Structure Of Natural Forests Research Articles

Woody species composition, structure, and diversity of homegarden agroforestry systems in southern Tigray, Northern Ethiopia

Nowadays, the conservation of biodiversity is a major environmental challenge globally. Homegarden agroforestry systems (HGAFs) have a large potential for biodiversity conservation. However, little attention has been given to the relative importance of HGAFs in terms of biodiversity conservation. The present study, therefore, aimed to estimate and compare the woody species diversity and structure of HGAFs and adjacent natural forest (NF) in Northern Ethiopia. Three sites were purposively selected based on the presence of HGAFs and NF adjacent to each other. A stratified sampling system was used to select representative homegardens from different wealth categories. In NF, a systematic transect sampling technique was employed. A total of 90 sample plots (10 m × 20 m) were used to collect vegetation data. A total of 32 species representing 26 genera and 20 families were identified from the studied HGAFs and NF. Thirty woody species belonging to 24 genera and 20 families were recorded in the HGAFs whereas, 11 species, belonging to 9 genera and 8 families were recorded in the NF. Native woody species accounted for 66% of all woody species recorded in both HGAFs and NF. Stem density, richness, and diversities of woody species were significantly higher in HGAFs than in NF (p ≤ 0.05). Trees and shrubs in the HGAFs had significantly lower stem diameters, height, and basal area than the adjacent NF (p ≤ 0.05). The results show that HGAFs complements the NF for biodiversity conservation and supports in counteracting the loss of woody species from the natural ecosystem. Hence, promoting HGAFs habitats in human-dominated landscapes should be part of the biodiversity conservation strategy.

Historical natural disturbances shape spruce primary forest structure and indirectly influence bird assemblage composition

Understanding the processes shaping the composition of assemblages in response to disturbance events is crucial for preventing ongoing biodiversity loss in forest ecosystems. However, studies of forest biodiversity responses to disturbance typically analyze immediate or short-term impacts only, while studies relating long-term disturbance history to biodiversity assemblage dynamics are rare. To address this important knowledge gap, we used a dendroecological approach to link natural disturbance history of 250 years (1750–2000) to structural habitat elements and, in turn, to breeding bird assemblages. We used data collected in 2017 and 2018 from 58 permanent study plots within 10 primary spruce forest stands distributed across the Western Carpathian Mountains of Europe. This dataset contained breeding bird counts and environmental variables describing forest density, tree diameter distribution, tree height, tree microhabitats, deadwood quantity and quality, and regeneration. Bird assemblages were significantly influenced by forest structure which was in turn shaped by disturbance dynamics (disturbance frequency, time since the last disturbance and its severity). Early successional species associated with more open habitats were positively influenced by disturbance-related structure (i.e. deadwood-related variables, canopy cover), while some species responded negatively. At the same time, overall abundance, species richness and Shannon diversity of the bird assemblage remained unchanged under variable disturbance histories. Our results support a view of primary spruce forests as a highly dynamic ecosystem, harbouring populations of bird species at all stages of succession despite significant structural changes and shifting patch mosaics over time due to natural disturbances.

Bunching as a Method to Reduce Wood Moisture through Transpirational Drying following Forest Restoration Treatments in Northern Arizona

Abstract Thinning is a necessary silvicultural activity for restoring the long-term sustainability of pine forests in much of the southwestern United States. In northern Arizona, a landscape-scale restoration effort, called the Four Forest Restoration Initiative, has been implemented to recover the long-term sustainability of 2.4 million acres on four national forests. Cost-effective and efficient thinning methods are needed due to the scale of the project to help improve habitat, conserve biodiversity, protect old growth, reduce risk of severe wildfire, and restore natural forest structure and function. Mechanical cutting using a feller-buncher is the primary method of thinning in these forests due to the extreme high number of small-diameter ponderosa pine trees. A feller-buncher places harvested trees into small piles known as “bunches.” In this review, we highlight advantages and disadvantages of bunching tree materials in restoration programs and review published studies on transpirational drying of bunches of various tree species in different forest habitats across the United States, including ponderosa pine in Arizona. Studies show that transpirational drying of trees in bunches can be an effective method to allow for wood drying, but this process can be affected by abiotic factors associated with seasonal climate and stand characteristics. Study Implications The Four Forest Restoration Initiative makes up the largest landscape-level collaborative project in the history of the USDA Forest Service with more than 2.4 million acres of forest habitat. Thinning is a necessary silvicultural activity for restoring the long-term sustainability of these forests in northern Arizona. Because of the extremely high number (i.e., average of 720 trees per acre) of small-diameter ponderosa pine (Pinus ponderosa) trees, mechanical cutting is more cost effective than individual saw cutting, which is why a feller-buncher machine is the primary thinning tool. During feller-buncher thinning, small piles of trees known as “bunches” are created. Bunching trees can allow for wood drying in the field that translates into lower operational costs because drier trees are lighter in weight, which reduces transportation costs. In northern Arizona, a 60-day time frame is allotted for transpirational drying before tree materials must be removed from the forest. However, because the drying process through bunching is affected by abiotic conditions, there may be a need to adjust this time frame to account for seasonal weather patterns. For example, during spring, when weather in northern Arizona is hot and dry, less time might be necessary for tree bunches to lose enough moisture while still rendering the thinning operation profitable and simultaneously avoiding bark beetle proliferation given that their life cycle consists of about 40 days. Furthermore, bunching studies should be developed to look at individual tree species in their respective locations and to investigate the effects of the presence, partial presence, or absence of branches and bark on trees within bunches. Studies should also be conducted to look at the effects of bunches on insect communities, particularly those that can cause extensive tree mortality.

A review of natural disturbances to inform implementation of ecological forestry in Nova Scotia, Canada

Like many jurisdictions across North America, the province of Nova Scotia (NS) is faced with the challenge of restoring its forests to a more natural, presettlement state through implementation of ecological forestry. At the core of ecological forestry is the idea that natural forest structures and processes may be approximated by designing management practices that emulate natural disturbances. Successful natural disturbance emulation depends on fundamental knowledge of disturbance characteristics, including identification of specific disturbance agents, their spatial extent, severity, and return interval. To date, no comprehensive synthesis of existing data has been undertaken to document the natural disturbance regime of NS forests, limiting the application of natural disturbance emulation. Using over 300 years of documents and available data, we identified the main natural disturbance agents that affect NS forests and characterized their regimes. Overall, fire, wind (predominantly hurricanes), and outbreaks of spruce budworm (Choristoneura fumiferana (Clemens)) are the most important disturbance agents, causing substantial areas of low- (<30% mortality), moderate- (30%–60%), and high- (>60%) severity disturbance. While characterization of natural historic fire is challenging, due to past human ignitions and suppression, we estimated that the mean annual disturbance rate of moderate- to high-severity fire ranged between 0.17% and 0.4%·year−1 (return interval of 250–600 years), depending on ecosystem type. Hurricanes make landfall in NS, on average, every 7 years, resulting in wide-scale (>500 ha) forest damage. While hurricane track and damage severity vary widely among storms, the return interval of low- to high-severity damage is 700–1250 years (0.14%–0.08%·year−1). Conversely, the return interval of host-specific spruce budworm outbreaks is much shorter (<50 years) but more periodic, causing wide-scale, low- to high-severity damage to spruce–fir forests every 30–40 years. Further disturbance agents such as other insects (e.g., spruce beetle), diseases, ice storms, drought, and mammals can be locally important and (or) detrimental to individual tree species but contribute little to overall disturbance in NS. Climate change is expected to significantly alter the disturbance regime of NS, affecting current disturbances (e.g., increased fire) and driving the introduction of novel agents (e.g., hemlock wooly adelgid), and continued monitoring is needed to understand these changes.

Mapping individual trees with airborne laser scanning data in an European lowland forest using a self-calibration algorithm

Traditional field-based forest inventories tend to be expensive, time-consuming, and cover only a limited area of a forested region. Remote sensing (RS), especially airborne laser scanning (ALS) has opened new possibilities for operational forest inventories, particularly at the single-tree level, and in the prediction of single-tree characteristics. Throughout the world, forests have varying characteristics that necessitate the development of modern, effective, and versatile tools for ALS data processing. To address this need, we aimed to develop a tool for individual tree detection (ITD) utilising a self-calibrating algorithm procedure and to verify its accuracy using the complicated forest structure of near natural forests in the temperate zone.This study was carried out in the Polish part of the Białowieża Forest (BF). The airborne laser scanner (ALS) and color-infrared (CIR) datasets were acquired for more than 60 000 ha. Field-based measurements were performed to provide reference data at the single tree level. We introduced a novel ITD method that is self-calibrated and uses a hierarchical analyses of the canopy height model.There were more than 20 000 000 of trees in first layer in BF above 7 m height. Trees visible from above were divided into coniferous, deciduous and mixed trees that were then matched with an accuracy of 85 %, 85 % and 75 %, respectively. Compared to existing methods, the proposed method is more flexible and achieves better results, especially for deciduous species. Before application of the presented method to other regions, the calibration based on the developed optimisation procedure is needed.

Analyzing the Biological and Structural Diversity of Hyrcanian Forests Dominated by Taxus baccata L.

The Hyrcanian Forests, well-known for its World Heritage site in the South Caspian region of Northern Iran, are refugia for a special tree flora. Some areas in particular feature a concentration of large and numerous trees of Taxus baccata, a species that has attracted the interest of many researchers given its medicinal importance. The objective of this study was to analyze the biological and structural features of these unique ecosystems based on three large tree-mapped field plots using new methods. We developed a species abundance distribution and three species–area relations, and analyzed the small-scale structural patterns of each of the 15 tree species that occur in the plots. Species-specific details are presented for each of the three field plots, including the tree densities and average tree sizes, as well as the associated structural indices “species mingling”, “dominance”, and “size differentiation”. This includes non-linear relationships between tree density and neighborhood mingling, and between the average tree size and neighborhood dominance, and a linear relation between the neighborhood dominance and the mean neighborhood differentiation. Based on the findings, we recommend the use of these methods and indices for analyzing the structure of natural forests in other regions of the world.

Spatial Structure Evaluation of Natural Secondary Forest around Dongting Lake Based on Entropy Weight - Cloud Model

Li, X.; Zhang, G., and Li, J., 2020. Spatial structure evaluation of natural secondary forest around Dongting Lake based on entropy weight - cloud model. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 484–489. Coconut Creek (Florida), ISSN 0749-0208.In order to provide theoretical support for the formulation of optimized measures of stand spatial structure, 15 sample plots are set up in Daweishan Nature Reserve, Longhushan national forest farm in Yuanjiang City and Lutou national forest farm in Pingjiang County to analyze and evaluate the stand spatial structure of natural secondary forest around Dongting Lake. After determining the spatial structure unit of trees by Voronoi diagram, the five indicators including mingling degree, neighborhood comparison, openness comparison index, neighborhood pattern and angle competition index are segmented to correspond to the five grades of stand spatial structure divided by the combination of qualitative and quantitative methods. Then through the comprehensive assessment on stand spatial structure by entropy weight-cloud model, the fifteen plots are evaluated as grade III and grade IV, respectively accounting for two-thirds and one-thirds of all plots, which indicates that the reasonable stand spatial structure of natural secondary forest around Dongting Lake is above the average. As a new evaluation method of stand spatial structure, the entropy weight-cloud model has solved the issue of qualitative and quantitative conversion, and objectively calculate the weights of indicators, so as to enrich the evaluation methods of stand spatial structure, overcome the one-way evaluation by single indicator, improve the objectivity and scientificity of evaluation results, and provide theoretical basis for the scientific guidance of stand spatial structure optimization.

Morfometria de Araucaria angustifolia em diferentes altitudes no Sul do Brasil

Os índices morfométricos podem ser usados para subsidiar o entendimento da dinâmica de florestas naturais. Diante disso, objetivou-se descrever e avaliar as características morfométricas e dendrométricas de Araucaria angustifolia, como subsídio para compreensão da estrutura da floresta natural de araucária. Os dados foram mensurados em três municípios de Santa Catarina, considerando diferentes altitudes de ocorrência da espécie, com amostragem de 247 árvores, utilizando o método de Bitterlich, sendo medida a circunferência a 1,30 m do solo, altura total e de inserção de copa e raios de copa. As relações interdimensionais das árvores foram descritas por meio de índices morfométricos. O sítio 2 apresentou árvores de maior porte em relação ao diâmetro e área de copa. O sítio 3 apresentou a maior densidade de árvores (403 árvores ha-1), enquanto nos sítios 1 e 2 foram observadas 362 e 232 árvores ha-1, respectivamente. No sítio 3, a maior parte das árvores apresentou proporção de copa superior a 50% e formal de copa menor que 1, indicando árvores de copas mais estreitas e largas. O diâmetro da árvore apresentou correlação negativa e superior a 70% com o grau de esbeltez. Nos três sítios, o diâmetro apresentou correlação positiva com o diâmetro de copa.

The ecological implications of rubber‐based agroforestry: Insect conservation and invasion control

AbstractProtected areas are increasingly threatened by biological invasions, especially in tropical Asia where extensive areas of natural habitats have been converted to monoculture plantations. Such disturbance provides a gateway for exotic species invasions, highlighting an urgent need for cross‐boundary solutions to mitigate invasion impacts.Agroforests, with multi‐storied trees and crops resembling the complex structure of natural forest, are known to promote native species compared to monoculture plantations. Yet, our knowledge on their roles in controlling exotic species is limited to plant invaders, with effects on animal invaders still unknown. Given that protected areas are increasingly threatened by invaders from surrounding plantations, with a majority of them represented by insects, it is important to evaluate the effect of agroforestry practice, and mechanisms of associated management to control invasions.By using both taxonomic and functional trait‐based approaches, we studied leaf litter ant communities in 12 rubber monoculture (mono‐rubber), 9 rubber plantation with understory crops (agro‐rubber), 16 secondary and 12 old‐growth secondary forest plots in and around protected areas in Hainan, China. Sampled ants were further classified into groups based on their invasive potential (tramp vs. non‐tramp) to determine the ecological values of agro‐rubber.We found that despite mono‐rubber and agro‐rubber presenting similar species richness, the latter (a) supports species composition and functional diversity more similar to secondary forests and (b) reduces tramp ant species occurrence, a novel management incentive. Nonetheless, agro‐rubber is not comparable to secondary forest in terms of non‐tramp ant species composition.Synthesis and applications.Against the increasing threat of biological invasions, preserving natural forests in human‐dominated landscapes is crucial. Increasing the area of agro‐rubber at the periphery of protected areas as a proactive mitigation can, however, be perceived as an additional measure to reduce invasive species' establishment and spread across the landscape. Plantation‐based agroforestry has emerged as a potential management avenue and incentive for transforming monoculture plantations into a less ‘harmful’ alternative.

The legacy of management approaches and abandonment on old-growth attributes in hardwood floodplain forests in the Pannonian Ecoregion

In the absence of primeval floodplain forests, near-natural remnants are key references for close-to-nature forestry and nature conservation. Old-growth forest characteristics (OGCs) were quantified in 16 managed (rotation or selection) and abandoned semi-natural floodplain forests by taking snapshot inventories of structural features. Principal component analysis revealed a short gradient from closed-canopy managed stands dominated by large trees (mainly oaks) and hornbeams, with less deadwood, to abandoned older stands with more gaps, very large trees and different kinds of deadwood. All the studied forests are mainly in the early and late biostatic phases of forest development, with innovation and degradation phases almost completely absent. Results showed that selection forests had significantly more very large trees compared to rotation stands. The difference in structure between abandoned selection stands and abandoned rotation stands was more pronounced than in their counterparts that are still managed. Based on diameter distribution and the amount of very large trees and deadwood, abandoned selection stands were closest to the structure of natural forests. Selection forests may recover certain OGCs more rapidly than rotation forests. We concluded that after 100–150 years of homogenising rotation forestry, OGCs are slow to develop in just 25 years of non-intervention. Based on our results, we recommend: (i) an increase in the rotation cycle with selective logging in order to restore and maintain OGCs in managed rotation forests and (ii) total abandonment in certain well-preserved, near-natural forests with natural flooding regimes. However, the failure of oak to regenerate naturally remains a challenge.

Structure and biomass accumulation of natural mangrove forest at Gazi Bay, Kenya

Abstract. Githaiga MN, Kotut K, Kariuki F, Kairo JG. 2019. Structure and biomass accumulation of natural mangrove forest at Gazi Bay, Kenya. Bonorowo Wetlands 9: 18-32. The goal of this study was to determine the forest structure and estimate biomass accumulation above and below ground in the mangrove forest of Gazi Bay. The western, middle, and eastern forest blocks of the Gazi Bay mangrove forest were investigated for forest structure, whereas the western forest block was determined for biomass accumulation. To calculate below-ground biomass accumulation, in-growth cores of 80 cm long, 20 cm broad, and 60 cm deep were employed. Above-ground biomass accumulation was calculated using data on tree height and stem diameter at breast height (DBH-130). Leaf phenology was observed by tagging shoots. At the start, environmental variables were measured every four months for a year across four mangrove species zones. The linear regeneration sampling approach was used to determine the composition and distribution pattern of natural regeneration (LRS). Salinity revealed a strong negative connection with above-ground biomass accumulation among the soil environment characteristics studied. Sonneratia alba had the highest biomass accretion rate of 10.5 1.9 t ha-1 yr-1 among the four forest zones. Rhizophora mucronata (8.5 0.8 t ha-1 yr-1), Avicennia marina (5.2 1.8 t ha-1 yr-1), and Ceriops tagal (2.6 1.5 t ha-1 yr-1) were the next most abundant species. Above-ground and below-ground biomass accumulation differed significantly among zones (F (3, 8) = 5.42, p = 0.025) and (F (3, 8) = 16.03, p = 0 001), respectively. There was a significant difference in total biomass accumulation across zones (F (3, 8) =15.56, p = 0.001). For the entire forest, a root : shoot biomass accumulation ratio of 2 : 5 was calculated. This study's findings provide more accurate estimates of mangrove carbon capture and storage, which can be used in carbon credit discussions in the emerging carbon market.

长白山白桦山杨次生林细根形态特征和解剖结构对氮沉降的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 长白山白桦山杨次生林细根形态特征和解剖结构对氮沉降的响应 DOI: 10.5846/stxb201807141528 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41773075，41575137，31370494，31170421） Response of fine root morphology and anatomical structure of Betula platyphylla and Populus davidiana natural secondary forest to nitrogen deposition in Changbai Mountains Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根系作为植物与土壤物质交换和养分循环的桥梁，长期以来一直是生态学研究的热点。于2017年7月植物生长季，对长白山模拟11年氮（N）沉降控制试验样地的白桦（Betula platyphylla）山杨（Populus davidiana）天然次生林进行了根系采样，并利用根序法研究了根系形态特征和解剖结构对不同梯度N添加处理的响应，旨在探求两物种根系之间潜在生态联系。本试验共设置了三个N添加梯度，分别为对照（CK，0 g N m-2 a-1）、低N处理（TL，2.5 g N m-2 a-1）和高N处理（TH，5.0 g N m-2 a-1）。研究结果如下：1） TL显著抑制白桦和山杨前三级细根皮层厚度的生长。白桦通过增加皮层细胞直径（一级根增加了72.77%，二级根增加了53.22%，三级根增加了39.96%）但减少皮层层数来降低皮层厚度，而山杨主要通过皮层细胞直径的减少（一级根下降了40.80%，二级根下降了28.17%）来降低其皮层厚度。2） TH显著抑制山杨前三级细根生长。主要通过增加皮层厚度（一级根增加了68.78%，二级根增加了50.81%，三级根增加了88.53%）以及降低导管横截面积来抑制吸收养分，从而达到影响生长的目的。3）白桦TH相比于TL细根直径呈抑制生长状态。其主要通过抑制中柱直径（一级根下降了17.61%，二级根下降了16.89%，三级根下降了20.62%）的生长来实现。以上结果表明，在同一立地条件下，白桦和山杨的细根对不同浓度N沉降的响应方式不同。 Abstract:As a bridge of material exchange and nutrient cycle between plant and soil, root system has been a research hot spot in ecology. The aim of this study was to explore the potential ecological relationship between the roots of two species. We carried out the research in the growing season in July 2017. The root system was collected in 11 years nitrogen (N) control simulation test sample of Betula platyphylla & Populus davidiana natural secondary forest in Changbai Mountains. The root sequence method was used to reveal responses of the root morphology and anatomical structure to different gradients of N addition. In the study, three N addition gradients were set, which were ambient environment (CK, 0.0 g N m-2 a-1), low nitrogen addition (TL, 2.5 g N m-2 a-1), and high nitrogen addition (TH, 5.0 g N m-2 a-1), respectively. The results were as follows. 1) The TL significantly inhibited growth of the cortical thickness of the first three levels of roots of Betula platyphylla and Populus davidiana. Betula platyphylla reduced cortical thickness by increasing cortical cell diameter (the primary root increased by 72.77%, the secondary root increased by 53.22%, and the third level root increased by 39.96%). While Populus davidiana reduced cortical thickness mainly by decreasing cortical cell diameter (the primary root and the secondary root decreased by 40.80% and 28.17%, respectively). 2) The TH significantly inhibited the growth of the first three levels of roots of Populus davidiana, which was inhibited mainly by increasing the thickness of the cortex (the primary root increased by 68.78%, the secondary root increased by 50.81%, and the third level root increased by 88.53%) and by decreasing the cross sectional area of the catheter so as to affect growth. 3) By comparing the TH with the TL, fine roots diameter of Betula platyphylla showed growth inhibition by inhibiting the growth of the stele diameter (the primary root decreased by 17.61%, the secondary root decreased by 16.89%, and the third level root decreased by 20.62%). The results indicate that the fine roots of Betula platyphylla and Populus davidiana respond differently to N deposition of different concentrations in the same site conditions. 参考文献 相似文献 引证文献

Dominance-caused differences in transpiration of trees in a Karst broadleaved mixed forest

Estimating stand transpiration of natural forests using traditional methods through up-scaling of sap flux density from sample trees based on stand sapwood area only is difficult because of the complexity of species, ages, and hierarchical structure of natural forests. To improve stand transpiration estimation, we developed an up-scaling method by considering the tree dominance effect based on the assumption that individual tree transpiration is affected by crown dominance and species, in addition to factors previously considered such as meteorological conditions, sapwood area, and soil moisture. In this study, the meteorological factors, soil moisture, and sap flux density of 15 sample trees of different species and dominance in a natural evergreen and deciduous broadleaved mixed forest were simultaneously monitored from March 2012 to February 2014 in the Karst mountain region in southwestern China. After establishing a single tree transpiration model which considers the effects of dominance and species, an up-scaling method was explored to estimate stand transpiration. The results show that the transpiration intensity increased exponentially with increasing tree dominance. The contribution to annual stand transpiration from a few dominant trees (5.4% of trees, 28.2% of basal area) was up to 65.0%. The corresponding contribution was 16.2% from sub-dominant trees (7.6% of trees, 16.2% of basal area) and 22.8% from middle- and lower-layer trees (87.0% of trees, 55.6% of basal area). The variation of individual tree transpiration was mainly (97.9%) explained by tree dominance, but very weakly by tree species. The estimated annual stand transpiration was 300.2 mm when using the newly developed method which considers tree dominance, 52.5 mm (14.9%) lower than the estimation (352.7 mm) of traditional method which considers only the sapwood area effect, and 8.5 mm (2.7%) lower than the estimation (308.6 mm) which considers the effects of both species composition and sapwood area. The main tree characteristics affecting stand transpiration are tree size (sapwood area) and dominance. Consideration of tree dominance will significantly improve stand transpiration estimation and provide a more solid basis for guiding integrated forest–water management at stand scale.

Forest recovery following extreme drought in California, USA: natural patterns and effects of pre-drought management.

Rising temperatures and more frequent and severe droughts are driving increases in tree mortality in forests around the globe. However, in many cases, the likely trajectories of forest recovery following drought-related mortality are poorly understood. In many fire-suppressed western U.S. forests, management is applied to reverse densification and restore natural forest structure and species composition, but it is unclear how such management affects post-mortality recovery. We addressed these uncertainties by examining forest stands that experienced mortality during the severe drought of 2012-2016 in California, USA. We surveyed post-drought vegetation along a gradient of overstory mortality severity in paired treated (mechanically thinned or prescribed-burned) and untreated areas in the Sierra Nevada. Treatment substantially reduced tree density, particularly in smaller tree size classes, and these effects persisted through severe drought-related overstory mortality. However, even in treated areas with severe mortality (>67% basal area mortality), the combined density of residual (surviving) trees (mean 44trees/ha) and saplings (mean 189saplings/ha) frequently (86% of plots) fell within or exceeded the natural range of variation (NRV) of tree density, suggesting little need for reforestation intervention to increase density. Residual tree densities in untreated high-mortality plots were significantly higher (mean 192trees/ha and 506saplings/ha), and 96% of these plots met or exceeded the NRV. Treatment disproportionately removed shade-tolerant conifer species, while mortality in the drought event was concentrated in pines (Pinus ponderosa and P.lambertiana); as a consequence, the residual trees, saplings, and seedlings in treated areas, particularly those that had experienced moderate or high drought-related mortality, were more heavily dominated by broadleaf ("hardwood") trees (particularly Quercus kelloggii and Q.chrysolepis). In contrast, residual trees and regeneration in untreated stands were heavily dominated by shade-tolerant conifer species (Abies concolor and Calocedrus decurrens), suggesting a need for future treatment. Because increased dominance of hardwoods brings benefits for plant and animal diversity and stand resilience, the ecological advantages of mechanical thinning and prescribed fire treatments may, depending on the management perspective, extend even to stands that ultimately experience high drought-related mortality following treatment.

Increased sensitivity to drought across successional stages in natural Norway spruce (Picea abies (L.) Karst.) forests of the Calimani Mountains, Romania

Winter drought becomes a limiting factor of forest stand growth by the end of the twentieth century. Disturbances strongly influence the structure of natural forests. The frequency and severity of natural disturbances, as well as drought events, are expected to increase with climate change. Our study investigated if forests with differing forest structures related to disturbance histories also differed in sensitivity to drought. In a natural forest landscape in the Calimani Mountains of the Eastern Carpathians, Romania, we used six forest patches to represent different successional stages, from early- to late-successional stages. We used two temporal resolutions of the Standardized Precipitation-Evapotranspiration Index to describe short and long water resource dynamics within or between hydrological years, respectively. We detected an increase in the importance of winter drought across all successional stages; it was first identified in the oldest patch in the 1970s, and it consecutively affected younger patches. We observed that different forest structures do not lead to substantial differences in trends in drought–growth relationships. A shift in sensitivity to water availability from early spring to winter occurred over the twentieth century. These findings suggest that the impact of climate change on Norway spruce forest ecosystems of the Eastern Carpathians will likely be difficult to mitigate at a local scale using traditional forestry practices.

The current state and productivity of oak plantations in the forest fund of Zhytomyr regional agricultural forest enterprise «Zhytomyroblagrolis»

On the territory of Zhytomyr region most forests subsidiaries of Zhytomyr Regional Municipal Agrarian-Forestry Enterprise (ZRMAFE) «Zhytomyroblahrolis» grow in Central Polissya which vegetation nature pertaining to the zone of coniferous-deciduous forests, characterized by the lack of large areas of homogeneous vegetation. Nowadays, in this area oak and pine plantations are dominated by places with a birch and aspen admixture, depending on the forest conditions. Species composition of stands of the region varies in the directions from the north to the south and from the west to the east. The southerntaiga forests are spread in the northern part. The aim of our study was to investigate the status and productivity of the plantations with oak in subsidiaries of ZRMAFE «Zhytomyroblahrolis». It will provide an opportunity to assess objectively stands’ potential under the influence of technogenesis on the structure and functioning of natural and artificial forests of central Polissia, the status and productivity especially valuable species of subsidiaries of ZRMAFE «Zhytomyroblahrolis». The conducted researches were based on the information of the relational database «Particular Taxation Characteristics of the Forest» of the production association «Ukrderzhlisproekt» with the use of materials for forest management of subsidiaries of ZRMAFE «Zhytomyroblahrolis». The data that was obtained in the form of a non-standard request for a tree stand in the composition of an oak was analyzed. The cadastral and mensurational description of each stratum of forest holdings, subordinated to the State Agency of Forest Resources of Ukraine, was the basis of abovementioned database. The data enable us to analyze the status and productivity of plantations with oak as a part of ZRMAFE «Zhytomyroblahrolis» and to compare the characteristics of forests in the state forest in both Central Polissia and Western-Sentral Polissia forest district as a whole.

Динаміка активності супероксиддисмутази та каталази у листках Аilanthus altissima за аеротехногенного забруднення

У листках айланту найвищого (Ailanthus altissima Swingle), особини якого зроста-ють на територіях з хронічним аеротехногенним навантаженням, визначено актив-ність основних оксидоредуктаз: супероксиддисмутази (СОД) (ЕС 1.15.1.1) і каталази(ЕС 1.11.1.6). Зміни сезонної динаміки активності антиоксидантних ферментів, що зне-шкоджують активні форми кисню, вказують на їх участь в реалізації виду Ailanthusaltissima Swingle стратегії адаптації до комбінованого впливу полютантів. Встановлено,що рослини айланту найвищого впродовж вегетації пристосовуються до несприятливихумов існування за рахунок підвищення активності супероксиддимутази та каталази.

Climate differentiates forest structure across a residential macrosystem

The extent of urban ecological homogenization depends on how humans build, inhabit, and manage cities. Morphological and socio-economic facets of neighborhoods can drive the homogenization of urban forest cover, thus affecting ecological and hydrological processes, and ecosystem services. Recent evidence, however, suggests that the same biophysical drivers differentiating composition and structure of natural forests can further counteract the homogenization of urban forests. We hypothesize that climate can differentiate forest structure across residential macrosystems at regional-to-continental spatial scales. To test this hypothesis, forest structure (tree and shrub cover and volume) was measured using LiDAR data and multispectral imagery across a residential macrosystem composed 1.4 million residential parcels contained in 9 cities and 1503 neighborhoods. Cities were selected along an evapotranspiration (ET) gradient in the conterminous United States, ranging from the colder continental climate of Fargo, North Dakota (ET = 464.43 mm) to the hotter subtropical climate of Tallahassee, Florida (ET = 1000.47 mm). The relative effects of climate, urban morphology, and socio-economic variables on residential forest structure were assessed by using generalized linear models. Climate differentiated forest structure of the residential macrosystem as hypothesized. Average forest cover doubled along the ET gradient (0.39–0.78 m2 m−2), whereas average forest volume had a threefold increase (2.50–8.12 m3 m−2). Forest volume across neighborhoods increased exponentially with forest cover. Urban morphology had a greater effect in homogenizing forest structure on residential parcels compared to socio-economics. Climate and urban morphology variables best predicted residential forest structure, whereas socio-economic variables had the lowest predictive power. Results indicate that climate can differentiate forest structure across residential macrosystems and may counteract the homogenizing effects of urban morphology and socio-economic drivers at city-wide scales. This resonates with recent empirical work suggesting the existence of complex multi-scalar mechanisms that regulate ecological homogenization and ecosystem convergence among cities. The study initiates high-resolution assessments of forest structure across entire urban macrosystems and breaks new ground for research on the ecological and hydrological significance of urban vegetation at subcontinental scale.

Assessing spatial dynamics of a Pinus nigra subsp. salzmannii natural stand combining point and polygon patterns analysis

This study analyzes the structure and regeneration dynamics of a Mediterranean high-altitude natural pine forest (Pinus nigra subsp. salzmannii) located in Sierra de Cazorla (Jaén, Spain). Spatial relationships among the adult tree overstory and understory strata are investigated in order to clarify the spatial dynamics of this unique forest stand. As regards the understory strata, we examine shrubs and pine recruitment separately. Both understory strata are better described by the area they occupy than by their constituent individuals. This approach invalidates using traditional spatial point pattern analysis with indicators such as the K-function, which only deal with vector data of the same dimension (points, lines or polygons). We use a recently developed approach in spatial association analysis to investigate spatial association between adult tree overstory (points) and understory strata (polygons) from both global and local spatial insights. Tree-stand overstory has been investigated regarding size and spatial tree-stand structure considering adult trees as points. The results show that the pine stand presents an irregular and uneven-aged structure of trees due to the effective and gradual recruitment of new trees over time, even if the forest cover is quite low. Spatial analysis of the overstory and understory relationship has shown a mainly attractive spatial relationship between the pine overstory and the pine regeneration understory, with seedling patches more likely to appear in the neighborhood of adult trees than away from them. In contrast, shrub patches presented a repelling location in relation with adult trees, and were less abundant near the pines than far from them. Shade intolerance of shrub species could account for this finding. The spatial relationship among shrubs and pine recruitment turned out to be clearly mutually exclusive in our study. Global and local spatial analysis using indices of point-polygon spatial assessment has proven to be a good tool to elucidate relationships among different forest stand strata.

One shape fits all, but only in the aggregate: Diversity in sub‐stand scale diameter distributions

AbstractQuestionsTo what extent are the sub‐stand size class distributions at the neighbourhood patch scale masked at the stand level via spatial smoothing? What are the implications for naturalness assessment of obscuring, at the stand level, structures that arise from endogenous processes at the neighbourhood scale?LocationElborz Mountains, south of the Caspian Sea, Iran.MethodsNatural uneven‐aged old‐growth Oriental beech (Fagus orientalis) forest subject to fine‐scale disturbances was stem‐mapped in a 1.2‐ha plot of live trees >7.5 cm DBH; neighbourhoods were delineated across multiple scales using the tree‐centred floating neighbourhood approach of spatial tessellation to connect trees to their natural neighbours. Cluster analysis was used to identify an optimal number of recurring diameter distribution types (DDT) based on the proportion of trees in each of the five size classes. The richness of DDTs was assessed and the extent of DDTs was modelled as a function of tree size.ResultsThe number of member trees and spatial extent increased with neighbourhood scale. While the stand‐level tree size class distribution exhibited a rotated sigmoid shape, the nine most distinct DDTs were characterized by four different distribution shapes (negative exponential, increasing‐q, rotated sigmoid and unimodal) and varied considerably in the abundance of trees in different size classes. Each individual tree contributed to at least three of the nine DDTs, which were nonetheless spatially distinct and varied in extent with size class composition. As expected, all metrics exhibited spatial smoothing (i.e., increasing homogeneity with increasing scale) as small, heterogeneous tree neighbourhoods were expanded into larger neighbourhoods with more similar average composition, which converged on a rotated sigmoid shape at the broadest scale.ConclusionsThe stand‐level rotated sigmoid distribution reflected spatial smoothing across more heterogeneous fine‐scale tree neighbourhood patches. Further studies are needed to assess if a better measure of natural forest structure may be the diversity of sub‐stand structures and the contribution of individual trees to that diversity, rather than an aggregated metric that averages across the hallmark heterogeneity of neighbourhood dynamics.