4.5 The effect land-use changes and pedo-climatic factors on the
response ratio of SOC storage
In addition to the potential method uncertainties (i.e., sample depths
and calculation methods), there are still some uncertainties in
estimating SOC and TN storages (Fig. 6). In our meta-analysis, all
available data are integrated and analyzed to study the relationship
between their factors and SOC response to LUCC (we only discussed SOC).
The uncertainties were mainly raised from four aspects: soil
physicochemical characteristics (BD, TN, pH, TP, TK, clay content, soil
water content), topographic factors (slope, altitude), climatic factors
(average temperature, average rainfall) and the year of land-use change.
In this study, there was a significant correlation between soil
characteristics and soil SOC storage (Fig. 6). Except for the soil BD,
other factors were positively correlated with SOC storage in the
deforestation (Fig. 6). Soil pH (r = 0.50, P < 0.01,n = 93) and total N storage (r = 0.80, P < 0.01,n = 69) were positively correlated with SOC storage. Taken
together, we highlight that soil properties have strong effects on SOC
storage based on the collected
database.
We focused on two topographic variables, altitude and slope. It is
generally believed that elevation could induce temperature changes and
thus the SOC and TN storage, showing a positive correlation with SOC
storage (Tashi et al., 2016). Recent studies have shown that the
contribution of elevation to different vegetation systems may be due to
rock exposure or human activities (Hu et al., 2018). On the other hand,
the effect of slope on the distribution of SOC storage may be associated
with soil erosion, microbial biomass and activity, evaporation and
infiltration (Moffet et al., 2005). Different vegetation types will be
formed with the combination of altitude and climate factors, resulting
in different types and quantities of plant residues entering the soil,
making SOC estimation more uncertain (Oskar et al., 2017). Temperature
and precipitation are another main climatic variable considered in this
study. These two variables not only affect the net primary productivity,
but also the soil microbial properties, and thus the SOC and TN dynamics
(Sotta et al., 2010). Besides, duration of LUCC is another important
factor impacting SOC storage. In the early stage of LUCC, the changes of
SOC is relatively higher, and
gradually
decreased with times (Morris and Sven, 2007; Wang et al., 2016;)
Taken together, it is a challenge to quantify the contribution of
environmental factors to estimating SOC and TN storage. To reduce the
estimated bias of SOC/TN storage, the interaction between human
activities and climatic factors should be comprehensively considered in
future work.