近日,，中科院華南植物園生態(tài)系統(tǒng)管理創(chuàng)新研究組魯顯楷博士和莫江明研究員等在鼎湖山國(guó)家級(jí)自然保護(hù)區(qū)開展的最新研究發(fā)現(xiàn)：大氣氮沉降通過誘導(dǎo)土壤酸化效應(yīng),，引起“富氮”（N-rich）森林生態(tài)系統(tǒng)的植物多樣性顯著減少。
當(dāng)今學(xué)術(shù)界普遍認(rèn)為,，大氣氮沉降將降低“氮限制”（N-limited）生態(tài)系統(tǒng)的生物多樣性而對(duì)“富氮”生態(tài)系統(tǒng)的影響則甚微,。以上觀點(diǎn)主要來源于“競(jìng)爭(zhēng)排斥機(jī)制”（Competitive exclusion mechanism）理論以及在溫帶和北方地區(qū)（通常為“氮限制”的生態(tài)系統(tǒng)）開展的相關(guān)研究。該理論認(rèn)為,，在“氮限制”的生態(tài)系統(tǒng)中,，氮的增加更有利于喜氮植物種類的生長(zhǎng)，使其在競(jìng)爭(zhēng)中處于優(yōu)勢(shì)從而排斥其它物種,，最終導(dǎo)致生物多樣性的降低,；而在“富氮”的生態(tài)系統(tǒng)中，因植物長(zhǎng)期適應(yīng)“富氮”狀態(tài),，氮的增加對(duì)植物生長(zhǎng)的影響不大,。
此項(xiàng)研究首次報(bào)道了氮沉降對(duì)“富氮”森林的植物多樣性的影響，其結(jié)果不僅填補(bǔ)了國(guó)際上熱帶和亞熱帶區(qū)域氮沉降對(duì)森林植物多樣性影響研究的空白,，同時(shí)表明了氮沉降可能威脅“富氮”森林的植物多樣性,。
該成果已在線發(fā)表在全球變化研究領(lǐng)域的權(quán)威雜志Global Change Biology 上。(生物谷Bioon.com)
生物谷推薦原文出處：
Global Change Biology DOI 10.1111/j.1365-2486.2010.02174.x
Effects of experimental nitrogen additions on plant diversity in an old-growth tropical forest
XIANKAI LU * , JIANGMING MO * , FRANK S. GILLIAM?, GUOYI ZHOU * and YUNTING FANG *
Response of plant biodiversity to increased availability of nitrogen (N) has been investigated in temperate and boreal forests, which are typically N-limited, but little is known in tropical forests. We examined the effects of artificial N additions on plant diversity (species richness, density and cover) of the understory layer in an N saturated old-growth tropical forest in southern China to test the following hypothesis: N additions decrease plant diversity in N saturated tropical forests primarily from N-mediated changes in soil properties. Experimental additions of N were administered at the following levels from July 2003 to July 2008: no addition (Control); 50 kg N ha?1 yr?1 (Low-N); 100 kg N ha?1 yr?1 (Medium-N), and 150 kg N ha?1 yr?1 (High-N). Results showed that no understory species exhibited positive growth response to any level of N addition during the study period. Although low-to-medium levels of N addition (≤100 kg N ha?1 yr?1) generally did not alter plant diversity through time, high levels of N addition significantly reduced species diversity. This decrease was most closely related to declines within tree seedling and fern functional groups, as well as to significant increases in soil acidity and Al mobility, and decreases in Ca availability and fine-root biomass. This mechanism for loss of biodiversity provides sharp contrast to competition-based mechanisms suggested in studies of understory communities in other forests. Our results suggest that high-N additions can decrease plant diversity in tropical forests, but that this response may vary with rate of N addition.
