| Six-year-old Betula platyphylla plantation at Maoershan Forest farm of Northeast Forestry University was studied. Birch trees stand growth, nutrition, photosynthetic indexes, root indexes were investigated after two years fertilization, with two factors(N, P) and three levels(no fertilizer(CK),1 (low fertilizer),2 (high fertilizer)) in uphill, and three phosphorus application treatments (control(CK), low phosphorus application(P1) and high phosphorus application(P2)) in downhill.The effects of different fertilization treatments on birch plantation growth were analyzed, and stand growth, photosynthetic indexes, root indexes with different fertilization treatments were discussed. Our findings provide some insights into birch plantation silviculture and establishing reasonable nutrition control measures and fertilization scheme. The results showed:(1)ertilization significantly promoted tree growth, and increased forest volume. DBH growth with N1P2 treatment was significantly higher than CK by 54.3%(P<0.01), and the effects of N2P1 and N2P2 treatments on DBH were significant by 45.6%?37.4%(P<0.05). Height growth with P1 and P2 treatment were higher than CK by 39.1%(P<0.01) and 36.8%(P<0.05); N2P1 and N2P2 treatment were higher than CK by 37.0% and 30.5% respectively (P<0.05). The volume growth with N2P1 fertilization treatment was higher than CK 55.9%(P<0.05). Phosphorus application in downhill promoted significantly DBH growth (P<0.05), while the volume growth were higher than CK by 56.0% and 51.0%(P>0.05).(2)The impact of fertilization treatment on nutrients in young birch plantation is different significant. N content of leaves were lower than that of CK, except N2P2 treatment fertilization in uphill. P content of leaves and branches were higher than CK, and N, P content in roots were higher than CK. N2P1 treatment K content of leaves were the highest, followed by P1. They were higher than CK by 16.0% and 8.8% respectively (P<0.05). K content of roots with P1 treatment, compared with CK, increased by 30.8%(P<0.05). P higher fertilization in downhill promoted the transfer of nutrient. N content of roots with P2 treatment in downhill was significantly lower than CK. P content, compared with CK, was undifferentiated, while N, P content of leaves were higher than that of CK. K content of roots with P1treatmentwere 18.5% higher than that of CK (P<0.05).(3) During the fast-growing periods of trees, fertilization treatment promoted seedling leaf photosynthetic characteristics. SLA with N1P2 treatment was 1.2 times (P<0.05)with CK, SLA with N and P mixed fertilization treatment, compared with CK, increased by 3.7%-9.4%. Photosynthetic rate with N1P2and N1treatment in uphill were higher than CK by 36.0% and 35.2%respectively (P<0.05). Photosynthetic ratewithP1 treatment in downhill, compared with CK, increased by 8.4%(P<0.05).(4) Fertilization for young birch trees has effects on root weight density significantly. Compared with CK, root weight density with P1 treatment and N1P2 treatment in uphill were 1.2 times and 1.1 times respectively(P<0.05). Root weight density with P treatment in downhill were P2>P1>CK, increased by 54.0% and 50.5% respectively(P>0.05).The results showed that The P element was the main limiting elements for the growth of Betula platyphylla in juvenile plantation, a certain amount of N and P mixed fertilization was conducive to growth; The effects of fertilization on photosynthesis rate of young birch trees was improved, the accumulation of forest biomass can increase by increasing the leaf area of forest and increasing the photosynthetic rate and producing more photosynthetic products; A certain amount of N and P mixed fertilization was conducive to growth, promoted the absorption of nutrients in trees, showed that the ratio of fertilizer to juvenile birch plantation is very important, and should pay attention to in the actual production of the type and amount of fertilizer ratio. |
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