天目山针阔混交林林木空间分布格局特征

森林中林木的空间位置和森林功能息息相关，为更好地掌握树种的空间分布规律，科学合理地开展森林经营管理活动，在浙江省天目山区设置了30 m×30 m的针阔混交林样地15个，使用全站仪对样地边界和胸径≥5cm的木琴植物个体进行精确测量定位，同时进行种类识别、挂牌、定位和每木检测，获取基础数据。利用混交度、大小比数和角尺度等3种结构参数表征针阔混交林林分空间结构。结果表明：林分空间分布格局上，混交度为0．700～0．900的比例较大，树种平均混交度为0．712。天目山针阔混交林的林木零度混交和轻度混交的比例不高，中度混交和强度、极强度混交占很大比例。林分空间大小分化差异较小，在空间结构单元里，林分平均的大小比数位0．477，大部分个体分化程度处于中等水平。林分中有近一半的树木处于优势地位，总体优势度有继续上升的潜力。树种问的大小比数有一定差异，马尾松Pinus massoniana生长空间比其他树种略小一些，枫香Liquidambar for-mos（ana，杉木Cunninghamia larweolata，短柄抱Quercus glandulifera var．brevipetiolata等优势不明显，其余树种生长占优势地位。天目山针阔混交林林分处于相对稳定的状态，角尺度为0．500等级的分布频率最大，林分平均角尺度为0．533，林分中极少有很均匀和很不均匀的结构单元出现，整体林木水平分布格局为团状分布。未来的演替过程中，林分分布有随机分布的趋势。天目山针阔混交林物种丰富，结构相对合理，林分处于较为稳定的状态中。图3表4参20

Spatial distribution patterns of a coniferous-broadleaved mixed forest in Mount Tianmu,China

Spatial position is close to the function of forest, in order to get the rule of spatial distribution and make forest management activities, fifteen mixed eonifer-broadleaf forest plots with 30 m × 30 m surveyed at Mount Tianmu, Zhejiang. Electronic Total Station was used to measure the plots border and the accurate loca- tion of trees which DBH was above 5 era, at the same time, species identifing, listing, and every tree detection were prepared. Three parameters-mingling index, neighborhood comparison, and uniform angle index-were used to describe spatial structure. Results showed that the mingling index was between 0.700 and 0.900 with a 0.712 average. For stand spacing distribution patterns, the zero and weak mixtures of tree species had the lowest pro- portion, the strong and extremely strong mixtures of many different tree species had the largest proportion. The average neighborhood comparison was 0.477 with relatively less heterogeneity within the spatial structure units and most of the individual differences at a medium level. Approximately half of the trees within the forest stand belonged to dominant tree species with overall dominance having the potential to increase. Tree species size varied. The growing space of Pinus massoniana was less than other species; no obvious differences in growing space were found for Cunninghamia lanceolata, Liquiclambar formosana, and Ouercus glanclulifera var. bre- vipetiolata, but other species occupied a dominant position. These mixed coniferous-broadleaved forests were relatively stable with an average uniform angle index of 0.533 most of which was close to 0.500. No obvious u- niform or uneven forest structure was noted with overall cluster distribution. Future succession of the forest stand was predicted to have a random distribution. In summary, the mixed coniferous-broadleaved forest at Tian mu Mountain had diverse species with a suitable, relatively stable forest structure. [Ch, 3 fig. 4 tab. 20 ref. ]