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题名: 半干旱区典型灌木降水再分配模式与影响机制研究
作者: 袁 川1
学位类别: 博士
答辩日期: 2017-05
授予单位: 中国科学院大学
授予地点: 北京
导师: 傅伯杰 ; 高光耀
关键词: 半干旱区,灌木,降水再分配,时间动态,空间分布 ; Semiarid region, Shrub, Rainfall redistribution, Temporal dynamics,Spatail pattern
其他题名: Rainfall redistribution and its influential mechanismof two dorminant shrub species in semi-arid region, China
学位专业: 生态学
中文摘要: 降水经植被冠层拦截后被分配为穿透雨、树干茎流和冠层截留损失。其中 树干茎流与穿透雨之和为净降水量,反映了最终到达冠层下、可转化为土壤水 的潜在降水量。在此过程中雨滴动能和势能达到新平衡,雨量分布形成新空间 格局,降水运移和入渗时间动态发生改变,最终影响植被冠层下土壤水分补给, 和土壤-植被-大气连续体的生物地球化学循环过程。穿透雨占次降水量比例最 大,是冠层下土壤水分的最大潜在补给源。树干茎流携带植被冠层积累的大气 干沉降和植物分泌物沿植物根系、土壤动物通道和土壤大空隙等优先通道直接 汇入植物根区,对维持植被(尤其旱区植被)正常生命活动意义重大。树干茎 流的“点输入”特性有助于发育水养分富集的“水力岛”、“肥力岛”或“资源 岛”,对形成旱区灌丛和裸地镶嵌斑块格局作用积极。较之均匀分布,斑块格局 的干旱生态系统生产力更高。因此,阐明干旱半干旱区灌木降水再分配(尤其 是树干茎流)比例、效率、时间动态和空间分布,有助于理解土壤有效水分的 维持机理,为荒漠生态恢复和干旱生态系统管理提供理论支持。 本研究选址黄土高原和毛乌素沙地过渡带的陕西省神木县六道沟小流域, 于2014 年和2015 年雨季对区域代表性灌木物种柠条(Caragana korshinskii) 和沙柳(Salix psammophila)的降水再分配模式和影响机制进行研究,研究内 容主要包括:(1)量化灌木植株的树干茎流、穿透雨和冠层截留损失比例,(2) 灌木枝干的树干茎流产量与效率,(3)刻画树干茎流时间动态,(4)阐明穿透 雨空间格局,(5)分析影响上述生态水文过程的气象因子和植被特征。为更好 的评价树干茎流效率,建立降水再分配过程与植物生长过程间联系,本研究首 次引入树干茎流生产效力(SFP, mL∙g–1),反映单位枝干生物量增长带来的树干 茎流形式的水资源收益。结合汇流率(FR),和以体积(SFb, mL)、深度(SFd, mm)、占次降水比例(SF%, %)表示的茎流量,重点在枝尺度上研究柠条和沙 柳树干茎流产量、效率及其影响机制,并以沙柳为例探讨利于茎流生产的优化 枝干结构。通过在雨季对比有叶植株(自然条件)和无叶植株(人工除叶)树 干茎流量,保证实验组和对照组相同的气象和立地条件以及除叶片状态外相似 的植被特征,本研究改进了对比植被生长季(有叶)和非生长季(无叶)树干 茎流量判定叶片作用的实验方法,提高了实验结果可靠性。此外,首次系统建立树干茎流时间动态指标体系,包括起流时滞(TLG, min)、止流时滞(TLE, min)、最大茎流强度时滞(TLM, min)和产流时长(SFD, h),连同次降水平均 茎流强度(SFI, mm∙h–1)和最大10 min 茎流强度(SFI10, mm∙h–1),分析树干茎 流随时间的动态变化特征,识别并量化对其影响最大的气象因子。本研究从不 同冠层方位和距枝基部距离角度,探讨穿透雨空间格局。 主要研究结果如下: (1)在补给冠层下土壤水分方面,树干茎流对柠条的重要性大于沙柳。柠 条和沙柳灌丛的树干茎流、穿透雨和冠层截留损失量在实验期内平均为1.1 mm vs. 0.8 mm、8.9 mm vs. 9.0 mm、1.2 mm vs. 1.6 mm,分别占同期降水的9.8% vs. 7.1%、79.5% vs. 78.9%、10.7% vs. 14.0%。二者树干茎流量分别占净降水量的 10.6%和8.2%。 (2)较之沙柳,相同20 年林龄的柠条具有树干茎流产量和效率优势。柠 条开始产生树干茎流的降水阈值更小(0.9 mm vs. 2.1 mm),能更高效的(FR: 173.3 vs. 69.3;SFP:1.95 mL∙g–1 vs. 1.19 mL∙g–1)获取更多树干茎流形式的水资 源(SFb:290.6 mL vs. 150.3 mL;SFd:1.0 mm vs. 0.8 mm)。二者茎流比例均随 降水量增长逐渐趋于稳定,柠条茎流比例更大(9.1% vs. 7.7%)。 (3)较之沙柳,在相同气象条件下柠条具有树干茎流产流时间优势。实验 期内,柠条起流时间更短(48.6 min vs. 46.2 min)、产流时间更长(5.6 h vs. 5.0 h),更易在降水结束后继续产流(72.5% vs. 67.7%),虽稍晚达最大茎流强度 (149.5 min vs. 144.3 min),但茎流强度更大(27.2 mm∙h–1 vs. 25.7 mm∙h–1)。 (4)冠层截留面积是解释有叶和无叶植株树干茎流产量差异的重要原因。 有叶状态时柠条由总叶面积代表的冠层截留面积和SFb 分别1.4 倍和1.6 倍于有 叶沙柳,无叶状态时沙柳以枝干总表面积代表的冠层截留面积和SFb 分别2.0 倍和1.8 倍于无叶柠条。 (5)较之沙柳,柠条具有穿透雨比例和空间格局优势。尽管柠条开始产生 穿透雨的降水阈值稍大(1.0 mm vs. 0.4 mm),但随降水量增加趋于稳定的穿透 雨比例更大(82% vs. 70%)。在不同冠层方位,柠条穿透雨量和比例总体更大 (9.2–10.5 mm vs. 7.4–8.9 mm;72.5%–78.0% vs. 66.4%–79.3%),变异性更小。
英文摘要: Precipitation is intercepted by vegetation canopies, and allocated into stemflow, throuhfall and interception loss. Rainfall redistribution rebalances the kinetic energy and potential energy of raindrops, fosters a new spatial distribution pattern of precipitation, and changes the temporal dynamics of precipitation funnelling and infiltration, thus to influencing soil moisture rechargement and the biogeochemical recycling of the “Soil-Plant-Atmosphere Continuum”. Throughfall takes the biggest share of incident precipitation, acting as one of the most important water resource for soil moisture under canopies. Stemflow carries the dry deposition on canopies and plant exudates, and infused into plant’s root zone directly along preferential paths including roots, worm paths, soil macro-pore channels, etc. That is of great significance for xerophytic plants, and contributes to the formation and maintenance of “hydraulic island”, “fertile island” and “resource island” in arid regions. Dryland ecosystems with this patch mosaic pattern of shrubs and bare land possesses greater productivity than those without it. Therefore, it is necessary to figure out the rainfall redistribution pattern, temporal dynamics, spatial distribution and its influential factors, for a better understanding on the maintenance mechanism of soil available water, and providing theoretical support to desert ecological restoration and dryland ecosystem management. This study was carried out in the 2014 and 2015 rainy seasons on rainfall redistribution pattern and its influential mechanism of C. korshinskii and S. psammophila, two dominant shrub species at the transitional belt between Yellow Loess plateau and Mu Us sand land. We aimed to (1) quantify stemflow, throughfall and interception loss at shrub scale, (2) and stemflow yield and efficiency at branch scale, (3) depict stemflow temporal dynamics on event base, (4) illustrate throughfall spatial pattern, and (5) explore the influential mechanism affecting these ecohydological processes. For building a tight connection with vegetation growth, stemflow productivity (SFP) was introduced for the first time to describe stemflow efficiency by comparing water resource return (stemflow) of each unit biomass investment to different-sized branches. Along with funnelling ratio (FR, unitless) and other stemflow yield indicators (SFb (mL), SFd (mm) and SF% (%)), we emphasized the stemflow yield, efficiency and its influential mechanism of individual branches of these two shrub species. The beneficial branch architecture for stemflow production had been summarized accordingly. Besides, the controlled experiment between the leafed and defoliated shrubs had been improved in this study, the results of which indicated the significance of newly exposed branch and its resulting rainfall intercepting effects affecting stemflow in the leafless period. Furthermore, we developed a comprehensive indicator system to describe stemflow temporal dynamics, including stemflow duration (SFD, h), time lag of stemflow generating (TLG, min), stemflow ending (TLE, min) and stemflow maximizing (TLM, min). Associated with the average stemflow intensity (SFI, mm∙h–1) and the maximum stemflow intensity in 10 min (SFI10, mm∙h–1), the stemflow temporal dynamics and its influential factors had been studied within incident rainfall events. Moreover, we analyzed throughfall spatial pattern in aspects of various canopy direction and distance gradiences from branch base. Main findings of this dissertation are listed as follows: (1) With regard to soil moisture rechargement, stemflow plays a greater role in C. korshinskii than in S. psammophila. The yield and percentage of stemflow, throughfall and interception loss were averaged 1.1 mm (9.8%), 8.9 mm (79.5%) and 1.2 (10.7%) for individual shrubs of C. korshinskii, and 0.8 mm (7.1%), 9.0 mm (78.9%) and 1.6 mm (14.0%) for individual shrubs of S. psammophila during the 2014 and 2015 experimental period. Net precipitation equals to the total amount of stemflow and throughfall, representing the precipitation amount that could fall onto ground and recharge soil moisture. Stemflow took 10.6% and 8.2% of net precipitation on average for C. korshinskii and S. psammophila, respectively. (2) C. korshinskii produces stemflow with a higher efficiency and a larger amount than S. psammophila. SFb, FR and SFP were averaged 290.6 mL, 173.3 and 1.95 mL∙g–1 for individual branch of C. korshinskii, and 150.3 mL, 69.3 and 1.19 mL∙g–1 for individual branches of S. psammophila. SFd were 1.0 mm and 0.8 mm for these two shrubs, respectively. Indicated by the linear relation of precipitation with SFb and SFd, stemflow could not be generated until precipitation was greater than 0.9 mm and 2.1 mm for C. korshinskii and S. psammophila. Indicated by the inverse proportion function relation with precipitation, SF% increased with increasing precipitation and approached 9.1% and 7.7%, respectively. (3) C. korshinskii possesses the advantage of stemflow temporal dynamics in comparison with S. psammophila. C. korshinskii started stemflow in a shorter time (48.6 min vs. 46.2 min), produced stemflow for a longer time (5.6 h vs. 5.0 h), and continued stemflow production after precipitation ceased at more rainfall events (72.5% vs. 67.7%). Although a bigger time lag to maximize stemflow intensidty (149.5 min vs. 144.3 min), C. korshinskii had larger SFI10 (27.2 mm∙h–1 vs. 25.7 mm∙h–1). (4) The canopy area for rainfall interception might be of great importance to explain different stemflow yield between the foliated and defoliated shrubs. A 1.4-fold larger total leaf area at the foliated canopy of C. korshinskii corresponded to a 1.6-fold larger SFb than that of S. psammophila. And, a 2.0-fold larger total branch surface area of the defoliated canopy of S. psammophila corresponded to a 1.8-fold larger SFb than that of C. korshinskii. (5) C. korshinskii possesses the advantage of throughfall spatial pattern in comparison with S. psammophila. Although a larger precipittaion threshold was required to start throughfall (1.0 mm vs. 0.4 mm), throughfall percentage of C. korshinskii gradually approached a larger proportion (82% vs. 70%) as precipittaion amount increased. Moreover, C. korshinskii generally had larger throughfall yield and percentage (9.2–10.5 mm vs. 7.4–8.9 mm;72.5%–78.0% vs. 66.4%–79.3%) and smaller variation at different canopy directions than that of S. psammophila.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38737
Appears in Collections:城市与区域生态国家重点实验室_学位论文

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袁 川. 半干旱区典型灌木降水再分配模式与影响机制研究[D]. 北京. 中国科学院大学. 2017.
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