Dw. Davenport et al., SOIL MORPHOLOGY OF CANOPY AND INTERCANOPY SITES IN A PINYON-JUNIPER WOODLAND, Soil Science Society of America journal, 60(6), 1996, pp. 1881-1887
Pinon-juniper woodlands in the semiarid western USA have expanded as m
uch as fivefold during the last 150 yr, often accompanied by Losses of
understory vegetation and increasing soil erosion. We conducted this
study to determine the differences in soil morphology between canopy a
nd intercanopy locations within a pinon (Pinus edulis Engelm.)-juniper
[Juniperus monosperma (Engelm.) Sarg.] woodland with uniform parent m
aterial, topography, and climate. The woodland studied, located near L
os Alamos, NM, has a mean tree age of 135 yr. We examined soil morphol
ogy by augering 135 profiles in a square grid pattern and comparing so
ils under pinon and juniper canopies with intercanopy soils. Only two
of the 17 morphological properties compared showed significant differe
nces. The B horizons make up a slightly greater proportion of total pr
ofile thickness in intercanopy soils, and there are higher percentages
of coarse fragments in the lower portions of canopy soil profiles. Ca
nopy soils have lower mean PEI and higher mean organic C than intercan
opy soils. Regression analysis showed that most soil properties did no
t closely correspond with tree size, but total soil thickness and B ho
rizon thickness are significantly greater under the largest pinon tree
s, and soil reaction is lower under the largest juniper trees. Our fin
dings suggest that during the period in which pinon-juniper woodlands
have been expanding, the trees have had only minor effects on soil mor
phology.