3.3. Ecosystem N and P stocks
In the present study, tree, shrubs, and herbaceous and litter components
N and P stock increased from 346.77 kg ha-1 in AER
(youngest) stand to 4662.06 kg ha-1 in the AOOM stand
(oldest) and 19.17 kg ha-1 in AER stand to 233.91 kg
ha-1 in AOOM stand, respectively. Across the forest
chronosequence, tree bole biomass N and P stock were significantly
greater than any other vegetation biomass components. The N and P stocks
in different vegetation biomass components follow similar patterns as
reported in our previous study (Joshi and Garkoti 2021b) and follow the
order: bole > branch > stump root
> twig > lateral root > foliage
> litter > fine root > shrub
aboveground > herbs aboveground > shrubs
belowground > herbs belowground and in all vegetation
components both N and P stocks increased with forest chronosequence
(Table 1). Average total soil N and P varied from 816.44 to 7334.24 kg
ha-1 and 56.95 to 595.36 kg ha-1,,
respectively, and increased along with the forest chronosequence
(Figures 5 and 6). Across the forest chronosequence, the contribution ofA. nepalensis trees to the ecosystem nitrogen and phosphorus
stock ranged from 9 % in ALR stand to 23.23 % in AMR stand and 3.31 %
in AYM stand to 12.31 % in the AMR stand, respectively (Figure 6 &
Figure 7). Of the total ecosystem N stock, the soil contributed from
48.82 % in the ALR stand to 70.18 % in the AER stand. Similarly, the
contribution of soil to the total ecosystem P stock ranged from 63.49 %
in the ALR stand to 74.8 % in the AER stand. The soil was the largest P
reservoir among all the ecosystem compartments. The understory
vegetation (shrubs, herbs) and litter layer added a small fraction to
the total N and P stock of the ecosystem. Overall, across the stands,
soil and trees were the two largest contributors to the total ecosystem
nitrogen and phosphorus stock (Figure 6, and Figure 7).