Breakdown of the species-area relationship in exotic but not in native forest patches

We studied the pattern of bird species richness in native and exotic forest patches in Hungary. We hypothesized that species-area relationship will depend on forest naturalness, and on the habitat specialization of bird species. Therefore, we expected strong species-area relationship in native forest patches and forest bird species, and weaker relationship in exotic forest patches containing generalist species. We censused breeding passerine bird communities three times in 13 forest patches with only native tree species, and 14 with only exotic trees in Eastern Hungary in 2003. Although most bird species (92%) of the total of 41 species occurred in both exotic and native forests, the species-area relationship was significant for forest specialist, but not for generalist species in the native forests. No relationship between bird species and area was found for either species group in the forest with exotic tree species. The comparison of native versus exotic forest patches of similar sizes revealed that only large (>100 ha) native forests harbor higher bird species richness than exotic forests for the forest specialist bird species. There is no difference between small and medium forest patches and in richness of generalist species. Thus, the species-area relationship may diminish in archipelago of exotic habitat patches and/or for habitat generalist species; this result supports the warning that the extension of exotic habitats have been significantly contributing to the decline of natural community patterns.     

小兴安岭阔叶红松林木本植物种-面积关系

种-面积关系研究是了解植物群落结构的重要途径,是群落生态学的基本问题。不同的研究方法对种-面积关系影响很大。利用黑龙江省小兴安岭两个10.4 hm2样地和5个1.0 hm2样地的调查数据,采用移动窗口法确定各样地的最小取样面积,避免了巢式取样法及随机样方法的不足。并采用4种种-面积关系模型进行拟合,评价各关系模型的适合度。在此基础上,基于最小面积进行模拟随机取样,探讨取样大小对物种数估计精度的影响。研究结果表明:由于拟合曲线模型的适用性及曲线外推可靠性问题的存在,采用拟合曲线的方法所估计的最小面积与实际值偏差较大。实际调查得到的各样地最小面积40 m×40 m—45 m×45 m,说明小兴安岭地区阔叶红松林群落所需的最小面积基本一致,但各样地群落结构的差异却在对取样数量的要求上体现出来。其中丰林与大亮子河样地物种数分布相对均匀,所需最小样方数量较少;而方正与胜山样地物种数分布异质性较大,差异的机理还有待于进一步研究。     

A model for species-area relationships in plant communities

Abstract. A model is proposed for the fitting of species-area curves to data from the Stellenbosch region, South Africa. Basic assumptions of the model are finiteness of the number of species in a finite area, and random distribution of plant species over the region. The model involves a distribution of densities of different species, and the parameters of this distribution are useful for describing and classifying communities. The data of the Stellenbosch region suggest that the assumptions of the model break down in areas greater than 500 m².     

Species-area curves, spatial aggregation, and habitat specialization in tropical forests

The relationship between species diversity and sampled area is fundamental to ecology. Traditionally, theories of the species-area relationship have been dominated by random-placement models. Such models were used to formulate the canonical theory of species-area curves and species abundances. In this paper, however, armed with a detailed data set from a moist tropical forest, we investigate the validity of random placement and suggest improved models based upon spatial aggregation. By accounting for intraspecific, small-scale aggregation, we develop a cluster model which reproduces empirical species-area curves with high fidelity. We find that inter-specific aggregation patterns, on the other hand, do not affect the species-area curves significantly. We demonstrate that the tendency for a tree species to aggregate, as well as its average clump size, is not significantly correlated with the species' abundance. In addition, we investigate hierarchical clumping and the extent to which aggregation is driven by topography. We conclude that small-scale phenomena such as dispersal and gap recruitment determine individual tree placement more than adaptation to larger-scale topography.     

The generation of diversity in systems of patches and ranked dominance

Aim Mac Nally and Lake proposed a statistic (η) for determining whether the diversity in archipelagos is better generated by several small patches (SS‐dominance) or by a few large patches (SL‐dominance). The η statistic improves the study of the generation of diversity in systems of patches, but the dependence of η on a particular species–area relationship may reduce its effectiveness. In this paper we show that η may be affected by the criterion used to distinguish between large and small patches. We propose alternative measures (ranked m‐dominance indices) for the detection of SS/SL dominance, which separate the effects of each class of patch size on the generation of diversity. Location We use previously published species lists from three archipelagos: lizard species on 25 islands in the Gulf of California; non‐introduced species of reptiles of the Canary Islands (order Squamata); and finch species from 19 islands of the West Indies. We also use one artificial data set. Methods Presence–absence data and the rank order of patch areas are used to define the m‐dominance indices, interpreted as measures of preferential size of patches occupied by m species. A Monte Carlo procedure is implemented for testing the significance of the observed indices. Row and column totals in the simulated presence–absence matrices are kept fixed in order to maintain differences in species richness among sites and differences in occurrence frequencies among species, but the allocation of each occurrence to a specific ranked area is randomized. The analyses are exemplified with the three published data sets taken from the literature, and a hypothetical patch system neither SS‐ nor SL‐dominated. Results The new m‐dominance indices identified correctly the hypothetical patch system, while η was positive, suggesting an incorrect SL‐dominant result. For the lizard data set, the standardized ranked m‐dominance was significantly large for small m, confirming an SL‐dominated system. Islands of varying size in the Canary archipelago hosted restricted reptile species, but matrix sparseness seems to have caused the non‐significant results for the m‐dominance indices in this case. The overall pattern of the West Indies system shows that medium‐large islands are dominant, but most Monte Carlo analyses were not significant, also possibly as a result of matrix sparseness. Main conclusions The m‐dominance indices have the virtue of summarizing composition–area relationships, and including Monte Carlo procedures for testing whether patch size and the type of species distribution (species restricted to m patches, m = 1,…,s) are random or not. When m is as low as 1 or 2, the m‐dominance indices may typify the role of restricted species on the generation of diversity in the system of patches. The procedure developed here can be generalized to include other ordinal properties of patches, such as isolation or habitat heterogeneity.     

Minimum sampling area for the monitoring of herb diversity in riparian zone of temperate rivers,China

Optimal sampling area for biodiversity monitoring is a classical scientific topic for the biodiversity research in view of the cost, human resources and ecological significance. However, how much sampling area is enough for biodiversity monitoring in riparian area, the ecotone among freshwater and terrestrial system? Whether the optimal sampling areas are different among ecoregions? To explore these scientific questions, the minimum sampling area of riparian herbs was studied in Taizi river, Liaoning province, China. The species-area relationship was modeled using average species richness in the same area (2.25, 4.5, 6.75 and 9 m²) of 55 sites distributed along riparian zone of Taizi river water course. The power model S = aA ^b modeled best, and was selected to fit species-area curves. The minimum sampling areas for total species and dominant families were calculated via the selected model and corresponding estimated species richness. Results showed that the minimum sampling areas (MSAs) for herbs diversity monitoring in whole basin, highland ecoregion, midland ecoregion and lowland ecoregion of Taizi river were 12.82, 12.06, 13.46 and 13.08 m²,respectively. The MSAs of dominant families Compositae species and Graminale species were similar to that of total species. The minimum sampling area of Taizi river riparian zone was similar to other temperate riparian grassland and wet grassland, larger than dry grassland and salt meadow. So we did not need consider ecoregion difference for temperate riparian herbs diversity monitoring in watershed scale.     

Isolation and patch size drive specialist plant species density within steppe islands: a case study of kurgans in southern Ukraine

The fragmentation and isolation of preserved habitat patches within intensive agricultural landscape threaten species survival in steppes. In Ukraine, <5 % of the original steppe area has survived, mostly in nature reserves, loess ravines and kurgans (burial mounds). The latter are small, but relatively numerous objects. The aim of this study was to investigate whether plant species density (= the number of species per plot) within small steppe patches on kurgans differs from that within large steppe enclaves in southern Ukraine. Another aim was to determine the influence of patch area, isolation and heat load index on species density on kurgans. Presence-absence data for vascular plant species were collected on plots of a size of 100 and 1 m². Thirty kurgans and ten sites within large steppe enclaves were sampled. Every noted species was classified as specialist or generalist. For kurgans data on area and degree of isolation were collected. Additionally the heat load index for plots on kurgans was calculated. The density of habitat specialists was higher in larger steppe enclaves than on kurgans at both spatial scales. On kurgans the most important predictors of specialist density were isolation (negative) and kurgan area (positive). The density of generalists was positively affected by the heat load index. Kurgans can provide refuges for steppe plant species. However, our results show that over a longer time period, proximity to larger steppe refuges is important to maintain species diversity within these small patches.     

Patch size has no effect on insect visitation rate per unit area in garden-scale flower patches

Previous studies investigating the effect of flower patch size on insect flower visitation rate have compared relatively large patches (10–1000s m²) and have generally found a negative relationship per unit area or per flower. Here, we investigate the effects of patch size on insect visitation in patches of smaller area (range c. 0.1–3.1 m²), which are of particular relevance to ornamental flower beds in parks and gardens. We studied two common garden plant species in full bloom with 6 patch sizes each: borage (Borago officinalis) and lavender (Lavandula × intermedia ‘Grosso’). We quantified flower visitation by insects by making repeated counts of the insects foraging at each patch. On borage, all insects were honey bees (Apis mellifera, n = 5506 counts). On lavender, insects (n = 737 counts) were bumble bees (Bombus spp., 76.9%), flies (Diptera, 22.4%), and butterflies (Lepidoptera, 0.7%). On both plant species we found positive linear effects of patch size on insect numbers. However, there was no effect of patch size on the number of insects per unit area or per flower and, on lavender, for all insects combined or only bumble bees. The results show that it is possible to make unbiased comparisons of the attractiveness of plant species or varieties to flower-visiting insects using patches of different size within the small scale range studied and make possible projects aimed at comparing ornamental plant varieties using existing garden flower patches of variable area.     

吉林蛟河42 hm2针阔混交林样地植物种-面积关系

 种-面积关系是生态学中的基本问题, 其构建方式对种-面积关系的影响以及最优种-面积模型的选择仍然存在争议。该文利用吉林蛟河42 hm²针阔混交林样地数据, 分别采用巢式样方法和随机样方法建立对数模型、幂函数模型和逻辑斯蒂克模型, 并通过赤池信息量准则(AIC)检验种-面积模型优度。结果表明, 种-面积关系受到取样方法的影响, 随机样方法的拟合效果优于巢式样方法。采用随机样方法构建的幂指数模型(AIC = 89.11)和逻辑斯蒂克模型(AIC = 71.21)优于对数模型(AIC = 113.81)。根据AIC值可知, 随机样方法构建的逻辑斯蒂克模型是拟合42 hm²针阔混交林样地种-面积关系的最优模型。该研究表明: 在分析种-面积关系时不仅应考虑尺度效应, 还需注意生境变化及群落演替的影响。     

Which Models Are Appropriate for Six Subtropical Forests: Species-Area and Species-Abundance Models

The species-area relationship is one of the most important topic in the study of species diversity, conservation biology and landscape ecology. The species-area relationship curves describe the increase of species number with increasing area, and have been modeled by various equations. In this paper, we used detailed data from six 1-ha subtropical forest communities to fit three species-area relationship models. The coefficient of determination and F ratio of ANOVA showed all the three models fitted well to the species-area relationship data in the subtropical communities, with the logarithm model performing better than the other two models. We also used the three species-abundance distributions, namely the lognormal, logcauchy and logseries model, to fit them to the species-abundance data of six communities. In this case, the logcauchy model had the better fit based on the coefficient of determination. Our research reveals that the rare species always exist in the six communities, corroborating the neutral theory of Hubbell. Furthermore, we explained why all species-abundance figures appeared to be left-side truncated. This was due to subtropical forests have high diversity, and their large species number includes many rare species.     

Peculiarities of the biotopic distribution of orthoptera in the typical steppe of European Russia

The taxonomic composition, ecological and spatial distribution of orthopterans were studied in different vegetation types of the typical steppe on the left bank of the Volga River basin (Saratov Prov.). Some species showed clear selectivity with respect to specific features of the soil and vegetation, despite significant annual fluctuations in the taxonomic composition and abundance of local populations. Two groups can be distinguished: the polytopic species and those inhabiting intrazonal communities but not typical steppe habitats. The orthopteran complexes of the zonal and halophytic habitats show a relatively high similarity; they differ well from those of mesophytic plant communities, restricted to the lower mesorelief areas. Intrazonal habitats with mesophytic conditions comprise almost 45% of the species diversity of orthopterans in the typical steppe subzone, and reveal the greatest diversity of life forms of these insects. The data obtained are of interest for monitoring the successive changes in steppe ecosystems affected by both climatic and anthropogenic factors.     

Species associations and nurse plant effects in patches of high-Andean vegetation

Abstract. In high-elevation communities of the southern Andes, plant cover is low due to severe environmental conditions and vegetation occurs mostly as isolated small (< 1 m²⁾ patches. Most patches are dominated by flat cushion plants. We evaluated patterns of plant species co-occurrence and species affinity for patches with and without cushion plants and different species richness. We mapped and recorded species composition of patches occurring within two 20 m × 20 m plots at the NE slope of Cerro Chall-Huaco, Nahuel Huapi National Park, Argentina. In these plots, we identified 32 and 24 plant species, and a maximum of 15 and 12 species per patch, respectively. The community was characterized by positive associations between species. Patches in which either of the common cushion plants Mulinum leptacanthum and Oreopolus glacialis occurred sustained richer communities than patches in which they were absent. Patches dominated by different cushion plants did not differ in species composition, but species differed in their affinities for patches with different numbers of species. Because richness increased with patch size and patch size with time, differential affinities of plant species suggest that successional changes take place in the patches. Some small herbaceous species appear to act as late colonizers, mostly restricted to species-rich patches. Flat cushion plants are considered ‘nurse plants’; they strongly modify micro-environmental conditions and allow establishment and survival of associated species.     

Temporal variation in species-area curves for invertebrates in clumps of an intertidal mussel

We examined the temporal variation in the relationships between the number of invertebrate species, and of total individuals inhabiting clumps of the intertidal mussel Brachidontes rostratus and the area of the clumps We collected clumps in four seasons - autumn, winter, spring and summer - from a rocky shore in south-eastern Australia Positive curvilinear relationships between species number and area were recorded for all seasons but fewer species for a given area were found in autumn and summer compared with winter and spring These species-area relationships were different from those predicted from a passive sampling model (Random Placement Model) Positive relationships between number of individuals and area were also recorded but these did not vary between seasons There was no short-term difference (i e between phases of tide and day) in species or individual number in clumps Seasonal variation, and small-scale spatial unpredictability in recruitment patterns are potentially important determinants of species numbers in this system The seasonal differences we have recorded for mussel clumps suggest that future studies on island systems particularly in marine habitats should consider temporal variation in species-area relationships and that conclusions from previous comparisons of species-area curves based on one-off sampling must only be tentative     

内蒙古锡林郭勒草原大针茅-克氏针茅群落的种间关联特征分析

内蒙古锡林郭勒草原处于我国典型草原分布区, 但部分地区有戈壁针茅(Stipa gobica)等荒漠成分侵入, 并与大针茅(S. grandis)和克氏针茅(S. krylovii)共同形成斑块状格局分布, 目前尚不清楚群落中优势种之间的相互作用关系。采用2 × 2列联表, 通过方差分析、Pearson相关分析和Spearman秩相关分析等研究方法, 对大针茅+克氏针茅群落的大针茅斑块、克氏针茅斑块和戈壁针茅斑块中的24种主要植物的种间联结动态进行了定量分析。结果表明: 1)群落主要成分总体上种间联结呈无关联, 种间关联松散; 2) 3种针茅斑块的种间关联分析, 验证了由于干扰、竞争、土壤环境与植物相互作用形成的斑块分布格局, 此结果为种对正、负关联理论提供了有力证据; 3) 同一种对的联结性质(正关联或负关联)或关联程度因斑块不同而发生改变, 根据24个优势种群对环境的适应方式和主导生态因素, 可将它们划分为3大生态种组。     

鄱阳湖湿地典型草洲植物群落种-面积关系

为了解鄱阳湖湿地草洲植物群落的结构,对其3种典型草洲植物群落种-面积关系进行了研究。采用巢式样方法调查植物物种数量,并用3种非饱和曲线拟合种-面积方程。结果表明,基于实测数据,3个草洲物种数随着取样面积的增加先快速增加后趋于平稳;群落最小取样面积均为30 m~2。幂函数模型对3个草洲群落的种-面积关系拟合效果均为最佳,3个草洲群落的RSE分别为0.35、0.35和0.56,AAD分别为0.23、0.17和0.35,AARD分别为0.06、0.02和0.07,而指数模型、Fisher模型的拟合效果一般。指数模型计算得到的不同比例因子下3个草洲最小取样面积与实际情况最为吻合。这为鄱阳湖区进行植物群落数据采集的样方设置提供了理论参考。     

塔里木荒漠河岸林灰胡杨群落最小面积确定与研究方法比较

荒漠河岸林是塔里木极端干旱区唯一的森林群落类型,群落结构组成简单。我们采用种-面积曲线、群落系数-面积曲线与重要值-面积曲线3种方法对塔里木河上游荒漠河岸林灰胡杨（Populus pruinosa Schrenk）群落最小面积进行研究。结果显示,4种饱和种-面积曲线的拟合效果差异明显,S=aA/（1+bA）和S=a（1-e^-bA）模型拟合的相关系数较高（P < 0.01）,拟合效果优于其它2种模型。当取样面积为100 m²时,可包括群落60%~80%的物种数,取样面积为200 m²时,则可包括群落90%的物种数。群落系数-面积曲线与重要值-面积曲线2种方法确定的群落最小面积均为400 m²,二者克服了种-面积曲线仅关注物种出现与否和饱和种的估算问题,拟合结果更符合实际情况,更适用于塔里木荒漠河岸林最小取样面积的确定。本研究结果表明荒漠河岸林包括60%、80%、90%群落物种的临界抽样面积分别为100 m²、200 m²和400 m ²,可以满足不同研究精度的要求;塔里木河上游荒漠河岸林灰胡杨群落学调查的最适取样面积是400 m²。     

Colonization of experimentally disturbed patches by stream macroinvertebrates in the Acheron River,Victoria

Twenty-five patches (1 m²) of natural stream substratum in the Acheron River, Victoria, were physically disturbed by kicking and raking during winter 1986 and summer 1987. The macroinvertebrate composition of these disturbed patches was examined at various times over the following 71 days, and compared with adjacent undisturbed control patches sampled concurrently. The disturbance did not alter the particle-size distribution (> 150 μm) of the disturbed patches. Organic material was reduced in the disturbed patches by about 70% in each season, but returned to control levels within 21 days in winter and 8 days in summer. The total number of species, and the density of species and individuals were all significantly reduced by the disturbance. Recovery of species density was complete after 21 days during winter and 8 days during summer, and the density of individuals recovered after 71 days during winter and 8 days during summer. The differences were due to the slower colonization rate of Chironomidae in winter, either because of a lower drift rate, or a slower recovery of detritus in winter. Individual species showed variations in colonization patterns, most increasing steadily at various rates, with some declining after an initial rapid increase (e.g. Baetis pp.). In the latter case, the density changes were mirrored in the control patches, emphasizing the need to take control samples concurrently with experimental samples. In each season, the species remaining immediately following the disturbance, and those subsequently colonizing the disturbed patches were in the same rank order (Spearman Rank correlation) as their occurrence in the control patches, suggesting that no taxa were differentially affected by the treatment. No evidence was found to allow the application of the Intermediate Disturbance Hypothesis to explain species diversity at the scale of this study. It appears that current hypotheses developed to explain the relationship between diversity and disturbance in sessile communities do not apply to highly mobile communities in streams.     

Evaluation of species-area functions using Sonoran Desert plant data: not all species-area curves are power functions

Ecologists have been studying the relationship between species richness and area for about a century. As area increases, more species are typically observed. Many mathematical functions have been proposed to describe the pattern of increase. Numerous researchers have assumed that the relationship is a power function despite the fact that there are many possible alternatives. There has been limited work in evaluating which species-area functions are most appropriate for field data. This study examines which of a variety of functions best describe how Sonoran Desert plant species richness of remnant habitat patches in the Phoenix metropolitan area vary with sampled area and the area of entire patches. No single species-area function was adequate for describing all empirical datasets. Sample curves of woody species were most frequently best described by the sigmoid logistic, Hill, and Lomolino functions, whereas herbaceous datasets were best fit by the sigmoid logistic or convex rational functions. A curve depicting the relationship between patch-level woody species richness and patch area was best fit by the convex exponential function. The power function provided the best fit for only one case. This study demonstrates the utility of testing alternative functions for statistical fit rather than assuming that any particular equation adequately describes the species-area relationship.     

Determination of species-area relationships and minimum sampling area for the shrub communities in the arid valley in the upper reach of the Minjiang River, China

The minimum sampling areas (MSAs) for the shrub communities in the arid valley in the upper reach of the Minjiang River, China, were studied by fitting community species-area relationships using 3 types of equations. The MSAs were determined at the proportional factor (ρ) 0.6, 0.7, 0.8 and 0.9. The proportional factors represent the proportion of the number of species within a sampling plot in the total number of species. The MSAs of the shrub communities at different elevations and on different slope faces for ρ = 0.6, 0.7 and 0.8 were all around 100 m². Hence, the MSAs could be set to be 100 m² (10 m × 10 m) at 60%–80% precision levels. For ρ = 0.9, that is, for a 90% precision level, the MSAs were less than 200 m² (10 m × 20 m). The MSAs and species richness increased gradually with the rising elevation. At the elevation below 2000 m, the MSAs and species richness on the north-facing slope were larger than those on the south-facing slope. However, at the elevation around 2200 m, there was no difference amongst different facing slopes. For the shrub communities in the arid valley in the upper reach of the Minjiang River, the species-area curves by fitting the first two equations are better than that by fitting the third equation.