Secondary Shrubland Research Articles

Green infrastructure design for the containment of biological invasions. Insights from a peri-urban case study in Rome, Italy

Secondary shrublands and transitional woodland/shrub formations are recognised to be particularly susceptible to plant invasions, one of the main global threats to biodiversity, especially in dynamic peri-urban landscapes. Urban fringes are in fact often the place for the sprawl of artificial surfaces, fragmentation of habitats, and complex land transitions (including both agriculture intensification and abandonment), which in turn increase propagule pressure of exotic species over residual semi-natural ecosystems. Within this framework, the present study was aimed at analysing i) how landscape composition and configuration affect the richness of woody exotic species in shrubland and transitional woodland/shrub patches, and ii) how this threat can be addressed by means of green infrastructure design in a peri-urban case study (Metropolitan City of Rome, Italy). Accordingly, the occurrence of exotic plants was recorded with field surveys and then integrated with landscape analyses, both at patch level and over a 250 m buffer area around each patch. Thus, the effect of landscape features on exotic plant richness was investigated with Generalised Linear Models, and the best model identified (pseudo R-square = 0.62) for inferring invasibility of shrublands throughout the study area. Finally, a Green Infrastructure (GI) to contain biological invasion was planned, based on inferred priority sites for intervention and respective, site-tailored, actions. The latter included not only the removal of invasive woody alien plants, but also reforestation and planting of native trees for containment of dispersal and subsequent establishment. Even though specifically developed for the study site, and consistent with local government needs, the proposed approach represents a pilot planning process that might be applied to other peri-urban regions for the combined containment of biological invasions and sustainable development of peripheral complex landscapes.

Patterns of Diversity and Community Assembly and Their Environmental Explanation across Different Types of Shrublands in the Western Loess Plateau

Shrubland is an important type of vegetation in the semi-arid region of the western Loess Plateau, and it is of great value to the maintenance of biodiversity and soil and water conservation. Equally, there may be significant differences in the level of diversity and the community assembly patterns across different types of shrublands (desert, alpine, and secondary shrublands). This study aimed to reveal the diversity and the community assembly patterns of different types of shrublands and the environmental explanations for these by using a taxonomic and phylogenetic analysis approach, as well as by considering soil and climate factors. The diversity level of the desert shrublands was low, and the habitats of the three types of shrubland were significantly different. Precipitation may be the main environmental factor driving the variation in and diversity of these types of shrubland. All three types of shrubland were strongly affected by environmental filtering and competitive exclusion, and their community assembly patterns were similar.

Using the Alternative Stable States Framework to understand the persistence of secondary shrubland within a Mexican oak forest with livestock and agricultural legacies

Many forests exist in human-modified mosaic landscapes subject to logging, agriculture, and livestock grazing. These disturbances can reduce ecosystem resilience and ultimately result in crossing thresholds, leading to the transition of the ecosystem into new stable states with different plant communities. The interaction between these disturbances and forest succession is still poorly understood, despite the growing need to manage these human-modified landscapes for biodiversity and productivity. We studied abrupt changes in vegetation composition in a Central Mexican oak forest and explored how these changes could indicate the coexistence of various alternative stable states caused by agricultural and livestock legacies. We established 36 strip transects covering 9000 m2 in patches with various land use legacies where we sampled vegetation, soil characteristics, and human disturbance. We assessed future and past tendencies in vegetation spatial patterns by evaluating seedling composition and analyzed time series of NDVI signals recorded by LANDSAT images (1972–2019). We utilized NMDS, PERMANOVA, and ANOVA analyses to assess if stable states can be distinguished based on historical and current variations in vegetation composition and structure in patches with different management legacies. We then assess potential factors that may contribute to differences in plant community composition by fitting edaphic, topographic, and anthropogenic disturbance variables to the ordination analyses.We identified three distinct plant communities: oak forest (dominated by late-successional Oak species), secondary shrubland (dominated by Vachellia-Dodonaea association), and a transitional forest-shrub community (a mixture of the first two communities). Time-series analyses and seedling composition provide evidence of long-term community segregation. Variation partition analysis demonstrated that anthropogenic disturbance (particularly livestock browsing), had a greater impact on species composition differentiation than environmental variables.A state-and-transition model is proposed, where cattle browsing and agricultural legacies trigger the transition from oak forests to a stable secondary shrubland community. Three potential self-reinforcing and interacting feedbacks are suggested: (i) micro-environmental filtering, (ii) plant-trait mediated assembly process, and (iii) cascading effects on tree recruitment caused by cattle browsing. The proposed state-and-transition model explains forest successional dynamics in systems with multiple anthropogenic disturbances and provides a conceptual framework for understanding and guiding successional trajectories.

Soil Moisture and Available Phosphorus as the Factors Driving Variation in Functional Characteristics across Different Restoration Communities in a Subtropical Mountain Ecosystem

Functional characteristics are increasingly used to evaluate the success of different vegetation restoration. Community functional diversity (FD) and the community-weighted mean (CWM), as two main complementary components, are closely linked to site environment and ecosystem functions. However, the patterns and driving factors of functional characteristics are still not clear in different vegetation restoration types. Here, four community restoration types (secondary shrubland, SL; Pinus yunnanensis forest, PF; mixed needle-broad-leaved forest, MF; natural secondary forest, NSF) were selected to investigate species diversity, FD, CWM, and soil physicochemical properties. The relative effects of species diversity and soil abiotic features on variation in functional characteristics were then evaluated. We found that different restoration communities altered most community structures and functional properties in terms of species diversity, FD, and CWM. CWM values and FD in different communities presented different distribution patterns depending on certain traits and parameters. Significant correlations between functional traits were found at the species and community scales, suggesting a potential covariation between these selected traits in communities. The results of redundancy analysis and variation partitioning showed that most of the variation in functional characteristics, especially CWM, was explained by soil moisture and available phosphorus, indicating that habitat filters regulate the functional characteristics of plant communities mainly by changing the dominant species composition and functional traits of species. Therefore, the selection of restoration species adapted to low soil moisture and available phosphorus and the construction of communities based on selected species as the dominant species can effectively drive community assembly and ecosystem functions in the vegetation restoration process.

Syntaxonomical survey of cork oak forests (Quercus suber L.) in the province of Tizi Ouzou, Kabylia, Northern Algeria

Abstract This study is a contribution to the knowledge of the floristic composition and syntaxonomical significance of Quercus suber woodlands of Tizi Ouzou province, which represent the last remnants of ancient forests. The field surveys were taken in several locations representative of cork oak woodlands, using the Braun-Blanquet method. A matrix of 96 phytosociological relevés and 160 plant taxa was treated with clustering analysis and correspondence analysis. These multivariate analyses showed congruent results and allowed the definition of four main clusters of cork oak woodlands, corresponding to four syntaxa according to synecological and syndynamic gradients. They belong to three associations, of which one is newly described, and two subassociations. They are: Sileno imbricatae-Quercetum suberis ass. nov., a mesophilous association newly described here, on siliceous soils and in the humid ombrotype; Cytiso villosi-Quercetum suberis, a mesophilous association, with two subassociations: quercetosum canariensis, and myrtetosum communis, this later reported for the first time in the study area, and both localized in the humid ombrotype and confined on markedly acid soils; Erico arboreae-Myrtetum communis, thermophilous secondary shrubland association developed in the subhumid ombrotype, on flysch substrates, also identified for the first time in this area. Syntaxonomic, synecological and syndynamic considerations are given for each syntaxon.

Temporal dynamics of soil nutrients in the riparian zone: Effects of water fluctuations after construction of the Three Gorges Dam

The Three Gorges Dam (TGD) plays a vital role in the hydropower supply of China, which has a substantial impact on the riparian zones along the Yangtze River. Knowledge about how riparian soil properties respond to such changes remains limited. To explore how water regulation disturbs the status of soil nutrients in the riparian zone, a long-term monitoring program was implemented at sites with secondary shrubland (SB) and abandoned farmland (AFD). A total of 288 composite soil samples collected from the two riparian areas were investigated. Compared with 2009, long-term flooding changed the distribution of soil organic matter (SOM) and available phosphorus (AP) contents in various soil layers. The fluctuation of the water level reduced the SOM content, which the range of SOM variation was greater in the early stage of submergence. In 2018, the SOM content in the 10–20 cm at 155–165 m above sea level (a.s.l.) of the AFD was 9.46 g/kg, which reduced by 74.30% compared with 2019. In all the 0–10 cm soil layer, except for 145–155 (a.s.l.) in the AFD plot, soil total nitrogen contents in 2018 were significantly higher than those in 2009. Compared with 2009, the soil AP content in the 10–20 cm layer at 145–155 m (a.s.l.) of SB decreased by 90.90% in 2018. The total potassium (TK) content of AFD increased from 2009 to 2015 but decreased in 2018. However, the soil TK content in 2018 was significantly higher than that in 2009. In AFD, soil pH increased from 2009 to 2015 and reached a maximum value (8.21). In 2018, the pH value of some soil samples showed a downward trend but was always significantly higher than during 2009. Moreover, according to the redundancy analysis, the elevation, soil layer, and flood cycle could explain 56.64% of the changes in soil properties. Our study demonstrates that dam operation was an indirect driver for the changes in the temporal dynamics of soil nutrients, providing a reference for the management of the TGD.

Effects of vegetation type, season, and soil properties on soil microbial community in subtropical forests

The diversity and composition of soil microbial community in forests are affected by vegetation type, season, and soil properties, but the relative importance of these factors on the diversity and composition of microbial community is poorly understood. In this study, high-throughput sequencing was used to assess the soil prokaryote (16S rRNA) and fungal (ITS rRNA) communities of five vegetation types (evergreen broad-leaved forest [EBL], deciduous broad-leaved forest, mixed coniferous–broad-leaved forest, coniferous forest [CF], and secondary shrubland [SS]) for four seasons in a secondary subtropical forest in Eastern China. Soil physicochemical properties and plant diversity were also surveyed for each vegetation type. Vegetation type, season, and their interaction significantly affected the Shannon diversity indexes of soil prokaryotes. The Shannon index of soil fungi was affected by vegetation type. The soil prokaryote and fungal compositions of the five vegetation types were significantly different. The prokaryote compositions of EBL, CF, and SS significantly changed in four seasons, but only the fungal composition of SS changed with the seasons. Variation partition showed that vegetation type and season individually explain 25% and 29% of the variance in prokaryote composition and 19% and 1% of the variance in fungal composition, respectively. Prokaryote diversity and composition were significantly driven by soil pH and organic carbon and fungal diversity and composition were significantly driven by soil pH and electrical conductivity when controlling the effects of vegetation types and seasons.

Shrub influences on seedling performance when restoring the slow‐growing conifer Pilgerodendron uviferum in southern bog forests

Forest restoration is most efficient if it can take advantage of facilitative interactions between established vegetation and planted trees. However, positive and negative interactions have been identified in a number of plant communities. After centuries of anthropogenic fires, forest recovery has been extremely slow in southern bog forests previously dominated by the slow‐growing and vulnerable conifer Pilgerodendron uviferum on Chiloé Island, Chile. Today, the landscape is dominated by secondary shrublands with scattered patches of Sphagnum moss and limited natural tree regeneration. We hypothesized that the retention of secondary shrubs facilitates the early performance of P. uviferum restoration plantings by providing better microsite conditions. To test this hypothesis, we compared the response of seedlings planted on sites prepared at two levels of intervention: after shrubs had been removed or where shrubs were retained. Shrub retention showed a nurse‐plant effect on P. uviferum seedlings 4 years after planting, which resulted in reduced physiological stress (measured as Fv/Fm) for seedlings, as well as reduced browsing. Consequently, the seedlings growing in areas with shrub retention had larger height increment and higher vitality than those in areas where shrubs had been removed. Thus, the more open micro‐site conditions created by shrub removal resulted in generally poorer seedling performance, although seedling mortality—which was low overall (approximately 2–4%)—showed no significant difference between the two levels of intervention. These findings have direct implications for the restoration of slow‐growing conifers that can tolerate extreme wet conditions in highly degraded forests.

Secondary Shrubby Communities Provide Nesting Habitat for Birds in a Semiarid Agricultural Landscape

Loss and fragmentation of natural and semi-natural vegetation caused by agricultural intensification are related to many declines in shrubland bird populations, but they have received little conservation attention and research effort. In the Llanos de Ojuelos, a semiarid agricultural landscape in Mexico, patches of natural shrubland and nopal (or prickly pear) Opuntia spp. orchards harbour 60% of the regional avifauna, but prior to this study their value as nesting habitat for birds has not been assessed. In 2014 we recorded 143 nests of 25 species, 45% of which were of Mourning Doves Zenaida macroura. The nesting birds recorded account for 38% of all species known to use these habitats in this region and the number of nesting species is larger than in other North American semiarid and arid shrublands. Shrublands and orchards were not different in any habitat attributes measured, nor in the densities of nests found in them, but there were significantly more species nesting in shrublands. Nest height and visibility were not different between habitats, except for Mourning Doves, which nested at a lower height in orchards. Neither attribute affected nest success, except for in Black-chinned Sparrow Spizella atrogularis for whom successful nests were less visible. The assemblages of nesting birds might be explained better by particular plants used as nest substrate than by habitat attributes. Catclaws Mimosa aculeaticarpa var. biuncifera, Huisaches Vachellia farnesiana and V. schaffneri and nopal plants supported 56% of all nests, the latter being particularly important for Mourning Doves, while scarce Central-Mexico Yucca Yucca decipiens trees supported 40% of nesting species. There were interspecific differences in the phenology of nesting, which matched the feeding requirements of the young. Nopal orchards seem to provide abundant complementary food for birds that nest in shrubland patches. Nopal orchards and shrubland patches dotting the landscape may make the dominant agricultural matrix of the southern part of the Central Plateau of Mexico less detrimental to shrubland birds. Our study supports the idea that small patches of secondary shrubland can aid in biodiversity conservation in anthropized landscapes, a role that in this region is provided by shrubland remnant patches as well as nopal orchards.

王朗自然保护区地栖脊椎动物群落结构和生境类型的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 王朗自然保护区地栖脊椎动物群落结构和生境类型的关系 DOI: 10.5846/stxb201606071094 作者: 作者单位: 中国科学院成都生物研究所,北京大学,王朗国家级自然保护区;王朗国家级自然保护区,王朗国家级自然保护区;王朗国家级自然保护区,北京大学,中国科学院成都生物研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 保护国际基金项目；中国生物多样性监测与研究网络项目 The relationship between community structure of ground-dwelling vertebrates and habitat types in the Wanglang Natural Reserve Author: Affiliation: Chengdu Institute of Biology, Chinese Academy of Sciences,,,,Peking University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:2006年8-11月，采用围栏陷阱法对四川省王朗自然保护区地栖脊椎动物的群落结构进行了研究，结合森林砍伐、旅游和植被恢复方式等干扰因子所推动的动物栖息生境变化，探讨了动物群落结构和生境类型的关系。监测历时75 d，8个样地共捕获3纲6目17科21种778只地栖脊椎动物，物种组成包括3种两栖类、1种鸟类和17种哺乳类。每百陷阱日的捕获率为32.4%；以普通鼩鼱、高山姬鼠、纹背鼩鼱、高原林蛙等4种为优势种，占全部捕获数的76.9%；其余17种的个体数均较少，物种多度和其分布区域呈显著线性相关（P < 0.001）。动物群落多样性指数，以干扰相对弱的原生针叶林物种多样性指数和均匀度指数为最高，而优势度指数最低；其次为旅游干扰的原生林灌丛和自然更新的次生林灌丛；人工种植的次生针叶林多样性指数和均匀度指数最低，而优势度指数最高。以动物群落相似性指数进行系统聚类，8个样地的动物群落聚为3类：即干扰相对弱的原生针叶林动物群落、严重干扰的人工针叶林动物群落、部分干扰的原生林灌丛和次生林灌丛动物群落。 Abstract:The community structure of grand-dwelling vertebrates in the Wanglang Natural Reserve, Sichuan Province, was examined in relation to a wide range of habitat changes associated with logging, tourism, and restoration measures. Eight sampling sites from a range of habitats were monitored using drift-fences and pitfall traps from August to November 2006. A total of 778 individuals representing 21 species of vertebrates were captured in 75 d, including three species of amphibians, one species of bird, and 17 species of mammals. The capture rate of vertebrates was 32.4%. The vertebrate community was dominated by four species with high abundance. The relative abundance of the species was correlated with their distribution ranges (P < 0.001). Each species was trapped on different dates. Fifteen species were captured within 14 d, no new species were captured from day 15 to 30, and rest of the six species were captured after 30 sampling days. For long-term investigations, 15-30 days interval is enough to encounter vertebrate species from this method. The cumulative number of species at the sampling site exhibited a logarithmic growth curve. After 40-60 specimens were trapped, 70% of the overall species richness in one sampling site was monitored. In general, changes in the quality of habitat resulted in considerable differences in species composition, abundance, and distribution pattern of community structure, with a marked decline in diversity and evenness indices, and a substantial increase in the proportion of dominant species. The diversity of vertebrates in different habitats indicated that species diversity index (2.099) and evenness index (0.875) was highest, but the species dominance index (0.149) was lowest in weakly disturbed primary forest. Both primary shrubland with tourism and secondary shrubland experiencing spontaneous recovery from logging had moderate indices. In contrast, the secondary forest with artificial recovery had the lowest species diversity index (1.337) and evenness index (0.520), but the highest species dominance index (0.454). Based on the similarity index of community structure, a phenogram was reflected in three assemblages representing weakly disturbed, partially disturbed, and heavily disturbed habitats. Among three disturbance factors, timber harvest accounted the high level of disturbance and 42.9% difference in species composition between logged and un-logged forest communities after 50 years of clear cutting. Species most affected by tourism were associated with primary forest under an intermediate level of disturbance, whereas after 50 years of regeneration, the spontaneous recovery produced a mixed community structure that had recovered and exhibited higher species diversity. 参考文献 相似文献 引证文献

Best management practices to face degraded territories occupied by Cistus ladanifer shrublands – Portugal case study

Land degradation in the Mediterranean Basin is clearly connected to the resilience of perturbed ecosystems, contributing to land abandonment, recurrent fires and biodiversity loss, with the prevalence of secondary shrublands that tend to occupy large areas. This is the case of Cistus ladanifer shrublands, one of the most widespread shrub communities in the Iberian Peninsula and a poor, uniform and resilient system. Here, we analyse the impact of several management practices in the recovery of territories largely occupied by this shrubland. We tested “non-intervention”, “cut”, “fire”, “mechanical mobilisation” and “pasture” in 100-m2 plots of Cistus ladaniferus L., in Central Portugal, and followed them from 1993. Flora were analysed using Braun–Blanquet's methodology and the plots were compared with hierarchical cluster analysis and principal component analysis. An analysis of variance was also performed to investigate differences in management practices, both between plots and between two periods of time. The results show that extensive grazing or continuous cut have a high impact on plant diversity and community structure, with extensive grazing being the best way to improve plant diversity in a short period of time, using fewer resources.

Spatial pattern analysis of dominant species in Exochorda giraldii community in Xingtang Temple of Taiyue Mountains, Shanxi, China

Aims The Exochorda giraldii community is a secondary shrubland developed following destruction of warm temperate and deciduous broad-leaved forests. The objective of this study was to explore the distribution and in- ter-relationships of dominant species in E. giraldii communities in Taiyue Mountains, Shanxi, China. Methods Based on the vegetation survey data on a 50 m × 50 m plot, point pattern analysis (O-ring) and fractal analyses (including box-counting dimension analysis, information dimension analysis and correlation dimension analysis) were performed to determine the spatial patterns of dominant species in a E. giraldii community. Important findings In the E. giraldii community, most of the dominant species showed the characteristics of aggregated distribution at smaller scales. However, Periploca sepium and Spiraea salicifolia showed an aggrega- tion distribution at all scales. With increases in scale, the distributions of E. giraldii and Forsythia suspensa changed from aggregation to random and to uniform. Based on the point pattern analysis, the dominant species in the E. giraldii community showed aggregation distribution characteristics at different scales. The box-counting dimension analysis indicated that the ability of dominant species to occupy the space in the E. giraldii community was in the order of E. giraldii > F. suspensa > S. salicifolia > P. sepium. The information dimension analysis in- dicated that the degree of changes in pattern intensity of dominant species with scale in the E. giraldii community was in the order of P. sepium > S. salicifolia > E. giraldii > F. suspensa. The correlation dimension analysis showed that the spatial correlations of dominant species in the E. giraldii community was in the order of P. sepi- um > E. giraldii > F. suspensa > S. salicifolia. On a smaller scale, the E. giraldii population showed aggregated distribution; the F. suspensa population and the E. giraldii population had a positive correlation; the S. salicifolia population and the E. giraldii population had a positive correlation; the P. sepium population and the E. giraldii population had a negative correlation. Point pattern analysis and fractal analyses produced consistent results, re- vealing the spatial distribution patterns of secondary shrubs following destruction of the warm temperate and de- ciduous broad-leaved forests.

Differential effects of vegetation restoration in Mediterranean abandoned cropland by secondary succession and pine plantations on bird assemblages

Two contrasting trajectories for vegetation restoration in agricultural landscapes are secondary succession following cropland abandonment that can regenerate woodlands (passive restoration) and conversion of cropland to tree plantations (active restoration), which have mostly focused on pine species in the Mediterranean Basin. We compared the effects of these two contrasting trajectories of vegetation restoration on bird assemblages in central Spain. Vegetation structure differed in the two restoration trajectories, pine plantations attaining higher tree cover and height (31% and 4.1 m, respectively) but lower strata complexity than secondary shrubland and holm oak woodland (which attained 10% and 1.4 m of tree cover and height, respectively). Bird species richness differed in stands under active or passive restoration trajectories, the former collecting a higher total number of species (4.2 species per 0.78 ha plot) than the latter (3.5 species per plot). The number of forest species increased with vegetation maturity in both restoration trajectories, but especially in stands under active restoration. The occurrence of woodland generalist species increased and of species inhabiting open habitats decreased in actively restored stands, being some of these latter species of high conservation priority in the European context but relatively common at the regional level. Bird species inhabiting pine plantations had broader habitat breadth at the regional level than those inhabiting secondary shrublands and woodlands. Maximum regional density did not differ between both restoration trajectories, but it increased with development of the herbaceous layer only at the secondary succession trajectory. The relative importance of species of European biogeographic origin was higher in mature pine plantations (58.9% of total bird abundance) than in mature holm oak woodlands (34.4%), whereas that of Mediterranean species was considerably higher in the latter (40.1%) than in the former (20%). Bird assemblages of relatively small patches of pine plantations are unable to reflect the regional avifauna, in contrast with the relationships between local and regional assemblage characteristics that can be found in isolated natural forests. We conclude that programs of vegetation restoration should base upon a range of approaches that include passive restoration, active restoration with a variety of tree and shrub species, and mixed models to conciliate agricultural production, vegetation restoration and conservation of target species.

Effects of nitrogen-fixing and non-nitrogen-fixing tree species on soil properties and nitrogen transformation during forest restoration in southern China

The role of different plantation tree species in soil nutrient cycling is of great importance for the restoration of degraded lands. The objective of the present study was to evaluate the potential of N-fixing and non-N-fixing tree species to recuperate degraded land in southern China. The soil properties and N transformations in six forest types (two N-fixing plantations, three non-N-fixing plantations and a secondary shrubland) established in 1984 were compared. The N-fixing forests had 40–50% higher soil organic matter and 20–50% higher total nitrogen concentration in the 0–5 cm soils than the non-N-fixing forests. Soil inorganic N was highest under the secondary shrubland. The N-fixing Acacia auriculiformis plantation had the highest soil available P. There were no significant differences in soil N mineralization and nitrification among the forest types, but seasonal variation in these N processes was highly significant. In the rainy season, the rates of N mineralization (7.41–11.3 kg N ha−1 month−1) were similar to values found in regional climax forests, indicating that soil N availability has been well recovered in these forest types. These results suggest that N-fixing species, particularly Acacia mangium, are more efficient in re-establishing the C and N cycling processes in degraded land in southern China. Moreover, the N-fixing species A. auriculiformis performed better than other species in improving soil P availability.

Vegetación de bordes en un bosque mesófilo de montaña del occidente de México

La composición, diversidad, estructura y microclima fueron comparadas en dos tipos de bordes de bosque mesófilo de montaña (BMM) en la Sierra de Manantlán (Jalisco, México), uno con borde suave (B-B, contiguo a bosque de pino-encino) y otro con borde abrupto (B-M, contiguo a matorral secundario). Se establecieron 9 parcelas permanentes (n=5 en B-B y 4= en B-M) perpendiculares al borde. El BMM presentó mayor riqueza (126 especies, de estas 52 exclusivas al interior) que el bosque de pino (84) y los matorrales (71). La riqueza y diversidad fueron similares en B-B, pero el reemplazo de especies fue mayor en B-M. La densidad, diámetros, área basal y cobertura del dosel fueron mayores en B-B. La variación en las condiciones del microclima y suelos fueron mayores en los B-M. Las especies arbóreas de BMM (alta densidad de juveniles y plántulas &lt;5cm de diámetro) están colonizando el sotobosque del bosque de pino adyacente, mientras que en los matorrales su establecimiento parece estar limitado por la competencia con los arbustos y hierbas, además de las condiciones del microclima. Los resultados obtenidos resaltan la importancia de considerar el contraste entre bordes en la conservación y restauración del BMM en paisajes forestales.

Naturalness-based habitat quality of the Hungarian (semi-)natural habitats

Effective conservation of (semi-)natural habitats needs knowledge on the naturalness, the actual quality of a habitat or vegetation patch. Nevertheless, there are only a few studies have been published in this topic so far. During the MÉTA project, between 2002–2005, we have surveyed the semi-natural vegetation of Hungary and assessed the naturalness of the predefined 86 habitat types. In this paper we present the country scale analysis on the naturalness of these habitat types. We compared the naturalness of the individual habitat types and also habitat groups, as well as the naturalness of the physical macroregions of Hungary. Euhydrophyte habitats and habitats deserving high abiotic stress are the most natural ones, while secondary shrublands, uncharacteristic forests and grasslands are the less natural. For the forest habitats we compared and discussed the naturalness values given by the MÉTA mappers and the values gained in the TERMERD (assessing forest naturalness in Hungary) project. In case of regions, Kisalföld has the lowest naturalness, and surprisingly the quality of the Alföld and the Középhegység is nearly equal if we consider only the remained vegetation.

Positive interaction between invasive plants: The influence of Pyracantha angustifolia on the recruitment of native and exotic woody species

Abstract: Positive interactions between species are known to play an important role in the dynamics of plant communities, including the enhancement of invasions by exotics. We studied the influence of the invasive shrub Pyracantha angustifolia (Rosaceae) on the recruitment of native and exotic woody species in a secondary shrubland in central Argentina mountains. We recorded woody sapling recruitment and micro‐environmental conditions under the canopies of Pyracantha and the dominant native shrub Condalia montana (Rhamnaceae), and in the absence of shrub cover, considering these situations as three treatments. We found that native and exotic species richness were higher under Pyracantha than under the other treatments. Ligustrum lucidum (Oleaceae), an exotic bird‐dispersed shade‐tolerant tree, was the most abundant species recruiting in the area, and its density was four times higher under the canopy of Pyracantha. This positive interaction may be related to Pyracantha's denser shading, to the mechanical protection of its canopy against ungulates, and/or to the simultaneous fruit ripening of both woody invaders.

Seasonality of forest invertebrates in Hong Kong, South China

Because of its position on the northern margin of the tropics (22° 17′N) and the southern coast of a huge continent, Hong Kong has a climate in which both temperature and rainfall are highly seasonal. Although summer temperatures are equatorial, the January mean is only 15.8 °C,and the absolute minimum recorded at sea level is 0 °C (Dudgeon &amp; Corlett 1994). As a result, all aspects of the ecology of Hong Kong show seasonal changes. The most dramatic changes occur in the bird fauna, with the majority of species migratory (Carey et al. 2001). The winter fruiting peak in secondary shrublands and the forest understorey coincides with the arrival of partially frugivorous migrant robins and thrushes (Corlett 1993). However, while resident insectivore-frugivores consume almost entirely fruit during this period (Corlett 1998), all the winter visitors continue to eat insects and some (e.g. Phylloscopus warblers) are entirely insectivorous. The study of insect seasonality reported here formed part of a 30-mo study of the seasonality of a forest bird community in Hong Kong (Kwok &amp; Corlett 1999, 2000). Plant names follow Corlett et al. (2000).

Pollination in a degraded tropical landscape: a Hong Kong case study

Although the pollination biology of many individual plant species has been investigated in the Oriental region, there have been very few community-level studies. The two most comprehensive of these were in the primary mixed dipterocarp forest of Lambir Hills National Park, Sarawak (4°20′N: Momose et al. 1998, Sakai et al. 1999) and in the warm temperate evergreen broad-leaved forest and cool temperate mixed forest on Yakushima Island (30°N: Yumoto 1987, 1988). Hong Kong (22°17′N) lies midway between these sites, at the northern margin of the tropics, where winter temperatures fall below 10 °C at sea-level for a few days every year and there are occasional frosts above 400 m (Dudgeon &amp; Corlett 1994). Latitudinal effects, however, are compounded in comparisons with other well-studied East Asian sites, by centuries of massive human impact, leaving a degraded landscape of steep, eroded hillsides, covered in fire-maintained grassland, secondary shrublands and, locally, secondary forests (Zhuang &amp; Corlett 1997). This history has left a relatively impoverished fauna but a surprisingly diverse flora, including 400 native tree species (Corlett &amp; Turner 1997). In these circumstances, failures of pollination and dispersal mutualisms might be expected to accelerate the loss of plant species from the landscape (Bond 1994, Kearns &amp; Inouye 1997). Previous studies have shown that most woody vegetation in Hong Kong is dominated by species whose seeds can be dispersed by the commonest avian frugivores, the light-vented and red-whiskered bulbuls (Pycnonotus sinensis (Gmelin) and P. jocosus (Linn.)) and the Japanese white-eye (Zosterops japonicus Swinhoe) (Corlett 1996, 1998), but there is no equivalent information available on pollination biology.

PRIMARY PRODUCTION AND NUTRIENTS IN A HONG KONG SHRUBLAND

Secondary shrubland is widespread in southern China. This study is a pioneer one of this plant community's distribution and seasonal dynamics of phytomass and nutrients, production of dry matter and nutrients, cycling and use of nutrients. These were studied for a period of two years in the shrubland at sites in Hong Kong's New Territories. Above-ground phytomass, including standing dead matter and litter, averaged 2 239 g/m2 and below-ground phytomass averaged 1 408 g/m2. Foliage production of the evergreen shrub Rhodomyrtus tomentosa, the dominant species, was continuous and gradual. The foliage phytomass depended upon a balance of production of new foliage and senescence and abscission. The phytomass of reproductive structures of R. tomentosa tended to increase regularly from April to July and exhibited a sudden decline after September. A study of the nutrient distribution showed that the distribution patterns of phytomass and nutrient resources are significantly different. For foliage and reproductive structures, the distribution ratios of nutrients were larger than those of phytomass. It is inverse for standing dead matter and stems and branches. The seasonal pattern of N, P and K contents in the foliage and reproductive structures of R. tomentosa paralleled that of the phytomass. R. tomentosa contained a relatively large amount of nutrients in the leaves throughout the year. Mean net primary production (NPP) of the shrubland was 972 g/m2/yr. The mean above-ground dry matter production was 757g/m2/yr which made up 77.9 per cent of the total NPP. The mean production of N, P and K in the shrubland were, respectively, 6 726, 464 and 4 282 mg/m2/yr. Litterfall occurred throughout year, but there was a marked seasonal pattern in the rates of litter production. Climatic factors have an important influence on litter fall seasonality. High litter production is associated with a period of dry weather or a typhoon. The mean return of dry matter by litter fall for two years was 477 g/m2/yr; the N, P and K returns were respectively 2 815,164 and 892 mg/m2/yr. This study showed that 45.1 per cent of the N requirement in NAPP and 51.3 per cent of the P requirement in NAPP came from internal cycling of the plants. Four definitions of nutrient-use efficiency are discussed and compared. An assessment of nutrient-use efficiency through the litter fall mass and concentration data indicated that efficiency for the use of nutrients in the shrubland was greater than the value for an efficient nutrient economy in tropical forest. A conservative utilization of phytomass resources based on reduced nutrient losses is stressed. It is suggested that the foliage, branchlets, bark and reproductive structures from shrubs and trees are not removed.