LAINet Leaf Area Index

Automatic LAINet Leaf Area Index Monitoring System

System composition:

LAINet consists of wireless sensor network nodes deployed in the field, including nodes under and above the canopy, as well as solar power supply systems.

The nodes on the upper layer of the canopy must be installed in open and unobstructed areas around. Generally installed at the top of the solar power supply system bracket in the LAINet system

The nodes under the canopy are generally installed under the lower layer of leaves of the plant, and the closer they are to the ground, the better.

Fix the node horizontally on the bracket and bury the bracket in place

Installation recommendations

Distribution principles and precautions

Layout principle: Arrange one to three nodes within a 30 * 30 sample plot; Large areas can be divided into small sample plots according to the actual situation and arranged according to the above principles

Suggest perpendicular to the ridge or forming a 45 degree angle

A more specific deployment plan can be formulated based on the actual situation of the sample site and with reference to the "Leaf Area Index Remote Sensing Product Authenticity Inspection Standards" drafted by the Institute of Cold and Drought and the Institute of Remote Sensing

Application fields:

·Long term monitoring of vegetation growth status, such as ecological fixed stations, agricultural long-term observation stations, etc

Automatic LAINet Leaf Area Index Monitoring SystemMeasurement principle:

·Vegetation (taking forests as an example) will form shadows on the ground under the sunlight, and the vegetation gap rate can be calculated based on the proportion of shadows in the field of view. Within * *, due to the change in the direction of incoming sunlight caused by the movement of the sun, the proportion of ground projection will vary with the change in the angle of the sun, allowing for the acquisition of canopy gap ratios from multiple angles.

·Canopy shadows at different solar angles (top: camera sees image at the upper part of the canopy, camera height 29 meters; bottom: camera sees image at the lower part of the canopy, where the black part is the tree trunk, camera height 4.5 meters)

·Applicable vegetation types (crops, forests, grasslands).

In response to the limitation that current leaf area index (LAI) measuring instruments are mainly suitable for uniform vegetation types, we have developed an automatic LAI measuring instrument based on wireless imaging mode, namely LAIPhoto.

LAIPhoto is suitable for the early stage of vegetation growth, when the vegetation canopy is low and the spatial distribution is very sparse. At present, domestic and foreign instruments for measuring leaf area index of vegetation canopy use the projection characteristics of vegetation canopy to sunlight to estimate leaf area index. In the case of vegetation * *, it is difficult for the instrument to accurately capture the canopy transmittance at the lower part of the canopy. Therefore, it becomes very difficult to use the canopy transmittance principle to measure leaf area index in this situation. However, in sparse vegetation, the canopy will cast very obvious shadows under direct sunlight, and there is a direct relationship between the shadow area ratio of the canopy and the canopy leaf area index. Therefore, we have designed a leaf area index measurement instrument suitable for situations where the vegetation canopy is very sparse.

LAIPhoto consists of wireless imaging sensors deployed in the field and a wireless image acquisition and transmission system.

We have developed a vegetation image fine classification algorithm, which can automatically extract the proportion of vegetation canopy shadows in the image under different lighting conditions. Based on the variation of vegetation shadow proportion with the solar zenith angle, the vegetation leaf area index is automatically calculated.