JSTOR CITATION LIST
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NUMBER OF CITATIONS : 6
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1.
Title: Remote Sensing of Forest Biophysical Structure Using
Mixture Decomposition and Geometric Reflectance Models
Author(s): Forrest G. Hall; Yosio E. Shimabukuro; Karl F.
Huemmrich
Source: Ecological Applications, Vol. 5, No. 4. (Nov., 1995), pp.
993-1013.
Stable URL: http://links.jstor.org/sici?sici=1051-0761%28199511%295%3A4%3C993%3ARSOFBS%3E2.0.CO%3B2-I
Abstract: Using geometric shadow and linear mixture models we
develop and evaluate an algorithm to infer several
important structural parameters of stands of black spruce
(Picea mariana), the most common boreal forest dominant.
We show, first, that stand reflectances for this species
can be represented as linear combinations of the
reflectances of more elemental radiometric components:
sunlit crowns, sunlit background, and shadow. Secondly,
using a geometric model, we calculate how the fractions of
these radiometric elements covary with each other. Then,
using hand-held measurements of the reflectances of the
sunlit background, sphagnum moss (Sphagnum spp.), and
assuming shadow reflectance to be that of deep, clear
lakes, we infer the reflectance of sunlit crowns from the
geometric shadow model and low-altitude reflectance
measurements acquired by a helicopter-mounted radiometer.
Next, we assume that the reflectance for all black spruce
stands is simply a linear combination of shadow, sunlit
crown, and sunlit background reflectance, weighted in
proportion to the relative areal fractions of these pixel
elements. We then solve a set of linear equations for the
areal fractions of these elements using as input
helicopter observations of total stand reflectance. Using
this algorithm, we infer the values for the areal
proportions of sunlit canopy, sunlit background, and
shadow for 31 black spruce stands of varying biomass
density, net primary productivity, etc. We show
empirically and theoretically that the areal proportions
of these radiometric elements are related to a number of
stand biophysical characteristics. Specifically, the
shadow fraction is increasing with increasing biomass
density, average diameter at breast height, leaf area
index (LAI), and aboveground net primary productivity
(NPP), while sunlit background fraction is decreasing. We
show that the end member fractions can be used to estimate
biomass with a standard error of $\approx$ 2 kg/m$^2$, LAI
with a standard error of 0.58, dbh with a standard error
of $\approx$ 2 cm, and aboveground NPP with a standard
error of 0.07 $\mathrm{kg}\cdot \mathrm{m}^{-2}\cdot
\mathrm{yr}$^{-1}$. We also show that the fraction of
sunlit canopy is only weakly correlated with the
biophysical variables and are thus able to show why a
popular vegetation index, Normalized Difference Vegetation
Index (NDVI), does not provide a useful measure of these
biophysical characteristics. We do show, however, that
NDVI should be related to the fraction of
photosynthetically active radiation incident upon and
absorbed by the canopy. This work has convinced us that a
paradigm shift in the remote sensing of biophysical
characteristics is in order--a shift away from direct
inference of biophysical characteristics from vegetation
indices and toward a two-step process, in which (1)
stand-level reflectance is approximated in terms of linear
combinations of reflectance-invariant, spectrally distinct
components (spectral end members) and mixture
decomposition used to infer the areal fractions of these
components, e.g., shadow, sunlit crown, and sunlit
background, followed by (2) the use of radiative transfer
models to compute biophysical characteristic values as a
function of the end member fractions.
2.
Title: Global Primary Production: A Remote Sensing Approach
Author(s): Stephen D. Prince; Samuel N. Goward
Source: Journal of Biogeography, Vol. 22, No. 4/5, Terrestrial
Ecosystem Interactions with Global Change, Volume 2. (Jul.
- Sep., 1995), pp. 815-835.
Stable URL: http://links.jstor.org/sici?sici=0305-0270%28199507%2F09%2922%3A4%2F5%3C815%3AGPPARS%3E2.0.CO%3B2-G
Abstract: A new model of global primary production (GLObal
Production Efficiency Model, GLO-PEM), based on the
production efficiency concept, is decribed. GLO-PEM is the
first attempt to model both global net and gross primary
production using the production efficiency approach and is
unique in that it uses satellite data to measure both
absorption of photosynthetically active radiation (APAR)
and also the environmrntal variables that affect the
utilization of APAR in primary production. The use of
satellite measurements gives global, repetitive, spatially
contiguous and time specific observations of the actual
vegetation. GLO-PEM is based on physiological principles,
in particular the amount of carbon fixed per unit absorbed
photosynthetically active radiation $(\varepsilon)$ is
modelled rather than fitted using field observations.
GLO-PEM is illustrated with the first available year
(1987) of the $8\times 8 km$ resolution NOAA/NASA AVHRR
land Pathfinder data set. The global net primary
production, respiration and $\varepsilon$ values obtained
indicate that even the rather simple AVHRR provides a
wealth of information relevant to biospheric monitoring.
The algorithms and results presented indicate that there
are significant possibilities of inferring biological and
environmental variables using multispectral techniques
that need to be explored if the new generation of
satellite remote sensing systems is to be exploited
productively.
3.
Title: Combining Remote Sensing and Climatic Data to Estimate Net
Primary Production Across Oregon
Author(s): Beverly E. Law; Richard H. Waring
Source: Ecological Applications, Vol. 4, No. 4. (Nov., 1994), pp.
717-728.
Stable URL: http://links.jstor.org/sici?sici=1051-0761%28199411%294%3A4%3C717%3ACRSACD%3E2.0.CO%3B2-4
Abstract: A range in productivity and climate exists along an
east-west transect in Oregon. Remote sensing and climatic
data for several of the Oregon Transect Ecosystem Research
Project (OTTER) forested sites and neighboring shrub sites
were combined to determined whether percentage intercepted
photosynthetically active radiation (%IPAR) can be
estimated from remotely sensed observations and to
evaluate climatic constraints on the ability of vegetation
to utilize intercepted of radition for production. The
Thematic Mappers Simulator (TMS) normalized difference
vegetation index (NDVI) provided a good linear estimate of
%IPAR (R^2 = 0.97). Vegetation intercepted from 24.8% to
99.9% of incident photosynthetically active radiation
(PAR), and aboveground net primary production (ANPP)
ranged from 53 to 1310 g@?m^-^2@?yr^-^1. The ANPP was
linearly related to annual IPAR across sites (R^2 = 0.70).
Constraints on the ability of each species to utilize
intercepted light, as defined by differential responses to
freezing temperatures, drought, and vapor pressure
deficit, were quantified from hourly meteorological
station measurements near the sites and field
physiological measurements. Vegetation could utilize from
30% of intercepted radiation at the eastside semiarid
juniper woodland and shrub sites to 97% at the maritime
coastal sites. Energy-size efficiency (@d@m), calculated
from aboveground production and IPAR modified by the
environmental limits, averaged 0.5 g/MJ for the shrub
sites and 0.9 g/MJ for the forested sites.
4.
Title: Climatic and Biotic Controls on Annual Carbon Storage in
Amazonian Ecosystems
Author(s): H. Tian; J. M. Melillo; D. W. Kicklighter; A. D. McGuire;
J. Helfrich III; B. Moore III; C. J. Vorosmarty
Source: Global Ecology and Biogeography, Vol. 9, No. 4. (Jul.,
2000), pp. 315-335.
Stable URL: http://links.jstor.org/sici?sici=1466-822X%28200007%299%3A4%3C315%3ACABCOA%3E2.0.CO%3B2-1
Abstract: 1 The role of undisturbed tropical land ecosystems in the
global carbon budget is not well understood. It has been
suggested that interannual climate variability can affect
the capacity of these ecosystems to store carbon in the
short term. In this paper, we use a transient version of
the Terrestrial Ecosystem Model (TEM) to estimate annual
carbon storage in undisturbed Amazonian ecosystems during
the period 1980-94, and to understand the underlying
causes of the year-to-year variations in net carbon
storage for this region. 2 We estimate that the total
carbon storage in the undisturbed ecosystems of the Amazon
Basin in 1980 was 127.6 Pg C, with about 94.3 Pg C in
vegetation and 33.3 Pg C in the reactive pool of soil
organic carbon. About 83% of the total carbon storage
occurred in tropical evergreen forests. Based on our
model's results, we estimate that, over the past 15 years,
the total carbon storage has increased by 3.1 Pg C (+2%),
with a 1.9-Pg C (+2%) increase in vegetation carbon and a
1.2-Pg C (+4%) increase in reactive soil organic carbon.
The modelled results indicate that the largest relative
changes in net carbon storage have occurred in tropical
deciduous forests, but that the largest absolute changes
in net carbon storage have occurred in the moist and wet
forests of the Basin. 3 Our results show that the strength
of interannual variations in net carbon storage of
undisturbed ecosystems in the Amazon Basin varies from a
carbon source of 0.2 Pg C/year to a carbon sink of 0.7 Pg
C/year. Precipitation, especially the amount received
during the drier months, appears to be a major controller
of annual net carbon storage in the Amazon Basin. Our
analysis indicates further that changes in precipitation
combine with changes in temperature to affect net carbon
storage through influencing soil moisture and nutrient
availability. 4 On average, our results suggest that the
undisturbed Amazonian ecosystems accumulated 0.2 Pg C/year
as a result of climate variability and increasing
atmospheric CO$_2$ over the study period. This amount is
large enough to have compensated for most of the carbon
losses associated with tropical deforestation in the
Amazon during the same period. 5 Comparisons with
empirical data indicate that climate variability and
CO$_2$ fertilization explain most of the variation in net
carbon storage for the undisturbed ecosystems. Our
analyses suggest that assessment of the regional carbon
budget in the tropics should be made over at least one
cycle of El Nino-Southern Oscillation because of
interannual climate variability. Our analyses also suggest
that proper scaling of the site-specific and subannual
measurements of carbon fluxes to produce Basin-wide flux
estimates must take into account seasonal and spatial
variations in net carbon storage.
5.
Title: Global Change and Terrestrial Ecosystems: An Initial
Integration
Author(s): William L. Steffen; John S. I. Ingram
Source: Journal of Biogeography, Vol. 22, No. 2/3, Terrestrial
Ecosystem Interactions with Global Change, Volume 1. (Mar.
- May, 1995), pp. 165-174.
Stable URL: http://links.jstor.org/sici?sici=0305-0270%28199503%2F05%2922%3A2%2F3%3C165%3AGCATEA%3E2.0.CO%3B2-I
Abstract: We present a framework for integrating GCTE's research
programme based on three interacting axes-time, space and
applicability. We use the contributed papers from the
First GCTE Science Conference to undertake an initial
integration of GCTE-type research using this three-axis
structure. We assess where progress in being made, where
progress is likely to be made in the near future, and
where critical gaps exist which require a major effort to
eliminate. Elevated $CO_2$ research is one of the most
mature areas within GCTE, and provides scope for initial
integration along all three axes. Soils, being key to the
functioning of all terrestrial ecosystems, provide another
excellent opportunity to integrate research along all
three axes. A major obstacle to further integration is our
lack of understanding of landscape-scale processes,
particularly disturbances, and our ability to simulate
global change impacts on them. GCTE's Focus 2, Change in
Ecosystem Structure, is perhaps best placed to attack many
of the gaps that prevent this further integration along
space and time scales, and is now entering a rapid
development phase; the other Foci also have a major role
to play. Integration specifically along the applicability
axis is being developed in some areas but requires an
enhanced effort to achieve its potential to increase
scientific efficiency and effectiveness. The emerging
field of global ecology, i.e. ecology at very large space
and time scales, is progressing rapidly on the basis of
linkages to more traditional ecological research at
smaller scales, but requires further interaction with work
along the applicability axis.
6.
Title: Tropical Secondary Forests
Author(s): Sandra Brown; Ariel E. Lugo
Source: Journal of Tropical Ecology, Vol. 6, No. 1. (Feb., 1990),
pp. 1-32.
Stable URL: http://links.jstor.org/sici?sici=0266-4674%28199002%296%3A1%3C1%3ATSF%3E2.0.CO%3B2-J
Abstract: The literature on tropical secondary forests, defined as
those resulting from human disturbance (e.g. logged
forests and forest fallows), is reviewed to address
questions related to their extent, rates of formation,
ecological characteristics, values and uses to humans, and
potential for management. Secondary forests are extensive
in the tropics, accounting for about 40% of the total
forest area and their rates of formation are about 9
million ha yr$^{-1}$. Geographical differences in the
extent, rates of formation and types of forest being
converted exist. Secondary forests appear to accumulate
woody plant species at a relatively rapid rate but the
mechanisms involved are complex and no clear pattern
emerged. Compared to mature forests, the structure of
secondary forest vegetation is simple, although age,
climate and soil type are modifying factors. Biomass
accumulates rapidly in secondary forests, up to 100 t
ha$^{-1}$ during the first 15 yr or so, but history of
disturbance may modify this trend. Like biomass, high
rates of litter production are established relatively
quickly, up to 12-13 t ha$^{-1}$ yr$^{-1}$ by age 12-15
yr. And, in younger secondary forests (<20 yr), litter
production is a higher fraction of the net primary
productivity than stemwood biomass production. More
organic matter is produced and transferred to the soil in
younger secondary forests than is stored in above-ground
vegetation. The impact of this on soil organic matter is
significant and explains why the recovery of organic
matter in the soil under secondary forests is relatively
fast (50 yr or so). Nutrients are accumulated rapidly in
secondary vegetation, and are returned quickly by
litterfall and decomposition for uptake by roots. We
propose a model of the gains and losses, yields and costs,
and benefits and tradeoffs to people from the current
land-use changes occurring in the tropics. When the
conversion of forest lands to secondary forests and
agriculture is too fast or land-use stages are skipped,
society loses goods and services. To avoid such a loss, we
advocate management of tropical forest lands within a
landscape perspective, a possibility in the tropics
because land tenures and development projects are often
large.
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