Annals of Forest Research

Topography affects the natural forest recovery on inland dunes in Central Europe

Piotr Sewerniak — 2024-07-11

Topography, by spatially altering site conditions, affects ecological processes, e.g. natural forest recovery. Until now the early dynamics of naturally encroaching trees on inland dunes with regard to topography has not been sufficiently studied in detail, and became the aim of our study. To achieve this aim, in 2011 we established a 14.87 ha long-term research site located in the Toruń artillery ground (N Poland), in one of the biggest inland dune fields of Central Europe. We surveyed twice (2011 and 2021) trees occurring in the site, and investigated their characteristics (GPS coordinates, height, diameter, age, annual stem increment, slenderness) regarding 5 topographical variants: north- (N), east- (E), west- (W), and south-facing (S) slopes, as well as intra-dune depressions (D). We found that within the investigated 10 years timespan the number of trees increased almost fourfold (from 560 to 2016). The natural encroaching of trees was the most advanced in north-facing slopes (88 ± 17 and 352 ± 89 trees ha-1 in 2011 and 2021, respectively). In turn, in sunny exposures and in intra-dune depressions the process was the least advanced (in 2021: 64 ± 21 and 25 ± 15 trees ha-1, respectively), which could be primarily linked to unfavourable moisture conditions occurring on south-facing slopes, and strong competitive effect of tall grasses on young trees regarding the depressions. By showing the rate and topographically controlled spatial pattern of trees encroachment, our study can be useful e.g. for practising managers when reforestation of inland dunes by natural means is planned.

Genetic diversity and population structuring of Pistacia lentiscus L. across Mediterranean region

Faten Mezni — 2024-07-11

Pistacia lentiscus L., the mastic tree, is an evergreen shrub distributed across the entire Mediterranean Basin. This species, known for millennia for its medicinal, food and cosmetic value is currently threatened by overexploitation and climate change. To help prioritize conservation actions, we studied its genetic diversity using seventy four Mediterranean accessions and seven microsatellite loci. Genomic DNA was extracted from mastic tree leaves. Allelic frequency and population structure estimates were calculated as well as the relationship between studied populations. The observed heterozygosity (Ho) and expected heterozygosity (He) ranged from 0.493 to 0.788 and 0.518 to 0.781 respectively. Shannon’s Information Index (I) ranged from 0.858 to 1.819 with a mean value of 1.420. The mean fixation index (Fst) value was estimated to 0.124. AMOVA analysis showed that only 7% of the variance existed among populations. In addition, the STRUCTURE analysis showed a clear distinction between the eastern and the western Mediterranean populations when the number of clusters (K) was set at 2. The study of genetic diversity of the Mediterranean P. lentiscus is of interest for conservation of genetic resources and it contributed to the understanding of the evolutionary history of this species.

Effects of species and tree size diversity on above-ground biomass in diverse heterogeneous tropical evergreen forests, Quangbinh Province, north central Vietnam

Nguyen Hong Hai — 2024-07-11

The relationships between species diversity and size structure complexity on above ground biomass (AGB) have theoretical and practical applications for biodiversity conservation and sustainable forest management. The relationships become more complex in the high-species diversity of tropical forests and heterogeneous environmental conditions. To disentangle the complicated relationships, structural equation models were applied to examine the relative effects of species and tree size diversity on above ground biomass under different topographical conditions of two tropical evergreen forest stands. Our results showed that: (i) species diversity contributes greater to AGB in the forest stand under homogeneous topography. (ii) Structural diversity positively affected AGB in the heterogeneous topographical stand. (iii) Slope revealed a negative effect on species diversity but positive effects on structural diversity and AGB in both studied plots. We concluded that maintaining high-stand structural diversity enhances above ground biomass and local topographical conditions constrain the relationship between species and size diversity in the study area.

Impact of Michelia champaca and Tectona grandis mono-species and their mixed plantation on chemical soil properties in a tropical semi-evergreen forest

Farzana Raihan — 2024-07-11

Understanding the effects of planted forests on soil properties is of great importance to meet increasing demands for wood production and contributing to forest ecosystem services and soil carbon sequestration. However, the influence of mono- and mixed tree plantations on soil chemical properties remains incompletely explained, particularly in tropical semi-evergreen forests. In this study, a mono-plantation of Michelia champaca and Tectona grandis, as well as their mixed plantation, were studied on soil variables (pH, SOC, N, P, K) at different depths (0-10, 10-20, and 20-30 cm) in tropical semi-evergreen forest of the Khadimnagar National Park, Bangladesh. All examined pedovariables showed no significant differences among plantation types, notably in the surface soil layer (up to 10 cm). However, significant oscillations were found in the deepest soil layer (20-30 cm), where M. champaca and mixed-species plantations obtained the lowest SOC (0.55-0.66%) and N (0.05-0.06%) concentrations. In the intermediate soil layer (10-20 cm) K concentrations were the lowest in M. champaca (19.6 mg/kg) and mixed-species plantation (17.6 mg/kg), while T. grandis recorded the highest K concentration (27.4 mg/kg). Additionally, the results indicated an increase in pH with soil depth (from 5.30 in the topsoil to 7.00 in the deepest layer), with T. grandis showing the lowest values across examined soil layers (5.76-5.95) and significantly differing from M. champaca, which exhibited the highest pH over the soil profile (6.29-6.51). Such results suggest the leaching of basic cations (Ca2+, Mg2+, K+) over the soil profile due to pronounced monsoon rainfalls. Further research is necessary to fully elucidate underlying mechanisms behind the observed impact of examined plantations on chemical soil variables. Considering other variables such as litter chemical composition and various physical and microbiological soil properties can offer valuable guidelines for enhancing more sustainable management of a tropical semi-evergreen forest, prone to soil acidity and water erosion.

Landscape fragmentation and connectivity as key variables on occurrence of human-wildlife interactions

Ileana Pătru-Stupariu — 2024-07-11

Human-wildlife interactions (HWI) are one of the most highly studied topics from the fields of wildlife management and are reported to be increasing globally as anthropogenic lands uses expand into wild lands, especially in mountainous areas where forest habitats are in the proximity of human settlements. The upper Prahova Valley in south-central Romania provides habitat to several native charismatic wildlife species. Since 1990 this area has become a major tourist destination now characterized by a high density of major transport infrastructures and homes. To assess how the changes in land use have affected HWIs, from September 2018 to August 2019, we discussed with 370 local citizens from the cities of Sinaia, Bușteni and Predeal. We developed maps of wildlife habitat fragmentation and connectivity and superimposed them over the locations with the HWI hotspots. According to the results, over 50% of the hotspots identified where located in areas exhibiting the greatest level of fragmentation, and the species frequently involved in interactions were the brown bear (Ursus arctos), wild boar (Sus scrofa), and red fox (Vulpes vulpes). The maps suggest that habitat fragmentation could represent a primal cause for the regions’ high frequency of animal descents into settlements, since wildlife habitats and ecological corridors are affected by the fragmentation of anthropogenic infrastructures especially in the proximity of major settlements. As a conclusion, our results highlight the need for sustainable landscape planning in order to optimize biodiversity management and diminish interactions between humans and wild animals, based on: a) mapping the areas characterized by high quality wildlife habitats and including them into a system of strict protection, b) developing or enhancing wildlife ecological corridors to favour animal movement between intact ecosystems, and c) regulating the expansion of human infrastructures in the proximity of strictly protected habitats.

Integration of Terrestrial Laser Scanning and field measurements data for tree stem volume estimation: Exploring parametric and non-parametric modeling approaches

Florin Capalb — 2024-07-11

Terrestrial laser scanning (TLS) has emerged as a powerful tool for acquiring detailed three-dimensional information about tree species. This study focuses on the development of models for tree volume estimation using TLS data for even aged Fagus sylvatica L. stands located in the western part of the Southern Carpathians, Romania. Both parametric and non-parametric modeling approaches were explored, leveraging variables extracted from TLS point clouds such as diameter at breast height (DBH), height, crown radius, and other relevant crown and height parameters. Reference data were collected through high-precision field measurements across 76 circular Permanent Sample Areas (PSA) spanning 500 m² each. A multi-scan approach was implemented for TLS data collection, involving four scanning stations within each PSA. Concurrently, parametric (regression equations) and non-parametric (Random Forest - RF) models were applied, leveraging all TLS-derived variables to explore potential enhancements in volume estimation accuracy. Among the parametric models, the most effective performer was the one featuring solely DBH as an input variable. The RF non-parametric model yielded more accurate stem volume estimates (RMSE = 1.52 m³*0.1ha^-1; RRMSE = 3.62%; MAE = 1.22m³*0.1ha^-1) compared to the best-performing regression model (RMSE = 5.24 m³*0.1ha^-1; RRMSE = 12.48%; MAE = 4.28 m³*0.1ha^-1). Both types of models identified DBH as the most important predictive variable, while the RF model also included height and crown related parameters among the variables of importance. Results demonstrate the effectiveness of the non-parametric RF model in providing accurate and robust estimates of tree stem volume within even aged European beech stands. This highlights the significance of TLS data, increasingly employed in diverse forest inventory and management applications. Nevertheless, additional research and refinement of the proposed models are needed. This includes thorough validation across various forest ecosystems and continued efforts to enhance the accuracy of tree height determination from point cloud data.

Opportunity to integrate machine management data, soil, terrain and climatic variables to estimate tree harvester and forwarder performance

Filippo Guerra — 2024-07-11

The Cut-to-Length (CTL) harvesting system is nowadays predominant in the field of mechanized forest operations, consisting mainly in harvesters and forwarders forestry machines. These machines are equipped with an On-Board Computer (OBC) that collects a large amount of information concerning machine parameters such as harvested timber, travelled distance or fuel consumption. Stream machine data are sent to the machine fleet management system (FMS) on cloud, stored and automatically summarized on hourly, daily, weekly, or monthly basis. Understanding the benefits of data mining techniques - in finding trends and patterns - exploiting FMS database in relation to topographic and climatic condition is still an ongoing open research question. The present work aims at verifying if and how machine´s performance indicators (e.g. fuel consumption) recorded and summarized on a hourly basis by the FMS are influenced by site specific parameters, such as terrain morphology, soil type, wet soil condition, and weather conditions, derived from open source portal. A specific methodology in machine data acquisition and datasets implementation has been set in this study. The dataset results in a combination of three sub-datasets, consequently merged, filtered and analyzed. A first sub-dataset is made up of “machine data”, a second is made up of “environmental data”, and a third set of data is made of “climatic data”. The obtained results revealed that the combination of different data sources’ provides significant insight into understanding machine performance. Moreover, the integration of terrain morphology and climatic data have direct impact on the machine fuel consumption, harvester machine in particular. However, in order to address specific interactions among variables with greater robustness, further investigations into this project will consider the whole set of variables on a smaller scale (e.g., case study) with higher data resolution.

Fungal diversity in chestnut galls induced by Dryocosmus kuriphilus from Basilicata Region (Southern Italy)

Stefania Mirela Mang — 2024-07-11

In recent years, the Asian chestnut gall wasp (ACGW) Dryocosmus kuriphilus has been reported to have a high incidence in Italy and other Mediterranean basin countries. In 2021-2022, a study was undertaken in the Basilicata Region (Southern Italy) to investigate the relationship between the galls produced by ACGW on sweet chestnut (Castanea sativa Mill.) and fungal pathogens. In particular, the fungal diversity from green and necrotic galls collected from two important sweet chestnut sites (Melfi and Rionero in Vulture) was investigated. Nineteen fungal taxa were identified based on their morphological and molecular traits. In both localities, the most frequent species isolated from green and necrotic galls were Gnomoniopsis castaneae, Colletotrichum acutatum, and Pestalotiopsis sp. It is essential to understand the role played by the galls as an inoculum source for sweet chestnut fungal pathogens, particularly for G. castaneae, an emerging pathogen of which biology is still poorly understood. Findings from the present study stressed that the complex relationship between host-insect-microbial community needs to be elucidated to be able to control the pathogenic fungi and consequently maintain sweet chestnut trees' health as they play a key role in the local agriculture (horticulture, forestry) and subsidiary economy

Recreation in suburban forests – monitoring the distribution of visits using the example of Rzeszów

Tomasz Dudek — 2024-07-11

The research aimed to determine the actual distribution of visits in suburban forests in the temperate climate zone, using the Rzeszów metropolitan area as an example. The study also examined whether there is a correlation between the number of visitors to the forests and weather conditions: average daily air temperature, total daily precipitation, and the maximum sustained wind speed within a day. The distribution of visits was determined based on a 365-day monitoring of recreational traffic intensity using a sensor in the form of a pyroelectric detector. Weather data for each day of observation were obtained from a meteorological station. An average of 51 daily visitors was recorded (29 on weekdays and 101 on weekends and holidays). Most people visited the forest during the vacations, in August (14.7%) and July (14.1%), and least in winter: in February (2.7%) and December (3.4%). It was observed that the number of visits to the forest increased with the rise in average daily air temperature. In contrast, as the maximum sustained wind speed increased throughout the day, the number of visits decreased. There was no clear correlation between the number of visits and the total daily rainfall, except for weekends and holidays (number of visits decreased with the increase in rainfall). The number of visitors to suburban forests was more influenced by public holidays than weather conditions. Many forest visitors were significantly more frequently observed on holidays and weekends than weekdays. More than half of all visits occurred on weekends. Forests were most frequently visited on Sundays (38.2%). Suburban forests were visited from 5 AM to 10 PM, with shorter weekend hours (from 6 AM to 8 PM). The results obtained in the study can be valuable for managing recreational activities in suburban forests.

Estimating canopy and stand structure in hybrid poplar plantations from multispectral UAV imagery

Elio Romano — 2024-07-11

Accurate estimates of canopy structure like canopy cover (CC), Leaf Area Index (LAI), crown volume (Vcr), as well as tree and stand structure like stem volume (V_st) and basal area (G), are considered essential measures to manage poplar plantations effectively as they are correlated with the growth rate and the detection of possible stress. This research exploits the possibility of developing a precision forestry application using an unmanned aerial vehicle (UAV), terrestrial digital camera and traditional field measurements to monitor poplar plantation variables. We set up the procedure using explanatory variables from the Grey Level Co-occurrence Matrix textural metrics (Entropy, Variance, Dissimilarity and Contrast) calculated based on UAV multispectral imagery. Our results show that the GCLM texture derived by multispectral ortomosaic provides adequate explanatory variables to predict poplar plantation characteristics related to plants' canopy and stand structure. The evaluation of the models targeting the different poplar plantation variables (i.e. Vcr, G_ha, Vst_ha, CC and LAI) with the four GLCM explanatory variables (i.e. Entropy, Variance, Dissimilarity and Contrast) consistently higher or equal resulted to R2 ≥0.86.

Vegetation predicts soil shear strength in Arctic Soils: Ground-based and remote sensing techniques

Wade A. Wall — 2024-07-11

Soil shear strength (SSS) is an important soil attribute that is influenced by vegetation. If aboveground biomass estimates can be used to predict soil shear strength, it would greatly enhance our ability to estimate SSS across large areas. Using data collected from 24 plots in Alaska, we analyzed the relationship between soil shear strength and ground-collected vegetation attributes and remotely sensed (RS) variables. We constructed both univariate and multivariate models to assess the predictive capabilities of the vegetation and RS variables. Total trees and total conifers were significant predictors of SSS, with a negative relationship existing between total trees/total conifers and SSS. Graminoid cover (%) was positively correlated with soil shear strength and was also a significant predictor of SSS. Of the RS variables, the bands B1 (0.443 μm), B2 (0.490 μm), and B3 (0.560 μm) from the Sentinel 2 satellite system were all significant predictors of SSS. A multivariate model improved model fit over the simple univariate models, with an R2 = 0.46. We have both demonstrated a connection between SSS and aboveground vegetation attributes for areas within interior Alaska and that it is possible to link SSS to RS variables using a multivariate model.