Coastal geomorphic evolution at the Denglou Cape, the Leizhou Peninsula

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Macroalgal turfs in the Azores

Studies on macroalgal communities of the Azores report algal turfs as one of the most conspicuous ecological entities occurring on the rocky shores of these islands. The present study investigates the influence of shore height and substratum on turf composition. Data were analysed using the software PRIMER and results confirmed the previous distinction between calcareous, dominated by articulated coralline algae, and non-calcareous turfs, characterized mainly by small red algae. However, no differences in species composition were found in either type of turf occurring on different substrata or at different shore levels.     

不同覆盖措施对高寒地区剥离的草皮块堆放温湿度及成活的影响

重大工程建设会扰动高寒草地,法规要求扰动区草皮层应予以剥离,待工程建设后再用于恢复原生植被,当前对剥离草皮堆放成活的影响研究较少。试验设计遮阳网与穿孔膜两种覆盖条件,探讨分析其对剥离的草皮块堆放与铺植利用后土壤温湿度及草皮块返青覆盖度的影响,研究结果表明：遮阳网覆盖堆体较自然地表日均土壤温度显著降低,同时各深度层极大延长冻结期,降水对土壤水分的补充效应延后,并造成堆放期水分大量损失;穿孔膜覆盖堆体较自然地表提高了土壤温度,阻碍了降水对土壤水分的补充,并造成堆放后土壤吸持水能力降低。遮阳网覆盖的草皮块返青覆盖度显著高于穿孔膜覆盖的返青覆盖度,堆放期日平均土壤温度>0 ℃的堆放日数与草皮块返青覆盖度的线性拟合较好。工程建设中应尽量缩短堆放时长,采用透水透气类覆盖材料,增加土壤与空气热量交换,以维持更长的冻结期,并适时补充水分,提高草皮块铺植的恢复成效。     

Growth and gonad production of the sea urchin Hemicentrotus pulcherrimus in the fucoid bed and algal turf in northern Japan

To clarify the differences in the growth and gonad size of the sea urchin Hemicentrotus pulcherrimus among algal sere, the study was conducted in June and July, and September 1998 at three fucoid beds in Oga and at three algal turfs in Hachimori, Akita Prefecture in northern Japan. The most rapid growth was observed in a large perennial fucoid bed at the climax stage. Growth in a small perennial Chondrus ocellatus‐dominated bed in algal turfs in the seral stage was then high. The slowest growth was observed in the small perennial Dictyopteris divaricata‐ and Laurencia spp.‐dominated beds which are known to possess chemicals which act as feeding deterrents against the sea urchins. The gonad index (gonad wet weight × 100/body wet weight) at a fucoid bed was high where standing crops exceeded 3 kg·m^?2. The gonad index in the Laurencia bed was lower than those at fucoid beds. These results suggest that growth and gonad production are affected by algal sere and differ among species of small perennial algae in the seral stage with or without chemical defense.     

The effects of trophic interactions and spatial competition on algal community composition on Hawaiian coral reefs

Much of coral reef ecology has focused on how human impacts change coral reefs to macroalgal reefs. However, macroalgae may not always be a good indicator of reef decline, especially on reefs with significant sea urchin populations, as found in Kenya and Hawaii. This study tests the effects of trophic interactions (i.e. herbivory by fishes and sea urchins) and spatial competition (between algae and coral) on algal community structure of reefs surrounding two Hawaiian Islands that vary in their level of human impacts. Reef‐building organisms (corals and crustose coralline algae) were less abundant and turf algae were more abundant on Maui as compared to Lanai, where human impacts are lower. In contrast to previous studies, we found no evidence that macroalgae increased with human impacts. Instead, low turf and macroalgal abundance were best explained by the interactive effects of coral cover and sea urchin abundance. Fishing sea urchin predators appeared to have cascading effects on the benthic community. The absence of sea urchin predators and high sea urchin densities correspond to a disproportionately high abundance of turf and crustose coralline algae. We propose that high turf algal abundance is a better indicator of reef decline in Hawaii than high macroalgal abundance because turf abundance was highest on reefs with low coral cover and few fish. The results of this study emphasize that understanding changes in community composition are context‐dependent and that not all degraded reefs look the same.     

Resistance to shallow landslide failure through root-derived cohesion in east coast hill country soils,North Island,New Zealand

Measured shear strength (cohesion and friction) of airfall-derived east coast hill country regolith is insufficient for the maintenance of existing regolith depth/slope angle relationships in the catchment of Lake Waikopiro in northern Hawke's Bay, New Zealand. If these regoliths are attributed with an additional increment of cohesion derived mechanically from a turf mat membrane, existing depth/slope angle distributions are explicable. Sites where failure has occurred have been measured, and back-analysis used to derive a range of values for additional mechanical cohesion. Values are in the range 0·2–7·6 kPa, consistent with earlier findings. This range is narrowed further, to 0·7–6·9 kPa, with assumptions regarding soil moisture status at failure. Copyright © 1999 John Wiley & Sons, Ltd.     

鼠害在若尔盖草原沙漠化进程中的作用与机理

若尔盖草原是中国高寒湿润地区发生大面积沙漠化的典型案例,其沙漠化的成因及发展趋势一直受到极大关注。通过野外考察、遥感卫星影像解译等,着重探讨了鼠害在若尔盖草原沙漠化的形成和发展过程中的作用。结果表明：旱獭洞的分布与丘陵沙丘在坡度和坡向上有高度的相似性。地表致密草皮层发生机械性破坏,致使下伏松散沙暴露是若尔盖草原沙漠化的关键一步。旱獭洞的坍塌在草皮层的破坏过程中起到了至关重要的作用。草皮层破坏后,下伏松散沙被侵蚀,引起草皮层坍塌,导致古沙丘活化,形成流动沙丘。在此过程中,自然因素如风、降水、冻融、重力,人为因素如过牧、牲畜活动,都起到了不同的作用。小型鼠类如高原鼢鼠、高原鼠兔的严重鼠害区可以形成轻度沙漠化。     

绿化修剪草与污水厂污泥混合中温厌氧消化的可行性研究

对城市绿化修剪草与污水厂污泥消化联合处理的可行性进行了研究.选择了10%,20%,30%,40%和50%共5个修剪草与污泥的干基投加比例,试验结果表明,随着修剪草投加量的增加污泥消化系统的产气率亦随之增加,当修剪草投加比例为50%时,消化系统产气率可达348L/kg.TS,与不加修剪草相比,产气率增幅达到30%,修剪草与污水厂污泥消化联合处理是可行的.     

晚更新世末期东海北部古冬季风盛衰变更的地质记录

末次冰期最盛时期,干、冷气候盛行,渤海、黄海的大部分地区出现沙漠化,形成众多的沙丘。随着干冷气候的减弱,长江三角洲一带出现硬粘土沉积。冰消期的到来,古季风活动的进一步衰退和海面的不断升高,来自陆架区的东北风不再是干冷的气流,而是湿度逐渐增大的冷湿气流,出现了有利于沼泽发育的环境,以致全新世海侵前夕往往形成薄层泥炭沉积。晚更新世末期以来古冬季风发生、发展和衰退过程与沙漠、硬粘土和泥炭层形成过程相对应。      

Turf exfoliation in the high Drakensberg, Southern Africa

Limited research attention has focussed on turf exfoliation as a denudation process in mountain environments. This paper examines some characteristics of turf exfoliation forms identified within particular valley zones in the Drakensberg alpine belt. Morphological and sedimentological data are presented for turf exfoliated sites investigated in the Mashai Valley of eastern Lesotho. It is found that a variety of processes, including needle ice action, biological activity, fluvial processes and deflation, operating synergistically, are responsible for contemporary turf exfoliation in the high Drakensberg. It is apparent that the strong seasonality from mild, wet summers to cold, dry winters has helped induce the annual cycle of dominating processes.