A method for evaluating water conservation function of semi-arid wetland by using root system characteristics

Abstract

The application discloses a method for evaluating water source conservation function of a semi-arid wetland by using root system characteristics, comprising root system layered sampling and characteristic quantification, soil suitability index determination and water source conservation quantity calculation, and solves the quantitative evaluation problem in the ecological hydrology field, reduces the survey and monitoring cost and result error by establishing a fine root volume as a key index and constructing an empirical formula for calculating the water source conservation quantity, and provides a standardized method for evaluating the water source conservation function of the semi-arid wetland by quantifying the fine root volume proportion, soil pore parameters and organic matter content.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wetland ecological restoration, in particular to a method for evaluating water conservation function of semi-arid wetland by using root traits. BACKGROUND

[0002] Wetlands in semi-arid regions carry 80% of the species diversity. For example, the Momoge Wetland in the western semi-arid region of the Songnen Plain, as a key node for the migration of East Asian migratory birds, shelters more than 200 species of rare birds such as white cranes every year, and their breeding success rate directly depends on the food chain foundation provided by the wetland. Although the semi-arid region has a limited area, the soil organic carbon density of the wetland is as high as 3 times that of the forest (average 200 t / ha). The carbon sequestration of semi-arid wetlands accounts for 15% of the global inland wetlands, making a significant contribution to offsetting regional carbon emissions. In addition, the degradation of the water conservation function of semi-arid wetlands, as the core water resource regulator of the ecological fragile belt, is triggering a chain ecological crisis. The wetland area of the Songnen Plain has decreased by 42% in the past three decades, and the imbalance pattern of the annual evaporation (1472 mm) far exceeding the precipitation (392 mm) aggravates the regional water crisis; the existing evaluation technology has a fundamental defect - the traditional hydrological model relies on long-term flow monitoring (cost > 200,000 yuan / site) and ignores the key role of plant roots, and the empirical vegetation restoration scheme has a high failure rate due to the neglect of the functional differences between species (for example, the soil water holding capacity decreases by 28% after reed planting). More seriously, existing researches focus on aboveground biomass or single soil indicators, and fail to break the mutual feedback mechanism of "root-soil-hydrology": although it is known that capillary porosity is related to water holding capacity, the synergistic effect of soil organic matter, fine sand content and other parameters has not been quantified; although it has been confirmed that roots affect soil structure, it is still unclear which root type (diameter, volume) dominates the conservation function, and it is urgent to build a causal chain of "root trait-soil structure-water holding efficiency". The present application aims to solve the problems of "blind species selection and delayed effectiveness evaluation" in semi-arid wetland restoration, and to develop a standardized process that can be quickly detected, to realize the millimeter-level quantitative output of water conservation capacity through a root-soil double-parameter coupling model, and to provide a technical engine for precise restoration of degraded wetlands. SUMMARY

[0003] Therefore, the present application provides a standardized method for evaluating the water conservation function of semi-arid wetlands by quantifying the proportion of fine root volume, soil porosity parameters and organic matter content.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] A method for evaluating the water conservation function of semi-arid wetlands by using root traits, comprising the following steps:

[0006] Step 1: Diagnosis and classification of soil water conservation basic capacity

[0007] Determination of soil capillary porosity CP, organic matter content SOM and fine sand content VFS of particle size 0.05-0.1mm, calculate soil suitability index SSI, formula as follows:

[0008] SSI = 0.5 × (CP / CP ref ) + 0.3 × (SOM / SOM ref ) + 0.2 × (1-VFS / VFS ref )

[0009] Wherein, CP ref = 60%, SOM ref = 10%, VFS ref = 20% ;

[0010] Step two: soil suitability index determination

[0011] According to the determination results of step one, the soil suitability index is determined, specifically:

[0012] SSI≥0.8: high water conservation potential soil, soil body function is good, no need to improve;

[0013] 0.6 ≤ SSI < 0.8: medium potential soil, soil has certain natural recovery potential, can be self-improved by vegetation recovery;

[0014] SSI < 0.6: low potential soil, poor water conservation capacity, need to be improved artificially and configure specific plants for ecological restoration;

[0015] Step three: plant root functional traits quantification

[0016] According to the determination results of step two, set quadrats in the diagnosed sample plot, collect 0-30 cm soil layer root samples, measure total root volume and fine root volume, and calculate fine root volume ratio FRVR.

[0017] Step four: comprehensive water conservation capacity calculation of soil-plant system

[0018] According to the calculation results of steps one to three, the comprehensive water conservation capacity of soil-plant system is calculated, specifically:

[0019] WCC= SSI×100 + (15×FRVR+10×CP+ 5×SOM)

[0020] Wherein, WCC is water conservation capacity, mm;

[0021] Wherein, formula theoretical explanation and coefficient source:

[0022] SSI x 100: As a base term, the dimensionless suitability index is converted into a water storage (mm) dimension with practical hydrological significance. The coefficient 100 represents that under the ideal state defined in the present application (SSI = 1), the soil body can provide a 100 mm standard of water conservation capacity;

[0023] (15 x FRVR + 10 x Capillary Porosity + 5 x Organic Matter Content): As an enhancement term, it quantifies the improvement range of the plant root system and its improvement on the base water conservation capacity;

[0024] Fine root volume ratio (FRVR): The coefficient is the largest (15), because living fine roots are the most important and active factors in forming new pores (especially biological pores) and secreting organic cementing substances, and their contribution weight is the highest;

[0025] Capillary porosity: The coefficient is 10, representing the soil water-holding pore condition maintained by the joint action of roots and organic matter;

[0026] Organic matter content: The coefficient is 5, which mainly plays a role in cementing aggregates and stabilizing pores. Its direct water-holding capacity has been partially reflected in the base term, so its weight in the enhancement term is lower;

[0027] The coefficient acquisition process is as follows:

[0028] Data collection: In the study area, select wetland samples under various vegetation covers, and simultaneously measure FRVR, CP, SOM, and actual soil maximum water holding capacity (Measured Water Holding Capacity, WHC_meas) (using the ring method, which is the national standard method);

[0029] Enhancement amount calculation: Calculate the difference between WHC_meas and (SSI x WCC_ref) for each sample, denoted as ΔWCC (enhanced water conservation), which is the excess gain brought by the action of vegetation roots;

[0030] Regression analysis: Take ΔWCC as the dependent variable and FRVR, CP, and SOM as the independent variables to perform multiple linear regression analysis (ΔWCC = α*FRVR + β*CP + γ*SOM + ε).

[0031] Coefficient determination: The standardized coefficients obtained by regression analysis reflect the relative contribution weight of each factor to ΔWCC. After normalization and regional adaptability adjustment, the final coefficients α, β, and γ are 15, 10, and 5, respectively.

[0032] Correlation evidence (proving the rationality of the formula factors and the reliability of the coefficient relationship):

[0033] The fine root volume ratio is significantly positively correlated with capillary porosity (r=0.546, p<0.01);

[0034] The fine root volume is extremely significantly positively correlated with organic matter content (r=0.606, p<0.001);

[0035] The very fine sand content is significantly negatively correlated with capillary porosity (r=-0.716, p<0.01).

[0036] Preferably, the capillary porosity in step one is the volume ratio of pores with a diameter of 0.002-0.05 mm.

[0037] Preferably, the capillary porosity in step one is measured by the immersion method specified in the national standard LY / T 1215-1999, the organic matter content is measured by the potassium dichromate oxidation method specified in the national standard GB 9834-88, and the very fine sand content is measured by a laser particle size instrument.

[0038] Preferably, the sample area in step three is 1m x 1m, and the fine root diameter is 0-2 mm.

[0039] Preferably, when the fine root volume ratio FRVR is greater than or equal to 20% in step three, it is considered that the improvement effect of the vegetation on the soil begins to be significantly apparent.

[0040] According to the technical solution, compared with the prior art, the method for evaluating the water conservation function of a semi-arid region wetland by using plant root system characteristics is provided, and has the following beneficial effects:

[0041] The core value of the application lies in solving the quantitative evaluation problem in the field of ecological hydrology. By establishing fine root volume as a key indicator and constructing an empirical formula for calculating water conservation capacity, the traditional time-consuming one-year hydrological monitoring is compressed into 3-day laboratory analysis, with a cost reduction of 90% and an error of less than 5%. The application first proposes rapid discrimination thresholds of fine root volume ratio ≥20% and soil suitability index ≥0.8. The technology has both scientificity and engineering practicability. On the scientific level, it reveals the shaping mechanism of root system morphology on soil pore structure, and promotes the cross-fusion of plant functional ecology and hydrology. On the application level, it forms a "sampling-detection-decision" closed-loop toolkit, which can guide the precise allocation of species resources in wetland restoration engineering and avoid the waste of funds caused by blind repair. On the ecological level, it enhances the water conservation capacity and regional drought resistance, and helps to achieve the goals of carbon neutralization and biodiversity protection in semi-arid regions. DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0043] Embodiment 1

[0044] Evaluation of water conservation function of Momoge wetland in semi-arid region of Songnen Plain:

[0045] The Momoge wetland in semi-arid region of Songnen Plain includes a small leaf chapter wetland and a gray vein sedge wetland, and the specific determination process is as follows:

[0046] Step one: soil determination

[0047] Key parameters:

[0048] Capillary porosity (CP): usually refers to the capillary porosity of soil (unit: %), representing the water retention capacity of soil, and is determined by soaking method (national standard LY / T 1215-1999);

[0049] Organic matter content: the content of organic matter in soil (unit: g / kg), reflecting soil fertility and structural stability, and is determined by potassium dichromate oxidation method (national standard GB 9834-88);

[0050] Fine sand content: the proportion of very fine sand particles in soil (unit: % or weight ratio), affecting the water and fertilizer retention capacity of soil, and is determined by laser particle size instrument (particle size 0.05-0.1mm particle proportion);

[0051] Determination results:

[0052] Small leaf chapter wetland: capillary porosity = 59.71%, organic matter content = 88.2 g / kg; fine sand content = 10.16%;

[0053] Gray vein sedge wetland: capillary porosity = 46.31%, organic matter content = 64.5 g / kg; fine sand content = 11.53%;

[0054] Reed wetland: capillary porosity = 38.34%, organic matter content = 32.1 g / kg; fine sand content = 19.32%;

[0055] Soil suitability index (SSI) = 0.5 × (CP / CP ref ) + 0.3 × (SOM / SOM ref ) + 0.2 ×(1-VFS / VFS ref );

[0056] SSI≥0.8: high water conservation potential soil (e.g. Carex meyeriana wetland index 0.86);

[0057] 0.6 ≤ SSI < 0.8: medium potential soil (e.g. Carex grayi wetland index 0.66);

[0058] SSI < 0.6: needs improvement (e.g. Phragmites australis wetland index 0.42);

[0059] Step two: root layer sampling and trait quantification

[0060] Set 1m x 1m quadrats in the target wetland, collect 0-30cm layer roots, use root analysis system (WinRHIZO) to measure total root volume (cm3) and fine root volume ratio (diameter 0-2mm root volume / total root volume), threshold value: fine root volume ratio ≥20%;

[0061] Measurement results:

[0062] Carex meyeriana wetland: fine root volume ratio = 27.7%;

[0063] Carex grayi wetland: fine root volume = 9.4%;

[0064] Phragmites australis wetland: fine root volume = 5.6%

[0065] Step three: comprehensive water conservation capacity calculation of soil-plant system

[0066] Water conservation capacity (WCC, mm) = SSI x 100 + (15 x fine root volume ratio (FRVR) + 10 x capillary porosity + 5 x organic matter content);

[0067] Among them, SSI x 100: is the basic item. The dimensionless suitability index is converted into the water storage capacity (mm) dimension with practical hydrological significance. The coefficient 100 represents that under the ideal state defined in the present application (SSI = 1), the soil body can provide a water conservation capacity benchmark of 100mm.

[0068] Calculation results:

[0069] Carex meyeriana wetland = 96.6mm;

[0070] Carex grayi wetland = 72.4mm.

[0071] Phragmites australis wetland = 46.8mm.

[0072] Actual verification:

[0073] The measured water holding capacity of the Carex leschiana wetland is 93.2 mm, the water holding capacity of the Carex atro-punctata wetland is 69.8 mm, and the water holding capacity of the reed wetland is 45.2 mm, and the errors are all less than 5%, which proves that the formula is reliable.

[0074] The present application has significant value in terms of accuracy of technical implementation, operation cost, etc.

[0075] The present application has significant value in terms of accuracy of technical implementation, operation cost, etc.

[0076] Evaluation metrics Traditional method (only looking at vegetation cover) Invention method Accuracy Misclassification rate > 35% (e.g. high cover of reed wetlands but low water retention) Error < 5% (root-soil two-parameter calibration) Operational cost Long-term hydrological monitoring required (> 1 year) Field sampling + 3-day laboratory determination Guidance value Qualitative description "high / medium / low" Quantitative output of water retention (mm value)

[0077] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the various embodiments can be mutually referred to. The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for assessing the water conservation function of semi-arid wetlands using root traits, characterized in that, Includes the following steps: Step 1: Diagnosis and Grading of Soil's Basic Water Conservation Capacity The soil capillary porosity (CP), organic matter content (SOM), and ultrafine sand content (VFS) with a particle size of 0.05-0.1 mm were measured, and the soil suitability index (SSI) was calculated using the following formula: SSI = 0.5 × (CP / CP ref ) + 0.3 × (SOM / SOM ref ) + 0.2 × (1-VFS / VFS ref ) Among them, CP ref = 60%, SOM ref = 10%, VFS ref = 20%; Step 2: Soil Suitability Index Determination Based on the measurement results of step one, the soil suitability index is determined, specifically as follows: SSI≥0.8: Soil with high water conservation potential; 0.6 ≤ SSI < 0.8: Soil with medium water conservation potential; SSI < 0.6: Soils with low water conservation potential; Step 3: Quantification of functional traits of plant roots Based on the judgment results of step two, quadrats were set up in the plots where the diagnosis had been completed, and root samples were collected from the 0-30 cm soil layer. The total root volume and fine root volume were measured, and the fine root volume ratio (FRVR) was calculated. Step 4: Calculation of the integrated water conservation capacity of the soil-plant system Based on the calculation results of steps one through three, the comprehensive water conservation capacity of the soil-plant system is calculated as follows: WCC= SSI×100 + (15×FRVR+10×CP+ 5×SOM) Where WCC represents water conservation capacity, in mm.

2. The method for assessing the water conservation function of semi-arid wetlands using root traits according to claim 1, characterized in that, The capillary porosity mentioned in step one refers to the pore volume ratio with a diameter of 0.002-0.05 mm.

3. The method for assessing the water conservation function of semi-arid wetlands using root traits according to claim 1, characterized in that, In step one, the capillary porosity was determined by the immersion method specified in the national standard LY / T 1215-1999, the organic matter content was determined by the potassium dichromate oxidation method specified in the national standard GB 9834-88, and the ultrafine sand content was determined by a laser particle size analyzer.

4. The method for evaluating the water conservation function of semi-arid wetlands using root traits according to claim 1, characterized in that, The area of ​​the quadrat in step three is 1m × 1m, and the diameter of the fine roots is 0-2mm.

5. The method for evaluating the water conservation function of semi-arid wetlands using root traits according to claim 1, characterized in that, When the fine root volume ratio (FRVR) in step three is ≥20%, the soil-improving effect of vegetation is considered to begin to show significant characteristics.