Modelling stemflow production by juvenile lodgepole pine(Pinus contorta var.latifolia)trees

Stemflow is a focused point source input of precipitation and nutrients at the base of a tree or plant and can have a significant impact on site hydrology. To date, no known studies have modelled stemflow production for juvenile lodgepole pine （Pinus contorta vat. latifolia）. Meteorological conditions, tree characteristics, and stemflow were sampled for two juvenile lodgepole pine stands over the course of the 2009 growing season. Step-wise multiple regression was used to assess which meteorological and tree architecture variables influenced stemflow production for each research plot. Once predictor variables were identified, models were produced for each stand and a generic model was produced that applied to both plots. A model employing precipitation depth and crown projection area successfully explained 71.3% of the variation in stemflow production from sampled trees. Stemflow was found to represent 1.8% of the study period rainfall and, although not a large component of the plot-scale canopy water balance, it is an order of magnitude greater than the fractioning of stemflow from mature lodgepole and lodgepole pine dominated forest. Additionally, stemflow funnelling ratios were found to average 22.2 and 24.3 from the two sample plots over the study period with a single tree, single event maximum of 111.7 recorded for a tree with a 3.3 cm bole diameter and a rain depth of 17.4 mm.

Dissolved organic carbon and nitrogen in precipitation, throughfall and stemflow from Schima superba and Cunninghamia lanceolata plantations in subtropical China

Despite growing attention to the role of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in forest nutrient cycling, their monthly concentration dynamics in forest ecosystems, especially in subtropical forests only were little known. The goal of this study is to measure the concentrations and monthly dynamics of DOC and DON in precipitation, throughfall and stemflow for two planta- tions of Schima superba (SS) and Chinese fir (Cunninghamia lanceolata, CF) in Jianou, Fujian, China. Samples of precipitation, throughfall and stemflow were collected on a rain event base from January 2002 to December 2002. Upon collection, all water samples were analyzed for DOC, NO3 -N, NH4 -N and total dissolved N (TDN). DON was calculated by subtracting NO3 -N and NH4 -N from TDN. The results - + - + showed that the precipitation had a mean DOC concentration of 1.7 mg·L-1 and DON concentration of 0.13 mg·L-1. The mean DOC and DON concentrations in throughfall were 11.2 and 0.24 mg·L-1 in the SS and 10.3 and 0.19 mg·L-1 in the CF respectively. Stemflow DOC and DON concentrations in the CF (19.1 and 0.66 mg·L-1 respectively) were significantly higher than those in the SS (17.6 and 0.48 mg·L-1 respectively). No clear monthly variation in precipitation DOC concentration was found in our study, while DON concentration in precipita- tion tended to be higher in summer or autumn. The monthly variations of DON concentrations were very similar in throughfall and stemflow at both forests, showing an increase at the beginning of the rainy season in March. In contrast, monthly changes of the DOC concentrations in throughfall of the SS and CF were different to those in stemflow. Throughfall DOC concentrations were higher from February to April, while relatively higher DOC concentrations in stemflow were found during September-November period.

Characteristics of Caragana korshinskii and Hippophae rhamnoides stemflow and their significance in soil moisture enhancement in Loess Plateau, China

Stemflow of xerophytic shrubs represents a significant component of water replenishment to the soil-root system and influences water utilization of plant roots at the stand scale,especially in water-scarce semi-arid ecosystems.The stemflow of two semi-arid shrubs(Caragana korshinskii and Hippophae rhamnoides)and its effect on soil moisture enhancement were evaluated during the growing season of 2011 in the semi-arid loess region of China.The results indicated that stemflow averaged 12.3%and 8.4%of the bulk precipitation for C.korshinskii and H.rhamnoides,respectively.Individual stemflow increased in a linear function with increasing rainfall depth.The relationship between funneling ratios and rainfall suggested that there existed a rainfall depth threshold of 11 mm for both C.korshinskii and H.rhamnoides.Averaged funneling ratios were 156.6±57.1 and49.5±30.8 for C.korshinskii and H.rhamnoides,respectively,indicating that the canopy architecture of the two shrubs was an effective funnel to channel stemflow to the root area,and C.korshinskii showed a greater potential to use stemflow water in the semi-arid conditions.For individual rainfall events,the wetting front depths were approximately 2 times deeper in the rooting zone around the stems than in the bare area outside canopy for both C.korshinskii and H.rhamnoides.Correspondingly,soil water content was also significantly higher in the root area around the shrub stem than in the area outside the shrub canopy.This confirms that shrub stemflow conserved in the deep soil layers may be an available moisture source for plant growth under semi-arid conditions.

Throughfall and stemflow nutrient depositions to soil in asubtropical evergreen broadleaved forest in the Wuyi Mountains

A study concerning the throughfall and stemflow chemistry in the Castanopsis eyrei forest was conducted during 1993—1994. The results showed that the net throughfall nutrient fluxes showed consistent canopy effects on precipitation chemistry. In general, potassium, calcium, magnesium, sodium and sulphur were added to precipitation by foliage, whereas the canopy absorbed nitrogen and phosphorus from precipitation. In stemflow, negative net deposition occurred for phosphorus only, and the rest nutrients were added to precipitation by tree stems and branches. The total net depositions of nutrients in both throughfall and stemflow followed the sequence of potassium>calcium>sodium>magnesium>sulphur, ranging between 2 56—52 54 kg/(hm 2·a). For potassium and calcium, net throughfall was the largest pathway, and the net throughfall contribution to the total yearly nutrient return to the forest soil was 54% and 42% respectively. Although the net stemflow contribution to the total yearly nutrient return was small (between 0 and 13%), stemflow represented the largest pathway of water and nutrient input to the stemflow zone of the forest floor in the C.eyrei forest ecosystem.

Intrastorm stemflow variability of a xerophytic shrub within a water-limited arid desert ecosystem of northern China

An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the temporal variability of stemflow volume within discrete rainfall events for xerophytic shrubs.Here,stemflow was monitored at 5-min intervals using a tipping-bucket rain gage during the 2015 growing season for a xerophytic shrub(Caragana korshinskii)within a water-limited arid desert ecosystem of northern China.We characterized the stemflow temporal variability,along with rainfall,and found the temporal heterogeneity of rainfall clearly affected the timing of stemflow inputs into basal soil within discrete rainfall events.The rainfall threshold value for stemflow generation is not a constant value but a range(0.6~2.1 mm,with an average of 1.1 mm)across rainfall events and is closely associated with the antecedent dry period.Time lags existed between the onset of rainfall and the onset of stemflow,and between rainfall peaks and stemflow peaks.Our findings are expected to be helpful for an improved process-based understanding of the temporal stemflow yield of xerophytic shrubs within water-limited arid desert ecosystems.

伏牛山三种天然林的树干茎流季节差异及胸径影响

[目的]探讨伏牛山三种森林类型的树干茎流差异及与林木胸径的关系,分析相同量级降雨的树干茎流季节差异。[方法]在伏牛山宝天曼地区选择三种典型天然林(华山松针叶林、锐齿栎阔叶林、华山松-鹅耳枥针阔混交林)的标准木,实测并收集树干茎流量后分析比较。[结果]生长季内的高降雨量事件(58.2 mm)导致的树干茎流体积与林木胸径呈正相关,然而在低降雨量事件(10.8 mm)下二者呈负相关。在单次降雨量相同或相近条件下,冬季的树干茎流体积(17 770~35 590 mL)和茎流率(0.106)显著高于春、夏和秋季,而树干茎流体积在前三个季节之间并无显著差异,针阔混交林在秋季和冬季的茎流率更高,这主要归因于冬季落叶阔叶树的林冠叶片截持作用消失。相比针叶林和阔叶林,针阔混交林的林分密度更高且胸径更小,导致其林分树干茎流量最高。[结论]不同森林类型的树干茎流量因降雨量和林木胸径大小而异,林木胸径和叶片形态是决定树干茎流季节差异的重要因素。

Characteristics of stemflow for sand-fixed shrubs in Mu Us sandy land, Northwest China

Little work has been done on stemflow for desert shrubs in China. This study measured stemflow in two shrubs of Salix psammophila C. Wang et Chang Y. Yang and Artemisia sphaerocephala Krasch in Mu Us sandy land and established a relationship between stemflow and canopy characteristics, rainfall amount and intensity. During the experimental period, the amount of stemflow for S. psammophila and A. sphaerocephala accounted for 7.6% and 2.7% of the gross rainfall respectively. Statistical analysis showed that there was a significant positive linear correlation between rainfall and stemflow for the two shrubs; while the relationship between stemflow percentage and rainfall suggested that there existed a rainfall depth threshold of 3―5 mm for S. psammophila and 5―7 mm for A. sphaerocephala. Stemflow percentage positively increased with rainfall depth increasing before the rainfall depth threshold values had been reached but showed stability after the threshold. A stepwise regression analysis suggested that the shrubs with more branches, larger crown volume and smaller branch angle inclination tended to collect more volumes of stemflow. Moreover, stemflow amount and percentage increased with the maximum rain intensity increasing in 10 minutes (I10) and the stemflow percentage tended to increase quickly with I10 when it was less than 3.0 mm h-1 for S. psammophila and 2.0 mm h-1 for A. sphaero- cephala, and then showed stable trend with increasing of I10.

基于GA-SVR的热源自适应茎流检测与调控系统研究

茎流测量是研究植物耗水规律的重要手段,现有茎流传感器多基于热平衡法进行设计,但在低温天气时,植物蒸腾作用不明显,茎流瞬时变化响应不灵敏,导致测量结果不精确。针对上述问题,设计了一种热源自适应茎流检测与调控系统。综合考虑不同因素下茎流消耗在热源提供能量占比中变化趋势的建模需求,设计融合外界温度、茎流速率、横截面积等多环境因子茎流标定嵌套试验。在此基础上,利用支持向量机回归算法(Support vector regression,SVR)和遗传算法(Genetic algorithm,GA),建立热源功率自适应模型。结果表明所建模型的最优决定系数与均方根误差分别为0.989和0.015 W。基于LoRa无线传感网络构建茎流检测与调控系统,实现多组温度信息和热源功率的监测,系统调用移植到嵌入式设备的热源自适应模型动态获取热源功率调控目标值,并发送至执行控制器,控制功率调控模块,实现热源自适应融合的功率动态控制。精度验证试验显示:在低温段时,本系统比FLOW-32KS型传感器平均相对误差小2.64(6℃)、2.53(11℃)、3.68个百分点(16℃)。在高温段时,自适应模型修正对结果影响不大,双系统相对误差互有高低。证明本系统嵌入基于热平衡法的GA-SVR算法热源自适应模型后,能确保茎流消耗能量Q_(f)在输入总能量P_(in)中占比稳定,满足提高热平衡茎流测量精度的需求。

城市森林冠层对大气金属输入的影响

为探究城市森林冠层与大气金属输入的相互作用关系,深入了解城市人工林生态系统金属迁移的环境路径,对哈尔滨市区樟子松人工林内穿透雨、树干茎流以及大气降雨进行监测,测定其中的K、Ca、Na、Mg、Cu、Fe、Zn和Mn 8种金属,分析伴随降雨分配过程的金属浓度变化特征和在森林生态系统中的输入量。结果表明:(1)大气降雨经过森林冠层后,穿透雨中K、Na、Mg、Fe、Mn和Cu浓度增加,Ca和Zn浓度减小;树干茎流中,仅有Cu浓度减小。(2)樟子松人工林冠层对K、Ca、Cu和Zn起到过滤作用,而对Na、Mg、Fe和Mn起到淋溶作用。

基于作物表型的温室精准灌溉策略研究进展

水分状况直接决定着温室作物的产量与品质,根据作物表型变化来反应其水分胁迫状况是当前研究的热点。作物表型参数综合考虑了由于土壤(或基质)水分减少和蒸腾蒸发需求量而引起水分胁迫的累积效应,据此可以更精确地判断作物水分胁迫水平,进而为实现精准灌溉提供相关依据。该文对国内外基于作物表型(茎直径变化、茎流、冠层温度)的温室精准灌溉策略研究现状进行了分析与总结,相关研究表明,茎直径变化、茎流和冠层温度3个诊断指标可以反映植物的水分状况,但作物表型受环境因子影响较大,一般需排除环境因子对作物表型的影响或与环境因子等外界因素进行综合分析建模,建立综合作物表型-环境因子等因素的作物需水模型,用以指导灌溉;同时提出了国内基于作物表型进行灌溉还存在基础理论不完善、技术研发不先进、设备监测不精确等问题,并对基于作物表型的灌溉策略未来的发展方向进行了展望,未来国内温室灌溉领域需向着加强作物表型与灌溉的基础理论研究、积极探索新技术、研发新装备、提升温室环境控制水平等方向前进。该文可推动该领域相关研究为实现温室作物的精准灌溉提供参考。

川西亚高山原始云杉林内降雨分配研究

The characteristics of throughfall and stemflow over one growing season were studied in a dark coniferous forest in the subalpine of the Western Sichuan. The results indicated that: 1) The distribution of precipitation by canopy was more relative to the rainfall, the higher the rainfall was, the more the throughfall and stemflow were, and the less the interception was; 2) The relationships between throughfall (T) and total rainfall (P) could be described significantly by a linear function (T=0.744P-0.937, R 2=0.954, p<0.001), while the reationship between crown interception (I) and total rainfall by a power function (I=0.759P 0.666, R 2=0.763, p<0.001); 3) The average canopy interception accounted for 35.8% of total rainfall and the average throughfall for 64.2%, and the average stemflow for 0.01%; 4) High water_hold capacity of moss on the surface of tree trunk and low rainfall intensity were the main reasons that the stemflow of the coniferous forest in the subalpine of Western Sichuan was less than other forests.

西双版纳地区热带季节雨林与橡胶林林冠水文效应比较研究

季节雨林和橡胶林是西双版纳热带森林系统中可以代表原始林和大面积种植的人工林两种林型 ,采用水量平衡法 ,利用对以上两种林分林冠水文各分量 1 996～ 2 0 0 1年的观测结果 ,初步分析其林冠水文效应 ,结果表明 :一年内 ,季节雨林林冠截留量 660 .6mm,树干径流量 80 .7mm,穿透降雨量 ,85 3.2 mm,分别占同期降雨总量的 41 .43%、5 .2 4 %、5 3.74% ;橡胶林林冠截留量 393.5 mm,树干径流量 1 0 4 .1 mm,穿透降雨量 1 0 96.8mm,分别占同期降雨总量的 2 4 .68%、6.68%、67.85 % ;两种林分森林水文各分量干、雨季差异显著 ;在研究中还发现 ,季节雨林中树干径流量随径级的增大而减小 ,干季出现密林 (季节雨林 )的穿透降雨量大于疏林 (橡胶林 )的反常现象 ;与我国其他地区相比 ,季节雨林和橡胶林有较大的林冠截留率及干流率。

太岳山不同郁闭度油松人工林降水分配特征

利用2011年5—9月生长季观测的30场降雨数据,分析了山西太岳山不同郁闭度下油松人工林林冠截留、穿透雨以及树干茎流与降雨量的关系,以及林冠截留过程的特点。结果表明:(1)实验观测期间,该地区降雨总量为634.79mm,单次平均降雨量为21.16mm,单次最大降雨量为58.15mm,单次最小降雨量为0.54mm。其中,8月份的降雨总量最大,为190.77mm,6月份的降雨总量最小,为41.81mm。(2)郁闭度为0.8的油松人工林林冠截留量与降雨量呈一元线性关系,郁闭度为0.7、0.6和0.5均呈幂函数关系;对于各郁闭度的油松人工林,其林冠截留率与降雨量均呈对数函数关系;穿透雨量、树干茎流量与降雨量均呈明显的一元线性关系,穿透雨量和树干茎流量都随着降雨量的增加而增加。(3)不同郁闭度油松人工林之间林冠截留、穿透雨和树干茎流不同,总的趋势为随着郁闭度的减小,林冠截留量减小,穿透雨量增大,树干茎流量增大。林冠截留量与郁闭度表现出正相关关系,而穿透雨量、树干茎流量都与郁闭度表现出负相关关系。(4)各郁闭度林冠截留量、穿透雨量和树干茎流量的月动态变化与总降水量的月变化基本一致。

六盘山华山松(Pinus armandii)林降雨再分配及其空间变异特征

利用2004和2005年生长季（6-9月份）六盘山自然保护区的香水河小流域内华山松天然林的穿透降雨、树干径流和冠层截留量观测资料,通过对华山松林降雨再分配特征和穿透降雨空间变异及其影响因素的综合分析,所得结果表明华山松天然林的穿透降雨量、树干径流量和冠层截留量,分别占大气降雨量的84.34%、0.72%和14.94%。穿透降雨在林内具有较大的空间变异,其变异程度随降雨量的增加而减小,冠层对穿透降雨具有一定的聚集效应,降雨量越高时效应越明显;华山松冠层结构特征是影响穿透降雨的重要因素,叶面积指数、冠层覆盖度、冠层厚度及距树干的距离等都会影响穿透降雨的空间分布,其中以叶面积指数的影响最大。由分析结果可知,冠层结构特征是决定大气降雨再分配和空间变异的重要生态因素之一。

毛乌素沙地沙柳灌丛降雨截留与树干茎流特征

通过对毛乌素沙地沙柳灌丛降雨截留量及树干茎流的实验观测,分析了降雨量和降雨强度对沙柳灌丛的降雨截留量、穿透雨量和树干茎流量的影响,并确定了截留量、穿透雨量和树干茎流量在降雨分配中的百分数。实验期间降雨总量为136.5 mm,沙柳灌丛的截留量、穿透雨量和树干茎流量分别为34.0、98.5和4.0 mm,占降雨量的百分比分别为24.9%、72.2%和2.9%。沙柳灌丛的降雨截留量、穿透雨量和树干茎流量与降雨量和10 min最大雨强之间均呈显著正相关,而截留量、穿透雨量占降雨量的百分比与降雨量之间呈显著的双曲线函数关系。

岷江上游亚高山川滇高山栎林的降雨再分配

基于2007年6—9月岷江上游地区的气象数据,采用定位研究方法对该区川滇高山栎林的降雨再分配进行了研究.结果表明:研究期间,林外总降雨量486.7mm,林内穿透雨量、树干茎流量和林冠截留量分别占总降雨量的82.6%、0.9%和16.5%;穿透雨量和树干茎流量与降雨量均呈极显著的线性关系(P<0.01,n=49),穿透雨率和树干茎流率与降雨量的关系可用非线性曲线表示;当林外降雨量>3.2mm时开始出现树干茎流,且树干茎流量(L)与树干基面积(cm2)呈明显的指数关系(R2=0.623).林冠截留率随降雨量(mm)的增加呈双曲线递减;林冠截留率与降雨量、降雨持续时间、降雨强度、降雨时空气相对湿度均呈极显著负相关(P<0.01,n=49),而与风速呈极显著正相关(P<0.01,n=49).

祁连山青海云杉林冠生态水文效应及其影响因素

以位于祁连山中段大野口关滩森林站的青海云杉林为研究对象,利用2008年观测期间(6月12日至10月8日)34场降雨的大气降雨量、穿透雨量和树干茎流量观测资料,对青海云杉林的降雨再分配特征及其影响因素进行综合分析。结果表明:青海云杉林的总穿透雨量、截留量和干流量分别为212.6、64.5 mm和3.4 mm,分别占大气降雨量的75.8%、23.0%和1.2%;穿透雨在林内具有较大的空间变异性,其变异程度随降雨量的增大而减小,叶面积指数和冠层郁闭度在一定程度上也影响穿透雨的空间分布,且降雨量越小其影响效果越明显;青海云杉林的总干流量为3.4 mm,平均干流率为0.58%,雨前林冠的湿润程度对树干流的产生有很大影响,导致当降雨量为5.6 mm时就开始产生树干茎流;青海云杉林冠截留率的大小主要取决于降雨量,且随着降雨量的增大先减小并逐渐趋于稳定,林冠截留量总体上随冠层郁闭度和叶面积指数的增大而增大,但当观测点位于树冠边缘或多个树冠重叠处时出现负截留现象。所以,就特定林分而言,冠层结构特征对于其林冠生态水文效应起着重要的作用。

模拟降雨条件下作物植株对降雨再分配过程的影响

为系统测定玉米（Zea mays L.）、大豆（Glycine max）、谷子（Setaria italica）和冬小麦（Triticum aestivum Linn.）不同生长阶段的穿透雨、茎秆流和冠层截留，研究采用室内模拟降雨法测定了不同降雨强度、不同叶面积指数作物冠下穿透雨和茎秆流，采用喷雾法测定了作物不同生长阶段的冠层截留。对其进行了量化分析，并探讨了3者与作物叶面积指数和降雨强度的关系。结果表明：在40和80 mm/h降雨强度下降雨30 min，玉米、大豆、谷子和冬小麦冠下穿透雨率分别平均为65.15%、85.52%、80.05%和72.18%；在40和80 mm/h降雨强度下降雨10～20 min，4种茎秆流率分别平均为34.59%、13.58%、19.42%和26.34%；在0.3 mm/min喷雾强度下，作物冠层截留量相对较小，冠层截留率分别为0.26%、0.90%、0.53%和1.48%。随作物生长，穿透雨量逐渐降低，茎秆流量和冠层截留量逐渐增加。降雨强度与穿透雨量和茎秆流量呈正相关关系，但是2者占总降雨量的比例与降雨强度关系不显著（p＞0.05）。随着作物生长，穿透雨冠下空间分布由均匀逐渐趋向于不均匀，具有趋于向行中汇集的趋势。该研究揭示了黄土高原地区主要作物对降雨的再分配作用特征，可为农田水分有效利用和坡耕地土壤侵蚀防治提供理论依据。

鼎湖山季风常绿阔叶林大气降雨、穿透雨和树干流的养分特征

对鼎湖山季风常绿阔叶林大气降雨、穿透雨和树干茎流中的5种养分元素K、Ca、Mg、N、P进行了测定,结合水量分配规律,研究了森林降雨过程中养分在水相中的含量变化特征和输入规律。结果表明:(1)所有离子浓度均为大气降水<穿透雨<树干流,且增幅较大,而平均浓度以K+和总氮(TN)含量最高;总磷(TP)、磷酸盐(HPO42-)、总有机磷(TOP)含量均最低。(2)大气降雨中的离子平均浓度中以总有机氮(TON)的变异系数最大,为1.282;最小的是NO3-(0.502);穿透雨中变异系数最大的是TOP(2.357);最小的是TN(0.621)。树干流中各养分元素浓度与树种的相关性不显著(P>0.05)。(3)季风常绿阔叶林树干流和穿透雨各养分对森林土壤的年输入量为TN>K+>Ca2+>Mg2+>TP,树干流和穿透雨对森林土壤层Ca2+的输入大于凋落物分解输入。因此,大气降雨是养分从林冠层转移到土壤层的重要因素。

秦岭天然次生油松林冠层降雨再分配特征及延滞效应

为了研究秦岭典型地带性植物油松林冠层降雨再分配特征及延滞效应,选择陕西宁陕县秦岭森林生态系统国家野外科学观测研究站55龄天然次生油松林,从2006—2008年(5—10月份)对林外降水、穿透降雨和树干茎流进行定位观测。利用其中100次实测数据进行分析研究,结果表明:总降雨量为1576.4 mm,穿透降雨量为982.9 mm,树干茎流量为69.5 mm,冠层截留量为524.0mm,分别占总降雨量的62.4%、4.4%和33.2%。降雨分配与降雨量级密切相关,降雨量级增大,穿透降雨率和茎流率呈增大趋势,截留率呈降低趋势,变化幅度分别为46.6%—68.9%、0.8%—9.2%、53.4%—22.0%。穿透降雨量、树干茎流量和林冠截留量与林外降雨量之间的关系分别为:TF=0.6548P-0.4937,R2=0.9596;SF=-0.2796+0.0452P+0.0005P2,R2=0.8179;I=0.5958P0.8175,R2=0.8064。降雨事件发生后,穿透降雨和树干茎流出现的时间与降雨发生的时间并不同步,均表现出一定的延滞性,随着降雨量级增大,滞后时间表现出逐渐缩短的趋势((78.5±8.8)—(16.0±0.0)min,(111.0±33.0)—(41.2±0.0)min)。降雨终止时,特别是当降雨量>10.0 mm,穿透降雨终止时间也存在一定的延滞性((3.2±2.6)—(12.0±0.0)min)。但树干茎流终止时间先于降雨终止时间,降雨量级越小,树干茎流终止时间愈早((-58.3±21.5)—(-9.8±0.0)min)。