[R] envfit output (vegan package) - not sure what it means

[cernst]

I'm pretty new to R and would appreciate some help interpreting the output of
a function that was recommended to me.

I've used the *envfit *function in the vegan package to plot vectors of four
climate variables onto a species matrix ordination.  The output indicates
that only a single variable (mean_temp) is significant:

***VECTORS

                        NMDS1          NMDS2        r2           Pr(>r)   
precip            0.41539         -0.90964      0.2948    0.112887   
wind              -0.61937          0.78510      0.0441     0.763237   
temp_mean  0.50571        -0.86270      0.5839     0.004995 **
pressure        -0.66891        0.74334      0.0688     0.622378   
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 
P values based on 1000 permutations.

I understand that the length of the plotted arrows is proportional to the
strength of the correlation between the variable and the ordination, but I'm
not sure how to interpret the direction of the arrows. I know that it is
"the direction of the gradient", but *I don't really understand what
gradient that is referring to*.  So I'm not sure how to interpret what I'm
seeing in the plot, other than the significance of the relationship.

Here is the plot, if that helps. Each point is a sampling period; they are
numbered from week 1 - week 8. The different shapes represent two different
habitats. 

http://r.789695.n4.nabble.com/file/n4623315/species_abunance_with_environment.jpeg 

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