First Report of Root Rot Caused by Fusarium oxysporum on Aralia elata in China.

Aralia elata (Miq.) Seem., is grown for its medicinal and nutritional properties in northeastern China. The tender shoots are used as wild vegetables. The plant saponin components have antioxidant and neuroprotective activities, and are used for the treatment of chronic disease (Xia et al. 2021). In July 2021, root rot disease was observed in five-year-old A. elata plants in Qingyuan County (41°91' N, 124°59' E), Liaoning Province, China. The incidence of roots rot was approximately 50% in old fields, with the leaves of the infected plants appearing chlorotic and wilting. The lesions on the taproots were dark brown and soft, with degraded internal organization. Leading edge of necrotic tissue from symptomatic roots was cut 5×5×3 mm, placed in 75% ethanol for 30 s, and then in 3% sodium hypochlorite for 2 min. After three rinses in sterile distilled water, the samples were dried on sterile filter paper before plating on potato dextrose agar (PDA) and incubation at 25℃. Monosporic cultures were obtained by the collection of single spores from individual isolates. After 7 days on PDA, mycelia in the colonies appeared cottony and pink, white, or purple in color, while their undersides were pink and white. Spore characteristics were evaluated after transfer to carnation leaf agar (CLA) and incubation for 20 days (Zhang et al. 2021). The macroconidia were falciform, slightly curved or straight, two to five septate, and 20.57 to 33.75 × 3.62 to 6.11 µm (n=40). The microconidia were ovoid or oval, zero to one septate, and 5.12 to 13.53 × 3.04 to 4.79 µm (n=40). Chlamydospores were globose to subglobose, intercalary or terminal, with an average diameter of 13.76 µm (n=40).To identify the pathogen, the internal transcribed spacer (ITS) region, large subunit (LSU) ribosomal DNA, and translation elongation factor 1 alpha (TEF-1α) gene were amplified using the respective primer pairs ITS1/ITS4, LR0R/LR7, and EF1-728F/EF1-986R (Cheng et al. 2020; Fu et al. 2019). Comparisons with GenBank, the sequences of ITS, LSU, and TEF-1 had 99 to 100% homology with Fusarium oxysporum (accessions numbers- MH707084, OQ380519, and GU250609, respectively). The sequences were deposited in GenBank: OP482273 (ITS), OP491955 (LSU), and OP503498 (TEF-1α). Maximum likelihood phylogeny of the identified sequences using MEGA-X software indicated that the isolate represented F. oxysporum. The taproots of 30 one-year-old A. elata were washed and inoculated with 1×106/ml of the conidial suspension for two hours, and another 30 used as controls with sterile water. After planting in sterilized forest soil in flowerpots (36×30 cm), the plants were grown in a greenhouse for two weeks at 25℃ with 14 h of light. It was found that 50% of the roots showed typical root rot symptoms, while the controls were asymptomatic. The pathogenicity test was repeated three times, and reisolation of F. oxysporum from the roots fulfilled Koch's postulates. This is the first report of root rot in A. elata caused by F. oxysporum in China and indicates the necessity for suitable management strategies to protect A. elata production. References: Cheng, Y., et al. 2020. Plant Dis. 104:3072. Fu, R., et al. 2019. Plant Dis. 103:1426. Xia, W., et al. 2021. Mini-Rev Med Chem. 21:2567. Zhang, X. M., et al. 2021. Plant Dis. 105:1223.

[Responses of radial growth of Quercus mongolica to stand density and climatic factors in a mountainous area of eastern Liaoning Province, China]. / è¾½ä¸œå±±åŒºè’™å¤æ Žå¾„å‘ç”Ÿé•¿å¯¹æž—åˆ†å¯†åº¦å’Œæ°”å€™å› å­çš„å“åº”.

To explore the effects of stand density and climatic factors on radial growth of Quercus mongolica, we used tree ring chronology to examine the radial growth changes in a secondary Q. mongolica forest under different levels of stand density (thinning). The meteorological data combined with the driving factors of Q. mongolica growth were analyzed. The results showed that the radial growth of Q. mongolica was significantly affected by stand density. The mean annual radial growth of Q. mongolica was 3.12 mm in low-density virgin forest, 1.55 and 1.42 mm in the two medium-density secondary forests, respectively, and 0.96 mm in high-density secondary forest. The thinning intensity of 20% had a limited effect on promoting the radial growth recovery of high-density forest (1900 trees·hm-2), but had a significant effect on medium-density forest (1600 trees·hm-2). The radial growth of Q. mongolica was sensitive to the precipitation changes in January and February of the current year. Thinning reduced the sensitivity of Q. mongolica radial growth to climate. Under scenarios of climate warming and drying, density regulation could be beneficial in mitigating the adverse effects of climate change on the growth of Q. mongolica.

[Evaluation of forest ecosystem services value in Liaoning Province].

Based on the long-term located observation of forest ecosystem, and by using the 2006 forest resources inventory data of Liaoning Province and the forest industry standard of the People's Republic of China( LY/T 1721-2008, specification for assessment of forest ecosystem services in China), an evaluation was made on the material quantity and services value of main forest ecosystems in fourteen cities of Liaoning Province. In this province, the forest ecosystem services value supplied by water storage, soil conservation, C fixation, O2 release, nutrients accumulation, environment purification, biodiversity conservation, and forest recreation in 2006 was 2591.72 x 10(8) yuan, which was 8.54 times of the forestry production value and 28.02% in the GDP of the province. The services value of water storage, biodiversity conservation, C fixation, and O2 release occupied 79.09% of the total, being the main forest ecosystem services in the province. Economic forest and shrub had smaller per unit services value but larger area, and hence, their ecosystem services value should not be ignored. Abies fargesii forest, Phellodendron amurense forest, Juglans mandshurica forest, and Fraxinus mandshurica forest were the representative zonal vegetations in Liaoning Province, which had high value in biodiversity conservation. Under the effects of climate and other factors, the forest area and forest quality in west Liaoning were lower than those in east Liaoning.

[Soil moisture characteristics at the boundary of forestland-grassland in hilly area of Loess Plateau].

In this paper, the spatial distribution pattern of soil moisture at the boundary of forestland-grassland in hilly area of Loess Plateau was studied in dry season of June and rainy season of August 2004. The results showed that the variance coefficient of soil moisture content was smaller, and the difference of moisture content between soil layers was less significant in forestland than in grassland in June while reversed in August. There was a weak or medium differentiation of moisture content in different soil layers at the boundary of forestland-grassland. The edge effect area at the boundary was from 2 m (0. 4 of tree height) outside forestland to 2 m inside forestland in June, and from 2 m outside forestland to 4 m (0. 8 of tree height) inside forestland in August. The forestland-grassland landscape could be divided into 3 parts, i.e., grassland area, forest edge area, and forestland area, and the vertical distribution of soil moisture in these three parts showed different traits. In June, soil moisture content increased with increasing soil depth, with a smaller increment in grassland than in forestland, but in August, it was reversed. The vertical distribution of soil moisture at forest edge area showed an in-between feature.

[Spatial heterogeneity of soil moisture after raining at forest-grassland landscape boundary in hilly area of Loess Plateau].

Soil moisture is a main factor limiting vegetation restoration in semi-arid region. In this paper, the spatial variability of different layers soil moisture after raining at the forest-grassland boundary in hilly area of Loess Plateau were studied by traditional and geostatistical analysis methods. The results showed that the moisture content in surface (0 - 10 cm) and subsurface soil layer (10 - 20 cm) of grassland was higher than that of forestland. The two layers soil moisture content at forest-grassland boundary showed a small variation but an obvious ecological distribution. By using moving split-window techniques, it was obtained that the width of edge influence in surface and subsurface layer was 8 and 6 m, respectively. Geostatistical analyses showed that the spatial distribution of two layers soil moisture had a pure nugget effect in grassland, linear model in forestland, and spherical model in forest-grassland boundary. The spatial heterogeneity of two layers soil moisture was higher at forest-grassland boundary than at forestland and grassland, which had a stronger spatial dependence and autorelation. Kriging maps expressed the spatial structural characters. The distribution of soil moisture in two layers showed a strip shape near forest edge, and a patch shape far from the edge.

[Natural regeneration of Pinus sylvestris var. mongolica plantation on sandy land].

By employing comparison analysis and field survey, the natural regeneration of Mongolian pine plantations on sandy soil was investigated. In plantation areas where regeneration can take place naturally, natural regeneration of Mongolian pine varied temporally and spatially. Natural regeneration wasn't temporally continuous; it had a close relationship with autumn precipitation in particular years. In spatial aspect, there were three regeneration types: regeneration in forest gaps, regeneration on edges of a forest, regeneration under young broadleaf forest. There was no significant difference between the growth of regeneration saplings and plantation trees.

[Analysis of natural regeneration barriers of Pinus sylvestris var. mongolica plantation on sandy land].

By employing comparison analysis, and field experiment of watering and soil-covering before overwintering for seedlings, the barriers of natural regeneration for Mongolian pine plantations on sandy soil were identified. The experimental area was divided into 3 parts according to the state of natural regeneration. Crown closure, litter, understory coverage, and site condition were the factors which affect natural regeneration. Water deficit, but not low temperature during overwintering, is the key factor that limits survival for 1-2 years old seedlings in plantation area. The water deficit is due to higher air temperature, less accumulated snow, higher soil evaporation, higher plant transpiration in plantation area than in the area in which Mongolian pine is naturally distributed. Based on the above research, it is necessary to take effective artificial measures to promote its natural regeneration so as to guarantee its successful development. The following measures are recommended: 1) covering the 1-2 years old seedlings with soil before wintering, 2) irrigating seedlings before wintering, 3) suitable forest harvest, e.g., belt clear-cutting, or patch cutting, 4) planting the pine with broadleaf species, 5) protecting forest stands from livestock grazing, seed collecting and litter gathering.