刈割频率对两种牧草越冬的影响

刈割频率对皇草和杂交狼尾草越冬影响的实验表明,两者的根系生物量、根系养分贮量、越冬返青率和越冬产量均随刈割次数的增加而减少,但影响程度两者略有不同。刈割次数对杂交狼尾草的越冬返青率的影响更大,皇草的根系生物量和越冬产量则随刈割次数的增加而明显下降,本文还就如何减低刈割对牧草越冬的影响进行了讨论．     

云南思茅亚洲象对栖息地的选择与利用

以思茅市境内栖居的一个由5 头雌象(3 头成年体, 1 头亚成体, 1 头幼体) 组成的象群为研究对象, 利用痕迹追踪、样线调查和村庄调查等方法对野生亚洲象的栖息地选择和行为进行了初步研究。在栖息地中共记录到野生高等植物457 种, 组成5 种植被类型。旱季象群的活动区域面积是35.67 km² , 该活动区域中有3 个核心活动区, 面积分别是3.65 km² , 2.79 km² 和3.29 km² , 象群对此3 个活动核心区域循环利用; 在旱季亚洲象经常取食19种野生植物, 其中主要取食的有8 种, 还取食7 种农作物, 对农作物有一定依赖性, 这种依赖的程度随着农田周围森林中野生食物丰富程度的增加而降低; 在季雨林中亚洲象主要取食的植物种类最丰富。雨季象群的活动区域面积是18.42 km² , 该区域中只有1 个核心活动区, 面积9.08 km² 。雨季亚洲象只取食5 种野生植物, 另取食5 种农作物, 农作物为其雨季主要食物。研究结果表明, 思茅地区亚洲象栖息地中的野生食物可能不足, 人类活动对亚洲象的生存干扰较为严重, 亚洲象的行为表现出对栖息地内食物条件和人类干扰的适应。建议尽快遏止日益严重的栖息地片断化趋势, 恢复自然植被并为亚洲象提供充足的野生食物是保护该物种的关键。     

云南西双版纳尚勇保护区亚洲象对栖息地的选择

以西双版纳国家级自然保护区尚勇子保护区内的亚洲象种群为研究对象, 利用村寨调查、样线调查和3S(GIS、GPS、RS) 技术对该地区野生亚洲象的栖息地状况和亚洲象对栖息地选择利用进行了初步的研究。结果表明亚洲象喜欢海拔1 000 m以下的区域, 坡度小于10°的区域, 坡位为平坦的沟谷和山坡的下部, 坡向为南、北两个方向。偏好的植被类型有竹阔混交林、灌丛和高山草甸。研究还发现尚勇保护区及周边区域亚洲象栖息地的丧失和日益增加的非法盗猎活动已经严重威胁到该地区野生亚洲象种群的生存。     

Kamala tree as an indicator of the presence of Asian elephants during the dry season in the Shivalik landscape of northwestern India

The availability of forage resources during the dry season is often a critical factor in determining the distribution and movement of large herbivores. It has long been suspected that the Kamala tree (Mallotus philippinensis) can serve as an indicator of the distribution for Asian elephants during the dry season in northwestern India. However, there is little direct evidence in support of this speculation, especially at a large landscape scale. Here, we predicted the distribution of Kamala trees in the Shivalik landscape of northwestern India based on topographic and bioclimatic variables, as well as satellite-derived vegetation indices and forest canopy height data using a presence-only ecological niche model. We used the area under the receiver operating characteristic curve (AUC) and true skill statistic (TSS) to validate the model. We then examined the relationship between the occurrence probability of Kamala trees and the presence of Asian elephants with data collected during dry seasons between 2010 and 2014 using logistic regression models. Our results showed that the probability of occurrence of Kamala trees was predicted with good accuracy (AUC = 0.88 and TSS = 0.51). The logistic regression models showed that the presence of Asian elephants can be adequately predicted by the occurrence probability of Kamala trees. This result suggests that the distribution of Kamala trees is a good indicator of the presence of Asian elephants during the dry season in the Shivalik landscape. These findings may have major implications for the conservation of Asian elephants, especially in designing wildlife corridors and mitigating human-elephant conflicts.     

Modelled mid-trophic pelagic prey fields improve understanding of marine predator foraging behaviour

Biophysical interactions are influential in determining the scale of key ecological processes within marine ecosystems. For oceanic predators, this means foraging behaviour is influenced by processes shaping the distribution of prey. However, oceanic prey is difficult to observe and its abundance and distribution is regionally generalised. We use a spatiotemporally resolved simulation model to describe mid-trophic prey distribution within the Southern Ocean and demonstrate insights that this modelled prey field provides into the foraging behaviour of a widely distributed marine predator, the southern elephant seal. From a five-year simulation of prey biomass, we computed climatologies of mean prey biomass (average prey conditions) and prey biomass variability (meso-scale variability). We also compiled spatially gridded metrics of seal density and diving behaviour from 13 yr of tracking data. We statistically modelled these metrics as non-linear functions of prey biomass (both mean and variability) and used these to predict seal distribution and behaviour. Our predictions were consistent with observations (R²_adj = 0.23), indicating that seals aggregate in regions of high mesoscale activity where eddies concentrate prey. Here, seals dived deeper (R²_marg = 0.12, R²_cond = 0.51) and spent less time hunting (R²_marg = 0.05, R²_cond = 0.56), likely targeting deep but profitable prey patches. Seals generally avoided areas of low eddy activity where prey was likely dispersed. Most seals foraged south of the Subantarctic Front, despite north of the front exhibiting consistently high simulated prey biomasses. This likely reflects seal prey or habitat preferences, but also emphasises the importance of mesoscale prey biomass variability relative to regionally high mean biomass. This work demonstrates the value of coupling mechanistic representations of prey biomass with predator observations to provide insight into how biophysical processes combine to shape species distributions. This will be increasingly important for the robust prediction of species’ responses to rapid system change.     

Seed protection through dispersal by African savannah elephants (Loxodonta africana africana) in northern Tanzania.

We examined effectiveness of African savannah elephant dung as a protective barrier for seeds of three tree species, Acacia tortilis Hayne, Tamarindus indica L. and Ximenia aegyptiaca L. Seeds were collected from dung and underneath fruiting trees in Tarangire National Park, Tanzania. Experimental treatments were established to test: (i) the efficacy of dung in protecting seeds of A. tortilis from bruchid beetle infestation and the role of animals larger than insects in removing seeds; (ii) the same tenets as in Experiment 1, using seeds of T. indica; and (iii) the effect of distance on survival of seeds of X. aegyptiaca. Sites were established during two field seasons underneath conspecific trees, where seed predation was likely highest. Repeated‐measures two‐way ANOVA indicated that there was no treatment effect for Experiment 1. For Experiments 2 and 3 in October 2013, seeds in dung experienced less beetle infestation than fresh seeds. Repeated‐measures two‐way ANOVA and Tukey's HSD indicated that treatment effect differed among all treatments. Passed seeds at distances ≥5 m experienced less beetle infestation than fresh seeds underneath conspecifics. African savannah elephants appear to be important seed dispersers of these three tree species.     

华南象草Pp4CL基因的克隆及其转基因烟草木质素含量分析

为探究华南象草(Pennisetum purpureumcv.Huanan)木质素合成关键酶基因的调控机制,通过同源克隆得到华南象草4-香豆酸:CoA连接酶基因(Pp4CL)的cDNA序列,长度为1 943bp,其中编码区序列1 662bp。Pp4CL蛋白由553个氨基酸组成,分子量为59.57kD,等电点为5.2,属于疏水性蛋白。该蛋白含有AMP结合结构域,属于AFD ClassⅠ超家族。在系统进化分析中,Pp4CL与At4CL1、Os4CL1遗传距离最近,聚为一支。Pp4CL氨基酸序列具有SSGTGLPKGV和GEICIRG等2个保守基序,是典型的植物4CL。构建原核表达载体pGEX-4CL,得到约88kD的Pp4CL-GST融合蛋白,为Pp4CL酶活性测定及Western免疫印迹分析奠定了基础。同时构建植物表达载体pBA-4CL,并通过叶盘法对烟草进行了遗传转化,得到3个转基因阳性株系(OX-9、OX-7、OX-4),它们中叶柄木质素总含量分别比非转基因植株(对照)提高了10.0%、16.2%和94.6%,茎秆基部节木质素总含量分别比对照提高了0.9%、4.0%和13.5%。研究结果表明,Pp4CL蛋白与木质素合成有关,过表达Pp4CL基因能够显著提高植株木质素含量。该研究结果为华南象草木质素改良工作打下了基础,同时也为深入开展牧草分子育种提供了依据。     

A landscape-level assessment of Asian elephant habitat,its population and elephant–human conflict in the Anamalai hill ranges of southern Western Ghats,India

Spatial information at the landscape scale is extremely important for conservation planning, especially in the case of long-ranging vertebrates. The biodiversity-rich Anamalai hill ranges in the Western Ghats of southern India hold a viable population for the long-term conservation of the Asian elephant. Through rapid but extensive field surveys we mapped elephant habitat, corridors, vegetation and land-use patterns, estimated the elephant population density and structure, and assessed elephant–human conflict across this landscape. GIS and remote sensing analyses indicate that elephants are distributed among three blocks over a total area of about 4600 km². Approximately 92% remains contiguous because of four corridors; however, under 4000 km² of this area may be effectively used by elephants. Nine landscape elements were identified, including five natural vegetation types, of which tropical moist deciduous forest is dominant. Population density assessed through the dung count method using line transects covering 275 km of walk across the effective elephant habitat of the landscape yielded a mean density of 1.1 (95% CI = 0.99–1.2) elephant/km². Population structure from direct sighting of elephants showed that adult male elephants constitute just 2.9% and adult females 42.3% of the population with the rest being sub-adults (27.4%), juveniles (16%) and calves (11.4%). Sex ratios show an increasing skew toward females from juvenile (1:1.8) to sub-adult (1:2.4) and adult (1:14.7) indicating higher mortality of sub-adult and adult males that is most likely due to historical poaching for ivory. A rapid questionnaire survey and secondary data on elephant–human conflict from forest department records reveals that villages in and around the forest divisions on the eastern side of landscape experience higher levels of elephant–human conflict than those on the western side; this seems to relate to a greater degree of habitat fragmentation and percentage farmers cultivating annual crops in the east. We provide several recommendations that could help maintain population viability and reduce elephant–human conflict of the Anamalai elephant landscape.     

Habitat use of the endangered golden‐rumped sengi Rhynchocyon chrysopygus

The endangered golden‐rumped sengi are found only in Arabuko‐Sokoke Forest with 395.4 km² of forest habitat, and perhaps in a few isolated forest and thicket fragments of total area less than 30 km² all within central coastal Kenya. Understanding its habitat use is an important requirement to develop better conservation measures for the species and its remaining forest habitat. A more reliable method for monitoring its status is also needed. We used the Bayesian occupancy modelling with camera trap data and habitat mapping to characterise the species habitat use in the Arabuko‐Sokoke Forest. The species uses 328 km² (95% CI: 289–364 km²) of Arabuko‐Sokoke Forest habitat, and its site use increases with distance from forest edge, with the highest site use in the Cynometra thicket (0.93; 95% CI: 0.82–1). Its use of the mixed forest habitat has been significantly reduced following years of logging of Afzelia quanzensis. We recommend the use of modelled occupancy, interpreted as the proportion of area used by the species, to monitor the species status. Occupancy models account for detection probability, and heterogeneity in site use and detection can be incorporated. Estimated territory sizes can be combined to obtain abundance estimates.