The purpose of this study is to monitor the fruit production of three woody tree species that occur on the Sevilleta National Wildlife Refuge (NWR). Two monoecious species, Pinus edulis and Quercus turbinella, are assessed, as is a dioecious species, Juniperus monosperma. In August, fruit production is estimated for the three species at five sites within the Sevilleta NWR. For each of the species different protocols are used for estimating fruit production: P. edulis estimates are made using the number of cones per mature tree, Q. turbinellla estimates utilize the number of acorns per 0.1m2 of canopy surface area, and J. monosperma estimates use the number of berries per twig on female trees. In addition, the age and/or size of each individual tree was assessed at the beginning of the study. For P. edulis and J. monosperma, distinctions continue to be made between young, medium, old, and very old trees; for Q. turbinella, canopy surface area is estimated.
This study is designed to monitor the fruit production of three woody tree species that occur on the Sevilleta National Wildlife Refuge (NWR).
At each study site, four 1 ha plots were established. Each plot was divided into four subplots.
Spatial structure of juniper, pinon pine and oak populations:
All trees and shrubs within the 1 ha plots were tagged and mapped using either GPS cordinates or compass headings. Height, canopy diameter (in both north-south and west-east directions) and diameter-at-breast-height (DBH) of trunk were measured for all woody plants, including those that died during the drought of the 1950's. Juniper and pinon trees were subdivided into four age/size groups based upon mean canopy radius for juniper and DBH for pinon. For oak trees, the canopy surface area of all individual trees was measured.
Measuring mast production:
Berry, cone, and acorn production is measured in August when fruits are ripening. Three different methods were developed to estimate annual production.
For juniper, the percent of twigs with berries and the quantity of berries per twig are determined every year for all trees in each plot. The average twig has a length of 45 cm and trunk diameter of 12 mm. Estimates of berry production are made separately for the upper and lower halves of the crown, and for the northwestern, northeastern, and southern sectors and the mean number of berries per twig calculated.
To determine berry production per tree and per hectare, the average number of twigs on trees of different size groups is estimated. Samples of 500-800 berries from a plot are taken randomly each year to determine the percentage of developed and underdeveloped berries, as well as berries with the pericarp damaged by insects.
The absolute number of third-year, ripened, green cones is estimated on all trees within the 1 hectare plots. Young brown cones of the second year are also counted to predict the yield of cones the following year. Cones are counted with binoculars. The unit of pinon mast production is cones/seeds per mature tree.
To estimate cone predation in the spring, the number of damaged female stems and the mortality of conelets are estimated. Then, in August of the following year, samples of 100 green ripened cones are collected randomly on 30-40 trees at each of three pinon sites, and the ratio of filled seeds to empty seeds, as well as the percentage of cones damaged by predatory insects, estimated.
Several hundred ripened cones and filled ripen seeds were initially measured to determine their average weight. The average dry weight of a ripened cone consisting of filled seeds was 3.5 g. The weight of a cone with no seeds was 2.1 g, representing 62% of total weight. The average number of filled seeds in a cone was six and the average dry weight of a filled seed 0.22 g, consisting of a seed shell of 0.13 g (59% of seed weight) and a seed core of 0.09 g (41% of seed weight).
A different method is used to estimate acorn production. First, the canopy surface area of each oak tree is determined. The number of acorns is counted separately for well-developed, undeveloped, and those damaged by Curculionidae beetle larvae within a 31 cm x 32 cm frame projected onto the crown surface of each oak tree in 3-5 repetitions. Acorns are subdivided into three size groups, small, medium, and large. Medium acorns are most common. To determine the weight of acorns, 100 acorns of each small, medium and large size were collected from 50 different trees.
A comparison of production of the three woody species was done on the basis of fruit biomass per unit of measure: well-developed, undamaged berries per twig for juniper, filled seeds per mature tree for pinon pine, and well-developed, undamaged acorns per 0.1 m2 of canopy surface for oak. Additionally, biomass of berries, pinon seeds and acorns per hectare was estimated in order to compare production at the five sites and quantify annual fluctuations.
Site abbreviations are as follows:
Plot refers to the 1 ha area and associated subplots where data is collected. Values range from I1-I4, II1-II4, III1-III4, IV1-IV4.
Data were compiled into a single file for all years. In addition, a year column was added. Cells that had a period (.) or were blank were changed to NA. Abbreviations were given for sites and Kartez codes assigned for juniper, pine, and oak. File was saved as CSV. TK. 6 February 2009. Data were qa/qc'd for obivous errors and metadata was updated. Added West Mesa site. 11 January 2010. tlk. Changed the order of variables so that "year" is first and "site" is second. The order of the other variables has not been changed, only shifted. Added information to West Mesa site. Added Biome Transition Area site, replacing previous name, McKenzie Flats. 8 March 2010, tlk. Kristin updated Roman's personal information. 12 March 2010, tlk.
Datasheets were visually assessed for any errors.
Data collection began in 1997 and is ongoing.