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1.
Duniway MC Karl JW Schrader S Baquera N Herrick JE 《Environmental monitoring and assessment》2012,184(6):3789-3804
Collection of standardized assessment and monitoring data is critically important for supporting policy and management at
local to continental scales. Remote sensing techniques, including image interpretation, have shown promise for collecting
plant community composition and ground cover data efficiently. More work needs to be done, however, evaluating whether these
techniques are sufficiently feasible, cost-effective, and repeatable to be applied in large programs. The goal of this study
was to design and test an image-interpretation approach for collecting plant community composition and ground cover data appropriate
for local and continental-scale assessment and monitoring of grassland, shrubland, savanna, and pasture ecosystems. We developed
a geographic information system image-interpretation tool that uses points classified by experts to calibrate observers, including
point-by-point training and quantitative quality control limits. To test this approach, field data and high-resolution imagery
(∼3 cm ground sampling distance) were collected concurrently at 54 plots located around the USA. Seven observers with little
prior experience used the system to classify 300 points in each plot into ten cover types (grass, shrub, soil, etc.). Good
agreement among observers was achieved, with little detectable bias and low variability among observers (coefficient of variation
in most plots <0.5). There was a predictable relationship between field and image-interpreter data (R
2 > 0.9), suggesting regression-based adjustments can be used to relate image and field data. This approach could extend the
utility of expensive-to-collect field data by allowing it to serve as a validation data source for data collected via image
interpretation. 相似文献
2.
Michael A. Wulder Joanne C. White Mark D. Gillis Nick Walsworth Matthew C. Hansen Peter Potapov 《Environmental monitoring and assessment》2010,170(1-4):417-433
Many countries undertake a national forest inventory to enable statistically valid monitoring in support of national and international reporting of forest conditions and change. Canada’s National Forest Inventory (NFI) program is designed to operate on a 10-year remeasurement cycle, with an interim report produced at the 5-year mid-point. The NFI is a sample-based inventory, with approximately 18,850 2 ×2-km photo plots across the country, distributed on a 20×20-km grid of sample points; these photo plots are the primary data source for the NFI. Capacity to provide annual monitoring information is required to keep policy and decision makers apprised of current forest conditions. In this study, we implemented a multistage monitoring framework and used a Moderate Resolution Imaging Spectroradiometer (MODIS) change product to successfully identify 78% of the changes in forest cover area that were captured with a Landsat change detection approach. Of the NFI photo plots that were identified by both the Landsat and MODIS approaches as having changes in forest cover, the proportion of change area within the plots was similar (R 2?=?0.78). Approximately 70% of the Landsat-derived change events occupied less than 40% of a single MODIS pixel, and more than 90% of the change events of this size were successfully detected with the MODIS product. Finally, MODIS estimates of the proportion of forest cover change at the NFI photo plot level were comparable to change estimates for the ecoregions as a whole (R 2?=?0.95). High-temporal, low-spatial resolution imagery such as MODIS, in combination with other remotely sensed data sources, can provide information on disturbance events within a national forest inventory remeasurement cycle, thereby satisfying the interim information needs of policy and decision makers as well as the requirements of national and international reporting commitments. 相似文献
3.
Accurate estimates of the extent and distribution of wetlands and streams are the foundation of wetland monitoring, management, restoration, and regulatory programs. Traditionally, these estimates have relied on comprehensive mapping. However, this approach is prohibitively resource-intensive over large areas, making it both impractical and statistically unreliable. Probabilistic (design-based) approaches to evaluating status and trends provide a more cost-effective alternative because, compared with comprehensive mapping, overall extent is inferred from mapping a statistically representative, randomly selected subset of the target area. In this type of design, the size of sample plots has a significant impact on program costs and on statistical precision and accuracy; however, no consensus exists on the appropriate plot size for remote monitoring of stream and wetland extent. This study utilized simulated sampling to assess the performance of four plot sizes (1, 4, 9, and 16 km2) for three geographic regions of California. Simulation results showed smaller plot sizes (1 and 4 km2) were most efficient for achieving desired levels of statistical accuracy and precision. However, larger plot sizes were more likely to contain rare and spatially limited wetland subtypes. Balancing these considerations led to selection of 4 km2 for the California status and trends program. 相似文献
4.
Biodiversity monitoring surveys are rarely optimised statistically before being initiated. Here, we optimised the monitoring
of plants in a temperate forest. The total inventory cost, the number and size of quadrats were optimised to detect a 10%
change in species richness over 5 years with α = β = 0.05, using data from ongoing long-term floristic monitoring programs. The procedure showed that the inventory cost would
be ca 15% lower using 100-, 200-m2 quadrats instead of 300- or 400-m2 quadrats. Despite the cost associated with the optimisation (e.g. gathering preliminary data) and the imprecise estimates
(due to the typically small sample size of the pilot studies), optimisation would often be a better option than expert opinion
when designing a monitoring survey. 相似文献
5.
Understanding the historical dynamics, composition, and environmental disturbances of forest landscapes provides a context
for monitoring changes, describing trends, and establishing reference conditions. This study analyses the temporal changes
in forest ecosystem structure in Artvin Forest Planning Unit (AFPU), Turkey, during 1972–2002 period based on digitized forest
stand type maps using geographic information system (GIS) and interpretation of satellite data. The results showed that there
was a net decrease of 450 ha in total forested areas between 1972 and 2002. Forest ecosystem structure changed over time depending
on a few factors such as demographic movements, insect outbreaks, dam and road construction, unregulated management actions,
and social pressure. In conclusion, temporal changes and the factors affecting these changes should be determined for sustainable
management of natural resources. 相似文献
6.
Recognition and understanding of landscape dynamics as a historical legacy of disturbances are necessary for sustainable management
of forest ecosystems. This study analyzed spatial and temporal changes in land use and land cover patterns in a typical mountain
watershed in the Gumushane district along the Northeastern part of Turkey. The area is investigated by comparing LANDSAT images
from 1987 to 2000 and evaluated the temporal changes of spatial structure of forest conditions through spatial analysis of
forest cover type maps from 1971 and 1987 using GIS and FRAGSTATS™.
The results show a general decreasing trend in area of natural land cover types including broadleaf and conifer forests as
well as coppice between 1971 and 1987 (0.54%, respectively). In contrast, between 1987 and 2000 this natural land cover types
show increasing trend (1.6%). In parallel with forest dynamics, the area of managed land including lowland and upland agricultural
areas, rangelands and grasslands increased during the first period and decreased during second period. In terms of spatial
configuration, Gümüşhane forests aren’t generally fragmented by intensive forest utilization in the latter periods. This is
partially due to out-migration of rural population in Gümüşhane. Nevertheless, land use pattern significantly changed over
time depending on a few factors such as unregulated management actions, social pressure and demographic movements. The study
revealed that demographic movements have a major effect on landscape dynamics. 相似文献
7.
Altun L Baskent EZ Gunlu A Kadiogullari AI 《Environmental monitoring and assessment》2008,137(1-3):149-161
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. 相似文献
8.
Podlaski R 《Environmental monitoring and assessment》2007,135(1-3):339-351
Tree damage, gauged by the amount of defoliation, is one of the basic criteria used to determine treatments for protected
and economic forests. Monitoring should include an assessment of the degree of tree damage in different spatial scales. Therefore,
in addition to the commonly applied large-area methods, small-area methods should be used. The aim of the paper is to present
the results of the accuracy assessment of a small-area method, proposed by Podlaski (2005) [Podlaski, R. (2005). Inventory of the degree of tree defoliation in small areas. Forest Ecology and Management, 215, 361–377], for monitoring the degree of tree damage. The degree of tree damage was shown in sub-blocks P3 of the system of information on natural environment (SINUS). To estimate the spatial distribution of the degree of tree defoliation,
survey sampling, based on simple random sampling with replacement (SRSWR), was used. The degree of damage to fir (Abies alba Mill.) and beech (Fagus sylvatica L.) was analysed in the Święty Krzyż forest section in the Świętokrzyski National Park. The maximum total estimation errors
for the proportion of trees with a degree zero of damage, and with second and third degrees of damage together (for α = 0.05) were at most 30.8% for fir and 24.3% for beech trees. For standard, small-area evaluations, these are satisfactory
values. In the Święty Krzyż forest section, the number of P3 sub-blocks with 0.00–5.00% of undamaged trees and with 80.01–100.00% of moderately- or severely-damaged trees was significantly
greater for fir than for beech. These results indicate that the fir population was unhealthier than the beech group in the
study area. P3 sub-blocks of the SINUS system, in which the proportion of the healthiest trees was highest, were situated at the forest
margin, bordering on meadows and arable fields (in the case of fir) and forming dense patches consisting of several sub-blocks,
or occurring singly in the whole study area (in the case of beech). The results show the significant differentiation of forest
tree health in small areas. 相似文献
9.
Salve PR Satapathy DR Katpatal YB Wate SR 《Environmental monitoring and assessment》2007,133(1-3):87-98
Stratospheric input and photochemical ozone formation in the troposphere are the two main sources determining the ozone levels
in the surface layer of the atmosphere. Because of the importance of ozone in controlling the atmospheric chemistry and its
decisive role in the heat balance of atmosphere, leading to climate change, the examination of its formation and destruction
are of great interest. This study characterized the distribution of Ground level Ozone (GLO) in Chandrapur district is lying
between 19°25′N to 20°45′N and 78°50′E to 80°10′E. Continuous ozone analyzer was used to quantify GLO at thirteen locations
fixed by Global Positioning System (GPS) during the winter of 2005–2006. The daily GLO at all the locations ranged between
6.4 and 24.8 ppbv with an average and standard deviation of 14.9 ± 6.5 ppbv. The maximum and minimum concentration occurs
during 1300–1600 h and 0300–0500 h may be due to high solar radiation facilitating photochemical production of O3 and downward mixing from the overlying air mass and in situ destruction of ozone by deposition and/or the reaction between
O3 and NO. GIS based spatial distribution of GLO in Chandrapur district is indicates that the central core of the district and
southern sites experienced elevated levels of GLO relative to the northern and western areas. The sites near by Chandrapur
city are particularly affected by elevated GLO. The average variation of GLO with temperature shows a significant correlation
of r = 0.55 indicating a direct relationship between GLO and temperature. Similarly an attempt has been made to compare the GLO
monitored data in Chandrapur district with the reported values for other locations in Indian cities. This generated database
helps regulatory agencies to identify locations where the natural resources and human health could be at risk. 相似文献
10.
The total petroleum hydrocarbons (TPH) pollution in regional agricultural soils was investigated. Seventy soil samples collected
from surface layers (0–20 cm) and horizons of five selected pedons in the vicinity of a petrochemical complex in Guangzhou,
China were analyzed, and the vertical variation and spatial variability of TPH were evaluated. The TPH concentration in top
soils around the petrochemical complex ranged from 1,179.3 to 6,354.9 mg kg − 1, with the average of 2,676.6 mg kg − 1. Furthermore, significant differences between land-use types showed that the TPH concentration in top soils was strongly
influenced by accidental spills. Both the TPH trends in pedons and the identified hot-spot areas also showed that the accidental
explosions or burning accidents were mainly responsible for the pollution. The results reported here suggest that the regular
monitoring and inspection shall be conducted for safety and to avoid or minimize the accidents, and the effective measures
should be taken to remediate the contaminated areas and to assure that the important industrialization of Guangzhou area would
not mean human health risks near the petrochemical complex. 相似文献
11.
Chrastný V Vaněk A Teper L Cabala J Procházka J Pechar L Drahota P Penížek V Komárek M Novák M 《Environmental monitoring and assessment》2012,184(4):2517-2536
The soils adjacent to an area of historical mining, ore processing and smelting activities reflects the historical background
and a mixing of recent contamination sources. The main anthropogenic sources of metals can be connected with historical and
recent mine wastes, direct atmospheric deposition from mining and smelting processes and dust particles originating from open
tailings ponds. Contaminated agriculture and forest soil samples with mining and smelting related pollutants were collected
at different distances from the source of emission in the Pb–Zn–Ag mining area near Olkusz, Upper Silesia to (a) compare the
chemical speciation of metals in agriculture and forest soils situated at the same distance from the point source of pollution
(paired sampling design), (b) to evaluate the relationship between the distance from the polluter and the retention of the
metals in the soil, (c) to describe mineralogy transformation of anthropogenic soil particles in the soils, and (d) to assess
the effect of deposited fly ash vs. dumped mining/smelting waste on the mobility and bioavailability of metals in the soil.
Forest soils are much more affected with smelting processes than agriculture soils. However, agriculture soils suffer from
the downward metal migration more than the forest soils. The maximum concentrations of Pb, Zn, and Cd were detected in a forest
soil profile near the smelter and reached about 25 g kg − 1, 20 g kg − 1 and 200 mg kg − 1 for Pb, Zn and Cd, respectively. The metal pollutants from smelting processes are less stable under slightly alkaline soil
pH then acidic due to the metal carbonates precipitation. Metal mobility ranges in the studied forest soils are as follows:
Pb > Zn ≈ Cd for relatively circum-neutral soil pH (near the smelter), Cd > Zn > Pb for acidic soils (further from the smelter).
Under relatively comparable pH conditions, the main soil properties influencing metal migration are total organic carbon and
cation exchange capacity. The mobilization of Pb, Zn and Cd in soils depends on the persistence of the metal-containing particles
in the atmosphere; the longer the time, the more abundant the stable forms. The dumped mining/smelting waste is less risk
of easily mobilizable metal forms, however, downward metal migration especially due to the periodical leaching of the waste
was observed. 相似文献
12.
The introduction of anthropogenic sounds into the marine environment can impact some marine mammals. Impacts can be greatly
reduced if appropriate mitigation measures and monitoring are implemented. This paper concerns such measures undertaken by
Exxon Neftegas Limited, as operator of the Sakhalin-1 Consortium, during the Odoptu 3-D seismic survey conducted during 17
August–9 September 2001. The key environmental issue was protection of the critically endangered western gray whale (Eschrichtius robustus), which feeds in summer and fall primarily in the Piltun feeding area off northeast Sakhalin Island. Existing mitigation
and monitoring practices for seismic surveys in other jurisdictions were evaluated to identify best practices for reducing
impacts on feeding activity by western gray whales. Two buffer zones were established to protect whales from physical injury
or undue disturbance during feeding. A 1 km buffer protected all whales from exposure to levels of sound energy potentially
capable of producing physical injury. A 4–5 km buffer was established to avoid displacing western gray whales from feeding
areas. Trained Marine Mammal Observers (MMOs) on the seismic ship Nordic Explorer had the authority to shut down the air guns if whales were sighted within these buffers.
Additional mitigation measures were also incorporated: Temporal mitigation was provided by rescheduling the program from June–August
to August–September to avoid interference with spring arrival of migrating gray whales. The survey area was reduced by 19%
to avoid certain waters <20 m deep where feeding whales concentrated and where seismic acquisition was a lower priority. The
number of air guns and total volume of the air guns were reduced by about half (from 28 to 14 air guns and from 3,390 in3 to 1,640 in3) relative to initial plans. “Ramp-up” (=“soft-start”) procedures were implemented.
Monitoring activities were conducted as needed to implement some mitigation measures, and to assess residual impacts. Aerial
and vessel-based surveys determined the distribution of whales before, during and after the seismic survey. Daily aerial reconnaissance
helped verify whale-free areas and select the sequence of seismic lines to be surveyed. A scout vessel with MMOs aboard was
positioned 4 km shoreward of the active seismic vessel to provide better visual coverage of the 4–5 km buffer and to help
define the inshore edge of the 4–5 km buffer. A second scout vessel remained near the seismic vessel. Shore-based observers
determined whale numbers, distribution, and behavior during and after the seismic survey. Acoustic monitoring documented received
sound levels near and in the main whale feeding area.
Statistical analyses of aerial survey data indicated that about 5–10 gray whales moved away from waters near (inshore of)
the seismic survey during seismic operations. They shifted into the core gray whale feeding area farther south, and the proportion
of gray whales observed feeding did not change over the study period.
Five shutdowns of the air guns were invoked for gray whales seen within or near the buffer. A previously unknown gray whale
feeding area (the Offshore feeding area) was discovered south and offshore from the nearshore Piltun feeding area. The Offshore
area has subsequently been shown to be used by feeding gray whales during several years when no anthropogenic activity occurred
near the Piltun feeding area.
Shore-based counts indicated that whales continued to feed inshore of the Odoptu block throughout the seismic survey, with
no significant correlation between gray whale abundance and seismic activity. Average values of most behavioral parameters
were similar to those without seismic surveys. Univariate analysis showed no correlation between seismic sound levels and
any behavioral parameter. Multiple regression analyses indicated that, after allowance for environmental covariates, 5 of
11 behavioral parameters were statistically correlated with estimated seismic survey-related variables; 6 of 11 behavioral
parameters were not statistically correlated with seismic survey-related variables. Behavioral parameters that were correlated
with seismic variables were transient and within the range of variation attributable to environmental effects.
Acoustic monitoring determined that the 4–5 km buffer zone, in conjunction with reduction of the air gun array to 14 guns
and 1,640 in3, was effective in limiting sound exposure. Within the Piltun feeding area, these mitigation measures were designed to insure
that western gray whales were not exposed to received levels exceeding the 163 dB re 1 μPa (rms) threshold.
This was among the most complex and intensive mitigation programs ever conducted for any marine mammal. It provided valuable
new information about underwater sounds and gray whale responses during a nearshore seismic program that will be useful in
planning future work. Overall, the efforts in 2001 were successful in reducing impacts to levels tolerable by western gray
whales. Research in 2002–2005 suggested no biologically significant or population-level impacts of the 2001 seismic survey.
M. W. Newcomer is deceased. 相似文献
13.
This study deals with numerical simulation of flow fields and dispersion of model passive admixtures in the planetary boundary
layer in a 10 × 10 km square area, centered on the Czech Republic’s Temelín Nuclear Power Plant. Numerical calculations of
three-dimensional flow fields with eight basic wind directions given for the inlet boundary of the computational domain are
performed using the FLUENT CFD code with the standard k – ε turbulence model. The resultant modeling of the flow fields provides information as to probable local directions and velocities
of flow vectors on a horizontal scale of 100 m, which are consistent with the data given for the boundaries of the calculation
area in the framework of a scale of 10 km. The modeled flow fields generate the input data for related Lagrangian simulation
of the ground concentration and deposition fields of passive particles assumedly emitted at the site of the Temelín plant.
Simulated plumes describe eight cases of potential ground-level distribution of model passive admixtures in the area. 相似文献
14.
Summer time haze characteristics of the urban atmosphere of Gwangju and the rural atmosphere of Anmyon, Korea 总被引:4,自引:0,他引:4
An extensive visibility monitoring was carried out simultaneously in the urban area of Gwangju and the rural area of Anmyon,
Korea. This study examines patterns of visibility impairment and haze-forming pollutant concentrations on both sites resulting
from natural and anthropogenic sources of gases and particles. Optical visibility measurements by a transmissometer, a nephelometer
and an aethalometer provide aerosol light extinction, scattering, and absorption coefficients for both sites. In order to
investigate the physico-chemical characteristics of atmospheric aerosols, aerosol samples were collected by various aerosol
samplers at GJVMS (Gwangju Visibility Monitoring Station) and at KGAWO (Korea Global Atmosphere Watch Observatory), respectively.
In addition, haze characteristics causing visibility impairment at those two sites were analyzed to obtain source contributions
by regionally transported aerosols using grid analysis and display system (GrADS) from NECP reanalysis data. During the intensive
monitoring period, ammonium sulfate was dominantly responsible for the fine particle mass loading at GJVMS, whereas organic
carbon was the largest contributor at KGAWO. Light scattering by particles accounted for 52.8 to 81.3% of the range at the
urban site, GJVMS and for 72.1 to 94.2% of the range at the rural site, KGAWO. Light absorption by the EC and NO2 was between 14.5 and 34.8% at GJVMS, which was higher than the observed 1.1 ∼ 6.8% at KGAWO, respectively. Light scattering
by aerosol was higher in the rural area than in the urban area. And organic carbon concentration was observed to be significantly
higher than the concentration of elemental carbon at KGAWO. These haze-forming carbonaceous particles originate from anthropogenic
pollutants at the urban atmosphere but they can be produced by natural environments such as marine and forest at the rural
atmosphere. 相似文献
15.
Using of high-resolution topsoil magnetic screening for assessment of dust deposition: comparison of forest and arable soil datasets 总被引:1,自引:0,他引:1
Magnetic susceptibility (κ) is an easily detectable geophysical parameter that can be used as a proxy or semi-quantitative
tracer of atmospheric industrial and urban dusts deposited in topsoil. An enhanced κ value of topsoil is in many cases also
associated with high concentrations of soil pollutants (mostly heavy metals). High-resolution magnetic screening of topsoil
in areas of high pollution influx is a useful tool for detection of pollution “hot spots”. General and regional screening
maps with a grid density of 10 or 5 km have been performed on the basis of forest topsoil measurement only. The purpose of
this study was to perform high-resolution magnetic screening with different grid densities in both forested and agricultural
areas (arable land). Our large study area (ca. 200 km2) was located in a relatively more polluted region of the central part of Upper Silesia, and a second (small) one (ca. 100
m2) was located in the western part of Upper Silesia, with considerably lower influx of pollution. In the framework of this
study, we applied a statistical comparison of data obtained in forested areas and on arable land. The arable soil showed statistically
significantly lower κ values, the result of “physical dilution” of the arable layer caused by annual ploughing. Thus arable
soils must be avoided during high-resolution field measurement. From semivariograms, it was clear that the spatial correlations
in forest topsoil are much stronger than in arable soil, which suggests that a denser measurement grid is required in forested
areas. 相似文献
16.
Distribution and abundance of western gray whales off northeastern Sakhalin Island, Russia, 2001’003
Meier SK Yazvenko SB Blokhin SA Wainwright P Maminov MK Yakovlev YM Newcomer MW 《Environmental monitoring and assessment》2007,134(1-3):107-136
In 2001–2003, >60,000 km of aerial surveys and 7,700 km of vessel surveys were conducted during June to November when critically
endangered Korean–Okhotsk or western gray whales (Eschrichtius robustus) were present off the northeast coast of Sakhalin Island, Russia. Results of surveys in all years indicated gray whales occurred
in predominantly two areas, (1) adjacent to Piltun Bay, and (2) offshore from Chayvo Bay, hereafter referred to as the Piltun
and offshore feeding areas. In the Piltun feeding area, the majority of whales were observed in waters shallower than 20 m
and were distributed from several hundred meters to ∼ 5 km from the shoreline. In the offshore feeding area during all years,
the distribution of gray whales extended from southwest to northeast in waters 30–65 m in depth. During all years, the distribution
and abundance of whales changed in both the Piltun and offshore feeding areas, and both north–south and inshore–offshore movements
were documented within and between feeding seasons. The discovery of a significant number of whales feeding in the offshore
area each year was a substantial finding of this study and raises questions regarding western gray whale abundance and population
levels, feeding behavior and ecology, and individual site-fidelity. Fluctuations in the number of whales observed within the
Piltun and offshore feeding areas and few sightings outside of these two areas indicate that gray whales move between the
Piltun and offshore feeding areas during their summer–fall feeding season. Seasonal shifts in the distribution and abundance
of gray whales between and within both the Piltun and offshore feeding areas are thought, in part, to be a response to seasonal
changes in the distribution and abundance of prey. However, the mechanism driving the movements of whales along the northeast
coast of Sakhalin Island is likely very complex and influenced by a multitude of factors.
*Deceased 相似文献
17.
This study aims to evaluate the quality of crown density data, based on independent, pairwise tree assessments. The data originates from monitoring of forest health (crown condition) in Norway; 250 plots, comprising 12 000 individual trees of Norway spruce, have been reassessed by a single observer during 1990–95. Of the trees, 2300 were controlled more than twice, providing the possibility of evaluating the quality of assessed temporal changes of crown density. True errors (standard deviation) are estimated to be about 10% for single trees and 5% for plot means, while the real standard deviation of the differences were slightly higher. The errors of the temporal changes of crown density were of similar magnitude. Systematic differences in crown density were found between sites and plot types, partly resulting from observer bias. However, the results suggest that observer bias is really the result of each observer's personal style in assessment. 相似文献
18.
A serious forest decline of Betula ermanii Cham. has been observed at Mt. Mae-Shirane, Oku-Nikko, Japan, where high ozone (O3) concentration and severe water deficiency have been measured. In order to consider the possibility whether O3 and/or water stresses could have been the causes of the forest decline of B. ermanii, plant growth experiments were conducted in environment-controlled growth cabinets. Two-year-old seedlings of B. ermanii were exposed to either charcoal-filtered air (O3 concentration <5 ppb) or 50 ppb O3 (daily average, ranging between 20–100 ppb) for 123 days at 20.0/12.5 ± 1.0°C (day/night) and 70/80 ± 7% relative humidity
(day/night). Simultaneously, seedlings were treated with three watering regime: 1.0 < pF < 1.8 (no water stress), 1.8 < pF < 2.5
(mild water stress) or 2.5 < pF < 3.0 (severe water stress). O3 exposure significantly reduced the dry weights of leaf, root and the whole plant, while water stress significantly reduced
the dry weights of each organ and the whole plant. Significant reductions of net photosynthesis, transpiration and stomatal
conductance were also observed under O3 and/or water deficiency treatments, while contents of RuBP carboxylase/oxygenase (Rubisco), chlorophyll
a+b
and some essential nutrient elements (N, P, K, Mg and Ca) were not markedly changed. It was suggested that the decrease in
net photosynthetic rate induced mainly by stomatal closure was the major cause of the growth reduction under O3 and/or water stresses. No significant interactions between O3 and water stresses were observed in terms of the depression of dry matter production, which suggested that simultaneous stress
treatments of O3 exposure and water deficiency could affect the tree growth of B. ermanii additively. 相似文献
19.
The degree at which tropical forests are exposed to human pressure is spatially dependent. Population density, proximity to
roads, terrain slope, logging activities and land distribution projects are well known factors inducing deforestation and
forest degradation in Latin America. Using expert knowledge to weight these threat factors and a Geographical Information
System for spatial modeling, a multi-criteria analysis procedure is presented, that allows stratifying a study region in categories
of deforestation threat. The procedure was implemented in the Central Volcanic Mountain Range Conservation Area (CVMRCA) in
Costa Rica with the purpose of finding areas with a combination of physical and socioeconomic characteristics that is particularly
predisposing to a high probability of deforestation. To validate the map, the CVMRCA was stratified in categories of deforestation
risk, and the result was superposed to historical deforestation data of the period 1986–1996. The good correlation between
risk category and historical deforestation (r = 0.91, p < 0.001) indicates that the map can be used as a decision support tool for defining priority areas for conservation action. 相似文献
20.
MAPPING TROPICAL DEFORESTATION IN CENTRAL AFRICA 总被引:3,自引:0,他引:3
Zhang Q Devers D Desch A Justice CO Townshend J 《Environmental monitoring and assessment》2005,101(1-3):69-83
The NASA Landsat Pathfinder Humid Tropical Deforestation Project was to map deforestation activities in the humid tropics using datasets from both the Landsat TM (Thematic Mapper) and MSS (Multispectral Scanner System). In Central Africa, its effort had been constrained by the availability of cloud-free satellite coverage, especially for the 1970s Landsat MSS imagery. Here, we reported the deforestation rate and its spatial variability in the region using 18 pairs of co-registered Landsat TM imagery from the 1980s to 1990s. Of the total classified area of 416000 km, there were approximately 217000 km2 of dense forest and 24000 km2 of degraded forest in the 1980s. A total of 1012 km2 of forest, including 542 km2 of dense forest and 470 km2 of degraded forest, were cleared annually with an annual deforestation rate of 0.42%, varying among scenes ranging from 0.03 to 2.72%. Additionally, an average of 0.12% (ranging from 0.01 to 0.77% among scenes) or 257 km2 of dense forest was degraded annually. Regression analyses indicated that extensive deforestation occurred in areas with larger forest cover, including dense and degraded forests. Image interpretation also confirmed the hypothesized relationship between deforestation and forest accessibility. The annual clearance of the dense forest was significantly related to the rural population density, and there was a positive relationship between the dense forest degraded during the 1980s–1990s and the degraded forest area in the 1980s. 相似文献