Vegetation restoration is a fundamental method of ecological reconstruction in disturbed areas, and revegetation can be achieved by passive (spontaneous succession) and active (human-induced) approaches. Plant community composition, productivity, and diversity were studied in coal mining subsidence areas after 0–15 years of restoration with active (AR) and passive (PR) revegetation approaches in a semiarid region. Moreover, plant community composition, succession, and their relationships with soil variables were analyzed. The results showed that both PR and AR contributed to the recovery of the plant community in terms of plant cover, density, biomass, and diversity, with AR accelerating the recovery of the plant comm unity to a greater extent than PR. Soil moisture and organic matter had close relationships with the plant community variables. The plant communities in PR sites had the same species composition as those in non-subsidence (NS) areas, which led to a more natural plant community in PR than AR sites. Plant community structure in AR sites was altered by the introduced shrubs, with mesophytes developing under the introduced shrubs. These changes produced a different successional trajectory in AR sites from that in NS sites; thus, environmental fluctuations may easily change AR community stability in semiarid environments.
Conventional site clearance and tending method for a plantation is labor intensive and time consuming,and is also destructive to the vegetation resulting in serious soil erosion.According to these problems,an experiment with different clearance and tending methods was conducted by two-factor split-plot design.After two years,the result showed that different clearance methods and difference tending methods had significantly different result.The best growth of Pinus massoniana was gained when methods of banded site Clearance(3m to 1m) and tending twice by both hook and hoe tools were adopted..
The root distribution and the influence of soil nutrient and soil moisture on root distribution of vegetation recovery slope on the hilly and gully Loess Plateau were studied.The results showed that the distribution of root varied with slope aspect,erosion belt,soil depth and vegetation types.The total root biomass of south-face slope was higher than that of east-face slope,but there was no significant difference.Significant differences in the total root biomass and ≤1 mm root biomass existed between the gully slope and each erosion belt on the inter-gully slope.The root biomass decreased with the increase of soil depth.Different vegetation types and coverage had great influence on root biomass.Among the different diameter levels,the biomass of root with the diameter less than 1 mm group was the largest,followed by the 1～2 mm group,and the 2～3 mm group and the 3 mm group were smaller,meanwhile there existed significant differences between the root biomass of ≤1 mm group and that of other diameter levels.There was a medium positive correlation between root biomass and soil nutrient(except total phosphorus),and the distribution of root biomass and soil moisture in different soil depth was inconsistent.Therefore,root distribution not only depends on its own characteristics,but also is affected by the soil environmental condition.
A phytogenic mound is a special microtopography that forms under a perennial plant canopy in erosion-affected areas. These mounds result in spatial microenvironmental heterogeneity and thus are important factors in determining plant community composition. We assessed whether and how plant composition and diversity differed on different parts of mounds in water erosion-affected areas and evaluated which environmental variables were related to the compositional difference. We compared plant community composition and diversity on the upslope (UP) and downslope (DN) parts of mounds and inter-canopy surfaces (IS) along four slope gradients. On slopes < 46.6%, vegetation cover, biomass, density and diversity of plant communities did not significantly differ between UP and DN. However, these plant community attributes were higher UP than in IS and DN on steeper slopes (> 46.6%). On such slopes phanerophytes and chamaephytes occurred only UP. Sediment accumulation, light intensity, soil moisture, and surface hardness were significantly correlated with the community composition on mounds, while soil N, P and K showed a weak relationship. Only the UP of mounds on steep slopes maintained high plant diversity in water erosion-affected areas, which is especially important for shaping plant community patterns on seriously eroded slopes where plant colonisation is limited.
We studied the effects of different ear removal treatments on the senescence order of functional leaves and the effects of removal of 3/4 ear on the chlorophyll content, net photosynthetic rate, transpiration rate, stomata conductance, malonaldehyde content and catalase activity in the functional leaves in wheat. The results showed that different ear removal resulted in different frequency of plants with leaf-color inversion (i.e., the green color of both the 2nd and 3rd leaf from the top or only the 2nd leaf was deeper than that of the flag leaf). Removal of 3/4 ear or whole ear, obviously increased the frequency of plants with leaf-color inversion. The chlorophyll content, photosynthetic rate, transpiration rate, stomata conductance and catalase activity in the flag leaf of plants with leaf-color inversion were mostly lower than those in the 2nd and 3rd leaf from the top, but the malonaldehyde content of flag leaf was obviously higher than that of the 2nd and 3rd leaf from the top. The experiments demonstrated that removal of 3/4 ear accelerated the senescence of flag leaf, delayed the senescence of the 2nd and the 3rd leaf from the top and altered the senescence order of wheat functional leaves.
A phytogenic mound is a special microtopography that forms under a perennial plant canopy in erosion-affected areas. These mounds result in spatial microenvironmental heterogeneity and thus are important factors in determining plant community composition. We assessed whether and how plant composition and diversity differed on different parts of mounds in water erosion-affected areas and evaluated which environmental variables were related to the compositional difference. We compared plant community composition and diversity on the upslope (UP) and downslope (DN) parts of mounds and inter-canopy surfaces (IS) along four slope gradients. On slopes < 46.6%, vegetation cover, biomass, density and diversity of plant communities did not significantly differ between UP and DN. However, these plant community attributes were higher UP than in IS and DN on steeper slopes (> 46.6%). On such slopes phanerophytes and chamaephytes occurred only UP. Sediment accumulation, light intensity, soil moisture, and surface hardness were significantly correlated with the community composition on mounds, while soil N, P and K showed a weak relationship. Only the UP of mounds on steep slopes maintained high plant diversity in water erosion-affected areas, which is especially important for shaping plant community patterns on seriously eroded slopes where plant colonisation is limited.
This paper studied the vegetation composition, bud composition, and the seasonal dynamics and vertical distribution pattern of bud bank in five erosion environments (sunny gully slope, sunny hilly slope, hilltop, shady hilly slope, and shady gully slope) on the hilly-gully Loess Plateau of North Shaanxi. In the study area, the perennial species with perennial bud bank accounted for 80.3% of the total species, while the annual species with seasonal bud bank took up 19.7% of the total. In vegetation turning-green season, there was a relatively large perennial bud bank stock on the sunny hilly-gully slope where serious erosion occurred, while seasonal bud bank showed a higher bud bank density in blossom and fruit-setting season on the hilltop and two shady slopes where soil erosion intensity was relatively gentle. The proportion of underground bud bank to total perennial bud bank in different erosion environments was relatively stable. On the land surface, the perennial bud bank stock was larger on the sunny slope where the soil disturbance often occurred, whereas the seasonal bud bank stock was larger on the shady slope and hilltop. Due to the different species composition of plant communities in different erosion environments, in addition to the disturbance of soil erosion and the seasonal plant regeneration, the seasonal dynamics and vertical distribution pattern of bud bank changed. It was suggested that bud bank played an important role in the vegetation regeneration after the disturbance of soil erosion on the hilly-gully Loess Plateau of North Shaanxi.
In order to reveal characteristics of ecological adaptabilities of dominant species and find out the relationship between ecological factors and leaf structures variations,the foliar anatomical structures of seven dominant species(including Bothriochloa ischaemum,Stipa bungeana,Artemisia scoparia,Artemisia giraldii,Artemisia sacrorum,Lespedeza daurica,Periploca sepium) in the north Shaanxi Loess Plateau were observed.The main results are as follow:(1)There are some special characteristics for each species to resist the drought and strong light stress in each species,such as special bulliform cells and kranz structure of Bothriochloa ischaemum;multilayer sclerenchyma under epidermis and stomatal pit of Stipa bungeana;Water storage parenchyma and ring palisade type mesophyll of A.scoparia;Palisade tissue of A.sacrorum;Secretory cavity and total palisade type mesophyll of A.giraldii;Mucilage cell of L.daurica;Epicutile wax layer of P.sepium.(2)In the arid and strong light intergully area,upper epidermis cuticular layer thickness,leaf thickness,palisade tissue thickness,water storage parenchyma thickness are getting thickness;upper epidermis cells size,phloem transect area makes larger;while in contrary for xylem transect area,xylem transect area/phloem transect area became decreased.(3)The average integrative coefficient of variance can measure the potential ability of acclimatization?In the sequence of coefficient of variance from high to low,seven plants were arranged by A.scoparia,A.giraldii,A.sacrorum,B.ischaemum,L.daurica,S.bungeana and P.sepium.The strongest potential ability of acclimatization make A.scoparia to one of the pioneer species for vegetation recovering in the North Shaanxi Loess Plateau.
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