Rodent burrow network dynamics under human‐induced landscape transformation from desert to steppe in Kalmykian rangelands

Rodents play an important role in rangelands through the engineering of extensive burrow systems, which provides key habitats for many animal and plant species. We have analyzed the long‐term variation in the abundance and distribution of rodent burrows in grazing ecosystems of southern Russia (Kalmykia) under the landscape change from desert to steppe caused by the drastic reduction of livestock after the collapse of the USSR in the early 1990s. We conducted burrow surveys in the “desert” (1980) and “steppe” (2017) periods on 19 3‐km transects. We found considerable changes in burrow abundance and distribution, as well as evidence of desert habitat fragmentation and isolation caused by the expansion of tall‐grass communities. Burrows of the open‐dwelling diurnal ground squirrel (Spermophilus pygmaeus), the dominant and the keystone species during the “desert” period, almost completely disappeared from the rodent burrow network by 2017, indicating significant habitat loss. In contrast, the burrows of the folivorous social vole (Microtus socialis) which was rare in the 1980s, became abundant and ubiquitously distributed. The burrow density of the desert‐dwelling psammophilous midday gerbil (Meriones meridianus) decreased, while the distances between occupied patches increased, indicating desert habitat fragmentation and loss of population connectivity. Burrows of the folivorous tamarisk gerbils (M. tamariscinus) were recorded only sporadically in both 1980 and 2017. The observed changes in the rodent burrow network, the key component of grazing ecosystems, correlate with rodent species ecology and can have long‐term and important consequences for ecosystem functioning.     

草原景观下昆虫群落及种群对生境破碎化的反应

生境破碎化是制约生物多样性重要的“瓶颈”之一。本研究在已有资料的基础上,论述了影响生物群落结构和种群动态过程的生境破碎化的生物反应特征,以及破碎化生境对生物多样性和种间关系的影响机理及基本理论假说,重点对草原景观下有关昆虫群落结构、丰富度、种群数量与动态、种间关系及群落次生演替等与生境破碎化关系的试验研究进行归纳总结, 提出了在草原环境下进行破碎化生境与昆虫群落和种群发生关系研究的问题及优势条件,指出了种间关系和次生演替与生境斑块格局的关系是草原生物多样性保护研究的关键之一。     

牛背梁国家级自然保护区羚牛种群状况及濒危原因分析

陕西牛背梁国家级自然保护区是中国目前唯一以羚牛及其栖息地为主要保护对象的森林和野生动物类型自然保护区。调查表明,保护区内分布有羚牛206～224头,呈片段化分布在6个生境斑块内,以210国道为界,保护区内羚牛的分布格局为西多东少。虽然保护区内羚牛种群数量和分布区均呈缓慢增长的趋势,但频繁的人为干扰,尤其是保护区内公路、铁路建设和由此导致的生境分割,仍威胁着保护区内羚牛种群的持续生存。     

Corridor connecting giant panda habitats from north to south in the Min Mountains,Sichuan, China

The giant panda faces severe threats from habitat fragmentation and isolation. Currently, giant panda populations have been fragmented into 30 habitat patches. The disappearance of isolated small populations and studies on the genetic diversity of various populations have shown that small isolated panda populations are at a high risk of dying out completely. Habitat fragmentation has seriously impaired the ability of the giant panda to resist climate changes and other natural disasters, such as large‐scale, synchronous bamboo blooming. The Min Mountains have the largest population of pandas in China, numbering 581 individuals and accounting for 52% of the total (1114) in China. Geographic isolation means that giant pandas in the Min Mountains are divided into two populations (population A in the north and population B in the south). Population B, which had only 42 individuals in 1989, is severely threatened by high‐density human populations and the loss of genetic diversity. However, we have identified an important corridor connecting the two populations. This paper explains the importance and the feasibility of reestablishing this corridor. Due to the special geographic locations of these two populations (two rivers block the migration of giant pandas between south and north), the corridor is the only passage for giant pandas in the region. Recent studies have also shown an increase of giant panda activity in the area of the corridor. However, vegetation in the corridor has been severely degraded. Bamboo forest must be restored in this area to provide food for the pandas during migration. The effects of human activities must be reduced in order to maintain panda habitat. We believe that a restored corridor will be of great benefit to the survival of giant pandas in the Min Mountains, especially for population B. Successful re‐establishment of a corridor will be a valuable model for corridor construction in the future.     

The integration of climate change,spatial dynamics,and habitat fragmentation: A conceptual overview

A growing number of studies have looked at how climate change alters the effects of habitat fragmentation and degradation on both single and multiple species; some raise concern that biodiversity loss and its effects will be exacerbated. The published literature on spatial dynamics (such as dispersal and metapopulation dynamics), habitat fragmentation and climate change requires synthesis and a conceptual framework to simplify thinking. We propose a framework that integrates how climate change affects spatial population dynamics and the effects of habitat fragmentation in terms of: (i) habitat quality, quantity and distribution; (ii) habitat connectivity; and (iii) the dynamics of habitat itself. We use the framework to categorize existing autecological studies and investigate how each is affected by anthropogenic climate change. It is clear that a changing climate produces changes in the geographic distribution of climatic conditions, and the amount and quality of habitat. The most thorough published studies show how such changes impact metapopulation persistence, source–sink dynamics, changes in species' geographic range and community composition. Climate‐related changes in movement behavior and quantity, quality and distribution of habitat have also produced empirical changes in habitat connectivity for some species. An underexplored area is how habitat dynamics that are driven by climatic processes will affect species that live in dynamic habitats. We end our discussion by suggesting ways to improve current attempts to integrate climate change, spatial population dynamics and habitat fragmentation effects, and suggest distinct areas of study that might provide opportunities for more fully integrative work     

Diet shift in bank voles induced by competition from grey‐sided voles?

Grey‐sided voles (Myodes rufocanus) and bank voles (Myodes glareolus) co‐exist in boreal forests in northern Scandinavia. Previous studies suggest that the 2 species interact interspecifically, the grey‐sided vole being the dominant species. We tested the hypothesis that bank voles shift their diet due to competition with the dominant grey‐sided vole by studying stable isotope ratios in both species. Muscle samples were taken from voles in patches of old forest occupied by only bank voles and patches of old forest occupied by both grey‐sided voles and bank voles. We found that: (i) stable isotope ratios of bank voles differed in areas with and without grey‐sided voles; and that (ii) the stable isotope ratios of bank voles were more similar to those of grey‐sided voles in areas where grey‐sided voles were absent. Our data suggests that grey‐sided voles forced bank voles to change their diet due to interspecific competition.     

Habitat evaluation for outbreak of Yangtze voles (Microtus fortis) and management implications

Rodent pests severely damage agricultural crops. Outbreak risk models of rodent pests often do not include sufficient information regarding geographic variation. Habitat plays an important role in rodent–pest outbreak risk, and more information about the relationship between habitat and crop protection is urgently needed. The goal of the present study was to provide an outbreak risk map for the Dongting Lake region and to understand the relationship between rodent–pest outbreak variation and habitat distribution. The main rodent pests in the Dongting Lake region are Yangtze voles (Microtus fortis). These pests cause massive damage in outbreak years, most notably in 2007. Habitat evaluation and ecological details were obtained by analyzing the correlation between habitat suitability and outbreak risk, as indicated by population density and historical events. For the source‐sink population, 96.18% of Yangtze vole disaster regions were covered by a 10‐km buffer zone of suitable habitat in 2007. Historical outbreak frequency and peak population density were significantly correlated with the proportion of land covered by suitable habitat (r = 0.68, P = 0.04 and r = 0.76, P = 0.03, respectively). The Yangtze vole population tends to migrate approximately 10 km in outbreak years. Here, we propose a practical method for habitat evaluation that can be used to create integrated pest management plans for rodent pests when combined with basic information on the biology, ecology and behavior of the target species.     

Habitat restoration is the greatest challenge for population recovery of Hainan gibbons (Nomascus hainanus)

Hainan gibbons are among the world's most critically endangered primates, with a remaining population of only 35 individuals distributed across 5 social groups in the Bawangling Branch of the Hainan Tropical Rainforest National Park, China. Habitat conversion and forest fragmentation over the past 40 years have reduced their geographical distribution by 95%. In the absence of a quantitative assessment of the availability of remaining suitable habitat, it is unclear whether this species can survive to the end of this century. We used behavioral observations, ArcGIS, remote sensing, stereo optical imagery, and MaxEnt modeling to identify patterns of Hainan gibbon range use and compare changes in the distribution of suitable forest types and areas of forest fragmentation over the past 20 years (2000–2020). The results indicate that the combined range of the 5 extant Hainan gibbon groups totaled 14.89 km². The home range of the smallest group (Group E, 3 individuals) was 1.51 km², which likely represents the minimum home range size for this species. The remaining area of highly suitable and moderately suitable habitat totals 26.9 km². However, habitat connectivity across the gibbon range is very low (less than 0.5), limiting the ability of Hainan gibbons to move between forest patches. The results of this study indicate that the availability of suitable habitat in Bawangling is insufficient to allow for future Hainan gibbon population growth. Therefore, immediate action must be taken to restore, reforest, and establish ecological corridors to reconnect areas of suitable habitat for these critically endangered gibbons.     

Influence of food availability,plant productivity,and indigenous forest use on ranging behavior of the endangered samango monkey (Cercopithecus albogularis schwarzi), in the Soutpansberg Mountains,South Africa

Understanding the determinants of ranging patterns in species susceptible to habitat fragmentation is fundamental for assessing their long‐term adaptability to an increasingly human‐dominated landscape. The aim of this study was to determine and compare the influence of ground‐based food availability, remotely sensed plant productivity, and indigenous forest use on the ranging patterns of the endangered samango monkey (Cercopithecus albogularis schwarzi). We collected monthly ranging data on two habituated samango monkey groups, from February 2012 to December 2016, from our field site in the Soutpansberg Mountains, South Africa. We used linear mixed models to explore how food availability, plant productivity, and indigenous forest use influenced monthly ranging patterns, while controlling for group size, number of sample days and day length. We found that as more areas of high plant productivity (derived from remotely sensed EVI) were incorporated into the ranging area, both total and core monthly ranging areas decreased. In addition, both total ranging area and mean monthly daily path length decreased as more indigenous forest was incorporated into the ranging area. However, we found no effect of either ground‐based food availability or remotely sensed plant productivity on ranging patterns. Our findings demonstrate the behavioral flexibility in samango monkey ranging, as samangos can utilize matrix habitat during periods of low productivity but are ultimately dependent on access to indigenous forest patches. In addition, we highlight the potential of using remotely sensed areas of high plant productivity to predict ranging patterns in a small ranging, forest‐dwelling guenon, over ground‐based estimates of food availability.     

Effect of ENSO-driven precipitation on population irruptions of the Yangtze vole Microtus fortis calamorum in the Dongting Lake region of China

The Yangtze vole (Microtus fortis Buechner, 1889) is a small herbivore species that inhabits lake beaches in the Dongting Lake region along the Yangtze River in Southern China. Its population shows strong oscillations during the wet season due to summer precipitation-induced immigration away from the lake into adjacent rice fields. The effect of El Niño-Southern Oscillation-driven precipitation on population abundance and growth of the vole species is not fully understood. We undertook an analysis of the combined data of 4 time series covering 1981–2006 from 4 different sites and a separate analysis on a single time series (1981–2006) from one site. Our results demonstrate that a dual effect of El Niño-Southern Oscillation-driven precipitation on the population abundance of voles is time-dependent: precipitation in the current year has a positive effect, whereas precipitation in the previous year has a negative effect. The dual effect of precipitation on vole population is well explained by the unique interactions among vole population, precipitation water level and the lake beach habitat around Dongting Lake. We found that drier than average weather of the previous year benefited voles because their breeding habitats, lake beaches, were exposed for long stretches of time. Wet weather was found to increase the number of voles inhabiting rice fields because as the water level of the lake rose they were forced from beaches into surrounding rice fields. Summer precipitation in the Dongting Lake region was found to be positively associated with the sea surface temperature (SST) of the eastern tropical Pacific Ocean of the previous year and winter SST and spring SST of the current year. Annual rates of increase in the vole population of the reconstructed time series are negatively associated with the vole abundance and autumn precipitation of the previous year and winter precipitation of the current years. These results suggest that both extrinsic and density-dependent intrinsic factors may affect population dynamics of the Yangtze voles.     

割草地群落特征与土壤化学性质对利用年限的响应

对呼伦贝尔不同利用年限的贝加尔针茅(Stipa baicalensis)+日阴菅(Carexpe pediformis)和羊草(Ley-mus chinensis)+杂类草两种类型的割草地群落特征、植物营养成分及土壤营养成分进行了比较分析。结果表明,多年刈割使群落盖度降低,贝加尔针茅株丛破碎化、小型化,羊草退化;多年刈割的贝加尔针茅+日阴菅样地群落Mar-garlef丰富度指数、Shannon-Wiener多样性指数均高于同类型围封3年的样地,羊草+杂类草割草利用多年的样地Margarlef丰富度指数高于利用5年的样地。随刈割年限的增加,蔷薇科、菊科、毛茛科等一年生植物随之增加,地上生物量、枯落物现存量随着刈割年限的增加而降低;多年刈割使土壤有机质、全氮、速效氮的含量降低。     

锡林郭勒草原布氏田鼠种群数量预测

布氏田鼠是锡林郭勒草原主要鼠种之一,是种群数量极不稳定种类,自20世纪70年代以来有过3次大发生:1972～1976年、1984～1988年、2003年至今;布氏田鼠数量变动经过低谷期、上升期、高峰期和下降期,一般上升期、下降期分别为2年,高峰期1～2年,低谷期7～12年.根据布氏田鼠数量变动规律,2005年为高峰期,2006年为高峰期后期,因此2006年春季数量较多,至秋季进入下降期.建议2006年春季开展大面积灭鼠,在锡林郭勒草原建立监测站,开展预测预报.     

Voles and weasels in the boreal Fennoscandian small mammal community: what happens if the least weasel disappears due to climate change?

Climate change, habitat loss and fragmentation are major threats for populations and a challenge for individual behavior, interactions and survival. Predator–prey interactions are modified by climate processes. In the northern latitudes, strong seasonality is changing and the main predicted feature is shortening and instability of winter. Vole populations in the boreal Fennoscandia exhibit multiannual cycles. High amplitude peak numbers of voles and dramatic population lows alternate in 3–5‐year cycles shortening from North to South. One key factor, or driver, promoting the population crash and causing extreme extended lows, is suggested to be predation by the least weasel. We review the arms race between prey voles and weasels through the multiannual density fluctuation, affected by climate change, and especially the changes in the duration and stability of snow cover. For ground‐dwelling small mammals, snow provides thermoregulation and shelter for nest sites, and helps them hide from predators. Predicted increases in the instability of winter forms a major challenge for species with coat color change between brown summer camouflage and white winter coat. One of these is the least weasel, Mustela nivalis nivalis. Increased vulnerability of wrong‐colored weasels to predation affects vole populations and may have dramatic effects on vole dynamics. It may have cascading effects on other small rodent–predator interactions and even on plant–animal interactions and forest dynamics.     

The potential use of fractals in epidemiology

For diseases that are transmitted through parasitic vectors (e.g. tick-borne diseases), the potential distribution and impact of such diseases can be anticipated by studying the distribution of their vectors. Vector distribution is a matter of suitable habitat, which is the sum of a wide range of environmental factors. From remotely sensed data, it is possible to distinguish areas that will provide the most beneficial habitat(s) for a given tick species. The key point is that such data come in the form of patches. The stability of these patches, and therefore that of the tick vectors and the diseases that they transmit, can be mathematically measured using fractal dimensions (D). These fractal dimensions can then be directly related to a non-Markovian (i.e. history dependent) rate of asymptotic decay (H) by using the equation (D=2−H). It is this rate of decay (H) that measures the stability of a given patch(es) of tick habitat(s). If a time series of remotely sensed data is available, changes in the stability (H) can be checked over time. Ultimately, fluctuations of these patches of suitable habitats suggest changes in the tick, and therefore disease, populations. Such fluctuations could destabilize enzootically stable disease populations, or introduce the vectors and diseases into previously naive herds.

As an example of this fractal based measurement of habitat stability, this paper presents empirical evidence of the stability of grass patches in a communal land in Zimbabwe, using data from an aerial photograph. Beyond the practical aspects of measuring the patches, and obtaining their H values, the test data demonstrate that there are at least two distinctive, size based, dynamical systems within the whole set of patches. Generally, patches of a larger size are mathematical less stable than those of a smaller size. The next research objective for the use of such a mathematical tool is to take the concept and apply it on an even larger scale, with the first step undoubtedly being to define what environmental factors constitute suitable habitats for the important tick vector species.     

Wildlife Responses to Vegetation Height Management in Cool-season Grasslands

Herbaceous vegetation comprises the main habitat type in cool-seasons grasslands and can be managed by various methods. We compared changes in plant communities and bird and mammal use of grasslands that were not managed, managed by mechanical methods (mowing), or managed by chemical methods (plant growth regulator). This 1-year study was conducted from May through October 2003 in Erie County, Ohio. Twelve circular 1.5 ha plots were established: 4 were not managed, 4 were mowed to maintain vegetation height between 9–15 cm, and 4 were sprayed with a plant growth regulator and mowed when vegetation exceeded 15 cm. We monitored vegetation growth, measured plant community composition, and observed all plots for wildlife activity each week. Vegetation in unmanaged plots was taller and denser (P < 0.001) than vegetation in mowed and growth regulator plots. Plant community characteristics differed among study plots (P < 0.001); managed plots had higher grass cover and lower woody cover than unmanaged plots. We observed more (P < 0.001) total birds per 5-minute survey in unmanaged than mowed or growth regulator plots. We observed more (P < 0.001) white-tailed deer (Odocoileus virginianus) in mowed plots than either control or growth regulator plots. We captured 13 small mammals in unmanaged plots and no small mammals in managed plots. Applying the plant growth regulator was not a cost-effective alternative to mowing for managing vegetation height in our study. Vegetation height management practices altered plant communities and animal use of grassland areas and thus might be useful for accomplishing species-specific habitat management objectives.     

Mowing Wyoming Big Sagebrush Communities With Degraded Herbaceous Understories: Has a Threshold Been Crossed?

Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis &lsqb;Beetle & A. Young] S.L. Welsh) plant communities with degraded native herbaceous understories occupy vast expanses of the western United States. Restoring the native herbaceous understory in these communities is needed to provide higher-quality wildlife habitat, decrease the risk of exotic plant invasion, and increase forage for livestock. Though mowing is commonly applied in sagebrush communities with the objective of increasing native herbaceous vegetation, vegetation response to this treatment in degraded Wyoming big sagebrush communities is largely unknown. We compared mowed and untreated control plots in five Wyoming big sagebrush plant communities with degraded herbaceous understories in eastern Oregon for 3 yr posttreatment. Native perennial herbaceous vegetation did not respond to mowing, but exotic annuals increased with mowing. Density of cheatgrass (Bromus tectorum L.), a problematic exotic annual grass, was 3.3-fold greater in the mowed than untreated control treatment in the third year posttreatment. Annual forb cover, largely consisting of exotic species, was 1.8-fold greater in the mowed treatment compared to the untreated control in the third year posttreatment. Large perennial grass cover was not influenced by mowing and remained below 2%. Mowing does not appear to promote native herbaceous vegetation in degraded Wyoming big sagebrush plant communities and may facilitate the conversion of shrublands to exotic annual grasslands. The results of this study suggest that mowing, as a stand-alone treatment, does not restore the herbaceous understory in degraded Wyoming big sagebrush plant communities. We recommend that mowing not be applied in Wyoming big sagebrush plant communities with degraded understories without additional treatments to limit exotic annuals and promote perennial herbaceous vegetation.     

修剪对高羊茅生长及草坪质量的影响

研究了不同修剪高度和修剪频率条件下,南京地区高羊茅的生长状况和草坪质量。方差分析表明,低剪（４ｃｍ）的生长量明显高于中剪（６ｖｍ）和高剪（９ｃｍ）,而草坪质量低于高、中剪;高频率修剪（１周２次）的生长量显著高于中频（１周１次）和低频（２周１次）,而草坪质量低于中、低频。因此,在管理上应适当采取高剪（６￣９ｃｍ）和低频（１￣２周１次）,既可以提高草坪质量,又可减轻管理强度。试验结果表明,南京地区高羊     

公路对天山马鹿（Cervus elaphus songaricus）种内遗传分化的影响

为研究公路对大型哺乳动物造成的影响,分别采集新疆省道110、203、303公路两侧的天山马鹿粪便样本,采用5个微卫星位点进行个体识别后利用Arlequin3．11进行遗传距离、基因多样性、杂合度等测定分析。结果表明：5个微卫星均具有很好的多态性,5地区中松树塘与寒气沟、白石头马鹿的遗传距离最远,松树塘马鹿的基因杂合度、基因型数量均最低;小西沟与白杨沟马鹿之间遗传距离为负值,其基因杂合度、基因型无显著性差异（P〉0．05）。说明公路对栖息地的分割状态不同,会导致种群的遗传情况改变。当公路仅深入栖息地没有将栖息地割裂时,公路两旁种群无差异;当栖息地被公路完全隔绝,则该栖息地内动物的基因杂合度、基因型数量降低;使用中的公路对临近种群的隔绝效果强于废弃旧公路。     

毛乌素沙地1990-2014年景观格局变化及驱动力

土地利用的改变受自然环境和人类活动影响,土地利用变化又会影响景观格局,本研究应用3S技术和景观指数相结合的方法,分析了毛乌素沙地1990、1995、2002、2008、2014年25年来土地利用动态过程与景观格局变化,并选取自然和人类活动等10个因子分析了其变化驱动力.结果显示,25年来固定沙地面积增加7.5%,半固定沙地增加3.8%,流动沙地减少42.95%,农田面积增加4.6%,低湿地和水体面积基本不变,城建用地面积增加.其中,增加的固定沙地主要由半固定沙地和流动沙地转变而来;增加的半固定沙地主要由流动沙地和固定沙地转变而来;减少的流动沙地主要转为固定沙地和半固定沙地.景观结构趋于复杂,类型斑块数增加,平均斑块面积减小,破碎度上升,呈现破碎化态势.各类型斑块数和分离度变化非常显著.研究区土地利用和景观格局变化主要是人为活动中的农牧民人均纯收入、人口、GDP和农林牧总产值因素所致,气候因素贡献不是很大.