Transcript Humagain et al. – Tree Distribution

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Tree distribution patterns in the southwest Jemez Mountains
Kamal Humagain1, Robert Cox1, and James Cain2
1Texas
Tech University
2New Mexico State University, 2New Mexico Cooperative Fish and Wildlife Research Unit
Results
Introduction
Trees are a major part of ecosystem function locally and globally as they are a large reservoir of carbon. The
herbaceous and shrub species constitute the understory mainly based on the tree types and canopy. Major
vegetation types of the project area include forests (aspen, ponderosa pine, spruce-fir), woodlands (oak,
pinyon-juniper) and grassland. Major trees include aspen (Populus tremuloides), ponderosa pine (Pinus
ponderosa), pinyon pine (Pinus edulis), junipers (Juniperus spp.), white fir (Abies concolor), Douglas fir
(Pseudotsuga menziesii), blue spruce (Picea pungens), Engelmann spruce (Picea engelmannii), and limber
pine (Pinus flexilis). The treatments types being applied as the ecological restoration process in these
vegetation types are prescribed burning (RX), thinning (TRT), and no treatment (NT).
Methods
DBH: DBH of the trees was mostly low in
the P-J woodlands, and increases in
PON, ASP, S-F mixed forest, and
grasslands (Fig 3). Mean/Median DBH in
grasslands is the highest among all,
since there are fewer trees and the trees
are larger in these open areas. Most of
the observations are in ponderosa (more
than 30%), followed by S-F, P-J, GRA,
OAK, and ASP(less than 10%) (Fig. 4).
Fig 3. DBH by vegetation type
Data Collection:
There are 224 plots established in the CFLRP
area based on vegetation type, canopy cover,
aspect and fire history .
Fig 1. Number of plots (veg type and aspect)
Fig 2. Sample Transect (200m)
Figure 1 shows the decreasing order of number of plots based on
vegetation type. The number of plots has been determined based
on the proportion of area covered by vegetation type. A majority
of the plots are south- and north-facing. The point centered
quarter method was used for tree measurements at every 40m in
a 200m transect. The distance and diameter-breast-height (DBH)
to the nearest tree were recorded for each quarter for every 40m
in a 200m transect which makes a total of 20 data points per
transect.
Fig 5. Density by vegetation type
Density: In general, TRT or RX sites are
denser than NT sites (Fig. 5). That is
what we expected and the treatment is
needed for the denser sites for
herbaceous vegetation and better tree
growth. Fig. 8 shows negative
relationship between the DBH and
density. As the DBH increases, the
density decreases. In general, this
suggests that smaller trees are
distributed densely than the larger trees.
Preliminary Analysis
Based on the collected information on distance and DBH, preliminary analysis was done to see the trend
on DBH across vegetation types and treatments types. Tree density was calculated using the distance
recorded in the field:
n = the number of sample points along the transect
4n = the number of samples or observations one for each quarter at each point
i = a particular transect point, where i = 1, … , n
j = a quarter at a transect point, where j = 1, …, 4
Rij = the point-to-tree distance at point i in quarter j
1
Absolute Denisty = 𝜆 = 2
𝑟
=
16𝑛2
4
2
( 𝑛
𝑅
)
𝑖=1 𝑗=1 𝑖𝑗
The cover or dominance of an individual tree is measured by its basal area or cross-sectional area.
A = πr2 = π(d/2)2 = πd2/4
where r = radius and d = DBH
Tree species richness is calculated as the number of species per transect.
Fig 7. Richness by vegetation type
Fig 4. Observations by veg type
Fig 8. Cover by vegetation type
Fig 6. DBH and Density relationship
Richness and Cover: Spruce-fir,
grassland and oak vegetation types are
the richest among others with up to 6
tree species (Fig. 7). Most of the
ponderosa plots have fewer types of
trees as they mostly have ponderosa
pine trees. There is no particular pattern
in cover based on treatment types (Fig
6). However, in most of the cases, basal
area (cover) is larger for TRT sites as
this is a function of DBH.
Conclusions
(1) Preliminary data exploration shows the bigger trees in the non-treatment sites for Ponderosa pine forests
which constitutes the majority of the project area.
(2) The trees are denser in the areas to be treated either with prescribed fire or thinning which supports
accuracy of the selection of the sites for treatment.
(3) Simple linear regression suggests that smaller trees are more densely distributed than the larger trees and
they needs to be thinned or treated with fire.