Jinxin Zhang

Optimum Conditions for Pure Culture of Major Ectomycorrhizal Fungi Obtained from Pinus sylvestris var. mongolica Plantations in Southeastern Keerqin Sandy Lands, China

The effects of medium, pH, water potential and temperature on the culture for three pure strains (Lactarius deliciosus, Boletus edulis and Lactarius insulsus) of ectomycorrhizal fungi from plantation forests of Mongolian pine (Pinus sylvestris var. mongolica) on sandy lands were observed to obtain the optimum conditions for the growth of ectomycorrhizal fungi. The results indicated that the three ectomycorrhizal fungi could grow well in the mediums containing natural components, such as vitamin, pine juice and yeast powder. pH had a slight effect on the growth of the three ectomycorrhizal fungi, and the optimum pH values were 6.0 for L. deliciosus, 5.0 for B. edulis, respectively. However, L. insulsus had a wide pH range, and it grew better than the other two strains in neutral and light alkalescent mediums. Water potential (produced by Polyethylene Glycol, PEG) had significant effects on the ecological adaptability for the tested three fungi strains. All of the three stains grow better at lower PEG concentration (100 g PEG·kg−1 H2O). The best water potential was 10% PEG concentration for all of the three stains. Temperatures, especially high temperatures induced the fungi death. The optimum temperature for the growth of ectomycorrhizal fungi was 25–28°C for all of the three stains.

Response of species and stand types to snow/wind damage in a temperate secondary forest, Northeast China

Abstract Snow/wind damage is one of the important natural disturbances in forest ecosystems, especially in a montane secondary forest. However, the effects of snow/wind damage remain unclear which affects the management of these forests. Therefore, we investigated the responses of species, individual tree traits and stand structure to snow/wind damage in a montane secondary forest. Results show that, amongst the canopy trees, Betula costata exhibited the most uprooting, bending and overall damage ratio (the number of damaged stems to the total number of stems in a plot); Quercus mongolica showed the highest breakage ratio and Fraxinus mandshurica and Juglans mandshurica the least overall damage ratios. Among the subcanopy trees, Carpinus cordata, Acer mono, Acer tegmentosum and Acer pseudo-sieboldianum showed the least uprooting and breakage, and the most bending damage. A. pseudo-sieboldianum demonstrated the lowest breakage and highest bending damage ratios. These findings indicate that different species have various sensitivities to snow/wind damage. Larger trees (taller, wider crowns) tend to break and become uprooted, while smaller trees are bent or remain undamaged, suggesting that tree characteristics significantly influence the types of damage from snow and wind. Stands of Q. mongolica and B. costata had the highest damage ratios, whereas A. pseudo-sieboldianum had the lowest snapping ratio. In summary, the severity and type of snow/wind damage are related to individual tree attributes and stand-level characteristics. Therefore, selection of suitable species (e.g., shorter, smaller with deep root systems, hard wood, bending resistance and compression resistance) and appropriate thinning are recommended for planting in the montane secondary forests.

Comparisons of radial growth and tree-ring cellulose δ13C for Pinus sylvestris var. mongolica in natural and plantation forests on sandy lands

ABSTRACT To reveal the effects of water stress on the decline in introduced Mongolian pine (Pinus sylvestris var. mongolica) plantations, radial growth (basal area increment, BAI) and tree-ring cellulose δ13C (carbon isotope composition) were compared in an introduced Mongolian pine plantation and a natural Mongolian pine forest during 1965–2009. Results showed that the BAI of plantation trees increased until 1990, followed by an abrupt decline from 1990 to 1996 and maintained a stable level thereafter. In contrast, no sign of decreased growth was found for natural trees. Tree-ring δ13Ccorr of plantation trees, corrected for atmospheric changes in δ13C, significantly increased before and after 1990. However, no significant variations in tree-ring δ13Ccorr for natural trees before and after 1990 indicated no obviously water stress. Intrinsic water-use efficiency (iWUE, calculated from tree-ring δ13C) significantly increased before and after 1990 for both forests. Significant negative relationship between BAI and δ13Ccorr or iWUE was found for plantation trees after 1990 when precipitation, Palmer Drought Severity Index (PDSI) and groundwater level decreased, suggesting water stress impact on growth. For plantation trees, PDSI was positively and negatively correlated with BAI and δ13Ccorr, respectively, after 1990. For natural trees, BAI had no relationship with PDSI after 1990. These findings suggested that a decrease in PDSI (e.g. decreased precipitation and higher temperature) and groundwater level had made plantation trees face a more serious water stress compared with that of natural trees, which decreased tree growth. However, other stressors such as nutrient limitation may also contribute to growth decline.