Circular Plots Research Articles

Ecological patterns and conservation opportunities with carbon credits in Brazil nut groves: a study-case in the Southeast Amazon

Background: Brazil Nuts (BN) tree is a species of high importance in Amazon region. Their continuous use by traditional communities is often related to disturbances that lead to larger degraded areas where this species is commonly found (“BN groves”). Here we aimed to explore the ecological patterns of BN groves vegetation and its relationship with BN trees and evaluate their potential as a source of carbon credits. We sampled 15 circular plots, with Brazilian Nut trees as the center (focal trees) and collected morphometric data from the focal trees. Additionally, we evaluated fruit production for a period of 5 years to obtain annual measurements, which were used as a proxy of the anthropic impact associated with the collection process. Through analysis of the data, we: i) examined the effects of BN trees on the adjacent vegetation; ii) quantified the potential amount of carbon credits in the adjacent vegetation and in the focal trees by converting carbon stock to equivalent CO2. Results: The adjacent vegetation structure was influenced by the size of BN trees (focal trees). No important effects of BN trees on the adjacent vegetation floristic composition and functional attributes were found. Additionally, we found that Brazilian Nut groves possess a significant potential for carbon credits that could be leveraged in the future carbon credit market, Conclusion: The study highlights the potential for carbon credit generation in Brazil nut groves in the Southeast Amazon as a means of supporting conservation and restoration efforts in these environments.

Bagdad, Berlin, Warschau

The paper examines the motif of the Bildungsreise in Sherko Fatah’s post-colonial novel Ein weißes Land (2011). Anwar, the novel’s protagonist, grows up in 1920s Baghdad under British administration, a diverse but profoundly unequal society rife with religious conflict. Driven by a desire for self-development and adventure characteristic of the European Bildungsroman tradition, Anwar sets out on a catastrophic coming-of-age journey. He falls in with thieves, nationalists and religious extremists and eventually ends up in Europe at the cusp of World War II. In a blurring of victim/perpetrator roles, Anwar is recruited by the Waffen-SS and takes part in the conquest of Lebensraum in Eastern Europe, the colonization project of the Third Reich. Beyond these thematic subversions of genre conventions, the paper also explores the novel’s structural innovations. While the classic Bildungsroman has been associated with circular plot patterns (‘return’ signals accommodation to social expectations after a temporary phase of youthful rebellion), Fatah’s novel eschews this conciliatory circularity. It is replaced by aberrant temporal structures such as repetition and regression. As a result, Anwar's youth is framed as a process of disrupted development in the context of European colonialism and the Nazi regime. Keywords: Sherko Fatah, Bildungsroman, travel, colonialism, national socialism, development

Tree-related Microhabitats and Trees Outside Forest along the Urban-Rural Gradient in Kathmandu Valley

Trees Outside Forests (TOF) are found in all strata as urban, suburban and rural. Some TOF serve as Tree Related Micro Habitats (TreMs). We conducted the assessment of TreMs on TOF in Kathmandu valley of central Nepal. Inventory was performed in 209 randomly selected points by Excel using circular plots with 20 m radius. Out of 6210 individuals of 150 tree species recorded from the study area, 1038 TOF of 64 species were found to serve as TreMs. 4 forms, 5 groups and 14 types of TreMs were recorded. Habitat types per tree varied from 1 to 6. 1, 2, 3, 4 and 5 habitat types were found in 665 (64.07 %), 293 (28.23 %), 67 (6.45 %), 8 (0.77 %) and 4 (0.38 %) trees respectively. 6 habitat types were found in one Cinnamomum camphora tree (0.10 %) with 8.60 m height and 75 cm DBH. Out of all the forms, groups and types, all were found in Urban TOF, one type (mistletoe) in suburban TOF and one form (fruiting bodies of saproxylic fungi and slime moulds) along with three types (mistletoe, invertebrate nest and sap run) were absent in rural TOF. The study explored the TreMs on TOF in Kathmandu valley. It provides the baseline data useful for micro habitats as well as biodiversity conservation.

Analysis of Vegetation Dynamics of Tree Species inside the Forest of Institute of Forestry, Hetauda

A vegetation analysis of tree species was undertaken in the 92.69 hectares (ha) of the forest connected to the Institute of Forestry (IOF), Hetauda Campus. The study separated the forest into two strata, and a total of 10 circular sample plots (each plot measuring 500 m2) were constructed using systematic sampling with a sampling intensity of 0.5%. Enumeration of tree species was carried out within the sample plots. A total of 139 individual trees representing 16 (10 in stratum 1 and 12 in stratum 2) different tree species were recorded (60 in stratum 1 and 79 in stratum 2). Diversity indices were used for calculating vegetation parameters. According to the Importance Value Index, Shorea robusta was dominant in both strata, followed by other heterogenous species. The Shannon Wiener’s index and Simpson’s Diversity Index were higher in stratum 2, but the dominance index was lower than in stratum 1. Stratum 2 had a marginally higher measure of both evenness and richness than stratum 1. The study investigated the vegetation structure of the riverine and tropical moist deciduous forest in the study area. Increasing human interference had no significant effect on diversity and number of species among the strata. This study provides the baseline data necessary to characterize the phytodiversity of the forest area of the Institute of Forestry, Hetauda Campus for conservation and sustainable management.

Valuation of timber and firewood of trees outside forest along the urban–rural gradient in Kathmandu valley, Nepal

This study aims to analyze diameter class, quality class, wood production potential and timber and firewood values of trees outside forest along the urban-rural gradient in Kathmandu valley of central Nepal. Inventory was performed in 209 randomly selected points. Circular plots of 20 m radius were used for inventory. All trees (height > 1.3 m and DBH ≥ 5 cm) in the plots were identified to species level and their height, DBH & quality class were recorded. In total 6,210 trees (236.35 ha-1) of 150 species belonging to 111 genera and 57 families were recorded. The total merchantable timber volumes of timber class A and B, and total timber volumes were highest in the urban stratum (537.08, 84.88 and 621.96 cu ft ha -1 respectively) followed by rural (442.94, 66.82 and 509.76 cu ft ha -1 respectively) and suburban (250.04, 47.31 and 297.35 cu ft ha -1 respectively) strata. But due to higher merchantable price of tree species recorded in rural stratum, total market value of class A timber was higher in rural stratum (NPR 7,89,871/US$ 6,085), class B timber was higher in urban stratum (NPR 1,08,255/US$ 834), total timber was higher in rural stratum (NPR 8,70,410/US$ 6,706), firewood was higher in urban stratum (NPR 4,88,709/US$ 3,765) and total wood was higher in urban stratum (NPR 12,95,531/US$ 9,981). Cinnamomum camphora was found as tree species with highest market price of total wood value in the study area. The study provides the baseline data of useful timber species through TOF suggesting a need for appropriate timber producing species selection for plantation.

Population Structure and Regeneration Status of Pinus-Quercus Mixed Forest in Bhardeu Village, Lalitpur District, Nepal

Understanding population structure and regeneration status reflects the biological and ecological characteristics of the forest. The present study aims to know the population structure and regeneration status of Pinus-Quercus mixed forest in Bhardeu village of Lalitpur district, central Nepal. The study was carried out by laying down twenty-eight concentric circular plots of 8.92-meter radius randomly during 2021-2022. Altogether 28 tree species belonging to 24 genera and 17 families are recorded. Five species (Miliusa velutina, Cinnamomum camphora, Eriobotrya dubia, Maesa chisia and Saurauia napaulensis) were only recorded in adult form. The forest was found to be dominated by the species of Pinus and Quercus with the important value index (IVI) values ranging from 49.91 to 35.24. The average Simpson’s Diversity Index (1/D) is 2.88, Shannon Weiner’s Index is 0.85, species evenness is 0.57 and species richness is 1.07. The overall regeneration of the different species was seedlings 6484 individuals/ha., saplings 533 individuals/ha. and adults 1198 individuals/ha. showing fair regeneration. The majority of tree species show fair regeneration status (32.14%) followed by none regeneration (25%), new regeneration (17.85%), poor regeneration (14.28%) and good regeneration status (10.71%). The density diameter curve of the forest shows slightly flat reverse j-shaped structure indicating that majority of tree species were not in good regenerating status. The present analysis thus revealed that the population structure may get altered in future. Those species with none to poor regeneration status should be prioritized for the conservation and the proper management strategies need to be developed for sustainability of tree species in the forest.

Natural regeneration and species diversification after seed-tree method cutting in a maritime pine reforestation

Forest adaptation to global change has become one of the main objectives of forest management in recent years. Species and structural diversification by thinning is a well-known adaptation measure, often applied by managers in monospecific even-aged stands. However, regeneration fellings may be more efficient for enhancing naturalization and resilience of monospecific reforested pine stands, widely distributed throughout the Mediterranean basin. This work focuses on the evaluation of natural regeneration after seed-tree method cuttings, adopted as a diversification strategy in a 60-year old P. pinaster reforestation with varying presence of broad-leaved species (mainly Quercus spp.) in mountains of Southern Spain. A trial consisting of 78 circular plots (1 m radius) was installed to monitor annual tree-species regeneration over seven years, classified into seedlings (0-10 cm height) and saplings (10-130 cm). Scrub coverage and other ecological variables were also measured. Sampling was carried out in three stand types (Pure, Mixed 1 and Mixed 2, in order of increasing presence of broad-leaved species), according to forest species composition before the felling. Maritime pine regeneration was successfully achieved by the end of the study period (over 2000 trees ha-1 widely distributed throughout the stand), whereas Quercus spp. seedlings even colonised plots in which there were no seed trees. Pine seedling density was positively affected by summer precipitation and the presence of conspecific adult pines, and negatively influenced by scrub coverage. High temperatures during the mid-summer months (especially August) negatively affected the seedling to sapling change ratio as well as sapling survival during the study period. Our results point to regeneration fellings with retention of pine and broadleaf species as a suitable method for diversifying species composition in Pinus pinaster reforestations in the Mediterranean region.

Sanitary condition of pine plantations of the Polyssia of Zhytomyr region

The sanitary condition of pine plantations in the conditions of Polissia of Ukraine was assessed. Derevostan grows in different types of forest vegetation conditions B2GDS, B3GDS, C2GDS, C3GDS. According to the data of 27 circular trial plots, which were established during 2018–2020 in the territory of the State Enterprise Zhytomyr LH Berezivske Forestry, the State Enterprise Korostyshivsk LH Ivnitske Forestry, the State Enterprise Korostensky LH APC Melenivske Forestry, which covered the typical growing conditions of pine plantations of Zhytomyr Oblast. The index of sanitary condition showed that the pine forest belonged to strongly weakened stands. Analyzing the sanitary condition during the research period, it is worth noting that in 2018, the tree stand of the plantations in the Ivnytsia Forestry was weakened, and the average index was 2.42. In Berezivsk and Melenivsk forests, the sanitary condition index was 2.58 and 2.67, which indicates that the degree of damage is average, and the plantations are strongly weakened. Based on the results of the research, it was established that in 2019 the sanitary condition in the Bereziv forestry improved and amounted to 2.12. By state category, the largest number of I category is 2019 – 40.0 %, 2019 II – 27.6 %. In the Ivnytsia forestry, the sanitary condition index was 2.52, the plantations were greatly weakened. In the Meleniv Forestry, the average sanitary condition index of 2.44 indicates that the tree stand is weakened. It is proven that in 2020 the sanitary condition improved compared to other years of research and amounted to 2.11. In Ivnytsia Forestry, the sa-nitary condition remains very weak. In the Meleniv Forestry, the average sanitary condition index was 2.29, which indicates that the tree stand is weakened. It has been established that pests, diseases and forest fires are the biggest deterioration of the sanitary condition in the territory of Zhytomyr Oblast. To prevent the development of these negative factors, it is necessary to create mixed pine plantations, to carry out timely felling of forest care. Key words: condition categories, sanitary condition index, type of fo-rest vegetation conditions, completeness, Scots pine.

Carbon Stock Assessment in Silvopastoral Systems along an Elevational Gradient: A Study from Cattle Producers in the Sumaco Biosphere Reserve, Ecuadorian Amazon

Silvopastoral system (SPS) has been considered as a sustainable management system contribute to greenhouse gas (GHG) reduction, among other benefits compared with open pasture. However, little research has been conducted on the soil and tree biomass carbon stored in traditional pasture with dispersed trees (PWT) compared with pasture in monoculture (PM). The present study was conducted in the Ecuadorian Amazon Region (EAR), along an elevational gradient from 400 to 2000 masl., within the buffer and transition zone of the Sumaco Biosphere Reserve (SBR), using 71 temporary circular plots of 2826 m2, where 26 plots were stablished in PWT and 45 plots in PM. The main results in PWT show significant differences (p ≤ 0.01) between aboveground carbon biomass (AGCtrees) from 41.1 (lowlands), 26.5 (Middle hills) and 16.7 (high mountains) Mg ha−1 respectively, with an average of 31.0 Mg ha−1 in the whole study area. The total carbon pool along the altitudinal gradient in five components: (AGCtrees), belowground carbon (BGCtrees), pasture carbon (AGClitter+pasture) and carbon in soil components (0–10 and 10–30 cm) for PWT ranged from 112.80 (lowlands) to 91.34 (high mountains) Mg ha−1; while for the PM systems assessing three components (AGClitter+pasture) and carbon in soil components (0–10 and 10–30 cm) ranged from 52.5 (lowlands) to 77.8 (middle zone) Mg ha−1. Finally, the paper shows the main dominant tree species in pasture systems that contribute to carbon storage along elevational gradient and concludes with recommendations for decision-making aimed at improving cattle ranching systems through a silvopastoral approach to mitigate the effects of climate change.

Edge Effects on Vegetation Structure and Resource Use Pattern at Two Community Forests of Surkhet, Nepal

This study assessed the forest structure and regeneration at the edge and core parts of two community forests, Ram Janaki and Furkesalli of Surkhet district, Western Nepal, and the forest resources use pattern. Different blocks designated by community forest user groups were considered to designate edge and core strata for stratified random sampling. For vegetation analysis and regeneration of tree 15 circular plots (n = 60) of 10m radii; for shrubs 5m radius subplot and for herbs three 1 m radii subplots within the 10 m radii circular plots were considered. Semi-structured questionnaire approach was employed for the collection of ethnobotanical data. Based on importance value index dominant herbs were Ageratum haustoniaum in edge and Heteropogon contortus core part; dominant shrub were Phoenix acaulis in both community forests (RCF and FCF); and Shorea robusta was dominant tree at edge forest of both RCF and FCF whereas Lagerstroemia parviflora was dominant at FCF coreforest. The species diversity was recorded higher in core parts in both forests. The forests are rich in the diversity of medicinal plants with 26 species under 25 genera and 23 families of which root parts were mostly used as ethnomedicine and mostly for gastrointestinal disorder. Besides medicines, firewood, fodder, fruits, vegetable, timber and bedding material were the other uses of forest resources.

Effects of forest structure and human influence on the call rate of owls in the Piedmont Forest of Northwestern Argentina

ABSTRACT Owls (Strigiformes) play an important ecological role as predators that structure and organize biological communities. Specialized owl species dependent on old-growth forests have suffered declines because of forest loss or degradation by human activities. Few studies have been conducted on Neotropical owls, especially in the Piedmont Forest of Northwestern Argentina. The scarcity of information on habitat requirements and the effect of human impacts preclude the establishment of conservation and management activities. The human footprint index (HFI) is a tool for mapping human impacts on biodiversity that is used at global and regional scales, based on the estimated and standardized contribution of different human impact variables (e.g. road networks, urban centers, agricultural land, etc.). The objectives of this work were to: 1) Determine the call rate of five owl species in the Piedmont Forest of Northwestern Argentina, 2) relate forest structure to the call rate of owl species, and 3) relate human footprint index to the call rate of owls. We placed 28 automatic recorders in the Piedmont Forest, in sites with low and high Human influence, and characterized the forest structure around each recorder within a circular plot of 25 m diameter. We obtained 241 vocalizations in 168 intervals of 2 h for Ferruginous pygmy owl (Glaucidium brasilianum), Tropical screech-owl (Megascops choliba), Black-banded owl (Ciccaba huhula), Spectacled owl (Pulsatrix perspicillata), and Buff-fronted owl (Aegolius harrisii). We found that for Tropical screech-owl live tree basal area had a positive and diameter at breast height standard deviation had a negative influence on call rate. While for Black-banded owl, the dead tree density had a positive and human footprint index >1 had a negative influence on call rate. For Spectacled owl, dead tree density and human footprint index >1 had a negative influence on call rate. We provide first insights into the effects of forest structure and human influence on the call rate of owls in the Piedmont Forest of Northwestern Argentina, information that may guide forest management guidelines and conservation strategies.

Analyzing TLS Scan Distribution and Point Density for the Estimation of Forest Stand Structural Parameters

In recent decades, the feasibility of using terrestrial laser scanning (TLS) in forest inventories was investigated as a replacement for time-consuming traditional field measurements. However, the optimal acquisition of point clouds requires the definition of the minimum point density, as well as the sensor positions within the plot. This paper analyzes the effect of (i) the number and distribution of scans, and (ii) the point density on the estimation of seven forest parameters: above-ground biomass, basal area, canopy base height, dominant height, stocking density, quadratic mean diameter, and stand density index. For this purpose, 31 combinations of TLS scan positions, from a single scan in the center of the plot to nine scans, were analyzed in 28 circular plots in a Mediterranean forest. Afterwards, multiple linear regression models using height metrics extracted from the TLS point clouds were generated for each combination. In order to study the influence of terrain slope on the estimation of forest parameters, the analysis was performed by using all the plots and by creating two categories of plots according to their terrain slope (slight or steep). Results indicate that the use of multiple scans improves the estimation of forest parameters compared to using a single one, although using more than three to five scans does not necessarily improves the accuracy. Moreover, it is also shown that lower accuracies are obtained in plots with steep slope. In addition, it was observed that each forest parameter has a strategic distribution depending on the field of view of the TLS. Regarding the point density analysis, the use of 1% to 0.1% (≈136 points·m−2) of the initial point cloud density (≈37,240.86 points·m−2) generates an R2adj difference of less than 0.01. These findings are useful for planning more efficient forest inventories, reducing acquisition and processing time as well as costs.

Emission factor for emission reduction estimation in reduced impact logging

Indonesia has a forest area of 125.92 million hectares and Production Forest has the largest area, which is approximately 55% of the total forest area of Indonesia. To ensure sustainability of forest management, the use of a logging system that provides minimal damage is highly desirable. Reduced Impact Logging (RIL) as one of the logging systems can minimize the impact of damage due to logging. It is important to provide the emission factor for emission reduction estimation in RIL to support achievement of Indonesian NDC target for net sinker in 2030. This research aims to estimate the emission factor of stands stock in forest concession areas that have applied conventional logging systems and RIL. The circular plot was used to conduct a vegetation survey in concessionaries areas in Central Kalimantan Province and the data collected were then analyzed further for carbon stock and emission factor for emission reduction. The results of the research in study sites showed that emission factor for emission reduction estimation in RIL compare to conventional logging (CL) amounted 30.03 tonC/ha and equivalent 110.2 tonCO2eq/ha or 55.71%. Thus, this value can be used as emission factor to estimate the emission reduction locally in RIL compare to the CL in Central Kalimantan.

Inventory of close-to-nature forest stands using terrestrial mobile laser scanning

• Hand-held mobile LiDAR data of a close-to-nature forest in the leaf-on season. • Fully automatic processing using modified mean-shift and RANSAC algorithms. • 96.5 % detection and 3.5 cm DBH RMSE for trees with DBHs from 4 to 80 cm. • A comparison of different levels of low-intensity filtering is performed. • A walking trajectory consisting of concentric circles is recommended. In this work, we evaluated mobile laser scanning (MLS) technology for the acquisition of individual tree data in a close-to-natural forest structure. The data was collected during the leaf-on period in a single-tree selection forest stand. Individual tree positions and diameters at breast height (DBHs) were acquired in an automatic process. MLS data was collected on 1000 m 2 circular inventory plots. We compared three trajectories consisting of the plot perimeter and 1), two perpendicular lines, 2) an additional concentric circle, and 3) four parallel lines. We compared two algorithms for tree segmentation: 1) a density-based approach and 2) a modified mean-shift algorithm. The diameters were estimated using a modified random sample consensus (RANSAC) algorithm. We tested a series of intensity thresholds for filtering returns from green vegetation. We achieved the best results with an intensity threshold of 0.7 quantile of point intensities, and mean-shift segmentation, resulting in the correct identification of trees representing 96.5 % of basal area and an overestimation of 6.8 % of the total basal area. The algorithm omitted mainly small trees and trees at close distances. False detections mainly comprised unvalidated detections of real trees that were not field-measured as their diameter did not exceed the registration limit, or were caused by point structures representing leaves and understory vegetation. Diameters were estimated with a mean error of 0.03 cm and a root mean square error of 3.5 cm. A joinpoint regression model demonstrated that for small trees (<9 cm) the diameters were generally overestimated. Diameters above 12 cm were underestimated consistently by 1 cm. The trajectory comprising two concentric circles was the most efficient.

Determinant of farmers’ participation and biodiversity status in the program of agroforestry rehabilitation in Sudan

Abstract. Hemida M, Mulyana B, Vityi A. 2022. Determinant of farmers’ participation and biodiversity status in the program of agroforestry rehabilitation in Sudan. Biodiversitas 23: 5638-5645. The agroforestry Rehabilitation Program (ARP) was launched in Nabag Reserve Forest (NRF), Sudan, to rehabilitate the forest cover and improve livelihoods for communities around the forest. To enhance the efficacy of such rehabilitation programs, it is crucial to understand the impact of various factors on community perception of participation in forest rehabilitation. The objectives of this study were to (i) examine the factors that influence farmers’ perceptions of their involvement in the program and (ii) assess the biodiversity of trees and crop species in the program. Data was gathered through a survey that included personal interviews with 200 farmers who participated in the program. A total of 250 circular sample plots were established randomly to achieve the second objective. The results showed that extension services, farming experience, family members, educational level, land size, and gum Arabic production positively influence farmers’ perceptions. The study findings identified nine tree species and five crop species in NRF. The dominant tree species were Acacia senegal and Balanites aegyptiaca which represented 62.8% and 12.4 % of the total species, respectively. At the same time, groundnut and watermelon were identified as favorite crops cultivated by farmers. Furthermore, the non-rehabilitated area has shown better value in richness, heterogeneity, and evenness than the rehabilitated areas.

Understanding the Impacts of Forest Management in Sal (Shorea robusta) Dominant Forest Stands in the Western Lowlands of Nepal

Sal (Shorea robusta) is an economically and ecologically important tree species found in Nepal. Since 2003, Nepal's government has been managing the Sal forest under the Scientific Forest Management (SciFM) scheme. Due to newly implemented approaches, the information regarding the Sal forest condition under regeneration felling and thinning is low. This study aimed to understand the regeneration status after regeneration felling and compare crop stands between thinned and unthinned plots. We selected three years of harvested, thinned, and unthinned blocks in the Tilaurakot collaborative forest. Vegetation sampling was carried out in 63 concentric circular plots. The results show that the number of seedlings and saplings in the harvested blocks was 14,000 and 3368 per hectare, respectively. The growing stock and basal area per hectare in the thinned blocks were lower than in the unthinned blocks. The numbers of trees and poles per hectare were lower in the thinned block than in the unthinned block. Sal's importance valve index (IVI) was higher than other species in all three block types. The study suggests that the regeneration condition was better after the canopy's opening, and thinning promotes the growth of trees and undergrowth vegetation.

Prescribed fire after thinning increased resistance of sub-Mediterranean pine forests to drought events and wildfires

Vegetation structure affects the vulnerability of a forest to drought events and wildfires. Management decisions, such as thinning intensity and type of understory treatment, influence competition for water resources and amount of fuel available. While heavy thinning effectively reduces tree water stress and intensity of a crown fire, the duration of these benefits may be limited by a fast growth response of the understory. Our aim was to study the effect of forest structure on pine forests vulnerability to extreme drought events and on the potential wildfire behaviour after management, with a special focus on the role of the understory. In three sub-Mediterranean sites of NE Spain dominated by Pinus nigra, two intensities of thinning (light: aiming at 70–75% canopy cover; and heavy: aiming at 50–60% canopy cover) followed by two understory treatments (mechanical only and mechanical plus prescribed burning) were applied, resulting in four differently managed stands plus an untreated control per site. Four to five years after management, we measured forest structure (overstory in one 314 m2 circular plot and understory in 20 quadrats of 1 m2 per treatment unit) and fuel load (in two 10 m transects per treatment unit) and simulated water balance and fire behaviour under extreme weather conditions. Understory contribution was assessed comparing the real structure with a virtual forest stand where understory vegetation equalled the one of the untreated control. Our results suggest that the resulting mid-term structure following treatments effectively reduced water stress and fire behaviour compared with untreated control, and that the most effective treatments were the ones where prescribed burning was applied after light or heavy thinning. While understory clearing contributes to increase the resistance to both disturbances, an additive effect of burning the debris reduced the vulnerability to drought and wildfires after treatments. Our study highlights the importance of managing the understory to further increase forest resistance to both disturbances.

Screening of Persea borbonia clones for resistance to the laurel wilt pathogen, Raffaelea lauricola

AbstractLaurel wilt, caused by the fungus Raffaelea lauricola, has caused widespread mortality to Persea borbonia across the southeastern United States. The invasive ambrosia beetle vector of the pathogen, Xyleborus glabratus, attacks and infects trees, leaving only P. borbonia seedlings, saplings, and stump sprouts in heavily affected areas. To facilitate mitigation of this ecological damage, we initiated a screening program for laurel wilt disease resistance. We established circular field plots (0.08 hectare) in six significantly impacted sites, measured laurel wilt epidemiological characteristics, and selected 61 survivor P. borbonia ortets (≥7.5 cm diameter at breast height [DBH]) for vegetative propagation, screening, and monitoring. Disease incidence in the plots ranged from 50% to 87% of P. borbonia stems thicker than 2.5 cm DBH and ortet survival per site ranged from 0% to 70% a decade after initial selection. Clonal ramets from 38 survivor ortets were out planted and screened for resistance to R. lauricola in a series of field inoculation trials. Results indicate variable levels of host susceptibility and suggest rare individuals exist with tolerance to R. lauricola. Scanning electron microscopy imaging of xylem samples from three infected P. borbonia clones suggests that reduced tylose production and granular deposition in xylem lumina are associated with increased resistance to R. lauricola. Results from this study will aid in the selection of disease‐resistant P. borbonia germplasm for restoration plantings in affected sites and provide new insights into the host–pathogen interaction of this deadly vascular disease.

Growth analysis of the lower layer trees in forest stands under conversion in the Starohorské vrchy Mts.: A case study

The case study analyses the structure and dynamics of the diameter growth on the example of two fir-spruce forest stands under conversion to a selection forest. In a series of 51 circular research plots (size 500 m&lt;sup&gt;2&lt;/sup&gt;), the biometric characteristics (tree species, diameter at breast height, height) of all the stems with a diameter above 8 cm were registered. From the selected stems, we collected 51 cross-sections and 178 tree cores in total and performed age and growth analyses. In addition, for the lower layer trees, we assessed the competition by the neighbouring stand quantified by the competition index. The results confirmed the differences in the age structure, despite the similar diameter distributions in the investigated stands, as well as the differences in the growth dynamics of the spruce and fir in the lower tree layer. Nevertheless, the competition of the neighbouring stand was not proven as a significant factor for the diameter growth of the lower layer trees.

Native and no-native herbivorous relationships have mutual benefit: Lepus flavigularis case

Lepus flavigularis is an endemic leporid from southeastern Oaxaca, México, listed as “endangered” under Mexican law and the IUCN Red List. The main threat to the species is severe habitat fragmentation due to human activities. The jackrabbit shares the grasslands with cattle (Bos taurus), but the trophic interaction between these herbivores is unknown. This study aimed to determine the seasonal diet of Lepus flavigularis and cattle, to identify the possible dietary overlap between these mammals. The study zone covers an area around the locality of Santa María del Mar in Oaxaca, southern México. Plant species were identified using linear transects, and vegetation cover was also estimated using circular plots. Throughout the study fresh L. flavigularis and B. taurus fecal samples were collected, which were processed using the microhistological technique to determine the seasonal botanical composition of diets from the two species. Twenty-three plant species were recorded in the diet of L. flavigularis and 29 species in the diet of B. taurus. Both herbivores fed primarily on Poaceae species throughout the year (L. flavigularis: dry season (ds) = 79.79 %, wet season (ws) = 91.54 %; B. taurus: ds = 78.02 %, ws = 84.63 %) despite the significant difference in the availability of plant species between seasons. No significant differences were found in the seasonal composition of the diet between the two species. Twelve plant species were consumed by both herbivores during the two seasons. The dietary overlap between the two species was high for both seasons (ds Ojk = 0.7311, ws Ojk = 0.8459). Trophic niche breadth was low for both species, with a high dietary overlap. We recorded low seasonal use values for L. flavigularis and B. taurus when compared to forage availability. Low trophic niche breadth and high dietary overlap between the two herbivores suggest forage resources competition. However, we expect that jackrabbits benefit from cattle presence, as long as the stocking rate does not increase. Furthermore, B. taurus grazing reduces height, cover, and density of vegetation, which could help L. flavigularis to avoid predators.