Wild pig populations in the National Parks

Populations of introduced European wild boar, feral pigs, and combinations of both types (all Susscrola L.) inhabit thirteen areas in the National Park Service system. All parks have relatively stable populations, with the exception of Great Smoky Mountains National Park, which reported a rapidly expanding wild boar population. Suspected and documented impacts were apparently related to pig densities and sensitivity of the ecosystem; the three largest units with dense wild pig populations reported the most damage. Overall, wild pigs are a relatively minor problem for the Park Service; however, problems are severe in at least three parks, and there is potential for invasion of wild boars into several additional parks in the Appalachian Mountains. More specific information is needed on numbers of wild pigs and their impacts in the various parks.     

Predicting the multiple pathways of plant succession

Classical concepts view succession as a deterministic, mechanistic regeneration of the disturbed community, and thus have limited applicability to fire-prone ecosystems, A recently developed multiple pathway succession model appears to have more realism and applicability in frequently disturbed ecosystems. It includes a set of species-specific attributes that are vital to reproduction and survival, and permits variable succession pathways depending on the stand's age (and thus species composition) when disturbed. Examples from Australia and the northern Rocky Mountains (USA) are presented, as are approaches to refining and improving the model.     

The effect of nitrogen additions on oak foliage and herbivore communities at sites with high and low atmospheric pollution

To evaluate plant and herbivore responses to nitrogen we conducted a fertilization study at a low and high pollution site in the mixed conifer forests surrounding Los Angeles, California. Contrary to expectations, discriminant function analysis of oak herbivore communities showed significant response to N fertilization when atmospheric deposition was high, but not when atmospheric deposition was low. We hypothesize that longer-term fertilization treatments are needed at the low pollution site before foliar N nutrition increases sufficiently to affect herbivore communities. At the high pollution site, fertilization was also associated with increased catkin production and higher densities of a byturid beetle that feeds on the catkins of oak. Leaf nitrogen and nitrate were significantly higher at the high pollution site compared to the low pollution site. Foliar nitrate concentrations were positively correlated with abundance of sucking insects, leafrollers and plutellids in all three years of the study.     

中条山东段植被垂直带的数量分类研究

在野外调查的基础上,应用有序样方聚类法对中条山东段植 垂直带进行了数量分类研究,结果为：１．落叶阔叶林带,包括４个亚带：（１）侧柏林带（５００￣８００ｍ）,（２０松栎林带（８００￣１８００ｍ）,（３）栓皮林带（１４００￣２０００ｍ）和（４）杨桦林带（１９００￣２２００ｍ）;２．山地草甸带（２１００￣２３５８ｍ）。此外,与前人的划分结果进行了比较,结果表明,有序样方聚类法的结果更符合实际情况。     

西昆仑地区土地资源

喀喇昆仑山和昆仑山地区,山势巍峨,交通边远不便,过去对其拥有的土地资源缺乏详尽地考察和系统地了解。现根据1987年的考察资料,对西昆仑地区土地资源的社会经济地位、垂直分异规律及其主要类别予以初步总结。     

哀牢山北段山地的地温气候资源分析

本文根据哀牢山北段东西坡山地不同海拔8个气象站的同期地温与气温资料,讨论了该山地的地温与气温差、地温及地积温气候资源。     

哀牢山西坡主要植被类型的特征与物种组成

研究了云南哀牢山西坡主要植被类型的物种组成和群落生态特征,结果如下: 1)物种多样性在低山季风常阔叶林中最高; 2)乔木径级在中山湿性常绿阔叶林中最大,而乔木密度则在山顶苔藓矮林最大; 3)当取样面积达1 500m2后,各植被类型物种增加速度变得缓和. 图 4表 3参 32     

四川白河自然保护区大熊猫对生境的利用

利用路线法在野外调查了四川九寨沟县白河自然保护区：109个样点的大熊猫粪便等痕迹及其所处生境的特征，共发现有29个大熊猫活动样点，其中，大熊猫粪便样点27个、食迹样点2个．把各样点的各种生境特征作为因素，把每一因素的不同情况设置为水平，进行独立性检验．检验的结果表明白河的大熊猫：1)主要在halt2600～3120m取食；2)偏好在有水源的生境活动；3)对坡向有明显的选择性；4)对华西箭竹有明显的偏好，且在生长良好、盖度较高的生境活动频繁；5)明显回避有挖药活动的生境，偏好在没有人类干扰的生境活动。     

Visitor impact on backcountry campsites in the Great Smoky Mountains

Over the last decade the Great Smoky Mountains National Park (GSMNP) has experienced a tremendous increase in visitation, especially in backcountry camping. In 1976 there were an estimated 117,500 backcountry visitor nights, with a peak of 16,865 visitor nights in April. The high use season extends from March to October. Visitation tends to be concentrated in certain sections of the park and at specific sites. The Appalachian Trail, which includes about 8 percent of the maintained trail mileage, carried 32 percent of the visitor nights in 1976.Campsite disturbance is also concentrated in specific sites and sections of the park. Maximum camping disturbance per km of maintained trail was 3,400 m² for the sites on the Appalachian Trail. Shelter sites have more visitation per site and more total disturbance per site than open campsites, but shelters tend to have less intensive disturbance, such as bare soil, because they concentrate trampling impacts. Visitation levels were strongly correlated with disturbances such as bare soil at open campsites. Visitation was significantly correlated to the number of firepits at shelter sites but not to other types of disturbance. Regressions indicate that for each additional visitor night at a site (annual average), one can expect an additional 9 m² of total disturbance and 1 m²of bare soil. The distance of a site from the nearest road was not significantly correlated with damage or visitation. Elevation was correlated to visitation levels, especially in the case of the shelters. More legal sites and large illegal sites are in mesic forest types. Illegal camping accounted for 10 percent of the total camping disturbance.The data imply that the suggested removal of shelters will require redistribution of visitor use or replacement developments, such as tent platforms, in order to mitigate damage. Zone camping is a possible alternative but presents difficulties because campers may concentrate in certain plant communities and topographic positions.     

基于GIS的祁连山植被NDVI对气温降水的旬响应分析

利用祁连山地区SPOTVGT-NDVI数据和气象站点旬平均气温、降水资料,运用最大化合成、趋势线分析和相关分析方法分析了祁连山植被的时空变化趋势,并从旬时间尺度上分析了祁连山植被对气温和降水的响应特征。结果表明：近10年来．祁连山年最大化植被NDVI增加了3．1％,植被改善、无变化和退化的面积分别占总面积的70．21％、21．44％和8．35％。祁连山植被NDVI对气温变化的响应大于降水,对气温和降水变化的最大响应滞后都为2句左右。秋季植被NDⅥ对气温和降水变化响应最大,夏季植被NDVI对气温和降水响应的滞后期长于春季和秋季。祁连山植被NDVI对气温和降水变化的旬最大响应表现为中段大于东段和西段,NDVI对气温和降水变化的最大响应滞后期呈现出西段〉中段〉东段的空间分布特征。