Resource use limit by plants
Generally, as plant grow, plant
suck and use resource, and then
resource amount reduces because the resource amount in a given space in
which plant crown or plant root develop is limit. Therefore, there is a
resource use limit by plants in soil and water conservation vegetation,
expressed by the indicator species in a plant or population community,
and resource use limit by plants can be defined as control amount of
plant utilization resources such as
soil water resources use limit by
plant. For example, soil water is the most important factor influencing
and limiting plant growth in water-limited regions. After soil water
resources appeared (Budagovski 1986),
soil water resources can be used
to express soil water condition because root system vertical distribute
in the soil and take soil water in a given soil
body, see figure 1. Two-curve
method can be used to determine maximum infiltration depth (MID) (Guo
2020), see figure 2. The utilization limit of soil water resources by
plants refers to the soil water
resources with the maximum
infiltration depth when the soil water content is equal to the wilting
coefficient. Soil water resources use limit by plant changes with
species and site condition (Guo 2014). The utilization limit of plants
to soil water resources is the control limit plant use soil water in
water-limited regions, which change with plant species and location. For
example, soil water resources use
limit by plant in the 16-years-old Caragana (Caragana
Korshinskii ) shrub land in the fish scale pit on the top of Heici
mountain is 252.8mm, see table 1. And soil water resource use limit by
plants in caragana shrub land in the middle of the Heici mountain is
222.8mm, see table 2. The soil water resource use limit by plants in red
plum apricot plantation is 212.7 mm in the semiarid loess hilly region
(Guyuan county, China).
The soil water contents at different soil suctions using a centrifuge or
pressure chamber, were measured and established the characteristic soil
moisture curve using least square method. And then estimate
the
wilting coefficient at different
soil depths. The wilting coefficient is the soil water content when soil
suctions equal 15bar based on the characteristic soil moisture curve at
different soil depth, see figure 3. As plant grow,
soil water resource reduces (Guo
2010,2014,2020,2021b).
Indicator species is the main cultivation or goal species for artificial
vegetation such as caragana in caragana shrubland. If soil and water
conservation vegetation is made up 2 or three plant species, the
indicator plant is the dominant tree species or the main tree species
with large coverage in mixed forest. The resource use limit by plants
includes space resource use limit by plants in areas rich in water and
fertilizer, soil water resource use limit by plants in the water-limited
regions (Guo 2010; Guo 2014,2021a and b) and soil fertilizer resource
use limit by plants in the fertilizer -limited regions (Guo 2021b).