Improving the precision of sample-based forest damage inventories through two-phase sampling and post-stratification using remotely sensed auxiliary information

Many countries have a national forest inventory (NFI) designed to produce statistically sound estimates of forest parameters. However, this type of inventory may not provide reliable results for forest damage which usually affects only small parts of the forest in a country. For this reason, specially designed forest damage inventories are performed in many countries, sometimes in coordination with the NFIs. In this study, we evaluated a new approach for damage inventory where existing NFI data form the basis for two-phase sampling for stratification and remotely sensed auxiliary data are applied for further improvement of precision through post-stratification. We applied Monte Carlo sampling simulation to evaluate different sampling strategies linked to different damage scenarios. The use of existing NFI data in a two-phase sampling for stratification design resulted in a relative efficiency of 50 % or lower, i.e., the variance was at least halved compared to a simple random sample of the same size. With post-stratification based on simulated remotely sensed auxiliary data, there was additional improvement, which depended on the accuracy of the auxiliary data and the properties of the forest damage. In many cases, the relative efficiency was further reduced by as much as one-half. In conclusion, the results show that substantial gains in precision can be obtained by utilizing auxiliary information in forest damage surveys, through two-phase sampling, through post-stratification, and through the combination of these two approaches, i.e., post-stratified two-phase sampling for stratification.     

Classification and mapping forest sites using geographic information system (GIS): a case study in Artvin Province

The productivity of forest sites has been indirectly determined with solo wood production objective in forest management. Forest site productivity should, however, be determined directly in order to implement ecosystem based multipurpose forest management philosophy. This article tackles the problem in distinguishing and mapping forest sites using both direct method and indirect method in Genya Mountain located in central of Artvin State Forest Enterprise. About 112 sample plots were designed and distributed over the area. In each sample plot, soil samples were collected and the classical timber inventory measurements were taken. According to direct method, Soil Moisture Regime (SMR) method is preferred due to a water deficiency in the study area. Water holding capacity was used as an essential criterion for the classification of the forest site. Forest site classifications were assigned regarding the physiographic factors such as landform, aspect, and slope. Five different forest sites classes; dry, moderate fresh, fresh, humid and hygric were determined. According to direct method, the guiding curve was used to generate anamorphic site index (SI) equations and three site index classes; good (SI=I–II), medium (SI=III) and low (SI=IV–V) were determined. Some important differences between the methods were realized. The forest sites determined with site index estimation method indicate that site index I and II is 505.99 ha, III 1095.79 ha and IV and V 992.95 ha, whereas forest sites determined with direct method related to dry site of 937.58 ha, moderate fresh site of 931.90 ha, fresh site of 1,797.71 ha, humid site of 80.48 ha and hygric site of 356.55 ha. The forest site maps of both methods were created using GIS functions. The forest sites of open and degraded areas should be determined according to direct method.     

Estimating and mapping forest biomass using regression models and Spot-6 images (case study: Hyrcanian forests of north of Iran)

Hyrcanian forests of North of Iran are of great importance in terms of various economic and environmental aspects. In this study, Spot-6 satellite images and regression models were applied to estimate above-ground biomass in these forests. This research was carried out in six compartments in three climatic (semi-arid to humid) types and two altitude classes. In the first step, ground sampling methods at the compartment level were used to estimate aboveground biomass (Mg/ha). Then, by reviewing the results of other studies, the most appropriate vegetation indices were selected. In this study, three indices of NDVI, RVI, and TVI were calculated. We investigated the relationship between the vegetation indices and aboveground biomass measured at sample-plot level. Based on the results, the relationship between aboveground biomass values and vegetation indices was a linear regression with the highest level of significance for NDVI in all compartments. Since at the compartment level the correlation coefficient between NDVI and aboveground biomass was the highest, NDVI was used for mapping aboveground biomass. According to the results of this study, biomass values were highly different in various climatic and altitudinal classes with the highest biomass value observed in humid climate and high-altitude class.     

Mapping of groundwater potential zones across Ghana using remote sensing, geographic information systems, and spatial modeling

Groundwater development across much of sub-Saharan Africa is constrained by a lack of knowledge on the suitability of aquifers for borehole construction. The main objective of this study was to map groundwater potential at the country-scale for Ghana to identify locations for developing new supplies that could be used for a range of purposes. Groundwater potential zones were delineated using remote sensing and geographical information system (GIS) techniques drawing from a database that includes climate, geology, and satellite data. Subjective scores and weights were assigned to each of seven key spatial data layers and integrated to identify groundwater potential according to five categories ranging from very good to very poor derived from the total percentage score. From this analysis, areas of very good groundwater potential are estimated to cover 689,680 ha (2.9 % of the country), good potential 5,158,955 ha (21.6 %), moderate potential 10,898,140 ha (45.6 %), and poor/very poor potential 7,167,713 ha (30 %). The results were independently tested against borehole yield data (2,650 measurements) which conformed to the anticipated trend between groundwater potential and borehole yield. The satisfactory delineation of groundwater potential zones through spatial modeling suggests that groundwater development should first focus on areas of the highest potential. This study demonstrates the importance of remote sensing and GIS techniques in mapping groundwater potential at the country-scale and suggests that similar methods could be applied across other African countries and regions.     

Review of indicators and field methods for monitoring biodiversity within national forest inventories. Core variable: Deadwood

Deadwood is one of the four elements taken into account in this review of indicators and field methods and is often considered as a key indicator of forest biodiversity. We have analysed the main types of surveys and have realised how greatly the needs and constraints used to monitor deadwood can vary among them. For instance, classical National Forest Inventories usually tend to avoid time-consuming collecting methods. In the wide variety of existing definitions of deadwood, such inventories require simple and clear definitions, especially in terms of quantified thresholds. Thus, deadwood is properly described by characterising several components, such as snags, logs, stumps, branches and fine woody debris. Deadwood sampling methods alter depending on the different components and dimensions considered (standing dead trees, lying dead trees and branches, etc. assessed quantitatively). Attributes such as tree species and stage of decay are used mainly to qualify the deadwood components. The deadwood volume estimations are usually based on classical approaches already applied to living or felled trees: volume equations and/or formulas giving the volumes of common geometric solids. The purpose of this paper is to focus on different deadwood assessment techniques and to provide the information necessary to identify the most relevant methods for collecting deadwood data. The latter is used to build indicators that characterise the evolution of forest biodiversity at the scale of large forest territories.     

Land desertification monitoring and assessment in Yulin of Northwest China using remote sensing and geographic information systems (GIS)

The objective of this study is to develop techniques for assessing and analysing land desertification in Yulin of Northwest China, as a typical monitoring region through the use of remotely sensed data and geographic information systems (GIS). The methodology included the use of Landsat TM data from 1987, 1996 and 2006, supplemented by aerial photos in 1960, topographic maps, field work and use of other existing data. From this, land cover, the Normalised Difference Vegetation Index (NDVI), farmland, woodland and grassland maps at 1:100,000 were prepared for land desertification monitoring in the area. In the study, all data was entered into a GIS using ILWIS software to perform land desertification monitoring. The results indicate that land desertification in the area has been developing rapidly during the past 40 years. Although land desertification has to some extent been controlled in the area by planting grasses and trees, the issue of land desertification is still serious. The study also demonstrates an example of why the integration of remote sensing with GIS is critical for the monitoring of environmental changes in arid and semi-arid regions, e.g. in land desertification monitoring in the Yulin pilot area. However, land desertification monitoring using remote sensing and GIS still needs to be continued and also refined for the purpose of long-term monitoring and the management of fragile ecosystems in the area.     

Modeling land use/land cover change using remote sensing and geographic information systems: case study of the Seyhan Basin,Turkey

Land use and land cover (LULC) changes affect several natural environmental factors, including soil erosion, hydrological balance, biodiversity, and the climate, which ultimately impact societal well-being. Therefore, LULC changes are an important aspect of land management. One method used to analyze LULC changes is the mathematical modeling approach. In this study, Cellular Automata and Markov Chain (CA-MC) models were used to predict the LULC changes in the Seyhan Basin in Turkey that are likely to occur by 2036. Satellite multispectral imagery acquired in the years 1995, 2006, and 2016 were classified using the object-based classification method and used as the input data for the CA-MC model. Subsequently, the post-classification comparison technique was used to determine the parameters of the model to be simulated. The Markov Chain analyses and the multi-criteria evaluation (MCE) method were used to produce a transition probability matrix and land suitability maps, respectively. The model was validated using the Kappa index, which reached an overall level of 77%. Finally, the LULC changes were mapped for the year 2036 based on transition rules and a transition area matrix. The LULC prediction for the year 2036 showed a 50% increase in the built-up area class and a 7% decrease in the open spaces class compared to the LULC status of the reference year 2016. About an 8% increase in agricultural land is also likely to occur in 2036. About a 4% increase in shrub land and a 5% decrease in forest areas are also predicted.     

The role of forest stand density in controlling soil erosion: implications to sediment-related disasters in Japan

The role of forest stand density in controlling soil erosion was investigated in Ehime Prefecture, Japan. The main objective was to compare soil erosion under different forest conditions including forest type, species composition, and stand density as influenced by thinning operations. Relative yield index (Ry) was used as an indicator of stand density to reflect the degree of management operations in the watershed. Eleven treatments were established based on the above forest conditions. Soil loss was collected in each of the 11 treatments after each rainfall event for a period of 1 year. The paper presents summary data on soil loss as affected by forest conditions and rainfall patterns. Findings showed that an appropriate forest management operation, which can be insured by stand density control, is needed to reduce soil loss. The present study plays an important role in clarifying technical processes related to soil erosion, while it helps linking these elements to current Japanese forestry issues and bringing new inputs to reducing sediment-related disasters in Japan.     

Evaluating forest fragmentation and its tree community composition in the tropical rain forest of Southern Western Ghats (India) from 1973 to 2004

A majority of the research on forest fragmentation is primarily focused on animal groups rather than on tree communities because of the complex structural and functional behavior of the latter. In this study, we show that forest fragmentation provokes surprisingly rapid and profound alterations in tropical tree community. We examine forest fragments in the tropical region using high-resolution satellite imagery taken between 1973 and 2004 in the Southern Western Ghats (India) in relation to landscape patterns and phytosociological datasets. We have distinguished fragmentation in six categories—interior, perforated, edge, transitional, patch, and undetermined—around each forested pixel. Furthermore, we have characterized each of the fragment class in the evergreen and semi-evergreen forest in terms of its species composition and richness, its species similarity and abundance, and its regeneration status. Different landscape metrics have been used to infer patterns of land-use changes. Contiguous patches of >1,000 ha covered 90% of evergreen forest in 1973 with less porosity and minimal plantation and anthropogenic pressures; whereas in 2004, the area had 67% forest coverage and a high level of porosity, possibly due to Ochlandra spread and increased plantations which resulted in the loss of such contiguous patches. Results highlight the importance of landscape metrics in monitoring land-cover change over time. Our main conclusion was to develop an approach, which combines information regarding land cover, degree of fragmentation, and phytosociological inputs, to conserve and prioritize tropical ecosystems.     

Spatiotemporal variations in species diversity to assess environmental impacts on aquatic communities: The use of biomass data versus density data

This paper discusses various methods for calculating the minimum instream flows for the protection of aquatic life for the purpose of illustrating its increasing complexity. These procedures are the Montana method (Tennant, 1976); the wetted perimeter method (Collings, 1974; Cochnauer, 1976) and the IFIM method (Instream Flow Incremental Methodology; Bovee, 1982). An analysis is then made of some regionalisation criteria based on these methods, from which useful suggestions can be drawn for the development of a procedure to be applied to basins. A method is thus proposed for calculating the recommended flows for protecting the aquatic environment based on simple hydrological variables, such as Q_{7 10}, which can be estimated for a basin on the basis of area A and a Base Flow Index (BFI) which summarises its hydrogeological characteristics. This approach can be used when the field data necessary for more complex methods is not available. These require the defining of the environmental suitability of a watercourse for certain designated reference fish species, according to the flow and the morphology of the channel. The positive results of this approach were verified by Leonard (1990) and this methodology was applied to the Tiber river basin.     

Application of the IPCC Waste Model to solid waste disposal sites in tropical countries: case study of Thailand

Measurements of landfill methane emission were performed at nine solid waste disposal sites in Thailand, including five managed sanitary landfills (four deep and one shallow landfills) and four unmanaged landfills (three deep and one shallow dumpsites). It was found that methane emissions during the rainy season were about five to six times higher than those during the winter and summer seasons in the case of managed landfills and two to five times higher in the case of unmanaged landfills. Methane emission estimate using the Intergovernmental Panel on Climate Change (IPCC) Waste Model was compared with the actual field measurement from the studied disposal sites with methane correction factors and methane oxidation factors that were obtained by error function analysis with default values of half-life parameters. The methane emissions from the first-order decay model from the IPCC Waste Model yielded fair results compared to field measurements. The best fitting values of methane correction factor were 0.65, 0.20, 0.15, and 0.1 for deep landfills, shallow landfills, deep dumpsites, and shallow dumpsites, respectively. Using these key parameters in the case of Thailand, it was estimated that 89.22 Gg of methane were released from solid waste disposal sites into the atmosphere in 2006.     

10th Anniversary Focus: an overview of trends related to tropical rainforest depletion and climate change

Public awareness about the problems related to rainforest depletion increased considerably in the 1990s, but the level of emphasis to the problems faced by the world's tropical rainforests has become conspicuously low in recent years. Yet, there is a heightened sense of urgency in respect of the need to handle the challenges posed by climate change and the role that rainforest depletion may play in this process. This paper reviews the relationships between rainforest depletion and climate change, and outlines some areas where action is needed.     

The environmental behaviour of polychlorinated phenols and its relevance to cork forest ecosystems: a review

Pentachlorophenol (PCP) has been used as a herbicide, biocide and preservative worldwide since the 1930s and as a result, extensive and prolonged contamination exists. The environmental impact increases when its many degradation products are taken into consideration. A number of chloroanisols and their related chlorophenols have been found in cork slabs collected from Portuguese oak tree forests before stopper manufacturing, and contamination by PCP and polychlorinated anisole (PCA) has been detected in Canadian forests. It is suggested that the use of polychlorinated phenols, in particular PCP, is thought to be a cause of the cork taint problem in wine, a major socio-economic impact not only for industry but on sensitive and highly biodiverse ecosystems. It also highlights particular issues relating to the regional regulation of potentially toxic chemicals and global economics world wide. To fully understand the impact of contamination sources, the mechanisms responsible for the fate and transport of PCP and its degradation products and assessment of their environmental behaviour is required. This review looks at the current state of knowledge of soil sorption, fate and bioavailability and identifies the challenges of degradation product identification and the contradictory evidence from field and laboratory observations. The need for a systematic evaluation of PCP contamination in relation to cork forest ecosystems and transfer of PCP between trophic levels is emphasised by discrepancies in bioaccumulation and toxicity. This is essential to enable long term management of not only transboundary contaminants, but also the sustainable management of socially and economically important forest ecosystems.     

Wildfire-induced reduction in the carbon storage of Mediterranean ecosystems: An application to brush and forest fires impacts assessment

Wildfire is one of the most dangerous and harmful phenomena in the world. Hence, fire impacts assessment could become very important in forest areas according to its environmental and landscape values. This paper suggests an approach to identify fire effects on biomass, in consonance with the potential carbon storage of each area used, and its biomass consumption based on fire behavior.Dense mature forests were the most vulnerable landscapes based on its aboveground biomass, mainly tree stem biomass. A significant correlation was found between fire intensity and biomass consumption. Biomass consumption ranged from 16.59% to 98.75% from the two studied wildfires. It is necessary to provide a scenario analysis according to the uncertain CO₂ market. As an example, carbon storage impacts in one fire were between 100,340.66 € (using the minimum price of CO₂) and 741,057.44 € (using the maximum price of CO₂). Differences between scenarios ranged from 35.30% to 46.51% of the total carbon storage impacts. This approach might be a solution to identify and prioritize areas for restoration activities and optimize the allocation of the resources.     

Restoration of areas degraded by alluvial sand mining: use of soil microbiological activity and plant biomass growth to assess evolution of restored riparian vegetation

River or alluvial sand mining is causing a variety of environmental problems in the Itajaí-açú river basin in Santa Catarina State (south of Brazil). When this type of commercial activity degrades areas around rivers, environmental restoration programs need to be executed. In this context, the aim of this study was to assess the evolution of a restored riparian forest based on data on the soil microbial activity and plant biomass growth. A reference site and three sites with soil degradation were studied over a 3-year period. Five campaigns were performed to determine the hydrolysis of the soil enzyme fluorescein diacetate (FDA), and the biomass productivity was determined at the end of the studied period. The variation in the enzyme activity for the different campaigns at each site was low, but this parameter did differ significantly according to the site. Well-managed sites showed the highest biomass productivity, and this, in turn, showed a strong positive correlation with soil enzyme activity. In conclusion, soil enzyme activity could form the basis for monitoring and the early prediction of the success of vegetal restoration programs, since responses at the higher level of biological organization take longer, inhibiting the assessment of the project within an acceptable time frame.     

Application of the UAM-V and Use of Indicator Species to Assess Control Strategies for Ozone Reduction in the Lower Fraser Valley of British Columbia

Modelled and measured indicator species ratios of O₃/NOz, O₃/NOy, H₂O₂/HNO₃, HCNO/NOy for the Lower Fraser Valley were compared with VOC-NO_x-O₃ sensitivity threshold values reported in previous studies. Modelled region - specific indicator ratio thresholds derived from 50% NOx and 50% VOC reduction scenarios are provided. They show strongest agreement with the H₂O₂/HNO₃ ratio values found elsewhere. A clear transition region for the LFV from VOC to NOx sensitivity could not be identified, but there is evidence that O₃ concentrations in the western valley, dominated by metropolitan Vancouver, are VOC sensitive, and the more rural eastern valley O₃ concentrations exhibit greater NO_x sensitivity. The UAM-V Process Analysis utility was used to identify physical and chemical mechanisms which contributed to O₃ formation and destruction and indicate the key importance of entrainment from elevated layers generated by the highly complex meteorological conditions in determining near surface O₃ concentrations.     

A GIS-based decision support system for determining the shortest and safest route to forest fires: a case study in Mediterranean Region of Turkey

The ability of firefighting vehicles and staff to reach a fire area as quickly as possible is critical in fighting against forest fires. In this study, a Geographical Information System-based decision support system was developed to assist fire managers in determining the fastest and the safest or more reliable access routes from firefighting headquarters to fire areas. The decision support system was tested in the Kahramanmaras Forestry Regional Directoratein the Mediterranean region of Turkey. The study area consisted of forested lands which had been classified according to fire sensitivity. The fire response routing simulations considered firefighting teams located in 20 firefighting headquarter locations. The road network, the locations of the firefighting headquarters, and possible fire locations were mapped for simulation analysis. In alternative application simulations, inaccessible roads which might be closed due to fire or other reasons were indicated in the network analysis so that the optimum route was not only the fastest but also the safest and most reliable path. The selection of which firefighting headquarters to use was evaluated by considering critical response time to potential fire areas based on fire sensitivity levels. Results indicated that new firefighting headquarters should be established in the region in order to provide sufficient firefighting response to all forested lands. In addition, building new fire access roads and increasing the design speed on current roads could also increase firefighting response capabilities within the study area.