations, the urea treatments resulted in short-term increases in total nitrogen. The DAP treatment increased total phosphorus and dissolved reactive phosphorus concentrations with peak concentrations declining within hours. In the post-application period, any increases in nutrient concentrations in stream water were mainly associated with rainfall events within six months of application and at one site, the resumption of stream flow following a dry spell. Riparian ‘no-spray’ buffers of varying widths assisted in mediating the impacts of fertiliser applications. Conclusions: Initial evidence from these trials indicates that mid-rotation fertiliser treatments have the potential to provide an alternate management option to increase forest productivity or disease resilience with minimal or only short-term effects to water quality. However, further research on their environmental effects would support the development of guidelines specific to mid-rotation fertiliser applications, particularly if mid-rotation fertiliser applications become standard management practice in the forest industry.
2024-04-19
Pablo J. Donoso, Tomás Riquelme-Buitano, Daniel P. Soto
Background: When possible, silviculture should aim to develop mixed-species multi-aged forests that can be more productive and resilient to disturbances, provide high-quality timber and sustain greater amounts of biomass. Southern Chile is covered by temperate rainforests dominated by a mixture of tree species, such as the Evergreen forest type (EFT). The irregular shelterwood regeneration method is a novel approach aimed at developing irregular multi-aged forests following the retention of the residual forest (no final cut). Here, we report mid-term results after implementing these cuttings in two EFT forests in the Coastal Range and discuss its prospects for other temperate rainforests. Methods: Two forests were sampled and evaluated in terms of composition, structure and growth, focusing on the new cohorts developed or released after the irregular shelterwood cuts. One forest was cut in a low-productivity site at 600 m (Hueicolla) in 1983, and the other in a medium-productivity site at 350 m (Llancahue) in 2009. In Hueicolla, 63% of the basal area was harvested from an old-growth forest where the main residual tree species were Eucryphia cordifolia , Laureliopsis philippiana and Saxegothaea conspicua . In Llancahue, 40% of the total basal area was harvested in a mature secondary forest dominated by Nothofagus dombeyi . Results: The understorey developed in Hueicolla had 3,600 trees per ha and a quadratic stand diameter of 15 cm. It was dominated by the mid-tolerant species Eucryphia cordifolia , Gevuina avellana and Lomatia ferruginea , plus the shade-tolerant Amomyrtus luma . In Llancahue, a dense lower canopy was dominated by Podocarpus salignus and Drimys winteri , both mid-tolerant species, which included 81,000 seedlings and saplings < 5 cm per hectare and 560 ingrowth 5-10 cm trees per hectare. Conclusions: The irregular shelterwood cuts allowed the development of dense understorey tree layers below the residual trees. However, the tree composition of the new cohorts largely differed from that of the residual trees and was dominated by mid-tolerant species, including some short-lived species. The irregular shelterwood method proves appropriate for the EFT and may likely be successful in other forest types with valuable mid-tolerant species.
2024-03-05
José Laurindo dos Santos Júnior, Elizamar Ciríaco da Silva
Background: Global climate changes have caused temperature increases that can harm plant development, especially the initial growth and establishment of seedlings for the recovery of degraded areas. However, there are species in which these losses are attenuated when the seeds are thermo-primed to sublethal temperatures. Therefore, the objective of the present study was to evaluate the influence of seed heat conditioning on germination and initial growth of Ceiba glaziovii (Kuntze) K. Schum seedlings, an endemic species occurring in seasonally tropical dry forest in Brazil. Methods: Seeds of C. glaziovii were exposed to 70 o C for 15, 30, 45, 60 and 90 minutes as pre-germination treatments. The control did not undergo heat treatment. Germination variables, vegetative growth, survival rate and normal leaves were evaluated. Results: Thermo-priming negatively affected the germination proportion of C. glaziovii seeds with increasing exposure time. However, it significantly enhanced vegetative growth and seedling survival rate of this species after transplanting, without impairing the formation of normal leaves. Conclusions: Thermo-priming of seeds was found to produce more vigorous seedlings of Ceiba glaziovii .