I was lucky enough to receive in the mail a treatise on "Keystone Grasslands"--Pennsylvania's open habitats--by Roger Latham and James Thorne. They introduce their subject by writing:
Grasslands, meadows, and savannahs... are crucial for biodiversity conservation out of proportion to their small total area, and they declined severely during the twentieth century.We tend to toss around the term "early successional" as somewhat synonymous with these open habitats. This is true only in degree: many of our open habitats are only temporarily so, recovering to forest from some human disturbance, as in an abandoned farmfield or dump site or roadside.
But what of the conservative meadow flora? The patches of prairie once tucked into our forested landscape? Where do the flowers of the once "mesic-diabase meadows in the Piedmont Triassic lowlands"--Latham's formulation-- now dwell? When might these plants colonize our current landscapes, or do they lurk in the seedbanks under people's driveways or in overgrown forests?
Many of these meadow rarities are also said to reside in "open woods". These are not, as I take it, the thickety woods of early successional growth but rather the deeply interlinked slow habitats of many years' gestation. Open woods-- through barrenness or wetness of soil? Through fire? Boulder-strewn steep slopes?
Generally, the flora of ancient meadow and open wood seem reliant on the endemic disturbances of our continent: drought, damp, fire, geology. These habitats arise seldom if at all from the disturbances of present-day: plow, bulldozer, herbicide, dumping. Where, then, reside the fringed gentian, Indian paintbrush, blazing star, New Jersey tea, rose pink, butterfly milkweed, showy goldenrod?
We took a walk today on the gas pipeline, the largest meadow-like habitat on our diabase Sourlands ridge, albeit the product of saw and dozer and buried petroleum. We wanted to find a stand of Blazing Star I had discovered last year while seed collecting and trying to shake the ghosts of our prairie trip from my mind. Luckily, we found the Liatris spicata in great plenty, looking taller and more slender than probable for a plant so rigidly upright. Drought seems to be delaying flowering somewhat, but we'll return in a week or two to see the purple spikes in dense blazing glory.
Practically at the feet of the Liatris were a number of patches of the diminutive herb Blood Milkwort ("fields, meadows, open woods" says the field guide). These were thriving in an occasionally mowed linear access path, blooming (or just past) at hardly over six inches tall. They were surrounded by short-statured path rush, but also by recently shorn Chinese bush clover and Bidens aristosa.
These latter two plants, both newcomers to our state, have become, together with the ubiquitous and ugly mugwort, scourges of the pipeline meadows. My friend Heidi, an old-timer who lives along the pipeline, claims that the Chinese bush clover arrived just in the last half-decade or so. Now huge swards stretch the girth of the pipeline for hundreds of feet virtually uninterrupted by other plants save the occasional goldenrod or switchgrass.
On Heidi's advice, we head next to North Hill in search of a population of butterfly milkweed which she remembers having seen there some years ago. On arriving, we surmised that it had been swallowed whole by the bush clover.
We did find a patch of pale-leaved sunflower, another denizen of open woods and fields seldom seen. It looked like a circular moon landing of native flora in the thick of the bush clover. How soon before this, too, becomes swallowed and forgotten?
The pipeline is an enigma, some patches weedy and gone too hell, others with a hint of deep meadow ancestry, like our patches of blazing star and perennial sunflower. Ed Laport commented in notes even in the 1970s that that pipeline contained large swaths of dullness punctuated by occasional great finds.
In some places the underlying geology may be a contributing factor to the patches of interesting flora, though between mugwort, Bidens, bush clover, autumn olive, multiflora rose, and Phragmites, there seems to be a too-hardy non-native scourge for all habitat types. Other places are probably better or worse because of their land use history. Was this an over-fertilized cornfield decades ago, or a rocky acidic oak forest? It is in the latter that the Liatris and milkwort now reside.
The pipeline, despite its destructive genesis, and continued potential for mismanagement, is the kind of occasional refuge for our longer-lived, more conservative meadow flora. It is hard to think that it is improving with time-- "If you had seen this then..." Heidi kept repeating when we botanized the pipeline a week ago. Yet, for a time, it is about the closest I've found to those "mesic-diabase meadows" Latham and Thorne mention.