Does re-creation of extensive pasture-forest mosaics provide an economically sustainable way of nature conservation in Sweden''s forest dominated regions?

There is a major risk that many of the remaining semi-natural pastures in Swedish forest dominated regions will lose their grazing in the near future with lost biodiversity as a result. The reason is the high costs of grazing small pastures with cattle from generally small herds. The approaching decoupling of the present EU income support per head of cattle will increase the risk. Calculations based on economies of scale in beef production and opportunity cost of forest and arable land suggest that re-creating extensive pasture-forest mosaics consisting of existing semi-natural pastures and adjacent arable fields and forests can secure economically sustainable grazing. The risk of local extinction of grassland species due to habitat isolation is also lower in large mosaics than in small, scattered pastures.     

The dead-arm evolution of river systems: A comparison between the information provided by living Copepoda and Cladocera populations and by Bosminidae and Chydroidae remains

Methodological investigations, using remains of Bosminidae and Chydoridae, were undertaken to study the development of ecosystems in former river channels. Four biotopes from two former channels of different ages were used in this work. The Copepoda and Cladocera populations characterized each of the 11 sampling stations in relation to ecological factors, which are linked to the development stage in each ecosystem. Analysis of only the Bosminidae and Chydoridae populations presented practically the same information as an analysis of the total populations of Copepoda and Cladocera. The distribution of Bosminidae and Chydoridae remains taken from the surficial sediments at the deepest point of each former channel strongly resembled the distribution of the living populations sampled at several stations during one full year. Therefore, Bosminidae and Chydoridae remains could provide us with pertinent information concerning each phase of ecological succession that occurs in abandoned river channels.     

The role of refuge areas in the phenology of Rhopalosiphum padi in low rainfall cropping areas of South Australia

Extensive surveys of possible aphid habitats in South Australia indicated that irrigated perennial grass pastures in the Mount Lofty Ranges and Lower Murray Valley were summer refuges for Rhopalosiphum padi (L.) (Hemiptera: Aphididae). Large numbers of aphids build up in these pastures each year during autumn (April and May) with numbers peaking in May. The size of the May peak was related to the number of aphids surviving the summer. The proportions of alates were highest in May and August/September. Both peaks coincided with a photoperiod of between 11.2 and 11.5 h, and partial correlations suggested that aphid density, photoperiod and temperature were all significant determinants of alate production.     

Senescence and decomposition of white clover stolons in grazed upland grass/clover swards

The fate of marked sections of stolons of white clover (Trifolium repens) over a 50-week period from May 1987 was followed in grazed grass/clover swards maintained at 5-cm sward surface height with and without N fertiliser. There was little effect of N treatment on the pattern of survival of stolon sections. The proportion of live stolons recovered decreased during the experiment, and in May 1988 on average only 29% of the marked sections remained alive. At all harvests only a small percentage of stolon sections showed signs of senescence; the maximum percentage, on average 20% of those marked, occurred in autumn, 15–20 weeks after marking. Following this period, i.e. in late autumn/winter, the most rapid increase in percentage of decomposed stolons was measured. Over 50% of stolon sections were buried within the 5-week period following marking and nearly all were buried after 20 weeks; generally a much smaller proportion of stolon tips was buried. Nutrient concentrations of N, P and K fell to their lowest levels in autumn, before increasing in the following spring. Results are discussed in relation to the cycling of nutrients via stolon senescence.     

Soil seed bank in different vegetation types in the Loess Plateau region and its role in vegetation restoration

In the Loess Plateau region, soil erosion is a serious problem. Vegetation restoration is an effective approach to control soil erosion and improve ecosystems. The soil seed bank generally plays an important role in vegetation restoration after disturbance. Thus, we reviewed soil seed bank studies to reveal the soil seed bank characteristics and its role in vegetation restoration in three vegetation types (forest, forest‐steppe, and steppe). We selected 38 seed bank studies and analyzed several seed bank characteristics, such as seed density, species composition, and the relationship between seed size and seed bank. We also assessed the role of the soil seed bank in vegetation restoration. The soil seed bank density ranged from 2,331 ± 1,993 to 6,985 ± 4,047 seeds/m² among the different vegetation types. In the soil seed bank, perennial herbs and grasses accounted for 51.5% of the total species. Native species that were dominant or common in the standing vegetation usually had relatively high seed bank densities. Moreover, species with smaller seeds generally had higher soil seed bank densities. The present study indicates that the soil seed bank plays a significant role in spontaneous vegetation restoration, especially during the early successional stages in abandoned slope farmlands and grazing‐excluded grasslands. However, species with large seeds or transient soil seed banks should be reintroduced through seeding to accelerate target species restoration. More studies on soil seed banks need to be conducted to comprehensively reveal their characteristics.     

河岸带农田不同恢复年限对土壤碳氮磷生态化学计量特征的影响——以温榆河为例

弃耕地撂荒是土壤与植被向自然方向进行的次生演替,研究河岸带土壤撂荒后碳氮磷生态化学计量特征,是恢复和重建由农田干扰导致的退化河岸带生态系统的重要科学基础之一。以河岸带农地为对照,不同撂荒年限(撂荒2年、撂荒8年、撂荒10年)的土壤为研究对象,探索不同撂荒年限对土壤碳、氮、磷含量及相互关系的影响。结果表明:(1)土壤有机碳、氮的含量均呈现撂荒10年撂荒8年农田撂荒2年;土壤中磷含量呈现撂荒10年撂荒8年撂荒2年农田;农田和各撂荒年限的土壤碳、氮、磷含量,均随着土层深度的增加而呈降低的规律,但土壤碳和氮差异的显著性比磷明显。(2)河岸带土壤中C/N、C/P的均值均呈现:撂荒10年农田撂荒8年撂荒2年趋势。N/P的均值呈现:撂荒10年(0.78)农田(0.77)撂荒8年(0.77)撂荒2年(0.67),表明N是本研究区河岸带植被恢复的限制性营养元素。(3)河岸带农田和不同撂荒年限土壤碳、氮含量均存在极显著的耦合线性关系,而碳与磷、氮与磷之间的线性拟合程度相对较低。(4)在农田撂荒演替的初期阶段(2年),土壤的容重没有显著的变化,而随着撂荒时间的增加(8年和10年),土壤容重均有显著的降低,土壤结构得到改善。     

会仙岩溶湿地4种覆被下土壤酶活性和微生物生物量

研究湿地系统中的稻田被撂荒以后土壤酶活性和微生物生物量的变化可以为湿地的保护提供参考依据。以桂林会仙岩溶湿地为研究样地,采集芦苇湿地、华科拉莎草湿地、稻田撂荒地（以双穗雀稗和莲子草为优势植被）和稻田的耕层土壤样品,采用比色法和氯仿熏蒸法分别检测土壤酶活性和微生物生物量。结果表明,稻田撂荒地的土壤微生物生物量碳（MBC）为（345.20±30.06） mg/kg,显著低于其它三种覆被下的土壤;微生物生物量氮（MBN）、微生物DNA、蔗糖酶活性和碱性磷酸酶活性分别为（48.03±18.48） mg/kg、（5.65±1.48）μg/kg、（19.16±1.43） mg g^-1（24h）^-1和（2.20±0.94） mg g^-1（24h）^-1,均显著低于稻田,而与两种天然湿地没有显著差异。主成分分析表明,稻田撂荒地能与稻田明显分开,而与其它两种覆被土壤有所交叉。统计分析表明,MBC和碱性磷酸酶活性均与pH呈显著正相关关系（P<0.05）;MBN、蔗糖酶活性和碱性磷酸酶活性均与土壤总有机碳（SOC）呈显著的正相关关系（P<0.05）;土壤微生物DNA与SOC、总氮（TN）和碱解氮（AN）均呈显著正相关关系（P<0.01）,与Mg²⁺呈显著正相关关系（P<0.05）。以上研究结果表明,会仙湿地中的稻田在撂荒以后,土壤微生物生物量和两种土壤酶活性显著降低,影响微生物生物量和土壤酶活性变化的主要因素是pH、SOC、TN、AN和Mg²⁺。因此,建议在稻田撂荒地上重新种植水稻,以加快会仙岩溶湿地的恢复过程。     

A phytosociological analysis of abandoned terraced olive grove shrublands in the Tyrrhenian district of Central Italy

ABSTRACT

A phytosociological study of the shrubland communities which colonise abandoned terraced olive groves in the Tyrrhenian district of Central Italy is presented here. The vegetational analysis was carried out using the Braun Blanquet phytosociological approach. Two main types of shrubland communities characterising distinct environmental conditions occur within abandoned terraced olive groves. On the one hand, there are those scrub types which tend to occupy the central part of the terrace; on the other hand, there are the scrubs types which develop along the stone walls bordering the terrace. Different phytosociological associations, sub-associations, and variants ranging from Pistacio-Rhamnetalia alaternii to Prunetalia spinosae are recognised and described. In the warm dry areas, both Myrto-Lentiscetum and Rhamno-Euphorbietum dendroidis occur. Also, a new Oleo-Ceratonion sub-association (Myrto-Lentiscetum spartietosum junceii) is presented here for the first time. In the inner zones of the study area, a range of aspects characterising a new Pruno-Rubion ulmifolii community type (Roso-Rubetum ulmifolii ass. nova) are identified.     

Azione della Cinetina sulla Degradazione della Clorofilla in Foglie di Orzo Irradiate

Abstract

The effects of kinetin on chlorophyll breakdown in irradiated barley leaves. — Kinetin is shown to inhibit the breakdown of chlorophyll in isolated barley leaves. Moreover the kinetin is shown to inhibit, even if with lower effect, the chlorophyll breakdown in irradiated barley leaves. This possible correlation of these observations, with kinetin promoted protein synthesis is suggested.     

Grazers: biocatalysts of terrestrial silica cycling

Silica is well known for its role as inducible defence mechanism countering herbivore attack, mainly through precipitation of opaline, biogenic silica (BSi) bodies (phytoliths) in plant epidermal tissues. Even though grazing strongly interacts with other element cycles, its impact on terrestrial silica cycling has never been thoroughly considered. Here, BSi content of ingested grass, hay and faeces of large herbivores was quantified by performing multiple chemical extraction procedures for BSi, allowing the assessment of chemical reactivity. Dissolution experiments with grass and faeces were carried out to measure direct availability of BSi for dissolution. Average BSi and readily soluble silica numbers were higher in faeces as compared with grass or hay, and differences between herbivores could be related to distinct digestive strategies. Reactivity and dissolvability of BSi increases after digestion, mainly due to degradation of organic matrices, resulting in higher silica turnover rates and mobilization potential from terrestrial to aquatic ecosystems in non-grazed versus grazed pasture systems (2 versus 20 kg Si ha⁻¹ y⁻¹). Our results suggest a crucial yet currently unexplored role of herbivores in determining silica export from land to ocean, where its availability is linked to eutrophication events and carbon sequestration through C–Si diatom interactions.