Method for Controlling Growth of Street Trees

Abstract

To solve various problems caused by overgrown trees such as the phenomenon of root heave where roots of roadside trees extend and lift up paving on streets.SOLUTION: Electrode plates 10 and 11 are installed in the ground so as to straddle street tree 8, these electrode plates 10, 11 are connected to a pulse electric field generator 12, and a pulse electric field is applied to a root 8A to induce a phenomenon of cytoclasis through the action of an electric shock to thereby suppress growth of the root 8A. Instead of the electric plates 10, 11, electrode rods 131, 132 ... 13n (141, 142 ... 14n) selected to form pairs via a switching means 15 (16) and serving as a plurality of sets of electrode rods 13, 14 inserted and installed in the ground, may be connected to the pulse electric field generator 12.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for controlling the growth of roadside trees to solve various problems caused by excessive growth of trees, such as the root heaving phenomenon where the roots of roadside trees grow and lift the pavement of the road.

Background Art

[0002] Conventionally, especially in urban areas, vegetation of roadside trees has been actively carried out for the purposes of improving the landscape, preserving the living environment, ensuring traffic safety, and conserving the natural environment.

[0003] However, as the roots grow, a root heaving phenomenon occurs where the roots lift the pavement of the road, causing problems such as obstacles to passage. Therefore, several methods for preventing the root heaving phenomenon caused by tree roots have been proposed conventionally.

[0004] For example, in Patent Document 1 below, there is a structure of a planting base for planting trees in an area that receives an upper load, which uses granular materials for forming a porous structure and a plant growth base filled in the voids of the granular materials having a porous structure. In the hole dug in the underground part, a backfill part formed with a coarse void only by the granular materials and a compaction filling part formed by a plant growth base material for filling the voids of the granular materials are unevenly distributed. A structure of a planting base has been proposed.

[0005] Also, in Patent Document 2 below, there is proposed a method for suppressing the elongation of tree roots in the direction of root heaving by arranging at least horizontally a root repellent sheet material having a repellent for suppressing the root heaving on a sheet having a large number of through holes with a pore diameter of 0.3 mm to 10 mm on the upper side of the tree roots at the root base of the tree.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the case of the method according to Patent Document 1, excavation is performed over a relatively wide range centered on the tree, and at the stage of backfilling, a layer of granular material and a layer of plant growth base are alternately formed. Since the construction is large-scale and traffic restrictions are required when the roadway is adjacent, the impact on others is significant. Therefore, there are problems such as difficulty in applying it particularly to existing roadside trees.

[0008] In addition, in the case of the method according to Patent Document 2, a root repellent sheet material is laid in the area including the tree, and it has the advantage of being simpler than the method of Patent Document 1. However, although this method can be expected to be effective when applied to newly planted roadside trees, its effect is limited even when applied to roadside trees whose root growth has already advanced, and all the paving blocks in the laying range need to be temporarily removed. There were also problems such as a large construction impact range.

[0009] In addition, roadside trees are often provided adjacent to roadways, and as the roadside trees grow, thick branches and trunks may protrude outward and come into contact with vehicles, resulting in accidents. Furthermore, the grown roadside trees may make it difficult for drivers to grasp the presence and behavior of other vehicles and pedestrians, etc., or may obstruct traffic safety such as hiding traffic lights, road signs, street lights, etc.

[0010] Therefore, the main object of the present invention is a growth control method for suppressing the growth of roadside trees in order to solve various problems such as the root uplifting phenomenon where the roots of roadside trees extend and lift the paving of the road. Without requiring large-scale construction, it can be easily applied not only to newly planted roadside trees but also to existing roadside trees, and to provide a roadside tree growth control method that requires a small construction impact range.

Means for Solving the Problems

[0011] As the invention according to claim 1 for solving the above problems, a growth control method for suppressing the growth of street trees, comprising: installing electrodes near the root of the street tree and connecting these electrodes to a pulsed electric field generator; Of street trees at the root , with an electric field strength of 1.1 kV / cm or more and 10.0 kV / cm or less applying a pulsed electric field to induce a cell destruction phenomenon through an electric shock effect to suppress the growth of the root, and providing a growth control method for street trees.

[0012] In the invention described in claim 1 above, problems such as the root of the street tree growing and lifting the pavement of the street, thick branches and trunks protruding outward and contacting vehicles as the street tree grows, accidents where traffic lights, road signs, street lights, etc. are blocked by the street tree are all due to excessive growth of the tree. Therefore, these problems are solved all at once by suppressing the growth of the tree.

[0013] Specifically, electrodes are installed near the root of the street tree, and these electrodes are connected to a pulsed electric field generator. Of street trees at the root , with an electric field strength of 1.1 kV / cm or more and 10.0 kV / cm or less A pulsed electric field is applied to induce a cell destruction phenomenon through an electric shock effect to suppress the growth of the root. That is, the growth of the root is suppressed by inducing a cell destruction phenomenon through an electric shock effect caused by the flow of conductive current or displacement current to the surface or inside of the root.

[0014] One of the present applicants has published a technique for promoting the growth of plants by applying a pulsed electric field to the root in Japanese Patent Application Laid-Open No. 2018-61456 and the paper "Growth Control of Lettuce by Pulsed Electric Field" (Douyan Wang, Takao Namihira, et al.). This is considered to be because the nutrient absorption worked in the increasing direction as a result of the electroporation effect caused by the pulsed application to the root. However, when a pulsed electric field with a high pulsed electric field strength above a predetermined value is applied, it becomes an excessive stimulus for the plant, and it has been found that irreversible cell perforation occurs due to the electric shock effect and a cell destruction phenomenon occurs.

[0015] The present invention has been achieved based on the idea that the growth of street trees can be suppressed by utilizing the aforementioned cell destruction phenomenon. By applying a pulsed electric field to the roots, the growth of the root system is suppressed, preventing the phenomenon of root heave that lifts the pavement of the street. At the same time, since the growth of the root system is suppressed, the growth of the entire tree is also suppressed, and problems such as thick branches and trunks protruding outward and contacting vehicles as the street tree grows, or traffic signals, road signs, street lights, etc. being blocked by the street tree are solved. The intensity of the pulsed electric field that induces the cell destruction phenomenon at the root of the street tree is set to 1.1 kV / cm or more and 10.0 kV / cm or less based on the experiments of the past submitted papers described later, in order to be in the range that induces the cell destruction phenomenon, suppresses growth, and does not cause withering and death.

[0016] In addition, in the case of this growth control method, a pair of electrodes is installed in the ground near the roots of the tree, and these electrodes are connected to a pulsed electric field generator, and only a pulsed electric field is applied to the roots. Therefore, without requiring large-scale construction, it can be easily applied not only to newly planted street trees but also to existing street trees, and the scope of influence of the construction can be reduced.

[0017] As the invention according to claim 2, there is provided the method for controlling the growth of a street tree according to claim 1, wherein the electrodes are at least a pair of electrode plates installed in the ground with the plate surface facing the roots so as to straddle the roots of the street tree.

[0018] The invention described in claim 2 above shows a first example of the installation mode of the electrodes. Specifically, the electrodes are at least a pair of electrode plates installed in the ground with the plate surface facing the roots so as to straddle the roots of the street tree. By using electrode plates having an area of a certain degree or more, for example, an area that covers the entire root surface, it becomes possible to effectively apply a pulsed electric field to the entire root. Incidentally, the electrode plates may be divided into a plurality of pieces and a plurality of sets of electrode plates may be installed.

[0019] As the invention according to claim 3, there is provided the method for controlling the growth of a street tree according to claim 1, wherein the electrodes are a plurality of sets of electrode rods inserted and installed in the ground, and are connected to the pulsed electric field generator via switching means for selecting a pair of electrode rods.

[0020] The invention described in claim 3 above shows a second example of the installation mode of the electrodes. Specifically, the electrodes are a plurality of sets of electrode rods inserted into the ground. In this case, since a pulsed electric field cannot be applied to the entire root part with only a pair of electrode rods, a plurality of sets of electrode rods are inserted and installed so as to straddle the root part, and are connected to the pulsed electric field generator via switching means for selecting a pair of electrode rods, so that a pulsed electric field can be applied to the entire root part by applying the pulsed electric field while switching the electrodes.

[0021] As the invention according to claim 4, there is provided a method for controlling the growth of roadside trees according to claim 1, wherein the electrodes are at least a pair of electrode plates installed with the plate surface facing the ground direction.

[0022] The invention described in claim 4 above shows a third example of the installation mode of the electrodes. Specifically, the electrodes are at least a pair of electrode plates installed with the plate surface facing the ground direction. Even with the electrode plates installed with the plate surface horizontal in this way, a pulsed electric field is induced in a curved shape toward the ground, and the roots extend in the ground direction of the roots so as to avoid this, so that problems such as the root lifting phenomenon where the roots of roadside trees grow and lift the paving of the road can be solved.

[0023] As the invention according to claim 5, there is provided a method for controlling the growth of roadside trees according to claim 1, wherein the first electrode is arranged so as to surround the entire circumference and the bottom surface of the root part of the roadside tree, and the second electrode is arranged so as to surround the entire circumference and the bottom surface of the root part at a predetermined distance outside the first electrode.

[0024] The invention described in claim 5 above shows a fourth example of the installation mode of the electrodes. Specifically, the electrodes are arranged such that the first electrode surrounds the entire circumference and the bottom surface of the root of the street tree, and the second electrode is arranged so as to surround the entire circumference and the bottom surface of the root at a predetermined distance outside the first electrode. In this case, a pulsed electric field is applied between the first electrode and the second electrode. Although a pulsed electric field is not applied to the root normally, when the root grows and reaches the area beyond the first electrode, a cell destruction phenomenon occurs due to the pulsed electric field, so that further growth of the root can be suppressed.

[0025] Claim 6 In the present invention according to claims 1 to 5 Any of the methods for controlling the growth of street trees described is provided.

[0026] The above claim 6 In the invention described, when it is not possible to easily prepare the power supply means, a solar power generation system is provided, and the pulsed electric field generator is automatically operated at regular intervals to apply a pulsed electric field, so that the pulsed electric field is automatically applied to the root without manual intervention.

Effect of the Invention

[0027] As described in detail above, according to the present invention, it is possible to solve various problems such as the root uplifting phenomenon in which the roots of street trees grow and lift the paving of the street. In addition, this control method can be easily applied not only to newly planted street trees but also to existing street trees without requiring large-scale construction, and the influence range of the construction can be reduced.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0030] 〔Example of Installation Structure of Street Trees〕 Fig. 1 shows an example of the installation structure of the street tree 8. In the illustrated example, a sidewalk 2 is provided adjacent to the roadway 1. At the boundary between the sidewalk and the roadway, a sidewalk-roadway boundary block 3 is installed, and the sidewalk 2 has a structure in which paving blocks 4 (interlocking blocks) are laid. The sidewalk 2 is, for example, as shown in Fig. 2, on the upper surface of the roadbed layer 5 made of crusher run or the like, with paving blocks 4 arranged in a lattice pattern with a gap (joint) of about several millimeters through a sand cushion layer (not shown) of about 20 to 30 mm, and the joints are filled with sand.

[0031] On the other hand, the roadway 1 is configured as the side end of the sidewalk-roadway boundary block 3. The roadway 1 has a structure in which a hot asphalt mixture 7 is laid on the upper surface of a roadbed 6 paved with crushed stone, crusher run, or the like.

[0032] Roadside trees 8 are planted at prescribed intervals, specifically 6 to 8 m apart, in the traffic direction on the side of the sidewalk 2 closer to the roadway 1. On the sidewalk 2, three frame blocks 9, 9... that are installed in a U-shape in plan view and the sidewalk-vehicle boundary block 3 form a rectangular vegetation frame, and usually one roadside tree 8 is planted inside this frame.

[0033] The present invention provides a growth control method for suppressing the growth of street trees in order to solve various problems caused by the overgrowth of street trees 8, namely, the root-raising phenomenon in which the roots of street trees grow and lift up the road pavement, accidents in which thick branches or trunks of street trees protrude outward as the trees grow and come into contact with vehicles, and problems such as traffic lights, road signs, street lights, etc. being blocked by street trees.

[0034] First, before explaining the growth regulation method of the present application, a paper on growth regulation promoting plant growth that formed the basis of the knowledge leading to the present invention will be introduced. [Plant growth regulation paper] Research has been conducted to promote plant growth and increase yields by applying a pulsed electric field to plants (mainly edible vegetables, etc.). In other words, applying a pulsed electric field to the roots produces an electroporation effect, which increases nutrient absorption and promotes plant growth.

[0035] Some of the inventors of the present application have reported in a non-patent document (Wang Douyan, Goto Takahiro, Yoshida Takashi, Namihira Takao, Akiyama Hidenori, Fujiwara Toshiyuki, Sato Daigo; "Lettuce Growth Control by Pulsed Electric Fields", Institute of Electrical Engineers Pulsed Power Study Group Materials, PPT-12, March 2012, pp. 13-16) the results of an experiment conducted on the relationship between the applied pulsed electric field intensity and lettuce yield, focusing on hydroponic lettuce, a major cultivar in plant factories, as the target crop to which a pulsed electric field is applied, with the aim of controlling plant growth by applying a pulsed electric field to the roots of the plant, with the aim of shortening the number of days required for crop cultivation, which is one of the solutions for the spread of plant factories. An outline of the experiment is given below.

[0036] 1. Experimental Method 〈Sample to Which Pulsed Electric Field is Applied〉 In the experiment, a pulsed electric field was applied to the roots of hydroponic lettuce (variety: Early Impulse). For cultivation, lettuce seeds were sown in seedling pots filled with culture soil and grown in the pots until the planting stage (around 20 days after sowing). After that, at the planting stage, the entire seedling pot was immersed in liquid fertilizer, and the liquid fertilizer was circulated. The seedling pot is made of thin resin, and a plurality of slits are provided at the lower part of the side surface at intervals in the circumferential direction. The liquid fertilizer is absorbed through these slits, and the grown roots extend to the outside. The harvesting time of the lettuce leaf part is around 40 days after sowing.

[0037] In the experiment, at the planting stage, it was transferred to an incubator (M-230F, manufactured by Taitec Corporation) and cultured for about 20 days until the harvesting day. During that time, a pulsed electric field application experiment was carried out. The culture conditions were a temperature of 20 - 21°C, a humidity of 30 - 95%, 24-hour fluorescent lighting, and an illuminance of 6800 - 10000 lux. Inside the incubator, the seedling pot was placed in a resin vat immersed in liquid fertilizer, and the liquid fertilizer was added by the amount that decreased due to evaporation inside the incubator to maintain a constant liquid fertilizer amount.

[0038] 〈Pulsed Electric Field Generator〉 For the generation of the pulsed electric field, a PFN (Pulse Forming Network) type single-pulse generation circuit was used. The schematic is shown in Fig. 7. The PFN was connected in 7 stages, with an inductance of 2 μH and a capacitance of 2.7 nF for each stage. The theoretical output pulse width was 400 ns, and the power supply characteristic impedance was 10 Ω. The characteristic impedance was calculated from the conductivity of the liquid fertilizer (about 1 ms / cm) used for the cultivation of hydroponic lettuce and the electrode shape for applying the electric field. In addition, by connecting a matching load of 10 Ω to the PFN input terminal, the reflected wave generated at the load terminal was absorbed on the input side to achieve single-pulse output.

[0039] A DC high-voltage power supply (PS / EW40R15.0 - 10, manufactured by GLASSMAN HIGH VOLTAGE) was used for charging the PFN. Also, to avoid the occurrence of discharge between the electrodes, a negative-polarity pulsed voltage was applied to the load.

[0040] The voltage waveform applied between the electrodes was measured using a high-voltage probe (P6015A-R3, manufactured by Tektronix), and the current to the load was measured using a current probe (Pearson current monitor, Model 110, manufactured by Pearson Electronics) with an oscilloscope (TDS3054B, manufactured by Tektronix).

[0041] As a reactor for applying a pulsed electric field to the lettuce roots, a stainless-steel parallel-plate electrode (diameter 80 mm, disk type) was fixed to the opposing wall surfaces of an acrylic container. To vary the applied pulsed electric field strength, a plurality of acrylic containers with different lengths were fabricated, and the parallel-plate electrodes were attached to the containers according to the target electric field strength.

[0042] 〈Method for Applying Pulsed Electric Field and Method for Evaluating Growth of Lettuce〉 The timing for starting the pulsed electric field application was set around 20 days before entering the planting stage, and the application was carried out once a day in the morning until the harvest day. The pulsed electric field application procedure was as follows: First, the inside of the reactor was filled with fresh liquid fertilizer, and the lettuce plants taken out from the incubator were placed between the parallel-plate electrodes so that the entire nursery pots were immersed in the liquid fertilizer (see Fig. 8). After applying the pulsed electric field to the lettuce roots, the nursery pots were taken out of the reactor and returned to the incubator. The liquid fertilizer used during the electric field application in the reactor was discarded and not used for lettuce cultivation.

[0043] Based on the findings of the preliminary tests, the frequency of the pulsed electric field applied to the lettuce roots was determined to be 1 Hz and the number of applications was 100 times, and the electric field strength was varied from 0.2 to 2.0 kV / cm. Considering the biological balance of the lettuce itself, three samples were used for each parameter. Also, for the control sample, the same treatment as the pulsed electric field application sample was applied, and the electric field strength was set to 0.0 kV / cm (no electric field application).

[0044] As a method for evaluating growth, the total weight of the harvested lettuce leaf parts was compared and evaluated between the samples for each electric field application parameter and the control samples. Also, at the time of harvesting, the lettuce leaf parts were cut according to the upper surface edge height of the seedling-raising pot, and the total weight of the leaf parts was measured using an electronic balance (PL3002, manufactured by METTLER TOLEDO Co., Ltd.).

[0045] Also, in order to examine the reproducibility, the experiment was carried out 3 times, and the average value was evaluated.

[0046] 2. Experimental Results Fig. 9 shows the dependence of the total weight of the lettuce leaf parts at the time of harvesting on the applied pulsed electric field strength. Also, Table 1 and Fig. 10 show the percentage increase or decrease in the average value of the total weight of the lettuce leaf parts at each electric field strength compared with the control when the control is set to 100%. From Fig. 9, Fig. 10, and Table 1, it is clear that the growth of lettuce can be controlled by applying a pulsed electric field to the lettuce roots. Also, there is an appropriate electric field strength value in order to obtain a growth promotion effect, and if an electric field strength that is too strong is applied, growth will be inhibited. Under the experimental conditions of this study (pulse duration 400 ns, 1 Hz, 100 pulses applied once a day after the planting period), the appropriate electric field strength for promoting the growth of the lettuce leaf parts is 0.5 to 1.0 kV / cm, and a strong stimulus of 2.0 kV / cm or more brings about an inhibitory effect on the growth of the leaf parts. Also, at 0.4 kV / cm where the most growth promotion effect was obtained, the yield increased by about 20% compared with the case where no pulsed electric field was applied.

[0047] Furthermore, at the time of harvesting, the lettuce roots in the plants with an applied electric field strength of 0.4 kV / cm where the most growth promotion effect was obtained were thicker, longer, and had a higher root hair density compared with the control. On the other hand, in the plants with an applied electric field strength of 2.0 kV / cm where growth inhibition was observed, the roots were less developed than the control plants, and the tip of the root broke easily when touched with a finger.

[0048] As shown in Table 1 and Fig. 10, the electric field strength at which the total weight of the lettuce leaf parts decreases compared with the control plants is about 1.1 kV / cm or more, and particularly when it is greater than 1.5 kV / cm, the decrease rate exceeds 20% and becomes significant.

Table 1

[0049] Growth control method of the present application In the above-mentioned plant growth control paper, as shown in Table 1, in the experiments for each of the 7 cases of pulse electric field strength, paying attention to the range where the increase or decrease ratio of the total weight of the lettuce leaf part increases with respect to the case without applying the pulse electric field, it is reported that by applying that pulse electric field strength to lettuce, an increase in yield can be achieved.

[0050] The inventors of the present application did not focus on the range where the increase or decrease ratio of the total weight of the lettuce leaf part is positive, but rather came up with the present invention by focusing on the region where the increase or decrease ratio of the total weight of the lettuce leaf part is negative. That is, although it has been found that by applying a pulse electric field strength within a predetermined range, a plant growth promoting effect due to the electroporation effect can be expected, when a higher pulse electric field strength is applied, the stimulus becomes too strong for the plant, and an irreversible cell perforation phenomenon occurs. This irreversible cell perforation causes cell destruction and suppresses the growth of the plant. Based on the idea of whether the growth of street trees can be suppressed by utilizing this phenomenon, the present invention has been achieved.

[0051] As shown in FIGS. 2 and 3, this growth control method is to install at least a pair of electrode plates 10 and 11 in the ground with the plate surfaces facing the root part 8A while straddling the street tree 8, and connect these electrode plates 10 and 11 to a pulse electric field generator 12, apply a pulse electric field to the root part 8A, and induce a cell destruction phenomenon to suppress the growth of the root part.

[0052] As the electrode plates 10 and 11, as shown in FIG. 2, a pair of electrode plates 10 and 11 are provided in the ground so as to straddle the root part 8A of the street tree 8 in a direction perpendicular to the direction of human passage. However, a pair of electrode plates may also be provided in the ground so as to straddle the root part 8A in the passage direction, and two sets of a pair of electrode plates may be provided. Also, in the drawing, they are linear flat plate electrodes in plan view, but it is also possible to use flat plate electrodes with a curved shape in plan view.

[0053] The dimensions of the electrode plates 10 and 11 shall be such that the width dimension (B) can apply a pulsed electric field to the entire shallow root portion 8A of the street tree 8, and the depth dimension (L) shall desirably be a length such that the root elongation does not affect the sidewalk blocks. The region K of the root portion 8A surrounded by the dashed-dotted line becomes the application region of the pulsed electric field. By using the electrode plates 10 and 11 as the electrode form, it becomes possible to efficiently apply a pulsed electric field to the entire shallow root portion 8A of the street tree.

[0054] It is desirable to apply a pulsed electric field having a voltage of a short pulse of about 400 nanoseconds, for example, to the root portion 8A about 100 to 1000 shots at a frequency of about 1 Hz. The application frequency of this pulsed electric field is desirably about 1 to 3 times per day.

[0055] The intensity of the pulsed electric field applied to the root portion 8A by the electrode plates 10 and 11 is desirably a pulsed electric field intensity that can induce a cell destruction phenomenon and suppress growth while not causing withering. Specifically, as a lower limit value capable of inducing a cell destruction phenomenon, it is desirably 1.1 kV / cm or more, preferably 1.5 kV / cm or more, and more preferably 2.0 kV / cm or more.

[0056] On the other hand, it is said that the electric field intensity required for electroporation of cells having a size of 1 μm is 10 kV / cm, and it is advisable to keep the cell destruction at this level of electric field intensity. Therefore, the upper limit value of the pulsed electric field intensity is desirably 10.0 kV / cm or less, preferably 5 kV / cm or less, as an electric field intensity that does not cause the plant to wither.

[0057] 〔Second aspect of the electrode installation example〕 The second aspect of the electrode installation example will be described in detail based on FIG. 4.

[0058] Instead of the electrode plates 10 and 11, as shown in FIG. 4, it is also possible to use a plurality of sets of electrode bars 13 and 14. The electrode bars 13 and 14 are a plurality of electrode bars 131, 132... 13 as one-side electrodes in order to apply a pulsed electric field to the entire root portion 8A of the street tree.n are arranged side by side at a predetermined interval, and a plurality of electrode bars 141, 142... 14 are used as the electrodes on the other side n are arranged side by side at a predetermined interval and inserted into the ground. In the illustrated example, the electrode bars 131, 132... 13 n (141, 142... 14 n ) are provided six by six on one side.

[0059] Also, a switching device 15 for switching the plurality of electrode bars 131, 132... 13 n is provided in the middle, and a switching device 16 for switching the plurality of electrode bars 141, 142... 14 n is provided in the middle and electrically connected to the pulse electric field generating device 12.

[0060] In this way, a plurality of electrode bars 131, 132... 13 n (141, 142... 14 n ) are installed at a predetermined interval, and switching means 15 and 16 for selecting paired electrode bars are provided, so that the paired electrode bars 131, 132... 13 n (141, 142... 14 n ) can be selected in a relay manner, so that a pulse electric field can be applied to the entire root 8A of the street tree 8.

[0061] Also, when applying to the root 8A of the street tree 8, it is often difficult to secure power itself. In such a case, as shown in FIG. 4, a solar power generation system, that is, a solar power generation facility 17 having a solar panel 18 held at the tip of a support column is provided in the vicinity, and the electricity generated here may be supplied to the pulse electric field generating device 12 as a power source. In addition, it is desirable to apply the pulse electric field automatically by operating the pulse electric field generating device at regular intervals without manual intervention so that the pulse electric field is applied to the root 8A automatically.

[0062] 〔Third Aspect of Electrode Installation Example〕 Next, the third aspect of the electrode installation example will be described in detail with reference to FIG. 5.

[0063] In the first and second aspects, the electrodes were installed so as to be inserted into the ground, that is, so as to face the root portion 8A. However, as shown in FIG. 5, at least a pair of electrode plates 19 and 20 may be provided with the plate surface facing the ground direction.

[0064] Even with the electrode plates 19 and 20 installed with the plate surface horizontal in this way, a pulsed electric field is induced in a curved line shape toward the ground, and the root portion 8A extends in the ground direction of the root so as to avoid this, so that problems such as the root of the street tree 8 growing and lifting the pavement of the street can be solved.

[0065] 〔Fourth form of electrode installation example〕 Next, the fourth aspect of the electrode installation example will be described in detail with reference to FIG. 6.

[0066] As shown in FIG. 6, the first electrode 19 is arranged so as to surround the entire circumference and the bottom surface of the root portion 8A of the street tree 8, and the second electrode 20 is arranged so as to surround the entire circumference and the bottom surface of the root portion 8A at a predetermined distance outside the first electrode 19. The separation distance between the first electrode 19 and the second electrode 20 is desirably made as small as possible in consideration of the required voltage and energy. Specifically, the minimum separation distance is 1 mm, and it is desirable to be about several mm to several cm. Also, the intensity of the pulsed electric field to be applied is desirably stronger than in the first to third aspects.

[0067] In this aspect, a pulsed electric field is not applied to the root portion 8A during normal times. However, since a pulsed electric field is generated between the first electrode 19 and the second electrode 20, when the root portion 8A grows and reaches a region beyond the first electrode 19, a cell destruction phenomenon occurs due to the pulsed electric field, so that further root growth can be suppressed.

[0068] 〔Other form examples〕 (1) In the above-described embodiment, a non-porous plate-shaped member is assumed as the electrode plates 10 and 11. However, it is also possible to use a mesh-shaped or perforated plate-shaped member as the electrode. Specifically, a wire mesh-shaped member, a punched metal plate, or the like can be used. By using a mesh-shaped member or a perforated plate, the flow of infiltrated water and groundwater is not inhibited.

[0069] (2) In the above-described first and second embodiments, a pair of left and right electrode plates 10 and 11 are provided so as to be arranged in the horizontal direction. However, it is also possible to provide a pair of upper and lower electrode plates 10 and 11 so as to straddle the root portion 8A of the street tree 8 in the vertical direction.

[0070] (3) In the above-described embodiment, a pair of left and right electrode plates 10 and 11 (19 and 20) are provided so as to straddle the root portion 8A of the street tree 8 in a direction orthogonal to the direction of human passage. However, a pair of electrode plates may also be provided so as to straddle the root portion 8A of the street tree 8 in the direction along the passage direction. Alternatively, a total of two sets of electrodes may be provided by providing a pair of electrode plates in both the direction orthogonal to the direction of human passage and the direction along the passage direction.

Explanation of Reference Numerals

[0071] 1…Lane, 2…Sidewalk, 3…Boundary block between pedestrian and vehicle lanes, 4…Pavement block, 5…Subbase layer, 6…Roadbed, 7…Hot mix asphalt, 8…Street tree, 9…Frame block, 10·11…Electrode plate, 12…Pulsed electric field generator, 13·14…Electrode rod, 15·16…Switching device, 17…Solar power generation facility, 18…Solar panel, 19·20…Electrode plate

Claims

1. A growth control method for suppressing the growth of roadside trees, comprising: installing electrodes near the roots of the roadside trees, connecting these electrodes to a pulsed electric field generator, and applying a pulsed electric field with an electric field strength of 1.1 kV / cm or more and 10.0 kV / cm or less to the roots of the roadside trees to induce a cell destruction phenomenon through an electric shock effect, thereby suppressing the growth of the roots. The growth control method for roadside trees is characterized by this.

2. The growth control method for roadside trees according to Claim 1, wherein the electrodes are at least a pair of electrode plates installed in the ground with the plate surfaces facing the roots so as to straddle the roots of the roadside trees.

3. The growth control method for roadside trees according to Claim 1, wherein the electrodes are a plurality of sets of electrode rods inserted and installed in the ground, and are connected to the pulsed electric field generator through a switching means for selecting a pair of electrode rods.

4. The growth control method for roadside trees according to Claim 1, wherein the electrodes are at least a pair of electrode plates installed with the plate surfaces facing the ground direction.

5. The growth control method for roadside trees according to Claim 1, wherein the first electrode is arranged so as to surround the entire circumference and the bottom surface of the roots of the roadside tree, and the second electrode is arranged so as to surround the entire circumference and the bottom surface of the roots at a predetermined distance outside the first electrode.

6. The growth control method for roadside trees according to any one of Claims 1 to 5, wherein a solar power generation system is provided, and the pulsed electric field generator is automatically operated at regular intervals to apply a pulsed electric field.

Images