Number Of Taxa Vs. Trail Length For Trails In Our Master Database
Which is the most diverse trail in our database, as defined by the one with the most species per mile? Which is the least diverse trail? How does the diversity depend on elevation, trail aspect, number of distinct habitats on the trail, or other parameters? How does this change if one excludes non-native taxa?
These are some of the burning questions that can be answered only when we have completed plant lists for many trails. However, it is fun to play with our preliminary data, even though some of the trails are horribly incomplete, due to the drought in 2002 and the near-complete absence of annuals on some trails, and due to our having visited a trail at only one time so far. So, with those huge caveats in mind, which trails are in the lead so far for diversity?
The following plots show the number of taxa (total, natives only and non-natives only) vs. mileage surveyed. The trails are color-coded by elevation:
In the plots above, the circled points should be given the most weight in interpreting the plots. The points represent trails we have surveyed both in 2001 and 2002, with many trips. Hence they are likely to be fairly complete.
Because the number of plants found in a given area usually scales with some power of the area, the number of plants will increase as the trail mileage increases. This expected general increase is shown on each plot, where two parameters (the normalization and the exponent) were fitted by eye to the circled points. The circled points, as well as some of the other upper points, follow this expected relation fairly closely, and those points are labeled in the top plot. Points that plot much lower than the upper points are very likely to be trails whose plant lists are incomplete for the reasons given above.
The most diverse trails for all taxa seem to be the ones at elevations below 6000 feet. However, if one considers only native taxa, the results from these preliminary data show that at least some higher elevation trails are just as diverse as the lower elevation trails. (Brown Mountain Fire Road is missing from the second two plots since its plant list is incomplete for the plant identification, although the first plot shows that its plant list appears to be fairly complete in terms of number of species.)
Clearly, the most significant conclusion that can be drawn so far is that higher elevations contain at most only a few species of non-natives.
The raw data for all of our trails is given below, so the reader can explore which points correspond to what trails for the unlabeled points. It is very important to look at the number of visits for a given trail. Trails with only a few visits will be much more incomplete than trails with many visits, and so the data from those trails should be given less weight.
The following plots gives an idea of how the non-circled points may move in the future, as their plant lists become more complete:
The history of the number of taxa is shown with red vertical lines. Each point on a line represents the number of taxa after each trip, beginning with the first trip. Only trails with a complete history, from the first trip, are plotted. Thus the lowermost red dot gives the number of taxa from our first trip, the red dot immediately above that one gives the total number of taxa after our second trip, and so on. The only exceptions are:
- the Vernal Pool Trail, where records of plants blooming from a number of trips in the previous year were folded into the total number of taxa between trips two and three; and
- the Granite Loop Trail, where similar records were added for the last point.
Most of the other big jumps come from the appearance of species on a given trip that weren't evident from previous trips, primarily annuals and herbaceous perennials. However, a significant amount of the increase comes from finding species that had escaped our attention previously.
We have records of the history for the other trails as well; they haven't been put into our database yet.
| name | Visits | latest | # visit | # taxa | #unk | #unk sp | #~ | #unk ssp | length | min altitude | max altitude | ave altitude | # natives | #non-natives | % native | |||||||
| Vincent Gap Parking Lot (SGM) | 8/10/01 | 3 | 38 | 4 | 0 | 38 | ||||||||||||||||
| Reef Point Trail (CCSP) | 7/26/02 | 2 | 44 | 5 | 1 | 1 | 0.93 | 0 | 100 | 50 | 30 | 14 | 68% | |||||||||
| Beach / Broken Hill Trail (TP) | 7/9/02 | 1 | 63 | 13 | 6 | 1 | 0.84 | 0 | 200 | 100 | 59 | 4 | 94% | |||||||||
| Green Route (CCSP) | 7/26/02 | 1 | 78 | 10 | 5 | 1 | 2.74 | 200 | 500 | 350 | 55 | 23 | 71% | |||||||||
| SMER: North gate to gorge (Fb) | 6/9/02 | 5 | 118 | 9 | 0 | 0.91 | 600 | 1000 | 800 | 81 | 37 | 69% | ||||||||||
| Monserate Mtn (Fallbrook) | 8/17/02 | 3 | 70 | 0 | 2 | 5 | 1 | 3.37 | 300 | 1400 | 850 | 55 | 15 | 79% | ||||||||
| SMER: North Rim Trail (Fb) | 6/9/02 | 3 | 58 | 1 | 0.63 | 900 | 1000 | 950 | 40 | 18 | 69% | |||||||||||
| SMER: South gate to gorge (Fb) | 4/7/02 | 4 | 161 | 26 | 3.61 | 600 | 1500 | 1050 | 123 | 38 | 76% | |||||||||||
| DS Campground (PM) | 3/8/02 | 3 | 69 | 22 | 0.55 | 1560 | 1640 | 1600 | 59 | 10 | 86% | |||||||||||
| Granite Loop (SRP) | 4/28/02 | 8 | 119 | 9 | 1 | 1.15 | 1700 | 1800 | 1750 | 98 | 21 | 82% | ||||||||||
| Brown Mountain Fire Road (SGM) | 1/30/02 | 1 | 122 | 22 | 1.92 | 1700 | 2100 | 1900 | ||||||||||||||
| Vernal Pool (SRP) | 5/10/02 | 12 | 140 | 0 | 1 | 1.71 | 1800 | 2000 | 1900 | 101 | 39 | 72% | ||||||||||
| DS Trail (PM) | 3/8/02 | 3 | 105 | 35 | 4.13 | 1640 | 3500 | 2570 | 98 | 7 | 93% | |||||||||||
| Sunset Ridge (fire road / trail to top; SGM) | 6/27/02 | 8 | 182 | 12 | 0 | 5 | 4.51 | 1900 | 3400 | 2650 | 130 | 52 | 71% | |||||||||
| Sulphur Spring (SGM) | 5/15/02 | 2 | 90 | 32 | 4 | 0.65 | 4000 | 3800 | 3900 | 82 | 8 | 91% | ||||||||||
| Self-Guided Nature Trail (Heise County Park) | 8/23/02 | 1 | 33 | 4 | 0 | 3 | 3 | 0.62 | 4400 | 4400 | 4400 | 30 | 3 | 91% | ||||||||
| BHMT (SGM) | 5/1/02 | 7 | 124 | 41 | 17 | 1.82 | 6000 | 6500 | 6250 | 118 | 6 | 95% | ||||||||||
| Manzanita (from top; SGM) | 7/19/02 | 8 | 99 | 10 | 2 | 3 | 2.35 | 6500 | 6000 | 6250 | 96 | 3 | 97% | |||||||||
| Lightning Ridge (SGM) | 8/30/02 | y | 1 | 53 | 3 | 6 | 5 | 4 | 0.54 | 7200 | 7300 | 7250 | 49 | 4 | 92% | |||||||
| Devils Slide (SJM) | 6/13/02 | 1 | 42 | 27 | 2 | 2.5 | 6500 | 8000 | 7250 | 42 | 0 | 100% | ||||||||||
| Baden-Powell (SGM) | 8/30/02 | y | 1 | 42 | 0 | 2 | 0 | 3 | 2.09 | 6500 | 8100 | 7300 | 41 | 1 | 98% | |||||||
| Mt. Lewis (SGM) | 8/26/02 | y | 1 | 13 | 0 | 2 | 0 | 0 | 0.43 | 7903 | 8200 | 8051.5 | 13 | 0 | 100% | |||||||
| Willow Creek (SJM) | 6/13/02 | 1 | 12 | 4 | 2.13 | 8000 | 8500 | 8250 | 12 | 0 | 100% | |||||||||||
| Dawson Saddle to Throop Peak (SGM) | 8/26/02 | y | 3 | 46 | 2 | 1 | 2 | 0 | 2.38 | 7903 | 9138 | 8520.5 | 45 | 1 | 98% | |||||||
| most altitudes were guessed! Need to be corrected | ||||||||||||||||||||||
| Manzanita (from bottom; SGM) | 1 | 77 | 36 | 2.06 | 4000 | 5000 | 4500 |