Editing Eastern Prickly Pear (section)

=== Inland Rocky Ridges ===

Even as early as the mid-1800s, it was observed by botanists that ''O. humifusa'' colonies were very fragmented in their inland distribution.  I would estimate, based upon historic records and my own field examinations of extant colonies, that there may be as many as a dozen inland colonies in the state, perhaps less.  I have thus far confirmed only five inland colonies in four towns (Hamden, New Haven, Old Saybrook and Plainville), though my research has revealed that at least eight inland towns in Connecticut were historically known to host wild ''O. humifusa'' colonies.

Indeed, research reveals that ''O. humifusa'' colonies on rocky or sandy inland habitats were once much more common than they are today.  In all likelihood, many inland colonies have been lost to the natural process of forest succession whereby areas that were cleared for timber or previously maintained as open pastures are abandoned (generally between 1650 and 1850) and recolonized, first by shrubs and pioneer trees and eventually by thick forest.  Since ''O. humifusa'' requires full sunlight, a good number of colonies are likely to have perished as the forest regenerated and shaded them out.

In my research, "inland colonies" are defined as those colonies living on the mainland that are more than 1000 feet from Long Island Sound.  This category also includes those colonies of ''O. humifusa'' that may be found nearby inland riparian habitats.  Any colonies living further south than this boundary are considered "coastal colonies" for the purposes of my research.  Typically, "inland colonies" are discovered at elevations no less than 100 feet AMSL, though elevation is not a determining factor in their categorization as "inland" colonies and it is possible that inland colonies may be found at lower elevations.

==== Habitat Requirements ====

===== Soil & Geology =====

<div style="float:right; display:inline-block;padding-left:15px;">
{| class="wikitable" style="text-align: left;" cellpadding="10"
! colspan="2" style="color: black; background-color: #ffffcc;"| Overview of Soil Characteristics of Inland ''O. humifusa'' Habitats
|-
! style="color: black; background-color: #ffffcc;text-align: left;"| Soil Characteristic
! style="color: black; background-color: #ffffcc;text-align: left;"| Description
|-
| style="font-weight: 700;"| Soil Type
| 80% : Holyoke-Rock Outcrop Complex (Soil Type 78)<br/>20% : Charlton-Chatfield Complex (Soil Type 73)
|-
| style="font-weight: 700;"| Soil Slope Types
| 60% : 3 to 15 percent slope (Soil Type 78C)<br/>40% : 15 to 45 percent slope (Soil Types 78E & 73E)
|-
| style="font-weight: 700;"| Soil Drainage
| 100% : Well-drained
|-
| style="font-weight: 700;"| Soil/Bedrock Reactivity
| 100% : Extremely acidic to moderately acidic
|-
| style="font-weight: 700;"| Soil Composition
| 100% : loam over glacial till deposits
|-
| style="font-weight: 700;"| Bedrock Composition
| 60% : (1) diabase, (2) basalt, (3) gabbro<br/>20% : (1) basalt, (2) gabbro<br/>20% : (1) gneiss, (2) granite, (3) schist 
|}
</div>
Approximately 80% of the inland ''O. humifusa'' colonies that I have thus far discovered are found upon terrain with a soil type described as '''Holyoke-Rock Outcrop Complex''' (Soil Type 78) by the Soil Survey of the State of Connecticut (SSSCT) produced by the United States Department of Agriculture and the Natural Resources Conservation Service.  Of that 80%, approximately 75% of those colony areas can further be sub-classified as exhibiting a 3 to 15 percent slope (Soil Type 78C).  The [[#West Rock Dunbar Colony & West Rock Shepard Colony|West Rock Shephard Colony]] of Hamden was found on terrain that is classified as having a 15 to 45 percent slope (Soil Type 78E), however the colony location is very close to the transition line between soil types 78C and 78E and is therefore not a significant outlier.  Thus, it can be stated that inland Connecticut ''O. humifusa'' colonies occur frequently on Holyoke-Rock Outcrop Complex with a slope between 3 and 45 degrees (or a mean slope of approximately 19 degrees).

The SSSCT describes Holyoke-Rock Outcrop Complex (78C and 78E) as "gently sloping to strongly sloping", "bedrock-controlled" hills and ridges "on uplands" where the depth to bedrock does not generally exceed 20 inches.  The parent material of these habitat areas includes "loamy eolian deposits over melt-out till derived from basalt and/or sandstone and shale".  Of particular interest is the fact that the soil of Holyoke-Rock Outcrop Complex is typically well-drained and "extremely acidic to moderately acidic".<ref name="ct-soil-survey">"Soil Survey of the State of Connecticut." ''Connecticut Environmental Conditions Online''. University of Connecticut, n.d. Web. 18 May 2012. <http://www.cteco.uconn.edu/docs/usda/connecticut.pdf>.</ref>

Further analysis using the Connecticut Environmental Conditions Online (CTECO) GIS Map of Critical Habitats revealed that 60% of Connecticut's confirmed inland ''O. humifusa'' colonies are found on habitat that is designated as '''Subacidic Rocky Summit Outcrops''' (SubRSO).  CTECO describes these habitat areas as "dry to xeric exposed summits, ledges and other outcrops", noting the geologic composition to be "primarily basalt and other mafic rocks", where vegetation is typically restricted to "low shrubs, grasses and herbs". <ref name="cteco-criticalhabitats">"Connecticut Critical Habitats." ''Connecticut Environmental Conditions Online''. University of Connecticut, Mar 2011. Web. 18 May 2012. <http://www.cteco.uconn.edu/guides/resource/CT_ECO_Resource_Guide_Critical_Habitat.pdf></ref>  While the Metacomet Colony habitat is not identified as Critical Habitat SubRSO, the conditions I observed there are congruent with the habitat description and it is likely this area was incidentally neglected on the CTECO Critical Habitat GIS Map.  

Approximately 60% of confirmed inland colonies are found upon West Rock Ridge in New Haven and Hamden, Connecticut on a bedrock type known as '''West Rock Dolerite''' (USGS Code Jwr).  The [[#Metacomet Colony (Plainville)|Metacomet Colony]] in Plainville, Connecticut has a bedrock type defined as '''Holyoke Basalt''' (USGS Code Jho).  However, basalt is the common thread between these two bedrock types, with Holyooke Basalt being comprised primarily of basalt with gabbro as a secondary rock type while West Rock Dolerite is primarily composed of diabase with basalt and gabbro as secondary and tertiary rock types.  The reactivity of these bedrock types ranges from subacidic (in the case of Holyoke Basalt) to somewhat pH neutral (in the case of West Rock Dolerite).

All of these observations seem to suggest that ''O. humifusa'' is partial to acidic soil which is rich in diabase, basalt and gabbro.  However, this conclusion was seriously challenged when I documented the [[#Ingham Hill Colony (Old Saybrook)|Ingham Hill Colony]] of ''O. humifusa'' in Old Saybrook.  The Ingham Hill Colony exists on soil defined as '''Charlton-Chatfield Complex''' (73E) (which contains a mix of granite, schist and gneiss) on a bedrock type defined as '''Monson Gneiss''' (USGS Code Omo).  The discovery of this colony seriously undermined my previous conclusion that inland ''O. humifusa'' had a special affinity for traprock ridges and I have since withdrawn my theory that the species exhibited a unanimous preference for basalt.

Instead, it is now my belief that the frequency at which ''O. humifusa'' appears on traprock ridges is merely a reflection of the fact that traprock ridges are especially common in Connecticut.  In many towns, the only sunny, exposed ledges are found upon these traprock ridges, so that ''O. humifusa'' simply has nowhere else to grow.  I do not believe that ''O. humifusa'' has any special preference for basalt, but that the high rate of occurrence of ''O. humifusa'' on basalt ridges is merely incidental.

While ''O. humifusa'' may not have any strong preference for soil of a specific composition, there are nonetheless certain characteristics of soil that must be met in order for it to qualify as acceptable habitat for ''O. humifusa''.  Every inland colony thus far discovered has been found upon soil that is especially well-drained and which is classified as moderately acidic to extremely acidic.  These soil characteristics are found at every ''O. humifusa'' colony site, including the unusual Ingham Hill Colony site.

===== Elevation =====

Prior to the discovery of the [[#Ingham Hill Colony (Old Saybrook)|Ingham Hill Colony]] at Old Saybrook, there seemed to be sufficient evidence that inland colonies of ''O. humifusa'' preferred elevations of between 350 and 550 feet above mean sea level (AMSL).  Since the discovery of the Ingham Hill Colony, though, this assertion has been seriosuly challenged and I no longer believe ''O. humifusa'' has any particular elevation preference.

With the exception of the Ingham Hill Colony, ''O. humifusa'' colonies upon inland ridges certainly present a tight correlation in elevation.  The [[#Metacomet Colony (Plainville)|Metacomet Colony]] is at an elevation of ~399 feet AMSL, the West Rock South Colony is at ~429 feet AMSL and both of the northern West Rock colonies range in elevation from ~515 feet AMSL at their highest to ~425 feet AMSL at their lowest.  These elevations are tightly clustered between 350 and 550 feet AMSL, which had hitherto lead me to believe that there was some advantageous quality to this range of elevations which ''O. humifusa'' preferred.  However, this theory seriously failed to account for those coastal colonies of ''O. humifusa'' that are found at significantly lower elevations (rarely exceeding 30 feet AMSL).  This fact was especially troubling when trying to determine some meaningful correlation between suitable ''O. humifusa'' habitat and elevation.

The discovery of the Ingham Hill Colony in Old Saybrook was particularly important, because the ''O. humifusa'' found growing there were at an elevation of roughly 145 feet AMSL.  This is the only instance that I have thus far encountered in which ''O. humifusa'' could be found at a distinctly intermediate elevation, significantly lower than colonies found on traprock ridges but significantly higher than colonies found in coastal scrubland.  Therefore, I have abandoned my previous suspicion that ''O. humifusa'' prefers elevations between 350 and 550 feet AMSL.  Instead, I would submit that the frequency at which inland ''O. humifusa'' occurs at these elevations is simply a product of the terrain of Connecticut, where the rocky cliffs of basalt ridges are very commonly found at elevations between 300 and 600 feet AMSL.

The Ingham Hill Colony proved to be something of a missing link, bridging the previously enormous gap in elevation between coastal colonies and inland colonies.