The historical development of a bog woodland on the north coast of British Columbia is reconstructed using pollen analysis, peat stratigraphy, and 14C dating. The succession spans 8700 ± 210 years in the following sequence: Pinuscontorta Dougl. – Alnusrubra Bong. – ferns/pioneer alluvial forest; Piceasitchensis (Bong.) Carr. – Alnus – Tsugaheterophylla (Raf.) Sarg. – (Thujaplicata) Donn. – Lysichitonamericanum Hulten & St. John – ferns/moist productive alluvial forest on regosols; Thuja – Chamaecyparisnootkatensis (D. Don) Spach – Tsuga – Pinus/scrub forest on peaty mineral soils; Pinus – Chamaecyparis – ericaceous shrubs – Sphagnum L. spp./bog woodland on organic soils. This ecosystem sequence is correlated with changes in paleoclimate reported for southwestern British Columbia and may also be associated with edaphic factors such as changing drainage patterns, the formation of cemented soil horizons, and the accumulation of thick organic surface horizons. The succession from forest to muskeg is contrasted with other evidence for succession from muskeg to forest in north-coastal British Columbia and southeast Alaska. We interpret the regional vegetation and soils as a dynamic complex of ecosystems linked successionally through climatically sensitive pathways. Local site factors such as topography, landform, drainage, and nutrient regime are important secondary factors controlling the direction of succession.
We compared height growth and nutrition (foliar nutrient concentrations and retranslocation rates from 1-year-old needles) of second-growth plantations on imperfectly drained, lower productivity cedarhemlocksalal forests with those of more productive ecosystems of north coastal British Columbia. Soils ranged from deep organic profiles to well-drained mineral soils derived from igneous to metamorphic bedrock. Leader increments on imperfectly drained sites were smaller than on well-drained sites, averaging 42% less for western hemlock (Tsuga heterophylla (Raf.) Sarg.), 56% less for Sitka spruce (Picea sitchensis (Bong.) Carrière), and 32% less for western redcedar (Thuja plicata Donn ex D. Don). Strong linear correlations were found between leader increment and foliar N, P, and S concentrations for all three tree species, and baseline foliar data for productive sites were presented. The foliar N ratios with P, S, and K were consistent across sites and indicated that many key foliar nutrients increased proportionally to the availability of N. A comparison of nutrient concentrations between current and 1-year-old foliage generally showed little difference on poorer sites, which suggested that there had been no retranslocation of nutrients from young needles within trees to compensate for low soil nutrient availability. This study confirmed the inherently low productivity of cedar-hemlock-salal forests, especially on granodiorite and gneissic diorite bedrock types, and suggested the need for site treatments or long rotations for sustainable management.
The wet, slow-growing forests of western redcedar (Thuja plicata Donn ex D. Don) and salal (Gaultheria shallon Pursh) on the north coast of British Columbia are characteristically low in available phosphorus (P) compared with more productive forest ecosystems. It has been suggested that declining P availability can eventually limit soil biological activity and restrict nitrogen (N) cycling. We investigated this potential link between P availability and N cycling for three forest types (cedarsalal, hemlock lanky moss and spruce sword fern) covering a wide gradient in site productivity. Forest floors (upper 20 cm) and mineral soils (20 cm depth) were collected from five replicate sites of each forest type and incubated for 20 weeks at field moisture content with and without an amendment of NaH2PO4. We found that organic P concentrations of both forest floors and mineral soils were positively correlated to extractable inorganic N concentrations (unamended soils over 20 weeks). The addition of P to the low-productivity cedarsalal soils led to significant increases in extractable inorganic N in the forest floors and mineral soils. P amendments led to either a smaller or nonsignificant increase in extractable N for moderately and highly productive soils. Soil respiration of CO2 and respiration quotients were substantially reduced in forest floors with a P amendment, suggesting N mineralization was governed by exoenzyme allocation rather than decomposition rates. These results demonstrate a possible enhancement in N supplies with an application of P to low-productivity cedarsalal forests.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.