Effect of krummholz establishment on soil previously occupied by tundra: inorganic and organic properties.

• Format: Dataset
• Language: unknown
• Published: Niwot Ridge LTER/University of Colorado1560 30th Street, CB [e-mail] 2001
• Subjects: NWT; Niwot Ridge LTER Site; LTER; Colorado; inorganic nitrogen; krummholz; moisture; nitrogen; soil; soil inorganic nitro; soil moisture; soil organic content; tree island; tundra; Tundra
• Online Access: http://hdl.handle.net/10255/dryad.9465; http://metacat.lternet.edu/knb/metacat/knb-lter-nwt.133.2/xml

Previous work has shown that passage of Englemann spruce (Picea Englemanii) and subalpine fir (Abies lasiocarpa) tree islands across tundra lowers the soil carbon and nitrogen storage capacity of the top 15cm of soil (A horizon) (Pauker and Seastedt 1996). This study shows that levels of KCl extractable ammonium and percent organic matter were also significantly higher in the A horizon of undisturbed tundra sites compared with soils underneath or immediately adjacent to (windward or leeward) the krummholz. The response of soil KCl extractable NO3- also showed this trend but was not statistically significant. Holtmeir and Broll (1992) suggested that the depletion of organics and nutrients following the passage of tree island may be associated with a reduced clay content. We analyzed a subsample of these soils for cation exchange capacity (CEC) and texture. We did not find significantly lower clay content in soils under or adjacent to krummholz compared with those from undisturbed tundra. In fact, percent clay was greater in krummholz and windward sites than in tundra sites. The percent clay of windward sites was significantly greater in windward soils than either krummholz or tundra soils. Clearly, depletion of organics following the passage of tree islands does not appear to be associated with a depleted clay content. We found that CEC was very highly significantly correlated with percent organic content (using percent organic data only from the subset of soils on which CEC was measured). Therefore, the CEC content of these soils would appear to be strongly associated with the organic content but not with the clay content. Percent soil moisture was significantly higher directly underneath the krummholz compared with the other sites. There was no effect of treatment on pH. We also investigated whether the organic matter lost in association with krummholz colonization (i.e. 1m from the tree) was replenished as tundra vegetation recolonized in the wake of the tree island. In order to do this we compared soils from tundra sites in the wake of the tree islands (5m or 10m windward of the tree -a distance that represents approximately 250 and 500 years since krummholz colonization) with soils from undisturbed tundra sites. We found no significant difference in organic matter contents along the windward transect, indicating that recovery of organic matter content following colonization by krummholz is an extremely sow process. The soil samples were collected on 7 sampling dates in the summers of 1995 and 1996 and all the variables are listed by their separate sampling dates in this file.