Bulk deposition of base cations in a subalpine natural forest landscape estimated by canopy budget model: A focus on the forest edge canopy

Calculations of base cation inputs of loads in forest edge canopies are rare, although forest edge canopies play a paradoxical role in the effective capture of atmospheric deposition. Throughfall deposition and canopy exchange of base cations were studied with a continuous throughfall investigation under a natural forest edge and a closed canopy in a subalpine forest over a period of 2 years. Compared with precipitation, the concentration of base cations in the throughfall of both canopies was enriched as expected, but the enrichment level in the forest edge was less than that in the closed canopy. Moreover, the throughfall deposition of base cation fluxes in the closed canopy (35.19 kg ha-1 y-1) was slightly higher than that in the forest edge canopy (33.50 kg ha-1 y-1). Seasonally, the base cation input in the rainy season was 2.32–2.70 times higher than that in the snowy season in throughfall in forest edge canopy and the closed canopy. Furthermore, the canopy budget model suggested that the direction and magnitude of canopy exchange and dry deposition controlled the net throughfall fluxes (NTF) of base cations, and obvious differences could be observed between the canopy and seasonal scales. Compared with other elements, K and Mg leached from the main canopy exchange process, while Ca was absorbed by both canopy types in the annual NTF. These results highlight the spatial variability of base cation chemical characteristics, enhance cognitive the deposition of nutrients and regulatory factors in different forest landscapes, preferably guide the formulation forest ecological management strategies.

Comparison between Empirical Models and the CBM-CFS3 Carbon Budget Model to Predict Carbon Stocks and Yields in Nova Scotia Forests

In response to the global climate crisis, the Nova Scotia Department of Lands and Forestry is using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) and associated methodologies to assess the carbon dynamics of the provincial forestry sector. The CBM-CFS3 bases simulations on a range of studies and national forest inventory plots to predict carbon dynamics using merchantable volume yield curves. Nova Scotia has also maintained thousands of permanent forest sample plots (PSPs) for decades, offering the opportunity to develop empirical, province-specific carbon models. This study used PSP tree measurements and allometric equations to compute plot-level forest carbon models from the PSP dataset and compared their output to that of the CBM-CFS3 model. The PSP-based models were stratified into five forest types and predict the carbon for seven carbon pools as a function of the plot age. Predictions with the PSP- and CBM-CFS3 models were compared to observed PSP data at the plot level and compared against each other at the stand and landscape level. At the plot level, the PSP-derived models predicted carbon closer to the observed data than the CBM-CFS3 model, the extent of over- or under-estimation depending on the carbon pool and forest type. At the stand scale, the CBM-CFS3 model predicted forest carbon to within 3.1–17.6% of the PSP method on average. Differences in predictions between the CBM-CFS3 and PSP models decreased to within 2.4% of the PSP-based models at the landscape level. Thus, the implications of using one method over the other decrease as the prediction scale increases from stand to landscape level, and the implications fluctuate as a function of the forest type and age.