UAV-Based LiDAR Scanning for Individual Tree Detection and Height Measurement in Young Forest Permanent Trials

The installation of research or permanent plots is a very common task in growth and forest yield research. At young ages, tree height is the most commonly measured variable, so the location of individuals is necessary when repeated measures are taken and if spatial analysis is required. Identifying the coordinates of individual trees and re-measuring the height of all trees is difficult and particularly costly (in time and money). The data used comes from three Pinus pinaster Ait. and three Pinus radiata D. Don plantations of 0.8 ha, with an age ranging between 2 and 5 years and mean heights between 1 and 5 m. Five individual tree detection (ITD) methods are evaluated, based on the Canopy Height Model (CHM), where the height of each tree is identified, and its crown is segmented. Three CHM resolutions are used for each method. All algorithms used for individual tree detection (ITD) tend to underestimate the number of trees. The best results are obtained with the R package, ForestTools and rLiDAR. The best CHM resolution for identifying trees was always 10 cm. We did not detect any differences in the relative error (RE) between Pinus pinaster and Pinus radiata. We found a pattern in the ITD depending on the height of the trees to be detected: the accuracy is lower when detecting trees less than 1 m high than when detecting larger trees (RE close to 12% versus 1% for taller trees). Regarding the estimation of tree height, we can conclude that the use of the CHM to estimate height tends to underestimate its value, while the use of the point cloud presents practically unbiased results. The stakeout of forestry research plots and the re-measurement of individual tree heights is an operation that can be performed by UAV-based LiDAR scanning sensors. The individual geolocation of each tree and the measurement of heights versus pole and/or hypsometer measurement is highly accurate and cost-effective, especially when tree height reaches 1–1.5 m.

Native Forests Show Resilience to Selective Timber Harvesting in Southeast Queensland, Australia

There is little published information on effects of management on the structure of mixed species forests in Queensland, Australia. We used long-term growth, abundance and dimension data from permanent plots to test the hypothesis that harvesting would reduce numbers of large trees and growth increments, while increasing recruitment. This hypothesis is key to policy and management decisions for forests covering about 9.5 million hectares. Inclusion of data on changes in forest structure (e.g., tree diameter, stem density) helps in assessment of forest suitability as habitat for a range of species. Growth rate (basal area) varied widely among forest types. Growth of each of four key species (i.e., Eucalyptus pilularis, Corymbia citriodora ssp. variegata, Callitris glaucophylla, and Eucalyptus crebra) reflected variation in rainfall across the study region. Callitris glaucophylla, a native conifer, is dominant when rainfall is < 600 mm per year. Corymbia citriodora ssp. variegata grows across much wider ranges in rainfall (600–1,200 mm year–1) at rates similar to Callitris glaucophylla. Historic harvesting increased recruitment and also increased the symmetry of diameter distributions. Harvesting has not reduced the current density of larger trees (diameter at breast height, DBH ≥ 60 cm) at a regional scale. Stand growth was unaffected by management principally owing to an increase in the density of trees of smaller diameter (10–20 cm DBH). Self-thinning limits potential stocking and we tested 3 methods for predicting self-thinning across forest types. We found that the slope of self-thinning lines under drier conditions is mostly < –2, suggesting highly dynamic self-thinning. Using a species-boundary line approach, growth is predicted to slow when basal areas reach around 66.1 m2 ha–1 in E. pilularis, 19.0 m2 ha–1 in C. citriodora ssp. variegata, 16.5 m2 ha–1 in Callitris glaucophylla, and 14.2 m2 ha–1 in E. crebra. The slope of the self-thinning line for E. pilularis was –1.662, similar to Reineke’s Stand Density Index (slope –1.605). To date, there is little evidence that selective harvesting and thinning have had negative impacts on rates of growth, on timber production, carbon sequestration or on aspects of forest structure regarded as important for biodiversity.

Temporal Development and Regeneration Dynamics of Restored Urban Forests

<p>Urban forest restoration programmes are a key tool used to initiate, re-create or accelerate the succession of forest species; improving ecosystem services, function, resilience and biodiversity. Succession is a temporal shift in species dominance driven by abiotic and biotic influences, but over decadal timescales the trajectory and success of restoration plantings in degraded urban environments can be hindered. To facilitate the successful reconstruction of forest ecosystems from scratch, an understanding of the temporal patterns in planted forest development, dynamics of seedling regeneration and dominant drivers of seedling diversity is required. Using a chronosequence approach, permanent plots were established at 44 restored urban forests aged 5 to 59 years since initial plantings took place, across five New Zealand cities between Wellington and Invercargill. Vegetation surveys were undertaken and data on micro-climate were collected. This study examined the 1) temporal dynamics of restored urban forest development and seedling regeneration and 2) dominant drivers of seedling regeneration. Data were analysed using linear regression models, breakpoint analysis and mixed-effects modelling. Early forest development (<20 years) exhibited the most changes in canopy composition and structure, forest floor dynamics, seedling community and microclimate. This period saw significant increases in canopy stem abundance, height, basal area and leaf litter cover. Significant declines occurred for light transmittance, herbaceous cover and daily soil and air temperature range within the same timeframe. Dominant traits amongst the seedling community included early successional species, tree species, shade and drought tolerant species, insect-pollinated species and frugivory dispersed species. Seedlings with these traits had higher species richness levels across the whole chronosequence. Collectively, five biotic drivers representing forest composition, structure and landscape factors strongly influenced seedling diversity. Seedling diversity increased with the proportion of surrounding natural landcover, sapling diversity, basal area, canopy diversity and herbaceous cover. The influence of these predictors of seedling diversity, was more significant when modelled as a set, than when viewed independently. Geographic location (city) was indicated as a stronger predictor for similarities in canopy and seedling community composition than the age of the restoration planting. This was shown by stronger clustering of sites according to their city, more so than forest planting age, in a non-metric multidimensional scaling analysis. Our results provide valuable insight to restoration practitioners on the outcomes of urban restoration programmes implemented across much of New Zealand and helps close the gap between the science of restoration ecology and the practice of ecological restoration.</p>

Temporal Development and Regeneration Dynamics of Restored Urban Forests

<p>Urban forest restoration programmes are a key tool used to initiate, re-create or accelerate the succession of forest species; improving ecosystem services, function, resilience and biodiversity. Succession is a temporal shift in species dominance driven by abiotic and biotic influences, but over decadal timescales the trajectory and success of restoration plantings in degraded urban environments can be hindered. To facilitate the successful reconstruction of forest ecosystems from scratch, an understanding of the temporal patterns in planted forest development, dynamics of seedling regeneration and dominant drivers of seedling diversity is required. Using a chronosequence approach, permanent plots were established at 44 restored urban forests aged 5 to 59 years since initial plantings took place, across five New Zealand cities between Wellington and Invercargill. Vegetation surveys were undertaken and data on micro-climate were collected. This study examined the 1) temporal dynamics of restored urban forest development and seedling regeneration and 2) dominant drivers of seedling regeneration. Data were analysed using linear regression models, breakpoint analysis and mixed-effects modelling. Early forest development (<20 years) exhibited the most changes in canopy composition and structure, forest floor dynamics, seedling community and microclimate. This period saw significant increases in canopy stem abundance, height, basal area and leaf litter cover. Significant declines occurred for light transmittance, herbaceous cover and daily soil and air temperature range within the same timeframe. Dominant traits amongst the seedling community included early successional species, tree species, shade and drought tolerant species, insect-pollinated species and frugivory dispersed species. Seedlings with these traits had higher species richness levels across the whole chronosequence. Collectively, five biotic drivers representing forest composition, structure and landscape factors strongly influenced seedling diversity. Seedling diversity increased with the proportion of surrounding natural landcover, sapling diversity, basal area, canopy diversity and herbaceous cover. The influence of these predictors of seedling diversity, was more significant when modelled as a set, than when viewed independently. Geographic location (city) was indicated as a stronger predictor for similarities in canopy and seedling community composition than the age of the restoration planting. This was shown by stronger clustering of sites according to their city, more so than forest planting age, in a non-metric multidimensional scaling analysis. Our results provide valuable insight to restoration practitioners on the outcomes of urban restoration programmes implemented across much of New Zealand and helps close the gap between the science of restoration ecology and the practice of ecological restoration.</p>

Quantifying Crown Morphology of Mixed Pine-Oak Forests Using Terrestrial Laser Scanning

Mixed forests make up the majority of natural forests, and they are conducive to improving the resilience and resistance of forest ecosystems. Moreover, it is in the crown of the trees where the effect of inter- and intra-specific interaction between them is evident. However, our knowledge of changes in crown morphology caused by density, competition, and mixture of specific species is still limited. Here, we provide insight on stand structural complexity based on the study of four response crown variables (Maximum Crown Width Height, MCWH; Crown Base Height, CBH; Crown Volume, CV; and Crown Projection Area, CPA) derived from multiple terrestrial laser scans. Data were obtained from six permanent plots in Northern Spain comprising of two widespread species across Europe; Scots pine (Pinus sylvestris L.) and sessile oak (Quercus petraea (Matt.) Liebl.). A total of 193 pines and 256 oaks were extracted from the point cloud. Correlation test were conducted (ρ ≥ 0.9) and finally eleven independent variables for each target tree were calculated and categorized into size, density, competition and mixture, which was included as a continuous variable. Linear and non-linear multiple regressions were used to fit models to the four crown variables and the best models were selected according to the lowest AIC Index and biological sense. Our results provide evidence for species plasticity to diverse neighborhoods and show complementarity between pines and oaks in mixtures, where pines have higher MCWH and CBH than oaks but lower CV and CPA, contrary to oaks. The species complementarity in crown variables confirm that mixtures can be used to increase above ground structural diversity.

Persistent fire effect on forest dynamics and species composition of an old-growth tropical forest

Aim of the study: To assess structure, recruitment and mortality rates of tree species over almost three decades, 14 years before and 15 years after a forest fire. Material and methods: All trees ≥ 5 cm in DBH were identified and measured in 12 permanent plots (50 m x 50 m), in 1983, 1987, 1989, 1995, 2008, and 2012 of a dense ombrophilous forest in Eastern Amazon, Brazil. The analyses were carried out including all sampled species and their ecological groups: shade-tolerant, light-demanding, and pioneer species. Treatments were compared through a Linear Mixed Effect Model. Main results: The 15-year post-fire period is not enough for the old-growth tropical forest to recover its pre-fire conditions of recruitment and mortality rates. The post-fire recruitment and mortality rates increased, mainly the recruitment of pioneer species (p-value < 0.05). Research highlights: In a period of 15 years after the occurrence of a surface fire, the old-growth tropical forest still has high recruitment rates of shade-tolerant and light-demanding species and high incidence of pioneer species, confirming the persistent fire effects on forest dynamics and species composition in this ecosystem.

The structure of Leguminosae-Detarioideae dominant rain forest in Korup National Park, Cameroon

Background and aims – We studied a cluster of trees in the Leguminosae subfamily Detarioideae, to: (1) determine the size, structure, and tree species composition of this cluster; (2) map the size, shape, and structure of groups of individual Detarioideae tree species in the cluster.Location – Lowland rain forest in southern Korup National Park, in the Southwest Region of Cameroon.Material and methods – Trees in permanent plots were recorded using standard plot enumeration techniques. Outside plots, single-species tree groups were recorded by a rapid technique. From this data, detailed maps of groups of trees were prepared.Key results – Detarioideae tree species occur co-dominant in a cluster of at least 32 km2 with an irregular shape. The cluster contained at least 42 Detarioideae tree species; at least 29 of these occurred in groups ranging in size from 50 to 4000 m across, depending on the species. Groups usually had circular shapes, caused by ballistic seed dispersal. In a group, trees were always mixed with trees of several other Detarioideae species. Every area within the cluster contained a specific set of Detarioideae species. The percentage of Detarioideae trees ≥ 60 cm stem diameter on 50 ha was up to 76% in Detarioideae-rich forest, to 6% in Detarioideae-poor forest. Of all trees in the centre of the cluster, 2.8% belonged to pioneer forest species, which indicates that disturbance levels were low during the past generations of trees.Discussion – The forests in the Detarioideae cluster have not been subject to substantial human and natural impacts in historic or prehistoric times. Such forests are exceptional in Africa. Detarioideae clusters may indicate glacial age forest refuges, especially clusters that contain both many different Detarioideae species and some Detarioideae species endemic to the cluster.

Impact of Secondary Succession in the Xerothermic Grassland on the Population of the Eastern Pasque Flower (Pulsatilla patens)—Preliminary Studies

We studied the impact of secondary succession in xerothermic grasslands on a population of Pulsatilla patens, a species of European Community interest. We established two permanent plots with a high number of individuals of P. patens in a xerothermic grassland in Southern Poland. We compared two areas, the first in open grassland (plot A), and the second with overgrowing vegetation (plot B). We assessed the population structure as well as the individual traits of the species. The total abundance of P. patens in the open xerothermic grassland was five times higher than in the overgrowing xerothermic grassland. A randomly clustering distribution was noted only in plot A; in plot B a random type of distribution occurred. The density structure of the rosettes was higher in plot A. The mean number of leaves in rosettes of P. patens as well as dimensions of intermediate stems and leaves of the species is strongly correlated with habitat conditions. The shadowing caused by shrubs and trees and high weeds observed in the overgrowing xerothermic grassland negatively impacted on the number of individuals, distribution, structure and morphology of P. patens.

Species diversity, abundance, and wildlife conservation status in Batang Gadis National Park, North Sumatra, Indonesia

Rambe IF, Rambey R, Siregar S. 2021. Species diversity, abundance, and wildlife conservation status in Batang Gadis National Park, North Sumatra, Indonesia. Biodiversitas 22: 5189-5196. Indonesia is one of the countries with the highest biodiversity in the world. Furthermore, the biodiversity of floral and faunal species is still being monitored and maintained, one of which is in the forest of the National Park. Batang Gadis National Park is a habitat for various species of endemic Sumatran wildlife, most of which are endangered species in the world. Therefore, this study aimed to inventory wild animals and to calculate their abundance in the Batang Gadis National Park. The study used camera traps as recording devices that were installed on permanent and non-permanent plots based on evidential animal trajectories in the National Park Management Section Region III Resort 7 Forest of Ampung Padang Forest in 2018. In the permanent plot, 10 species were documented within nine families, namely the Felidae, Tapiridae, Cervidae, Viverridae, Ursidae, Tragulidae, Suidae, Tupaiidae, and the Cercopithecidae. The highest species abundance was Macaca nemestrina (36.17%), and the second-highest was Muntiacus muntjak Zimmermann (14.89%), and then Tapirus indicus Desmarest (10,64%). Also, the Sumatran tiger (Panthera tigris sumatrae Pocock) was in the fourth position with a value of 10.63% of species abundance. Meanwhile, the lowest abundance index value was from clouded leopard (Neofelis diardi Cuvier) with 2.12%. The abundance of species from the non-permanent plots using camera trap documented a total of 13 species with 12 families namely Felidae, Tapiridae, Cervidae, Hystricidae, Viverridae, Muridae, Phasianidae, Tragulidae, Suidae, Muscicapidae, Tupaiidae, and Cercopithecidae. The highest was documented from wild boar (Sus scrofa Linnaeus) at 42.48% and the second-highest species abundance was macaque (N. nemestrina) at 26.144%. The lowest species abundance index values were tapir (T. indicus) and Javan blue robin (Myiomela diana Lesson) with 0,33% and 0,33 %, respectively. The existence of documented wildlife species in our study affirmsed the importance of Batang Gadis National Park as a natural habitat for some key and protected species.