Long-term variations of rainfall interception in different growth stages of Chinese fir plantations

Abstract

The dynamic properties of rainfall interception were investigated at three growth stages in Chinese fir plantations. The results showed that the annual interception ratio was significantly higher in mature stands than in young stands. For a storm event, interception rainfall amount increased with increasing rainfall, but interception ratio decreased. In contrast to dry season conditions, the interception amount was high in the wet seasons, while the interception ratio was low. The rates of change in interception ratio were extremely rapid in small rainfall events. There was little stemflow in Chinese fir forests due to the pyramid-shaped crowns and thick rough bark of the trees. The power model was suitable to describe the interception process for an individual rainfall event for stands of any age. Our results indicate that the interception process varied for stands of different ages in Chinese fir plantations due to contrasting canopy structures.     

Hydro-climatic variability and forest fires in Mexico’s northern temperate forests

Global warming is likely modifying the hydrological cycle of forested watersheds. This report set as objectives to: a) assess the hydrological variables interception loss, I, potential and actual evapo-transpiration, E, Et, runoff, Q, and soil moisture content, θ; b) evaluate whether these variables are presenting consistent trends or oscillations that can be associated to global warming or climate variability; and c) relate θ to the number of wildfires and the burned area in Durango, Mexico. A mass balance approach estimated daily variables of the water cycle using sub-models for I and Et to calculate Q and θ for a time series from 1945 to 2007. Regression and auto-regressive and moving averaging (ARIMA) techniques evaluated the statistical significance of trends. The cumulative standardized z value magnified and ARIMA models projected statistically similar monthly and annual time series data of all variables of the water cycle. Regression analysis and ARIMA models showed monthly and annual P, I, E, and Et, Q, and θ do not follow consistent up or downward linear tendencies over time with statistical significance; they rather follow oscillations that could be adequately predicted by ARIMA models (r² ≥ 0.70). There was a consistent statistical association (p ≤ 0.05) of θ with the number of wildfires and the area burned regardless of the different spatial scales used in evaluating these variables. The analysis shows seasonal variability is increasing over time as magnifying pulses of dryness and wetness, which may be the response of the hydrological cycle to climate change. Further research must center on using longer time series data, testing seasonal variability with additional statistical analysis, and incorporating new variables in the analysis.     

A new approach to estimate canopy evaporation and canopy interception capacity from evapotranspiration and sap flow measurements during and following wetting

Canopy interception and its evaporation into the atmosphere during irrigation or a rainfall event are important in irrigation scheduling, but are challenging to estimate using conventional methods. This study introduces a new approach to estimate the canopy interception from measurements of actual total evapotranspiration (ET) using eddy covariance and estimation of the transpiration from measurements of sap flow. The measurements were conducted over a small‐scale sprinkler‐irrigated cotton field before, during and after sprinkler irrigation. Evaporation and sap flow dynamics during irrigation show that the total ET during irrigation increased significantly because of the evaporation of free intercepted water while transpiration was suppressed almost completely. The difference between actual ET and transpiration (sap flow) during and immediately following irrigation (post irrigation) represents the total canopy evaporation while the canopy interception capacity was calculated as the difference between actual ET and transpiration (sap flow) during drying (post irrigation) following cessation of the irrigation. The canopy evaporation of cotton canopy was calculated as 0.8 mm, and the interception capacity was estimated to be 0.31 mm of water. The measurement uncertainty in both the non‐dimensional ET and non‐dimensional sap flow was shown to be very low. Copyright © 2015 John Wiley & Sons, Ltd.     

清洗频率对固定床生物滤器水处理性能的影响

本实验基于一种新型的具有自洁功能的固定床生物滤器, 研究了不同的清洗频率: 0.5次/d (S1)、1次/d(S2)和2次/d(S3)对生物滤器的硝化性能、截污能力和硝酸盐氮积累的影响。研究表明: 清洗频率对生物滤器去除氨氮(NH₄⁺-N)没有显著影响(P > 0.05); 在第6~9 d对生物滤器内亚硝酸盐氮(NO₂^–-N)的浓度有显著影响(P < 0.05), 第11 d后均无显著影响(P > 0.05); 在整个实验过程中, S3处理组与S1、S2处理组相比总固体悬浮物(TSS)去除分别提高53.52%和19.01%, 化学需氧量(COD_Mn)去除分别提高57.94%和27.01%, 差异性显著(P < 0.05); 在硝酸盐氮(NO₃^–-N)积累方面, S3处理组积累最少, 在整个实验过程期间与S1、S2处理组相比分别降低16.04%和23.01%, 差异性显著(P < 0.05)。总体来说, 高清洗频率对生物滤器的硝化性能无显著影响, 但能使生物滤器截留的TSS快速排出系统, 从而减少系统内的水处理负荷和硝酸盐氮积累, 有利于系统的长期稳定运行。     

江西泰和县森林生态系统水源涵养功能评估

森林生态系统综合水源涵养能力是林冠层、枯落物层和土壤层蓄水能力的总和。本文根据江西泰和县 2003 年森林资源二类调查,结合文献收集,从3 个作用层评估了泰和县森林生态系统的水源涵养量及其空间分布格局,比较了不同森林类型、林龄、海拔、坡度下的林冠降雨截留能力,枯落物最大持水量和土壤蓄水能力。结果表明,林冠层平均截留率为16.31%,枯落物层持水率为2.14%,土壤层蓄水率为81.55%,3 个层次总截留和蓄水量为1.41 亿m³。各种森林类型水源涵养量由大到小依次为：杉木林>马尾松林>湿地松林>阔叶林>毛竹林>灌木林> 混交林>经济林。幼林龄、中林龄、近熟林、成熟林和过熟林水源涵养贡献率分别为17.58%、65.39%、14.18%、 2.48%和0.37%,涵养水源能力随林龄的增加而增加。空间上,泰和县森林生态系统的综合水源涵养力表现出从东西两侧向中部递减的分布。不同立地条件下林分的合理经营与管理对于整个森林生态系统水源涵养功能的发挥具有重要的作用。     

Using aerial photography and in situ measurements to estimate the quantity of macro-litter on beaches

This study has demonstrated a reliable method of quantifying the total mass of litter on a beach. It was conducted on Ookushi beach, Goto-Islands, Japan, and uses a combination of balloon-assisted aerial photography and in situ mass measurements. The total mass of litter over the beach was calculated to be 716 ± 259 kg. This figure was derived by multiplying the litter-covered area (calculated using balloon-assisted aerial photography) by the mass of litter per unit area. Light plastics such as polyethylene made up 55% of all plastic litter on the beach, although more work is needed to determine whether lighter plastics are transported to beaches more readily by winds and ocean currents compared with heavier plastics, or whether lighter plastics comprise a greater percentage of marine litter. Finally, the above estimates were used to calculate the total mass of metals released into coastal ecosystems via plastic litter on beaches.     

太湖流域上游西苕溪源头溪流中毛竹、石栎和山胡椒落叶分解比较

比较了毛竹、石栎和山胡椒叶片的理化属性,采用粗网叶袋法研究了三种落叶在太湖流域上游西苕溪中的分解过程,探讨了毛竹叶成为溪流优势外来能源后对溪流生态过程和底栖动物群落结构的影响.三种落叶的氮、磷含量及叶片厚度都存在显著差异,毛竹叶的氮含量(30.23 g/kg)远高于石栎(20.98 g/kg)和山胡椒(9.69 g/kg),其中毛竹叶的分解速率最快(k=0.00592 d-1),山胡椒(0.00297 d-1)和石栎叶(0.00212 d-1)较慢.三种落叶叶袋间的大型底栖无脊椎动物包括各取食功能团的多度和生物量无显著差异,而4次采样间的差异很显著.大型底栖动物的取食功能团中,撕食者的数量比例最高(40.3%),生物量比例为41.6%,是落叶分解的重要功能类群.撕食者中,利用阔叶筑巢的鳞石蛾Lepi-dostoma数量最多,占全部底栖动物的14%,是该溪流中主要的撕食者类群.因此,由于毛竹叶具有氮、磷含量较高、叶形较窄,以及两年进行一次换叶的特点,当毛竹叶替代其他阔叶秋季落叶的树种成为源头溪流优势外来能源后,可能会改变源头溪流中的氮磷含量、溪流外来能源的量和滞留时间以及底栖动物群落结构.     

Hydraulics of overland flow influenced by litter incorporation under extreme rainfall

Water erosion on hillslopes is a worldwide environmental problem, which is a rainfall‐induced process, especially extreme rainfall. The great intensity of extreme rainfall strongly enhances the power of overland flow to detach soil and transport sediment. Plant litter is one of the most important constituents of ecosystems that often covers the soil surface and can be incorporated into topsoil. However, little attention has been paid to its effect on flow hydraulics owing to the veiled nature. This study aimed to examine the effects of incorporated litter on the hydraulic properties under extreme rainfall condition. To reach this goal, six litter rates of 0, 0.05, 0.10, 0.20, 0.35, and 0.50 kg m^?2 and four litter types collected from deciduous trees, coniferous trees, shrubs, and herbs were incorporated into topsoil. Then, simulated rainfall experiments were performed on five slope gradients (5°, 10°, 15°, 20°, and 25°) with an extreme rainfall intensity of 80 mm h^?1. The results showed that Froude number and flow velocity of the overland flow decreased, whereas flow resistance increased exponentially with litter incorporation rate. Litter type had an influence on flow hydraulics, which can mainly be attributed to the variations in surface coverage of the exposed litter and the litter morphology. Flow velocity and Darcy–Weisbach coefficient increased markedly with slope gradient. However, the variation of slope gradient did not modify the relationships between flow hydraulics and incorporated litter rate. The random roughness, resulting from heterogeneous erosion due to the uneven protection of surface exposed litter, increased linearly with litter incorporated rate. As rainfall proceeded, flow hydraulics varied with incorporated litter rate and slope gradient complicatedly due to the increases in flow rate and coverage of the exposed litter and the modification of soil surface roughness.     

Dynamics and relationships of Ca, Mg, Fe in litter, soil fauna and soil in Pinus koraiensis-broadleaf mixed forest

The Liangshui Natural Reserve in Heilongjiang Province of China was selected as the study area. The authors collected the samples of forest litter （Tilia amurensis, Fraxinus mandshurica, Pinus koraiensis, Acer mono, Betula costata, and mixed litter）, soil in humus horizon （0--5cm） and soil horizon （5-20cm）, and soil macrofauna （Oligochaeta, Geophiloporpha and Juliformia） from 2001 to 2002. The role of soil macrofauna in the material cycle was analyzed through comparing the macro-element contents among various parts of the subsystems and using enrichment index （El）. The results indicate that dynamic changes of various litters are very complicated. The contents of Fe in each kind of litter increase firstly, and then decrease in the study period. The changes of macro-element contents are greater in the broad-leaf litter than in the coniferous litter, and the mixed litter is in the middle level, but the differences among them are not significant. The contents of Mg and Fe in humus are higher than those in soil, but the contents of Ca in soil are higher than that in humus. The dynamic changes of macro-element contents in soil and soil fauna are not consistent with those in litter. The diplopod presented obvious enrichment of Ca and Mg （E1〉1）, but it does not significantly enrich Fe. Earthworm has a stronger enrichment ability of Fe than diplopod and scolopendra, but E1〈1. Soil fauna can make great influences on the material cycle of the subsystems.     

腾格里沙漠东南缘人工固沙植被区表层土壤有机碳矿化对凋落物添加的响应

土壤有机碳矿化是调控土壤碳库时空格局、土壤碳收支平衡和植物养分供应的重要过程,植物残体和凋落物分解释放CO₂直接影响着土壤有机碳矿化。研究了不同类型凋落物对腾格里沙漠东南缘建植于1956年的人工固沙植被区土壤有机碳矿化过程及其对水分和温度的响应特征。结果表明：凋落物添加显著促进了有机碳矿化,添加柠条锦鸡儿（Caragana korshinskii）、油蒿（Artemisia ordosica）、小画眉草（Eragrostis minor）凋落物后,CO₂-C最大矿化速率分别增大了6.94、5.17、3.46倍,0~5 cm层土壤是5~10 cm层土壤的1.09、1.55、1.22倍;CO₂-C累积释放量分别增加了3.73、3.38、2.34倍,0~5 cm层土壤是5~10 cm层土壤的1.17、1.30、1.57倍。凋落物对有机碳矿化的促进作用与温度和水分密切相关,25℃时,CO₂-C平均释放速率、最大释放速率、累积碳释放量分别是10℃的2.21、3.60、2.21倍,而含水量10%时,CO₂-C平均释放速率、最大释放速率和累积碳释放量分别是含水量5%时的1.25、1.20、1.25倍。相关性分析表明,凋落物碳氮含量、碳氮比、木质素比氮和土壤有机碳以及全氮是影响有机碳矿化的主要因子。凋落添加土壤后潜在可矿化碳表现为柠条锦鸡儿>油蒿>小画眉草>对照。凋落物添加显著促进了有机碳矿化过程及碳周转,植被恢复过程中草本植物凋落物的输入更有利于土壤碳固存,凋落物对土壤碳库的调控作用受土壤理化性质和水热等环境因子的共同作用影响。