综合构成指数在森林生态系统健康评估中的应用

Health assessment on forest ecosystem by using integrated compose index (ICI)

首次提出综合构成指数(IntegratedComposeIndex,ICI)模型ICI=ln∑B×∑IV×CAV。通过选取目前长白山阔叶红松林生态系统区主要林分类型(原始阔叶红松林,不同干扰模式造成的择伐林、次生白桦林和人工落叶松林等)共29块样地进行群落结构和生物量调查,以原始阔叶红松林作为健康基准,定量评估了各受损生态系统的健康现状及恢复趋势。结果表明综合构成指数是一种易操作的能定量描述受干扰系统健康差距的度量方法。利用分层[主林层(H≥18m)、亚主林层(18m>H≥10m)、演替层(10m>H≥2.5m)和更新层(H<2.5m)]的综合构成指数值可定量不同干扰模式造成的受损系统与健康基准之间的健康差距。健康基准是12.77,与之差距越大,表明受干扰破坏越大,系统健康程度越低。29块样地分为8个类型,6个受干扰类型依距离原始健康基准的远近排序为:结构转换型0.64<结构破坏型0.75<结构保留型0.85<严重干扰类型1.95<白桦林系列2.07<人工落叶松系列2.89。综合构成指数的上层(主林层和亚主林层)指数能表示群落结构现状和目前处于演替阶段的位置;下层(演替层和更新层)指数能表示群落向健康基准类型恢复的潜力,值越大,潜力越大。上下两层综合能说明群落受到干扰的强度和后果。上下两层差值D对于阔叶红松林生态系统来说,健康基准类型D位于0.28～0.35之间,如0<D<0.28说明目前群落结构还是针阔混交类型,但群落上层的针叶树(主要是红松)比例明显减少;或者群落受干扰,下层结构活跃,红松更新现象明显。D>0.35说明群落主林层和亚主林层的阔叶树种受到干扰破坏,且红松更新困难或还没大量更新。D≤0说明群落遭受很大强度的干扰,如70%以上的生物存量被破坏取走,或直接导致裸地重新发育演替的白桦林、营造人工落叶松林等情况,差值D越大,红松的侵入程度越高,红松更新状况良好,该群落向顶级恢复的趋势良好。

Integrated comapose index （ICI） model, ICI = In（∑B×∑IV×CAV）, was first put forward to and used in this study. Twenty nine plots were selected in original broadleaved and Korean pine mixed forest in Changbai Mountain, Northeast China, to investigate the structure and biomass of various disturbed conifer hardwood mixed selective cutting forests, secondary birch forests and larch plantation forests. Original broadleaved and Korean pine was viewed as a healthy benchmark. The health states and developing trends of various disturbed ecosystems were quantitatively assessed by ICI. The results indicts that ICI is a new practical and easily operational assessment method on forest ecosystem health. The vertical structure of stand was divided into four layers by tree height. They are upper overstory （H ≥18m）, subdominant overstory （18〉H≥10m）, succession layer （10m〉H≥2.5m） and regeneration-layer（H〈2.5m）. The ICI values of each layer were calculated and analyzed to express the relationship between disturbance, succession and health. Twenty nine plots were divided into 8 categories; ICI distance values of 6 disturbed types were calculated. Compared with the original broadleaved and Korean pine mixed forest, the healthy standard forest type （at 12.77）, distance values of each disturbed type were as following；structure switched stand （at 0.64） 〈 structure destroyed stand （at 0.75） 〈 structure reserved stand （at 0.85） 〈 heavy destroyed stand （at 1.95） 〈 birch stand （at 2.07） 〈 larch plantation （at 2.89）. The stronger stress on ecosystem, the bigger distance value, the lower degree of ecosystem health is. The ICI of overstory layer （i.e. upper canopy overstory and subdominant overstory） can express structure condition and succession stage of community, and ICIof understorylayer （i.e. of successionlayer and regeneration-layer） can suggest resilience to healthy ecosystem, the higher ICI value, the bigger resilience is. Hence, the intensity and sequent of various disturbances could be explained by ICI. The difference distance （D） between overstory layer and understory layer of the healthy standard type （Original broadleaved and Korean pine mixed forest） ranged from 0.28 to 0.35. This result suggested community structure was symmetrical and steady. Overstorylayer was composed of Pinus koraiensis, Tilia arnurensis, Abies nephrolepis, Acer rnono and so on, which had high climax adaptation value and could remain its dominant status. The understory layer was composed of species with medium climax adaptation value, and some other species with low climax adaptation value. If 0〈D〈0.28, it suggests this stand is still conifer hardwood mixed forest, but conifer species （most Pinus koraiensis） in overstory layer were removed, the ratio between conifer and broadleaved decreased greatly; the other explanation is that community is disturbed, making understory active and many korean pine show up. If D〉0.35, this result suggested that the main dominant hardwood species in overstory layer （upper canopy overstory and subdominant overstory） had suffered heavy disturbance, maybe regeneration of korean pine was difficult in understory layer or it has not started yet. If D^0, it shows a great heavy destroy happened, such as, over 70% biomass had been taken away, secondary birch forest or larch plantation in a naked slash. The bigger D, the easier invasion of Korean pine into community and well regeneration, the better the restoration capability and trend is.