Du You-Xin, Pan Gen-Xing, Li Lian-Qing, Hu Zhong-Liang, Wang Xin-Zhou
Institute of Resources, Ecosystem and Environment for Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
Ying Yong Sheng Tai Xue Bao. 2010 Aug;21(8):1926-32.
The degeneration of karst ecosystem is closely associated with the reduction of soil nutrients and fine root biomass, and the retention of soil nutrients is of significance in sustaining ecosystem functioning. To understand the changes in the fine root biomass and soil nutrient retention in degenerated karst ecosystems, a comparative study was conducted with three typical vegetation stands (forest, shrub, and shrub-grass) in Central Guizhou of Southwest China. Soil samples with fine roots were collected from the depths 0-5 cm, 5-10 cm, and 10-15 cm, with the related indices of fine roots and nutrients measured. In the three stands, fine roots dominantly distributed in 0 -10 cm soil layer, and decreased sharply with soil depth. The living fine root biomass in 0-10 cm soil layer under forest, shrub, and shrub-grass occupied 83.36%, 86.91%, and 93.79% of the total fine root biomass, and 42.78%, 56.75%, and 53.38% of the total living fine root biomass within the 0-15 cm soil layer, respectively. The fine root biomass of predominant plant species varied with vegetation types. The N and P storage of the living fine roots in 0-5 cm soil layer under forest stand was significantly higher than those under shrub stand and shrub-grass stand, and no significant differences were observed between the latter two stands. However, the N and P storage of the living fine roots in 5-10 cm soil layer under different stands decreased in the order of forest > shrub > shrub-grass (P < 0.05). There was a significant positive correlation between the plant aboveground biomass and the living fine root biomass in 0-10 cm soil layer, and a significant negative correlation between the N and P contents of plant leaves and the specific length of living fine roots, illustrating that the nutrient uptake and retention by the living fine roots could have particular importance in the aboveground biomass establishment and ecosystem functioning.
喀斯特生态系统的退化与土壤养分和细根生物量的减少密切相关，而土壤养分的保持对于维持生态系统功能具有重要意义。为了解退化喀斯特生态系统中细根生物量和土壤养分保持的变化情况，在中国西南地区贵州中部对三种典型植被林分（森林、灌木和灌草丛）进行了对比研究。采集了0 - 5厘米、5 - 10厘米和10 - 15厘米深度带有细根的土壤样本，并测定了细根和养分的相关指标。在这三种林分中，细根主要分布在0 - 10厘米土层，且随土壤深度急剧减少。森林、灌木和灌草丛下0 - 10厘米土层的活细根生物量分别占总细根生物量的83.36%、86.91%和93.79%，分别占0 - 15厘米土层总活细根生物量的42.78%、56.75%和53.38%。优势植物物种的细根生物量随植被类型而变化。森林林分下0 - 5厘米土层活细根的氮和磷储量显著高于灌木林分和灌草丛林分，后两者之间未观察到显著差异。然而，不同林分下5 - 10厘米土层活细根的氮和磷储量按森林＞灌木＞灌草丛的顺序递减（P＜0.05）。植物地上生物量与0 - 10厘米土层的活细根生物量之间存在显著正相关，植物叶片的氮和磷含量与活细根的比根长之间存在显著负相关，这说明活细根对养分的吸收和保持在地上生物量形成和生态系统功能方面可能具有特殊重要性。
