Average Tree Height Research Articles

Forest age mapping based on multiple-resource remote sensing data.

Forest age is an important stand description factor and plays an important role in the carbon cycle of forest ecosystems. However, forest age data are typically lacking or are difficult to acquire at large spatial scale. Thus, it is important to develop a method of spatial forest age mapping. In this study, a method of forest age estimation based on multiple-resource remote sensing data was developed. Forest age was estimated by using average tree height estimated from the ICESat/GLAS and MODIS BRDF products. The results showed that forest age was significantly related to average tree height with a correlation coefficient of 0.752. Then, the average tree height was inversed using a waveform parameter extracted from ICESat/GLAS and was extended to continuous space with the help of the MODIS BRDF product. Thus, forest age mapping was realized. Lastly, the structure of forest age in the study area was evaluated. The results indicated that this method can be used to estimate forest age at the local scale and at large scale and can facilitate understandings of the real forest age structure features of a research area.

Population structure and regeneration of Himalayan endemic Larix species in three high-altitude valleys in Nepal Himalaya

BackgroundThe Himalayan forests are of great importance to sustain the nature and community resource demands. These forests are facing pressures both from anthropogenic activities and ongoing global climatic changes. Poor natural regeneration has been considered a major problem in mountainous forests. To understand the population structure and regeneration status of Larix (Larix griffithiana and Larix himalaica), we conducted systematic vegetation surveys in three high-altitude valleys namely Ghunsa (Kanchenjunga Conservation Area, KCA), Langtang (Langtang National Park, LNP), and Tsum (Manaslu Conservation Area, MCA) in Nepal Himalaya. The average values of diameter at breast height (DBH), height, and sapling height were compared for three sites and two species using Kruskal-Wallis test. Population structure was assessed in terms of proportion of seedlings, saplings, and trees. Regeneration was analyzed using graphical representation of frequencies of seedlings, saplings, and trees in histograms.ResultsThe results showed that the population structure of Larix in terms of the proportion of seedling, sapling, and tree varied greatly in the three study areas. KCA had the highest record of seedling, sapling, and tree compared to other two sites. Seedlings were the least among three forms and many plots were without seedlings. We found no seedling in MCA study plots. The plot level average DBH variation among sites was significant (Kruskal-Wallis χ2 = 7.813, df = 2, p = 0.02) as was between species (Kruskal-Wallis χ2 = 5.9829, df = 1, p = 0.014). Similarly, the variation in average tree height was significant (Kruskal-Wallis χ2 = 134.23, df = 2, p < 0.001) among sites as well as between species (Kruskal-Wallis χ2 = 128.01, df = 1, p < 0.001). All the sites showed reverse J-shaped curve but more pronounced for KCA and MCA. In comparing the two species, Larix griffithiana has clear reverse J-shaped diameter distribution but not Larix himalaica.ConclusionThe varied responses of Larix manifested through regeneration status from spatially distinct areas show that regeneration limitations might be more pronounced in the future. In all the three studied valleys, regeneration of Larix is found to be problematic and specifically for Larix griffithiana in MCA and Larix himalaica in LNP. To address the issues of disturbances, especially serious in LNP, management interventions are recommended to sustain the unique Himalayan endemic conifer.

The legacy of biogeographic history on the composition and structure of Andean forests.

The biogeographic origin of species may help to explain differences in average tree height and aboveground biomass (AGB) of tropical mountain forests. After the Andean uplift, small-statured trees should have been among the initial colonizers of the highlands (new cold environment) from the lowland tropics, since these species are pre-adapted to cold conditions with narrow vessels that are relatively resistant to freezing. If the descendants of these small-statured clades continue to dominate tropical highland forests, there will be a high co-occurrence of close relatives at high elevations. In other words, this scenario predicts a systematic decline in tree size, AGB, and phylogenetic diversity with elevation. In contrast, the colonization of Andean forests by some large-statured clades that originated in temperate regions may modify this expectation and promote a mixing of tropical and temperate clades, thereby increasing the phylogenetic diversity in tropical highland forests. This latter scenario predicts an increase or no change of tree size, AGB, and phylogenetic diversity with elevation. We assessed how the historical immigration of large-statured temperate-affiliated tree lineages adapted to cold conditions may have influenced the composition and structure of Andean forests. Specifically, we used 92 0.25-ha forest inventory plots distributed in the tropical Andes Mountains of Colombia to assess the relationship between the phylogenetic diversity and AGB along elevational gradients. We classified tree species as being either "tropical affiliated" or "temperate affiliated" and estimated their independent contribution to forest AGB. We used structural equation modeling to separate the direct and indirect effect of elevation on AGB. We found a hump-shaped relationship of phylogenetic diversity, AGB, and tree size with elevation. The high phylogenetic diversity found between 1,800-2,200m above sea level (asl) was due to the mixing of highland floras containing many temperate-affiliated species, and lowland floras containing mostly tropical-affiliated species. The high AGB in highland forests, which contrasted with the expected decline of AGB with elevation, was likely due to the significant contribution of temperate-affiliated species. Our findings highlight the lasting importance of biogeographic history on the composition and structure of Andean mountain forests.

Determination of Actual Evapotranspiration and Crop Coefficients of California Date Palms Using the Residual of Energy Balance Approach

As water scarcity becomes of greater concern in arid and semi-arid regions due to altered weather patterns, greater and more accurate knowledge regarding evapotranspiration of crops produced in these areas is of increased significance to better manage limited water resources. This study aimed at determining the actual evapotranspiration (ETa) and crop coefficients (Ka) in California date palms. The residual of energy balance method using a combination of surface renewal and eddy covariance techniques was applied to measure ETa in six commercial mature date palm orchards (8–22 years old) over one year. The experimental orchards represent various soil types and conditions, irrigation management practices, canopy characteristics, and the most common date cultivars in the region. The results demonstrated considerable variability in date palm consumptive water use, both spatially and temporally. The cumulative ETa (CETa) across the six sites ranged from 1299 to 1501 mm with a mean daily ETa of 7.2 mm day−1 in June–July and 1.0 mm day−1 in December at the site with the highest crop water consumption. The mean monthly Ka values varied between 0.63 (December) and 0.90 (June) in the non-salt-affected, sandy loam soil date palms with an average density of 120 plants ha−1 and an average canopy cover and tree height of more than 80% and 11.0 m, respectively. However, the values ranged from 0.62 to 0.75 in a silty clay loam saline-sodic date palm orchard with 55% canopy cover, density of 148 plants ha−1, and 7.3 m tree height. Inverse relationships were derived between the CETa and soil salinity (ECe) in the crop root zone; and between the mean annual Ka and ECe. This information addresses the immediate needs of date growers for irrigation management in the region and enables them to more efficiently utilize water and to achieve full economic gains in a sustainable manner, especially as water resources become less available or more expensive.

Effects of provenance and initial planting density on growth and wood properties in young sawtooth oak (Quercus acutissima) plantations

Provenance and stand management regimes greatly affect individual tree growth and stand productivity. The effects of provenance and initial planting density on growth and wood properties of 11-year-old sawtooth oak (Quercus acutissima Carruth.) plantations in eastern China were investigated. The average tree height growth, calorific values, and ash content of stem wood were greatly affected by provenance but not by initial planting density. The average tree diameter varied significantly among the three planting densities (5000, 2500, and 1667 trees ha−1) from tree age 6–11 years, and density-associated competition between trees mainly occurred at tree ages 6, 7, and 11 years for different provenances. The initial planting density and provenance had significant effects on the stand basal area (BA) and aboveground biomass (AGB). The annual growth in BA and AGB decreased in the eighth year after planting, especially in plots with an initial planting density of 5000 trees ha−1. The variances explained by the provenance exceeded the variance explained by the planting density for AGB at age 11 years. No significant interaction effect between initial planting density and provenance was observed for growth traits, but there was a significant effect on survival rate. Therefore, the suitable combination between provenance and planting density is crucial to increase productivity of sawtooth oak plantations. Additionally, our study confirms that, when the stands were young, initial planting density had a greater effect on productivity than provenance did, but this pattern reversed as stands aged.

The Pattern of Genetic Variation, Survival and Growth in the Abies alba Mill. Population within the Introgression Zone of Two Refugial Lineages in the Carpathians

Background and Objectives: The contact zones of different refugial lineages, where mixing of genetic backgrounds leads to new gene combinations or pre-adaptations, represent hotspots of genetic diversity. The aim of the study was to compare patterns in the genetic structure of the Abies alba Mill. population in the Eastern and Western Carpathians (Eastern Europe) within the introgression zone of two refugial lineages and the growth response of provenances located in a gradient of pollen-mediated gene fluxes. Materials and Methods: The mitochondrial nad5-4 marker and five polymorphic microsatellite nuclear markers (nSSR) were analyzed in 56 subpopulations from Romania, Ukraine, Slovakia and Poland. The survival rate and height growth up to an age of 15 years were compared for 33 subpopulations, forming a distance gradient between 170 and 470 km from the meeting zone of the refugial lineages. Results: The results of the analysis of molecular variance indicated that 8.2% of the total genetic variation is attributable to the between-subpopulation level and 1.7% to the between-lineage level. The pollen-mediated influence of the eastern lineage was detectable at a distance of at least 300 km in the western direction. Eastern provenances with origin sites closer to the meeting zone of the refugial lineages were characterized by lower survival rate and lower heights (about 8% lower than the average tree height) compared to subpopulations from the central and western part of the studied region. Conclusions: Pollen-mediated gene flow between lineages appears to have been sufficient to cause a significant change in phenotypic traits related to tree growth. Subpopulations from the central and western parts of the studied region are better adapted to current climatic conditions. Nonetheless, given the increasing aridity of the regional climate, a safe guideline is to increase genetic mixing.

Stunted Mangrove Trees in the Oligotrophic Central Red Sea Relate to Nitrogen Limitation

Mangroves are important coastal ecosystems of warm climatic regions that often grow in shallow saline or brackish waters of estuaries and river mouths affected by wide tidal intervals and receive abundant nutrient supply. However, mangroves also occur in areas of little tidal influence and devoid of riverine inputs, where they can develop a stunted plant form. Here we report that Avicennia marina trees in the fringe of the Red Sea have maximum heights toward the lower range of that reported elsewhere (average maximum canopy height of 4.95 m), especially in the central region, where mangroves are stunted with an average tree height of 2.7 m. Maximum tree height and chlorophyll a concentration correlated positively with nitrogen concentration in the leaves of A. marina. We conclude that the stunted nature of mangrove trees in the central Red Sea is likely driven by nitrogen limitation.

Spatial distribution characteristics of soil and vegetation in a reclaimed area in an opencast coalmine

Opencast coal mining activities result in severe damage to soil and vegetation, and the reconstruction of soil and vegetation is critical in opencast coalmine areas. To better understand the spatial distribution characteristics of soil and vegetation in opencast coalmines, a spatial correlation analysis was conducted on the soil and vegetation properties of the Anjialing and Antaibao opencast coalmines in the Pingshuo coal mining area in China. A total of 70 sample points were selected using grid and transect methods, from which the soil and vegetation properties were determined. The spatial autocorrelation, spatial clustering, and spatial variability of the soil and vegetation indicators were analyzed using global Moran’s index, local Moran’s index, and the geostatistics method based on ArcGIS 10.2 or Geoda 7.0 analysis software. The soil and vegetation indicators were divided into three categories, including vegetation indicators (arbor quantity, AQ; average diameter at breast height, ADBH; herb coverage, HC; average tree height, ATH; canopy density, CD), soil physical properties (soil bulk density, BD; clay content; silt content; sand content; gravel content, GC), and soil chemical properties (soil organic matter, SOM; total nitrogen, TN; available phosphorus, AP; available potassium, AK; pH). There was a strong global autocorrelation among ADBH, clay content, AQ, HC, and SOM. Dumping and reclamation activities affected the spatial distribution characteristics of soil and vegetation. The “high-high” and “low-low” types in all the indicators possessed a large spatial distribution, and the soil and vegetation properties had relatively high spatial clustering. This study can provide a reference for the reclamation practice in opencast coalmine areas.

Вплив кореневої губки на ріст, структуру та санітарний стан соснових насаджень, створених на староорних землях у Лісостепу Харківської області

Одним із найнебезпечніших збудників хвороб хвойних лісів є коренева губка (Heterobasidion annosum (Fr.) Bref.). Всихання насаджень, уражених кореневою губкою, відбувається нерівномірно, тому їх можна умовно розподіляти на фрагменти, що мають різні стан, лісівничо-таксаційні показники та швидкість росту: осередок всихання, міжосередковий простір та еталонна частина міжосередкового простору. Встановлено, що за розподілом кількості стовбурів за ступенями товщини різні фрагменти уражених кореневою губкою насаджень належать до різних генеральних сукупностей. Виявлено, що в Лівобережному Лісостепу густота штучних соснових насаджень ІІІ–Х класів віку, створених на староорних землях і уражених кореневою губкою, в осередках усихання є достовірно меншою, ніж у міжосередковому просторі та еталонній частині міжосередкового простору (на 1–31 та 24–50 % відповідно). Середні висота й діаметр дерев, що ростуть в осередку всихання, є меншими на 1,6 та 1,8 % відповідно проти висоти й діаметра дерев, що ростуть у міжосередковому просторі, та на 5,2 та 3,7 % – проти відповідних показників еталонної частини міжосередкового простору. Визначено, що уражена частина соснового насадження – осередок всихання та міжосередковий простір – за станом є ослабленою та всихаючою: індекс санітарно стану становить від 2,0 до 3,7 та від 1,8 до 3,4 для осередку всихання та міжосередкового простору відповідно. Не уражена кореневою губкою частина насадження (еталонна частина міжосередкового простору) має ослаблений та сильно ослаблений санітарний стан через загущеність і відсутність рубок догляду. Запас ураженого кореневою губкою насадження залежить від поширення осередків усихання та від площі, яку займають власне осередки хвороби, міжосередковий простір та еталонна частина міжосередкового простору.

Assessment of carbon stocks in oak forests along the altitudinal gradient: A case study in the Panchase Conservation Area in Nepal

Little study was done to understand the role of high-altitude oak forests in climate change mitigation. Here, we analyzed data from 30 sample plots collected along the four altitudinal gradients to assess species distribution and carbon stocks in the Panchase Conservation Area in Nepal. Three carbon pools were considered, namely aboveground carbon (AGC), belowground carbon (BGC), and carbon in litters (leaf litters, grass, and herb biomass, CiL). Seven species were found, of which two are oak tree species (Quercus semecarpifolia and Quercus lamellosa). Quercus semecarpifolia is the most dominant species in terms of stem density and carbon stocks, followed by Quercus lamellose. Average tree diameter, height, and total carbon stocks were 27.7 cm, 8.4 m, and 127.6 MgC ha−1, respectively. Our study found higher carbon stocks at the higher altitudinal gradient. Pearson’s correlation analysis shows a strong effect of altitudinal gradients on carbon stocks (r = 0.7124), moderate effect on tree height (r = 0.5263), and less effects on diameter (r = 0.1733). A stepwise multiple regression analysis shows strong relationship between carbon stocks with height (P = 0.0059) and carbon stocks with tree diameter (P = 0.0148). Our ground observations and random interviews indicate that the low carbon stocks at the low altitude were due to human disturbance. Oak forests at lower altitudes are sparse forest stands with poor regeneration capacity, overgrazing, and extensive lopping. If such disturbance is prevented, oak forest can increase carbon stocks to 361.7 MgC ha−1 as found at the higher altitude. Conservation of oak forests in the Panchase Conservation Area could result in emission reductions of 633.0 MgCO2 ha−1. These reductions could be eligible for financial incentives under the REDD + scheme.

Factors promoting the natural regeneration of Larix principis-rupprechtii plantation in the Lvliang Mountains of central China.

Given their complexity, targeted care and management of different areas and tree species are necessary for enhancing the natural regeneration of forests. Thus, an understanding of changes in the overstory and understory is essential for ensuring successful regeneration. Promoting the natural regeneration of Larix principis-rupprechtii plantations is considered challenging; indeed, regional sustainable development through natural regeneration of many stands has often been considered unattainable. Here, we studied several plots with varying extents of regeneration to identify the most important factors that affect regeneration. The plots were divided into three forest types based on the number of regenerating plants. For each type of plot, we measured various factors that might potentially affect regeneration. Representational difference analysis was used to identify the most important factors >9% contribution). Based on these factors, multiple corrections were made to construct a structural equation model of topography, stand structure, soil properties and litter to identify the most important factors driving variation in regeneration. Positive correlations were detected between regeneration with diameter at breast height (0.21) and litter thickness (0.57). Regeneration was negatively correlated with soil (−0.54) and slope (−0.48). Additionally, the number of regenerating plants and the height of regenerating plants were strongly positively correlated. However, there was no significant relationship between regeneration and litter accumulation, stand density, altitude, average tree height, total P and total N. Overall, our study showed that key factors for promoting natural regeneration include appropriate litter thickness, strong parent trees, a gentle slope and sufficient quantities of soil nutrients. Moreover, our findings provide a reference for the design of effective management and restoration plans.

Habitat use by a primate community in a lowland dipterocarp forest in Danum Valley, Borneo.

Knowledge of niche partitioning with respect to habitat is indispensable to understand the mechanism of coexistence of multiple species. Among primates, however, data are still deficient because repeated survey for a sufficiently long time, covering seasonal changes over a large area, is the only way to clarify habitat segregation within a seasonally fluctuating environment. Southeast Asia is particularly interesting because of the supra-annual, highly unpredictable seasonality in fruiting known as mast fruiting. We conducted repeated route census, habitat monitoring, and group tracking for 25 months in two study sites (ca. 10 km apart) in the largely primary lowland dipterocarp forest of the Danum Valley Conservation Area, eastern Sabah, northern Borneo, Malaysia. The five species of diurnal primates (Bornean orangutan Pongo pygmaeus, Müeller's gibbon Hylobates muelleri, red leaf monkey Presbytis rubicunda, long-tailed macaque Macaca fascicularis, and southern pig-tailed macaque M. nemestrina) did not show horizontal spatial segregation. Red leaf monkeys showed preferences for places with short tree height, but their distribution was not confined to such places. In response to the fruiting peak observed once during the study period, orangutans increased their numbers simultaneously in the two study sites. The average tree height used by the five species was different, but their range overlapped substantially. Compared with other primate communities, the lack of horizontal spatial segregation and the suggested long-distance movement of orangutans seem to be unique characteristics in Borneo, although the use of different forest strata is a widespread phenomenon among primate communities throughout the world.

Особливості формування мішаних дубових молодняків в умовах Закарпаття

Розглянуто особливості формування мішаних дубових молодняків в умовах Закарпаття, що передбачає здійснення комплексу лісогосподарських заходів, які забезпечують умови для появи самосіву дуба звичайного, або штучне створення способом висаджування саджанців дуба на лісокультурних площах. Встановлено, що молоді деревостани за участю дуба звичайного характеризуються високою інтенсивністю нагромадження запасу та формування видового складу на початкових етапах росту і потребують належної оцінки їх таксаційних параметрів у молодому віці. Виконано низку облікових робіт, які спрямовані на оцінення лісівничо-таксаційних параметрів мішаних дубових молодняків на стаціонарних дослідних об'єктах з реалізацією різних варіантів системи рубок формування деревостанів. Відповідно до виконаних розрахунків на дослідних секціях зосереджені грабово-дубові та грабово-ясенево-дубові молодняки ІІ класу бонітету. Оцінка відносної повноти таких об'єктів показує, що мішані деревостани в цьому віці здатні рости з більшою фактичною продуктивністю. Показник відносної повноти перевищує норму в 2–3 рази. За густотою аналізовані об'єкти також істотно відрізняються між собою (приблизно в 4 рази). Сильно змінюється і частка дуба в деревостані (приблизно 5 одиниць). Отже, попри однакову потенційну продуктивність, дубові молодняки на секціях стаціонарів сильно відрізняються за іншими таксаційними параметрами. Відзначено, що за одночасного врахування показників частки дуба в складі, запасу деревостану, середньої висоти та кількості дерев дуба звичайного – оптимальним варіантом формування корінних, високопродуктивних мішаних деревостанів за участю дуба є лісостани, що сформовані за програмою заходів, які реалізовано на секції С-1 та секції СВ-1(1/3Гр), де зрубано 1/3 висоти стовбурів підросту граба. У будь-якому разі система лісогосподарських заходів, реалізована на стаціонарі С-1 та СВ-1(1/3Гр), дає на початковому етапі формування мішаних дубових деревостанів оптимальний результат, як для досягнення високого загального запасу деревостаном, так і для формування дубового елемента лісу, зокрема. На підставі здійснених досліджень встановлено, що зволікання з проведенням освітлення дуба звичайного у віці до 10 років, може зумовити різке випадання зі складу молодого насадження сіянців та саджанців головної лісотвірної деревної породи (Контроль та секція С-4). Своєчасне регулювання висоти граба звичайного (секція С-1 та СВ-1) дає змогу істотно посилити позиції дуба звичайного у конкурентній боротьбі з другорядними деревними породами. Недоцільною, на нашу думку, є суцільне вирубування підросту граба та інших деревних видів, тому що такий захід спричиняє сповільнення приросту верхівкового пагона дуба звичайного та сприяє розростанню бокових.

Site index research: a literature review

Abstract The purpose of this paper was to review literature covering the topic of site index with particular emphasis on Scots pine, the most important forest-forming species in Poland. We discuss the history of the site index, research on various tree species, statistical modelling methods, the spatial application of site index and age impact assessment. The history of research on the site index of forest species is long and dates back to the 18th century. Many researchers thought that determining the quality of the habitat is very important from the point of view of rational forest management. The site index, as a measure of the potential of the habitat on which the forest grows, is one of the most important characteristics of forest stands. The site index depends on the selected model, but is most often expressed as the average or top height of trees of a given species at a certain age. In our review, we point out several insufficiencies of studies on the site index, external influences and the connection of the site index with spatial conditions. Furthermore, research conducted so far has not explicitly confirmed that there is a relationship between the site index of pine stands and their geographical location in Poland. More research on the site index, especially in regard with climate change, is needed.

Estimation of aboveground biomass using aerial photogrammetry from unmanned aerial vehicle in teak (Tectona grandis) plantation in Thailand

Abstract. Rinnamang S, Sirirueang K, Supavetch S, Meunpong P. 2020. Estimation of aboveground biomass using aerial photogrammetry from unmanned aerial vehicles in teak (Tectona grandis) plantation in Thailand. Biodiversitas 21: 2369-2376. Thailand is one of the best teak planting locations in the world. Teak is one of the most species planting and a significant source of high-value timber in Thailand. For plantation management, biomass is one of the important factors while determining the production of a plantation and also for sustainable forest management. Unmanned Aerial Vehicles (UAV) have the ability to produce 3D RGB digital images which can be used to study the plantation characteristics. This study aimed to use aerial images and photogrammetry techniques derived from unmanned aerial vehicles (UAV) to estimate teak biomass in Thong Pha Phum plantation, Kanchanaburi Province, Thailand. We conducted our study on 15-and 36-year-old teak stands, and compared the tree dimension between data obtained from field measurement and that from aerial images and photogrammetry techniques. In the 15-year-old stand, the average tree height estimated from the UAV and ground-truthing were 12.34 and 13.06 m, respectively. In the 36-year-old stand, the average tree height from the UAV and ground-truthing were 28.87 and 29.39 m, respectively. We found that in both stands, the difference between data generated from the UAV and ground-truthing data was not significant (p-value = 0.07 and 0.306, respectively). There was also a strong correspondence between tree height estimated from the UAV and that measured on the ground which is indicated by the high R2 (i.e. 0.70 and 0.64 for the 15-and 36-year-old stands, respectively). Using UAV generated data, the total biomass of 15-and 36-year-old stands was estimated to be around 42.07 t ha-1 and 67.13 t ha-1, respectively. The overall results suggest that UAV can be used as an effective tool to survey and monitor stand’s productivity in teak plantation.

Assessment on the growth performance of planted Dryobalanops beccarii at reforestation sites after implementation of selective girdling

Abstract. Wasli ME, Ambun DB, Kalu M, Sidi M, Nahrawi H, Elias H. 2020. Assessment on the growth performance of planted Dryobalanops beccarii at reforestation sites after implementation of selective girdling. Biodiversitas 21: 1880-1889. This study was conducted to evaluate the growth performance of planted Dryobalanops beccarii Dyer at reforestation sites after silvicultural practices in Gunung Apeng National Park (GANP), Sarawak. The assessed area was planted with D. beccarii in 2005 and undergo silvicultural treatment by understory clearing which implemented annually. Due to the suppressed growth rate of the planted trees, an additional silvicultural treatment, the selective girdling on selected pioneer species, was implemented once, in 2012. In this study, study plots with two treatments were established: T1: understory clearing only (control plot), and T2: additional selective girdling of existing pioneer species in addition to the understory clearing practice applied in T1. The growth performance of the planted D. beccarii in terms of DBH, height, survival and mean annual increments in diameter (MaiD) and height (MaiH) were assessed and monitored at the initial stage when the selective girdling treatment was applied and 4, 24, 36, 48, 60 and 72 months after girdling. Our findings showed that the survival rates of planted trees at 72 months under treatments T1 and T2 were 82.9% and 79.2%, respectively. The average tree DBH in T2 was significantly higher than that in T1, and the average tree DBH values for T1 and T2 were 7.5 cm and 9.4 cm, respectively. The average tree heights for T1 and T2 were 8.3 m and 9.2 m, respectively. In terms of the mean annual increments in height (MaiH) and diameter (MaiD), those in T2 were significantly higher than those in T1. Our findings indicated that T2 started to show better growth performance than T1 after a period of 36 months. In conclusion, the additional silvicultural treatment by selective girdling at the reforestation site had a long-term, progressive effect on the growth performance of the planted trees.

The secret lives of mangroves: Exploring New Zealand's urban mangroves with integrated biodiversity assessments

Integrated biodiversity assessments were conducted at four mangrove sites bordering urban parks in the Manukau Harbour, Auckland, New Zealand. Mangrove habitat complexity was also surveyed. Sites selected were adjacent to areas of mangrove removal between 2010 and 2018. Assessments were conducted in late summer 2018 and with a duration of one week per site. This study provides a snap-shot of biodiversity within mangroves and a baseline dataset on many species little studied in these habitats. A wide-range of equipment and techniques were used in order to record both terrestrial and marine vertebrates and invertebrates, through the least invasive methods. Forty-nine arboreal arthropod, fifteen bird, six mammalian, two fish, two crab, one shrimp, one gastropod, one jellyfish and one amphipod species were recorded in the study period. Results show much heterogeneity in terms of habitat complexity among sites. Habitat complexity parameters of adult tree density, average crown spread and height of adult trees explained 39% of arboreal arthropod abundance at the sites. Sites with lowest tree density, height and greatest crown spread had the highest relative abundance of arboreal arthropods. There was a significant difference between species richness of arthropods among sites, and sites with lowest adult tree density have the greatest richness. All eleven habitat complexity parameters contributed 34.4% of overall differences in richness among sites. Area of connected mangrove was negatively correlated with both arboreal arthropod abundance (r2 = 0.77) and richness (r2 = 0.99). This research shows that mangroves are important habitats for a wide variety of both native and non-native animal species in New Zealand. Simple non-invasive techniques can be used to record different species occupying mangroves throughout tidal cycles. Long-term integrated ecological monitoring is required in these habitats and removal of mangrove should be considered on a site-by-site basis.

Ріст дерев головних порід на ділянках реконструкції малоцінних молодняків коридорним способом

Одним із важливих лісогосподарських заходів для відтворення корінних, продуктивних, стійких і довговічних деревостанів є реконструкція похідних та малоцінних деревостанів. Для заміни малоцінних і похідних молодняків на цільові проводять реконструктивні рубки та заходи, пов’язані зі штучним відновленням лісу. Розглянуто особливості росту дерев сосни звичайної, ялини європейської, дуба звичайного, ясена зеленого на ділянках реконструкції малоцінних молодняків коридорним способом. Визначено параметри поточного приросту за висотою дерев головних порід протягом 10-річного періоду після реконструкції залежно від деревного виду, ширини та напрямків коридорів, методу створення лісових культур, що ростуть у коридорах реконструйованих малоцінних молодняків до та після проведення рубок догляду. Визначено санітарний стан дерев головних порід і надано пропозиції для проведення наступних лісогосподарських заходів. Вивчено вплив освітленості, температури повітря, вологості та щільності ґрунту на стан і показники росту дерев головних порід.

Vegetation composition and structure determine wild bee communities in a tropical dry forest

Understanding the factors that influence the composition and structure of bee communities in natural habitats is critical for conservation and restoration efforts, mainly in disturbed ecosystems that are widely used for agricultural crop production, such as tropical dry forests (TDF). The aim of this study was to evaluate the effects of tree species composition and vegetation structure on the composition, abundance and species richness of eusocial and non-eusocial wild bee assemblages. Bees (19.909 individuals of 96 species) were collected in fifteen plots in different secondary succession stages in a TDF in the state of Minas Gerais, Brazil. We found a positive relationship between tree community similarity and bee community similarity, for both eusocial and non-eusocial bees. Average tree height positively affected the abundance and species richness of eusocial bees, while the abundance of non-eusocial bees was negatively affected by tree species richness. Similar tree species composition and vegetation structure between plots at the same stage of secondary succession probably determined more similar bee communities than dissimilar tree communities. Most eusocial bee species are dependent on cavities in large trees to house their colonies, while most non-eusocial bees probably prefer open habitats because they provide a greater density and diversity of floral resources, and suitable areas for ground-nesting species. Since eusocial bees represented 94% of the individuals sampled, the conservation and restoration of mature forests is of primary importance in order to increase eusocial bee diversity, and the maintenance of these areas in the vicinity of agricultural systems is crucial to increase the ecosystem service of pollination.

Impacts of Urban Form on Thermal Environment Near the Surface Region at Pedestrian Height: A Case Study Based on High-Density Built-Up Areas of Nanjing City in China

The continuous worsening of urban thermal environments poses a severe threat to human health and is among the main problems associated with urban climate change and sustainable development. This issue is particularly severe in high-density built-up areas. Existing studies on the thermal environments (temperature data extracted from satellite remote sensing images) are mainly focused on urban canopy areas (airspace below the average height of trees or buildings) rather than the near surface region (at pedestrian height). However, the main outdoor activity space of urban residents is the area near surface region. Hence, this study aims to investigate the influence of urban form (i.e., building density, height, and openness) on thermal environment near the surface region. The high-density built-up areas of a typical megacity (i.e., Nanjing) in China were selected, and the thermal environments of 26 typical blocks were simulated using ENVI-met software. Temperature field measurements were carried out for simulation validation. On this basis, a classified and comparative study was conducted by selecting the key spatial form elements that affect thermal environments. The results showed that in actual high-density built-up areas, single urban form parameter does not determine the thermal environments near the urban surface but mainly affected by the use (function) of space. For this study, the overall thermal environment of a street block is optimal when the building density is between 40% and 50% and the average building height is between 8 and 17 stories. Nonetheless, the urban form can be improved to optimize the overall effects on building functions and thermal environments. Furthermore, function-specific urban form optimization strategies were proposed to optimize thermal environments according to specific functional needs.