Vegetation characteristics

Measurement of vegetation properties is an important aspect of the SMAPVEX12 campaign with a main focus on major crops (spring wheat, canola, oats, barley, corn and soybeans). Some fields of perennial land cover (grassland and tame hay including alfalfa and grass) will also be selected.

During SMAPVEX12, a number of vegetation properties will be measured in order to assess the vegetation effect in both passive and active microwave measurements, at the SMAP scale, and in soil moisture retrieval algorithms. Some of these properties are static (Plant Density, Row Spacing, Row direction) and will be measured only once. Others are dynamic (Leaf Area Index, Biomass and Canopy Water Content, size, Phenology, etc.) and require repeated measurements.

For the dynamic properties, the sampling strategy will consist of collecting vegetation data at three sites per field, once per week. The location of these three sites will be selected with the goal to capture, as best as possible, the mean field crop conditions. The number of replicates required for each vegetation properties will vary.

In addition, reflectance of the crop canopy will be measured using CropScan multi-spectral instrument to characterize the general crop condition and growth state. Mesaurements will be recorded once a week, every meter over 5 meters distance, diagonally across rows; 5 replicates will be taken at each site.

A summary of vegetation sampling strategies is given in the table below. More details can be found in the experimental plan of SMAPVEX12.

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Summary of vegetation sampling strategies

Property	Sample sites per field	Replicates per site	Instrument	Temporal frequency	Description of approach	Assigned team
Static vegetation parameters
Plant density	1	3	–	Once	Count number of plants along 10 or 1 metre(s); replicate for 10 rows	AAFC students, prior to campaign
Row spacing	1	3	Meter stick/tape measure	Once	–	AAFC students, prior to campaign
Row direction	1	1	Compass	Once	–	AAFC students, prior to campaign
Dynamic vegetation parameters
Leaf Area Index	3	1	Camera and fish eye lense	Once per week	7 photos taken along 2 transects (14 in total)	Biomass
Biomass and canopy water content	3	1	0.5 x 0.5 m square	Once per week	For wheat, oats barley, grassland, ame hay, collect all biomass within square	Biomass
	3	1	0.5 x 0.5 m square	Once per week	For canola, corn, soybeans, collect 5 plants along each of 3 rows (15 in total)	Biomass
Height	3	10 plants	Meter stick/tape measure	Once per week	–	Biomass
Stem diameter	3	10 plants	Calliper	Once per week	–	Biomass
Phenology	1	1	–	Once per week	–	Lab tech
Canopy structure	3	1	Digital Camera and gridded board	Once per week	Gridded marker board is placed behind one row and photo taken	Structure
Canopy architecture	3	1	Calliper, ruler, protractor	Once per week	–	Structure
Canopy reflectance	3	5	CropScan	Once per week	Measure every metre over 5 m distance, diagonally across rows	Structure

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