云南省自然休闲地与桤木休闲地地上部分生物量与养分蓄积量的研究

Accumulation of above-ground biomass and nutrients in swidden fallows: A comparison between planted alder fallows and unmanaged grassy fallows in Yunnan

通过样方调查和采样 ,对云南省西盟县新厂乡阿莫村自然条件相似、经历了相同休闲年限的桤木休闲地和自然休闲地的地上部分植被生物量和养分蓄积量进行了比较研究 ,结果表明 ,休闲 3a后 ,桤木休闲地的休闲效果显著高于自然休闲地。表现在桤木休闲地的地上部分生物量高于自然休闲地 ,休闲 6 a后 ,桤木林的地上部分生物量干重达到 6 9,6 4 0 kg/hm2 ,是自然休闲地的 4倍 ;桤木休闲地 N、P、K三大营养元素的地上部分蓄积量 ,经过 2～ 3a超过自然休闲地 ,并在休闲 3a后显著高于自然休闲地 ,休闲 6 a后 ,N蓄积量达到 5 5 7kg/hm2 ,是自然休闲地的 3倍 ,P、K的蓄积量分别达到 4 1kg/hm2 、2 6 5 kg/hm2 ,是自然休闲地的 2倍。目前研究说明桤木种植有改进轮歇农业的明显作用 ,具有在类似地区推广应用的价值。

Planting alder (Alnus nepalensis D.Don) in swidden fields has long been a traditional fallow management practice in Yunnan province of southwestern China. Farmers may harvest the trees for firewood after about six years or, in the case of longer fallow periods, they may be harvested for timber. To compare the above-ground biomass and nutrient accumulation in planted alder fallows with those of unmanaged grassy fallows, plot measurements were taken in sample fallows in Ximeng county, Yunnan province. The results confirm a higher above-ground biomass in the alder fallows than compared grass fallows of similar ages. Nutrient accumulation in alder fallows exceeds that of grass fallows after two or three years. By six years, the above-ground biomass in alder stands reaches about 69,640kg/hm^2,roughly four times greater than grass fallows. This alder biomass contains 557 kg/hm^2 of N,which is three times that of grass fallows, 41 kg/hm^2 of P and 265 kg/hm^2 of K,both about double the levels found in compared grass fallows. These findings highlight alder's role as an efficient fallow species that both accelerates soil rejuvenation and provides harvestable products.