作 者 ：杜有新,潘根兴*,李恋卿,胡忠良,王新洲
期 刊 ：生态学报 2010年 30卷 23期 页码：6338~6347
关键词：喀斯特生态系统；植被退化；生物量结构；养分；循环特征；
Keywords:Karst ecosystems, vegetation decline, biomass partitioning, major nutrients, elemental cycling,
摘 要 ：喀斯特生态系统退化导致植被群落结构简单、系统生态功能逐渐丧失与稳定性不断下降，这些退化特征皆与系统生物量结构和生物地球化学循环特征密切相关。采用实地调查和典型取样方法，探讨了贵州省普定县3个不同退化程度的喀斯特生态系统生物量结构与养分分布格局。结果表明：(1) 随着生态系统不断退化，植被地上部分生物量和土壤有效态养含量呈下降趋势，植物营养物质通过凋落物返还土壤的比例也呈类似的趋势，而细根和草本植物等活性生物组分的生物量却呈现上升趋势。(2) 对应于生物量结构的变化，各组分主要养分储量也呈现相似的变化特征。乔木林枯落物层养分(N和P)累积量显著高于草本层和细根部分，而灌木林和灌草丛系统草本层和细根部分的养分储量超过或接近枯落物层。(3) 随着生态系统不断退化，N和P的生物吸收率、生物返还率、生物迁移率和生物分解率出现明显变化，生物吸收率和生物分解率呈现明显下降趋势，而生物迁移率和生物返还率却表现出上升趋势。
Abstract:The system functioning and stability for resilience and sustainability has been increasingly concerned with restoration and re-establishment of degraded karst ecosystems in the areas with rock desertification in Southwest China. However, decline in vegetation biomass and nutrient pool has been generally associated with changes in ecosystem functioning and sustainability. To address the relations between biomass, nutrient storage and ecosystem functioning, the partitioning of biomass and major nutrients among the different vegetation pools were studied by a pilot study using a degradation sequence of three karst ecosystems with different degree of vegetation decline from Puding County, Central Guizhou, South West China. The results showed that: (1) there was a decreasing trend both in vegetation biomass above ground and in soil nutrient availability as well as nutrient returning through littering, an increasing trend of fine root biomass and herbaceous biomass with the degradation trend of the ecosystems. The organic matter storage in forest floor was respectively 10 times as the herbaceous biomass and 2 times as the fine root biomass in the forest stand (FO). Whereas, the herbaceous biomass and fine root biomass were 3.5 times and 2.1 times as that of floor organic matter in the shrubland stand (SH), and 2.4 times and 1.4 times as that of floor organic matter in the shrub-and-grassland (SHG) respectively. (2) The nutrient accumulations in ecosystem components varied with the vegetation biomass pattern. The N and P accumulations in forest floor organic matter were significantly higher than that in herbaceous layer and in fine roots in the FO, while the N and P accumulations in herbaceous layer and in fine roots were higher than or similar to that in floor organic matter in the SH and the SHG. (3) There was a sharp decline in nutrient uptake and decomposition percentage, with an increase in percentage of nutrient translocated and returned to soil with the increasing degradation in vegetation from forest to grassland. In particular, the bio-migration and bio-return ratios of N was in the order of SHG > SH > FO, but its uptake and decomposition ratio in order of FO > SHG > SH and FO > SH > SHG respectively. Similarly, the migration and decomposition ratios of P in FO > SHG> SH and FO > SH > SHG, and bio-absorption ratio as SH > FO > SHG, and its bio-return ratio in order of SH > SHG > FO. The results showed that the nutrient return to soil through litterfall was gradually decreased, whereas the biomass of fine roots increased gradually with the increasing trend of vegetation decline. This suggested that major nutrients such as N have undergone a relatively intense translocation and been exhausted in rhizospheric zone for their use in vegetable parts due to loss under vegetation decline in degraded ecosystems. Compared with the forest stand, the shrubland and the shrub-and-grassland have been vulnerable due to lower capability in self-sustaining and regulating under serious disturbances. Finally, it is suggested that the biogeochemical characterization of major nutrients would be an important sector for the functional stability of karst ecosystems.
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