Invasive sequence and ecological niche of main insect borers of Larix gmelinii forest in Aershan, Inner Mongolia

After the outbreak of Dendrolimus superans Buter in 2002, many insect borers quickly invaded larch （Larix gmelinii Rupr.） forests in the Aershan of Inner Mongolia. Methods involved included setting sample plots, collecting adults in iron traps and measuring areas of galleries to study the invasive sequence, their ecological niche and the extent of the different effects by the main insect borers to their hosts. The results showed that the damage of D. superans weakened L. gmelinii, first Ips subelongatus Motschulsky invaded, followed by Acanthocinus carinulatus Gebler, Monochamus urussovi Fisher and M. sutor L. After the outbreak of D. superans, the average density of longhorn beetles per L. gmelinii tree increased. The ecological niche of Ips subelongatus stretches almost from the base to the top of the trunk. The number of insects in older stands of L. gmelinii is larger than those in middle aged stands. They do not damage healthy trees of L. gmelinii. The ecological niche of A. carinulatus is higher in dead L. gmelinii trees than in weak ones. The degree of damage is directly proportional with age and depth of bark. M. urussovi mainly damages trunks below 4 m in weak trees; in dead trees they can do damage up to 6 m in height. M. sutor mainly damages trunks below 5 m in weak L. gmelinii trees; in dead trees they cause damage up to 7 m. Again, the degree of damage is directly proportional with age. None of the three species of longhorn beetles damage healthy L. gmelinii and younger trees. Among the main insect borers, the degree of damage caused by I. subelongatus is more serious than that of other insects.

Review on the Theory of Ecological Environment Damage Assessment

In the rapid industrialization and urbanization of China,the damage of ecological environment hinders the people's pursuit of good environmental quality.As a technical means of ecological environment protection,the assessment of ecological environment damage has been attached great importance by all walks of life.However,there are still some problems in the current practice of environmental damage assessment.Therefore,based on the understanding of ecological environment damage assessment and related concepts,this study systematically studies the theory of ecological environment damage assessment.Based on the research,it can be seen that the assessment of ecological environment damage is the inevitable product of social and economic development and the promotion of environmental protection awareness,and ecological environment damage belongs to the subordinate concept of"environmental damage".The assessment of ecological environment damage includes the assessment of ecological damage and environmental damage,paying attention to the interests of human society and the unclaimed pure environment and pure ecological damage.The assessment of ecological environmental damage determines the goal and direction for the construction of environmental damage compensation system.This study enriches the theory of environmental damage assessment and provides theoretical reference and method basis for environmental damage assessment.

Prosperity and Disappearance of Introduced Fishes in Xiangmoshan Reservoir

In order to enhance the resources, some fishes were introduced into Xiangmoshan reservoir. The introduced fishes consisted of different ecotypes such as silver carp （Hypophthahnichthys rnolitrix （Cuvier et Valenciennes））, big head （Aristichthys nobilis （Richardso）） and lake herring （Coregonus clupeaformis （Mitchill）） that were plankton feeders, common carp （Cyprinus carpio Linnaeus） and crucian carp （Carassius auratus gibelio） belonging to the polyphagia, and also the non-native predator Walleye （Stizostedion vitreum （Mitchill）） and big mouth （Silurus soldatovi rneridonalis Chen）, et al. Among there were not only the cool water fish Peled （Coregonus peled （Gmelin））, but also the warm water fish big mouth. The introduction of non-native fishes resulted in ecosystem changes of the reservoir and some native fishes had gone to decrease their population sizes or been in the condition of depopulation such as Opsariichthys uncirostris arnurensis （Berg）, Rhodeus sericeus （Pallas） and Silurus asotus （Linnaeus）. The native common carp had disappeared after the introduction of non-native species. Roach （Rutilus rutilus lacustris （Pallas） had been thriven for one or two generations after its introduction and immeidiatly disappeared. Silver fish （Protosalanx hyalocranius （Abbott））, Lake herring （Coregonus clupeaformis （Mitchill）） and Walleye （Stizostedion vitreum （Mitchill）） died several years after the introduction, so most of the introduced species has passed out of existence. Via many years introduction of different fishes, composition of species and the structure of the population in the reservoir had been changed obviously. It was necessary to further estimate whether the ecosystem of the reservoir had been damaged.