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世界各国的发展都必须面对的是这样一个共同性的基本问题，即人类社会对物质产品数量、性能、品种追求的无限性与自然环境、物质生产及供给能力的有限性之间的矛盾。人类自出现以来就开始努力从自然界中谋求生存并争取更好的生存（发展的本质就在于此），这种努力永不停歇。尽管人类社会追求物质产品的无限性和自然环境供给能力的有限性是客观存在的，但人类认识到他们的存在，特别是认识到这二者之间矛盾的严重性和普遍性，却有一个相当漫长的过程。 相似文献
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We investigated the quantity and quality 0f fallen l0gs in different Tsuga l0ngibracteata f0rest c0mmunities in the Tianba0yan Nati0nal Nature Reserve. We used redundancy analysis t0 determine the spatial distributi0n 0f fallen l0gs in the different f0rest c0mmunities and t0 analyze the relati0nships am0ng stand structure, t0p0graphic fact0rs and human disturbance. The v0lume, c0vered area, mean l0g length and number 0f fallen l0gs differed significantly am0ng f0rest types （P 〈 0.05）, but mean diameter at breast height sh0wed n0 significant difference （P 〉 0.05）. The l0g v0lume and c0vered area in different f0rest types sh0wed the f0ll0wing trend： T. l0ngibracteata pure f0rest 〈 T. l0ngibracteata ＋ Olig0staehyum scabrifl0rur 〈 T. l0ngibraeteata ＋ hardw00d 〈 Rh0d0dendr0n simiarum ＋ T. l0ngibraeteata 〈 T. l0ngibraeteata ＋ Phyll0stachys heter0cycla pubescens. The spatial distributi0n patterns 0f l0gs quantity and quality indicated that l0g v0lume and c0vered area were str0ngly affected by envir0nmental fact0rs in the f0ll0wing 0rder： human disturbance 〉 elevati0n 〉 sl0pe p0siti0n 〉 b0le height 〉 tree height 〉 sl0pe aspect 〉 density 〉 basal area 〉 sl0pe gradient. The relative c0ntributi0n 0f envir0nmental variables 0n the t0tal variance was t0p0graphy （76%） 〉 disturbance （42%） 〉 stand structure （35%）. T0p0graphy and disturbance c0mbined explained 8.2% 0f the variance. Fallen l0~s auantitv and aualitvwere negatively related t0 elevati0n and sl0pe p0siti0n, and p0sitively ass0ciated t0 human disturbance. The l0g v0lume decreased fr0m n0rthern t0 s0uthern sl0pes. Envir0nmental fact0rs had the highest impact 0n class I （slightly decayed）, and l0west impact 0n class V （highly decayed）. 相似文献
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