Simulation -based Model ling of Growth and Pollination of Greenhouse Strawberry Zhihao Cao Hongchun Qu

2025-05-03 1 0 1.13MB 29 页 10玖币

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Simulation-based Modelling of Growth and

Pollination of Greenhouse Strawberry

Zhihao Cao, Hongchun Qu*

College of Information Science and Engineering, Zaozhuang University,

Zaozhuang 277160, China

Abstract

The cultivated strawberry Fragaria × ananassa Duch. is widely

planted in greenhouses in China. Its production heavily depends on

pollination services. Compared with artificial pollination, bee pollination

can significantly improve fruit quality and save considerable labor

requirement. Multiple factors such as bee foraging behavior, planting

pattern and the spatial complexity of the greenhouse environment

interacting over time and space are major obstacles to understanding of bee

pollination dynamics. We propose a spatially-explicit agent-based

simulation model which allows users to explore how various factors

including bee foraging behavior and strawberry phenology conditions as

well as the greenhouse environment influence pollination efficiency and

fruit quality. Simulation experiments allowed us to compare pollination

efficiencies in different conditions. Especially, the cause of bee pollination

advantage, optimal bee density and bee hive location were discussed based

on sensitivity analysis. In addition, simulation results provide some

insights for strawberry planting in a greenhouse. The firmly validated

open-source model is a useful tool for hypothesis testing and theory

development for strawberry pollination research.

Keywords: Greenhouse strawberry, Bee pollination; Simulation-based

modelling; GAMA platform;

1. Introduction

Strawberry is any of the various, low-growing perennial plants of

the genus Fragaria in the rose family. The most common strawberries

grown commercially are cultivars of the garden strawberry Fragaria ×

ananassa Duch., which has been the most widely distributed fruit crop in

the world. It is grown in every country with a temperate or subtropical

climate and even in many tropical countries in highland areas, where the

climate is mild. Strawberry fruits are highly prized for their universal

appeal to the human senses of sight, smell, and taste [9].

Strawberries can be pollinated by self, wind, and bees. Honey bees

(Apis mellifera ligustica) are recognized as the main pollinator of the

strawberry crop [16]. If there are no honey bees, the combined action of

gravity and wind assures the basis of the pollination because the stamens

can scatter pollen onto many of the pistils as they crack open [13]. However,

these flowers may not be completely self-fertilizing in this way, which may

result in a low fruit setting rate and malformed fruits. In practical

strawberry planting, bees are important for pollination. Pollination by bees

not only increases crop yield, but also improves aspects of fruit quality,

including nutritional value and shelf life [34]. Recent research suggested

that when strawberry plants in greenhouses were isolated from honeybees,

the fruit set was 50–59% lower compared to the case where bees were

present, which can achieve on average 80% of fruit set when bees were

present [16,40,41].

Understanding the bee pollination process is rewarding for

improving strawberry yield and quality [31,41,48]. However, many factors

such as bee foraging behavior, planting pattern and the spatial complexity

of greenhouse environment interacting over time and space are major

obstacles to understanding of bee pollination dynamics. For example, bees

are attracted by the appearance of plant inflorescence during foraging, so

the foraging patterns might differ in various landscapes [45]. This suggests

that planting pattern in a greenhouse could affect bee foraging distance and

direction and consequently result in the dynamics of pollination efficiency.

This interaction in space is difficult to understand quantitively without the

help of simulation models, because bee behavior and plant floral exhibit

obvious spatial heterogeneities and vary across individuals [46]. Previous

strawberry models focused on strawberry growth processes [22] including

modelling the water-balance for irrigation [49], statistical yield forecasting

via weather conditions [50], and prediction of phenological stages based

on regressions [51]. These models do not include pollination processes.

Modelling the spatial and stochastic process, spatial-explicit individual

based models are much more intuitive and powerful than conventional

ordinary differential equations.

Hence, we modelled the strawberry plants and honey bee foraging

behavior for the first time and use quantitative methods to analyze

simulation results of fruit production. Modelling strawberry pollination

allows us to decipher hidden relationships between variant organisms to

better understand the pollination service in greenhouse strawberries. This

model was used to study the bee pollination process in a strawberry

greenhouse. Specifically, we studied the influence of bee density on

strawberry quality, the cause of advantage for bee pollination over artificial

pollination, and the influence of hive location on strawberry quality. We

proposed some planting suggestions for strawberry growers based on the

experiment results. The main contributions of this paper are as follows:

(1) We propose an open-source model that provides multi-scale

simulation from strawberry pollen to plant, including simulation of

strawberry growth in a greenhouse and interaction with bees. This model

incorporates much of what is known and hypothesized about the

pollination ecology of strawberry agroecosystem. The model codes include

many adjustable parameters that allow users to adapt to different cultivars

and planting environments.

(2) We analyzed the optimal bee density based on the proposed

model. The results suggested that when the bee density was higher than

1.00 bee/clone, the fruit quality was not significantly improved due to a

saturation effect. In practical greenhouse planting, strawberry pollination

may be affected by mechanical actions, diseases and other factors, with a

result that it is necessary for growers to ensure the bees outnumber the

strawberry clones in a greenhouse.

(3) The effect of hive location and bed spacing in a greenhouse on

pollination efficiency was analyzed based on the model. We suggested that

strawberry growers can place bees in multiple hives not only one hive and

then place these hives in different locations in a greenhouse to diminish the

influence of bee foraging distance constraints.

(4) Practical planting experience suggests that bee pollination is

better than artificial pollination in many respects. For the first time, the

quantitative effects of viability of pollen and stigma, self-compatibility on

strawberry fruit quality were analyzed through simulation experiments.

The results revealed that the even distribution of pollen in pistil during bee

pollination is the primary cause and stigma receptivity is a secondary cause

of advantage for bee pollination over artificial pollination. Not only the

pollen transport but the even pollen distribution caused by bee behavior are

significantly important.

2. Materials and methods

2.1 Strawberry

The cultivated strawberry Fragaria × ananassa Duch. is widely

planted in greenhouses in China [41]. Therefore, we selected this cultivar

because of its extensive history of study [4,8,11,13,21,34] and economic

importance. Specifically, its bee pollination process was studied through

simulation-based modelling. For other cultivars, the simulation software

codes include a variety of adjustable parameters on strawberry growth that

users can modify to adapt to different cultivars of strawberry.

2.1.1 Greenhouse

The most popular strawberry cultivation system in China is solar-

powered plastic greenhouse and this type of cultivation system uses only

solar energy for crop production, as shown in Figure S1. The greenhouse

not only prevents the damage caused by adverse climatic conditions but

also provides a suitable environment for strawberry cultivation and

protects the crop from insects and pets [32]. The microclimate in

greenhouses is significantly more suitable than that in open environment.

Strawberry fruit production in China generally takes place from

November to April, starting with the planting of bareroot transplants in

November. In this simulation, it is assumed that the cultivation site is in

China and the simulation starts on January 1st and lasts until April, lasting

around 120 days. There is a close relationship between solar light and

inside temperature in a greenhouse. All the greenhouses were managed by

experienced fruit growers and were controlled at a fixed temperature and

relative humidity (RH) condition [1]. Low temperatures will increase the

possibility of damaged fruits as well as changes in fruit size and high

temperatures reduce the plant’s photosynthetic rate [33]. Among the

environmental conditions, temperature is one of the most important factors

[44] that affect fruit and seed set at different stages of the reproductive

developing process. The general temperature ranges [15,32] in two weather

conditions and months are shown in Table 1.

Table 1 The setting of general temperature range of the greenhouse in

simulation

Month

Temperature

range

(sunny)

Temperature

range

(cloudy)

Day of

simulation

January

6-22℃

6-12℃

1-30

February

10-26℃

12-14℃

31-60

March

14-28℃

13-16℃

61-90

April

16-30℃

14-18℃

91-120

Standard greenhouses in China are usually 80 m long and 8 m wide.

Strawberry plants were grown in raised beds with a plastic film cover on

the soil (plastic mulching). Distance between two strawberry beds is

usually about 0.4 m, and the single bed width is about 0.6 m. There are two

rows of strawberry clones per bed, about 0.24 m apart. The distance

between two strawberry clones is about 0.2 m. As a result, there are 12

rows in the greenhouse and 390 strawberry clones in each row. Totally,

this standard greenhouse includes 390*12*2=9,360 strawberry clones. The

bee hive is generally arranged on the east side of the greenhouse where the

temperature is high according to practical planting experience. The

simplified greenhouse diagram is shown in Figure 1.

Fig.1 A simulated strawberry greenhouse. The out rectangle represents the

greenhouse boundary. Inside the boundary, black open circles represent

strawberry clones, green dots represent different inflorescences. Green dots

of different sizes represent different inflorescence rank. In the east open

site of the greenhouse, the grey dot represents bee hive.

2.1.2 Inflorescence and flower

Strawberry flower clusters occur on a series of double branches with

a flower in the fork of each branch [45]. Generally, strawberry plants have

one primary flower, two secondary flowers and up to four tertiary flowers

per inflorescence. The existence of competition within inflorescences was

demonstrated by obtaining heavier secondary berries after removing the

primary [11]. Therefore, only primary and secondary fruits were used to

estimate yield, as they are the only fruits usually considered marketable

[11]. In order to improve yield and quality of strawberry fruits, it is usually

necessary to cut off some low-level inflorescences in production, i.e.,

flower thinning. In our simulation, each strawberry clone retains one

primary inflorescence and two secondary inflorescences. There are of 6

flowers in each primary inflorescence and 3 in each secondary

inflorescence in simulation, as shown in Table 2. Therefore, a strawberry

clone can bear up to 12 fruits.

Table 2. Flower information of strawberry in simulation

Inflorescence

Number

per clone

Number of

flowers per

inflorescence

Number of

pistils(ovules)

per flower

GDD*

Primary

350

N(586, 70)

Secondary

260

N(946, 70)

*: The Growth Degree Day for strawberry plants is assumed to follow

normal distribution.

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Simulation-basedModellingofGrowthandPollinationofGreenhouseStrawberryZhihaoCao,HongchunQu*CollegeofInformationScienceandEngineering,ZaozhuangUniversity,Zaozhuang277160,ChinaAbstractThecultivatedstrawberryFragaria×ananassaDuch.iswidelyplantedingreenhousesinChina.Itsproductionheavilydependsonpollinati...

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Simulation -based Model ling of Growth and Pollination of Greenhouse Strawberry Zhihao Cao Hongchun Qu

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