Structural Diversity Of Forests Research Articles

Structural diversity and carbon stocks in a tropical semi-evergreen forest in Bangladesh

Tropical forests are well-known as highly productive terrestrial ecosystems, which contribute significantly to the global carbon (C) cycle. Studies indicate a correlation between the structural diversity of forests and carbon stocks in the overall forest carbon stocks, and this relationship varies across tropical ecosystems. Understanding this connection is crucial to preventing the transfer of threats to unprotected areas when safeguarding specific forests. The present study was conducted in the undisturbed natural forests of Rema Kalenga Wildlife Sanctuary, Habigonj, Bangladesh. The study aimed to estimate C stocks within the soil-vegetation system of this forest ecosystem and elucidate relationships with stand structural diversity, focusing on vertical stratification and spatial association of tree species. Stand-level C stock models, constructed through tree-level carbon stocks using allometric equations, were based on stand variables such as basal area and mean or dominant tree height. Results identified five canopy strata, with strata two and three accounting for 60% of C stocks. The importance value index of tree species demonstrated a significant association with the C stocks contribution of tree species. The total ecosystem carbon stock ranged from 185 to 220 Mg ha−1, with aboveground 103 to 132 Mg ha−1, belowground 21 to 26 Mg ha−1, litter 2.4 to 4.4 Mg ha−1, dead wood 0.5 to 4.9 Mg ha−1 and soil 11 to 44 Mg ha−1. Species diversity indices exhibited weaker relationships with C stocks, while Pielou's evenness index demonstrated a strong negative relationship (P < 0.05) to C stocks. This comprehensive assessment provides insights into the C dynamics of the forest ecosystem. It offers valuable information for policymakers devising climate change mitigation strategies through the conservation management of tropical forests as crucial C sinks.

Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site

Evening Grosbeak (Coccothraustes vespertinus) populations have been hypothesized to be in steep decline across North America. Data characterizing long-term changes are needed to quantify the magnitude of the declines. We surveyed grosbeaks at a spring migratory stop-over site in Corvallis, Oregon, USA, where birds gather annually during April and May to feast on elm (Ulmus spp.) seeds before departing to breeding sites. An estimate produced by a statistics professor in the 1970s indicated peak numbers were 150,000 to 250,000 birds. Our surveys in 2013–2015 found annually variable numbers, from a few hundred grosbeaks in the lowest year to less than five thousand birds in the highest year. If the original estimate is approximately true, Evening Grosbeak numbers have experienced dramatic declines, averaging −2.6%/year, over the last four decades. Our local observation of declines during spring aligns with declines documented in winter across North America by bird feeder studies and in summer by the Breeding Bird Survey. We explore potential explanations for the changes in population size, such as influences of spruce budworm outbreaks, disease, and decreased structural diversity of forests owing to harvest practices. We also consider the challenges of interpreting changes in abundance of species with exceptionally variable populations, especially if population fluctuations or cycles may have long periodicities. Finally, we call for additional planned surveys to track the numbers of this enigmatic and charismatic species.

BIODIVERSITY AND CLIMATE-REGULATING FUNCTIONS OF FORESTS: CURRENT ISSUES AND RESEARCH PROSPECTS

The problem of assessing the impact of biodiversity on the climate-regulating functions of forests is fundamental. It is of great applied importance for sustainable forest management in the context of global climate change. On the one hand, climate change affects biodiversity; on the other hand, biodiversity underlies the mechanisms of adaptation of forests and society to these changes, because it is a provider of all ecosystem functions. This article aims to discuss scientific issues currently faced by scientists, such as the relationships between biodiversity and climate-regulating functions of forests, and to outline the perspective of the studies. There are numerous studies that describe the influence of certain plant and animal species – ecosystem engineers – on the ecosystem, including climate-regulating functions of forests. However, we lack estimates of the combined effect of the diversity of biota of different trophic levels and groups on the completeness of the implementation of climate-regulating functions of forests of different types/at different succession stages. We emphasise the importance of accounting for such estimates as taxonomic, including genetic, and the functional and structural diversity of forests. We considered various concepts of forest management, taking into account the conservation and restoration of biodiversity. The most important aspect of this problem is estimates and forecasts of interrelationships (trade-offs and synergies) between climate-regulating and other ecosystem functions of forests characterised by different levels of biodiversity, with their natural development and with the combined impact of various natural and anthropogenic factors on forests, including climate change, fires, and forest management regimes. Integration of mathematical models is a promising approach to assess and predict the dynamics of relationships between various ecosystem functions of forests.

Биоразнообразие и климаторегулирующие функции лесов: актуальные вопросы и перспективы исследований

The problem of assessing the impact of biodiversity on the climate-regulating functions of forests has fundamental character and great importance for sustainable forest management in the context of global climate change. On the one hand, climate changes affect biodiversity, on the other hand, it is biodiversity, as a provider of all ecosystem functions, underlies the mechanisms of adaptation to these changes. This paper aims to discuss scientific questions about the links between biodiversity and climate-regulating functions of forests, and to outline the prospects for these studies. It is shown that studies of the influence of plant and animal species – ecosystem engineers on forest ecosystem’s functioning, including climate-regulating processes and functions, are quite numerous. However, studies of the combined effects of the diversity of biota belonging to different trophic levels and groups on climate-regulating functions of forests of different types/different stages of succession are not carried out. In such studies, it is important to take into account both taxonomic, including genetic, and functional biodiversity as well as structural diversity of forests. Various concepts of forest management taking into account the conservation and restoration of biodiversity are considered. An important aspect of this problem is the assessment and prediction of relationships (synergy or trade-offs) between climate-regulating and other ecosystem functions of forests with different levels of biodiversity functioning in natural conditions and under the combined impact of natural and anthropogenic factors, including climate change, fires, and forestry regimes. It is shown that a promising approach to assessing and predicting the dynamics of relationships between different ecosystem functions of forests is the integration of mathematical models.

Assessing the influence of harvesting intensities on structural diversity of forests in south-west Germany

BackgroundTo increase ecosystem resilience and biodiversity, the maintenance and improvement of structural and compositional diversity of forests has become an important goal in forest management for many forest owners and jurisdictions. At the same time, future harvesting intensity (HI) may increase to meet the demand for woody biomass by an increasing bioeconomy sector. Yet, the influence of HI on forest structural diversity is largely unknown. Here, we address this issue by analyzing the relationship between HI and structural diversity based on large-scale national forest inventory (NFI) data, where the latter is quantified using a previously developed Forest Structure Index and HI is expressed as wood volume removal during the period 2002–2012 for the same inventory plots.ResultsOur results show a surprisingly small impact of harvesting intensity on changes in structural diversity for most of the analysed types of forests. Only intense harvesting (> 80%–90% of initial growing stock) led to a significant reduction in structural diversity. At low to moderate HI most aspects of structural diversity were positively influenced. Only the quadratic mean DBH and the volume of large trees (≥ 40 cm DBH) were substantially negatively influenced at HI > 60% and 70% of initial growing stock, respectively.ConclusionsIn several forest types, HI could be increased without a reduction in overall structural diversity. Hence, structural diversity in these selectively managed forests appears to be a very resistant forest property in relation to HI. Other indicators at stand and landscape scale may be needed to adjust levels of HI that are suited to maintain forest biodiversity.

The German Forest Strategy 2020: Target achievement control using National Forest Inventory results

In the year 2011 the German Federal Government adopted its Forest Strategy 2020. This strategy includes 60 goal formulations in nine action fields. The present paper analyses to which extent the results of the German National Forest Inventory (BWI) prove achievements of those of the 60 goals, which are quantitatively verifiable. The results reveal that forestry in Germany in general meets its own standard of multi-functionality, securing that forests fulfil manifold demands of the society. However, while the objectives of nature and climate protection are on track for being achieved, the prospects for objectives related to employment, income and value added are less encouraging. Total forest area and forest growth are increasing, forests currently constitute a carbon sink, and the naturalness and structural diversity of forests are growing. Also the high but sustainable use of the wood fosters currently the income of and employment in forest enterprises and timber industries. But the ongoing regeneration of forest stands predominantly with deciduous tree species is expected to cause a long-term lack of faster growing and higher valuated coniferous stands. The resulting lack of highly demanded softwood of small or medium-sized diameters will raise problems to timber industries. Moreover, shrinking timber production due to a decreasing share of coniferous forests has adverse consequences not only from the economic point of view. It will also decrease the climate-friendly use of wood products, in particular due to the foregone substitution effect. The results of the study also show that BWI is an indispensable source of information for forest politics and forest science particularly in view of its long-term time series. The preservations of time series must be kept in mind whenever changes in the methods of BWI are considered.

Effects of partial cutting on logging productivity, economic returns and dead wood in boreal pine forest

Structural diversity of forests is important for biodiversity. In managed forests, structural diversity can be maintained by retaining living and dead trees, and by creating dead wood during logging operations. In Sweden, a small percentage of the trees is currently retained on each clear-cut. Since retention decreases revenues from forest harvesting, it is important to understand the consequences of retention for both forestry economy and biodiversity conservation. Thus, in this study we compared effects of retaining percentages ranging from 5% to 50% of the initial number of trees in 12 Scots pine-dominated stands in central Sweden. The retained trees in each stand consisted of equal proportions of green living trees, felled trees, high-cut trees and girdled trees. We estimated costs associated with tree retention and, as indicators of biodiversity conservation values, dead wood volumes, number of dead wood types, and dead wood diversity. We also estimated the damage caused by the logging operations on old dead wood. Revenue declined with increases in retention level, due mainly to associated reductions in harvested volumes, but partly to increases in logging costs. Both harvester and forwarder performance were lower at high than at low retention levels. The volume of dead wood increased with increases in retention level, since the numberof retained trees killed per standwas proportional to the retention level. The number of dead wood types and dead wood diversity increased continuously up to the highest retention level of almost 50%. Moreover, old dead wood that was deemed particularly valuable for biodiversity was not destroyed at retention levels above 30%. In conclusion, dead wood destruction decreased with increasing retention level and costs increased proportionally to the retained volume. There were no signs of saturation of dead wood diversity as retention level increased. Therefore, mainly economic restrains will determine the retention level.

Assessment of Diversity of Forest Structure in Gunja-Dong, Siheung City, Korea

Habitats loss and fragmentation are major threats to biodiversity. There are various kinds of environmental assessment have been developed for various problems to solve. Yet, there are no well-developed methods for quantifying and predicting about biodiversity. To achieve a sustainable conservation for biodiversity, the structural diversity of forest must be assessed by proper indexes. This study aim to quantitatively assess the diversity of forest structure as habitats and results of the verification by bird survey for objective presentation of evidence. As a result of literature review, some indexes were selected as potential prediction tools for biodiversity; area of patch, area of core regions, shape of patch and average age of stand. The assessment results were estimated by monitoring of birds for accuracy verification and the results were almost in agreement with each others. But, 1 and 2 level of forests were showed ambiguous results. Certainly, this study was limited in some valuation indexes on landscape scale. Further studies should be considered that different environmental factors such as land use, disturbances by human and vegetation index. Also, we expect that the additional monitoring of birds should give rise to the result which is improved assessment results.

Structural diversity of forest communities on Baihuashan Mountain, Beijing

The structural diversity of forests on Baihuashan Mountain, Beijing, was surveyed by a plotless method combined with branch and leaf coverage estimation in the different layers. New structural indices were constructed, calculated and compared among different communities. On the basis of previous work, structural diversity of forest communities at the stand level was described by a vertical complexity index and a horizontal heterogeneity index. From a correlational analysis among the new indices and other commonly used biodiversity indices, we concluded that the new indices are closely related to a tree height inequality index and the Shannon-Wiener index of the tree and shrub layer, which indicated that the new indices were good at indicating structural diversity in the different forests on Baihuashan Mountain. The results show that, in natural forests, structural diversity of pioneer communities is much lower than in late successive communities. In plantations, structural diversity is determined by the stage of development and tree species. Tending would increase horizontal heterogeneity and decrease vertical complexity.

Forest management and biotechnology: the case of a selective-logging regime

One of the most important instruments to support the sustainable development of forests, and reinforce the multiple services that they provide is the selective-logging regime. This paper aims to quantify the potential benefits of biotechnology under this type of regime. With this purpose, an empirical analysis is conducted to determine the optimal selective-logging management for a stand of Pinus sylvestris, and it is then compared with the outcome generated when biotechnology is employed to accelerate forest growth. Additionally, the results of the different optimisations are compared to determine if biotechnology might be a prospective instrument to enhance the structural diversity of forests.

Using historic management records to characterize the effects of management on the structural diversity of forests

The current structure of managed forests reflects the forest management system and silvicultural treatments applied in each stand, as well as the ecological conditions and natural disturbances which have taken place. This study focuses on forest structural diversity as a key component of biodiversity assessments and aims to analyse the effects of silvicultural management on the structural diversity of forests. The area chosen for this study is Pinar de Valsaín, a Scots pine ( Pinus sylvestris L.) forest in the Central mountains of Spain. In Pinar de Valsaín the effects of uniform shelterwood management, individual tree selection and thinning can be assessed. Data from the periodic inventories and historic management records as early as 1889 were complemented by our own calculations, and have been used to characterize the applied silvicultural treatments as well as to determine the time elapsed since each intervention. Data from a sample survey carried out in 1998 was used to characterize current forest structure. Forest structure was defined by the spatial variability of stem density and basal area within the block, tree size variability at microstructure level (coefficient of variation of diameter at breast height, and height differentiation within the sample plots), and species diversity of stems, regeneration and shrub at block level calculated as Shannon index and Simpson index. In Pinar de Valsaín, the application of uniform shelterwood system has lead to a greater heterogeneity in the spatial structure within blocks but also to a more homogeneous microstructure. Thinning resulted in homogenisation at both stand and microstructure level. Potential problems of the presented approach as well as possibilities to include the findings in forestry decision making are discussed.

Accuracy of digitized aerial photographs for assessing forest habitats at plot level

The objective of the present study was to determine the accuracy of digitized colour‐infrared aerial photographs for predicting forest habitats defined by dominant tree species, stand age and ground vegetation in order to assess the structural diversity of forests. The solar direction and viewing angle at exposure time exert strong effects on illumination by causing a bidirectional reflectance effect. As a result, the same forest habitat will have totally different reflectance values, depending on its position in the photograph. Digital tone values were thus calibrated prior to the stratification, using empirical regression‐calibration or rationing methods. Linear regression calibration to the principal‐point level of the photographs, in which the mean pixel value was modelled as a function of sun and sensor position at the time of exposure, was shown to be the most effective method. The results showed that regression calibration significantly improved stratification accuracies. Separation of 12 habitat types was accomplished with 85.3% accuracy and 48 habitat types with 57.7% accuracy. The results also indicated that final stratification accuracy is very dependent on the prestratification needed, since the bidirectional reflectance effect in aerial photographs differs in various habitat types.