Acorn Yield Research Articles

Airborne hyperspectral imaging for estimating acorn yield based on the PLS B-matrix calibration technique

Alternate bearing of acorn is a well-marked yield variability phenomenon in forest production. In Japan, this phenomenon is also related to wildlife management (e.g. of animals such as wild pigs, that rely on acorn as their major feed source). Effective management of animals dependent on acorn will require accurate estimation of acorn yield at an early stage. In this paper, we proposed a way to estimate acorn yield from the canopy reflectance values of individual trees. Using an Airborne Imaging Spectrometer for Application (AISA) Eagle System, hyperspectral images in 72 visible and near-infrared wavelengths (407–898 nm) were acquired over an acorn forest in Japan 10 times over three consecutive years (2003–2005) during the early acorn growing season. The canopy spectral reflectance values for individual trees at each wavelength were extracted from the images, and important wavelengths were determined as estimating factors by the B-matrix technique based on partial least squares (PLS) analysis. Yield-estimating models were then developed by multiple linear regression (MLR). Three models obtained from images acquired on June 27 in 2003, July 13 in 2004 and June 21 in 2005 estimated acorn yield well in comparison with ground truth, indicating that the procedure has considerable potential. The study also demonstrated the B-matrix technique based on PLS analysis to be reliable and efficient in identifying important wavelengths for determining suitable estimating factors that best contribute to the estimation model.

Spatial autocorrelation in masting phenomena of Quercus serrata detected by multi-spectral imaging

We developed a multiple linear regression methodology for estimating acorn yield of Quercus serrata from airborne multi-spectral images. Using the models developed, we estimated the spatial distribution of acorn yields on the aerial images. We also calculated spatial autocorrelation from the estimated spatial distribution of yields, and evaluated the spatial pattern by comparison with the simulation output from Satake and Iwasa's [Satake, A., Iwasa, Y., 2002a. Spatially limited pollen exchange and a long-range synchronization of trees. Ecology 83, 993–1005] theoretical models, which assume internal allocation and pollen exchange between trees within a finite range. A significant correlation was found between logarithmic acorn yield and the multi-spectral data observed on June 6, 2003 ( R 2 = 0.37, p < 0.05) and on May 26, 2004 ( R 2 = 0.44, p < 0.01); these relationships were also confirmed by leave-one-out cross-validation ( p < 0.05). Through an image segmentation procedure, approximately 5700 canopies were identified. The acorn yields of these canopies were estimated by applying the model developed. The correlation coefficients calculated from the estimated spatial distributions of yield decreased as distance increased. Our experimentally estimated spatial distribution agrees with the patterns of the correlograms of spatial pattern derived from Sakate and Iwasa's models. Combinations of our findings and their simulation results suggest that an endogenous mechanism may drive the masting of Q. serrata.

Influence of pruning and the climatic conditions on acorn production in holm oak (Quercus ilex L.) dehesas in SW Spain

Acorn production by Quercus ilex L. ssp. ballota (Desf.) Samp. in SW Spain was assessed, and variations between years and the influence of pruning on it were examined. To this end, an experimental study was conducted at two different sites (Calanas and San Bartolome, in the province of Huelva) where trees were subjected to traditional (light, moderate or heavy) pruning and also to a new (crown-regeneration) pruning method. Acorn yield was quantified over a period of 5 years in the Calanas plot and 4 in the San Bartolome plot, and found to average at 95.61 ± 0.76 g DM/m2, which is equivalent to 6.5 ± 0.05 kg DM/tree; however, yield figures varied markedly between years depending on the particular climatic conditions. The average acorn production was correlated with the water potential in mid summer (end of July); the annual, spring and autumn rainfall; and the actual evapotranspiration for the period from September (previous year) to August. No significant differences in acorn production between traditional pruning intensities were detected; in fact, there were only hints that heavy pruning might result in decreased acorn yields. The new pruning method used, crown-regeneration, seems promising with a view to increasing acorn yield; however, it should be tested on larger sample sizes before any final conclusions can be drawn in this respect. Based on the results, the present health status of holm oaks in southwestern Spain (a result of sustained decline) and the low value of firewood — which used to be a very important source of income from pruning a few decades ago -, the authors recommend reducing the frequency and intensity of pruning in the dehesas of the study area.

Acorn yield and insect damage of Quercus mongolica var. grosseserrata

Acorn yield and insect damage of Quercus mongolica var. grosseserrata

Cumulative Effect of Winter on Acorn Yield and Deer Body Weight

We examined the effects of cumulative winter climate on acorn yield and body weight of immature white-tailed deer (Odocoileus virginianus) the following autumn, and spring population density of deer on Land Between the Lakes (LBL), Tennessee. Body weights of male and female fawns and yearlings were positively correlated with acorn yield the previous autumn and inversely correlated with estimated spring population density of deer. Acorn yield was positively related, and spring population density of deer inversely related, with the cumulative number of days with >0.25 cm of precipitation during the previous 3 and 4 winters. Acorn yield and associated body weights were not related to total amount of precipitation, presumably because of the topography of the study area. Cumulative effects of winter climate should be considered in deer population models. J. WILDL. MANAGE. 53(2):292-295 Severe winter weather can adversely affect ungulate fetal development and weight and potential survival of young. Most studies on effects of winter weather on cervid population dynamics have been at northern latitudes (45-50*) with corresponding low mean temperatures and significant accumulation of snow (Verme 1963, Peterson et al. 1982, Picton 1984). Recently, Mech et al. (1987) showed that snow accumulation had a strong cumulative effect on fawn: doe ratios of white-tailed deer and twinning rates and cow: calf ratios of moose (Alces alces). Our objectives were to determine if observed variation in body weights of immature white-tailed deer from a mid-southern latitude was related to winter climate and if there were cumulative effects of relatively moderate climate. T. Davin assisted with computer analyses. Computer time was provided by Southern Illinois University at Carbondale, Computing Affairs. R. A. Brandon, L. P. Hansen, H. A. Jacobson, and G. H. Waring provided helpful comments on the manuscript. Support for this study was provided by Land Between the Lakes, Tennessee Valley Authority, with additional funding from the National Rifle Association. STUDY AREA AND METHODS The study area was LBL, a 69,636-ha peninsula between Barkley and Kentucky lakes in western Kentucky and Tennessee. The area represents the midwest oak (Quercus spp.)-hickory (Carya spp.) forest region (Braun 1964) and consists of rolling uplands with steep hillsides 120170 m above sea level. Forest cover was approximately 90% dominated by oak and hickory. Vegetation in forest openings was dominated by lespedezas (Lespedeza spp.), Kentucky 31 fescue (Festuca elatior), white clover (Trifolium repens), grasses, and sedges. Deer body weight, acorn yield, and climate variables from the Tennessee portion (22,980 ha) of LBL (36830'N, 88000'W) were used because of the extent of available data from LBL records. Dressed weights of fawns and yearlings taken by hunters from October through December 1974-86 were recorded to the nearest 0.4 kg. Only fawns and yearlings were analyzed. Changes in cervid weight and growth are most evident at these ages (Halls 1978, Clutton-Brock et al. 1982) and reproductive activity, with the possible exception of yearling females, is not expected to affect body weight. Winter (Dec, Jan, and Feb) climatic data were recorded daily at the LBL Empire Farm Station (Golden Pond, Ky.). We analyzed the following variables that affect energy expenditure and nutritional plane of deer: mean minimum temperature in January, mean minimum temperature during the 3-month winter period, total precipitation in January, total precipitation during winter, and number of winter days with precipitation >0.25

Acorn Yields, Characteristics, and Management Criteria of Oaks for Wildlife

Acorn Yields, Characteristics, and Management Criteria of Oaks for Wildlife

Flowering and Fruiting in the White Oaks. Pistillate Flowering, Acorn Development, Weather, and Yields

Female flowering and acorn development in three species of which oaks were studied in Pennsylvania from April 1949 through August 1962 with emphasis on the effect of weather on floral development and acorn production. Pistillate flowers emerge in late April or early May, 5—10 days after the appearance of staminate flowers. After pollination and fertilization, developemnt of acorn forms begins, and filled acorns mature late in August. Spring air temperatures strongly affect acorn yields. Good white oak acorn crops were obtained in years when a warm 10—day period occurred late in April, with average night temperatures 55—60°F, followed by cooler periods (45—50°F) for 13—20 days early in May. During years when April remained cool and was followed by warm days and nights in May, acorn production was poor. Wind, precipitation, relative humidity, and vapor pressure deficits did not significantly influence acorn yields. While some individual trees were inherently copious acorn producers, others in the same stand produced none or a light crop throughout the 14—year period.