Changes In Forest Biomass Research Articles

Practicalities of Non-Destructive Methodologies in Monitoring Anthropogenic Greenhouse Gas Emissions from Tropical Forests under the Influence of Human Intervention

We examined non-destructive methodologies for practicalities in monitoring anthropogenic greenhouse gas (GHG) emissions from tropical dry-land forest under the influence of various forms of human intervention. Spaceborne SAR withstood comparison with Landsat ETM+ in land cover classification of degraded tropical forest. For measurement of carbon stock and GHG flux per unit land area, the gain-loss method requires both growth rate and removal rate of forest carbon stock. However, the latter has rarely been obtained in tropical forest. For the stock-difference method, permanent sampling plot data can be used to estimate mean carbon stock per unit land area of each forest type. For cyclic land use that includes a clear-cutting stage such as slash-and-burn agriculture, chronosequential changes in carbon stock can be predicted by determining the time and spatial-distribution of cleared land. Changes in forest biomass by logging, storm-damage, etc., may be identified by monitoring the presence and diameter of the crowns of overstory trees. We developed five equations containing the parameter for crown diameter for estimating tree biomass. Overstory height can be a parameter for estimating ecosystem carbon stock of various plant communities, and forest height can be measured by airborne and spaceborne sensors, etc. Generic equations containing the parameter for overstory height are available for estimating community biomass of tropical and subtropical forests. PALSAR has an advantage over other remote systems by enabling frequent sensing and semi-direct biomass estimation using backscattering coefficients. However, no reasonable remote sensing methods exist for monitoring the amount of carbon loss by forest conversion and logging in forests with high biomass. To compensate for the faults of the present PALSAR methodologies and to enable practical and frequent monitoring of all types of forests by humans, it is vital to devise a new methodology to detect changes in high-biomass forests.

Estimating the risk of Amazonian forest dieback

*Climate change will very likely affect most forests in Amazonia during the course of the 21st century, but the direction and intensity of the change are uncertain, in part because of differences in rainfall projections. In order to constrain this uncertainty, we estimate the probability for biomass change in Amazonia on the basis of rainfall projections that are weighted by climate model performance for current conditions. *We estimate the risk of forest dieback by using weighted rainfall projections from 24 general circulation models (GCMs) to create probability density functions (PDFs) for future forest biomass changes simulated by a dynamic vegetation model (LPJmL). *Our probabilistic assessment of biomass change suggests a likely shift towards increasing biomass compared with nonweighted results. Biomass estimates range between a gain of 6.2 and a loss of 2.7 kg carbon m(-2) for the Amazon region, depending on the strength of CO(2) fertilization. *The uncertainty associated with the long-term effect of CO(2) is much larger than that associated with precipitation change. This underlines the importance of reducing uncertainties in the direct effects of CO(2) on tropical ecosystems.

Scaling giant kelp field measurements to regional scales using satellite observations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 403:13-27 (2010) - DOI: https://doi.org/10.3354/meps08467 Scaling giant kelp field measurements to regional scales using satellite observations Kyle C. Cavanaugh1,*, David A. Siegel1,2, Brian P. Kinlan3, Daniel C. Reed3 1Institute for Computational Earth System Science, 2Department of Geography, and 3Marine Science Institute, University of California, Santa Barbara, Santa Barbara, California 93106-3060, USA *Email: kyle@icess.ucsb.edu ABSTRACT: Little is known about the local to regional scale variability in biomass and productivity of many subtidal ecosystems, as appropriate field surveys are both time and labor intensive. Here, we combined high-resolution satellite imagery with aerial photos and diver sampling to assess changes in giant kelp Macrocystis pyrifera canopy cover and biomass along a ~60 km stretch of coastline in the Santa Barbara Channel, California, USA. Our objectives were to (1) develop new methods for estimating giant kelp canopy cover and biomass using satellite imagery, and (2) assess temporal changes in kelp forest biomass across multiple spatial scales. Results of the satellite kelp cover classification compared very favorably with near-coincident high-resolution aerial camera surveys (r2 = 0.90). Monthly diver observations of biomass for fixed plots at 3 kelp forest sites were strongly correlated with satellite determinations of normalized difference vegetation index (NDVI) signals (r2 = 0.77). This allowed us to examine variation in giant kelp biomass across multiple spatial scales (pixel, plot, site, and region). The relationship between plot scale (40 m) changes in biomass and remote assessments of site scale (~1 km) changes varied among sites and depended on the relative location of the plot and the size of the kelp forest at each site. Changes in biomass among sites were well correlated with each other and with the aggregated regional (~60 km) total. Linking field measurements of giant kelp biomass made on a plot scale with regional estimates made by satellite facilitates an understanding of the regional patterns and drivers of biomass and primary production of giant kelp forest ecosystems. KEY WORDS: Scaling · Remote sensing · Spatial and temporal variability · Giant kelp · Satellite data Full text in pdf format PreviousNextCite this article as: Cavanaugh KC, Siegel DA, Kinlan BP, Reed DC (2010) Scaling giant kelp field measurements to regional scales using satellite observations. Mar Ecol Prog Ser 403:13-27. https://doi.org/10.3354/meps08467 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 403. Online publication date: March 22, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Effects of climate change, land-use change, and invasive species on the ecology of the Cumberland forests

Model projections suggest that both climate and land-use changes have large effects on forest biomass and composition in the Cumberland forests of Tennessee and Kentucky. These forests have high levels of diversity, ecological importance, land-use changes, and pressures due to invasive herbivorous insects and climate change. Three general circulation models project warming for all months in 2030 and 2080 and complex patterns of precipitation change. Climate changes from 1980 to 2100 were developed from these projections and used in the forest ecosystem model LINKAGES to estimate transient changes in forest biomass and species composition over time. These projections show that climate changes can instigate a decline in forest stand biomass and then recovery as forest species composition shifts. In addition, a landscape model (LSCAP) estimates changes in land-cover types of the Cumberlands based on projected land-use changes and the demise of eastern hemlock ( Tsuga canadensis (L.) Carrière) due to the spread of the hemlock adelgid ( Adelges tsugae Annand). LSCAP suggests that land-cover changes can be quite large and can cause a decline not only in the area of forested lands but also in the size and number of large contiguous forest patches that are necessary habitat for many forest species characteristic of the Cumberlands.

Changes in composition, structure and aboveground biomass over seventy-six years (1930-2006) in the Black Rock Forest, Hudson Highlands, southeastern New York State

We sought to quantify changes in tree species composition, forest structure and aboveground forest biomass (AGB) over 76 years (1930-2006) in the deciduous Black Rock Forest in southeastern New York, USA. We used data from periodic forest inventories, published floras and a set of eight long-term plots, along with species-specific allometric equations to estimate AGB and carbon content. Between the early 1930s and 2000, three species were extirpated from the forest (American elm (Ulmus americana L.), paper birch (Betula papyrifera Marsh.) and black spruce (Picea mariana (nigra) (Mill.) BSP)) and seven species invaded the forest (non-natives tree-of-heaven (Ailanthus altissima (Mill.) Swingle) and white poplar (Populus alba L.) and native, generally southerly distributed, southern catalpa (Catalpa bignonioides Walt.), cockspur hawthorn (Crataegus crus-galli L.), red mulberry (Morus rubra L.), eastern cottonwood (Populus deltoides Bartr.) and slippery elm (Ulmus rubra Muhl.)). Forest canopy was dominated by red oak and chestnut oak, but the understory tree community changed substantially from mixed oak-maple to red maple-black birch. Density decreased from an average of 1500 to 735 trees ha(-1), whereas basal area doubled from less than 15 m(2) ha(-1) to almost 30 m(2) ha(-1) by 2000. Forest-wide mean AGB from inventory data increased from about 71 Mg ha(-1) in 1930 to about 145 Mg ha(-1) in 1985, and mean AGB on the long-term plots increased from 75 Mg ha(-1) in 1936 to 218 Mg ha(-1) in 1998. Over 76 years, red oak (Quercus rubra L.) canopy trees stored carbon at about twice the rate of similar-sized canopy trees of other species. However, there has been a significant loss of live tree biomass as a result of canopy tree mortality since 1999. Important constraints on long-term biomass increment have included insect outbreaks and droughts.

Species and Spacing Effects of Northern Conifers on Forest Productivity and Soil Chemistry in a 50-Year-Old Common Garden Experiment

Species and Spacing Effects of Northern Conifers on Forest Productivity and Soil Chemistry in a 50-Year-Old Common Garden Experiment

The role of gap phase processes in the biomass dynamics of tropical forests

The responses of tropical forests to global anthropogenic disturbances remain poorly understood. Above-ground woody biomass in some tropical forest plots has increased over the past several decades, potentially reflecting a widespread response to increased resource availability, for example, due to elevated atmospheric CO2 and/or nutrient deposition. However, previous studies of biomass dynamics have not accounted for natural patterns of disturbance and gap phase regeneration, making it difficult to quantify the importance of environmental changes. Using spatially explicit census data from large (50 ha) inventory plots, we investigated the influence of gap phase processes on the biomass dynamics of four 'old-growth' tropical forests (Barro Colorado Island (BCI), Panama; Pasoh and Lambir, Malaysia; and Huai Kha Khaeng (HKK), Thailand). We show that biomass increases were gradual and concentrated in earlier-phase forest patches, while biomass losses were generally of greater magnitude but concentrated in rarer later-phase patches. We then estimate the rate of biomass change at each site independent of gap phase dynamics using reduced major axis regressions and ANCOVA tests. Above-ground woody biomass increased significantly at Pasoh (+0.72% yr(-1)) and decreased at HKK (-0.56% yr(-1)) independent of changes in gap phase but remained stable at both BCI and Lambir. We conclude that gap phase processes play an important role in the biomass dynamics of tropical forests, and that quantifying the role of gap phase processes will help improve our understanding of the factors driving changes in forest biomass as well as their place in the global carbon budget.

Uncertainty estimation of biomass expansion factors for Norway spruce in the Czech Republic

Nation wide estimates of the changes in forest biomass are needed for the greenhouse gas (GHG) reporting under the Climate Convention. The bases for national GHG reporting concerning forest sector are the national forest inventory (NFI) programmes. Since these programmes were mostly established for monitoring of timber resources, one of the current challenges for the NFIs is the development of methodology, such as biomass expansion factors (BEFs). The methodology for carbon stock change estimation should be transparent and verifiable, but this demand is not currently met due to the fact that the source data and uncertainty in the applied BEFs are not known. Here we developed BEFs with uncertainty estimation applicable to stand wise inventory of Norway spruce forests in the Czech Republic. BEFs were constructed, based on tree wise data from permanent research plots, by applying biomass and volume models to tree-level data. These BEFs were age-dependent and their uncertainty was sensitive to the dependencies among errors. Most of the uncertainty in the BEFs was due to uncertainty in the biomass and volume models applied. biomass expansion factor / Monte Carlo simulation / greenhouse gas inventory / national forest inventory

Fire Severity and Long-term Ecosystem Biomass Dynamics in Coniferous Boreal Forests of Eastern Canada

The objective of this study was to characterize the effects of soil burn severity and initial tree composition on long-term forest floor dynamics and ecosystem biomass partitioning within the Picea mariana [Mill.] BSP-feathermoss bioclimatic domain of northwestern Quebec. Changes in forest floor organic matter and ecosystem biomass partitioning were evaluated along a 2,355-year chronosequence of extant stands. Dendroecological and paleoecological methods were used to determine the time since the last fire, the soil burn severity of the last fire (high vs. low severity), and the post-fire tree composition of each stand (P. mariana vs. Pinus banksiana Lamb). In this paper, soil burn severity refers to the thickness of the organic matter layer accumulated above the mineral soil that was not burned by the last fire. In stands originating from high severity fires, the post-fire dominance by Pinus banksiana or P. mariana had little effect on the change in forest floor thickness and tree biomass. In contrast, stands established after low severity fires accumulated during the first century after fire 73% thicker forest floors and produced 50% less tree biomass than stands established after high severity fires. Standing tree biomass increased until approximately 100 years after high severity fires, and then decreased at a logarithmic rate in the millennial absence of fire. Forest floor thickness also showed a rapid initial accumulation rate, and continued to increase in the millennial absence of fire at a much slower rate. However, because forest floor density increased through time, the overall rate of increase in forest floor biomass (58 g m−2 y−1) remained constant for numerous centuries after fire (700 years). Although young stands ( 200 years) sequester the majority (> 80%) of it in their forest floor. The results from this study illustrate that, under similar edaphic conditions, a single gradient related to time since disturbance is insufficient to account for the full spectrum of ecosystem biomass dynamics occurring in eastern boreal forests and highlights the importance of considering soil burn severity. Although fire severity induces diverging ecosystem biomass dynamics in the short term, the extended absence of fire brings about a convergence in terms of ecosystem biomass accumulation and partitioning.

Assessment of temporal changes in aboveground forest tree biomass using aerial photographs and allometric equations

Studies of forest biomass dynamics typically use long-term forest inventory data, available in only a few places around the world. We present a method that uses photogrammetric measurements from aerial photographs as an alternative to time-series field measurements. We used photogrammetric methods to measure tree height and crown diameter, using four aerial photographs of Yatir Forest, a semi-arid forest in southern Israel, taken between 1978 and 2003. Height and crown-diameter measurements were transformed to biomass using an allometric equation generated from 28 harvested Aleppo pine (Pinus halepensis Mill.) trees. Mean tree biomass increased from 6.37 kg in 1978 to 97.01 kg in 2003. Mean plot biomass in 2003 was 2.48 kg/m2 and aboveground primary productivity over the study period ranged between 0.14 and 0.21 kg/m2 per year. There was systematic overestimation of tree height and systematic underestimation of crown diameter, which was corrected for at all time points between 1978 and 2003. The estimated biomass was significantly related to field-measured biomass, with an R2 value of 0.78. This method may serve as an alternative to field sampling for studies of forest biomass dynamics, assuming that there is sufficient spatial and temporal coverage of the investigated area using high-quality aerial photography, and that the tree tops are distinguishable in the photographs.

Radiative transfer model for microwave bistatic scattering from forest canopies

A bistatic forest scattering model is developed to simulate scattering coefficients from forest canopies. The model is based on the Michigan Microwave Canopy Scattering (MIMICS) model (hence called Bi-MIMICS) and uses radiative transfer theory, where the first-order fully polarimetric transformation matrix is used. Bistatic radar systems offer advantages over monostatic radar systems because of the additional information provided by the diversity of the geometry. By simulating the forest canopy scattering from multiple viewpoints, we can better understand how the forest scatterers' shape, orientation, density, and permittivity affect the canopy scattering. Bi-MIMICS is parametrized using selected forest stands with different canopy compositions and structure. The simulation results show that bistatic scattering is more sensitive to forest biomass changes than backscattering. Analyzing scattering contributions from different parts of the canopy gives us a better understanding of the microwave's interaction with the tree components. The ground effects can also be studied. Knowledge of the canopy's bistatic scattering behavior combined with additional synthetic aperture radar measurements can be used to improve forest parameter retrievals. The simulation results of the model provide the required information for the design of future bistatic radar systems for forest sensing applications.

Effects of climate, disturbance, and species on forest biomass across Russia

We used detailed forest inventory data from 43 forests (3.5 × 103 – 115.2 × 103 stands each) and meteorological data from 30 weather stations located in proximity to these forests to assess the effects of disturbance and climate on biomass accumulation patterns across the forest zone of Russia. Chronosequences of biomass accumulation following disturbance were developed for each of the two to five dominant tree species in each forest using stand survey data collected by forest inventories in different regions of Russia between 1986 and 2003. These chronosequences represent changes in average live biomass of forest stands between age 10 and 210 years at 10-year intervals. The correlation of attributes of biomass accumulation (i.e., maximum biomass, biomass at age 40, and maximum biomass increment) with climatic and disturbance attributes was significant but weak (adjusted R2 = 0.20–0.37). The effect of the most influential disturbance attributes (percent clear-cut and percent old forest) was as strong or stronger than the effect of climatic attributes (30-year averages of the sum of positive daily temperatures and climate moisture index). The effect of tree species was significant, but weaker than the effects of climate or disturbance. Combining climate, disturbance, and species attributes generally improved the models (adjusted R2 = 0.37–0.53). The patterns of biomass change observed in chronosequences are influenced by the tendency of harvesting to target more productive forest stands of commercially valuable species, creating a disparity in productivity among the age cohorts. The apparent link between disturbance attributes of forests and biomass accumulation patterms in forest stands may be used to improve broad-scale modeling of changes in forest biomass with remotely sensed data.

Aboveground Forest Biomass and the Global Carbon Balance

AbstractThe long‐term net flux of carbon between terrestrial ecosystems and the atmosphere has been dominated by two factors: changes in the area of forests and per hectare changes in forest biomass resulting from management and regrowth. While these factors are reasonably well documented in countries of the northern mid‐latitudes as a result of systematic forest inventories, they are uncertain in the tropics. Recent estimates of carbon emissions from tropical deforestation have focused on the uncertainty in rates of deforestation. By using the same data for biomass, however, these studies have underestimated the total uncertainty of tropical emissions and may have biased the estimates. In particular, regional and country‐specific estimates of forest biomass reported by three successive assessments of tropical forest resources by the FAO indicate systematic changes in biomass that have not been taken into account in recent estimates of tropical carbon emissions. The ‘changes’ more likely represent improved information than real on‐the‐ground changes in carbon storage. In either case, however, the data have a significant effect on current estimates of carbon emissions from the tropics and, hence, on understanding the global carbon balance.

Late Quaternary changes in Amazonian ecosystems and their implications for global carbon cycling

The current role of Amazonia in the terrestrial carbon budget is the focus of intensive scientific interest, in large part due to its potential to accelerate global warming. However, its role in mediating CO2 changes over millennial time-scales since the last glacial maximum (LGM) has generally been overlooked and is the subject of speculation. Recent advances in our understanding of the Late Quaternary history of Amazonian ecosystems offers an opportunity to make more informed inferences about Late Quaternary changes in the magnitude of Amazon carbon storage than has hitherto been possible. Therefore, in this paper, we reconstruct changes in the magnitude of Amazon carbon storage over the last 21,000 years (since the LGM) by reference to recently published palaeohydrological and palaeoecological data and compare these data with results from simulations using a process-based terrestrial ecosystem model for the Mid-Holocene and the LGM. Building on these results further, we interpret changes in tropical forest biomass in the context of Late Quaternary polar ice-core records of atmospheric methane and carbon dioxide concentrations. Palaeo-data and model simulations show that Amazonia was predominantly forested at the LGM, although there is evidence for savanna expansion near the margins of the Basin and southern Amazonia may have been covered by deciduous/semi-deciduous dry forests rather than evergreen rain forests. We estimate Amazon C storage at the LGM to be only 135 Gt C (50% smaller than today), but find that its proportion of the entire terrestrial carbon store was almost twice that of today. The model shows that between the LGM and the Mid-Holocene there is a significant increase in evergreen broad-leaf forests at the expense of deciduous forests and a 67% increase in total Amazon C storage, attributable to rising temperatures and atmospheric CO2 levels. Although our results indicate that the Amazon Basin was dominated by rain forests throughout the Holocene, rain forest cover expanded in the Late Holocene (at the expense of savannas) and total Amazon carbon storage is simulated to have risen by 22% between the Mid-Holocene (225 Gt C) and the present day (Pre-Industrial) (225 Gt C). Comparison of these Amazon carbon fluxes with palaeo-data from other parts of the world suggests that, contrary to previous hypotheses, the terrestrial biosphere acted as a net carbon sink throughout the Holocene, and that the observed CO2 rise from 260 to 285 ppmv between 8 and 1 ka BP (revealed by the Antarctic Taylor Dome ice-core record) may have been driven by release of carbon from the oceans rather than land.

Late Quaternary changes in Amazonian ecosystems and their implications for global carbon cycling

The current role of Amazonia in the terrestrial carbon budget is the focus of intensive scientific interest, in large part due to its potential to accelerate global warming. However, its role in mediating CO 2 changes over millennial time-scales since the last glacial maximum (LGM) has generally been overlooked and is the subject of speculation. Recent advances in our understanding of the Late Quaternary history of Amazonian ecosystems offers an opportunity to make more informed inferences about Late Quaternary changes in the magnitude of Amazon carbon storage than has hitherto been possible. Therefore, in this paper, we reconstruct changes in the magnitude of Amazon carbon storage over the last 21,000 years (since the LGM) by reference to recently published palaeohydrological and palaeoecological data and compare these data with results from simulations using a process-based terrestrial ecosystem model for the Mid-Holocene and the LGM. Building on these results further, we interpret changes in tropical forest biomass in the context of Late Quaternary polar ice-core records of atmospheric methane and carbon dioxide concentrations. Palaeo-data and model simulations show that Amazonia was predominantly forested at the LGM, although there is evidence for savanna expansion near the margins of the Basin and southern Amazonia may have been covered by deciduous/semi-deciduous dry forests rather than evergreen rain forests. We estimate Amazon C storage at the LGM to be only 135 Gt C (50% smaller than today), but find that its proportion of the entire terrestrial carbon store was almost twice that of today. The model shows that between the LGM and the Mid-Holocene there is a significant increase in evergreen broad-leaf forests at the expense of deciduous forests and a 67% increase in total Amazon C storage, attributable to rising temperatures and atmospheric CO 2 levels. Although our results indicate that the Amazon Basin was dominated by rain forests throughout the Holocene, rain forest cover expanded in the Late Holocene (at the expense of savannas) and total Amazon carbon storage is simulated to have risen by 22% between the Mid-Holocene (225 Gt C) and the present day (Pre-Industrial) (225 Gt C). Comparison of these Amazon carbon fluxes with palaeo-data from other parts of the world suggests that, contrary to previous hypotheses, the terrestrial biosphere acted as a net carbon sink throughout the Holocene, and that the observed CO 2 rise from 260 to 285 ppmv between 8 and 1 ka BP (revealed by the Antarctic Taylor Dome ice-core record) may have been driven by release of carbon from the oceans rather than land.

RECOVERY OF BIOMASS FOLLOWING SHIFTING CULTIVATION IN DRY TROPICAL FORESTS OF THE YUCATAN

Land-use change in the tropics is creating secondary forest at an unprece- dented rate. In the tropical Americas, mature dry tropical forest is rapidly being converted to secondary forest during the fallow period of shifting cultivation. This study addresses changes in forest biomass during forest recovery following shifting cultivation of maize (corn) in the Southern Yucatan Peninsular Region (SYPR), Mexico. We sampled stems .1 cm diameter at breast height at 36 study sites in three regions located along a precipitation gradient of 900-1400 mm/yr. Using allometric equations developed in the tropical Americas, we estimated total aboveground (TAG) biomass of trees, palms, and lianas. Biomass differed little between regions when considering forests of a given age. Over the entire area, forest biomass increased rapidly during succession, from 20.9 Mg/ha in 2-5-yr-old forests to 136.4 Mg/ha in mature forests (logged in the past half century, but not cultivated). Within 12-25 yr, biomass reached half of mature forest levels, and we estimate recovery to pre- cultivation levels in 55-95 yr. Recovery to a pre-logged state may take 65-120 yr. In mature forests, the contribution of stems 1-4.9 cm dbh was consequential, comprising 15% of TAG biomass. Trends in both TAG biomass and basal area were driven by the contribution of trees, although in a few sites, the importance of palms and lianas to forest structure and biomass was considerable. Our results suggest that forest biomass in secondary dry tropical forests of the SYPR is profoundly influenced by forest age, and less so by annual precip- itation, while variability in forest structure depends more on differences in water availability and recent human disturbance.

Calculating Forest Biomass Changes in China

Fang et al. (1), using forest inventory data to estimate changes in forest biomass carbon storage in China during the past 50 years, demonstrated that China's carbon storage in living forest biomass has increased since the 1980s. We appreciate their valuable effort; however, the equation used to estimate forest biomass [note 20 in (1)] is questionable.

Calculating Forest Biomass Changes in China

Calculating Forest Biomass Changes in China

Changes in Forest Cover in a Central Himalayan Catchment: Inadequacy of Assessment Based on Forest Area Alone

The Central Himalayan region experiences severe ecological problems as a result of continuous deforestation, which threatens the subsistence population of the region. In the present study, changes in the forest cover of a catchment over a period of 16 years have been quantified. Baliya catchment (7783 ha) contains 2865·47 ha of different types of forest, i.e. sal (Shorea robusta), mixed sal, pine (Pinus roxburghii), pine-mixed broadleaf, mixed oak (Quercusspp.), cupressus (Cupressus torulosa). The process of fragmentation has been studied through changes in forest area and biomass. There has been a sharp decline in biomass, although only a marginal reduction in forest area (3·5%) has occurred. Decline in the stocking density has also been substantial. Forest area with higher crown cover (>60%) declined from 736·32 ha to 292 ha during 1973–1989, indicating the intensity of human interference.

The effects of changes in forest biomass on radar backscatter from tree canopies

Abstract We validated a canopy backscatter model for loblolly pine forest stands at the Duke Forest, North Carolina, by comparing the observed and modelled SAR backscatter from the stands. Given the SAR backscatter data calibration uncertainty, the model made good predictions of C-HH, C-HV, L-HH, L-HV, L-VV, P-HH, and P-HV backscatter for most of 25 stands studied. The model overestimated C-VV backscatter for several stands, and largely overestimated P-VV backscatter for most of the stands. Using the collected SAR backscatter and ground data, and the backscatter model, we studied the influences of changes in biomass on SAR backscatter as a function of radar frequency and polarization, and evaluated the feasibility of deriving the biomass from the backscatter. This study showed that C-HH, C-HV, C-VV, L-VV, and P-VV SAR backscatter may be insensitive to the biomass change. L-HH, L-HV, P-HH, and P-HV SAR backscatter changed more than 5dB as the biomass varied. This study also showed that the L-HH and P-HH backscatter or L-HV and P-H V backscatter may be used to develop algorithms to retrieve trunk biomass or canopy biomass of the loblolly pine forests.