ISWC OpenIR  > 水保所知识产出(1956---)
退耕还草坡地植被覆盖与土壤侵蚀强度响应的 7 Be 示踪研究
张博
Subtype硕士
2013-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Keyword7 Be示踪 植被覆盖 土壤侵蚀速率 侵蚀强度 降雨量
Abstract

近年来,黄土高原地区因实施退耕还林还草及封禁牧政策,植被覆盖逐渐好转,
侵蚀方式发生了明显变化,针对这种情况,需要开发和利用新的研究方法来研究有植
被覆盖坡面的土壤侵蚀问题。 7 Be 示踪技术近年来已被成功应用于土壤侵蚀的研究,
但目前只应用在裸露坡面,因此把
7 Be 示踪技术应用到有植被覆盖坡面土壤侵蚀的研
究,不仅可以拓宽
7 Be 示踪技术的应用范围,而且对现阶段黄土高原坡面土壤侵蚀的
研究具有重要的科学意义。基于此目的,本项研究以黄土高原地区安塞县为研究区,
分析了该区域内未扰动土壤中
7 Be 含量变化及 7 Be 的沉降特征,量化植物中 7 Be 含量
变化及对土壤中
7 Be 量的影响,结合径流小区的实测值,探讨植被覆盖对利用 7 Be 示
踪估算土壤侵蚀速率的影响,并通过引入植被覆盖因子对 Walling 提出的
7 Be 示踪土
壤侵蚀速率模型进行修正,将之用于有植被覆盖坡面土壤侵蚀的研究。通过分析得到
以下主要结论:
(1)研究区域内
7 Be 的沉降量具有明显的年内及年际变化,年均沉降量为
1759±416 Bq m -2 ,沉降量变化主要受降雨量控制,夏季沉降量大,约占年沉降量的
50%,冬季小,约占年沉降量的 5%。与国内外其他相似区域相比,研究区域
7 Be 年
沉降量较大,估计与研究区降尘、霜及露水对
7 Be 沉降的贡献较大有关。
(2)未扰动土壤中
7 Be 量的日变化及月均变化都呈现明显的单峰分布,日变化
值在 89.2-941.8 Bq m -2 ,平均值为 392±210 Bq m -2 ,土壤中
7 Be 量的变化主要受降雨
量及其时间分布的影响,最大值一般出现在每年的 8 月或 9 月,最小值一般在冬季或
初春。
(3)研究时段内混合干枯植物中
7 Be 含量在 212±46 和 964±122 Bq kg -1
之间,
混合活植物中
7 Be 含量在 173±86 和 703±18 Bq kg -1 之间,混合干枯植物样中 7 Be 含
量高于混合活植物样含量,在年内二者具有相同的变化趋势,春末夏初含量差异较大,
夏秋季相差逐渐缩小,在雨季末(9 月份)达到最大,之后又降低。不同年份内,相同类型地被物中
7 Be 含量的变化趋势一致,在春季含量比较接近,但在雨季,因降雨
的差异,增加的快慢不同。分析发现混合植物中
7 Be 含量和衰变累积降雨量呈显著性
正相关,衰变累积降雨量可解释植物样中约 80%的变异性。
(4)同种植物在雨季
7 Be 含量呈增加趋势,但不同植物种增加的比例不同,主
要受茎秆比例及叶面积指数的影响,植物所处生长阶段对于其
7 Be 含量的多少也有重
要影响。同种植物叶和茎秆中
7 Be 含量不同,叶中的 7 Be 含量高于茎秆中的含量,不
同植物种叶和茎秆
7 Be 含量的比例相差较大。
(5)通过 2011 年和 2012 年裸露地小区、荒草地小区和谷子地小区的
7 Be 示踪
对比研究,发现利用 Walling 模型计算有植被覆盖坡面土壤侵蚀速率的结果与实测值
相差很大,相对误差超过 100%,说明坡面植被覆盖对利用
7 Be 估算坡面土壤侵蚀速
率有重要影响。因此对 Walling 模型进行修正,引入植被盖度因子,并用之估算荒草
地小区坡面的土壤侵蚀速率,发现计算值与实测值比较接近,相对误差明显减小,在
10%-26%,说明利用修正的 Walling 模型来估算有植被覆盖坡面土壤侵蚀速率是可行
的,为量化植被覆盖坡面土壤侵蚀提供了有效手段。
(6)植物叶面积指数和植被覆盖与土壤侵蚀强度之间存在一定的对应关系,整
体表现在坡面植被稀少的地方,土壤侵蚀速率大,植被茂盛的地方,土壤侵蚀速率小。
但它们之间在数值上并不具有显著相关性。主要原因可能是由于分析的尺度效应及植
被覆盖对土壤侵蚀控制的阈值造成的。
关键词:
7 Be示踪;植被覆盖;土壤侵蚀速率;侵蚀强度;降雨量

Other Abstract

In recent years, due to the national policy of returning farmland to forest or to grass
land, vegetation coverage gradually improved and the erosion patterns have changed.
Therefore new research methods are needed to find and exploit to deal with the emerging
issue. The  7 Be tracer technique has been successfully applied to study the soil erosion, but
7 Be tracer technique can only be applied to bare slope, so  7 Be tracer technique is
introduced for soil erosion study of vegetation coverage slope has an important scientific
significance. It could broad the application fields for the
7 Be tracing technology. This
research to analysis the concentration of  7 Be in undisturbed soil and the deposition flux of
7 Be in Ansai. At the same time, quantify of  7 Be mass activity in plants and the effects  7 Be
in soil through  7 Be tracer model building and verification with vegetation according to the
observation samples in runoff plots, and using the modified model to quantitative analysis
of the response relationship of soil erosion intensity and vegetation cover in waste
grassland slope. The research conclusions are as follows:
(1) The deposition flux of  7 Be was obvious of annual and interannual changes in study
area. The annual deposition flux was 1759±416 Bq m -2 . The deposition flux was mainly
affected by precipitation, a high of 50% deposition of a year in summer and a low of 5%
only in winter. Compared with the other researched areas, the study area had a high
deposition flux of  7 Be, which was possibly to be involved in the great contribution of dust,
frost and dew to the deposition.
(2) The change of the activity of  7 Be within day and month mean value in undisturbed
soil appeared a distribution curve with single-peak. Within a day, the activity of  7 Be ranged
from 89.2 to 941.8 Bq m -2 , and the mean value is 392±210 Bq m -2 . The highest activity of
7 Be appeared in August or in September, the lowest often in winter or the early sprin because of the effect of the precipitation and time distribution.
(3) The activity of
7 Be in the mixing withered plants in study phases ranged from
212±46 Bq kg -1 to 964±122 Bq kg -1 . However, the mixing live plants are ranged from
173±86 Bq kg -1  to 703±18 Bq kg -1 . The activity of  7 Be in the mixing withered plants was
higher than it in the mixing live plants. The activity of  7 Be in the mixing withered plants
had the same tendency of changes with it in the mixing live plants within a year. The
difference in the activity of
7 Be between the mixing withered plants and the mixing live
plants was large in the end of spring and the beginning of the summer. Then, it was smaller
in summer and autumnal. However, it was highest in rainy season of September, then, it
has decreased. The activity of
7 Be in the same ground cover had a same tendency of
changes in different years, and the values were close to each other in spring but the
increasing rates were of a significant difference in rainy season. The results showed that
there was a significant positive correlation between the activity of  7 Be in mixing plants and
the decayed cumulative precipitation. And the 80% of the variability could be explained by
decayed cumulative precipitation.
(4) The activity of
7 Be in the same plant increased in rainy season. However, the
rations of the increase in different plants were different, which was mainly affected by the
stem ratio and leaf area index. The activity of  7 Be in the same plant was different between
leaves and stems, and the activity of  7 Be in leaves were higher than in stems, and the ratio
of activity of  7 Be in leaves to it in stems was significantly different in different plants.
(5)  7 Be tracing technology was applied to document soil erosion on the bare plots、
weed plots and millet plots in 2011 and 2012, and compared soil erosion rate with the
calculated rate. The relative errors exceed 100%, and results indicated that vegetation
cover had obvious effect on the estimate of soil erosion rate on the weed plot using
7 Be
measurement. Therefore, a factor of vegetation had been introduced into the Walling’s
model of converting  7 Be activity to soil erosion rate for estimating soil erosion rate on the
weed slope surface. It was found that the soil erosion rates calculated by modified model
were well close to the measured values on weed plot, the relative errors decreased by
10%-26%, which illustrated that the modified model could be well used to estimate the
rates of soil loss on the weed slope surface. These findings provide effective means for
further study on the relationship between vegetation cover and soil erosion.  (6) The analysis shows that some relationship between vegetation coverage and soil
erosion intensity. The global aspect was that soil erosion rate is high in vegetation scarcity
and low in the lush vegetation. However, there was no significant correlation in both
vegetation coverage and soil erosion intensity. The scale effects and threshold of vegetation
coverage to soil erosion are main reasons for results.
Keywords:  7 Be tracer; vegetation coverage; rates of soil erosion; erosion intensity; rainfall 

Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8956
Collection水保所知识产出(1956---)
Recommended Citation
GB/T 7714
张博. 退耕还草坡地植被覆盖与土壤侵蚀强度响应的 7 Be 示踪研究[D]. 北京. 中国科学院研究生院,2013.
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