不同植被类型对堆积体坡面径流特性的影响

针对植被防护堆积体侵蚀动力机制的问题,通过野外模拟降雨试验,分析直根系和须根系植被对堆积体径流流速、水力和水动力参数的影响。结果表明:植被削减堆积体平均侵蚀速率达88.34%~92.88%,直根系消减平均流速效益为50.51%,须根系为21.32%~35.61%;裸坡和植被堆积体径流流型均属于层流(雷诺数<40),裸坡径流在降雨强度≤1.2 mm/min时处于急流态,直根系堆积体均处于缓流态,须根系堆积体在急流态和缓流态间变化。直根系对坡面径流的阻滞作用大于须根系;植被防护下堆积体侵蚀速率、水力和水动力参数与裸坡呈显著性差异(P<0.05),径流剪切力和径流功率可用于较好地刻画坡面侵蚀动态过程,呈显著线性关系(R²为0.63~0.96)。研究成果可为生产建设项目工程堆积体水土流失量预测模型的植被因子修订提供科学依据。     

滦河上游植被指数NDVI及EVI对SPEI的响应差异

在全球气候变化和人类活动的双重影响下,干旱呈广发、频发态势,使植被生长受到限制,进而影响生态系统结构,威胁区域生态安全。以滦河上游为研究区,基于2000-2019年归一化植被指数NDVI和增强型植被指数EVI,并结合标准化降水蒸散指数SPEI,分析滦河上游气象干旱和植被生长状况的变化趋势及空间分布特征,探讨植被变化对多时间尺度SPEI指数的响应差异。结果表明：近20年滦河上游SPEI呈波动式增大趋势,年尺度SPEI增大速率为0.040 1/a;干旱面积总体减少,减少速率为-1.430 4％/a;NDVI和EVI空间分布特征和变化趋势大体一致,植被覆盖度呈东南高西北低的特征,NDVI和EVI增大速率分别达0.027/a和0.026/a;大部分区域SPEI与植被指数呈正相关,其中NDVI对SPEI-3的响应最强,EVI对SPEI-6的响应最强,总体上EVI与SPEI的相关性强于NDVI;草地对气象干旱最敏感,农田次之,林地最弱。     

2000—2014年辽宁省植被动态演变特征分析

基于MODIS － NDVI 数据,辅以线性回归法与分段线性回归法,并借助ArcGIS 软件,对辽宁 省2000—2014 年植被覆盖的动态演变过程进行分析。结果表明: ( 1) 时间上,辽宁省植被NDVI 在年 际尺度上呈现出明显的增大趋势,2005 年出现突变,多年平均NDVI 值为0. 496; 春季、夏季、秋季 以及植被生长季NDVI 突变年份分别为2006 年、2005 年、2009 年和2004 年,秋季波动变化的突变点 明显滞后; 植被生长最旺盛的季节为夏季,且集中于8 月。( 2) 空间上,辽宁省植被覆盖具有明显的 地域性差异,呈现出东部高、中西部低的分布特征; 辽宁省植被覆盖优良区与辽东山地的界限基本吻 合,植被覆盖贫乏区主要集中在朝阳市和阜新市的东北部地区。( 3) 辽宁省植被覆盖程度呈山地阴坡 高于阳坡的形态,并且植被覆盖程度最好的坡向为北偏西方向。( 4) 2000—2014 年辽宁省植被覆盖度 整体以维持现状和轻微改善为主,保持不变的区域集中于中东部地区,辽阳市与沈阳市一带有轻微退 化现象,辽西北地区改善情况较为明显。     

陕北无定河流域土壤侵蚀与植被覆盖和降雨关系研究

基于2000—2014年陕北无定河流域日降水、DEM、土壤类型、MODIS NDVI等数据,利用修正通用土壤流失方程(RUSLE)估算了流域土壤侵蚀情况,定量分析了植被覆盖和降雨在土壤侵蚀中的作用,结果表明:(1)无定河流域土壤侵蚀以微度侵蚀为主,平均占流域面积的88.35%,各土壤侵蚀等级面积比例随等级的升高而降低。2000—2014年微度侵蚀面积比例为下降趋势,轻度及以上等级面积比例均为上升趋势。(2)不考虑降雨因子影响时,无定河流域仍以微度侵蚀为主,且为增加趋势,而其他土壤侵蚀等级均为下降趋势。不考虑植被覆盖因子时,流域土壤侵蚀与模型计算结果的变化趋势基本一致。(3)植被覆盖对土壤侵蚀面积比例和变化速率的贡献率分别为13.67%和24.55%,而降雨作用达到86.33%和75.44%,表明降雨是流域土壤侵蚀的主要动力和控制因子,降雨变化主导着流域土壤侵蚀变化过程。     

Consequences of different cutting regimes on regrowth and nutrient stoichiometry of Sparganium erectum L. and Potamogeton natans L.

Aquatic vegetation forms an essential component in freshwater ecosystems but due to changed environmental and anthropogenic conditions often needs management to reduce nuisance for human land‐use. In this paper, the authors looked at the regrowth of two macrophyte species (Potamogeton natans and Sparganium erectum) in two lowland rivers under different cutting treatments. After an initial cross‐sectional transect was manually removed from bank to bank at the beginning of the growth season, a monthly repetitive removal of biomass in plots on that transect was done during the rest of the growth season (testing frequency of mowing). Additional new transects were also cut in subsequent months (testing timing of mowing). Finally, biomass was repetitively removed in plots in those additional transects too (testing frequency of mowing × timing of mowing). The biomass at the end of the growth season was analysed for C, N, P, and Si. It was demonstrated that timing and frequency of vegetation cutting has an important effect on the capacity and rate of species' recovery and therefore on the efficiency of the applied management. Nutrient stoichiometry of the regrown biomass was directly affected by cutting. Caused by differences in the applied timing and frequency of the cutting, C/N and N/P ratios and BSi concentrations were highly variable. Yet, overall, there was a clear tendency towards a higher C/N ratio and BSi concentration and lower N/P ratio in biomass that recovered after cutting. This human impact on the quantity and quality of autochthonous organic matter may have knock‐on effects on the decomposers food web and mineralization process.     

植被排列方式及坡度对坡面流Fr影响的试验研究

为探究植被的排列方式及坡度大小对坡面流弗劳德数Fr的影响,以期揭示坡面流弗劳德数Fr的内在规律。利用人工模拟试验,系统研究了6个坡度、3种植物排列方向与水流方向呈不同走向角的条件下Fr与单位底面积的空间摩阻表面积K值的特征关系。表明在非淹没状态下,Fr与K值的关系为随K值的增大Fr呈现先减小后趋于平稳的趋势;Fr的取值随坡度的增大而增大;在一定的坡度范围内,同一坡度下,当Fr1时,同一K值下,走向角越大对应的Fr值越小,当Fr1时则相反;同一走向角下,在同一K值下,坡度越大对应的Fr就越大。得出在坡度一定的条件下,坡面植被的排列方式不同,弗劳德数Fr的取值也不相同;坡度是影响Fr取值范围的重要因素之一。     

加筋生态护坡技术的应用与发展

在越来越注重工程生态性的今天,生态护坡在道路、堤防、城市水利等方面得到了广泛应用。然而很多情况下,生态护坡在强度上无法满足工程设计的要求。加筋生态护坡是土工织物与植草相结合形成的一种护坡形式,在保证工程生态性的同时大大提高了生态护坡的强度,近年来逐渐得到重视与应用。综合介绍了加筋生态护坡的发展历程,将其概括为传统生态护坡、普通加筋生态护坡和高性能加筋生态护坡3个阶段,在此基础上对加筋生态护坡使用的不同结构型式和材质的土工合成材料进行了分类总结,针对国内外加筋生态护坡技术的研究现状和主要结论,结合实例分析了加筋生态护坡的工程应用,指出在保护边坡、减少水土流失及改善生态环境方面的作用。最后,展望了未来需要研究的方向。     

Nutrient balance of shifting cultivation by burning or mulching in the Eastern Amazon – evidence for subsoil nutrient accumulation

For over a hundred years shifting cultivation with slash-and-burn land preparation has been the predominant type of land use by smallholders in the Bragantina region of the Brazilian Eastern Amazon. This study contrasts the nutrient balance of slash-and-burn agriculture with a fire-free cultivation. Therefore, one half of a 3.5-year-old (28.7 t DM ha^–1) and a 7-year-old woody fallow vegetation (46.5 t DM ha^–1) was burnt and the other half mulched, leaving the biomass as a surface residue. Subsequently, a sequence of maize, beans and cassava was cropped for 1.5 year. Burning the 3.5- and 7-year-old fallow removed 97 and 94% of the C, 98 and 96% of the N, 90 and 63% of the P-stocks, and between 45 and 70% of the cations K, Mg and Ca of the aboveground biomass by volatilization or ash-particle transfer. These losses were avoided with the slash-and-mulch land preparation. Mulching did not increase the losses of nutrients by leaching, despite the high amount of rapidly decomposing surface mulch. Also the length of preceding fallow had no significant influence on leaching losses. At a depth of 3 m, leached nutrients were quantitatively negligible in both treatments. Comparing the nutrient fluxes at soil depths of 0.9 m, 1.8 m and 3 m, the amounts of all mobile nutrients, and also of chloride and sodium were markedly reduced during percolation and must have been retained. It is likely that nutrient retention in the subsoil layer is only temporary, emphasizing the need for a rapid re-establishment of the naturally deep-rooting secondary vegetation after abandonment of sites to enable uptake of these nutrients. The overall nutrient balance was highly negative for slash-and-burn. 291 and 403 kg N ha^–1, 21 and 18 kg P ha^–1, and 70 and 132 kg K ha^–1 were removed from the burnt plots with a preceding fallow of 3.5 and 7 years, respectively. A reduced fallow period (3.5 years), which is a common trend in the region, resulted in a higher mean annual rate of nutrient loss averaged over the duration of the cycle than a fallow period of 7 years. Eliminating the burning losses by mulching brought the agricultural system back to an equilibrated or even slightly positive nutrient balance, even after a reduced fallow period. Thus, slash-and-mulch is a viable alternative to maintain agricultural productivity and ecosystem functioning.     

水土流失遥感调查中植被覆盖度因子提取研究

植被覆盖度是水土流失的主要影响因子,而利用遥感影像判读可以快速有效地获得大范围的植被覆盖度。简要介绍了水土流失遥感调查中植被覆盖度因子提取的方法。基于遥感与实地野外调查数据,采用MODIS时序数据融合高分遥感数据的方法,以湖南省蓝山县为试验区,对植被覆盖度因子进行了提取。结果表明,该方法提取植被覆盖度因子的结果较理想。提出的植被覆盖度因子提取方法对今后的水土流失动态监测研究具有重要的理论意义和实践意义。     

新型生态植被毯边坡防护技术水土保持效应研究

新型生态植被毯边坡防护效果良好,目前常用的植被毯种类有椰丝型、麦秸型以及椰丝麦秸混合型。为优选出性价比最高的植被毯材料,对这3种植被毯上建植植被的植被覆盖度、有效根密度、地表径流量、土壤侵蚀量和土壤抗蚀性能进行了对比分析。结果表明,与在自然坡面上建植植被相比,植被毯护坡均可以增加土壤的覆盖度,减少降水的径流量与土壤侵蚀量。结合植被毯的产品质量指标,椰丝麦秸混合型植被毯性价比较高,可以作为普遍推广的植被毯品种。研究成果可为植被毯的施工及推广应用提供一定科学依据。