Method for identifying influence of grassland vegetation root system on slope runoff production
Technical Field
The invention relates to the technical field of hydrology and water resources, in particular to a method for identifying influence of grass land vegetation root systems on slope runoff production.
Background
The global land surface area affected by changes in grass vegetation coverage is greatest and is therefore closely related to ecosystem health levels. Unreasonable grass vegetation coverage directly causes a decrease in the quantity and quality of grass vegetation, and furthermore, problems such as climatic, hydrological and geological disasters also emerge endlessly due to changes in the underlying surface. The reduction of the quantity and quality of the surface vegetation causes the unbalance of the global climate system, accelerates the destruction of other biological habitats and reduces the biodiversity.
The grassland vegetation keeps water and soil, preserves water resources and improves soil fertility through the interception of leaf surfaces and the consolidation of plant roots to soil. Earlier researches show that the higher the grassland vegetation coverage, the better the effect of the grassland vegetation in preventing and controlling water loss and soil erosion.
The capability of the grassland vegetation in unit area for fixing soil and retaining water is generally divided into two parts, namely, the interception of the leaves on the grassland vegetation to precipitation; secondly, the consolidation of the grassland vegetation underground root system to the soil. For the interception effect of the leaf surface part of the grassland vegetation on the rainfall, the leaf area size can be calculated by methods such as leaf area index and the like, and the interception capacity of the grassland vegetation on the rainfall is estimated. However, relatively little research has been done on the consolidation of portions of the subterranean root system. The biomass size of the root system can represent the density degree of the root system to a certain extent, and the density degree of the root system is closely related to the consolidation of the root system and the soil crust.
By quantitatively estimating the underground biomass of the grassland vegetation, the method has clear understanding on runoff production in the slope environment, can provide theoretical basis for the slope runoff production and confluence process, corresponding water resource change and management, flood prevention and the like, and is of great importance for understanding of the movement of the runoff in the slope and slope hydrological research such as the distribution of slope soil water. Therefore, quantitative evaluation of the influence of the grassland vegetation root system on the slope runoff is very important.
Disclosure of Invention
The invention aims to provide a method for identifying influence of grassland vegetation root systems on slope runoff production.
In order to solve the technical problem, the invention provides a method for identifying the influence of the grass land vegetation root system on the slope runoff yield, which comprises the following steps:
(1) analyzing the grassland vegetation in the research area to obtain N types of grassland vegetation and the respective areas Ai(i=1,2,…,N);
(2) Respectively selecting representative experimental sample plots aiming at the N grassland vegetation types, and sampling to obtain the aboveground biomass (S) of the grassland vegetationi) And the biomass (S) of the underground part of the grassland vegetationi') calculating the ratio (P) of the aboveground-underground biomass of different grassland vegetationi);
(3) According to the ratio (P) of aboveground-underground biomass of different grassland vegetationi) And different grassland vegetation type areas (A)i) Obtaining the comprehensive ratio (P) of the overground biomass to the underground biomass of the grassland vegetation;
(4) obtaining the biomass (S) of the overground part of the grassland vegetation in the research area obtained by inversion;
(5) obtaining the biomass (S') of the underground part of the grassland vegetation in the research area according to the comprehensive ratio (P) of the aboveground biomass to the underground biomass of the grassland vegetation in the research area obtained by inversion and the biomass (S) of the aboveground part of the grassland vegetation in the research area obtained by inversion;
(6) obtaining runoff production data of a research area;
(7) the influence of the grassland vegetation root system on the slope runoff is quantitatively identified by constructing the relationship between the biomass (S') of the underground part of the grassland vegetation in the research area and the runoff.
In a preferred embodiment, in the step (1), the N types of vegetation are obtained by processing and analyzing remote sensing image data of a research area. In an alternative embodiment, in step (1), the N types of vegetation are obtained from a multi-characteristic spectral band.
In a preferred embodiment, in the step (2), when representative experimental plots are respectively selected, the experimental plots refer to experimental grassland vegetation fields with representative meanings in the research area, five points are selected in a 10m by 10m sample square, and the area of each plot is respectively sampled by 1m according to the grassland sampling standard.
In a preferred embodiment, in the step (2), the ratio (P) of aboveground-underground biomass of the different grass vegetation isi) The biomass (S) of the overground part of the grassland vegetation is collected through experimentsi) And the underground part of the grassland vegetation is biomass (S)i') numberAccording to the result, the calculation formula is as follows: pi=f(Si,Si′),f(Si,Si') is PiAnd SiAnd Si' statistical relationship between.
In a preferred embodiment, in the step (3), the above-ground-to-underground biomass comprehensive ratio (P) of the grassy vegetation is calculated by the formula:
in a preferred embodiment, in the step (4), data are acquired by using a remote sensing technology, and then biomass (S) of the overground part of the grassland vegetation of the research area obtained by inversion is obtained by an inversion method, and a calculation formula is as follows:
s is biomass of the overground part of grassland vegetation in the research area obtained by inversion, NDVI is a normalized vegetation index, and NIR and R are reflectance values at a near infrared band and a red band respectively; (NDVI) is the statistical relationship between S and NDVI.
In a preferred embodiment, in the step (5), the calculation formula of the underground biomass (S') of the grassland vegetation in the research area according to the above-ground biomass comprehensive ratio (P) of the grassland vegetation and the above-ground biomass (S) of the grassland vegetation in the research area obtained by the inversion is as follows:
in a preferred embodiment, in the step (6), regarding the runoff data of the research area, for the research area with hydrologic monitoring sites at the outlet of the drainage basin, the real-scale runoff data is directly adopted, if the water balance formula calculation or the distributed hydrologic model simulation is not adopted.
In a preferred embodiment, in the step (7), the relationship between the biomass of the vegetation root and the runoff yield is specifically calculated as:
R=f(S'),
s ' is the biomass of the underground part of the grassland vegetation in the research area, R is the yield, and f (S ') is the statistical relationship between S ' and R.
The above mentioned statistical relationship may be linear, exponential or a unitary quadratic fit.
According to the method for identifying the influence of the grassland vegetation root system on the slope runoff yield, the underground biomass of the grassland vegetation is quantitatively estimated, and theoretical basis is provided for the slope runoff yield and confluence process, corresponding water resource change and management, flood prevention and the like.
Drawings
Some example embodiments of the invention will be described more fully hereinafter with reference to the accompanying drawings; this invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, the drawings illustrate some example embodiments of the invention, together with the description, and serve to explain the principles and aspects of the invention.
FIG. 1 is a flow chart of a method for identifying the influence of the root system of vegetation in a grassland on the runoff yield of a slope according to the invention.
Detailed Description
In the following detailed description, certain exemplary embodiments of the present invention are shown and described, simply by way of illustration. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
Hereinafter, a method for identifying the influence of the roots of the grassland vegetation on the runoff yield of the slope according to the present invention will be described in more detail with reference to the accompanying drawings.
As shown in fig. 1, the invention provides a method for identifying influence of grass land vegetation root systems on slope runoff production, which comprises the following steps:
(1) analyzing the grassland vegetation in the research area to obtain N types of grassland vegetation and the respective areas Ai(i=1,2,…,N);
(2) Respectively selecting representative experimental sample plots aiming at the N grassland vegetation types, and sampling to obtain the aboveground biomass (S) of the grassland vegetationi) And the biomass (S) of the underground part of the grassland vegetationi') calculating the ratio (P) of the aboveground-underground biomass of different grassland vegetationi);
(3) According to the ratio (P) of aboveground-underground biomass of different grassland vegetationi) And different grassland vegetation type areas (A)i) Obtaining the comprehensive ratio (P) of the overground biomass to the underground biomass of the grassland vegetation;
(4) obtaining the biomass (S) of the overground part of the grassland vegetation in the research area obtained by inversion;
(5) obtaining the biomass (S') of the underground part of the grassland vegetation in the research area according to the comprehensive ratio (P) of the aboveground biomass to the underground biomass of the grassland vegetation in the research area obtained by inversion and the biomass (S) of the aboveground part of the grassland vegetation in the research area obtained by inversion;
(6) obtaining runoff production data of a research area;
(7) the influence of the grassland vegetation root system on the slope runoff is quantitatively identified by constructing the relationship between the biomass (S') of the underground part of the grassland vegetation in the research area and the runoff.
In a preferred embodiment, in the step (1), the N types of vegetation are obtained by processing and analyzing remote sensing image data of a research area. In an alternative embodiment, in step (1), the N types of vegetation are obtained from a multi-characteristic spectral band.
In a preferred embodiment, in the step (2), when representative experimental plots are respectively selected, the experimental plots refer to experimental grassland vegetation fields with representative meanings in the research area, five points are selected in a 10m by 10m sample square, and the area of each plot is respectively sampled by 1m according to the grassland sampling standard.
In a preferred embodiment, in the step (2), the ratio (P) of aboveground-underground biomass of the different grass vegetation isi) The biomass (S) of the overground part of the grassland vegetation is collected through experimentsi) And the underground part of the grassland vegetationQuantity (S)i') data, the calculation formula is: pi=f(Si,Si′),f(Si,Si') is PiAnd SiAnd Si' statistical relationship between.
In a preferred embodiment, in the step (3), the above-ground-to-underground biomass comprehensive ratio (P) of the grassy vegetation is calculated by the formula:
in a preferred embodiment, in the step (4), data are acquired by using a remote sensing technology, and then biomass (S) of the overground part of the grassland vegetation of the research area obtained by inversion is obtained by an inversion method, and a calculation formula is as follows:
s is biomass of the overground part of grassland vegetation in the research area obtained by inversion, NDVI is a normalized vegetation index, and NIR and R are reflectance values at a near infrared band and a red band respectively; (NDVI) is the statistical relationship between S and NDVI.
In a preferred embodiment, in the step (5), the calculation formula of the underground biomass (S') of the grassland vegetation in the research area according to the above-ground biomass comprehensive ratio (P) of the grassland vegetation and the above-ground biomass (S) of the grassland vegetation in the research area obtained by the inversion is as follows:
in a preferred embodiment, in the step (6), regarding the runoff data of the research area, for the research area with hydrologic monitoring sites at the outlet of the drainage basin, the real-scale runoff data is directly adopted, if the water balance formula calculation or the distributed hydrologic model simulation is not adopted.
In a preferred embodiment, in the step (7), the relationship between the biomass of the vegetation root and the runoff yield is specifically calculated as:
R=f(S'),
s ' is the biomass of the underground part of the grassland vegetation in the research area, R is the yield, and f (S ') is the statistical relationship between S ' and R.
The above mentioned statistical relationship may be linear, exponential or a unitary quadratic fit.
According to the method for identifying the influence of the grassland vegetation root system on the slope runoff yield, the underground biomass of the grassland vegetation is quantitatively estimated, and theoretical basis is provided for the slope runoff yield and confluence process, corresponding water resource change and management, flood prevention and the like.