Potential impacts of climate change on a mixed ... - Semantic Scholar
P O T E N T I A L IMPACTS O F C L I M A T E C H A N G E ON A M I X E D B R O A D L E A V E D - K O R E A N P I N E F O R E S T STAND: A GAP MODEL APPROACH GUOFAN SHAO Department of Environmental Sciences, Clark Hall, University of Virginia, Charlottesville, VA 22903, USA
Abstract. A gap-typed forest dynamic model KOPIDE was used to assess the dynamic responses of a mixed broadleaved-Korean pine forest stand to climate change in northeastem China. The GFDL climate change scenario was applied to derive the changes in environmental variables, such as 10 ~ based DEGD and PET~P,which were used to implement the model. The simulation result suggests that the climate change would cause important changes in stand structure. Korean pine, the dominant species in the area under current climate conditions, would disappear under the GFDL equilibrium scenario. Oak and elm would becomethe dominant speciesreplacing Korean pine, ash and basswood. Such a potential change in forest structure would require different strategies for forest management in northeastern China.
Introduction The mixed broadleaved-Korean pine (Pinus koraiensis) forest is one of the most complex and valuable forest ecosystem types in northeast China. Decades ago, this mixed forest used to cover almost the entire eastern mountainous area of northeastern China, and has been one of the primary timber sources for the country. The dominant species is Korean pine though there are tens of broadleaved species in the region. Because of timber harvesting practices over the past several decades, the extent of the mixed forest has been greatly reduced and only some "islands" of the old-growth forest stands can be found in reserves and remote areas of northeastern China. A better understanding of the dynamics of the isolated old-growth forests under various climate conditions is important to address issues for purposes of maintaining biodiversity, conservation, and future management options for the region. The study of the mixed forest succession began in the early 1950's with the start of extensive forest logging. Ecological experiments and observations predicted that Korean pine would be the dominant species under natural succession despite the method of cutting (i.e., clear or selective) that was applied (Chen, 1982). A JABOWA (Botkin et al., 1972) and FORET (Shugart and West, 1977) typed gap model, called KOPIDE, has been used to supplement observational data and to predict forest dynamics under current climate conditions (Shao, 1989; Shao et al., 1994). The simulations were validated against the old-growth forests at Changbaishan Biosphere Reserve in northeastern China, and the results supported Climatic Change 34" 263-268, 1996. (~) 1996Kluwer Academic Publishers. Printed in the Netherlands.
264
GUOFANSHAO
the traditional conclusions that Korean pine dominates the equilibrium forest stages. In this paper, KOPIDE will be used to explore the impacts of climate change on the dynamics of a mixed broadleaved-Korean pine forest stand in the reserve.
Model Structure The basic structure of KOPIDE is very similar to other earlier forest gap models (Shugart, 1984), but there are some differences which should be highlighted here. The number of saplings (i.e. DBH is between 0.3 and 1.0 cm) for each species found under canopies of different leaf area indices (LAD were recorded. According to the field observations, each species has a characteristic distribution pattern against the maximum number of saplings for a given LAI. This relationship was mathematically defined as:
(1)
X = A e B(LAI-LAI~
where, X = maximum number of saplings for a given LAI; A =maximum number of saplings for the optimal LAI; B = curve-fitting parameter that defined the range of suitable LAI; LA[opt ----optimal LAI for regeneration. The value of A is a function of seed production. Aspen and birch have larger values of A, and Korean pine has a smaller value. The value of B is a function of the light sensitivity of a species. Shade- intolerant species have lower values than shade-tolerant species. The value of LA]opt is also related to species shade tolerance, and has higher values for more shade-tolerant species. Regeneration is then calculated as the product of the X and a uniform random number ranging from 0 to 1. The height (H) of a tree determines its competition status in a stand. In contrast to other gap models, the Richard's function was used for describing the relation of DBH (D) to height: H = Hmax(1 -
aebD)w
(2)
where, a, b, and w are species-specific constants. This function was found to better fit the remeasured data than other more standard growth equations for all the species studied (Shao, 1991). Also, when D = 0, H was set to 1.3 m. Following the techniques of Botkin et al. 0972), the differential equation describing the maximum growth of DBH was derived as:
(-~-~)
= max
1
GcDd2(DH +
DH Omaxamax
D2Hmaxabw( 1 - aebD) (w-1)ebo
(3)
where, c and d are the two parameters of the power function estimating leaf biomass from DBH.
IMPACTSOF CLIMATECHANGE
265
Table I Species-specific parameters used in implementing the gap model KOPIDE Parameters
Maple
Arnax (yr) [Max. Age] 200 Dmax (cm) (in Eq. (3)) 70 Hmax (cm) (in Eq. (3)) 2200 a (inEq. (2) and (3)) 0.926 b (in Eq. (2) and (3)) (-) 0.058 w (in Eq. (2) and (3)) 1.08 c (in Eq. (3)) 8.13 d (in Eq. (3)) 2.01 G (in Eq. (3)) 16 Dlmax[Max. PET~P] 1.39 DEGDmax(~ 3800 DEGDm~a(~ 1450 cl [Shugart, 1984, p. 52] 1.00 c2 [Shugart, 1984, p.52] 6.66 c3 [Shugart, 1984, p. 52] 0.05 A (in Eq. (1)) 5 B (inEq. (1)) (-) 0.100 LAlopt (in Eq. (1)) 2 dDmt~ (mm)a 0.01 t (yr)a 10 LA/LB (m2/kg) 126
Birch
Ash
Aspen Pine
Oak
Bassw Elm
100 80 2700 0.875 0.071 1.45 19.5 1.69 36 1.70 4000 1350 1.73 1.15 0.25 60 3.91 0 0.05 5 165
300 110 3300 0.940 0.042 1.14 43.6 1.61 13 1.25 3400 1600 1.06 3.14 0.10 5 0.178 2 0.03 10 150
60 60 2400 0.713 0.096 1.83 29.7 1.70 29 1.75 4000 1400 1.73 1.15 0.25 50 3.91 0 0.05 5 150
350 140 2800 0.915 0.040 1.24 17.9 1.72 18 1.64 3800 1450 1.06 3.14 0.10 5 0.402 2 0.03 10 150
300 120 3100 0.790 0.052 2.03 13.4 1.75 25 1.40 3400 1500 1.06 3.14 0.10 5 0.178 2 0.03 10 148
400 160 3500 0.967 0.025 0.95 29.3 1.75 11 1.05 3250 1350 1.00 4.66 0.07 2 0.038 2 0.01 20 175
250 90 2600 0.832 0.057 1.67 20.0 1.75 15 1.55 3800 1450 1.06 3.14 0.10 5 0.100 2 0.03 10 115
a If diameter growth rate of a tree is less than dDmm,the tree will be able to grow for up to t years.
K O P I D E assumes that the actual D B H growth (dD) results from restrictive environmental effects representing the response o f species to water availability (PET~P, the ratio o f annual potential evapotranspiration to precipitation), temperature (DEGD, the accumulated daily temperature above 10 ~ and light regimes on the inherent growth properties (dD)max o f the tree species. The growth response to water availability and temperature is assumed to be parabolic, and response to light is assumed to follow a three-parameter exponential function (Shugart, 1984). Two causes o f tree mortality are considered: (1) random senescence (assumes that 1% o f trees will live to m a x i m u m age); and (2) due to critically reduced carbon gain (i.e. respiration nearly equals assimilation). Stress-related mortality is dependent upon a species- specific critical growth rate o f D B H and the m a x i m u m possible n u m b e r o f years for survival if growth rate is below the defined value. In this paper the species pool includes: maple (Acer mono), birch (Betula platyphylla), ash (Fraxinus mandshurica), pine (Pinus koraiensis), aspen (Populus davidiana), oak (Quercus mongolica), basswood (Tilia amurensis), and elm (Ulmus japonica). Parameter values for the species are listed in Table I.
266
GUOFAN SHAO Table II The current and GFDL-predicted climate conditions for the area studied Climate variables
Current condition
GFDL scenario
Average monthly temperature (~C) Annual precipitation (mm) Accumulated daily temperature above 10 ~ (DEGD) Potential evapotranspiration to precipitation ratio (PET~P)
2.9 871 2275 0.75
8.5 963 3564 0.92
Simulation and Results The forest stand studied is located at Changbaishan Biosphere Reserve (42~ ~N, 128000 ' E) of China. The simulation output is the average result of one hundred 15 by 15 m plots. The model was run from an old-growth forest stand as the initial condition. Earlier simulations suggested that this forest stand is at an almost equilibrium stage and the forest structure would remain relatively unchanged for at least hundreds of years under current climate conditions (Shao et al., 1994). The same initial conditions were used for studying the potential impacts of climate change on the forest dynamics. For the first fifty years, the model was run under the current climate conditions, that is, DEGD = 2275 and PET/P = 0.75. From year 50 to 150, DEGD and PET/P are assumed to linearly increase to 3564 and 0.92, corresponding to the predicted values for the GFDL 2 x CO2 climate change scenario (Lauenroth, this issue). Following year 150, the climate conditions were assumed to be constant (Table II). The simulation results show that the structure and composition of the mixed broadleaved-Korean pine forest stand would change greatly under GFDL scenario (Figure 1). During the first 50 years, pine, ash, oak, and basswood are the dominant species as in an earlier simulations by Shao et al. (1994). Forest structure remains relatively unchanged even after DEGD and PET/P have increased during the first 50 years. However, by year 130, 80 years after climate change is initiated, pine, ash and basswood begin to decrease sharply, and within about 15 years, these three dominant species have totally disappeared from the stand. To some degree, oak also decreases along with the other three co-dominant species, but this species soon recovers and its abundance in the stand becomes much higher following the decline of pine, ash and basswood. Elm, functioning as an understory species at present, also benefits from the changes of Canopy tree species and becomes a co-dominant species. Maple is also an understory species, but does not show an obvious reaction to the climate change and the change in species dominance. Birch and aspen are pioneer species and cannot invade the stand as long as the canopy is closed. Though some trees of these two species can grow during the transitions of dominant species, they do not persist for long.
IMPACTSOFCLIMATECHANGE
267
250 t~ r
200 , I f ~'~ v" ~ ~ ~ \ ,,~ v~
E
~
150 (D
E
-"~,~. . . . . . . . =~
100
~..
~.o,*~'
,,,., ~
,~.,
O >
I
J 9~
(!)
5O
I--
0
J ~h~.~
0
50
o...."
100
.~
....... 9. . . . . . . . .
.o~
~..ooo..OO..~
150
200
250
300
Time (year) Acer mono ...........
Betula platiphylla
Fraxinus mandshurica
........
Populus
davidiana
Pinus koraiensis
. . . .
Quercus mongolica
Tilia a m u r e n s i s
.............
Ulmus japonica
Climatechange impacts on the compositionaldynamicsof a mixed broadleaved-Korean pine forest at Changbaishan BiosphereReserve in China. Changes in temperatureand precipitation are based on the GFDL 2 x CO2 equilibriumscenarioand were applied using a linear interpolation betweenyears 50 and 150 of the simulation.Climatewas assumedto be constantfollowingyear 150.
F i g u r e 1.
Discussion and Conclusions It has been noticed that gap models are a potentially useful tool to assess climate change impacts on forest ecosystems (Shugart et al., 1992), though this approach cannot meet the requirement of modeling large-scale landscape patterns (Shugart et al., 1992; Malanson, 1993). This paper indicates that the behaviors of the gap model is very sensitive to the changes of climate variables, and thus the gap model approach has potential for examining the responses of forest dynamics to climate change. The GFDL scenario, like other similar scenarios, predicts that the climate conditions will become much warmer and drier for the study area though annual precipitation increases slightly. Such potential changes of climate would change the existing tree species composition. The temperature and moisture conditions predicted under the GFDL scenario exceed or approach the maximum boundary conditions for the growth of Korean pine, ash and basswood in the region. This is the major factor that results in the decline of the three species on the stand. Oak, elm and maple can adapt to a wider range of temperature than Korean pine, ash and basswood, so their growth is not reduced as greatly by the warmer temperatures. Among oak, elm and maple, oak and elm can grow under drier conditions than maple. Oak and elm increase their abundance as a result of their broader environ-
268
GUOFANSHAO
mental tolerances and the dieback of the former dominant species. In other words, the positive effects of reduced competition on the growth of oak and elm may be greater than the negative effects of climate change. For maple, the tree growth may be equally compensated by these two different effects. That is why the biomass of maple remains relative unchanged on the stand. The hardwood forest stands dominated by oak and elm can be found at lower elevation of Changbai Mountain and southern northeastern China where the climate conditions are much warmer and drier than the area studied. The transition from the mixed broadleaved-Korean pine forest to the hardwood forest caused by climate change may represent a general dynamic pattern for the region in the future. Such a large change in the forest structure and composition of the region would have potential influences on forest management activities in northeastern China. Korean pine is important because of its timber values, and the mixed forest dominated by Korean pine is important because of its ecological values (Chen, 1982; Yang and Wu, 1986). The possibility of significant changes in patterns of species dominance is a challenge to forest managers, to conservation biologists, and to ecologists. The traditional Korean pine-centered forest management may have to be modified accordingly. References Botkin, D. B., Janak, J. F., and Wallis, J. R.: 1972, 'Some Ecological Consequences of a Computer Model of Forest Growth', J. Ecol. 60, 849-873. Chen, D.: 1982, 'Evaluation on the Development of Korean Pine- Broadleaved Forest Ecosystems', J. North. For. Univ., Vol. Monograph on Korean Pine Forests, pp. 1-17 (in Chinese). Lauenroth, W. K.: 1996, 'Application of Patch Models to Examine Regional Sensitivity to Climate Change', Clim. Change 34, 155-160 (this issue). Malanson, G. P.: 1993, 'Comment on Modeling Ecological Response to Climatic Change', Clim. Change 23, 95-109. Pastor, J. and Post, W. M.: 1988, 'Response of Northern Forests to CO2-Induced Climate Change', Nature 334, 55-58. Shao, G.: 1989, 'KOPIDE: A Computer Model of Growth and Succession for Broadleaved-Pinus koraiensis Forests on Changbaishan Mountain', Ph.D. dissertation, Chinese Academy of Sciences (in Chinese). Shao, G.: 1991, 'Moisture-Therm Indices and Optimum-Growth Modeling for the Main Species of Korean Pine-Deciduous Mixed Forests', Scientia Silvae Sinicae 27, 21-27 (in Chinese). Shao, G., Schall, P., and Weishampel, J. F.: 1994, 'Dynamic Simulations of Mixed Broadleaved-Pinus koraiensis Forests in the Changbaishan Biosphere Reserve of China', Forest Ecol. and Manage. 70, 169-181. Shugart, H. H.: 1984, A Theory of Forest Dynamics, Springer-Verlag, New York. Shugart, H. H. and West, D. C.: 1977, 'Development of an Appalachian Deciduous Forest Succession Model and its Application to Assessment of the Impacts of the Chestnut Blight', J. Environ. Manage. 5, 161-179. Shugart, H. H., Smith, T. M., and Post, W. M.: 1992, 'The Potential for Application of IndividualBased Simulation Models for Assessing the Effects of Global Change', Annu. Rev. Ecol. Syst. 23, 15-38. Yang, H. and Wu, Y.: 1986, 'Tree Composition, Age Structure and Regeneration Strategy of the Mixed Broadleaved-Pinus koraiensis (Korean Pine) forest in Changbaishan Mountain Reserve', in Yang, H., Wang, Z., Jeffers, J. N. R., and Ward, P. A. (eds.), The Temperate Forest Ecosystem, Proceedings of the ITE symposium, 5-11 July 1986, at Antu, China. Institute of Terrestrial Ecology, Grange-over-Sands, United Kingdom, 20: 12-20.
Abstract. A gap-typed forest dynamic model KOPIDE was used to assess the dynamic responses of a mixed broadleaved-Korean pine forest stand to climate change in northeastem China. The GFDL climate change scenario was applied to derive the changes in environmental variables, such as 10 ~ based DEGD and PET~P,which were used to implement the model. The simulation result suggests that the climate change would cause important changes in stand structure. Korean pine, the dominant species in the area under current climate conditions, would disappear under the GFDL equilibrium scenario. Oak and elm would becomethe dominant speciesreplacing Korean pine, ash and basswood. Such a potential change in forest structure would require different strategies for forest management in northeastern China.
Introduction The mixed broadleaved-Korean pine (Pinus koraiensis) forest is one of the most complex and valuable forest ecosystem types in northeast China. Decades ago, this mixed forest used to cover almost the entire eastern mountainous area of northeastern China, and has been one of the primary timber sources for the country. The dominant species is Korean pine though there are tens of broadleaved species in the region. Because of timber harvesting practices over the past several decades, the extent of the mixed forest has been greatly reduced and only some "islands" of the old-growth forest stands can be found in reserves and remote areas of northeastern China. A better understanding of the dynamics of the isolated old-growth forests under various climate conditions is important to address issues for purposes of maintaining biodiversity, conservation, and future management options for the region. The study of the mixed forest succession began in the early 1950's with the start of extensive forest logging. Ecological experiments and observations predicted that Korean pine would be the dominant species under natural succession despite the method of cutting (i.e., clear or selective) that was applied (Chen, 1982). A JABOWA (Botkin et al., 1972) and FORET (Shugart and West, 1977) typed gap model, called KOPIDE, has been used to supplement observational data and to predict forest dynamics under current climate conditions (Shao, 1989; Shao et al., 1994). The simulations were validated against the old-growth forests at Changbaishan Biosphere Reserve in northeastern China, and the results supported Climatic Change 34" 263-268, 1996. (~) 1996Kluwer Academic Publishers. Printed in the Netherlands.
264
GUOFANSHAO
the traditional conclusions that Korean pine dominates the equilibrium forest stages. In this paper, KOPIDE will be used to explore the impacts of climate change on the dynamics of a mixed broadleaved-Korean pine forest stand in the reserve.
Model Structure The basic structure of KOPIDE is very similar to other earlier forest gap models (Shugart, 1984), but there are some differences which should be highlighted here. The number of saplings (i.e. DBH is between 0.3 and 1.0 cm) for each species found under canopies of different leaf area indices (LAD were recorded. According to the field observations, each species has a characteristic distribution pattern against the maximum number of saplings for a given LAI. This relationship was mathematically defined as:
(1)
X = A e B(LAI-LAI~
where, X = maximum number of saplings for a given LAI; A =maximum number of saplings for the optimal LAI; B = curve-fitting parameter that defined the range of suitable LAI; LA[opt ----optimal LAI for regeneration. The value of A is a function of seed production. Aspen and birch have larger values of A, and Korean pine has a smaller value. The value of B is a function of the light sensitivity of a species. Shade- intolerant species have lower values than shade-tolerant species. The value of LA]opt is also related to species shade tolerance, and has higher values for more shade-tolerant species. Regeneration is then calculated as the product of the X and a uniform random number ranging from 0 to 1. The height (H) of a tree determines its competition status in a stand. In contrast to other gap models, the Richard's function was used for describing the relation of DBH (D) to height: H = Hmax(1 -
aebD)w
(2)
where, a, b, and w are species-specific constants. This function was found to better fit the remeasured data than other more standard growth equations for all the species studied (Shao, 1991). Also, when D = 0, H was set to 1.3 m. Following the techniques of Botkin et al. 0972), the differential equation describing the maximum growth of DBH was derived as:
(-~-~)
= max
1
GcDd2(DH +
DH Omaxamax
D2Hmaxabw( 1 - aebD) (w-1)ebo
(3)
where, c and d are the two parameters of the power function estimating leaf biomass from DBH.
IMPACTSOF CLIMATECHANGE
265
Table I Species-specific parameters used in implementing the gap model KOPIDE Parameters
Maple
Arnax (yr) [Max. Age] 200 Dmax (cm) (in Eq. (3)) 70 Hmax (cm) (in Eq. (3)) 2200 a (inEq. (2) and (3)) 0.926 b (in Eq. (2) and (3)) (-) 0.058 w (in Eq. (2) and (3)) 1.08 c (in Eq. (3)) 8.13 d (in Eq. (3)) 2.01 G (in Eq. (3)) 16 Dlmax[Max. PET~P] 1.39 DEGDmax(~ 3800 DEGDm~a(~ 1450 cl [Shugart, 1984, p. 52] 1.00 c2 [Shugart, 1984, p.52] 6.66 c3 [Shugart, 1984, p. 52] 0.05 A (in Eq. (1)) 5 B (inEq. (1)) (-) 0.100 LAlopt (in Eq. (1)) 2 dDmt~ (mm)a 0.01 t (yr)a 10 LA/LB (m2/kg) 126
Birch
Ash
Aspen Pine
Oak
Bassw Elm
100 80 2700 0.875 0.071 1.45 19.5 1.69 36 1.70 4000 1350 1.73 1.15 0.25 60 3.91 0 0.05 5 165
300 110 3300 0.940 0.042 1.14 43.6 1.61 13 1.25 3400 1600 1.06 3.14 0.10 5 0.178 2 0.03 10 150
60 60 2400 0.713 0.096 1.83 29.7 1.70 29 1.75 4000 1400 1.73 1.15 0.25 50 3.91 0 0.05 5 150
350 140 2800 0.915 0.040 1.24 17.9 1.72 18 1.64 3800 1450 1.06 3.14 0.10 5 0.402 2 0.03 10 150
300 120 3100 0.790 0.052 2.03 13.4 1.75 25 1.40 3400 1500 1.06 3.14 0.10 5 0.178 2 0.03 10 148
400 160 3500 0.967 0.025 0.95 29.3 1.75 11 1.05 3250 1350 1.00 4.66 0.07 2 0.038 2 0.01 20 175
250 90 2600 0.832 0.057 1.67 20.0 1.75 15 1.55 3800 1450 1.06 3.14 0.10 5 0.100 2 0.03 10 115
a If diameter growth rate of a tree is less than dDmm,the tree will be able to grow for up to t years.
K O P I D E assumes that the actual D B H growth (dD) results from restrictive environmental effects representing the response o f species to water availability (PET~P, the ratio o f annual potential evapotranspiration to precipitation), temperature (DEGD, the accumulated daily temperature above 10 ~ and light regimes on the inherent growth properties (dD)max o f the tree species. The growth response to water availability and temperature is assumed to be parabolic, and response to light is assumed to follow a three-parameter exponential function (Shugart, 1984). Two causes o f tree mortality are considered: (1) random senescence (assumes that 1% o f trees will live to m a x i m u m age); and (2) due to critically reduced carbon gain (i.e. respiration nearly equals assimilation). Stress-related mortality is dependent upon a species- specific critical growth rate o f D B H and the m a x i m u m possible n u m b e r o f years for survival if growth rate is below the defined value. In this paper the species pool includes: maple (Acer mono), birch (Betula platyphylla), ash (Fraxinus mandshurica), pine (Pinus koraiensis), aspen (Populus davidiana), oak (Quercus mongolica), basswood (Tilia amurensis), and elm (Ulmus japonica). Parameter values for the species are listed in Table I.
266
GUOFAN SHAO Table II The current and GFDL-predicted climate conditions for the area studied Climate variables
Current condition
GFDL scenario
Average monthly temperature (~C) Annual precipitation (mm) Accumulated daily temperature above 10 ~ (DEGD) Potential evapotranspiration to precipitation ratio (PET~P)
2.9 871 2275 0.75
8.5 963 3564 0.92
Simulation and Results The forest stand studied is located at Changbaishan Biosphere Reserve (42~ ~N, 128000 ' E) of China. The simulation output is the average result of one hundred 15 by 15 m plots. The model was run from an old-growth forest stand as the initial condition. Earlier simulations suggested that this forest stand is at an almost equilibrium stage and the forest structure would remain relatively unchanged for at least hundreds of years under current climate conditions (Shao et al., 1994). The same initial conditions were used for studying the potential impacts of climate change on the forest dynamics. For the first fifty years, the model was run under the current climate conditions, that is, DEGD = 2275 and PET/P = 0.75. From year 50 to 150, DEGD and PET/P are assumed to linearly increase to 3564 and 0.92, corresponding to the predicted values for the GFDL 2 x CO2 climate change scenario (Lauenroth, this issue). Following year 150, the climate conditions were assumed to be constant (Table II). The simulation results show that the structure and composition of the mixed broadleaved-Korean pine forest stand would change greatly under GFDL scenario (Figure 1). During the first 50 years, pine, ash, oak, and basswood are the dominant species as in an earlier simulations by Shao et al. (1994). Forest structure remains relatively unchanged even after DEGD and PET/P have increased during the first 50 years. However, by year 130, 80 years after climate change is initiated, pine, ash and basswood begin to decrease sharply, and within about 15 years, these three dominant species have totally disappeared from the stand. To some degree, oak also decreases along with the other three co-dominant species, but this species soon recovers and its abundance in the stand becomes much higher following the decline of pine, ash and basswood. Elm, functioning as an understory species at present, also benefits from the changes of Canopy tree species and becomes a co-dominant species. Maple is also an understory species, but does not show an obvious reaction to the climate change and the change in species dominance. Birch and aspen are pioneer species and cannot invade the stand as long as the canopy is closed. Though some trees of these two species can grow during the transitions of dominant species, they do not persist for long.
IMPACTSOFCLIMATECHANGE
267
250 t~ r
200 , I f ~'~ v" ~ ~ ~ \ ,,~ v~
E
~
150 (D
E
-"~,~. . . . . . . . =~
100
~..
~.o,*~'
,,,., ~
,~.,
O >
I
J 9~
(!)
5O
I--
0
J ~h~.~
0
50
o...."
100
.~
....... 9. . . . . . . . .
.o~
~..ooo..OO..~
150
200
250
300
Time (year) Acer mono ...........
Betula platiphylla
Fraxinus mandshurica
........
Populus
davidiana
Pinus koraiensis
. . . .
Quercus mongolica
Tilia a m u r e n s i s
.............
Ulmus japonica
Climatechange impacts on the compositionaldynamicsof a mixed broadleaved-Korean pine forest at Changbaishan BiosphereReserve in China. Changes in temperatureand precipitation are based on the GFDL 2 x CO2 equilibriumscenarioand were applied using a linear interpolation betweenyears 50 and 150 of the simulation.Climatewas assumedto be constantfollowingyear 150.
F i g u r e 1.
Discussion and Conclusions It has been noticed that gap models are a potentially useful tool to assess climate change impacts on forest ecosystems (Shugart et al., 1992), though this approach cannot meet the requirement of modeling large-scale landscape patterns (Shugart et al., 1992; Malanson, 1993). This paper indicates that the behaviors of the gap model is very sensitive to the changes of climate variables, and thus the gap model approach has potential for examining the responses of forest dynamics to climate change. The GFDL scenario, like other similar scenarios, predicts that the climate conditions will become much warmer and drier for the study area though annual precipitation increases slightly. Such potential changes of climate would change the existing tree species composition. The temperature and moisture conditions predicted under the GFDL scenario exceed or approach the maximum boundary conditions for the growth of Korean pine, ash and basswood in the region. This is the major factor that results in the decline of the three species on the stand. Oak, elm and maple can adapt to a wider range of temperature than Korean pine, ash and basswood, so their growth is not reduced as greatly by the warmer temperatures. Among oak, elm and maple, oak and elm can grow under drier conditions than maple. Oak and elm increase their abundance as a result of their broader environ-
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mental tolerances and the dieback of the former dominant species. In other words, the positive effects of reduced competition on the growth of oak and elm may be greater than the negative effects of climate change. For maple, the tree growth may be equally compensated by these two different effects. That is why the biomass of maple remains relative unchanged on the stand. The hardwood forest stands dominated by oak and elm can be found at lower elevation of Changbai Mountain and southern northeastern China where the climate conditions are much warmer and drier than the area studied. The transition from the mixed broadleaved-Korean pine forest to the hardwood forest caused by climate change may represent a general dynamic pattern for the region in the future. Such a large change in the forest structure and composition of the region would have potential influences on forest management activities in northeastern China. Korean pine is important because of its timber values, and the mixed forest dominated by Korean pine is important because of its ecological values (Chen, 1982; Yang and Wu, 1986). The possibility of significant changes in patterns of species dominance is a challenge to forest managers, to conservation biologists, and to ecologists. The traditional Korean pine-centered forest management may have to be modified accordingly. References Botkin, D. B., Janak, J. F., and Wallis, J. R.: 1972, 'Some Ecological Consequences of a Computer Model of Forest Growth', J. Ecol. 60, 849-873. Chen, D.: 1982, 'Evaluation on the Development of Korean Pine- Broadleaved Forest Ecosystems', J. North. For. Univ., Vol. Monograph on Korean Pine Forests, pp. 1-17 (in Chinese). Lauenroth, W. K.: 1996, 'Application of Patch Models to Examine Regional Sensitivity to Climate Change', Clim. Change 34, 155-160 (this issue). Malanson, G. P.: 1993, 'Comment on Modeling Ecological Response to Climatic Change', Clim. Change 23, 95-109. Pastor, J. and Post, W. M.: 1988, 'Response of Northern Forests to CO2-Induced Climate Change', Nature 334, 55-58. Shao, G.: 1989, 'KOPIDE: A Computer Model of Growth and Succession for Broadleaved-Pinus koraiensis Forests on Changbaishan Mountain', Ph.D. dissertation, Chinese Academy of Sciences (in Chinese). Shao, G.: 1991, 'Moisture-Therm Indices and Optimum-Growth Modeling for the Main Species of Korean Pine-Deciduous Mixed Forests', Scientia Silvae Sinicae 27, 21-27 (in Chinese). Shao, G., Schall, P., and Weishampel, J. F.: 1994, 'Dynamic Simulations of Mixed Broadleaved-Pinus koraiensis Forests in the Changbaishan Biosphere Reserve of China', Forest Ecol. and Manage. 70, 169-181. Shugart, H. H.: 1984, A Theory of Forest Dynamics, Springer-Verlag, New York. Shugart, H. H. and West, D. C.: 1977, 'Development of an Appalachian Deciduous Forest Succession Model and its Application to Assessment of the Impacts of the Chestnut Blight', J. Environ. Manage. 5, 161-179. Shugart, H. H., Smith, T. M., and Post, W. M.: 1992, 'The Potential for Application of IndividualBased Simulation Models for Assessing the Effects of Global Change', Annu. Rev. Ecol. Syst. 23, 15-38. Yang, H. and Wu, Y.: 1986, 'Tree Composition, Age Structure and Regeneration Strategy of the Mixed Broadleaved-Pinus koraiensis (Korean Pine) forest in Changbaishan Mountain Reserve', in Yang, H., Wang, Z., Jeffers, J. N. R., and Ward, P. A. (eds.), The Temperate Forest Ecosystem, Proceedings of the ITE symposium, 5-11 July 1986, at Antu, China. Institute of Terrestrial Ecology, Grange-over-Sands, United Kingdom, 20: 12-20.
