Rangeland Analysis Platform

New data source for In-Season NDVI:  Rangeland Analysis Platform. (RAP) https://rangelands.app/rap/ 

RAP allows mapping of Cover and Biomass, and generates reports for an Area of Interest for Cover, Annual biomass, and 16-day biomass.  I'm hopeful they will upgrade the map to include 16-day biomass.  If they did, I could add it to the comparisons of the other NDVI sources.  Mapping would allow in-season management decisions based on forage production.

Case Example: Dugas, AZ

This series of years from 2018-2023 shows the variability in biomass production by season in a desert grassland at mid-elevation (4,000 ft) in AZ:

2018 shows a drought year, when there was little to no spring green-up due to a lack of winter precipitation, and a low green-up in response to summer monsoons.

2019 and 2020 were the "nonsoon" years, when the summer monsoons failed to materialize.  However, because the winter rains were good in 2019 and exceptional in 2020, total production was high.

2021 and 2022 show the potential for growth in years of good monsoon rains.  2023 shows a "normal" year with bimodal peaks in production corresponding to the spring green-up peaking in late March, and the summer monsoons peaking in mid-August.  However, for some reason this year had almost no annual biomass production associated with the monsoon.  Each year is different!

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Case Example: Congress, AZ

This series from around Congress, AZ shows the extreme variability of plant growth in the Sonoran desert (2,500 ft).

In drought years like 2018 and 2022, there is almost no plant growth, whereas the extreme winter precipitation year of 2020 annuals produced almost 130 pounds/acre of spring growth.  None of the years hadmuch perennial herbaceous production, and monsoons inconsistently produce up to 40 pound/acre of growth in good years.  

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Case Example:  Grand Canyon Junction 

SR-64 and SR 180 intersection, just south of Grand Canyon high-elevation grassland (6,000 ft).

Maximum production compared to the lower elevation sites is lower, only reaching 50 pounds/acre in good years.   However, total annual production is usually more consistent.  There is still the potential for bimodal production peaking in the late spring (early June) (2023 and 2017, not shown) and in the monsoons.  The monsoon peak seems to be most consistent, except in 2019 and 2020 when the monsoons failed - luckily those years had relatively good spring growth.   

In contrast to the low desert site, annual production (red) is usually less important than perennial production (green) at this site:

Finding the Greenest Place in Arizona

 I love plants, and I love places where plants are happy.  But how can I find the greenest places, especially when I live in Arizona?

In the Southwest deserts, plant phenology and growth are dependent on intermittent rains.  But the rains can be variable between nearby areas. 

Rainfall totals and percent of normal can be viewed using https://water.weather.gov/precip/ This uses observed (radar) precipitation. 

Displaying Last 90-Day Percent of Normal Precipitation from Sep. 20.

However, more important than total rainfall over the growing season is timing of rainfall.  A single deluge that brought 3 inches last week to an area that hasn't seen rain in 6 months, is not as effective in stimulating plant growth as regular weekly or biweekly 0.5 inch storms.

A better approach to locating areas of high plant growth is using NDVI (Normalized Difference Vegetation Index), or observed "greenness" from satellites.  Data updates every week or couple of weeks, depending on the satellite.

But some areas, like forests, will always look greener than other areas, like deserts.  What we really want to locate are areas of anomalous greenness.

This UA webpage calculates departures from last week, last year, and from the average year.

VIIRS NDVI difference from average from Sep 6.

Other resources include the USGS Vegetation Drought Model, VegDRI.  The Vegetation Drought Response Index (VegDRI) shows seasonal drought impacts on vegetation. The weekly index is produced using a model trained on the self-calibrated Palmer Drought Severity Index using MODIS satellite-derived greenness anomaly integrated with precipitation, land cover, soils, and other biophysical data sets. Updated every Monday by 10 AM. 

VIIRS NDVI as shown by the USGS VegDRI model.

Clicking on the map generates a time series, which can be useful to compare seasonal and yearly changes at a location.

Graph of VegDRI drought index for a location in Yavapai County over the last 4 years.

The United Nation's FAO also maintains an NDVI anomaly drought mapper that uses the European satellite AVHRR.  However, the data is only provided at the scale of entire nations.  

So where is the greenest place in Arizona?  As you may have noticed from the screenshots above, that depends on who you're asking!  I hope to "ground-truth" some of these models to learn which are most reliable for greenness-hunting.

Analysis of Soil and Vegetation Maps:  Accuracy and Utility for Describing Actual Habitats

There are four sources of landscape information from maps at the project level a few miles on a side.  Topogaphic maps, satellite maps, soil service maps, and vegetation maps.   

Comparing soil and vegetation maps at this scale is complicated by inaccuracies of both map sources and the strange ambiguity of aerial photography.  Soil was mapped by NRCS into 6 major soils.  However, two of the soils are described as compound soils, regions of undefined patches possibly intergrading continuously into one another.  For example, Pyote-Maljamar soils (PU on soil map) have a layer of fine sand everywhere, but there are unmapped bits and pieces of caliche at around 50 inches (Maljamar soils) in a matrix of deep sand (Pyote soils).

Soil map created using the NRCS Web Soil Survey showing major soil types.  PT and PU are deep sands, BH and KO are shallower silty soils, and TF is intermediate.  (PA and BA are extensions of PT and TF, respectively, in Eddy county.)

Soil Profiles:

	PT	PU		TF	BH		KO
Soil Name	Pyote	Pyote	Maljamar	Tunuco	Berino	Cacique	Kimbrough
0-10	A: Loamy fine sand	A: fine sand	A: fine sand	A: loamy fine sand	A: fine sand	A: fine sand	A: gravelly loam
10-20				AC: loamy fine sand	Btk: sandy clay loam	Bt: sandy clay loam	Bkm: cemented material
20-30				Bkm: cemented material
30-40	Bt: Fine sandy loam	Bt: fine sandy loam	Bt: sandy clay loam			Bkm: cemented material
40-50
50-60			Bkm: cemented material
Type	Sandy eolian deposits	Sandy eolian deposits	Sandy eolian deposits	Sandy eolian deposits	Sandy eolian deposits over sandy calcaereous alluvium	Calcaerous eolian deposits	Calcaerous alluvium and/or eolian deposits

Selected Soil Properties

	PT	PU	TF	BH	KO
Depth to restrictive layer	>200cm	127cm	43cm	>200cm	15cm
Calcium Carbonate (CaCO3)%	2%	2%	0%	17%	15%
% sand	75.8%	81.9%	78.6%	62.6%	43.0%
Ksat (inches/hour)	7.8	8.5	12.6	1.7	0.5

In this part of NM, depth to a restrictive soil layer indicates the presence of caliche near the surface.  These petrocalcic horizons are denoted Bkm on the soil profile.  KO has the shallowest effective soil, followed by TF.  Some parts of BH appear quite shallow, but in the table the depth to a restrictive layer is listed as greater than 200cm, possibly because some of the soil (i.e. the Berino component) lacks a caliche layer. Caliche is composed of calcium carbonate, so BH and KO are listed with the most calcium, and the least sand in their profile. 

Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a saturated soil transmit water. The estimates are expressed in inches/hour for ease of comparison to possible rainfall rates. They are based on soil characteristics observed in the field, particularly structure, porosity, and texture.

Restrictive soil layers and overall soil texture contribute to the ability of a soil to drain water.  PT, PU, and TF are listed as very well drained soils because they can all drain more than 7 inches of rain an hour, whereas BH and KO are significantly less porous, draining only 1.7 and 0.5 inches of rain an hour, respectively.  Most of the water from heavy rains probably runs off of these soil types, limiting the amount available to grow plants. 

Saturated hydraulic conductivity is considered in the design of soil drainage systems and septic tank absorption fields. It probably has the greatest impact on plant production of any soil parameter in SE NM.

Hydraulic conductivity is the rate at which a soil can absorb water.  Red areas have the least ability to absorb rainfall, while blue areas have the greatest ability to absorb rainfall. Map created using NRCS Web Soil Survey.  

Vegetation Map

Vegetation map from USGS GAP Vegetation Mapper uses NatureServe Ecological System Classification.

Vegetation Map Key and Attributes

Table 3. Vegetation Map Key and Attributes

Color	ReGAP Community Name	Vegetation Type	Dominant Species	Accuracy
	Great Plains Shortgrass Prairie	Grassland	Biennial wormwood, Russian thistle	Low – should be mapped as disturbed area
	Mesquite Upland	Thornscrub	Mesquite, Catclaw Acacia, Mimosa, Yucca	High - mesquite dominant
	Sandhill Shrubland	Shrub	Shinnery oak, Catclaw acacia, Giant dropseed	Medium – not all dune
N/A	Sandy Plains Semi-Desert Grassland	Grassland	Purple three-awn, Sand dropseed, Sand muhly	Low – not mapped

The GAP national land cover data, based on the NatureServe Ecological Systems Classification, are the foundation of the most detailed, consistent map of vegetative associations available for the United States.  The soil map is interpolated based on soil pits and vegetation patterns, so in a way it functions as a hand-drawn vegetation map.  Vegetation patterns have changed from the time the soil survey was completed (1960’s?) to now.  This GAP high-resolution vegetation map was produced via satellite mapping and computer algorithms. 

The prairies of the southern Great Plains are also called the Llano Estacado, a region where vast flat to rolling uplands are covered with blue grama grass.  However, this vegetation type is misclassified.  GAP maps roads and disturbed areas with low grass as shortgrass prairie (brown on image) because these areas look similar to prairie in multispectral satellite imagery.  It maps the rest of the project area as a fractal pattern of mesquite upland (mauve) patches and sandhill shrubland (green) patches. 

Mesquite has spread throughout areas with deep sandy soils and now forms the default vegetation community across much of the area. Mesquite can also invade sandhills and desert washes and other coarse-textured soil areas. It is especially invasive in grasslands such as Sandy Plains Semi-Desert Grasslands, Great Plains Shortgrass Prairie, and Chihuahan Semi-Desert Grasslands. 

Mesquite grows best when soils are deep, lacking the caliche or clay pan that would limit infiltration and storage of winter precipitation in deeper soils layers. Mesquite and other deep-rooted shrubs exploit the deep soil moisture that is unavailable to cacti or grasses. 

The effects of major soil boundaries are evident: deep sand (PT and PU) soils support more sandhill shrubland, whereas soils with shallow restrictive horizons (BH and KO) tend to have more mesquite upland patches.  The vegetation map fails to identify patches of Lehman lovegrass grasslands, or catclaw acacia shrublands, but it does correctly identify shinnery oak areas as sandhill shrubland. 

However, the map misses out on an important intermediate community, sandy plains semi-desert grassland.  Sandy plains grasslands are actually the dominant community throughout much of the project area.  It is distinguishable on the ground by the greater proportion of grass than shrubs on sandy soils, often with Aristida purpurea, Muhlenbergia arenicola, and especially Sporobolus flexuousus.  However, this community has been invaded by mesquite shrubs (some areas of which have been recently killed with herbicides) so these grassland patches can be difficult to distinguish from true shrublands.

Topo Map

A topo map shows that areas with accumulating sand are typically uplands, especially breaks in slope where winds drop eolian deposits.  Eroding, exposed slopes reveal deeper, more-developed paleosoils, possibly Pleistocene clays (Steve Hall, 2006 Geomorphology of Mescalero Sand Dunes).  

On top of soil and geomorphic landscape-determined vegetation patterns, local populations of invasive species have overlaid an unpredictable pattern of monocultures of Lehman Lovegrass, Artemisia biennis, and occasional plants of Salsola tragus around wellpads.  Note that none of these invasive species are NM state-listed noxious weeds.  There are also surprising areas of intact, diverse Chihuahuan grasslands with healthy stands of black grama , muhly arenicola, and sporobolus cryptandrus.  All of the sand dunes here, despite presence of shinnery oak, and even some Artemisia filifolia, are coppice or hummock dunes that formed around shrubs during historical time (Hall, 2006). 

 Conclusion

Unfortunately, there are no map sources of reliable data on habitats and vegetation communities at field- or project area-scale.  Each source provides valuable clues along with misleading simplifications, errors, and obfuscations of actual on-the-ground conditions. 

Appendix: Soil Properties Maps

Depth to a restrictive soil layer:

Percent sand:

Percent calcium carbonate:

Threatened and Endangered Species of the Williamette Valley Prairie Savannas

There are 6 listed species endemic to the ecoregion.

Fender's Blue butterfly (E) (Icaricia icarioides fenderi)
Willamette daisy (E) (Erigeron decumbens var. decumbens)
Bradshaw's desert-parsley (E) (Lomatium bradshawii)
Kincaid's Lupine (T) (Lupinus sulphureus ssp. kincaidii)
Nelson's checker-mallow (T) (Sidalcea nelsoniana)
Golden Paintbrush (T) (Castilleja levisecta) - extirpated from Williamette valley

Several other nonlisted species are also considered sensitive:

Taylor’s (whulge) checkerspot butterfly, Euphydryas editha taylori
Pale larkspur, Delphinium leucophaeum
Willamette Valley larkspur, Delphinium oreganum
Peacock larkspur, Delphinium pavonaceum
Shaggy horkelia, Horkelia congesta ssp. congesta
White-topped aster, Sericocarpus rigidus
Hitchcock’s blue-eyed grass, Sisyrinchium hitchcockii

There are two major rare habitats in the Williamette valley responsible for the listed and sensitive species: upland prairies and wet prairies. Prairies are dependent on disturbance to prevent succession, and many have been either plowed under or allowed to develop into forests or shrublands.  A recovery plan extends throughout the Williamette valley, and south of Roseburg to the Douglas county line to include a third disjunct habitat in the Umpqua valley.  

The plant composition of upland prairies is dominated by bunchgrasses, including Festuca idahoensis, Danthonia californica, Elymus glaucus, Achnatherum lemmonii, and Koeleria macrantha.  The spaces between the bunchgrasses are typically covered by mosses, fruticose lichens, or native forbs. Showy, slow-growing perennial forbs include Eriophyllum lanatum, Potentilla gracilis, Fragaria virginiana, Sidalcea malviflora, and Symphotrichum (=Aster) hallii, and the bulbs Calochortus tolmiei and Dichelostemma congestum. Some fast-growing annual forbs, including various species of tarweed (Madia spp.) and Clarkia, are also prominent members   The main threat are vegetatively spreading non native grasses included Agrostis, Festuca, as well as Rubus (blackberry).

Wet praries are dominated by herbs. Deschampsia cespitosa (tufted hairgrass),and tufted microhabitats. Non-native Agrostis and Cirsiums are threat.

Fence Line Contrasts

Sitting on the fence has become a metaphor for ambivalence, but actual fence lines are some of the clearest lessons in land management.  Fencelines can be the best place to study ecology, because most fences divide two different land management histories.  The easiest places to learn from fence line contrasts is where the land management history is known.  For example, along highway right-of-ways (ROWs), the strip of land between the road and the fence is almost never grazed, whereas the private or public alotment on the other side of the fence has almost certainly been grazed and/or farmed.

However, just because the ROW hasn't been grazed doesn't mean that it has escaped disturbance. While comparing two disturbed areas can yield some insights, the multiple factors at work will make cause and effect deductions extremely difficult. To find a good comparison, look for areas that are relatively far from the road; immediately adjacent to the road is a zone of disturbance, which can include vehicle traffic, trash, mowing, and runoff from the road (i.e. increased moisture).

The best comparison areas occur where the ROW is relatively higher than road (so there is no possibility of runoff and little chance of other human disturbance).  However, areas with cutbanks below them are not good for comparisons, because of excess erosion, different microclimates around bare rock or exposed subsoil, and lowered water table.   A zone of depression in soil moisture can also occur around ditches, trenches, gullies, roadcuts, etc.

The actual fence-line itself may have different species due to fence-line drip of dew and the ability of fences to catch seeds, especially tumbleweeds. (photo).

On the ground immediately beyond the fence there may be an area of extra disturbance due to cattle trails, etc, and any areas near stock tanks or gates are also likely more heavily used (and hence a more extreme contrast).  In cases with less grazing on the private land, such as on steep hill slopes, vegetation and soils may look quite similar across fence-lines.  Of course, there will always be variable disturbance on both sides of the fence, but that is part of the challenge and opportunity of observing fence-line contrasts.

The best comparisons are between areas relatively far from disturbance, close to but not immediately adjacent to the fence-line.  With a good undisturbed ROW as a control, the vegetation on the other side of the fence can be compared to the potential climax community of the site.  

Case Example:

I was recently watching fence-lines along NM highway 285 from Vaughn to Clines Corners, and noticed that typical overgrazed areas are Grama Grass (Bouteloua gracilis) monocultures or low-stature annuals with large amounts of bare dirt.  The ungrazed roadsides still have bare ground, but the vegetation has a starkly different structure and composition:  multiple grass species occur with different growth forms.  But even more noticeable than the grass growth is the shrub encroachment in an area that is pure grassland.  Without fire or grazing, woody growth, especially saltbush (Atriplex canescens) and  Chimisa (Ericameria nauseosa) increases markedly.

While some trees and shrubs (e.g. E. nauseosa) are resistant to grazing when mature, their seedlings are highly palatable.  Cows can completely eliminate woody overstories from riparian areas in a single generation simply be eliminating recruitment (through both grazing and trampling) of Cottonwood and Willow seedlings.  Grazing pressure on seedlings is important, but easily overlooked: as long as there are trees, we describe an ecosystem as a forest. And it may seem strange to say that cows are eating a forest. But without seedling regeneration, no ecosystem is sustainable.

That grazing impacts woody growth as much or more than herbaceous growth is well-known along rivers and wetlands, but I think has been less remarked on in uplands.  From this brief study of fence-line contrasts, it appears that even more of our grasslands would support shrublands were it not for either grazing or fire limiting woody plant establishment.

NRCS Ecological Site Descriptions

Ecological Site Descriptors.  Map.

Suburban Development Transect: Biodiverse Desert to Trash-filled Parking Lot

2000

2003

2008

2011

A transect walking a few miles from the indisturbed desert through new housing developments into the city looks like time played in fast-motion.  The ecologist's glasses allow us to see the moving picture of life rather than limiting our vision to the usual single frame.  By substituting space-for-time, we can put on time-travel goggles.  What do we see?

Normally we visit a site for a day, maybe once a year for intensive longitudinal studies, maybe never again.  With this transect we could see the changes in species composition from unique, biodiverse desert with its gnarled shrubs to fresh asphalt streets, planted landscaping and lawns, and a monoculture of weeds in the bladed 'empty patches' between houses and in right-of-ways.  The stream channels were all filled in and replaced with impoundments or concrete-lined ditches.

Eventually we ended up in the back lot behind a storage unit complex.  The slight depression there caught water and supported some of the tallest native flowering trees we'd seen.  The lot was also used, apparently, as a dumping ground and was filled with all kinds of trash.

Later that night, back in my home neighborhood, I saw dual-images of what the land looked like before and after development.  I saw the rocky ground thick with idiosyncratic cacti and weird four O'clock flowers.  And I saw wide asphalt streets, joggers, tall pine trees, oleander, and grass lawns.  It is so difficult to see the past, I felt that my dual-vision was a kind of X-ray superpower, a new found ability to see through reality to what might have been.  Reality has a way of erasing the possibility that things could have turned out differently.

A nice walk in the wilderness can sometimes substitute space for space, so that you can see your neighborhood space as the absence of native wildlife instead of the presence of cars, roads, and lawns.  I suppose some people see nature as empty, and even I see it this way sometimes too: some areas are devoid of active communal life.  For example, on this particular transect we saw no rabbits, no ground squirrels, and no other mammals in the wild.  I don't think we saw a lizard until we got to the rock walls of suburbia.  But I was amazed at the botanical emptiness of our developed landscapes: out of the more than 70 native species of wildflowers and Chihuahan desert shrubs, I saw less than 5 after we crossed the first freshly paved asphalt road.

Of course, there are a diverse mix of landscaping plants, many of them native somewhere, if not in the Chihuahan desert.  Interestingly, the mexican palo verde seems to have escaped cultivation and is now growing up into the wild watercourses that snake off the mountains.  Few other weeds seem able to invade intact ecosystems, although Russian thistle is omnipresent wherever the ground has been cleared.

I think, though, that if the transect had continued further into the past/future, through abandoned neighborhoods or restored areas, the native wildflowers and shrubs would reappear.  Especially with the rains this monsoon, they seem quite happy where they are, and old pipelines have a nice covering of desert marigold, creosote, and javalena bush.  I don't really feel that the desert is destroyed by development...maybe in the long-term view it just goes away for awhile, or changes shape for a spell.  Until the wave of bulldozers breaks and subsides, the desert remains as potential...

Herbaceous Vegetation in Southwestern Pine Forests

Herbaceous forage in southwestern pine forests can be few and far between.  Especially in unnaturally-overgrown thickets, there is simply not enough light and too much acidic leaf needle litter to grow robust grasses and forbs.  The high carbon content and resistant nature of conifer bark and needles means that few nutrients are available to growing plants.  

Even when forest thinning restores natural stand densities, the recalcitrant accumulated biomass often seems to limit production.  There is simply too much carbon and it is clogging up microbial turnover of nutrients.  Sure, you'll find plenty of aboveground mushrooms and mycelial hypahe at work in the soil, but I have to wonder if there isn't a more productive alternate-stable state.

What is the limiting resource?  I've theorized that light may still be limiting when forests aren't thinned enough to create light gaps in the canopy.  But it also seems that the overabundance of carbon may be soaking up nitrogen.  In these nutrient-poor systems we typically find 'tolerator' species like sedges, that can eke out a frugal living in acidic conditions.

What about blueberries?  In some parts of the world, conifers and blueberries go together like apples and pie, but in many of the southwestern mountain ranges we have no native Vaccinium.  I'm still not sure why, except that they seem to prefer colder (moister?) climes than New Mexico can provide....

There are two species of Vaccinium in the southwest, with Vaccinium myrtillus much more common.  However, south of Santa Fe even this species only occurs at scattered locations in mixed conifer and subalpine forests.  These high-elevation forests are being rapidly lost to stand-replacing forest fires.  Even with current climate change, it is unlikely that extensive tracts of cooler forests will be able to regrow.

What about legumes?  Fabaceae are often able to supply their own nitrogen requirements and eventually supplement total ecosystem N.  But I'm surprised by how rarely I find good legumes in the forest.  Thermopsis is surprisingly rare, as are Lotus and I almost never find clovers growing in conifer needle duff.  

Robinia neomexicana seems to be one legume shrub that has found its way into a diversity of habitats, growing almost like a weedy in mountainous areas throughout the southwest.  

Seeding mixtures in forests typically use annual grasses, but I wonder if there isn't a Fabaceae that could dramatically enhance production to increase ground-cover, forage, pollinator, and wildlife habitat?  Should standard thin-and-chip treatments be supplemented with seeding efforts?

What about increasing disturbance to disrupt pine duff accumulation?  These thick, undecomposed layers and inhibit germination of many forbs...