Line Index Variables

What is the Line Index? It is my quantitative description of the best nut producers (the ‘3’ trees, if you are familiar with the term from previous blogs), using the variables I currently think the most important. These are:

· Anthracnose Score (AS)

· Nut Yield (NY)

· Shell Index (SI)

· Kernel Percentage (K%)

· And, derived from NY, the Alternate Bearing Index (ABI or ABNY)

Below is an explanation of each variable, but not the reason why I consider them the most important. Just be content for the moment that a range of quantitative descriptors has been attached to each line (line = a single tree, which may or may not have an identifiable maternal parent on or off-farm). DBH (Diameter at Breast Height) is included for interpretation.

Anthracnose Score (1-5). The expressed incidence of leaf-spotting disease (which may have non-anthracnose components), which is commonly considered to depress a tree’s productive ability. 1=low, 5=high, thus a 1 indicates nill expression, which can be considered a strong tolerance (if not outright resistance) to leaf-spotting disease.

Nut Yield (no.nuts per cm² of trunk diameter at DBH). A measure of productivity based on nut count per tree, adjusted for the tree’s size. All trees in a plantation will vary in growth rate.

Shell Index (shell wt proportional to nut volume: g per cm³). A measure of the energy partition occurring at the individual nut level.

Kernel Percentage (kernel weight as a proportion of dry nut weight). A measure of the edible yield of the nut. Can be used in combination with NY to determine Kernel Yield (KY).

Alternate Bearing Index (0-1). A measure of the consistency in nut production. Black walnut shows variable biennial productivity. Here adjusted for DBH, thus accounting for tree size, and calculated from NY, thus more truly ABNY, not ABI which, used by others, does not account for change in potential productivity across time based on tree growth.

Diameter at Breast Height (cm). A standard, convenient measure used to determine annual change in tree size at 135cm from the ground. DBH, for all its convenience, is a moving target. While it remains constant in relation to the ground, it does not remain constant in relation to the top of the tree. Thus, successive annual measures of DBH are taken at different points within a tree’s geometry.