Classification, biodiversity and conservation: explain question

An ecologist investigated the relationship between soil pH and the abundance of a rare orchid species, Orchis rara, in a grassland ecosystem. At 10 randomly selected sample sites, she measured soil pH and counted the number of Orchis rara individuals in 1 m² quadrats. She then calculated Spearman's rank correlation coefficient using the formula provided:

$r_s = 1 - \frac{6 \sum d^2}{n(n^2 - 1)}$

She obtained a value of $r_s = -0.82$. The critical value at $p = 0.05$ for $n = 10$ is 0.648.

Explain what this correlation coefficient indicates about the relationship between soil pH and Orchis rara abundance, and how this information helps define the niche of Orchis rara within this ecosystem.