CN113919747A - Method for determining reasonable forest stand density based on forest-water relationship - Google Patents
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Abstract
The invention relates to a method for determining reasonable forest stand density based on forest-water relation, which is characterized in that under the condition of rainfall resource supply, the forest stand density is automatically determined by a computer program according to the environmental capacity of the rainfall resource. The determination process comprises: (1) determining technical parameters, (2) establishing a reasonable forest stand density model of the forest-water relationship, and (3) determining reasonable forest stand density. The technical parameters comprise: the method has the advantages of rainfall resource environment capacity V and water consumption V of evaporation dispersion under forests1And the water consumption of each plant of the arbor tree species with different breast diameters is v2. The invention starts from the most main restrictive factor water resource of the forest vegetation in the north, comprehensively considers the environmental capacity of regional rainfall resources and the dynamic change of transpiration water consumption, effectively solves the problem of reasonable operation density of the whole life cycle of different trees under the environmental capacity of the regional rainfall resources, and improves the forest vegetationThe quality and the stability of the forest ecosystem play an important role.
Description
Technical Field
The invention belongs to the technical field of forest management and production, and relates to a method for determining reasonable forest stand density based on forest-water relation.
Background
The forest stand density is the basis of the reasonable spatial structure formed by the forest and is also a decisive factor of the size of the individual growth and development space of the forest. The determination of reasonable density of forest stands in different growth stages is one of core problems of forestry, and whether the density of forest stands reasonably and directly influences the health, quality, stability, production structure and productivity of forest stands. By correctly applying reasonable density theory and technology and regulating and controlling the forest production structure, the full utilization potential of the forest to the existing environmental resources is exerted, the productivity and the resistance to external interference are improved, and the stability of the forest ecological system is increased. The forest management density is always a problem, and how large the forest management density is, the forest management density is reasonable, and different climates, different tree species and different breast-height diameters should be different. The existing methods for determining the density, such as the methods for determining the density according to different configuration forms and the methods for determining the density according to business purposes, generally have certain experience and arbitrariness, and have less consideration on main factors for restricting the density of forest stands. The relatively scientific determination method is a comparison test method for different operating densities, but the method has long test period, large influence on the site conditions and no universal applicability.
The forestation stands in the sixty-seventy years of the last century have obvious degradation trend due to overlarge forestation density and lack of reasonable density management for a long time. The main reason is that as the water consumption increases with the growth of the forest, the water resource amount which can be satisfied by the young forest cannot satisfy the growth requirement of the forest after the forest is grown. The water shortage is common in northern areas, the available water resource quantity inevitably becomes a limiting factor for determining the reasonable density of the forest stand, so the basis for determining the density of the forest stand is the precipitation resource environment capacity, the precipitation resource environment capacity refers to the types and the quantity of trees which can be accommodated by certain precipitation resources under the premise of maintaining the ecological balance and the water balance of areas under the condition of no irrigation and no groundwater for supplementing the soil moisture, and the quantity is expressed on the forest stand structure and is the forest stand density of a certain tree at different development stages or the maximum number of trees which can be accommodated on a unit area of forest stand.
The reasonable forest stand density determination must follow the basic principle of 'forest determination by water', and is embodied in that the forest stand structure determines the proper forest stand density on the premise of water balance, so that the bearing capacity of precipitation resources is rationalized, and a stable and continuously developed forest stand structure is formed.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for determining reasonable forest stand density based on forest-water relationship, fully considering rainfall resource environment capacity and water consumption dynamics of different diameter levels of forest trees, perfecting the existing method for determining forest management density, and improving the scientificity and applicability of forest management density determination.
The technical scheme of the invention is as follows: a reasonable forest stand density determination method based on forest-water relation automatically determines forest stand density by a computer program according to rainfall resource environment capacity under the condition of rainfall resource supply. The determination process comprises: (1) determining technical parameters, (2) establishing a reasonable forest stand density model of the forest-water relationship, and (3) determining reasonable forest stand density. The technical parameters comprise: the method has the advantages of rainfall resource environment capacity V and water consumption V of evaporation dispersion under forests1And the water consumption of each plant of the arbor tree species with different breast diameters is v2The reasonable forest stand density model based on the forest-water relationship is as follows:
in the formula: h is stand density, plant/hm2；aSoil for soilIs the storage proportion of the atmospheric precipitation soil,%; vDescendIs the average rainfall for many years, mm; t is the number of growing months; w is the evaporation rate under forest, kg.m-2·d-1(ii) a t is the diurnal transpiration time, h; s is the area of the edge material in cm2Or xylem circumference, cm; f is the average value of the flow rate of the tree trunk in the growing season, kg.h-1·cm-2Or kg.h-1·cm-1。
The rainfall resource environment capacity V represents the rainfall soil storage capacity and is calculated by the following formula:
V＝asoil for soil×VDescend×104 (2)
In the formula: v is the environmental capacity of precipitation resources in kg/hm2；aSoil for soilIs the storage proportion of the atmospheric precipitation soil,%; vDescendIs the average rainfall for many years, mm;
wherein VDescendObtained by consulting local meteorological data, aSoil for soilThe method needs to be obtained by monitoring the redistribution process of atmospheric precipitation and water quantity of forest vegetation;
asoil for soil＝VSoil for soil/VGeneral assembly (3)
VSoil for soil＝VWearing device+VTree (R)-VSlope-VSoil for building (4)
VSoil for soilThe storage capacity of the soil for atmospheric precipitation is kg/hm2；VGeneral assemblyIs the atmospheric precipitation in kg/hm2；VWearing deviceIn order to pass through the rainfall by the atmospheric precipitation in kg/hm2；VTree (R)Is the trunk diameter flow of kg/hm2；VSlopeIs the slope runoff volume, kg/hm2；VSoil for buildingIs medium flow in soil, kg/hm2。
To ensure aSoil for soilThe accuracy of the measurement and calculation needs to monitor each component value of atmospheric precipitation with different intensities for at least more than 10 times, and a is takenSoil for soilIs calculated as the arithmetic mean of (1).
Volume of water consumed by under-forest evapotranspiration v1Characterizing the evapotranspiration of shrubs, herbs and soil under a forest stand, calculated from the formula:
v1＝30×T×W×104 (5)
in the formula: v. of1The water consumption of the evaporation dispersion under the forest in one growing season is kg/hm2(ii) a T is the number of months of a growing season, W is the mean evapotranspiration rate under a growing season, kg · m-2·d-1；
T, determining the month of monitoring the trunk liquid flow through a trunk liquid flow monitoring system; w was monitored using a small lysimeter and calculated from the formula:
in the formula: wiThe evaporation rate of one evaporation process, kg.m-2·d-1(ii) a i is the evapotranspiration process of each growth season, Z1Starting the weight of the soil column in the lysimeter for the primary evapotranspiration process, kg; z2The weight of the soil column in the lysimeter is kg after the primary evapotranspiration process is finished; m is the area of lysimeter, M2(ii) a D is the duration days of one evapotranspiration process, D.
Individual water consumption v of arbor species with different breast diameters2The transpiration water consumption per plant of a certain arbor species in the whole growing season under a certain breast diameter is characterized and calculated by the following formula:
v2＝30×T×t×s×F (8)
in the formula: v. of2The water consumption of each plant is kg/plant for a certain tree species in the next growing season with a certain breast diameter; t is the number of months in a growing season, T is the diurnal transpiration duration, h; s is the area of the edge material in cm2Or xylem circumference, cm; f is the average value of the flow rate of the tree trunk in the growing season, kg.h-1·cm-2Or kg.h-1·cm-1(ii) a When s is the area of the edge material (cm)2) The unit of the flow rate of the liquid flow corresponding to the trunk is kg.h-1·cm-2When s is the wood perimeter (cm) corresponding to the trunk liquid flow rate unit is kg.h-1·cm-1。
T is determined by the tree trunk flow monitoring system monitoring the months with tree trunk flow. And t, monitoring the starting time and the ending time of the liquid flow through a trunk liquid flow monitoring system, and further determining the average value of the growing season. And F, measuring by using a trunk liquid flow monitoring system, and taking the average value of the trunk liquid flow rate in daytime during the growing season. s calculating the area of the sapwood or the girth of the xylem through the breast diameter, establishing a large sample model (n is more than or equal to 50) of the breast diameter of the tree species to be measured and the area of the sapwood or the girth of the xylem, and substituting the model into the breast diameter to obtain the tree species to be measured. The application of a reasonable forest stand density model based on forest-water relations can lead the forest stand water consumption to be less than or equal to the environmental capacity of rainfall resources.
Plants with different breast diameters are selected, the breast diameters are distributed as uniformly as possible, and the large and small breast diameters are included. Measuring the chest diameter by using a girth gauge, measuring the thickness of an edge timber or the diameter of a xylem by using a growth cone, and calculating to obtain the area of the edge timber or the circumference of the xylem; establishing the correlation between the breast diameter and the area of the sapwood or the girth of the xylem, and determining the coefficient R2Should achieve a very significant correlation, R2If the calculation result is more than 0.80, the calculation result is more accurate.
The traditional density test method can only test the same breast diameter, and if the breast diameter changes, the test is needed to be carried out again for the breast diameter. The invention solves the problem of the operating density of different breast diameters of a certain tree. The traditional density test method is equivalent to a trial-and-error method, the test period is long, the test result is greatly influenced on site, and the method has no universal applicability. The invention applies basic research to production practice, aims at solving problems from the root and has higher popularization value.
The method for determining reasonable forest stand density based on forest-water relationship comprehensively considers regional rainfall resource environmental capacity and dynamic changes of transpiration water consumption of different tree species and different breast diameters from the most main limiting factor water resource of northern forest vegetation, and effectively solves the problem of reasonable management density of the whole life cycle of different tree species under the regional rainfall resource environmental capacity. Compared with the prior art experience method and different density test method, the method is more scientific, reasonable, time-saving and labor-saving. The method brings the evaporation dispersion amount into consideration, considers the water demand of the shrub and grass under the forest while considering the operating density of the trees, and reserves the water demand of the shrub and grass under the forest, so that the problem of the degradation of vegetation under the forest caused by overlarge density of the existing forest stand can be effectively solved. The method for determining the reasonable operation density of the forest stand in the whole life cycle in different areas can be provided, and the method plays an important role in improving the forest quality and the stability of a forest ecological system.
Drawings
FIG. 1 shows the water redistribution components and proportions of Chinese pine forest;
FIG. 2 is a process of evapotranspiration under pine forest;
FIG. 3 shows the daily variation of the flow rate of the pine tree trunk in different months (1);
FIG. 4 shows the daily variation of the flow rate of the pine tree trunk in different months (2);
FIG. 5 is a monthly change in the rate of fluid flow through the trunks of Pinus sylvestris;
fig. 6 is a model of the correlation between the circumference of xylem of Chinese pine and the diameter at breast height.
Detailed Description
The present invention will be described in detail with reference to the following examples and drawings. The scope of protection of the invention is not limited to the embodiments, and any modification made by those skilled in the art within the scope defined by the claims also falls within the scope of protection of the invention.
The method is applied to the national natural protection area of the Wutai mountain in Hebei province, and the forest stand type is the artificial forest of the Chinese pine. The test plots were selected on a relatively uniform typical slope with plot size 40 x 50m, altitude 1336m, north west slope, slope 14 °, and grade position. Forest stand density of 915 plants/hm 240 years old in forest, 78% of canopy density and 76% of earth surface coverage. The average diameter at breast height of Chinese pine is 17.15 + -5.58 cm, the average tree height is 9.26 + -2.42 m, and the average crown width is 4.52m × 4.12 m.
The invention relates to a method for determining reasonable forest stand density based on forest water relation, which automatically determines forest stand density by using a computer program according to the water supply and water consumption balance principle of forest trees and the environmental capacity of rainfall resources under the condition of rainfall resource supply, wherein the determination process comprises the following steps: (1) determining technical parameters, (2) establishing a reasonable forest stand density model of forest-water relationship, and (3) determining reasonable forest stand density; the technical parameters comprise: the method has the advantages of rainfall resource environment capacity V and water consumption V of evaporation dispersion under forests1And the water consumption of each plant of the arbor tree species with different breast diameters is v2The formula for calculating forest stand density based on rainfall resource environment capacity is as follows:
h is stand density, plant/hm2(ii) a V is the environmental capacity of precipitation resources in kg/hm2；v1The water consumption is kg/hm for evaporation and dispersion under the forest2，v2The water consumption of each plant of arbor species with different breast diameters is kg/plant.
(1) Determining technical parameters
Water resource environmental capacity V
V＝aSoil for soil×VDescend×104 (2)
Determining a parameter aSoil for soil、VDescend
According to the water redistribution monitoring in the Chinese pine forest in 2017-year plus 2019 years, 23 rainfalls with different intensities are counted; as the soil interflow is not monitored, the soil infiltration amount is the soil water storage amount, and as can be seen from the figure 1, the soil infiltration amount accounts for 71.84% of the total precipitation amount, and the parameter aSoil for soil＝71.84％。
Through the measurement of the annual precipitation of five small regions, the annual average precipitation is 500mm, the annual differential characteristic and the altitude differential characteristic are obvious, and the precipitation span of different ages and altitudes is 600mm, so that the parameter V is set to be 450-DescendWas determined as 450-600mm with a gradient every 50 mm.
Volume v of water consumed for evaporation under forests1
v1＝30×T×W×104 (5)
In the formula: v. of1The water consumption of the evaporation dispersion under the forest in one growing season is kg/hm2(ii) a T is the number of months of a growing season, W is the mean evapotranspiration rate under a growing season, kg · m-2·d-1。
Water consumption per plant of three arbor species with different breast diameters v2
v2＝30×T×t×s×F (8)
In the formula: v. of2The water consumption of each plant is kg/plant for a certain tree species in the next growing season with a certain breast diameter; t is a growthThe number of months of the season, t is the diurnal transpiration time, h; s is the area of the edge material in cm2Or xylem circumference, cm; f is the average value of the flow rate of the tree trunk in the growing season, kg.h-1·cm-2Or kg.h-1·cm-1(ii) a When s is the area of the edge material (cm)2) The unit of the flow rate of the liquid flow corresponding to the trunk is kg.h-1·cm-2When s is the wood perimeter (cm) corresponding to the trunk liquid flow rate unit is kg.h-1·cm-1。
Determining a parameter W
The undergrowth evapotranspiration process was monitored by placing a small lysimeter in the pine plots, see figure 2. The weight of the soil body in the evaporation and infiltration barrel is expressed as the process of circular reciprocation after the part of days rises linearly and then falls along a certain slope. When the straight line rises, the water content of the soil body in the barrel is increased when the water falls; the slope descending is caused by the reduction of the water content of the soil in the barrel due to the evaporation of the soil in the barrel and the transpiration of the vegetation in the barrel. Calculating the average evaporation intensity of 1.46 kg.m under the pine forest in the whole growing season by calculating the slope of each descending line segment and then averaging-2·d-1The parameter W is 1.46kg m-2·d-1。
Determining parameters T, T and F
Through the analysis of annual continuous observation data, the pine trunk liquid flow is started at about 4 months and 20 days, and ended at about 10 months and 21 days, wherein the time is 184 days before and after. As shown in fig. 3 and 4, most of the flow of the stem of the pinus sylvestris in the month starts at 8:00 and ends at 20:00, and the diurnal transpiration time is 12 h. The average value of the flow rate of the trunk in the growing season of the Chinese pine is 0.013 kg.h, which is a monthly change from the flow rate of the trunk in the Chinese pine shown in FIG. 4-1·cm-1. Thus, the parameters T6 months, T12 h, and F0.013 kg · h-1·cm-1。
Determining a parameter s
As shown in fig. 5, the xylem circumference s is calculated from the breast diameter by establishing a model relating the breast diameter of pinus tabulaeformis and the xylem circumference. The correlation model is that y is 2.6499x +0.3487, and the coefficient R is determined20.9792, very significant correlation was achieved; n-52 meets the requirement of a large sample model; the radial-grade span is 5-35cm, and meets the radial-grade distribution requirement. According toAnd (3) calculating the xylem perimeter s according to 5-35cm of the chest diameter of the Chinese pine and every 1cm of the Chinese pine by the aid of the Chinese pine diameter grade distribution condition included in the large sample model.
(2) Establishment of reasonable forest stand density model based on forest-water relation
The reasonable forest stand density model based on the forest-water relationship is as follows:
in the formula: h is stand density, plant/hm2；aSoil for soilIs the storage proportion of the atmospheric precipitation soil,%; vDescendIs the average rainfall for many years, mm; t is the number of growing months; w is the evaporation rate under forest, kg.m-2·d-1(ii) a t is the diurnal transpiration time, h; s is the area of the edge material in cm2Or xylem circumference, cm; f is the average value of the flow rate of the tree trunk in the growing season, kg.h-1·cm-2Or kg.h-1·cm-1。
(3) Determining reasonable stand density based on forest-water relationship
Substituting the parameters in the step (1) into a reasonable forest stand density model based on forest-water relation in the step (2) for calculation, wherein the parameter aSoil for soil＝71.84％；VDescendCalculating according to the gradient of 450-600mm and every 50 mm; w is 1.46kg m-2·d-1T is 6 months, T is 12h, and F is 0.013kg · h-1·cm-1(ii) a And s, solving the chest diameter according to the introduction of the model related to the girth and the chest diameter of the xylem, wherein the chest diameter is calculated according to 5-35cm and every 1cm in a gradient manner. The calculation results are shown in Table 1.
As can be seen from table 1, forest density control follows two basic rules, one is that as rainfall increases, forest stand density exhibits a significant increase rule; secondly, as the breast diameter increases, the stand density appears to decrease significantly. Mainly by water resource bearing capacity and forest water consumption law decision, rainfall increases the corresponding increase of water resource bearing capacity, and the forest vegetation forest quantity that can bear increases naturally. The breast height of the trees is increased, the water consumption of the single tree is correspondingly increased, and the number of the trees capable of being borne under the condition of certain water resource bearing capacity is naturally reduced.
The average rainfall of five small areas is about 500mm in many years, and the average rainfall can reach 600mm in individual places. The density can reach 1279 strains/hm when the diameter of the pine is 10cm under 500mm rainfall2856 strain/hm density at breast diameter of 15cm2And the density is 644 strains/hm at the breast diameter of 20cm2Only 430 plants per hectare can be reserved when the breast diameter is 30 cm. It can be seen that the density of the forest stand decreases rapidly along with the increase of the breast diameter, so that intermediate cutting operation can be properly carried out when the breast diameter is increased to a certain degree, so as to control the density of the forest stand to reach the proper density standard.
TABLE 1 operating density meter for different diameter levels of pinus sylvestris under different rainfall conditions
Claims (7)
1. A method for determining reasonable forest stand density based on forest-water relation is characterized by comprising the following steps: under the condition of rainfall resource supply, automatically determining forest stand density by using a computer program according to the environmental capacity of the rainfall resource, wherein the determination process comprises the following steps: (1) determining technical parameters, (2) establishing a reasonable forest stand density model of the forest-water relationship; (3) determining reasonable forest stand density; the technical parameters comprise: the method has the advantages of rainfall resource environment capacity V and water consumption V of evaporation dispersion under forests1And the water consumption of each plant of the arbor tree species with different breast diameters is v2And the reasonable forest stand density model of the forest-water relation is as follows:
in the formula: h is stand density, plant/hm2；aSoil for soilIs the storage proportion of the atmospheric precipitation soil,%; vDescendIs the average rainfall for many years, mm; t is growing seasonThe number of months; w is the evaporation rate under forest, kg.m-2·d-1(ii) a t is the diurnal transpiration time, h; s is the area of the edge material in cm2Or xylem circumference, cm; f is the average value of the flow rate of the tree trunk in the growing season, kg.h-1·cm-2Or kg.h-1·cm-1。
2. The method of claim 1, wherein the method comprises: the rainfall resource environment capacity V represents the rainfall soil storage capacity and is calculated by the following formula:
V＝asoil for soil×VDescend×104 (2)
In the formula: v is the environmental capacity of precipitation resources in kg/hm2；aSoil for soilIs the storage proportion of the atmospheric precipitation soil,%; vDescendIs the average rainfall for many years, mm;
wherein VDescendObtained by consulting local meteorological data, aSoil for soilThe method needs to be obtained by monitoring the redistribution process of atmospheric precipitation and water quantity of forest vegetation;
asoil for soil＝VSoil for soil/VGeneral assembly (3)
VSoil for soil＝VWearing device+VTree (R)-VSlope-VSoil for building (4)
VSoil for soilThe storage capacity of the soil for atmospheric precipitation is kg/hm2；VGeneral assemblyIs the atmospheric precipitation in kg/hm2；VWearing deviceIn order to pass through the rainfall by the atmospheric precipitation in kg/hm2；VTree (R)Is the trunk diameter flow of kg/hm2；VSlopeIs the slope runoff volume, kg/hm2；VSoil for buildingIs medium flow in soil, kg/hm2。
3. The method of claim 1, wherein the method comprises: the volume of water consumed by the under forest evapotranspiration v1Characterizing the evapotranspiration of shrubs, herbs and soil under a forest stand, calculated from the formula:
v1＝30×T×W×104 (5)
in the formula: v. of1The water consumption of the evaporation dispersion under the forest in one growing season is kg/hm2(ii) a T is the number of months of a growing season, W is the mean evapotranspiration rate under a growing season, kg · m-2·d-1；
The T is determined by monitoring the months with the trunk liquid flow through a trunk liquid flow monitoring system; w was monitored using a small lysimeter and calculated from the formula:
in the formula: wiThe evaporation rate of one evaporation process, kg.m-2·d-1(ii) a i is the evapotranspiration process of each growth season, Z1Starting the weight of the soil column in the lysimeter for the primary evapotranspiration process, kg; z2The weight of the soil column in the lysimeter is kg after the primary evapotranspiration process is finished; m is the area of lysimeter, M2(ii) a D is the duration days of one evapotranspiration process, D.
4. The method of claim 1, wherein the method comprises: the water consumption of the arbor species with different breast diameters per plant v2The transpiration water consumption per plant of a certain arbor species in the whole growing season under a certain breast diameter is characterized and calculated by the following formula:
v2＝30×T×t×s×F (8)
in the formula: v. of2The water consumption of each plant is kg/plant for a certain tree species in the next growing season with a certain breast diameter; t is the number of months in a growing season, T is the diurnal transpiration duration, h; s is the area of the edge material in cm2Or xylem circumference, cm; f is the average value of the flow rate of the tree trunk in the growing season, kg.h-1·cm-2Or kg.h-1·cm-1(ii) a When s is the area correspondence of the sapwoodThe flow rate of the trunk liquid is kg.h-1·cm-2When s is the wood perimeter and the trunk liquid flow rate unit is kg.h-1·cm-1。
5. The method of claim 4, wherein the method comprises: the T is determined by monitoring the months with the trunk liquid flow through a trunk liquid flow monitoring system; the t is monitored for the starting time and the ending time of the liquid flow through a trunk liquid flow monitoring system, and then the average value of the growing season is taken for determination; and F, measuring by using a trunk liquid flow monitoring system, and taking the average value of the trunk liquid flow rate in daytime during the growing season.
6. The method of claim 4, wherein the method comprises: and (5) calculating the area of the sapwood or the girth of the xylem through the breast diameter, establishing a large sample model of the breast diameter of the tree species to be measured and the area of the sapwood or the girth of the xylem, and substituting the model into the breast diameter to obtain the tree species to be measured.
7. The method of claim 1, wherein the method comprises: the application of the reasonable forest stand density model based on the forest-water relationship can enable the forest stand water consumption to be less than or equal to the rainfall resource environment capacity.
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