Stuart Chapin F, Slack Mari
Institute of Arctic Biology, University of Alaska, 99701, Fairbanks, Alaska.
Oecologia. 1979 Jan;42(1):67-79. doi: 10.1007/BF00347619.
Moderate experimental defoliation stimulated root respiration and phosphate absorption in two tundra graminoids, Eriophorum vaginatum and Carex aquatilis, growing under nutrient-limited field conditions in northern Alaska. The increase in phosphate absorption rate following defoliation of Eriophorum was associated with a decrease in root phosphate and available carbohydrate contents per unit root length but a constant root nitrogen content. Only after four repeated defoliations did phosphate absorption rate decrease below control levels. We suggest that the stimulation of root respiration and phosphate absorption immediately following defoliation resulted from lowered root phosphorus status as nutrient reserves were reallocated to support shoot regrowth. Root growth was affected more severely by defoliation than was root activity. Two or more defoliations reduced root elongation, initiation and weight per unit length, but root mortality increased only after four defoliations. Carex aquatilis, a species with large belowground biomass, was less sensitive to defoliation than Eriophorum. Phosphate absorption rate increased only after four defoliations in this species, and root elongation, initiation and mortality were affected only by the most severe clipping regimes. Responses of plants to repeated defoliation over two growing seasons were consistent with results of short-term studies.
在阿拉斯加北部养分有限的田间条件下生长的两种苔原禾本科植物——毛果苔草和水苔草，适度的实验性去叶处理刺激了它们的根系呼吸和磷吸收。毛果苔草去叶后磷吸收速率的增加与单位根长的根系磷含量和有效碳水化合物含量的降低有关，但根系氮含量保持不变。仅在四次重复去叶处理后，磷吸收速率才降至对照水平以下。我们认为，去叶处理后立即刺激根系呼吸和磷吸收是由于养分储备重新分配以支持地上部再生长，从而降低了根系磷状态。去叶处理对根系生长的影响比对根系活性的影响更为严重。两次或更多次去叶处理降低了根系伸长、起始和单位长度重量，但仅在四次去叶处理后根系死亡率才增加。水苔草是一种地下生物量较大的物种，对去叶处理的敏感性低于毛果苔草。该物种仅在四次去叶处理后磷吸收速率才增加，根系伸长、起始和死亡率仅受最严重的修剪处理影响。植物在两个生长季节对重复去叶处理的反应与短期研究结果一致。
