Film-mulched rock outcrops are a proven way to effectively prevent preferential flow at the rock–soil interface in rocky karst areas, but the impact on rainwater redistribution and maize growth in farmland areas has never been studied. This paper used the dye tracer method at a sprinkling intensity of 1 mm min−1 to study the rainwater redistribution in soils for three different treatments: away from rock (AR), close to rock (CR), and close to film-mulched rock (CFMR). The growth situation of maize (Zea mays L.) according to the different treatments was also studied. It was shown in the study that the rainwater gathered by rock outcrops was mainly confined only within a narrow flow path at the rock–soil interface in the CR treatment, with a preferential flow fraction of 35.78~55.54% and dyeing depth of 15.37~20.00 cm across the three dye application amounts (850 mL, 1700 mL, and 3400 mL) in contrast to the uniform distribution of the rainwater in the soil of the AR treatment, with a preferential flow fraction of 12.31~37.15% and dyeing depth of 6.93~14.00 cm. Interestingly, in the CFMR treatment, there was no preferential flow at the rock–soil interface benefiting from the film’s blocking action, and the redistribution of rainwater was mainly based on the matrix flow, with a preferential flow fraction of 24.93~39.62% and dyeing depth of 10.27~18.00 cm, indicating that the film-mulched rock outcrops improved the rock’s output capability for gathering rainwater into the surrounding soil. In addition, film-mulched rock outcrops can promote the growth of maize, as indicated by the results for plant height, stem diameter, maximum leaf area, SPAD value, and floral development of maize, which increased in order from AR, CR, to CFMR. Our study suggests that film-mulched rock outcrops have important implications for the efficient use of rainwater and the growth of crops in rocky karst areas, as well as in regions with similar geological characteristics.
Anthropogenic disturbance and peculiar geochemistry have resulted in rocky desertification in many karst regions of the world.Seed banks are crucial to vegetation regeneration in degraded karst ecosystems characterized by a discontinuous distribution of soil and seasonal drought stress.However, the dynamics of seed banks across one complete series of secondary succession and the underlying mechanisms remain unclear.We selected eight typical stages during secondary succession, conducted aboveground vegetation survey and collected 960 soil samples in the Guiyang karst landscape of China.Seed density, species richness and plant life forms in seed banks were determined via the germination method.The results indicated that the seed density in seed banks before and after field seed germination was significantly different among most succession stages.Community succession had impacts on the seed density of seed banks before and after field seed germination.Seed density ranged from 1042 seedlings.m-2 in evergreen broadleaf forests to 3755 seedlings.m-2 in the herb community, which was a relatively high density.The seed density and similar species composition between the seed banks and vegetation declined with succession from early to later stages.Species richness in seed banks was highest in middle succession stages and increased with increasing species richness of aboveground vegetation.The species richness of the five life forms in the seed banks showed different variations across these succession stages.The conservation of diverse aboveground vegetation can maintain the diversity of seed banks for restoration.
Seeds are the potential populations of plant. Using germination method after washing soil samples through a fine and a course sieve, soil seeds were studied for 3 kinds of soils covered with various vegetations at 3 karst locations in Eastern Yunnan. The results showed that there were abundant seeds stored in soils. There were 40.9～149.3 seeds for each of 10 cm×10 cm×10 cm soil unit which were much higher than that of karst soils in Guizhou and that of forest soils of Guangdong at the same latitude. Generally, seed density of secondary forest soil was higher than that of grassland. There was no any regular trend between seeds of scrub soils and that of grassland. Most of seeds were herbacious, shrub seeds came next, tree and liana were rare. Seeds were unevenly distributed horizontally at all the soils across the vegetation types and locations. Seeds density was dropped down vertically with a slow rate in the soil of secondary forest. The physical characteristics of soil might contribute to this difference of vertical drop rate. Higher organic matter made the soil less compact and easier for seeds to move into deep soil.
The composition of Karst SHEBF was very rich in terms of species,genera and families. 163 species of 142 genera of 95 families were identified within 10 000 m~2 area at Suoyishan and 125 species of 110 genera of 95 families at Yuehu,among which herb species were the largest group,followed by tree species,liana was the smallest group. Judged by the important value(IV)calculated based on the individuals with DBH≥3 cm,major tree species were Cyclobalanopsis glaucoides,Pistacia weinmannifolia,Neolitsea homilanthaandOlea yunnanensis. There were less species and individuals with big DBH size. Species dominance was constituted by individuals with small and medium DBH size. Phanerophytes(54.9% at Suoyishan and 8.8% at Yuehu)and hemicryptophytes(39.6% at Suoyishan and 41.6% at Yuehu)were the major Raunkiaer life forms. According to the life form of monograph “Vegetation of China”,tree were medium and small size species,with a percentage of 25% in total;Perennials accounted for a higher percentage(42.7% at Suoyishan and 45.6% at Yuehu). The number of evergreen tree species was almost equal to the number of deciduous species. But if we counted with individuals,DBH or IV,the highest percentage of deciduous components was only 24.7% and then we defined the community as semi-humid evergreen broad-leaved forest with deciduous components. The species-area curve showed a very sharp transition point at 400 m~2. With these results,we proposed this size as the smallest survey area of Karst SHEBF.
Abstract We studied seasonal variation in density and species richness of seeds in the 0–10 cm soil depth layer in primary, secondary and pine forests, and in shrubland and grassland in the Shilin Stone Forest Geographical Park, Yunnan, SW China. Soil samples were collected four times during the year at 3-month intervals. Seeds from 119 species were identified by germination tests in the soil samples. Density and species richness of seeds of herbaceous plants were greater than woody plants at all five sites throughout the year. Sampling time and site differences had significant effects on the mean number of species and on seed-bank density. Mean number of species per sample increased from February, reached the highest value in May, decreased to the lowest value in August and then increased in November. An exception was in the primary forest, where the highest number of species was found in February. Mean seed-bank density peaked in May at all five sites, and no significant differences were found between densities in February, November and August, except for the primary forest. The peak in seed-bank density in May might be due to dispersal of new seeds of spring-fruiting species, combined with persistence of seeds dispersed in previous years. This seasonal variation of individual species was due primarily to differences in species phenology rather than to differences between sites. Four seasonal seed-bank strategies were identified: two transient and two persistent. At all sites, similar numbers of seeds of herbaceous species were found between seasons, but the number of species of trees and shrubs decreased in August.
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