4.4. Implications for management
Our results revealed that the ecosystem C pools in the above and
below-ground parts of the tree, shrubs, herbs, litter, and soil were
changed significantly during A.nepalensis forests stand
development. Developing forests has had a significant impact on biotic
and abiotic factors, such as plant species, soil physicochemical
properties, microbial communities, and the quantity and quality of
inputs and outputs of organic matter (Myrold et al., 1994; Susaetaet
al., 2014; Uri et al., 2014; Uri et al., 2017; Taeroe et al., 2017). The
distribution of C between the plants and the soil during the development
of the forest stand depends on the species of trees and A.
nepalensis is a nitrogen-fixing tree that can change soil carbon more
than any other non-nitrogen fixing tree.
(Binkley
et al., 1992; Myrold et al., 1994). A. nepalensis has been shown
to support carbon storage in temperate forests in central Himalaya. The
ecosystem C storage came primarily from A. nepalensis , which were
more abundant and had a higher basal area than Q.
leucotrichophora and R. arboreum. Our results provide new
qualitative insight into the role of A. nepalensis in the
temperate forest C sink in the central Himalaya. The Himalayan range is
among the most fragile and unstable mountain regions of the world.
Forest degradation in the Himalayas is a major challenge for forest
managers and policymakers.The interplanting of nitrogen-fixing A.
nepalensis with non-nitrogen-fixing tree species (Q.
leucotrichophora and R. arboreum ) may enhance the growth of the
non-nitrogen-fixing tree species by increasing nitrogen availability
(Binkley
et al., 1992; Myrold et al., 1994; Semwal et al., 2013) improving
nutrient cycling and soil fertility
(Binkley.,
2003; Khan et al., 2007; Bissonnette et al., 2014) and increasing carbon
sequestration rate and improving risk management. The observation thatAlnus raising soil nitrogen levels and subsequently influence the
growth of the neighbor’s non-nitrogen-fixing species (Anthony and Klaus
2004). Maintaining or including nitrogen-fixing species in mixed forests
appears to be an option for enhancing soil carbon sequestration rate
(Resh et al., 2002). Previous study indicates that Alnus species
contribute significantly to the supply of nitrogen in the forest
ecosystem thus markedly benefits soil fertility. In addition to being an
early successional species, A. nepalensis colonize the
recently-disturbed area with low levels of nitrogen availability. The
obtained results show that A. nepalensis may play the role of
early successional species in the temperate forest in central Himalaya.
High nitrogen-rich litter of A. nepalensis reduced requirement of
nitrogen in the soil and thus increase the forest productivity,
regulating C cycle and mitigate global climate change. In the central
Himalaya, A. nepalensis is currently of little impotence in
plantation forestry, although the potential for future use of A.
nepalensis in forestry seems great and the opportunities are diverse.
Although A. nepalensis does offer an alternative to chemical
application of nitrogen to the forest, this potential of A.
nepalensis systems in forest management is much more. That knowledge
can contribute to the sustainability of forest practices which can
ensure the restore the degraded forest and maintain their capacity to
provide other goods and services for the benefit of current and future
generations.
CONCLUSION
Our results revealed that the abundance of A.nepalenis affect the
ecosystem carbon storage. We found that tree biomass in different stands
AER, APDF, ALR, AMOM, AMR, and AMOO were 8.97, 51.41, 16.07, 53.74,
144.77, and 101.14 Mg ha-1 respectively. Soil organic
C (SOC) storage of soil in different soil depth in successional stages
AER (0-10 cm), APDF (0-30 cm), ALR (0-100 cm), AMOM (0-100 cm), AMR
(0-100 cm), and AMOO (0-100 cm) was 3.31, 31.21, 75.47, 157.04, 159.43
and 210.13 Mg ha-1, respectively, with SOC
concentration decreasing with increasing soil depth. The ecosystem
carbon storage in the stand developing stand averaged 15.85, 183,216.26,
390.32, 403.66, and 500.08 Mg ha-1 in the AER, APDF,
ALR, AMOM, AMR, and AMOO respectively. In addition, trees and soils were
the two largest contributors to the total ecosystem carbon pool in all
stands. The soil carbon content and storage were highly heterogeneous
among different stands and soil depths. Species community structure and
composition had a significant influence on the biomass carbon storage
and soil organic carbon storage of the stands. Our results are useful in
estimating the total ecosystem C stock value of A. nepalensisforests in the study area. The A. nepalensis play an important
role in stand development and enhancing ecosystem carbon storage by
ecological succession. The expansion of A. nepalensis in central
Himalaya can play an important role in regional carbon budge and
degraded forest protection. Long-term monitoring and research are
required to further explore the role of A. nepalensis forest
stands in central Himalaya.