0111-B1

Primary Productivity and Energy Flow of Hardwood Forests

Zhengfei Ma, Li Xiao and Shanjin Zhu^[1]

ABSTRACT

The characteristics of primary productivity, energy products and process of energy flow were studied in Juglans mandshurica, Fraxinus mandshurica, and Phellodendron amurense hardwood forests, based on the theory and method of community energetics, by using fixed position measuration, quantitative test and experimental analysis. The time-space dynamics of sun-radiation in the hardwood forests were measured and an energy compartment model was set up. This research provides us with a scientific basis in the primary productivity and energy converting of the hardwood forests.

INTRODUCTION

The Juglans mandshurica, Fraxinus mandshurica, and Phellodendron amurense hardwood forests are the more important hardwood forests in the Chongfeng Forest Farm of Cuiluan Forest Bureau, Yinchun of China. They distribute in patches scattered on the east slope of the mountain, Xiaoxingan Range. The existence, development and dynamics of the forest communities depend on the energy, energy flow and substance circulation, and bio-production processes. Energy flow, however, is the basic function of the forests. The study was focused on the energy flow and community productivity. Energy flow is the process of sun-radiation energy which is absorbed, fixed, transformed and consumed by forest communities, which influences the structure, succession and productivity of the communities. In order to develop the productivity, promote the material cycle, improve the utilizing rate of energy flow and provide basic information for the management of the hardwood forests, studying ecosystem productivity and energy flow is becoming more necessary.

METHODS

Sun-radiation intensity was determined on a 17m high observing tower in the field sampling land. From forest canopy to ground, in line with canopy structure and layer feature, 4-layer observing platforms were set up. Sun-radiation energy was measured by using DFY-2 type sky-radiation meter and DFY-1 radiation galvanometer. Photosynthesis available radiation was measured by using GTJ-1 available radiation meter. Illuminance of different layer in the community was determined by QZ-CZ type micro-illuminometer. Leaf area was measured by using CY-400 type light-electron area meter. Bio-productivity was measured by harvest method. Caloricity was determined by DAOJIN CA-3 type oxygen-bomb caloricity.

RESULTS AND ANALYSES

Characteristics of Energy Environment in the Hardwood Forests Characteristics of energy environment in the communities are composed of various energy forms that consist of and are controlled by sun-radiation in living space of the communities.

Sun-radiation energy reaching to the forest canopy In the growing season, May to September, sun-radiation intensity is 5,453,787.00 KJ/m², 46% of which reaches to the canopy of the hardwood forests (2,525,926.66 KJ/m², with 54% decreased).

Time dynamics of sun-radiation energy distribution Day-dynamics of direct radiation is a single-peak curve whose peak value occurs at about 12 o’clock. Season’s dynamics changes greatly, and the first peak value is 44725.3 KJ/m². month., appearing in September. The second peak value is in May, and the lowest in July. The dynamics of scattering-radiation is similar to the direct-radiation, and a wave curve showed in its season’s dynamics. The highest value is in July, the relatively high one is in May and the lowest in September.

Dynamics of photosynthesis available radiation (PAR) in the hardwood forests (Fig.1 and 2)

Fig.1. Day dynamics of PAR value.

PAR= photosynthesis available radiation (KJ/m².h).

Fig.2. Season’s dynamics of total PAR value.

PAR= photosynthesis available radiation (10⁶ KJ/m².month).

Energy Production Status Energy production of the hardwood forests is the primary productivity that consists of various energy-contained products made in net photosynthesis of community. Generally, the caloricity is used to indicate energy value of plant energy-contained products.

Distribution and changes of energy in the hardwood forests

Arborous layer: Average caloricity in order is: Juglans mandshurica > Tilia amurensis > Ulmus propinqua > Fraxinus mandshurica > Phellodendron amurense > Acer mono.

Brushwood layer: Caloricity of roots (18.396 KJ/g) is greater than that of stems (16.866 KJ/g). The order is root > leaf > stem and branch.

Herbaceous layer: Average energy is lower above ground (16.642 KJ/g) than underground (19.052 KJ/g).

Energy distribution: The distribution of energy in the hardwood forests is arborous layer > brushwood layer > herbaceous layer (Tab. 1).

Distribution of biomass energy in the hardwood forests.

(1) Distribution of biomass energy in arborous layer and different organs: The order of biomass energy is tree trunk > root > branch > bark > leaf > new branch. (Tab. 2).

(2) Biomass energy in brushwood layer mainly distributes in the roots, trunk, and branch, few in the leaves (Tab. 3).

Table 1. The Energy distribution in the hardwood forests (KJ/g)

Table.2. Biomass (T/hm²) and biomass energy (10⁶ KJ/hm²) of different organs in arborous layer

Table 3. Distribution characteristics of biomass energy in brushwood layer (T/hm²)(10⁶ KJ/hm²)

(3) Biomass energy is greater under ground than above ground in herbaceous layer (Tab. 4)

Table 4. Distribution feature of biomass energy in herb layer (KJ/m²) (10³ KJ/m²)

(4) The Biomass energy in the hardwood forests mainly exists in the arborous layer, the brushwood layer is secondary, and the herb layer is the lowest. (Tab. 5)

Net primary productivity (NPP) and distribution in the hardwood forests

(1) Arborous layer: The order of NPP in arborous layer is leaf > trunk > root > branch > bark (Tab. 6).

(2) Brushwood layer: Net primary productivity is slightly greater in roots than in trunks, branches and leaves. (Tab. 7)

(3) Herb layer: Net primary productivity of herb layer is about 10.817 X 10⁶ KJ/hm².a

Table 5. Distribution of biomass energy in the hardwood forests (T/hm²)(10⁶ KJ/hm²)

(4) Net primary productivity of the hardwood forests is manly distributed in arborous layer, taking up 64%; brushwood layer is secondary, taking up round 30% (Tab. 8).

Table 6. Distribution of net primary productivity in arborous layer (10⁶ KJ/hm²)

Table 7. Distribution of NPP in brushwood layer (10⁶ KJ/hm².a)

Table 8. Distribution of NPP in the hardwood forests (10⁶ KJ/hm².a)

Fig.3. Compartment model of energy flow process in the hardwood forests (Unit: KJ/m²)

Analysis of Energy Flow Process in the Hardwood Forests Energy flow of forests is a biophysical-chemical process of sun-radiation energy that is absorbed, located transformed and consumed by forest communities. The compartment model as Fig 3 can show the energy flow process in the hardwood forests.

REFERENCE

1. Chidumayo, E.N. 1990. Above-ground woody biomass structure and productivity in a Zambezion Woodland, Forest Ecology and Management 36: 33-46.

2. Viswanadham Y et al. 1990. Radiation Balance of the Amason Forest, Proceedings of IUFRO XIX World Congress. Vol. 2:90-101