RESUMEN
In comparison with ectomycorrhizal (EM) tree species, arbuscular mycorrhizal (AM) trees have different litter quality and nitrogen cycle modes, which may affect mycorrhizal colonization and the community composition and diversity. However, available studies addressing the mycorrhizal fungal colonization rate, diversity and community composition in mixed forest stands composed of AM and EM trees are rare. In the present study, we assessed litter quality, soil physicochemical properties and correlated them with mycorrhizal community characteristics in rhizosphere soils of monoculture and mixture plantation stands of AM tree species (Fraxinus mandschurica Rupr.) and EM tree species (Larix gmelinii Rupr., Picea koraiensis Nakai) in Northeast China. We hypothesized that (1) the effect of mixture pattern on mycorrhizal colonization rate and diversity would change with tree species, (2) the effect of mixture pattern on mycorrhizal community composition would be less pronounced in comparison with that of tree species. We found that mixture did not change AMF colonization rate regardless of mixture identity, whereas mixture and tree species exerted significant effects on EMF colonization rate. For AMF community, both M-AS (Fraxinus mandschurica Rupr. and Picea koraiensis Nakai) and M-AL (Fraxinus mandschurica Rupr. and Larix gmelinii Rupr.) mixtures significantly increased Pielou index and Simpson index, whereas only M-AS significantly increased Sobs. For EMF community, mixture significantly affected examined diversity indices except for Chao1. Mixture significantly shifted AMF and EMF community, and the magnitude was tree species dependent. The dominant genera in AMF and EMF communities in plantation stands were Glomus and Tomentella, respectively. The EnvFit analysis showed that the determinant factors of EMF community are soil moisture, pH, nitrate nitrogen content, dissolved organic nitrogen content, soil organic matter content, soil organic carbon/total nitrogen and litter carbon/total nitrogen. In conclusion, mixed conifer-broadleaf trees significantly changed soil physicochemical properties, litter quality as well as mycorrhizal fungi community diversity and composition.
RESUMEN
The whole root excavation method was used to examine root configuration of Juglans mandshurica, with the age of 5-6 years in three habitats (forest edge, gap, and canopy) in a secondary forest on the western part of Zhangguangcailing Mountains. Root structure and fine root function were measured. The root topological index, average joint length, cross-sectional area ratio before and after root branching were calculated and fine root chemical compositions were analyzed. Roots of J. mandshurica at forest edge tended to be dichotomous branch (Topological index:TI=0.68), that under the canopy were herringbone-like branch (TI=0.79), and the gap was between the two (TI=0.72). The average connection length of roots among the three habitats was not significant. The cross-sectional area ratio of roots before and after root branching in three habitats was 1.06, 1.04 and 1.07, respectively, which was not affected by root diameter, in accordance with the Leonardo da Vinci rule. For the same order fine root in different habitats, its length and specific surface area gradually increased from the edge of the forest to the canopy. The N content decreased first and then increased, while the C content and C/N increased first and then decreased. From the forest edge to the gap and to the under canopy, roots tended to move from the dichotomous branch to the herringbone-like branch by reducing the overlap between the secondary branches and roots, increasing specific root length, specific surface area and changing the contents of C and N to cope with environmental change and improve nutrient absorption efficiency.
Asunto(s)
Juglans , China , Ecosistema , Bosques , Raíces de PlantasRESUMEN
In this paper, the chloroplast psbK-psbI intergenic spacers of 18 species of Dendrobium and their adulterants were amplified and sequenced, and then the sequence characteristics were analyzed. The sequence lengths of chloroplast psbK-psbI regions of Dendrobium ranged from 474 to 513 bp and the GC contents were 25.4%-27.6%. The variable sites were 71 while the informative sites were 46. The inter-specific genetic distances calculated by Kimura 2-parameter (K2P) of Dendrobium were 0.006 1-0.058 1, with an average of 0.028 4. The K2P genetic distances between Dendrobium species and Bulbophyllum odoratissimum were 0.093 2-0.120 4. The NJ tree showed that the Dendrobium species can be easily differentiated from each other and 6 samples of the inspected Dendrobium species were identified successfully through sequencing the psbK-psbI intergenic spacer. Therefore, the chloroplast psbK-psbI intergenic spacer can be used as a candidate marker to identify Dendrobium species and its adulterants.
