The signs of an early end to the end of a very mild winter for 2015-2016 have come to Ithaca New York. The migratory ground foraging birds such as cardinals (Cardinalis) and american robins (Turdus migratorius) are back. However, as a soil scientist, the real sign of spring is when the soil thaws. Unless you have a probe to measure soil temperature, it can be difficult to tell if the entire soil profile has thawed or just the surface.
In forested ecosystems of the northeastern US, the blooming of the snowdrops (Galanthus) signals that the surface soils have become warm enough for their seeds to germinate. And these flowers are quite ready for spring to occur. But one other sign of springs approach is the annual rise of the earthworms.
“Without the work of this humble creature, who knows nothing
of the benefits he confers upon mankind, agriculture, as we
know it, would be very difficult, if not wholly impossible”
-Charles Darwin, 1881
I have witnessed this event to occur as one act and two acts. The first warm rain of the season awakens the earthworms from their burrows to rise to the surface. I generally see the anecic earthworms, generally the exotic Lumbricus terrestris in the northeastern US, are the first earthworms to rise. After months of being cooped up belowground, they crawl to the surface to ‘stretch’ their segments, forage, and ‘say hello’ to their neighbors. Because the anecic burrows are linked with the surface, they are more prone to feeling the warm spring water than other earthworms. For this reason, I believe the second ‘rise of the earthworms’ wave can be quite indicative that the entire soil profile is thawed.
These endogeic earthworms that live in the soil without permanent burrows come to the surface after a the entire soil profile has warmed up sufficiently to reach their hibernating positions in the soil. And in early March 2016, the wave of endogeic earthworms, in this case Aporrectodea rosea, have emerged and I snapped this photo on my way trip across the Cornell University campus. We may be in for one or two more snowfalls, but it seems spring is here to stay.
