Friday, March 27, 2015

Two Soils from the Manzano Mountains

Overview SOIL 1

Apparently frost -heaving has raised very weak physical (WP) crust-mounds.

Closeup of a crust mound:  The surface has been softened and the top centimeter has filled in with fine sediments.  This top layer actually has more structure than the frost-heaved material below it, which readily crumbles into its constituent soil particles.  Note the plant root, at top center of the photo, growing in the fine sediment layer.

Where litter is present, but too discontinuous to form duff, the action of frost heaving rapidly incorporates pine and juniper litter into the mineral horizon.

Overview SOIL 2

Some areas have much more biological crust than others.  In these photos, the blue grama grass Bouteloua gracilis (BOGR) is more abundant with denser cryptobiotic crust.  The darkened biological soil crust (BSC) consists of free-living blue-green algae such as Nostoc

Compact SP (strong physical) crust with roots and moisture evident underneath.  These cracked peds come up in 5-8 inch radius plates.  Note how different this crust is from the previous “frost-heaved” crust.  This crust has significant structure to it and doesn’t immediately crumble into constituent particles.  

Monday, March 23, 2015

To Burn or Decay? What is the best management practice to deal with excess biomass?

 Conventional forest restoration in Western pine ecosystems involves reduction of biomass through thinning, which is sometimes followed by prescribed burning to further reduce fuels.  Burning slash piles sterilizes soil patches and doesn't decrease overall site litter, so broad-scale prescribed burns have traditionally been the best management practice to reduce fuel loads.

Passing over the discussion of what was historically "natural," is fire the best tool for increasing site productivity?

Apparently not.  Duff burning kills fungi, small roots, and (obviously) removes duff. “EMF mortality and complete duff reduction after fire have been implicated with poor tree survival and slow stand recovery in forest ecosystems world-wide.”  (Smith, McKay, Brenner, mcIver, Spatafora.  2005: Early impacts of forest restoration treatments on the ectomycorrhizal fungal community and fine root biomass in a mixed conifer forest.  (PDF)

As Stametz and others have pointed out, burning is not the best use of available resources: fire volatilizes stored nutrients such as nitrogen and organic carbon (N and SOC).  Fire can also form hydrophobic soil crusts, kill flora and fauna, decrease soil microbiota (important for decomposition), destroy tree roots, mycelial networks, and sometimes mature trees.  In contrast, decomposing organic material could increase site productivity.

Permaculture forest restoration?
Restoration projects proceed with multiple goals, either explicit or implicit.  One such goal has been the return of historical fire to degraded forests.  According to a large body of research, at least some pine forests historically experienced short return-interval, low-intensity fire.  However, using this to justify current prescribed fire approaches assumes that we can --and should-- attempt to replicate historical ecosystems.  I believe it is a fallacy to assume that ecosystems, like species, must be maintained in the face of changing environmental conditions; paleoecology clearly shows that species migrated independently throughout prehistory, indicating that the ecosystems we see today are only contingent associations of species; there may be better arrangements of species and better ways of managing ecosystems than relying on historical norms.

That being said, there are even better reasons to question prescribed fire in forest restoration.  If we abandon the idea of mimicking natural disturbances we are free to innovate more productive restoration methods.  For example, Permaculture-inspired ideas of maximizing species diversity and ecosystem services could inspire a new type of forest restoration.  I envisage a restoration program designed to optimize current site conditions rather than recreate history...

What Controls Decomposition Rate in Conifer Forests?

Source: Litter decomposition, climate, and litter quality. Link.

Nutrients:  Mn and N
Manganese and Nitrogen control forest decomposition, but in an unexpected way. Mn is an essential component of ligninolytic enzymes important for degrading litter in the later stages of decomposition.  But high available N can limit decomposition. The most efficient degraders of lignin and humic acids are wood-rotting or litter-decomposing white-rot fungi (Hintikka 1970; Hatakka 2001).  For several of the lignin-degrading white-rot fungi, high concentrations of low-molecular weight N compounds suppress the synthesis of the lignin-degrading enzymes (Keyser et al. 1978; Eriksson et al. 1990; Carreiro et al. 2000). 

Further, N has repeatedly been reported to react with remains of degrading lignin to form recalcitrant condensation products. Such products form chemically (Vahtras 1982; Stevenson 1982) rather than biologically.  Spaccini (1999) suggested that such bonds create a hydrophobic surface thereby resisting decomposition. The higher the concentrations of lignin and N in a litter material the more likely it seems that such covalent bonds will be formed. Using 106 sets of foliar litter comprising 21 tree species (both coniferous and deciduous) representing a wide range in chemical composition, Berg (2000) found a highly significant negative relationship between limit values and initial N concentrations in litter.

Many examples exist in which addition of N to a N-deficient system slows down decomposition, especially where organic matter with high lignin content is present (Verhoef and Brussaard, 1990; Carreiro et al., 2000). Nitrogen and other fertilizers may negatively influence specific groups of organisms, particularly microbes.  Any shift in microbial composition can have a negative effect on other soil fauna.  As a result, decomposition and mineralization may decrease. Additionally, plants can compete successfully with decomposers for nutrients.  (Neher 2003.)

What about pH?
In a review of 58 studies, Wardle (1998) found that temporal variability in soil carbon (C) was related most closely to soil N content in forests and soil pH in arable and grassland ecosystems. (Neher 2003.)
But a study by Parn et al adding ash to a pine forest to increase soil pH did not observe increased decomposition.  A large meta-review noted that 22-85% of treatment trials have failed to affect decomposition: “This analysis shows that Ca additions are not universally beneficial and provides insight into when Ca additions to forest soils are likely to be most effective." (Evaluating the effects of liming and wood-ash treatment on forest ecosystems through systematic meta-analysis. Carolyn Reid, Shaun A. Watmough)

Decomposition Rate and Ecosystem Integrity
Neher 2003 "Effects of disturbance and ecosystem on decomposition." is a great review of this topic.  (PDF)  They conclude that "decomposition of organic matter is a useful indicator of soil condition because it is measured easily and serves as integrator of the collective activities of organisms within the soil food web."  For example, slowing rates of decomposition serve as an early warning sign of pathology in forest ecosystems (Bormann and Likens 1979),  A difference in decomposition rate between similar sites implies either a change in the decomposer community or quality of the biotic and abiotic resources at a site. 

This WSU website has a great review of pine forest decomposition.

Tuesday, March 17, 2015

What stand density is optimal in Ponderosa pine forest restoration?

 In my humble opinion, there is really only one chart needed to answer the question of what density is best for Ponderosa pine trees:
Source: The role of stand density on growth efficiency, leaf area index, and resin flow in southwestern ponderosa pine forests.  McDowell, Adams, Bailey, and Kolb.  (link)
 The lower the basal area, the more trees grow.  Growth is especially important in drought-stressed trees because lower growth can weaken tree defenses.  The lowest treatment in this study reduced trees to 7 m2 ha-1, and trees in this treatment had the highest leaf area per tree, indicating that they were healthiest at the time of the study.

Leaf area of understory plants was also highest at the lowest stand densities:
Source: ibid.
However, in the interest of full disclosure, this chart also shows (in panel B) that total forest resource utilization, measured by total leaf area, is highest at medium tree densities.

NRCS Ecological Site Descriptions

Ecological Site Descriptors.  Map.

Monday, March 16, 2015

Air Quality in New Mexico

The New Mexico Environment Department maintains a network of 22 air quality stations scattered across the state in high-risk areas.  Stations are color-coded to reflect air quality, and currently it looks like all stations are green, representing "good" air quality.

(Albuquerque has their own air quality monitoring data)

The Carlsbad station shows levels of common pollutants over the last week:

And here is the Hobbs station data for the same time period (note the different y-axis scales):

Carlsbad has had much worse air quality over the last week, especially in the early mornings, when nitrate and nitrite spike.  Ozone and PM2.5 are not visible on the Carlsbad graph because of the large NO spikes.  In Hobbes, increases in ozone (O3) are associated with winds blowing more pollution over the sensor.

These time periods experienced moderate wind and rain.  It will be interesting to check back in during a temperature inversion.

For good national data, check out the U.S. Air Quality Smog Blog

Friday, March 06, 2015

BLM Wilderness Study Areas in NM

A clickable map with links to all 57 Wilderness Study Areas is available at the BLM Website.

This website has an online map of ACECs.

Thursday, March 05, 2015

Predicting Plant Phenology

Plants in the Southwestern deserts respond to water availability and temperature:
Map from AHPS Precipitation Analysis from January and February
NM is doing good on water so far this year!
Growing degree day map from
On average NM is about 6 growind degree days (GDD) behind 2014, but 11 days ahead of 2013 and 6 days ahead of normal.

Wednesday, March 04, 2015

25 Years Without Cows: Hart Mountain National Antelope Refuge

From an article about a recent publication documenting changes on the Refuge:

"By comparing the new photos with the historical ones, the researchers determined that following 23 years of passive recovery after cattle were excluded from the Hart Mountain National Antelope Refuge, stream channels narrowed, woody vegetarian increased, and there was a noticeable reduction in eroding stream banks. Nearly all sites displayed a decrease in bare soil, resulting in an overall 90% increase in plant cover, mainly thanks to grasses, sedges, forbs, and willow. Willow and rush cover increased fourfold. "

The conclusion is clear: “Simply removing cattle from areas may be all that is required to restore many degraded riparian areas in the American West.”

Seed Zones for Western Wheatgrass

The USDA Pacific Northwest Field Station has published research examining the population geographic structure of Western Wheatgrass.  They measured three major phenotypic factors from grass seed collected throughout the interior northwest: height, flowering date, and leaf width.