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91.
Browse of multipurpose tree species such as black locust could be used to broaden grazing options, but the temporal distribution
of foliage has not been adequately studied. Our objective was to determine effects of harvest date, P fertilization (0 and
600 kg ha−1 yr−1), and pollard height (shoots clipped at 5-, 50-, and 100-cm above ground) on foliar and shoot allometry of black locust.
The experiment was conducted on a naturally regenerated 2-yr-old black locust stand (15,000 trees ha−1). Basal shoot diameter and foliar mass were measured monthly in June to October 2002 and 2003. Foliar and shoot dry mass
(Y) was estimated from basal shoot diameter (D) by the function Y = aD
b
, with regression explaining ≥95% of variance. Allometry of foliar mass was affected by harvest date, increasing at a greater
rate with D in September than in June or July, but not by P fertilization or pollard height. Foliar mass was predicted best by month-specific
equations for the June to October growth interval. Allometry of shoot dry mass was unaffected by harvest date, P fertilization,
or pollard height. These equations could be used as a first approximation of foliar and shoot mass for pollarded black locust. 相似文献
92.
93.
We derived an allometric model of the height–diameter curve for even-aged pure stands, which was a modification of the earlier
model proposed by Inoue (2000a). An individual-dependent allometric equation was used as the height–diameter curve. Using
the discriminant analysis method, all trees composed of a stand were stratified into upper and lower trees. It was assumed
that both relationships between mean tree height H
m
and upper tree height H
u
and between mean DBH D
m
and mean DBH of upper trees D
u
could be described by the time-dependent allometric power equations. The height–diameter curve showed an average relationship
between tree height and DBH of a given stand at a given time, and hence it could be assumed that the height–diameter curve
contained two points (D
m
, H
m
) and (D
u
, H
u
). With these assumptions, we derived an allometirc model of height–diameter curve, which allowed the coefficients of the
curve to be estimated from mean tree height and mean DBH. The proposed model was fitted to Japanese cedar (Cryptomeria japonica D. Don) data. The error ratio of the allometric model ranged from 2.254% to 13.412% (mean = 6.785%), which was significantly
smaller than that of the earlier model. When the error of mean tree height was ±1.0 m or less, the effect of the error of
mean tree height on the error ratio was comparatively small. This suggested that the error of ±1.0 m in mean tree height could
be accepted in the estimation of height–diameter curve using the allometric model. These features enable us to combine the
allometric model with Hirata’s vertical angle-count sampling or growth models. In conclusion, the allometric model would be
one of the most practical and convenient approaches for estimating the height–diameter relationship of even-aged pure stands. 相似文献
94.
Dahurianlarch(Larixgmelinii)isamaintreesPeciesinartificialstandsandManchuriaash(Fnainusma:dehurica)isavaluabIehardwoodsPeciesinti1eforestareaofnortheastChina.SomestUdiesrevealedthatthemixedstandbythetwospecieshadpositivemixedeffectSandnutritionrelationshipwasoneofthemaincausesforthepositiveeffects.lnsomeresearches,itwasfoundthatinline-belttwoflarch-ashmixedstand,theconcentra-tionofavailablephosphorusofsoilinlarchbeltwas2ntimesoftl1atinashbelt.Itisdeducedthatinsuchmixedstandtheashcanabsorbmo… 相似文献
95.
Guillermo Trincado Curtis L. VanderSchaaf Harold E. Burkhart 《European Journal of Forest Research》2007,126(2):253-262
A height–diameter mixed-effects model was developed for loblolly pine (Pinus taeda L.) plantations in the southeastern US. Data were obtained from a region-wide thinning study established by the Loblolly
Pine Growth and Yield Research Cooperative at Virginia Tech. The height–diameter model was based on an allometric function,
which was linearized to include both fixed- and random-effects parameters. A test of regional-specific fixed-effects parameters
indicated that separate equations were needed to estimate total tree heights in the Piedmont and Coastal Plain physiographic
regions. The effect of sample size on the ability to estimate random-effects parameters in a new plot was analyzed. For both
regions, an increase in the number of sample trees decreased the bias when the equation was applied to independent data. This
investigation showed that the use of a calibrated response using one sample tree per plot makes the inclusion of additional
predictor variables (e.g., stand density) unnecessary. A numerical example demonstrates the methodology used to predict random
effects parameters, and thus, to estimate plot specific height–diameter relationships. 相似文献
96.
On the basis of nine Norway spruce (Picea abies (L.) Karst.) and ten European beech (Fagus sylvatica L.) thinning experiments in Germany, for which both residual and removed stock had been registered first during 1870, I scrutinize
how moderate and heavy thinning from below (B-, C-grade) affects the production of merchantable volume compared with light
thinning (A-grade). In relation to A-grade, cumulative merchantable volume (CV) of B- and C-grade amounts in average to 103–107%
in juvenile and to 97–102% in mature Norway spruce stands. The corresponding findings for European beech are 101–106% and
94–102%. CV of individual stands varies between 89% and 130% for Norway spruce and 73% and 155% for European beech (CV of
A-grade = 100%). These findings are substantiated by the relation between stand density (SDI) and periodic annual increment
(PAI). On the B- and C-grade plots of spruce and beech, respectively, SDI was reduced down to 41–91% and 31–83% of the A-grade.
When SDI is reduced in young stands, PAI follows a unimodal curve. Norway spruce’s PAI culminates in 109% if SDI is reduced
to 59%; European beech’s PAI culminates in 123% when density is reduced to 50%. Whereas Norway spruce’s growth reacts most
positively on thinning under poor site conditions and with increment reduction on favourable sites, European beech behaves
oppositely. With stand development the culmination point of the unimodal relation moves towards maximum density, so that in
older stands PAI follows the increasing pattern, which is the left portion of a unimodal curve. A model is presented which
apparently unifies contradictory patterns of stand density–growth reactions by integrating relative stand density, average
tree size and site fertility effects, and makes the findings operable for forest management. 相似文献
97.
98.
为了解猪雷极氏普罗菲登斯菌(P.rettgeri)的生物学特性、致病性及16SrRNA基因系统进化关系,从发生严重腹泻、血便的哺乳仔猪群的内脏器官中分离到1株病原菌,根据形态特征、培养特性、生化特性、16SrRNA基因序列分析鉴定为P.rettgeri。小鼠攻毒试验证实,该分离菌株对试验小鼠有较强致病力,哺乳仔猪回归试验可复制出与临床上相似的典型症状,并从发病死亡小鼠及哺乳仔猪中分离到攻毒菌株。系统进化分析表明,分离菌株与雷极氏普罗菲登斯菌系统进化关系最为密切,其16SrRNA基因序列与雷极氏普罗菲登斯菌代表菌株的同源性在97.3%~99.6%之间。药敏试验结果表明,分离菌株对头孢哌酮钠、头孢噻肟钠、头孢曲松钠、头孢唑啉、头孢呋肟、头孢吡肟、阿莫西林、链霉素、氨曲南、诺氟沙星、左氟沙星、恩诺沙星、卡那霉素、氨苄青霉素、米诺环素、链霉素、阿米卡星等多数药物敏感。首次报道了雷极氏普罗菲登斯菌可以引起哺乳仔猪严重腹泻,提示在仔猪腹泻中应注意该菌感染的诊断、监测和防控。 相似文献
99.
Shengtao FAN Tiecheng WANG Xiaolong GAO Ying YING Xue LI Yongcheng LI Yuanguo LI Jinzhu MA Heting SUN Dong CHU Yu XU Songtao YANG Qihan LI Yuwei GAO Xianzhu XIA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(9):1143-1149
Newcastle disease virus (NDV) causes a highly contagious viral disease in poultry and
wild birds, and it can cause significant economic loss worldwide. Eight viral strains were
isolated by inoculating embryonated chicken eggs from the Poyang Lake region of China with
swab samples. All eight of the NDV isolates were identified as class I genotype 3 strains,
but they diverged notablely from class II viruses. Further analysis revealed that all
eight NDV isolates were lentogenic strains containing the
112ERQER↓L117 motif at the F protein cleavage site. The strains
were highly identical and were more species specific (chicken and waterfowl) than site
specific (Nanchang and Duchang regions). The close phylogenetic proximity of these
isolates indicates that viral transmission may happen between poultry and wild birds. Our
study demonstrates that lentogenic class I NDVs exist in clinically healthy wild waterfowl
and poultry within the Poyang Lake region. Active surveillance of these viruses to
determine their evolution and origin is one of the most realistic strategies for
preventing and controlling NDV outbreaks. 相似文献
100.
The effect of including genomic relationships in the estimation of genetic parameters of functional traits in pigs 下载免费PDF全文
T. Aasmundstad I. Andersen‐Ranberg Ø. Nordbø T. Meuwissen O. Vangen E. Grindflek 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2015,132(5):386-391
The term functionality in animal breeding is used for traits that increase the efficiency of production by lowering the input cost, such as animal health and leg weakness related to longevity. The main objective of the study was to investigate the impact of genomic information, in a multivariate variance component analysis, on some of these traits. In addition, the effect of the inclusion was studied by testing the model's prediction ability based on best linear unbiased estimates for fixed and random effects. The material in this study consists of phenotypes from 76 683 animals, of which 4933 animals are genotyped. The heritabilities for front leg conformation, stayability, osteochondrosis and arched back, estimated using the traditional pedigree, were found to be between 0.12 and 0.29. When using the combined genomic and pedigree relationship matrix, the heritabilities were between 0.14 and 0.36. The results show that the combined relationship matrix can be used for the estimation of (co)variance components, and that the predictive ability of the model in this study marginally increases with the inclusion of genomic information. 相似文献