Gypsophile vegetation patterns under a range of soil properties induced by topographical position

Iberian gypsophile plant communities are considered a priority for conservation by the European Community because of their highly specialized flora in gypsum outcrops in arid and semiarid regions. Despite the ecological importance of these ecosystems, the edaphic factors that constrain plant communities on gypsiferous soils remain unclear. It has been proposed that both the chemical and physical restrictive conditions of gypsum soils determine gypsophily in plants. Here we hypothesize that the rigors of the gypsum soil environment depends on topography, decreasing from flat areas on hilltops to south-oriented slopes and finally to slopes oriented to the north. We also hypothesized that the relaxation of the rigors of the gypsum soil environment with topography affects both to individual plant and community characteristics of gypsophile vegetation: we expect a reduction of gypsophyte abundance, an increase of diversity and the amelioration of facilitative interactions of plant species. We analysed the physical and chemical properties of gypsum soils that have been proposed that determine the rigors of the gypsum soil environment (i.e.: unbalanced ion concentrations and superficial soil crust). The predicted rigor gradient along topographical locations was confirmed and was mainly caused by superficial soil crust. The decreasing rigor gradient was accompanied by a fall in the abundance of gypsophytes. However, when gypsophytes were considered separately, several patterns were observed, indicating distinct tolerance to relaxation of rigor of the gypsum soil conditions and different competition abilities between gypsophytes. Plant species were more clumped, and gypsophile communities presented higher diversity, evenness and richness values where rigor of gypsum soil conditions were maximum (flat hilltop positions). Relaxation of rigor (north-oriented slopes) was characterized by loss of facilitative interaction between species and the dominance of the gypsovag Rosmarinus officinalis L., although richness was still very high, which can be attributed to the coexistence of gypsophytes and gypsovags. We conclude that the rigor of gypsum soil environment gradient with topography is mainly determined by superficial soil crust, and it is a crucial determinant of gypsophile plant communities.     

Effects of temperature on phenological synchrony and altitudinal distribution of jumping plant lice (Hemiptera: Psylloidea) on dwarf willow (Salix lapponum) in Norway

Summary.

• 1 The geographical distributions of three species of jumping plant lice (psyllids) along an altitudinal transect (988–1300 m a.s.l.) in southern Norway were restricted within the range of their host plant Salix lapponum. One species, Cacopsylla propinqua, occurred at all sampling locations between 988 and 1222 m, whereas C.palmeni was confined to higher altitudes (1153–1222 m) and C.brunneipennis was more abundant at lower altitudes (988–1101 m).
• 2 C.brunneipennis and C.palmeni developed only on female catkins. Development times of catkins and psyllids were similar (approximately 50 days) and successful psyllid development depended on close phenological synchrony with catkins.
• 3 Thermal requirements for development of female catkins were greater at low altitude (988 m) compared with higher altitude (1222 m), showing local adaptation of S.lapponum to altitude. In general, thermal requirements of psyllids were less than those of catkins at the same location. C.brunneipennis had higher thermal requirements than C.palmeni.
• 4 Field experiments, using polythene enclosures to elevate temperatures at two sites at different altitudes (by 0.6–1.4 deg. C), showed that insects had an enhanced relative rate of development under elevated temperatures compared with their host plants.
• 5 Indices of phenological synchrony were calculated from thermal requirements of psyllids and catkins. Under elevated temperatures, phenological synchrony decreased at both sites. This resulted in the subsequent development of smaller adult insects at low altitude, although at higher altitude, insects developing under elevated temperatures were larger and had a higher survival rate compared with controls.
• 6 Effects of temperature on phenological synchrony may explain the limits to the geographical range of psyllids. The consequences of climate change on psyllid populations will depend on the effects of decreased phenological synchrony on insect development and this may differ within the insect's geographical range.

     

云南花椒园中昆虫群落特征的海拔间差异分析

分析了金沙江畔7个不同海拔区域花椒园中昆虫群落特征的动态变化及其与温、湿度变化的关系。结果表明:花椒园中昆虫群落的多样性、均匀度、丰富度、Ss/Si、Sn/Sp指标随海拔升高先增加后减少,而个体数、优势集中性指数则随海拔升高先减少后增加;低海拔(450—750 m)区域花椒园中由于总体温度高、湿度低,较高海拔(1300—1550 m)区域总体温度低、湿度高,均不利昆虫群落多样性、均匀度、丰富度、Ss/Si、Sn/Sp指标的提高和群落的稳定,而中等海拔(750—1300 m)区域的温度、湿度较为适中,昆虫群落的物种数及个体数量均相对较高,昆虫群落多样性、均匀度、丰富度、Ss/Si、Sn/Sp指标也较高,群落较稳定;相反,低海拔、较高海拔区域花椒园中昆虫群落优势集中性指数较高,而中等海拔区域却相对较低。综合分析表明,海拔高度及温湿度对花椒园昆虫群落特征影响较大,而海拔高度及温湿度的测量和分析较为方便。     

Alien seedling recruitment as a response to altitude and soil disturbance in the mountain grasslands of central Argentina

Climate and disturbance are considered key factors in explaining plant invasion, mainly by their effect on alien seedling recruitment. We tested whether soil disturbance by digging and altitude, as a sub-set of climate, affected the seedling recruitment of two alien species (Cirsium vulgare and Melilotus alba) in the mountain grasslands of central Argentina. We performed a seed-addition factorial experiment with altitude as a fixed factor co-variable (6 levels), time since sowing (6 levels) as an autoregressive co-variable, and soil disturbance by digging (two levels) and seed addition (two levels) as fixed factors. Seeds of the studied species were sown in replicated undisturbed and disturbed soil plots, in grassland stands located every 200 m from 1200 to 2200 m a.s.l. The number of emerging seedlings at each plot was recorded during a period of 8 months, at intervals of 30–60 days. Seedlings of both alien species emerged at all the studied altitudes, but only the recruitment of C. vulgare increased linearly with altitude. Moreover, the time window of seedling recruitment for this species increased with altitude. Soil disturbance produced a significant decrease in overall seedling emergence of both species; however, an increase in emergence was observed for C. vulgare at an altitude over 2000 m a.s.l. Natural emergence inside control plots without seed addition was only observed for Cirsium vulgare, which indicates that this species was not seed limited. Our results show that altitude and the absence of disturbance do not restrict the recruitment of C. vulgare and M. alba in these natural mountain grasslands. Moreover, these alien species seem to be tolerant to and even favoured by conditions occurring at higher altitudes and in absence of micro-site soil disturbances in the Córdoba mountain grasslands.     

Altitudinal gradients in seed dynamics of Calluna vulgaris in eastern Scotland

Abstract. Relationships between seed deposition, size of soil seed banks and some of the environmental factors affecting them were assessed for Calluna vulgaris throughout its altitudinal range (150–960 m a.s.l.) in eastern Scotland. Seed rain was assessed using pitfall traps, collected every 5–10 wk for 3 yr; germinability was determined by laboratory incubation. Seed bank size was estimated, once only, by counting seedlings emerging from soil cores kept for 50 wk in a glasshouse. Seed deposition varied annually, was related to parent plant cover but always declined with altitude, falling sharply above 600 m a.s.l. Seed bank size was more closely correlated with the proportion of organic matter in the soil than with the amount of seed rain. Seed bank sizes declined gradually with altitude but did not differ significantly between four altitudinal zones. The mean density of buried seeds was less than half the mean annual seed rain at sites below 300 m a.s.l. but was over 200 × greater than annual seed rain above 800 m, suggesting that seeds buried at high altitudes remain viable for much longer than those at lower altitudes.     

亚热带不同海拔黄山松林土壤磷组分及微生物特征

磷是亚热带地区植物生长必需的养分元素之一,海拔梯度可能会改变土壤-植物-微生物系统并影响土壤磷形态及有效性。了解不同海拔土壤磷组分状况,对维持山地森林生态系统可持续发展具有重要的意义。以戴云山地区不同海拔梯度(1300m和1600 m)黄山松林为研究对象,分析了土壤磷组分、微生物群落特征和磷酸酶活性。结果显示:海拔显著影响黄山松林土壤磷组分,与海拔1300 m相比,海拔1600 m处土壤总磷含量减少了48.4%—49.8%,且各磷组分(易分解态磷、中等易分解态磷和难分解态磷)含量也显著降低,淋溶层(A层)土壤的降低程度分别为45.7%、58.6%和38.7%,淀积层(B层)为82.6%、59.9%和31.1%。海拔对土壤微生物群落特征和酶活性亦有显著影响,各类微生物群落和总微生物磷脂脂肪酸含量(PLFAs),以及磷酸双酯酶(PD)活性均表现为海拔1600 m 1300 m,但酸性磷酸单酯酶(ACP)活性呈相反的趋势。冗余分析(RDA)表明,土壤磷组分主要受有机碳(SOC)调控,且SOC与有机磷组分(Na HCO3-Po和Na OH-Po)呈显著正相关;磷酸酶和外生菌根真菌(EMF)也是影响土壤磷组分变化的重要因素。研究表明,土壤有机质含量和微生物群落结构及功能的变化可能是不同海拔黄山松林土壤磷有效性的关键调控因素。     

Identifying factors determining the altitudinal distribution of the invasive pest leafminers Liriomyza huidobrensis and Liriomyza sativae

Abiotic and biotic factors that change with altitude can influence the distribution of herbivorous insects. We examined factors influencing the distribution of the generalist leafminers Liriomyza sativae Blanchard and Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae), two pests of agricultural crops, in the tropical Dieng mountainous area of Central Java, Indonesia. Liriomyza huidobrensis predominated at altitudes above 700 m a.s.l. and was the only species collected above 1 400 m a.s.l. In contrast, L. sativae predominated below 600 m a.s.l. and was not found above 1 200 m where the average temperature was 20.7 °C. Parasitoid diversity decreased with altitude, but parasitism did not change. The distribution of neither species was affected by parasitoids; L. huidobrensis predominant at high altitudes was preferred by Opius parasitoids common at these altitudes. Intra‐ and interspecific competition was detected in laboratory experiments where larval density was high, but led to coexistence rather than species displacement. No competition was detected in a field experiment when larval density was low. However, L. sativae failed to reproduce at the highest altitude, whereas L. huidobrensis established at all altitudes. Host composition varied with altitude and one host (faba beans) preferred by L. huidobrensis was common at high altitudes. By relating published data on the performance of the leafminer species to altitudinal temperature changes, we were partly successful in predicting the altitude at which the dominant species switched. Temperature plays an overriding influence on the altitudinal distribution of leafminers.     

Gypsum Physical Soil Crusts and the Existence of Gypsophytes in Semi-arid Central Spain

Probably gypsophytes are the most interesting set of edaphic specialists of arid and semiarid climates. Despite they conform a global biodiversity priority, there are almost no information about those adaptive traits that confer such a specialised behaviour. Our broad hypothesis is that gypsophytes are “refuge-endemics” that are able to grow on gypsum soils due to their ability to surpass extremely hard gypsum soil physical crust during emergence. With this in mind we have conducted an experimental approach combining field and greenhouse assays. Seeds from two gypsophytes, genuine and widely distributed in the Iberian Peninsula gypsophytes (Helianthemum squamatum and Lepidium subulatum) and one gypsovag (Teucrium capitatum), a generalist plant that can also grow on gypsum soils were used in our experiments. Two complementary experimental approaches were conducted. The first involved a field experiment in which the presence or absence of the physical crust together with the sowing date were manipulated and a greenhouse experiment in which the irrigation amount and the types of soil were controlled. Variables of interest were the percentage of germination, growth and survival. In the field experiment we found a significant decrease in the final germination of the gypsovag in the plots with intact crusts. On the other hand, H. squamatum is able to grow in the three tested soils, despite higher survival and growth on genuine gypsum soils. Our results confirm the hypothesis that gypsum edaphic specialists base their behaviour to a great extent on the ability to surpass extremely hard gypsum surface crusts, although this seems a marginal adaptive trait as shown by the capability to grow on a complete array of soils and the negative effect of the crust along the earlier development life stages of gypsophytes. Furthermore, a gypsovag such as Teucrium capitatum presents extreme difficulties to emerge on non-disturbed gypsum physical crusts but once surpassed its growth and survival is not limited.     

Are there predictable clines in plant–pollinator interactions along altitudinal gradients? The example of Cytisus scoparius (L.) Link in the Sierra de Guadarrama (Central Spain)

Abstract. We analyse the hypothesis that predictable gradients occur in plant–pollinator interactions along altitudinal gradients due to thermal constraints on insect body size and floral traits being selected for by pollinators. Pollinators’ size should follow Bergmann's rule in mountains (larger body size at higher altitudes) and selection should, in turn, lead to larger flower size at higher altitudes. The study focuses on the flower and pollinator size variation in 11 Cytisus scoparius populations located between 680 and 1300 m a.s.l., and on the relationship between flower size and pollination success of plants in each population. Significant differences among populations were found in flower size, pollinator size and fruiting success (anova , P < 0.001 in all cases). Regression models show that (i) pollinator size increases significantly with altitude, (ii) a parallel quadratic increase in flower size and (iii) a quadratic decrease in pollination success with altitude. Moreover, there is a tendency of plants with smaller flowers in each population to have a higher percentage of flowers initiating development into fruits (ancova , P < 0.05). All these observations support the presence of the predicted gradient in the studied species and they suggest the possibility of it to be somewhat common among plants that occupy large altitudinal ranges due to the simple basis on which it could be rooted.     

Ajania semnanensis sp. nov. (Asteraceae–Anthemideae), from northeast Iran: insights from karyological and micromorphological data

Ajania semnanensis (Compositae: Anthemideae), a new species of Ajania from northeast of Iran, Semnan province, is described and illustrated. Ajania semnanensis is a suffruticose perennial growing on rocky and stony slopes of mountains at altitudes of 1500–2800 m a.s.l. Karyological and micromorphological data of the pollen and achenes, as well as a distribution map for the species are provided. The cytotype of the species was found to be diploid (2n = 2x = 18) based on x = 9. The karyotype formula is 2n = 2x = 4M + 6m + 6sm + 2st. Pollen grains of A. semnanensis are prolate‐spheroidal (P/E = 1.1), 3‐zonocolporate and echinate (Anthemis type). The achenes of A. semnanensis are obovate, 1.0–1.5 × 0.5–0.6 mm, light brown, with 4–6 fine and inconspicuous ribs, glabrous, without pappus and with a subbasal carpopodium. The IUCN status of the new species is suggested to be ‘Least Concern’ (LC).     

The relative contribution of symbiotic N2 fixation and other nitrogen sources to grassland ecosystems along an altitudinal gradient in the Alps

The significance of symbiotic N₂ fixation in legumes (Trifolium alpinum L., T. nivale Sieber, T. pratense L., T. badium Schreber, T. thalii Vill., T. repens L., Lotus alpinus [DC.] Schleicher, L. corniculatus L., Vicia sativa L.) and other N sources for the N budget of grassland ecosystems was studied along an altitudinal gradient in the Swiss Alps. The total annual symbiotic N₂ fixation was compared with other sources of N for plant growth of the total plant community (mineralisation and wet deposition). The contribution of symbiotically fixed N to total above-ground N yield of the swards decreased from at least 16% to 9% with increasing altitude where legumes were present. This decrease was due to a decrease in the yield proportion of legumes from 15% at 900 and 1380 m a.s.l. to 5% at 2100 and 2300 m a.s.l. (no legumes were found above 2750 m a.s.l.) and not to a decline in the activity of symbiotic N₂ fixation. With increasing altitude legumes are more patchily distributed. The high symbiotic N₂ fixation of individual plants up to their altitudinal limit is not primarily the result of low mineral N availability since an addition of NH₄ ⁺ or NO₃ ⁻ fertiliser at 2300 m a.s.l. led either to no decrease or only to a minor decrease in symbiotic N₂ fixation. At 1380 m a.s.l., N mineralisation (13.45 g N m⁻² yr⁻¹) appeared to be the main source of N for growth of the sward; N from symbiosis (at least 1.0 g to 2.6 g N m⁻² yr⁻¹) and wet deposition (0.4 g to 0.6 g m⁻² yr⁻¹) was not a significant N source for plant growth at this altitude. At 2100 m a.s.l., the combined amounts of N from symbiotic N₂ fixation (at least 0.1 g N m⁻² yr⁻¹) and wet deposition (0.3 g N m⁻² yr⁻¹) appeared to be similarly important for plant growth as soil N mineralisation (0.47 g N m⁻² yr⁻¹). At high altitudes, wet N deposition and symbiotic N₂ fixation together represent a significant source of N for the grassland ecosystem while at low altitudes these N inputs appear to be much less important. This revised version was published online in June 2006 with corrections to the Cover Date.     

Changes in plant form and function across altitudinal and wetness gradients in the wetlands of the Maloti-Drakensberg,South Africa

A survey of 93 wetlands in six catchments across the Maloti-Drakensberg is used to assess the distribution of plant functional types across altitudinal and wetness gradients. Altitudes range from 1,000 to 3,200 m a.s.l. Within each catchment, the wetlands were selected to cover the complete range in altitude and wetland types. In each of the selected wetlands, vegetation was sampled in 3 by 3 m quadrats covering the entire range of wetness represented in the wetland, from temporarily wet to permanently inundated soils. Plant species were allocated to one of 11 different functional types (examples are C₃ grasses, C₄ sedges, rosette plants, and shrubs), and the proportion of the vegetation in each sample occupied by each functional type was calculated from the species’ abundances. Canonical Correspondence Analysis shows that “wetness” clearly has the highest impact on the distribution of functional types, followed by altitude. The most important plant functional types in wetlands are grasses and sedges, however, at higher altitudes, forbs (especially rosette plants) and bulbous plants become a more prominent feature in the wetlands. The total amount of graminoids gradually decreases with altitude. The general trend is that sedges tend to increase with increasing wetness and C₃ plants (grasses and sedges) increase with increasing altitude, but these effects are not independent. The distributions of C₄ sedges and C₄ grasses along an altitudinal gradient are quite different, and C₄ grasses grow abundantly at much higher altitudes than C₄ sedges. C₄ sedges are very scarce at the altitudes represented in the Maloti-Drakensberg area, whereas C₃ grasses occur in the permanently wet parts of the wetlands, especially at higher altitudes (normally mostly occupied by sedges). Shrubs are rare in wetlands and tend to be an indication of disturbance. This study complements previous studies on the distribution of grasses and sedges at the lower altitudes within KwaZulu-Natal, which found that at altitudes below 1,000 m a.s.l. C₄ sedges were much more prominent, while forbs and rosette plants were largely absent. This confirms that C₄ as an adaptation to hotter and warmer climates is sometimes a less favorable metabolism in wet high altitude areas. At high altitudes, rosette plants and bulbous plants become more competitive in wetlands, probably because grasses and sedges present at these altitudes generally grow smaller than they do in low altitude wetlands.     

Influence of environmental conditions on the distribution of Central Asian green toads with three ploidy levels

We studied the distribution of Palearctic green toads (Bufo viridis subgroup), an anuran species group with three ploidy levels, inhabiting the Central Asian Amudarya River drainage. Various approaches (one‐way, multivariate, components variance analyses and maximum entropy modelling) were used to estimate the effect of altitude, precipitation, temperature and land vegetation covers on the distribution of toads. It is usually assumed that polyploid species occur in regions with harsher climatic conditions (higher latitudes, elevations, etc.), but for the green toads complex, we revealed a more intricate situation. The diploid species (Bufo shaartusiensis and Bufo turanensis) inhabit the arid lowlands (from 44 to 789 m a.s.l.), while tetraploid Bufo pewzowi were recorded in mountainous regions (340–3492 m a.s.l.) with usually lower temperatures and higher precipitation rates than in the region inhabited by diploid species. The triploid species Bufo baturae was found in the Pamirs (Tajikistan) at the highest altitudes (2503–3859 m a.s.l.) under the harshest climatic conditions.     

Modularity Reveals the Tendency of Arbuscular Mycorrhizal Fungi To Interact Differently with Generalist and Specialist Plant Species in Gypsum Soils

Patterns in plant–soil biota interactions could be influenced by the spatial distribution of species due to soil conditions or by the functional traits of species. Gypsum environments usually constitute a mosaic of heterogeneous soils where gypsum and nongypsum soils are imbricated at a local scale. A case study of the interactions of plants with arbuscular mycorrhizal fungi (AMF) in gypsum environments can be illustrative of patterns in biotic interactions. We hypothesized that (i) soil characteristics might affect the AMF community and (ii) there are differences between the AMF communities (modules) associated with plants exclusive to gypsum soils (gypsophytes) and those associated with plants that show facultative behavior on gypsum and/or marly-limestone soils (gypsovags). We used indicator species and network analyses to test for differences between the AMF communities harbored in gypsophyte and gypsovag plants. We recorded 46 operational taxonomic units (OTUs) belonging to nine genera of Glomeromycota. The indicator species analysis showed two OTUs preferentially associating with gypsum soils and three OTUs preferentially associating with marly-limestone soils. Modularity analysis revealed that soil type can be a major factor shaping AMF communities, and some AMF groups showed a tendency to interact differently with plants that had distinct ecological strategies (gypsophytes and gypsovags). Characterization of ecological networks can be a valuable tool for ascertaining the potential influence of above- and below-ground biotic interactions (plant-AMF) on plant community composition.     

Role of altitude and water temperature as regulating factors for the geographical distribution of Tetracapsuloides bryosalmonae infected fishes in Switzerland

The role of water temperature and altitude of the river sites on distribution, prevalence and infection intensity of Tetracapsuloides bryosalmonae infected salmonids was investigated. The study is based on a 6 year survey of salmonids, mainly brown trout, Salmo trutta from 2000 to 2006 at 287 sampling sites across Switzerland. Almost 7000 fishes were tested for the presence of T. bryosalmonae by histological and immunohistochemical techniques. A good correlation between altitude and water temperature in Swiss rivers could be demonstrated. Therefore, the relation between altitude and sites tested for T. bryosalmonae infected fishes was investigated since water temperature values from these sites were not available. Percentage of sites with positive (infected) fishes was identical for altitudes between 200 and 800 m above sea level (m a.s.l.), while above 800 m a.s.l. only three sites with infected fishes were recorded. Site‐specific prevalence values ranging from 0 to 100% and infection intensities from 0 to 6 were found over the whole altitude range from 200 to 800 m a.s.l., and no correlation with altitude was found. Conditions at altitudes >800 m may not be favourable for the establishment of the infection in fishes. With rising temperatures due to climatic changes, however, the prevalence of T. bryosalmonae infected fishes in altitudes >800 m a.s.l. could increase.     

Photosynthetic pathway,chilling tolerance and cell sap osmotic potential values of grasses along an altitudinal gradient in Papua New Guinea

Summary A total of 22 grass species were examined from 5 sites spanning the altitudinal range 1550–4350 m.a.s.l. The presence of the C₃ or C₄ photosynthetic pathway was determined from ¹³C values and chilling tolerance was assessed on the basis of electrolyte leakage from leaf slices incubated on melting ice. Most of the grasses studied at the lower altitude sites of 1550 m.a.s.l. (annual mean of daily minimum temperature, 14.6° C) and 2600 m.a.s.l. (9.4° C) possessed C₄ photosynthesis and were chill-sensitive. The single except ion was Agrostis avenacea, a montane chill-resistant C₃ species which occurred at 2600 m.a.s.l. The three species apparently most sensitive to chilling were Ischaemum polystachyum, Paspalum conjugatum and Saccharum robustum, all occurring at 1550 m.a.s.l. At the higher altitude sites of 3280 (5.6° C), 3580 (4.0° C) and 4350 (–0.7°C) m.a.s.l., most of the grasses exhibited C₃ photosynthesis and were chill-resistant. However, an Upland population of the C₄ species, Miscanthus floridulus was found at 3280 m.a.s.l. which had acquired chill-resistance as confirmed by additional in vivo variable chlorophyll fluorescence measurements. Cell sap osmotic potential values of the upland grasses at altitudes of 3280–4350 m.a.s.l. were lower (–8.1 to –19.8 bars) than values in grasses from 1550 and 2600 m.a.s.l. (–3.9 to –7.5 bars) due mainly to the presence of non-electrolyte osmoticants, which may be involved in frost avoidance mechanism(s).Abbreviations ABA abscisic acid - F_R the maximal rate of rise of induced chlorophyll fluorescence - s osmotic potential     

Rapid altitudinal migration of mountain plants in Taiwan and its implications for high altitude biodiversity

Mountain systems throughout the globe are characterized by high levels of species richness and species endemism. Biodiversity, however, is not distributed evenly with altitude, but often declines from mid to high altitudes. Conversely, endemic species may be over‐represented at high altitudes. Upward elevational range shifts of mountain species have been reported in response to ongoing changes in climate, yet the reports are dominated by studies on woody species and mountains at high latitudes. We investigated spatial and temporal changes in the mountain biodiversity in the subtropical island of Taiwan, based on historical survey and resurvey data during the period 1906–2006. We found that upper altitudinal limits of mountain plant distributions have risen by ca 3.6 m yr^?1 during the last century, in parallel with rising temperatures in the region. Although species, genus, and family richness decline with altitude, ca 55% of species at the highest altitudes are endemic to the island. Given the steep decline in land area with increasing elevation, these high altitude areas are disproportionately important for plant biodiversity when richness and endemism are standardized by available land area. We argue that the distributional shift that we report, in combination with the altitudinal distribution of plant diversity, is likely to pose a major threat to high mountain species of this highly biodiverse island, a threat that is becoming increasingly evident for high mountain plants throughout the globe.     

海拔梯度变化对中亚热带黄山松土壤微生物生物量和群落结构的影响

全球变暖对陆地生态系统造成一系列生态问题,使这些问题将随着全球平均气温的升高而进一步加剧。海拔梯度变化是研究气候变暖对陆地生态系统影响的一种重要手段。目前为止利用海拔梯度对微生物影响的研究尚未定论,其主要原因是忽略了植被类型的影响。因此,以中亚热带戴云山的3个海拔(1300、1450、1600 m)的黄山松(Pinus taiwanensis)林为研究对象,探究沿海拔梯度的变化,森林土壤微生物生物量和微生物群落结构的响应变化。结果表明:土壤碳氮磷养分(SOC、TN、TP)、微生物生物量氮(MBN)、微生物生物量磷(MBP)和丛枝菌根真菌(AMF)、革兰氏阴性菌(GN)、真菌(Fungi)、总磷脂脂肪酸(T_(PLFA)),细菌∶真菌(F∶B)均随海拔升高显著下降,而革兰氏阳性菌∶革兰氏阴性菌(GP∶GN)随海拔升高呈相反的趋势。冗余分析(RDA)表明,温度(T)和可溶性有机氮(DON)是影响微生物群落结构的最重要的环境因子。研究表明:与1600 m海拔相比,1300 m海拔温度较高,土壤有机质矿化作用较强,土壤速效养分及微生物生物量随之增加,从而提高(Fungi)、细菌(Bacteria)等。因此,未来气候变暖将通过改变土壤碳氮磷养分来影响本区域微生物群落组成结构。这对进一步深入了解气候变化对山地生态系统土壤养分循环过程具有重要意义。     

武夷山不同海拔梯度黄山松土壤有机氮解聚酶活性及其影响因素

土壤有机氮(SON)解聚酶对土壤大分子有机氮的解聚是土壤氮循环的限速步骤,对土壤氮循环至关重要。然而,目前亚热带森林中、高海拔梯度下SON解聚酶活性的动态及其影响因素尚不明确。在武夷山自然保护区海拔1200—2000 m的黄山松林,通过测定5个海拔梯度的土壤环境因子、理化性质和8种SON解聚酶活性的变化,探究了不同海拔梯度下SON解聚酶活性的分布规律及其影响因素。结果表明,除土壤DON含量外,其他测量的土壤环境因子和理化性质在不同海拔梯度下均存在显著的差异。SON解聚酶活性随海拔梯度呈现不同的分布规律：碱性蛋白酶(ALPT)、中性蛋白酶(NPT)、漆酶(Lac)和亮氨酸氨基肽酶(LAP)随海拔升高显著增加,酸性蛋白酶(ACPT)和几丁质酶(Chi)呈现先增后降的趋势,而锰过氧化物酶(Mnp)和谷氨酰胺酶(GLS)在海拔1800 m显著降低(P<0.05)。冗余分析表明,不同海拔梯度下SON解聚酶活性存在明显的聚类,土壤环境因子和理化性质对SON解聚酶活性的解释度高达88.18%。土壤温度(ST),含水率(SM),微生物生物量碳(MBC)和矿质氮(NH~+₄,...     

Do plant families with contrasting functional traits show similar patterns of endemism? A case study with Central African Orchidaceae and Rubiaceae

The influence of functional traits on floristic patterns remains poorly understood in tropical rain forests. This contribution explores whether patterns of endemism of plant species are influenced by their life form and mode of dispersal. We used a comprehensive dataset of 3650 georeferenced plant specimens collected in Cameroon belonging to 115 taxa of Orchidaceae and 207 Rubiaceae endemic to Atlantic Central Africa. Species diversity of each family was compared using raw species richness (SR) and an index of species diversity (S _k ) using subsampling procedure to correct for sampling bias. Measures were compared at three scales (square grids of one half-degree and one-degree per side and ecoregions) and according to elevation and continentality gradients. Species similarity between grid cells was measured using the sample-size corrected NNESS index. For both families, SR and S _k decreased along the continentality gradient. In forest habitats below 1500 m altitude, both Orchidaceae and Rubiaceae show similar endemism patterns, but they differ in intensity. At higher altitudes, S _k is higher for orchids due to the presence of endemic terrestrial taxa in grasslands, where the endemic Rubiaceae flora is rather poor. Substantial endemism observed at the ecoregion level and turnover analysis supported the role of the Sanaga River as a phytogeographical boundary. Similar endemism patterns were observed in lowland forests for Orchidaceae and Rubiaceae, even though Orchidaceae are assumed to have better long distance dispersal capabilities. The dispersal ability of Orchidaceae could be limited by the need of specific mycorhizal fungi for seed germination or host specificity for epiphytic orchids.