高寒嵩草草甸不同土地管理措施对植被生产力的影响

Effects of different land management measures on vegetation productivity on alpine Kobresia meadow

将原生高寒嵩草草甸封育系统作为对照,研究了土地退化对植被生产力的影响,检验了退化土地在不同人工重建措施下对植被生产力的相对影响程度.研究结果表明:原生植被封育处理总地上生物量为265.1 g/m^2,0～30 cm土层地下根系生物量达6982 g/m^2;而重度退化处理总地上生物量仅为139.9 g/m^2,0～30 cm土层地下根系生物量为916 g/m^2,仅占原生植被封育处理地下根系生物量的13%,因此重度退化地主要特征之一是天然嵩草草甸坚实而富有弹性的草皮层的丧失.土地退化使地下根系生物量的损失量大约为地上损失量的50倍.混播、松耙单播和翻耕单播人工种植处理经过7个生长季后,总地上生物量分别为原生封育处理的116%,75%,68%;自然恢复处理总地上生物量为原生植被封育处理的76%.与重度退化草地相比较,种植可以有效恢复地上生物量,尤其是禾草生物量,这对于提供冬季饲草、减少天然草地的压力是至关重要的.混播、松耙单播、翻耕单播和自然恢复处理,经过7个生长季后,地下根系生物量分别为1 323,1 094,1 169,1412 g/m^2,重建措施(如混播)自然恢复处理可部分恢复地下根系生物量;恢复重建处理与原生植被封育处理相比较而言,有更多的生物量是分配在地上的.但随恢复年限的增加,恢复重建草地都是将更多的生物量分配给地下,且随恢复时间的增加,人工种植处理向地下转移生物量的速率比自然封育处理的更快.

In order to explore a management approach for sustainable development of vegetation quality on alpine Kobresia meadow, we studied the effect of land degradation on vegetation productivity, examined the relative influence of various rehabilitation practices on vegetation productivity in early secondary succession. The results showed that in the non-disturbed native meadow （YF）, the total above-ground biomass was 265.1 g/m^2 and root biomass in the uppermost 30 cm had an average value of 6 982 g/m^2; in severely degraded grassland （SDL）, the above ground biomass was only 139.9 g/m^2 and root biomass in the uppermost 30 cm was only 916 g/m^2, amounting to just 13% of that in the YF. One of the main features of the severely degraded land was the loss of the originally dense sod layer in the native Kobresia meadow. Loss of biomass in below-ground to above-grpund was about 50 times during land degradation on the alpine meadow. The above-ground biomass in the mixed seed treatment （HB）, harrowing ＋ the single seed treatment （DBB）, plowing ＋ the single seed treatment （DBF） and the natural recovery treatment （NR） was 116%, 75%, 68% and 76%, respectively, of that in the YF. Therefore, compared with severely degraded grassland, seeding treatment might be more effective in improving the above-ground biomass, particular in grass biomass. It was very important for the region to supply winter forage and to lessen pressure on natural grassland. Root biomass in the HB, DBB, DBF and NR treatments was 1323, 1094, 1 169 and 1412 g/m^2, respectively, after seven growing seasons. The rehabilitation measures, such as HB and NR, might in part have recovered below-ground biomass in seven growing seasons. Compared with YF treatment, more biomass was distributed aboveg round in rehabilitation treatments. But with rehabilitation time, more biomass was distributed below ground in all rehabilitation treatments, and the rate of biomass transfer to belowground was quicker on seeding treatments than on the natural recovery treatment.