Tree distribution patterns in the southwest Jemez MountainsKamal Humagain1, Robert Cox1, and James Cain2

1Texas Tech University 2New Mexico State University, 2New Mexico Cooperative Fish and Wildlife Research Unit

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(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.

Conclusions

Results

Methods

Introduction

Preliminary Analysis

Data Collection: There are 224 plots established in the CFLRP area based on vegetation type, canopy cover,

aspect and fire history . Fig 2. Sample Transect (200m)

Distance

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 1. Number of plots (veg type and aspect)

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 transect4n = the number of samples or observations one for each quarter at each pointi = a particular transect point, where i = 1, … , nj = a quarter at a transect point, where j = 1, …, 4Rij = the point-to-tree distance at point i in quarter jAbsolute Denisty = = = 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 = DBHTree species richness is calculated as the number of species per transect.

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

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).

Fig 4. Observations by veg type

Fig 5. Density by vegetation type Fig 6. DBH and Density relationship

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.

Fig 7. Richness by vegetation type Fig 8. Cover by vegetation type

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.