Radiata Plantations Research Articles

Restoring native forests from Pinus radiata plantations: natural regeneration of native tree species in response to different harvesting treatments in central Chile

The natural forests of south‐central Chile are known as world biodiversity hotspot. Due to increasing societal demands and certification commitments, a vast extension of these forests that was replaced by commercial exotic tree plantations is now to be restored. Given the magnitude of the area involved, large‐scale approaches based on natural regeneration require consideration. However, experimental evidence for this approach to restoration is lacking in different regions. We conducted a large‐scale replicated experiment to evaluate the response of natural regeneration of native tree species to different harvesting treatments (clearcut, strip‐cutting, and unharvested control) in 20‐year‐old Pinus radiata plantations. For 2 years, we monitored variations in (1) regeneration basal area (dRBA), (2) maximum sapling height (dMH), (3) frequency of free‐growing regeneration (dFGR), and (4) diversity of regenerating tree species. The harvesting treatment had significant effects on dRBA, dMH, and dFGR. The clearcuts showed the highest values of dRBA and dFGR of native species, but also, the highest dRBA of P. radiata regeneration. The strip‐cuttings showed the highest dMH of native species and the highest values of richness, Shannon, and Simpson diversity. Our results suggest that both clearcuts and strip‐cuttings facilitate natural regeneration. Although clearcuts may allow higher rates of natural regeneration establishment than strip‐cuttings, they require periodic control of P. radiata regeneration to prevent suppression of established native regeneration. Strip‐cuttings may require fewer management interventions and allow for higher initial species diversity, although with a potentially longer establishment period and higher risk of damage from residual P. radiata trees experiencing wind throw.

Characterizing annual leaf area index changes and volume growth using ALS and satellite data in forest plantations

While Leaf Area Index (LAI) is critical for understanding forest canopy, photosynthesis and forest growth, traditional field-based LAI measurements are laborious and costly. Remote sensing offers a practical alternative for extensive assessments. Satellite imagery provides broad-scale, long-term monitoring; however, may lack detail needed to guide specific forest management actions. Conversely, Airborne Laser Scanning (ALS) provides accurate LAI estimates at fine spatial detail but is limited by cost and temporal monitoring constraints. Combining ALS data with satellite observations could enhance plantation management decisions by balancing extensive coverage with detailed observations. This study explores the integration of ALS and satellite remote sensing as a comprehensive alternative for assessing LAI and stand volume growth rate (m3/ha/year) in operational Pinus radiata plantations in central-south Chile. Our approach comprised four major steps. First, we applied the Beer-Lambert law using ALS vertical profiles to estimate LAI across a forest plantation (LAIALS). We found that ALS accurately estimated LAI across 121 plots (R2 = 0.82 and RMSE = 0.51). Second, we built a simple linear regression to link LAIALS with the Normalized Difference Moisture Index (NDMI) derived from surface reflectance information from the Landsat/Sentinel-2 satellites, resulting in an R2 of 0.53 and an RMSE of 1.17. This step showed a higher correlation with satellite data compared to using only ground-based LAI estimates (R2 = 0.38; RMSE = 1.18). Third, we transformed biweekly NDMI time series to LAI, then derived peak annual LAI as an indicator of mean annual increment (MAI) (R2 = 0.51; RMSE = 5.27 m³/ha/year). This allowed us to characterize stand growth and LAI on a yearly wall-to-wall basis. Throughout the modelling steps, we incorporated error propagation, allowing final estimates to be error bounded. This integrated approach serves as a tool for identifying and visualizing growth irregularities, guiding adaptive management strategies to maintain or enhance stand productivity over time.

Optimal Rotation Age in Fast Growing Plantations: A Dynamical Optimization Problem.

Forest plantations are economically and environmentally relevant, as they play a key role in timber production and carbon capture. It is expected that the future climate change scenario affects forest growth and modify the rotation age for timber production. However, mathematical models on the effect of climate change on the rotation age for timber production remain still limited. We aim to determine the optimal rotation age that maximizes the net economic benefit of timber volume in a negative scenario from the climatic point of view. For this purpose, a bioeconomic optimal control problem was formulated from a system of Ordinary Differential Equations (ODEs) governed by the state variables live biomass volume, intrinsic growth rate, and area affected by fire. Then, four control variables were associated to the system, representing forest management activities, which are felling, thinning, reforestation, and fire prevention. The existence of optimal control solutions was demonstrated, and the solutions of the optimal control problem were also characterized using Pontryagin's Maximum Principle. The solutions of the model were approximated numerically by the Forward-Backward Sweep method. To validate the model, two scenarios were considered: a realistic scenario that represents current forestry activities for the exotic species Pinus radiata D. Don, and a pessimistic scenario, which considers environmental conditions conducive to a higher occurrence of forest fires. The optimal solution that maximizes the net benefit of timber volume consists of a strategy that considers all four control variables simultaneously. For felling and thinning, regardless of the scenario considered, the optimal strategy is to spend on both activities depending on the amount of biomass in the field. Similarly, for reforestation, the optimal strategy is to spend as the forest is harvested. In the case of fire prevention, in the realistic scenario, the optimal strategy consists of reducing the expenses in fire prevention because the incidence of fires is lower, whereas in the pessimistic scenario, the opposite is true. It is concluded that the optimal rotation age that maximizes the net economic benefit of timber volume in P. radiata plantations is 24 and 19 years for the realistic and pessimistic scenarios, respectively. This corroborates that the presence of fires influences the determination of the optimal rotation age, and as a consequence, the net economic benefit.

Differences in dissolved organic matter (DOM) composition of soils from native eucalypt forests and exotic pine plantations impacted by wildfire in Southwest Australia

In recent decades, plantations of exotic species have transformed large tracts of forested landscapes, where they often form a mosaic with the surrounding native forest. Wildfires have also increased in frequency and intensity globally, impacting both plantation and native forests and affecting soil organic matter (SOM), including dissolved organic matter (DOM). DOM of soils is considered highly labile and likely sensitive to effects of fire and changes in land use. However, it is unclear how wildfire influences key characteristics of DOM in exotic plantations compared to native forest. In this study, we investigated the impacts of wildfire on chemical properties of DOM in exotic Pinus radiata plantations and adjacent native jarrah (Eucalyptus marginata) forest in southwest Australia. We coupled fluorescence excitation-emission matrix parallel factor analysis (EEM-PARAFAC) and 1H‐NMR with soil nutrient analyses to characterise soil DOM (0–5 cm) from burned and unburned plots of each forest type, four months after the fire. Four fluorescent components (humic-, fulvic-, microbial and protein-like substances) were derived from soil DOM using the PARAFAC model. DOM from burnt forest soils was predominantly of lower molecular weight (E2:E3) and contained a greater microbial-derived component and a lower fulvic component than unburnt forest. As expected, soil pH and labile inorganic P increased in both forest types after fire. By contrast, an increase in the amount of DOC after fire was only recorded in native forest, while δ15N signatures were more enriched in pine plantation soils after fire but not in native forest soils. Differences in impacts of fire on DOC and δ15N between forest types suggest a different response to fire according forest type, even though these differences were not evident above ground. The 1H NMR spectra of DOM revealed all samples were largely dominated by aliphatic structures. However, there were no significant differences in the overall spectra between forest types or between burnt and unburnt forests. Overall, our findings suggest that transformations in soil DOM after fire were affected by feedbacks between forest type and fire (where soils from pine plantations appeared to be more affected by fire).

Propensity of Sawmills to Produce Structural Sawn Wood in Chile

Abstract The goals of Chile’s forest policy regarding the use of wood in construction are far from being achieved. Chile is the ninth-largest global producer of sawn softwood and has an industry with numerous sawmills; however, structural sawn wood (SSW) represents less than 1 percent of the industry’s total production, which is insufficient to address large-scale construction programs with wood. Therefore, policy instruments are needed to lead to an increase in the volume of SSW production. This research aimed to design a typology of sawmills that facilitates the definition and implementation of these policy instruments to ensure attainment of the 2035 goal of the forest policy. Multiple linear regression and multiple logistic regression were used to assess the impact of various variables on SSW production; variable selection was done using stepwise regression. The number of clusters was determined using the gap method, and sawmill clusters were determined using k means. The result is a typology with five categories of sawmills based on their propensity to produce SSW. The most significant variable was the quality of the supply, so it is suggested to prioritize the management of Pinus radiata plantations. With this result, a map for the application of policy instruments was created, proposing an intervention pathway. The proposed typology will stimulate decisions to provide direct support to the sawmill industry, thereby increasing SSW production.

Effect of climate change on the land rent of radiata pine plantations in Chile: Site productivity and forest fires

Climate change can severely affect forest plantation productivity and fire regimes in temperate regions. The economic evaluation of these impacts is challenging because of the spatially differentiated effects expected to occur across planted areas. We calculated the combined effect of projected climate change on the stochastic land expectation value (SLEV) for a random sample of stands covering the Pinus radiata plantations in central-southern Chile. To simplify the stochastic evaluation problem with changing productivity and fire frequencies over time, we divided rotations into stages, before and after commercial thinning, and assumed that reforestation is at the end of each stage. The SLEV was calculated through Monte Carlo simulations using the coefficients from previously estimated productivity and fire risk statistical models. The predicted combined effect on the SLEV is negative in most regions except those in the southern limit of the specie distribution. In the economically crucial coastal area of the central regions, the negative effect of more frequent fires outweighs faster growth. In the northern drier areas, the SLEV becomes negative due to a large drop in site productivity. Anticipatory reassignments of management regimes have a large adaptation value in these low-productivity sites. Our optimization-simulation results suggest that relative to prescribed management regimes, the optimal rotation age in most low-productivity sites is longer and in most high-productivity sites shorter. Shortening the rotation age by one to two years has an important adaptation value in highly productive coastal sites.

Genetic Diversity of Lecanosticta acicola in Pinus Ecosystems in Northern Spain.

Lecanosticta acicola is one of the most damaging species affecting Pinus radiata plantations in Spain. Favourable climatic conditions and unknown endogenous factors of the pathogen and host led to a situation of high incidence and severity of the disease in these ecosystems. With the main aim of understanding the factors intrinsic to this pathogenic species, a study of the population structure in new established plantations with respect to older plantations was implemented. The genetic diversity, population structure and the ability of the pathogen to spread was determined in Northern Spain (Basque Country), where two thirds of the total Pinus radiata plantations of Spain are located. From a total of 153 Lecanosticta acicola isolates analysed, two lineages were present; the southern lineage, which was prevalent, and the northern lineage, which was scarce. A total of 22 multilocus genotypes were detected with a balanced composition of both mating types and evidence for sexual reproduction. In addition to the changing environmental conditions enhancing disease expression, the complexity and diversity of the pathogen will make it difficult to control and to maintain the wood productive system fundamentally based on this forest species.

Influence of Sowing Date on Phenology, Biometric, and Yield of Mungbean (Vigna radiata) Cultivars in Chitwan, Nepal

Mungbean is a commercially promising legume crop, accounting for a very low productivity of approximately 0.5 tons ha1 in the Terai region of Nepal. This study aimed to achieve the potential yield of mungbean promising cultivars planting at optimum sowing time. An experiment was conducted at the Agriculture and Forestry University (AFU), Rampur, Chitwan, during the spring of 2019 in a split-plot design (SPD) with three replications and 16 treatment combinations. Four sowing dates at 15 days intervals (13th February, 28th February, 15th March, and 30th March) of 2019; cultivars viz. Kalyan, Pratikshya, Pratigya, and Pant-5 are considered as main and subplot factors. The Dunken test was carried out to compare the mean in R-software at p ≤ 0.05 level of significance. The results revealed that earlier planting (Feb 13 planting) resulted in delayed emergence, slower growth, and the lowest yield (1.79 tons/ha). The March 15 to March 30 plantations resulted in significantly faster emergence, germination, and growth showing a higher yield. Pant-5 yielded a higher grain yield, which was statistically at par with Partigya (2.08 tons/ha) and Partikshya (1.983 tons/ha). Vigna radiata plantations from March 15 to March 30 are the optimum sowing times for higher productivity (2.119 tons/hectare) and high potential yield, which can be applied for perfect decision-making in mungbean plantations. Future work on least-squares analysis for understanding the genotypic-environment interaction of economic traits and the effect of different nutrient sources on cultivars has scope.

Comparison of Errors Produced by ABA and ITC Methods for the Estimation of Forest Inventory Attributes at Stand and Tree Level in Pinus radiata Plantations in Chile

Airborne laser scanning (ALS) technology is fully implemented in forest resource assessment processes, providing highly accurate and spatially continuous results throughout the area of interest, thus reducing inventory costs when compared with traditional sampling inventories. Several approaches have been employed to estimate forest parameters using ALS data, such as the Area-Based Approach (ABA) and Individual Tree Crown (ITC). These two methodologies use different information processing and field data collection approaches; thus, it is important to have a selection criterion for the method to be used based on the expected results and admissible errors. The objective of this study was to compare the prediction errors of forest inventory attributes in the functioning of ABA and ITC approaches. A plantation of 500 ha of Pinus radiata (400–600 trees ha−1) in Chile was selected; a forest inventory was conducted using the ABA and ITC methods and the accuracy of both methods was analyzed. The ITC models performed better than the ABA models at low tree densities for all forest inventory attributes (15% MAPE in tree density—N—and 11% in volume—V). There was no significant difference in precision regarding the volume and basal area (G) estimations at medium densities, although ITC obtained better results for density and dominant height (Ho). At high densities, ABA performed better for all the attributes except for height (6.5% MAPE in N, 8.7% in G, and 8.9% in V). Our results showed that the precision of forest inventories based on ALS data can be adjusted depending on tree density to optimize the selected approach (ABA and ITC), thus reducing the inventory costs. Hence, field efforts can be greatly decreased while achieving better prediction accuracies.

Reduced growth of Pinus radiata in the presence of the Australian native Allocasuarina nana via direct allelopathy and inhibition of the pine-supporting mycorrhizal community

The establishment and productivity of new forest plantations can be significantly impacted by the presence of native vegetation. In a study site in New South Wales, Australia, the growth of a Pinus radiata plantation has been virtually halted in areas dominated by the native shrub Allocasuarina nana, effects that persist for decades even after its physical removal. To determine the mechanism by which A. nana impedes P. radiata growth, we compared the fungal soil community and metabolomic profile of soils in patches rich in A. nana with adjacent healthy P. radiata patches and the transition zone between them. This data was complemented by a pot experiment to assess P. radiata growth in soils from the different vegetation areas with and without a viable soil community or the addition of A. nana roots or exudates. Together, the data demonstrates that these A. nana soils are likely inhibitory to P. radiata growth through a dual mechanism: impacting the growth of the pine directly through root associated metabolites and indirectly through the inhibition of the fungal community supporting P. radiata health, including ectomycorrhizal fungi.

How much carbon do Argentine Pampas Pinus radiata plantations store?

Aim of study: To quantify the biomass and carbon stored in the main ecosystem components in Pinus radiata D. Don plantations across an age sequence in the Pampean region of Argentina.
 Area of study: Plantations were established on non-agricultural land, southeast of the province of Buenos Aires.
 Material and methods: Fourteen sites were selected of Pinus radiata plantations, 9-, 13-, 15-, 19- and 21-years-old, in a first forest rotation. Forty-two trees were destructively sampled, allometric functions were set and biomass was estimated for the different compartments (needles, branches, stem). Root biomass was estimated from equations adjusted by the sampling of twenty-four trees. At 4 sites, C-stock was determined in the tree component, in the forest floor and understory, and soil organic carbon (SOC) was determined to a 50 cm depth.
 Main results: C-stock in the tree component increased with stand age, whereas SOC and C-stock in the forest floor and understory were not related to stand age. The system-level C-stock was 273.1, 263.7, 269.7 and 324.1 Mg ha-1 for the 9-, 13-, 19- and 21-year-old stands. On average, 69% of the total system-level C-stock was in the soil, while 28% was in the tree biomass and 3% was in the forest floor and understory.
 Research highlights: The forestry component contributed to C sequestration with no changes in SOC-stocks reserves for the age range studied.

Interaction of site, spacing, weed control and fertiliser in Pinus radiata plantations in southeast New South Wales

ABSTRACT Two trials addressing soil preparation, weed control, fertiliser application and planting density were established on dry, high-elevation sites as part of a program to develop site-specific management. The sites differed in soils and the level of pasture improvement. The objectives included identifying treatment combinations that had greatest productivity and best stem and branch form, considering that poor stem form is an issue on pasture sites. The trials were assessed at 13 years of age. Volume production was high compared with a plantation established earlier on a native forest site, but it was not possible to determine whether this was a result of higher survival, higher nutrition, improved weed control or improved genetics. There was little difference in the effects of soil preparation treatments, and there was no effect at 13 years of the small early-fertiliser application. Weed control was important, with effects on volume production varying between sites and having a greater effect on the highly improved pasture site. Increasing stocking from 1000 stems ha−1 to 1500 stems ha−1 increased volume production by about 24% where weed control was applied. There were differences in stem and branch form between sites, and the highly improved pasture site had a higher level of multi-leaders, probably attributable to low boron. The study shows the value of small, standardised silvicultural trials in the development of site-specific management.

First report of Phytophthora pluvialis causing needle lesions on Pinus pinea in New Zealand

During routine surveillance in October 2020, needle lesions and necrosis were observed in two 42-year-old stone pines (Pinus pinea) situated in an amenity planting within an infected Pinus radiata plantation in Nelson, New Zealand. Symptoms were widespread across the foliage of infected trees and samples were sent to Scion's Forest Health Reference Laboratory. Approximately fifteen needles displaying yellow and red bands (Fig. 1) tested positive for Phytophthora using a Phytophthora ImmunoStrip® (Agdia, USA), and PCR and subsequent DNA sequencing with Ypap2F/Ypap2R primers (McDougal et al., 2021), indicated Phytophthora pluvialis. A Phytophthora species was isolated from diseased tissue. Morphological characteristics were consistent with those described by Reeser et al. (2013) for P. pluvialis. This identification was confirmed by sequencing the internal transcribed spacer region (White et al., 1990). The isolate was deposited in the National Forest Culture Collection (NZFS 5280) and symptomatic needles were lodged into the National Forest Mycological Herbarium (NZFRI 5931). Foliage symptoms caused by P. pluvialis on other conifers, including Pinus radiata, Pseudotsuga menziesii and Tsuga heterophylla, typically express as distinct khaki/red lesions and black resinous bands (Dick et al., 2014), rather than the yellow and red bands observed on the stone pines (Fig. 2). Pathogenicity testing was done by inoculating stone pine needles with P. pluvialis zoospores using a needle dip assay according to Dick et al. (2014). Stone pine needles from young healthy seedlings were placed in sterile pond water inoculated with P. pluvialis zoospores and incubated in darkness at 17°C for 24 hours. Control needles were placed in sterile pond water. Needles were then lain on moist paper towels in a sealed tray and incubated at 17°C at a 14-hour photoperiod. After ten days, olive/yellow lesions were observed on needles (Fig. 3). These lesions were lighter than those observed on field samples, however, this is common in detached needle assays of other species, such as P. pluvialis infection of Pinus radiata (Dick et al., 2014). Sporangia were observed near the lesion margin of needles (Fig. 4). Sections of symptomatic needles were surface sterilised and plated onto a Phytophthora-selective media (10% carrot agar + ampicillin, pimaricin, rifampicin, nystatin and hymexazol). The resultant cultures displayed morphological features of P. pluvialis, fulfilling Koch's postulates (Fig. 5). Control needles remained healthy (Fig. 3). To our knowledge, this is the first report of P. pluvialis causing needle disease on stone pine. Stone pine is an economically important species due to the production of high value pine nuts and timber. Although stone pine accounts for a small proportion (<1%) of New Zealand's forests, continued monitoring is recommended to assess the impact of disease on the growth and yield of these plantations. Forest Growers Levy Trust funded surveillance and diagnosis through the Forest Biosecurity Surveillance system.

Long-Term Responses to Competing Vegetation Management for Pinus radiata

Numerous studies have been carried out to quantify the response to competing vegetation control (CVC) in P. radiata plantations. Most of these publications have reported on the early response in tree growth; however, a knowledge gap exists regarding the growth responses throughout the rotation. In this study, we analyzed the long-term response of P. radiata plantations across a gradient of seven sites in central Chile. Treatments included a no-action control, two spot (circular) areas of competing vegetation control using herbicides around individual P. radiata seedlings (spot herbicide application of 0.75 and 1.5 m), and total competing vegetation control using herbicides. Additionally, three different timings for control regimes were included (0, 1, and 2 years after planting). Competing vegetation biomass abundance during the first growing season ranged from 0.6 to 5.7 Mg ha−1 across all sites. The total competing vegetation control treatment maintained for 2 years (TotalY012) showed the largest gain in stem volume per hectare (VOL) in most of the sites. The sites included in this study showed contrasting values in productivity, having volume yields for the TotalY012 treatment ranging from 238 m3 ha−1 at the site with the lowest annual rainfall (age 12 years) to 471 m3 ha−1 at the southern site (age 14 years). Across all sites, maximum gain in VOL ranged between 21 and 175 m3 ha−1 at age 11 to 14 years and was linearly correlated to the amount of competing biomass controlled during the first year after planting. At the southern, wetter site, plots with only pre-planting spot herbicide application achieved 87% of VOL of plots with TotalY012. Our results suggest that CVC improved the availability of resources at the site for P. radiata seedlings, increasing volume production by reducing environmental constraints to tree growth differentially at each site.

Efficacy of cuprous oxide for control of dothistroma needle blight in Pinus radiata plantations in Australia

ABSTRACT Dothistroma needle blight (DNB, Dothistroma septosporum) is a significant disease in Pinus radiata plantations on the Northern Tablelands of New South Wales and in the Murray Valley region of Victoria/New South Wales, Australia. Aerial application of copper oxychloride has been used to control DNB in these regions since soon after it was established. Research in New Zealand, however, has identified cuprous oxide as a more efficient and cheaper fungicide for controlling DNB. In this study, we test the efficacy of a single (applied in late October–early November) and double (October and February) application of cuprous oxide for controlling severe (50%) DNB in P. radiata plantations on the Northern Tablelands. We established replicated blocks 5–10 ha in size to ensure the results were operationally valid. Disease severity and defoliation were assessed on individual trees pre- and post-treatment, and aerial surveys were conducted to gauge the effect of treatments on the subsequent operational fungicide spray program. Cuprous oxide application significantly (P 0.01) reduced disease severity compared with no application, with a second application reducing severity even further. Ten months post-treatment, tree-level disease severity was 39% in unsprayed plots, 31% in single-sprayed plots and 8.5% in double-sprayed plots. The double application effectively reduced disease to negligible levels, while the single application provided adequate control for up to three months. At an operational level, even the single fungicide application reduced disease severity at the block scale when mapped during aerial surveys. Based on aerial assessments that trigger control action, all unsprayed plots required fungicide application in the season after the study (2013), while only two of seven single-sprayed blocks and none of the double-sprayed blocks required additional control. Extrapolating from this, a single fungicide application meant that 70% of the area did not require a fungicide application in the subsequent year. Based on these results and evidence from New Zealand, we recommend that cuprous oxide replace copper oxychloride for DNB control in Australia and that a double application is used in areas with severe (50%) levels of the disease.

Current and future risks of drought-induced mortality in Pinus radiata plantations in New South Wales, Australia

ABSTRACT Drought is a regular feature of Australian landscapes, and its intensity and frequency are likely to increase in a changing climate. Land managers are grappling with managing the impacts of drought, with large-scale die-offs occurring more frequently in forests globally. Drought-induced tree mortality has caused major impacts in Pinus radiata plantations in New South Wales, Australia, with extended drought, heatwaves and pest and disease attacks all recognised as predisposing, inciting or contributing factors. The extent and severity of drought-induced tree mortality has been mapped across the Pinus plantation estate in New South Wales annually since 1996. In this study, we used this long-term empirical data to develop a model of drought risk for P. radiata plantations. Using random forest, we identified site index, annual temperature, annual rainfall, elevation and increasing number of hot days (above 20°C and 35°C) as the influencing variables associated with drought-induced tree mortality. We then used this model to look at the risk of drought-induced tree mortality under climate-change scenarios in 2050 and 2070. Although forest managers already understand the drought risk in their estates, we developed an empirical model and produced GIS layers at high resolution (100 m) to assist in more accurately and effectively managing drought. The accuracy and precision of our model (overall accuracy 89.2%, kappa 0.75) enables forest managers to include it in their decision-making in the management of the potential impacts of drought on the current plantation estate (e.g. via modified silvicultural regimes) as well as in the future (e.g. modified silvicultural regimes or planting drought-tolerant genotypes).

Cryptosporidium spp. and Giardia spp. in wild rodents: using occupancy models to estimate drivers of occurrence and prevalence in native forest and exotic Pinus radiata plantations from Central Chile

The conversion of native forest to forestry plantations is a worldwide practice, affecting biodiversity and host-parasite interactions. One of the most common timber plantations in the world are monocultures of Monterey pine (Pinus radiata). Using occupancy models, we analyzed the occurrence and prevalence of Cryptosporidium spp. oocysts and Giardia spp. cysts in fecal samples of wild rodents from a landscape dominated by extensive Monterey pine plantations in central Chile. We aimed to assess drivers of parasite infection such as habitat type, abundance of rodent hosts, species richness, and season. Small mammals were sampled seasonally for two years in three habitat types: native forests, adult pine plantations and young pine plantations. A total of 1091 fecal samples from seven small mammal species were analyzed by coprological analysis. Occurrence probability of Cryptosporidium spp. and Giardia spp. was similar for the most abundant rodent species (Abrothrix longipilis, A. olivacea, and Oligoryzomys longicaudatus) and for all habitat types. For Cryptosporidium spp., variation in prevalence was mostly explained by season with higher prevalence during winter season and lower during spring. For Giardia spp., the prevalence was significantly higher in young pine plantations, followed by adult pine plantations and native forests. In addition, higher prevalence of Giardia spp. was associated with lower host richness, suggesting a possible dilution effect. Our findings reveal that Monterey pine plantations increase Giardia spp. transmission among rodents, but has no clear effect on Cryptosporidium spp., providing evidence that the impact of land use on parasitism can be idiosyncratic. Since both parasites have zoonotic potential, our findings may be useful for land use planning and management considering health issues.

Lecanosticta pharomachri and Its Newly Discovered Sexual State Causing a Serious Needle Disease of Pinus spp. in Colombia.

Brown spot needle blight (BSNB), caused by the fungal pathogen Lecanosticta acicola, is a well-known disease of Pinus spp. in several northern hemisphere countries. In the southern hemisphere, this disease has been reported only in Colombia and, apart from a single report of severe defoliation of Pinus radiata plantations in the early 1980s, has not caused serious damage in this country. An outbreak of a disease resembling BSNB on Mesoamerican Pinus spp. grown in Colombia has raised concern that L. acicola may have reemerged as a pathogen. DNA sequence-based analyses for the internal transcribed spacers, translation elongation factor 1-α and RNA polymerase II second largest subunit regions showed that the outbreaks were caused by L. pharomachri, a species distinct from, but closely related to, L. acicola. The discovery of L. pharomachri in Colombia is the first incidence of the pathogen causing a serious disease problem and the first occurrence on the hosts P. patula and P. maximinoi. A sexual state for L. pharomachri was discovered for the first time, and the description of the species has thus been emended.

Tree Cover Species Modify the Diversity of Rhizosphere-Associated Microorganisms in Nothofagus obliqua (Mirb.) Oerst Temperate Forests in South-Central Chile

Chilean native forests have been subjected to several types of disturbances, with one of them being the replacement by exotic species. Pinus radiata D. Don is a widespread exotic tree that forms extensive plantations in southern Chile. It covers extended areas, affecting the landscape, biodiversity, and ecosystem services associated with native forest ecosystems. Although advances in assessing the impact of exotic plant species have been conducted, few studies have focused on the alteration of soil microorganisms. This study aimed to characterize the rhizosphere bacterial and fungal communities associated with the tree species Nothofagus obliqua inside a native forest stand and within a P. radiata plantation growing nearby. We used a 16S rRNA gene and ITS region metabarcoding approach. Using bioinformatics, diversity indices, relative abundance, preferential taxa, and predicted functions and guilds were estimated. The β-diversity analysis showed that both factors, the type of soil (rhizosphere or bulk soil) and the type of site (native forest or P. radiata plantation), were significant, with the site explaining most of the variation among bacterial and fungal communities. Proteobacteria and Basidiomycota were the most abundant bacterial and fungal phyla in both types of soil and sites. Similarly, bacteria showed similar abundant taxa at the family level, independent of the soil type or the site. The main fungal taxa associated with native forests were Tricholomataceae and Cantharellales, whereas in P. radiata plantations, Russulaceae and Hyaloscyphaceae were the most abundant families. The main bacteria functional groups were chemoheterotrophy and aerobic chemoheterotrophy, without significant differences between the type of soil or sites. Overall, these results demonstrate that the composition and diversity of bacterial and fungal communities associated with native N. obliqua forest are influenced by the surrounding forest, and mainly depend on the site’s characteristics, such as the lignin-rich wood source. These results improve our understanding of the impact of native forest replacement on soil microbial communities, which can alter microbial-related soil ecosystem services.

Differentiating individuals of Armillaria species in New Zealand forests

Background: Armillaria novae-zelandiae and A. limonea occur naturally as wood decay fungi in native forests in New Zealand. As pathogens they are responsible for significant root disease in trees and shrubs in plantations, crops and urban parks and gardens. A thorough understanding of their population dynamics entails knowledge of the spatial arrangement of their individual mycelia or genets. In previous work the distributions of vegetative compatibility groups (VCGs) of these fungi were mapped in an area of native forest prior to and after replacement by a young Pinus radiata plantation. With the advent of molecular technology, it has become possible to test species identities made earlier using culture techniques and to verify whether or not their VCGs, determined by incompatibility reactions between paired cultures, represent distinct individual genets. Methods: Stock subcultures of isolates representing each VCG were recovered from storage in order to obtain DNA. Extracted DNA was subjected to a polymerase chain reaction procedure (UP-PCR) using 11 universal primers to assess genetic variation between subcultures. Bands were scored as either present or absent for each primer-subculture combination and cluster analysis was undertaken by generating dendrogram trees to reveal genetic groupings among subcultures. Results: DNA cluster analysis divided subcultures of isolates into two species groups, A. novae-zelandiae and A. limonea, corresponding to identities determined through culture morphology. Within species, subcultures grouped into clusters that matched VCGs determined by earlier culture pairing. There was little indication of genetic variation within VCGs, except for one of A. limonea, which comprised two sub-clusters. Conclusions: The Armillaria species and VCGs identified by culture techniques in the laboratory were verified by independent molecular methodology. In general, the VCGs represent discrete individual genets or colonies in the field. Techniques that differentiate isolates based on differences in their DNA sequence provide a quick alternative to time-consuming laboratory culture methods for resolving population spatial structure. However, some complementary isolate pairing may be necessary when rationalising the significance of groupings in dendrogram trees.