COMPETITION IN OLD GROWTH KOREAN PINE FOREST

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Cacao-coconut intercropping in Ghana: agronomic and economic perspectives

In Ghana, shade for cacao (Theobroma cacao L.) is becoming a critical issue because of extensive deforestation. Unlike in some other cacao-growing countries, cacao is not grown under the shade of coconut (Cocos nucifera) in Ghana. An experiment to compare the merits of four cacao-coconut intercropping systems with the traditional cultivation of cacao under Gliricidia sepium shade was undertaken at the Cocoa Research Institute of Ghana. Cacao seedling girth was not affected when intercropped with coconut but was significantly (P = 0.01) reduced when intercropped with G. sepium. High density cacao facilitated better early canopy formation. Yield of cacao spaced at 2.5 m triangular (1739 plants ha^–1) with coconut at 9.8 m triangular (105 plants ha^–1) was significantly higher (P = 0.05) than from the other treatments during 1993/94 to 1995/96. There were no major disease problems associated with intercropping cacao with coconuts. Widely spaced coconuts intercropped with cacao spaced at 3 m × 3 m showed better flowering and gave higher coconut yields, but cacao spaced at 2.5 m triangular under coconuts spaced at 9.8 m triangular was more profitable than the other treatments. Moisture stress was the greatest in cacao system with G. sepium shade and this could be responsible for the low yield of cacao in that treatment. It is suggested that properly arranged high density cacao under widely spaced coconuts can be a profitable intercrop system for adoption by cacao farmers in Ghana.This revised version was published online in November 2005 with corrections to the Cover Date.     

Development of Pinus sylvestris Main Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.     

Effects of Vegetation-Free Strip Width and Irrigation on Newly Planted Peach

Field experiments were conducted at two locations (Clayton and Jackson Springs, NC) to determine the influence of vegetation-free strip width (VFSW) and irrigation on newly planted peach growth and yield in a low-density orchard with a volunteer weedy ground cover. The experiments included VFSW of 0, 0.6, 1.2, 2.4, 3, or 3.6 m under irrigated or nonirrigated conditions. Seasonal variation in the orchard floor vegetation was observed as different weed species reported in summer and winter. However, this difference was not apparent with respect to VFSF and irrigation. At Jackson Springs, NC, the predicted irrigated VFSW which would produce the same trunk cross-sectional area (TCSA) as the grower standard (3-m nonirrigated) was 1.5, 1.3, and 0.8 m for one-, two-, and three-year-old trees, respectively. The predicted irrigated VFSW which would produce the same yield as the grower standard was 1.16 m. At Clayton, TCSA and fruit yield were not different by irrigation, but did increase linearly with VFSW. At both locations, leaf nitrogen (N) concentration was lower in irrigated trees than nonirrigated trees. Leaf N, leaf area, and SPAD were positively related to VFSW at Jackson Springs. In contrast, leaf N concentration was not different by VFSW at Clayton. However, leaf area and SPAD were positively related to VFSW at Clayton. These results suggest that a 1.5 m VFSW combined with proper irrigation and fertilization will produce tree growth and yield in newly planted orchard with volunteer weedy vegetation similar to the current grower standard in the southeastern USA.     

江西主要农产品竞争力评价及对策研究

从规模竞争力、成本竞争力、出口竞争力3个方面对江西主要农产品的竞争力进行了评价,分析了影响江西农产品竞争力的主要因素,提出了提高江西农产品竞争力的对策。     

Effect of low root temperature on symbiotic nitrogen fixation and competitive nodulation of Onobrychis viciifolia (sainfoin) by strains of arctic and temperate rhizobia

Summary Symbiotic effectiveness and competitive nodulation of the temperate forage legume sainfoin (Onobrychis viciifolia cv. Melrose) by two strains of arctic rhizobia (from Astragalus or Oxytropis sp.) and two strains of temperate rhizobia (from sainfoin) were evaluated at temperatures of 9, 12, or 15°C for roots and 20°C (day) and 15°C (night) for shoots. The inocula consisted of effective individual or paired arctic and temperate strains which were identified on the basis of differential growth. At 9°C, the arctic strains were generally more competitive than the temperate strains, whereas at the highest temperature tested, the converse was apparent. Symbiotic effectiveness (shoot dry weight, nitrogenase activity, and number of nodules) was similarly affected by root temperature, except that at 15°C the arctic strains were generally as effective as the temperate strains. The marked interaction between temperature and strain on competitiveness or on effectiveness indicates symbiotic adaptation of the arctic rhizobia to low temperatures. On the basis of these data we suggest that the use of selected, cold-adapted rhizobia in sainfoin inoculants may be beneficial in temperate regions where low soil temperatures occur early in the growing season.Contribution no. 413 and 1334 of the Agriculture Canada Sainte-Foy Research Station and Plant Research Centre, respectively     

浒苔与中肋骨条藻竞争关系的初步研究

[目的]研究浒苔与中肋骨条藻的竞争关系。[方法]以种群密度为变量,采用试验生态学手段研究了浒苔与中肋骨条藻的生长竞争关系,以及浒苔培养液对中肋骨条藻生长的影响。[结果]在一次性共培养及半连续共培养体系中,初始接种量为0.2～0.6 g/L的浒苔均能显著抑制初始接种量为1×104cells/ml的中肋骨条藻的生长,且其抑制作用随着浒苔初始接种量的增大而增大。综合一次性培养及半连续培养试验可以初步推断,活性磷酸盐可能是一次性培养试验中影响到两种藻类竞争的主要原因。初始接种密度为1×104、1×105cells/ml的中肋骨条藻亦能显著抑制浒苔的生长。浒苔初始接种量为5 g/L的培养滤液能够对中肋骨条藻的生长产生抑制作用(P0.05),且8 d培养时长滤液抑制作用大于4 d培养时长滤液抑制作用。[结论]该研究可为藻类水华生物防治提供一定的科学依据。     

Growth effect of Manchurian ash in mixed stands

lntroductionThepIantingofFraxiusm8ndShurfoabeganatShangzhi,Kedong,YianandFujincountiesofHei-longjiangProvincein196o'.Ash(hainusmand-shurica)andlarch(LarisgmehnI),AshandKoreanpine(PinuskoraiensiS)mixedstandwereremainednow,whichwereartificial,orformedbyplantingAshatterpIantingpureconiferousforest,orinducedbyestablishingeffectareainnaturalashforest.TherearemanyreferencesonthegrowthofashmixedstandinChina.Butinthepast,thestudyoftherela-tionshipbetWeentheincreasinggrowthofmixedstandwithdiffe…     

Small-scale effects of historical land use and topography on post-cultural tree species composition in an Alpine valley in southern Switzerland

Investigations of spatial patterns in forest tree species composition are essential in the understanding of landscape dynamics, especially in areas of land-use change. The specific environmental factors controlling the present patterns, however, vary with the scale of observation. In this study we estimated abundance of adult trees and tree regeneration in a Southern Alpine valley in Ticino, Switzerland. We hypothesized that, at the present scale, spatial pattern of post-cultural tree species does not primarily depend on topographic features but responds instead to small-scale variation in historical land use. We used multivariate regression trees to relate species abundances to environmental variables. Species matrices were comprised of single tree species abundance as well as species groups. Groups were formed according to common ecological species requirements with respect to shade tolerance, soil moisture and soil nutrients. Though species variance could only be partially explained, a clear ranking in the relative importance of environmental variables emerged. Tree basal area of formerly cultivated Castanea sativa (Mill.) was the most important factor accounting for up to 50% of species’ variation. Influence of topographic attributes was minor, restricted to profile curvature, and partly contradictory in response. Our results suggest the importance of biotic factors and soil properties for small-scale variation in tree species composition and need for further investigations in the study area on the ecological requirements of tree species in the early growing stage.     

Genetic analysis of competition data on Icelandic horses

In a study of the possibility of using competition data in the genetic evaluation of Icelandic horses, data from competitions held in Iceland between 1999 and 2004 and in Sweden between 1998 and 2004 were analyzed to estimate the genetic parameters of competition performance traits. The data-sets from both countries included 18 982 records of 3790 horses in 379 different events. Two types of competition were included: sport competitions and gæðinga competitions performed on oval tracks and on a straight track. Each type of competition involves several disciplines in which the horses are ridden in the various gaits. The traits analyzed were two different measures of four-gait, five-gait and tölt, and one pace trait. In both the four-gait and five-gait tests the gaits walk, trot, tölt and gallop are exhibited. In the five-gait test, pace is also exhibited. The traits tölt and pace are performances of these single gaits. Highly correlated and similar traits were combined, and three new traits relating to tölt, four-gait and five-gait were formed. No large differences in means or standard deviations of traits were found between countries. All traits were approximately normally distributed. Genetic parameters were estimated using linear animal models including the fixed effects of sex, age and event for all traits, and the level of discipline was included for some traits. Random permanent environmental effects were also included. Estimated heritabilities were moderate to high, ranging from 0.18 to 0.21 for sport-competition traits, from 0.33 to 0.35 for gæðinga-competition traits and from 0.19 to 0.22 for combined traits. Estimated genetic correlations between different sport-competition traits varied from 0.63 to 0.96, and between the two gæðinga-competition traits it was estimated at 0.43. Genetic correlations between sport- and gæðinga-competition traits ranged from − 0.42 to 1.00. It was concluded that competition traits are suitable to include in genetic evaluations.