Beach Litter Sampling Strategies: is there a ‘Best’ Method?

Ten methods for sampling beach litter were tested on 16 beaches located around the Firth of Forth, Scotland in order to ascertain the effectiveness of the various methods. Both fresh and/or accumulated litter were sampled. Some methods were more effective for recording gross amounts of litter. Maximum litter counts could be obtained by surveying the top boundary of the beach (e.g. vegetation line, retaining wall, rocks). Lowest amounts were obtained by surveying one five metre wide belt transect from the vegetation line to the shore. Some bias towards highlighting particular litter types was shown by specific methods. It was concluded that there were advantages and disadvantages for each method and that the aims of the study would in the end determine the method.     

Sonoran Desert productivity and the effect of trap size on litterfall estimates in dryland vegetation

We describe the temporal and spatial litterfall and test the accuracy of different litter collection devices in a Sonoran Desert community. Two low-lying PVC litter trap designs were tested and compared against a standard IBP trap. The test traps collected significantly more plant litter than the IBP traps, which failed to capture most of the litter of ephemerals and low shrubs. The largest differences between the traps appeared after the pulses of growth of ephemeral plants. Data collection for a period of almost 2 years showed an annual total litterfall of 3·43 Mg ha⁻¹for the test traps and 2·77 Mg ha⁻¹for the IBP traps. These values are well above the average for deserts and fit better into the lower range of tropical dry forests. The test PVC traps are inexpensive, economical in collecting and sorting effort, and less prone to vandalism. Also, they can be laid in higher numbers than IBP traps, thus providing a better representation of the highly heterogeneous desert environment.     

凤眼莲凋落物及其残体的沉降

水生植物凋落物和残体的沉降在水体生态系统物质循环和能鼍流动中具有重要作用,在有凤眼莲生长的自然水体中,利用沉降物捕获器原位采集凤眼莲生长、衰亡及腐烂分解等不同阶段的沉降物,分析测定其沉降量、沉降通量、有机碳、总氮和总磷的动态变化,结果显示:自凤眼莲死亡至残体从水面消失的4个月中,沉降瓶内的沉降量呈明显上升趋势,在残体从水面完全消失时(4月中旬)沉降量达到最大值579.59g/m2,同时,沉降通量亦达到最高值7.54g/(m2·d),二者与水温呈极显著正相关(P＜0.01);在凤眼莲生长期,沉降物的有机碳、总氮、总磷含量较低,而随着风眼莲衰亡,残体的不断沉降,至次年4月中旬残体基本沉降进入水体底部时,沉积物的有机碳、总氮、总磷含量达到最大值,分别为40.29%、3.66%、0.90%,之后逐渐下降,并趋于稳定.     

Winter rainfall interception by two mature open‐grown trees in Davis,California

A rainfall interception measuring system was developed and tested for open‐grown trees. The system includes direct measurements of gross precipitation, throughfall and stemflow, as well as continuous collection of micrometeorological data. The data were sampled every second and collected at 30‐s time steps using pressure transducers monitoring water depth in collection containers coupled to Campbell CR10 dataloggers. The system was tested on a 9‐year‐old broadleaf deciduous tree (pear, Pyrus calleryana ‘Bradford’) and an 8‐year‐old broadleaf evergreen tree (cork oak, Quercus suber) representing trees having divergent canopy distributions of foliage and stems. Partitioning of gross precipitation into throughfall, stemflow and canopy interception is presented for these two mature open‐grown trees during the 1996–1998 rainy seasons. Interception losses accounted for about 15% of gross precipitation for the pear tree and 27% for the oak tree. The fraction of gross precipitation reaching the ground included 8% by stemflow and 77% by throughfall for the pear tree, as compared with 15% and 58%, respectively, for the oak tree. The analysis of temporal patterns in interception indicates that it was greatest at the beginning of each rainfall event. Rainfall frequency is more significant than rainfall rate and duration in determining interception losses. Both stemflow and throughfall varied with rainfall intensity and wind speed. Increasing precipitation rates and wind speed increased stemflow but reduced throughfall. Analysis of rainfall interception processes at different time‐scales indicates that canopy interception varied from 100% at the beginning of the rain event to about 3% at the maximum rain intensity for the oak tree. These values reflected the canopy surface water storage changes during the rain event. The winter domain precipitation at our study site in the Central Valley of California limited our opportunities to collect interception data during non‐winter seasons. This precipitation pattern makes the results more specific to the Mediterranean climate region. Copyright © 2000 John Wiley & Sons, Ltd.     

大型海藻龙须菜凋落物分解对水质的影响

大型海藻龙须菜(Gracilaria lemaneiformis)规模栽培具有重要的经济和环境效益, 但藻体的凋落分解会对栽培区和邻近海域水环境造成一定影响。为探讨龙须菜凋落对水环境的影响, 本文通过45d的室内受控实验, 评估了龙须菜凋落分解过程中水体溶解氧和氮、磷的含量变化。结果发现, 干龙须菜实验组在实验期内水体溶解氧浓度显著降低(较对照组降低了82.81%); 水体氮、磷浓度显著提高, 总氮、总磷浓度较对照组分别上升了161.78%和759.93%。鲜龙须菜+海水+沉积物组在实验前中期(第0~21天)水体溶解氧浓度持续降低(较对照组降低了53.92%), 但在21d后又逐渐恢复至对照组水平; 其水体氮、磷浓度在实验中末期亦显著提高, 分解过程总氮、总磷浓度分别较对照组上升了36.65%和177.80%, 水体氮、磷变化曲线较干龙须菜组平缓且迟滞。鲜龙须菜凋落分解过程中的营养盐释放率低于干龙须菜, 沉积物对鲜龙须菜的分解及氮、磷和碳释放有促进作用, 但对干龙须菜的分解及氮、磷和碳释放有一定程度的减缓作用。龙须菜失重率、分解速率及营养盐释放率均呈现如下规律: 干龙须菜+海水组>干龙须菜+海水+沉积物组>鲜龙须菜+海水+沉积物组>鲜龙须菜+海水组。依据上述结果, 建议在龙须菜规模栽培和收获过程中应及时打捞脱落或衰老藻体, 尤其对已收获的大型海藻应妥善处理, 避免大型海藻腐烂而导致水体污染。     

滇石林地质公园喀斯特山地天然林和人工林凋落物与死地被物的动态特征

对云南石林地质公园景区及其保护区内喀斯特山地典型森林类型凋落物组成与数量及其动态,地表死地被物现存量与持水特性等进行了研究。结果表明,本区域保护较好的滇青冈(Cyclobalanopsis glaucoides)林的年凋落量达7.26 t/hm2;而以团花木新姜子(Neolitsea homiantha)为主的次生林只有1.98 t/hm2;云南松(Pinus yun-nanensis)人工林和干香柏(Cupressus duclouxiana)人工林年凋落量分别是2.49 t/hm2和4.07 t/hm2。这些森林的凋落节律相似,都呈明显的“双峰型”。在地表死地被物现存量方面,干香柏林因其叶片难以分解而具有较高的地表现存量,为13.59 t/hm2,随后依次为滇青冈林(7.57 t/hm2),团花新木姜子次生林(5.02 t/hm2)和云南松人工林(4.83 t/hm2),死地被物的持水量与其现存量的大小顺序一致。根据森林年凋落量与死地被物现存量的数量关系,表明保护较好的滇青冈林内枯枝落叶的分解率明显大于次生林和人工林,周转期也短,涵养水分能力也较强。因此,应加强对喀斯特山地自然森林的保护,同时也注意对现有人工林的改造,引进一些阔叶树种,提高群落结构的整体效应。     

祁连山青海云杉林截留对降水的分配效应

为了评估青海云杉林的水源涵养服务功能,选择祁连山西水林区排露沟流域青海云杉林,定位监测了在2006年中共83次降水事件的截留分配效应,观测期降水总量为394.2 mm,林冠截留、茎流和穿透水量分别是139.1、1.96和253.1 mm,林冠截留率、茎流率、穿透率分别为35.28%、0.50%和64.22%,当林外降水量>0.8 mm时才观测到林内穿透雨,而大于13.60 mm时,才观测到树干茎流。林冠对降水的截留分配与降水量、降水形态以及林分特征密切相关。冠层截留量、茎流量和穿透量与降水量均呈正相关,冠层截留率与降水量呈负相关,而茎流率和穿透率呈正相关;林冠对降雪的截留强于降雨,而降雨的穿透量强于降雪,同一降水事件下树干茎流量随着胸径的增大而增加。青海云杉林冠的几何形态结构(枝叶的分布与排列)不利于形成树干茎流。     

三江平原小叶章湿地枯落物和根分解及其硫元素释放动态

在三江平原小叶章(Calamagrostis angustifolia)典型草甸湿地和小叶章沼泽化草甸湿地中,利用分解袋法研究了小叶章的枯落物和根的分解及其硫元素释放动态。结果表明,在两种类型湿地中,小叶章枯落物和根的分解模式相同,都为快、慢交替的变化模式;但它们的分解速率不同,其原因主要是两种湿地的微环境和分解袋的投放方式不同。经过450 d的分解之后,在小叶章典型草甸和小叶章沼泽化草甸湿地中,小叶章枯落物的干物质损失率分别为32.31%和36.10%,相应的分解速率分别为0.0005797 d-1和0.0006321 d-1,而小叶章根的干物质损失率分别为60.75%和33.68%,其相应的分解速率分别为0.00153 d-1和0.0006412 d-1。在两种类型湿地中,小叶章枯落物和根中的总硫含量都呈波动性变化,小叶章枯落物中硫的释放模式为淋溶、固持、释放,根中硫的释放模式为固持、释放,C/S比值是影响硫发生固持或释放的主要因素。     

Effect of moisture content on ammonia emissions from broiler litter: A laboratory study

A dynamic flow-through chamber system was designed to measure ammonia emissions from broiler litter and to investigate the responses of ammonia emissions to litter moisture content under laboratory-controlled conditions. It was observed that ammonia emissions from litter were very sensitive to litter moisture content. As water was added to the litter, the total ammoniac nitrogen content (TAN) in the litter increased, and can potentially increase ammonia emissions. However, measurements of ammonia concentrations in the chamber and total nitrogen losses from litter samples all suggested that water applied to the litter also had an effect of suppressing ammonia emissions for a short time. After enough time (1 to 2 weeks) was allowed, higher moisture content in litter eventually resulted in higher ammonia emissions. It was also noticed that, at very high litter moisture content, even when more time was allowed, ammonia concentrations began to decrease as moisture content further increased.     

Canopy interception by a spruce forest in the upper reach of Heihe River basin,Northwestern China

The aim of this study is to understand the canopy interception of Qinghai spruce forest under conditions of different precipitation characteristics and canopy structures in the upper reach of Heihe River basin, northwestern China. On the basis of a continuous record covering our investigating period by an automatic throughfall‐collecting system, we analysed the relationships between the canopy interception and the precipitation characteristics. Our results support the well‐established exponential decay relationship between the gross precipitation and the interception percentage after the canopy is saturated. But our results sufficiently illustrate a notable point that the variations in the interception percentage are almost independent from the variations in the gross precipitation before the canopy is saturated. Our examination into the relationship between the interception and the 10‐min average intensity of precipitation demonstrates a divergent relationship, and the divergent relationship is bracketed by an upper ‘dry line’ indicating that 100% of gross precipitation was intercepted before saturation and by a lower ‘wet line’ suggesting that the actual canopy storage capacity reached the maximum and evaporation was the only component of the interception. To search for the relationship between canopy structures and interception, we grouped the canopy covers over the 90 throughfall‐collecting tanks into ten categories ranging from 0 (no cover) to 0.9 (nearly completely covered), and the corresponding canopy interception was calculated by subtracting the averaged throughfall of each canopy‐cover category from the gross precipitation. The results show that the interception percentage increases faster with increasing canopy cover under intermediate rainfall conditions than that under heavy rainfall conditions. Unexpectedly, under light rainfall conditions the increasing rate of interception percentage with increasing canopy cover and also with increasing plant area index is not faster than that under the intermediate rainfall conditions simply because the tank‐measured percentage of interception was extremely high at near‐zero canopy cover conditions. Copyright © 2013 John Wiley & Sons, Ltd.