Interspecific relationship of artificial forests on upper reach of Minjiang river of China

Long-term growth of artificial pure forest will lead to continuous planting obstacle. The best solution is to form mixed forest through introducing other regenerated tree species. In order to direct the option of mixed tree species and ratios on upper reach of Minjiang river, sltu incubations of soil mixture of depth O-lOcm （humus soil of coniferous with deciduous tbrest, in this way to model mixed-forest） of typical forests of Cercidiphyllum japonicum（L）, Betula utilis（H）, Pinus yunnansinsis（M） and Picea asperata（Y） were carried out and the interspecific relationships were studied through analyzing the influences of soil mixing on the biochemical characteristics of soil and Jitter decomposition. The results can be concluded as following： （1） In forestlands of C.japonicum, P.yunnansinsis amt P.asperata, enzyme activities of urease, invertase and catalase of soil were intensified after soil mixing. Whereas, in forestland of B.utilis, all the three enzyme activities of soil were decreased after mixing with soil of P.yunnansinsis, but after mixing with soil of P.asperata, enzyme activities of urease and catalase were intensified and enzyme activity of invertase was decreased （2） Litter decomposition were popularly advanced after soil mixing. In forestlands of C.japonieum, P.yunnansinsis, the contents of organic-C and total N in soil were increased after soil mixing. Whereas, in forestland of B.utilis and P.asperata, the contents of N in soil were increased while organic-C decreased after soil mixing. （3） The acidities or alkalinity of soil were neutralized and further intensified after soil mixing, which means that soil of deciduous forest develops toward acidity while soil of coniferous forest develops toward to alkalinity. （4） Mixed ratios of LM0.15-0.50 and LY0.15-0.35 in forestland of C.japonicum, HM0.15 and HY0.15-0.50 in forestland of B.utilis, MI.,0.15-0.50 and MH0.35-0.50 in forest/and of P.yunnansinsis, YL0.35-0.50 and YH0.35 in forestland of P.asperata are betterchoice for soil mixing relatively, which can be taken as reference in decision of introducing regenerated tree species and ratio of mixed forest in practice.

Investigation on Evolutionary Relationships of the Subgenomes in Interspecific Triploid Cotton via Meiotic FISH

We report in this paper primary studies on interspecific species of cotton vis GISH(genomic in situ hybridization).We use interspecific triploid hybrids(F1 from hybridization of allotetraploid cultivated species with diploid A,D,or C genome species) and two cultivated tetraploids to study

Effects of grazing disturbance of spatial distribution pattern and interspecies relationship of two desert shrubs

Grazing significantly affects the distribution,growth,and productivity of shrubs.In this study,we evalu-ated the effects of grazing disturbance on the spatial distri-bution patterns and interspecific relationships of two desert shrubs,Ammopiptanthus mongolicus and Sarcozygium xan-thoxylon.Three types of grazing conditions were considered,including enclosed area(EA),seasonal rotational grazing area(SRGA),and grazing area(GA)(100 m×100 m),in the West Ordos Nature Reserve of Inner Mongolia,China.The results showed that A.mongolicus and S.xanthoxylon populations were uniformly distributed at a small scale,and the distribution in EA and SRGA became gradually ran-dom.In GA,A.mongolicus population showed aggregated distribution but S.xanthoxylon population showed random distribution at a small scale. Moreover, both A. mongolicus and S. xanthoxylon populations at the 5-7 m scale showed random distribution. At the small and intermediate scales, the two species showed positive interspecific relationships of GA. However, no interspecific relationship was noted between the two species in EA and SRGA. A significant positive relationship (P < 0.01) was noted between the two species at 2-9 m and a negative relationship (P < 0.01) at 13-17 m scales in GA. Positive relationship (P < 0.01) was noted between the two species at 6-13 m scales and a sig-nificant negative relationship (P < 0.01) at 14-24 m scales in SRGA. The two species of desert shrubs showed posi-tive interspecific relationships at the small scale, and they showed negative relationships as the interspecific compe-tition intensified in the presence of grazing disturbance. When the grazing intensity exceeds a certain threshold, the interspecific relationships become weak. Therefore, moder-ate grazing would facilitate interspecific competition and species succession, whereas excessive grazing would disrupt natural competition causing desertification ultimately.

Observation on Behavior of Procambarus clarkii and Eriocheir sinensis in Polyculture System

[Objective] This study aimed to observe and explore the behavior of Procambarus clarkii and Eriocheir sinensis in polyculture system. [Method] P. clarkii and E. sinensis with the same weight were used for the experiment in a relatively small polyculture system. The agonistic behavior of P. clarkii and E. sinensis in the first 30 min of the initial encounter and the fighting results were observed and recorded; the approach-avoidance behavior of P. clarkii to bigger E. sinensis in a relatively large space （the ＂Y＂ maze） was observed and recorded. [Result] The re- sults showed that the times of first aggressions and approaches and the total times of active aggressions and approaches of P. clarkii in the initial period of polyculture experiment were all significantly more than E. sinensis （/：＇〈0.05）; after 30 d of poly- culture, P. clarkfi died in 30% of the groups while E. sinensis died in only 10% of the groups, and they coexisted in 60% of the groups. In the experiment of ap- proach-avoidance behavior of P. clarkii to bigger E. sinensis, with the increase of experiment times, the tendency of approach and avoidance of P. clarkii to the con- trol and E. sinensis became control-prefer （P〈0.05） from insignificantly different （P〉 0.05）, which indicated that the recognition ability of P. clarkii for E. sinensis was sig- nificantly improved, and the selection behavior of E. sinensis was obviously inhibited. [Conclusion] Presumably, polyculture of crayfishes and crabs can achieve better effi- ciency when under appropriate habitat conditions.

Mixing planting proportions in a plantation affects functional traits and biomass allocation of Cunninghamia lanceolata and Phoebe bournei seedlings

Functional traits of trees are significantly associated with their adaptation strategies and productivity.However,the effects of species composition and mixing proportion on the functional traits of trees grown in mixed plantations have not been studied extensively.In this study,planting experiments(duration about seven months)were used to study variations in functional traits and biomass allocation of C unninghamia lanceolata(Lamb.)Hook and Phoebe bournei(Hemsley)Yang seedlings in five different mixes(0C:4P,1C:3P,1C:1P,3C:1P,and 4C:0P).Total leaf area per seedling increased in each species as its respective proportion in the mixture decreased.However,the specific leaf area decreased for P.bournei under low percent composition,and the specific leaf area for C.lanceolata differed only marginally among the plantings.The net photosynthetic rates of the two species were higher in the mixed plantings than in their corresponding monocultures,whereas the transpiration rate,stomatal conductance,and instantaneous water use efficiency were not different among the plantings.The average root length and root surface area of C.lanceolata and P.bournei were higher in the mixed plantings than in their monocultures.Specifically,root surface area of C.lanceolate and both root length and surface area of P.bournei increased significantly in the 1C:3P and 2C:2P mixed plantings.Leaf,stem,root,and total dry mass per seedling for C.lanceolata decreased with its increasing percent composition in the mixed plantings,while these variables varied less for P.bournei.The plasticity of biomass allocation was relatively low for both species.Total biomass per planting was higher in the mixed plantings than in the monocultures.Our study indicates that species composition and mixing proportion can considerably affect the functional traits of C.lanceolata and P.bournei.The increase in productivity in the mixed plantings may be partially attributed to low rates of competition between the two species,and future studies should examine the different interspecies relationships.The results of this study can be used to improve plantation productivity and ultimately increase the sustainability of tree products and help to better understand the adaptation strategies of plant coexistence.

THE CHARACTERS AND EFFECTS OF AVAILABLE PHOSPHORUS IN DAHURIAN LARCH-MANCHURICA ASH MIXED SEEDLING STAND

The characters and effects of available phosphorus in dahurian larch-Manchuria ash mixed stand was analyzed through measuring available phosphorus of rhizosphere-soil, phosphorus of living and withered leaves and tree height The study results showed that the phosphorus of living leaves of larch was equal to or less than that of ash. For 5-year-old larch-ash ndxed seedlings stand,larch has more available phosphorus in soil, which is not caused by the decomposition of leaves, but the acts of root. The root of larch activates available phosphorus by acidoid fme rhisosphere-soil. At the site with a high concentration of available phosphorus (grondg bean before), 5 aged larch grows faster than the same aged ash in pure stand. The ash at the site with a high concentration of available phosphorus at 20 cm soil layer showed a trend to grow over larch, and at the site, with a low concentration of available phosphorus at 20 cm soil layer, had a trend to be suppressed by same aged larch.

Reduced Mythimna separata infestation on Bt corn could benefit aphids

Use of genetically engineered plants that express insecticidal Cry proteins derived from Bacillus thuringiensis(Bt)have been proven efficacious for managing lepidopteran pests.However,in some cases herbivores that are not targeted by the Bt trait have increased in importance.It has been suggested that reduced caterpillar damage to Bt crops could lead to decreased levels of induced plant defensive compounds which might benefit other non-target herbivores.Here we investigated the potential effect of reduced damage by larvae of Mythimna separata on aphid populations in Bt corn.We compared the performance of Rhopalosiphum maidis feeding on non-Bt corn plants that had been infested by M.separata larvae or were uninfested.The results showed that caterpillar-infested corn plants significantly reduced the fitness of R.maidis leading to a prolonged nymphal development time,reduced adult longevity and fecundity compared to uninfested plants.Consequently,the population growth rate of corn aphids feeding on caterpillar-infested corn plants was significantly lower than on uninfested plants.As expected,the aphids performed significantly better on Lepidoptera-resistant Bt corn than on non-Bt corn when plants were infested with M.separata,since the caterpillars caused very little damage to the Bt plants.The current findings indicate that reduced M.separata infestation could benefit aphid development in Bt corn.Bt corn has the potential to be commercialized in China in the near future and aphids and other non-target pests should be monitored in the farming fields.