Carbon Storage And Density Of Natural Pinus Shekannesis Forest In Ziwuling Area

With global warming, scientists pay more attention to carbon source or sink. As the largest terrestrial ecosystem organic carbon pool, Forest ecosystem has great significance for increasing carbon sinks, offsetting CO₂ emissions, and mitigating greenhouse effect. In order to make clear source/sink, we should determine carbon storage size of existing forest ecosystems. But because of scale and methods, great uncertainty and complexity have appeared, even not accurately reflection the real carbon storage level of forest ecosystem. Based on those, this paper had chosen natural Pinus shekannesis, a single unit-based forest ecosystem, in Ziwuling area of Loess Plateau. Using inventory, mesh bags harvesting and soil drilling methods, we got vegetation, litter layer biomass and soil samples. Combined with laboratory analysis, we studied carbon storage and its density distributing characteristics of Pinus shekannesis in spatial growth scales. Main findings are as following:1,According to allometric model, we built the biomass model: B_truck= 3.122(D²H)^0.277; B_branch=0.622(D²H)⁽0.402_; B_leaf=0.029(D²H)⁽0.574_; B_bark= 0.058(D²H)⁽0.367 ; B_fruit= 0.049(D²H)⁽0.528_; B_root= 1.156(D²H)^{0.367_; B₉whole} tree= 4.562(D²H)⁽0.352_. The results showed that: the total biomass of vegetation layer was 194.47 t/hm². Tree layer biomass was the largest about 115.35 t/hm², taken up to 59.32% of whole vegetation layer; shrubs was 64.59 t/hm², accounting for 33.21%; herbs was the least about 14.53 t/hm², only taken up to 7.47%. Meanwhile, we used mesh bags harvesting litter biomass. The result released that total litter biomass was 88.59t/hm², and the thickness and biomass had a good linear relationship with each other. Besides, a contribution rate of different decomposition level respectively was 48.35%, 27.93% and 23.73%.2,The carbon rate of research-level characteristics: vegetation layer (tree layer, shrub layer, herb layer) carbon rate was 0.4137⁰.5413 g/g , with a mean of 0.4697 g/g. Furthermore, carbon rate had great significance among different organs. Then mean Carbon rate were 0.5068 g/g, 0.4469 g/g, respectively for tree and shrub/herb. The average carbon content of litter was 335.91 g/kg. But the rate decreased with decomposition increasing, and also had great significance among different levels. Soil organic carbon content was 3.94³4.99 g/kg, range ability up to 89%, descended with depth, and reflected significant difference among soil layer. In addition, we also studied the relationship between organic carbon content and phy-chemical properties of soil. The results showed that a highly significant correlation had appeared between organic carbon content and soil water content, pH, total nitrogen, total phosphorus, potassium, nitrate and ammonium in the whole soil profile.3,Carbon density of forest ecosystem was 236.04 t/hm². In spatial scale, carbon density characteristics was soil layer > vegetation layer > litters layer. Furthermore, carbon density was 95.16 t/hm², 33.29 t/hm², and 107.55 t/hm², respectively of vegetation, litters and soil layer. These results may closely relate with regional, climate characteristics, vegetation types and soil parent material.4,According to study results, the total carbon storage capacity of Pinus shekannesis forest ecosystem was 15.97 Tg. The largest carbon pool is soil for 7.27 Tg, taking up to 45.52% of total carbon storage, and is 1.14 and 3.22 times respectively than vegetation and litter layer. In this case, we found that soil carbon pool is the most important for forest ecosystems. Consequently, we should pay more attention to soil carbon storage and provide the basic data for regional and global climate change.