Arazi Kullanımı ve Arazi Kullanım Değişimlerinin Toprak Mikrobiyel Biyokütle Değişimleri Üzerine Etkileri
Tez Türü: Doktora
Tezin Yürütüldüğü Kurum: Niigata University, Ziraat Fakültesi, Toprak Bilimi Laboratuvarı, Japonya
Tez Danışmanı: Nonaka Masanori
Tezin Onay Tarihi: 2002
Tezin Dili: İngilizce
Desteklendiği Program: Diğer
Özet:
In the present study, the I examined the impacts of soil
management and land-use changes on microbial biomass and soil ergosterol
content in two different investigations.
In the first study, effects of management practices on
microbial biomass and soil ergosterol content were studied in Japanese
Andosols. Although the relationships between agricultural practices and
microbial biomass have been documented well, there is a lack of information on
microbial biomass and especially on ergosterol content of Japanese Andosols. The
objective of the first study is therefore to elucidate the relationships
between management practices, microbial biomass and soil ergosterol content in
a group of Japanese soils under permanent forest, grassland, fruit production
and annual crop production in Niigata Prefecture, Japan.
In the second study, I investigated microbial biomass and
ergosterol content in a group of Indonesian soils, which have been suffering
from drastic land-use changes due to the transmigration policy for the last two
decades. Transmigration is an Indonesian Government program
whereby people from overpopulated areas within the archipelago, such as Java,
are relocated to less populated areas, such as Sumatra Island. However
considerable resources have been wasted in settling people who have not been
able to move beyond subsistence level, with extensive damage to the environment
by destroying forests. In the past two decades, the area covered by primarily
forest decreased by 44% whereas, coffee-planted areas increased by 60% in South
Sumatra, Indonesia. In the second study, my objective was to clarify the effect
of intensive land-use changes on microbial biomass in forest, deforested,
coffee-planted, bush regrowth and traditional orchard soils located in a hilly
area in Lampung Province, South Sumatra, Indonesia.
My results showed that microbial biomass and
ergosterol content were larger in the order of intensive crop production <
permanent pasture < forest. Forest soils have a larger biomass pool because
the main source of organic input to the biomass in natural ecosystems is from
plant material, consisting of roots, leaf and stem litter and actual biomass
pool does not change except for the effects of seasonal changes. Larger biomass
and ergosterol content in pasture and orchard soils compared to intensively
cropped soils are probably related to the management practices such as leaving
residue on the soil surface after harvest and very low field traffic. These
treatments result in higher concentrations of soluble organic compounds and
relatively stabile nutrient flow which may result in the enhancement of
microbial biomass. Lower microbial biomass and ergosterol content in
intensively cropped soils are probably due to fact that intensive cultivation
and conventional tillage alter nutrient input-output frequently and cause
significant disturbance to soil microorganisms. Seasonal observations indicated
that microbial biomass did not show a significant change, especially in permanent
grassland soils where microbial biomass should have been in equilibrium with
local management and conditions. This observation is consistent with those
suggested by several authors who reported that fertilizer amendments did not
affect the amount of microbial biomass because microbial is largely derived from
a stabilized form of organic matter and short-term fluctuations created by
flushes of labile forms of nutrients in long-established permanent grassland
soils. In contrast to the microbial biomass, seasonal changes in soil
ergosterol content were significant in most of the soils. These findings
demonstrate that even though seasonal changes may not affect the actual size of
total microbial biomass, soil ergosterol content can be ascribed to a sensitive
parameter showing the effects of seasonal changes on fungal biomass. Although
soil ergosterol content showed clear distinctions between intensively cropped
and permanent grassland or orchard soils, no meaningful relationship could be
observed in the respect of management practices between similarly or differently
treated soils sites. This can be due to interspecific variations of ergosterol
content between fungal communities and different fertilization periods in different
soil sites.