[Variation characteristics of soil seed bank during vegetation restoration in red soil erosion area]. / 红壤侵蚀区植被恢复过程中土壤种子库变化特征.

As a natural disturbance agent, soil erosion could affect secondary distribution and species composition of soil seed bank. The composition, storage and distribution pattern of the soil seed banks in five different vegetation recovery areas, including bare ground (1), pine forest land (2-4) and secondary forest (5) in the typical red soil erosion area, were studied to explore the effects of soil erosion on soil seed bank during vegetation restoration. The results showed that a total of 21 species were recorded in the soil seed bank. Species richness was low, and dominated by herbaceous species. The density of soil seed bank varied from 56.7 to 793.3 seeds·m-2 and differed significantly among the sampling plots. Further, the density of soil seed bank decreased obviously with the increasing soil erosion intensity. The seed bank density of 0-2 cm soil layer increased along uphill, middle slope, and downhill. The soil seed banks of severely eroded and strongly eroded plots were mainly distributed in the 5-10 cm soil layer, with almost no seeds in 0-2 cm soil layer on the middle slope and uphill. Soil erosion made the distribution of soil seed bank to deeper soil layer, the accumulation of which will need a long time after vegetation restoration.

[Effects of Chinese fir litter cover on its seedling emergence and early growth]. / 杉木凋落物覆盖对自身幼苗出土和早期生长的影响.

Litter accumulation can strongly affect seedling emergence and early growth through both physical and chemical mechanisms, and can further influence natural regeneration. Chinese fir (Cunninghamia lanceolata) is one of the most important afforestation tree species. Its natural regeneration is poor, possibly due to the thick leaf accumulation inhibiting seedling emergence and growth. We used natural and plastic litter to study the effects of Chinese fir litter on its own seedling emergence and early growth, as well as to assess whether the effect was physical or chemical. In this experiment, two litter types (natural and plastic litter) and four different litter amounts (control, 0 g·m-2; low, 200 g·m-2; medium, 400 g·m-2; high, 800 g·m-2) were used. The results showed that compared to the control (0 g·m-2), low litter amount (200 g·m-2) exerted a slight positive effect on seedling emergence, whereas high litter amount (800 g·m-2) significantly reduced the seedling emergence and survival rate in the case of both natural and plastic litter. With increasing litter amount, root length of seedlings decreased and stem length increased. The highest and lowest root mass, leaf mass, and total mass of seedlings were observed for the low and high litter amount, respectively, in the case of both natural and plastic litter. The root:shoot ratio of seedlings decreased with the increasing litter amount for both natural and plastic litter. The photosynthesis:non-photosynthesis biomass ratio of the seedlings was higher under all litter cover treatments, compared to that in the control. Because the effect of the same amounts of the natural and plastic litter on seedling emergence and early growth did not differ, the litter layer's short-term influence was primarily physical. As the litter cover increased, the initial slight positive effects on seedling emergence and early growth could shift to inhibitory effects. Moreover, to penetrate the thick litter layer, Chinese fir seedlings allocated more resources toward stems and aboveground growth. This study provided evidence for litter amount being a key ecological factor that affects the seedling development and subsequent natural regeneration of Chinese fir.

[Responses of seed germination and seedling growth of Cunninghamia lanceolata and Schima superba to different light intensities.] / æ‰æœ¨å’Œæœ¨è·ç§å­èŒå‘åŠå¹¼è‹—ç”Ÿé•¿å¯¹å ‰æ¢¯åº¦çš„å“åº”.

Light is a key factor affecting seed germination and seedling growth. In this study, seed germination and seedling growth of Cunninghamia lanceolata and Schima superba were compared under controlled conditions with five light treatments (100%, 60%, 40%, 15% and 5% of full sunlight). The results showed that light intensity significantly impacted seed germination and seedling growth of both species. With decreasing light intensity, the germination rate and germination index of C. lanceolata increased, while those of S. superba showed a trend which increased first and then decreased, with the maximum at 40% light intensity. The seedling survival rate of both species was 0 under full sunlight, while significantly decreased with decreasing light intensity from 60% to 5%. Root length, basal stem diameter and height showed a consistent trend with the change of light availability in both species. Root length significantly decreased, basal stem diameter and height increased first and then decreased with decreasing light intensity, with the minimum at 5% light intensity. With decreasing light intensity, root biomass, stem biomass, leaf biomass and total biomass of C. lanceolata seedlings declined, while high biomass accumulation of S. superba seedlings were observed in 15%-60% light intensities, and lowest at 5% light intensity. Biomass accumulation in each organ of S. superba seedlings was greater than that of C. lanceolata seedlings under the same light intensity. High stem biomass and leaf biomass, low root biomass and root to shoot ratio were a phenotypic response to low light intensity in C. lanceolata and S. superba seedlings grown under poor light condition. The growth of C. lanceolata is better under relatively high light intensity than S. superba. Whereas S. superba is moderately shade-tolerant at the seedling stage, thus is more suitable for planting under closed canopy.

[Composition and seasonal dynamics of seed rain in Chinese fir (Cunninghamia lanceolata) plantation.] / 杉木人工林种子雨组成和季节动态.

Chinese fir plantation is an important part of the subtropical forests in southern China. It has a sustainable natural regeneration ability, which is the foundation of determining community succession direction and maintaining their large area. The main objective of this study was to investigate whether the seed pool was the main restricting factor for the natural regeneration of Chinese fir plantation. Mixed broad leaf-conifer forest and pure plantation of Chinese fir were selected to study the species composition, quantity and seasonal dynamics of all species and dominant species. The results showed that seeds from 21 species belonged to 13 families and 18 genera were collected in the mixed forest, while seeds from 19 species belonged to 12 families and 16 genera were collected from pure forest. Seed rain intensities of all species were 3797 and 3300 seeds·m-2 in mixed forest and pure plantation, respectively. The number of seeds from tree species was absolutely dominant in seed rain (mixed forest 89.1%, pure plantation 86.2%). The number of Chinese fir seeds was the largest, the intact seeds intensities were 825 and 345 seeds·m-2, respectively. The proportion of all types of seeds in both stands followed the order: the intact seeds > empty or rotten seeds > feeding seeds. The seed rain of both stands had significant seasonal dynamics, both reaching the peak in autumn. The seed rain mainly was intact seeds at the peak of seed-falling. Both mixed forest and pure plantation of Chinese fir had plenty of seeds. The results indicated that the seed rain is not the main factor that restricts natural regeneration in Chinese fir plantations.

[Rainfall and soil moisture redistribution induced by xerophytic shrubs in an arid desert ecosystem]. / è’æ¼ çŒä¸›å† é™é›¨å’ŒåœŸå£¤æ°´åˆ†å†åˆ†é .

Rainfall partitioning by desert shrub canopy modifies the redistribution of incident rainfall under the canopy, and may affect the distribution pattern of soil moisture around the plant. This study examined the distribution of rainfall and the response of soil moisture beneath the canopy of two dominant desert shrubs, Caragana korshinskii and Artemisia ordosica, in the revegetation area at the southeastern edge of the Tengger Desert. The results showed that throughfall and stemflow ave-ragely occupied 74.4%, 11.3% and 61.8%, 5.5% of the gross precipitation for C. korshinskii and A. ordosica, respectively. The mean coefficients of variation (CV) of throughfall were 0.25 and 0.30, respectively. C. korshinski were more efficient than A. ordosica on stemflow generation. The depth of soil wetting front around the stem area was greater than other areas under shrub canopy for C. korshinski, and it was only significantly greater under bigger rain events for A. ordosica. The shrub canopy could cause the unevenness of soil wetting front under the canopy in consequence of rainfall redistribution induced by xerophytic shrub.