Open Journal of Forestry
2013. Vol.3, No.1, 17-22
Published Online January 2013 in SciRes (http://www.scirp.org/journal/ojf) http://dx.doi.org/10.4236/ojf.2013.31004
Review and Progress of China’s Forest
Continuous Inventory System
Guozhong Lin, Xiaorong Wen, Chunguo Zhou, Guanghui She*
College of Forest Resources and Environment, Nanjing Forestry University, Nanjing, China
Received November 18th, 2012; revised December 21st, 2012; accepted Dec ember 29th, 2012
China was one of the earliest countries to set up a system to continuously inventory natural forest re-
sources. From the beginning of the 1970s until today, seven forest resource inventories have been carried
out. This research summarizes the progress of forest continuous inventories and analyzes the existing de-
ficiencies of China’s forest continuous inventory system and forest management plan inventory. As stated
above, this research offers corresponding countermeasures and suggestions: establishing a sample plot
system for comprehensive national forest inventory and monitoring with each province’s continuous for-
est inventory based on the foundation of the national sample plot system, able to develop the province as a
subset of the overall province-level forest resource inventory according to the actual conditions in each
province. Through annual multi-resource/multi-benefit surveying of the forests, the monitoring of forest
amounts, quality, functions and benefits will be assisted in its entirety. The further integration of the forest
continuous inventory and the forest management plan inventory is also discussed. This research also pro-
poses the varied probability sampling method with sub-compartments as the basic sampling unit (or com-
binations of sub-compartments). This will also satisfy the requirements of ecological inventory by region.
Keywords: Review; China’s Forest Inventory System; Forest Continuous Inventory System; China Forest
Resource
Introduction
Forest Inventory proceeds with relevant scientific methods
and standards according to the needs of forest management,
ecological environment construction, forestry production, sci-
entific research and other factors. One of the important tasks of
forest resource management is to collect, count, analyze and
assess the data according to a defined scale of time and space,
for forest resource distribution, amount, quality, and trends of
development, as well as relevant natural and social economic
factors (IUFRO, 1994).
The survey of forest resources carried out in order to under-
stand the current situation of the forest resources and dynamic
is known as Forest Continuous Inventory.
The Forest Continuous Inventory system includes the sam-
pling method plot settings and survey index, time interval, and
statistics and analysis etc. China’s work on the forest inventory
system actually took place after 1950. It e xperienced 4 stages: 1)
the initial establishing forest inventory system in nationwide in
1950s; 2) Sampling techniques using mathematical statistics as
a theoretical basis from 1960s to1980s; 3) Remote sensing (RS),
geographic information systems (GIS), global positioning sys-
tem (GPS) technology was gradually introduced forest con-
tinuous inventory technology from 1990s to 2000s; 4) The ex-
pansion of inventory contents towards a multi-resource format
includes forest productivity, biomass, carbon storage, etc. from
2000s to now.
The national inventory system only operates once every 5
years. Thr ough the review o f China’s forest re source continu-
ous inventory of progress, to further improve the perfecting
forest continuous inventory system, how to improve the effi-
ciency of inventory expanded inventory results application,
some useful advice put forward in this paper.
China’s Forest Inventory System and Its Course
of Development
The Main Types of Forest Inventory
The forest inventory system and its contents, methods, tech-
nology, form of results, etc. develop parallel to the rapid ad-
vance of information technology and the widespread use of
mathematical statistics. These new technologies and techniques
enable integration of the macro-requirements of national for-
estry construction and development with forestry production,
and lead to the gradual establishment and perfection of man-
agement practice requirements (Xiao, 2005).
After nearly 60 years of development, China’s large-scale
forest continuous inventory took shape as a relatively perfect
forest resource inventory system in view of the special charac-
teristics and requirements of China’s forestry development.
According to the research goal, content, and technical methods,
China’s forest resource survey system can be divided into:
1) The nationwide forest inventory is referred to as a first
class survey. Beginning in the 1970s, China’s forest continuous
inventory was gradually established at the province level (re-
gion, municipality), with the data from the provinces making up
the main body of the overall forest Continuous inventory sys-
tem. Every 5 years the inventory was repeated, using fixed
sample plot surveys as the main method of carrying out regular
monitoring. Within a unified time, and according to unified
inventory requirements, a clear picture of the macroscopic
*Corresponding author.

G. Z. LIN ET AL.
situation of national forest resources and its succession of pat-
terns was created. This provided scientific evidence for the
forestry development strategy and adjustment of forestry poli-
cies in a timely and efficacious way. The national forest con-
tinuous inventory used a systematic sampling method, and the
stratified sampling method was integrated into the sampling
estimation. For the systematically extracted samples a stratified
sampling estimation was completed according to forest volume
or other survey factors, the principle being to make the factor
variation as small as possible for all points within the layer and
larger between the layers, in order to improve the accuracy of
stratified sampling estimations. In addition, in order to improve
the efficiency of sample plot extraction, double samples and
double regression method estimates are frequently used. This
takes advantage of easily measured auxiliary tree survey factors
to realize estimates of forest accumulation. When the forest
resource inventory also has other spatial data sources, such as
aerial or satellite imaging, the multi-source data joint estimation
method is usually still adopted.
2) The forest management plan inventory is referred to as a
second class survey. The Forest Management Plan Inventory is
one kind of forest resource inventory method. It uses state-
owned forestry bureaus, nature preserves, forest parks and other
areas of forest management units or administrative units above
the county level as its departments, and is carried out with for-
est management sub-compartments as the basic unit. It is done
once every 10 years, to provide evidence for the forest man-
agement plan, the overall plan and county-level or above forest
planning, and the sub-compartment data files which take shape
provide a data platform for forest management and tasks.
3) The forest task planning survey is known as a third class
survey. This inventory is a carried out as a task-based survey
with a particular scope or operational area as the basic unit.
Usually it adopts the real measurement or sampling inventory
method. For the forest resources in each operational area, site
conditions and forest regeneration status are used to undertake a
detailed survey, with the goal of satisfying the requirements of
specific production tasks (e.g. afforestation, deforestation, for-
est tending etc.) arranged by basic level forestry production
units, usually carried out in the production tasks of the previous
year.
4) The annual special forest resource inventory is known as
the verification survey. Its goal is to achieve a timely grasp of
the situation regarding completion of the annual forestry pro-
duction plan by forestry production units or project implement-
tation units. It evaluates the effectiveness of forestry production
assignments, so that the Forestry Department and other related
departments can adjust their annual production plan, to provide
a basis to boost the effectiveness of carrying out the Forest
Management Unit’s forestry production plans. The verification
inventory method usually takes a locality (city) or county (for-
estry bureau) as its basic units, using the terrain verification
survey method.
5) Specialized inventory. Specialized forestry inventory in-
cludes site-type surveys, fore st soil surveys, forest regeneration
surveys, forest disease and pest surveys, preparation of forestry
tables, forest growth surveys, forest multi-benefit measurement
surveys and assessments, wild animal resource surveys, and
other specialized inquiries. Its findings provide basic data di-
rectly to main specialized surveys, district, planning, design and
establishment of forestry production.
The Shape of the Forest Continuous Inventory
System
China’s work on the forest inventory system actually took
place after the founding of the new China, beginning in 1950
(Yi, 1991). At that time, forest inventory technology from the
former Soviet Union was comprehensively introduced. The
Soviet technology was in reality originally from Germany, and
in addition the previous knowledge in the country on forest
inventory came from European and Japanese systems, so
China’s technology was close to the European system from the
beginning (Goran & Hans, 1998; Kleinn et al., 1998; American
Forest Council, 1992).
Table 1 shows the 4 stages of shape and progress of China’s
Forest Continuous Inventory.
In the early part of the 1950s, theodolites or compasses were
principally used for measurement, and to regulate the survey
area, using a grid method to divide the land into compartments
and sub-compartments, set up banded standard plots, and mea-
sure each tree’s diameter in the standard plot to calculate forest
volume. Since the workload of the survey was too large, in the
middle of the 1950s, aerial forest surveys were developed,
along with aerial forest inventories and ground based compre-
hensive inventories. By the end of the 1950s, angle gauge mea-
surement technology was also introduced (Scott, 1947; Ware &
Cunia, 1962), since the method was simple, accurate and reli-
able, and it received a wide range of applications throughout
the country. According to the needs of that time, year after year
the whole country was surveyed piece by piece. Since there
were many investigation methods in different areas, survey
quality was not consistent, and the scope of the inventory was
incomplete. The statistical calculation methods were also rather
poor at that time and remained so until the early 1960s. In 1962
the Forestry Department, responding to the requirements of
forestry production development, organized the provinces (re-
gions, city) to further the development of statistical work in the
forest resource inventory across the whole country. For the 12-
year period from 1950 to 1962, all of the various forest resource
survey data wa s syste matiz ed, st atistically processed and finally
brought into a nationwide summary.
During the 1960s, sampling techniques using mathematical
statistics as a theoretical basis were introduced and large-scale
experiments and measurement verification was organized. In
terms of the survey’s accuracy, quality, benefits and other as-
pects, remarkable results were achieved across the board. This
laid the foundation for the sampling techniques we use in our
forest inventories today.
In the 1970s, China began to explore a national forest con-
tinuous inventory system. This was due to the consideration
Table 1.
The 4 stages of shape and progress of China’s Forest Continuous In-
ventory.
Stage Period Feature
Initial
establishment 1950s theodolites or compasses, angle gauge measurement
Exploration &
Shape 1960s to 1980s sampling te chniques, fixed sample plots at 5-year intervals
Development 1990s to
2000s RS, GIS, GPS technology application.
Optimization &
Expansion 2000s to now multi-resource monitoring includes forest productivity, biomass, carbon storage, etc.
18

G. Z. LIN ET AL.
that the former survey methods were all independent investiga-
tions and the results from before and after lack continuity and
comparability. It was impossible to achieve precise information
on trends of growth and decline of forest resources (Cunia &
Chevrou, 1969; Newton et al., 1974). In 1973, the Ministry of
Agriculture and Forestry (MAF) arranged a national forest con-
tinuous inventory project in each province (region, city), de-
veloping the administrative districts and counties (bureaus) as
basic units in the inventory system. This was the first time since
the founding of the new China that a comprehensive forest con-
tinuous inventory was carried out in a relatively unified time
scale and on a national scope (Taiwan temporarily excluded). In
this inventory, through the establishment of a pilot program, the
country’s forest continuous inventory utilized systematic sam-
pling methods and hierarchical regression estimate methods.
Beginning in 1978, this system was fully developed in every
province (region, city). The forest continuous inventory system
is in accordance with the systematic sampling principle. Fixed
sample plots were set up at ground level, the diameter of each
tree in the standard plot was measured, and at 5-year intervals
there was a review. This kind of inventory system can accu-
rately obtain the current conditions of forest resources and un-
cover growth and decline trends. Regular patterns of resource
development can be grasped, the effectiveness of resource ma-
nagement can be analyzed, and predictions of resource devel-
opment trends can be predicted.
Thus China became one of the earliest countries to set up a
forest continuous inventory system. From the 1970s until today,
seven forest inventories have been carried out. The surveying
period was divided into the years 1973-1976, 1977-1981, 1984-
1988, 1989-1993, 1994-1998, 1999-2003, and 2004-2008. The
8th inventory is a l r e a dy underway.
The first country-wide forest inventory was the first forest
continuous inventory with the counties (bureaus) as the basic
units which reached a national scope (excluding Taiwan) since
the founding of the People’s Republic of China. Its main focus
was on ascertaining the current forest resource conditions. Star-
ting with the second national forest continuous inventory, the
inventory system used the province (district, municipality) as
the basic unit rather than the county. In subsequent inventories
a review of previous inventory data, a gradual perfection of
methods, and unceasingly enriched survey indices can be seen.
At the end of the 1970s systematic sampling technology was
first deployed, and by the 1990s remote sensing (RS), geo-
graphic information systems (GIS), global positioning system
(GPS) technology was gradually introduced. Forest continuous
inventory technology has shown continuous improvement. Be-
fore the 5th inventory, priority was given to timber production.
For the most part, traditional ground level sampling was under-
taken on the sample plots at this time. The 6th inventory in-
creased forest ownership, plant disease and insect pest con-
tents, and comprehensively introduced remote sensing technol-
ogy, with 3S technology as the foundation. It used remote sen-
sory monitoring and ground surveying technology combined
with the double stratified sampling remote monitoring system
(Wang et al., 2007; Gregoire, 1993; Lyncii, 1995; Martin,
1982). At present, the 7th national forest continuous inventory
has incorporated the forest’s ecological functions, forest healthy
class and biodiversity into the measurement categories as re-
flections of ecological status. The forest continuous inventory
system is moving in the direction of development of a compre-
hensive monitoring system for both resources and ecological
conditions (Xiao, 2005).
In the 1980s, China’s forest continuous inventory system was
further improved, unifying the technological system for the en-
tire country. As information technology developed, remote sen-
sing technology began to be used during surveying, and satel-
lite imaging and aerial sample plot imaging also made their ap-
pearance. Within the statistical work of the inventory, unified
survey factor coding and unified data storage formats came into
usage. A complete statistical summary was entered into the
computer system, guaranteeing the comparability and accuracy
of survey results. This summary provides reliable basic data for
the current national forest resource situation and its growth and
decline status. In the area of sampling technology, an accurate
two-stage and multi-stage estimation method for forest con-
tinuous inventory was proposed (The Forestry Department of
the People’s Republic of China, 1983).
Forest continuous inventories before the 1990s were mainly
undertaken with the forest resources themselves as the focus.
Beginning in the 1990s, the country began the development of
the forest resource monitoring system. In 1991 the United Na-
tions Food and Agricultural Organization provided China with
aid projects in order to support the establishment of the moni-
toring system. Research was begun on the establishment of a
national Forest Resource Monitoring Body. This period of for-
est resource inventory saw the beginning of widespread usage
of 3S (remote sensing (RS), geographic information systems
(GIS), the global positioning system (GPS)) technology, and
improved investigative factors in the areas of forest ecology,
health class, ownership and intensity of management (The For-
estry Department of the People’s Republic of China, 1994).
After the year 2000, China gradually established a forestry
development strategy that gives priority to ecological construc-
tion. China’s “Forest Continuous Inventory Technical Regula-
tions” (The Forestry Department of the People’s Republic of
China, 2004; Arner et al., 2004; Cochran, 1997), issued in 2004,
embody the survey indices of forestry development with a fo-
cus on ecological construction. Beginning with the 8th national
forest resource inventory, the surveying system will gradually
develop into a comprehensive monitoring system which will
give equal priority to the forest resources and the ecological si-
tuation. There are 75 investigative factors for sample plots in
the 8th inventory which can be divided into six aspects: land
usage and coverage; site and soil; stand characteristics, forest
function; ecological situation, and other forest land manage-
ment related survey indices. At present the 8th national invent-
tory is underway, and the comprehensive monitoring system
projects are divided into six projects and 133 monitoring factors
(Ye et al., 2000): such as land cover and land usage, soil and
site, land degradation, forest function efficiency, wood and
other forest products, forest health conditions and disasters, and
biomass and biological diversity.
The Progress of Continuous Forest Resources
Inventory
Since the 1990s, China has carried out a series of optimiza-
tion and improvement tasks on the current forest resource mo-
nitoring system. From 1993-1997, China received aid from the
United Nations Development Program (UNDP) and other in-
stitutions and launched research on the “National Forest Re-
sources Monitoring System”. In 1997 the original forestry de-
partment proposed a conception of a monitoring and assessment

G. Z. LIN ET AL.
system for national forest resources and the environment, and
the State Forestry Bureau Planning and Design Institute com-
pleted the overall design. In 1998, the compilation of the tech-
nological plan and regulations was completed. On December 12,
2004, research was initiated on establishing a framework for a
comprehensive monitoring system for forest resources and the
ecological situation (Bu, 2005). The general ideas and basic
framework for such a system were put forth. The monitoring of
water, air and soil at a microscopic level can accurately assess
the status of forest resources and lead to the discovery of regu-
lar patterns of forest growth, and can also find the external fac-
tors influencing natural forest growth. This environmentally-
focused monitoring will represent a new direction of develop-
ment for the comprehensive monitoring of forest resources, and
also mirrors international development trends.
The characteristics of information on forest resources and
ecological conditions come from many sources, and in many
forms, shapes, grades and structures (Lie, 2006). Under the gui-
ding idea of systemic integration, computer network technology,
database technology, 3S technology, model simulation tech-
nology, and resources will be comprehensively integrated. Es-
tablishing a public service platform for comprehensive moni-
toring of forest resources, and promoting the further develop-
ment, application and integration of information resource for
forestry development and ecological construction to provide a
real-time, dynamic, open information service will improve eva-
luation and forecasting ability to help avert disasters and ensure
the success of engineering projects.
Remote sensing, aerial remote sensing, global positioning
system, global information systems, database technology and
computer network technology are widely applied in the mod-
ernization of forest resource monitoring. In particular, the use
of remote radar sensing data to carry out local survey s, such as
coastal shelter forest surveys, has been gradually increasing.
The expansion of inventory contents towards a multi-re-
source format includes forest productivity, biomass, carbon sto-
rage, forest products, temperate area resources, desertification,
rocky desertification of soil resources and wild animal and
plant resources. The development towards a multi-benefit for-
mat mainly includes investigation of the ecological conditions
and functions of the forest, relating to sample plot biodiversity,
forest health, and information output on ecological functions
and forestry engineering effectiveness. Multi-resource, multi-
benefit monitoring will guarantee comprehensive monitoring of
the forest volume, quality, functions and benefits.
In recent years, due to China’s forest resource management
requirements, each province hopes to have forest resource and
ecological conditions information for every year. One key trend
of variation in forest resource monitoring is how to use the 5-
year cycle of forest continuous inventories to realize annual
forest resource monitoring. The method mainly used is to add
detail to the original inventory sampling grid and review every
year. Due to the heavy workload and high costs this method is
not adopted by many. Another method is to utilize the data
from the inventory, and carry out an update using the growth
and consumption model. A third method is to correct and con-
trol the original inventory data through the use of remote sens-
ing to provide annual data to combine with the original data
(Roesch & Reams, 1999; Reosch et al., 1993; Scott et al.,
1999).
In 1999 Zhejiang province took the lead in performing an
annual forest resource monitoring trial taking the requirements
of the new situation into account. The method they adopted
involves tightening the original forest inventory sampling grid
and reviewing every year. Minor forest zones utilize modeling
to update their data as an auxiliary method. Annual forest re-
source monitoring not only improves the usefulness of the re-
sults of the forest continuous inventory, but also provides an-
nual forest resource data for resource management. Every year
Zhejiang Province will make their annual monitoring of forest
resources and ecological conditions into a public announcement,
helping the society to understand the forest, and increasing
public participation and enthusiasm for forestry.
Discussion
Modern forest inventory monitoring technology is not a sin-
gle-source technology. Its development is also not an inde-
pendent development of one branch of science. It is rather a
comprehensive integration of many types of technology and
even many different scientific fields (Zhu, 2001). At present,
spatial remote sensing, aerial remote sensing, global positioning,
global information systems, database technology and computer
network technology, along with other high-technology products,
have received different degrees of national usage in forestry
(Wynne et al., 1999). Looking at each kind of technology in
turn, it can be seen that ground surveying can’t satisfy the needs
of a macroscopic analysis; aerial digital imaging has too large
an information content to be useful in the monitoring of forest
resources over vast areas; and satellite monitoring can’t satisfy
the demands for level of detail needed in resource monitoring
information. Therefore, as far as monitoring technology, it is
necessary to organically combine ground surveying, aerial and
satellite imaging as the information content, accuracy and time
period requires. The technique of combining 3S technology and
ground survey methods, promoting space/ground/sky-integrated
monitoring, receiving information from many channels and on
many levels, can be an effective forest resource monitoring
method.
The rapid growth of the national economy and the need for
sustainable forestry development has given rise to some contra-
dictions. On the one hand there is a requirement for the conno-
tation of forest resource inventory to broaden, resource data to
be updated year by year, and to develop forest resource moni-
toring in the direction of multi-resource comprehensive moni-
toring. On the other hand, although the establishment of a forest
continuous inventory system played a very important role in
promoting digital forestry and has become an important foun-
dation for forest resource management, people have questioned
the spending of such enormous sums of money to develop for-
est continuous inventories. How to further expand the sphere of
application of the forest resource inventory results, and research
low-cost continuous forest inventory methods remains a crucial
research topic today.
China’s forest continuous inventory system is set up so the
provinces are the basic units providing data, with all of them
using the systematic sampling method. Due to the limitations of
that method, the results of monitoring only apply to the prov-
inces, and break down into local municipalities. At the county
level there is no guarantee of sampling precision. Another fac-
tor is that the national inventory system only operates once
every 5 years, and in reality it is very hard to synchronize the
inventory activities of the various provinces within that 5-year
period. National statistics come with certain difficulties for the
20

G. Z. LIN ET AL.
continuous forest resource inventory, and there is no way to
utilize the forest inventory system to directly provide data on
annual forest resource status and growth and decline status. To
this end, some specialists have proposed surveying 1/5 of the
provincial sample plots every year, and leaving the remaining
4/5 to use data updating methods to take the place of annual
ground surveys. But what is urgently needed to solve this prob-
lem is 1) the basis for this statistical theory; 2) a method to
extract 1/5 of the sample plots and 3) a concrete method to
update the data for the remaining 4/5.
Moreover, the further integration of the forest continuous in-
ventory and the second class (sub-compartment) forest resource
inventory is also an important purpose of research in this paper.
Under normal conditions, on the basis of the fixed sample plots
usually used for the province level continuous inventory, the
county level inventory sampling system can be established to
act as a control on the sub-compartment survey precision. For
this reason, realization of the data of the forest inventory can
make the sub-compartment management more practical. The
actual situation shows that costs and workload will be greatly
increased by establishing such a system. Many counties have
abandoned the increased-precision sample plot system that de-
pends on county level data because it brings unavoidable prob-
lems of precision control in sub-compartment survey. At the
same time, new requirements have been put forward for the
progress of forest ecology monitoring which use mountain mas-
sif or even river basin areas (combined sub-compartments) as
basic units. Some specialists (She, 1998; She et al., 2007) have
proposed the varied probability sampling method with the
county-level data making up the main body of data, and sub-
compartments as the basic sampling unit (or combinations of
sub-compartments). This proposal is directed at the existing
problems in second-class forest resource inventory, specifically
in the south of China. With this type of sub-compartment sam-
ple plot a forest resource fixed angle gauge plot dynamic meas-
urement system can be established in each province. At the
same time, the statistical estimations of sub-compartment class
sample plots can serve as a control on the precision of the entire
second class forest (sub-compartment) inventory. This method
not only uses the high efficiency of varied probability sampling
established in the forest resource monitoring system, but also
can combine the sampling estimation method with sub-com-
partment inventory. This will satisfy the requirements of eco-
logical inventory by region. Sub-compartment class fixed sam-
ple plots can become a new forest resource monitoring system,
according to the inventory being carried out.
First and second class forest resource inventories are both
important components of the national and local forest resource
monitoring system. The amount of sample plot data used in the
nationwide province-based inventory estimates is rather large,
and the corresponding workload and costs are prohibitive. On
this basis it is suggested to establish a national forest continu-
ous inventory system and sample plot monitoring system that
takes the whole country as its basic unit. In this way, the
amount of sample plots in each province can be greatly reduced,
and also it will be beneficial to the development of an annual
national forest inventory. At the same time the statistical data
can control the precision of each province’s own inventory data
collection. Each province’s continuous forest inventory can be
implemented according to the method suggested above on a
national sample plot basis according to the really existing con-
ditions in the province, creating a more perfect forest resource
monitoring system. The new forest continuous inventory sys-
tem Put forward by this paper not only can play a role in origin-
nal system but also can realize two classes of survey combina-
tion.
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