Friedman Deb, Alpert Peter
Botany Department, University of Massachusetts, 01003, Amherst, MA, USA.
Oecologia. 1991 Mar;86(1):76-80. doi: 10.1007/BF00317392.
Fragaria chiloensis is a stoloniferous perennial herb that grows on coastal sand dunes where scattered shrubs create small patches of lower photon flux density (PFD) but higher soil nitrogen availability. The potential effects of resource transport between ramets when PFD and soil nitrogen are negatively associated in space were tested by comparing the growth of pairs of ramets in which the vascular connection between ramets was either severed or left intact. One ramet in each pair was given high PFD but a low level of soil nitrogen and the other ramet was given low PFD but high N. The analogous effects of resource transport likely to be realized in nature were tested by substituting a more realistic medium soil nitrogen level in place of the high level. Results suggested that connected ramets exchanged carbon and nitrogen under both regimes of soil nitrogen heterogeneity. In the low versus high nitrogen regime, connected ramets had higher combined dry biomass and different patterns of dry mass partitioning from those of severed ramets; effect of connection was greater on ramets given low PFD and high N and on younger ramets. In the low versus medium nitrogen regime, connected ramets had different patterns of partitioning only. Apparent reciprocal resource transport between ramets can enhance the growth of ramets with complementary resource deficiencies, but may affect growth in dry mass only when maximum resource levels are high.
智利草莓是一种多年生匍匐草本植物，生长在沿海沙丘上，那里散布的灌木形成了小块光子通量密度（PFD）较低但土壤氮有效性较高的区域。通过比较分株对之间维管束连接被切断或保持完整的情况下分株对的生长情况，测试了在空间上PFD和土壤氮呈负相关时分株之间资源运输的潜在影响。每对分株中的一个给予高PFD但低水平的土壤氮，另一个分株给予低PFD但高氮。通过用更现实的中等土壤氮水平代替高水平来测试在自然中可能实现的资源运输的类似影响。结果表明，在两种土壤氮异质性情况下，相连的分株都能交换碳和氮。在低氮与高氮情况下，相连的分株具有更高的总干生物量，并且干物质分配模式与切断的分株不同；连接对给予低PFD和高氮的分株以及较年轻的分株影响更大。在低氮与中等氮情况下，相连的分株仅具有不同的分配模式。分株之间明显的相互资源运输可以增强具有互补资源缺陷的分株的生长，但只有在最大资源水平较高时才可能影响干物质生长。
