3.1 AGB of grasses and plant community
AGB of grasses and community
decreased significantly with land
degeneration intensifying. Compared to ND grassland, AGB of grasses and
community decreased by 21.3% and 9.6%, 66.2% and 32.6%, 75.9% and
54.8%, and 95.0% and 69.2% in the SLD, MD, HD and ED grasslands,
respectively (Fig.1a, 1c). Meanwhile, The AGB of grasses decreased
significantly with the increase of the replanting time in active
restoration grasslands. Compared to 5Ys, AGB of grasses decreased by
8.3%, 32.9%, 65.5% and 81.3% in the 9Ys, 11Ys, 14Ys and 17Ys
grasslands, respectively (Fig.1b). Compared to 5Ys, AGB of community
kept stable in 9Ys grasslands and then decreased with the increase of
replanting time (Fig. 1d).
# Insert Figure 1 #
3.2. Photosyntheticcapacity and its
relationship with AGB of grasses
In
native grasslands, Pn decreased with land
degradation intensifying (Fig.
2a).
Compared to control (ND
grassland), Pn significantly decreased by 4%, 18.7%, 35.8% and 39.6%
in the SLD, MD, HD and ED grasslands, respectively. In addition,gs and WUEi initially kept stable and later
decreased with land degradation
intensifying (Fig. 2c, 2e).
Intercellular CO2 concentration initially increased and
later decreased with land degeneration (Fig. 2g). In active restoration
grasslands, Pn (Fig. b),WUEi (Fig. 2f) andCi(Fig.
2h) significantly decreased with
the increase of replanting time. Compared to 5Ys grassland, Pn,WUEi and Ci significantly decreased by 0.6%, 4.0%, and
4.7%, 15.1%, 23.0% and 9.1%, 24.3%, 23.0% and 12.2%, 31.4%,
35.3% and 13.6% in the 9Ys, 11Ys, 14Ys and 17Ys grasslands,
respectively. Stomatal conductance increased first and then decreased
with the increase of replanting time.
# Insert Figure 2 #
Net photosynthetic rate
(R2 =0.938, P <0.001) (Fig. 3a)
and WUEi (R2 =0.302, P =0.007)
(Fig. 3c) were positive correlated with AGB in native
grasslands.
Net photosynthetic rate
(R2 =0.881,P <0.001),WUEi(R2 =0.839, P<0.001), gs(R2 =0.803, P <0.001) andCi (R2 =0.665, P <0.001)
were highly positive correlated
with AGB in active restoration grasslands (Fig. 3).
Plant photosynthetic capacity in
active restoration grasslands shows stronger association with its AGB
than native grasslands.
# Insert Figure 3 #