Method for determining ecological hydrological threshold value of key hygrophytes of dished lake

Abstract

The invention discloses a method for determining an ecological hydrological threshold value of key hygrophytes of a butterfly-shaped lake. The method comprises the following steps: constructing a test device near the butterfly-shaped lake; healthy seedlings of key hygrophytes are collected in a butterfly lake area, and the seedlings are transplanted into a planting barrel filled with in-situ soil for pre-culture; a plurality of flooding simulation scenes are set, simulation tests of the flooding simulation scenes are carried out respectively, and growth parameter data of key hygrophytes in the flooding simulation scenes are measured; according to the measured growth parameter data, respectively performing polynomial fitting on the flooding depth and the flooding duration with each growth parameter; and according to the polynomial fitting equation, determining the appropriate flooding depth and the appropriate flooding duration of the key hygrophytes. According to the method, the ecological hydrological threshold value of the key hygrophytes of the dish-shaped lake is determined, and the influence rule of the hydrological rhythm on the growth and development of the hygrophytes of the dish-shaped lake is quantified, so that a scientific support is provided for biodiversity protection and ecological environment restoration of a dish-shaped lake region.

Description

Technical Field

[0001] This application belongs to the technical field of wetland plant ecological research, and specifically relates to a method for determining the ecological hydrological thresholds of key hygrophytic plants in dish-shaped lakes. Background Art

[0002] Dish-shaped lakes are lakes exposed between sandbanks. Seasonal changes in wetland water levels can cause the sandbanks to alternate between dry and wet, which in turn leads to significant differences in aquatic plant communities in different seasons. During the dry season, the sandbanks are exposed above the water surface, and a hygrophytic plant community dominated by Carex and an emergent plant community dominated by Phragmites australis appear. During the wet season, the hygrophytic plant community and the emergent plant community disappear as the sandbanks are flooded, and a submerged plant community dominated by Potamogeton malaianus, Vallisneria natans, and Hydrilla verticillata is formed.

[0003] The structure and spatial pattern of lake wetland vegetation are jointly affected by the external environment and the biological characteristics of the vegetation species themselves. Water regime factors such as water level, flood frequency, submergence depth, and submergence duration are the main driving forces for wetland vegetation succession. Different plant communities respond differently to water regime factors. In particular, different plant communities have formed their own unique ecological adaptation strategies to different hydrological rhythms during their growth and development processes.

[0004] Since 2003, due to the impoundment operation of reservoirs in the upper reaches of the Yangtze River and the discharge of clear water, the riverbed of the main stream of the Yangtze River has been severely scoured. The water levels of lakes in the middle and lower reaches of the Yangtze River have continued to be low and dry, the dry season has advanced and prolonged, and the low water level has become lower. As a result, the species and quantity of submerged plants have decreased, while hygrophytic plants tend to move towards the center of the lake and increase in distribution. Especially for dish-shaped lakes in the middle and lower reaches of the Yangtze River, due to their typical rising and falling water processes and the sensitivity of hygrophytic plant communities to such hydrological changes, it is necessary to study the influence law of hydrological rhythms on the growth and development of key hygrophytic plants in dish-shaped lakes, so as to provide theoretical support for wetland biodiversity protection and ecological environment restoration. Summary of the Invention

[0005] The purpose of this application is to provide a method for determining the ecological hydrological thresholds of key hygrophytic plants in dish-shaped lakes. This application studies and quantifies the influence law of hydrological rhythms on the growth and development of key hygrophytic plants in dish-shaped lakes, and provides more scientific theoretical support for wetland biodiversity protection and ecological environment restoration.

[0006] A method for determining the ecological hydrological thresholds of key hygrophytic plants in dish-shaped lakes provided by this application, which is used to determine the suitable submergence depth and suitable submergence duration of key hygrophytic plants, includes the steps of:

[0007] Build a test device near the dish-shaped lake. The test device includes a container;

[0008] Collect healthy seedlings of key hygrophytic plants in the Butterfly Lake area with consistent seedling heights, transplant the seedlings into planting buckets filled with in-situ soil, and pre-culture them for 7d - 15d;

[0009] Set up multiple flooding simulation scenarios, where one flooding simulation scenario corresponds to a combination of a flooding depth experimental value and a flooding duration node. Conduct simulation tests for each flooding simulation scenario, including: introducing the water body of the Butterfly Lake into a container, hanging the planting bucket in the container and making the flooding depth of the key hygrophytic plants reach the flooding depth experimental value corresponding to the flooding simulation scenario. When the flooding duration node corresponding to the flooding simulation scenario is reached, take out the planting bucket and measure the growth parameter data of the key hygrophytic plants;

[0010] According to the growth parameter data, perform polynomial fitting of the flooding depth and flooding duration with each growth parameter respectively;

[0011] Determine the suitable flooding depth corresponding to the growth parameter according to the polynomial fitting equation of the growth parameter and the flooding depth, and take the intersection of the suitable flooding depths of all growth parameters, which is the suitable flooding depth of the key hygrophytic plants; determine the suitable flooding duration corresponding to the growth parameter according to the polynomial fitting equation of the growth parameter and the flooding duration, and take the intersection of the suitable flooding durations of all growth parameters, which is the suitable flooding duration of the key hygrophytic plants;

[0012] Among them, to determine the suitable flooding depth and suitable flooding duration corresponding to the growth parameter, specifically: First, draw the curve of the polynomial fitting equation; then, when the hydrological element is the flooding depth, take the decreasing section of the curve within the given flooding depth range (0, h mas ); when the hydrological element is the flooding duration, take the decreasing section of the curve within the given flooding duration range (0, t mas ); finally, calculate the flooding depth value h max or the flooding duration value t max when the growth parameter drops from the maximum value y 0 to y 0 / 2 on the decreasing section. The suitable flooding depth and suitable flooding duration corresponding to the growth parameter are respectively (0, h 0 ) and (0, t 0 ).

[0013] Furthermore, the setting of the flooding simulation scenario is as follows:

[0014] According to the community characteristics of the key hygrophytic plants to be studied and the hydrological change characteristics of the Butterfly Lake area, determine the maximum flooding depth h mas and the maximum flooding duration t max of the key hygrophytic plants to be studied in the Butterfly Lake. Take within the flooding depth range (0, h mas) The multiple waterlogging depth values within are used as the waterlogging depth experimental values, and the multiple waterlogging duration values within the waterlogging duration range (0, t max ) are used as the waterlogging duration nodes. For each waterlogging depth experimental value, it is combined with each waterlogging duration node respectively, and one combination corresponds to one waterlogging simulation scenario.

[0015] Furthermore, polynomial fitting is performed on the waterlogging depth and waterlogging duration respectively with each growth parameter, including:

[0016] When performing polynomial fitting on the waterlogging depth and each growth parameter respectively, the waterlogging duration is fixed to obtain the polynomial fitting of the waterlogging depth and each growth parameter under multiple waterlogging durations;

[0017] When performing polynomial fitting on the waterlogging duration and each growth parameter respectively, the waterlogging depth is fixed to obtain the polynomial fitting of the waterlogging duration and each growth parameter under multiple waterlogging depths.

[0018] Preferably, before performing polynomial fitting, principal component analysis is first performed on the growth parameter data to separately screen out the principal component growth parameters corresponding to the waterlogging depth and waterlogging duration; when performing polynomial fitting, the data of the principal component growth parameters are taken for polynomial fitting.

[0019] Another method provided by this application for determining the ecological hydrological threshold of key hygrophytic plants in a dish-shaped lake, which is used to determine the suitable rising and falling water speeds of key hygrophytic plants, includes the steps:

[0020] Set up a test device near the dish-shaped lake. The test device includes a container and a peristaltic pump. The peristaltic pump is connected to a water suction pipe, and one end of the water suction pipe is located inside the container;

[0021] Collect healthy seedlings of key hygrophytic plants in the dish-shaped lake area. The seedling heights are the same. Transplant the seedlings into a planting bucket filled with in-situ soil and pre-culture for 7d - 15d;

[0022] Set up multiple rising water simulation scenarios and multiple falling water simulation scenarios. One rising water simulation scenario corresponds to one rising water humidity experimental value, and one falling water simulation scenario corresponds to one falling water speed experimental value; the simulation test for the rising water simulation scenario is: Hang the planting bucket in the container, control the peristaltic pump to pump the water from the outside dish-shaped lake into the container at the rising water speed corresponding to the rising water simulation scenario, take out the planting bucket and measure the growth parameter data of the key hygrophytic plants; the simulation test for the falling water simulation scenario is: Hang the planting bucket in the container, control the peristaltic pump to pump the water in the container out at the falling water speed corresponding to the falling water simulation scenario, take out the planting bucket and measure the growth parameter data of the key hygrophytic plants;

[0023] According to the growth parameter data, polynomial fitting is performed on the rising water speed and falling water speed respectively with each growth parameter;

[0024] Determine the suitable rising water speed corresponding to the growth parameters according to the polynomial fitting equation of the growth parameters and the rising water speed, and take the intersection of the suitable rising water speeds corresponding to all growth parameters, that is, the suitable rising water speed of the key hygrophytic plants; determine the suitable falling water speed corresponding to each growth parameter according to the polynomial fitting equation of the growth parameters and the falling water speed, and take the intersection of the suitable falling water speeds corresponding to all growth parameters, that is, the suitable falling water speed of the key hygrophytic plants;

[0025] Among them, to determine the suitable rising water speed and the suitable falling water speed corresponding to the growth parameters, specifically: First, draw the curve of the polynomial fitting equation; then, when the hydrological element is the rising water speed, take the decreasing section of the curve within the given rising water speed range (0, V 涨mas ); when the hydrological element is the falling water speed, take the decreasing section of the curve within the given falling water speed range (-V 退mas , 0); finally, calculate the rising water speed value V max or the falling water speed value V max when the growth parameter value drops from the maximum value y 涨0 to y 退0 / 2, and the suitable rising water speed and the suitable falling water speed corresponding to the growth parameter are respectively (0, V 涨0 ) and (-V 退mas , V 退0 ).

[0026] Furthermore, the settings of the rising water simulation scenario and the falling water simulation scenario are as follows:

[0027] According to the hydrological change characteristics of the butterfly-shaped lake area, determine the maximum rising water speed V 涨mas and the maximum falling water speed V 退mas of the butterfly-shaped lake, take multiple rising water speed values within the rising water speed range (0, V 涨mas ) as the rising water speed experimental values, take multiple falling water speed values within the falling water speed range (-V 退mas , 0) as the falling water speed experimental values, each rising water speed experimental value corresponds to a rising water simulation scenario, and each falling water speed experimental value corresponds to a falling water simulation scenario.

[0028] Furthermore, it also includes: determining the suitable rising and falling water speed according to the suitable rising water speed and the suitable falling water speed of the key hygrophytic plants, specifically:

[0029] Record the suitable rising water speed and the suitable falling water speed of the key hygrophytic plants as (0, V 涨 ) and (-V 退mas , -V 退 ) respectively, and the suitable rising and falling water speed is the intersection of the suitable rising water speed and the suitable absolute value falling water speed, where the suitable absolute value falling water speed is expressed as (V 退， V退mas )。

[0030] Preferably, before performing polynomial fitting, principal component analysis is first performed on the growth parameter data to screen out the principal component growth parameters corresponding to the rising and falling water speeds; when performing polynomial fitting, the data of the principal component growth parameters are taken for polynomial fitting.

[0031] In the above method, the plant height of the collected seedlings is not less than 15 cm and not higher than 30 cm.

[0032] In the above method, the growth parameter data includes data of multiple growth parameters such as plant height, number of leaves, number of tillers, rhizome length, aboveground biomass, underground biomass, specific leaf area, root biomass ratio, root-shoot ratio, and leaf photosynthetic rate.

[0033] In the above method, polynomial fitting preferably uses quadratic polynomial fitting.

[0034] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0035] Since 2003, due to the impoundment operation of the reservoirs in the upper reaches of the Yangtze River, the hydrological rhythm of the butterfly lakes in the middle and lower reaches of the Yangtze River has been greatly affected. Under the hydrological situations such as "extremely abundant and extremely dry" and "rapid transition from abundant to dry", the hygrophytic plants in the butterfly lakes have an increasing trend, which affects the ecological environment of the butterfly lake area. Therefore, it is urgent to study the influence law of the hydrological rhythm on the growth and development of the hygrophytic plants in the butterfly lakes. Thus, the present application proposes a method for determining the ecological hydrological thresholds of the key hygrophytic plants in the butterfly lakes, quantifying the influence law of the hydrological rhythm on the growth and development of the hygrophytic plants in the butterfly lakes, so as to provide scientific support for the biodiversity protection and ecological environment restoration in the butterfly lake area. In addition, the present application also has the advantages of low cost, easy operation, and accurate threshold identification. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of the test device adopted in the embodiment;

[0037] Figure 2 It is a schematic diagram for determining the ecological hydrological threshold according to the polynomial fitting equation in the embodiment.

[0038] Reference numerals: 10 - container, 11 - barrel wall, 12 - base, 13 - scale, 14 - inlet valve, 15 - inlet pipe, 16 - outlet valve, 20 - suspension rack, 21 - suspension rod, 30 - peristaltic pump, 31 - suction pipe, 32 - drainage bucket, 40 - planting bucket, 41 - hygrophytic plant, 50 - suspension rope. Detailed Embodiments

[0039] To make the objectives, technical solutions and advantages of this application more clear, the following will, in conjunction with the accompanying drawings and embodiments, clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of rather than all of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0040] Embodiment

[0041] In this embodiment, the research object is the key hygrophytic plants in a butterfly-shaped lake in Poyang Lake. First, determine the key hygrophytic plants in the butterfly-shaped lake. The key hygrophytic plants are the dominant species or constructive species in the butterfly-shaped lake area. In this embodiment, the key hygrophytic plants in the butterfly-shaped lake area include Carex cinerascens. Below, taking Carex cinerascens as an example, a method for determining the eco-hydro threshold of key hygrophytic plants will be provided. The specific steps are as follows:

[0042] (1) Set up a test device near the butterfly-shaped lake.

[0043] This test device includes a container 10 with an open upper end, a suspension rack 20 placed at the open end of the container 10, and a peristaltic pump 30; a water inlet valve 14 and a water outlet valve 16 are respectively installed at the top and bottom of the side wall of the container 10; the peristaltic pump 30 is connected to a water suction pipe 31, one end of the water suction pipe 31 is located inside the container 10, and the peristaltic pump 30 is used to pump the water inside the container 10 out through the water suction pipe 31 or pump the external water into the container 10.

[0044] Introduce the water body in the butterfly-shaped lake into the container 10 through the water inlet valve 14, thereby forming a simulated habitat environment for key hygrophytic plants inside the container 10; simulate the rising and falling water scenarios by controlling the peristaltic pump 30 to pump the water inside the container 10 out or pump the external water into it at a specific speed; the suspension rack 20 is used to suspend the planting bucket 40 planted with key hygrophytic plants inside the container 10, and by observing the growth of the key hygrophytic plants in the planting bucket 40 under different simulated scenarios, to assist in studying the influence law of the butterfly hydrological rhythm on the growth of key hygrophytic plants.

[0045] Please refer to Figure 1 , which shows the specific structural schematic diagram of the test device built in this embodiment. Below, the structure of the test device will be described in detail in conjunction with Figure 1 this.

[0046] The container 10 is cylindrical, generally with a height of 1.5 m - 3.0 m and a bottom diameter of generally 0.5 m - 2 m. The material can be selected from PVC, PU or acrylic, and a material with a corresponding light transmittance is selected according to the requirements of the key hygrophytic plants to be studied for light. The container 10 can be an integrally formed container, or can be formed by connecting a barrel wall 11 and a base 12. The connection method is not limited, as long as it ensures that the container 10 does not leak or seep water. For example, the barrel wall 11 and the base 12 can be connected by a hot melt method, or the barrel wall 11 and the base 12 can be connected by a mechanical connection method, or the barrel wall 11 and the base 12 can be connected by a ferrule method. In this embodiment, the container 10 is formed by connecting the barrel wall 11 and the base 12 by a hot melt method, with a height of 2 m and a bottom diameter of 1 m, and the material is translucent PVC.

[0047] To facilitate the observation of the water level in the container 10, a scale 13 perpendicular to the bottom surface of the container 10 can be provided on the inner or outer side wall of the container 10. Specifically, when the material of the container 10 is opaque or translucent, the scale 13 is provided on the inner side wall of the container 10; when the material of the container 10 is transparent, the scale 13 is provided on the outer side wall of the container 10.

[0048] To reduce the disturbance of the water inlet, a water inlet pipe 15 can be connected to the water outlet end of the water inlet valve 14. The water inlet pipe 15 is placed inside the container 10 and the water outlet end of the water inlet pipe 15 is closely attached to the inner wall of the container 10. Through the water inlet valve 14 and the water inlet pipe 15, the water in the butterfly-shaped lake is introduced into the container 10.

[0049] The suspension frame 20 is made of a metal material or a wooden material with good load-bearing performance, and the planting bucket 40 is suspended in the container 10 by a suspension rope 50 made of nylon material; specifically, the bottom end of the suspension rope 50 is connected to the handle of the planting bucket 40, and its top end is connected to a hook or a hanging ring, and the hook or the hanging ring is fixed on the suspension frame 20.

[0050] To be able to suspend a larger number of planting buckets 40, in this embodiment, the suspension frame 20 is composed of a number of suspension rods 21 cross-connected in the middle. The lengths of the suspension rods 21 are equal, and the material can be steel or wood; when the suspension rods 21 are made of steel, the middle parts of the suspension rods 21 are crossed and welded at the crossing points; when the suspension rods 21 are made of wood, the middle parts of the suspension rods 21 are crossed and fixedly connected at the crossing points by bolts.

[0051] One end of the water suction pipe 31 connected to the peristaltic pump 30 is located inside the container 10 and fixed to the inner wall of the container 10 and is lower than the bottom ends of all the suspended planting buckets 40, and the other end is connected to a graduated drainage bucket 32, and this drainage bucket 32 is used to receive the water discharged by the peristaltic pump 30. In this embodiment, the flow rate range of the peristaltic pump 30 is 0.03 mL / min - 1500 mL / min.

[0052] (2) Collect healthy seedlings of the key hygrophytic plants to be studied in the Butterfly Lake area. The collected healthy seedlings have the same plant height. Transplant the healthy seedlings into the planting bucket 40 filled with in-situ soil and pre-culture them for 7d - 15d. Select the hygrophytic plants growing normally for the simulation experiments in step (3) and step (4).

[0053] In this application, the requirement for the plant height of healthy seedlings is not less than 15 cm and not higher than 30 cm. In this embodiment, collect the seedlings of Carex cinerascens with a plant height of 25 cm near the Butterfly Lake. Fill the planting bucket 40 with 8 cm thick in-situ soil, and transplant the seedlings of Carex cinerascens into the planting bucket 40 for pre-culturing for 7 days.

[0054] (3) Set multiple flooding simulation scenarios. One flooding simulation scenario corresponds to a combination of a flooding depth experimental value and a flooding duration node. Conduct the simulation tests for each flooding simulation scenario respectively. The simulation test of the flooding simulation scenario is as follows: Introduce the water body of the Butterfly Lake into the container 10, hang the planting bucket 40 in the container 10 and make the flooding depth of the key hygrophytic plants reach the flooding depth experimental value corresponding to the flooding simulation scenario. When reaching the flooding duration node corresponding to the flooding simulation scenario, take out the planting bucket 40 and measure the growth parameter data of the key hygrophytic plants.

[0055] In this embodiment, hang the planting bucket 40 on the hanging rack 20 through the suspension rope 50, and adjust the hanging height of the planting bucket 40 by adjusting the suspension rope 50, so as to adjust the flooding depth of the key hygrophytic plants in the planting bucket 40.

[0056] In this embodiment, the setting of the flooding simulation scenario is as follows:

[0057] According to the community characteristics of the key hygrophytic plants to be studied and the hydrological change characteristics of the Butterfly Lake area, determine the maximum flooding depth h of the key hygrophytic plants to be studied in the Butterfly Lake mas and the maximum flooding duration t mas , and take multiple flooding depth values within the flooding depth range (0, h mas ) as the flooding depth experimental values, take multiple flooding duration values within the flooding duration range (0, t mas ) as the flooding duration nodes. For each flooding depth experimental value, combine it with each flooding duration node respectively. One combination corresponds to one flooding simulation scenario.

[0058] For example, set I flooding depth experimental values hi and J flooding duration nodes tj, where, hi ∈ (0, h mas ), tj ∈ (0, t mas) For each experimental value hi of the flooding depth, it is combined with J flooding duration nodes respectively to obtain J combinations: (hi, t1), (hi, t2),... (hi, tJ). One combination corresponds to one flooding simulation scenario. There are I experimental values hi of the flooding depth, so finally I×J flooding simulation scenarios are obtained. For the combination (hi, tj), it represents a flooding simulation scenario with a flooding depth of hi and a flooding duration of tj.

[0059] In this embodiment, the determined flooding depth range and flooding duration range are (0, 120 cm) and (0, 90 d) respectively. The set experimental values of the flooding depth are 0 cm, 20 cm, 40 cm, 60 cm, 80 cm, 100 cm, 120 cm respectively, and the set flooding duration nodes are 0 d, 5 d, 15 d, 30 d, 45 d, 60 d, 75 d, 90 d respectively. A total of 56 flooding simulation scenarios are obtained.

[0060] In this step, through the simulation experiments of multiple flooding simulation scenarios, the growth parameter data of key hygrophytic plants under different flooding simulation scenarios are collected. The growth parameter data is the quantification of the growth situation of key hygrophytic plants. Subsequently, based on the collected growth parameter data, the eco-hydrological thresholds of key hygrophytic plants are determined.

[0061] The growth parameter data includes but is not limited to plant height, number of leaves, number of tillers, rhizome length, aboveground biomass, underground biomass, specific leaf area, root biomass ratio, root-shoot ratio, leaf photosynthetic rate, etc. Some of the growth parameters can be selected according to actual needs. In this embodiment, the selected growth parameter data includes plant height, number of tillers, number of leaves, aboveground biomass, underground biomass and rhizome length.

[0062] In this embodiment, multiple test devices are used to simulate different flooding simulation scenarios at the same time. The water levels in the containers 10 of multiple test devices are fixed at 150 cm. Multiple planting buckets 40 with the same hanging height are hung in the same container 10, that is, the flooding depths are the same. When reaching each flooding duration node, different planting buckets 40 are taken out in turn, and the growth parameter data of key hygrophytic plants are measured.

[0063] (4) Set multiple rising water simulation scenarios and multiple falling water simulation scenarios. One rising water simulation scenario corresponds to one experimental value of the rising water speed, and one falling water simulation scenario corresponds to one experimental value of the falling water speed. The simulation tests of each rising water simulation scenario and each falling water simulation scenario are carried out respectively.

[0064] Among them, the simulation test of the rising water simulation scenario is as follows: The planting bucket 40 is suspended in the container 10, and the peristaltic pump 30 is controlled to pump the water from the external butterfly-shaped lake into the container 10 at the rising water speed corresponding to the rising water simulation scenario, and then the planting bucket 40 is taken out to measure the growth parameter data of the key hygrophytic plants; the simulation test of the falling water simulation scenario is as follows: The planting bucket 40 is suspended in the container 10, and the peristaltic pump 30 is controlled to pump the water in the container 10 out at the falling water speed corresponding to the falling water simulation scenario, and then the planting bucket 40 is taken out to measure the growth parameter data of the key hygrophytic plants.

[0065] In this step, the growth parameter data of the key hygrophytic plants under multiple rising water simulation scenarios and multiple falling water simulation scenarios can be collected.

[0066] In this embodiment, the settings of the rising water simulation scenario and the falling water simulation scenario are specifically as follows:

[0067] According to the hydrological change characteristics of the butterfly-shaped lake area, determine the maximum rising water speed V 涨mas and the maximum falling water speed V 退mas . Take multiple rising water speed values within the rising water speed range (0, V 涨mas ) as the rising water speed experimental values, and take multiple falling water speed values within the falling water speed range (-V 退mas , 0) as the falling water speed experimental values. Each rising water speed experimental value corresponds to a rising water simulation scenario, and each falling water speed experimental value corresponds to a falling water simulation scenario.

[0068] In this embodiment, the determined rising water speed range is (0, 5 cm / d), and the determined falling water speed range is (-5 cm / d, 0). The symbol "-" represents "falling water". The set rising water speed experimental values are 0 cm / d, 0.5 cm / d, 1 cm / d, 2 cm / d, 3 cm / d, 5 cm / d, and the falling water speed experimental values are 0 cm / d, -1 cm / d, -2 cm / d, -3 cm / d, -5 cm / d. A total of 6 rising water simulation scenarios and 6 falling water simulation scenarios are set, and 12 test devices are used to conduct rising and falling water simulations respectively. Among them, 6 test devices are used to simulate the rising water simulation scenarios respectively, and the other 6 test devices are used to simulate the falling water simulation scenarios respectively. Multiple planting buckets 40 with the same hanging height can be suspended in each container 10 for parallel experiments.

[0069] In this embodiment, when performing the rising water simulation and the falling water simulation, the hanging heights of the planting buckets 40 are the same, and they are all hung at the bottom end of the container 10. When performing the rising water simulation, control the peristaltic pump 30 to pump water into the container 10 at the rising water speed until the water levels in the multiple containers 10 all rise to the preset water level, take out the planting bucket 40 and measure the growth parameter data of the key hygrophytic plants; when performing the falling water simulation, first introduce the water in the butterfly-shaped lake into the container 10 and reach the preset water level, and then control the peristaltic pump 30 to pump out the water in the container 10 at the falling water speed until the water level in the container 10 drops to the bottom end of the planting bucket 40, take out the planting bucket 40 and measure the growth parameter data of the key hygrophytic plants. The rising and falling water speeds in the container 10 can be accurately adjusted by adjusting the rotation speed of the peristaltic pump 30. The above preset water level is set according to the plant height of the key hygrophytic plants. Generally speaking, the preset water level is greater than the plant height but does not exceed twice the plant height.

[0070] (5) According to the growth parameter data of the key hygrophytic plants under multiple flooding simulation scenarios collected in step (3), perform polynomial fitting on the flooding depth and flooding duration respectively with each growth parameter; according to the growth parameter data of the key hygrophytic plants under multiple rising water simulation scenarios and multiple falling water simulation scenarios collected in step (4), perform polynomial fitting on the rising water speed and falling water speed respectively with each growth parameter.

[0071] In this embodiment, the polynomial fitting adopts quadratic polynomial fitting, and the fitting equation is expressed as follows:

[0072] y = A + B1*x + B2*x 2 (1)

[0073] Among them, x represents the hydrological element. In this embodiment, the hydrological elements are flooding depth, flooding duration, rising water speed, and falling water speed; y represents the growth parameter of the key hygrophytic plants; A, B1, and B2 are fitting coefficients.

[0074] In this embodiment, before performing the polynomial fitting, first perform normalization processing on the growth parameter data; and perform a significance test on the obtained fitting equation, and the significance level p is set to 0.05.

[0075] When performing polynomial fitting on the flooding depth and each growth parameter respectively, fix the flooding duration to obtain the polynomial fitting of the flooding depth and each growth parameter under multiple flooding durations; when performing polynomial fitting on the flooding duration and each growth parameter respectively, fix the flooding depth to obtain the polynomial fitting of the flooding duration and each growth parameter under multiple flooding depths.

[0076] Table 1 shows the polynomial fitting equations of the hydrological elements and various growth parameters of Carex cinerascens in this embodiment. In the table, polynomial fitting equations (1)-(3) are the fitting equations of the flooding depth and the number of leaves under flooding durations of 30 d, 45 d, and 60 d respectively. Polynomial fitting equations (4)-(5) are the fitting equations of the flooding depth and the underground biomass under flooding durations of 15 d and 75 d respectively. Polynomial fitting equations (6)-(8) are the fitting equations of the flooding duration and the number of leaves under flooding depths of 40 cm, 100 cm, and 120 cm respectively. Polynomial fitting equations (9)-(10) are the fitting equations of the flooding duration and the underground biomass under flooding depths of 80 cm and 120 cm respectively. Polynomial fitting equations (11)-(12) are the fitting equations of the rising water speed and the plant height, and the tiller number respectively. Polynomial fitting equations (13)-(14) are the fitting equations of the falling water speed and the plant height, and the tiller number respectively.

[0077] Table 1 Polynomial fitting equations of Carex cinerascens in the embodiment

[0078]

[0079]

[0080] (6) According to the polynomial fitting equations of the flooding depth and various growth parameters, determine the suitable flooding depth of the key hygrophytic plants; according to the polynomial fitting equations of the flooding duration and various growth parameters, determine the suitable flooding duration of the key hygrophytic plants; according to the polynomial fitting equations of the rising water speed, falling water speed and various growth parameters, determine the suitable rising and falling water speeds of the key hygrophytic plants; in this application, the ecological hydrological thresholds of the key hygrophytic plants include the suitable flooding depth, the suitable flooding duration and the suitable rising and falling water speeds.

[0081] In this application, each hydrological element is analyzed separately, including: analyzing each polynomial fitting equation corresponding to the hydrological element separately to obtain the ecological hydrological threshold corresponding to each polynomial fitting equation, so as to obtain the ecological hydrological threshold of the hydrological element. For example, when the hydrological element is the flooding depth, analyze each polynomial fitting equation of the flooding depth and various growth parameters separately to obtain the suitable flooding depth corresponding to each polynomial fitting equation, and take the intersection of all the suitable flooding depths, which is the suitable flooding depth of the key hygrophytic plants.

[0082] In this application, the method for determining the suitable flooding depth of the key hygrophytic plants is as follows:

[0083] First, determine the suitable flooding depth corresponding to each growth parameter separately, and then take the intersection of the suitable flooding depths of all growth parameters, which is the suitable flooding depth of the key hygrophytic plants. Among them, the suitable flooding depth corresponding to the growth parameter is determined according to the polynomial fitting equation of the growth parameter and the flooding depth. Specifically: draw the curve of the polynomial fitting equation, and take the decreasing segment of the curve within the given flooding depth range (0, h mas ) to calculate the maximum value y max of the growth parameter on the decreasing segment. Further calculate the flooding depth value h max when the growth parameter value drops from y max to y 0 / 2. Then the suitable flooding depth corresponding to the growth parameter is (0, h 0 ).

[0084] When there are multiple polynomial fitting equations for the flooding depth and a certain growth parameter, the suitable flooding depth corresponding to the growth parameter is determined based on each polynomial fitting equation respectively, and the intersection of the suitable flooding depths determined based on each polynomial fitting equation is taken, which is the suitable flooding depth of the growth parameter.

[0085] In this application, the method for determining the suitable flooding duration of the key hygrophytic plants is as follows:

[0086] First, determine the suitable flooding duration corresponding to each growth parameter separately, and then take the intersection of the suitable flooding durations of all growth parameters, which is the suitable flooding duration of the key hygrophytic plants. Among them, the suitable flooding duration corresponding to the growth parameter is determined according to the polynomial fitting equation of the growth parameter and the flooding duration. Specifically: draw the curve of the polynomial fitting equation, and take the decreasing segment of the curve within the given flooding duration range (0, t mas ) to calculate the maximum value y max of the growth parameter on the decreasing segment. Further calculate the flooding duration t max when the growth parameter value drops from y max to y 0 / 2. Then the suitable flooding duration of the growth parameter is (0, t 0 ).

[0087] When there are multiple polynomial fitting equations for the flooding duration and a certain growth parameter, the suitable flooding duration corresponding to the growth parameter is determined based on each polynomial fitting equation respectively, and the intersection of the suitable flooding durations determined based on each polynomial fitting equation is taken, which is the suitable flooding duration of the growth parameter.

[0088] It should be noted that in the above given flooding depth range (0, h mas ) and flooding duration range (0, t mas ), h mas represents the maximum flooding depth of the key hygrophytic plants in the simulation experiment, and t masIndicates the maximum flooding duration of key hygrophytic plants in the simulation test, h mas and t mas should be consistent with the actual flooding situation of key hygrophytic plants in the butterfly-shaped lake.

[0089] In this application, the method for determining the appropriate rising and falling water speeds of key hygrophytic plants is as follows:

[0090] Determine the appropriate rising water speeds corresponding to each growth parameter, and take the intersection of the appropriate rising water speeds corresponding to all growth parameters, which is the appropriate rising water speed of the key hygrophytic plants, denoted as (0, V 涨 ); determine the appropriate falling water speeds corresponding to each growth parameter, and take the intersection of the appropriate falling water speeds corresponding to all growth parameters, which is the appropriate falling water speed of the key hygrophytic plants, denoted as (-V 退mas , -V 退 ); the appropriate rising and falling water speeds of the key hygrophytic plants are the intersection of the appropriate rising water speed and the appropriate absolute value of the falling water speed of the key hygrophytic plants, where the appropriate absolute value of the falling water speed is expressed as (V 退， V 退mas ).

[0091] The appropriate rising water speed corresponding to the growth parameter is determined according to the polynomial fitting equation of the growth parameter and the rising water speed. Specifically: First, draw the curve of the polynomial fitting equation; then, take the decreasing section of the curve within the given rising water speed range (0, V 涨mas ); finally, calculate the rising water speed value V max when the growth parameter value decreases from the maximum value y max to y 涨0 / 2, and the appropriate rising water speed corresponding to the growth parameter is (0, V 涨0 );

[0092] The appropriate falling water speed corresponding to the growth parameter is determined according to the polynomial fitting equation of the growth parameter and the falling water speed. Specifically: First, draw the curve of the polynomial fitting equation; then, take the decreasing section of the curve within the given falling water speed range (-V 退mas , 0); finally, calculate the falling water speed value V max when the growth parameter value decreases from the maximum value y max to y 退0 / 2, and the appropriate falling water speed corresponding to the growth parameter is (-V 退mas , V 退0 ).

[0093] It should be noted that in the above given rising water speed range (0, V 涨mas ) and falling water speed range (-V 退mas , 0), V 涨mas represents the maximum rising water speed in the simulation test, V退mass represents the maximum water recession speed in the simulation test, V 涨mas and V 退mass should conform to the actual water level rise and fall conditions of the target butterfly lake.

[0094] For the sake of easy understanding, the following will take the curve of a quadratic polynomial as an example to elaborate in detail on the idea of determining the eco-hydrological threshold. Please refer to Figure 2 , where Figures (a)-(c) are respectively three possible parabolic curves. The x-axis in the figure represents hydrological elements, such as flooding depth, flooding duration, etc. The red segments on the x-axis represent the given range of hydrological elements. The y-axis represents growth parameters. The dashed line segments in Figures (a) and (b) represent the determined decreasing segments, and x 0 is the determined hydrological element threshold; there is no decreasing segment in Figure (c). For the polynomial curve without a decreasing segment, it is deleted and the eco-hydrological threshold corresponding to this polynomial curve is no longer determined.

[0095] In this embodiment, the eco-hydrological thresholds to be determined include the suitable flooding depth, suitable flooding duration, and suitable water level rise and fall speed of Carex cinerascens. The following will take the polynomial fitting equations in Table 1 as examples to describe in detail the determination of the eco-hydrological threshold of Carex cinerascens.

[0096] When the hydrological element is flooding depth, by analyzing the polynomial fitting equation, the suitable flooding depths for the number of leaves and underground biomass are 0 - 56 cm and 0 - 38 cm respectively. Taking the intersection of the suitable flooding depths of 0 - 56 cm and 0 - 38 cm, the suitable flooding depth of Carex cinerascens is 0 - 38 cm.

[0097] When the hydrological element is flooding duration, by analyzing the polynomial fitting equation, the suitable flooding durations for the number of leaves and underground biomass are 0 - 25 d and 0 - 32 d respectively. Taking the intersection of the suitable flooding durations of 0 - 25 d and 0 - 32 d, the suitable flooding duration of Carex cinerascens is 0 - 25 d.

[0098] When the hydrological elements are rising water speed and recession water speed, by analyzing the polynomial fitting equation, the suitable rising water speeds for plant height and tiller number are 0 - 2.4 cm / d and 0 - 2.6 cm / d respectively, and the suitable recession water speeds for both plant height and tiller number are -5 cm / d to -1.0 cm / d. Taking the intersection of the suitable rising water speeds of 0 - 2.4 cm / d and 0 - 2.6 cm / , the suitable rising water speed of Carex cinerascens is 0 - 2.4 cm / d, and the suitable recession water speed of Carex cinerascens is -5 cm / d to -1.0 cm / d; then the suitable water level rise and fall speed of Carex cinerascens is 1.0 cm / d to 2.4 cm / d.

[0099] Therefore, the ecological hydrological thresholds of Carex cinerascens determined in this embodiment are as follows: within the range of a flooding depth of 0 - 120 cm, a flooding duration of 0 - 90 d, and a rising and falling water speed of 0 - 5 cm / d, the suitable flooding depth, suitable flooding duration, and suitable rising and falling water speed of Carex cinerascens are 0 - 38 cm, 0 - 25 d, and 1.0 cm / d - 2.4 cm / d, respectively.

[0100] As a preferred solution of this embodiment, before performing step (5), it further includes: performing principal component analysis on the growth parameter data of key hygrophytic plants under different flooding simulation scenarios, and screening out the principal component growth parameters corresponding to the flooding depth and flooding duration; performing principal component analysis on the growth parameter data of key hygrophytic plants under different rising water simulation scenarios and different falling water simulation scenarios, and screening out the principal component growth parameters corresponding to the rising and falling water speed.

[0101] In this embodiment, the collected original growth parameter data includes the plant height, tiller number, leaf number, aboveground biomass, underground biomass, and rhizome length of Carex cinerascens. By performing principal component analysis on the original growth parameter data and calculating the weights of each growth parameter under hydrological elements respectively, the two growth parameters with the largest weights are taken as the principal component growth parameters. The principal component analysis of the growth parameter data of Carex cinerascens in this embodiment is shown in Table 2. The principal component growth parameters corresponding to the flooding depth and flooding duration are the leaf number and underground biomass, and the principal component growth parameters corresponding to the rising and falling water speed are the plant height and tiller number.

[0102] Table 2 Comparison table of principal component analysis of growth parameters

[0103]

[0104]

[0105] In step (5), polynomial fitting is performed according to the data of the principal component growth parameters. In this embodiment, for the flooding depth, polynomial fitting equations of the flooding depth with the leaf number and underground biomass are constructed respectively; for the flooding duration, polynomial fitting equations of the flooding duration with the leaf number and underground biomass are constructed respectively; for the rising and falling water speed, polynomial fitting equations of the rising and falling water speed with the plant height and tiller number are constructed respectively.

[0106] Note that the above is only a preferred embodiment of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described here. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments. Without departing from the concept of the present application, more other equivalent embodiments can be included, all of which belong to the protection scope of the present application.

Claims

1. A method for determining the eco-hydrological threshold of key wetland plants in a saucer-shaped lake, characterized by: Used to determine the appropriate flooding depth and duration for key wetland plants, including the following steps: Building a test device near Butterfly Lake, the test device comprising a container; Healthy seedlings of key wetland plants were collected in the Butterfly Lake area. The seedlings had the same height and were transplanted into planting buckets filled with original soil and pre-cultivated for 7-15 days. A plurality of flooding simulation scenarios are set, each flooding simulation scenario corresponds to a combination of a flooding depth experimental value and a flooding duration node, and simulation tests of each flooding simulation scenario are respectively conducted, including: introducing butterfly lake water into a container, hanging a planting barrel in the container and making the flooding depth of the key wetland plants reach the flooding depth experimental value corresponding to the flooding simulation scenario, and when the flooding duration node corresponding to the flooding simulation scenario is reached, taking out the planting barrel and measuring the growth parameter data of the key wetland plants; According to the growth parameter data, the flooding depth and flooding duration were fitted with polynomials of each growth parameter; According to the polynomial fitting equation of growth parameters and flooding depth, the appropriate flooding depth corresponding to the growth parameters is determined, and the intersection of the appropriate flooding depths of all growth parameters is taken, that is, the appropriate flooding depth of the key wetland plants; according to the polynomial fitting equation of growth parameters and flooding duration, the appropriate flooding duration corresponding to the growth parameters is determined, and the intersection of the appropriate flooding durations of all growth parameters is taken, that is, the appropriate flooding duration of the key wetland plants; The appropriate flooding depth and appropriate flooding duration corresponding to the growth parameters are determined as follows: first, a curve of the polynomial fitting equation is drawn; then, when the hydrological element is the flooding depth, the curve is taken in the given flooding depth range (0, h mas ) within the decreasing section; when the hydrological element is the flooding duration, the curve is taken in the given flooding duration range (0, t mas ) in the decreasing section; finally, the growth parameter on the decreasing section is calculated from the maximum value y max Descend to y max / 2, the appropriate flooding depth and appropriate flooding duration corresponding to the growth parameters are (0, h0) and (0, t0) respectively.

2. A method for determining the eco-hydrological threshold of key wetland plants in a saucer-shaped lake, characterized by: Used to determine the appropriate water flow rate for key wetland plants, including the following steps: A test device is built near the butterfly lake, the test device comprising a container and a peristaltic pump, the peristaltic pump is connected to a water pumping pipe, one end of the water pumping pipe is located in the container; Healthy seedlings of key wetland plants were collected in the Butterfly Lake area. The seedlings had the same height and were transplanted into planting buckets filled with original soil and pre-cultivated for 7-15 days. A plurality of flooding simulation scenes and a plurality of receding simulation scenes are set, wherein one flooding simulation scene corresponds to one flooding humidity experimental value, and one receding simulation scene corresponds to one receding speed experimental value; the simulation test of the flooding simulation scene is as follows: a planting bucket is hung in a container, a peristaltic pump is controlled to pump water from the butterfly lake into the container at a flooding speed corresponding to the flooding simulation scene, and the planting bucket is taken out to measure the growth parameter data of key wetland plants; the simulation test of the receding simulation scene is as follows: a planting bucket is hung in a container, a peristaltic pump is controlled to pump water out of the container at a receding speed corresponding to the receding simulation scene, and the planting bucket is taken out to measure the growth parameter data of key wetland plants; According to the growth parameter data, the water rise speed and water retreat speed are respectively fitted with polynomials of each growth parameter; According to the polynomial fitting equation of growth parameters and water rising speed, the suitable water rising speed corresponding to the growth parameters is determined, and the intersection of the suitable water rising speeds corresponding to all growth parameters is taken, that is, the suitable water rising speed of the key wetland plants; according to the polynomial fitting equation of growth parameters and water retreat speed, the suitable water retreat speed corresponding to each growth parameter is determined, and the intersection of the suitable water retreat speeds corresponding to all growth parameters is taken, that is, the suitable water retreat speed of the key wetland plants; The suitable water rise speed and water retreat speed corresponding to the growth parameters are determined as follows: first, a curve of the polynomial fitting equation is drawn; then, when the hydrological element is the water rise speed, the curve is taken in a given water rise speed range (0, V 涨mas ) within the decreasing section; when the hydrological element is the water withdrawal rate, take the curve in the given water withdrawal rate range (-V 退mas , 0) within the decreasing segment; finally, the growth parameter value on the decreasing segment is calculated from the maximum value y max Descend to y max The water rise velocity V at 2 涨0 Or water withdrawal speed value V 退0 The appropriate water rise speed and water retreat speed corresponding to the growth parameters are (0, V 涨0 )、(-V 退mas , V 退0 ).

3. The method according to claim 1, characterized in that: The flood simulation scenario is set up as follows: According to the characteristics of the key wetland plant community to be studied and the hydrological changes in the Butterfly Lake area, the maximum flooding depth h of the key wetland plants to be studied in Butterfly Lake was determined. mas and maximum flooding duration t max , take the flooding depth range (0, h mas ) as the experimental flooding depth values, and take the values ​​in the flooding duration range (0, t max ) as flooding duration nodes, and each flooding depth experimental value is combined with each flooding duration node, and one combination corresponds to a flooding simulation scene.

4. The method according to claim 1, characterized in that: The polynomial fitting of the flooding depth, flooding duration and each growth parameter comprises: When polynomial fitting is performed on the flooding depth and each growth parameter, the flooding duration is fixed to obtain polynomial fitting of the flooding depth and each growth parameter under multiple flooding durations; When polynomial fitting is performed on the flooding duration and each growth parameter respectively, the flooding depth is fixed to obtain the polynomial fitting of the flooding duration and each growth parameter at multiple flooding depths.

5. The method according to claim 1, characterized in that: Before performing polynomial fitting, the principal component analysis of the growth parameter data is first performed to screen out the principal component growth parameters corresponding to the flooding depth and flooding duration respectively; when performing polynomial fitting, the principal component growth parameter data is taken for polynomial fitting.

6. The method according to claim 2, characterized in that: The settings of the flood simulation scene and the receding water simulation scene are: According to the hydrological variation characteristics of the Butterfly Lake area, the maximum water rise velocity V of the Butterfly Lake is determined. 涨mas and maximum water withdrawal velocity V 退mas , take the water rise speed range (0, V 涨mas ) as the experimental value of the water rising speed, and take the water receding speed range (-V 退mas , 0) are used as the receding speed experimental values, each rising speed experimental value corresponds to a rising water simulation scene, and each receding speed experimental value corresponds to a receding water simulation scene.

7. The method according to claim 2, characterized in that: It also includes: determining the appropriate water rise and fall speeds according to the appropriate water rise and fall speeds of key wetland plants, specifically: The suitable water-rising speed and water-receding speed of key wetland plants are recorded as (0, V 涨 )、(-V 退mas , -V 退 ), the suitable water rise and fall speed is the intersection of the suitable water rise speed and the suitable absolute water fall speed, where the suitable absolute water fall speed is expressed as (V 退， V 退mas ).

8. The method according to claim 2, characterized in that: Before performing polynomial fitting, the principal component analysis is first performed on the growth parameter data to screen out the principal component growth parameters corresponding to the water rise and fall speed; when performing polynomial fitting, the principal component growth parameter data is taken for polynomial fitting.

9. The method according to claim 1 or 2, characterized in that: The growth parameter data include data of multiple growth parameters such as plant height, number of leaves, number of ramets, rhizome length, aboveground biomass, underground biomass, specific leaf area, root biomass ratio, root-to-crown ratio, and leaf photosynthetic rate.

10. The method according to claim 1 or 2, characterized in that: The polynomial fitting is a quadratic polynomial fitting.

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